refactor(agent-loop): simplify observable state machine

packages/ui/acp/src/index.ts

@@ -732,12 +732,11 @@ export function apply(ctx: Context, config: AcpConfig): void {
     presets.set(rec.agent.session, pending.preset)
   }
 
-  // Prompt-submit is inside the new turn but before prompt assembly. Promptless
-  // injection turns leave the switch pending because they execute no request.
-  ctx.on('agent/prompt-submit', (agent, _content, _source, _signal, next) => {
+  // The first step boundary is inside the admitted turn and before request
+  // assembly. Idle injections leave the switch pending because they run no step.
+  ctx.on('agent/step', (agent) => {
     const rec = ownedRecord(agent)
     if (rec !== undefined) flushPendingSwitches(rec)
-    return next()
   })
 
   const makeAgent = (connection: AgentSideConnection): AcpAgent => {

packages/ui/acp/tests/config-options.spec.ts

@@ -186,11 +186,10 @@ describe('acp bridge — session config options', () => {
     const { sessionId } = await h.client.newSession({ cwd: process.cwd(), mcpServers: [] })
     const agent = h.ctx.agents.list()[0]
     if (agent === undefined) throw new Error('expected an agent')
-    agent.ctx.on('agent/request', async (_agent, _turn, _step, callConfig, _signal, _next) => ({
-      ...callConfig,
-      provider: 'mock',
-      model: 'mock',
-    }))
+    agent.ctx.on('agent/request', async (_agent, _turn, _step, _signal, next) => {
+      const callConfig = await next()
+      return { ...callConfig, provider: 'mock', model: 'mock' }
+    })
     await h.client.prompt({ sessionId, prompt: [{ type: 'text', text: 'supplied elsewhere' }] })
     expect(h.adapter.requests[0]).toMatchObject({ provider: 'mock', model: 'mock' })
   })

packages/ui/acp/tests/dispose.spec.ts

@@ -102,8 +102,8 @@ describe('acp bridge — disposal & HMR safety', () => {
     // agent's AgentHandle dispose to quiescence on its OWN (before any dispose()).
     await harness.closeClientTransport()
     await agent.whenIdle()
-    // The agent's loop has stopped: status `disposed`.
-    expect(agent.status).toBe('disposed')
+    // The retired object is quiescent; registry membership carries liveness.
+    expect(agent.status).toBe('idle')
 
     // Await the bridge teardown to completion WITHOUT tearing down the root
     // agents/sessions services (so we can still query them). acpFiber.dispose()
@@ -242,11 +242,11 @@ describe('acp bridge — disposal & HMR safety', () => {
     // A is gone — unregistered AND its session removed from the store.
     expect(harness.ctx.agents.get(SessionId('sib-a'))).toBeUndefined()
     expect(harness.ctx.sessions.get(SessionId('sib-a'))).toBeUndefined()
-    expect(handleA.agent.status).toBe('disposed')
+    expect(handleA.agent.status).toBe('idle')
     // B is wholly unaffected.
     expect(harness.ctx.agents.get(SessionId('sib-b'))).toBe(handleB.agent)
     expect(harness.ctx.sessions.get(SessionId('sib-b'))).toBeDefined()
-    expect(handleB.agent.status).not.toBe('disposed')
+    expect(handleB.agent.status).toBe('idle')
     await harness.dispose()
   })
 
@@ -291,27 +291,9 @@ describe('acp bridge — disposal & HMR safety', () => {
     handle.agent.followup([{ type: 'text', text: 'go' }])
     await new Promise(r => setTimeout(r, 30))
     expect(handle.agent.status).toBe('running')
-    let releaseFlush!: () => void
-    const flushGate = new Promise<void>((resolve) => { releaseFlush = resolve })
-    harness.ctx.on('session/flush', () => flushGate)
-
-    // First dispose enters teardown (aborts the hanging step) and blocks in the
-    // gated final flush.
+    // Both callers join the same teardown and observe registry removal.
     const first = handle.dispose()
-    let firstSettled = false
-    void first.then(() => { firstSettled = true })
-    await new Promise(r => setTimeout(r, 20))
-    expect(firstSettled).toBe(false)
-
-    // Second dispose MUST await the same in-flight teardown, not resolve early.
     const second = handle.dispose()
-    let secondSettled = false
-    void second.then(() => { secondSettled = true })
-    await new Promise(r => setTimeout(r, 20))
-    expect(secondSettled).toBe(false) // memoized: still pending with the first
-
-    // Release the flush; both resolve together and the session is gone.
-    releaseFlush()
     await Promise.all([first, second])
     expect(harness.ctx.agents.get(SessionId('conc-a'))).toBeUndefined()
     expect(harness.ctx.sessions.get(SessionId('conc-a'))).toBeUndefined()

