diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6d22ca0d4..1c3d06ae2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,15 @@ history.
 
 ## Unreleased
 
+- **BREAKING CHANGES:** `fjs/media/json/parser` migrates from authored
+  TypeScript (`.f.ts`) to JSDoc-typed JavaScript (`.f.mjs`) under the
+  stage-1 TypeScript-to-mjs migration, splitting `_JsonObject`,
+  `_JsonArray`, `_JsonStack`, `_StateParse`, and `_JsonState` into a
+  sibling `types.ts` — importers must use the `.f.mjs` specifier for the
+  runtime value and the `types.ts` specifier for the types. `proof.f.ts`
+  stays TypeScript for now (it depends on `fjs/media/json/module.f.ts`,
+  still unmigrated)
+  [#1499](https://github.com/functionalscript/functionalscript/pull/1499)
 - **BREAKING CHANGES:** the JSON rtti schemas `primitive`, `unknown`,
   `object`, and `array` move from `fjs/media/json/module.f.ts` to a new
   JSDoc-typed `fjs/media/json/rtti/module.f.mjs`, and the `Primitive`,
diff --git a/fjs/asn.1/module.f.mjs b/fjs/asn.1/module.f.mjs
index 3b7316f0f..9da03a9ad 100644
--- a/fjs/asn.1/module.f.mjs
+++ b/fjs/asn.1/module.f.mjs
@@ -3,10 +3,12 @@
  * helpers, length-prefixed payloads, and OID conversion via Base-128.
  *
  * @module
+ *
+ * @import { Unpacked, Vec } from '../types/bit_vec/types.ts'
+ * @import { ObjectIdentifier, Raw, Record, Sequence, SupportedRecord, _Tag } from './types.ts'
  */
 
 import { bitLength, divUp8 } from '../types/bigint/module.f.mjs'
-
 import {
     empty,
     isVec,
@@ -17,19 +19,8 @@ import {
     vec,
     vec8,
 } 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'
-
 import { max } from '../types/function/compare/module.f.mjs'
-
 import { encode as b128encode, decode as b128decode } from '../basen/base128/module.f.mjs'
 
 //
diff --git a/fjs/asn.1/proof.f.mjs b/fjs/asn.1/proof.f.mjs
index b60271924..bd47ad005 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/types.ts' */
+import { empty, isVec, length, msb, uint, unpack, vec, vec8 } from '../types/bit_vec/module.f.mjs'
 
 import { asBase } from '../types/nominal/module.f.mjs'
 
diff --git a/fjs/basen/base128/module.f.mjs b/fjs/basen/base128/module.f.mjs
index 0d59fcb5b..87541bcd3 100644
--- a/fjs/basen/base128/module.f.mjs
+++ b/fjs/basen/base128/module.f.mjs
@@ -2,10 +2,11 @@
  * Base-128 encoding and decoding utilities over bit vectors.
  *
  * @module
+ *
+ * @import { Vec } from '../../types/bit_vec/types.ts'
  */
 
 import { vec8, msb, empty } 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 0e1a7d3a6..84ef10528 100644
--- a/fjs/basen/base128/proof.f.mjs
+++ b/fjs/basen/base128/proof.f.mjs
@@ -1,8 +1,7 @@
-import { empty, vec, vec8 } from '../../types/bit_vec/module.f.mjs'
 /** @import { Vec } from '../../types/bit_vec/types.ts' */
 
+import { empty, vec, vec8 } from '../../types/bit_vec/module.f.mjs'
 import { asBase } from '../../types/nominal/module.f.mjs'
-
 import { encode, decode } from './module.f.mjs'
 
 //
diff --git a/fjs/basen/base64/module.f.mjs b/fjs/basen/base64/module.f.mjs
index 37d79fe4e..25f8cae2f 100644
--- a/fjs/basen/base64/module.f.mjs
+++ b/fjs/basen/base64/module.f.mjs
@@ -2,13 +2,12 @@
  * Standard Base64 encoding and decoding (RFC 4648).
  *
  * @module
+ *
+ * @import { Vec } from '../../types/bit_vec/types.ts'
+ * @import { Nullable } from '../../types/nullable/types.ts'
  */
 
 import { msb, length, vec, maxLength } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/types.ts' */
-
-/** @import { Nullable } from '../../types/nullable/types.ts' */
-
 import { baseN } from "../module.f.mjs"
 
 const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
diff --git a/fjs/basen/base64/proof.f.mjs b/fjs/basen/base64/proof.f.mjs
index c71534f12..78a437270 100644
--- a/fjs/basen/base64/proof.f.mjs
+++ b/fjs/basen/base64/proof.f.mjs
@@ -1,8 +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/types.ts' */
 
+import { assertEq } from '../../asserts/module.f.mjs'
+import { empty, vec, repeat, vec8, maxLength } from '../../types/bit_vec/module.f.mjs'
 import { encode, decode } from './module.f.mjs'
 
 /**
diff --git a/fjs/basen/cbase32/module.f.mjs b/fjs/basen/cbase32/module.f.mjs
index 172593cd9..d8ab0488d 100644
--- a/fjs/basen/cbase32/module.f.mjs
+++ b/fjs/basen/cbase32/module.f.mjs
@@ -2,13 +2,12 @@
  * Content-addressable Base32 encoding and decoding helpers.
  *
  * @module
+ *
+ * @import { Vec } from '../../types/bit_vec/types.ts'
+ * @import { Nullable } from '../../types/nullable/types.ts'
  */
 
 import { msb, lsb, length, vec, empty } from '../../types/bit_vec/module.f.mjs'
-/** @import { Vec } from '../../types/bit_vec/types.ts' */
-
-/** @import { Nullable } from '../../types/nullable/types.ts' */
-
 import { baseN } from '../module.f.mjs'
 
