diff --git a/indexnow.py b/indexnow.py
index 84bbc40..1bf3422 100644
--- a/indexnow.py
+++ b/indexnow.py
@@ -36,10 +36,58 @@ _STATE_PATH = os.environ.get("THERMOGRAPH_INDEXNOW_STATE_FILE") or os.path.join(
 _ENDPOINT = "https://api.indexnow.org/indexnow"   # a shared endpoint; it fans out to all participants
 _BATCH = 10000                                    # IndexNow's max URLs per request
 
+# One shared client instead of a bare httpx.post per batch — same reused-client
+# pattern as web/app.py's _frontend_client and notifications/discord.py's _client.
+# 30s default matches submit()'s own prior per-call default; still overridable
+# per call (submit_all's fan-out passes its own `timeout` through unchanged).
+_client = httpx.Client(timeout=30)
+
 _lock = threading.Lock()
 _key = None
 
 
+def _claim_file(value: str) -> str:
+    """Persist a freshly generated key as `_KEY_PATH`'s content, atomic
+    first-writer-wins — same race, same fix as push.py's VAPID `_claim_file`
+    (see its docstring): on a cold /state volume several workers can hit the
+    missing-file branch at once, and without this each would generate and cache
+    its OWN key, diverging from the file and from each other (the key served at
+    /{key}.txt would then randomly mismatch whichever key a given worker signed
+    a submission with). Write to a private temp file, then claim the real path
+    with a hard link (atomic; a loser gets EEXIST with no half-written window);
+    a loser reads back the winner's file instead of keeping its own generation."""
+    tmp_path = f"{_KEY_PATH}.{os.getpid()}.tmp"
+    try:
+        os.makedirs(_DATA_DIR, exist_ok=True)
+        with open(tmp_path, "w", encoding="utf-8") as f:
+            f.write(value)
+        os.chmod(tmp_path, 0o600)
+    except OSError:
+        log.warning("could not persist IndexNow key to %s; using an in-memory key", _KEY_PATH)
+        return value
+    try:
+        try:
+            os.link(tmp_path, _KEY_PATH)
+            return value
+        except FileExistsError:
+            try:
+                with open(_KEY_PATH, encoding="utf-8") as f:
+                    winner = f.read().strip()
+                if winner:
+                    return winner
+            except OSError:
+                pass
+            return value
+        except OSError:
+            log.warning("could not persist IndexNow key to %s; using an in-memory key", _KEY_PATH)
+            return value
+    finally:
+        try:
+            os.unlink(tmp_path)
+        except OSError:
+            pass
+
+
 def key() -> str:
     """The IndexNow key (env → file → generate-and-persist), cached for the process."""
     global _key
@@ -60,14 +108,10 @@ def key() -> str:
                 return _key
         except OSError:
             pass
-        _key = secrets.token_hex(16)   # 32 hex chars — within IndexNow's 8–128 range
-        try:
-            os.makedirs(_DATA_DIR, exist_ok=True)
-            with open(_KEY_PATH, "w", encoding="utf-8") as f:
-                f.write(_key)
-            os.chmod(_KEY_PATH, 0o600)
-        except OSError:
-            log.warning("could not persist IndexNow key to %s; using an in-memory key", _KEY_PATH)
+        # Cache whatever _claim_file settles on — see its docstring: our own
+        # generation if we won the race to create the file, the winner's key
+        # read back from disk if we lost it.
+        _key = _claim_file(secrets.token_hex(16))   # 32 hex chars — within IndexNow's 8–128 range
         return _key
 
 
@@ -83,8 +127,8 @@ def submit(urls, host: str, key_location: str, scheme: str = "https", timeout: f
         batch = urls[i:i + _BATCH]
         payload = {"host": host, "key": k, "keyLocation": key_location, "urlList": batch}
         try:
-            r = httpx.post(_ENDPOINT, json=payload, timeout=timeout,
-                           headers={"Content-Type": "application/json; charset=utf-8"})
+            r = _client.post(_ENDPOINT, json=payload, timeout=timeout,
+                             headers={"Content-Type": "application/json; charset=utf-8"})
         except httpx.HTTPError as e:
             log.warning("IndexNow request failed: %s", e)
             statuses.append("error")
diff --git a/notifications/discord.py b/notifications/discord.py
index 776fa2f..2eb0e24 100644
--- a/notifications/discord.py
+++ b/notifications/discord.py
@@ -47,6 +47,12 @@ _COLD = 0x4393C3
 
