Merge remote-tracking branch 'origin/master' into codex/system-prompt-snapshots

# Conflicts:
#	examples/acp-agent/tests/snapshots/both-mode-turn/session.jsonl
#	examples/acp-agent/tests/snapshots/code-mode-turn/session.jsonl
#	examples/acp-agent/tests/snapshots/text-turn/session.jsonl
#	packages/support/acp-snapshot/src/suite.ts

packages/support/acp-snapshot/tests/fixtures/fake-acp-agent.ts

@@ -58,6 +58,13 @@ interface Behavior {
   strayBucketFile?: boolean
   /** Delete the sessions root entirely (harvest must yield no logs). */
   deleteSessionsRoot?: boolean
+  /**
+   * Vocabulary for `session/set_config_option`: allowed values per config id.
+   * A set naming an unknown id or an out-of-vocabulary value rejects (the
+   * real bridge's rule); a valid set answers with the complete refreshed
+   * option state, `currentValue` updated. Absent: every set rejects.
+   */
+  configOptions?: Record<string, string[]>
 }
 
 const sessionsRoot = process.env.DSH_SNAPSHOT_SESSIONS_ROOT ?? ''
@@ -81,6 +88,8 @@ let sessionCwd = ''
 let parkedPromptId: number | string | null = null
 /** Resolvers for permission-probe responses, keyed by outbound request id. */
 const pendingPermission = new Map<number, (outcome: unknown) => void>()
+/** Per-run `session/set_config_option` state: config id → current value (first vocabulary entry until set). */
+const currentConfig: Record<string, string> = {}
 
 function send(frame: Record<string, unknown>): void {
   process.stdout.write(`${JSON.stringify({ jsonrpc: '2.0', ...frame })}\n`)
@@ -195,6 +204,32 @@ function handleFrame(frame: Record<string, unknown>): void {
     case 'session/prompt':
       void handlePrompt(id as number | string)
       return
+    case 'session/set_config_option': {
+      const vocabulary = behavior.configOptions
+      const configId = params.configId as string
+      const value = params.value as string
+      const values = vocabulary?.[configId]
+      if (values === undefined) {
+        respondError(id as number | string, `unknown config option ${configId}`)
+        return
+      }
+      if (!values.includes(value)) {
+        respondError(id as number | string, `unknown ${configId} value ${value}`)
+        return
+      }
+      currentConfig[configId] = value
+      // The real bridge's contract: every set answers with the COMPLETE
+      // refreshed option state, not just the changed entry.
+      respond(id as number | string, {
+        configOptions: Object.entries(vocabulary as Record<string, string[]>).map(([cid, vs]) => ({
+          id: cid,
+          type: 'select',
+          currentValue: currentConfig[cid] ?? vs[0],
+          options: vs.map(v => ({ value: v, name: v })),
+        })),
+      })
+      return
+    }
     case 'session/cancel':
       if (parkedPromptId !== null) {
         const parked = parkedPromptId

packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/behavior.json

@@ -5,7 +5,8 @@
     "lines": [
       { "type": "session", "id": "{{SID}}", "createdAt": 100, "cwd": "{{CWD}}" },
       { "type": "request/header", "seq": 0, "time": 100, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } },
-      { "type": "turn/start", "seq": 1, "time": 100, "data": { "turn": 1 } }
+      { "type": "request/header-delta", "seq": 1, "time": 100, "data": { "system": { "keepStart": 1, "keepEnd": 0, "insert": ["NEW PROMPT LINE"] } } },
+      { "type": "turn/start", "seq": 2, "time": 100, "data": { "turn": 1 } }
     ]
   }]
 }

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

@@ -1,3 +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":"turn/start","seq":1,"time":7,"data":{"turn":1}}
+{"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/system-prompt.golden.md

@@ -1 +1,5 @@
 SYS PROMPT
+
+<!-- request/header-delta 1: keepStart=1, keepEnd=0 -->
+
+NEW PROMPT LINE

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

@@ -168,6 +168,8 @@ describe('runScenario', () => {
     [{ op: 'promptExpectError', text: 'x' }, /promptExpectError before newSession/],
     [{ op: 'promptAndCancel', text: 'x' }, /promptAndCancel before newSession/],
     [{ op: 'cancel' }, /cancel before newSession/],
+    [{ op: 'setConfigOption', configId: 'sandbox-mode', value: 'read-only' }, /setConfigOption before newSession/],
+    [{ op: 'setConfigOptionExpectError', configId: 'sandbox-mode', value: 'yolo' }, /setConfigOptionExpectError before newSession/],
   ] as [InputStep, RegExp][])('rejects %j before newSession', { timeout: 20_000 }, async (step, message) => {
     const { fixtureFile } = await scenario({})
     await expect(runScenario(
@@ -176,6 +178,53 @@ describe('runScenario', () => {
     )).rejects.toThrow(message)
   })
 
