diff --git a/apps/desktop/src/app/chat/composer/focus.test.ts b/apps/desktop/src/app/chat/composer/focus.test.ts
index f3987982274..bc92932bb8f 100644
--- a/apps/desktop/src/app/chat/composer/focus.test.ts
+++ b/apps/desktop/src/app/chat/composer/focus.test.ts
@@ -1,6 +1,13 @@
 import { afterEach, describe, expect, it } from 'vitest'
 
-import { blurComposerInput } from './focus'
+import {
+  blurComposerInput,
+  getActiveComposer,
+  markActiveComposer,
+  onComposerFocusRequest,
+  releaseActiveComposer,
+  requestComposerFocus
+} from './focus'
 import { RICH_INPUT_SLOT } from './rich-editor'
 
 /**
@@ -21,8 +28,23 @@ function mountInput(hidden = false) {
   return input
 }
 
+/** A chat surface stamp — the same `data-composer-target` ChatView hangs. */
+function mountSurface(target: string, hidden = false) {
+  const layer = document.createElement('div')
+  layer.toggleAttribute('data-pane-hidden', hidden)
+  const surface = document.createElement('div')
+  surface.dataset.composerTarget = target
+  layer.append(surface)
+  document.body.append(layer)
+
+  return surface
+}
+
 afterEach(() => {
   document.body.innerHTML = ''
+  // `activeTarget` is module-level — a case that leaves a stale claim behind
+  // would otherwise decide the next one.
+  markActiveComposer('main')
 })
 
 describe('blurComposerInput', () => {
@@ -48,3 +70,149 @@ describe('blurComposerInput', () => {
     expect(document.activeElement).toBe(outside)
   })
 })
+
+/**
+ * `markActiveComposer` has four call sites and, unguarded, no counterpart: an
+ * unmounting or keep-alive-buried composer left `activeTarget` pointing at
+ * itself, so every `'active'`-routed request was delivered to a target with no
+ * on-screen subscriber. Type-to-focus preventDefaults the keystroke BEFORE the
+ * request, so a dead target swallows the character and focuses nothing.
+ */
+describe('releaseActiveComposer', () => {
+  it('falls back to the main composer when the claimant releases', () => {
+    const root = document.createElement('div')
+    root.dataset.slot = 'aui_edit-composer-root'
+    document.body.append(root)
+
+    markActiveComposer('edit')
+    expect(getActiveComposer()).toBe('edit')
+
+    root.remove()
+    releaseActiveComposer('edit')
+
+    expect(getActiveComposer()).toBe('main')
+  })
+
+  it('leaves the key with the live claimant when a stale composer releases late', () => {
+    markActiveComposer('edit')
+    markActiveComposer('tile:abc')
+
+    releaseActiveComposer('edit')
+
+    expect(getActiveComposer()).toBe('tile:abc')
+  })
+
+  it('prefers the visible chat surface over a hard main default', () => {
+    const root = document.createElement('div')
+    root.dataset.slot = 'aui_edit-composer-root'
+    document.body.append(root)
+    mountSurface('tile:visible')
+    markActiveComposer('edit')
+
+    root.remove()
+    releaseActiveComposer('edit')
+
+    expect(getActiveComposer()).toBe('tile:visible')
+  })
+
+  it('routes an active-target request to the main composer once the edit composer closes', async () => {
+    // Mirrors the per-composer filter in use-composer-draft / user-edit-composer:
+    // a composer ignores any request not addressed to its own target.
+    const mainComposerSaw: string[] = []
+
+    const off = onComposerFocusRequest(({ target }) => {
+      if (target === 'main') {
+        mainComposerSaw.push(target)