 _TIMEOUT = httpx.Timeout(10.0)
 
+# One shared client instead of a bare httpx.post per call — same reused-client
+# pattern as web/app.py's _frontend_client, so every webhook/bot-REST call in
+# this module reuses one connection pool instead of paying a fresh TCP+TLS
+# handshake per notification.
+_client = httpx.Client(timeout=_TIMEOUT)
+
 
 def enabled() -> bool:
     return bool(WEBHOOK_URL) or weather_enabled()
@@ -131,7 +137,7 @@ def post_daily_feed(feed: dict | None = None) -> bool:
             "embeds": [embed],
         }
         try:
-            resp = httpx.post(WEBHOOK_URL, json=payload, timeout=_TIMEOUT)
+            resp = _client.post(WEBHOOK_URL, json=payload, timeout=_TIMEOUT)
             ok = 200 <= resp.status_code < 300
         except Exception:  # noqa: BLE001 - best-effort side channel
             pass
@@ -159,10 +165,10 @@ def _bot_post(path: str, json_body: dict) -> httpx.Response | None:
     """POST to the bot REST API with one 429 retry. None on a transport error."""
     headers = {"Authorization": f"Bot {BOT_TOKEN}"}
     try:
-        resp = httpx.post(f"{_API}{path}", json=json_body, headers=headers, timeout=_TIMEOUT)
+        resp = _client.post(f"{_API}{path}", json=json_body, headers=headers, timeout=_TIMEOUT)
         if resp.status_code == 429:
             time.sleep(_retry_after(resp))
-            resp = httpx.post(f"{_API}{path}", json=json_body, headers=headers, timeout=_TIMEOUT)
+            resp = _client.post(f"{_API}{path}", json=json_body, headers=headers, timeout=_TIMEOUT)
         return resp
     except Exception:  # noqa: BLE001 - best-effort side channel
         return None
diff --git a/notifications/notify.py b/notifications/notify.py
index d7c82d9..a26702f 100644
--- a/notifications/notify.py
+++ b/notifications/notify.py
@@ -23,6 +23,7 @@ A forecast-fetch failure just skips the cell, so a pass never dies on a rate lim
 """
 import concurrent.futures
 import datetime
+import logging
 import os
 import threading
 import time
@@ -42,6 +43,8 @@ from notifications import push
 from accounts.db import sync_session_maker
 from accounts.models import AccessToken, Notification, PushSubscription, Subscription, User
 
+log = logging.getLogger("thermograph.notify")
+
 _BASE = os.environ.get("THERMOGRAPH_BASE", "/thermograph").strip("/")
 BASE = f"/{_BASE}" if _BASE else ""
 
@@ -57,6 +60,14 @@ FORECAST_HORIZON_DAYS = 7
 # — the rest are picked up on later passes.
 MAX_ARCHIVE_FETCHES_PER_PASS = int(os.environ.get("THERMOGRAPH_NOTIFY_ARCHIVE_FETCHES", "4"))
 
+# Soft wall-clock budget for one whole pass, same discipline as the archive-fetch
+# cap above: checked between cells (never mid-cell) so one pathological pass — a
+# slow upstream, a DB hiccup, hundreds of cells each doing real work — can't run
+# unbounded and push the next pass's wake past its own interval. 2x INTERVAL by
+# default: generous enough that an ordinarily-slow pass still finishes, but a
+# genuinely runaway one still yields before it would overlap the next wake.
+PASS_DEADLINE_SECONDS = int(os.environ.get("THERMOGRAPH_NOTIFY_PASS_DEADLINE", str(INTERVAL * 2)))
+
 # Metrics whose low tail also counts as unusual when a subscription is two-sided
 # (cold snaps, unusually calm/dry). Precipitation is one-directional (high only).
 TWO_SIDED_METRICS = set(grading.TEMP_METRICS)
@@ -171,19 +182,40 @@ def _send_discord_job(job: tuple[str, str, str, str]) -> None:
 # hundreds of subscribers no longer stretches a pass out send-by-send.
 SEND_WORKERS = int(os.environ.get("THERMOGRAPH_NOTIFY_SEND_WORKERS", "8"))
 
