diff --git a/AGENTS.md b/AGENTS.md
index 7d5ba8a94..9fe210800 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -212,7 +212,7 @@ new uncovered branch.
 
 To prove that a type resolves to what you claim, write
 `type _Name = Assert<Equal<Actual, Expected>>` — `Assert` from
-`fjs/asserts/module.f.mjs`, `Equal` from `fjs/types/ts/module.f.mjs`. A wrong
+`fjs/asserts/types.ts`, `Equal` from `fjs/types/ts/types.ts`. A wrong
 claim is then a compile error (TS2344, "Type 'false' does not satisfy the
 constraint 'true'"), and the check costs nothing at runtime.
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16ac1818b..69bea2846 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,12 @@ history.
 
 ## Unreleased
 
+- **BREAKING CHANGES:** every public type exported by an authored `.f.mjs`
+  module moves to a sibling `types.ts` (31 modules, including `asserts`,
+  `types/list`, `types/bit_vec`, `types/result`, `text`, `crypto/sha2`) —
+  importers of these types must use the `types.ts` specifier. The runtime-empty
+  `fjs/types/option/module.f.mjs` becomes `fjs/types/option/types.ts`
+  [#1483](https://github.com/functionalscript/functionalscript/pull/1483)
 - `fjs/types/nullable/proof.f.ts`, `fjs/types/range/proof.f.ts`,
   `fjs/types/function/proof.f.ts`, `fjs/types/result/proof.f.ts`, and
   `fjs/types/function/compare/proof.f.ts` migrate to `proof.f.mjs` under
diff --git a/fjs/asn.1/module.f.mjs b/fjs/asn.1/module.f.mjs
index b73c6bee7..3b7316f0f 100644
--- a/fjs/asn.1/module.f.mjs
+++ b/fjs/asn.1/module.f.mjs
@@ -18,7 +18,13 @@ import {
     vec8,
 } from '../types/bit_vec/module.f.mjs'
 
-/** @import { Unpacked, Vec } from '../types/bit_vec/module.f.mjs' */
+/** @import { Unpacked, Vec } from '../types/bit_vec/types.ts' */
+
+/**
+ * @import {
+ *  ObjectIdentifier, Raw, Record, Sequence, SupportedRecord, _Tag,
+ * } from './types.ts'
+ */
 
 import { identity } from '../types/function/module.f.mjs'
 
@@ -57,12 +63,6 @@ const tagNumberMask = 0b000_11111n
  * @typedef {readonly[_ClassPc, bigint]} _ParsedTag
  */
 
-/**
- * ASN.1 tag number.
- *
- * @typedef {bigint} _Tag
- */
-
 /** @type {([classPc, number]: _ParsedTag) => Vec} */
 const parsedTagEncode = ([classPc, number]) => {
     const [firstByteNumber, rest] = number < tagNumberMask
@@ -179,12 +179,6 @@ const lenDecode = v => {
 
 // raw
 
-/**
- * Raw ASN.1 TLV tuple.
- *
- * @typedef {readonly [_Tag, Vec]} Raw
- */
-
 /**
  * Encodes a raw ASN.1 TLV tuple into a bit vector.
  *
@@ -265,12 +259,6 @@ export const decodeOctetString = v => v
 
 // object identifier
 
-/**
- * ASN.1 OBJECT IDENTIFIER components.
- *
- * @typedef {readonly bigint[]} ObjectIdentifier
- */
-
 /**
  * Encodes an OBJECT IDENTIFIER value.
  *
@@ -313,12 +301,6 @@ export const decodeObjectIdentifier = v => {
 
 // sequence
 
-/**
- * ASN.1 ordered collection of records.
- *
- * @typedef {readonly Record[]} Sequence
- */
-
 /**
  * @param {(vec: readonly Vec[]) => readonly Vec[]} map
  * @return {(...records: Sequence) => Vec}
@@ -343,12 +325,6 @@ export const decodeSequence = v => decodeAll(decode)(v)
 
 // set
 
-/**
- * ASN.1 SET represented as a sequence of records.
- *
- * @typedef {Sequence} Set
- */
-
 /**
  * Encodes a SET payload with canonical byte ordering.
  *
@@ -364,43 +340,6 @@ export const encodeSet =
  */
 export const decodeSet = decodeSequence
 
-// Record
-
-/**
- * Supported ASN.1 record variants.
- *
- * @typedef {|
- *  readonly[typeof boolean, boolean] |
- *  readonly[typeof integer, bigint] |
- *  readonly[typeof octetString, Vec] |
- *  readonly[typeof objectIdentifier, ObjectIdentifier] |
- *  readonly[typeof constructedSequence, Sequence] |
- *  readonly[typeof constructedSet, Set]
- * } SupportedRecord
- */
-
-// Alternative:
-//
-// export type SupportedRecord =
-//     | boolean
-//     | bigint                                                    // integer
-//     | { tag: typeof octetString, value: Vec }
-//     | { tag: typeof objectIdentifier, value: ObjectIdentifier }
-//     | readonly Record[]                                         // sequence
-//     | { tag: typeof constructedSet, value: readonly Record[] }
-//
-// export type UnsupportedRecord =
-//     | { tag: null, value: Vec }
-
-/**
- * For unsupported tags, we just store the raw value including the tag and length,
- * so that it can be re-encoded without loss of information.
- *
- * @typedef {Vec} UnsupportedRecord
- */
-
-/** @typedef {SupportedRecord | UnsupportedRecord} Record */
-
 // encode
 
 /** @type {(_: SupportedRecord) => Vec} */
diff --git a/fjs/asn.1/proof.f.mjs b/fjs/asn.1/proof.f.mjs
index 8f75a410a..b60271924 100644
--- a/fjs/asn.1/proof.f.mjs
+++ b/fjs/asn.1/proof.f.mjs
@@ -1,5 +1,5 @@
 import { empty, isVec, length, msb, uint, unpack, vec, vec8 } from '../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../types/bit_vec/types.ts' */
 
 import { asBase } from '../types/nominal/module.f.mjs'
 
@@ -18,7 +18,7 @@ import {
     encodeObjectIdentifier,
     decodeObjectIdentifier,
 } from './module.f.mjs'
-/** @import { SupportedRecord, ObjectIdentifier } from './module.f.mjs' */
+/** @import { SupportedRecord, ObjectIdentifier } from './types.ts' */
 
 import { assert, assertEq } from '../asserts/module.f.mjs'
 
diff --git a/fjs/asn.1/todo/65z-asn1-tag-codec-table.md b/fjs/asn.1/todo/65z-asn1-tag-codec-table.md
index e78b9d1cc..86d811bb1 100644
--- a/fjs/asn.1/todo/65z-asn1-tag-codec-table.md
+++ b/fjs/asn.1/todo/65z-asn1-tag-codec-table.md
@@ -82,7 +82,7 @@ declaration site per (tag, encode, decode) triple.
 
 ### Caveats
 
-- `SupportedRecord` is a discriminated union keyed by tag (`fjs/asn.1/module.f.mjs:272-278`),
+- `SupportedRecord` is a discriminated union keyed by tag (`fjs/asn.1/types.ts:45-51`),
   so the codec values are heterogeneously typed. The table approach loses the
   per-branch payload typing that the switch currently gives `recordToRaw`. A
   small per-tag helper that types `encode` against the union branch may be
diff --git a/fjs/asn.1/types.ts b/fjs/asn.1/types.ts
new file mode 100644
index 000000000..98bed3594
--- /dev/null
+++ b/fjs/asn.1/types.ts
@@ -0,0 +1,72 @@
+/**
+ * Types for ASN.1 BER/DER encoding and decoding over bit vectors.
+ *
+ * @module
+ */
+
+import type { Vec } from '../types/bit_vec/types.ts'
+import type {
+    boolean as booleanTag,
+    constructedSequence,
+    constructedSet,
+    integer,
+    objectIdentifier,
+    octetString,
+} from './module.f.mjs'
+
+/**
+ * ASN.1 tag number.
+ */
+export type _Tag = bigint
+
+/**
+ * Raw ASN.1 TLV tuple.
+ */
+export type Raw = readonly [_Tag, Vec]
+
+/**
+ * ASN.1 OBJECT IDENTIFIER components.
+ */
+export type ObjectIdentifier = readonly bigint[]
+
+/**
+ * ASN.1 ordered collection of records.
+ */
+export type Sequence = readonly Record[]
+
+/**
+ * ASN.1 SET represented as a sequence of records.
+ */
+export type Set = Sequence
+
+/**
+ * Supported ASN.1 record variants.
+ */
+export type SupportedRecord =
+    | readonly [typeof booleanTag, boolean]
+    | readonly [typeof integer, bigint]
+    | readonly [typeof octetString, Vec]
+    | readonly [typeof objectIdentifier, ObjectIdentifier]
+    | readonly [typeof constructedSequence, Sequence]
+    | readonly [typeof constructedSet, Set]
+
+// Alternative:
+//
+// export type SupportedRecord =
+//     | boolean
+//     | bigint                                                    // integer
+//     | { tag: typeof octetString, value: Vec }
+//     | { tag: typeof objectIdentifier, value: ObjectIdentifier }
+//     | readonly Record[]                                         // sequence
+//     | { tag: typeof constructedSet, value: readonly Record[] }
+//
+// export type UnsupportedRecord =
+//     | { tag: null, value: Vec }
+
+/**
+ * For unsupported tags, we just store the raw value including the tag and
+ * length, so that it can be re-encoded without loss of information.
+ */
+export type UnsupportedRecord = Vec
+
+export type Record = SupportedRecord | UnsupportedRecord
diff --git a/fjs/asserts/module.f.mjs b/fjs/asserts/module.f.mjs
index 2e2ec4f81..83f0599bf 100644
--- a/fjs/asserts/module.f.mjs
+++ b/fjs/asserts/module.f.mjs
@@ -33,15 +33,6 @@ export const assertEq = (...x) => {
     assert(a === b, x)
 }
 
-/**
- * Compile-time-only check: a type resolves only if it is exactly `true`.
- * Used to assert type-level properties without any runtime cost, e.g.
- * `type _ = Assert<Equal<A, B>>`.
- *
- * @template {true} T
- * @typedef {T} Assert
- */
-
 /**
  * Asserts that `a` is neither `null` nor `undefined` and returns it,
  * narrowed to `T`.
diff --git a/fjs/asserts/types.ts b/fjs/asserts/types.ts
new file mode 100644
index 000000000..6cfbcb354
--- /dev/null
+++ b/fjs/asserts/types.ts
@@ -0,0 +1,12 @@
+/**
+ * Type-level assertion helpers.
+ *
+ * @module
+ */
+
+/**
+ * Compile-time-only check: a type resolves only if it is exactly `true`.
+ * Used to assert type-level properties without any runtime cost, e.g.
+ * `type _ = Assert<Equal<A, B>>`.
+ */
+export type Assert<T extends true> = T
diff --git a/fjs/basen/base128/module.f.mjs b/fjs/basen/base128/module.f.mjs
index 6bfb85007..0d59fcb5b 100644
--- a/fjs/basen/base128/module.f.mjs
+++ b/fjs/basen/base128/module.f.mjs
@@ -5,7 +5,7 @@
  */
 
 import { vec8, msb, empty } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
 const { concat, popFront } = msb
 
diff --git a/fjs/basen/base128/proof.f.mjs b/fjs/basen/base128/proof.f.mjs
index 83bb830f1..0e1a7d3a6 100644
--- a/fjs/basen/base128/proof.f.mjs
+++ b/fjs/basen/base128/proof.f.mjs
@@ -1,5 +1,5 @@
 import { empty, vec, vec8 } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
 import { asBase } from '../../types/nominal/module.f.mjs'
 
diff --git a/fjs/basen/base64/module.f.mjs b/fjs/basen/base64/module.f.mjs
index 65341ed95..37d79fe4e 100644
--- a/fjs/basen/base64/module.f.mjs
+++ b/fjs/basen/base64/module.f.mjs
@@ -5,9 +5,9 @@
  */
 
 import { msb, length, vec, maxLength } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
-/** @import { Nullable } from '../../types/nullable/module.f.mjs' */
+/** @import { Nullable } from '../../types/nullable/types.ts' */
 
 import { baseN } from "../module.f.mjs"
 
diff --git a/fjs/basen/base64/proof.f.mjs b/fjs/basen/base64/proof.f.mjs
index 3f5ac37ef..c71534f12 100644
--- a/fjs/basen/base64/proof.f.mjs
+++ b/fjs/basen/base64/proof.f.mjs
@@ -1,7 +1,7 @@
 import { assertEq } from '../../asserts/module.f.mjs'
 
 import { empty, vec, repeat, vec8, maxLength } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
 import { encode, decode } from './module.f.mjs'
 
diff --git a/fjs/basen/cbase32/module.f.mjs b/fjs/basen/cbase32/module.f.mjs
index c934b1664..172593cd9 100644
--- a/fjs/basen/cbase32/module.f.mjs
+++ b/fjs/basen/cbase32/module.f.mjs
@@ -5,9 +5,9 @@
  */
 
 import { msb, lsb, length, vec, empty } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
-/** @import { Nullable } from '../../types/nullable/module.f.mjs' */
+/** @import { Nullable } from '../../types/nullable/types.ts' */
 
 import { baseN } from '../module.f.mjs'
 
diff --git a/fjs/basen/cbase32/proof.f.mjs b/fjs/basen/cbase32/proof.f.mjs
index ca43ef7b7..8aa1aeabb 100644
--- a/fjs/basen/cbase32/proof.f.mjs
+++ b/fjs/basen/cbase32/proof.f.mjs
@@ -1,5 +1,5 @@
 import { empty, vec } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 
 import { cBase32ToVec, cBase32ToVec5x, vec5xToCBase32, vecToCBase32 } from './module.f.mjs'
 
diff --git a/fjs/basen/module.f.mjs b/fjs/basen/module.f.mjs
index ac81bdbb7..166ea3e48 100644
--- a/fjs/basen/module.f.mjs
+++ b/fjs/basen/module.f.mjs
@@ -13,14 +13,14 @@
  */
 
 import { msb, lsb, vec, chunkList, unpack } from '../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../types/bit_vec/types.ts' */
 
 import { fold } from '../types/list/module.f.mjs'
-/** @import { List } from '../types/list/module.f.mjs' */
+/** @import { List } from '../types/list/types.ts' */
 
 import { compose } from '../types/function/module.f.mjs'
 
-/** @import { Nullable } from '../types/nullable/module.f.mjs' */
+/** @import { BaseN } from './types.ts' */
 
 const { unpackSplit } = msb
 
@@ -30,15 +30,6 @@ const { tryListToVec: reversedListToVec } = lsb
 // `baseN(...)` codec (base64, cbase32, ...).
 const chunkListMsb = chunkList(msb)
 
-/**
- * The encode/decode pair returned by {@link baseN}.
- *
- * @typedef {{
- *  readonly vecToString: (v: Vec) => string
- *  readonly stringToVec: (s: string) => Nullable<Vec>
- * }} BaseN
- */
-
 /**
  * Builds a {@link BaseN} codec for a fixed chunk width and alphabet.
  *
diff --git a/fjs/basen/types.ts b/fjs/basen/types.ts
new file mode 100644
index 000000000..a7dc081f4
--- /dev/null
+++ b/fjs/basen/types.ts
@@ -0,0 +1,16 @@
+/**
+ * Types for the shared bit-codec factory.
+ *
+ * @module
+ */
+
+import type { Vec } from '../types/bit_vec/types.ts'
+import type { Nullable } from '../types/nullable/types.ts'
+
+/**
+ * The encode/decode pair returned by `baseN` in `./module.f.mjs`.
+ */
+export type BaseN = {
+    readonly vecToString: (v: Vec) => string
+    readonly stringToVec: (s: string) => Nullable<Vec>
+}
diff --git a/fjs/bnf/descent/module.f.ts b/fjs/bnf/descent/module.f.ts
index a55d7be69..85d38a2e1 100644
--- a/fjs/bnf/descent/module.f.ts
+++ b/fjs/bnf/descent/module.f.ts
@@ -13,7 +13,7 @@
  *
  * @module
  */
-import { type CodePoint } from '../../text/utf16/module.f.mjs'
+import type { CodePoint } from '../../text/utf16/types.ts'
 import { rangeDecode, type TerminalRange } from '../module.f.ts'
 import { contains as rangeContains } from '../../types/range/module.f.mjs'
 import { definedEntries } from '../../types/object/module.f.ts'
diff --git a/fjs/bnf/descent/proof.f.ts b/fjs/bnf/descent/proof.f.ts
index 2022a8643..de3c3a5e5 100644
--- a/fjs/bnf/descent/proof.f.ts
+++ b/fjs/bnf/descent/proof.f.ts
@@ -1,4 +1,5 @@
-import { type CodePoint, stringToCodePointList } from '../../text/utf16/module.f.mjs'
+import type { CodePoint } from '../../text/utf16/types.ts'
+import { stringToCodePointList } from '../../text/utf16/module.f.mjs'
 import { map, toArray } from '../../types/list/module.f.mjs'
 import { commaJoin0Plus, option, range, repeat0Plus, set } from '../module.f.ts'
 import { deterministic } from '../testlib.f.ts'
diff --git a/fjs/bnf/ll1/module.f.ts b/fjs/bnf/ll1/module.f.ts
index eaf63007c..f2436d759 100644
--- a/fjs/bnf/ll1/module.f.ts
+++ b/fjs/bnf/ll1/module.f.ts
@@ -10,10 +10,11 @@
  *
  * @module
  */
-import { type CodePoint } from '../../text/utf16/module.f.mjs'
+import type { CodePoint } from '../../text/utf16/types.ts'
 import { strictEqual } from '../../types/function/operator/module.f.mjs'
 import { toArray } from '../../types/list/module.f.mjs'
-import { rangeMap, type RangeMapArray } from '../../types/range_map/module.f.mjs'
+import type { RangeMapArray } from '../../types/range_map/types.ts'
+import { rangeMap } from '../../types/range_map/module.f.mjs'
 import { contains, set, type StringSet } from '../../types/string_set/module.f.ts'
 import { rangeDecode } from '../module.f.ts'
 import { definedEntries, type StringMap } from '../../types/object/module.f.ts'
diff --git a/fjs/bnf/module.f.ts b/fjs/bnf/module.f.ts
index e73b61c0e..a80d2489a 100644
--- a/fjs/bnf/module.f.ts
+++ b/fjs/bnf/module.f.ts
@@ -6,9 +6,12 @@
  *
  * @module
  */
+
+import type { Tuple } from '../types/array/types.ts'
+
 import { codePointListToString, stringToCodePointList } from '../text/utf16/module.f.mjs'
 import { definedValues, type StringMap } from '../types/object/module.f.ts'
-import { isTuple, type Tuple } from '../types/array/module.f.mjs'
+import { isTuple } from '../types/array/module.f.mjs'
 import { map, toArray, repeat as listRepeat } from '../types/list/module.f.mjs'
 import { contains } from '../types/range/module.f.mjs'
 import { assert } from '../asserts/module.f.mjs'
diff --git a/fjs/bnf/token_symbol/module.f.ts b/fjs/bnf/token_symbol/module.f.ts
index 4a04edd7a..3a54c6bac 100644
--- a/fjs/bnf/token_symbol/module.f.ts
+++ b/fjs/bnf/token_symbol/module.f.ts
@@ -9,7 +9,8 @@
  * @module
  */
 import { assert } from '../../asserts/module.f.mjs'
-import { fromUndefined, type Nullable } from '../../types/nullable/module.f.mjs'
+import type { Nullable } from '../../types/nullable/types.ts'
+import { fromUndefined } from '../../types/nullable/module.f.mjs'
 import { eof, rangeDecode, unicodeRange } from '../module.f.ts'
 
 const [, unicodeLast] = rangeDecode(unicodeRange)
diff --git a/fjs/cas/evo/module.f.ts b/fjs/cas/evo/module.f.ts
index 4d7b8e7d9..e80d5b83f 100644
--- a/fjs/cas/evo/module.f.ts
+++ b/fjs/cas/evo/module.f.ts
@@ -50,11 +50,12 @@ import { cBase32ToVec, vecToCBase32 } from '../../basen/cbase32/module.f.mjs'
 import { fromVec } from '../../text/utf8/module.f.mjs'
 import { tryUtf8 } from '../../text/module.f.mjs'
 import { decodeText, encodeText, dialect, checkReferences, isHash, type LockMap, type Revision } from '../../media/revision/module.f.ts'
-import { ok, error, type Ok, type Result } from '../../types/result/module.f.mjs'
+import type { Ok, Result } from '../../types/result/types.ts'
+import { ok, error } from '../../types/result/module.f.mjs'
 import { nonEmpty, empty as elEmpty } from '../../effects/list/module.f.ts'
 import { at, definedEntries, type StringMap } from '../../types/object/module.f.ts'
 import { unwrap } from '../../types/nullable/module.f.mjs'
-import type { Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
 import { isNotFound, type IoResult } from '../../effects/node/module.f.ts'
 
 /** A cBase32 content hash, as accepted/returned by `Cas<O>`. */
diff --git a/fjs/cas/evo/proof.f.ts b/fjs/cas/evo/proof.f.ts
index 40b2f073b..d06810337 100644
--- a/fjs/cas/evo/proof.f.ts
+++ b/fjs/cas/evo/proof.f.ts
@@ -3,10 +3,12 @@ import { pure } from '../../effects/module.f.ts'
 import { fileCas, type Cas } from '../module.f.ts'
 import { sha256 } from '../../crypto/sha2/module.f.mjs'
 import { emptyState, virtual } from '../../effects/node/virtual/module.f.ts'
-import { vec, vec8, type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { vec, vec8 } from '../../types/bit_vec/module.f.mjs'
 import { cBase32ToVec, vecToCBase32 } from '../../basen/cbase32/module.f.mjs'
 import { unwrap } from '../../types/nullable/module.f.mjs'
-import { ok, error, type Ok } from '../../types/result/module.f.mjs'
+import type { Ok } from '../../types/result/types.ts'
+import { ok, error } from '../../types/result/module.f.mjs'
 import { nonEmpty, empty as elEmpty } from '../../effects/list/module.f.ts'
 import type { IoResult } from '../../effects/node/module.f.ts'
 import { tryUtf8 } from '../../text/module.f.mjs'
diff --git a/fjs/cas/module.f.ts b/fjs/cas/module.f.ts
index 72ba62ecb..11433ea51 100644
--- a/fjs/cas/module.f.ts
+++ b/fjs/cas/module.f.ts
@@ -3,9 +3,11 @@
  *
  * @module
  */
-import { sha256, type Sha2, type State as Sha2State } from '../crypto/sha2/module.f.mjs'
+import type { Sha2, State as Sha2State } from '../crypto/sha2/types.ts'
+import { sha256 } from '../crypto/sha2/module.f.mjs'
 import { join, normalize, parse } from '../path/module.f.ts'
-import { empty, length, maxLength, maxLengthBytes, msb, vec, type Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
+import { empty, length, maxLength, maxLengthBytes, msb, vec } from '../types/bit_vec/module.f.mjs'
 import { cBase32ToVec, vecToCBase32 } from '../basen/cbase32/module.f.mjs'
 import { foldStep, forEachStep, history, historyStep, okStep, pure, step, type Effect, type Operation } from '../effects/module.f.ts'
 import { eff } from '../effects/eff/module.f.ts'
@@ -37,7 +39,7 @@ import {
 } from '../effects/node/module.f.ts'
 import { toOption } from '../types/nullable/module.f.mjs'
 import { error, ok, unwrap } from '../types/result/module.f.mjs'
-import { splitAt } from '../types/string/module.f.ts'
+import { splitAt } from '../types/string/module.f.mjs'
 import { nonEmpty, empty as elEmpty, type List } from '../effects/list/module.f.ts'
 
 const split2 = splitAt(2)
diff --git a/fjs/cas/proof.f.ts b/fjs/cas/proof.f.ts
index 3945149e6..026282639 100644
--- a/fjs/cas/proof.f.ts
+++ b/fjs/cas/proof.f.ts
@@ -1,10 +1,12 @@
-import { length, maxLength, msb, vec, vec8, type Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
+import { length, maxLength, msb, vec, vec8 } from '../types/bit_vec/module.f.mjs'
 import { cBase32ToVec, vecToCBase32 } from '../basen/cbase32/module.f.mjs'
 import { computeSync, sha256 } from '../crypto/sha2/module.f.mjs'
 import { fileCas, casAddFile, collectRead, type FileCasOperation, casUpload } from './module.f.ts'
 import { match, pure, runPure, step, type Effect } from '../effects/module.f.ts'
 import { mkdir, writeFile, rm, readFile, type ReadFile, type WriteFile, type Rm, type Mkdir, type IoResult, access } from '../effects/node/module.f.ts'
-import { error, ok, type Ok } from '../types/result/module.f.mjs'
+import type { Ok } from '../types/result/types.ts'
+import { error, ok } from '../types/result/module.f.mjs'
 import { emptyState, virtual } from '../effects/node/virtual/module.f.ts'
 import { join } from '../path/module.f.ts'
 import { nonEmpty, empty, type List } from '../effects/list/module.f.ts'
diff --git a/fjs/common/monoid/module.f.mjs b/fjs/common/monoid/module.f.mjs
index 7cabb8d5d..f22d4637f 100644
--- a/fjs/common/monoid/module.f.mjs
+++ b/fjs/common/monoid/module.f.mjs
@@ -6,57 +6,11 @@
  *
  * @module
  */
-/** @import { Fold, Reduce } from '../../types/function/operator/module.f.mjs' */
+/** @import { Fold } from '../../types/function/operator/types.ts' */
 import { reduce } from '../../types/list/module.f.mjs'
-/** @import { List } from  '../../types/list/module.f.mjs' */
+/** @import { List } from  '../../types/list/types.ts' */
 import { flip } from '../../types/function/module.f.mjs'
-
-/**
- * Represents a monoid, an algebraic structure with a binary operation
- * and an identity (neutral) element.
- *
- * A monoid satisfies the following properties:
- * 1. **Associativity**: The operation must be associative.
- *    For all `a`, `b`, and `c` in the set, `(a operation b) operation c = a operation (b operation c)`.
- *    {@link https://en.wikipedia.org/wiki/Associative_property Learn more about associativity}.
- * 2. **Identity Element**: There exists an element (called the identity) such that,
- *    when combined with any other element under the operation, it leaves the other element unchanged.
- *    {@link https://en.wikipedia.org/wiki/Identity_element Learn more about identity elements}.
- *
- * Learn more about monoids: {@link https://en.wikipedia.org/wiki/Monoid}.
- *
- * @template T The type of the elements in the monoid.
- * @typedef {{
- *  readonly identity: T
- *  readonly operation: Reduce<T>
- * }} Monoid
- *
- * @property identity
- *
- * The identity (neutral) element for the monoid.
- * When combined with any value under the `operation`, it leaves the other value unchanged.
- *
- * Examples:
- * - `0` for addition
- * - `1` for multiplication
- * - `""` for string concatenation
- * - `[]` for array concatenation
- *
- * Learn more: {@link https://en.wikipedia.org/wiki/Identity_element}
- *
- * @property operation
- *
- * The associative binary operation of the monoid.
- * Takes one value of type `T` and returns a function that takes another value of type `T`,
- * producing a result of type `T`.
- *
- * Examples:
- * - `(a, b) => a + b` for addition
- * - `(a, b) => a * b` for multiplication
- * - `(a, b) => a.concat(b)` for arrays or strings
- *
- * Learn more: {@link https://en.wikipedia.org/wiki/Binary_operation}
- */
+/** @import { Monoid } from './types.ts' */
 