+      }
+    })
+
+    const root = document.createElement('div')
+    root.dataset.slot = 'aui_edit-composer-root'
+    document.body.append(root)
+    markActiveComposer('edit')
+    root.remove()
+    releaseActiveComposer('edit')
+    requestComposerFocus('active')
+
+    // `dispatch` defers to a macrotask so click/keydown handlers settle first.
+    await new Promise(resolve => window.setTimeout(resolve, 0))
+    off()
+
+    expect(mainComposerSaw).toEqual(['main'])
+  })
+})
+
+describe('resolveActive / keep-alive tab heal', () => {
+  it('heals type-to-focus onto the visible main tab when a tile is buried', async () => {
+    // Repro for the reported main-tab miss: user typed in a session tile, then
+    // clicked the main/workspace tab without focusing its input. The tile stays
+    // mounted under data-pane-hidden, so activeTarget still reads tile:… and
+    // every type-to-focus request is dropped by the visible main composer.
+    mountSurface('tile:buried', true)
+    mountSurface('main')
+    markActiveComposer('tile:buried')
+
+    expect(getActiveComposer()).toBe('main')
+
+    const mainSaw: string[] = []
+    const tileSaw: string[] = []
+
+    const off = onComposerFocusRequest(({ target }) => {
+      if (target === 'main') {
+        mainSaw.push(target)
+      }
+
+      if (target === 'tile:buried') {
+        tileSaw.push(target)
+      }
+    })
+
+    requestComposerFocus('active', { typeChar: 'h' })
+    await new Promise(resolve => window.setTimeout(resolve, 0))
+    off()
+
+    expect(mainSaw).toEqual(['main'])
+    expect(tileSaw).toEqual([])
+    // Cache stays honest so dict/insert/Esc path all agree thereafter.
+    expect(getActiveComposer()).toBe('main')
+  })
+
+  it('keeps a live tile claim while that tile is the visible surface', () => {
+    mountSurface('main', true)
+    mountSurface('tile:front')
+    markActiveComposer('tile:front')
+
+    expect(getActiveComposer()).toBe('tile:front')
+  })
+
+  it('heals an edit claim once the edit root is gone (no release site needed)', async () => {
+    mountSurface('main')
+    markActiveComposer('edit')
+    // No edit root in the document → claim is dead. getActiveComposer heals.
+    expect(getActiveComposer()).toBe('main')
+
+    const mainSaw: string[] = []
+
+    const off = onComposerFocusRequest(({ target }) => {
+      if (target === 'main') {
+        mainSaw.push(target)
+      }
+    })
+
+    requestComposerFocus('active', { typeChar: 'a' })
+    await new Promise(resolve => window.setTimeout(resolve, 0))
+    off()
+
+    expect(mainSaw).toEqual(['main'])
+  })
+
+  it('holds an edit claim while the edit composer root is mounted', () => {
+    const root = document.createElement('div')
+    root.dataset.slot = 'aui_edit-composer-root'
+    document.body.append(root)
+    mountSurface('main')
+    markActiveComposer('edit')
+
+    expect(getActiveComposer()).toBe('edit')
+  })
+})
diff --git a/apps/desktop/src/app/chat/composer/focus.ts b/apps/desktop/src/app/chat/composer/focus.ts
index 7120fde2b1a..3302d031078 100644
--- a/apps/desktop/src/app/chat/composer/focus.ts
+++ b/apps/desktop/src/app/chat/composer/focus.ts
@@ -43,6 +43,21 @@ const INSERT_REFS_EVENT = 'hermes:composer-insert-refs'
 const SUBMIT_EVENT = 'hermes:composer-submit'
 const VOICE_TOGGLE_EVENT = 'hermes:composer-voice-toggle'
 
