diff --git a/public/queue.ts b/public/queue.ts
new file mode 100644
index 0000000..ccbabac
--- /dev/null
+++ b/public/queue.ts
@@ -0,0 +1,70 @@
+/**
+ * public/queue.ts — W2: client helper for the server-side PTY-inject queue.
+ *
+ * Enqueue a follow-up prompt that the server fires into a session's PTY the next
+ * time Claude goes idle (so "run tests → open a PR" advances itself while you're
+ * away). Enqueue is a same-origin HTTP POST (Origin-guarded server-side), NOT a
+ * WS frame — it must work with zero tabs open and target any session (e.g. from
+ * the manage page), not just the WS-bound one.
+ *
+ * Discipline (mirrors quick-reply): every call NEVER throws — a failed fetch or
+ * non-2xx response returns a falsy result the caller can ignore. Byte-shuttle:
+ * `text` is sent verbatim; `appendEnter` tells the server to append \r.
+ */
+
+/** Result of an enqueue attempt. `length` = the new queue depth on success. */
+export interface EnqueueResult {
+  ok: boolean
+  /** New queue depth (present on success). */
+  length?: number
+  /** HTTP status on a non-2xx response (absent on network error). */
+  status?: number
+}
+
+/** POST a follow-up prompt to a session's inject queue. Never throws. */
+export async function enqueueFollowup(
+  sessionId: string,
+  text: string,
+  appendEnter: boolean,
+): Promise<EnqueueResult> {
+  try {
+    if (typeof fetch === 'undefined') return { ok: false }
+    const res = await fetch(`/live-sessions/${encodeURIComponent(sessionId)}/queue`, {
+      method: 'POST',
+      credentials: 'same-origin',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ text, appendEnter }),
+    })
+    if (!res.ok) return { ok: false, status: res.status }
+    const data = (await res.json()) as { length?: unknown }
+    return { ok: true, length: typeof data.length === 'number' ? data.length : undefined }
+  } catch {
+    return { ok: false }
+  }
+}
+
+/** DELETE all pending entries for a session (cancel-all). Returns success. Never throws. */
+export async function clearQueue(sessionId: string): Promise<boolean> {
+  try {
+    if (typeof fetch === 'undefined') return false
+    const res = await fetch(`/live-sessions/${encodeURIComponent(sessionId)}/queue`, {
+      method: 'DELETE',
+      credentials: 'same-origin',
+    })
+    return res.ok
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Extract the queue depth from an incoming server frame. Returns the length for a
+ * `{type:'queue',length}` frame, else null (so callers can filter unrelated
+ * frames). Defensive: tolerates any unknown input shape.
+ */
+export function queueLengthFromFrame(msg: unknown): number | null {
+  if (msg === null || typeof msg !== 'object') return null
+  const o = msg as Record<string, unknown>
+  if (o['type'] !== 'queue') return null
+  return typeof o['length'] === 'number' ? o['length'] : null
+}
diff --git a/public/quick-reply.ts b/public/quick-reply.ts
index 998e1b7..ae16ab0 100644
--- a/public/quick-reply.ts
+++ b/public/quick-reply.ts
@@ -147,6 +147,10 @@ function clearChildren(parent: HTMLElement): void {
 export interface QuickReplyOpts {
   /** Called with the full byte string to inject into the terminal. */
   onSend: (data: string) => void
+  /** W2: optional. When provided, the snippet editor gains a "Queue" button that
+   *  enqueues the typed text as a follow-up prompt (fired on next idle) instead of
+   *  sending it now. `appendEnter` mirrors the editor checkbox. */
+  onQueue?: (text: string, appendEnter: boolean) => void
 }
 
 /** Returned by mountQuickReply to allow cleanup. */
@@ -165,7 +169,7 @@ export interface QuickReplyHandle {
  * Labels are set via textContent — never innerHTML (SEC-L3).
  */
 export function mountQuickReply(container: HTMLElement, opts: QuickReplyOpts): QuickReplyHandle {
-  const { onSend } = opts
+  const { onSend, onQueue } = opts
   // Track disposers for all event listeners so dispose() is clean.
   const disposers: Array<() => void> = []
 
@@ -233,6 +237,22 @@ export function mountQuickReply(container: HTMLElement, opts: QuickReplyOpts): Q
     editor.appendChild(labelInput)
     editor.appendChild(enterWrap)
     editor.appendChild(saveBtn)
+
+    // W2: "Queue" defers the typed text as a follow-up prompt (fires on next
+    // idle) rather than saving it as a chip. Shown only when a handler is wired.
+    if (onQueue !== undefined) {
+      const queueBtn = el('button', 'qr-editor-queue', 'Queue')
+      queueBtn.title = 'Queue as a follow-up (runs when Claude next goes idle)'
+      function onQueueClick() {
+        const text = textInput.value.trim()
+        if (!text) return // empty text — no-op, editor stays open
+        onQueue?.(text, enterCheck.checked)
+        editor.remove()
+      }
+      queueBtn.addEventListener('click', onQueueClick)
+      editor.appendChild(queueBtn)
+    }
+
     editor.appendChild(cancelBtn)
 
     container.appendChild(editor)
diff --git a/public/tabs.ts b/public/tabs.ts
index 1c41178..d8cca91 100644
--- a/public/tabs.ts
+++ b/public/tabs.ts
@@ -31,6 +31,7 @@ import { renderDiffFile } from './diff.js'
 import { renderTelemetryGauge } from './preview-grid.js'
 import { mountPushToggle } from './push.js'
 import { mountQuickReply } from './quick-reply.js'
+import { enqueueFollowup } from './queue.js'
 import { mountTimeline, type TimelineHandle } from './timeline.js'
 import { createVoiceInput, type VoiceInput } from './voice.js'
 import { matchCommand, type VoiceMatchContext } from './voice-commands.js'
@@ -216,7 +217,21 @@ export class TabApp {
     const keybar = document.getElementById('keybar')
     if (keybar?.parentElement) keybar.parentElement.insertBefore(host, keybar)
     else document.body.appendChild(host)
-    mountQuickReply(host, { onSend: (data) => this.sendToActive(data) })
+    mountQuickReply(host, {
+      onSend: (data) => this.sendToActive(data),
+      // W2: "Queue" in the snippet editor enqueues a follow-up for the active
+      // session instead of sending it now (fires when Claude next goes idle).
+      onQueue: (text, appendEnter) => this.enqueueToActive(text, appendEnter),
+    })
+  }
+
+  /** W2: enqueue a follow-up prompt for the active session (best-effort — the
+   *  POST is Origin-guarded server-side; failures are surfaced only via the badge
+   *  not updating). No-op when no tab has attached yet. */
+  enqueueToActive(text: string, appendEnter: boolean): void {
+    const id = this.activeSessionId()
+    if (id === null) return
+    void enqueueFollowup(id, text, appendEnter)
   }
 
   /** A4: hidden activity-timeline panel; toggled per active session. */
@@ -725,6 +740,8 @@ export class TabApp {
       },
       // B2: telemetry is the single source of truth on the session; just re-render.
       onTelemetry: () => this.refreshTab(entry),
+      // W2: pending inject-queue depth changed — re-render the "N queued" badge.
+      onQueue: () => this.refreshTab(entry),
       // Split-grid: clicking anywhere in this pane makes it the focused quadrant.
       onFocus: () => this.setFocused(this.tabs.indexOf(entry)),
     })
@@ -1417,6 +1434,12 @@ export class TabApp {
     if (label) label.textContent = title
     const claude = el.querySelector('.tab-claude')
     if (claude) claude.textContent = claudeIcon(cs)
+    // W2: "⧗N" when the session has queued follow-ups, else empty (badge hidden).
+    const queue = el.querySelector('.tab-queue')
+    if (queue) {
+      const n = entry.session.queueLength
+      queue.textContent = n > 0 ? `⧗${n}` : ''
+    }
     const gauge = el.querySelector<HTMLElement>('.tab-gauge')
     if (gauge) renderTelemetryGauge(gauge, entry.session.telemetry, STATUSLINE_TTL_MS) // B2
   }
@@ -1512,6 +1535,11 @@ export class TabApp {
         claude.className = 'tab-claude'
         tabEl.appendChild(claude)
 
