diff --git a/src/main/runtime/orca-runtime.test.ts b/src/main/runtime/orca-runtime.test.ts
index ef5a340e02e..71d74396f8f 100644
--- a/src/main/runtime/orca-runtime.test.ts
+++ b/src/main/runtime/orca-runtime.test.ts
@@ -31409,6 +31409,41 @@ describe('OrcaRuntimeService', () => {
     )
   })
 
+  // Why (#10562): the renderer purges its state regardless of the sweep result, so
+  // revalidating against a cached scan (30s TTL) that still lists an already-deleted
+  // directory would strand those PTYs permanently — nothing asks a second time.
+  it('revalidates against a fresh scan instead of a warm worktree-scan cache', async () => {
+    const deletedId = `${TEST_REPO_ID}::/tmp/deleted`
+    const localProvider = {
+      listProcesses: vi.fn(async () => [
+        { id: `${deletedId}@@deleted-session`, cwd: '/tmp/deleted', title: 'shell' }
+      ]),
+      shutdown: vi.fn(async () => {})
+    }
+    const runtime = new OrcaRuntimeService(store, undefined, {
+      getLocalProvider: () => localProvider as never
+    })
+
+    // Warm the scan cache while the worktree still exists.
+    vi.mocked(listWorktrees).mockResolvedValueOnce([
+      { path: '/tmp/deleted', head: 'abc', branch: 'd', isBare: false, isMainWorktree: false }
+    ])
+    await runtime.teardownMissingManagedWorktreeTerminals(`id:${TEST_REPO_ID}`, [deletedId])
+    expect(localProvider.shutdown).not.toHaveBeenCalled()
+
+    // The worktree is now gone; the cached scan must not mask that.
+    vi.mocked(listWorktrees).mockResolvedValue([])
+    const result = await runtime.teardownMissingManagedWorktreeTerminals(`id:${TEST_REPO_ID}`, [
+      deletedId
+    ])
+
+    expect(result).toEqual({ stoppedWorktreeIds: [deletedId] })
+    expect(localProvider.shutdown).toHaveBeenCalledWith(
+      `${deletedId}@@deleted-session`,
+      expect.objectContaining({ immediate: true })
+    )
+  })
+
   it('does not stop sessions after a non-authoritative revalidation', async () => {
     const localProvider = {
       listProcesses: vi.fn(async () => []),
diff --git a/src/main/runtime/orca-runtime.ts b/src/main/runtime/orca-runtime.ts
index 92a4c3ee7f3..14cf1eaf807 100644
--- a/src/main/runtime/orca-runtime.ts
+++ b/src/main/runtime/orca-runtime.ts
@@ -18005,6 +18005,10 @@ export class OrcaRuntimeService {
     connectionId?: string | null
   ): Promise<{ stoppedWorktreeIds: string[] }> {
     const repo = await this.resolveRepoSelectorForConnection(repoSelector, connectionId)
+    // Why: killing PTYs must be proven against the host right now — a cached scan
+    // (30s TTL) can still list a directory git already dropped, and the renderer
+    // purges its state either way, so a stale miss strands those processes for good.
+    this.invalidateWorktreeScanCacheForRepo(repo.id)
     const detected = await this.listDetectedManagedWorktrees(`id:${repo.id}`, connectionId)
     if (!detected.authoritative) {
       return { stoppedWorktreeIds: [] }
diff --git a/src/renderer/src/store/slices/worktrees.test.ts b/src/renderer/src/store/slices/worktrees.test.ts
index ae8bf057aa8..3894e65384b 100644
--- a/src/renderer/src/store/slices/worktrees.test.ts
+++ b/src/renderer/src/store/slices/worktrees.test.ts
@@ -656,6 +656,82 @@ describe('fetchWorktrees', () => {
     expect(mockApi.worktrees.listDetected).toHaveBeenCalledTimes(1)
   })
 
+  // Why (#10562): the scan coalesces but each caller carries its own known-id
+  // snapshot, so a caller that joined an in-flight scan must still request
+  // teardown — otherwise it purges renderer state and strands live PTYs.
+  it('stops terminals for a caller that coalesced onto an in-flight scan', async () => {
+    const store = createTestStore()
+    const deleted = makeWorktree({ id: 'repo1::/p/deleted', repoId: 'repo1', path: '/p/deleted' })
+    const surviving = makeWorktree({ id: 'repo1::/p/surv', repoId: 'repo1', path: '/p/surv' })
+
+    // Caller A starts before hydration, so its known-id snapshot is empty.
