diff --git a/src/cli/specs/orchestration-worker-specs.ts b/src/cli/specs/orchestration-worker-specs.ts
index 3de5ba03ddf..798cb16c42e 100644
--- a/src/cli/specs/orchestration-worker-specs.ts
+++ b/src/cli/specs/orchestration-worker-specs.ts
@@ -34,7 +34,7 @@ export const ORCHESTRATION_WORKER_COMMAND_SPECS: CommandSpec[] = [
       '--model supports Claude, Codex, and Cursor opaque provider model ids; --effort requires --model. Neither can combine with --terminal.',
       'New worktrees use agent-first creation and default --setup to run. Repository start-immediately runs setup beside the agent; wait-for-setup gates agent readiness and task input.',
       'Creation flags (--name, --repo, --base-branch, --display-name, --comment, --setup) are rejected for current/existing worktrees. Use exact --repo on the selected server; project/host convenience routing remains on worktree create.',
-      '--structured starts the worker as a native structured chat session instead of a terminal agent. Local claude/codex only; it cannot combine with --terminal or a remote --on.',
+      '--structured starts the worker as a native structured chat session instead of a terminal agent. Local claude/codex only, outside WSL; it cannot combine with --terminal, --model, --effort, a remote --on, or a new-child/new-top-level worktree.',
       '--on selects only the worker server; the Run and this command remain on the current Orca server.',
       'Remote current and new-child are invalid; discover an exact remote selector or use new-top-level.',
       '--retry-of links the replacement attempt but does not inherit placement; repeat the intended --on/worktree and --agent/terminal choices.',
diff --git a/src/main/runtime/orchestration/structured-mailbox-pointer-host.test.ts b/src/main/runtime/orchestration/structured-mailbox-pointer-host.test.ts
new file mode 100644
index 00000000000..8968709374d
--- /dev/null
+++ b/src/main/runtime/orchestration/structured-mailbox-pointer-host.test.ts
@@ -0,0 +1,132 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import type { AgentJournalRenderItem } from '../../../shared/agent-session-journal-types'
+
+const hostRef: { current: unknown } = { current: null }
+
+vi.mock('../../native-chat/agent-session-wire/structured-agent-session-registry', () => ({
+  getStructuredAgentSessionHost: () => hostRef.current
+}))
+
+const { createStructuredMailboxPointerHost, structuredPointerCallerKey } =
+  await import('./structured-mailbox-pointer-host')
+
+function runningTurn(): AgentJournalRenderItem {
+  return {
+    itemId: 'lifecycle-1',
+    revision: 1,
+    body: { kind: 'status', text: 'working', turnLifecycle: { turnId: 'turn-1', state: 'running' } }
+  } as unknown as AgentJournalRenderItem
+}
+
+function transcript(count: number): AgentJournalRenderItem[] {
+  return Array.from(
+    { length: count },
+    (_unused, index) =>
+      ({
+        itemId: `tool-${index}`,
+        revision: 1,
+        body: { kind: 'tool-call', name: 'Bash', input: {}, state: 'completed' }
+      }) as unknown as AgentJournalRenderItem
+  )
+}
+
+describe('structured mailbox pointer host', () => {
+  beforeEach(() => {
+    hostRef.current = null
+  })
+
+  it('reads the gate facts from the FULL timeline, never a bounded tail', () => {
+    // The defect this pins: a running turn is announced by ONE lifecycle item, and settlement
+    // tombstones it rather than rewriting it. A long tool-calling turn pushes that item arbitrarily
+    // far from the tail, so any page-sized read reports a busy worker as idle — and the pointer is
+    // then delivered mid-turn, which Codex answers with `turn already running` and Claude settles
+    // `unknown` while the message is really queued.
