diff --git a/CHANGELOG.md b/CHANGELOG.md
index e5fbd7d3..c3b0a9ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 ## [Unreleased]
 
+## [v0.50.248] — 2026-04-30
+
+### Added
+- **Real-time approval notifications via SSE long-connection** — replaces the 1.5s HTTP polling loop with a Server-Sent Events endpoint at `/api/approval/stream?session_id=` that pushes approval events to the browser the instant they fire. Cuts approval latency from up to 1.5s down to near-instant and eliminates the "always polling" network noise users observed. Backend uses a thread-safe subscriber registry (`_approval_sse_subscribers` dict, bounded `queue.Queue(maxsize=16)` per subscriber, silent drop on full to prevent leaks from slow tabs). 30s keepalive comments prevent proxy/CDN timeouts; `_CLIENT_DISCONNECT_ERRORS` + `finally` block guarantee subscriber cleanup on any exit path. **Subscribe and snapshot are taken atomically under a single `_lock` acquisition** so a `submit_pending()` arriving in the gap can't be lost. **Notify runs inside the queue-mutation lock** in both `submit_pending` and `_handle_approval_respond` so two parallel callers can't deliver out-of-order with stale `pending_count`. **SSE payload always reflects head-of-queue, never tail**, matching `/api/approval/pending`'s contract — with parallel tool-call approvals (#527), the just-appended entry is at the tail but the UI must show the head. **`_handle_approval_respond` now re-emits the new head after popping** so a trailing approval queued behind the one being responded to is surfaced immediately instead of getting stuck until the next event. Frontend uses `EventSource` with automatic 1.5s HTTP polling fallback on `onerror` (preserves degraded-mode parity with v0.50.247). 50 tests cover wiring, lifecycle, multi-subscriber, cross-session isolation, queue overflow, concurrent subscribe/notify stress, atomic-lock invariants, head-fidelity, trailing-approval re-emission, and notify-order monotonicity. (`api/routes.py`, `static/messages.js`, `tests/test_approval_sse.py`, `tests/test_pr1350_sse_atomic_subscribe.py`, `tests/test_pr1350_sse_notify_correctness.py`) @fxd-jason — PR #1350
+
+### Fixed
+- **Context indicator percentage shows even without explicit `context_length`** — frontend companion to the v0.50.246 backend fix. The context ring used to display `·` (no data) whenever `context_length` was 0 or missing — fresh agents, interrupted streams, or models without compressor state. Now defaults to **128K** when `usage.context_length` is falsy and labels the indicator with `(est. 128K)` so users can tell apparent vs. measured. Falls back to `input_tokens` for `last_prompt_tokens` so the ring lights up immediately on the first user message. (`static/ui.js`) @fxd-jason — PR #1349
+
 ## [v0.50.247] — 2026-04-30
 
 ### Added
diff --git a/api/routes.py b/api/routes.py
index d1ece383..bc2ac1d0 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -545,6 +545,67 @@ except ImportError:
     _permanent_approved = set()
 
 
+# ── Approval SSE subscribers (long-connection push) ──────────────────────────
+_approval_sse_subscribers: dict[str, list[queue.Queue]] = {}
+
+
+def _approval_sse_subscribe(session_id: str) -> queue.Queue:
+    """Register an SSE subscriber for approval events on a given session."""
+    q = queue.Queue(maxsize=16)
+    with _lock:
+        _approval_sse_subscribers.setdefault(session_id, []).append(q)
+    return q
+
+
+def _approval_sse_unsubscribe(session_id: str, q: queue.Queue) -> None:
+    """Remove an SSE subscriber."""
+    with _lock:
+        subs = _approval_sse_subscribers.get(session_id)
+        if subs and q in subs:
+            subs.remove(q)
+            if not subs:
+                _approval_sse_subscribers.pop(session_id, None)
+
+
+def _approval_sse_notify_locked(session_id: str, head: dict | None, total: int) -> None:
+    """Push an approval event to all SSE subscribers for a session.
+
+    CALLER MUST HOLD `_lock`. Snapshots the subscriber list under the held
+    lock and then calls `q.put_nowait()` on each (which is itself thread-safe).
+
+    `head` is the approval entry currently at the head of the queue (the one
+    the UI should display) — NOT the just-appended entry. With multiple
+    parallel approvals (#527), the just-appended entry is at the TAIL, but
+    `/api/approval/pending` always returns the HEAD, so SSE must match.
+
+    `total` is the total number of pending approvals.
+
+    Pass `head=None` and `total=0` when the queue has just been emptied (e.g.
+    `_handle_approval_respond` popped the last entry) so the client knows to
+    hide its approval card.
+    """
+    payload = {"pending": dict(head) if head else None, "pending_count": total}
+    subs = _approval_sse_subscribers.get(session_id, ())
+    for q in subs:
+        try:
+            q.put_nowait(payload)
+        except queue.Full:
+            pass  # drop if subscriber is slow (bounded queue prevents memory leak)
+
+
+def _approval_sse_notify(session_id: str, head: dict | None, total: int) -> None:
+    """Convenience wrapper that takes `_lock` itself.
+
+    Use only from contexts that don't already hold `_lock`. Production call
+    sites (submit_pending, _handle_approval_respond) MUST hold the lock and
+    call `_approval_sse_notify_locked` directly to avoid a notify-ordering
+    race where a later append's notify can fire before an earlier append's
+    notify (resulting in stale `pending_count`).
+    """
+    with _lock:
+        _approval_sse_notify_locked(session_id, head, total)
+
+
 def submit_pending(session_key: str, approval: dict) -> None:
     """Append a pending approval to the per-session queue.
 
@@ -553,16 +614,23 @@ def submit_pending(session_key: str, approval: dict) -> None:
       a specific entry even when multiple approvals are queued simultaneously.
     - Change the storage from a single overwriting dict value to a list, so
       parallel tool calls each get their own approval slot (fixes #527).
+    - Notify any connected SSE subscribers immediately.
     """
     entry = dict(approval)
     entry.setdefault("approval_id", uuid.uuid4().hex)
     with _lock:
-        queue = _pending.setdefault(session_key, [])
+        queue_list = _pending.setdefault(session_key, [])
         # Replace a legacy non-list value if the agent version uses the old pattern.
-        if not isinstance(queue, list):
-            _pending[session_key] = [queue]
-            queue = _pending[session_key]
-        queue.append(entry)
+        if not isinstance(queue_list, list):
+            _pending[session_key] = [queue_list]
+            queue_list = _pending[session_key]
+        queue_list.append(entry)
+        total = len(queue_list)
+        head = queue_list[0]  # /api/approval/pending always returns head
+        # Push to SSE subscribers from inside _lock so two parallel
+        # submit_pending calls can't deliver out-of-order (T2's later
+        # notify arriving before T1's earlier notify with a stale count).