 //                         0123456789abcdef
diff --git a/fjs/basen/cbase32/proof.f.mjs b/fjs/basen/cbase32/proof.f.mjs
index 8aa1aeabb..44bee687c 100644
--- a/fjs/basen/cbase32/proof.f.mjs
+++ b/fjs/basen/cbase32/proof.f.mjs
@@ -1,8 +1,7 @@
-import { empty, vec } from '../../types/bit_vec/module.f.mjs'
 /** @import { Vec } from '../../types/bit_vec/types.ts' */
 
+import { empty, vec } from '../../types/bit_vec/module.f.mjs'
 import { cBase32ToVec, cBase32ToVec5x, vec5xToCBase32, vecToCBase32 } from './module.f.mjs'
-
 import { assertEq } from '../../asserts/module.f.mjs'
 
 //
diff --git a/fjs/basen/module.f.mjs b/fjs/basen/module.f.mjs
index 166ea3e48..7d1259fc7 100644
--- a/fjs/basen/module.f.mjs
+++ b/fjs/basen/module.f.mjs
@@ -10,18 +10,16 @@
  * `vecToString` / `stringToVec`.
  *
  * @module
+ *
+ * @import { Vec } from '../types/bit_vec/types.ts'
+ * @import { List } from '../types/list/types.ts'
+ * @import { BaseN } from './types.ts'
  */
 
 import { msb, lsb, vec, chunkList, unpack } 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/types.ts' */
-
 import { compose } from '../types/function/module.f.mjs'
 
-/** @import { BaseN } from './types.ts' */
-
 const { unpackSplit } = msb
 
 const { tryListToVec: reversedListToVec } = lsb
diff --git a/fjs/bnf/data/module.f.mjs b/fjs/bnf/data/module.f.mjs
index 720f5d7ce..826358e06 100644
--- a/fjs/bnf/data/module.f.mjs
+++ b/fjs/bnf/data/module.f.mjs
@@ -11,16 +11,16 @@
  * See `./types.ts` for the type-level API.
  *
  * @module
+ *
+ * @import { DataRule, Rule as FRule, Sequence as FSequence } from '../types.ts'
+ * @import { StringMap } from '../../types/object/types.ts'
+ * @import { EmptyTag, Rule, RuleSet, Sequence, Variant } from './types.ts'
  */
+
 import { stringToCodePointList } from '../../text/utf16/module.f.mjs'
 import { map, toArray } from '../../types/list/module.f.mjs'
-import {
-    oneEncode,
-} from '../module.f.mjs'
-/** @import { DataRule, Rule as FRule, Sequence as FSequence } from '../types.ts' */
+import { oneEncode } from '../module.f.mjs'
 import { definedEntries } from '../../types/object/module.f.mjs'
-/** @import { StringMap } from '../../types/object/types.ts' */
-/** @import { EmptyTag, Rule, RuleSet, Sequence, Variant } from './types.ts' */
 
 /** @typedef {StringMap<EmptyTag>} _EmptyTagMap */
 
diff --git a/fjs/bnf/data/proof.f.ts b/fjs/bnf/data/proof.f.ts
index f41d8ae06..dde48f392 100644
--- a/fjs/bnf/data/proof.f.ts
+++ b/fjs/bnf/data/proof.f.ts
@@ -1,12 +1,14 @@
-import { stringify } from '../../media/json/module.f.ts'
+import type { RuleSet } from './types.ts'
+
 import { identity } from '../../types/function/module.f.mjs'
 import { sort } from '../../types/object/module.f.mjs'
 import { oneEncode, option, range, rangeDecode, repeat0Plus, set } from '../module.f.mjs'
-import { classic, deterministic } from '../testlib.f.ts'
 import { emptyTagMap, toData } from './module.f.mjs'
-import type { RuleSet } from './types.ts'
 import { assertEq } from '../../asserts/module.f.mjs'
 
+import { stringify } from '../../media/json/module.f.ts'
+import { classic, deterministic } from '../testlib.f.ts'
+
 export const proof = {
     rangeDecode: () => {
         const decoded1 = stringify(sort)(rangeDecode(0x000079_000087))
diff --git a/fjs/bnf/descent/module.f.mjs b/fjs/bnf/descent/module.f.mjs
index 7a2587bf1..871f714eb 100644
--- a/fjs/bnf/descent/module.f.mjs
+++ b/fjs/bnf/descent/module.f.mjs
@@ -14,15 +14,17 @@
  * See `./types.ts` for the type-level API.
  *
  * @module
+ *
+ * @import { TerminalRange } from '../types.ts'
+ * @import { Rule as DataRule, Sequence } from '../data/types.ts'
+ * @import { Rule as FRule } from '../types.ts'
+ * @import { AstTag, AstSequenceMeta, DescentFailure, DescentMatch, DescentMatchResult, DescentMatchRule } from './types.ts'
  */
+
 import { rangeDecode } from '../module.f.mjs'
-/** @import { TerminalRange } from '../types.ts' */
 import { contains as rangeContains } from '../../types/range/module.f.mjs'
 import { definedEntries } from '../../types/object/module.f.mjs'
 import { emptyTagMap, toData } from '../data/module.f.mjs'
-/** @import { Rule as DataRule, Sequence } from '../data/types.ts' */
-/** @import { Rule as FRule } from '../types.ts' */
-/** @import { AstTag, AstSequenceMeta, DescentFailure, DescentMatch, DescentMatchResult, DescentMatchRule } from './types.ts' */
 
 /**
  * Folds one rejected terminal into the furthest-failure record: further along
diff --git a/fjs/bnf/descent/proof.f.ts b/fjs/bnf/descent/proof.f.ts
index 6948dc47a..0963de37f 100644
--- a/fjs/bnf/descent/proof.f.ts
+++ b/fjs/bnf/descent/proof.f.ts
@@ -1,13 +1,15 @@
 import type { CodePoint } from '../../text/utf16/types.ts'
+import type { DescentMatch, CodePointMeta, DescentMatchResult } from './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.mjs'
-import { deterministic } from '../testlib.f.ts'
 import { emptyTagMap, toData } from '../data/module.f.mjs'
 import { descentParser } from './module.f.mjs'
-import type { DescentMatch, CodePointMeta, DescentMatchResult } from './types.ts'
 import { assertEq, assertNotNullish } from '../../asserts/module.f.mjs'
 