 /**
  * Repeats a monoid operation `n` times on the given element `a`.
diff --git a/fjs/common/monoid/proof.f.ts b/fjs/common/monoid/proof.f.ts
index 4ef43d7a2..6685432ae 100644
--- a/fjs/common/monoid/proof.f.ts
+++ b/fjs/common/monoid/proof.f.ts
@@ -1,4 +1,5 @@
-import { repeat, fold, type Monoid } from "./module.f.mjs";
+import type { Monoid } from "./types.ts"
+import { repeat, fold } from "./module.f.mjs";
 import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
diff --git a/fjs/common/monoid/types.ts b/fjs/common/monoid/types.ts
new file mode 100644
index 000000000..169ed5717
--- /dev/null
+++ b/fjs/common/monoid/types.ts
@@ -0,0 +1,52 @@
+/**
+ * The `Monoid<T>` algebraic structure.
+ *
+ * @module
+ */
+
+import type { Reduce } from '../../types/function/operator/types.ts'
+
+/**
+ * Represents a monoid, an algebraic structure with a binary operation
+ * and an identity (neutral) element.
+ *
+ * A monoid satisfies the following properties:
+ * 1. **Associativity**: The operation must be associative.
+ *    For all `a`, `b`, and `c` in the set, `(a operation b) operation c = a operation (b operation c)`.
+ *    {@link https://en.wikipedia.org/wiki/Associative_property Learn more about associativity}.
+ * 2. **Identity Element**: There exists an element (called the identity) such that,
+ *    when combined with any other element under the operation, it leaves the other element unchanged.
+ *    {@link https://en.wikipedia.org/wiki/Identity_element Learn more about identity elements}.
+ *
+ * Learn more about monoids: {@link https://en.wikipedia.org/wiki/Monoid}.
+ *
+ * @property identity
+ *
+ * The identity (neutral) element for the monoid.
+ * When combined with any value under the `operation`, it leaves the other value unchanged.
+ *
+ * Examples:
+ * - `0` for addition
+ * - `1` for multiplication
+ * - `""` for string concatenation
+ * - `[]` for array concatenation
+ *
+ * Learn more: {@link https://en.wikipedia.org/wiki/Identity_element}
+ *
+ * @property operation
+ *
+ * The associative binary operation of the monoid.
+ * Takes one value of type `T` and returns a function that takes another value of type `T`,
+ * producing a result of type `T`.
+ *
+ * Examples:
+ * - `(a, b) => a + b` for addition
+ * - `(a, b) => a * b` for multiplication
+ * - `(a, b) => a.concat(b)` for arrays or strings
+ *
+ * Learn more: {@link https://en.wikipedia.org/wiki/Binary_operation}
+ */
+export type Monoid<T> = {
+    readonly identity: T
+    readonly operation: Reduce<T>
+}
diff --git a/fjs/crypto/hmac/module.f.ts b/fjs/crypto/hmac/module.f.ts
index 5c88daed7..dc2e51cf3 100644
--- a/fjs/crypto/hmac/module.f.ts
+++ b/fjs/crypto/hmac/module.f.ts
@@ -18,8 +18,10 @@
  * ```
  */
 
-import { length, type Vec, msb, vec, vec8, type Reduce, repeat } from '../../types/bit_vec/module.f.mjs'
-import { computeSync, type Sha2 } from '../sha2/module.f.mjs'
+import type { Vec, Reduce } from '../../types/bit_vec/types.ts'
+import { length, msb, vec, vec8, repeat } from '../../types/bit_vec/module.f.mjs'
+import type { Sha2 } from '../sha2/types.ts'
+import { computeSync } from '../sha2/module.f.mjs'
 
 const { concat, xor } = msb
 
diff --git a/fjs/crypto/pow/module.f.mjs b/fjs/crypto/pow/module.f.mjs
index b6e2acd5e..690c7709d 100644
--- a/fjs/crypto/pow/module.f.mjs
+++ b/fjs/crypto/pow/module.f.mjs
@@ -7,10 +7,11 @@
 
 import { mask } from '../../types/bigint/module.f.mjs'
 import { uint } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
-/** @import { Nullable } from '../../types/nullable/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
+/** @import { Nullable } from '../../types/nullable/types.ts' */
 import { computeSync, sha256 } from '../sha2/module.f.mjs'
-/** @import { Sha2 } from '../sha2/module.f.mjs' */
+/** @import { Sha2 } from '../sha2/types.ts' */
+/** @import { Pow } from './types.ts' */
 
 const nBitsMantissa = mask(24n)
 const mantissaSign = 0x00800000n
@@ -66,21 +67,6 @@ export const targetFromNBits = nBits => {
     return target
 }
 
-/**
- * @typedef {{
- *  readonly hashInt: (data: Vec) => bigint
- *  readonly meets: (nBits: bigint) => (data: Vec) => boolean
- * }} Pow
- *
- * @property hashInt
- *
- * Hash `data` with the configured `Sha2`; digest as big-endian uint256.
- *
- * @property meets
- *
- * Whether `hashInt(data) <= targetFromNBits(nBits)`; `false` when **nBits** is invalid.
- */
-
 /**
  * Builds PoW helpers for a hash function (typical consumer: {@link sha256}).
  *
diff --git a/fjs/crypto/pow/types.ts b/fjs/crypto/pow/types.ts
new file mode 100644
index 000000000..7de8b37f0
--- /dev/null
+++ b/fjs/crypto/pow/types.ts
@@ -0,0 +1,21 @@
+/**
+ * Types for Bitcoin-style proof-of-work verification.
+ *
+ * @module
+ */
+
+import type { Vec } from '../../types/bit_vec/types.ts'
+
+/**
+ * @property hashInt
+ *
+ * Hash `data` with the configured `Sha2`; digest as big-endian uint256.
+ *
+ * @property meets
+ *
+ * Whether `hashInt(data) <= targetFromNBits(nBits)`; `false` when **nBits** is invalid.
+ */
+export type Pow = {
+    readonly hashInt: (data: Vec) => bigint
+    readonly meets: (nBits: bigint) => (data: Vec) => boolean
+}
diff --git a/fjs/crypto/secp/module.f.mjs b/fjs/crypto/secp/module.f.mjs
index 9d8cb63ee..c28fee3a2 100644
--- a/fjs/crypto/secp/module.f.mjs
+++ b/fjs/crypto/secp/module.f.mjs
@@ -6,45 +6,10 @@
  * @module
  */
 
-/** @import { Equal, Fold, Reduce } from '../../types/function/operator/module.f.mjs' */
+/** @import { Equal, Fold, Reduce } from '../../types/function/operator/types.ts' */
 import { prime_field, sqrt } from '../../types/prime_field/module.f.mjs'
-/** @import { PrimeField } from '../../types/prime_field/module.f.mjs' */
 import { repeat } from '../../common/monoid/module.f.mjs'
-
-/** A 2D point represented as a pair of `bigint` values `[x, y]`. @typedef {readonly [bigint, bigint]} Point2D */
-
-/**
- * A 2D point on an elliptic curve, represented as a pair of `bigint` values.
- * `null` represents the point at infinity (`O`).
- *
- * @typedef {Point2D | null} Point
- */
-
-/**
- * Initialization parameters for an elliptic curve.
- *
- * @typedef {{
- *  readonly p: bigint
- *  readonly a: readonly [bigint, bigint]
- *  readonly g: readonly [bigint, bigint]
- *  readonly n: bigint
- * }} Init
- */
-
-/**
- * Represents an elliptic curve and its associated operations.
- *
- * @typedef {{
- *  readonly pf: PrimeField
- *  readonly nf: PrimeField
- *  readonly g: Point
- *  readonly y2: (x: bigint) => bigint
- *  readonly y: (x: bigint) => bigint | null
- *  readonly neg: (a: Point) => Point
- *  readonly add: Reduce<Point>
- *  readonly mul: Fold<bigint, Point>
- * }} Curve
- */
+/** @import { Curve, Init, Point, Point2D } from './types.ts' */
 
 /**
  * Constructs an elliptic curve with the given initialization parameters.
diff --git a/fjs/crypto/secp/proof.f.mjs b/fjs/crypto/secp/proof.f.mjs
index 67481e8dc..22ca728c1 100644
--- a/fjs/crypto/secp/proof.f.mjs
+++ b/fjs/crypto/secp/proof.f.mjs
@@ -1,7 +1,7 @@
 import { assert, assertEq, assertNotNullish } from '../../asserts/module.f.mjs'
 import { prime_field } from '../../types/prime_field/module.f.mjs'
 import { curve, secp256k1, secp192r1, secp256r1, eq, secp384r1, secp521r1 } from './module.f.mjs'
-/** @import { Point, Curve, Init } from './module.f.mjs' */
+/** @import { Point, Curve, Init } from './types.ts' */
 
 /** @type {(param: Curve) => () => void} */
 const poker = param => () => {
diff --git a/fjs/crypto/secp/todo/init-named-coefficients.md b/fjs/crypto/secp/todo/init-named-coefficients.md
index 29111cbcd..b0ce6cbef 100644
--- a/fjs/crypto/secp/todo/init-named-coefficients.md
+++ b/fjs/crypto/secp/todo/init-named-coefficients.md
@@ -5,29 +5,27 @@
 
 ### Problem
 
-`Init` (`fjs/crypto/secp/module.f.mjs:26-31`) stores the curve-equation
+`Init` (`fjs/crypto/secp/types.ts:22-27`) stores the curve-equation
 coefficients as a pair under the name `a`:
 
-```js
-/**
- * @typedef {{
- *  readonly p: bigint
- *  readonly a: readonly [bigint, bigint]
- *  readonly g: readonly [bigint, bigint]
- *  readonly n: bigint
- * }} Init
- */
+```ts
+export type Init = {
+    readonly p: bigint
+    readonly a: readonly [bigint, bigint]
+    readonly g: readonly [bigint, bigint]
+    readonly n: bigint
+}
 ```
 
 The pair's convention is index = power of `x`: `curve` unpacks
-`({ a: [a0, a1] })` (`:72`) and builds the equation (`:86`) as
+`({ a: [a0, a1] })` (`:37`) and builds the equation (`:51`) as
 `x³ + a1·x¹ + a0·x⁰`. The indexed scheme itself is good — the index states
 the coefficient's defining property (its power) — but the letter `a` is a
 bad fit: in the standard Weierstrass notation `y² = x³ + a·x + b`, `a` is
 specifically the *linear* coefficient, so a field named `a` whose slot `a0`
 holds Weierstrass `b` invites misreading. That's why every non-trivial curve
-literal needs prose comments to decode it (`secp256r1` `:198-199`,
-`secp384r1` `:214-215`, `secp521r1` `:230-231`):
+literal needs prose comments to decode it (`secp256r1` `:163-164`,
+`secp384r1` `:179-180`, `secp521r1` `:195-196`):
 
 ```ts
 a: [
@@ -82,9 +80,9 @@ c: [
 
 and add the same comments to `secp192r1` and `secp256k1`, which have none
 today. Update all **five** active curve literals in
-`fjs/crypto/secp/module.f.mjs` (`secp192r1` `:146`, `secp256k1` `:181`,
-`secp256r1` `:195`, `secp384r1` `:211`, `secp521r1` `:227`), the
-commented-out `secp224r1` block (`:164-175`, so it doesn't rot on the old
+`fjs/crypto/secp/module.f.mjs` (`secp192r1` `:111`, `secp256k1` `:146`,
+`secp256r1` `:160`, `secp384r1` `:176`, `secp521r1` `:192`), the
+commented-out `secp224r1` block (`:129-140`, so it doesn't rot on the old
 shape), and the `example` init in `fjs/crypto/secp/proof.f.mjs:63-68`. This is
 a breaking
 change to an exported type — update every importer in the same PR per
@@ -103,9 +101,9 @@ AGENTS.md; `curve`'s behavior and all curve constants are unchanged.
 
 ### Related
 
-- `fjs/crypto/secp/module.f.mjs:14` (`Point2D`), `:26-31` (`Init`), `:72-86`
-  (`curve`/`y2`), `:146-238` (curve literals, including the commented-out
-  `secp224r1`).
+- `fjs/crypto/secp/types.ts:11` (`Point2D`), `:22-27` (`Init`).
+- `fjs/crypto/secp/module.f.mjs:37-51` (`curve`/`y2`), `:111-203` (curve
+  literals, including the commented-out `secp224r1`).
 - `fjs/crypto/todo/666-crypto-sign-fromcurve.md` — reshapes the
   `sign`→`curve` boundary; independent of this record cleanup, but land
   whichever goes first and rebase the other.
diff --git a/fjs/crypto/secp/types.ts b/fjs/crypto/secp/types.ts
new file mode 100644
index 000000000..33e5aaff4
--- /dev/null
+++ b/fjs/crypto/secp/types.ts
@@ -0,0 +1,41 @@
+/**
+ * Types for short Weierstrass elliptic-curve arithmetic over a prime field.
+ *
+ * @module
+ */
+
+import type { Fold, Reduce } from '../../types/function/operator/types.ts'
+import type { PrimeField } from '../../types/prime_field/types.ts'
+
+/** A 2D point represented as a pair of `bigint` values `[x, y]`. */
+export type Point2D = readonly [bigint, bigint]
+
+/**
+ * A 2D point on an elliptic curve, represented as a pair of `bigint` values.
+ * `null` represents the point at infinity (`O`).
+ */
+export type Point = Point2D | null
+
+/**
+ * Initialization parameters for an elliptic curve.
+ */
+export type Init = {
+    readonly p: bigint
+    readonly a: readonly [bigint, bigint]
+    readonly g: readonly [bigint, bigint]
+    readonly n: bigint
+}
+
+/**
+ * Represents an elliptic curve and its associated operations.
+ */
+export type Curve = {
+    readonly pf: PrimeField
+    readonly nf: PrimeField
+    readonly g: Point
+    readonly y2: (x: bigint) => bigint
+    readonly y: (x: bigint) => bigint | null
+    readonly neg: (a: Point) => Point
+    readonly add: Reduce<Point>
+    readonly mul: Fold<bigint, Point>
+}
diff --git a/fjs/crypto/sha2/module.f.mjs b/fjs/crypto/sha2/module.f.mjs
index 9736a5e2c..f8145ecb0 100644
--- a/fjs/crypto/sha2/module.f.mjs
+++ b/fjs/crypto/sha2/module.f.mjs
@@ -4,9 +4,9 @@
  * @module
  */
 
-/** @import { Tuple } from '../../types/array/module.f.mjs' */
+/** @import { Tuple } from '../../types/array/types.ts' */
 import { mask } from '../../types/bigint/module.f.mjs'
-/** @import { Reduce } from '../../types/bigint/module.f.mjs' */
+/** @import { Reduce } from '../../types/bigint/types.ts' */
 import {
     vec,
     length,
@@ -15,10 +15,11 @@ import {
     chunkList,
     uint,
 } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
-/** @import { Fold } from '../../types/function/operator/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
+/** @import { Fold } from '../../types/function/operator/types.ts' */
 import { fold } from '../../types/list/module.f.mjs'
-/** @import { List } from '../../types/list/module.f.mjs' */
+/** @import { List } from '../../types/list/types.ts' */
+/** @import { Base, Sha2, State, V16, V8 } from './types.ts' */
 
 const { concat, front } = msb
 
@@ -30,41 +31,6 @@ const chunkListMsb = chunkList(msb)
 
 /** @typedef {Tuple<4, bigint>} _V4 */
 
-/**
- * 8-word SHA-2 state vector.
- *
- * @typedef {Tuple<8, bigint>} V8
- */
-
-/**
- * 16-word SHA-2 message schedule chunk.
- *
- * @typedef {Tuple<16, bigint>} V16
- */
-
-/**
- * State of the SHA-2 algorithm: `hash` is the current hash value, `len` the
- * length of the data processed so far, and `remainder` the data that has not
- * yet been processed.
- *
- * @typedef {{
- *   readonly hash: V8,
- *   readonly len: bigint,
- *   readonly remainder: Vec,
- * }} State
- */
-
-/**
- * @typedef {{
- *   readonly bitLength: bigint,
- *   readonly chunkLength: bigint,
- *   readonly compress: (i: V8) => (u: bigint) => V8,
- *   readonly fromV8: (a: V8) => bigint,
- *   readonly append: Fold<Vec, State>,
- *   readonly end: (hashLength: bigint) => (state: State) => Vec,
- * }} Base
- */
-
 /**
  * @typedef {{
  *   readonly logBitLen: bigint,
@@ -284,14 +250,6 @@ const base = ({ logBitLen, k, bs0, bs1, ss0, ss1 }) => {
  * state = sha224.append(state)(s)
  * const h = sha224.end(state) // 0x1_619cba8e8e05826e9b8c519c0a5c68f4fb653e8a3d8aa04bb2c8cd4cn
  * ```
- *
- * @typedef {{
- *   readonly hashLength: bigint,
- *   readonly blockLength: bigint,
- *   readonly init: State,
- *   readonly append: Fold<Vec, State>,
- *   readonly end: (state: State) => Vec,
- * }} Sha2
  */
 
 /** @type {(base: Base, hash: V8, hashLength: bigint) => Sha2} */
diff --git a/fjs/crypto/sha2/proof.f.ts b/fjs/crypto/sha2/proof.f.ts
index 35f9b682d..d6d929a0f 100644
--- a/fjs/crypto/sha2/proof.f.ts
+++ b/fjs/crypto/sha2/proof.f.ts
@@ -3,18 +3,8 @@ import { repeat, uint, vec } from '../../types/bit_vec/module.f.mjs'
 import { flip } from '../../types/function/module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
 import { map } from '../../types/list/module.f.mjs'
-import {
-    base32,
-    base64,
-    computeSync,
-    type Sha2,
-    sha224,
-    sha256,
-    sha384,
-    sha512,
-    sha512x224,
-    sha512x256,
-} from './module.f.mjs'
+import type { Sha2 } from './types.ts'
+import { base32, base64, computeSync, sha224, sha256, sha384, sha512, sha512x224, sha512x256 } from './module.f.mjs'
 
 const checkEmpty = ({ init, end, hashLength }: Sha2) => (x: bigint) => {
     const result = end(init)
diff --git a/fjs/crypto/sha2/types.ts b/fjs/crypto/sha2/types.ts
new file mode 100644
index 000000000..f4b94adf3
--- /dev/null
+++ b/fjs/crypto/sha2/types.ts
@@ -0,0 +1,63 @@
+/**
+ * Types for the SHA-2 family of hash functions.
+ *
+ * @module
+ */
+
+import type { Tuple } from '../../types/array/types.ts'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import type { Fold } from '../../types/function/operator/types.ts'
+
+/**
+ * 8-word SHA-2 state vector.
+ */
+export type V8 = Tuple<8, bigint>
+
+/**
+ * 16-word SHA-2 message schedule chunk.
+ */
+export type V16 = Tuple<16, bigint>
+
+/**
+ * State of the SHA-2 algorithm: `hash` is the current hash value, `len` the
+ * length of the data processed so far, and `remainder` the data that has not
+ * yet been processed.
+ */
+export type State = {
+    readonly hash: V8
+    readonly len: bigint
+    readonly remainder: Vec
+}
+
+export type Base = {
+    readonly bitLength: bigint
+    readonly chunkLength: bigint
+    readonly compress: (i: V8) => (u: bigint) => V8
+    readonly fromV8: (a: V8) => bigint
+    readonly append: Fold<Vec, State>
+    readonly end: (hashLength: bigint) => (state: State) => Vec
+}
+
+/**
+ * SHA2. See https://en.wikipedia.org/wiki/SHA-2
+ *
+ * `hashLength` is a hash length, `blockLength` an internal block length,
+ * `init` the initial state of the SHA-2 algorithm, `append` adds data to a
+ * state and returns the new state, and `end` finalizes the hash of a state.
+ *
+ * @example
+ *
+ * ```js
+ * const s = msbUtf8("The quick brown fox jumps over the lazy dog.")
+ * let state = sha224.init
+ * state = sha224.append(state)(s)
+ * const h = sha224.end(state) // 0x1_619cba8e8e05826e9b8c519c0a5c68f4fb653e8a3d8aa04bb2c8cd4cn
+ * ```
+ */
+export type Sha2 = {
+    readonly hashLength: bigint
+    readonly blockLength: bigint
+    readonly init: State
+    readonly append: Fold<Vec, State>
+    readonly end: (state: State) => Vec
+}
diff --git a/fjs/crypto/sign/module.f.ts b/fjs/crypto/sign/module.f.ts
index 45e7f00aa..4abb1e064 100644
--- a/fjs/crypto/sign/module.f.ts
+++ b/fjs/crypto/sign/module.f.ts
@@ -4,12 +4,14 @@
  * @module
  */
 import { assertNotNullish } from '../../asserts/module.f.mjs'
-import type { Tuple } from '../../types/array/module.f.mjs'
+import type { Tuple } from '../../types/array/types.ts'
 import { bitLength, divUp8, roundUp8 } from '../../types/bigint/module.f.mjs'
-import { empty, length, msb, repeat, unpack, vec, vec8, type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { empty, length, msb, repeat, unpack, vec, vec8 } from '../../types/bit_vec/module.f.mjs'
 import { hmac } from '../hmac/module.f.ts'
-import type { Curve } from '../secp/module.f.mjs'
-import { computeSync, type Sha2 } from '../sha2/module.f.mjs'
+import type { Curve } from '../secp/types.ts'
+import type { Sha2 } from '../sha2/types.ts'
+import { computeSync } from '../sha2/module.f.mjs'
 
 export type All = {
     readonly q: bigint
diff --git a/fjs/crypto/sign/proof.f.ts b/fjs/crypto/sign/proof.f.ts
index 676893938..ba26f5c1e 100644
--- a/fjs/crypto/sign/proof.f.ts
+++ b/fjs/crypto/sign/proof.f.ts
@@ -1,9 +1,12 @@
 import { utf8 } from "../../text/module.f.mjs"
-import type { Tuple } from "../../types/array/module.f.mjs"
-import { empty, msb, repeat, vec, vec8, type Vec } from "../../types/bit_vec/module.f.mjs"
+import type { Tuple } from "../../types/array/types.ts"
+import type { Vec } from "../../types/bit_vec/types.ts"
+import { empty, msb, repeat, vec, vec8 } from "../../types/bit_vec/module.f.mjs"
 import { hmac } from "../hmac/module.f.ts"
-import { secp192r1, secp256r1, secp384r1, secp521r1, type Curve } from "../secp/module.f.mjs"
-import { computeSync, sha224, sha256, sha384, sha512, type Sha2 } from "../sha2/module.f.mjs"
+import type { Curve } from "../secp/types.ts"
+import { secp192r1, secp256r1, secp384r1, secp521r1 } from "../secp/module.f.mjs"
+import type { Sha2 } from "../sha2/types.ts"
+import { computeSync, sha224, sha256, sha384, sha512 } from "../sha2/module.f.mjs"
 import { all, concat, computeK, fromCurve, sign } from "./module.f.ts"
 import { assertEq } from '../../asserts/module.f.mjs'
 
