peter
3709b71a94
`add_pin`'s IntegrityError handler assumed the unique constraint was the only way in and re-raised otherwise, so a target row pruned between `resolve_ref` confirming it and the INSERT (a Plex sync dropping a removed item) tripped the FK and handed the user a 500. Semantically that is the same "no such thing" the pre-check already returns. Untested: the race needs two concurrent transactions. The five per-kind unique constraints had no test at all — the route's own dedupe returns before reaching the DB, and the migration drift check filters constraint diffs out as noise, so they could go missing with every lane green. Frontend, all from the same review: the shelf's unpin row is now `danger` like every other destructive row in the app; the hero's artwork button says what it will actually do and names the item instead of always announcing "Play"; the empty-budget message offers a reroll rather than `StateMessage`'s "Retry", which promised a re-run of something that had not failed; `setState` and the watch-later toggle catch their rejections instead of leaving an unhandled promise and a click that silently does nothing. `StateMessage` gained a `compact` rung, which retires the frontend's only two `!important` overrides — they existed to beat the primitive's own padding from the call site, and were the copyable idiom for the next surface that wanted a compact empty state. Dead vocabulary removed or made load-bearing: `DISCOVER_BUDGETS` was exported, re-exported and consumed by nothing while `Home.tsx` re-typed the same four bands (a `readonly DiscoverBudget[]` accepts any subset, so a fifth band would have typechecked green and rendered no chip); `PIN_KINDS`' value export had no consumer at all; `useComfortPin` no longer publishes `pinIdOf`/`toggle`, which nothing outside the module calls. Three comments corrected against the code they describe: a pointer to a `resolve.py` that was never written, the file header's claim that Home defines no card component of its own, and the `seen` window still quoting the 8 that was measured and abandoned for 32. The rest of the review's survivors are logged on ROADMAP.md under "Deferred — E24 epic-end deep-review (2026-09-08)" — the ones whose dissent was substantive, and the ones whose fix is wider than the finding.
Backend conventions
The rules below are already followed across backend/app — they lived only in a few module
docstrings (demo.py, userscope.py, routes/_common.py) until this file collected them (E3 S3,
B-core-20). When you add code, match these so the next reader doesn't have to guess "which pattern do
I copy".
Module layering
Three layers, by who runs the code — not by feature:
-
routes/…— request-only. A route module holds HTTP concerns: auth dependencies, request/ response models, status-code mapping, serialization. It owns logic that runs only on a request. Business logic that a request happens to trigger does not live here if anything else runs it too. -
plex/,downloads/,sync/— domain logic shared by more than one caller. Anything the scheduler or the worker runs (not just a request) lives in one of these domain packages, so the route, the worker, and the scheduler share one definition. Examples from this codebase:downloads/service.pyowns enqueue + the job state transitions (routes call it);plex/sync.pyis run by both the admin route and the scheduler;downloads/pipeline.pyis the worker's child pipeline. -
Flat
app/*.pycore modules — cross-cutting primitives.auth,sysconfig,quota,audit,notifications,userscope,realtime,ratelimit,progress, … are single-file primitives many layers import. They depend on nothing above them (a core module must never import aroutes/…module).
Extraction trigger: the SECOND consumer. Keep new logic inline in its first caller. The moment a second caller needs it (a worker as well as a route; a scheduler as well as a route), extract it down a layer — into the relevant domain package, or a flat core module if it's cross-cutting. Don't pre-abstract for a single caller; don't leave shared logic duplicated once there are two.
Transaction ownership
This follows CLAUDE.md's canonical rule verbatim — "the handler/job-wrapper commits; helpers flush
(only quota owns its session)" — so read it that way, not as an exception to it. The commit belongs
to the operation owner; anything called inside another transaction only stages its change
(db.add / flush) and lets the owner commit, so the whole operation is one transaction.
audit.record() is the reference: it adds the audit row and the caller commits it together with the
mutation it records, so an audit entry can never exist without its change (or vice-versa).
- The operation owner is usually the route handler. A
service.*operation the handler delegates a whole transition to (e.g.service.cancel) is that owner and commits its one transition — it isn't a mid-operation helper. A helper that owns its OWN short-lived session (the worker'sjobdbwrites, the same carve-out CLAUDE.md grantsquota) commits that session. Everything else flushes. SessionLocalisexpire_on_commit=False: after a rawUPDATE+ commit, an ORM object you already loaded is stale. Read the fresh value from the row (RETURNING, or a re-SELECT), not the ORM attribute — seeservice.decr_ref_count.
Shared counters and status: do it atomically at the DB
- Never read-modify-write a shared counter in Python (
x.count = x.count + 1). Concurrent sessions lose an update. Use a DB-atomic statement —col = col + 1, orgreatest(col - 1, 0)withRETURNINGso the caller branches on the post-value under the row lock (service.incr_ref_count/decr_ref_count). - Download job status is a
JobStatusStrEnum (downloads/status.py), not bare strings. TheHOLDINGset defines which states hold aMediaAsset(so release accounting stays correct);STOPPED_BY_ROUTEis the route-initiated stop set. A worker child's terminal write goes throughservice.finalize_if_running(an atomicUPDATE … WHERE status='running') so a finishing child can't resurrect a job a route just stopped.
Config: one home per kind
app.config.settings— boot/env config (DB URL, download root, worker concurrency): read once at startup, not user-tunable at runtime.sysconfig.SPECS— the runtime admin knobs (DB-override-or-default). A new admin-tunable value goes inSPECS; don't invent a fourth store. (state.py'smaintenance_batchpredates this and is slated to fold intosysconfig— do not add more like it.)
The gate
Everything below must be green before a change is done (run via siftlode check):
ruff (backend) · tsc ×3 + eslint + prettier + knip (frontend) · vitest · pytest. The
pytest lane runs in backend/docker-compose.test.yml — an ephemeral Postgres + the backend tree
bind-mounted — so the DB-backed integration tests (the db fixture) actually run; SIFTLODE_TEST_ REQUIRE_DB=1 there turns a would-be silent skip into a hard failure. See docs/development.md.