+        // W2: pending inject-queue depth badge (filled in by refreshTab).
+        const queue = document.createElement('span')
+        queue.className = 'tab-queue'
+        tabEl.appendChild(queue)
+
         // B2: per-tab telemetry gauge container (filled in by refreshTab).
         const gauge = document.createElement('span')
         gauge.className = 'tab-gauge'
diff --git a/public/terminal-session.ts b/public/terminal-session.ts
index 979b317..210dd78 100644
--- a/public/terminal-session.ts
+++ b/public/terminal-session.ts
@@ -115,6 +115,9 @@ export interface TerminalSessionOpts {
   /** Optional: fired when new statusLine telemetry arrives (B2). Single source of
    *  truth — T-tabs reads session.telemetry via the getter, not its own copy. */
   onTelemetry?: (telemetry: StatusTelemetry) => void
+  /** Optional: fired when the pending inject-queue depth changes (W2), so the tab
+   *  can render an "N queued" badge. Broadcast to every mirrored device. */
+  onQueue?: (length: number) => void
   /** Optional: fired on a pointerdown anywhere in this pane (split-grid focus).
    *  Lets TabApp move the focused-pane (activeIndex) to the clicked quadrant. */
   onFocus?: () => void
@@ -137,6 +140,7 @@ export class TerminalSession {
   private readonly onStatus: ((status: SessionStatus) => void) | undefined
   private readonly onClaudeStatus: ((status: ClaudeStatus, detail?: string) => void) | undefined
   private readonly onTelemetry: ((telemetry: StatusTelemetry) => void) | undefined
+  private readonly onQueue: ((length: number) => void) | undefined
   private readonly onFocus: (() => void) | undefined
   private readonly spawnCwd: string | undefined
   private readonly initialInput: string | undefined
@@ -147,6 +151,7 @@ export class TerminalSession {
   private pendingApprovalValue = false
   private pendingToolValue: string | undefined = undefined
   private telemetryValue: StatusTelemetry | null = null
+  private queueLengthValue = 0
   private pendingGateValue: PermissionGate | null = null
   // W1: bounded command/diff preview of the held tool, from the last pending
   // status frame. Null when no approval is held or the tool wasn't previewable.
@@ -179,6 +184,7 @@ export class TerminalSession {
     this.onStatus = opts.onStatus
     this.onClaudeStatus = opts.onClaudeStatus
     this.onTelemetry = opts.onTelemetry
+    this.onQueue = opts.onQueue
     this.onFocus = opts.onFocus
     this.spawnCwd = opts.cwd
     this.initialInput = opts.initialInput
@@ -255,6 +261,12 @@ export class TerminalSession {
     return this.telemetryValue
   }
 
+  /** W2: current pending inject-queue depth (0 when empty), from the last
+   *  `queue` frame. Every mirrored device sees the same value (broadcast). */
+  get queueLength(): number {
+    return this.queueLengthValue
+  }
+
   /** The gate kind from the last pending status frame (B4): 'plan' or 'tool'.
    *  Null when no approval is held or the last status had no gate. */
   get pendingGate(): PermissionGate | null {
@@ -393,6 +405,13 @@ export class TerminalSession {
         this.onTelemetry?.(msg.telemetry)
         break
       }
+      case 'queue': {
+        // W2: pending inject-queue depth changed — update the badge on every
+        // mirrored device (shared session).
+        this.queueLengthValue = msg.length
+        this.onQueue?.(msg.length)
+        break
+      }
       case 'exit': {
         this.setStatus('exited')
         const reason = msg.reason ? ` (${msg.reason})` : ''
diff --git a/src/config.ts b/src/config.ts
index aa4f10f..6b517f5 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -63,6 +63,10 @@ const DEFAULT_DIFF_MAX_FILES = 300
 const DEFAULT_STATUSLINE_TTL_MS = 30_000
 // B3 worktrees
 const DEFAULT_WORKTREE_TIMEOUT_MS = 10_000
+// W2 inject queue
+const DEFAULT_QUEUE_MAX_ITEMS = 10
+const DEFAULT_QUEUE_ITEM_MAX_BYTES = 4096
+const DEFAULT_QUEUE_SETTLE_MS = 1500
 
 /** Valid --permission-mode values (R0-confirmed). Whitelist for validation. */
 const PERMISSION_MODES: readonly PermissionMode[] = ['default', 'acceptEdits', 'plan', 'auto']
@@ -384,6 +388,16 @@ export function loadConfig(env: EnvLike): Config {
   )
   const allowAutoMode = parseBool(env['ALLOW_AUTO_MODE'], false)  // default off (SEC-M5)
 
+  // W2 server-side PTY-inject follow-up queue
+  const queueEnabled = parseBool(env['QUEUE_ENABLED'], true)
+  const queueMaxItems = parseNonNegativeInt(env['QUEUE_MAX_ITEMS'], 'QUEUE_MAX_ITEMS', DEFAULT_QUEUE_MAX_ITEMS)
+  const queueItemMaxBytes = parseNonNegativeInt(
+    env['QUEUE_ITEM_MAX_BYTES'],
+    'QUEUE_ITEM_MAX_BYTES',
+    DEFAULT_QUEUE_ITEM_MAX_BYTES,
+  )
+  const queueSettleMs = parseNonNegativeInt(env['QUEUE_SETTLE_MS'], 'QUEUE_SETTLE_MS', DEFAULT_QUEUE_SETTLE_MS)
+
   // ── assemble + freeze ───────────────────────────────────────────────────────
   // `satisfies Config` on the base object verifies all existing Config fields
   // are present without triggering excess-property checks on the v0.7 additions.
@@ -435,5 +449,10 @@ export function loadConfig(env: EnvLike): Config {
     worktreeTimeoutMs,
     defaultPermissionMode,
     allowAutoMode,
+    // W2 inject queue
+    queueEnabled,
+    queueMaxItems,
+    queueItemMaxBytes,
+    queueSettleMs,
   })
 }
diff --git a/src/server.ts b/src/server.ts
index fe90388..eec054f 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -32,7 +32,7 @@ import type { WebSocket as WsWebSocket } from 'ws'
 import type { IncomingMessage } from 'node:http'
 
 import { loadConfig } from './config.js'
-import { parseClientMessage, serialize } from './protocol.js'
+import { parseClientMessage, serialize, SESSION_ID_RE } from './protocol.js'
 import { isOriginAllowed } from './http/origin.js'
 import { parseHookEvent } from './http/hook.js'
 import { deriveApprovalPreview } from './http/approval-preview.js'
@@ -76,6 +76,7 @@ const LOG_FIELD_MAX = 200
 const RATE_LIMIT_WINDOW_MS = 60_000
 const DECISION_RATE_MAX = 10 // POST /hook/decision ≤ 10/min/IP
 const SUBSCRIBE_RATE_MAX = 5 // POST/DELETE /push/subscribe ≤ 5/min/IP
+const QUEUE_RATE_MAX = 20 // W2: POST/DELETE /live-sessions/:id/queue ≤ 20/min/IP
 
 /** The four permission modes the WS approve relay accepts (B4); else undefined. */
 const PERMISSION_MODES: ReadonlySet<string> = new Set<PermissionMode>([
@@ -219,6 +220,47 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
   // Per-IP rate limiters for the new state-changing routes (SEC-H9).
   const decisionLimiter = createRateLimiter(DECISION_RATE_MAX, RATE_LIMIT_WINDOW_MS)
   const subscribeLimiter = createRateLimiter(SUBSCRIBE_RATE_MAX, RATE_LIMIT_WINDOW_MS)
+  const queueLimiter = createRateLimiter(QUEUE_RATE_MAX, RATE_LIMIT_WINDOW_MS) // W2
+
+  // W2: per-session settle timers for the idle-drain. A Stop/SessionEnd hook
+  // schedules a debounced drain of one queue entry after cfg.queueSettleMs, so
+  // the injected text lands once the prompt is ready. Cleared on shutdown; the
+  // fired callback re-checks idle + a stable lastOutputAt cursor before draining.
+  const drainTimers = new Map<string, ReturnType<typeof setTimeout>>()
+
+  /**
+   * W2: schedule (or reschedule) a single idle-drain for `sessionId`. Debounced
+   * per session — each Stop clears any pending timer and restarts the window, so
+   * flapping Stop events fire at most one drain. On fire we drain ONE entry only
+   * if the session is still idle, unexited, and its lastOutputAt has not moved
+   * since scheduling (no output mid-settle = Claude really finished, not
+   * mid-render). One entry per idle → natural pacing (the injected prompt makes
+   * Claude work again, and its next Stop drains the next entry).
+   */
+  function scheduleDrain(sessionId: string): void {
+    if (!cfg.queueEnabled) return
+    const session = manager.get(sessionId)
+    if (session === undefined || session.exitedAt !== null) return
+    if (session.queue.length === 0) return
+
+    const existing = drainTimers.get(sessionId)
+    if (existing !== undefined) clearTimeout(existing)
+
+    const outputCursor = session.lastOutputAt
+    const timer = setTimeout(() => {
+      drainTimers.delete(sessionId)
+      const s = manager.get(sessionId)
+      if (s === undefined || s.exitedAt !== null) return
+      // Settle guard: new output since scheduling → Claude is still active; skip
+      // (a later genuine Stop reschedules). Also require the idle status to hold.
+      if (s.lastOutputAt !== outputCursor) return
+      if (s.claudeStatus !== 'idle') return
+      manager.drainOne(sessionId)
+    }, cfg.queueSettleMs)
+    // Don't let a pending drain keep the process alive; a stale fire is harmless.
+    timer.unref()
+    drainTimers.set(sessionId, timer)
+  }
 
