diff --git a/.env.example b/.env.example
new file mode 100644
index 0000000..59d5171
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,68 @@
+# Bolt Assistant settings.
+#
+# Copy this file to .env and fill in the three required values:
+#
+#     cp .env.example .env          (bash)      copy .env.example .env    (cmd/PowerShell)
+#
+# Lines that carry a value below are working defaults; remove the leading #
+# only to change one. Blank means "not set".
+
+# ── server ───────────────────────────────────────────────────────────────────
+# Where your Bolt server's desk API listens (port 5002 in the default setup).
+BOLT_SERVER_URL=
+# A desk API key for this device (ask Bolt to "create an api key for Bolt
+# Assistant" — it arrives as a file through the heartbeat).
+DESK_API_KEY=
+# Its own conversation on the server. Defaults to pet-assistant-<computer>;
+# the "pet-" prefix gives it voice-client behaviour (short, speakable replies).
+# DESK_SESSION_ID=
+# The ElevenLabs voice the server's /desk/tts speaks in (a voice id).
+ELEVENLABS_VOICE_ID=
+# TTS_SAMPLE_RATE=16000
+# STREAMING_REPLIES=true           # speak sentences as they form; false waits for the whole reply
+
+# ── audio devices ────────────────────────────────────────────────────────────
+# Blank = the system default; a number = the device index; anything else is a
+# name substring (sounddevice's rules). `run.bat --devices` lists them.
+# MIC_DEVICE=
+# SPEAKER_DEVICE=
+
+# ── wake phrases ─────────────────────────────────────────────────────────────
+# With REQUIRE_WAKE_WORD off (the default) the open mic itself is the
+# activation: anything that sounds like speech is sent and answered. Set it to
+# true to need a phrase first ("Hey Bolt", "Thunderbolt", "Hey Assistant"...).
+# REQUIRE_WAKE_WORD=false
+# WAKE_WORDS=hey bolt,bolt,thunderbolt,hey thunderbolt,ok bolt,okay bolt,yo bolt,hi bolt,hey assistant,ok assistant,okay assistant,hey bolts,hey volt,hey bold,hey boat,okay volt,hey thunder bolt,thunder bolt
+# These count anywhere in what was said ("what's the weather, assistant?").
+# ANYWHERE_WAKE_WORDS=assistant
+
+# ── listening (local voice-activity detection) ───────────────────────────────
+# Nothing leaves the machine until the detector hears speech. Raise
+# VAD_RMS_THRESHOLD if background noise keeps getting transcribed; lower it if
+# you have to shout.
+# VAD_RMS_THRESHOLD=500
+# VAD_START_FRAMES=3               # loud 80 ms frames in a row before speech starts
+# VAD_SILENCE_END_SEC=0.8          # quiet seconds that end an utterance
+# MIN_UTTERANCE_SEC=0.35           # shorter bursts are never sent
+# MAX_UTTERANCE_SEC=12             # the longest utterance sent
+# COMMAND_WAIT_SEC=8               # after a bare "Hey Bolt", how long for the request
+# FOLLOW_UP_SEC=8                  # when the reply ends on a question, keep listening
+# FOLLOW_UP_MAX_TURNS=5
+# CHIMES=true
+
+# ── what Bolt may do on this machine ─────────────────────────────────────────
+# There's no screen to approve things on, so ASSISTANT_COMMANDS decides:
+#   off   nothing runs
+#   read  (default) filectl list/read only
+#   all   everything, shell commands and file writes included, like Bolt-Pet
+ASSISTANT_COMMANDS=read
+# COMMAND_TIMEOUT_SECONDS=60
+
+# ── heartbeat: reminders and delivered files ─────────────────────────────────
+# Every HEARTBEAT_SECONDS the assistant reports in to the server — the channel
+# Bolt's reminders and any files he delivers to this client arrive on.
+# Announcements are spoken when the mic is idle, and files land in
+# BOLT_DOWNLOAD_DIR (default ~/Downloads/Bolt) without overwriting what is
+# already there. Set to 0 to turn the heartbeat off.