+        _approval_sse_notify_locked(session_key, head, total)
     # NOTE: We do NOT call _submit_pending_raw here — that function overwrites
     # _pending[session_key] with a single dict, which would undo the list we just
     # built. The gateway blocking path uses _gateway_queues (a separate mechanism
@@ -1191,6 +1259,9 @@ def handle_get(handler, parsed) -> bool:
     if parsed.path == "/api/approval/pending":
         return _handle_approval_pending(handler, parsed)
 
+    if parsed.path == "/api/approval/stream":
+        return _handle_approval_sse_stream(handler, parsed)
+
     if parsed.path == "/api/approval/inject_test":
         # Loopback-only: used by automated tests; blocked from any remote client
         if handler.client_address[0] != "127.0.0.1":
@@ -2720,6 +2791,66 @@ def _handle_approval_pending(handler, parsed):
     return j(handler, {"pending": None, "pending_count": 0})
 
 
+def _handle_approval_sse_stream(handler, parsed):
+    """SSE endpoint for real-time approval notifications.
+
+    Long-lived connection that pushes approval events the moment they arrive,
+    replacing the 1.5s polling loop.  The frontend uses EventSource and falls
+    back to HTTP polling if the connection fails.
+    """
+    sid = parse_qs(parsed.query).get("session_id", [""])[0]
+    if not sid:
+        return bad(handler, "session_id is required")
+
+    # Subscribe AND snapshot atomically under a single _lock acquisition so a
+    # submit_pending() that fires between the two cannot be lost. If we
+    # snapshot first then subscribe (the naive ordering), an approval that
+    # arrives in the gap is appended to _pending (after our snapshot) AND
+    # notified to subscribers (before we joined) — leaving the client unaware
+    # until the next event arrives.
+    q = queue.Queue(maxsize=16)
+    initial_pending = None
+    initial_count = 0
+    with _lock:
+        _approval_sse_subscribers.setdefault(sid, []).append(q)
+        q_list = _pending.get(sid)
+        if isinstance(q_list, list):
+            initial_pending = dict(q_list[0]) if q_list else None
+            initial_count = len(q_list)
+        elif q_list:
+            initial_pending = dict(q_list)
+            initial_count = 1
+
+    handler.send_response(200)
+    handler.send_header('Content-Type', 'text/event-stream; charset=utf-8')
+    handler.send_header('Cache-Control', 'no-cache')
+    handler.send_header('X-Accel-Buffering', 'no')
+    handler.send_header('Connection', 'keep-alive')
+    handler.end_headers()
+
+    from api.streaming import _sse
+
+    # Push initial state immediately so the client doesn't miss anything.
+    _sse(handler, 'initial', {"pending": initial_pending, "pending_count": initial_count})
+
+    try:
+        while True:
+            try:
+                payload = q.get(timeout=30)
+            except queue.Empty:
+                # Keepalive — SSE comment line prevents proxy/CDN timeout.
+                handler.wfile.write(b': keepalive\n\n')
+                handler.wfile.flush()
+                continue
+            if payload is None:
+                break  # signal to close
+            _sse(handler, 'approval', payload)
+    except _CLIENT_DISCONNECT_ERRORS:
+        pass  # client went away — normal for long-lived connections
+    finally:
+        _approval_sse_unsubscribe(sid, q)
+
+
 def _handle_approval_inject(handler, parsed):
     """Inject a fake pending approval -- loopback-only, used by automated tests."""
     qs = parse_qs(parsed.query)
@@ -3783,6 +3914,16 @@ def _handle_approval_respond(handler, body):
         elif queue:
             # Legacy single-dict value.
             pending = _pending.pop(sid, None)
+        # Notify SSE subscribers of the new head (or empty state) so the UI
+        # surfaces any trailing approvals that were queued behind this one
+        # without waiting for the next submit_pending. Without this, a parallel
+        # tool-call scenario (#527) would leave the second approval invisible
+        # in the SSE path until the next event ever fired (the agent thread
+        # would be parked indefinitely from the user's perspective).
+        if isinstance(_pending.get(sid), list) and _pending[sid]:
+            _approval_sse_notify_locked(sid, _pending[sid][0], len(_pending[sid]))
+        else:
+            _approval_sse_notify_locked(sid, None, 0)
 
     if pending:
         keys = pending.get("pattern_keys") or [pending.get("pattern_key", "")]
diff --git a/static/messages.js b/static/messages.js
index 8ea4fd35..c4f92d9f 100644
--- a/static/messages.js
+++ b/static/messages.js
@@ -1314,6 +1314,50 @@ async function respondApproval(choice) {
 
 function startApprovalPolling(sid) {
   stopApprovalPolling();
+  // ── SSE (preferred): long-lived connection, server pushes instantly ──
+  try {
+    const es = new EventSource('/api/approval/stream?session_id=' + encodeURIComponent(sid));
+    let _fallbackActive = false;
+
+    es.addEventListener('initial', e => {
+      const d = JSON.parse(e.data);
+      if (d.pending) { d.pending._session_id = sid; showApprovalCard(d.pending, d.pending_count || 1); }
+      else { hideApprovalCard(); }
+    });
+
+    es.addEventListener('approval', e => {
+      const d = JSON.parse(e.data);
+      if (d.pending) { d.pending._session_id = sid; showApprovalCard(d.pending, d.pending_count || 1); }
+      else { hideApprovalCard(); }
+    });
+
+    es.onerror = () => {
+      // SSE failed — fall back to HTTP polling (3s interval)
+      if (_fallbackActive) return;
+      _fallbackActive = true;
+      try { es.close(); } catch(_){}
+      _startApprovalFallbackPoll(sid);
+    };
+
+    // If the session changes or stops being busy, close the SSE.
+    // We detect this via a periodic check (cheap — no network request).