+    const items = [runningTurn(), ...transcript(500)]
+    hostRef.current = { journalSnapshot: () => ({ items }) }
+    expect(createStructuredMailboxPointerHost().readGateFacts('s1')).toEqual({
+      turnRunning: true,
+      awaitingHuman: false
+    })
+  })
+
+  it('answers null rather than idle when the session cannot be read', () => {
+    // Null retains the pointer; `{turnRunning:false}` would deliver a nudge into a session this
+    // runtime cannot see at all.
+    expect(createStructuredMailboxPointerHost().readGateFacts('s1')).toBeNull()
+    hostRef.current = {
+      journalSnapshot: () => {
+        throw new Error('agent_session_ownership_unknown')
+      }
+    }
+    expect(createStructuredMailboxPointerHost().readGateFacts('s1')).toBeNull()
+  })
+
+  it('reports an unattached host rather than a rejection when nothing can be sent', async () => {
+    await expect(
+      createStructuredMailboxPointerHost().send({
+        sessionId: 's1',
+        dispatchId: 'd1',
+        operationId: 'op1',
+        expectedRuntimeFence: 1,
+        payloadFingerprint: 'fp',
+        body: { kind: 'message', role: 'user', blocks: [] }
+      } as never)
+    ).resolves.toEqual({ kind: 'unattached' })
+  })
+
+  it.each([
+    ['accepted', 'accepted'],
+    ['rejected', 'rejected'],
+    // Neither is an acknowledgement, and only `accepted` may consume mail: both have to reach the
+    // caller as `unknown` so the pointer is retained for the next journal edge.
+    ['pending', 'unknown'],
+    ['unknown', 'unknown']
+  ])('maps a %s submission to %s', async (dispatchState, expected) => {
+    const send = vi.fn(
+      async (_caller: { callerKey: string }, _payload: { retryUnknown?: boolean }) => ({
+        ok: true,
+        value: { submission: { dispatchState } }
+      })
+    )
+    hostRef.current = { send }
+    await expect(
+      createStructuredMailboxPointerHost().send({
+        sessionId: 's1',
+        dispatchId: 'd1',
+        operationId: 'op1',
+        expectedRuntimeFence: 1,
+        payloadFingerprint: 'fp',
+        body: { kind: 'message', role: 'user', blocks: [] }
+      } as never)
+    ).resolves.toEqual({ kind: 'sent', state: expected })
+    // Per-dispatch, so one worker's nudges cannot exhaust the shared operation-ledger budget.
+    expect(send.mock.calls[0]![0]).toEqual({ callerKey: structuredPointerCallerKey('d1') })
+    expect(send.mock.calls[0]![1]!.retryUnknown).toBe(true)
+  })
+
+  it('separates a not-attached refusal from a real one', async () => {
+    for (const [code, expected] of [
+      ['agent_session_ownership_unknown', { kind: 'unattached' }],
+      ['agent_session_conflict', { kind: 'sent', state: 'rejected' }]
+    ] as const) {
+      hostRef.current = { send: async () => ({ ok: false, refusal: { code, message: 'no' } }) }
+      await expect(
+        createStructuredMailboxPointerHost().send({
+          sessionId: 's1',
+          dispatchId: 'd1',
+          operationId: 'op1',
+          expectedRuntimeFence: 1,
+          payloadFingerprint: 'fp',
+          body: { kind: 'message', role: 'user', blocks: [] }
+        } as never)
+      ).resolves.toEqual(expected)
+    }
+  })
+
+  it('reads the runtime fence off the durable record', () => {
+    hostRef.current = { deps: { store: { getRecord: () => ({ lease: { runtimeFence: 9 } }) } } }
+    expect(createStructuredMailboxPointerHost().currentFence('s1')).toBe(9)
+    hostRef.current = { deps: { store: { getRecord: () => null } } }
+    expect(createStructuredMailboxPointerHost().currentFence('s1')).toBeNull()
+  })
+})
diff --git a/src/main/runtime/rpc/methods/orchestration-structured-worker-session.test.ts b/src/main/runtime/rpc/methods/orchestration-structured-worker-session.test.ts
index f98588546aa..618b0707f84 100644
--- a/src/main/runtime/rpc/methods/orchestration-structured-worker-session.test.ts
+++ b/src/main/runtime/rpc/methods/orchestration-structured-worker-session.test.ts
@@ -10,8 +10,13 @@ vi.mock('./structured-agent-session-create', () => ({
   createStructuredAgentSessionForWorktree: (...args: unknown[]) => createSpy(...args)
 }))
 