   // H3/A1: held PermissionRequest responses, keyed by sessionId. `res` is parked
   // until approve/reject or timeout. `token`+`expiresAt` = the per-decision
@@ -350,6 +392,70 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
     })
   })
 
+  // ── W2 inject queue: enqueue a follow-up prompt fired on next idle ────────
+  // State-changing (causes shell input on idle) → Origin guard (CSRF) + per-IP
+  // rate limit. Body: { text: string, appendEnter?: boolean }. Bytes are stored
+  // and later injected VERBATIM (byte-shuttle) — bounded in size and count, never
+  // parsed as a shell command. `text` + optional trailing \r is capped by
+  // queueItemMaxBytes; the queue depth is capped by queueMaxItems.
+  app.post('/live-sessions/:id/queue', express.json({ limit: '16kb' }), (req, res) => {
+    if (!requireAllowedOrigin(req, res)) return
+    if (!cfg.queueEnabled) {
+      res.status(503).json({ error: 'queue disabled' })
+      return
+    }
+    if (!queueLimiter(req.socket.remoteAddress ?? '', Date.now())) {
+      res.status(429).end()
+      return
+    }
+    const id = req.params.id
+    if (!SESSION_ID_RE.test(id)) {
+      res.status(400).json({ error: 'invalid session id' })
+      return
+    }
+    const body = (req.body ?? {}) as Record<string, unknown>
+    const rawText = body['text']
+    if (typeof rawText !== 'string' || rawText.length === 0) {
+      res.status(400).json({ error: 'text must be a non-empty string' })
+      return
+    }
+    // FE decides Enter (mirrors quick-reply's appendEnter): materialize the exact
+    // bytes to inject here so the stored entry is byte-identical to a keystroke.
+    const text = body['appendEnter'] === true ? rawText + '\r' : rawText
+    if (Buffer.byteLength(text, 'utf8') > cfg.queueItemMaxBytes) {
+      res.status(413).json({ error: 'text too large' })
+      return
+    }
+    const result = manager.enqueueFollowup(id, text)
+    if (!result.ok) {
+      // full → 409 (never silently drop); unknown/exited → 404.
+      res.status(result.reason === 'full' ? 409 : 404).json({ error: result.reason })
+      return
+    }
+    res.json({ length: result.length })
+  })
+
+  // Read-only queue view (depth + the user's own queued text). No Origin guard —
+  // same threat model as GET /live-sessions.
+  app.get('/live-sessions/:id/queue', (req, res) => {
+    const session = manager.get(req.params.id)
+    if (session === undefined) {
+      res.status(404).end()
+      return
+    }
+    res.json({ length: session.queue.length, items: [...session.queue] })
+  })
+
+  // Cancel all pending entries (escape hatch). State-changing → Origin guard.
+  app.delete('/live-sessions/:id/queue', (req, res) => {
+    if (!requireAllowedOrigin(req, res)) return
+    if (!manager.clearQueue(req.params.id)) {
+      res.status(404).end()
+      return
+    }
+    res.json({ length: 0 })
+  })
+
   // CSRF guard for the state-changing DELETE routes (Arch 5b / Sec H2): the WS
   // upgrade checks Origin, but plain HTTP routes don't — without this, a foreign
   // page could fire a no-preflight DELETE and Kill-All sessions. Reuse the same
@@ -426,6 +532,9 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
     if (ev.eventClass === 'Stop' || ev.eventClass === 'SessionEnd') {
       const session = manager.get(ev.sessionId)
       if (session !== undefined) void pushService.notify(session, 'done')
+      // W2: Claude just went idle — schedule a debounced drain of the next queued
+      // follow-up (fires after the settle delay iff still idle + output stable).
+      scheduleDrain(ev.sessionId)
     }
     res.status(204).end()
   })
@@ -962,6 +1071,9 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
   // ── Graceful shutdown helper ──────────────────────────────────────────────
   function doShutdown(): void {
     clearInterval(reapTimer)
+    // W2: cancel any pending idle-drain timers so they can't fire post-shutdown.
+    for (const t of drainTimers.values()) clearTimeout(t)
+    drainTimers.clear()
     manager.shutdown()
   }
 
diff --git a/src/session/manager.ts b/src/session/manager.ts
index c7cbf50..ed7594c 100644
--- a/src/session/manager.ts
+++ b/src/session/manager.ts
@@ -30,6 +30,7 @@ import type {
   ClaudeStatus,
   Config,
   Dims,
+  EnqueueResult,
   LiveSessionInfo,
   NotifyService,
   PermissionGate,
@@ -41,7 +42,7 @@ import type {
 } from '../types.js';
 import { WS_OPEN } from '../types.js';
 import { serialize } from '../protocol.js';
-import { createSession, attachWs, broadcast, kill } from './session.js';
+import { createSession, attachWs, broadcast, kill, writeInput } from './session.js';
 import { appendEvent, makeTimelineEvent } from './timeline.js';
 import { hasSession, tmuxName } from './tmux.js';
 
@@ -194,6 +195,7 @@ export function createSessionManager(
         rows: s.pty.rows,
         telemetry: s.telemetry, // B2: latest telemetry for the thumbnail wall
         lastOutputAt: s.lastOutputAt, // T-iOS-37: unread watermark (M3 record)
+        queueLength: s.queue.length, // W2: pending inject-queue depth
       }))
       .sort((a, b) => b.createdAt - a.createdAt);
   }
@@ -323,6 +325,57 @@ export function createSessionManager(
     return count;
   }
 