+# Belt-and-suspenders on top of push.py's own send timeout: f.result() below has
+# no timeout by default and would otherwise wait forever for a future that never
+# resolves, which — same as an untimed webpush() call — wedges the notifier for
+# the process's life under the singleton flock. Generous on purpose; this only
+# needs to fire if a per-send timeout was somehow bypassed, not to race it.
+SEND_RESULT_TIMEOUT = int(os.environ.get("THERMOGRAPH_NOTIFY_SEND_RESULT_TIMEOUT", "60"))
+
 
 def _flush_sends(push_jobs, discord_jobs) -> list[int]:
     """Deliver every gathered push/Discord job concurrently. Returns the
     push-subscription row ids the push service reported gone, for the caller
-    to prune. Blocks until every job has finished (or errored) — a pass still
-    waits for delivery to complete, it just no longer does so serially."""
+    to prune. Blocks until every job has finished or errored, and gives up
+    waiting on (but does not lose track of) any single job past
+    SEND_RESULT_TIMEOUT — a pass still waits for delivery to complete, it just
+    no longer does so serially, and no misbehaving future can hang the result
+    loop past a bounded wait."""
     with concurrent.futures.ThreadPoolExecutor(max_workers=SEND_WORKERS) as pool:
         futures = [pool.submit(_send_push_job, job) for job in push_jobs]
         futures += [pool.submit(_send_discord_job, job) for job in discord_jobs]
         gone = []
         for f in futures:
             try:
-                result = f.result()
+                result = f.result(timeout=SEND_RESULT_TIMEOUT)
+            except concurrent.futures.TimeoutError:
+                # f.result() gave up waiting, but the worker thread itself can't be
+                # killed — ThreadPoolExecutor.__exit__ still calls shutdown(wait=True),
+                # so the pool as a whole won't return until that thread actually
+                # finishes. The real backstop is the per-call socket timeouts this
+                # commit adds (push.py's _SEND_TIMEOUT, discord.py's _TIMEOUT): they
+                # bound how long a "stuck" send can truly run. This catch just stops
+                # THIS result from being reported/counted as gone, and keeps checking
+                # the remaining futures instead of getting stuck on one.
+                log.warning("push/Discord send exceeded %ss timeout; treating as failed", SEND_RESULT_TIMEOUT)
+                continue
             except Exception:  # noqa: BLE001 - one bad send must not lose the rest
                 continue
             if result is not None:
@@ -370,7 +402,18 @@ def run_pass() -> int:
         by_cell: dict[str, list] = {}
         for sub in subs:
             by_cell.setdefault(sub.cell_id, []).append(sub)
-        for cell_id, cell_subs in by_cell.items():
+        cells_skipped = 0
+        for i, (cell_id, cell_subs) in enumerate(by_cell.items()):
+            # Checked BETWEEN cells, not inside _process_cell — a soft budget, not
+            # a hard per-item timeout. Once tripped, every remaining cell this pass
+            # is skipped outright (not attempted-and-abandoned mid-flight) so a
+            # skipped cell's subscriptions are simply picked up whole on the next
+            # pass, same as a rate-limited one already is.
+            if time.perf_counter() - t0 > PASS_DEADLINE_SECONDS:
+                cells_skipped = len(by_cell) - i
+                log.warning("notifier pass exceeded %ss deadline; skipping %d/%d remaining cell(s)",
+                           PASS_DEADLINE_SECONDS, cells_skipped, len(by_cell))
+                break
             try:
                 created += _process_cell(session, cell_id, cell_subs, today, now, archive_budget)
             except Exception:  # noqa: BLE001 - one bad cell must not abort the pass
@@ -382,6 +425,7 @@ def run_pass() -> int:
     audit.log_activity("notify.pass", {
         "subs_evaluated": len(subs), "cells": len(by_cell), "created": created,
         "archives_fetched": MAX_ARCHIVE_FETCHES_PER_PASS - archive_budget[0],
+        "cells_skipped_deadline": cells_skipped,
         "duration_ms": round((time.perf_counter() - t0) * 1000.0, 1)})
     return created
 
diff --git a/notifications/push.py b/notifications/push.py
index 0c40a51..594607f 100644
--- a/notifications/push.py
+++ b/notifications/push.py
@@ -39,6 +39,15 @@ _VAPID_PATH = os.environ.get("THERMOGRAPH_VAPID_FILE") or os.path.join(_DATA_DIR
 # The VAPID "sub" claim — a contact the push service can reach about our traffic.
 _CONTACT = os.environ.get("THERMOGRAPH_VAPID_CONTACT", "mailto:admin@thermograph.app")
 
