test(snapshot): split pinned schemas into sidecars

packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/session.jsonl

@@ -1,2 +1,2 @@
 {"type":"session","id":"ccdc749f-56f3-4267-9750-598b5c60b7b2","createdAt":600,"cwd":"/var/folders/2g/b32ct0qn1d728l_v6tdkjytr0000gn/T/acp-snap-cwd-nOQ4Gy"}
-{"type":"request/header","seq":0,"time":4,"data":{"header":{"config":{"model":"fake"},"system":"{{system}}","tools":[{"name":"t1","description":"D1","parameters":{"type":"object"}}]},"reason":"initial"}}
+{"type":"request/header","seq":0,"time":4,"data":{"header":{"config":{"model":"fake"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}

packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/tool-schemas.golden.json

@@ -0,0 +1,12 @@
+{
+  "initial": [
+    {
+      "name": "t1",
+      "description": "D1",
+      "parameters": {
+        "type": "object"
+      }
+    }
+  ],
+  "deltas": []
+}

packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/session.jsonl

@@ -1,4 +1,4 @@
 {"type":"session","id":"12121212-3434-4545-8686-787878787878","createdAt":7,"cwd":"/rec/pin-cwd"}
-{"type":"request/header","seq":0,"time":7,"data":{"header":{"config":{"model":"fake"},"system":"{{system}}","tools":[{"name":"t1","description":"D1","parameters":{"type":"object"}}]},"reason":"initial"}}
+{"type":"request/header","seq":0,"time":7,"data":{"header":{"config":{"model":"fake"},"system":"{{system}}","tools":"{{tools}}"},"reason":"initial"}}
 {"type":"request/header-delta","seq":1,"time":7,"data":{"system":{"keepStart":1,"keepEnd":0,"insert":["{{system}}"]}}}
 {"type":"turn/start","seq":2,"time":7,"data":{"turn":1}}

packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/tool-schemas.golden.json

@@ -0,0 +1,12 @@
+{
+  "initial": [
+    {
+      "name": "t1",
+      "description": "D1",
+      "parameters": {
+        "type": "object"
+      }
+    }
+  ],
+  "deltas": []
+}

packages/support/acp-snapshot/tests/normalize.spec.ts

@@ -5,6 +5,7 @@ import {
   normalizeStdout,
   scrubRequestHeaders,
   scrubSystemPrompts,
+  scrubToolSchemas,
 } from '../src/normalize.ts'
 
 /**
@@ -306,3 +307,45 @@ describe('scrubSystemPrompts', () => {
     expect(scrubSystemPrompts(out)).toBe(out)
   })
 })
+
+describe('scrubToolSchemas', () => {
+  it('scrubs only tool-schema payloads while keeping prompts and prefixes verbatim', () => {
+    const header = JSON.stringify({
+      type: 'request/header', seq: 1, time: 2,
+      data: {
+        header: {
+          system: 'full prompt',
+          tools: [{ name: 'read', description: 'full schema', parameters: { type: 'object' } }],
+          messagePrefix: [{ role: 'user', content: [{ type: 'text', text: 'full prefix' }] }],
+        },
+        reason: 'initial',
+      },
+    })
+    const delta = JSON.stringify({
+      type: 'request/header-delta', seq: 2, time: 3,
+      data: {
+        system: { keepStart: 1, keepEnd: 2, insert: ['new prompt line'] },
+        tools: { added: [{ name: 'grep', description: 'new schema' }], changed: [{ name: 'read', description: 'changed schema' }] },
+        messagePrefix: [{ role: 'user', content: [{ type: 'text', text: 'changed prefix' }] }],
+      },
+    })
+    const systemOnly = JSON.stringify({
+      type: 'request/header', seq: 3, time: 4,
+      data: { header: { system: 'prompt only' }, reason: 'resume' },
+    })
+
+    const out = scrubToolSchemas(`${header}\n${delta}\n${systemOnly}\n`)
+    expect(out).toContain('"tools":"{{tools}}"')
+    expect(out).toContain('"added":[{"name":"grep","description":"{{tools}}"}]')
+    expect(out).toContain('"changed":[{"name":"read","description":"{{tools}}"}]')
+    expect(out).not.toContain('full schema')
+    expect(out).not.toContain('new schema')
+    expect(out).not.toContain('changed schema')
+    expect(out).toContain('full prompt')
+    expect(out).toContain('new prompt line')
+    expect(out).toContain('full prefix')
+    expect(out).toContain('changed prefix')
+    expect(out.split('\n')[2]).toBe(systemOnly)
+    expect(scrubToolSchemas(out)).toBe(out)
+  })
+})

packages/support/acp-snapshot/tests/suite.spec.ts

@@ -9,11 +9,16 @@ import {
   childFixturePaths,
   fixtureContext,
   formatSystemPromptSnapshot,
+  formatToolSchemasSnapshot,
   headerDeltaCount,
   normalizedHeaders,
   normalizedSystemPromptDeltas,
   normalizedSystemPrompts,
+  normalizedToolSchemaDeltas,
+  normalizedToolSchemas,
+  parseToolSchemasSnapshot,
   refreshFixtureReplacements,
+  restorePinnedToolSchemas,
   stabilizeRefreshLog,
   unknownToolCallIds,
 } from '../src/suite.ts'
@@ -71,6 +76,7 @@ afterAll(async () => {
 function staleRefreshFixtures(dir: string): void {
   writeFileSync(join(dir, 'plain-turn', 'stdout.golden.jsonl'), 'stale stdout\n')
   writeFileSync(join(dir, 'pin-turn', 'system-prompt.golden.md'), 'STALE PROMPT\n')
+  writeFileSync(join(dir, 'pin-turn', 'tool-schemas.golden.json'), '{"initial":[{"name":"stale"}],"deltas":[]}\n')
 