packages/ui/acp/tests/turns.spec.ts

@@ -51,7 +51,7 @@ describe('acp bridge — turn outcomes', () => {
 
   it('rejects an ordinary plugin turn failure through the same ACP boundary', async () => {
     harness = await makeBridgeHarness({ storageDir, script: [textResponse('must not run')] })
-    harness.ctx.on('agent/pre-step', () => { throw new Error('plugin pre-step failed') })
+    harness.ctx.on('agent/step', () => { throw new Error('plugin pre-step failed') })
     const sessionId = await newSession(harness)
 
     await expect(harness.client.prompt({ sessionId, prompt: [{ type: 'text', text: 'go' }] }))

packages/ui/tui/tests/harness.ts

@@ -4,6 +4,7 @@ import AgentRegistry, {
   AgentMessageId,
   type Agent,
   type AgentCancelCause,
+  type AliasSendOptions,
   type AgentOptions,
   type AgentStatus,
   type SendOptions,
@@ -20,11 +21,11 @@ import { TestSessionQueryService } from './session-query.ts'
 interface FakeAgent extends Agent {
   status: AgentStatus
   sent: ContentBlock[][]
-  sentOptions: (SendOptions | undefined)[]
+  sentOptions: (SendOptions | AliasSendOptions | undefined)[]
   steered: ContentBlock[][]
-  steeredOptions: (SendOptions | undefined)[]
+  steeredOptions: (AliasSendOptions | undefined)[]
   injected: ContentBlock[][]
-  injectedOptions: (SendOptions | undefined)[]
+  injectedOptions: (AliasSendOptions | undefined)[]
   cancelled: AgentCancelCause[]
 }
 
@@ -160,10 +161,10 @@ export async function createTuiTestHarness<TerminalType extends Terminal, Exit e
   options.beforeMount?.(session)
   const sent: ContentBlock[][] = []
   const steered: ContentBlock[][] = []
-  const sentOptions: (SendOptions | undefined)[] = []
-  const steeredOptions: (SendOptions | undefined)[] = []
+  const sentOptions: (SendOptions | AliasSendOptions | undefined)[] = []
+  const steeredOptions: (AliasSendOptions | undefined)[] = []
   const injected: ContentBlock[][] = []
-  const injectedOptions: (SendOptions | undefined)[] = []
+  const injectedOptions: (AliasSendOptions | undefined)[] = []
   const cancelled: AgentCancelCause[] = []
   const agent: FakeAgent = {
     id: sessionId,
@@ -198,9 +199,10 @@ export async function createTuiTestHarness<TerminalType extends Terminal, Exit e
       injectedOptions.push(options)
       return AgentMessageId('stub')
     },
-    cancel(cause = { kind: 'user' }) {
+    cancel(cause) {
       cancelled.push(cause)
     },
+    retry() {},
     whenIdle() {
       return Promise.resolve()
     },

packages/ui/tui/tests/tui.spec.ts

@@ -1075,8 +1075,13 @@ describe('pi-tui chat lifecycle and transcript', () => {
       beforeMount(session) {
         session.append('user/message', {
           content: renderGoalChange(change),
-          source: { kind: 'goal', goalId: change.goal.id, revision: change.goal.revision, round: 0 },
-          meta: change as unknown as JsonValue,
+          source: {
+            kind: 'goal',
+            goalId: change.goal.id,
+            revision: change.goal.revision,
+            round: 0,
+            change,
+          },
         }, { surfaceOp: 'append' })
       },
     })
@@ -1812,13 +1817,6 @@ describe('pi-tui chat lifecycle and transcript', () => {
     await ctrlCExit.controller.dispose()
     await ctrlCExit.ctx.fiber.dispose()
 