+# pywebpush 2.0.0 forwards `timeout` straight to requests.post with no default of
+# its own — omit the kwarg here and the send blocks with NO timeout at all (the
+# "10s default" people expect only applies if requests itself is called bare).
+# One hung push endpoint must never wedge the notifier: the singleton flock
+# (core/singleton.py) is held for the process's whole life, so no other worker
+# can take over while this thread is stuck, and /healthz keeps reporting green
+# on a notifier that's actually frozen.
+_SEND_TIMEOUT = 15
+
 _lock = threading.Lock()
 _keys = None  # cached {"private_key": str, "public_key": str} (base64url-raw)
 
@@ -60,6 +69,59 @@ def _generate() -> dict:
     return {"private_key": _b64url(scalar), "public_key": _b64url(raw_pub)}
 
 
+def _claim_file(data: dict) -> dict:
+    """Persist a freshly generated keypair as `_VAPID_PATH`'s content, atomic
+    first-writer-wins. `_lock` only keeps this process's own threads from racing
+    each other — on a cold /state volume every uvicorn *worker* (a separate
+    process) hits the missing-file branch at boot together, and without this each
+    would generate its OWN keypair and cache it in-process, silently diverging
+    from the file and from each other (a subscription signed against one worker's
+    public key fails to verify under another's private key — the exact incident
+    class deploy/entrypoint.sh's comments name).
+
+    Write the full keypair to a private temp file first, then claim the real path
+    with a hard link: `os.link` is atomic and the loser gets EEXIST immediately,
+    with no window where `_VAPID_PATH` exists but is only half-written (unlike
+    O_CREAT|O_EXCL directly on the destination followed by a separate write). A
+    loser discards its own generation and reads back the winner's file instead,
+    so every process ends up caching the SAME keys the file actually holds."""
+    tmp_path = f"{_VAPID_PATH}.{os.getpid()}.tmp"
+    try:
+        os.makedirs(_DATA_DIR, exist_ok=True)
+        with open(tmp_path, "w", encoding="utf-8") as f:
+            json.dump(data, f)
+        os.chmod(tmp_path, 0o600)
+    except OSError:
+        log.warning("could not persist VAPID keys to %s; using an in-memory pair", _VAPID_PATH)
+        return data
+    try:
+        try:
+            os.link(tmp_path, _VAPID_PATH)
+            return data
+        except FileExistsError:
+            # Lost the race — someone else's file is now the truth. Read IT back
+            # rather than keep our own now-orphaned generation.
+            try:
+                with open(_VAPID_PATH, encoding="utf-8") as f:
+                    winner = json.load(f)
+                if winner.get("private_key") and winner.get("public_key"):
+                    return winner
+            except (OSError, ValueError):
+                pass
+            # Winner's file was unreadable/corrupt (very rare) — fall back to our
+            # own in-memory generation rather than crash; the next _load() call
+            # (a new process, or after the file heals) retries the file.
+            return data
+        except OSError:
+            log.warning("could not persist VAPID keys to %s; using an in-memory pair", _VAPID_PATH)
+            return data
+    finally:
+        try:
+            os.unlink(tmp_path)
+        except OSError:
+            pass
+
+
 def _load() -> dict:
     """Resolve the keypair once (env → file → generate) and cache it."""
     global _keys
@@ -81,14 +143,10 @@ def _load() -> dict:
                 return _keys
         except (OSError, ValueError):
             pass
-        _keys = _generate()
-        try:
-            os.makedirs(_DATA_DIR, exist_ok=True)
-            with open(_VAPID_PATH, "w", encoding="utf-8") as f:
-                json.dump(_keys, f)
-            os.chmod(_VAPID_PATH, 0o600)
-        except OSError:
-            log.warning("could not persist VAPID keys to %s; using an in-memory pair", _VAPID_PATH)
+        # Cache whatever _claim_file settles on — our own generation if we won
+        # the race to create the file, or the winner's keys read back from disk
+        # if we lost it. Either way this process's cache matches the file.
+        _keys = _claim_file(_generate())
         return _keys
 