+HEARTBEAT_SECONDS=60
+# BOLT_DOWNLOAD_DIR=
diff --git a/.gitignore b/.gitignore
index f6664e3..50ec8e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ __pycache__/
 *.pyc
 .env
 .pytest_cache/
+.claude/
diff --git a/README.md b/README.md
index c190498..048101d 100644
--- a/README.md
+++ b/README.md
@@ -45,6 +45,11 @@ other than the system default. `run.bat --type` lets you type instead of speak,
    without needing the wake phrase again.
 4. **While Bolt speaks, the mic is ignored**, so his own voice through the speakers (which often
    says "Bolt") can't wake him.
+5. **Reminders and delivered files ride a heartbeat.** Every `HEARTBEAT_SECONDS` (default 60) the
+   assistant reports in to `/desk/report_status`, which is how Bolt's reminders and any files he
+   sends to this client arrive — the same channel Bolt-Pet uses. Announcements are spoken when the
+   mic is idle, and files download to `BOLT_DOWNLOAD_DIR` (default `~/Downloads/Bolt`), never
+   overwriting what's already there. Set `HEARTBEAT_SECONDS=0` to turn it off.
 
 ## Cost and privacy
 
@@ -85,6 +90,9 @@ See `.env.example`. The ones you're most likely to change:
   (default `assistant`: "what's the weather, assistant?"). Blank to turn off.
 - `COMMAND_WAIT_SEC`, `FOLLOW_UP_SEC`: how long it waits after "Hey Bolt", or after asking you
   something.
+- `HEARTBEAT_SECONDS`: how often it checks in for reminders and delivered files (default 60;
+  `0` turns the heartbeat off).
+- `BOLT_DOWNLOAD_DIR`: where delivered files land (default `~/Downloads/Bolt`).
 
 It has its own conversation on the server (`pet-assistant-<computer>`), which shows up in Bolt
 Console's Chats list.
diff --git a/bolt_assistant/__main__.py b/bolt_assistant/__main__.py
index 41290c6..ba77254 100644
--- a/bolt_assistant/__main__.py
+++ b/bolt_assistant/__main__.py
@@ -99,6 +99,25 @@ def main(argv=None) -> int:
             return 0
 
     stop = threading.Event()
+    from . import heartbeat
+
+    heartbeat.fetch_server_health()
+
+    def _on_heartbeat(result: dict) -> None:
+        # What the server hands out is popped the moment it is handed over, so
+        # everything goes into the spoken queue — announced when the mic is idle.
+        if result.get("announcement"):
+            assistant.announce(result["announcement"])
+        saved = result.get("saved") or []
+        if saved:
+            names = ", ".join(path.name for path in saved)
+            folder = str(saved[0].parent)
+            assistant.announce(
+                f"Saved {names} to {folder}."
+                if len(saved) <= 3 else f"Saved {len(saved)} files to {folder}.")
+
+    threading.Thread(target=heartbeat.heartbeat_loop, args=(stop, _on_heartbeat),
+                     name="bolt-heartbeat", daemon=True).start()
     try:
         mic = audio.open_mic(assistant.on_mic_frame)
     except Exception as exc:
diff --git a/bolt_assistant/assistant.py b/bolt_assistant/assistant.py
index 09f0a05..49f8293 100644
--- a/bolt_assistant/assistant.py
+++ b/bolt_assistant/assistant.py
@@ -20,6 +20,10 @@ background thread, so the mic keeps being segmented meanwhile and whatever
 is said next becomes its own utterance and is sent off too. Finished
 transcripts are delivered oldest-first between mic frames.
 
+Announcements (Bolt's reminders, delivered-file notices) ride the heartbeat
+thread and wait in a queue; the run loop speaks them one at a time whenever
+it is idle, then flushes the echo of Bolt's own voice like after a reply.
+
 Everything that touches hardware or the network is injected, so the flow
 is tested with fakes; __main__ wires in the real mic, server and speaker.