+  /**
+   * W2: append a verbatim byte string to a session's inject queue.
+   *
+   * The queue is a bounded FIFO (cfg.queueMaxItems). The HTTP route validates and
+   * size-caps `text` before calling; here we only enforce depth + existence.
+   * Immutable update: replace the frozen array wholesale, never mutate in place.
+   * Broadcasts the new depth so every mirrored device updates its badge.
+   */
+  function enqueueFollowup(id: string, text: string): EnqueueResult {
+    const session = sessions.get(id);
+    if (session === undefined) return { ok: false, reason: 'unknown' };
+    if (session.exitedAt !== null) return { ok: false, reason: 'exited' };
+    if (session.queue.length >= cfg.queueMaxItems) return { ok: false, reason: 'full' };
+
+    session.queue = Object.freeze([...session.queue, text]);
+    const length = session.queue.length;
+    broadcast(session, { type: 'queue', length });
+    return { ok: true, length };
+  }
+
+  /**
+   * W2: pop the head entry and write it to the PTY (byte-identical to a keystroke;
+   * writeInput broadcasts the resulting output to all mirrors). Returns the
+   * injected string, or null when there is nothing to drain / the session is
+   * unknown or already exited (double-guards L4 — writeInput is itself a no-op
+   * after exit). Broadcasts the new depth.
+   */
+  function drainOne(id: string): string | null {
+    const session = sessions.get(id);
+    if (session === undefined || session.exitedAt !== null) return null;
+    if (session.queue.length === 0) return null;
+
+    const head = session.queue[0] as string;
+    session.queue = Object.freeze(session.queue.slice(1));
+    writeInput(session, head);
+    broadcast(session, { type: 'queue', length: session.queue.length });
+    return head;
+  }
+
+  /**
+   * W2: clear all pending entries (cancel-all escape hatch). Broadcasts depth 0.
+   * Returns false for an unknown session.
+   */
+  function clearQueue(id: string): boolean {
+    const session = sessions.get(id);
+    if (session === undefined) return false;
+    session.queue = Object.freeze([] as string[]);
+    broadcast(session, { type: 'queue', length: 0 });
+    return true;
+  }
+
   /**
    * Called on SIGINT/SIGTERM/close. For non-tmux sessions, kill the PTY. For
    * tmux sessions (H1), kill only the client pty — the tmux server keeps the
@@ -348,6 +401,9 @@ export function createSessionManager(
     handleStatusLine,
     sweepStuck,
     reapIdle,
+    enqueueFollowup,
+    drainOne,
+    clearQueue,
     shutdown,
   };
 }
diff --git a/src/session/session.ts b/src/session/session.ts
index 228ed71..8e5371d 100644
--- a/src/session/session.ts
+++ b/src/session/session.ts
@@ -137,6 +137,8 @@ export function createSession(
     timeline: Object.freeze([] as TimelineEvent[]),
     stuckNotified: false,   // A5: re-armed to false by each pty output
     telemetry: null,         // B2: updated by manager.handleStatusLine
+    // W2: inject follow-up queue — empty at spawn; replaced wholesale by manager.
+    queue: Object.freeze([] as string[]),
   };
 
   // onData: persist to scrollback, refresh liveness, broadcast to all clients.
diff --git a/src/types.ts b/src/types.ts
index 3e5cf03..bdb4c35 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -70,6 +70,11 @@ export interface Config {
   // B4 permission-mode relay
   readonly defaultPermissionMode: PermissionMode; // DEFAULT_PERMISSION_MODE, default 'default'
   readonly allowAutoMode: boolean; // ALLOW_AUTO_MODE, default false (SEC-M5)
+  // W2 server-side PTY-inject follow-up queue
+  readonly queueEnabled: boolean; // QUEUE_ENABLED, default true (routes 503 when off)
+  readonly queueMaxItems: number; // QUEUE_MAX_ITEMS, default 10 (bounded depth, DoS guard)
+  readonly queueItemMaxBytes: number; // QUEUE_ITEM_MAX_BYTES, default 4096 (bounded size)
+  readonly queueSettleMs: number; // QUEUE_SETTLE_MS, default 1500 (drain-after-idle delay)
 }
 
 /** process.env is structurally assignable to this; keeps the file free of `NodeJS.*`. */
@@ -136,7 +141,11 @@ export type ServerMessage =
        *  ignore it (additive + optional). */
       preview?: ApprovalPreview;
     }
-  | { type: 'telemetry'; telemetry: StatusTelemetry };
+  | { type: 'telemetry'; telemetry: StatusTelemetry }
+  /** W2: the current pending-inject queue depth for this session. Broadcast to
+   *  every attached device so all mirrors show the same "N queued" badge. Older
+   *  clients ignore it (additive variant). */
+  | { type: 'queue'; length: number };
 
 /** parseClientMessage result — never throws; errors flow here (§5.3). */
 export type ParseResult =
@@ -247,6 +256,11 @@ export interface Session {
   stuckNotified: boolean;
   /** B2: latest statusLine telemetry for this session; null until first report. */
   telemetry: StatusTelemetry | null;
+  /** W2: bounded FIFO of verbatim byte strings to inject when Claude next goes
+   *  idle. Head fires first. Mutable runtime handle on the immutable meta (like
+   *  timeline): replaced wholesale (Object.freeze of a new array), never mutated
+   *  in place. Capped by cfg.queueMaxItems; each entry capped by queueItemMaxBytes. */
+  queue: readonly string[];
   readonly pty: IPty;
 }
 
@@ -278,6 +292,9 @@ export interface LiveSessionInfo {
    *  (lastOutputAt > local last-seen). Additive OPTIONAL: older consumers
    *  that build or read LiveSessionInfo without it stay valid. */
   readonly lastOutputAt?: number;
+  /** W2: number of pending inject-queue entries (0 when empty). Additive OPTIONAL
+   *  so the manage grid and /live-sessions can surface queue depth per session. */
+  readonly queueLength?: number;
 }
 
 /* ───────────────── project manager (v0.6, §4.3 FEATURE doc) ──────────────── */
@@ -330,6 +347,13 @@ export interface ProjectDetail {
   claudeMd?: string; // its content (truncated for display) when present
 }
 
+/** W2: outcome of SessionManager.enqueueFollowup. Success carries the new depth;
+ *  failure names the reason so the HTTP route can pick the right status code
+ *  (unknown/exited → 404, full → 409). */
+export type EnqueueResult =
+  | { ok: true; length: number }
+  | { ok: false; reason: 'unknown' | 'full' | 'exited' };
+
 export interface SessionManager {
   handleAttach(
     ws: WebSocketLike,
@@ -366,6 +390,18 @@ export interface SessionManager {
   sweepStuck(now: number): void;
   /** reclaim when now - max(detachedAt, lastOutputAt) > idleTtlMs (M3). Returns count. */
   reapIdle(now: number): number;
+  /** W2: append verbatim `text` to a session's inject queue (bounded by
+   *  queueMaxItems); broadcasts the new depth. The route validates/sizes `text`
+   *  before calling. Never spawns; only mutates the queue handle. */
+  enqueueFollowup(id: string, text: string): EnqueueResult;
+  /** W2: pop the head entry and write it to the PTY (byte-identical to a
+   *  keystroke, broadcast to all mirrors); broadcasts the new depth. Returns the
+   *  injected string, or null when the queue is empty / session is unknown or
+   *  exited (double-guards L4). */
+  drainOne(id: string): string | null;
+  /** W2: clear all pending entries (cancel-all escape hatch); broadcasts depth 0.
+   *  Returns false for an unknown session. */
+  clearQueue(id: string): boolean;
   shutdown(): void;
 }
 