+import { deterministic } from '../testlib.f.ts'
+
 const mapCodePoint = (cp: CodePoint): CodePointMeta<unknown> => [cp, undefined]
 
 // The code point of a one-character string, for expectations that would
diff --git a/fjs/bnf/ll1/module.f.mjs b/fjs/bnf/ll1/module.f.mjs
index 8767a7580..c2bc6261e 100644
--- a/fjs/bnf/ll1/module.f.mjs
+++ b/fjs/bnf/ll1/module.f.mjs
@@ -11,19 +11,21 @@
  * See `./types.ts` for the type-level API.
  *
  * @module
+ *
+ * @import { Properties } from '../../types/range_map/types.ts'
+ * @import { StringSet } from '../../types/string_set/types.ts'
+ * @import { EmptyTag, RuleSet } from '../data/types.ts'
+ * @import { Rule as FRule } from '../types.ts'
+ * @import { AstSequence, AstTag, Match, MatchResult, MatchRule, Remainder, _Dispatch, _DispatchMap, _DispatchResult, _DispatchRule } from './types.ts'
  */
+
 import { strictEqual } from '../../types/function/operator/module.f.mjs'
 import { toArray } from '../../types/list/module.f.mjs'
 import { rangeMap } from '../../types/range_map/module.f.mjs'
-/** @import { Properties } from '../../types/range_map/types.ts' */
 import { contains, set } from '../../types/string_set/module.f.mjs'
-/** @import { StringSet } from '../../types/string_set/types.ts' */
 import { rangeDecode } from '../module.f.mjs'
 import { definedEntries } from '../../types/object/module.f.mjs'
 import { emptyTagMap, toData } from '../data/module.f.mjs'
-/** @import { EmptyTag, RuleSet } from '../data/types.ts' */
-/** @import { Rule as FRule } from '../types.ts' */
-/** @import { AstSequence, AstTag, Match, MatchResult, MatchRule, Remainder, _Dispatch, _DispatchMap, _DispatchResult, _DispatchRule } from './types.ts' */
 
 /** @type {Properties<_DispatchResult>} */
 const dispatchProps = {
diff --git a/fjs/bnf/ll1/proof.f.ts b/fjs/bnf/ll1/proof.f.ts
index d483aec93..2e636e15a 100644
--- a/fjs/bnf/ll1/proof.f.ts
+++ b/fjs/bnf/ll1/proof.f.ts
@@ -1,13 +1,15 @@
+import type { RuleSet } from '../data/types.ts'
+import type { MatchResult } from './types.ts'
+
 import { stringToCodePointList } from '../../text/utf16/module.f.mjs'
 import { toArray } from '../../types/list/module.f.mjs'
 import { commaJoin0Plus, option, range, repeat0Plus, set } from '../module.f.mjs'
-import { deterministic } from '../testlib.f.ts'
 import { toData } from '../data/module.f.mjs'
-import type { RuleSet } from '../data/types.ts'
 import { dispatchMap, parser, parserRuleSet } from './module.f.mjs'
-import type { MatchResult } from './types.ts'
 import { assertEq } from '../../asserts/module.f.mjs'
 
+import { deterministic } from '../testlib.f.ts'
+
 export const proof = {
     dispatch: [
         () => {
diff --git a/fjs/bnf/module.f.mjs b/fjs/bnf/module.f.mjs
index dfa13b9b7..ff074cd22 100644
--- a/fjs/bnf/module.f.mjs
+++ b/fjs/bnf/module.f.mjs
@@ -6,17 +6,17 @@
  * See `./types.ts` for the type-level API.
  *
  * @module
+ *
+ * @import { Tuple } from '../types/array/types.ts'
+ * @import { TerminalRange, Sequence, Rule, RangeVariant, None, Option, Repeat0Plus, Repeat1Plus, Join1Plus, Repeat } from './types.ts'
  */
 
-/** @import { Tuple } from '../types/array/types.ts' */
-
 import { codePointListToString, stringToCodePointList } from '../text/utf16/module.f.mjs'
 import { definedValues } from '../types/object/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'
-/** @import { TerminalRange, Sequence, Variant, DataRule, LazyRule, Rule, RangeVariant, None, Option, Repeat0Plus, Repeat1Plus, Join1Plus, Join0Plus, Repeat } from './types.ts' */
 
 // Internals:
 
diff --git a/fjs/bnf/proof.f.ts b/fjs/bnf/proof.f.ts
index 67d46c600..fd2468a40 100644
--- a/fjs/bnf/proof.f.ts
+++ b/fjs/bnf/proof.f.ts
@@ -1,5 +1,6 @@
+import type { Rule } from './types.ts'
+
 import { assert, assertEq } from '../asserts/module.f.mjs'
-import { classic, deterministic } from './testlib.f.ts'
 import {
     rangeEncode,
     str,
@@ -10,7 +11,8 @@ import {
     oneEncode,
     repeat1Plus,
 } from './module.f.mjs'
-import type { Rule } from './types.ts'
+
+import { classic, deterministic } from './testlib.f.ts'
 
 export const proof = {
     test: () => {
diff --git a/fjs/bnf/testlib.f.ts b/fjs/bnf/testlib.f.ts
index 191f889ca..c3e4e9b13 100644
--- a/fjs/bnf/testlib.f.ts
+++ b/fjs/bnf/testlib.f.ts
@@ -1,3 +1,5 @@
+import type { Rule } from './types.ts'
+
 import {
     commaJoin0Plus,
     none,
@@ -9,7 +11,6 @@ import {
     set,
     unicodeMax,
 } from './module.f.mjs'
-import type { Rule } from './types.ts'
 