 
@@ -111,6 +169,7 @@ def send(subscription_info: dict, payload: dict) -> str:
             vapid_private_key=keys["private_key"],
             vapid_claims={"sub": _CONTACT},
             ttl=86400,
+            timeout=_SEND_TIMEOUT,
         )
         return "ok"
     except WebPushException as e:
diff --git a/tests/notifications/test_discord.py b/tests/notifications/test_discord.py
index f62763e..64a50a6 100644
--- a/tests/notifications/test_discord.py
+++ b/tests/notifications/test_discord.py
@@ -1,5 +1,5 @@
 """Discord daily-feed post: embed shape, webhook delivery, and the once-a-day guard.
-No network — httpx.post is stubbed, like the IndexNow tests."""
+No network — the shared client's .post is stubbed, like the IndexNow tests."""
 import datetime
 import time
 
@@ -63,7 +63,7 @@ def test_build_embed_rejects_empty_feed():
 def test_post_disabled_without_webhook(monkeypatch):
     monkeypatch.setattr(discord, "WEBHOOK_URL", "")
     posted = []
-    monkeypatch.setattr(discord.httpx, "post", lambda *a, **k: posted.append(a) or None)
+    monkeypatch.setattr(discord._client, "post", lambda *a, **k: posted.append(a) or None)
     assert discord.post_daily_feed(_feed([_CARD_HOT])) is False
     assert posted == []   # never touched the network
 
@@ -75,7 +75,7 @@ class _Resp:
 def test_post_sends_embed_to_the_webhook(monkeypatch):
     monkeypatch.setattr(discord, "WEBHOOK_URL", "https://discord.test/webhook/abc")
     calls = []
-    monkeypatch.setattr(discord.httpx, "post",
+    monkeypatch.setattr(discord._client, "post",
                         lambda url, json=None, **k: (calls.append((url, json)), _Resp(204))[1])
     assert discord.post_daily_feed(_feed([_CARD_HOT])) is True
     (url, payload), = calls
@@ -91,7 +91,7 @@ def test_post_also_broadcasts_to_weather_channel(monkeypatch):
     monkeypatch.setattr(discord, "BOT_TOKEN", "bot-abc")
     monkeypatch.setattr(discord, "WEATHER_CHANNEL_ID", "chan-weather")
     calls = []
-    monkeypatch.setattr(discord.httpx, "post",
+    monkeypatch.setattr(discord._client, "post",
                         lambda url, json=None, **k: (calls.append((url, json)), _Resp(204))[1])
     assert discord.post_daily_feed(_feed([_CARD_HOT])) is True
     (url, body), = calls
@@ -104,14 +104,14 @@ def test_post_is_best_effort_on_http_error(monkeypatch):
 
     def _boom(*a, **k):
         raise RuntimeError("network down")
-    monkeypatch.setattr(discord.httpx, "post", _boom)
+    monkeypatch.setattr(discord._client, "post", _boom)
     # Never raises; just reports failure.
     assert discord.post_daily_feed(_feed([_CARD_HOT])) is False
 
 
 def test_post_skips_stale_or_empty_feed(monkeypatch):
     monkeypatch.setattr(discord, "WEBHOOK_URL", "https://discord.test/webhook/abc")
-    monkeypatch.setattr(discord.httpx, "post", lambda *a, **k: _Resp(204))
+    monkeypatch.setattr(discord._client, "post", lambda *a, **k: _Resp(204))
     # Yesterday's feed is stale -> no post.
     yesterday = (datetime.date.today() - datetime.timedelta(days=1)).isoformat()
     assert discord.post_daily_feed(_feed([_CARD_HOT], date=yesterday)) is False
diff --git a/tests/notifications/test_discord_dm.py b/tests/notifications/test_discord_dm.py
index 1e1b34e..aa9cc56 100644
--- a/tests/notifications/test_discord_dm.py
+++ b/tests/notifications/test_discord_dm.py
@@ -28,7 +28,7 @@ class _Resp:
 
 
 def _mock_posts(monkeypatch, script):
-    """Route discord.httpx.post by URL; `script` maps a URL substring -> _Resp."""
+    """Route discord._client.post by URL; `script` maps a URL substring -> _Resp."""
     calls = []
 
     def _post(url, json=None, headers=None, timeout=None):
@@ -37,7 +37,7 @@ def _mock_posts(monkeypatch, script):
             if frag in url:
                 return resp
         return _Resp(404)
-    monkeypatch.setattr(discord.httpx, "post", _post)
+    monkeypatch.setattr(discord._client, "post", _post)
     return calls
 