+    _approvalSSEHealthTimer = setInterval(() => {
+      if (!S.busy || !S.session || S.session.session_id !== sid) {
+        stopApprovalPolling(); hideApprovalCard(true);
+      }
+    }, 5000);
+
+    _approvalEventSource = es;
+  } catch(_e) {
+    // EventSource constructor failed — use polling directly
+    _startApprovalFallbackPoll(sid);
+  }
+}
+
+let _approvalEventSource = null;
+let _approvalSSEHealthTimer = null;
+
+function _startApprovalFallbackPoll(sid) {
   _approvalPollTimer = setInterval(async () => {
     if (!S.busy || !S.session || S.session.session_id !== sid) {
       stopApprovalPolling(); hideApprovalCard(true); return;
@@ -1323,11 +1367,13 @@ function startApprovalPolling(sid) {
       if (data.pending) { data.pending._session_id=sid; showApprovalCard(data.pending, data.pending_count||1); }
       else { hideApprovalCard(); }
     } catch(e) { /* ignore poll errors */ }
-  }, 1500);
+  }, 1500);  // matches the v0.50.247 polling cadence so degraded-mode users see the same responsiveness
 }
 
 function stopApprovalPolling() {
   if (_approvalPollTimer) { clearInterval(_approvalPollTimer); _approvalPollTimer = null; }
+  if (_approvalEventSource) { try { _approvalEventSource.close(); } catch(_){} _approvalEventSource = null; }
+  if (_approvalSSEHealthTimer) { clearInterval(_approvalSSEHealthTimer); _approvalSSEHealthTimer = null; }
 }
 
 // ── Clarify polling ──
diff --git a/static/ui.js b/static/ui.js
index 5f6e2fc9..6d01dec3 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -850,9 +850,12 @@ function _syncCtxIndicator(usage){
   const wrap=$('ctxIndicatorWrap');
   const el=$('ctxIndicator');
   if(!el)return;
+  // Use input_tokens as fallback when last_prompt_tokens is not available
   const promptTok=usage.last_prompt_tokens||usage.input_tokens||0;
   const totalTok=(usage.input_tokens||0)+(usage.output_tokens||0);
-  const ctxWindow=usage.context_length||0;
+  // Default context window to 128K when not provided by backend
+  const DEFAULT_CTX=128*1024;
+  const ctxWindow=usage.context_length||DEFAULT_CTX;
   const cost=usage.estimated_cost;
   // Show indicator whenever we have any usage data (tokens or cost)
   if(!promptTok&&!totalTok&&!cost){
@@ -860,8 +863,8 @@ function _syncCtxIndicator(usage){
     return;
   }
   if(wrap) wrap.style.display='';
-  const hasCtxWindow=!!(promptTok&&ctxWindow);
-  const pct=hasCtxWindow?Math.min(100,Math.round((promptTok/ctxWindow)*100)):0;
+  const hasPromptTok=!!promptTok;
+  const pct=hasPromptTok?Math.min(100,Math.round((promptTok/ctxWindow)*100)):0;
   const ring=$('ctxRingValue');
   const center=$('ctxPercent');
   const usageLine=$('ctxTooltipUsage');
@@ -873,7 +876,8 @@ function _syncCtxIndicator(usage){
     ring.style.strokeDasharray=String(circumference);
     ring.style.strokeDashoffset=String(circumference*(1-pct/100));
   }
-  if(center) center.textContent=hasCtxWindow?String(pct):'\u00b7';
+  if(center) center.textContent=hasPromptTok?String(pct):'\u00b7';
+  const hasExplicitCtx=!!usage.context_length;
   el.classList.toggle('ctx-mid',pct>50&&pct<=75);
   el.classList.toggle('ctx-high',pct>75);
   // ── Compress affordance (#524) ──
@@ -900,11 +904,12 @@ function _syncCtxIndicator(usage){
       compressWrap.style.display='none';
     }
   }
-  let label=hasCtxWindow?`Context window ${pct}% used`:`${_fmtTokens(totalTok)} tokens used`;
+  let label=hasPromptTok?`Context window ${pct}% used`:`${_fmtTokens(totalTok)} tokens used`;
+  if(!hasExplicitCtx&&hasPromptTok) label+=' (est. 128K)';
   if(cost) label+=` \u00b7 $${cost<0.01?cost.toFixed(4):cost.toFixed(2)}`;
   el.setAttribute('aria-label',label);
-  if(usageLine) usageLine.textContent=hasCtxWindow?`${pct}% used (${Math.max(0,100-pct)}% left)`:`${_fmtTokens(totalTok)} tokens used`;
-  if(tokensLine) tokensLine.textContent=hasCtxWindow?`${_fmtTokens(promptTok)} / ${_fmtTokens(ctxWindow)} tokens used`:`In: ${_fmtTokens(usage.input_tokens||0)} \u00b7 Out: ${_fmtTokens(usage.output_tokens||0)}`;
+  if(usageLine) usageLine.textContent=hasPromptTok?`${pct}% used (${Math.max(0,100-pct)}% left)`:`${_fmtTokens(totalTok)} tokens used`;
+  if(tokensLine) tokensLine.textContent=hasPromptTok?`${_fmtTokens(promptTok)} / ${_fmtTokens(ctxWindow)} tokens used`:`In: ${_fmtTokens(usage.input_tokens||0)} \u00b7 Out: ${_fmtTokens(usage.output_tokens||0)}`;
   const threshold=usage.threshold_tokens||0;
   if(thresholdLine){
     if(threshold&&ctxWindow){
diff --git a/tests/test_approval_queue.py b/tests/test_approval_queue.py
index fbcac019..5d94e828 100644
--- a/tests/test_approval_queue.py
+++ b/tests/test_approval_queue.py
@@ -23,8 +23,8 @@ INDEX_HTML = (REPO_ROOT / "static" / "index.html").read_text(encoding="utf-8")
 
 def test_submit_pending_appends_to_list():
     """submit_pending() must append to a list, not overwrite."""
-    # The new wrapper must contain queue.append
-    assert "queue.append(entry)" in ROUTES_SRC, \
+    # The new wrapper must contain a queue append (list mutation pattern)
+    assert "queue_list.append(entry)" in ROUTES_SRC or "queue.append(entry)" in ROUTES_SRC, \
         "submit_pending() must append entry to a list queue, not overwrite _pending[sid]"
 
 
diff --git a/tests/test_approval_sse.py b/tests/test_approval_sse.py
new file mode 100644
index 00000000..89670747
--- /dev/null
+++ b/tests/test_approval_sse.py
@@ -0,0 +1,487 @@
+"""Tests for the approval SSE (Server-Sent Events) long-connection implementation.
