Add background auto-review worker with SQLite cache

Pre-compute PR reviews so they are ready the moment a PR is opened in the queue, instead of waiting on an on-demand Fireworks call each time. A daemon worker polls the queue every POLL_INTERVAL and reviews new or changed non-draft PRs into a local SQLite cache (gitignored). Change detection is two-level: skip when the PR's updated_at is unchanged, and even when it moved, skip the model call when the diff's SHA-256 matches, so comment-only bumps do not burn tokens. Failed reviews retry up to MAX_REVIEW_ATTEMPTS with 429 backoff; departed PRs are closed with a grace window before purge. Singletons are initialized eagerly in the FastAPI lifespan before the worker thread starts to avoid an init race; all cache writes are serialized. New endpoints GET /api/reviews and POST /api/refresh back a dashboard that polls for status (reviewing/ready/error) and opens a ready review instantly. Nothing is posted automatically; the human still decides. Stdlib-only, so no new runtime or test dependencies.
2026-09-30 03:23:14 +00:00 · 2026-07-01 14:28:11 -04:00 · 2026-07-01 14:28:11 -04:00 · 15a52bff40
commit 15a52bff40
parent 46cd856fb3
11 changed files with 996 additions and 51 deletions
--- a/.env.example
+++ b/.env.example
@ -3,7 +3,7 @@
 GITHUB_TOKEN=
 GITHUB_ORG=Sea-Haven-Industries
 PR_SEARCH_FILTER=is:pr state:open archived:false sort:updated-desc org:Sea-Haven-Industries
-MAX_PRS=30
+MAX_PRS=100
 MAX_DIFF_BYTES=120000

 # --- Fireworks ---
@ -21,3 +21,13 @@ MENTION_AUTHORS=openswe

 HOST=127.0.0.1
 PORT=8765
+
+# --- Background auto-review worker ---
+# Seconds between poll cycles (pre-reviews new/changed non-draft PRs).
+POLL_INTERVAL=300
+# How many PRs to review in parallel per cycle (kept low to respect rate limits).
+WORKER_CONCURRENCY=2
+# Stop auto-retrying a PR that keeps failing until its diff changes.
+MAX_REVIEW_ATTEMPTS=3
+# SQLite cache path. Defaults to pr_cache.db in the repo root (gitignored).
+# CACHE_DB=/absolute/path/to/pr_cache.db
--- a/.gitignore
+++ b/.gitignore
@ -1,6 +1,10 @@
 # Secrets and local env
 .env

+# Local review cache (SQLite + WAL/SHM sidecars)
+pr_cache.db
+pr_cache.db-*
+
 # Python virtualenv and caches
 .venv/
 __pycache__/
--- a/README.md
+++ b/README.md
@ -2,6 +2,8 @@

 A local dashboard that pulls open PRs from your GitHub org, reviews each one with a Fireworks model using the BLOCK / FIX / NIT / QUESTION skill format, and lets you request revisions or post the review to GitHub as yourself.

+A background worker pre-reviews non-draft PRs on an interval, so a review is usually ready the moment you open one in the queue. You still decide whether and how to post; nothing is ever posted automatically.
+
 Everything runs on your machine. This is a local, single-user tool. It is not deployed anywhere, so there is no AWS stack, no CI deploy path, and secrets live only in a local `.env` (gitignored). Your GitHub token and Fireworks key stay in the backend and never reach the browser.

 ## Setup
@ -30,11 +32,18 @@ Open http://127.0.0.1:8765

 ## How it works

-1. **Refresh queue** runs your filter (`PR_SEARCH_FILTER`, default matches your org filter) and lists the PRs.
-2. **Run review** fetches the PR diff and sends it to Fireworks. The result is parsed into the four categories plus a summary line and a recommended event.
+1. **Background worker** polls your filter (`PR_SEARCH_FILTER`) every `POLL_INTERVAL` seconds and pre-reviews any new or changed non-draft PR, caching the result. The queue shows each PR's status: `reviewing`, `ready`, `error`, or `closed`. **Refresh now** forces an immediate poll.
+2. **Open a PR** — if its review is `ready`, it appears instantly. Otherwise you see its status, and you can **Run review now** on demand.
 3. **Request revision** re-runs the review with your notes folded in as a trusted instruction, separate from the untrusted diff.
 4. **Post review to GitHub** submits it as a PR review. You confirm the event type (COMMENT / APPROVE / REQUEST_CHANGES) and can edit the body first.

+### Auto-review worker
+
+- Reviews are cached in a local SQLite file (`CACHE_DB`, default `pr_cache.db` in the repo root, gitignored) so they survive restarts and aren't recomputed for unchanged PRs.
+- Change detection is two-level: a PR is skipped if its `updated_at` hasn't moved since the last review, and even when it has, the diff's SHA-256 is compared so a comment-only bump doesn't burn tokens.
+- Drafts are skipped. Failed reviews are retried on later cycles up to `MAX_REVIEW_ATTEMPTS`, then left until the PR changes. Rate-limit (HTTP 429) responses back off and retry.
+- `WORKER_CONCURRENCY` controls how many PRs are reviewed in parallel per cycle (default 2).
+
 ## The @mention rule

 Any PR whose author login is in `MENTION_AUTHORS` (default `openswe`) gets an `@author` mention prepended to the review summary. Add more logins comma-separated.
@ -42,9 +51,21 @@ Any PR whose author login is in `MENTION_AUTHORS` (default `openswe`) gets an `@
 ## Notes

 - The diff is treated as untrusted input; the model is instructed to ignore any embedded instructions.
- State is in memory and resets on restart. This is a single-user local tool, not a shared service.
+- Cached reviews persist in a local SQLite file. This is a single-user local tool, not a shared service.
 - Large diffs are truncated at `MAX_DIFF_BYTES` to control token cost.