 """
@@ -115,6 +119,7 @@ class Assistant:
         self._mute_until = 0.0
         self._voice = ""  # a voice the server picked (speak_as) sticks for later replies
         self._tts_failed = False
+        self._announcements: "queue.Queue[str]" = queue.Queue()  # heartbeat notices, spoken when idle
 
     # ── audio in ─────────────────────────────────────────────────────────
 
@@ -135,6 +140,7 @@ class Assistant:
             else:
                 self.process(frame)
             self.handle_transcripts()
+            self._drain_announcements()
 
     def listening_banner(self) -> str:
         if not self.wake_required:
@@ -208,6 +214,29 @@ class Assistant:
                 self.log("  (stopped waiting)")
             self.state = "idle"
 
+    # ── heartbeat announcements ──────────────────────────────────────────
+
+    def announce(self, text: str) -> None:
+        """Queue something to say once the room is free — a reminder Bolt
+        fired, a delivered-file notice. Never interrupts: it waits for idle."""
+        text = (text or "").strip()
+        if text:
+            self._announcements.put(text)
+
+    def _drain_announcements(self) -> None:
+        """Say what the heartbeat brought, one at a time, while idle — never
+        mid-sentence, while a transcript is still in flight, or during the
+        echo guard after Bolt's own voice."""
+        if (self.state != "idle" or self._pending or self.segmenter.in_speech
+                or self.clock() < self._mute_until):
+            return
+        try:
+            text = self._announcements.get_nowait()
+        except queue.Empty:
+            return
+        self.speak(text)
+        self._back_to_listening("idle")  # flush the mic's echo of Bolt's own voice
+
     # ── what was said ────────────────────────────────────────────────────
 
     def heard(self, text: str) -> None:
diff --git a/bolt_assistant/config.py b/bolt_assistant/config.py
index 6eba79c..90938b6 100644
--- a/bolt_assistant/config.py
+++ b/bolt_assistant/config.py
@@ -50,6 +50,17 @@ VOICE_ID = os.environ.get("ELEVENLABS_VOICE_ID", "")
 TTS_SAMPLE_RATE = int(os.environ.get("TTS_SAMPLE_RATE", "16000"))
 STREAMING_REPLIES = _flag("STREAMING_REPLIES", "true")
 
+# ── heartbeat: reminders and delivered files ─────────────────────────────────
+# Every HEARTBEAT_SECONDS the assistant reports in to /desk/report_status —
+# the channel Bolt's reminders and any files he delivers to this client
+# arrive on. Announcements are spoken when the mic is idle (see
+# assistant.announce), and files download to DOWNLOAD_DIR without
+# overwriting what is already there. Set HEARTBEAT_SECONDS to 0 to turn the
+# heartbeat off entirely.
+HEARTBEAT_SECONDS = max(0, int(os.environ.get("HEARTBEAT_SECONDS", "60")))
+DOWNLOAD_DIR = Path(os.environ.get("BOLT_DOWNLOAD_DIR", "").strip()
+                    or str(Path.home() / "Downloads" / "Bolt"))
+
 # ── audio devices ───────────────────────────────────────────────────────────
 
 MIC_DEVICE = _device(os.environ.get("MIC_DEVICE", ""))
diff --git a/bolt_assistant/heartbeat.py b/bolt_assistant/heartbeat.py
new file mode 100644
index 0000000..fea6356
--- /dev/null
+++ b/bolt_assistant/heartbeat.py
@@ -0,0 +1,193 @@
+"""The heartbeat that brings Bolt's reminders and delivered files in.
+
+Same protocol as Bolt-Pet's heartbeat (desk_client/bolt_desk.py):
+
+    POST /desk/report_status  {"session_id", "download_dir"}
+        -> {"ok": true} or {"reply": "<announcement to speak>"} (plus
+           "suggestions" when there are any)
+    GET  /desk/files?session_id=...     -> {"files": [{"id", "name", "size"}]}
+    GET  /desk/files/<id>?session_id=...-> the bytes; the server *dequeues*
+           on this GET, so write to a .part first and rename only once the
+           whole file is here, and never overwrite an existing file.
+
+A heartbeat thread is the only thing standing between a delivered file and
+this machine, so every failure is logged and swallowed: one bad beat must
+never stop the loop, and a refused key gets a loud warning once at startup
+instead of silent nothing-ever-arrives.