+/** Inline edit composer root — mounted only while a user bubble is being edited. */
+const EDIT_COMPOSER_ROOT = '[data-slot="aui_edit-composer-root"]'
+
+/** Attribute-safe selector fragment. jsdom (vitest) does not ship `CSS.escape`. */
+const cssEscape = (value: string): string => {
+  if (typeof CSS !== 'undefined' && typeof CSS.escape === 'function') {
+    return CSS.escape(value)
+  }
+
+  // Our targets are `'main'` / `'edit'` / `'tile:<id>'` — alphanumerics plus `:`
+  // and `-`. Escape anything outside that set so a weird id cannot break the
+  // attribute selector.
+  return value.replace(/[^a-zA-Z0-9_:-]/g, ch => `\\${ch}`)
+}
+
 interface SubmitDetail {
   target: ComposerTarget
   text: string
@@ -50,7 +65,76 @@ interface SubmitDetail {
 
 let activeTarget: ComposerTarget = 'main'
 
-const resolve = (target: ComposerTarget | 'active') => (target === 'active' ? activeTarget : target)
+/**
+ * The chat surface currently on screen (`data-composer-target` hung off each
+ * ChatView). Inactive tabs stay mounted with `data-pane-hidden`, so this uses
+ * the same visibility policy as every other document-wide surface lookup.
+ */
+const visibleChatTarget = (): ComposerTarget | null => {
+  if (typeof document === 'undefined') {
+    return null
+  }
+
+  const surface = queryVisible<HTMLElement>('[data-composer-target]')
+  const target = surface?.dataset.composerTarget
+
+  return target ? (target as ComposerTarget) : null
+}
+
+/** True when `target` still has a live, on-screen subscriber. */
+const targetIsReachable = (target: ComposerTarget): boolean => {
+  if (typeof document === 'undefined') {
+    return true
+  }
+
+  // The edit composer is an in-thread overlay, not a chat surface — it never
+  // stamps `data-composer-target`. While its root is mounted it still owns the
+  // bus; once it tears down the claim is dead.
+  if (target === 'edit') {
+    return Boolean(document.querySelector(EDIT_COMPOSER_ROOT))
+  }
+
+  // Exact match on a VISIBLE surface. Background keep-alive tabs carry the same
+  // `data-composer-target` but sit under `data-pane-hidden`, so queryVisible
+  // filters them out.
+  if (queryVisible(`[data-composer-target="${cssEscape(target)}"]`)) {
+    return true
+  }
+
+  // A different chat surface is on screen → this claim is buried or gone.
+  // (A claim with zero stamped surfaces yet — first paint, pure-unit tests —
+  // keeps the marked key until the DOM contradicts it.)
+  if (queryVisible('[data-composer-target]')) {
+    return false
+  }
+
+  return true
+}
+
+/**
+ * The composer `'active'` should route to right now.
+ *
+ * The cached claim (`activeTarget`) wins while its surface is still on screen.
+ * Tab stacks keep inactive panes mounted, so focusing a tile then clicking the
+ * main tab leaves `activeTarget` pointing at a buried composer — with no
+ * subscriber on the visible surface, every type-to-focus keystroke is
+ * preventDefault'd and dropped. Heal to the visible chat surface (or main)
+ * whenever the claim is off-screen or gone, and keep the cache honest so Esc /
+ * voice / soft `/` agree with the keyboard path.
+ */
+const resolveActive = (): ComposerTarget => {
+  if (targetIsReachable(activeTarget)) {
+    return activeTarget
+  }
+
+  const visible = visibleChatTarget() ?? 'main'
+
+  activeTarget = visible
+
+  return visible
+}
+
+const resolve = (target: ComposerTarget | 'active') => (target === 'active' ? resolveActive() : target)
 
 const dispatch = <T>(name: string, detail: T) => {
   if (typeof window === 'undefined') {
@@ -82,9 +166,33 @@ export const markActiveComposer = (target: ComposerTarget) => {
   activeTarget = target
 }
 
+/** Hand the routing key back when a composer unmounts, so `'active'` can never
+ *  resolve to a composer that no longer has a subscriber — such a request is
+ *  dispatched and then dropped by every mounted composer's target filter, and
+ *  nothing re-marks the active composer on its own.
+ *
+ *  Guarded on identity: a composer unmounting AFTER another one claimed the key
+ *  (closing a background tile, a deferred edit-close cleanup) must not steal it
+ *  from the live claimant. Falls through to {@link resolveActive} when the
+ *  caller's surface is buried rather than gone, so closing on a tab switch that
+ *  already re-fronted another chat surfaces there immediately. */
+export const releaseActiveComposer = (target: ComposerTarget) => {
+  if (activeTarget !== target) {
+    return
+  }
+
+  // Prefer the visible chat surface over a hard `'main'` default — releasing a
+  // closed tile while another tile is fronted should land there, not the
+  // (possibly buried) workspace tab.
+  activeTarget = visibleChatTarget() ?? 'main'
+}
+
 /** The composer that last held focus — the target `'active'` resolves to.
- *  Used by broadcast listeners (voice, Esc-to-stop) to act on exactly one. */
-export const getActiveComposer = (): ComposerTarget => activeTarget
+ *  Used by broadcast listeners (voice, Esc-to-stop) to act on exactly one.
+ *  Heals a stale claim the same way {@link requestComposerFocus} does, so Esc
+ *  and type-to-focus never disagree after a tab switch left the bus pointing at
+ *  a keep-alive-mounted background composer. */
+export const getActiveComposer = (): ComposerTarget => resolveActive()
 
 export const requestComposerFocus = (
   target: ComposerTarget | 'active' = 'active',
diff --git a/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.test.tsx b/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.test.tsx
index 81401482f69..7707c8ae753 100644
--- a/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.test.tsx
+++ b/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.test.tsx
@@ -5,6 +5,8 @@ import { afterEach, describe, expect, it, vi } from 'vitest'
 import { type ComposerAttachment, mainComposerScope, stashSessionDraft } from '@/store/composer'
 
 import type { QueueEditState } from '../composer-utils'
+import { type ComposerTarget, getActiveComposer, markActiveComposer } from '../focus'
+import { type ComposerScope, ComposerScopeProvider, MAIN_COMPOSER_SCOPE } from '../scope'
 
 import { useComposerDraft } from './use-composer-draft'
 