+## Configuration
+
+Set in `.env` (see `.env.example`). Beyond the GitHub/Fireworks keys:
+
+| Var | Default | Purpose |
+|---|---|---|
+| `POLL_INTERVAL` | `300` | seconds between background poll cycles |
+| `WORKER_CONCURRENCY` | `2` | PRs reviewed in parallel per cycle |
+| `MAX_REVIEW_ATTEMPTS` | `3` | error retries before giving up until the PR changes |
+| `MAX_PRS` | `100` | cap on PRs pulled per cycle (GitHub search page max) |
+| `CACHE_DB` | `pr_cache.db` | SQLite cache path (absolute, repo root by default) |
+
 ## Layout

 ```
@ -52,7 +73,9 @@ app/
  config.py          settings from .env
  github_client.py   search PRs, fetch diffs, post reviews
  reviewer.py        Fireworks call + skill format + markdown rendering
-  main.py            FastAPI endpoints
+  store.py           SQLite cache of pre-computed reviews
+  worker.py          background poll + auto-review (run_cycle)
+  main.py            FastAPI endpoints (incl. /api/reviews, /api/refresh)
 static/
  index.html         the dashboard
 ```
--- a/app/config.py
+++ b/app/config.py
@ -6,11 +6,14 @@ backend; the backend holds the GitHub PAT and Fireworks key.

 import os
 from functools import lru_cache
+from pathlib import Path

 from dotenv import load_dotenv

 load_dotenv()

+_REPO_ROOT = Path(__file__).resolve().parent.parent
+

 class Config:
    # --- GitHub ---
@ -23,8 +26,9 @@ class Config:
        "PR_SEARCH_FILTER",
        "is:pr state:open archived:false sort:updated-desc org:Sea-Haven-Industries",
    ).strip()
-    # Cap how many PRs we pull per refresh.
-    MAX_PRS: int = int(os.getenv("MAX_PRS", "30"))
+    # Cap how many PRs we pull per refresh. GitHub search returns at most 100
+    # per page; PRs beyond that are not paginated (fine at current org volume).
+    MAX_PRS: int = int(os.getenv("MAX_PRS", "100"))
    # Skip diffs larger than this many bytes (keeps token cost sane).
    MAX_DIFF_BYTES: int = int(os.getenv("MAX_DIFF_BYTES", "120000"))

@ -54,6 +58,19 @@ class Config:
    HOST: str = os.getenv("HOST", "127.0.0.1")
    PORT: int = int(os.getenv("PORT", "8765"))

+    # --- Background auto-review worker ---
+    # Seconds between poll cycles. The worker fetches the queue, then pre-reviews
+    # any new or changed non-draft PR so results are ready before you open them.
+    POLL_INTERVAL: int = int(os.getenv("POLL_INTERVAL", "300"))
+    # How many PRs to review in parallel per cycle. Kept low for a single-user
+    # tool to stay well under Fireworks rate limits.
+    WORKER_CONCURRENCY: int = int(os.getenv("WORKER_CONCURRENCY", "2"))
+    # Give up auto-retrying a PR that keeps failing until its diff changes.
+    MAX_REVIEW_ATTEMPTS: int = int(os.getenv("MAX_REVIEW_ATTEMPTS", "3"))
+    # SQLite cache of pre-computed reviews. Absolute path resolved from the repo
+    # root so it lands in the same place regardless of the working directory.
+    CACHE_DB: str = os.getenv("CACHE_DB", str(_REPO_ROOT / "pr_cache.db"))
+

@lru_cache
 def get_config() -> Config:
--- a/app/main.py
+++ b/app/main.py
@ -2,37 +2,47 @@

 Endpoints:
  GET  /                      -> serves the dashboard
-  GET  /api/prs               -> list PRs matching the filter (no review yet)
-  POST /api/review            -> run a Fireworks review for one PR
+  GET  /api/config            -> org/filter/model info for the UI
+  GET  /api/prs               -> live list of PRs matching the filter
+  GET  /api/reviews           -> cached, pre-computed reviews + per-PR status
+  POST /api/refresh           -> ask the background worker to poll now (202)
+  POST /api/review            -> run a Fireworks review for one PR on demand
  POST /api/revise            -> re-run review with the user's revision notes
  POST /api/post              -> submit the review to GitHub (side-effectful)

-In-memory store only; state resets on restart. This is a single-user local tool.
+A background worker (app/worker.py) pre-reviews non-draft PRs into a SQLite cache
+(app/store.py) so reviews are ready when opened. Nothing is ever posted
+automatically. Single-user local tool.
 """

 from __future__ import annotations

+import hashlib
+import json
+from contextlib import asynccontextmanager
 from pathlib import Path
 from typing import Any

 from fastapi import FastAPI, HTTPException
-from fastapi.responses import FileResponse
+from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
 from pydantic import BaseModel

 from .config import get_config
 from .github_client import GitHubClient, GitHubError
 from .reviewer import Reviewer
+from .store import ReviewStore
+from .worker import Worker

 cfg = get_config()
-app = FastAPI(title="PR Review Dashboard")

 STATIC_DIR = Path(__file__).parent.parent / "static"
-app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")

 # lazy singletons so a missing token doesn't crash import
 _gh: GitHubClient | None = None
 _reviewer: Reviewer | None = None
+_store: ReviewStore | None = None
+_worker: Worker | None = None


 def gh() -> GitHubClient:
@ -49,6 +59,35 @@ def reviewer() -> Reviewer:
    return _reviewer


+def store() -> ReviewStore | None:
+    return _store
+
+
+def worker() -> Worker | None:
+    return _worker
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    # Initialize the singletons eagerly, before the worker thread starts, so the
+    # worker and request handlers never race to lazily create them.
+    global _store, _worker
+    gh()
+    reviewer()
+    _store = ReviewStore(cfg.CACHE_DB)
+    _worker = Worker(cfg, _gh, _reviewer, _store)
+    _worker.start()
+    try:
+        yield
+    finally:
+        if _worker is not None:
+            _worker.stop()
+
+
+app = FastAPI(title="PR Review Dashboard", lifespan=lifespan)
+app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")
+
+
@app.get("/")
 def index() -> FileResponse:
    return FileResponse(STATIC_DIR / "index.html")
@ -73,6 +112,50 @@ def api_prs() -> dict[str, Any]:
        raise HTTPException(400, str(e))


+def _serialize_review(row: dict[str, Any]) -> dict[str, Any]:
+    review = None
+    if row.get("review_json"):
+        try:
+            review = json.loads(row["review_json"])
+        except (json.JSONDecodeError, TypeError):
+            review = None
+    return {
+        "owner": row["owner"],
+        "repo": row["repo"],
+        "number": row["number"],
+        "title": row.get("pr_title"),
+        "author": row.get("pr_author"),
+        "url": row.get("pr_url"),
+        "status": row["status"],
+        "updated_at": row.get("pr_updated_at"),
+        "cached_at": row.get("cached_at"),
+        "attempts": row.get("attempts", 0),
+        "error": row.get("error"),
+        "review": review,
+    }
+
+
+@app.get("/api/reviews")
+def api_reviews() -> dict[str, Any]:
+    s = store()
+    if s is None:
+        raise HTTPException(503, "Review worker is not running yet.")
+    rows = s.list()
+    return {
+        "reviews": [_serialize_review(r) for r in rows],
+        "poll_interval": cfg.POLL_INTERVAL,
+    }
+
+
+@app.post("/api/refresh")
+def api_refresh() -> JSONResponse:
+    w = worker()
+    if w is None:
+        raise HTTPException(503, "Review worker is not running yet.")
+    w.trigger()  # non-blocking: the worker thread runs the cycle
+    return JSONResponse(status_code=202, content={"ok": True, "scheduled": True})
+
+
 class ReviewReq(BaseModel):
    owner: str
    repo: str
@ -82,12 +165,35 @@ class ReviewReq(BaseModel):
    body: str = ""