 export const classic = (): Rule => {
 
diff --git a/fjs/bnf/token_symbol/module.f.mjs b/fjs/bnf/token_symbol/module.f.mjs
index 9950e0506..02adbc5c1 100644
--- a/fjs/bnf/token_symbol/module.f.mjs
+++ b/fjs/bnf/token_symbol/module.f.mjs
@@ -9,11 +9,13 @@
  * See `./types.ts` for the `Encoding<T>` type-level API.
  *
  * @module
+ *
+ * @import { Encoding } from './types.ts'
  */
+
 import { assert } from '../../asserts/module.f.mjs'
 import { fromUndefined } from '../../types/nullable/module.f.mjs'
 import { eof, rangeDecode, unicodeRange } from '../module.f.mjs'
-/** @import { Encoding } from './types.ts' */
 
 const [, unicodeLast] = rangeDecode(unicodeRange)
 
diff --git a/fjs/bnf/types.ts b/fjs/bnf/types.ts
index 7803a0d53..dae80ca96 100644
--- a/fjs/bnf/types.ts
+++ b/fjs/bnf/types.ts
@@ -3,6 +3,7 @@
  *
  * @module
  */
+
 import type { StringMap } from '../types/object/types.ts'
 
 /**
diff --git a/fjs/cas/cli/module.f.mjs b/fjs/cas/cli/module.f.mjs
index 1d33e77fa..516e4879c 100644
--- a/fjs/cas/cli/module.f.mjs
+++ b/fjs/cas/cli/module.f.mjs
@@ -2,18 +2,19 @@
  * CAS CLI command handlers.
  *
  * @module
+ *
+ * @import { All, Read, Write, WriteFile } from '../../effects/node/types.ts'
+ * @import { Commands } from '../../cli/types.ts'
+ * @import { MemOp } from '../../effects/memory/types.ts'
+ * @import { FileCasOperation } from '../types.ts'
  */
 
 import { sha256 } from '../../crypto/sha2/module.f.mjs'
 import { cBase32ToVec, vecToCBase32 } from '../../basen/cbase32/module.f.mjs'
 import { forEachStep, pure, step } from '../../effects/module.f.mjs'
 import { errorExit, log, writeFromStream } from '../../effects/node/module.f.mjs'
-/** @import { All, Read, Write, WriteFile } from '../../effects/node/types.ts' */
 import { dispatch } from '../../cli/module.f.mjs'
-/** @import { Commands } from '../../cli/types.ts' */
-/** @import { MemOp } from '../../effects/memory/types.ts' */
 import { casAddFile, fileCas } from '../module.f.mjs'
-/** @import { FileCasOperation } from '../types.ts' */
 
 /** @type {Commands<FileCasOperation | WriteFile | Write | All | MemOp | Read>} */
 export const commands = [
diff --git a/fjs/cas/cli/proof.f.mjs b/fjs/cas/cli/proof.f.mjs
index 772237359..f6a3f8f71 100644
--- a/fjs/cas/cli/proof.f.mjs
+++ b/fjs/cas/cli/proof.f.mjs
@@ -1,8 +1,9 @@
+/** @import { NodeProgramOptions } from '../../effects/node/types.ts' */
+
 import { commands } from './module.f.mjs'
 import { computeSync, sha256 } from '../../crypto/sha2/module.f.mjs'
 import { maxLength, vec, vec8 } from '../../types/bit_vec/module.f.mjs'
 import { defaultNodeProgramOptions, emptyState, virtual } from '../../effects/node/virtual/module.f.mjs'
-/** @import { NodeProgramOptions } from '../../effects/node/types.ts' */
 import { dispatch } from '../../cli/module.f.mjs'
 import { vecToCBase32 } from '../../basen/cbase32/module.f.mjs'
 import { assert, assertEq } from '../../asserts/module.f.mjs'
diff --git a/fjs/cas/evo/module.f.ts b/fjs/cas/evo/module.f.ts
index c6b5b4513..2ecde3e95 100644
--- a/fjs/cas/evo/module.f.ts
+++ b/fjs/cas/evo/module.f.ts
@@ -42,26 +42,29 @@
  *
  * @module
  */
-import { pure, foldStep } from '../../effects/module.f.mjs'
+
 import type { Effect, Operation } from '../../effects/types.ts'
+import type { Key, MemOp } from '../../effects/memory/types.ts'
+import type { Cas } from '../types.ts'
+import type { Ok, Result } from '../../types/result/types.ts'
+import type { StringMap } from '../../types/object/types.ts'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import type { IoResult } from '../../effects/node/types.ts'
+
+import { pure, foldStep } from '../../effects/module.f.mjs'
 import { eff } from '../../effects/eff/module.f.mjs'
 import { create, read, write } from '../../effects/memory/module.f.mjs'
-import type { Key, MemOp } from '../../effects/memory/types.ts'
 import { collectRead } from '../module.f.mjs'
-import type { Cas } from '../types.ts'
 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 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.mjs'
 import { at, definedEntries } from '../../types/object/module.f.mjs'
-import type { StringMap } from '../../types/object/types.ts'
 import { unwrap } from '../../types/nullable/module.f.mjs'
-import type { Vec } from '../../types/bit_vec/types.ts'
 import { isNotFound } from '../../effects/node/module.f.mjs'
-import type { IoResult } from '../../effects/node/types.ts'
+
+import { decodeText, encodeText, dialect, checkReferences, isHash, type LockMap, type Revision } from '../../media/revision/module.f.ts'
 