diff --git a/fjs/crypto/vdf/module.f.ts b/fjs/crypto/vdf/module.f.ts
index 38c6eefb2..82562ee64 100644
--- a/fjs/crypto/vdf/module.f.ts
+++ b/fjs/crypto/vdf/module.f.ts
@@ -14,9 +14,10 @@
  * if (y === null || !sloth.verify(steps)(x)(y)) { throw y }
  * ```
  */
-import { modSqrt, prime_field, type PrimeField } from '../../types/prime_field/module.f.mjs'
-import type { Nullable } from '../../types/nullable/module.f.mjs'
-import type { Unary } from '../../types/bigint/module.f.mjs'
+import type { PrimeField } from '../../types/prime_field/types.ts'
+import { modSqrt, prime_field } from '../../types/prime_field/module.f.mjs'
+import type { Nullable } from '../../types/nullable/types.ts'
+import type { Unary } from '../../types/bigint/types.ts'
 
 /** Sloth VDF modulus (3072-bit safe prime, same as reference implementations). */
 export const p =
diff --git a/fjs/crypto/vdf/todo/iterate-combinator.md b/fjs/crypto/vdf/todo/iterate-combinator.md
index ccc67cce9..4dbaa074d 100644
--- a/fjs/crypto/vdf/todo/iterate-combinator.md
+++ b/fjs/crypto/vdf/todo/iterate-combinator.md
@@ -51,7 +51,7 @@ export const iterate = (n: bigint) => <T>(f: (v: T) => T) => (value: T): T => {
 (keeping the internal `let`/`while` — a recursive form would overflow the
 stack for the large step counts VDFs use). `squareLoop`/`modSqrtLoop` call
 `iterate`; the local `repeatSeq` is deleted. Alternative home: a
-bigint-typed form next to `Unary` in `fjs/types/bigint/module.f.mjs`, but the
+bigint-typed form next to `Unary` in `fjs/types/bigint/types.ts`, but the
 combinator is not bigint-specific in `T` — only the counter is — so
 `fjs/types/function` is the natural owner.
 
diff --git a/fjs/dev/module.f.ts b/fjs/dev/module.f.ts
index a13d1f21e..80ea5265b 100644
--- a/fjs/dev/module.f.ts
+++ b/fjs/dev/module.f.ts
@@ -13,7 +13,7 @@ import {
     type Import,
     type Readdir
 } from '../effects/node/module.f.ts'
-import { cmp as strCmp } from '../types/string/module.f.ts'
+import { cmp as strCmp } from '../types/string/module.f.mjs'
 import type { StringMap } from '../types/object/module.f.ts'
 import { unwrap } from '../types/result/module.f.mjs'
 import { pure, step, type Effect } from '../effects/module.f.ts'
diff --git a/fjs/dev/package_json/module.f.ts b/fjs/dev/package_json/module.f.ts
index 4642d4ea2..955c364cc 100644
--- a/fjs/dev/package_json/module.f.ts
+++ b/fjs/dev/package_json/module.f.ts
@@ -9,7 +9,8 @@ import { option, record, string } from '../../types/rtti/module.f.ts'
 import { validate as rttiValidate } from '../../types/rtti/validate/module.f.ts'
 import type { ValidationError } from '../../types/rtti/validate/module.f.ts'
 import type { Ts } from '../../types/rtti/ts/module.f.ts'
-import { error, ok, type Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { error, ok } from '../../types/result/module.f.mjs'
 
 export const packageJsonSchema = {
     name: option(string),
diff --git a/fjs/djs/ast/module.f.ts b/fjs/djs/ast/module.f.ts
index 42b68206d..1c4b26e06 100644
--- a/fjs/djs/ast/module.f.ts
+++ b/fjs/djs/ast/module.f.ts
@@ -4,9 +4,11 @@
  * @module
  */
 import type { Primitive, Array, Unknown } from '../module.f.ts'
-import { type List, concat, fold, last, map, take, toArray } from '../../types/list/module.f.mjs'
-import type { Entry } from '../../types/ordered_map/module.f.ts'
+import type { List } from '../../types/list/types.ts'
+import { concat, fold, last, map, take, toArray } from '../../types/list/module.f.mjs'
+import type { Entry } from '../../types/ordered_map/types.ts'
 import { fromEntries } from '../../types/object/module.f.ts'
+
 const { entries } = Object
 
 /**
diff --git a/fjs/djs/parser/module.f.ts b/fjs/djs/parser/module.f.ts
index 08acf5d83..08d8a09a7 100644
--- a/fjs/djs/parser/module.f.ts
+++ b/fjs/djs/parser/module.f.ts
@@ -3,11 +3,14 @@
  *
  * @module
  */
-import { error, ok, type Result } from '../../types/result/module.f.mjs'
-import { fold, next, toArray, length, concat, type List } from '../../types/list/module.f.mjs'
-import type { Fold } from '../../types/function/operator/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { error, ok } from '../../types/result/module.f.mjs'
+import type { List } from '../../types/list/types.ts'
+import { fold, next, toArray, length, concat } from '../../types/list/module.f.mjs'
+import type { Fold } from '../../types/function/operator/types.ts'
 import type { DjsToken, DjsTokenWithMetadata } from '../tokenizer/module.f.ts'
-import { setReplace, at, type OrderedMap } from '../../types/ordered_map/module.f.ts'
+import { setReplace, at } from '../../types/ordered_map/module.f.mjs'
+import type { OrderedMap } from '../../types/ordered_map/types.ts'
 import { fromMap } from '../../types/object/module.f.ts'
 import type { AstArray, AstConst, AstModule, AstModuleRef } from '../ast/module.f.ts'
 import type { TokenMetadata } from '../../js/tokenizer/module.f.ts'
diff --git a/fjs/djs/proof.f.ts b/fjs/djs/proof.f.ts
index b34c6e1ea..63d6c7aa7 100644
--- a/fjs/djs/proof.f.ts
+++ b/fjs/djs/proof.f.ts
@@ -1,7 +1,7 @@
 import { compile } from './module.f.ts'
 import { virtual, emptyState } from '../effects/node/virtual/module.f.ts'
 import { utf8, utf8ToString } from '../text/module.f.mjs'
-import type { Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
 import { assert, assertEq } from '../asserts/module.f.mjs'
 
 const readOutput = (root: typeof emptyState.root, path: string): string => {
diff --git a/fjs/djs/serializer/module.f.ts b/fjs/djs/serializer/module.f.ts
index 22669e284..4ff61cbfd 100644
--- a/fjs/djs/serializer/module.f.ts
+++ b/fjs/djs/serializer/module.f.ts
@@ -4,11 +4,12 @@
  * @module
  */
 import type { Unknown, Object } from '../module.f.ts'
-import type { Fold } from '../../types/function/operator/module.f.mjs'
+import type { Fold } from '../../types/function/operator/types.ts'
 import type { Entry as ObjectEntry } from '../../types/object/module.f.ts'
 import { fold } from '../../types/list/module.f.mjs'
-import { concat } from '../../types/string/module.f.ts'
-import { type List, flat, flatMap, map, concat as listConcat } from '../../types/list/module.f.mjs'
+import { concat } from '../../types/string/module.f.mjs'
+import type { List } from '../../types/list/types.ts'
+import { flat, flatMap, map, concat as listConcat } from '../../types/list/module.f.mjs'
 const { entries } = Object
 import { compose, fn } from '../../types/function/module.f.mjs'
 import { serialize as bigintSerialize } from '../../types/bigint/module.f.mjs'
diff --git a/fjs/djs/tokenizer/module.f.ts b/fjs/djs/tokenizer/module.f.ts
index 7923fce92..35bd44bee 100644
--- a/fjs/djs/tokenizer/module.f.ts
+++ b/fjs/djs/tokenizer/module.f.ts
@@ -52,10 +52,12 @@ import {
     latinSmallLetterN, latinSmallLetterR, latinSmallLetterT, latinSmallLetterU,
     range as asciiRange,
 } from "../../text/ascii/module.f.mjs"
-import { type CodePoint, codePointListToString, stringToCodePointList } from "../../text/utf16/module.f.mjs"
-import type { StateScan } from "../../types/function/operator/module.f.mjs"
+import type { CodePoint } from "../../text/utf16/types.ts"
+import { codePointListToString, stringToCodePointList } from "../../text/utf16/module.f.mjs"
+import type { StateScan } from "../../types/function/operator/types.ts"
 import { contains } from "../../types/range/module.f.mjs"
-import { concat, empty, filter, flat, flatMap, fold, map, stateScan, toArray, type List } from "../../types/list/module.f.mjs"
+import type { List } from "../../types/list/types.ts"
+import { concat, empty, filter, flat, flatMap, fold, map, stateScan, toArray } from "../../types/list/module.f.mjs"
 import { stringifyAsTree } from "../serializer/module.f.ts"
 import { sort } from "../../types/object/module.f.ts"
 import type { Unknown } from "../module.f.ts"
diff --git a/fjs/djs/transpiler/module.f.ts b/fjs/djs/transpiler/module.f.ts
index 3fabb7228..d3fc00cd1 100644
--- a/fjs/djs/transpiler/module.f.ts
+++ b/fjs/djs/transpiler/module.f.ts
@@ -4,10 +4,13 @@
  * @module
  */
 import { type Unknown } from '../module.f.ts'
-import { type Result, error, ok } from '../../types/result/module.f.mjs'
-import { drop, map as listMap, type List, toArray, includes } from '../../types/list/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { error, ok } from '../../types/result/module.f.mjs'
+import type { List } from '../../types/list/types.ts'
+import { drop, map as listMap, toArray, includes } from '../../types/list/module.f.mjs'
 import { tokenize } from '../tokenizer/module.f.ts'
-import { setReplace, at, type OrderedMap } from '../../types/ordered_map/module.f.ts'
+import { setReplace, at } from '../../types/ordered_map/module.f.mjs'
+import type { OrderedMap } from '../../types/ordered_map/types.ts'
 import { stringToList } from '../../text/utf16/module.f.mjs'
 import { concat as pathConcat } from '../../path/module.f.ts'
 import { type ParseError, parseFromTokens } from '../parser/module.f.ts'
diff --git a/fjs/effects/memory/module.f.ts b/fjs/effects/memory/module.f.ts
index 592e34151..1973d76db 100644
--- a/fjs/effects/memory/module.f.ts
+++ b/fjs/effects/memory/module.f.ts
@@ -13,8 +13,9 @@
  * @module
  */
 
-import type { Phantom } from '../../types/phantom/module.f.ts'
-import { type Nominal, asBase as nominalAsBase, asNominal as nominalAsNominal } from '../../types/nominal/module.f.mjs'
+import type { Phantom } from '../../types/phantom/types.ts'
+import type { Nominal } from '../../types/nominal/types.ts'
+import { asBase as nominalAsBase, asNominal as nominalAsNominal } from '../../types/nominal/module.f.mjs'
 import { do_, type Effect } from '../module.f.ts'
 
 /** Nominal brand version for memory keys. */
diff --git a/fjs/effects/module.f.ts b/fjs/effects/module.f.ts
index 5c523f3c4..5ddece098 100644
--- a/fjs/effects/module.f.ts
+++ b/fjs/effects/module.f.ts
@@ -96,10 +96,11 @@
  */
 
 import { assert } from '../asserts/module.f.mjs'
-import { fold, type List } from '../types/list/module.f.mjs'
+import type { List } from '../types/list/types.ts'
+import { fold } from '../types/list/module.f.mjs'
 import { at } from '../types/object/module.f.ts'
-import type { Option } from '../types/option/module.f.mjs'
-import type { Result } from '../types/result/module.f.mjs'
+import type { Option } from '../types/option/types.ts'
+import type { Result } from '../types/result/types.ts'
 
 export type Operation =
     readonly[string, (..._: readonly never[]) => unknown]
diff --git a/fjs/effects/node/module.f.ts b/fjs/effects/node/module.f.ts
index bd9912794..cbf3e280a 100644
--- a/fjs/effects/node/module.f.ts
+++ b/fjs/effects/node/module.f.ts
@@ -11,11 +11,14 @@
 import { utf8, utf8ToString } from '../../text/module.f.mjs'
 import { toCodePointList } from '../../text/utf8/module.f.mjs'
 import { codePointListToString } from '../../text/utf16/module.f.mjs'
-import { reverse, type List as EffectList } from '../../types/list/module.f.mjs'
-import { length, type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { List as EffectList } from '../../types/list/types.ts'
+import { reverse } from '../../types/list/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { length } from '../../types/bit_vec/module.f.mjs'
 import type { MemOp } from '../memory/module.f.ts'
-import type { Nominal } from '../../types/nominal/module.f.mjs'
-import { ok, error as resultError, mapOk, type Result } from '../../types/result/module.f.mjs'
+import type { Nominal } from '../../types/nominal/types.ts'
+import type { Result } from '../../types/result/types.ts'
+import { ok, error as resultError, mapOk } from '../../types/result/module.f.mjs'
 import type { StringMap } from '../../types/object/module.f.ts'
 import { type Effect, type Func, type Operation, type ToAsyncOperationMap, do_, mapStep, okStep, pure, step } from '../module.f.ts'
 import type { List } from '../list/module.f.ts'
diff --git a/fjs/effects/node/module.ts b/fjs/effects/node/module.ts
index 7ae382ddc..7d7512688 100644
--- a/fjs/effects/node/module.ts
+++ b/fjs/effects/node/module.ts
@@ -39,7 +39,8 @@ import {
     usesInlineTestContext,
 } from './module.f.ts'
 import { asBase, asNominal } from '../../types/nominal/module.f.mjs'
-import { error, ok, type Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { error, ok } from '../../types/result/module.f.mjs'
 import { asyncTryCatch } from '../../types/result/module.ts'
 import { fromVec, listToVec, toVec } from '../../types/uint8array/module.f.mjs'
 import type { StringMap } from '../../types/object/module.f.ts'
diff --git a/fjs/effects/node/proof.f.ts b/fjs/effects/node/proof.f.ts
index 62ac1bcfe..bd1480de4 100644
--- a/fjs/effects/node/proof.f.ts
+++ b/fjs/effects/node/proof.f.ts
@@ -1,4 +1,5 @@
-import { empty, isVec, uint, vec, vec8, type Vec } from "../../types/bit_vec/module.f.mjs"
+import type { Vec } from "../../types/bit_vec/types.ts"
+import { empty, isVec, uint, vec, vec8 } from "../../types/bit_vec/module.f.mjs"
 import { utf8, utf8ToString } from "../../text/module.f.mjs"
 import { match, pure, step } from "../module.f.ts"
 import { both, fetch, mkdir, now, readdir, readFile, readUtf8File, rm, sandbox, writeFile, writeUtf8File, rename, readBytes, randomInt, writeFromStream, usesInlineTestContext, versionLessThan, type IoResult, type ReadFile } from "./module.f.ts"
diff --git a/fjs/effects/node/virtual/module.f.ts b/fjs/effects/node/virtual/module.f.ts
index 48ff0e058..1e1b921a5 100644
--- a/fjs/effects/node/virtual/module.f.ts
+++ b/fjs/effects/node/virtual/module.f.ts
@@ -6,7 +6,8 @@
 import { todo } from '../../../asserts/module.f.mjs'
 import { isProperPrefix, join, parse } from '../../../path/module.f.ts'
 import { utf8ToString } from '../../../text/module.f.mjs'
-import { empty, length, maxLengthBytes, msb, vec, type Vec } from '../../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../../types/bit_vec/types.ts'
+import { empty, length, maxLengthBytes, msb, vec } from '../../../types/bit_vec/module.f.mjs'
 import { error, ok } from '../../../types/result/module.f.mjs'
 import { run, type MemOperationMap, type RunInstance } from '../../mock/module.f.ts'
 import { asBase, asNominal, type Key } from '../../memory/module.f.ts'
diff --git a/fjs/effects/todo/fold-stream-combinator.md b/fjs/effects/todo/fold-stream-combinator.md
index 78b9bbebc..addb4f11f 100644
--- a/fjs/effects/todo/fold-stream-combinator.md
+++ b/fjs/effects/todo/fold-stream-combinator.md
@@ -66,7 +66,7 @@ so write the signature in terms of `Result` — call sites that hold
 `IoResult` values type-check unchanged:
 
 ```ts
-import type { Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
 
 export const foldStream =
     <O extends Operation, A>(step: (acc: A) => (chunk: Vec) => Effect<O, Result<A, unknown>>) =>
diff --git a/fjs/fsc/module.f.mjs b/fjs/fsc/module.f.mjs
index d8cf4731f..0964eda1d 100644
--- a/fjs/fsc/module.f.mjs
+++ b/fjs/fsc/module.f.mjs
@@ -5,13 +5,13 @@
  */
 import { strictEqual } from '../types/function/operator/module.f.mjs'
 import { merge as rangeMapMerge, fromRange, get } from '../types/range_map/module.f.mjs'
-/** @import { RangeMapArray, RangeMerge } from '../types/range_map/module.f.mjs' */
+/** @import { RangeMapArray, RangeMerge } from '../types/range_map/types.ts' */
 import { reduce as listReduce, toArray, map } from '../types/list/module.f.mjs'
-/** @import { List } from '../types/list/module.f.mjs' */
+/** @import { List } from '../types/list/types.ts' */
 import { range as asciiRange } from '../text/ascii/module.f.mjs'
 import { flip, fn } from '../types/function/module.f.mjs'
 import { one } from '../types/range/module.f.mjs'
-/** @import { Range } from '../types/range/module.f.mjs' */
+/** @import { Range } from '../types/range/types.ts' */
 import { assertEq } from '../asserts/module.f.mjs'
 
 const fromCharCode = String.fromCharCode
diff --git a/fjs/fsm/module.f.ts b/fjs/fsm/module.f.ts
index f9c5fc6a4..0541c795c 100644
--- a/fjs/fsm/module.f.ts
+++ b/fjs/fsm/module.f.ts
@@ -3,23 +3,19 @@
  *
  * @module
  */
-import { equal, isEmpty, fold, toArray, scan, foldScan, empty as emptyList, type List } from '../types/list/module.f.mjs'
+import type { List } from '../types/list/types.ts'
+import { equal, isEmpty, fold, toArray, scan, foldScan, empty as emptyList } from '../types/list/module.f.mjs'
 import type { StringMap } from '../types/object/module.f.ts'
 import { toRangeMap, union as byteSetUnion, one, empty, range, type ByteSet } from '../types/byte_set/module.f.ts'
 import { intersect, type SortedSet, union as sortedSetUnion } from '../types/sorted_set/module.f.ts'
-import {
-    merge,
-    get as rangeMapGet,
-    type RangeMap,
-    type Properties,
-    type RangeMapArray,
-    type Entry
-} from '../types/range_map/module.f.mjs'
-import { type Fold, type Scan, strictEqual } from '../types/function/operator/module.f.mjs'
+import type { RangeMap, Properties, RangeMapArray, Entry } from '../types/range_map/types.ts'
+import { merge, get as rangeMapGet } from '../types/range_map/module.f.mjs'
+import type { Fold, Scan } from '../types/function/operator/types.ts'
+import { strictEqual } from '../types/function/operator/module.f.mjs'
 import { stringify } from '../media/json/module.f.ts'
 import { identity } from '../types/function/module.f.mjs'
 import { stringToList } from '../text/utf16/module.f.mjs'
-import { cmp } from '../types/string/module.f.ts'
+import { cmp } from '../types/string/module.f.mjs'
 
 type Rule = readonly [string, ByteSet, string]
 