-const { createStructuredWorkerSession, releaseStructuredWorkerSession, structuredWorkerHoldId } =
-  await import('./orchestration-structured-worker-session')
+const {
+  createStructuredWorkerSession,
+  releaseStructuredWorkerSession,
+  sendStructuredWorkerPreamble,
+  structuredWorkerHoldId
+} = await import('./orchestration-structured-worker-session')
+const { isUnknownWorkerStartOutcome } = await import('./orchestration-worker-topology')
 const { structuredWorkerIdentities } = await import('../../structured-worker-identity')
 const { structuredWorkerChildIdentityEnv } =
   await import('../../structured-worker-child-identity-env')
@@ -216,3 +221,45 @@ describe('structured worker session hold', () => {
     ).rejects.toThrow(/local execution host/)
   })
 })
+
+describe('structured worker dispatch preamble', () => {
+  function hostWithSubmission(submission: Record<string, unknown>) {
+    return {
+      deps: { store: { getRecord: () => ({ lease: { runtimeFence: 7 } }) } },
+      send: async () => ({ ok: true, value: { clientMessageId: 'c1', submission } })
+    } as never
+  }
+
+  const send = (host: never) =>
+    sendStructuredWorkerPreamble({ host, sessionId: 's1', dispatchId: 'd1', preamble: 'spec' })
+
+  it('reports the preamble delivered only on an accepted submission', async () => {
+    await expect(
+      send(hostWithSubmission({ dispatchState: 'accepted', reason: null }))
+    ).resolves.toBeUndefined()
+  })
+
+  it('never claims delivery for a submission the provider never acknowledged', async () => {
+    // `dispatchSafely` turns ANY thrown adapter call — provider child dead, transport dropped —
+    // into `unknown`, and `performSend` still returns ok. Reporting that as `dispatch_input:
+    // accepted` marks the worker ready with no task, and the coordinator blocks in
+    // `check --wait --types worker_done` until it times out.
+    for (const dispatchState of ['unknown', 'pending'] as const) {
+      const error = await send(
+        hostWithSubmission({ dispatchState, reason: 'provider child exited' })
+      ).catch((thrown: unknown) => thrown)
+      expect((error as { code?: string }).code).toBe('operation_unknown')
+      // The wiring, not just the throw: this is the code that makes the start receipt
+      // `outcome_unknown` with the worker-show / worker-abandon recovery commands.
+      expect(isUnknownWorkerStartOutcome(error, 'dispatch_input')).toBe(true)
+    }
+  })
+
+  it('keeps a rejected preamble a proven failure rather than an unknown one', async () => {
+    const error = await send(
+      hostWithSubmission({ dispatchState: 'rejected', reason: 'fence moved' })
+    ).catch((thrown: unknown) => thrown)
+    expect((error as Error).message).toMatch(/rejected: fence moved/)
+    expect(isUnknownWorkerStartOutcome(error, 'dispatch_input')).toBe(false)
+  })
+})
diff --git a/src/main/runtime/rpc/methods/orchestration-structured-worker-session.ts b/src/main/runtime/rpc/methods/orchestration-structured-worker-session.ts
index 9d5fcfeca22..1769c7d95e0 100644
--- a/src/main/runtime/rpc/methods/orchestration-structured-worker-session.ts
+++ b/src/main/runtime/rpc/methods/orchestration-structured-worker-session.ts
@@ -235,11 +235,21 @@ export async function sendStructuredWorkerPreamble(args: {
   if (!result.ok) {
     throw new Error(`The dispatch preamble was refused: ${result.refusal.message}`)
   }
-  if (result.value.submission.dispatchState === 'rejected') {
-    throw new Error(
-      `The dispatch preamble was rejected: ${result.value.submission.reason ?? 'no reason given'}`
-    )
+  const submission = result.value.submission
+  if (submission.dispatchState === 'accepted') {
+    return
   }
+  if (submission.dispatchState === 'rejected') {
+    throw new Error(`The dispatch preamble was rejected: ${submission.reason ?? 'no reason given'}`)
+  }
+  // Only `accepted` is an acknowledgement — the same rule the mail lane already applies. A thrown
+  // adapter call settles as `unknown`, which is indistinguishable from a lost reply, so the start
+  // may claim neither delivery nor failure: `operation_unknown` is what turns this into the
+  // `outcome_unknown` receipt whose nextCommands send the coordinator to look.