 /** A cBase32 content hash, as accepted/returned by `Cas<O>`. */
 export type Hash = string
diff --git a/fjs/cas/evo/proof.f.ts b/fjs/cas/evo/proof.f.ts
index d60962a1c..a07f2ae7e 100644
--- a/fjs/cas/evo/proof.f.ts
+++ b/fjs/cas/evo/proof.f.ts
@@ -1,18 +1,20 @@
+import type { Cas } from '../types.ts'
+import type { Vec } from '../../types/bit_vec/types.ts'
+import type { Ok } from '../../types/result/types.ts'
+import type { IoResult } from '../../effects/node/types.ts'
+
 import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { pure } from '../../effects/module.f.mjs'
 import { fileCas } from '../module.f.mjs'
-import type { Cas } from '../types.ts'
 import { sha256 } from '../../crypto/sha2/module.f.mjs'
 import { emptyState, virtual } from '../../effects/node/virtual/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 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.mjs'
-import type { IoResult } from '../../effects/node/types.ts'
 import { tryUtf8 } from '../../text/module.f.mjs'
+
 import { dialect as revisionDialect } from '../../media/revision/module.f.ts'
 import {
     buildCache, decodeRevisionBlob, initEvo, evo, emptyCache, syncRevision,
diff --git a/fjs/cas/module.f.mjs b/fjs/cas/module.f.mjs
index dac866789..819485c99 100644
--- a/fjs/cas/module.f.mjs
+++ b/fjs/cas/module.f.mjs
@@ -2,16 +2,27 @@
  * Content-addressable storage utilities for hashing, addressing, and path parsing.
  *
  * @module
+ *
+ * @import { Sha2, State as Sha2State } from '../crypto/sha2/types.ts'
+ * @import { Vec } from '../types/bit_vec/types.ts'
+ * @import { Effect, Operation } from '../effects/types.ts'
+ * @import {
+ *  IoResult,
+ *  Now,
+ *  RandomInt,
+ *  ReadBytes,
+ *  Readdir,
+ *  Rm,
+ * } from '../effects/node/types.ts'
+ *  @import { List } from '../effects/list/types.ts'
+ * @import { Cas, FileCas, FileCasOperation } from './types.ts'
  */
 
-/** @import { 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.mjs'
-/** @import { 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 } from '../effects/module.f.mjs'
-/** @import { Effect, Operation } from '../effects/types.ts' */
 import { eff } from '../effects/eff/module.f.mjs'
 import {
     access,
@@ -27,26 +38,10 @@ import {
     stat,
     writeBytes,
 } from '../effects/node/module.f.mjs'
-/** @import {
-    Access,
-    CreateExclusive,
-    IoResult,
-    Mkdir,
-    Now,
-    RandomInt,
-    ReadBytes,
-    Readdir,
-    Rename,
-    Rm,
-    Stat,
-    WriteBytes,
-} from '../effects/node/types.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.mjs'
 import { nonEmpty, empty as elEmpty } from '../effects/list/module.f.mjs'
-/** @import { List } from '../effects/list/types.ts' */
-/** @import { Cas, FileCas, FileCasOperation } from './types.ts' */
 
 const split2 = splitAt(2)
 
diff --git a/fjs/cas/proof.f.mjs b/fjs/cas/proof.f.mjs
index 9b74cf9ff..d19cce297 100644
--- a/fjs/cas/proof.f.mjs
+++ b/fjs/cas/proof.f.mjs
@@ -1,19 +1,22 @@
-/** @import { Vec } from '../types/bit_vec/types.ts' */
+/**
+ * @import { Vec } from '../types/bit_vec/types.ts'
+ * @import { FileCasOperation } from './types.ts'
+ * @import { Effect } from '../effects/types.ts'
+ * @import { ReadFile, WriteFile, Rm, Mkdir, IoResult } from '../effects/node/types.ts'
+ * @import { Ok } from '../types/result/types.ts'
+ * @import { List } from '../effects/list/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, casUpload } from './module.f.mjs'
-/** @import { FileCasOperation } from './types.ts' */
 import { match, pure, runPure, step } from '../effects/module.f.mjs'
-/** @import { Effect } from '../effects/types.ts' */
 import { mkdir, writeFile, rm, readFile, access } from '../effects/node/module.f.mjs'
-/** @import { ReadFile, WriteFile, Rm, Mkdir, IoResult } from '../effects/node/types.ts' */
-/** @import { Ok } from '../types/result/types.ts' */
 import { error, ok } from '../types/result/module.f.mjs'
 import { emptyState, virtual } from '../effects/node/virtual/module.f.mjs'
 import { join } from '../path/module.f.mjs'
 import { nonEmpty, empty } from '../effects/list/module.f.mjs'
-/** @import { List } from '../effects/list/types.ts' */
 import { assert, assertEq, assertNotNullish } from '../asserts/module.f.mjs'
 