diff --git a/test/config.test.ts b/test/config.test.ts
index cfe6202..21ce127 100644
--- a/test/config.test.ts
+++ b/test/config.test.ts
@@ -730,3 +730,40 @@ describe('loadConfig — v0.7 all new fields present in frozen result', () => {
     expect(cfg).toHaveProperty('allowAutoMode')
   })
 })
+
+// ── W2 inject-queue config ────────────────────────────────────────────────────
+describe('loadConfig — W2 inject queue', () => {
+  beforeEach(() => {
+    mockNetworkInterfaces.mockReturnValue({})
+    mockHomedir.mockReturnValue('/home/testuser')
+  })
+
+  it('defaults: queueEnabled true, queueMaxItems 10, queueItemMaxBytes 4096, queueSettleMs 1500', () => {
+    const cfg = loadConfig({})
+    expect(cfg.queueEnabled).toBe(true)
+    expect(cfg.queueMaxItems).toBe(10)
+    expect(cfg.queueItemMaxBytes).toBe(4096)
+    expect(cfg.queueSettleMs).toBe(1500)
+  })
+
+  it('reads env overrides', () => {
+    const cfg = loadConfig({
+      QUEUE_ENABLED: '0',
+      QUEUE_MAX_ITEMS: '3',
+      QUEUE_ITEM_MAX_BYTES: '256',
+      QUEUE_SETTLE_MS: '500',
+    })
+    expect(cfg.queueEnabled).toBe(false)
+    expect(cfg.queueMaxItems).toBe(3)
+    expect(cfg.queueItemMaxBytes).toBe(256)
+    expect(cfg.queueSettleMs).toBe(500)
+  })
+
+  it('throws for a negative QUEUE_MAX_ITEMS (fail-fast)', () => {
+    expect(() => loadConfig({ QUEUE_MAX_ITEMS: '-1' })).toThrow()
+  })
+
+  it('throws for a non-integer QUEUE_SETTLE_MS', () => {
+    expect(() => loadConfig({ QUEUE_SETTLE_MS: 'soon' })).toThrow()
+  })
+})
diff --git a/test/integration/queue.test.ts b/test/integration/queue.test.ts
new file mode 100644
index 0000000..55ac1de
--- /dev/null
+++ b/test/integration/queue.test.ts
@@ -0,0 +1,395 @@
+/**
+ * W2 — integration tests for the server-side PTY-inject queue routes and the
+ * idle-drain wiring, against a real startServer.
+ *
+ * Sandbox-runnable (no PTY): Origin/CSRF guard, id/text validation, size + depth
+ * caps, rate limit, QUEUE_ENABLED=0 → 503, unknown-session 404.
+ *
+ * itPty-gated (needs a real shell — auto-skips where posix_spawn is blocked):
+ *   - happy path: POST queue → 200 {length:1}; GET /live-sessions shows
+ *     queueLength; GET/DELETE .../queue.
+ *   - idle-drain: enqueue → POST Stop → the marker echoes through the PTY.
+ *   - one-per-idle pacing: two entries, one Stop drains only the first.
+ *   - settle guard: a non-idle hook during the window cancels the drain.
+ */
+
+import net from 'node:net'
+
+import { afterEach, describe, expect, it } from 'vitest'
+import WebSocket from 'ws'
+import * as nodePty from 'node-pty'
+
+import { loadConfig } from '../../src/config.js'
+import { startServer } from '../../src/server.js'
+
+const PTY_AVAILABLE = (() => {
+  try {
+    const p = nodePty.spawn(process.env['SHELL'] ?? '/bin/sh', [], { cols: 80, rows: 24 })
+    p.kill()
+    return true
+  } catch {
+    return false
+  }
+})()
+const itPty = PTY_AVAILABLE ? it : it.skip
+
+function getFreePort(): Promise<number> {
+  return new Promise((resolve, reject) => {
+    const srv = net.createServer()
+    srv.listen(0, '127.0.0.1', () => {
+      const addr = srv.address()
+      if (addr === null || typeof addr === 'string') {
+        srv.close()
+        reject(new Error('bad addr'))
+        return
+      }
+      const port = addr.port
+      srv.close(() => resolve(port))
+    })
+    srv.on('error', reject)
+  })
+}
+
+const handles: { close(): Promise<void> }[] = []
+
+async function spawnServer(
+  overrides: Record<string, string | undefined> = {},
+): Promise<{ port: number; origin: string }> {
+  const port = await getFreePort()
+  const cfg = loadConfig({
+    PORT: String(port),
+    BIND_HOST: '127.0.0.1',
+    SHELL_PATH: process.env['SHELL'] ?? '/bin/zsh',
+    ALLOWED_ORIGINS: `http://127.0.0.1:${port}`,
+    USE_TMUX: '0',
+    IDLE_TTL: '86400',
+    ...overrides,
+  })
+  const handle = startServer(cfg)
+  handles.push(handle)
+  await new Promise<void>((r) => setTimeout(r, 80))
+  return { port, origin: `http://127.0.0.1:${port}` }
+}
+
+function waitForOpen(ws: WebSocket): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const t = setTimeout(() => reject(new Error('open timeout')), 3000)
+    ws.once('open', () => {
+      clearTimeout(t)
+      resolve()
+    })
+    ws.once('error', (e) => {
+      clearTimeout(t)
+      reject(e)
+    })
+  })
+}
+
+function waitForMessage(
+  ws: WebSocket,
+  pred: (m: Record<string, unknown>) => boolean,
+  timeoutMs = 6000,
+): Promise<Record<string, unknown>> {
+  return new Promise((resolve, reject) => {
+    const t = setTimeout(() => {
+      ws.off('message', onMsg)
+      reject(new Error('message timeout'))
+    }, timeoutMs)
+    const onMsg = (raw: WebSocket.RawData): void => {
+      let m: Record<string, unknown>
+      try {
+        m = JSON.parse(raw.toString('utf8')) as Record<string, unknown>
+      } catch {
+        return
+      }
+      if (pred(m)) {
+        clearTimeout(t)
+        ws.off('message', onMsg)
+        resolve(m)
+      }
+    }
+    ws.on('message', onMsg)
+  })
+}
+
+/** Resolve once no WS message has arrived for `quietMs` (the shell prompt settled). */
+function waitForQuiet(ws: WebSocket, quietMs = 300, maxMs = 4000): Promise<void> {
+  return new Promise((resolve) => {
+    let quietTimer: ReturnType<typeof setTimeout>
+    const done = (): void => {
+      clearTimeout(quietTimer)
+      clearTimeout(hardStop)
+      ws.off('message', onMsg)
+      resolve()
+    }
+    const arm = (): void => {
+      clearTimeout(quietTimer)
+      quietTimer = setTimeout(done, quietMs)
+    }
+    const onMsg = (): void => arm()
+    const hardStop = setTimeout(done, maxMs)
+    ws.on('message', onMsg)
+    arm()
+  })
+}
+
+/** Collect every output-frame's data string for `windowMs`. */
+function collectOutput(ws: WebSocket, windowMs: number): Promise<string> {
+  return new Promise((resolve) => {
+    let acc = ''
+    const onMsg = (raw: WebSocket.RawData): void => {
+      try {
+        const m = JSON.parse(raw.toString('utf8')) as Record<string, unknown>
+        if (m['type'] === 'output') acc += String(m['data'])
+      } catch {
+        /* ignore */
+      }
+    }
+    ws.on('message', onMsg)
+    setTimeout(() => {
+      ws.off('message', onMsg)
+      resolve(acc)
+    }, windowMs)
+  })
+}
+
+const isAttached = (m: Record<string, unknown>): boolean => m['type'] === 'attached'
+
+async function attachSession(port: number, origin: string): Promise<{ ws: WebSocket; sessionId: string }> {
+  const ws = new WebSocket(`ws://127.0.0.1:${port}/term`, { headers: { Origin: origin } })
+  await waitForOpen(ws)
+  ws.send(JSON.stringify({ type: 'attach', sessionId: null }))
+  const attached = await waitForMessage(ws, isAttached)
+  return { ws, sessionId: attached['sessionId'] as string }
+}
+
+function postQueue(
+  port: number,
+  id: string,
+  body: unknown,
+  headers: Record<string, string> = {},
+): Promise<globalThis.Response> {
+  return fetch(`http://127.0.0.1:${port}/live-sessions/${id}/queue`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', ...headers },
+    body: JSON.stringify(body),
+  })
+}
+
+function postStop(port: number, sessionId: string): Promise<globalThis.Response> {
+  return fetch(`http://127.0.0.1:${port}/hook`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', 'X-Webterm-Session': sessionId },
+    body: JSON.stringify({ hook_event_name: 'Stop' }),
+  })
+}
+
+afterEach(async () => {
+  while (handles.length > 0) await handles.pop()?.close()
+  await new Promise<void>((r) => setTimeout(r, 30))
+})
+
+const UNKNOWN = '00000000-0000-4000-8000-000000000000'
+
+// ── Route guards + validation (no PTY needed) ─────────────────────────────────
+
+describe('POST /live-sessions/:id/queue — guards & validation', () => {
+  it('rejects a foreign Origin with 403 (CSRF)', async () => {
+    const { port } = await spawnServer()
+    const res = await postQueue(port, UNKNOWN, { text: 'x' }, { Origin: 'http://evil.example' })