+
+Verifies:
+  - SSE subscribe/unsubscribe/notify lifecycle
+  - Initial snapshot delivery on connect
+  - Instant push when submit_pending() fires
+  - Client disconnect triggers unsubscribe cleanup
+  - Multiple concurrent subscribers per session
+  - Queue overflow (slow subscriber) drops silently
+  - Cross-session isolation (notify only reaches matching subscribers)
+  - Frontend EventSource / fallback polling patterns
+"""
+
+import json
+import pathlib
+import queue
+import re
+import sys
+import threading
+import time
+import uuid
+
+REPO_ROOT = pathlib.Path(__file__).parent.parent.resolve()
+sys.path.insert(0, str(REPO_ROOT))
+
+ROUTES_SRC = (REPO_ROOT / "api" / "routes.py").read_text(encoding="utf-8")
+MESSAGES_JS = (REPO_ROOT / "static" / "messages.js").read_text(encoding="utf-8")
+
+
+# ═══════════════════════════════════════════════════════════════════════════════
+# 1. Static-analysis tests (no server needed)
+# ═══════════════════════════════════════════════════════════════════════════════
+
+class TestSSEStaticAnalysis:
+    """Verify the SSE infrastructure exists and is wired correctly in routes.py."""
+
+    def test_sse_route_registered(self):
+        """The /api/approval/stream route must be registered."""
+        assert '"/api/approval/stream"' in ROUTES_SRC, \
+            "Route /api/approval/stream must be registered in the URL dispatch"
+
+    def test_sse_handler_function_exists(self):
+        """_handle_approval_sse_stream handler must exist."""
+        assert "def _handle_approval_sse_stream(" in ROUTES_SRC, \
+            "_handle_approval_sse_stream handler function must exist"
+
+    def test_subscribe_function_exists(self):
+        """_approval_sse_subscribe must exist and use a Queue."""
+        assert "def _approval_sse_subscribe(" in ROUTES_SRC, \
+            "_approval_sse_subscribe must be defined"
+
+    def test_unsubscribe_function_exists(self):
+        """_approval_sse_unsubscribe must exist and clean up empty lists."""
+        assert "def _approval_sse_unsubscribe(" in ROUTES_SRC, \
+            "_approval_sse_unsubscribe must be defined"
+
+    def test_notify_function_exists(self):
+        """_approval_sse_notify must exist and push to subscriber queues."""
+        assert "def _approval_sse_notify(" in ROUTES_SRC, \
+            "_approval_sse_notify must be defined"
+
+    def test_sse_subscribers_dict_exists(self):
+        """Module-level _approval_sse_subscribers dict must exist."""
+        assert "_approval_sse_subscribers" in ROUTES_SRC, \
+            "_approval_sse_subscribers module-level dict must exist"
+
+    def test_sse_content_type(self):
+        """SSE handler must set text/event-stream content type."""
+        assert "text/event-stream" in ROUTES_SRC, \
+            "SSE handler must set Content-Type to text/event-stream"
+
+    def test_sse_keepalive(self):
+        """SSE handler must send keepalive comments to prevent proxy timeout."""
+        assert "keepalive" in ROUTES_SRC, \
+            "SSE handler must send keepalive comments"
+
+    def test_sse_cache_control(self):
+        """SSE handler must set Cache-Control: no-cache."""
+        assert "no-cache" in ROUTES_SRC, \
+            "SSE handler must set Cache-Control: no-cache"
+
+    def test_sse_initial_snapshot(self):
+        """SSE handler must send initial snapshot on connect."""
+        assert "'initial'" in ROUTES_SRC, \
+            "SSE handler must send an 'initial' event with snapshot data"
+
+    def test_sse_approval_event(self):
+        """SSE handler must send 'approval' events on push."""
+        assert "'approval'" in ROUTES_SRC, \
+            "SSE handler must send 'approval' events when pushing notifications"
+
+    def test_notify_called_from_submit_pending(self):
+        """submit_pending must call _approval_sse_notify_locked."""
+        # Pinned to the inner-lock variant: must run inside the same `with _lock:`
+        # block as the queue mutation so two parallel submit_pending calls can't
+        # deliver out-of-order with stale pending_count. Tracks the v0.50.248
+        # MUST-FIX A fix.
+        assert "_approval_sse_notify_locked(session_key, head, total)" in ROUTES_SRC, \
+            ("submit_pending() must call _approval_sse_notify_locked(session_key, head, total) "
+             "from inside the `with _lock:` block — not the unlocked _approval_sse_notify wrapper, "
+             "and head must be queue_list[0] (the head, not the just-appended entry).")
+
+    def test_unsubscribe_in_finally(self):
+        """SSE handler must unsubscribe in a finally block."""
+        # Find the finally block that calls _approval_sse_unsubscribe
+        assert re.search(r"finally:.*\n.*_approval_sse_unsubscribe\(", ROUTES_SRC, re.DOTALL), \
+            "SSE handler must call _approval_sse_unsubscribe in a finally block"
+
+    def test_client_disconnect_handled(self):
+        """SSE handler must catch client disconnect errors."""
+        assert "_CLIENT_DISCONNECT_ERRORS" in ROUTES_SRC, \
+            "SSE handler must catch client disconnect errors"
+
+    def test_subscriber_queue_maxsize(self):
+        """Subscriber queues must have a bounded maxsize to prevent memory leaks."""
+        assert "queue.Queue(maxsize=" in ROUTES_SRC, \
+            "Subscriber queues must have maxsize set to prevent unbounded memory growth"
+
+    def test_notify_drops_on_full(self):
+        """_approval_sse_notify must silently drop events when subscriber is slow."""
+        # The queue.Full exception handler
+        assert "queue.Full" in ROUTES_SRC, \
+            "_approval_sse_notify must handle queue.Full to drop events for slow subscribers"
+
+    def test_subscribe_uses_shared_lock(self):
+        """subscribe/unsubscribe/notify must all use the same _lock."""
+        # All three functions must use _lock
+        for func in ["_approval_sse_subscribe", "_approval_sse_unsubscribe", "_approval_sse_notify"]:
+            # Find the function and verify it uses "with _lock"
+            func_start = ROUTES_SRC.find(f"def {func}(")
+            assert func_start != -1, f"{func} must exist"
+            # Find the next function definition after this one
+            next_func = ROUTES_SRC.find("\ndef ", func_start + 1)
+            func_body = ROUTES_SRC[func_start:next_func] if next_func != -1 else ROUTES_SRC[func_start:]
+            assert "with _lock:" in func_body, \
+                f"{func} must use 'with _lock:' for thread safety"
+
+    def test_unsubscribe_cleans_empty_session(self):
+        """Unsubscribe must remove empty session keys from the dict."""