+def _cache_write_through(req: ReviewReq, diff: str, result: dict[str, Any]) -> None:
+    """Best-effort: store an on-demand review in the cache so the dashboard and
+    the worker share one source of truth. Never fails the request."""
+    if _store is None:
+        return
+    try:
+        _store.upsert(
+            req.owner,
+            req.repo,
+            req.number,
+            status="ready",
+            diff_hash=hashlib.sha256(diff.encode("utf-8", "ignore")).hexdigest(),
+            review_json=json.dumps(result),
+            error=None,
+            attempts=0,
+            pr_title=req.title,
+            pr_author=req.author,
+        )
+    except Exception:  # noqa: BLE001 - caching is best-effort
+        pass
+
+
@app.post("/api/review")
 def api_review(req: ReviewReq) -> dict[str, Any]:
    try:
        diff = gh().pr_diff(req.owner, req.repo, req.number)
        pr = req.model_dump()
        result = reviewer().review(pr, diff)
+        _cache_write_through(req, diff, result)
        return {"review": result}
    except GitHubError as e:
        raise HTTPException(400, str(e))
--- a/app/store.py
+++ b/app/store.py
@ -0,0 +1,157 @@
+"""SQLite cache of pre-computed PR reviews.
+
+One row per PR, keyed by ``(owner, repo, number)``. The background worker writes;
+the API reads. SQLite allows only a single writer at a time, so every write goes
+through one module-level lock and connections use a busy timeout; readers open
+their own short-lived connection. The DB file is local and gitignored.
+
+Status lifecycle:
+  reviewing -> ready | error         (worker reviews a new/changed PR)
+  ready     -> ready                 (unchanged; refreshed metadata only)
+  *         -> closed                (PR left the queue; kept briefly, then purged)
+"""
+
+from __future__ import annotations
+
+import sqlite3
+import threading
+import time
+from typing import Any
+
+# One writer at a time. SQLite serializes writes anyway; this keeps the Python
+# side from piling up concurrent write transactions from the worker pool.
+_WRITE_LOCK = threading.Lock()
+
+_SCHEMA = """
+CREATE TABLE IF NOT EXISTS reviews (
+    owner         TEXT    NOT NULL,
+    repo          TEXT    NOT NULL,
+    number        INTEGER NOT NULL,
+    status        TEXT    NOT NULL,          -- reviewing | ready | error | closed
+    diff_hash     TEXT,
+    review_json   TEXT,
+    error         TEXT,
+    attempts      INTEGER NOT NULL DEFAULT 0,
+    pr_title      TEXT,
+    pr_author     TEXT,
+    pr_url        TEXT,
+    pr_updated_at TEXT,                       -- PR's updatedAt on GitHub
+    cached_at     REAL    NOT NULL,           -- when this row was last written
+    closed_at     REAL,                       -- when the PR left the queue
+    PRIMARY KEY (owner, repo, number)
+);
+"""
+
+# Columns a caller may set via upsert(); owner/repo/number are the key and
+# cached_at is stamped automatically.
+_UPSERTABLE = (
+    "status",
+    "diff_hash",
+    "review_json",
+    "error",
+    "attempts",
+    "pr_title",
+    "pr_author",
+    "pr_url",
+    "pr_updated_at",
+    "closed_at",
+)
+
+
+class ReviewStore:
+    def __init__(self, db_path: str) -> None:
+        self.db_path = db_path
+        with _WRITE_LOCK, self._connect() as conn:
+            conn.executescript(_SCHEMA)
+
+    def _connect(self) -> sqlite3.Connection:
+        conn = sqlite3.connect(self.db_path, timeout=30)
+        conn.row_factory = sqlite3.Row
+        conn.execute("PRAGMA journal_mode=WAL")
+        conn.execute("PRAGMA busy_timeout=30000")
+        return conn
+
+    # --- reads --------------------------------------------------------------
+    def get(self, owner: str, repo: str, number: int) -> dict[str, Any] | None:
+        with self._connect() as conn:
+            row = conn.execute(
+                "SELECT * FROM reviews WHERE owner=? AND repo=? AND number=?",
+                (owner, repo, number),
+            ).fetchone()
+        return dict(row) if row else None
+
+    def list(self, *, include_closed: bool = True) -> list[dict[str, Any]]:
+        sql = "SELECT * FROM reviews"
+        if not include_closed:
+            sql += " WHERE status != 'closed'"
+        sql += " ORDER BY pr_updated_at DESC"
+        with self._connect() as conn:
+            rows = conn.execute(sql).fetchall()
+        return [dict(r) for r in rows]
+
+    # --- writes (serialized) ------------------------------------------------
+    def upsert(self, owner: str, repo: str, number: int, **fields: Any) -> None:
+        """Insert or update one PR row. Only recognized columns are written;
+        ``cached_at`` is stamped automatically. Unspecified columns keep their
+        previous value on update (and their default on insert)."""
+        bad = set(fields) - set(_UPSERTABLE)
+        if bad:
+            raise ValueError(f"unknown review columns: {sorted(bad)}")
+
+        cols = ["owner", "repo", "number", "cached_at", *fields]
+        vals = [owner, repo, number, time.time(), *fields.values()]
+        placeholders = ", ".join("?" for _ in cols)
+        # On conflict, update every provided column plus cached_at.
+        updates = ", ".join(f"{c}=excluded.{c}" for c in ("cached_at", *fields))
+        sql = (
+            f"INSERT INTO reviews ({', '.join(cols)}) VALUES ({placeholders}) "
+            f"ON CONFLICT(owner, repo, number) DO UPDATE SET {updates}"
+        )
+        with _WRITE_LOCK, self._connect() as conn:
+            conn.execute(sql, vals)
+            conn.commit()
+
+    def reset_stale_reviewing(self) -> int:
+        """On startup, any row still marked ``reviewing`` was interrupted by a
+        crash/restart. Flip it to ``error`` so the next cycle retries it."""
+        with _WRITE_LOCK, self._connect() as conn:
+            cur = conn.execute(
+                "UPDATE reviews SET status='error', error='interrupted' "
+                "WHERE status='reviewing'"
+            )
+            conn.commit()
+            return cur.rowcount
+
+    def mark_missing_closed(self, live_keys: set[tuple[str, str, int]]) -> None:
+        """Mark rows whose PR is no longer in the queue as ``closed`` (keeping
+        them briefly so an open dashboard doesn't lose a review mid-read)."""
+        now = time.time()
+        with _WRITE_LOCK, self._connect() as conn:
+            rows = conn.execute(
+                "SELECT owner, repo, number FROM reviews WHERE status != 'closed'"
+            ).fetchall()
+            gone = [
+                (r["owner"], r["repo"], r["number"])
+                for r in rows
+                if (r["owner"], r["repo"], r["number"]) not in live_keys
+            ]
+            for owner, repo, number in gone:
+                conn.execute(
+                    "UPDATE reviews SET status='closed', closed_at=? "
+                    "WHERE owner=? AND repo=? AND number=?",
+                    (now, owner, repo, number),
+                )
+            conn.commit()
+
+    def purge_closed(self, older_than_seconds: float) -> int:
+        """Hard-delete rows that have been ``closed`` longer than the grace
+        window."""
+        cutoff = time.time() - older_than_seconds
+        with _WRITE_LOCK, self._connect() as conn:
+            cur = conn.execute(
+                "DELETE FROM reviews WHERE status='closed' AND closed_at IS NOT NULL "
+                "AND closed_at < ?",
+                (cutoff,),
+            )
+            conn.commit()
+            return cur.rowcount
--- a/app/worker.py
+++ b/app/worker.py
@ -0,0 +1,232 @@
+"""Background auto-review worker.
+
+A daemon thread polls the PR queue on an interval and pre-reviews any new or
+changed non-draft PR into the SQLite cache, so a review is ready by the time you
+open it in the dashboard. Nothing is ever posted automatically.
+
+Change detection is two-level to keep token spend down:
+  1. cheap gate  - skip if the PR's ``updated_at`` is unchanged since the last
+     ready review (no diff fetched at all);
+  2. precise gate - if it did change, fetch the diff and skip the LLM call when
+     the diff's SHA-256 matches (e.g. the PR was only commented on).
+
+``run_cycle`` takes its GitHub client, reviewer, and store as parameters so it is
+directly testable with fakes; the ``Worker`` class only owns the thread/timing.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import logging
+import random
+import threading
+import time