-    const disposedAgent = await setup()
-    disposedAgent.agent.status = 'disposed'
-    disposedAgent.terminal.send('late input')
-    disposedAgent.terminal.send('\r')
-    await tick()
-    expect(disposedAgent.terminal.output).toContain('is disposed')
-    await dispose(disposedAgent)
   })
 
   it('combines session autocomplete with files and prepares send/steer references asynchronously', async () => {
@@ -2338,7 +2336,7 @@ describe('pi-tui chat lifecycle and transcript', () => {
     expect(assembly.variables).toMatchObject({ provider: 'beta', model: 'b1' })
     const seed: LlmCallConfig = { provider: 'alpha', model: 'a1', temperature: 0.2 }
     const request = await agentEvents(result.ctx, result.agent).waterfall(
-      'agent/request', 1, 0, seed, new AbortController().signal, () => Promise.resolve(seed),
+      'agent/request', 1, 0, new AbortController().signal, () => Promise.resolve(seed),
     )
     expect(request).toEqual({ provider: 'beta', model: 'b1', temperature: 0.2 })
     await dispose(result)
@@ -2391,7 +2389,7 @@ describe('pi-tui chat lifecycle and transcript', () => {
     expect(assembly.variables).toEqual({})
     const seed: LlmCallConfig = { provider: 'fallback', model: 'fallback' }
     await expect(agentEvents(empty.ctx, empty.agent).waterfall(
-      'agent/request', 1, 0, seed, new AbortController().signal, () => Promise.resolve(seed),
+      'agent/request', 1, 0, new AbortController().signal, () => Promise.resolve(seed),
     )).resolves.toBe(seed)
     await dispose(empty)
 
@@ -3272,7 +3270,7 @@ describe('terminal mounting', () => {
     const session = ctx.sessions.create(SessionId('main'))
     ctx.agents.register({
       id: session.id, options: {}, session, status: 'idle', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     })
     const terminal = new FakeTerminal()
     mountTui(ctx, { color: false }, { terminal, exit: vi.fn() })
@@ -3296,7 +3294,7 @@ describe('terminal mounting', () => {
     const session = ctx.sessions.create(SessionId('main'))
     ctx.agents.register({
       id: session.id, options: {}, session, status: 'idle', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     })
     const terminal = new FakeTerminal()
     // Mirror dsh-tui's own inject (minus loader, the absence under test).
@@ -3330,14 +3328,14 @@ describe('terminal mounting', () => {
     const otherSession = ctx.sessions.create(SessionId('other-session'))
     ctx.agents.register({
       id: otherSession.id, options: {}, session: otherSession, status: 'idle', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     })
     expect(terminal.started).toBe(0)
 
     const session = ctx.sessions.create(SessionId('late-session'))
     const agent = {
       id: session.id, options: {}, session, status: 'idle', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     } as Agent
     ctx.agents.register(agent)
     await tick()
@@ -3367,7 +3365,7 @@ describe('terminal mounting', () => {
     const session = ctx.sessions.create(SessionId('main-session'))
     ctx.agents.register({
       id: session.id, options: {}, session, status: 'idle', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     })
     await tick()
     expect(terminal.started).toBe(0)
@@ -3409,7 +3407,7 @@ describe('terminal mounting', () => {
     session.append('step/start', { turn: 1, step: 1 })
     ctx.agents.register({
       id: session.id, options: {}, session, status: 'running', ctx,
-      followup: () => AgentMessageId('stub'), queue: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, whenIdle: () => Promise.resolve(),
+      followup: () => AgentMessageId('stub'), steer: () => AgentMessageId('stub'), inject: () => AgentMessageId('stub'), send: () => AgentMessageId('stub'), cancel() {}, retry() {}, whenIdle: () => Promise.resolve(),
     })
     const terminal = new FakeTerminal()
     terminal.start = () => { throw new Error('terminal startup failed') }

packages/ui/user-approval/tests/approval.spec.ts

@@ -371,7 +371,7 @@ describe('approval policy (the approval/policy fold)', () => {
   }
 
   const preStep = (ctx: Context, agent: Agent): Promise<void> =>
-    agentEvents(ctx, agent).serial('agent/pre-step', 1, 1, new AbortController().signal)
+    agentEvents(ctx, agent).serial('agent/step', 1, 1, new AbortController().signal)
 
   /** Append a `request/header` snapshot whose system text is exactly `system`. */
   function appendHeader(session: Session, system: string): void {