diff --git a/fjs/fsm/todo/scan-as-map.md b/fjs/fsm/todo/scan-as-map.md
index 174180395..c111f639f 100644
--- a/fjs/fsm/todo/scan-as-map.md
+++ b/fjs/fsm/todo/scan-as-map.md
@@ -39,9 +39,9 @@ const scanFetch = map(([item]: Entry<SortedSet<string>>) => item)
 ```
 
 Note the explicit `Entry<string>` return annotation instead of `as const`:
-`Entry<T>` (`fjs/types/range_map/module.f.mjs:48`) is the *mutable* tuple
+`Entry<T>` (`fjs/types/range_map/types.ts:11`) is the *mutable* tuple
 `[T, number]`, and `Dfa` stores `RangeMapArray<string> = readonly
-Entry<string>[]` (`:58`), so a `readonly [string, number]` produced by
+Entry<string>[]` (`:19`), so a `readonly [string, number]` produced by
 `as const` would not be assignable where
 `toArray(scanStringify(setMap))` lands in `newDfa`. The annotation pins the
 tuple type without widening and matches what `stringifyOp` returns today.
diff --git a/fjs/js/tokenizer/module.f.ts b/fjs/js/tokenizer/module.f.ts
index 471a133e4..50fdc9891 100644
--- a/fjs/js/tokenizer/module.f.ts
+++ b/fjs/js/tokenizer/module.f.ts
@@ -5,12 +5,17 @@
  *
  * @module
  */
-import { strictEqual, type Scan, type StateScan } from '../../types/function/operator/module.f.mjs'
-import { merge, fromRange, get, type RangeMapArray, type RangeMerge } from '../../types/range_map/module.f.mjs'
-import { empty, stateScan, flat, toArray, reduce as listReduce, scan, map as listMap, type List } from '../../types/list/module.f.mjs'
-import { at, fromEntries, type Entry } from '../../types/ordered_map/module.f.ts'
-import { one, type Range as NumberRange } from '../../types/range/module.f.mjs'
-import type { BigFloat } from '../../types/bigfloat/module.f.mjs'
+import type { Scan, StateScan } from '../../types/function/operator/types.ts'
+import { strictEqual } from '../../types/function/operator/module.f.mjs'
+import type { RangeMapArray, RangeMerge } from '../../types/range_map/types.ts'
+import { merge, fromRange, get } from '../../types/range_map/module.f.mjs'
+import type { List } from '../../types/list/types.ts'
+import { empty, stateScan, flat, toArray, reduce as listReduce, scan, map as listMap } from '../../types/list/module.f.mjs'
+import { at, fromEntries } from '../../types/ordered_map/module.f.mjs'
+import type { Entry } from '../../types/ordered_map/types.ts'
+import type { Range as NumberRange } from '../../types/range/types.ts'
+import { one } from '../../types/range/module.f.mjs'
+import type { BigFloat } from '../../types/bigfloat/types.ts'
 import {
     range,
     //
diff --git a/fjs/mcp/cas/module.f.ts b/fjs/mcp/cas/module.f.ts
index f816c0922..1d967ae3e 100644
--- a/fjs/mcp/cas/module.f.ts
+++ b/fjs/mcp/cas/module.f.ts
@@ -111,8 +111,10 @@ import { tryUtf8 } from '../../text/module.f.mjs'
 import { detectStream } from '../../media/type/module.f.ts'
 import { detect } from '../../media/module.f.ts'
 import { revisionDialect } from '../../media/revision/module.f.ts'
-import { maxLengthBytes, type Vec } from '../../types/bit_vec/module.f.mjs'
-import { ok, type Ok } from '../../types/result/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { maxLengthBytes } from '../../types/bit_vec/module.f.mjs'
+import type { Ok } from '../../types/result/types.ts'
+import { ok } from '../../types/result/module.f.mjs'
 import {
     toolEntry, errorResult, okResult,
     type ToolEntry, type ToolsCallResult,
diff --git a/fjs/mcp/proof.f.ts b/fjs/mcp/proof.f.ts
index bc0d13b0e..df44c0087 100644
--- a/fjs/mcp/proof.f.ts
+++ b/fjs/mcp/proof.f.ts
@@ -5,7 +5,8 @@ import { parse as parseJson, type Unknown } from '../media/json/module.f.ts'
 import { number as rttiNumber, option, string as rttiString } from '../types/rtti/module.f.ts'
 import { parse as rttiParse } from '../types/rtti/parse/module.f.ts'
 import type { Response } from '../protocol/json_rpc/module.f.ts'
-import { msb, u8ListToVec, vec8, repeat, length, type Vec, maxLengthBytes } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
+import { msb, u8ListToVec, vec8, repeat, length, maxLengthBytes } from '../types/bit_vec/module.f.mjs'
 import { vecToCBase32 } from '../basen/cbase32/module.f.mjs'
 import { encode as base64Encode } from '../basen/base64/module.f.mjs'
 import { utf8 } from '../text/module.f.mjs'
diff --git a/fjs/media/html/module.f.ts b/fjs/media/html/module.f.ts
index 3924ca663..42b6f6307 100644
--- a/fjs/media/html/module.f.ts
+++ b/fjs/media/html/module.f.ts
@@ -4,13 +4,14 @@
  *
  * @module
  */
-import { map, flatMap, flat, concat as listConcat, type List } from '../../types/list/module.f.mjs'
-import { concat, concat as stringConcat } from '../../types/string/module.f.ts'
+import type { List } from '../../types/list/types.ts'
+import { map, flatMap, flat, concat as listConcat } from '../../types/list/module.f.mjs'
+import { concat, concat as stringConcat } from '../../types/string/module.f.mjs'
 import { definedEntries, type Entry, type StringMap } from '../../types/object/module.f.ts'
 import { compose } from '../../types/function/module.f.mjs'
 import { stringToList } from '../../text/utf16/module.f.mjs'
 import { includes } from '../../types/array/module.f.mjs'
-import { type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
 import { utf8 } from '../../text/module.f.mjs'
 import { quotationMark, ampersand, lessThanSign, greaterThanSign } from '../../text/ascii/module.f.mjs'
 
diff --git a/fjs/media/json/module.f.ts b/fjs/media/json/module.f.ts
index 4da406224..ea5adfcd9 100644
--- a/fjs/media/json/module.f.ts
+++ b/fjs/media/json/module.f.ts
@@ -11,10 +11,11 @@
  *
  * @module
  */
-import { next, flat, map, type List } from '../../types/list/module.f.mjs'
-import { concat } from '../../types/string/module.f.ts'
+import type { List } from '../../types/list/types.ts'
+import { next, flat, map } from '../../types/list/module.f.mjs'
+import { concat } from '../../types/string/module.f.mjs'
 import { stringToList } from '../../text/utf16/module.f.mjs'
-import type { Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
 import { parse as parseTokens } from './parser/module.f.ts'
 import { tokenize } from './tokenizer/module.f.ts'
 import { at, definedEntries, type Entry as ObjectEntry } from '../../types/object/module.f.ts'
@@ -22,8 +23,8 @@ import { compose, fn } from '../../types/function/module.f.mjs'
 import { objectWrap, arrayWrap, stringSerialize, numberSerialize, nullSerialize, boolSerialize } from './serializer/module.f.ts'
 import { boolean as rttiBoolean, number as rttiNumber, string as rttiString, or, record, array as rttiArray } from '../../types/rtti/module.f.ts'
 import type { Ts } from '../../types/rtti/ts/module.f.ts'
-import type { Assert } from '../../asserts/module.f.mjs'
-import type { Equal } from '../../types/ts/module.f.mjs'
+import type { Assert } from '../../asserts/types.ts'
+import type { Equal } from '../../types/ts/types.ts'
 
 // ── rtti schemas ──────────────────────────────────────────────────────────────
 
diff --git a/fjs/media/json/parser/module.f.ts b/fjs/media/json/parser/module.f.ts
index 4dc65064e..0a9f238fd 100644
--- a/fjs/media/json/parser/module.f.ts
+++ b/fjs/media/json/parser/module.f.ts
@@ -3,11 +3,14 @@
  *
  * @module
  */
-import { error, ok, type Result } from '../../../types/result/module.f.mjs'
-import { type List, fold, next, toArray, concat } from '../../../types/list/module.f.mjs'
-import { type Fold } from '../../../types/function/operator/module.f.mjs'
+import type { Result } from '../../../types/result/types.ts'
+import { error, ok } from '../../../types/result/module.f.mjs'
+import type { List } from '../../../types/list/types.ts'
+import { fold, next, toArray, concat } from '../../../types/list/module.f.mjs'
+import type { Fold } from '../../../types/function/operator/types.ts'
 import { type JsonToken } from '../tokenizer/module.f.ts'
-import { setReplace, type OrderedMap } from '../../../types/ordered_map/module.f.ts'
+import { setReplace } from '../../../types/ordered_map/module.f.mjs'
+import type { OrderedMap } from '../../../types/ordered_map/types.ts'
 import { type Unknown } from '../module.f.ts'
 import { fromMap } from '../../../types/object/module.f.ts'
 import { assertEq } from '../../../asserts/module.f.mjs'
diff --git a/fjs/media/json/schema/module.f.ts b/fjs/media/json/schema/module.f.ts
index 849b126bc..156068965 100644
--- a/fjs/media/json/schema/module.f.ts
+++ b/fjs/media/json/schema/module.f.ts
@@ -10,7 +10,7 @@ import { type Struct, type Tuple, type Type as RttiType, array, option, or, reco
 import { visit, type Visitor } from '../../../types/rtti/common/module.f.ts'
 import type { Primitive } from '../../../djs/module.f.ts'
 import type { Ts } from '../../../types/rtti/ts/module.f.ts'
-import type { Phantom } from '../../../types/phantom/module.f.ts'
+import type { Phantom } from '../../../types/phantom/types.ts'
 import { unknown as jsonUnknown } from '../module.f.ts'
 
 const unknownThunk = () => ['const', unknownConst] as const
diff --git a/fjs/media/json/serializer/module.f.ts b/fjs/media/json/serializer/module.f.ts
index 63943dcae..c87ae0659 100644
--- a/fjs/media/json/serializer/module.f.ts
+++ b/fjs/media/json/serializer/module.f.ts
@@ -7,14 +7,12 @@
  *
  * @module
  */
-import { flat, map, reduce, empty, type List } from '../../../types/list/module.f.mjs'
-import { type Reduce } from '../../../types/function/operator/module.f.mjs'
-import { concat } from '../../../types/string/module.f.ts'
-import {
-    codePointToString,
-    stringToCodePointList,
-    type CodePoint,
-} from '../../../text/utf16/module.f.mjs'
+import type { List } from '../../../types/list/types.ts'
+import { flat, map, reduce, empty } from '../../../types/list/module.f.mjs'
+import type { Reduce } from '../../../types/function/operator/types.ts'
+import { concat } from '../../../types/string/module.f.mjs'
+import type { CodePoint } from '../../../text/utf16/types.ts'
+import { codePointToString, stringToCodePointList } from '../../../text/utf16/module.f.mjs'
 import { errorMask } from '../../../text/code_point/module.f.mjs'
 import {
     backspace,
diff --git a/fjs/media/json/serializer/proof.f.ts b/fjs/media/json/serializer/proof.f.ts
index 77db1773d..52751da23 100644
--- a/fjs/media/json/serializer/proof.f.ts
+++ b/fjs/media/json/serializer/proof.f.ts
@@ -1,6 +1,6 @@
 import { arrayWrap, boolSerialize, numberSerialize, objectWrap, stringSerialize } from './module.f.ts'
 import * as list from '../../../types/list/module.f.mjs'
-import { concat } from '../../../types/string/module.f.ts'
+import { concat } from '../../../types/string/module.f.mjs'
 import { assertEq } from '../../../asserts/module.f.mjs'
 
 const { toArray } = list
diff --git a/fjs/media/json/tokenizer/module.f.ts b/fjs/media/json/tokenizer/module.f.ts
index 891be1c04..be2c57049 100644
--- a/fjs/media/json/tokenizer/module.f.ts
+++ b/fjs/media/json/tokenizer/module.f.ts
@@ -3,8 +3,9 @@
  *
  * @module
  */
-import { type StateScan } from '../../../types/function/operator/module.f.mjs'
-import { concat, empty, flat, stateScan, type List } from '../../../types/list/module.f.mjs'
+import type { StateScan } from '../../../types/function/operator/types.ts'
+import type { List } from '../../../types/list/types.ts'
+import { concat, empty, flat, stateScan } from '../../../types/list/module.f.mjs'
 import { multiply } from '../../../types/bigfloat/module.f.mjs'
 import {
     tokenize as jsTokenize,
diff --git a/fjs/media/module.f.ts b/fjs/media/module.f.ts
index 87a8f2b85..a3c26d611 100644
--- a/fjs/media/module.f.ts
+++ b/fjs/media/module.f.ts
@@ -41,7 +41,7 @@
  *
  * @module
  */
-import type { Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
 import { fromVec } from '../text/utf8/module.f.mjs'
 import { detectVec, type DetectMeta } from './type/module.f.ts'
 import { parse } from './json/module.f.ts'
diff --git a/fjs/media/nix/module.f.ts b/fjs/media/nix/module.f.ts
index 402c266f9..8aa671622 100644
--- a/fjs/media/nix/module.f.ts
+++ b/fjs/media/nix/module.f.ts
@@ -7,8 +7,9 @@
  *
  * @module
  */
-import { toArray, type List as ChunkList } from '../../types/list/module.f.mjs'
-import { concat } from '../../types/string/module.f.ts'
+import type { List as ChunkList } from '../../types/list/types.ts'
+import { toArray } from '../../types/list/module.f.mjs'
+import { concat } from '../../types/string/module.f.mjs'
 import { includes } from '../../types/array/module.f.mjs'
 import {
     digitRange,
diff --git a/fjs/media/proof.f.ts b/fjs/media/proof.f.ts
index 6cdb4de87..b92e89538 100644
--- a/fjs/media/proof.f.ts
+++ b/fjs/media/proof.f.ts
@@ -1,5 +1,6 @@
 import { assertEq } from '../asserts/module.f.mjs'
-import { msb, u8ListToVec, repeat, vec8, type Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
+import { msb, u8ListToVec, repeat, vec8 } from '../types/bit_vec/module.f.mjs'
 import { detect, dialectEntry, type DialectEntry } from './module.f.ts'
 import { dialect, revisionDialect } from './revision/module.f.ts'
 import { number, string } from '../types/rtti/module.f.ts'
diff --git a/fjs/media/revision/module.f.ts b/fjs/media/revision/module.f.ts
index 36d074bc7..f5b0c19e0 100644
--- a/fjs/media/revision/module.f.ts
+++ b/fjs/media/revision/module.f.ts
@@ -19,7 +19,8 @@ import { validate as rttiValidate, type ValidationError } from '../../types/rtti
 import type { Ts } from '../../types/rtti/ts/module.f.ts'
 import { parse as parseJson, type Unknown } from '../json/module.f.ts'
 import { cBase32ToVec } from '../../basen/cbase32/module.f.mjs'
-import { error, ok, type Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { error, ok } from '../../types/result/module.f.mjs'
 import { dialectEntry, type DialectEntry } from '../module.f.ts'
 import { definedEntries, sort } from '../../types/object/module.f.ts'
 import { stringify } from '../json/module.f.ts'
diff --git a/fjs/media/type/module.f.ts b/fjs/media/type/module.f.ts
index 6984d082d..193bdafcf 100644
--- a/fjs/media/type/module.f.ts
+++ b/fjs/media/type/module.f.ts
@@ -32,15 +32,17 @@
  *
  * @module
  */
-import { msb, fromSentinel, length, u8List, type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { msb, fromSentinel, length, u8List } from '../../types/bit_vec/module.f.mjs'
 import { iterable } from '../../types/list/module.f.mjs'
-import type { Nullable } from '../../types/nullable/module.f.mjs'
+import type { Nullable } from '../../types/nullable/types.ts'
 import { pure, step, type Effect, type Operation } from '../../effects/module.f.ts'
 import type { List } from '../../effects/list/module.f.ts'
 import type { IoResult } from '../../effects/node/module.f.ts'
 import { ok, error } from '../../types/result/module.f.mjs'
 import { isValidCodePoint, isTextCodePoint } from '../../text/code_point/module.f.mjs'
-import { utf8ByteToCodePointOp, type Utf8State } from '../../text/utf8/module.f.mjs'
+import type { Utf8State } from '../../text/utf8/types.ts'
+import { utf8ByteToCodePointOp } from '../../text/utf8/module.f.mjs'
 
 const { startsWith, removeFront } = msb
 
diff --git a/fjs/media/type/proof.f.ts b/fjs/media/type/proof.f.ts
index 99f9fa44a..e4d227eb0 100644
--- a/fjs/media/type/proof.f.ts
+++ b/fjs/media/type/proof.f.ts
@@ -1,8 +1,10 @@
 import { assert, assertEq } from '../../asserts/module.f.mjs'
-import { msb, u8ListToVec, vec8, repeat, empty, type Vec } from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { msb, u8ListToVec, vec8, repeat, empty } from '../../types/bit_vec/module.f.mjs'
 import { runPure } from '../../effects/module.f.ts'
 import { nonEmpty, empty as emptyList, type List } from '../../effects/list/module.f.ts'
-import { ok, type Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
+import { ok } from '../../types/result/module.f.mjs'
 import { detect, detectStream, detectVec, type DetectMeta } from './module.f.ts'
 
 // Builds a big-endian `Vec` from a list of byte values — mirrors how the CAS
diff --git a/fjs/path/module.f.ts b/fjs/path/module.f.ts
index 97a9baf8b..d48ce5542 100644
--- a/fjs/path/module.f.ts
+++ b/fjs/path/module.f.ts
@@ -3,9 +3,10 @@
  *
  * @module
  */
-import type { Fold, Reduce, Unary } from '../types/function/operator/module.f.mjs'
-import { type List, fold, last, take, length, concat as listConcat, toArray } from '../types/list/module.f.mjs'
-import { join as listJoin, concat as stringConcat } from '../types/string/module.f.ts'
+import type { Fold, Reduce, Unary } from '../types/function/operator/types.ts'
+import type { List } from '../types/list/types.ts'
+import { fold, last, take, length, concat as listConcat, toArray } from '../types/list/module.f.mjs'
+import { join as listJoin, concat as stringConcat } from '../types/string/module.f.mjs'
 
 const foldNormalizeOp: Fold<string, List<string>>
 = input => state => {
diff --git a/fjs/protocol/json_rpc/module.f.ts b/fjs/protocol/json_rpc/module.f.ts
index 4fbcf84bb..8c1c227db 100644
--- a/fjs/protocol/json_rpc/module.f.ts
+++ b/fjs/protocol/json_rpc/module.f.ts
@@ -17,7 +17,7 @@
 import { number, string, or, option } from '../../types/rtti/module.f.ts'
 import type { Ts } from '../../types/rtti/ts/module.f.ts'
 import { validate } from '../../types/rtti/validate/module.f.ts'
-import type { Result } from '../../types/result/module.f.mjs'
+import type { Result } from '../../types/result/types.ts'
 import { unknown, type Unknown } from '../../media/json/module.f.ts'
 
 export const jsonrpc = '2.0' as const
diff --git a/fjs/sul/id/module.f.ts b/fjs/sul/id/module.f.ts
index 6a1896d30..4bc0cb2c8 100644
--- a/fjs/sul/id/module.f.ts
+++ b/fjs/sul/id/module.f.ts
@@ -7,22 +7,18 @@
  */
 
 import { toArray } from '../../types/list/module.f.mjs'
-import {
-    length,
-    msb,
-    uint,
-    uintChunkList,
-    unpack,
-    vec,
-    type Vec
-} from '../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import { length, msb, uint, uintChunkList, unpack, vec } from '../../types/bit_vec/module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
 import { utf8 } from '../../text/module.f.mjs'
-import { secp256r1, type Point2D } from '../../crypto/secp/module.f.mjs'
-import { base32, type V8 } from '../../crypto/sha2/module.f.mjs'
+import type { Point2D } from '../../crypto/secp/types.ts'
+import { secp256r1 } from '../../crypto/secp/module.f.mjs'
+import type { V8 } from '../../crypto/sha2/types.ts'
+import { base32 } from '../../crypto/sha2/module.f.mjs'
 import { literal3ToVec } from '../level/literal/module.f.ts'
 import { log2 } from '../../types/bigint/module.f.mjs'
-import { asBase, asNominal, type Nominal } from '../../types/nominal/module.f.mjs'
+import type { Nominal } from '../../types/nominal/types.ts'
+import { asBase, asNominal } from '../../types/nominal/module.f.mjs'
 
 /** A 256-bit SUL identifier. One of three variants: level-3 literal, raw bit vector, or SHA2 hash. */
 export type Id = Nominal<
diff --git a/fjs/sul/level/hash/module.f.ts b/fjs/sul/level/hash/module.f.ts
index c1b96af5c..55be612d2 100644
--- a/fjs/sul/level/hash/module.f.ts
+++ b/fjs/sul/level/hash/module.f.ts
@@ -4,7 +4,8 @@
  * @module
  */
 
-import { emptyState, patriciaTrie, type Create, type State } from '../../../types/patricia_trie/module.f.mjs'
+import type { Create, State } from '../../../types/patricia_trie/types.ts'
+import { emptyState, patriciaTrie } from '../../../types/patricia_trie/module.f.mjs'
 import { compress, type Id } from '../../id/module.f.ts'
 import { asBase } from '../../../types/nominal/module.f.mjs'
 
diff --git a/fjs/sul/level/literal/module.f.ts b/fjs/sul/level/literal/module.f.ts
index a6b8bc3a3..4f2395100 100644
--- a/fjs/sul/level/literal/module.f.ts
+++ b/fjs/sul/level/literal/module.f.ts
@@ -6,11 +6,14 @@
  */
 
 import { log2 } from '../../../types/bigint/module.f.mjs'
-import { msb, vec, type Vec } from '../../../types/bit_vec/module.f.mjs'
-import type { Func } from '../../../types/function/module.f.mjs'
-import { strictEqual, type Equal, type StateScan } from '../../../types/function/operator/module.f.mjs'
-import { equal, map, type List } from '../../../types/list/module.f.mjs'
-import { join } from '../../../types/string/module.f.ts'
+import type { Vec } from '../../../types/bit_vec/types.ts'
+import { msb, vec } from '../../../types/bit_vec/module.f.mjs'
+import type { Func } from '../../../types/function/types.ts'
+import type { Equal, StateScan } from '../../../types/function/operator/types.ts'
+import { strictEqual } from '../../../types/function/operator/module.f.mjs'
+import type { List } from '../../../types/list/types.ts'
+import { equal, map } from '../../../types/list/module.f.mjs'
+import { join } from '../../../types/string/module.f.mjs'
 
 export const symbolToString = (s: bigint): string => s.toString(16)
 
diff --git a/fjs/sul/level/literal/proof.f.ts b/fjs/sul/level/literal/proof.f.ts
index 36709b43d..753405664 100644
--- a/fjs/sul/level/literal/proof.f.ts
+++ b/fjs/sul/level/literal/proof.f.ts
@@ -1,4 +1,5 @@
-import { chunkList, msb, vec, type Vec } from '../../../types/bit_vec/module.f.mjs'
+import type { Vec } from '../../../types/bit_vec/types.ts'
+import { chunkList, msb, vec } from '../../../types/bit_vec/module.f.mjs'
 import { assert, assertEq } from '../../../asserts/module.f.mjs'
 import { map, stateScan, toArray } from '../../../types/list/module.f.mjs'
 import {
diff --git a/fjs/sul/module.f.ts b/fjs/sul/module.f.ts
index 762605fa9..4834d008d 100644
--- a/fjs/sul/module.f.ts
+++ b/fjs/sul/module.f.ts
@@ -8,7 +8,7 @@
 import { emptyPipelineState, pipelineStep, type PipelineState } from './level/literal/module.f.ts'
 import { encode as hashEncode, type Add } from './level/hash/module.f.ts'
 import { level3Id, type Id } from './id/module.f.ts'
-import type { InternalState } from '../types/patricia_trie/module.f.mjs'
+import type { InternalState } from '../types/patricia_trie/types.ts'
 
 type HashState = InternalState<Id>
 
diff --git a/fjs/text/ascii/module.f.mjs b/fjs/text/ascii/module.f.mjs
index fbfb5e023..f1f5d6947 100644
--- a/fjs/text/ascii/module.f.mjs
+++ b/fjs/text/ascii/module.f.mjs
@@ -4,7 +4,7 @@
  * @module
  */
 
-/** @import { Range } from '../../types/range/module.f.mjs' */
+/** @import { Range } from '../../types/range/types.ts' */
 
 /** @type {(s: string) => (i: number) => number} */
 const at = s => i => {
diff --git a/fjs/text/code_point/module.f.mjs b/fjs/text/code_point/module.f.mjs
index bde8229e9..1c7c3ac7b 100644
--- a/fjs/text/code_point/module.f.mjs
+++ b/fjs/text/code_point/module.f.mjs
@@ -10,9 +10,9 @@
  */
 
 import { flat, stateScan } from '../../types/list/module.f.mjs'
-/** @import { List } from '../../types/list/module.f.mjs' */
+/** @import { List } from '../../types/list/types.ts' */
 
-/** @import { StateScan } from '../../types/function/operator/module.f.mjs' */
+/** @import { StateScan } from '../../types/function/operator/types.ts' */
 
 import { contains } from '../../types/range/module.f.mjs'
 
diff --git a/fjs/text/module.f.mjs b/fjs/text/module.f.mjs
index 536282849..2119c8e6c 100644
--- a/fjs/text/module.f.mjs
+++ b/fjs/text/module.f.mjs
@@ -7,21 +7,13 @@
  */
 
 import { msb, tryU8ListToVec, u8List } from '../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../types/bit_vec/module.f.mjs' */
 import { flatMap } from '../types/list/module.f.mjs'
-/** @import { List } from '../types/list/module.f.mjs' */
+/** @import { List } from '../types/list/types.ts' */
 import { fromCodePointList, toCodePointList } from './utf8/module.f.mjs'
 import { stringToCodePointList, codePointListToString } from './utf16/module.f.mjs'
 import { mapUnwrap } from '../types/nullable/module.f.mjs'
-/** @import { Nullable } from '../types/nullable/module.f.mjs' */
-
-/** @typedef {_ItemThunk | _ItemArray} Block */
-
-/** @typedef {readonly Item[]} _ItemArray */
-
-/** @typedef {() => List<Item>} _ItemThunk */
-
-/** @typedef {string | _ItemArray | _ItemThunk} Item */
+/** @import { Nullable } from '../types/nullable/types.ts' */
+/** @import { Block, Item, Utf8 } from './types.ts' */
 
 /** @type {(indent: string) => (text: Block) => List<string>} */
 export const flat = indent => {
@@ -37,8 +29,6 @@ export const flat = indent => {
 
 const tryU8ListToVecMsb = tryU8ListToVec(msb)
 
-/** @typedef {Vec} Utf8 */
-
 /**
  * Converts a string to an UTF-8, represented as an MSB first bit vector,
  * returning `null` instead of throwing if the result would exceed
diff --git a/fjs/text/proof.f.ts b/fjs/text/proof.f.ts
index 9bca741e0..2b34b35bc 100644
--- a/fjs/text/proof.f.ts
+++ b/fjs/text/proof.f.ts
@@ -1,6 +1,7 @@
 import { assertEq, assertNotNullish } from '../asserts/module.f.mjs'
-import { flat, utf8, utf8ToString, tryUtf8, type Block } from './module.f.mjs'
-import { join } from '../types/string/module.f.ts'
+import type { Block } from './types.ts'
+import { flat, utf8, utf8ToString, tryUtf8 } from './module.f.mjs'
+import { join } from '../types/string/module.f.mjs'
 import { empty, maxLengthBytes } from '../types/bit_vec/module.f.mjs'
 
 const overflowStr = 'a'.repeat(Number(maxLengthBytes) + 1)
diff --git a/fjs/text/types.ts b/fjs/text/types.ts
new file mode 100644
index 000000000..43e126b26
--- /dev/null
+++ b/fjs/text/types.ts
@@ -0,0 +1,18 @@
+/**
+ * Types for indented text blocks and UTF-8 bit vectors.
+ *
+ * @module
+ */
+
+import type { Vec } from '../types/bit_vec/types.ts'
+import type { List } from '../types/list/types.ts'
+
+type _ItemArray = readonly Item[]
+
+type _ItemThunk = () => List<Item>
+
+export type Block = _ItemThunk | _ItemArray
+
+export type Item = string | _ItemArray | _ItemThunk
+
+export type Utf8 = Vec
diff --git a/fjs/text/utf16/module.f.mjs b/fjs/text/utf16/module.f.mjs
index 38f2e2120..7f44253e3 100644
--- a/fjs/text/utf16/module.f.mjs
+++ b/fjs/text/utf16/module.f.mjs
@@ -12,10 +12,10 @@ import {
     flatMap,
     empty,
 } from '../../types/list/module.f.mjs'
-/** @import { List, Result, Thunk } from '../../types/list/module.f.mjs' */
+/** @import { List, Result, Thunk } from '../../types/list/types.ts' */
 
 import { concat } from '../../types/function/operator/module.f.mjs'
-/** @import { StateScan } from '../../types/function/operator/module.f.mjs' */
+/** @import { StateScan } from '../../types/function/operator/types.ts' */
 
 import { contains } from '../../types/range/module.f.mjs'
 
@@ -37,24 +37,7 @@ import {
  * @typedef {number | null} _Utf16State
  */
 
-/**
- * Represent an unsigned UTF16, used to store one word UTF-16 (code unit).
- *
- * @typedef {number} U16
- */
-
-/**
- * [0, 0x10_FFFF]: 16+5 = 21 bits
- *
- * 121_0000_0000: 16+16+9 = 41 bits
- */
-
-/**
- * Represent an Unicode code point.
- * Has range: from 0x0000 to 0x10_FFFF (21 bits).
- *
- * @typedef {number} CodePoint
- */
+/** @import { CodePoint, U16 } from './types.ts' */
 
 /**
  * The BMP / surrogate / supplementary-plane predicates used below live in
diff --git a/fjs/text/utf16/types.ts b/fjs/text/utf16/types.ts
new file mode 100644
index 000000000..5ca45fdbd
--- /dev/null
+++ b/fjs/text/utf16/types.ts
@@ -0,0 +1,22 @@
+/**
+ * Types for UTF-16 code units and Unicode code points.
+ *
+ * @module
+ */
+
+/**
+ * Represent an unsigned UTF16, used to store one word UTF-16 (code unit).
+ */
+export type U16 = number
+
+/**
+ * [0, 0x10_FFFF]: 16+5 = 21 bits
+ *
+ * 121_0000_0000: 16+16+9 = 41 bits
+ */
+
+/**
+ * Represent an Unicode code point.
+ * Has range: from 0x0000 to 0x10_FFFF (21 bits).
+ */
+export type CodePoint = number
diff --git a/fjs/text/utf8/module.f.mjs b/fjs/text/utf8/module.f.mjs
index 4fc6b673f..7b15a40af 100644
--- a/fjs/text/utf8/module.f.mjs
+++ b/fjs/text/utf8/module.f.mjs
@@ -5,36 +5,16 @@
  */
 
 import { flatMap, toArray } from '../../types/list/module.f.mjs'
-/** @import { List, Thunk } from '../../types/list/module.f.mjs' */
-/** @import { StateScan } from '../../types/function/operator/module.f.mjs' */
-/** @import { Tuple } from '../../types/array/module.f.mjs' */
+/** @import { List, Thunk } from '../../types/list/types.ts' */
+/** @import { StateScan } from '../../types/function/operator/types.ts' */
 import { decoder, errorMask, isValidCodePoint } from '../code_point/module.f.mjs'
 import { msb, u8List, length } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/module.f.mjs' */
+/** @import { Vec } from '../../types/bit_vec/types.ts' */
 import { codePointListToString } from '../utf16/module.f.mjs'
-
-/** An unsigned 8-bit integer, represents a single byte. @typedef {number} U8 */
-
-/** A singed 32-bit integer. @typedef {number} I32 */
-
-/**
- * Represents an unsigned 8-bit type - U8 or the end-of-file indicator.
- * The U8 represents the byte itself, and null indicates that reading does not return anything else.
- *
- * @typedef {U8 | null} ByteOrEof
- */
-
-/**
- * Represents the state of a UTF-8 decoding operation that contains at least one byte.
- *
- * @typedef {Tuple<1, number> | Tuple<2, number> | Tuple<3, number>} Utf8NonEmptyState
- */
-
 /**
- * Represents the state of a UTF-8 decoding operation, which can be either `null` (no state)
- * or a non-empty state containing one or more bytes.
- *
- * @typedef {null | Utf8NonEmptyState} Utf8State
+ * @import {
+ *  ByteOrEof, I32, U8, Utf8NonEmptyState, Utf8State,
+ * } from './types.ts'
  */
 
 /**
diff --git a/fjs/text/utf8/types.ts b/fjs/text/utf8/types.ts
new file mode 100644
index 000000000..5767645b3
--- /dev/null
+++ b/fjs/text/utf8/types.ts
@@ -0,0 +1,33 @@
+/**
+ * Types for UTF-8 byte-level encoding and decoding.
+ *
+ * @module
+ */
+
+import type { Tuple } from '../../types/array/types.ts'
+
+/** An unsigned 8-bit integer, represents a single byte. */
+export type U8 = number
+
+/** A singed 32-bit integer. */
+export type I32 = number
+
+/**
+ * Represents an unsigned 8-bit type - U8 or the end-of-file indicator.
+ * The U8 represents the byte itself, and null indicates that reading does not
+ * return anything else.
+ */
+export type ByteOrEof = U8 | null
+
+/**
+ * Represents the state of a UTF-8 decoding operation that contains at least one
+ * byte.
+ */
+export type Utf8NonEmptyState =
+    Tuple<1, number> | Tuple<2, number> | Tuple<3, number>
+
+/**
+ * Represents the state of a UTF-8 decoding operation, which can be either
+ * `null` (no state) or a non-empty state containing one or more bytes.
+ */
+export type Utf8State = null | Utf8NonEmptyState
diff --git a/fjs/types/array/module.f.mjs b/fjs/types/array/module.f.mjs
index 159446ec3..f24e5d493 100644
--- a/fjs/types/array/module.f.mjs
+++ b/fjs/types/array/module.f.mjs
@@ -6,49 +6,13 @@
 
 import { fromUndefined, map } from '../nullable/module.f.mjs'
 
-/** @import { Assert } from '../../asserts/module.f.mjs' */
-/** @import { Equal } from '../ts/module.f.mjs' */
+/** @import { Tuple } from './types.ts' */
 
 /**
  * @type {(value: unknown) => value is readonly unknown[]}
  */
 export const isArray = value => value instanceof Array
 
-/**
- * @template {number} N
- * @template T
- * @template {readonly T[]} R
- * @typedef {N extends R['length'] ? R : _Tuple<N, T, readonly[...R, T]>} _Tuple
-*/
-
-/**
- * @template {number} N
- * @template {readonly unknown[]} R
- * @typedef {R['length'] extends N ? never : R['length'] | _Index<N, readonly[...R, unknown]>} _Index
- */
-
-/**
- * @template {number} N
- * @typedef {number extends N ? number : N extends number ? _Index<N, readonly[]> : never} Index
- */
-
-/**
- * @template {number} N
- * @template T
- * @typedef {_Tuple<N, T, readonly[]>} Tuple
- */
-
-/**
- * @template {readonly unknown[]} T
- * @typedef {Index<T['length']>} KeyOf
- */
-
-/**
- * @typedef {Assert<Equal<KeyOf<readonly number[]>, number>>} _X0
- * @typedef {Assert<Equal<KeyOf<readonly [true]>, 0>>} _X1
- * @typedef {Assert<Equal<KeyOf<readonly [true] | readonly [false, false]>, 0 | 1>>} _X2
- */
-
 /**
  * Currently, TypeScript can't narrow the type of `readonly T[]` to `Array2<T>`
  * only by checking `a.length === 2`, so we need a user-defined type guard.
@@ -67,11 +31,6 @@ export const isTuple =
     a =>
         a.length === n
 
-/**
- * @template T
- * @typedef {Tuple<1, T> | Tuple<2, T> | Tuple<3, T> | Tuple<4, T> | Tuple<5, T>} Array1_5
- */
-
 /**
  * @type {<T>(a: readonly T[]) => readonly T[]}
  */
@@ -127,12 +86,6 @@ export const splitLast = a => {
  */
 export const empty = /** @type {const} */([])
 
-/**
- * @template I
- * @template {readonly I[]} T
- * @typedef {(v: I) => v is T[number]} Includes
- */
-
 export const includes =
     /**
      * @template I
diff --git a/fjs/types/array/types.ts b/fjs/types/array/types.ts
new file mode 100644
index 000000000..368cd9b14
--- /dev/null
+++ b/fjs/types/array/types.ts
@@ -0,0 +1,32 @@
+/**
+ * Types for JavaScript immutable arrays.
+ *
+ * @module
+ */
+
+import type { Assert } from '../../asserts/types.ts'
+import type { Equal } from '../ts/types.ts'
+
+type _Tuple<N extends number, T, R extends readonly T[]> =
+    N extends R['length'] ? R : _Tuple<N, T, readonly [...R, T]>
+
+type _Index<N extends number, R extends readonly unknown[]> =
+    R['length'] extends N
+        ? never
+        : R['length'] | _Index<N, readonly [...R, unknown]>
+
+export type Index<N extends number> =
+    number extends N ? number : N extends number ? _Index<N, readonly []> : never
+
+export type Tuple<N extends number, T> = _Tuple<N, T, readonly []>
+
+export type KeyOf<T extends readonly unknown[]> = Index<T['length']>
+
+type _X0 = Assert<Equal<KeyOf<readonly number[]>, number>>
+type _X1 = Assert<Equal<KeyOf<readonly [true]>, 0>>
+type _X2 = Assert<Equal<KeyOf<readonly [true] | readonly [false, false]>, 0 | 1>>
+
+export type Array1_5<T> =
+    Tuple<1, T> | Tuple<2, T> | Tuple<3, T> | Tuple<4, T> | Tuple<5, T>
+
+export type Includes<I, T extends readonly I[]> = (v: I) => v is T[number]
diff --git a/fjs/types/bigfloat/module.f.mjs b/fjs/types/bigfloat/module.f.mjs
index f2d54d8f5..dd590dcd8 100644
--- a/fjs/types/bigfloat/module.f.mjs
+++ b/fjs/types/bigfloat/module.f.mjs
@@ -5,8 +5,7 @@
  */
 
 import { abs, sign } from '../bigint/module.f.mjs'
-
-/** @typedef {readonly [bigint, number]} BigFloat */
+/** @import { BigFloat } from './types.ts' */
 
 /** @typedef {readonly [BigFloat, bigint]} _BigFloatWithRemainder */
 
diff --git a/fjs/types/bigfloat/types.ts b/fjs/types/bigfloat/types.ts
new file mode 100644
index 000000000..8e8217629
--- /dev/null
+++ b/fjs/types/bigfloat/types.ts
@@ -0,0 +1,7 @@
+/**
+ * Types for big-floats built from bigint mantissa and exponent parts.
+ *
+ * @module
+ */
+
+export type BigFloat = readonly [bigint, number]
diff --git a/fjs/types/bigint/module.f.mjs b/fjs/types/bigint/module.f.mjs
index f085899c1..3c05792a2 100644
--- a/fjs/types/bigint/module.f.mjs
+++ b/fjs/types/bigint/module.f.mjs
@@ -18,23 +18,11 @@
  */
 
 import { cmp } from '../function/compare/module.f.mjs'
-/** @import { Sign } from '../function/compare/module.f.mjs' */
-/** @import { Unary as OpUnary, Reduce as OpReduce } from '../function/operator/module.f.mjs' */
-/** @import { List } from '../list/module.f.mjs' */
+/** @import { Sign } from '../function/compare/types.ts' */
+/** @import { List } from '../list/types.ts' */
+/** @import { Reduce, Unary } from './types.ts' */
 import { fold } from '../../common/monoid/module.f.mjs'
 
-/**
- * Type representing a unary operation on `bigint`.
- *
- * @typedef {OpUnary<bigint, bigint>} Unary
- */
-
-/**
- * Type representing a reduction operation on `bigint` values.
- *
- * @typedef {OpReduce<bigint>} Reduce
- */
-
 /**
  * Adds two `bigint` values.
  * TODO: should be combined with `addition` for `number`.
diff --git a/fjs/types/bigint/types.ts b/fjs/types/bigint/types.ts
new file mode 100644
index 000000000..359da1f23
--- /dev/null
+++ b/fjs/types/bigint/types.ts
@@ -0,0 +1,20 @@
+/**
+ * Operator types specialized to `bigint`.
+ *
+ * @module
+ */
+
+import type {
+    Unary as OpUnary,
+    Reduce as OpReduce,
+} from '../function/operator/types.ts'
+
+/**
+ * Type representing a unary operation on `bigint`.
+ */
+export type Unary = OpUnary<bigint, bigint>
+
+/**
+ * Type representing a reduction operation on `bigint` values.
+ */
+export type Reduce = OpReduce<bigint>
diff --git a/fjs/types/bit_vec/module.f.mjs b/fjs/types/bit_vec/module.f.mjs
index bd54b837f..5baea7f94 100644
--- a/fjs/types/bit_vec/module.f.mjs
+++ b/fjs/types/bit_vec/module.f.mjs
@@ -23,32 +23,30 @@
  */
 
 import { bitLength, divUp, mask, maxLength, xor } from '../bigint/module.f.mjs'
-/** @import { Reduce as BigintReduce } from '../bigint/module.f.mjs' */
+/** @import { Reduce as BigintReduce } from '../bigint/types.ts' */
 
 import { flip, identity } from '../function/module.f.mjs'
 
-/** @import { Binary, Fold, Reduce as OpReduce } from '../function/operator/module.f.mjs' */
+/** @import { Fold } from '../function/operator/types.ts' */
 
 import { map, tryFold } from '../list/module.f.mjs'
-/** @import { Accumulator, List, Thunk } from '../list/module.f.mjs' */
+/** @import { Accumulator, List, Thunk } from '../list/types.ts' */
 
 import { asBase, asNominal } from '../nominal/module.f.mjs'
-/** @import { Nominal } from '../nominal/module.f.mjs' */
 
 import { repeat as mRepeat } from '../../common/monoid/module.f.mjs'
 
 import { cmp, max, min } from '../function/compare/module.f.mjs'
-/** @import { Sign } from '../function/compare/module.f.mjs' */
+/** @import { Sign } from '../function/compare/types.ts' */
 
 import { mapUnwrap } from '../nullable/module.f.mjs'
-/** @import { Nullable } from '../nullable/module.f.mjs' */
-
-/** @typedef {'1a23a4336197e6158b6936cad34e90d146cd84b9b40ff7ab75a17c6d79e31d89'} _Revision */
+/** @import { Nullable } from '../nullable/types.ts' */
 
 /**
- * A vector of bits represented as a signed `bigint`.
- *
- * @typedef {Nominal<'bit_vec', _Revision, bigint>} Vec
+ * @import {
+ *  BitOrder, PopFront, Reduce, Unpacked, Vec,
+ *  _NormOp, _UnpackConcat,
+ * } from './types.ts'
  */
 
 /**
@@ -150,14 +148,6 @@ export const uint = v => {
     return u ^ (1n << (len - 1n))
 }
 
-/**
- * Structure describing the unpacked view of a vector.
- * @typedef {{
- *  readonly length: bigint
- *  readonly uint: bigint
- * }} Unpacked
- */
-
 /**
  * Extracts the logical length and unsigned integer from the vector.
  *
@@ -178,17 +168,6 @@ export const pack = ({ length, uint }) => vec(length)(uint)
 /** @type {({ uint }: Unpacked) => bigint} */
 export const unpackedUint = ({ uint }) => uint
 
-/**
- * @typedef {(len: bigint) => {
- *  readonly a: bigint
- *  readonly b: bigint
- * }} _Norm
- */
-
-/** @typedef {Binary<Unpacked, Unpacked, _Norm>} _NormOp */
-
-/** @typedef {OpReduce<Vec>} Reduce */
-
 /**
  * Normalizes two vectors to the same length before applying a bigint reducer.
  *
@@ -202,33 +181,6 @@ const op = norm => op => ap => bp => {
     return vec(len)(op(a)(b))
 }
 
-/**
- * @template T
- * @typedef {(len: bigint) => (u: T) => readonly [bigint, T]} PopFront
- */
-
-/**
- * Represents operations for handling bit vectors with a specific bit order.
- *
- * https://en.wikipedia.org/wiki/Bit_numbering
- *
- * @typedef {{
- *  readonly front: (len: bigint) => (v: Vec) => bigint
- *  readonly removeFront: (len: bigint) => (v: Vec) => Vec
- *  readonly popFront: PopFront<Vec>
- *  readonly concat: Reduce
- *  readonly tryListToVec: (list: List<Vec>) => Nullable<Vec>
- *  readonly listToVec: (list: List<Vec>) => Vec
- *  readonly xor: Reduce
- *  readonly unpackPopFront: PopFront<Unpacked>
- *  readonly norm: _NormOp
- *  readonly cmp: (a: Vec) => (b: Vec) => Sign
- *  readonly unpackSplit: (len: bigint) => (u: Unpacked) => readonly[bigint, bigint]
- *  readonly unpackConcat: _UnpackConcat
- *  readonly startsWith: (prefix: Vec) => (v: Vec) => boolean
- * }} BitOrder
- */
-
 /**
  * @typedef {{
  *  readonly front: (len: bigint) => (v: Vec) => bigint
@@ -242,8 +194,6 @@ const op = norm => op => ap => bp => {
 
 const unpackEmpty = /** @type {const} */{ length: 0n, uint: 0n }
 
-/** @typedef {(a: Unpacked) => (b: Unpacked) => Unpacked} _UnpackConcat */
-
 /**
  * @typedef {{
  *  readonly len: bigint
diff --git a/fjs/types/bit_vec/proof.f.ts b/fjs/types/bit_vec/proof.f.ts
index 41c2209c4..ce8f06ca5 100644
--- a/fjs/types/bit_vec/proof.f.ts
+++ b/fjs/types/bit_vec/proof.f.ts
@@ -1,9 +1,11 @@
 import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { mask } from '../bigint/module.f.mjs'
-import type { Sign } from '../function/compare/module.f.mjs'
+import type { Sign } from '../function/compare/types.ts'
 import { asBase, asNominal } from '../nominal/module.f.mjs'
-import { length, empty, uint, type Vec, vec, lsb, msb, type BitOrder, repeat, vec8, maxLength, u8ListToVec, tryU8ListToVec, u8List, chunkList, fromSentinel } from './module.f.mjs'
-import { repeat as listRepeat, toArray, type List } from '../list/module.f.mjs'
+import type { Vec, BitOrder } from './types.ts'
+import { length, empty, uint, vec, lsb, msb, repeat, vec8, maxLength, u8ListToVec, tryU8ListToVec, u8List, chunkList, fromSentinel } from './module.f.mjs'
+import type { List } from '../list/types.ts'
+import { repeat as listRepeat, toArray } from '../list/module.f.mjs'
 
 const unsafeVec = (a: bigint): Vec => asNominal(a)
 
diff --git a/fjs/types/bit_vec/types.ts b/fjs/types/bit_vec/types.ts
new file mode 100644
index 000000000..93b1d7bed
--- /dev/null
+++ b/fjs/types/bit_vec/types.ts
@@ -0,0 +1,64 @@
+/**
+ * Types for bit vectors normalized on the most-significant bit.
+ *
+ * @module
+ */
+
+import type { Sign } from '../function/compare/types.ts'
+import type {
+    Binary,
+    Reduce as OpReduce,
+} from '../function/operator/types.ts'
+import type { List } from '../list/types.ts'
+import type { Nominal } from '../nominal/types.ts'
+import type { Nullable } from '../nullable/types.ts'
+
+type _Revision =
+    '1a23a4336197e6158b6936cad34e90d146cd84b9b40ff7ab75a17c6d79e31d89'
+
+/**
+ * A vector of bits represented as a signed `bigint`.
+ */
+export type Vec = Nominal<'bit_vec', _Revision, bigint>
+
+/**
+ * Structure describing the unpacked view of a vector.
+ */
+export type Unpacked = {
+    readonly length: bigint
+    readonly uint: bigint
+}
+
+export type _Norm = (len: bigint) => {
+    readonly a: bigint
+    readonly b: bigint
+}
+
+export type _NormOp = Binary<Unpacked, Unpacked, _Norm>
+
+export type _UnpackConcat = (a: Unpacked) => (b: Unpacked) => Unpacked
+
+export type Reduce = OpReduce<Vec>
+
+export type PopFront<T> = (len: bigint) => (u: T) => readonly [bigint, T]
+
+/**
+ * Represents operations for handling bit vectors with a specific bit order.
+ *
+ * https://en.wikipedia.org/wiki/Bit_numbering
+ */
+export type BitOrder = {
+    readonly front: (len: bigint) => (v: Vec) => bigint
+    readonly removeFront: (len: bigint) => (v: Vec) => Vec
+    readonly popFront: PopFront<Vec>
+    readonly concat: Reduce
+    readonly tryListToVec: (list: List<Vec>) => Nullable<Vec>
+    readonly listToVec: (list: List<Vec>) => Vec
+    readonly xor: Reduce
+    readonly unpackPopFront: PopFront<Unpacked>
+    readonly norm: _NormOp
+    readonly cmp: (a: Vec) => (b: Vec) => Sign
+    readonly unpackSplit: (len: bigint) => (u: Unpacked) => readonly [bigint, bigint]
+    readonly unpackConcat: _UnpackConcat
+    readonly startsWith: (prefix: Vec) => (v: Vec) => boolean
+}
diff --git a/fjs/types/btree/find/module.f.mjs b/fjs/types/btree/find/module.f.mjs
index a9c61f5c2..d8ab53db2 100644
--- a/fjs/types/btree/find/module.f.mjs
+++ b/fjs/types/btree/find/module.f.mjs
@@ -3,53 +3,13 @@
  *
  * @module
  */
-/** @import { Leaf1, Leaf2, Branch3, Branch5, TNode } from '../types/module.f.mjs' */
-/** @import { List } from '../../list/module.f.mjs' */
+/** @import { TNode } from '../types/types.ts' */
 
 import { index3, index5 } from '../../function/compare/module.f.mjs'
-/** @import { Compare } from '../../function/compare/module.f.mjs' */
+/** @import { Compare } from '../../function/compare/types.ts' */
 
-/** @import { KeyOf, Index } from '../../array/module.f.mjs' */
-
-/**
- * @template T
- * @typedef {readonly[Index<3>, Leaf1<T>]} _FirstLeaf1
- */
-
-/**
- * @template T
- * @typedef {readonly[1, Branch3<T>]} _FirstBranch3
- */
-
-/**
- * @template T
- * @typedef {readonly[Index<5>, Leaf2<T>]} _FirstLeaf2
- */
-
-/**
- * @template T
- * @typedef {readonly[1|3, Branch5<T>]} _FirstBranch5
- */
-
-/**
- * @template T
- * @typedef {_FirstLeaf1<T> | _FirstBranch3<T> | _FirstLeaf2<T> | _FirstBranch5<T>} First
- */
-
-/**
- * @template T
- * @typedef {readonly[0|2, Branch3<T>]} _PathItem3
- */
-
-/**
- * @template T
- * @typedef {readonly[0|2|4, Branch5<T>]} _PathItem5
- */
-
-/**
- * @template T
- * @typedef {_PathItem3<T> | _PathItem5<T>} PathItem
- */
+/** @import { KeyOf } from '../../array/types.ts' */
+/** @import { First, Path, PathItem, Result } from './types.ts' */
 
 /** @type {<T>(item: PathItem<T>) => TNode<T>} */
 const child = item => {
@@ -57,19 +17,6 @@ const child = item => {
     return /** @type {TNode<T>} */ (item[1][item[0]])
 }
 
-/**
- * @template T
- * @typedef {List<PathItem<T>>} Path
- */
-
-/**
- * @template T
- * @typedef {{
- *   readonly first: First<T>,
- *   readonly tail: Path<T>
- * }} Result
- */
-
 /** @type {<T>(c: Compare<T>) => (node: TNode<T>) => Result<T>} */
 export const find = c => {
     /** @typedef {typeof c extends Compare<infer T> ? T : never} T */
diff --git a/fjs/types/btree/find/proof.f.ts b/fjs/types/btree/find/proof.f.ts
index c9cba85f9..52e6ebfcb 100644
--- a/fjs/types/btree/find/proof.f.ts
+++ b/fjs/types/btree/find/proof.f.ts
@@ -1,9 +1,10 @@
-import { type Result, find as btreeFind } from './module.f.mjs'
+import type { Result } from './types.ts'
+import { find as btreeFind } from './module.f.mjs'
 import { map, toArray } from '../../list/module.f.mjs'
 import { stringify, type Unknown } from '../../../media/json/module.f.ts'
 import { sort } from '../../object/module.f.ts'
-import { type TNode } from '../types/module.f.mjs'
-import { cmp } from '../../string/module.f.ts'
+import type { TNode } from '../types/types.ts'
+import { cmp } from '../../string/module.f.mjs'
 import { set as setSet } from '../set/module.f.mjs'
 import { assertEq } from '../../../asserts/module.f.mjs'
 
diff --git a/fjs/types/btree/find/types.ts b/fjs/types/btree/find/types.ts
new file mode 100644
index 000000000..e688e5cd1
--- /dev/null
+++ b/fjs/types/btree/find/types.ts
@@ -0,0 +1,33 @@
+/**
+ * Types for B-tree lookup results and paths.
+ *
+ * @module
+ */
+
+import type { Index } from '../../array/types.ts'
+import type { List } from '../../list/types.ts'
+import type { Branch3, Branch5, Leaf1, Leaf2 } from '../types/types.ts'
+
+type _FirstLeaf1<T> = readonly [Index<3>, Leaf1<T>]
+
+type _FirstBranch3<T> = readonly [1, Branch3<T>]
+
+type _FirstLeaf2<T> = readonly [Index<5>, Leaf2<T>]
+
+type _FirstBranch5<T> = readonly [1 | 3, Branch5<T>]
+
+export type First<T> =
+    _FirstLeaf1<T> | _FirstBranch3<T> | _FirstLeaf2<T> | _FirstBranch5<T>
+
+type _PathItem3<T> = readonly [0 | 2, Branch3<T>]
+
+type _PathItem5<T> = readonly [0 | 2 | 4, Branch5<T>]
+
+export type PathItem<T> = _PathItem3<T> | _PathItem5<T>
+
+export type Path<T> = List<PathItem<T>>
+
+export type Result<T> = {
+    readonly first: First<T>
+    readonly tail: Path<T>
+}
diff --git a/fjs/types/btree/module.f.mjs b/fjs/types/btree/module.f.mjs
index e087a1631..de9b9d852 100644
--- a/fjs/types/btree/module.f.mjs
+++ b/fjs/types/btree/module.f.mjs
@@ -5,9 +5,9 @@
  */
 
 import { flat } from '../list/module.f.mjs'
-/** @import { List, Thunk } from '../list/module.f.mjs' */
+/** @import { List, Thunk } from '../list/types.ts' */
 import { map } from '../nullable/module.f.mjs'
-/** @import { TNode, Tree } from './types/module.f.mjs' */
+/** @import { TNode, Tree } from './types/types.ts' */
 
 /** @type {<T>(node: TNode<T>) => Thunk<T>} */
 const nodeValues
diff --git a/fjs/types/btree/proof.f.ts b/fjs/types/btree/proof.f.ts
index a66df1752..66a5b1c25 100644
--- a/fjs/types/btree/proof.f.ts
+++ b/fjs/types/btree/proof.f.ts
@@ -1,9 +1,10 @@
-import type { TNode } from './types/module.f.mjs'
+import type { TNode } from './types/types.ts'
 import { values } from './module.f.mjs'
 import { stringify as jsonStringify, type Unknown } from '../../media/json/module.f.ts'
 import { sort } from '../object/module.f.ts'
-import { cmp } from '../string/module.f.ts'
-import { next, toArray, type List, type Result } from '../list/module.f.mjs'
+import { cmp } from '../string/module.f.mjs'
+import type { List, Result } from '../list/types.ts'
+import { next, toArray } from '../list/module.f.mjs'
 import { set as setSet } from './set/module.f.mjs'
 import { value, find as findFind } from './find/module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
diff --git a/fjs/types/btree/remove/module.f.mjs b/fjs/types/btree/remove/module.f.mjs
index 77600dd73..3b1a24cf6 100644
--- a/fjs/types/btree/remove/module.f.mjs
+++ b/fjs/types/btree/remove/module.f.mjs
@@ -4,16 +4,16 @@
  * @module
  */
 import { collapseRoot } from '../types/module.f.mjs'
-/** @import { Leaf1, TNode, Branch1, Branch3, Branch5, Tree } from '../types/module.f.mjs' */
+/** @import { Leaf1, TNode, Branch1, Branch3, Branch5, Tree } from '../types/types.ts' */
 
-/** @import { Compare } from '../../function/compare/module.f.mjs' */
+/** @import { Compare } from '../../function/compare/types.ts' */
 
 import { find } from '../find/module.f.mjs'
-/** @import { Path, PathItem } from '../find/module.f.mjs' */
+/** @import { Path, PathItem } from '../find/types.ts' */
 
 import { fold, concat, next } from '../../list/module.f.mjs'
 
-/** @import { Tuple } from '../../array/module.f.mjs' */
+/** @import { Tuple } from '../../array/types.ts' */
 
 import { map } from '../../nullable/module.f.mjs'
 
diff --git a/fjs/types/btree/remove/proof.f.ts b/fjs/types/btree/remove/proof.f.ts
index 8edbd60d5..7f03924b2 100644
--- a/fjs/types/btree/remove/proof.f.ts
+++ b/fjs/types/btree/remove/proof.f.ts
@@ -1,7 +1,7 @@
 import { nodeRemove } from './module.f.mjs'
-import type { TNode } from '../types/module.f.mjs'
+import type { TNode } from '../types/types.ts'
 import { set as setSet } from '../set/module.f.mjs'
-import { cmp } from '../../string/module.f.ts'
+import { cmp } from '../../string/module.f.mjs'
 import { stringify } from '../../../media/json/module.f.ts'
 import { sort } from '../../object/module.f.ts'
 import { assertEq, assertNotNullish } from '../../../asserts/module.f.mjs'
diff --git a/fjs/types/btree/set/module.f.mjs b/fjs/types/btree/set/module.f.mjs
index 1f2a8b8c0..9337a6d9a 100644
--- a/fjs/types/btree/set/module.f.mjs
+++ b/fjs/types/btree/set/module.f.mjs
@@ -4,12 +4,12 @@
  * @module
  */
 import { collapseRoot } from '../types/module.f.mjs'
-/** @import { Branch1, Branch3, Branch5, Branch7, TNode, Tree } from '../types/module.f.mjs' */
+/** @import { Branch1, Branch3, Branch5, Branch7, TNode, Tree } from '../types/types.ts' */
 
 import { find } from '../find/module.f.mjs'
-/** @import { First, PathItem, Result } from '../find/module.f.mjs' */
+/** @import { First, PathItem, Result } from '../find/types.ts' */
 
-/** @import { Compare } from '../../function/compare/module.f.mjs' */
+/** @import { Compare } from '../../function/compare/types.ts' */
 
 import { fold } from '../../list/module.f.mjs'
 
diff --git a/fjs/types/btree/set/proof.f.ts b/fjs/types/btree/set/proof.f.ts
index d4e80cca8..57148260f 100644
--- a/fjs/types/btree/set/proof.f.ts
+++ b/fjs/types/btree/set/proof.f.ts
@@ -1,6 +1,6 @@
 import { set as setSet } from './module.f.mjs'
-import type { TNode } from '../types/module.f.mjs'
-import { cmp } from '../../string/module.f.ts'
+import type { TNode } from '../types/types.ts'
+import { cmp } from '../../string/module.f.mjs'
 import { stringify } from '../../../media/json/module.f.ts'
 import { sort } from '../../object/module.f.ts'
 import { assertEq } from '../../../asserts/module.f.mjs'
diff --git a/fjs/types/btree/types/module.f.mjs b/fjs/types/btree/types/module.f.mjs
index bb3a559f2..0f9e798c7 100644
--- a/fjs/types/btree/types/module.f.mjs
+++ b/fjs/types/btree/types/module.f.mjs
@@ -1,49 +1,10 @@
 /**
- * Shared type definitions for persistent B-tree modules.
+ * Node helpers shared by the persistent B-tree modules. The node types
+ * themselves live in `./types.ts`.
  *
  * @module
  */
-/** @import { Tuple } from '../../array/module.f.mjs' */
-
-/**
- * @template T
- * @typedef {Tuple<1, T>} Leaf1
- */
-
-/**
- * @template T
- * @typedef {Tuple<2, T>} Leaf2
- */
-
-/**
- * @template T
- * @typedef {readonly[TNode<T>, T, TNode<T>]} Branch3
- */
-
-/**
- * @template T
- * @typedef {readonly[TNode<T>, T, TNode<T>, T, TNode<T>]} Branch5
- */
-
-/**
- * @template T
- * @typedef {Leaf1<T> | Leaf2<T> | Branch3<T> | Branch5<T>} TNode
- */
-
-/**
- * @template T
- * @typedef {TNode<T> | null} Tree
- */
-
-/**
- * @template T
- * @typedef {readonly[TNode<T>]} Branch1
- */
-
-/**
- * @template T
- * @typedef {readonly[...Branch5<T>, T, TNode<T>]} Branch7
- */
+/** @import { Branch1, Branch3, Branch5, TNode } from './types.ts' */
 
 /**
  * Demotes a single-child branch root to its only child.
diff --git a/fjs/types/btree/types/types.ts b/fjs/types/btree/types/types.ts
new file mode 100644
index 000000000..d16c93e71
--- /dev/null
+++ b/fjs/types/btree/types/types.ts
@@ -0,0 +1,23 @@
+/**
+ * Shared type definitions for persistent B-tree modules.
+ *
+ * @module
+ */
+
+import type { Tuple } from '../../array/types.ts'
+
+export type Leaf1<T> = Tuple<1, T>
+
+export type Leaf2<T> = Tuple<2, T>
+
+export type Branch3<T> = readonly [TNode<T>, T, TNode<T>]
+
+export type Branch5<T> = readonly [TNode<T>, T, TNode<T>, T, TNode<T>]
+
+export type TNode<T> = Leaf1<T> | Leaf2<T> | Branch3<T> | Branch5<T>
+
+export type Tree<T> = TNode<T> | null
+
+export type Branch1<T> = readonly [TNode<T>]
+
+export type Branch7<T> = readonly [...Branch5<T>, T, TNode<T>]
diff --git a/fjs/types/byte_set/module.f.ts b/fjs/types/byte_set/module.f.ts
index 7c8bc6688..4c0fbf5e0 100644
--- a/fjs/types/byte_set/module.f.ts
+++ b/fjs/types/byte_set/module.f.ts
@@ -4,7 +4,7 @@
  * @module
  */
 import { compose } from '../function/module.f.mjs'
-import type { RangeMap } from '../range_map/module.f.mjs'
+import type { RangeMap } from '../range_map/types.ts'
 import type { SortedSet } from '../sorted_set/module.f.ts'
 import { reverse, countdown, flat, map } from '../list/module.f.mjs'
 
diff --git a/fjs/types/function/compare/module.f.mjs b/fjs/types/function/compare/module.f.mjs
index 2cab3d8ac..e2c5d1a25 100644
--- a/fjs/types/function/compare/module.f.mjs
+++ b/fjs/types/function/compare/module.f.mjs
@@ -3,19 +3,8 @@
  *
  * @module
  */
-/** @import { Index, Tuple } from '../../array/module.f.mjs' */
-
-/** @typedef {-1 | 0 | 1} Sign */
-
-/**
- * @template T
- * @typedef {(_: T) => Sign} Compare
- */
-
-/**
- * @template T
- * @typedef {(a: T) => Compare<T>} Cmp
- */
+/** @import { Index, Tuple } from '../../array/types.ts' */
+/** @import { Cmp1, Cmp2, Compare, Sign } from './types.ts' */
 
 /** @type {<T>(cmp: Compare<T>) => (value: T) => Index<3>} */
 export const index3
@@ -27,19 +16,6 @@ export const index5 = cmp => ([v0, v1]) => {
     return /** @type {Index<5>} */(_0 <= 0 ? _0 + 1 : cmp(v1) + 3)
 }
 
-/** @typedef {boolean | string | number | bigint} Cmp1 */
-
-/**
- * @template A
- * @template B
- * @typedef {[A, B] extends [boolean, boolean] ? boolean :
- *  [A, B] extends [string, string] ? string :
- *  [A, B] extends [number, number] ? number :
- *  [A, B] extends [bigint, bigint] ? bigint :
- *  never
- * } Cmp2
- */
-
 /** @type {<A extends Cmp1>(a: A) => <B extends Cmp2<A, B>>(b: B) => Sign} */
 export const cmp = a => b =>
     /** @type {any} */(a) < b ? -1 : /** @type {any} */(a) > b ? 1 : 0
diff --git a/fjs/types/function/compare/types.ts b/fjs/types/function/compare/types.ts
new file mode 100644
index 000000000..dec10fca7
--- /dev/null
+++ b/fjs/types/function/compare/types.ts
@@ -0,0 +1,20 @@
+/**
+ * Comparison function types.
+ *
+ * @module
+ */
+
+export type Sign = -1 | 0 | 1
+
+export type Compare<T> = (_: T) => Sign
+
+export type Cmp<T> = (a: T) => Compare<T>
+
+export type Cmp1 = boolean | string | number | bigint
+
+export type Cmp2<A, B> =
+    [A, B] extends [boolean, boolean] ? boolean :
+    [A, B] extends [string, string] ? string :
+    [A, B] extends [number, number] ? number :
+    [A, B] extends [bigint, bigint] ? bigint :
+    never
diff --git a/fjs/types/function/module.f.mjs b/fjs/types/function/module.f.mjs
index 92682f2bf..974e4f509 100644
--- a/fjs/types/function/module.f.mjs
+++ b/fjs/types/function/module.f.mjs
@@ -1,9 +1,4 @@
-/**
- * A generic function type.
- *
- * @template I, O
- * @typedef {(_: I) => O} Func
- */
+/** @import { Func, Fn } from './types.ts' */
 
 /**
  * A postfix compose function.
@@ -26,16 +21,6 @@ export const identity = value => value
  */
 export const flip = f => b => a => f(a)(b)
 
-/**
- * A functional utility type that enables seamless chaining of transformations.
- *
- * @template I, O
- * @typedef {{
- *   readonly result: Func<I, O>
- *   readonly map: <T>(g: Func<O, T>) => Fn<I, T>
- * }} Fn
- */
-
 /**
  * Creates an `Fn` instance from a function, enabling chaining of transformations.
  *
diff --git a/fjs/types/function/operator/module.f.mjs b/fjs/types/function/operator/module.f.mjs
index 67d4e9018..aec7e66eb 100644
--- a/fjs/types/function/operator/module.f.mjs
+++ b/fjs/types/function/operator/module.f.mjs
@@ -4,23 +4,7 @@
  * @module
  */
 
-/**
- * @template A
- * @template B
- * @template R
- * @typedef {(a: A) => (b: B) => R} Binary
- */
-
-/**
- * @template I
- * @template O
- * @typedef {Binary<I, O, O>} Fold
- */
-
-/**
- * @template T
- * @typedef {Fold<T, T>} Reduce
- */
+/** @import { Fold, Reduce, Scan, StateScan, Unary } from './types.ts' */
 
 /** @type {(separator: string) => Reduce<string>} */
 export const join = separator => value => prior =>
@@ -29,20 +13,9 @@ export const join = separator => value => prior =>
 /** @type {Reduce<string>} */
 export const concat = i => acc => `${acc}${i}`
 
-/**
- * @template T
- * @template R
- * @typedef {(value: T) => R} Unary
- */
-
 /** @type {Unary<boolean, boolean>} */
 export const logicalNot = v => !v
 
-/**
- * @template T
- * @typedef {Binary<T, T, boolean>} Equal
- */
-
 /**
  * See also `Object.is` which should be used for deep comparison instead of the `structEqual`.
  * TODO: add `binaryEqual = a => b => Object.is(a, b)`.
@@ -51,44 +24,6 @@ export const logicalNot = v => !v
  */
 export const strictEqual = a => b => a === b
 
-/**
- * @template I
- * @template O
- * @typedef {(input: I) => readonly[O, Scan<I,O>]} Scan
- */
-
-/**
- * One step of a stream transducer: given an `input` symbol and the `prior`
- * state, produce an `output` and the next state. It both maps an input stream
- * to an output stream and threads state, so it models tokenizers, decoders, and
- * other stream-to-stream stages.
- *
- * This is the *shape* of a [Mealy machine](https://en.wikipedia.org/wiki/Mealy_machine)
- * — a [finite-state transducer](https://en.wikipedia.org/wiki/Finite-state_transducer)
- * — but only its signature. The state `S` (and `I`, `O`) is an arbitrary type,
- * not a finite set, so a `StateScan` is strictly more expressive than a Mealy
- * machine — its power is the power of `S`:
- * - a finite `S`/`I`/`O` recovers the classical finite-state machine (e.g. the
- *   DFA states in `../../../fsm/module.f.ts`);
- * - an `S` that is a stack makes it a
- *   [pushdown / stack machine](https://en.wikipedia.org/wiki/Pushdown_automaton)
- *   (context-free power — balanced brackets, nested structure, the AST tier);
- * - an unbounded `S` like `bigint` can count, which no finite automaton can.
- *
- * And `O` may be a list (0+ symbols per input), not the single symbol strict
- * Mealy emits. (Functional/coalgebraic usage still calls this `(input, state)
- * => [output, state]` shape a "Mealy machine", finiteness aside.)
- *
- * A {@link Fold} is the output-less special case (state only); driving a
- * `StateScan` over a `List` is `stateScan` in `../../list/module.f.ts`, and
- * {@link stateScanToScan} hides the state to recover a {@link Scan}.
- *
- * @template I
- * @template S
- * @template O
- * @typedef {(input: I, prior: S) => readonly[O, S]} StateScan
- */
-
 /** @type {<I, S, O>(op: StateScan<I, S, O>) => (prior: S) => Scan<I, O>} */
 export const stateScanToScan = op => prior => i => {
     const [o, s] = op(i, prior)
diff --git a/fjs/types/function/operator/types.ts b/fjs/types/function/operator/types.ts
new file mode 100644
index 000000000..e69365564
--- /dev/null
+++ b/fjs/types/function/operator/types.ts
@@ -0,0 +1,46 @@
+/**
+ * Common higher-order operator type aliases.
+ *
+ * @module
+ */
+
+export type Binary<A, B, R> = (a: A) => (b: B) => R
+
+export type Fold<I, O> = Binary<I, O, O>
+
+export type Reduce<T> = Fold<T, T>
+
+export type Unary<T, R> = (value: T) => R
+
+export type Equal<T> = Binary<T, T, boolean>
+
+export type Scan<I, O> = (input: I) => readonly [O, Scan<I, O>]
+
+/**
+ * One step of a stream transducer: given an `input` symbol and the `prior`
+ * state, produce an `output` and the next state. It both maps an input stream
+ * to an output stream and threads state, so it models tokenizers, decoders, and
+ * other stream-to-stream stages.
+ *
+ * This is the *shape* of a [Mealy machine](https://en.wikipedia.org/wiki/Mealy_machine)
+ * — a [finite-state transducer](https://en.wikipedia.org/wiki/Finite-state_transducer)
+ * — but only its signature. The state `S` (and `I`, `O`) is an arbitrary type,
+ * not a finite set, so a `StateScan` is strictly more expressive than a Mealy
+ * machine — its power is the power of `S`:
+ * - a finite `S`/`I`/`O` recovers the classical finite-state machine (e.g. the
+ *   DFA states in `../../../fsm/module.f.ts`);
+ * - an `S` that is a stack makes it a
+ *   [pushdown / stack machine](https://en.wikipedia.org/wiki/Pushdown_automaton)
+ *   (context-free power — balanced brackets, nested structure, the AST tier);
+ * - an unbounded `S` like `bigint` can count, which no finite automaton can.
+ *
+ * And `O` may be a list (0+ symbols per input), not the single symbol strict
+ * Mealy emits. (Functional/coalgebraic usage still calls this `(input, state)
+ * => [output, state]` shape a "Mealy machine", finiteness aside.)
+ *
+ * A {@link Fold} is the output-less special case (state only); driving a
+ * `StateScan` over a `List` is `stateScan` in `../../list/module.f.mjs`, and
+ * {@link ./module.f.mjs | `stateScanToScan`} hides the state to recover a
+ * {@link Scan}.
+ */
+export type StateScan<I, S, O> = (input: I, prior: S) => readonly [O, S]
diff --git a/fjs/types/function/types.ts b/fjs/types/function/types.ts
new file mode 100644
index 000000000..652102337
--- /dev/null
+++ b/fjs/types/function/types.ts
@@ -0,0 +1,18 @@
+/**
+ * Types for function composition.
+ *
+ * @module
+ */
+
+/**
+ * A generic function type.
+ */
+export type Func<I, O> = (_: I) => O
+
+/**
+ * A functional utility type that enables seamless chaining of transformations.
+ */
+export type Fn<I, O> = {
+    readonly result: Func<I, O>
+    readonly map: <T>(g: Func<O, T>) => Fn<I, T>
+}
diff --git a/fjs/types/list/module.f.mjs b/fjs/types/list/module.f.mjs
index fd5a7cfa6..8571e85a6 100644
--- a/fjs/types/list/module.f.mjs
+++ b/fjs/types/list/module.f.mjs
@@ -4,7 +4,7 @@
  * @module
  */
 import { identity, fn, compose } from '../function/module.f.mjs'
-/** @import { Nullable } from '../nullable/module.f.mjs' */
+/** @import { Nullable } from '../nullable/types.ts' */
 import {
     addition,
     logicalNot,
@@ -13,50 +13,8 @@ import {
     foldToScan,
     reduceToScan,
 } from '../function/operator/module.f.mjs'
-/** @import {Scan, StateScan, Fold, Reduce, Equal} from '../function/operator/module.f.mjs' */
-
-/**
- * @template T
- * @typedef {NotLazy<T> | Thunk<T>} List
- */
-
-/**
- * @template T
- * @typedef {Result<T> |
- *   Concat<T> |
- *   readonly T[]
- * } NotLazy
- */
-
-/** @typedef {null} Empty */
-
-/**
- * @template T
- * @typedef {Empty | NonEmpty<T>} Result
- */
-
-/**
- * @template T
- * @typedef {() => List<T>} Thunk
- */
-
-/**
- * See also https://en.wikipedia.org/wiki/Cons#Lists
- *
- * @template T
- * @typedef {{
- *  readonly first: T
- *  readonly tail: List<T>
- * }} NonEmpty
- */
-
-/**
- * @template T
- * @typedef {{
- *  readonly head: List<T>
- *  readonly tail: List<T>
- * }} Concat
- */
+/** @import {Scan, StateScan, Fold, Reduce, Equal} from '../function/operator/types.ts' */
+/** @import { Accumulator, Concat, Entry, List, NonEmpty, NotLazy, Result, Thunk } from './types.ts' */
 
 export const fromArrayLike =
     /**
@@ -274,24 +232,6 @@ export const fold = op => init => compose(foldScan(op)(init))(last(init))
 /** @type {<T>(op: Reduce<T>) => <D>(def: D) => (input: List<T>) => D | T} */
 export const reduce = op => def => compose(scan(reduceToScan(op)))(last(def))
 
-/**
- * A fold that can bail out early, packaged as plain data.
- *
- * `init` is the starting state, `update` advances the state by one item and
- * returns `null` to abort the whole fold, and `end` finalizes the surviving
- * state into a result. Keeping the three parts together lets `tryFold` drive
- * any short-circuiting accumulation without knowing its domain.
- *
- * @template I
- * @template T
- * @template R
- * @typedef {{
- *  readonly init: T
- *  readonly update: (i: I, state: T) => Nullable<T>
- *  readonly end: (state: T) => R
- * }} Accumulator
- */
-
 /**
  * Folds `input` with an {@link Accumulator}, short-circuiting to `null` the
  * moment `update` rejects an item; otherwise finalizes with `end`. This is the
@@ -327,11 +267,6 @@ const sum = reduce(addition)(0)
 /** @type {<T>(input: List<T>) => number} */
 export const length = input => sum(lengthList(input))
 
-/**
- * @template T
- * @typedef {readonly [number, T]} Entry
- */
-
 /** @type {<T>(value: T, index: number) => readonly [Entry<T>, number]} */
 const entryOperator = (value, index) => [[index, value], index + 1]
 
diff --git a/fjs/types/list/proof.f.ts b/fjs/types/list/proof.f.ts
index 6cca9eb4e..ba60716c3 100644
--- a/fjs/types/list/proof.f.ts
+++ b/fjs/types/list/proof.f.ts
@@ -1,33 +1,5 @@
-import {
-    length,
-    concat,
-    countdown,
-    cycle,
-    drop,
-    dropWhile,
-    entries,
-    every,
-    filter,
-    find,
-    flat,
-    flatMap,
-    map,
-    next,
-    reduce,
-    reverse,
-    scan,
-    some,
-    take,
-    takeWhile,
-    toArray,
-    zip,
-    type List,
-    first,
-    filterMap,
-    isEmpty,
-    equal,
-    tryFold
-} from './module.f.mjs'
+import type { List } from './types.ts'
+import { length, concat, countdown, cycle, drop, dropWhile, entries, every, filter, find, flat, flatMap, map, next, reduce, reverse, scan, some, take, takeWhile, toArray, zip, first, filterMap, isEmpty, equal, tryFold } from './module.f.mjs'
 import { stringify, type Unknown } from '../../media/json/module.f.ts'
 import { sort } from '../object/module.f.ts'
 import { addition, strictEqual, reduceToScan } from '../function/operator/module.f.mjs'
diff --git a/fjs/types/list/todo/simplify-list-type.md b/fjs/types/list/todo/simplify-list-type.md
index bd586b224..ceb984241 100644
--- a/fjs/types/list/todo/simplify-list-type.md
+++ b/fjs/types/list/todo/simplify-list-type.md
@@ -5,7 +5,7 @@
 
 ### Problem
 
-`List` (`fjs/types/list/module.f.mjs`) currently has four shapes behind two
+`List` (`fjs/types/list/types.ts`) currently has four shapes behind two
 type aliases:
 