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from typing import Any, Callable
+
+# Keep a review for a closed/merged PR this long before hard-deleting it, so an
+# open dashboard doesn't lose a review the moment the PR merges.
+CLOSED_GRACE_SECONDS = 600
+
+_log = logging.getLogger("pr_reviewer.worker")
+
+
+def _sha256(text: str) -> str:
+    return hashlib.sha256(text.encode("utf-8", "ignore")).hexdigest()
+
+
+def _is_rate_limited(exc: Exception) -> bool:
+    resp = getattr(exc, "response", None)
+    return getattr(resp, "status_code", None) == 429
+
+
+def _review_with_backoff(
+    reviewer: Any,
+    pr: dict[str, Any],
+    diff: str,
+    *,
+    retries: int = 3,
+    base: float = 2.0,
+    sleep: Callable[[float], None] = time.sleep,
+) -> dict[str, Any]:
+    """Call the reviewer, backing off on HTTP 429 with exponential delay +
+    jitter. Non-429 errors (and the final 429) propagate to the caller."""
+    for attempt in range(retries + 1):
+        try:
+            return reviewer.review(pr, diff)
+        except Exception as e:  # noqa: BLE001 - re-raised below unless retriable
+            if _is_rate_limited(e) and attempt < retries:
+                sleep(base * (2**attempt) + random.uniform(0, 1))
+                continue
+            raise
+
+
+def _review_one(
+    gh: Any,
+    reviewer: Any,
+    store: Any,
+    pr: dict[str, Any],
+    sleep: Callable[[float], None],
+) -> str:
+    """Review a single PR and persist the outcome. Returns an outcome label and
+    never raises (failures are stored as ``error`` rows)."""
+    owner, repo, number = pr["owner"], pr["repo"], pr["number"]
+    meta = {
+        "pr_title": pr.get("title"),
+        "pr_author": pr.get("author"),
+        "pr_url": pr.get("url"),
+        "pr_updated_at": pr.get("updated_at"),
+    }
+    try:
+        diff = gh.pr_diff(owner, repo, number)
+        diff_hash = _sha256(diff)
+        existing = store.get(owner, repo, number)
+        if (
+            existing
+            and existing.get("diff_hash") == diff_hash
+            and existing.get("review_json")
+        ):
+            # Diff unchanged (updated_at moved for a non-code reason) and we
+            # already have a review: keep it, just mark ready and refresh metadata
+            # so the cheap gate catches it next time. (Status is "reviewing" here
+            # because run_cycle marks queued PRs before handing them off.)
+            store.upsert(owner, repo, number, status="ready", **meta)
+            return "unchanged"
+        review = _review_with_backoff(reviewer, pr, diff, sleep=sleep)
+        store.upsert(
+            owner,
+            repo,
+            number,
+            status="ready",
+            diff_hash=diff_hash,
+            review_json=json.dumps(review),
+            error=None,
+            attempts=0,
+            **meta,
+        )
+        return "reviewed"
+    except Exception as e:  # noqa: BLE001 - stored as an error row, surfaced in UI
+        existing = store.get(owner, repo, number)
+        attempts = (existing.get("attempts", 0) if existing else 0) + 1
+        store.upsert(
+            owner,
+            repo,
+            number,
+            status="error",
+            error=str(e),
+            attempts=attempts,
+            **meta,
+        )
+        return "error"
+
+
+def run_cycle(
+    gh: Any,
+    reviewer: Any,
+    store: Any,
+    *,
+    concurrency: int = 2,
+    max_attempts: int = 3,
+    grace_seconds: float = CLOSED_GRACE_SECONDS,
+    sleep: Callable[[float], None] = time.sleep,
+) -> dict[str, int]:
+    """One poll cycle: refresh the queue, close/purge departed PRs, and review
+    every new or changed non-draft PR (bounded concurrency). Returns per-outcome
+    counts."""
+    prs = gh.search_prs()
+    active = [p for p in prs if not p.get("draft")]
+    live_keys = {(p["owner"], p["repo"], p["number"]) for p in active}
+    store.mark_missing_closed(live_keys)
+    store.purge_closed(grace_seconds)
+
+    todo: list[dict[str, Any]] = []
+    for p in active:
+        existing = store.get(p["owner"], p["repo"], p["number"])
+        if existing:
+            same_update = existing.get("pr_updated_at") == p.get("updated_at")
+            if existing.get("status") == "ready" and same_update:
+                continue  # cheap gate: nothing changed since last ready review
+            if (
+                existing.get("status") == "error"
+                and same_update
+                and existing.get("attempts", 0) >= max_attempts
+            ):
+                continue  # keeps failing: wait until the PR itself changes
+        todo.append(p)
+
+    # Mark queued PRs as reviewing up front so the UI reflects in-flight work.
+    for p in todo:
+        store.upsert(
+            p["owner"],
+            p["repo"],
+            p["number"],
+            status="reviewing",
+            pr_title=p.get("title"),
+            pr_author=p.get("author"),
+            pr_url=p.get("url"),
+            pr_updated_at=p.get("updated_at"),
+        )
+
+    results = {
+        "reviewed": 0,
+        "unchanged": 0,
+        "error": 0,
+        "skipped": len(active) - len(todo),
+    }
+    if todo:
+        with ThreadPoolExecutor(max_workers=max(1, concurrency)) as ex:
+            futures = [
+                ex.submit(_review_one, gh, reviewer, store, p, sleep) for p in todo
+            ]
+            for fut in as_completed(futures):
+                results[fut.result()] += 1
+    return results
+
+
+class Worker:
+    """Owns the poll thread and its timing; delegates the work to ``run_cycle``."""
+
+    def __init__(self, cfg: Any, gh: Any, reviewer: Any, store: Any) -> None:
+        self.cfg = cfg
+        self.gh = gh
+        self.reviewer = reviewer
+        self.store = store
+        self._stop = threading.Event()
+        self._wake = threading.Event()
+        self._thread: threading.Thread | None = None
+
+    def start(self) -> None:
+        n = self.store.reset_stale_reviewing()
+        if n:
+            _log.info("reset %d interrupted review(s) from a prior run", n)
+        self._thread = threading.Thread(
+            target=self._loop, name="review-worker", daemon=True
+        )
+        self._thread.start()
+
+    def trigger(self) -> None:
+        """Ask the loop to run a cycle now (non-blocking)."""
+        self._wake.set()
+
+    def stop(self) -> None:
+        self._stop.set()
+        self._wake.set()
+        if self._thread:
+            self._thread.join(timeout=5)
+
+    def _loop(self) -> None:
+        while not self._stop.is_set():
+            try:
+                res = run_cycle(
+                    self.gh,
+                    self.reviewer,
+                    self.store,
+                    concurrency=self.cfg.WORKER_CONCURRENCY,
+                    max_attempts=self.cfg.MAX_REVIEW_ATTEMPTS,
+                )
+                _log.info("review cycle: %s", res)
+            except Exception:
+                _log.exception("review cycle failed")
+            self._wake.wait(timeout=self.cfg.POLL_INTERVAL)
+            self._wake.clear()
--- a/static/index.html
+++ b/static/index.html
@ -54,8 +54,12 @@
  .queue-item .title { font-weight: 500; margin: 2px 0; }
  .queue-item .sub { font-size: 12px; color: var(--ink-dim); display: flex; gap: 8px; align-items: center; }
  .badge { font-size: 10px; font-family: var(--mono); padding: 1px 6px; border-radius: 4px; border: 1px solid var(--line); }
-  .badge.reviewed { color: var(--nit); border-color: var(--nit); }
+  .badge.reviewed, .badge.ready { color: var(--nit); border-color: var(--nit); }
+  .badge.reviewing { color: var(--fix); border-color: var(--fix); }
+  .badge.error { color: var(--block); border-color: var(--block); }
+  .badge.closed { color: var(--ink-dim); border-color: var(--line); }
  .badge.mention { color: var(--accent); border-color: var(--accent); }
+  .queue-item.closed { opacity: .55; }
  .detail { overflow-y: auto; padding: 24px 28px; }
  .detail h2 { font-size: 17px; margin: 0 0 4px; }
  .detail .prlink { font-family: var(--mono); font-size: 12px; color: var(--accent); text-decoration: none; }
@ -102,18 +106,19 @@
  <h1>PR Review Desk</h1>
  <span class="meta" id="cfgMeta">loading config...</span>
  <span class="spacer"></span>
-  <button id="refreshBtn">Refresh queue</button>
+  <span class="meta" id="syncMeta"></span>
+  <button id="refreshBtn">Refresh now</button>
 </header>