+        assert "_approval_sse_subscribers.pop(session_id, None)" in ROUTES_SRC, \
+            "_approval_sse_unsubscribe must pop session_id when subscriber list is empty"
+
+
+class TestFrontendSSEImplementation:
+    """Verify the frontend JavaScript SSE implementation."""
+
+    def test_eventsource_used(self):
+        """Frontend must use EventSource for SSE connection."""
+        assert "new EventSource(" in MESSAGES_JS, \
+            "startApprovalPolling must create an EventSource for SSE"
+
+    def test_sse_url_matches_backend(self):
+        """Frontend SSE URL must match backend /api/approval/stream route."""
+        assert "/api/approval/stream" in MESSAGES_JS, \
+            "EventSource must connect to /api/approval/stream"
+
+    def test_initial_event_listener(self):
+        """Frontend must listen for 'initial' SSE events."""
+        assert "'initial'" in MESSAGES_JS or '"initial"' in MESSAGES_JS, \
+            "Frontend must addEventListener for 'initial' SSE events"
+
+    def test_approval_event_listener(self):
+        """Frontend must listen for 'approval' SSE events."""
+        assert "'approval'" in MESSAGES_JS or '"approval"' in MESSAGES_JS, \
+            "Frontend must addEventListener for 'approval' SSE events"
+
+    def test_onerror_fallback_to_polling(self):
+        """onerror must fall back to HTTP polling."""
+        assert "_startApprovalFallbackPoll" in MESSAGES_JS, \
+            "SSE onerror handler must call _startApprovalFallbackPoll"
+
+    def test_fallback_poll_interval(self):
+        """Fallback polling interval must match v0.50.247's 1500ms cadence."""
+        assert "1500" in MESSAGES_JS, \
+            "Fallback polling interval must be 1500ms to match degraded-mode parity with v0.50.247"
+
+    def test_fallback_closes_eventsource(self):
+        """onerror handler must close the EventSource before falling back."""
+        # The onerror handler should call es.close()
+        assert "es.close()" in MESSAGES_JS, \
+            "onerror handler must close the EventSource before falling back"
+
+    def test_stop_closes_eventsource(self):
+        """stopApprovalPolling must close EventSource."""
+        assert "_approvalEventSource.close()" in MESSAGES_JS, \
+            "stopApprovalPolling must close _approvalEventSource"
+
+    def test_health_timer_cleanup(self):
+        """stopApprovalPolling must clear the SSE health timer."""
+        assert "_approvalSSEHealthTimer" in MESSAGES_JS, \
+            "SSE health timer must be tracked and cleared in stopApprovalPolling"
+
+
+# ═══════════════════════════════════════════════════════════════════════════════
+# 2. Unit tests (in-process, no HTTP server)
+# ═══════════════════════════════════════════════════════════════════════════════
+
+class TestSSESubscribeUnsubscribe:
+    """Test the subscribe/unsubscribe lifecycle."""
+
+    def setup_method(self):
+        """Clean SSE subscriber state before each test."""
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+
+    def teardown_method(self):
+        """Clean up after each test."""
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+
+    def test_subscribe_returns_queue(self):
+        """_approval_sse_subscribe must return a Queue."""
+        from api import routes as r
+        sid = f"sse-test-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        assert isinstance(q, queue.Queue), "subscribe must return a queue.Queue"
+        # Cleanup
+        r._approval_sse_unsubscribe(sid, q)
+
+    def test_subscribe_registers_subscriber(self):
+        """After subscribe, the queue must appear in _approval_sse_subscribers."""
+        from api import routes as r
+        sid = f"sse-reg-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            with r._lock:
+                subs = r._approval_sse_subscribers.get(sid, [])
+            assert q in subs, "Subscribed queue must be in the subscribers list"
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+    def test_unsubscribe_removes_queue(self):
+        """After unsubscribe, the queue must not be in the subscribers list."""
+        from api import routes as r
+        sid = f"sse-unsub-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        r._approval_sse_unsubscribe(sid, q)
+        with r._lock:
+            subs = r._approval_sse_subscribers.get(sid, [])
+        assert q not in subs, "Unsubscribed queue must not be in the list"
+
+    def test_unsubscribe_removes_empty_session_key(self):
+        """When the last subscriber is removed, the session key must be cleaned up."""
+        from api import routes as r
+        sid = f"sse-empty-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        r._approval_sse_unsubscribe(sid, q)
+        with r._lock:
+            assert sid not in r._approval_sse_subscribers, \
+                "Session key must be removed when subscriber list is empty"
+
+    def test_unsubscribe_idempotent(self):
+        """Unsubscribing twice must not raise."""
+        from api import routes as r
+        sid = f"sse-idem-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        r._approval_sse_unsubscribe(sid, q)
+        r._approval_sse_unsubscribe(sid, q)  # should not raise
+
+    def test_unsubscribe_unknown_queue_noop(self):
+        """Unsubscribing a queue that was never subscribed must not crash."""
+        from api import routes as r
+        sid = f"sse-noop-{uuid.uuid4().hex[:8]}"
+        q = queue.Queue()
+        r._approval_sse_unsubscribe(sid, q)  # should not raise
+
+
+class TestSSENotify:
+    """Test the notification mechanism."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+
+    def test_notify_delivers_payload(self):
+        """_approval_sse_notify must put the payload on subscriber queues."""
+        from api import routes as r
+        sid = f"sse-notify-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            entry = {"command": "rm -rf /tmp/test", "pattern_key": "delete"}
+            r._approval_sse_notify(sid, entry, 1)
+            payload = q.get(timeout=1)
+            assert payload["pending"]["command"] == "rm -rf /tmp/test"
+            assert payload["pending_count"] == 1
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+    def test_notify_multiple_subscribers(self):
+        """All subscribers for a session must receive the notification."""
+        from api import routes as r
+        sid = f"sse-multi-{uuid.uuid4().hex[:8]}"
+        q1 = r._approval_sse_subscribe(sid)
+        q2 = r._approval_sse_subscribe(sid)
+        q3 = r._approval_sse_subscribe(sid)
+        try:
+            entry = {"command": "test-cmd"}
+            r._approval_sse_notify(sid, entry, 2)
+            for q in [q1, q2, q3]:
+                payload = q.get(timeout=1)
+                assert payload["pending"]["command"] == "test-cmd"
+                assert payload["pending_count"] == 2
+        finally:
+            for q in [q1, q2, q3]:
+                r._approval_sse_unsubscribe(sid, q)
+
+    def test_notify_cross_session_isolation(self):
+        """Notify for session A must NOT deliver to session B subscribers."""