 ```ts
diff --git a/fjs/types/list/types.ts b/fjs/types/list/types.ts
new file mode 100644
index 000000000..a564eca58
--- /dev/null
+++ b/fjs/types/list/types.ts
@@ -0,0 +1,46 @@
+/**
+ * Types for the immutable list data structure.
+ *
+ * @module
+ */
+
+import type { Nullable } from '../nullable/types.ts'
+
+export type List<T> = NotLazy<T> | Thunk<T>
+
+export type NotLazy<T> = Result<T> | Concat<T> | readonly T[]
+
+export type Empty = null
+
+export type Result<T> = Empty | NonEmpty<T>
+
+export type Thunk<T> = () => List<T>
+
+/**
+ * See also https://en.wikipedia.org/wiki/Cons#Lists
+ */
+export type NonEmpty<T> = {
+    readonly first: T
+    readonly tail: List<T>
+}
+
+export type Concat<T> = {
+    readonly head: List<T>
+    readonly tail: List<T>
+}
+
+/**
+ * A fold that can bail out early, packaged as plain data.
+ *
+ * `init` is the starting state, `update` advances the state by one item and
+ * returns `null` to abort the whole fold, and `end` finalizes the surviving
+ * state into a result. Keeping the three parts together lets `tryFold` drive
+ * any short-circuiting accumulation without knowing its domain.
+ */
+export type Accumulator<I, T, R> = {
+    readonly init: T
+    readonly update: (i: I, state: T) => Nullable<T>
+    readonly end: (state: T) => R
+}
+
+export type Entry<T> = readonly [number, T]
diff --git a/fjs/types/nibble_set/module.f.mjs b/fjs/types/nibble_set/module.f.mjs
index f09d563ed..e0f1706d0 100644
--- a/fjs/types/nibble_set/module.f.mjs
+++ b/fjs/types/nibble_set/module.f.mjs
@@ -15,9 +15,7 @@
  * @module
  */
 