 <div class="layout">
-  <div class="queue" id="queue"><div class="empty">Click Refresh to load PRs.</div></div>
-  <div class="detail" id="detail"><div class="empty">Select a PR to review.</div></div>
+  <div class="queue" id="queue"><div class="empty spin">Loading queue...</div></div>
+  <div class="detail" id="detail"><div class="empty">Select a PR. Reviews are prepared automatically in the background.</div></div>
 </div>

 <div id="toastHost"></div>

 <script>
-const state = { prs: [], me: "", active: null, reviews: {} };
+const state = { items: [], byKey: {}, me: "", active: null, mentions: [], shownKey: null, pollMs: 8000 };

 function key(pr){ return `${pr.owner}/${pr.repo}#${pr.number}`; }

@ -139,63 +144,108 @@ async function loadConfig(){
  state.mentions = c.mention_authors;
 }

-async function refresh(){
-  const q = document.getElementById("queue");
-  q.innerHTML = '<div class="empty spin">Loading PRs...</div>';
-  try {
-    const data = await j("/api/prs");
-    state.prs = data.prs; state.me = data.me;
-    renderQueue();
-  } catch(e){ q.innerHTML = `<div class="empty">Failed: ${e.message}</div>`; }
+// The reviewer identity (for the post confirmation) comes from /api/prs, which
+// also returns the authenticated login. Best-effort, non-blocking.
+async function loadMe(){
+  try { const data = await j("/api/prs"); state.me = data.me || ""; } catch(e){ /* ignore */ }
 }