 const testDir = './test-cas-cli'
diff --git a/fjs/media/json/module.f.ts b/fjs/media/json/module.f.ts
index b673e1c9d..a43e94c3e 100644
--- a/fjs/media/json/module.f.ts
+++ b/fjs/media/json/module.f.ts
@@ -16,7 +16,7 @@ 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/types.ts'
-import { parse as parseTokens } from './parser/module.f.ts'
+import { parse as parseTokens } from './parser/module.f.mjs'
 import { tokenize } from './tokenizer/module.f.mjs'
 import { at, definedEntries } from '../../types/object/module.f.mjs'
 import type { Entry as ObjectEntry } from '../../types/object/types.ts'
diff --git a/fjs/media/json/parser/module.f.mjs b/fjs/media/json/parser/module.f.mjs
new file mode 100644
index 000000000..449e835a0
--- /dev/null
+++ b/fjs/media/json/parser/module.f.mjs
@@ -0,0 +1,219 @@
+/**
+ * JSON parser that consumes tokenizer output into JSON values.
+ *
+ * @module
+ *
+ * @import { Unknown } from '../types.ts'
+ * @import { Result } from '../../../types/result/types.ts'
+ * @import { List } from '../../../types/list/types.ts'
+ * @import { Fold } from '../../../types/function/operator/types.ts'
+ * @import { JsonToken } from '../tokenizer/types.ts'
+ * @import { _JsonObject, _JsonArray, _StateParse, _JsonState, _JsonStack } from './types.ts'
+ */
+
+import { error, ok } from '../../../types/result/module.f.mjs'
+import { fold, next, toArray, concat } from '../../../types/list/module.f.mjs'
+import { setReplace } from '../../../types/ordered_map/module.f.mjs'
+import { fromMap } from '../../../types/object/module.f.mjs'
+import { assertEq } from '../../../asserts/module.f.mjs'
+
+/** @type {(obj: _JsonObject) => (key: string) => _JsonObject} */
+const addKeyToObject =
+    obj => key => ({ kind: 'object', values: obj.values, key: key })
+
+/** @type {(obj: _JsonObject) => (value: Unknown) => _JsonObject} */
+const addValueToObject =
+    obj => value => ({ kind: 'object', values: setReplace(obj.key)(value)(obj.values), key: '' })
+
+/** @type {(array: _JsonArray) => (value: Unknown) => _JsonArray} */
+const addToArray =
+    array => value => ({ kind: 'array', values: concat(array.values)([value]) })
+
+/** @type {(state: _StateParse) => (key: string) => _JsonState} */
+const pushKey = state => value => {
+    if (state.top?.kind === 'object') { return { status: '{k', top: addKeyToObject(state.top)(value), stack: state.stack } }
+    return { status: 'error', message: 'error' }
+}
+
+/** @type {(state: _StateParse) => (value: Unknown) => _JsonState} */
+const pushValue = state => value => {
+    if (state.top === null) { return { status: 'result', value: value } }
+    if (state.top.kind === 'array') { return { status: '[v', top: addToArray(state.top)(value), stack: state.stack } }
+    return { status: '{v', top: addValueToObject(state.top)(value), stack: state.stack }
+}
+
+/** @type {(state: _StateParse) => _JsonState} */
+const startArray = state => {
+    const newStack = state.top === null ? null : { first: state.top, tail: state.stack }
+    return { status: '[', top: { kind: 'array', values: null }, stack: newStack }
+}
+
+/**
+ * Pops the enclosing container off `stack`. `next` is forced here rather than
+ * left as a `drop(1)` thunk: the stack is written only by startArray/startObject,
+ * always as a literal cons, and a lazy pop would leave one unforced thunk per
+ * closed container — a chain that overflows the stack when it is finally forced.
+ *
+ * @type {(stack: _JsonStack) => _StateParse}
+ */
+const popStack = stack => {
+    const ne = next(stack)
+    return ne === null
+        ? { status: '', top: null, stack: null }
+        : { status: '', top: ne.first, stack: ne.tail }
+}
+
+/** @type {(state: _StateParse) => _JsonState} */
+const endArray = state => {
+    const array = state.top !== null ? toArray(state.top.values) : null
+    const newState = popStack(state.stack)
+    return pushValue(newState)(array)
+}
+
+/** @type {(state: _StateParse) => _JsonState} */
+const startObject = state => {
+    const newStack = state.top === null ? null : { first: state.top, tail: state.stack }
+    return { status: '{', top: { kind: 'object', values: null, key: '' }, stack: newStack }
+}
+
+/** @type {(state: _StateParse) => _JsonState} */
+const endObject = state => {
+    const obj = state.top?.kind === 'object' ? fromMap(state.top.values) : null
+    const newState = popStack(state.stack)
+    return pushValue(newState)(obj)
+}
+
+/** @type {(token: JsonToken) => Unknown} */
+const tokenToValue = token => {
+    switch (token.kind) {
+        case 'null': return null
+        case 'false': return false
+        case 'true': return true
+        case 'number': return parseFloat(token.value)
+        case 'string': return token.value
+        default: return null
+    }
+}
+
+/** @type {(token: JsonToken) => boolean} */
+const isValueToken = token => {
+    switch (token.kind) {
+        case 'null':
+        case 'false':
+        case 'true':
+        case 'number':
+        case 'string': return true
+        default: return false
+    }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseValueOp = token => state => {
+    switch (token.kind) {
+        // A value is required here (top level, after `[`+`,`, or after `:`),
+        // so `]` is never valid — strict JSON has no trailing commas.
+        case ']':
+            return { status: 'error', message: 'unexpected token' }
+        case '[': return startArray(state)
+        case '{': return startObject(state)
+        default:
+            if (isValueToken(token)) { return pushValue(state)(tokenToValue(token)) }
+            return { status: 'error', message: 'unexpected token' }
+    }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseArrayStartOp = token => state => {
+    if (isValueToken(token)) { return pushValue(state)(tokenToValue(token)) }
+    if (token.kind === '[') { return startArray(state) }
+    if (token.kind === ']') { return endArray(state) }
+    if (token.kind === '{') { return startObject(state) }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseArrayValueOp = token => state => {
+    if (token.kind === ']') { return endArray(state) }
+    if (token.kind === ',') { return { status: '[,', top: state.top, stack: state.stack } }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseObjectStartOp = token => state => {
+    if (token.kind === 'string') { return pushKey(state)(token.value) }
+    if (token.kind === '}') { return endObject(state) }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseObjectKeyOp = token => state => {
+    if (token.kind === ':') { return { status: '{:', top: state.top, stack: state.stack } }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseObjectNextOp = token => state => {
+    if (token.kind === '}') { return endObject(state) }