+        from api import routes as r
+        sid_a = f"sse-iso-a-{uuid.uuid4().hex[:8]}"
+        sid_b = f"sse-iso-b-{uuid.uuid4().hex[:8]}"
+        qa = r._approval_sse_subscribe(sid_a)
+        qb = r._approval_sse_subscribe(sid_b)
+        try:
+            entry = {"command": "only-for-a"}
+            r._approval_sse_notify(sid_a, entry, 1)
+            # qa should have the event
+            payload = qa.get(timeout=1)
+            assert payload["pending"]["command"] == "only-for-a"
+            # qb should be empty
+            assert qb.empty(), "Session B subscriber must not receive session A events"
+        finally:
+            r._approval_sse_unsubscribe(sid_a, qa)
+            r._approval_sse_unsubscribe(sid_b, qb)
+
+    def test_notify_no_subscribers_is_noop(self):
+        """Notifying a session with no subscribers must not raise."""
+        from api import routes as r
+        sid = f"sse-nosub-{uuid.uuid4().hex[:8]}"
+        r._approval_sse_notify(sid, {"command": "test"}, 1)  # should not raise
+
+    def test_notify_drops_on_full_queue(self):
+        """When subscriber queue is full, events must be silently dropped."""
+        from api import routes as r
+        sid = f"sse-full-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            # Fill the queue (maxsize=16)
+            for i in range(20):
+                r._approval_sse_notify(sid, {"command": f"cmd-{i}"}, i + 1)
+            # Queue should have at most 16 items
+            assert q.qsize() <= 16, "Queue must not exceed maxsize"
+            assert q.qsize() > 0, "Queue should have some items"
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+
+class TestSSENotifyFromSubmitPending:
+    """Test that submit_pending triggers SSE notifications."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def test_submit_pending_notifies_sse_subscriber(self):
+        """submit_pending must push an SSE event to subscribers."""
+        from api import routes as r
+        sid = f"sse-submit-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            r.submit_pending(sid, {
+                "command": "rm -rf /tmp/test",
+                "pattern_key": "recursive delete",
+                "pattern_keys": ["recursive delete"],
+                "description": "recursive delete",
+            })
+            payload = q.get(timeout=1)
+            assert payload["pending"]["command"] == "rm -rf /tmp/test"
+            assert payload["pending_count"] == 1
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+    def test_submit_pending_delivers_count(self):
+        """Multiple submit_pending calls must report correct pending_count."""
+        from api import routes as r
+        sid = f"sse-count-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            for i in range(3):
+                r.submit_pending(sid, {
+                    "command": f"cmd-{i}",
+                    "pattern_key": f"p{i}",
+                    "pattern_keys": [f"p{i}"],
+                    "description": f"d{i}",
+                })
+            for expected_count in [1, 2, 3]:
+                payload = q.get(timeout=1)
+                assert payload["pending_count"] == expected_count, \
+                    f"Expected pending_count={expected_count}, got {payload['pending_count']}"
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+
+class TestSSEConcurrency:
+    """Test thread safety of SSE subscribe/unsubscribe/notify."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def test_concurrent_subscribe_unsubscribe(self):
+        """Concurrent subscribe/unsubscribe must not corrupt state."""
+        from api import routes as r
+        sid = f"sse-conc-{uuid.uuid4().hex[:8]}"
+        errors = []
+        queues = []
+
+        def worker():
+            try:
+                for _ in range(50):
+                    q = r._approval_sse_subscribe(sid)
+                    queues.append(q)
+                    r._approval_sse_unsubscribe(sid, q)
+            except Exception as e:
+                errors.append(e)
+
+        threads = [threading.Thread(target=worker) for _ in range(4)]
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join(timeout=10)
+
+        assert not errors, f"Concurrent subscribe/unsubscribe errors: {errors}"
+        # After all threads finish, no queues should remain
+        with r._lock:
+            subs = r._approval_sse_subscribers.get(sid, [])
+        assert len(subs) == 0, "All subscribers should be cleaned up"
+
+    def test_concurrent_notify_while_subscribing(self):
+        """Notify while new subscribers are joining must not deadlock or crash."""
+        from api import routes as r
+        sid = f"sse-notsub-{uuid.uuid4().hex[:8]}"
+        errors = []
+
+        def notifier():
+            try:
+                for i in range(100):
+                    r._approval_sse_notify(sid, {"command": f"cmd-{i}"}, 1)
+            except Exception as e:
+                errors.append(e)
+
+        def subscriber():
+            try:
+                for _ in range(50):
+                    q = r._approval_sse_subscribe(sid)
+                    time.sleep(0.001)
+                    r._approval_sse_unsubscribe(sid, q)
+            except Exception as e:
+                errors.append(e)
+
+        threads = [
+            threading.Thread(target=notifier),
+            threading.Thread(target=subscriber),
+            threading.Thread(target=subscriber),
+        ]
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join(timeout=15)
+
+        assert not errors, f"Concurrent notify/subscribe errors: {errors}"
+        with r._lock:
+            r._approval_sse_subscribers.clear()
diff --git a/tests/test_pr1350_sse_atomic_subscribe.py b/tests/test_pr1350_sse_atomic_subscribe.py
new file mode 100644
index 00000000..fad3ea29
--- /dev/null
+++ b/tests/test_pr1350_sse_atomic_subscribe.py
@@ -0,0 +1,108 @@
+"""Test that the SSE subscribe + snapshot are taken atomically under _lock.
+
+Regression test for the snapshot/subscribe race condition: if subscribe
+happens AFTER the snapshot, a submit_pending() that fires in the gap is
+both appended to _pending (after our snapshot) AND notified to subscribers
+(before we joined) — the client never learns about it until the next event.
+
+The fix in v0.50.248 takes the lock once, registers the subscriber queue,
+THEN reads the snapshot — all under the same lock acquisition.
+
+This test verifies the source-level invariant rather than the runtime
+behavior: the subscriber-registration line MUST appear inside the same
+`with _lock:` block as the snapshot read, and BEFORE the snapshot read.
+"""
+
+import pathlib
+import sys
+
+REPO_ROOT = pathlib.Path(__file__).parent.parent.resolve()
+sys.path.insert(0, str(REPO_ROOT))
+
+ROUTES_SRC = (REPO_ROOT / "api" / "routes.py").read_text(encoding="utf-8")
+
+
+def _extract_lock_block(body: str) -> str:
+    """Extract the body of the first `with _lock:` block from the handler.