-/** A set of nibbles as a 16-bit mask. JSON-serializable. @typedef {number} NibbleSet */
-
-/** A 4-bit value, `0..15`. @typedef {number} Nibble */
+/** @import { Nibble, NibbleSet } from './types.ts' */
 
 export const empty = 0
 
diff --git a/fjs/types/nibble_set/types.ts b/fjs/types/nibble_set/types.ts
new file mode 100644
index 000000000..e83e40de7
--- /dev/null
+++ b/fjs/types/nibble_set/types.ts
@@ -0,0 +1,11 @@
+/**
+ * Types for compact 4-bit membership tracking.
+ *
+ * @module
+ */
+
+/** A set of nibbles as a 16-bit mask. JSON-serializable. */
+export type NibbleSet = number
+
+/** A 4-bit value, `0..15`. */
+export type Nibble = number
diff --git a/fjs/types/nominal/module.f.mjs b/fjs/types/nominal/module.f.mjs
index d87162d59..331e9108c 100644
--- a/fjs/types/nominal/module.f.mjs
+++ b/fjs/types/nominal/module.f.mjs
@@ -5,18 +5,7 @@
  */
 
 import { identity } from "../function/module.f.mjs"
-
-/**
- * Nominal type.
- *
- * It doesn't allow `===` between different nominal types.
- * It doesn't allow `<`, `>`, `<=`, `>=` comparisons at all.
- *
- * @template {string} N
- * @template {string} R
- * @template B
- * @typedef {symbol & {[k in N]: readonly[R, B]}} Nominal
- */
+/** @import { Nominal } from './types.ts' */
 
 export const asNominal =
     /** @type {<N extends string, R extends string, B>(b: B) => Nominal<N, R, B>} */
diff --git a/fjs/types/nominal/proof.f.ts b/fjs/types/nominal/proof.f.ts
index 126214038..ed35f2982 100644
--- a/fjs/types/nominal/proof.f.ts
+++ b/fjs/types/nominal/proof.f.ts
@@ -1,4 +1,5 @@
-import { asBase, asNominal, type Nominal } from "./module.f.mjs"
+import type { Nominal } from "./types.ts"
+import { asBase, asNominal } from "./module.f.mjs"
 import { assert } from '../../asserts/module.f.mjs'
 
 declare const noCompareBrand: unique symbol
diff --git a/fjs/types/nominal/types.ts b/fjs/types/nominal/types.ts
new file mode 100644
index 000000000..8e335e462
--- /dev/null
+++ b/fjs/types/nominal/types.ts
@@ -0,0 +1,14 @@
+/**
+ * Types for nominal typing (branded TypeScript types).
+ *
+ * @module
+ */
+
+/**
+ * Nominal type.
+ *
+ * It doesn't allow `===` between different nominal types.
+ * It doesn't allow `<`, `>`, `<=`, `>=` comparisons at all.
+ */
+export type Nominal<N extends string, R extends string, B> =
+    symbol & { [k in N]: readonly [R, B] }
diff --git a/fjs/types/nullable/module.f.mjs b/fjs/types/nullable/module.f.mjs
index c7e72c03f..797323181 100644
--- a/fjs/types/nullable/module.f.mjs
+++ b/fjs/types/nullable/module.f.mjs
@@ -5,12 +5,8 @@
  */
 import { assert } from '../../asserts/module.f.mjs'
 import { fn } from '../function/module.f.mjs'
-/** @import { Option } from '../option/module.f.mjs' */
-
-/**
- * @template T
- * @typedef {T | null} Nullable
- */
+/** @import { Option } from '../option/types.ts' */
+/** @import { Nullable } from './types.ts' */
 