+    if (token.kind === ',') { return { status: '{,', top: state.top, stack: state.stack } }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {(token: JsonToken) => (state: _StateParse) => _JsonState} */
+const parseObjectCommaOp = token => state => {
+    // After a `,` a member (string key) is required — `}` here would be a
+    // trailing comma, which strict JSON rejects.
+    if (token.kind === 'string') { return pushKey(state)(token.value) }
+    return { status: 'error', message: 'unexpected token' }
+}
+
+/** @type {Fold<JsonToken, _JsonState>} */
+const foldOp = token => state => {
+    if (token.kind === 'eof')
+        return state
+
+    switch (state.status) {
+        case 'result': return { status: 'error', message: 'unexpected token' }
+        case 'error': return { status: 'error', message: state.message }
+        case '': return parseValueOp(token)(state)
+        case '[': return parseArrayStartOp(token)(state)
+        case '[v': return parseArrayValueOp(token)(state)
+        case '[,': return parseValueOp(token)(state)
+        case '{': return parseObjectStartOp(token)(state)
+        case '{k': return parseObjectKeyOp(token)(state)
+        case '{:': return parseValueOp(token)(state)
+        case '{v': return parseObjectNextOp(token)(state)
+        case '{,': return parseObjectCommaOp(token)(state)
+    }
+}
+
+/**
+ * Parses a list of JSON tokens into a JSON-compatible value.
+ *
+ * Returns `ok` with the parsed value on success, or `error` with a message
+ * when the token sequence is invalid or incomplete.
+ *
+ * @type {(tokenList: List<JsonToken>) => Result<Unknown, string>}
+ */
+export const parse = tokenList => {
+    const state = fold(foldOp)({ status: '', top: null, stack: null })(tokenList)
+    switch (state.status) {
+        case 'result': return ok(state.value)
+        case 'error': return error(state.message)
+        default: return error('unexpected end')
+    }
+}
+
+export const proof = {
+    pushKey: {
+        // `pushKey` is only ever invoked while `state.top` is an object (the
+        // state machine's `'{'`/`'{,'` statuses guarantee it), so its
+        // non-object guard is a defensive branch unreachable through `parse`.
+        // Call it directly to cover that branch.
+        nonObjectTop: () => {
+            /** @type {_StateParse} */
+            const state = { status: '[', top: { kind: 'array', values: null }, stack: null }
+            const result = pushKey(state)('key')
+            assertEq(result.status, 'error')
+        },
+    },
+}
diff --git a/fjs/media/json/parser/module.f.ts b/fjs/media/json/parser/module.f.ts
deleted file mode 100644
index 54d97d396..000000000
--- a/fjs/media/json/parser/module.f.ts
+++ /dev/null
@@ -1,270 +0,0 @@
-/**
- * JSON parser that consumes tokenizer output into JSON values.
- *
- * @module
- */
-
-import type { Unknown } from '../types.ts'
-
-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/types.ts'
-import { setReplace } from '../../../types/ordered_map/module.f.mjs'
-import type { OrderedMap } from '../../../types/ordered_map/types.ts'
-import { fromMap } from '../../../types/object/module.f.mjs'
-import { assertEq } from '../../../asserts/module.f.mjs'
-
-type JsonObject = {
-    readonly kind: 'object'
-    readonly values: OrderedMap<Unknown>
-    readonly key: string
-}
-
-type JsonArray = {
-    readonly kind: 'array'
-    readonly values: List<Unknown>
-}
-
-type JsonStackElement = |
-    JsonObject |
-    JsonArray
-
-type JsonStack = List<JsonStackElement>
-
-type StateParse = {
-    readonly status: '' | '[' | '[v' | '[,' | '{' | '{k' | '{:' | '{v' | '{,'
-    readonly top: JsonStackElement | null
-    readonly stack: JsonStack
-}
-
-type StateResult = {
-    readonly status: 'result'
-    readonly value: Unknown
-}
-
-type StateError = {
-    readonly status: 'error'
-    readonly message: string
-}
-
-type JsonState = |
-    StateParse |
-    StateResult |
-    StateError
-
-const addKeyToObject
-    : (obj: JsonObject) => (key: string) => JsonObject
-    = obj => key => ({ kind: 'object', values: obj.values, key: key })
-
-const addValueToObject
-    : (obj: JsonObject) => (value: Unknown) => JsonObject
-    = obj => value => ({ kind: 'object', values: setReplace(obj.key)(value)(obj.values), key: '' })
-
-const addToArray
-    : (array: JsonArray) => (value: Unknown) => JsonArray
-    = array => value => ({ kind: 'array', values: concat(array.values)([value]) })
-
-const pushKey
-    : (state: StateParse) => (key: string) => JsonState
-    = state => value => {
-        if (state.top?.kind === 'object') { return { status: '{k', top: addKeyToObject(state.top)(value), stack: state.stack } }
-        return { status: 'error', message: 'error' }
-    }
-
-const pushValue
-    : (state: StateParse) => (value: Unknown) => JsonState
-    = state => value => {
-        if (state.top === null) { return { status: 'result', value: value } }
-        if (state.top.kind === 'array') { return { status: '[v', top: addToArray(state.top)(value), stack: state.stack } }
-        return { status: '{v', top: addValueToObject(state.top)(value), stack: state.stack }
-    }
-
-const startArray
-    : (state: StateParse) => JsonState
-    = state => {
-        const newStack = state.top === null ? null : { first: state.top, tail: state.stack }
-        return { status: '[', top: { kind: 'array', values: null }, stack: newStack }
-    }
-
-// Pops the enclosing container off `stack`. `next` is forced here rather than
-// left as a `drop(1)` thunk: the stack is written only by startArray/startObject,
-// always as a literal cons, and a lazy pop would leave one unforced thunk per
-// closed container — a chain that overflows the stack when it is finally forced.
-const popStack
-    : (stack: JsonStack) => StateParse
-    = stack => {
-        const ne = next(stack)
-        return ne === null
-            ? { status: '', top: null, stack: null }
-            : { status: '', top: ne.first, stack: ne.tail }
-    }
-
-const endArray
-    : (state: StateParse) => JsonState
-    = state => {
-        const array = state.top !== null ? toArray(state.top.values) : null
-        const newState = popStack(state.stack)
-        return pushValue(newState)(array)
-    }
-
-const startObject
-    : (state: StateParse) => JsonState
-    = state => {
-        const newStack = state.top === null ? null : { first: state.top, tail: state.stack }
-        return { status: '{', top: { kind: 'object', values: null, key: '' }, stack: newStack }
-    }
-
-const endObject
-    : (state: StateParse) => JsonState
-    = state => {
-        const obj = state.top?.kind === 'object' ? fromMap(state.top.values) : null
-        const newState = popStack(state.stack)
-        return pushValue(newState)(obj)
-    }
-
-const tokenToValue
-    : (token: JsonToken) => Unknown
-    = token => {
-        switch (token.kind) {