+    store.setState({
+      repos: [{ id: 'repo1', path: '/p/repo1', displayName: 'R', badgeColor: '#000', addedAt: 0 }],
+      worktreesByRepo: {},
+      detectedWorktreesByRepo: {},
+      tabsByWorktree: {}
+    } as unknown as Partial<AppState>)
+
+    let releaseScan!: () => void
+    const scanStarted = new Promise<void>((resolve) => {
+      mockApi.worktrees.listDetected.mockImplementationOnce(async ({ repoId }) => {
+        resolve()
+        await new Promise<void>((release) => {
+          releaseScan = release
+        })
+        return makeDetectedResult(repoId, [surviving])
+      })
+    })
+
+    const callerA = store.getState().fetchDetectedWorktrees('repo1')
+    await scanStarted
+
+    // Hydration lands mid-scan: the renderer now owns `deleted` and its tabs.
+    store.setState({
+      worktreesByRepo: { repo1: [deleted, surviving] },
+      detectedWorktreesByRepo: { repo1: makeDetectedResult('repo1', [deleted, surviving]) },
+      tabsByWorktree: { [deleted.id]: [{ id: 'tab-d', worktreeId: deleted.id }] }
+    } as unknown as Partial<AppState>)
+
+    const callerB = store.getState().fetchWorktrees('repo1')
+    releaseScan()
+    await Promise.all([callerA, callerB])
+
+    // One shared scan, but the coalesced caller still asked the host to sweep.
+    expect(mockApi.worktrees.listDetected).toHaveBeenCalledTimes(1)
+    expect(mockApi.runtime.call).toHaveBeenCalledWith({
+      method: 'worktree.teardownMissingTerminals',
+      params: { repo: 'repo1', worktreeIds: [deleted.id], connectionId: null }
+    })
+    expect(store.getState().tabsByWorktree[deleted.id]).toBeUndefined()
+  })
+
+  // Why: teardown rides outside the scan coalescer, so identical fan-out requests
+  // must share one host sweep instead of re-scanning the host per caller.
+  it('shares one teardown sweep across identical concurrent refreshes', async () => {
+    const store = createTestStore()
+    const deleted = makeWorktree({ id: 'repo1::/p/deleted', repoId: 'repo1', path: '/p/deleted' })
+    const surviving = makeWorktree({ id: 'repo1::/p/surv', repoId: 'repo1', path: '/p/surv' })
+
+    store.setState({
+      repos: [{ id: 'repo1', path: '/p/repo1', displayName: 'R', badgeColor: '#000', addedAt: 0 }],
+      worktreesByRepo: { repo1: [deleted, surviving] },
+      detectedWorktreesByRepo: { repo1: makeDetectedResult('repo1', [deleted, surviving]) },
+      tabsByWorktree: { [deleted.id]: [{ id: 'tab-d', worktreeId: deleted.id }] }
+    } as unknown as Partial<AppState>)
+
+    mockApi.worktrees.listDetected.mockResolvedValueOnce(makeDetectedResult('repo1', [surviving]))
+
+    await Promise.all([
+      store.getState().fetchWorktrees('repo1'),
+      store.getState().fetchDetectedWorktrees('repo1'),
+      store.getState().fetchWorktrees('repo1')
+    ])
+
+    expect(mockApi.runtime.call).toHaveBeenCalledTimes(1)
+    expect(store.getState().tabsByWorktree[deleted.id]).toBeUndefined()
+  })
+
   it('coalesces fetchDetectedWorktrees with a matching fetchWorktrees refresh', async () => {
     const store = createTestStore()
     const refreshed = makeWorktree({
diff --git a/src/renderer/src/store/slices/worktrees.ts b/src/renderer/src/store/slices/worktrees.ts
index 9276b19ab98..319d48fad6a 100644
--- a/src/renderer/src/store/slices/worktrees.ts
+++ b/src/renderer/src/store/slices/worktrees.ts
@@ -633,6 +633,11 @@ function isRuntimeMethodNotFoundError(error: unknown): boolean {
   return error instanceof RuntimeRpcCallError && error.code === 'method_not_found'
 }
 
+// Why: teardown cannot ride the scan's coalescing (each caller has its own known-id
+// snapshot), so dedupe on the request it actually produces — identical fan-out
+// requests share one host sweep instead of re-scanning per caller.