+// Force an immediate background poll cycle, then refresh the view shortly after.
+async function refreshNow(){
+  try { await fetch("/api/refresh", {method:"POST"}); toast("Refresh scheduled."); }
+  catch(e){ toast("Could not schedule refresh: "+e.message, true); }
+  setTimeout(poll, 1500);
+}
+
+// Poll the cached reviews and repaint the queue. Runs on a timer.
+async function poll(){
+  let data;
+  try { data = await j("/api/reviews"); }
+  catch(e){
+    document.getElementById("syncMeta").textContent = "sync failed";
+    return;
+  }
+  state.items = data.reviews || [];
+  state.byKey = {};
+  state.items.forEach(it => { state.byKey[key(it)] = it; });
+  if(data.poll_interval){ document.getElementById("cfgMeta").dataset.poll = data.poll_interval; }
+  const now = new Date();
+  document.getElementById("syncMeta").textContent =
+    "synced " + now.toLocaleTimeString();
+  renderQueue();
+  // Upgrade a placeholder to the full review once it becomes ready.
+  if(state.active){
+    const it = state.byKey[state.active];
+    if(it && it.status === "ready" && it.review && state.shownKey !== state.active){
+      renderReview(it, it.review);
+    } else if(it && it.status !== "ready" && state.shownKey === state.active){
+      // it went back to reviewing/error after being shown
+      state.shownKey = null; selectPR(state.active);
+    }
+  }
+}
+
+const STATUS_LABEL = { reviewing: "reviewing", ready: "ready", error: "error", closed: "closed" };
+
 function renderQueue(){
  const q = document.getElementById("queue");
-  if(!state.prs.length){ q.innerHTML = '<div class="empty">No PRs match the filter.</div>'; return; }
+  if(!state.items.length){ q.innerHTML = '<div class="empty">No PRs in the queue yet. The worker reviews new PRs automatically.</div>'; return; }
  q.innerHTML = "";
-  state.prs.forEach(pr => {
-    const k = key(pr);
+  state.items.forEach(it => {
+    const k = key(it);
    const div = document.createElement("div");
-    div.className = "queue-item" + (state.active===k ? " active":"");
-    const mention = (state.mentions||[]).includes((pr.author||"").toLowerCase());
+    div.className = "queue-item" + (state.active===k ? " active":"") + (it.status==="closed" ? " closed":"");
+    const mention = (state.mentions||[]).includes((it.author||"").toLowerCase());
+    const statusBadge = `<span class="badge ${it.status}">${STATUS_LABEL[it.status]||it.status}</span>`;
    div.innerHTML = `
-      <div class="repo">${pr.owner}/${pr.repo} #${pr.number}</div>
-      <div class="title">${escapeHtml(pr.title)}</div>
+      <div class="repo">${it.owner}/${it.repo} #${it.number}</div>
+      <div class="title">${escapeHtml(it.title||"(no title)")}</div>
      <div class="sub">
-        <span>@${escapeHtml(pr.author)}</span>
+        <span>@${escapeHtml(it.author||"")}</span>
        ${mention ? '<span class="badge mention">will @mention</span>':''}
-        ${state.reviews[k] ? '<span class="badge reviewed">reviewed</span>':''}
+        ${statusBadge}
      </div>`;
    div.onclick = ()=>selectPR(k);
    q.appendChild(div);
  });
 }

-function findPR(k){ return state.prs.find(p=>key(p)===k); }
-
-async function selectPR(k){
+function selectPR(k){
  state.active = k; renderQueue();
-  const pr = findPR(k);
+  const it = state.byKey[k];
+  if(!it) return;
  const d = document.getElementById("detail");
-  if(state.reviews[k]){ renderReview(pr, state.reviews[k]); return; }
+  if(it.status === "ready" && it.review){ renderReview(it, it.review); return; }
+  state.shownKey = null;
+  let inner;
+  if(it.status === "reviewing"){
+    inner = '<span class="spin">Reviewing with Fireworks in the background...</span>';
+  } else if(it.status === "error"){
+    inner = `<div class="cat block"><h3>REVIEW FAILED</h3><div>${escapeHtml(it.error||"unknown error")} (attempt ${it.attempts||0})</div></div>
+             <div class="toolbar"><button class="primary" id="runBtn">Retry now</button></div>`;
+  } else if(it.status === "closed"){
+    inner = '<div class="spin">This PR left the queue (merged or closed).</div>';
+  } else {
+    inner = '<div class="toolbar"><button class="primary" id="runBtn">Run review now</button></div>';
+  }
  d.innerHTML = `
-    <h2>${escapeHtml(pr.title)}</h2>
-    <a class="prlink" href="${pr.url}" target="_blank">${pr.owner}/${pr.repo} #${pr.number}</a>
-    <div class="toolbar"><button class="primary" id="runBtn">Run review</button></div>`;
-  document.getElementById("runBtn").onclick = ()=>runReview(pr);
+    <h2>${escapeHtml(it.title||"(no title)")}</h2>
+    <a class="prlink" href="${it.url||"#"}" target="_blank">${it.owner}/${it.repo} #${it.number}</a>
+    <div style="margin-top:16px">${inner}</div>`;
+  const runBtn = document.getElementById("runBtn");
+  if(runBtn) runBtn.onclick = ()=>runReview(it);
 }

 async function runReview(pr){
  const d = document.getElementById("detail");
-  d.querySelector(".toolbar").innerHTML = '<span class="spin">Reviewing with Fireworks...</span>';
+  d.querySelector(".toolbar") && (d.querySelector(".toolbar").innerHTML = '<span class="spin">Reviewing with Fireworks...</span>');
  try {
    const res = await j("/api/review", {
      method:"POST", headers:{"Content-Type":"application/json"},
-      body: JSON.stringify(pr)
+      body: JSON.stringify({owner:pr.owner, repo:pr.repo, number:pr.number, title:pr.title||"", author:pr.author||""})
    });
-    state.reviews[key(pr)] = res.review;
-    renderQueue();
    renderReview(pr, res.review);
+    poll();
  } catch(e){
    toast("Review failed: "+e.message, true);
    selectPR(key(pr));
@ -204,6 +254,7 @@ async function runReview(pr){

 function renderReview(pr, rv){
  const d = document.getElementById("detail");
+  state.shownKey = key(pr);
  const cats = [["block","BLOCK"],["fix","FIX"],["nit","NIT"],["question","QUESTION"]];
  let catHtml = "";
  cats.forEach(([k,label])=>{
@ -251,9 +302,8 @@ async function revise(pr){
  try {
    const res = await j("/api/revise", {
      method:"POST", headers:{"Content-Type":"application/json"},
-      body: JSON.stringify({...pr, notes})
+      body: JSON.stringify({owner:pr.owner, repo:pr.repo, number:pr.number, title:pr.title||"", author:pr.author||"", notes})
    });
-    state.reviews[key(pr)] = res.review;
    renderReview(pr, res.review);
    toast("Review revised.");
  } catch(e){ toast("Revision failed: "+e.message, true); btn.disabled=false; btn.textContent="Request revision"; }
@ -279,8 +329,11 @@ async function postReview(pr){
 function escapeHtml(s){ return (s||"").replace(/[&<>"']/g, c=>({"&":"&amp;","<":"&lt;",">":"&gt;",'"':"&quot;","'":"&#39;"}[c])); }
 function mdInline(s){ return escapeHtml(s).replace(/`([^`]+)`/g, '<code>$1</code>'); }

-document.getElementById("refreshBtn").onclick = refresh;
+document.getElementById("refreshBtn").onclick = refreshNow;
 loadConfig();
+loadMe();
+poll();
+setInterval(poll, state.pollMs);
 </script>
 </body>
 </html>
--- a/tests/test_endpoints.py
+++ b/tests/test_endpoints.py
@ -7,6 +7,7 @@ already-installed httpx2, so no extra test deps.

