diff --git a/src/main/runtime/orchestration/db.ts b/src/main/runtime/orchestration/db.ts
index 1c4b68f9d10..3a64150060c 100644
--- a/src/main/runtime/orchestration/db.ts
+++ b/src/main/runtime/orchestration/db.ts
@@ -694,6 +694,28 @@ export class OrchestrationDb {
     return this.findActiveDispatchForAssignee(handle)
   }
 
+  // Why: attributing an id-less lifecycle message is only safe when the sender owns
+  // exactly one active dispatch (#7429) — more than one match must not be guessed.
+  getSoleActiveDispatchForSender(
+    assigneeHandle: string,
+    assigneePaneKey?: string | null
+  ): DispatchContextRow | undefined {
+    const matches = (
+      this.db
+        .prepare("SELECT * FROM dispatch_contexts WHERE status IN ('pending', 'dispatched')")
+        .all() as DispatchContextRow[]
+    ).filter(
+      (row) =>
+        row.assignee_handle === assigneeHandle ||
+        Boolean(
+          assigneePaneKey &&
+          row.assignee_pane_key &&
+          isEquivalentPaneKey(row.assignee_pane_key, assigneePaneKey)
+        )
+    )
+    return matches.length === 1 ? matches[0] : undefined
+  }
+
   private findActiveDispatchForAssignee(
     assigneeHandle: string,
     assigneePaneKey?: string
diff --git a/src/main/runtime/orchestration/lifecycle-reconciliation.test.ts b/src/main/runtime/orchestration/lifecycle-reconciliation.test.ts
index 8fed046d421..5f13eb7075a 100644
--- a/src/main/runtime/orchestration/lifecycle-reconciliation.test.ts
+++ b/src/main/runtime/orchestration/lifecycle-reconciliation.test.ts
@@ -409,4 +409,87 @@ describe('lifecycle reconciliation', () => {
     expect(db.getMessageById(lateHeartbeat.id)).toMatchObject({ read: 1 })
     expect(db.getMessageById(lateHeartbeat.id)?.delivered_at).not.toBeNull()
   })
+
+  it('completes a null-id worker_done sent from the pane that owns the sole dispatch', () => {
+    db = new OrchestrationDb(':memory:')
+    const task = db.createTask({ spec: 'work' })
+    const dispatch = db.createDispatchContext(task.id, 'term_worker', `tab_w:${LEAF_A}`)
+    const done = db.insertMessage({
+      from: 'term_worker',
+      to: 'term_coordinator',
+      subject: 'Done',
+      type: 'worker_done',
+      payload: JSON.stringify({}),
+      senderPaneKey: `tab_w:${LEAF_A}`
+    })
+
+    expect(reconcileLifecycleMessage(db, done)).toEqual({
+      action: 'completed',
+      taskId: task.id,
+      dispatchId: dispatch.id
+    })
+    expect(db.getTask(task.id)?.status).toBe('completed')
+    expect(db.getDispatchContextById(dispatch.id)?.status).toBe('completed')
+  })
+
+  it('ignores a null-id worker_done sent from a foreign pane and handle', () => {
+    db = new OrchestrationDb(':memory:')
+    const task = db.createTask({ spec: 'work' })
+    const dispatch = db.createDispatchContext(task.id, 'term_owner', `tab_w:${LEAF_A}`)
+    const logs: string[] = []
+    const done = db.insertMessage({
+      from: 'term_stranger',
+      to: 'term_coordinator',
+      subject: 'Done',
+      type: 'worker_done',
+      payload: JSON.stringify({}),
+      senderPaneKey: `tab_w:${LEAF_B}`
+    })
+
+    expect(reconcileLifecycleMessage(db, done, (line) => logs.push(line))).toEqual({
+      action: 'ignored'
+    })
+    expect(db.getTask(task.id)?.status).toBe('dispatched')
+    expect(db.getDispatchContextById(dispatch.id)?.status).toBe('dispatched')
+    expect(logs.some((line) => line.includes('without taskId'))).toBe(true)
+  })
+
+  it('ignores a null-id worker_done when the sender has no active dispatch', () => {
+    db = new OrchestrationDb(':memory:')
+    const task = db.createTask({ spec: 'work' })
+    const dispatch = db.createDispatchContext(task.id, 'term_worker', `tab_w:${LEAF_A}`)
+    db.updateTaskStatus(task.id, 'completed')
+    const done = db.insertMessage({
+      from: 'term_worker',
+      to: 'term_coordinator',
+      subject: 'Done again',
+      type: 'worker_done',
+      payload: JSON.stringify({}),
+      senderPaneKey: `tab_w:${LEAF_A}`
+    })
+
+    expect(reconcileLifecycleMessage(db, done)).toEqual({ action: 'ignored' })
+    expect(db.getDispatchContextById(dispatch.id)?.status).toBe('completed')
+  })
+
+  it('ignores a null-id worker_done when the sender matches two active dispatches', () => {
+    db = new OrchestrationDb(':memory:')
+    const ownTask = db.createTask({ spec: 'work' })
+    const ownDispatch = db.createDispatchContext(ownTask.id, 'term_worker', `tab_w:${LEAF_A}`)
+    const paneTask = db.createTask({ spec: 'other work' })
+    const paneDispatch = db.createDispatchContext(paneTask.id, 'term_other', `tab_w:${LEAF_B}`)
+    // Sender matches one dispatch by handle and another by pane, so neither can be attributed.
+    const done = db.insertMessage({
+      from: 'term_worker',
+      to: 'term_coordinator',
+      subject: 'Done',
+      type: 'worker_done',
+      payload: JSON.stringify({}),
+      senderPaneKey: `tab_w:${LEAF_B}`
+    })
+
+    expect(reconcileLifecycleMessage(db, done)).toEqual({ action: 'ignored' })
+    expect(db.getDispatchContextById(ownDispatch.id)?.status).toBe('dispatched')
+    expect(db.getDispatchContextById(paneDispatch.id)?.status).toBe('dispatched')
+  })
 })
diff --git a/src/main/runtime/orchestration/lifecycle-reconciliation.ts b/src/main/runtime/orchestration/lifecycle-reconciliation.ts
index 96917babaf6..a4efd7cf448 100644
--- a/src/main/runtime/orchestration/lifecycle-reconciliation.ts
+++ b/src/main/runtime/orchestration/lifecycle-reconciliation.ts
@@ -170,17 +170,11 @@ function reconcileWorkerDoneMessage(
     return persistedRejection
   }
 