+  throw new OrchestrationError(
+    'operation_unknown',
+    `The dispatch preamble was submitted but not acknowledged (${submission.dispatchState}): ${submission.reason ?? 'no reason given'}.`
+  )
 }
 
 function requireInstalledHost(): StructuredAgentSessionHost {
diff --git a/src/main/runtime/rpc/methods/orchestration-structured-worker-start-refusals.test.ts b/src/main/runtime/rpc/methods/orchestration-structured-worker-start-refusals.test.ts
new file mode 100644
index 00000000000..ca7db8719f0
--- /dev/null
+++ b/src/main/runtime/rpc/methods/orchestration-structured-worker-start-refusals.test.ts
@@ -0,0 +1,42 @@
+import { describe, expect, it } from 'vitest'
+import { assertStructuredWorkerStartSupported } from './orchestration-workers'
+
+// Refusals rather than silent ignores. Each one names a start option `createStructuredWorkerSession`
+// cannot honour; accepting any of them hands the coordinator a worker that differs from the receipt
+// it is given back.
+describe('structured worker-start refusals', () => {
+  it('leaves every option alone when --structured was not asked for', () => {
+    expect(() =>
+      assertStructuredWorkerStartSupported({
+        on: 'server-1',
+        terminal: 'term_1',
+        worktree: 'new-child',
+        model: 'opus',
+        effort: 'high'
+      })
+    ).not.toThrow()
+  })
+
+  it('accepts the combinations a structured worker can actually honour', () => {
+    expect(() =>
+      assertStructuredWorkerStartSupported({ structured: true, worktree: 'current' })
+    ).not.toThrow()
+    expect(() => assertStructuredWorkerStartSupported({ structured: true })).not.toThrow()
+  })
+
+  it.each([
+    ['on', { on: 'server-1' }, /--on/],
+    ['terminal', { terminal: 'term_1' }, /--terminal/],
+    ['new-child', { worktree: 'new-child' }, /create the worktree first/],
+    ['new-top-level', { worktree: 'new-top-level' }, /create the worktree first/],
+    // Launch preferences reach the terminal path as `launch.preferences` and the structured path
+    // not at all, while `launch.receipt.effective` echoes whatever was requested either way. Left
+    // accepted, `--model opus` runs on the workspace default and the receipt still says `opus`.
+    ['model', { model: 'opus' }, /--model and --effort/],
+    ['effort', { model: 'opus', effort: 'high' }, /--model and --effort/]
+  ])('refuses --structured with %s', (_name, params, message) => {
+    expect(() => assertStructuredWorkerStartSupported({ structured: true, ...params })).toThrow(
+      message
+    )
+  })
+})
diff --git a/src/main/runtime/rpc/methods/orchestration-workers.ts b/src/main/runtime/rpc/methods/orchestration-workers.ts
index ead13db334c..b45d79be834 100644
--- a/src/main/runtime/rpc/methods/orchestration-workers.ts
+++ b/src/main/runtime/rpc/methods/orchestration-workers.ts
@@ -76,15 +76,26 @@ export const ORCHESTRATION_WORKER_START_METHODS: RpcMethod[] = [
  * Refused rather than ignored: silently starting a terminal worker under a structured request
  * would hand the coordinator a worker of a different kind than it asked for.