 from __future__ import annotations

+import json
 from typing import Any

 import pytest
@ -14,6 +15,7 @@ from fastapi.testclient import TestClient

 from app import main as main_mod
 from app.github_client import GitHubError
+from app.store import ReviewStore


@pytest.fixture
@ -203,3 +205,71 @@ def test_api_post_github_error_maps_to_400(client: TestClient, monkeypatch) -> N
    )
    assert r.status_code == 400
    assert "Invalid event" in r.json()["detail"]
+
+
+# --------------------------------------------------------------------------- #
+# /api/reviews and /api/refresh (background-worker cache)
+# --------------------------------------------------------------------------- #
+
+
+def test_api_reviews_returns_cached(client: TestClient, monkeypatch, tmp_path) -> None:
+    s = ReviewStore(str(tmp_path / "cache.db"))
+    s.upsert(
+        "o",
+        "r",
+        1,
+        status="ready",
+        review_json=json.dumps({"summary": "hi"}),
+        pr_title="t",
+        pr_author="a",
+        pr_url="u",
+        pr_updated_at="2026-01-01",
+    )
+    monkeypatch.setattr(main_mod, "_store", s)
+    r = client.get("/api/reviews")
+    assert r.status_code == 200
+    data = r.json()
+    assert data["poll_interval"] > 0
+    item = data["reviews"][0]
+    assert item["status"] == "ready"
+    assert item["review"]["summary"] == "hi"
+
+
+def test_api_reviews_503_without_store(client: TestClient, monkeypatch) -> None:
+    monkeypatch.setattr(main_mod, "_store", None)
+    assert client.get("/api/reviews").status_code == 503
+
+
+def test_api_refresh_triggers_worker(client: TestClient, monkeypatch) -> None:
+    class FakeWorker:
+        def __init__(self) -> None:
+            self.triggered = False
+
+        def trigger(self) -> None:
+            self.triggered = True
+
+    w = FakeWorker()
+    monkeypatch.setattr(main_mod, "_worker", w)
+    r = client.post("/api/refresh")
+    assert r.status_code == 202
+    assert r.json()["scheduled"] is True
+    assert w.triggered is True
+
+
+def test_api_refresh_503_without_worker(client: TestClient, monkeypatch) -> None:
+    monkeypatch.setattr(main_mod, "_worker", None)
+    assert client.post("/api/refresh").status_code == 503
+
+
+def test_api_review_writes_through_to_cache(
+    client: TestClient, monkeypatch, tmp_path
+) -> None:
+    s = ReviewStore(str(tmp_path / "cache.db"))
+    monkeypatch.setattr(main_mod, "_store", s)
+    _patch(monkeypatch, gh=FakeGH(), reviewer=FakeReviewer())
+    r = client.post("/api/review", json=_review_body())
+    assert r.status_code == 200
+    row = s.get("o", "r", 1)
+    assert row is not None
+    assert row["status"] == "ready"
+    assert json.loads(row["review_json"])["summary"] == "ok"
--- a/tests/test_store.py
+++ b/tests/test_store.py
@ -0,0 +1,93 @@
+"""Tests for the SQLite review cache (stdlib sqlite3, temp DB per test)."""
+
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from app.store import ReviewStore
+
+
+@pytest.fixture
+def store(tmp_path) -> ReviewStore:
+    return ReviewStore(str(tmp_path / "cache.db"))
+
+
+def test_upsert_insert_then_get(store: ReviewStore) -> None:
+    store.upsert(
+        "o",
+        "r",
+        1,
+        status="ready",
+        diff_hash="abc",
+        review_json=json.dumps({"summary": "hi"}),
+        pr_title="Title",
+        pr_author="octocat",
+        pr_url="https://x/1",
+        pr_updated_at="2026-01-01",
+    )
+    row = store.get("o", "r", 1)
+    assert row is not None
+    assert row["status"] == "ready"
+    assert row["diff_hash"] == "abc"
+    assert row["pr_title"] == "Title"
+    assert json.loads(row["review_json"])["summary"] == "hi"
+    assert row["cached_at"] > 0
+
+
+def test_get_missing_returns_none(store: ReviewStore) -> None:
+    assert store.get("o", "r", 999) is None
+
+
+def test_update_preserves_unspecified_columns(store: ReviewStore) -> None:
+    store.upsert("o", "r", 1, status="ready", diff_hash="h1", review_json="{}")
+    # Update only status; diff_hash and review_json must survive.
+    store.upsert("o", "r", 1, status="reviewing")
+    row = store.get("o", "r", 1)
+    assert row["status"] == "reviewing"
+    assert row["diff_hash"] == "h1"
+    assert row["review_json"] == "{}"
+
+
+def test_unknown_column_raises(store: ReviewStore) -> None:
+    with pytest.raises(ValueError, match="unknown review columns"):
+        store.upsert("o", "r", 1, status="ready", bogus="x")
+
+
+def test_list_orders_and_filters_closed(store: ReviewStore) -> None:
+    store.upsert("o", "r", 1, status="ready", pr_updated_at="2026-01-01")
+    store.upsert(
+        "o", "r", 2, status="closed", pr_updated_at="2026-02-02", closed_at=1.0
+    )
+    all_rows = store.list()
+    assert [r["number"] for r in all_rows] == [2, 1]  # updated_at desc
+    open_rows = store.list(include_closed=False)
+    assert [r["number"] for r in open_rows] == [1]
+
+
+def test_reset_stale_reviewing(store: ReviewStore) -> None:
+    store.upsert("o", "r", 1, status="reviewing")
+    store.upsert("o", "r", 2, status="ready")
+    n = store.reset_stale_reviewing()
+    assert n == 1
+    assert store.get("o", "r", 1)["status"] == "error"
+    assert store.get("o", "r", 1)["error"] == "interrupted"
+    assert store.get("o", "r", 2)["status"] == "ready"
+
+
+def test_mark_missing_closed_and_purge(store: ReviewStore) -> None:
+    store.upsert("o", "r", 1, status="ready")
+    store.upsert("o", "r", 2, status="ready")
+    # Only PR 1 is still live; PR 2 should be closed.
+    store.mark_missing_closed({("o", "r", 1)})
+    assert store.get("o", "r", 1)["status"] == "ready"
+    closed = store.get("o", "r", 2)
+    assert closed["status"] == "closed"
+    assert closed["closed_at"] is not None
+
+    # A long grace keeps it; a zero grace purges it.
+    assert store.purge_closed(older_than_seconds=10_000) == 0
+    assert store.get("o", "r", 2) is not None