+    expect(res.status).toBe(403)
+  })
+
+  it('rejects a missing Origin with 403 (default-deny)', async () => {
+    const { port } = await spawnServer()
+    const res = await postQueue(port, UNKNOWN, { text: 'x' }) // no Origin header
+    expect(res.status).toBe(403)
+  })
+
+  it('rejects a malformed session id with 400', async () => {
+    const { port, origin } = await spawnServer()
+    const res = await postQueue(port, 'not-a-uuid', { text: 'x' }, { Origin: origin })
+    expect(res.status).toBe(400)
+  })
+
+  it('rejects empty / non-string text with 400', async () => {
+    const { port, origin } = await spawnServer()
+    expect((await postQueue(port, UNKNOWN, { text: '' }, { Origin: origin })).status).toBe(400)
+    expect((await postQueue(port, UNKNOWN, { text: 42 }, { Origin: origin })).status).toBe(400)
+    expect((await postQueue(port, UNKNOWN, {}, { Origin: origin })).status).toBe(400)
+  })
+
+  it('rejects oversized text with 413', async () => {
+    const { port, origin } = await spawnServer({ QUEUE_ITEM_MAX_BYTES: '16' })
+    const res = await postQueue(port, UNKNOWN, { text: 'x'.repeat(17) }, { Origin: origin })
+    expect(res.status).toBe(413)
+  })
+
+  it('returns 404 for a well-formed but unknown session id', async () => {
+    const { port, origin } = await spawnServer()
+    const res = await postQueue(port, UNKNOWN, { text: 'x' }, { Origin: origin })
+    expect(res.status).toBe(404)
+  })
+
+  it('returns 503 when QUEUE_ENABLED=0', async () => {
+    const { port, origin } = await spawnServer({ QUEUE_ENABLED: '0' })
+    const res = await postQueue(port, UNKNOWN, { text: 'x' }, { Origin: origin })
+    expect(res.status).toBe(503)
+  })
+
+  it('rate-limits after QUEUE_RATE_MAX requests with 429', async () => {
+    const { port, origin } = await spawnServer()
+    // 20 allowed (each 400 on empty text — rate is checked before validation),
+    // the 21st exceeds the per-IP window and returns 429.
+    let sawRate = false
+    for (let i = 0; i < 21; i++) {
+      const res = await postQueue(port, UNKNOWN, { text: '' }, { Origin: origin })
+      if (res.status === 429) sawRate = true
+    }
+    expect(sawRate).toBe(true)
+  })
+})
+
+describe('GET/DELETE /live-sessions/:id/queue — guards', () => {
+  it('GET returns 404 for an unknown session', async () => {
+    const { port } = await spawnServer()
+    const res = await fetch(`http://127.0.0.1:${port}/live-sessions/${UNKNOWN}/queue`)
+    expect(res.status).toBe(404)
+  })
+
+  it('DELETE rejects a foreign Origin with 403', async () => {
+    const { port } = await spawnServer()
+    const res = await fetch(`http://127.0.0.1:${port}/live-sessions/${UNKNOWN}/queue`, {
+      method: 'DELETE',
+      headers: { Origin: 'http://evil.example' },
+    })
+    expect(res.status).toBe(403)
+  })
+
+  it('DELETE returns 404 for an unknown session', async () => {
+    const { port, origin } = await spawnServer()
+    const res = await fetch(`http://127.0.0.1:${port}/live-sessions/${UNKNOWN}/queue`, {
+      method: 'DELETE',
+      headers: { Origin: origin },
+    })
+    expect(res.status).toBe(404)
+  })
+})
+
+// ── Happy path + drain (real PTY) ─────────────────────────────────────────────
+
+describe('inject queue — real session', () => {
+  itPty('enqueues, surfaces queueLength, lists items, and clears', async () => {
+    const { port, origin } = await spawnServer()
+    const { ws, sessionId } = await attachSession(port, origin)
+    await waitForQuiet(ws)
+
+    const enq = await postQueue(port, sessionId, { text: 'echo hi', appendEnter: true }, { Origin: origin })
+    expect(enq.status).toBe(200)
+    expect(await enq.json()).toEqual({ length: 1 })
+
+    // /live-sessions surfaces the depth.
+    const live = (await (await fetch(`http://127.0.0.1:${port}/live-sessions`)).json()) as Array<{
+      id: string
+      queueLength?: number
+    }>
+    expect(live.find((s) => s.id === sessionId)?.queueLength).toBe(1)
+
+    // GET .../queue returns the stored (verbatim) items.
+    const view = (await (
+      await fetch(`http://127.0.0.1:${port}/live-sessions/${sessionId}/queue`)
+    ).json()) as { length: number; items: string[] }
+    expect(view.length).toBe(1)
+    expect(view.items).toEqual(['echo hi\r'])
+
+    // DELETE clears the queue.
+    const del = await fetch(`http://127.0.0.1:${port}/live-sessions/${sessionId}/queue`, {
+      method: 'DELETE',
+      headers: { Origin: origin },
+    })
+    expect(del.status).toBe(200)
+    const view2 = (await (
+      await fetch(`http://127.0.0.1:${port}/live-sessions/${sessionId}/queue`)
+    ).json()) as { length: number }
+    expect(view2.length).toBe(0)
+
+    ws.close()
+  })
+
+  itPty('drains the head into the PTY after a Stop hook (idle-drain)', async () => {
+    const { port, origin } = await spawnServer({ QUEUE_SETTLE_MS: '50' })
+    const { ws, sessionId } = await attachSession(port, origin)
+    await waitForQuiet(ws)
+
+    const enq = await postQueue(
+      port,
+      sessionId,
+      { text: 'echo QUEUED_MARKER_A', appendEnter: true },
+      { Origin: origin },
+    )
+    expect(enq.status).toBe(200)
+
+    const marker = waitForMessage(
+      ws,
+      (m) => m['type'] === 'output' && String(m['data']).includes('QUEUED_MARKER_A'),
+    )
+    const stop = await postStop(port, sessionId)
+    expect(stop.status).toBe(204)
+
+    await marker // the shell echoed the injected keystrokes → marker present
+    ws.close()
+  })
+
+  itPty('fires only one entry per idle (Stop) — the next waits for the next Stop', async () => {
+    const { port, origin } = await spawnServer({ QUEUE_SETTLE_MS: '50' })
+    const { ws, sessionId } = await attachSession(port, origin)
+    await waitForQuiet(ws)
+
+    await postQueue(port, sessionId, { text: 'echo MARK_ONE', appendEnter: true }, { Origin: origin })
+    await postQueue(port, sessionId, { text: 'echo MARK_TWO', appendEnter: true }, { Origin: origin })
+
+    // First Stop → only MARK_ONE drains.
+    const one = waitForMessage(ws, (m) => m['type'] === 'output' && String(m['data']).includes('MARK_ONE'))
+    await postStop(port, sessionId)
+    await one
+
+    // Without another Stop, MARK_TWO must NOT be injected.
+    const idleWindow = await collectOutput(ws, 500)
+    expect(idleWindow.includes('MARK_TWO')).toBe(false)
+
+    // A second Stop drains MARK_TWO.
+    await waitForQuiet(ws)
+    const two = waitForMessage(ws, (m) => m['type'] === 'output' && String(m['data']).includes('MARK_TWO'))
+    await postStop(port, sessionId)
+    await two
+
+    ws.close()
+  })
+
+  itPty('settle guard: a non-idle hook during the window cancels the drain', async () => {
+    const { port, origin } = await spawnServer({ QUEUE_SETTLE_MS: '300' })
+    const { ws, sessionId } = await attachSession(port, origin)
+    await waitForQuiet(ws)
+
+    await postQueue(
+      port,
+      sessionId,
+      { text: 'echo SHOULD_NOT_RUN', appendEnter: true },
+      { Origin: origin },
+    )
+
+    // Stop schedules a drain at +300ms; a PreToolUse immediately flips the status
+    // back to 'working', so the settle-time idle re-check skips the drain.
+    await postStop(port, sessionId)
+    await fetch(`http://127.0.0.1:${port}/hook`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json', 'X-Webterm-Session': sessionId },
+      body: JSON.stringify({ hook_event_name: 'PreToolUse', tool_name: 'Bash' }),
+    })
+
+    const window = await collectOutput(ws, 600) // past the 300ms settle
+    expect(window.includes('SHOULD_NOT_RUN')).toBe(false)
+
+    ws.close()
+  })
+})
diff --git a/test/manager.test.ts b/test/manager.test.ts
index f167782..021c126 100644
--- a/test/manager.test.ts
+++ b/test/manager.test.ts
@@ -88,6 +88,11 @@ const CFG: Config = {
   worktreeTimeoutMs: 10_000,
   defaultPermissionMode: 'default',
   allowAutoMode: false,
+  // W2 inject queue
+  queueEnabled: true,
+  queueMaxItems: 10,
+  queueItemMaxBytes: 4096,
+  queueSettleMs: 1500,
 };
 