 
@@ -97,7 +97,7 @@ def test_bot_post_retries_once_on_429(monkeypatch):
     monkeypatch.setattr(discord, "BOT_TOKEN", "bot-abc")
     monkeypatch.setattr(discord.time, "sleep", lambda s: None)     # don't actually wait
     seq = iter([_Resp(429, {"retry_after": 0.01}), _Resp(200, {"id": "c"})])
-    monkeypatch.setattr(discord.httpx, "post", lambda *a, **k: next(seq))
+    monkeypatch.setattr(discord._client, "post", lambda *a, **k: next(seq))
     resp = discord._bot_post("/users/@me/channels", {"recipient_id": "d"})
     assert resp.status_code == 200        # the retry succeeded
 
diff --git a/tests/notifications/test_notify.py b/tests/notifications/test_notify.py
index 8c22038..74399f1 100644
--- a/tests/notifications/test_notify.py
+++ b/tests/notifications/test_notify.py
@@ -2,12 +2,14 @@
 wording (pure logic), plus an integration check that a full pass fetches a MISSING
 archive once but never re-fetches a cached one (against conftest's throwaway DB)."""
 import datetime
+import time
 import types
 import uuid
 
 import numpy as np
 import polars as pl
 
+from core import audit
 from data import climate
 from accounts import db
 from notifications import notify
@@ -211,3 +213,72 @@ def test_inapp_notification_survives_push_error(monkeypatch):
 