+const missingWorktreeTeardownsInFlight = new Map<string, Promise<void>>()
+
 async function teardownMissingWorktreeTerminalsBestEffort(
   settings: AppState['settings'],
   repoId: string,
@@ -648,16 +653,38 @@ async function teardownMissingWorktreeTerminalsBestEffort(
   if (missingIds.length === 0) {
     return
   }
+  const target = getActiveRuntimeTarget(settings)
+  const normalizedConnectionId = connectionId ?? null
+  const key = [
+    target.kind === 'local' ? 'local' : `runtime:${target.environmentId}`,
+    repoId,
+    normalizedConnectionId ?? '',
+    [...missingIds].sort().join('\n')
+  ].join('\0')
+  const existing = missingWorktreeTeardownsInFlight.get(key)
+  if (existing) {
+    return existing
+  }
+  const teardown = (async () => {
+    try {
+      await callRuntimeRpc(
+        target,
+        'worktree.teardownMissingTerminals',
+        { repo: repoId, worktreeIds: missingIds, connectionId: normalizedConnectionId },
+        { timeoutMs: 30_000 }
+      )
+    } catch (error) {
+      if (!isRuntimeMethodNotFoundError(error)) {
+        console.warn(`Failed to stop terminals for missing worktrees in repo ${repoId}:`, error)
+      }
+    }
+  })()
+  missingWorktreeTeardownsInFlight.set(key, teardown)
   try {
-    await callRuntimeRpc(
-      getActiveRuntimeTarget(settings),
-      'worktree.teardownMissingTerminals',
-      { repo: repoId, worktreeIds: missingIds, connectionId: connectionId ?? null },
-      { timeoutMs: 30_000 }
-    )
-  } catch (error) {
-    if (!isRuntimeMethodNotFoundError(error)) {
-      console.warn(`Failed to stop terminals for missing worktrees in repo ${repoId}:`, error)
+    await teardown
+  } finally {
+    if (missingWorktreeTeardownsInFlight.get(key) === teardown) {
+      missingWorktreeTeardownsInFlight.delete(key)
     }
   }
 }
@@ -1075,35 +1102,40 @@ async function listDetectedWorktreesForRepoCoalesced(
       ? getRuntimeEnvironmentConnectionGeneration(target.environmentId)
       : null
   const existing = detectedWorktreeRefreshesInFlight.get(key)
-  if (existing) {
-    return existing
-  }
-  // Why: startup/event fan-out can request the same repo/host refresh many times at once; share only the scan promise so state-merge semantics stay local.
-  const refresh = listDetectedWorktreesForRepo(settings, repoId, {
-    reuseRecentCompatibilityFailure: options.reuseRecentCompatibilityFailure
-  })
-  detectedWorktreeRefreshesInFlight.set(key, refresh)
-  try {
-    const result = await refresh
-    if (
-      target.kind === 'environment' &&
-      (getEnvironmentSshStateGeneration(target.environmentId) !== connectionGeneration ||
-        getRuntimeEnvironmentConnectionGeneration(target.environmentId) !==
-          runtimeConnectionGeneration)
-    ) {
-      throw new Error('runtime_environment_generation_changed')
-    }
-    await teardownMissingWorktreeTerminalsBestEffort(
-      settings,
-      repoId,
-      options.connectionId,
-      options.knownWorktreeIds,
-      result
-    )
-    return result
-  } finally {
-    if (detectedWorktreeRefreshesInFlight.get(key) === refresh) {
-      detectedWorktreeRefreshesInFlight.delete(key)
+  // Why: the scan coalesces, but teardown must not — each caller carries its own
+  // known-id snapshot and purges its own state, so a caller that joined an
+  // in-flight scan would otherwise purge without ever stopping those terminals.
+  const result = existing ? await existing : await runCoalescedDetectedWorktreeScan()
+  await teardownMissingWorktreeTerminalsBestEffort(
+    settings,
+    repoId,
+    options.connectionId,
+    options.knownWorktreeIds,
+    result
+  )
+  return result
+
+  async function runCoalescedDetectedWorktreeScan(): Promise<DetectedWorktreeListResult> {
+    // Why: startup/event fan-out can request the same repo/host refresh many times at once; share only the scan promise so state-merge semantics stay local.
+    const refresh = listDetectedWorktreesForRepo(settings, repoId, {
+      reuseRecentCompatibilityFailure: options.reuseRecentCompatibilityFailure
+    })
+    detectedWorktreeRefreshesInFlight.set(key, refresh)
+    try {
+      const scanned = await refresh
+      if (
+        target.kind === 'environment' &&
+        (getEnvironmentSshStateGeneration(target.environmentId) !== connectionGeneration ||
+          getRuntimeEnvironmentConnectionGeneration(target.environmentId) !==
+            runtimeConnectionGeneration)
+      ) {
+        throw new Error('runtime_environment_generation_changed')
+      }
+      return scanned
+    } finally {
+      if (detectedWorktreeRefreshesInFlight.get(key) === refresh) {
+        detectedWorktreeRefreshesInFlight.delete(key)
+      }
     }
   }
 }