+
+Announcements returned by report_status are popped server-side the moment
+they are handed out, so the caller (__main__) feeds them to
+assistant.announce() rather than dropping them. Everything network-shaped
+is injectable for the tests.
+"""
+
+from __future__ import annotations
+
+import os
+import re
+import time
+from pathlib import Path
+from typing import Callable, List, Optional
+
+import requests
+
+from . import config
+from .server import _headers
+
+log: Callable[[str], None] = print
+
+
+def _url(path: str) -> str:
+    return f"{config.SERVER_URL}{path}"
+
+
+def _safe_filename(name: str) -> str:
+    """A server-sent name is a display hint, not a trusted path: strip path
+    separators, control characters and leading dots before it touches disk."""
+    cleaned = re.sub(r'[\\/:*?"<>|\x00-\x1f]', "_", str(name or "")).strip().strip(".")
+    return cleaned or "download"
+
+
+def _free_path(folder: Path, name: str) -> Path:
+    """A name that doesn't exist yet: the server never overwrites, and neither
+    do we. "note (2).txt" after "note.txt" and "note (1).txt", like a browser."""
+    target = folder / name
+    if not target.exists():
+        return target
+    stem, suffix = target.stem, target.suffix
+    for n in range(1, 1000):
+        candidate = folder / f"{stem} ({n}){suffix}"
+        if not candidate.exists():
+            return candidate
+    return folder / f"{stem} ({int(time.time())}){suffix}"
+
+
+def fetch_server_health(timeout: float = 10.0, get: Callable = requests.get) -> None:
+    """One keyed probe at startup. A refusal gets a loud warning — a dead
+    DESK_API_KEY means total silence (no answers, no files, no reminders)
+    with no other symptom."""
+    try:
+        response = get(_url("/desk/health"), headers=_headers(), timeout=timeout)
+        info = response.json()
+        log(f"server: {info}")
+        if info.get("key_ok") is False:
+            log("!! the server refused this device's DESK_API_KEY — no files, no reminders,")
+            log("!! and no answers will reach this assistant until it is updated")
+            log("!! set DESK_API_KEY in .env — it is re-read on the next request,")
+            log("!! so no restart is needed once the file is corrected")
+    except Exception as exc:
+        log(f"warning: server not reachable yet ({exc}) — will keep trying per-request")
+
+
+def _download(file_id: str, name: str, folder: Path,
+              get: Callable = requests.get) -> Optional[Path]:
+    """Fetch one queued file and save it. The server dequeues on this GET, so
+    write to a .part first and rename only once the bytes are all here."""
+    try:
+        response = get(
+            _url(f"/desk/files/{file_id}"),
+            params={"session_id": config.SESSION_ID}, headers=_headers(),
+            timeout=(10, 120), stream=True,
+        )
+        if response.status_code != 200:
+            log(f"file download refused ({response.status_code}) for {name}")
+            return None
+        folder.mkdir(parents=True, exist_ok=True)
+        target = _free_path(folder, _safe_filename(name))
+        part = target.with_name(target.name + ".part")
+        try:
+            with open(part, "wb") as handle:
+                for chunk in response.iter_content(65536):
+                    if chunk:
+                        handle.write(chunk)
+            os.replace(part, target)
+        except Exception:
+            try:
+                part.unlink()
+            except OSError:
+                pass
+            raise
+        return target
+    except Exception as exc:
+        log(f"file download failed for {name}: {exc}")
+        return None
+
+
+def _fetch_outbox(folder: Path, get: Callable = requests.get) -> List[Path]:
+    try:
+        response = get(
+            _url("/desk/files"),
+            params={"session_id": config.SESSION_ID}, headers=_headers(),
+            timeout=(5, 30),
+        )
+    except Exception as exc:
+        log(f"couldn't list queued files: {exc}")
+        return []
+    if response.status_code != 200:
+        return []
+    try:
+        body = response.json()
+    except ValueError:
+        return []
+    entries = body.get("files") if isinstance(body, dict) else None
+    saved: List[Path] = []
+    for entry in entries or []:
+        if not isinstance(entry, dict) or not entry.get("id"):
+            continue
+        target = _download(str(entry["id"]), str(entry.get("name") or "download"), folder, get)
+        if target is not None:
+            saved.append(target)
+    return saved
+
+
+def heartbeat_once(download_dir=None, post: Callable = requests.post,
+                   get: Callable = requests.get) -> dict:
+    """One beat: report in (reminders, files and presence all flow), then
+    collect whatever the server is holding for this device. Returns
+    {"ok", "announcement", "saved"} — *announcement* is something Bolt wants
+    spoken, *saved* the Paths just downloaded."""