     assert len(_user_notifications(uid)) == 1        # the in-app write is unaffected
     assert _push_count() == 1                         # a mere error doesn't prune
+
+
+# --- send-result timeout: one hung future must not wedge the pass -----------
+def test_flush_sends_treats_timeout_as_a_failed_send(monkeypatch):
+    monkeypatch.setattr(notify, "SEND_RESULT_TIMEOUT", 0.05)
+
+    def _hang(job):
+        time.sleep(0.3)   # longer than the timeout above
+        return None
+    monkeypatch.setattr(notify, "_send_push_job", _hang)
+
+    # Must not raise, and a timed-out send is never reported as a "gone"
+    # endpoint to prune (it never actually got a definitive answer).
+    gone = notify._flush_sends([object()], [])
+    assert gone == []
+
+
+def test_flush_sends_still_returns_gone_ids_within_the_timeout(monkeypatch):
+    monkeypatch.setattr(notify, "SEND_RESULT_TIMEOUT", 5)
+    monkeypatch.setattr(notify, "_send_push_job", lambda job: job)   # echoes the id straight back
+    gone = notify._flush_sends([7, 8], [])
+    assert sorted(gone) == [7, 8]
+
+
+# --- pass wall-clock deadline: one pathological pass can't run unbounded ----
+def _seed_two_cell_subscriptions():
+    db.Base.metadata.create_all(db.sync_engine)
+    with db.sync_session_maker() as s:
+        s.execute(delete(User))
+        s.commit()
+        uid1, uid2 = uuid.uuid4(), uuid.uuid4()
+        s.add(User(id=uid1, email="deadline1@example.com", hashed_password="x", is_active=True))
+        s.add(User(id=uid2, email="deadline2@example.com", hashed_password="x", is_active=True))
+        s.commit()
+        s.add(Subscription(user_id=uid1, cell_id="500_600", label="A", lat=1.0, lon=2.0,
+                           threshold=95, metrics=["tmax"], kind="observed", two_sided=False))
+        s.add(Subscription(user_id=uid2, cell_id="700_800", label="B", lat=3.0, lon=4.0,
+                           threshold=95, metrics=["tmax"], kind="observed", two_sided=False))
+        s.commit()
+    return uid1, uid2
+
+
+def test_run_pass_stops_at_wall_clock_deadline(monkeypatch):
+    uid1, uid2 = _seed_two_cell_subscriptions()
+    _cached_extreme(monkeypatch)   # every cell would otherwise trigger a notification
+    monkeypatch.setattr(notify, "PASS_DEADLINE_SECONDS", 0)   # trips before the first cell
+
+    logged = []
+    monkeypatch.setattr(audit, "log_activity",
+                        lambda kind, data: logged.append((kind, data)))
+
+    notify.run_pass()
+
+    # A deadline of 0 must skip every cell rather than process any of them.
+    assert _user_notifications(uid1) == []
+    assert _user_notifications(uid2) == []
+    pass_log = next(data for kind, data in logged if kind == "notify.pass")
+    assert pass_log["cells_skipped_deadline"] == 2
+
+
+def test_run_pass_processes_normally_within_the_deadline(monkeypatch):
+    uid1, uid2 = _seed_two_cell_subscriptions()
+    _cached_extreme(monkeypatch)
+    monkeypatch.setattr(notify, "PASS_DEADLINE_SECONDS", 300)   # generous — shouldn't trip
+
+    notify.run_pass()
+
+    assert len(_user_notifications(uid1)) == 1
+    assert len(_user_notifications(uid2)) == 1
diff --git a/tests/notifications/test_push.py b/tests/notifications/test_push.py
new file mode 100644
index 0000000..422583f
--- /dev/null
+++ b/tests/notifications/test_push.py
@@ -0,0 +1,96 @@
+"""VAPID key resolution: the atomic first-writer-wins claim of the keypair file
+(push.py's `_claim_file`), and that `_load()` caches whatever that settles on
+rather than its own local generation when it loses the race.
+
+No network — `send()`'s pywebpush call isn't exercised here (that's notify.py's
+`test_push_dispatched_on_new_notification` etc., which stub `push.send` itself)."""
+import json
+
+from notifications import push
+
+
+def _reset_state(monkeypatch, path):
+    monkeypatch.setattr(push, "_VAPID_PATH", str(path))
+    monkeypatch.setattr(push, "_DATA_DIR", str(path.parent))
+    monkeypatch.setattr(push, "_keys", None)
+    monkeypatch.delenv("THERMOGRAPH_VAPID_PRIVATE_KEY", raising=False)
+    monkeypatch.delenv("THERMOGRAPH_VAPID_PUBLIC_KEY", raising=False)
+
+
+def test_claim_file_first_writer_wins(monkeypatch, tmp_path):
+    path = tmp_path / "vapid.json"
+    _reset_state(monkeypatch, path)
+    data = {"private_key": "priv-a", "public_key": "pub-a"}
+
+    result = push._claim_file(data)
+
+    assert result == data
+    assert json.loads(path.read_text()) == data
+    # No leftover temp file.
+    assert list(tmp_path.iterdir()) == [path]
+
+
+def test_claim_file_reads_back_winner_on_race(monkeypatch, tmp_path):
+    """A process that loses the os.link() race must discard its own freshly
+    generated keypair and use whatever the winner actually persisted."""
+    path = tmp_path / "vapid.json"
+    _reset_state(monkeypatch, path)
+    winner = {"private_key": "priv-winner", "public_key": "pub-winner"}
+    path.write_text(json.dumps(winner))   # simulates another process winning first
+    loser = {"private_key": "priv-loser", "public_key": "pub-loser"}
+
+    result = push._claim_file(loser)
+
+    assert result == winner
+    assert json.loads(path.read_text()) == winner   # the loser never touched the file
+
+
+def test_load_caches_winner_keys_not_its_own_generation(monkeypatch, tmp_path):
+    """End-to-end through _load(): on a cold /state volume, a worker that hits the
+    generate branch but loses the write race must end up with the SAME in-process
+    cached keys the file actually holds — not the keys it generated locally,
+    which would silently diverge from every other worker (a subscription signed
+    against one worker's public key then fails to verify under another's
+    private key)."""
+    path = tmp_path / "vapid.json"
+    _reset_state(monkeypatch, path)
+    winner = {"private_key": "priv-winner", "public_key": "pub-winner"}
+
+    def _generate_and_lose_the_race():
+        # Between our cache-miss file read and our own _claim_file() call, a
+        # concurrent worker wins and writes the real file first.
+        path.write_text(json.dumps(winner))
+        return {"private_key": "priv-mine", "public_key": "pub-mine"}
+
+    monkeypatch.setattr(push, "_generate", _generate_and_lose_the_race)
+
+    result = push._load()
+
+    assert result == winner
+    assert push._keys == winner            # the process-wide cache matches the file
+    assert push.public_key() == "pub-winner"
+
+
+def test_load_reads_existing_file_without_generating(monkeypatch, tmp_path):
+    path = tmp_path / "vapid.json"
+    _reset_state(monkeypatch, path)
+    existing = {"private_key": "priv-x", "public_key": "pub-x"}
+    path.write_text(json.dumps(existing))
+
+    def boom():
+        raise AssertionError("must not generate when a valid file already exists")
+    monkeypatch.setattr(push, "_generate", boom)
+
+    assert push._load() == existing
+
+
+def test_load_prefers_env_over_file(monkeypatch, tmp_path):
+    path = tmp_path / "vapid.json"
+    _reset_state(monkeypatch, path)
+    path.write_text(json.dumps({"private_key": "priv-file", "public_key": "pub-file"}))
+    monkeypatch.setenv("THERMOGRAPH_VAPID_PRIVATE_KEY", " priv-env ")
+    monkeypatch.setenv("THERMOGRAPH_VAPID_PUBLIC_KEY", " pub-env ")
+
+    result = push._load()
+
+    assert result == {"private_key": "priv-env", "public_key": "pub-env"}
diff --git a/tests/test_indexnow.py b/tests/test_indexnow.py
index d8a7c42..9045ad1 100644
--- a/tests/test_indexnow.py
+++ b/tests/test_indexnow.py
@@ -69,7 +69,7 @@ def test_indexnow_submit_all_builds_payload(monkeypatch):
         status_code = 200
         text = "ok"
 