+
+    Lines are part of the block as long as they are blank or start with the
+    block's indent (>= 8 spaces, since the handler body itself is at 4 spaces
+    and the lock block indents one level deeper).
+    """
+    lines = body.split("\n")
+    out: list[str] = []
+    in_block = False
+    block_indent = None
+    for line in lines:
+        if not in_block:
+            if line.strip() == "with _lock:":
+                in_block = True
+            continue
+        # Determine block indent from the first non-empty line we see inside.
+        if block_indent is None:
+            stripped = line.lstrip(" ")
+            if stripped == "":
+                continue  # blank lines don't set indent
+            block_indent = len(line) - len(stripped)
+            out.append(line)
+            continue
+        # Continuation: blank lines OK, otherwise must be at >= block_indent.
+        if line.strip() == "":
+            out.append(line)
+            continue
+        line_indent = len(line) - len(line.lstrip(" "))
+        if line_indent >= block_indent:
+            out.append(line)
+        else:
+            break
+    return "\n".join(out)
+
+
+def _handler_body() -> str:
+    start = ROUTES_SRC.find("def _handle_approval_sse_stream(")
+    assert start != -1, "_handle_approval_sse_stream must exist"
+    end = ROUTES_SRC.find("\ndef ", start + 1)
+    return ROUTES_SRC[start:end if end != -1 else len(ROUTES_SRC)]
+
+
+def test_snapshot_taken_under_lock():
+    """The initial _pending snapshot must be guarded by `with _lock:`."""
+    lock_body = _extract_lock_block(_handler_body())
+    assert lock_body, "_handle_approval_sse_stream must contain a `with _lock:` block"
+    assert "_pending.get(sid)" in lock_body, \
+        "Initial snapshot of _pending must be read inside the `with _lock:` block"
+
+
+def test_subscriber_registered_inside_lock():
+    """The subscriber queue must be registered inside the same `with _lock:` block."""
+    lock_body = _extract_lock_block(_handler_body())
+    assert lock_body, "Handler must contain a `with _lock:` block"
+    assert "_approval_sse_subscribers" in lock_body and "append(q)" in lock_body, \
+        ("Subscriber registration (`_approval_sse_subscribers.setdefault(sid, []).append(q)`) "
+         "must happen inside the same `with _lock:` block as the snapshot. "
+         "Otherwise a submit_pending() between snapshot-and-subscribe is lost.")
+
+
+def test_subscribe_before_snapshot_in_lock():
+    """Inside the lock, the subscriber must be registered BEFORE reading the snapshot."""
+    lock_body = _extract_lock_block(_handler_body())
+    assert lock_body, "Handler must contain a `with _lock:` block"
+
+    sub_idx = lock_body.find("_approval_sse_subscribers")
+    snap_idx = lock_body.find("_pending.get(sid)")
+
+    assert sub_idx != -1, "Subscriber registration must be inside the lock"
+    assert snap_idx != -1, "Snapshot read must be inside the lock"
+    assert sub_idx < snap_idx, (
+        "Subscriber registration must come BEFORE the snapshot read inside the lock. "
+        "Otherwise an approval arriving between subscribe and snapshot is silently dropped."
+    )
+
+
+def test_no_double_subscribe_outside_lock():
+    """The handler must not also call `_approval_sse_subscribe()` (legacy code path)."""
+    body = _handler_body()
+    assert "= _approval_sse_subscribe(sid)" not in body, (
+        "_handle_approval_sse_stream must not call _approval_sse_subscribe() — "
+        "the atomic version inlines subscribe inside the snapshot lock block."
+    )
diff --git a/tests/test_pr1350_sse_notify_correctness.py b/tests/test_pr1350_sse_notify_correctness.py
new file mode 100644
index 00000000..ead05e61
--- /dev/null
+++ b/tests/test_pr1350_sse_notify_correctness.py
@@ -0,0 +1,259 @@
+"""Regression tests for the v0.50.248 SSE notify-on-respond fix.
+
+Originally PR #1350 only called `_approval_sse_notify` from `submit_pending`,
+not from `_handle_approval_respond`. With the parallel-tool-call scenario
+that PR #527 supports:
+
+  1. submit_pending(A)  -> SSE pushes (A, 1). UI shows A.
+  2. submit_pending(B)  -> SSE pushes (B, 2). UI shows B.   (bug: was sending B as head, not A)
+  3. respond(B)         -> queue still contains A. UI hides card.
+                           NO event fires. A is invisible until next event.
+
+Pre-release Opus review caught two MUST-FIX bugs:
+  A. notify-ordering race: notify outside _lock could deliver out-of-order
+     under contention.
+  C. Trailing approval lost: respond never re-emitted the new head.
+  D. Payload was tail-not-head: with #527 parallel approvals, /api/approval/pending
+     returns head, but SSE was returning the just-appended entry (tail).
+
+The fix:
+  - `_approval_sse_notify_locked(sid, head, total)` runs inside the caller's
+    held `_lock` so two parallel callers serialize their notifies in the same
+    order they serialize their queue mutations.
+  - submit_pending now passes `head = queue_list[0]` (head-of-queue), not the
+    just-appended entry.
+  - _handle_approval_respond now calls _approval_sse_notify_locked after the
+    pop with the new head (or None/0 if queue is empty).
+"""
+
+import pathlib
+import queue
+import sys
+import time
+import uuid
+
+REPO_ROOT = pathlib.Path(__file__).parent.parent.resolve()
+sys.path.insert(0, str(REPO_ROOT))
+
+
+class TestParallelApprovalsHeadFidelity:
+    """SSE payload must always reflect head-of-queue, never tail."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def test_second_submit_pending_sends_head_not_tail(self):
+        """When B is appended while A is still pending, SSE payload must show A as head."""
+        from api import routes as r
+        sid = f"sse-headtail-{uuid.uuid4().hex[:8]}"
+        q = r._approval_sse_subscribe(sid)
+        try:
+            r.submit_pending(sid, {
+                "command": "first-A",
+                "pattern_key": "first",
+                "pattern_keys": ["first"],
+                "description": "A",
+            })
+            r.submit_pending(sid, {
+                "command": "second-B",
+                "pattern_key": "second",
+                "pattern_keys": ["second"],
+                "description": "B",
+            })
+            # First payload should be A (just-appended, also head).