 const DIMS: Dims = { cols: 80, rows: 24 };
@@ -1145,3 +1150,137 @@ describe('list — lastOutputAt field (T-iOS-37)', () => {
     });
   });
 });
+
+// ── W2: inject-queue methods (enqueueFollowup / drainOne / clearQueue) ────────
+describe('W2 inject queue — enqueueFollowup', () => {
+  it('appends and returns {ok,length}, broadcasting {type:queue,length} to clients', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    ws.sent.length = 0;
+
+    const r1 = mgr.enqueueFollowup(s.meta.id, 'echo one\r');
+    expect(r1).toEqual({ ok: true, length: 1 });
+    expect(s.queue).toEqual(['echo one\r']);
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 1)).toBe(true);
+
+    const r2 = mgr.enqueueFollowup(s.meta.id, 'echo two\r');
+    expect(r2).toEqual({ ok: true, length: 2 });
+    expect(s.queue).toEqual(['echo one\r', 'echo two\r']);
+  });
+
+  it('caps at queueMaxItems → {ok:false,reason:full}, no broadcast, queue unchanged', () => {
+    const mgr = createSessionManager({ ...CFG, queueMaxItems: 2 });
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+    ws.sent.length = 0;
+
+    const r = mgr.enqueueFollowup(s.meta.id, 'c');
+    expect(r).toEqual({ ok: false, reason: 'full' });
+    expect(s.queue).toEqual(['a', 'b']); // immutable: unchanged
+    expect(parseSent(ws).some((m) => m.type === 'queue')).toBe(false); // no broadcast
+  });
+
+  it('unknown id → {ok:false,reason:unknown}', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.enqueueFollowup('11111111-1111-4111-8111-111111111111', 'x')).toEqual({
+      ok: false,
+      reason: 'unknown',
+    });
+  });
+
+  it('exited session → {ok:false,reason:exited}', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    s.exitedAt = 2_000;
+    expect(mgr.enqueueFollowup(s.meta.id, 'x')).toEqual({ ok: false, reason: 'exited' });
+  });
+});
+
+describe('W2 inject queue — drainOne', () => {
+  it('pops the head, writes it to the PTY, shrinks the queue, and broadcasts depth', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'HEAD\r');
+    mgr.enqueueFollowup(s.meta.id, 'TAIL\r');
+    ws.sent.length = 0;
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    const drained = mgr.drainOne(s.meta.id);
+    expect(drained).toBe('HEAD\r');
+    expect(pty.writes).toEqual(['HEAD\r']); // byte-identical inject
+    expect(s.queue).toEqual(['TAIL\r']); // length now 1
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 1)).toBe(true);
+  });
+
+  it('empty queue → null, no PTY write', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    expect(mgr.drainOne(s.meta.id)).toBeNull();
+    expect(pty.writes).toEqual([]);
+  });
+
+  it('exited session with items queued → null (double-guards L4), no write', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'x');
+    s.exitedAt = 2_000;
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    expect(mgr.drainOne(s.meta.id)).toBeNull();
+    expect(pty.writes).toEqual([]);
+  });
+
+  it('unknown id → null', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.drainOne('11111111-1111-4111-8111-111111111111')).toBeNull();
+  });
+});
+
+describe('W2 inject queue — clearQueue', () => {
+  it('empties the queue, broadcasts length 0, returns true', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+    ws.sent.length = 0;
+
+    expect(mgr.clearQueue(s.meta.id)).toBe(true);
+    expect(s.queue).toEqual([]);
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 0)).toBe(true);
+  });
+
+  it('unknown id → false', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.clearQueue('11111111-1111-4111-8111-111111111111')).toBe(false);
+  });
+});
+
+describe('W2 inject queue — list() surfaces queueLength', () => {
+  it('reports the pending depth per session', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+
+    const entry = mgr.list().find((e) => e.id === s.meta.id);
+    expect(entry?.queueLength).toBe(2);
+  });
+});
diff --git a/test/queue.test.ts b/test/queue.test.ts
new file mode 100644
index 0000000..88ff2e9
--- /dev/null
+++ b/test/queue.test.ts
@@ -0,0 +1,97 @@
+// @vitest-environment jsdom
+/**
+ * test/queue.test.ts — W2 frontend inject-queue helper (public/queue.ts).
+ *
+ * fetch is mocked; every helper must NEVER throw (mirrors quick-reply's
+ * never-throw discipline). Covers: POST url/body + parsed result, non-2xx →
+ * {ok:false,status}, network reject → {ok:false}, DELETE, and the frame parser.
+ */
+
+import { describe, it, expect, vi, afterEach } from 'vitest'
+
+import { enqueueFollowup, clearQueue, queueLengthFromFrame } from '../public/queue.js'
+
+afterEach(() => {
+  vi.restoreAllMocks()
+  // @ts-expect-error — reset the mocked global between tests
+  delete globalThis.fetch
+})
+
+function mockFetch(impl: (url: string, init?: RequestInit) => Promise<Response> | Response): void {
+  globalThis.fetch = vi.fn(impl as unknown as typeof fetch)
+}
+
+describe('enqueueFollowup', () => {
+  it('POSTs to the session queue URL with a JSON {text,appendEnter} body', async () => {
+    const calls: Array<{ url: string; init?: RequestInit }> = []
+    mockFetch((url, init) => {
+      calls.push({ url, init })
+      return new Response(JSON.stringify({ length: 1 }), { status: 200 })
+    })
+
+    const result = await enqueueFollowup('sess-1', 'run tests', true)
+
+    expect(result).toEqual({ ok: true, length: 1 })
+    expect(calls).toHaveLength(1)
+    expect(calls[0]!.url).toBe('/live-sessions/sess-1/queue')
+    expect(calls[0]!.init?.method).toBe('POST')
+    expect(JSON.parse(String(calls[0]!.init?.body))).toEqual({
+      text: 'run tests',
+      appendEnter: true,
+    })
+  })
+
+  it('returns {ok:false,status} on a non-2xx response and never throws', async () => {
+    mockFetch(() => new Response('nope', { status: 409 }))
+    const result = await enqueueFollowup('sess-1', 'x', false)
+    expect(result).toEqual({ ok: false, status: 409 })
+  })
+
+  it('returns {ok:false} on a network reject and never throws', async () => {
+    mockFetch(() => Promise.reject(new Error('offline')))
+    const result = await enqueueFollowup('sess-1', 'x', false)
+    expect(result).toEqual({ ok: false })
+  })
+
+  it('returns {ok:true} with undefined length when the body omits length', async () => {
+    mockFetch(() => new Response(JSON.stringify({}), { status: 200 }))
+    const result = await enqueueFollowup('sess-1', 'x', false)
+    expect(result).toEqual({ ok: true, length: undefined })
+  })
+})
+
+describe('clearQueue', () => {
+  it('DELETEs the session queue URL and returns true on success', async () => {
+    const calls: Array<{ url: string; init?: RequestInit }> = []
+    mockFetch((url, init) => {
+      calls.push({ url, init })
+      return new Response(JSON.stringify({ length: 0 }), { status: 200 })
+    })
+
+    const ok = await clearQueue('sess-2')
+    expect(ok).toBe(true)
+    expect(calls[0]!.url).toBe('/live-sessions/sess-2/queue')
+    expect(calls[0]!.init?.method).toBe('DELETE')
+  })
+
+  it('returns false on a non-2xx and on a network reject (never throws)', async () => {
+    mockFetch(() => new Response('', { status: 404 }))
+    expect(await clearQueue('sess-2')).toBe(false)
+
+    mockFetch(() => Promise.reject(new Error('offline')))
+    expect(await clearQueue('sess-2')).toBe(false)
+  })
+})
+
+describe('queueLengthFromFrame', () => {
+  it('returns the length for a {type:queue,length} frame', () => {
+    expect(queueLengthFromFrame({ type: 'queue', length: 3 })).toBe(3)
+  })
+
+  it('returns null for unrelated or malformed frames', () => {
+    expect(queueLengthFromFrame({ type: 'status', status: 'idle' })).toBeNull()
+    expect(queueLengthFromFrame({ type: 'queue' })).toBeNull()
+    expect(queueLengthFromFrame(null)).toBeNull()
+    expect(queueLengthFromFrame('nope')).toBeNull()
+  })
+})
diff --git a/test/quick-reply.test.ts b/test/quick-reply.test.ts
index 4bc132c..2b454da 100644
--- a/test/quick-reply.test.ts
+++ b/test/quick-reply.test.ts
@@ -549,4 +549,45 @@ describe('mountQuickReply — DOM', () => {
     expect(countAfter).toBe(countBefore)
     handle.dispose()
   })
+
+  // ── W2: the editor's "Queue" button (only shown when onQueue is wired) ────────
+  it('shows no Queue button when onQueue is not provided', () => {
+    const container = document.createElement('div')
+    const handle = mountQuickReply(container, { onSend: vi.fn() })
+    ;(container.querySelector('.qr-add-btn') as HTMLButtonElement).click()
+    expect(container.querySelector('.qr-editor-queue')).toBeNull()
+    handle.dispose()
+  })
+
+  it('Queue button calls onQueue with the typed text + appendEnter and closes the editor', () => {
+    const container = document.createElement('div')
+    const onQueue = vi.fn()
+    const handle = mountQuickReply(container, { onSend: vi.fn(), onQueue })
+    ;(container.querySelector('.qr-add-btn') as HTMLButtonElement).click()
+
+    const textInput = container.querySelector('.qr-editor-text') as HTMLInputElement
+    textInput.value = 'run tests then open a PR'
+    const enterCheck = container.querySelector('.qr-editor-enter') as HTMLInputElement
+    enterCheck.checked = true
+
+    ;(container.querySelector('.qr-editor-queue') as HTMLButtonElement).click()
+
+    expect(onQueue).toHaveBeenCalledWith('run tests then open a PR', true)
+    // Enqueue must NOT persist a chip nor send immediately.
+    expect(loadPalette().some((c) => c.text === 'run tests then open a PR')).toBe(false)
+    expect(container.querySelector('.qr-editor')).toBeNull()
+    handle.dispose()
+  })
+
+  it('Queue button with empty text is a no-op (onQueue not called, editor stays)', () => {
+    const container = document.createElement('div')
+    const onQueue = vi.fn()
+    const handle = mountQuickReply(container, { onSend: vi.fn(), onQueue })
+    ;(container.querySelector('.qr-add-btn') as HTMLButtonElement).click()
+    ;(container.querySelector('.qr-editor-queue') as HTMLButtonElement).click()
+
+    expect(onQueue).not.toHaveBeenCalled()
+    expect(container.querySelector('.qr-editor')).not.toBeNull()
+    handle.dispose()
+  })
 })
diff --git a/test/tabs.test.ts b/test/tabs.test.ts
index dba92db..ddd2946 100644
--- a/test/tabs.test.ts
+++ b/test/tabs.test.ts
@@ -29,6 +29,8 @@ class FakeTerminalSession {
   pendingEpoch = 0
   /** B2: latest statusLine telemetry (single source of truth). */
   telemetry: unknown = null
+  /** W2: pending inject-queue depth (tests set it before driving onQueue). */
+  queueLength = 0
   /** Captured so tests can assert initialInput ends with \r (Finding 1). */
   initialInput: string | undefined = undefined
   connect = vi.fn()
@@ -50,6 +52,7 @@ class FakeTerminalSession {
     onActivity?: () => void
     onTitle?: (t: string) => void
     onTelemetry?: (t: unknown) => void
+    onQueue?: (n: number) => void
   }
   static instances: FakeTerminalSession[] = []
   constructor(opts: {
@@ -60,6 +63,7 @@ class FakeTerminalSession {
     onActivity?: () => void
     onTitle?: (t: string) => void
     onTelemetry?: (t: unknown) => void
+    onQueue?: (n: number) => void
     [key: string]: unknown
   }) {
     constructed += 1
@@ -89,13 +93,28 @@ vi.mock('../public/cell-monitor.js', () => ({ mountCellMonitor }))
 const mountPushToggle = vi.fn()
 vi.mock('../public/push.js', () => ({ mountPushToggle }))
 