+    folder = Path(download_dir) if download_dir is not None else config.DOWNLOAD_DIR
+    result: dict = {"ok": False, "announcement": "", "saved": []}
+    try:
+        folder.mkdir(parents=True, exist_ok=True)
+    except OSError as exc:
+        log(f"can't create the download folder {folder}: {exc}")
+    payload = {"session_id": config.SESSION_ID, "download_dir": str(folder)}
+    try:
+        response = post(_url("/desk/report_status"), json=payload,
+                        headers=_headers(), timeout=20)
+    except Exception as exc:
+        log(f"heartbeat failed: {exc}")
+        return result
+    if response.status_code != 200:
+        return result
+    try:
+        body = response.json()
+    except ValueError:
+        body = {}
+    announcement = body.get("reply") if isinstance(body, dict) else None
+    if isinstance(announcement, str) and announcement.strip():
+        result["announcement"] = " ".join(announcement.split())
+    result["saved"] = _fetch_outbox(folder, get)
+    if result["saved"]:
+        names = ", ".join(path.name for path in result["saved"])
+        log(f"saved {len(result['saved'])} file(s) to {folder}: {names}")
+    result["ok"] = True
+    return result
+
+
+def heartbeat_loop(stop, on_result: Optional[Callable[[dict], None]] = None) -> None:
+    """Beat every HEARTBEAT_SECONDS until *stop* is set, handing each result
+    to *on_result*. A bad iteration is logged, never fatal; a typo in the
+    interval must not become a request flood (10 s floor)."""
+    if config.HEARTBEAT_SECONDS <= 0:
+        return
+    interval = max(10, config.HEARTBEAT_SECONDS)
+    while not stop.is_set():
+        try:
+            result = heartbeat_once()
+            if on_result is not None:
+                on_result(result)
+        except Exception as exc:
+            log(f"heartbeat iteration failed: {exc}")
+        stop.wait(interval)
diff --git a/tests/test_assistant.py b/tests/test_assistant.py
index e99c9d4..dc3f660 100644
--- a/tests/test_assistant.py
+++ b/tests/test_assistant.py
@@ -411,3 +411,55 @@ def test_transcription_falls_back_to_one_upload():
     t.add([frame(LOUD)])  # nowhere to go: the live socket never opened
     assert t.finish(frame(LOUD) * 2) == "hey bolt"
     assert b"".join(late.audio) == frame(LOUD) * 2
+
+
+# ── heartbeat announcements ──────────────────────────────────────────────────
+
+def test_announcements_are_spoken_when_idle():
+    a, asked, played, logs, _ = make([])
+    a.announce("You have a reminder.")
+    a._drain_announcements()
+    assert "You have a reminder." in spoken(played)
+    assert a.state == "idle"
+
+
+def test_announcements_wait_for_idle():
+    a, asked, played, logs, _ = make(["It's three o'clock."])
+    a.state = "busy"
+    a.announce("You have a reminder.")
+    a._drain_announcements()
+    assert spoken(played) == []  # held back while Bolt is talking
+    a.state = "idle"
+    a._drain_announcements()
+    assert "You have a reminder." in spoken(played)
+
+
+def test_announcements_hold_while_a_transcript_is_in_flight():
+    a, asked, played, logs, _ = make([])
+    a._pending.append(object())  # an utterance is still at the server
+    a.announce("You have a reminder.")
+    a._drain_announcements()
+    assert spoken(played) == []
+    a._pending.clear()
+    a._drain_announcements()
+    assert "You have a reminder." in spoken(played)
+
+
+def test_announcements_hold_while_someone_is_speaking():
+    a, asked, played, logs, _ = make([])
+    FakeTranscription.script.append("")  # the start event still mints a transcriber
+    for f in [frame(LOUD)] * 3:
+        a.process(f)  # the segmenter is mid-utterance
+    a.announce("You have a reminder.")