  */
-function assertStructuredWorkerStartSupported(params: {
+export function assertStructuredWorkerStartSupported(params: {
   structured?: boolean
   on?: string
   terminal?: string
   worktree?: string
+  model?: string
+  effort?: string
 }): void {
   if (!params.structured) {
     return
   }
+  if (params.model || params.effort) {
+    // Structured session creation takes no launch preferences, so accepting these would run the
+    // worker on the workspace default while the start receipt's `launch.effective` reported the
+    // model that was asked for. Refused for the same reason `--terminal` refuses them.
+    throw new OrchestrationError(
+      'invalid_argument',
+      '--model and --effort cannot be applied to a structured worker; its session uses the workspace default.'
+    )
+  }
   if (params.on) {
     throw new OrchestrationError(
       'invalid_argument',
diff --git a/src/main/runtime/structured-worker-identity.test.ts b/src/main/runtime/structured-worker-identity.test.ts
index 55c4dedaf59..f78fa6a2143 100644
--- a/src/main/runtime/structured-worker-identity.test.ts
+++ b/src/main/runtime/structured-worker-identity.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, it, beforeEach } from 'vitest'
 import { isTerminalLeafId, parsePaneKey } from '../../shared/stable-pane-id'
 import { structuredAgentSessionPaneKey } from '../../shared/structured-agent-session-projection'
 import { selectExactWorkerProviderSession } from './orchestration/worker-provider-session'
+import { structuredWorkerChildIdentityEnv } from './structured-worker-child-identity-env'
 import {
   StructuredWorkerIdentityRegistry,
   isStructuredWorkerHandle,
@@ -10,6 +11,7 @@ import {
   sessionIdFromStructuredWorkerIncarnation,
   structuredWorkerHostScope,
   structuredWorkerPaneKeyBelongsToSession,
+  structuredWorkerIdentities,
   structuredWorkerProcessIncarnation,
   structuredWorkerRecordIsCurrent
 } from './structured-worker-identity'
@@ -185,9 +187,31 @@ describe('structured worker identity registry', () => {
 })
 
 describe('structured workers stay outside the PTY-only fail-closed paths', () => {
-  it('never selects an exact provider session', () => {
-    // Fail-closed because a structured session emits no hook agent status. It stays closed only
-    // while ORCA_PANE_KEY is absent from the structured child's environment.
+  it('keeps the selector shut by never letting a structured pane key reach a hook status', () => {
+    // The selector matches on pane key, so it is fail-closed for a structured worker only while
+    // ORCA_PANE_KEY is absent from its child's environment. That absence IS the guard: put the key
+    // back and the first assertion below is what an attacker gets.
+    // The PROCESS registry, because that is the one the spawn path reads.
+    const handle = mintStructuredWorkerHandle()
+    structuredWorkerIdentities.register({
+      handle,
+      sessionId: SESSION_ID,
+      agent: 'claude',
+      paneKey: mintStructuredWorkerPaneKey(SESSION_ID),
+      processIncarnation: structuredWorkerProcessIncarnation(SESSION_ID),
+      worktreeId: 'wt_1',
+      hostScope: { kind: 'local', hostId: 'local' }
+    })
+    try {
+      const env = structuredWorkerChildIdentityEnv(SESSION_ID)
+      // Registered, so this is a populated env — not the empty one an unregistered session gets,
+      // which would satisfy the pane-key assertion for the wrong reason.
+      expect(env.ORCA_TERMINAL_HANDLE).toBe(handle)
+      expect(Object.keys(env)).not.toContain('ORCA_PANE_KEY')
+    } finally {
+      structuredWorkerIdentities.forget(handle)
+    }
+
     const paneKey = mintStructuredWorkerPaneKey(SESSION_ID)
     expect(
       selectExactWorkerProviderSession({