   const plainBehaviorFile = join(dir, 'plain-turn', 'behavior.json')
   const plainBehavior = JSON.parse(readFileSync(plainBehaviorFile, 'utf8')) as Record<string, unknown>
@@ -126,6 +132,9 @@ describe('defineAcpSnapshotSuite: refresh write-back', () => {
       'NEW PROMPT LINE',
       '',
     ].join('\n'))
+    const schemas = readFileSync(join(refreshDir, 'pin-turn', 'tool-schemas.golden.json'), 'utf8')
+    expect(schemas).toContain('"description": "D1"')
+    expect(schemas).not.toContain('"name":"stale"')
   })
 })
 
@@ -236,6 +245,40 @@ describe('normalizedSystemPrompts', () => {
   })
 })
 
+describe('normalizedToolSchemas', () => {
+  it('extracts normalized schema arrays and omits absent or non-array fields', () => {
+    const log = [
+      '{"type":"session","id":"a","createdAt":5,"cwd":"/w"}',
+      '{"type":"request/header","seq":0,"time":9,"data":{"header":{"tools":[{"name":"read","description":"work in /w"}]}}}',
+      '{"type":"request/header","seq":1,"time":9,"data":{"header":{}}}',
+      '{"type":"request/header","seq":2,"time":9,"data":{"header":{"tools":null}}}',
+      '{"type":"request/header","seq":3,"time":9,"data":{"header":null}}',
+      '{"type":"request/header","seq":4,"time":9,"data":{"header":"invalid"}}',
+      '',
+    ].join('\n')
+    expect(normalizedToolSchemas(log, { sessionIds: [], cwd: '/w' })).toEqual([
+      [{ name: 'read', description: 'work in {{cwd}}' }],
+    ])
+  })
+})
+
+describe('normalizedToolSchemaDeltas', () => {
+  it('extracts and normalizes object-valued schema edits', () => {
+    const log = [
+      '{"type":"request/header-delta","data":{"tools":{"added":[{"name":"read","description":"work in /w"}]}}}',
+      '{"type":"request/header-delta","data":{"tools":null}}',
+      '{"type":"request/header-delta","data":{"tools":"invalid"}}',
+      '{"type":"request/header-delta","data":{"tools":[]}}',
+      '{"type":"request/header-delta","data":{"system":{"insert":[]}}}',
+      '{"type":"request/header","data":{"tools":{"added":[]}}}',
+      '',
+    ].join('\n')
+    expect(normalizedToolSchemaDeltas(log, { sessionIds: [], cwd: '/w' })).toEqual([
+      { added: [{ name: 'read', description: 'work in {{cwd}}' }] },
+    ])
+  })
+})
+
 describe('normalizedSystemPromptDeltas', () => {
   it('extracts and normalizes well-formed system edits', () => {
     const log = [
@@ -270,6 +313,39 @@ describe('formatSystemPromptSnapshot', () => {
   })
 })
 
+describe('tool-schema snapshots', () => {
+  const snapshot = {
+    initial: [{ name: 'read', description: 'Read a file.' }],
+    deltas: [{ added: [{ name: 'grep', description: 'Search files.' }] }],
+  }
+
+  it('formats and parses canonical structured JSON', () => {
+    const formatted = formatToolSchemasSnapshot(snapshot.initial, snapshot.deltas)
+    expect(formatted).toBe(`${JSON.stringify(snapshot, null, 2)}\n`)
+    expect(parseToolSchemasSnapshot(formatted)).toEqual(snapshot)
+  })
+
+  it('rejects invalid top-level and field shapes', () => {
+    expect(() => parseToolSchemasSnapshot('null')).toThrow(/must be an object/)
+    expect(() => parseToolSchemasSnapshot('"invalid"')).toThrow(/must be an object/)
+    expect(() => parseToolSchemasSnapshot('[]')).toThrow(/must be an object/)
+    expect(() => parseToolSchemasSnapshot('{"initial":{},"deltas":[]}')).toThrow(/array-valued/)
+    expect(() => parseToolSchemasSnapshot('{"initial":[],"deltas":{}}')).toThrow(/array-valued/)
+  })
+
+  it('restores initial schemas into the pinned header token', () => {
+    expect(restorePinnedToolSchemas({ system: '{{system}}', tools: '{{tools}}' }, snapshot))
+      .toEqual({ system: '{{system}}', tools: snapshot.initial })
+  })
+
+  it('rejects invalid headers and a missing tool token', () => {
+    expect(() => restorePinnedToolSchemas(null, snapshot)).toThrow(/must be an object/)
+    expect(() => restorePinnedToolSchemas('invalid', snapshot)).toThrow(/must be an object/)
+    expect(() => restorePinnedToolSchemas([], snapshot)).toThrow(/must be an object/)
+    expect(() => restorePinnedToolSchemas({ tools: [] }, snapshot)).toThrow(/must equal/)
+  })
+})
+
 describe('headerDeltaCount', () => {
   it('counts request/header-delta events, ignoring blanks and other lines', () => {
     const delta = JSON.stringify({ type: 'request/header-delta', seq: 2, time: 9, data: {} })