-    monkeypatch.setattr(indexnow.httpx, "post",
+    monkeypatch.setattr(indexnow._client, "post",
                         lambda url, json=None, **kw: (calls.append((url, json)), _Resp())[1])
     res = indexnow.submit_all("https://thermograph.org")
     assert res["submitted"] == res["total"] > 100
@@ -87,3 +87,53 @@ def test_indexnow_if_changed_state(monkeypatch, tmp_path):
     assert indexnow._read_state() == ""                         # first deploy → would submit
     indexnow._write_state(sig)
     assert indexnow._read_state() == sig                        # unchanged → deploy would skip
+
+
+# --- key() race: atomic first-writer-wins on a cold /state volume -----------
+# Same race, same fix as push.py's VAPID keypair (see tests/notifications/
+# test_push.py) — several workers can hit the missing-key-file branch at once;
+# only one may actually create the file, everyone else must read IT back.
+
+def _reset_key_state(monkeypatch, path):
+    monkeypatch.setattr(indexnow, "_KEY_PATH", str(path))
+    monkeypatch.setattr(indexnow, "_DATA_DIR", str(path.parent))
+    monkeypatch.setattr(indexnow, "_key", None)
+    monkeypatch.delenv("THERMOGRAPH_INDEXNOW_KEY", raising=False)
+
+
+def test_claim_file_first_writer_wins(monkeypatch, tmp_path):
+    path = tmp_path / "indexnow_key.txt"
+    _reset_key_state(monkeypatch, path)
+
+    result = indexnow._claim_file("key-a")
+
+    assert result == "key-a"
+    assert path.read_text() == "key-a"
+    assert list(tmp_path.iterdir()) == [path]   # no leftover temp file
+
+
+def test_claim_file_reads_back_winner_on_race(monkeypatch, tmp_path):
+    path = tmp_path / "indexnow_key.txt"
+    _reset_key_state(monkeypatch, path)
+    path.write_text("key-winner")   # simulates another process winning first
+
+    result = indexnow._claim_file("key-loser")
+
+    assert result == "key-winner"
+    assert path.read_text() == "key-winner"   # the loser never touched the file
+
+
+def test_key_caches_winner_not_its_own_generation(monkeypatch, tmp_path):
+    path = tmp_path / "indexnow_key.txt"
+    _reset_key_state(monkeypatch, path)
+
+    def _lose_the_race(*a, **k):
+        path.write_text("key-winner")
+        return "a" * 32   # what secrets.token_hex(16) would have produced locally
+
+    monkeypatch.setattr(indexnow.secrets, "token_hex", _lose_the_race)
+
+    result = indexnow.key()
+
+    assert result == "key-winner"
+    assert indexnow._key == "key-winner"   # the process-wide cache matches the file