+            p1 = q.get(timeout=1)
+            assert p1["pending"]["command"] == "first-A"
+            assert p1["pending_count"] == 1
+            # Second payload's HEAD is still A (we appended B but A is still queued).
+            p2 = q.get(timeout=1)
+            assert p2["pending"]["command"] == "first-A", (
+                "SSE payload must show head-of-queue (A), not tail (B). "
+                f"Got: {p2['pending']['command']}"
+            )
+            assert p2["pending_count"] == 2
+        finally:
+            r._approval_sse_unsubscribe(sid, q)
+
+
+class TestRespondNotifiesTrailingApproval:
+    """After respond() pops one approval, SSE must re-emit the new head if any."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def test_respond_to_first_pushes_second_as_new_head(self):
+        """submit A; submit B; respond(A) -> SSE must push (B, 1) so the UI surfaces B."""
+        from api import routes as r
+        sid = f"sse-trailing-{uuid.uuid4().hex[:8]}"
+
+        # Subscribe BEFORE any submit so we capture all events deterministically.
+        sub_q = r._approval_sse_subscribe(sid)
+        try:
+            r.submit_pending(sid, {
+                "command": "first-A",
+                "pattern_key": "p1",
+                "pattern_keys": ["p1"],
+                "description": "A",
+                "approval_id": "id-A",
+            })
+            r.submit_pending(sid, {
+                "command": "second-B",
+                "pattern_key": "p2",
+                "pattern_keys": ["p2"],
+                "description": "B",
+                "approval_id": "id-B",
+            })
+            # Drain the two submit-driven events.
+            sub_q.get(timeout=1)  # head=A, total=1
+            sub_q.get(timeout=1)  # head=A, total=2 (head is still A)
+
+            # Now simulate respond(A) by directly invoking the lock+pop+notify
+            # sequence the route handler runs. (Calling _handle_approval_respond
+            # would require an HTTP handler mock; the inner sequence is what we
+            # need to verify.)
+            from api.routes import _approval_sse_notify_locked, _lock, _pending
+            with _lock:
+                qlist = _pending.get(sid)
+                # Pop A by approval_id
+                for i, e in enumerate(qlist):
+                    if e.get("approval_id") == "id-A":
+                        qlist.pop(i)
+                        break
+                # Re-emit head
+                if isinstance(_pending.get(sid), list) and _pending[sid]:
+                    _approval_sse_notify_locked(sid, _pending[sid][0], len(_pending[sid]))
+                else:
+                    _approval_sse_notify_locked(sid, None, 0)
+
+            # SSE must push (B, 1) so the UI surfaces the trailing approval.
+            p3 = sub_q.get(timeout=1)
+            assert p3["pending"] is not None, \
+                "After responding to A, SSE must emit the new head B (not None)"
+            assert p3["pending"]["command"] == "second-B", \
+                f"New head should be B, got: {p3['pending']['command']}"
+            assert p3["pending_count"] == 1
+        finally:
+            r._approval_sse_unsubscribe(sid, sub_q)
+
+    def test_respond_to_only_pending_pushes_empty_state(self):
+        """If respond pops the last entry, SSE must push a None/0 sentinel so UI hides card."""
+        from api import routes as r
+        sid = f"sse-empty-{uuid.uuid4().hex[:8]}"
+
+        sub_q = r._approval_sse_subscribe(sid)
+        try:
+            r.submit_pending(sid, {
+                "command": "only-A",
+                "pattern_key": "p",
+                "pattern_keys": ["p"],
+                "description": "A",
+                "approval_id": "id-only-A",
+            })
+            sub_q.get(timeout=1)  # drain submit notify
+
+            from api.routes import _approval_sse_notify_locked, _lock, _pending
+            with _lock:
+                qlist = _pending.get(sid)
+                for i, e in enumerate(qlist):
+                    if e.get("approval_id") == "id-only-A":
+                        qlist.pop(i)
+                        break
+                if not qlist:
+                    _pending.pop(sid, None)
+                if isinstance(_pending.get(sid), list) and _pending[sid]:
+                    _approval_sse_notify_locked(sid, _pending[sid][0], len(_pending[sid]))
+                else:
+                    _approval_sse_notify_locked(sid, None, 0)
+
+            payload = sub_q.get(timeout=1)
+            assert payload["pending"] is None, \
+                "After responding to the only approval, SSE must push pending=None"
+            assert payload["pending_count"] == 0
+        finally:
+            r._approval_sse_unsubscribe(sid, sub_q)
+
+
+class TestNotifyOrderUnderContention:
+    """Two parallel submit_pending callers must deliver in queue-mutation order."""
+
+    def setup_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def teardown_method(self):
+        from api import routes as r
+        with r._lock:
+            r._approval_sse_subscribers.clear()
+            r._pending.clear()
+
+    def test_pending_count_is_monotonic_under_contention(self):
+        """Under parallel submit_pending, pending_count must be monotonically increasing.
+
+        Pre-fix: notify outside _lock meant T2's notify could fire before T1's,
+        with subscribers seeing pending_count=2 then pending_count=1. Now that
+        notify runs inside _lock alongside the append, the order is guaranteed.
+        """
+        import threading
+        from api import routes as r
+        sid = f"sse-order-{uuid.uuid4().hex[:8]}"
+
+        sub_q = r._approval_sse_subscribe(sid)
+        try:
+            errors = []
+            barrier = threading.Barrier(8)
+
+            def submitter(idx):
+                try:
+                    barrier.wait(timeout=2)
+                    r.submit_pending(sid, {
+                        "command": f"cmd-{idx}",
+                        "pattern_key": f"p{idx}",
+                        "pattern_keys": [f"p{idx}"],
+                        "description": f"d{idx}",
+                    })
+                except Exception as e:
+                    errors.append(e)
+
+            threads = [threading.Thread(target=submitter, args=(i,)) for i in range(8)]
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join(timeout=5)
+
+            assert not errors, f"Submitter errors: {errors}"
+
+            # Drain payloads — count must go 1, 2, 3, ..., 8 in some order
+            # consistent with the queue serialization. Specifically, never decrease.
+            counts = []
+            for _ in range(8):
+                p = sub_q.get(timeout=2)
+                counts.append(p["pending_count"])
+
+            assert counts == sorted(counts), (
+                f"pending_count must be monotonically increasing under contention. "
+                f"Got: {counts}. Pre-fix this could be out-of-order."
+            )
+            assert counts == list(range(1, 9)), \
+                f"Expected [1..8], got {counts}"
+        finally:
+            r._approval_sse_unsubscribe(sid, sub_q)