-            case 'null': return null
-            case 'false': return false
-            case 'true': return true
-            case 'number': return parseFloat(token.value)
-            case 'string': return token.value
-            default: return null
-        }
-    }
-
-const isValueToken
-    : (token: JsonToken) => boolean
-    = token => {
-        switch (token.kind) {
-            case 'null':
-            case 'false':
-            case 'true':
-            case 'number':
-            case 'string': return true
-            default: return false
-        }
-    }
-
-const parseValueOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        switch (token.kind) {
-            // A value is required here (top level, after `[`+`,`, or after `:`),
-            // so `]` is never valid — strict JSON has no trailing commas.
-            case ']':
-                return { status: 'error', message: 'unexpected token' }
-            case '[': return startArray(state)
-            case '{': return startObject(state)
-            default:
-                if (isValueToken(token)) { return pushValue(state)(tokenToValue(token)) }
-                return { status: 'error', message: 'unexpected token' }
-        }
-    }
-
-const parseArrayStartOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        if (isValueToken(token)) { return pushValue(state)(tokenToValue(token)) }
-        if (token.kind === '[') { return startArray(state) }
-        if (token.kind === ']') { return endArray(state) }
-        if (token.kind === '{') { return startObject(state) }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const parseArrayValueOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        if (token.kind === ']') { return endArray(state) }
-        if (token.kind === ',') { return { status: '[,', top: state.top, stack: state.stack } }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const parseObjectStartOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        if (token.kind === 'string') { return pushKey(state)(token.value) }
-        if (token.kind === '}') { return endObject(state) }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const parseObjectKeyOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        if (token.kind === ':') { return { status: '{:', top: state.top, stack: state.stack } }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const parseObjectNextOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        if (token.kind === '}') { return endObject(state) }
-        if (token.kind === ',') { return { status: '{,', top: state.top, stack: state.stack } }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const parseObjectCommaOp
-    : (token: JsonToken) => (state: StateParse) => JsonState
-    = token => state => {
-        // After a `,` a member (string key) is required — `}` here would be a
-        // trailing comma, which strict JSON rejects.
-        if (token.kind === 'string') { return pushKey(state)(token.value) }
-        return { status: 'error', message: 'unexpected token' }
-    }
-
-const foldOp
-    : Fold<JsonToken, JsonState>
-    = token => state => {
-        if (token.kind === 'eof')
-            return state
-
-        switch (state.status) {
-            case 'result': return { status: 'error', message: 'unexpected token' }
-            case 'error': return { status: 'error', message: state.message }
-            case '': return parseValueOp(token)(state)
-            case '[': return parseArrayStartOp(token)(state)
-            case '[v': return parseArrayValueOp(token)(state)
-            case '[,': return parseValueOp(token)(state)
-            case '{': return parseObjectStartOp(token)(state)
-            case '{k': return parseObjectKeyOp(token)(state)
-            case '{:': return parseValueOp(token)(state)
-            case '{v': return parseObjectNextOp(token)(state)
-            case '{,': return parseObjectCommaOp(token)(state)
-        }
-    }
-
-/**
- * Parses a list of JSON tokens into a JSON-compatible value.
- *
- * Returns `ok` with the parsed value on success, or `error` with a message
- * when the token sequence is invalid or incomplete.
- */
-export const parse
-    : (tokenList: List<JsonToken>) => Result<Unknown, string>
-    = tokenList => {
-        const state = fold(foldOp)({ status: '', top: null, stack: null })(tokenList)
-        switch (state.status) {
-            case 'result': return ok(state.value)
-            case 'error': return error(state.message)
-            default: return error('unexpected end')
-        }
-    }
-
-export const proof = {
-    pushKey: {
-        // `pushKey` is only ever invoked while `state.top` is an object (the
-        // state machine's `'{'`/`'{,'` statuses guarantee it), so its
-        // non-object guard is a defensive branch unreachable through `parse`.
-        // Call it directly to cover that branch.
-        nonObjectTop: () => {
-            const state: StateParse = { status: '[', top: { kind: 'array', values: null }, stack: null }
-            const result = pushKey(state)('key')
-            assertEq(result.status, 'error')
-        },
-    },
-}
diff --git a/fjs/media/json/parser/proof.f.ts b/fjs/media/json/parser/proof.f.ts
index 66387429e..c895c17df 100644
--- a/fjs/media/json/parser/proof.f.ts
+++ b/fjs/media/json/parser/proof.f.ts
@@ -1,4 +1,4 @@
-import { parse } from './module.f.ts'
+import { parse } from './module.f.mjs'
 import { tokenize } from '../tokenizer/module.f.mjs'
 import type { JsonToken } from '../tokenizer/types.ts'
 import { toArray } from '../../../types/list/module.f.mjs'
diff --git a/fjs/media/json/parser/types.ts b/fjs/media/json/parser/types.ts
new file mode 100644
index 000000000..7bae291f3
--- /dev/null
+++ b/fjs/media/json/parser/types.ts
@@ -0,0 +1,47 @@
+/**
+ * Internal state types for the JSON parser.
+ *
+ * @module
+ */
+
+import type { Unknown } from '../types.ts'
+import type { OrderedMap } from '../../../types/ordered_map/types.ts'
+import type { List } from '../../../types/list/types.ts'
+
+export type _JsonObject = {
+    readonly kind: 'object'
+    readonly values: OrderedMap<Unknown>
+    readonly key: string
+}
+
+export type _JsonArray = {
+    readonly kind: 'array'
+    readonly values: List<Unknown>
+}
+
+type _JsonStackElement = |
+    _JsonObject |
+    _JsonArray
+
+export type _JsonStack = List<_JsonStackElement>
+
+export type _StateParse = {
+    readonly status: '' | '[' | '[v' | '[,' | '{' | '{k' | '{:' | '{v' | '{,'
+    readonly top: _JsonStackElement | null
+    readonly stack: _JsonStack
+}
+
+type _StateResult = {
+    readonly status: 'result'
+    readonly value: Unknown
+}
+
+type _StateError = {
+    readonly status: 'error'
+    readonly message: string
+}
+
+export type _JsonState = |
+    _StateParse |
+    _StateResult |
+    _StateError