-const quickReply: { onSend?: (d: string) => void } = {}
-const mountQuickReply = vi.fn((_c: HTMLElement, opts: { onSend: (d: string) => void }) => {
-  quickReply.onSend = opts.onSend
-  return { dispose: vi.fn() }
-})
+const quickReply: {
+  onSend?: (d: string) => void
+  onQueue?: (text: string, appendEnter: boolean) => void
+} = {}
+const mountQuickReply = vi.fn(
+  (
+    _c: HTMLElement,
+    opts: { onSend: (d: string) => void; onQueue?: (text: string, appendEnter: boolean) => void },
+  ) => {
+    quickReply.onSend = opts.onSend
+    quickReply.onQueue = opts.onQueue
+    return { dispose: vi.fn() }
+  },
+)
 vi.mock('../public/quick-reply.js', () => ({ mountQuickReply }))
 
+// ── Mock the W2 queue helper (assert enqueue routing without real fetch) ──────
+const enqueueFollowupMock = vi.fn(async () => ({ ok: true, length: 1 }))
+vi.mock('../public/queue.js', () => ({
+  enqueueFollowup: (...args: unknown[]) => enqueueFollowupMock(...(args as [])),
+}))
+
 const timelineDispose = vi.fn()
 const mountTimeline = vi.fn(() => ({ dispose: timelineDispose }))
 vi.mock('../public/timeline.js', () => ({ mountTimeline }))
@@ -179,6 +198,8 @@ beforeEach(() => {
   voiceStart.mockClear()
   voiceStop.mockClear()
   quickReply.onSend = undefined
+  quickReply.onQueue = undefined
+  enqueueFollowupMock.mockClear()
   voice.onTranscript = undefined
   voice.onInterim = undefined
   // Default: server forbids 'auto' (loadUiConfig resolves to allowAutoMode=false).
@@ -1636,3 +1657,64 @@ describe('TabApp — split-grid watch board (v1)', () => {
     expect(mountCellMonitor.mock.lastCall?.[1]).toBe('sess-1')
   })
 })
+
+// ── W2: inject-queue badge + enqueue affordance ──────────────────────────────
+describe('TabApp — W2 inject queue', () => {
+  it('a queue frame (onQueue) updates the active tab’s ⧗N badge in place', () => {
+    const { paneHost, tabBar } = makeHosts()
+    const app = new TabApp(paneHost, tabBar)
+    app.newTab()
+    const inst = FakeTerminalSession.instances[0]!
+
+    // No queued items → empty badge.
+    expect((tabBar.querySelector('.tab-queue') as HTMLElement).textContent).toBe('')
+
+    // Server broadcasts depth 3 → badge shows ⧗3.
+    inst.queueLength = 3
+    inst.cbs.onQueue?.(3)
+    expect((tabBar.querySelector('.tab-queue') as HTMLElement).textContent).toBe('⧗3')
+
+    // Drains back to 0 → badge clears.
+    inst.queueLength = 0
+    inst.cbs.onQueue?.(0)
+    expect((tabBar.querySelector('.tab-queue') as HTMLElement).textContent).toBe('')
+  })
+
+  it('enqueueToActive routes to enqueueFollowup with the active session id', () => {
+    const { paneHost, tabBar } = makeHosts()
+    const app = new TabApp(paneHost, tabBar)
+    app.openSession('11111111-1111-4111-8111-111111111111')
+
+    app.enqueueToActive('run tests', true)
+
+    expect(enqueueFollowupMock).toHaveBeenCalledWith(
+      '11111111-1111-4111-8111-111111111111',
+      'run tests',
+      true,
+    )
+  })
+
+  it('the quick-reply Queue affordance enqueues for the active session', () => {
+    const { paneHost, tabBar } = makeHosts()
+    const app = new TabApp(paneHost, tabBar)
+    app.openSession('22222222-2222-4222-8222-222222222222')
+
+    // The onQueue handler wired into mountQuickReply routes through enqueueToActive.
+    quickReply.onQueue?.('open a PR', true)
+
+    expect(enqueueFollowupMock).toHaveBeenCalledWith(
+      '22222222-2222-4222-8222-222222222222',
+      'open a PR',
+      true,
+    )
+  })
+
+  it('enqueueToActive is a no-op when no session has attached (id null)', () => {
+    const { paneHost, tabBar } = makeHosts()
+    const app = new TabApp(paneHost, tabBar)
+    app.newTab() // fresh session → id null until server assigns
+
+    app.enqueueToActive('x', false)
+    expect(enqueueFollowupMock).not.toHaveBeenCalled()
+  })
+})
diff --git a/vitest.config.ts b/vitest.config.ts
index 37d23f8..804a0f9 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -24,6 +24,7 @@ export default defineConfig({
         'src/**/*.ts',
         'public/terminal-session.ts',
         'public/link-paths.ts',
+        'public/queue.ts',
         'public/tabs.ts',
         'public/grid-layout.ts',
         'public/grid-presets.ts',