@@ -128,3 +130,48 @@ describe('useComposerDraft — rehydrate diagnostic log stays redacted', () => {
     })
   })
 })
+
+describe('useComposerDraft — a closing composer hands the focus-bus key back', () => {
+  afterEach(() => {
+    cleanup()
+    mainComposerScope.clear()
+    markActiveComposer('main')
+  })
+
+  function renderScoped(target: ComposerTarget) {
+    const scope: ComposerScope = { ...MAIN_COMPOSER_SCOPE, target }
+
+    return render(
+      <ComposerScopeProvider value={scope}>
+        <ProbeHarness
+          activeQueueSessionKey="session-tile"
+          onLayoutSnapshot={() => undefined}
+          sessionId="session-tile"
+        />
+      </ComposerScopeProvider>
+    )
+  }
+
+  it('stops `active` resolving to a session tile once the tile unmounts', () => {
+    const { unmount } = renderScoped('tile:abc')
+
+    // Mounting claims the bus for this tile — the leak precondition.
+    expect(getActiveComposer()).toBe('tile:abc')
+
+    unmount()
+
+    expect(getActiveComposer()).toBe('main')
+  })
+
+  it('leaves the key alone when another composer claimed it before this one unmounted', () => {
+    const { unmount } = renderScoped('tile:abc')
+    expect(getActiveComposer()).toBe('tile:abc')
+
+    // The user clicks into a second tile, which claims the bus.
+    markActiveComposer('tile:other')
+
+    unmount()
+
+    expect(getActiveComposer()).toBe('tile:other')
+  })
+})
diff --git a/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.ts b/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.ts
index 43b8514cc35..d981d6435d8 100644
--- a/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.ts
+++ b/apps/desktop/src/app/chat/composer/hooks/use-composer-draft.ts
@@ -17,7 +17,8 @@ import {
   markActiveComposer,
   onComposerFocusRequest,
   onComposerInsertRefsRequest,
-  onComposerInsertRequest
+  onComposerInsertRequest,
+  releaseActiveComposer
 } from '../focus'
 import { type InlineRefInput, insertInlineRefsIntoEditor } from '../inline-refs'
 import { composerPlainText, placeCaretEnd, REF_RE, renderComposerContents } from '../rich-editor'
@@ -153,6 +154,15 @@ export function useComposerDraft({
     }
   }, [focusInput, focusKey, focusRequestId, inputDisabled])
 
+  // The mirror of the `markActiveComposer` above: give the key back when this
+  // composer goes away (a session tile closing, a pane unmounting). Covers both
+  // claim sites for this composer — `focusInput` here and ChatBar's `onFocus` —
+  // since they mark the same scope target. Without it `'active'` keeps
+  // resolving to a dead tile and every routed focus/insert request is dropped.
+  // (Heal-to-visible in focus.ts covers the keep-alive-tab case where the pane
+  // stays mounted behind the front tab; this covers true unmounts.)
+  useEffect(() => () => releaseActiveComposer(target), [target])
+
   useEffect(() => {
     if (inputDisabled) {
       return undefined
diff --git a/apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx b/apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx
index bf8df4ea01e..8791ac3b75e 100644
--- a/apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx
+++ b/apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx
@@ -19,7 +19,8 @@ import {
   focusComposerInput,
   markActiveComposer,
   onComposerFocusRequest,
-  onComposerInsertRequest
+  onComposerInsertRequest,
+  releaseActiveComposer
 } from '@/app/chat/composer/focus'
 import { useAtCompletions } from '@/app/chat/composer/hooks/use-at-completions'
 import { useComposerUndo } from '@/app/chat/composer/hooks/use-composer-undo'
@@ -111,7 +112,17 @@ export const UserEditComposer: FC<UserEditComposerProps> = ({ cwd, gateway, sess
   const at = useAtCompletions({ cwd, gateway, sessionId })
   const slash = useSlashCompletions({ gateway })
 
-  useEffect(() => () => notifyThreadEditClose(), [])
+  // This is the one composer that routinely unmounts, so it is where the focus
+  // bus leaks: confirming or cancelling an edit tears the composer down while
+  // `'edit'` is still the active target. Release it alongside the thread-scroll
+  // cleanup so keyboard routing falls back to the visible chat composer.
+  useEffect(
+    () => () => {
+      notifyThreadEditClose()
+      releaseActiveComposer('edit')
+    },
+    []
+  )
 
   const focusEditor = useCallback(() => {
     const editor = editorRef.current