+  it('setConfigOption switches a value and receives the complete refreshed option state', { timeout: 20_000 }, async () => {
+    const { fixtureFile } = await scenario({
+      configOptions: { 'sandbox-mode': ['read-only', 'workspace-write'], 'approval-policy': ['ask', 'never'] },
+    })
+    const result = await runScenario(
+      {
+        steps: [...boot,
+          { op: 'setConfigOption', configId: 'sandbox-mode', value: 'workspace-write' },
+          { op: 'setConfigOption', configId: 'approval-policy', value: 'never' }],
+      },
+      { agent: AGENT, mode: 'replay', fixtureFile },
+    )
+    // Every set answers with the FULL state: the second response carries the
+    // first switch's value too — the complete-refreshed-state contract.
+    const frames = result.rawStdout.trim().split('\n').map(line => JSON.parse(line) as { result?: { configOptions?: { id: string; currentValue: string }[] } })
+    const states = frames
+      .map(f => f.result?.configOptions)
+      .filter(options => options !== undefined)
+      .map(options => Object.fromEntries((options as { id: string; currentValue: string }[]).map(o => [o.id, o.currentValue])))
+    expect(states).toEqual([
+      { 'sandbox-mode': 'workspace-write', 'approval-policy': 'ask' },
+      { 'sandbox-mode': 'workspace-write', 'approval-policy': 'never' },
+    ])
+  })
+
+  it('setConfigOptionExpectError swallows the rejection for unknown ids and out-of-vocabulary values', { timeout: 20_000 }, async () => {
+    const { fixtureFile } = await scenario({ configOptions: { 'sandbox-mode': ['read-only'] } })
+    const result = await runScenario(
+      {
+        steps: [...boot,
+          { op: 'setConfigOptionExpectError', configId: 'sandbox-mode', value: 'yolo' },
+          { op: 'setConfigOptionExpectError', configId: 'reasoning-effort', value: 'max' }],
+      },
+      { agent: AGENT, mode: 'replay', fixtureFile },
+    )
+    expect(result.rawStdout).toContain('unknown sandbox-mode value yolo')
+    expect(result.rawStdout).toContain('unknown config option reasoning-effort')
+  })
+
+  it('setConfigOptionExpectError throws when the set unexpectedly succeeds', { timeout: 20_000 }, async () => {
+    const { fixtureFile } = await scenario({ configOptions: { 'sandbox-mode': ['read-only'] } })
+    await expect(runScenario(
+      { steps: [...boot, { op: 'setConfigOptionExpectError', configId: 'sandbox-mode', value: 'read-only' }] },
+      { agent: AGENT, mode: 'replay', fixtureFile },
+    )).rejects.toThrow(/expected set_config_option to be rejected/)
+  })
+
   it('rejects an unknown input op', { timeout: 20_000 }, async () => {
     const { fixtureFile } = await scenario({})
     const bogus = { op: 'reticulate' } as unknown as InputStep

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

@@ -11,6 +11,7 @@ import {
   formatSystemPromptSnapshot,
   headerDeltaCount,
   normalizedHeaders,
+  normalizedSystemPromptDeltas,
   normalizedSystemPrompts,
   refreshFixtureReplacements,
   stabilizeRefreshLog,
@@ -50,7 +51,7 @@ const RECORD_SRC = fileURLToPath(new URL('./fixtures/record-suite', import.meta.
 // is what this suite can exercise; the real overlay boot is the acp-agent
 // example's code-mode scenarios).
 const REPLAY_SCENARIOS: Scenario[] = [
-  { name: 'pin-turn', hasModelTurn: true, recorded: true, pinsHeader: true, headerClass: 'main' },
+  { name: 'pin-turn', hasModelTurn: true, recorded: true, pinsHeader: true, expectedHeaderDeltas: 1, headerClass: 'main' },
   { name: 'plain-turn', hasModelTurn: true, recorded: true, childSessions: 1, headerClass: 'main', configPath: AGENT.configPath },
   { name: 'no-model', hasModelTurn: false, recorded: false, headerClass: 'main' },
   { name: 'blocked-log', hasModelTurn: false, comparesLog: true, recorded: false, headerClass: 'main' },
@@ -128,7 +129,14 @@ describe('defineAcpSnapshotSuite: refresh write-back', () => {
     expect(authored).toContain('"error":"model exploded"')
     expect(authored).not.toContain('"error":"stale"')
 
-    expect(readFileSync(join(refreshDir, 'pin-turn', 'system-prompt.golden.md'), 'utf8')).toBe('SYS PROMPT\n')
+    expect(readFileSync(join(refreshDir, 'pin-turn', 'system-prompt.golden.md'), 'utf8')).toBe([
+      'SYS PROMPT',
+      '',
+      '<!-- request/header-delta 1: keepStart=1, keepEnd=0 -->',
+      '',
+      'NEW PROMPT LINE',
+      '',
+    ].join('\n'))
   })
 })
 
@@ -239,11 +247,32 @@ describe('normalizedSystemPrompts', () => {
   })
 })
 
+describe('normalizedSystemPromptDeltas', () => {
+  it('extracts and normalizes well-formed system edits', () => {
+    const log = [
+      '{"type":"request/header-delta","data":{"system":{"keepStart":1,"keepEnd":0,"insert":["work in /w"]}}}',
+      '{"type":"request/header-delta","data":{"tools":{"replace":[]}}}',
+      '{"type":"request/header-delta","data":{"system":{"keepStart":"1","keepEnd":0,"insert":[]}}}',
+      '{"type":"request/header-delta","data":{"system":{"keepStart":1,"keepEnd":0,"insert":[null]}}}',
+      '',
+    ].join('\n')
+    expect(normalizedSystemPromptDeltas(log, { sessionIds: [], cwd: '/w' })).toEqual([
+      { keepStart: 1, keepEnd: 0, insert: ['work in {{cwd}}'] },
+    ])
+  })
+})
+
 describe('formatSystemPromptSnapshot', () => {
   it('adds a missing terminal newline without changing an existing one', () => {
     expect(formatSystemPromptSnapshot('prompt')).toBe('prompt\n')
     expect(formatSystemPromptSnapshot('prompt\n')).toBe('prompt\n')
   })
+
+  it('renders readable system-prompt delta sections', () => {
+    expect(formatSystemPromptSnapshot('prompt', [
+      { keepStart: 1, keepEnd: 0, insert: ['new', 'lines'] },
+    ])).toBe('prompt\n\n<!-- request/header-delta 1: keepStart=1, keepEnd=0 -->\n\nnew\nlines\n')
+  })
 })
 
 describe('headerDeltaCount', () => {