+    a._drain_announcements()
+    assert spoken(played) == []
+    a.segmenter.reset()
+    a._drain_announcements()
+    assert "You have a reminder." in spoken(played)
+
+
+def test_blank_announcements_are_dropped():
+    a, asked, played, logs, _ = make([])
+    a.announce("   ")
+    a._drain_announcements()
+    assert spoken(played) == []
diff --git a/tests/test_heartbeat.py b/tests/test_heartbeat.py
new file mode 100644
index 0000000..6eb6779
--- /dev/null
+++ b/tests/test_heartbeat.py
@@ -0,0 +1,191 @@
+"""The heartbeat that brings reminders and delivered files in — with fakes
+for the network. Covers the report_status POST, the outbox list, the
+download rules (.part first, never overwrite, clean up on failure) and the
+loop's stop/disable behaviour."""
+
+import sys
+import threading
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+import pytest
+
+from bolt_assistant import config, heartbeat
+
+
+class FakeResponse:
+    def __init__(self, payload=None, data=b"", status_code=200):
+        self._payload = payload
+        self._data = data
+        self.status_code = status_code
+
+    def json(self):
+        return self._payload
+
+    def iter_content(self, chunk_size=65536):
+        yield self._data
+
+
+@pytest.fixture(autouse=True)
+def _quiet(monkeypatch):
+    monkeypatch.setattr(heartbeat, "log", lambda msg: None)
+
+
+def _files_get(data=b"hello", files=None, status_code=200):
+    def get(url, params=None, headers=None, timeout=None, stream=None):
+        if url.endswith("/desk/files"):
+            return FakeResponse(payload={"files": files or []})
+        return FakeResponse(data=data, status_code=status_code)
+
+    return get
+
+
+# ── one beat ─────────────────────────────────────────────────────────────────
+
+def test_heartbeat_once_reports_in_and_returns_ok(tmp_path):
+    seen = {}
+
+    def post(url, json=None, headers=None, timeout=None):
+        seen["url"], seen["json"], seen["headers"] = url, json, headers
+        return FakeResponse(payload={"ok": True})
+
+    result = heartbeat.heartbeat_once(tmp_path, post=post, get=_files_get())
+    assert result == {"ok": True, "announcement": "", "saved": []}
+    assert seen["url"].endswith("/desk/report_status")
+    assert seen["json"] == {"session_id": config.SESSION_ID, "download_dir": str(tmp_path)}
+    assert seen["headers"] == {"X-Desk-Api-Key": config.API_KEY}
+
+
+def test_heartbeat_once_carries_the_announcement(tmp_path):
+    def post(url, json=None, headers=None, timeout=None):
+        return FakeResponse(payload={"reply": "  You have   a reminder. "})
+
+    result = heartbeat.heartbeat_once(tmp_path, post=post, get=_files_get())
+    assert result["announcement"] == "You have a reminder."