 /**
  * @type {<T, R>(f: (value: T) => R) => (value: Nullable<T>) => Nullable<R>}
diff --git a/fjs/types/nullable/types.ts b/fjs/types/nullable/types.ts
new file mode 100644
index 000000000..81b3ce6a2
--- /dev/null
+++ b/fjs/types/nullable/types.ts
@@ -0,0 +1,7 @@
+/**
+ * Types for nullable (`null`) value handling.
+ *
+ * @module
+ */
+
+export type Nullable<T> = T | null
diff --git a/fjs/types/number/module.f.mjs b/fjs/types/number/module.f.mjs
index 8acb209d1..1f9191a96 100644
--- a/fjs/types/number/module.f.mjs
+++ b/fjs/types/number/module.f.mjs
@@ -6,11 +6,11 @@
  */
 
 import { reduce } from '../list/module.f.mjs'
-/** @import { List } from '../list/module.f.mjs' */
+/** @import { List } from '../list/types.ts' */
 import { addition } from '../function/operator/module.f.mjs'
-/** @import { Reduce } from '../function/operator/module.f.mjs' */
+/** @import { Reduce } from '../function/operator/types.ts' */
 import { cmp as uCmp, min as uMin, max as uMax } from '../function/compare/module.f.mjs'
-/** @import { Sign } from '../function/compare/module.f.mjs' */
+/** @import { Sign } from '../function/compare/types.ts' */
 import { fold } from '../../common/monoid/module.f.mjs'
 
 /** @type {(input: List<number>) => number} */
diff --git a/fjs/types/object/module.f.ts b/fjs/types/object/module.f.ts
index fa7f32864..dc6f21414 100644
--- a/fjs/types/object/module.f.ts
+++ b/fjs/types/object/module.f.ts
@@ -6,10 +6,15 @@
  *
  * @module
  */
+
+import type { List } from '../list/types.ts'
+import type { Nullable } from '../nullable/types.ts'
+import type { OrderedMap } from '../ordered_map/types.ts'
+
 import { isArray } from '../array/module.f.mjs'
-import { iterable, type List } from '../list/module.f.mjs'
-import { fromUndefined, type Nullable } from '../nullable/module.f.mjs'
-import { entries as mapEntries, fromEntries as mapFromEntries, type OrderedMap } from '../ordered_map/module.f.ts'
+import { iterable } from '../list/module.f.mjs'
+import { fromUndefined } from '../nullable/module.f.mjs'
+import { entries as mapEntries, fromEntries as mapFromEntries } from '../ordered_map/module.f.mjs'
 
 const { getOwnPropertyDescriptor, fromEntries: objectFromEntries } = Object
 
diff --git a/fjs/types/object/proof.f.ts b/fjs/types/object/proof.f.ts
index 0d082a950..b37859392 100644
--- a/fjs/types/object/proof.f.ts
+++ b/fjs/types/object/proof.f.ts
@@ -1,7 +1,8 @@
 import { at } from './module.f.ts'
 import type { OptionalMap, RequiredMap, StringMap } from './module.f.ts'
-import { assertEq, type Assert } from '../../asserts/module.f.mjs'
-import type { Equal } from '../ts/module.f.mjs'
+import { assertEq } from '../../asserts/module.f.mjs'
+import type { Assert } from '../../asserts/types.ts'
+import type { Equal } from '../ts/types.ts'
 
 type _StringMapIsOptional = Assert<Equal<
     StringMap<bigint>,
diff --git a/fjs/types/option/module.f.mjs b/fjs/types/option/types.ts
similarity index 70%
rename from fjs/types/option/module.f.mjs
rename to fjs/types/option/types.ts
index 70a8cf301..fc7937afb 100644
--- a/fjs/types/option/module.f.mjs
+++ b/fjs/types/option/types.ts
@@ -6,7 +6,5 @@
 
 /**
  * Represents an optional value as an empty tuple or a tuple with one value.
- *
- * @template T
- * @typedef {readonly [T] | readonly []} Option
  */
+export type Option<T> = readonly [T] | readonly []
diff --git a/fjs/types/ordered_map/module.f.mjs b/fjs/types/ordered_map/module.f.mjs
new file mode 100644
index 000000000..ac6d8d52b
--- /dev/null
+++ b/fjs/types/ordered_map/module.f.mjs
@@ -0,0 +1,54 @@
+/**
+ * Ordered map operations with deterministic key traversal.
+ *
+ * @module
+ */
+
+import { value, find } from '../btree/find/module.f.mjs'
+import { set } from '../btree/set/module.f.mjs'
+import { remove as btreeRemove } from '../btree/remove/module.f.mjs'
+import { values } from '../btree/module.f.mjs'
+/** @import { Sign } from '../function/compare/types.ts' */
+import { cmp } from '../string/module.f.mjs'
+/** @import { List } from '../list/types.ts' */
+import { fold } from '../list/module.f.mjs'
+/** @import { Reduce } from '../function/operator/types.ts' */
+/** @import { Entry, OrderedMap } from './types.ts' */
+
+/** @type {(a: string) => <T>(b: Entry<T>) => Sign} */
+const keyCmp = a => ([b]) => cmp(a)(b)
+
+/** @type {(name: string) => <T>(map: OrderedMap<T>) => T | null} */
+export const at = name => map => {
+    if (map === null) { return null }
+    const result = value(find(keyCmp(name))(map).first)
+    return result === null ? null : result[1]
+}
+
+/** @type {<T>(reduce: Reduce<T>) => (entry: Entry<T>) => (map: OrderedMap<T>) => OrderedMap<T>} */
+const setReduceEntry = reduce => entry =>
+    set(keyCmp(entry[0]))(old => old === null ? entry : [old[0], reduce(old[1])(entry[1])])
+
+/** @type {<T>(reduce: Reduce<T>) => (name: string) => (value: T) => (map: OrderedMap<T>) => OrderedMap<T>} */
+export const setReduce =
+    reduce => name => value => setReduceEntry(reduce)([name, value])
+
+/** @type {<T>(a: T) => (b: T) => T} */
+const replace = () => b => b
+
+/** @type {(name: string) => <T>(value: T) => (map: OrderedMap<T>) => OrderedMap<T>} */
+export const setReplace =
+    name => value => setReduceEntry(replace)([name, value])
+
+/** @type {<T>(map: OrderedMap<T>) => List<Entry<T>>} */
+export const entries = values
+
+/** @type {<T>(entries: List<Entry<T>>) => OrderedMap<T>} */
+export const fromEntries =
+    fold(setReduceEntry(replace))(null)
+
+/** @type {(name: string) => <T>(map: OrderedMap<T>) => OrderedMap<T>} */
+export const remove =
+    name => btreeRemove(keyCmp(name))
+
+export const empty = null
diff --git a/fjs/types/ordered_map/module.f.ts b/fjs/types/ordered_map/module.f.ts
deleted file mode 100644
index c16516b58..000000000
--- a/fjs/types/ordered_map/module.f.ts
+++ /dev/null
@@ -1,59 +0,0 @@
-/**
- * Ordered map operations with deterministic key traversal.
- *
- * @module
- */
-import type { Tree } from '../btree/types/module.f.mjs'
-import { value, find } from '../btree/find/module.f.mjs'
-import { set } from '../btree/set/module.f.mjs'
-import { remove as btreeRemove } from '../btree/remove/module.f.mjs'
-import { values } from '../btree/module.f.mjs'
-import type { Sign } from '../function/compare/module.f.mjs'
-import { cmp } from '../string/module.f.ts'
-import { fold, type List } from '../list/module.f.mjs'
-import type { Reduce } from '../function/operator/module.f.mjs'
-
-export type Entry<T> = readonly [string, T]
-
-export type OrderedMap<T> = Tree<Entry<T>>
-
-const keyCmp: (a: string) => <T>(b: Entry<T>) => Sign
-    = a => ([b]) => cmp(a)(b)
-
-export const at
-    = (name: string) => <T>(map: OrderedMap<T>): T | null => {
-        if (map === null) { return null }
-        const result = value(find(keyCmp(name))(map).first)
-        return result === null ? null : result[1]
-    }
-
-const setReduceEntry
-    : <T>(reduce: Reduce<T>) => (entry: Entry<T>) => (map: OrderedMap<T>) => OrderedMap<T>
-    = reduce => entry =>
-        set(keyCmp(entry[0]))(old => old === null ? entry : [old[0], reduce(old[1])(entry[1])])
-
-export const setReduce
-    : <T>(reduce: Reduce<T>) => (name: string) => (value: T) => (map: OrderedMap<T>) => OrderedMap<T>
-    = reduce => name => value => setReduceEntry(reduce)([name, value])
-
-const replace
-    : <T>(a: T) => (b: T) => T
-    = () => b => b
-
-export const setReplace
-    : (name: string) => <T>(value: T) => (map: OrderedMap<T>) => OrderedMap<T>
-    = name => value => setReduceEntry(replace)([name, value])
-
-export const entries
-    : <T>(map: OrderedMap<T>) => List<Entry<T>>
-    = values
-
-export const fromEntries
-    : <T>(entries: List<Entry<T>>) => OrderedMap<T>
-    = fold(setReduceEntry(replace))(null)
-
-export const remove
-    : (name: string) => <T>(map: OrderedMap<T>) => OrderedMap<T>
-    = name => btreeRemove(keyCmp(name))
-
-export const empty = null
diff --git a/fjs/types/ordered_map/proof.f.ts b/fjs/types/ordered_map/proof.f.mjs
similarity index 84%
rename from fjs/types/ordered_map/proof.f.ts
rename to fjs/types/ordered_map/proof.f.mjs
index 8a2eb79a9..27e90be1a 100644
--- a/fjs/types/ordered_map/proof.f.ts
+++ b/fjs/types/ordered_map/proof.f.mjs
@@ -1,4 +1,5 @@
-import { at, setReplace, setReduce, empty, entries, remove, fromEntries, type OrderedMap } from './module.f.ts'
+import { at, setReplace, setReduce, empty, entries, remove, fromEntries } from './module.f.mjs'
+/** @import { OrderedMap } from './types.ts' */
 import { toArray } from '../list/module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
 
@@ -44,7 +45,7 @@ export const proof = {
             m = remove('Hello world!')(m)
             assertEq(at('Hello world!')(m), null)
 
-            m = setReduce((a: number) => (b: number) => a + b)('a')(43)(m)
+            m = setReduce((/** @type {number} */a) => (/** @type {number} */b) => a + b)('a')(43)(m)
             assertEq(at('a')(m), 44)
         },
         () => {
@@ -58,18 +59,20 @@ export const proof = {
         },
     ],
     fromEntries: () => {
-        const list: readonly (readonly [string, number])[] = [['a', 1], ['b', 2], ['c', 3]]
+        /** @type {readonly (readonly [string, number])[]} */
+        const list = [['a', 1], ['b', 2], ['c', 3]]
         const m = fromEntries(list)
         assertEq(at('a')(m), 1)
         assertEq(at('b')(m), 2)
         assertEq(at('c')(m), 3)
         assertEq(at('d')(m), null)
         // duplicate key: last one wins
-        const m2 = fromEntries([['x', 10], ['x', 20]] as const)
+        const m2 = fromEntries(/** @type {const} */([['x', 10], ['x', 20]]))
         assertEq(at('x')(m2), 20)
     },
     stress: () => {
-        let m: OrderedMap<number> = empty
+        /** @type {OrderedMap<number>} */
+        let m = empty
         for (let i = 0; i < 100_000; ++i) {
             m = setReplace((i * i).toString())(i)(m)
             /*
diff --git a/fjs/types/ordered_map/types.ts b/fjs/types/ordered_map/types.ts
new file mode 100644
index 000000000..22e15922e
--- /dev/null
+++ b/fjs/types/ordered_map/types.ts
@@ -0,0 +1,11 @@
+/**
+ * Types for the ordered map data structure.
+ *
+ * @module
+ */
+
+import type { Tree } from '../btree/types/types.ts'
+
+export type Entry<T> = readonly [string, T]
+
+export type OrderedMap<T> = Tree<Entry<T>>
diff --git a/fjs/types/patricia_trie/module.f.mjs b/fjs/types/patricia_trie/module.f.mjs
index 27d08894b..5e529b3b8 100644
--- a/fjs/types/patricia_trie/module.f.mjs
+++ b/fjs/types/patricia_trie/module.f.mjs
@@ -4,51 +4,7 @@
  * @module
  */
 
-/**
- * Merges two child identities into a parent. Values first, storage last in both params and return.
- *
- * @template S
- * @template T
- * @typedef {(a: T, b: T, storage: S) => readonly [T, S]} Create
- */
-
-/**
- * A leaf entry: `[sortKey, identity]`. The sort key is used only for XOR comparisons.
- *
- * @template T
- * @typedef {readonly [bigint, T]} Candidate
- */
-
-/**
- * @template T
- * @typedef {readonly Candidate<T>[]} InternalState
- */
-
-/**
- * Streaming state: `[storage, right-spine stack]`.
- *
- * @template S
- * @template T
- * @typedef {readonly [S, InternalState<T>]} State
- */
-
-/**
- * @template S
- * @template T
- * @typedef {{
- *  readonly push: (c: Candidate<T>, state: State<S, T>) => State<S, T>
- *  readonly end: (state: State<S, T>) => readonly [T | undefined, S]
- * }} PatriciaTrie
- *
- * @property push
- *
- * Add one leaf. Merges any tightly-coupled stack candidates before pushing.
- *
- * @property end
- *
- * Drain the stack right-to-left, returning the root identity and final storage.
- * Returns `undefined` as the root if no leaves were pushed.
- */
+/** @import { Candidate, Create, PatriciaTrie } from './types.ts' */
 
 /**
  * Creates a Patricia trie whose node merging is delegated to `create`.
diff --git a/fjs/types/patricia_trie/proof.f.mjs b/fjs/types/patricia_trie/proof.f.mjs
index 8031eaa5a..415376d6a 100644
--- a/fjs/types/patricia_trie/proof.f.mjs
+++ b/fjs/types/patricia_trie/proof.f.mjs
@@ -1,6 +1,6 @@
 import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { emptyState, patriciaTrie } from './module.f.mjs'
-/** @import { State } from './module.f.mjs' */
+/** @import { State } from './types.ts' */
 
 /** @typedef {readonly [bigint, bigint, bigint][]} _NodeList */
 
diff --git a/fjs/types/patricia_trie/types.ts b/fjs/types/patricia_trie/types.ts
new file mode 100644
index 000000000..cb36cf4e1
--- /dev/null
+++ b/fjs/types/patricia_trie/types.ts
@@ -0,0 +1,39 @@
+/**
+ * Types for the streaming Patricia trie.
+ *
+ * @module
+ */
+
+/**
+ * Merges two child identities into a parent. Values first, storage last in both
+ * params and return.
+ */
+export type Create<S, T> = (a: T, b: T, storage: S) => readonly [T, S]
+
+/**
+ * A leaf entry: `[sortKey, identity]`. The sort key is used only for XOR
+ * comparisons.
+ */
+export type Candidate<T> = readonly [bigint, T]
+
+export type InternalState<T> = readonly Candidate<T>[]
+
+/**
+ * Streaming state: `[storage, right-spine stack]`.
+ */
+export type State<S, T> = readonly [S, InternalState<T>]
+
+/**
+ * @property push
+ *
+ * Add one leaf. Merges any tightly-coupled stack candidates before pushing.
+ *
+ * @property end
+ *
+ * Drain the stack right-to-left, returning the root identity and final storage.
+ * Returns `undefined` as the root if no leaves were pushed.
+ */
+export type PatriciaTrie<S, T> = {
+    readonly push: (c: Candidate<T>, state: State<S, T>) => State<S, T>
+    readonly end: (state: State<S, T>) => readonly [T | undefined, S]
+}
diff --git a/fjs/types/phantom/module.f.ts b/fjs/types/phantom/types.ts
similarity index 100%
rename from fjs/types/phantom/module.f.ts
rename to fjs/types/phantom/types.ts
diff --git a/fjs/types/prime_field/module.f.mjs b/fjs/types/prime_field/module.f.mjs
index ce3d3ea81..1ab5d3ce8 100644
--- a/fjs/types/prime_field/module.f.mjs
+++ b/fjs/types/prime_field/module.f.mjs
@@ -7,43 +7,10 @@
  * @module
  */
 
-/** @import { Unary, Reduce } from '../bigint/module.f.mjs' */
+/** @import { Reduce, Unary } from '../bigint/types.ts' */
 import { repeat } from '../../common/monoid/module.f.mjs'
 import { assertNotNullish } from '../../asserts/module.f.mjs'
-
-/**
- * A type representing a prime field and its associated operations.
- *
- * @typedef {{
- *  readonly p: bigint
- *  readonly middle: bigint
- *  readonly max: bigint
- *  readonly neg: Unary
- *  readonly sub: Reduce
- *  readonly add: Reduce
- *  readonly abs: Unary
- *  readonly mul: Reduce
- *  readonly reciprocal: Unary
- *  readonly div: Reduce
- *  readonly pow: Reduce
- *  readonly pow2: Unary
- *  readonly pow3: Unary
- *  readonly reduce: Unary
- *  readonly quadRes: (x: bigint) => boolean
- * }} PrimeField
- *
- * @property reduce
- *
- * Reduces an arbitrary `bigint` into `[0, p)`.
- *
- * @property quadRes
- *
- * `true` when `x` is a square modulo `p`, including `0`.
- *
- * Nonzero values are tested with Euler's criterion:
- * `x^((p - 1) / 2) === 1 (mod p)`.
- * For `p === 2n`, both field elements are squares.
- */
+/** @import { PrimeField } from './types.ts' */
 
 /**
  * Creates a prime field with the specified prime modulus and associated operations.
diff --git a/fjs/types/prime_field/types.ts b/fjs/types/prime_field/types.ts
new file mode 100644
index 000000000..e09c3b81b
--- /dev/null
+++ b/fjs/types/prime_field/types.ts
@@ -0,0 +1,40 @@
+/**
+ * Types for prime field arithmetic over `bigint`.
+ *
+ * @module
+ */
+
+import type { Reduce, Unary } from '../bigint/types.ts'
+
+/**
+ * A type representing a prime field and its associated operations.
+ *
+ * @property reduce
+ *
+ * Reduces an arbitrary `bigint` into `[0, p)`.
+ *
+ * @property quadRes
+ *
+ * `true` when `x` is a square modulo `p`, including `0`.
+ *
+ * Nonzero values are tested with Euler's criterion:
+ * `x^((p - 1) / 2) === 1 (mod p)`.
+ * For `p === 2n`, both field elements are squares.
+ */
+export type PrimeField = {
+    readonly p: bigint
+    readonly middle: bigint
+    readonly max: bigint
+    readonly neg: Unary
+    readonly sub: Reduce
+    readonly add: Reduce
+    readonly abs: Unary
+    readonly mul: Reduce
+    readonly reciprocal: Unary
+    readonly div: Reduce
+    readonly pow: Reduce
+    readonly pow2: Unary
+    readonly pow3: Unary
+    readonly reduce: Unary
+    readonly quadRes: (x: bigint) => boolean
+}
diff --git a/fjs/types/range/module.f.mjs b/fjs/types/range/module.f.mjs
index 9fc941f7f..a5b0735fc 100644
--- a/fjs/types/range/module.f.mjs
+++ b/fjs/types/range/module.f.mjs
@@ -4,7 +4,7 @@
  * @module
  */
 
-/** @typedef { readonly [number, number]} Range */
+/** @import { Range } from './types.ts' */
 
 /** @type {(...range: Range) => (i: number) => boolean} */
 export const contains = (b, e) => i => b <= i && i <= e
diff --git a/fjs/types/range/types.ts b/fjs/types/range/types.ts
new file mode 100644
index 000000000..cc0da8f6c
--- /dev/null
+++ b/fjs/types/range/types.ts
@@ -0,0 +1,7 @@
+/**
+ * Range and interval types for numeric boundaries.
+ *
+ * @module
+ */
+
+export type Range = readonly [number, number]
diff --git a/fjs/types/range_map/module.f.mjs b/fjs/types/range_map/module.f.mjs
index cb410de27..548076f0d 100644
--- a/fjs/types/range_map/module.f.mjs
+++ b/fjs/types/range_map/module.f.mjs
@@ -37,53 +37,21 @@
  */
 
 import { genericMerge } from '../sorted_list/module.f.mjs'
-/** @import { TailReduce, ReduceOp, SortedList } from '../sorted_list/module.f.mjs' */
+/** @import { TailReduce, ReduceOp } from '../sorted_list/types.ts' */
 import { next } from '../list/module.f.mjs'
-/** @import { Nullable } from '../nullable/module.f.mjs' */
+/** @import { Nullable } from '../nullable/types.ts' */
 import { cmp } from '../number/module.f.mjs'
 import { bsearch } from '../function/compare/module.f.mjs'
-/** @import { Reduce, Equal } from '../function/operator/module.f.mjs' */
-/** @import { Range } from '../range/module.f.mjs' */
-
-/** @template T @typedef {[T, number]} Entry */
-
-/**
- * A sorted list of entries, where each entry is a tuple `[T, number]` that maps a value of type `T` to an upper boundary
- * of a numeric range.
- *
- * @template T
- * @typedef {SortedList<Entry<T>>} RangeMap
- */
-
-/** @template T @typedef {readonly Entry<T>[]} RangeMapArray */
-
+/** @import { Equal } from '../function/operator/types.ts' */
+/** @import { Range } from '../range/types.ts' */
 /**
- * Defines the properties and operations required for managing range maps.
- *
- * @template T
- * @typedef {{
- *  readonly union: Reduce<T>
- *  readonly equal: Equal<T>
- *  readonly def: T
- * }} Properties
- *
- * @property union
- *
- * A function to merge two values of type `T`. This defines how overlapping ranges are combined.
- *
- * @property equal
- *
- * A function to check equality between two values of type `T`.
- *
- * @property def
- *
- * The default value used when no range matches or for initializing ranges.
+ * @import {
+ *  Entry, Properties, RangeMapArray, RangeMapOp, RangeMerge,
+ * } from './types.ts'
  */
 
 /** @template T @typedef {Nullable<Entry<T>>} _RangeState */
 
-/** @template T @typedef {Reduce<RangeMap<T>>} RangeMerge */
-
 const reduceOp =
     /**
      * @template T
@@ -148,29 +116,6 @@ export const fromRange =
             /** @param {Range} r */
             ([a, b]) => /** @type {RangeMapArray<T>} */([[def, a - 1], [v, b]])
 
-/**
- * Represents a set of operations for managing range maps.
- *
- * @template T
- * @typedef {{
- *  readonly merge: RangeMerge<T>
- *  readonly get: (rm: RangeMapArray<T>) => (value: number) => T
- *  readonly fromRange: (value: T) => (r: Range) => RangeMapArray<T>
- * }} RangeMapOp
- *
- * @property merge
- *
- * Merges two range maps into a single range map.
- *
- * @property get
- *
- * Retrieves the value associated with a given numeric range.
- *
- * @property fromRange
- *
- * Constructs a range map for a single numeric range and value.
- */
-
 /**
  * Creates a set of operations for managing range maps using the specified properties.
  *
diff --git a/fjs/types/range_map/proof.f.ts b/fjs/types/range_map/proof.f.ts
index a821193c4..13c3aa268 100644
--- a/fjs/types/range_map/proof.f.ts
+++ b/fjs/types/range_map/proof.f.ts
@@ -1,10 +1,11 @@
-import { get, merge, type RangeMapArray, type Properties, type RangeMap, fromRange, rangeMap } from './module.f.mjs'
+import type { RangeMapArray, Properties, RangeMap } from './types.ts'
+import { get, merge, fromRange, rangeMap } from './module.f.mjs'
 import { stringify, type Unknown } from '../../media/json/module.f.ts'
 import { sort } from '../object/module.f.ts'
 import { union, type SortedSet } from '../sorted_set/module.f.ts'
 import { equal, toArray } from '../list/module.f.mjs'
 import { strictEqual } from '../function/operator/module.f.mjs'
-import { cmp } from '../string/module.f.ts'
+import { cmp } from '../string/module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
 
 const str
diff --git a/fjs/types/range_map/types.ts b/fjs/types/range_map/types.ts
new file mode 100644
index 000000000..d60b59b24
--- /dev/null
+++ b/fjs/types/range_map/types.ts
@@ -0,0 +1,63 @@
+/**
+ * Types for managing and merging range maps.
+ *
+ * @module
+ */
+
+import type { Equal, Reduce } from '../function/operator/types.ts'
+import type { Range } from '../range/types.ts'
+import type { SortedList } from '../sorted_list/types.ts'
+
+export type Entry<T> = [T, number]
+
+/**
+ * A sorted list of entries, where each entry is a tuple `[T, number]` that maps
+ * a value of type `T` to an upper boundary of a numeric range.
+ */
+export type RangeMap<T> = SortedList<Entry<T>>
+
+export type RangeMapArray<T> = readonly Entry<T>[]
+
+/**
+ * Defines the properties and operations required for managing range maps.
+ *
+ * @property union
+ *
+ * A function to merge two values of type `T`. This defines how overlapping ranges are combined.
+ *
+ * @property equal
+ *
+ * A function to check equality between two values of type `T`.
+ *
+ * @property def
+ *
+ * The default value used when no range matches or for initializing ranges.
+ */
+export type Properties<T> = {
+    readonly union: Reduce<T>
+    readonly equal: Equal<T>
+    readonly def: T
+}
+
+export type RangeMerge<T> = Reduce<RangeMap<T>>
+
+/**
+ * Represents a set of operations for managing range maps.
+ *
+ * @property merge
+ *
+ * Merges two range maps into a single range map.
+ *
+ * @property get
+ *
+ * Retrieves the value associated with a given numeric range.
+ *
+ * @property fromRange
+ *
+ * Constructs a range map for a single numeric range and value.
+ */
+export type RangeMapOp<T> = {
+    readonly merge: RangeMerge<T>
+    readonly get: (rm: RangeMapArray<T>) => (value: number) => T
+    readonly fromRange: (value: T) => (r: Range) => RangeMapArray<T>
+}
diff --git a/fjs/types/range_set/proof.f.mjs b/fjs/types/range_set/proof.f.mjs
index e7e208501..ed46c7539 100644
--- a/fjs/types/range_set/proof.f.mjs
+++ b/fjs/types/range_set/proof.f.mjs
@@ -1,7 +1,7 @@
 import { assert } from '../../asserts/module.f.mjs'
 import { toArray } from '../list/module.f.mjs'
 import { fromRange, merge, get } from './module.f.mjs'
-/** @import { Range } from '../range/module.f.mjs' */
+/** @import { Range } from '../range/types.ts' */
 