+    assert store.purge_closed(older_than_seconds=0) == 1
+    assert store.get("o", "r", 2) is None
--- a/tests/test_worker.py
+++ b/tests/test_worker.py
@ -0,0 +1,180 @@
+"""Tests for the auto-review worker's run_cycle and backoff (no network).
+
+Uses a real ReviewStore on a temp DB plus fake GitHub/reviewer objects, and
+drives run_cycle directly (its deps are injected, so no thread/timer needed).
+"""
+
+from __future__ import annotations
+
+import json
+from types import SimpleNamespace
+
+import pytest
+
+from app.store import ReviewStore
+from app.worker import _review_with_backoff, run_cycle
+
+
+class FakeGH:
+    def __init__(self, prs: list[dict], diffs: dict[int, str]) -> None:
+        self.prs = prs
+        self.diffs = diffs
+
+    def search_prs(self) -> list[dict]:
+        return [dict(p) for p in self.prs]  # copy: mimic a fresh fetch
+
+    def pr_diff(self, owner: str, repo: str, number: int) -> str:
+        return self.diffs[number]
+
+
+class CountingReviewer:
+    def __init__(self) -> None:
+        self.calls = 0
+
+    def review(self, pr: dict, diff: str) -> dict:
+        self.calls += 1
+        return {"summary": f"review {pr['number']}", "recommended_event": "COMMENT"}
+
+
+def _pr(number: int, *, updated_at: str, draft: bool = False) -> dict:
+    return {
+        "owner": "o",
+        "repo": "r",
+        "number": number,
+        "title": f"PR {number}",
+        "author": "octocat",
+        "url": f"https://x/{number}",
+        "updated_at": updated_at,
+        "draft": draft,
+    }
+
+
+@pytest.fixture
+def store(tmp_path) -> ReviewStore:
+    return ReviewStore(str(tmp_path / "cache.db"))
+
+
+def test_reviews_nondraft_skips_draft(store: ReviewStore) -> None:
+    gh = FakeGH(
+        [_pr(1, updated_at="d1"), _pr(2, updated_at="d1", draft=True)],
+        {1: "diff-1", 2: "diff-2"},
+    )
+    rev = CountingReviewer()
+    res = run_cycle(gh, rev, store, concurrency=1)
+
+    assert res["reviewed"] == 1
+    assert rev.calls == 1
+    row = store.get("o", "r", 1)
+    assert row["status"] == "ready"
+    assert json.loads(row["review_json"])["summary"] == "review 1"
+    assert store.get("o", "r", 2) is None  # draft never touched
+
+
+def test_cheap_gate_skips_unchanged_updated_at(store: ReviewStore) -> None:
+    gh = FakeGH([_pr(1, updated_at="v1")], {1: "diff-1"})
+    rev = CountingReviewer()
+    run_cycle(gh, rev, store, concurrency=1)
+    res2 = run_cycle(gh, rev, store, concurrency=1)
+
+    assert res2["reviewed"] == 0
+    assert res2["skipped"] == 1
+    assert rev.calls == 1  # not re-reviewed, and no diff even compared
+
+
+def test_precise_gate_skips_when_diff_unchanged(store: ReviewStore) -> None:
+    gh = FakeGH([_pr(1, updated_at="v1")], {1: "diff-1"})
+    rev = CountingReviewer()
+    run_cycle(gh, rev, store, concurrency=1)
+
+    # updated_at bumped (e.g. a comment) but the diff is identical.
+    gh.prs[0]["updated_at"] = "v2"
+    res = run_cycle(gh, rev, store, concurrency=1)
+
+    assert res["unchanged"] == 1
+    assert rev.calls == 1  # LLM not called again
+    assert store.get("o", "r", 1)["pr_updated_at"] == "v2"  # metadata refreshed
+
+
+def test_changed_diff_triggers_rereview(store: ReviewStore) -> None:
+    gh = FakeGH([_pr(1, updated_at="v1")], {1: "diff-1"})
+    rev = CountingReviewer()
+    run_cycle(gh, rev, store, concurrency=1)
+
+    gh.prs[0]["updated_at"] = "v2"
+    gh.diffs[1] = "diff-1-CHANGED"
+    res = run_cycle(gh, rev, store, concurrency=1)
+
+    assert res["reviewed"] == 1
+    assert rev.calls == 2
+
+
+def test_error_stored_and_attempts_capped(store: ReviewStore) -> None:
+    class BoomReviewer:
+        def review(self, pr, diff):
+            raise ValueError("fireworks exploded")
+
+    gh = FakeGH([_pr(1, updated_at="v1")], {1: "diff-1"})
+    rev = BoomReviewer()
+
+    r1 = run_cycle(gh, rev, store, concurrency=1, max_attempts=2)
+    assert r1["error"] == 1
+    assert store.get("o", "r", 1)["status"] == "error"
+    assert store.get("o", "r", 1)["attempts"] == 1
+
+    run_cycle(gh, rev, store, concurrency=1, max_attempts=2)
+    assert store.get("o", "r", 1)["attempts"] == 2
+
+    # attempts now >= max and updated_at unchanged -> stop retrying
+    r3 = run_cycle(gh, rev, store, concurrency=1, max_attempts=2)
+    assert r3["skipped"] == 1
+    assert r3["error"] == 0
+    assert store.get("o", "r", 1)["attempts"] == 2
+
+
+def test_departed_pr_is_closed(store: ReviewStore) -> None:
+    gh = FakeGH([_pr(1, updated_at="v1")], {1: "diff-1"})
+    rev = CountingReviewer()
+    run_cycle(gh, rev, store, concurrency=1)
+
+    gh.prs = []  # PR merged/closed, no longer in the queue
+    run_cycle(gh, rev, store, concurrency=1)
+    assert store.get("o", "r", 1)["status"] == "closed"
+
+
+# --- backoff helper --------------------------------------------------------- #
+
+
+def _http_error(status: int) -> Exception:
+    e = Exception(f"HTTP {status}")
+    e.response = SimpleNamespace(status_code=status)
+    return e
+
+
+def test_backoff_retries_on_429_then_succeeds() -> None:
+    class Flaky:
+        def __init__(self) -> None:
+            self.n = 0
+
+        def review(self, pr, diff):
+            self.n += 1
+            if self.n < 3:
+                raise _http_error(429)
+            return {"summary": "ok"}
+
+    sleeps: list[float] = []
+    out = _review_with_backoff(
+        Flaky(), {}, "d", retries=3, base=0.01, sleep=sleeps.append
+    )
+    assert out["summary"] == "ok"
+    assert len(sleeps) == 2  # two 429s -> two backoffs
+
+
+def test_backoff_does_not_retry_non_429() -> None:
+    class Boom:
+        def review(self, pr, diff):
+            raise ValueError("nope")
+
+    sleeps: list[float] = []
+    with pytest.raises(ValueError):
+        _review_with_backoff(Boom(), {}, "d", retries=3, sleep=sleeps.append)
+    assert sleeps == []  # non-429 fails fast