+
+
+def test_heartbeat_once_downloads_the_outbox(tmp_path):
+    seen = {}
+
+    def get(url, params=None, headers=None, timeout=None, stream=None):
+        if url.endswith("/desk/files"):
+            seen["list"] = params
+            return FakeResponse(payload={"files": [{"id": "abc", "name": "note.txt", "size": 5}]})
+        seen["download"] = params
+        return FakeResponse(data=b"hello")
+
+    def post(url, json=None, headers=None, timeout=None):
+        return FakeResponse(payload={"ok": True})
+
+    result = heartbeat.heartbeat_once(tmp_path, post=post, get=get)
+    assert seen["list"] == seen["download"] == {"session_id": config.SESSION_ID}
+    assert len(result["saved"]) == 1
+    target = result["saved"][0]
+    assert target.parent == tmp_path and target.name == "note.txt"
+    assert target.read_bytes() == b"hello"
+    assert not list(tmp_path.glob("*.part"))
+
+
+def test_heartbeat_once_network_failure_is_not_fatal(tmp_path):
+    def post(url, json=None, headers=None, timeout=None):
+        raise OSError("no network")
+
+    result = heartbeat.heartbeat_once(tmp_path, post=post, get=_files_get())
+    assert result == {"ok": False, "announcement": "", "saved": []}
+
+
+def test_heartbeat_once_refused_does_not_touch_the_outbox(tmp_path):
+    got = []
+
+    def get(url, params=None, headers=None, timeout=None, stream=None):
+        got.append(url)
+        return FakeResponse(payload={"files": []})
+
+    def post(url, json=None, headers=None, timeout=None):
+        return FakeResponse(payload={"error": "unauthorized"}, status_code=401)
+
+    result = heartbeat.heartbeat_once(tmp_path, post=post, get=get)
+    assert result == {"ok": False, "announcement": "", "saved": []}
+    assert got == []
+
+
+# ── download rules ───────────────────────────────────────────────────────────
+
+def test_download_never_overwrites(tmp_path):
+    (tmp_path / "note.txt").write_text("old")
+    target = heartbeat._download("abc", "note.txt", tmp_path, get=_files_get(data=b"new"))
+    assert target.name == "note (1).txt"
+    assert (tmp_path / "note.txt").read_text() == "old"
+    assert target.read_bytes() == b"new"
+
+
+def test_download_refused(tmp_path):
+    assert heartbeat._download("abc", "note.txt", tmp_path,
+                               get=_files_get(status_code=500)) is None
+    assert list(tmp_path.iterdir()) == []
+
+
+def test_download_cleans_up_the_part_file_on_failure(tmp_path):
+    class Exploding(FakeResponse):
+        def iter_content(self, chunk_size=65536):
+            yield b"part of"
+            raise OSError("connection reset")
+
+    assert heartbeat._download("abc", "note.txt", tmp_path,
+                               get=lambda **kw: Exploding()) is None
+    assert list(tmp_path.iterdir()) == []  # no .part left behind
+
+
+def test_safe_filename_strips_paths_and_control_characters():
+    assert heartbeat._safe_filename("a/b\\c:d.txt") == "a_b_c_d.txt"
+    assert heartbeat._safe_filename("..") == "download"
+    assert heartbeat._safe_filename("") == "download"
+    assert heartbeat._safe_filename("  fine name.txt  ") == "fine name.txt"
+
+
+# ── health probe and the loop ────────────────────────────────────────────────
+
+def test_fetch_server_health_warns_loudly_on_a_refused_key(monkeypatch):
+    lines = []
+    monkeypatch.setattr(heartbeat, "log", lines.append)
+
+    def get(url, headers=None, timeout=None):
+        return FakeResponse(payload={"key_ok": False})
+
+    heartbeat.fetch_server_health(get=get)
+    assert any("DESK_API_KEY" in line for line in lines)
+
+
+def test_fetch_server_health_logs_a_healthy_server(monkeypatch):
+    lines = []
+    monkeypatch.setattr(heartbeat, "log", lines.append)
+
+    def get(url, headers=None, timeout=None):
+        return FakeResponse(payload={"key_ok": True, "version": "1"})
+
+    heartbeat.fetch_server_health(get=get)
+    assert lines and lines[0].startswith("server:")
+
+
+def test_heartbeat_loop_reports_each_beat(monkeypatch):
+    monkeypatch.setattr(config, "HEARTBEAT_SECONDS", 60)
+    stop = threading.Event()
+    results = []
+    monkeypatch.setattr(heartbeat, "heartbeat_once",
+                        lambda: {"ok": True, "announcement": "hi", "saved": []})
+
+    def on_result(result):
+        results.append(result)
+        stop.set()
+
+    heartbeat.heartbeat_loop(stop, on_result)
+    assert results == [{"ok": True, "announcement": "hi", "saved": []}]
+
+
+def test_heartbeat_loop_disabled_when_heartbeat_seconds_is_zero(monkeypatch):
+    monkeypatch.setattr(config, "HEARTBEAT_SECONDS", 0)
+    called = []
+    monkeypatch.setattr(heartbeat, "heartbeat_once", lambda: called.append(1))
+    heartbeat.heartbeat_loop(threading.Event(), None)
+    assert called == []