-  const taskId = payload.taskId
-  if (typeof taskId !== 'string' || taskId.length === 0) {
-    onLog(`Warning: worker_done without taskId from ${msg.from_handle}`)
-    return { action: 'ignored' }
-  }
-
-  const dispatchId = payload.dispatchId
-  if (typeof dispatchId !== 'string' || dispatchId.length === 0) {
-    onLog(`Warning: worker_done without dispatchId from ${msg.from_handle}`)
+  const target = resolveWorkerDoneTarget(db, msg, payload, onLog)
+  if (!target) {
     return { action: 'ignored' }
   }
+  const { taskId, dispatchId } = target
 
   const task = db.getTask(taskId)
   if (!task) {
@@ -239,6 +233,36 @@ function reconcileWorkerDoneMessage(
   return { action: 'completed', taskId, dispatchId }
 }
 
+// Why: a worker_done from the pane that owns the sole in-flight dispatch is still
+// authoritative (#7429); the payload ids are a convenience, not the authority.
+function resolveWorkerDoneTarget(
+  db: OrchestrationDb,
+  msg: MessageRow,
+  payload: Record<string, unknown>,
+  onLog: LogFn
+): { taskId: string; dispatchId: string } | undefined {
+  const payloadTaskId = payload.taskId
+  const payloadDispatchId = payload.dispatchId
+  const taskId = typeof payloadTaskId === 'string' && payloadTaskId.length > 0 ? payloadTaskId : ''
+  const dispatchId =
+    typeof payloadDispatchId === 'string' && payloadDispatchId.length > 0 ? payloadDispatchId : ''
+  if (taskId && dispatchId) {
+    return { taskId, dispatchId }
+  }
+
+  const fallback = db.getSoleActiveDispatchForSender(msg.from_handle, msg.sender_pane_key)
+  if (fallback && hasLifecycleAuthority(fallback, msg)) {
+    return { taskId: taskId || fallback.task_id, dispatchId: dispatchId || fallback.id }
+  }
+
+  onLog(
+    taskId
+      ? `Warning: worker_done without dispatchId from ${msg.from_handle}`
+      : `Warning: worker_done without taskId from ${msg.from_handle}`
+  )
+  return undefined
+}
+
 function buildLifecycleAuthorityRejectionReason(
   dispatchId: string,
   dispatch: { assignee_handle: string | null; assignee_pane_key: string | null },
diff --git a/src/main/runtime/rpc/methods/orchestration.test.ts b/src/main/runtime/rpc/methods/orchestration.test.ts
index 95339cb3190..8fa360618d6 100644
--- a/src/main/runtime/rpc/methods/orchestration.test.ts
+++ b/src/main/runtime/rpc/methods/orchestration.test.ts
@@ -748,11 +748,26 @@ describe('orchestration RPC methods', () => {
       expect(db.getUnreadMessages('term_coord', ['worker_done'])).toHaveLength(1)
     })
 
-    it('does not complete worker_done missing taskId or dispatchId', async () => {
+    it('completes worker_done missing taskId or dispatchId from the assigned terminal', async () => {
       setup()
       const { task, dispatch } = createDispatchedTask()
       insertWorkerDone({ dispatchId: dispatch.id })
-      insertWorkerDone({ taskId: task.id })
+
+      const result = (await call('orchestration.check', {
+        terminal: 'term_coord',
+        types: 'worker_done'
+      })) as { count: number }
+
+      expect(result.count).toBe(1)
+      expect(db.getTask(task.id)?.status).toBe('completed')
+      expect(db.getDispatchContextById(dispatch.id)?.status).toBe('completed')
+    })
+
+    it('does not complete worker_done missing taskId or dispatchId from another terminal', async () => {
+      setup()
+      const { task, dispatch } = createDispatchedTask()
+      insertWorkerDone({ from: 'term_other', dispatchId: dispatch.id })
+      insertWorkerDone({ from: 'term_other', taskId: task.id })
 
       const result = (await call('orchestration.check', {
         terminal: 'term_coord',