 /** @type {(a: string) => number} */
 const c = a => a.charCodeAt(0)
diff --git a/fjs/types/result/module.f.mjs b/fjs/types/result/module.f.mjs
index db49cb6bd..8974c1567 100644
--- a/fjs/types/result/module.f.mjs
+++ b/fjs/types/result/module.f.mjs
@@ -19,27 +19,7 @@
  * ```
  */
 
-/**
- * Represents a successful result.
- *
- * @template T
- * @typedef {readonly ['ok', T]} Ok
- */
-
-/**
- * Represents a failed result.
- *
- * @template E
- * @typedef {readonly ['error', E]} Error
- */
-
-/**
- * Represents a result that can be either successful or failed.
- *
- * @template T
- * @template E
- * @typedef {Ok<T> | Error<E>} Result
- */
+/** @import { Ok, Error, Result } from './types.ts' */
 
 /**
  * Creates a successful result.
diff --git a/fjs/types/result/module.ts b/fjs/types/result/module.ts
index 740f04d97..6e532bfdb 100644
--- a/fjs/types/result/module.ts
+++ b/fjs/types/result/module.ts
@@ -1,4 +1,5 @@
-import { ok, error, type Result } from './module.f.mjs'
+import type { Result } from './types.ts'
+import { ok, error } from './module.f.mjs'
 
 export const tryCatch
     : <T>(f: () => T) => Result<T, unknown>
diff --git a/fjs/types/result/proof.f.mjs b/fjs/types/result/proof.f.mjs
index be3ad6c2d..e64196e56 100644
--- a/fjs/types/result/proof.f.mjs
+++ b/fjs/types/result/proof.f.mjs
@@ -1,5 +1,5 @@
 import { error, ok, unwrap, invert, mapOk } from './module.f.mjs'
-/** @import { Result } from './module.f.mjs' */
+/** @import { Result } from './types.ts' */
 import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const example = () => {
diff --git a/fjs/types/result/types.ts b/fjs/types/result/types.ts
new file mode 100644
index 000000000..3a03999b8
--- /dev/null
+++ b/fjs/types/result/types.ts
@@ -0,0 +1,20 @@
+/**
+ * Types for representing operations that can succeed or fail.
+ *
+ * @module
+ */
+
+/**
+ * Represents a successful result.
+ */
+export type Ok<T> = readonly ['ok', T]
+
+/**
+ * Represents a failed result.
+ */
+export type Error<E> = readonly ['error', E]
+
+/**
+ * Represents a result that can be either successful or failed.
+ */
+export type Result<T, E> = Ok<T> | Error<E>
diff --git a/fjs/types/rtti/common/module.f.ts b/fjs/types/rtti/common/module.f.ts
index 90456fa6e..6f337e2b0 100644
--- a/fjs/types/rtti/common/module.f.ts
+++ b/fjs/types/rtti/common/module.f.ts
@@ -37,7 +37,8 @@ import {
     type Tuple,
     type Type,
 } from '../module.f.ts'
-import { error, ok, type Error, type Result as CommonResult } from '../../result/module.f.mjs'
+import type { Error, Result as CommonResult } from '../../result/types.ts'
+import { error, ok } from '../../result/module.f.mjs'
 import type { Ts } from '../ts/module.f.ts'
 import { isArray as commonIsArray } from '../../array/module.f.mjs'
 import { isObject as commonIsObject, type StringMap } from '../../object/module.f.ts'
diff --git a/fjs/types/rtti/common/proof.f.ts b/fjs/types/rtti/common/proof.f.ts
index e102a14ec..a66b94c8a 100644
--- a/fjs/types/rtti/common/proof.f.ts
+++ b/fjs/types/rtti/common/proof.f.ts
@@ -1,5 +1,6 @@
 import { eachEntry } from './module.f.ts'
-import { error, ok, type Result } from '../../result/module.f.mjs'
+import type { Result } from '../../result/types.ts'
+import { error, ok } from '../../result/module.f.mjs'
 import type { ValidationError } from './module.f.ts'
 import { assert, assertEq } from '../../../asserts/module.f.mjs'
 
diff --git a/fjs/types/rtti/module.f.ts b/fjs/types/rtti/module.f.ts
index 5e0f8cf31..4c7998ee1 100644
--- a/fjs/types/rtti/module.f.ts
+++ b/fjs/types/rtti/module.f.ts
@@ -36,9 +36,10 @@
  *
  * See `./ts/module.f.ts` for `Ts<T>` and the `*Ts` transformer types.
  */
-import type { Assert } from '../../asserts/module.f.mjs'
-import { includes, type Includes } from '../array/module.f.mjs'
-import type { Equal } from '../ts/module.f.mjs'
+import type { Assert } from '../../asserts/types.ts'
+import type { Includes } from '../array/types.ts'
+import { includes } from '../array/module.f.mjs'
+import type { Equal } from '../ts/types.ts'
 import type { StringMap } from '../object/module.f.ts'
 
 /** A constant schema: a primitive literal, a struct object, or a tuple. */
diff --git a/fjs/types/rtti/parse/module.f.ts b/fjs/types/rtti/parse/module.f.ts
index 575916159..a3df0b961 100644
--- a/fjs/types/rtti/parse/module.f.ts
+++ b/fjs/types/rtti/parse/module.f.ts
@@ -33,9 +33,11 @@ import {
     type Tuple,
     type Type,
 } from '../module.f.ts'
-import { ok, type Result as CommonResult } from '../../result/module.f.mjs'
+import type { Result as CommonResult } from '../../result/types.ts'
+import { ok } from '../../result/module.f.mjs'
 import type { StringMap } from '../../object/module.f.ts'
-import { reverse, toArray, type List } from '../../list/module.f.mjs'
+import type { List } from '../../list/types.ts'
+import { reverse, toArray } from '../../list/module.f.mjs'
 import {
     constPrimitiveValidate,
     eachEntry,
diff --git a/fjs/types/rtti/parse/proof.f.ts b/fjs/types/rtti/parse/proof.f.ts
index a832379d6..f05d923c6 100644
--- a/fjs/types/rtti/parse/proof.f.ts
+++ b/fjs/types/rtti/parse/proof.f.ts
@@ -1,9 +1,9 @@
 import { parse, type ValidationError } from './module.f.ts'
 import { boolean, number, string, bigint, unknown, array, record, or, option } from '../module.f.ts'
-import type { Equal } from '../../ts/module.f.mjs'
+import type { Equal } from '../../ts/types.ts'
 import type { Ts } from '../ts/module.f.ts'
 import type { Unknown as DjsUnknown } from '../../../djs/module.f.ts'
-import type { Assert } from '../../../asserts/module.f.mjs'
+import type { Assert } from '../../../asserts/types.ts'
 import { assert, assertEq } from '../../../asserts/module.f.mjs'
 
 const assertOk = ([k]: readonly [string, unknown]) => { assertEq(k, 'ok', 'expected ok') }
diff --git a/fjs/types/rtti/ts/module.f.ts b/fjs/types/rtti/ts/module.f.ts
index a6a60bb15..23a0b86ce 100644
--- a/fjs/types/rtti/ts/module.f.ts
+++ b/fjs/types/rtti/ts/module.f.ts
@@ -7,10 +7,11 @@
  * The runtime `toTs` function mirrors `Ts<T>` at value level, returning a TypeScript
  * type expression string for a given RTTI schema.
  */
-import { type Equal, primitive, union, printer as tsPrinter } from '../../ts/module.f.mjs'
+import type { Equal } from '../../ts/types.ts'
+import { primitive, union, printer as tsPrinter } from '../../ts/module.f.mjs'
 import type { Tag0, Tag1, Const, Or, String as RttiString, Struct, Tuple, Type, ConstObject } from '../module.f.ts'
-import type { Assert } from '../../../asserts/module.f.mjs'
-import type { phantomKey } from '../../phantom/module.f.ts'
+import type { Assert } from '../../../asserts/types.ts'
+import type { phantomKey } from '../../phantom/types.ts'
 import type { StringMap } from '../../object/module.f.ts'
 
 /**
@@ -96,11 +97,11 @@ export type StructTs<T extends Struct> =
  *
  * **Recursive schemas and TS2589:** when a schema is self-referential, `StructTs` would
  * expand infinitely and TypeScript raises TS2589. Break the cycle by annotating the
- * schema value with `Phantom<typeof myThunk, MyType>` from `fjs/types/phantom/module.f.ts`.
+ * schema value with `Phantom<typeof myThunk, MyType>` from `fjs/types/phantom/types.ts`.
  * `Ts<>` detects the phantom key and returns `MyType` directly without recursing:
  *
  * ```ts
- * import { type Phantom } from '../types/phantom/module.f.ts'
+ * import { type Phantom } from '../../phantom/types.ts'
  *
  * type MyType = { readonly self?: MyType }
  * const myThunk = () => ['const', myConst] as const
diff --git a/fjs/types/rtti/validate/proof.f.ts b/fjs/types/rtti/validate/proof.f.ts
index b84326b68..93619f698 100644
--- a/fjs/types/rtti/validate/proof.f.ts
+++ b/fjs/types/rtti/validate/proof.f.ts
@@ -1,9 +1,9 @@
 import { validate, type ValidationError } from './module.f.ts'
 import { boolean, number, string, bigint, unknown, array, record, or, option } from '../module.f.ts'
-import type { Equal } from '../../ts/module.f.mjs'
+import type { Equal } from '../../ts/types.ts'
 import type { Ts } from '../ts/module.f.ts'
 import type { Unknown as DjsUnknown } from '../../../djs/module.f.ts'
-import type { Assert } from '../../../asserts/module.f.mjs'
+import type { Assert } from '../../../asserts/types.ts'
 import { assert, assertEq } from '../../../asserts/module.f.mjs'
 
 const assertOk = ([k]: readonly [string, unknown]) => { assertEq(k, 'ok', 'expected ok') }
diff --git a/fjs/types/sorted_list/module.f.mjs b/fjs/types/sorted_list/module.f.mjs
index 02535f4a6..092eb8e41 100644
--- a/fjs/types/sorted_list/module.f.mjs
+++ b/fjs/types/sorted_list/module.f.mjs
@@ -5,37 +5,14 @@
  */
 
 import { bsearch } from '../function/compare/module.f.mjs'
-/** @import { Sign, Cmp } from '../function/compare/module.f.mjs' */
+/** @import { Cmp } from '../function/compare/types.ts' */
 import { next } from '../list/module.f.mjs'
-/** @import { List } from '../list/module.f.mjs' */
-/** @import { Nullable } from '../nullable/module.f.mjs' */
+/** @import { List } from '../list/types.ts' */
 import { identity } from '../function/module.f.mjs'
-
-/** @template T @typedef {List<T>} SortedList */
+/** @import { ReduceOp, SortedList, TailReduce, _MergeReduce } from './types.ts' */
 
 /** @template T @typedef {readonly T[]} _SortedArray */
 
-/**
- * @template T
- * @template S
- * @typedef {(state: S) => (a: T) => (b: T) => readonly [Nullable<T>, Sign, S]} ReduceOp
- */
-
-/**
- * @template T
- * @template S
- * @typedef {(state: S) => (tail: List<T>) => List<T>} TailReduce
- */
-
-/**
- * @template T
- * @template S
- * @typedef {{
- *  readonly reduceOp: ReduceOp<T, S>
- *  readonly tailReduce: TailReduce<T, S>
- * }} _MergeReduce
- */
-
 /**
  * Two-way sorted-list merge.
  * `reduceOp` returns `[output, sign, nextState]` where sign `-1` advances `a`, `1` advances `b`, `0` advances both; `null` output skips emission.
diff --git a/fjs/types/sorted_list/types.ts b/fjs/types/sorted_list/types.ts
new file mode 100644
index 000000000..bad600921
--- /dev/null
+++ b/fjs/types/sorted_list/types.ts
@@ -0,0 +1,21 @@
+/**
+ * Types for sorted immutable lists and their merge operations.
+ *
+ * @module
+ */
+
+import type { Sign } from '../function/compare/types.ts'
+import type { List } from '../list/types.ts'
+import type { Nullable } from '../nullable/types.ts'
+
+export type SortedList<T> = List<T>
+
+export type ReduceOp<T, S> =
+    (state: S) => (a: T) => (b: T) => readonly [Nullable<T>, Sign, S]
+
+export type TailReduce<T, S> = (state: S) => (tail: List<T>) => List<T>
+
+export type _MergeReduce<T, S> = {
+    readonly reduceOp: ReduceOp<T, S>
+    readonly tailReduce: TailReduce<T, S>
+}
diff --git a/fjs/types/sorted_set/module.f.ts b/fjs/types/sorted_set/module.f.ts
index 2c070ce45..d24dbd55f 100644
--- a/fjs/types/sorted_set/module.f.ts
+++ b/fjs/types/sorted_set/module.f.ts
@@ -26,7 +26,7 @@
  * has(cmp)(2)(setA) // false
  * ```
  */
-import type { Cmp } from '../function/compare/module.f.mjs'
+import type { Cmp } from '../function/compare/types.ts'
 import { toArray } from "../list/module.f.mjs"
 import { merge, intersect as listIntersect, find } from '../sorted_list/module.f.mjs'
 
diff --git a/fjs/types/string/module.f.mjs b/fjs/types/string/module.f.mjs
new file mode 100644
index 000000000..faa24be31
--- /dev/null
+++ b/fjs/types/string/module.f.mjs
@@ -0,0 +1,58 @@
+/**
+ * Utility functions for working with strings and lists of strings.
+ *
+ * @module
+ *
+ * @example
+ *
+ * ```js
+ * import { join, concat, repeat, cmp } from './module.f.mjs'
+ *
+ * const words = ['hello', 'world']
+ * join(' ')(words) // 'hello world'
+ * concat(words) // 'helloworld'
+ * repeat('abc')(3) // 'abcabcabc'
+ * cmp('apple')('banana') // -1
+ * ```
+ */
+
+/** @import { List } from '../list/types.ts' */
+import { reduce as listReduce, repeat as listRepeat } from '../list/module.f.mjs'
+import { compose } from '../function/module.f.mjs'
+/** @import { Sign } from '../function/compare/types.ts' */
+import { cmp as uCmp } from '../function/compare/module.f.mjs'
+/** @import { Reduce } from '../function/operator/types.ts' */
+import { join as joinOp } from '../function/operator/module.f.mjs'
+import { fold } from '../../common/monoid/module.f.mjs'
+
+/**
+ * `join`'s per-separator reduction is seeded at `''` but is *not* a monoid fold:
+ * `joinOp(sep)` has no identity (`joinOp(sep)('')(x)` prepends a separator), so
+ * it stays a hand-seeded `reduce` rather than going through `monoid.fold`.
+ *
+ * @type {(o: Reduce<string>) => (input: List<string>) => string}
+ */
+const reduce = o => listReduce(o)('')
+
+/** @type {(_: string) => (input: List<string>) => string} */
+export const join = compose(joinOp)(reduce)
+
+/**
+ * String concatenation with identity `''` is a lawful monoid, so `concat` is a
+ * monoid fold. The operation is accumulator-first (`a` on the left), matching
+ * `monoid.fold`'s convention — unlike the element-first `concat` in
+ * `function/operator`, which is written for `list.reduce`.
+ *
+ * @type {(input: List<string>) => string}
+ */
+export const concat = fold({ identity: '', operation: a => b => a + b })
+
+/** @type {(n: string) => (v: number) => string} */
+export const repeat = v => compose(listRepeat(v))(concat)
+
+/** @type {(a: string) => (b: string) => Sign} */
+export const cmp = uCmp
+
+/** @type {(p: number) => (v: string) => readonly[string, string]} */
+export const splitAt = p => v =>
+    [v.substring(0, p), v.substring(p)]
diff --git a/fjs/types/string/module.f.ts b/fjs/types/string/module.f.ts
deleted file mode 100644
index 5cc884bbc..000000000
--- a/fjs/types/string/module.f.ts
+++ /dev/null
@@ -1,47 +0,0 @@
-/**
- * Utility functions for working with strings and lists of strings.
- *
- * @module
- *
- * @example
- *
- * ```js
- * import { join, concat, repeat, cmp } from './module.f.ts'
- *
- * const words = ['hello', 'world']
- * join(' ')(words) // 'hello world'
- * concat(words) // 'helloworld'
- * repeat('abc')(3) // 'abcabcabc'
- * cmp('apple')('banana') // -1
- * ```
- */
-import { type List, reduce as listReduce, repeat as listRepeat } from '../list/module.f.mjs'
-import { compose } from '../function/module.f.mjs'
-import { type Sign, cmp as uCmp } from '../function/compare/module.f.mjs'
-import { join as joinOp, type Reduce } from '../function/operator/module.f.mjs'
-import { fold } from '../../common/monoid/module.f.mjs'
-
-// `join`'s per-separator reduction is seeded at `''` but is *not* a monoid fold:
-// `joinOp(sep)` has no identity (`joinOp(sep)('')(x)` prepends a separator), so
-// it stays a hand-seeded `reduce` rather than going through `monoid.fold`.
-const reduce: (o: Reduce<string>) => (input: List<string>) => string
-    = o => listReduce(o)('')
-
-export const join: (_: string) => (input: List<string>) => string
-    = compose(joinOp)(reduce)
-
-// String concatenation with identity `''` is a lawful monoid, so `concat` is a
-// monoid fold. The operation is accumulator-first (`a` on the left), matching
-// `monoid.fold`'s convention — unlike the element-first `concat` in
-// `function/operator`, which is written for `list.reduce`.
-export const concat: (input: List<string>) => string
-    = fold({ identity: '', operation: a => b => a + b })
-
-export const repeat: (n: string) => (v: number) => string
-    = v => compose(listRepeat(v))(concat)
-
-export const cmp: (a: string) => (b: string) => Sign
-    = uCmp
-
-export const splitAt = (p: number) => (v: string): readonly[string, string] =>
-    [v.substring(0, p), v.substring(p)]
diff --git a/fjs/types/string/proof.f.ts b/fjs/types/string/proof.f.mjs
similarity index 96%
rename from fjs/types/string/proof.f.ts
rename to fjs/types/string/proof.f.mjs
index 49548d9c9..69d2ab6e7 100644
--- a/fjs/types/string/proof.f.ts
+++ b/fjs/types/string/proof.f.mjs
@@ -1,4 +1,4 @@
-import { join, concat, repeat, cmp, splitAt } from './module.f.ts'
+import { join, concat, repeat, cmp, splitAt } from './module.f.mjs'
 import { repeat as repeatList } from '../list/module.f.mjs'
 import { assert, assertEq } from '../../asserts/module.f.mjs'
 
diff --git a/fjs/types/string_set/module.f.ts b/fjs/types/string_set/module.f.ts
index 2b4fd019a..1efec81cb 100644
--- a/fjs/types/string_set/module.f.ts
+++ b/fjs/types/string_set/module.f.ts
@@ -20,13 +20,14 @@
  * ```
  */
 
-import type { Tree } from '../btree/types/module.f.mjs'
+import type { Tree } from '../btree/types/types.ts'
 import { empty as btEmpty, values as btValues } from '../btree/module.f.mjs'
 import { find, isFound } from '../btree/find/module.f.mjs'
 import { remove as btreeRemove } from '../btree/remove/module.f.mjs'
 import { set as btreeSet } from '../btree/set/module.f.mjs'
-import { cmp } from "../string/module.f.ts"
-import { fold, type List } from '../list/module.f.mjs'
+import { cmp } from "../string/module.f.mjs"
+import type { List } from '../list/types.ts'
+import { fold } from '../list/module.f.mjs'
 import { compose } from '../function/module.f.mjs'
 
 export const values: (s: StringSet) => List<string> = btValues
diff --git a/fjs/types/todo/bit-set-factory.md b/fjs/types/todo/bit-set-factory.md
index d1e7fceba..1df2109e5 100644
--- a/fjs/types/todo/bit-set-factory.md
+++ b/fjs/types/todo/bit-set-factory.md
@@ -54,7 +54,7 @@ AGENTS.md). `byte_set`'s `toRangeMap` stays local — it is genuinely
 byte-specific.
 
 Rider: both modules inline `readonly [number, number]` for `range`'s
-parameter; the factory should use `Range` from `fjs/types/range/module.f.mjs`.
+parameter; the factory should use `Range` from `fjs/types/range/types.ts`.
 
 `has` on a `bigint` set may deserve a domain-specific override if the
 generic form costs (see [185](./185.md) for the mask-based direction) —
diff --git a/fjs/types/ts/module.f.mjs b/fjs/types/ts/module.f.mjs
index ec0d2fd5a..176d43f76 100644
--- a/fjs/types/ts/module.f.mjs
+++ b/fjs/types/ts/module.f.mjs
@@ -6,10 +6,7 @@
  * @module
  */
 
-/**
- * @template A, B
- * @typedef {(<T>() => T extends A ? 1 : 2) extends (<T>() => T extends B ? 1 : 2) ? true : false} Equal
- */
+/** @import { Printer } from './types.ts' */
 
 /** @type {(open: string, close: string) => (i: readonly string[]) => string} */
 const complex = (open, close) => i =>
@@ -17,17 +14,6 @@ const complex = (open, close) => i =>
 
 const structX = complex('{', '}')
 
-/**
- * Functions for emitting TypeScript type expression strings.
- *
- * @typedef {{
- *  readonly tuple: (types: readonly string[]) => string
- *  readonly struct: (fields: readonly (readonly[string, string])[]) => string
- *  readonly array: (type: string) => string
- *  readonly record: (type: string) => string
- * }} Printer
- */
-
 /**
  * Creates a `Printer`. Pass `true` to emit mutable (non-`readonly`) types.
  *
diff --git a/fjs/types/ts/proof.f.ts b/fjs/types/ts/proof.f.ts
index d864307db..9269da2b9 100644
--- a/fjs/types/ts/proof.f.ts
+++ b/fjs/types/ts/proof.f.ts
@@ -1,5 +1,6 @@
-import type { Assert } from '../../asserts/module.f.mjs'
-import { printer, primitive, union, type Equal } from './module.f.mjs'
+import type { Assert } from '../../asserts/types.ts'
+import type { Equal } from './types.ts'
+import { printer, primitive, union } from './module.f.mjs'
 import { assertEq } from '../../asserts/module.f.mjs'
 
 const ro = printer()
diff --git a/fjs/types/ts/types.ts b/fjs/types/ts/types.ts
new file mode 100644
index 000000000..82407c8fd
--- /dev/null
+++ b/fjs/types/ts/types.ts
@@ -0,0 +1,21 @@
+/**
+ * Types for the TypeScript source emitter: the `Equal` compile-time predicate
+ * and the `Printer` interface.
+ *
+ * @module
+ */
+
+export type Equal<A, B> =
+    (<T>() => T extends A ? 1 : 2) extends (<T>() => T extends B ? 1 : 2)
+        ? true
+        : false
+
+/**
+ * Functions for emitting TypeScript type expression strings.
+ */
+export type Printer = {
+    readonly tuple: (types: readonly string[]) => string
+    readonly struct: (fields: readonly (readonly [string, string])[]) => string
+    readonly array: (type: string) => string
+    readonly record: (type: string) => string
+}
diff --git a/fjs/types/uint8array/module.f.mjs b/fjs/types/uint8array/module.f.mjs
index 5f5899393..718304789 100644
--- a/fjs/types/uint8array/module.f.mjs
+++ b/fjs/types/uint8array/module.f.mjs
@@ -13,10 +13,10 @@
 import { assert, assertNotNullish } from '../../asserts/module.f.mjs'
 import { utf8, utf8ToString } from '../../text/module.f.mjs'
 import { maxLengthBytes, msb, tryU8ListToVec, u8List, u8ListToVec } from '../bit_vec/module.f.mjs'
-/** @import { Vec } from '../bit_vec/module.f.mjs' */
+/** @import { Vec } from '../bit_vec/types.ts' */
 import { compose } from '../function/module.f.mjs'
 import { flat, fromArrayLike, iterable, map } from '../list/module.f.mjs'
-/** @import { List } from '../list/module.f.mjs' */
+/** @import { List } from '../list/types.ts' */
 
 const u8ListToVecMsb = u8ListToVec(msb)
 const tryU8ListToVecMsb = tryU8ListToVec(msb)
diff --git a/fjs/website/module.f.ts b/fjs/website/module.f.ts
index 67030cbbb..bed1b4a02 100644
--- a/fjs/website/module.f.ts
+++ b/fjs/website/module.f.ts
@@ -6,7 +6,7 @@
 import { htmlUtf8 } from '../media/html/module.f.ts'
 import { writeFile, type WriteFile } from '../effects/node/module.f.ts'
 import { pure, step, type Effect } from '../effects/module.f.ts'
-import type { Vec } from '../types/bit_vec/module.f.mjs'
+import type { Vec } from '../types/bit_vec/types.ts'
 
 const html: Vec = htmlUtf8()(
     ['a',