docs(adr): ADR-033 upload audio -> private Swedish transcript -> chat (#33)

Proposed, decider pending. Supersedes ADR-007's STT deferral for
user-supplied audio only; the YouTube audio-download rejection stands.
Settles #28 decision 1 as a separate RLS-scoped uploaded_transcripts table
and records the measured length ceiling, the ingress 413, and the 18k-char
chat truncation that #33 assumed did not exist. Two DECISION NEEDED items
(ffmpeg in the runtime image; berget fallback for private audio).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

DECISIONS.md

@@ -123,7 +123,9 @@ secret surface (see VISION Stage 2); it gets the existing, vetted secret path.
 ## ADR-007 — Captions-first; audio-download + speech-to-text deferred
 
 **Status:** Accepted (2026-06-02). Acquisition mechanism superseded by ADR-010 (Data API
-`captions.download` → player/timedtext baseUrl); captions-first stance and STT deferral stand.
+`captions.download` → player/timedtext baseUrl); captions-first stance and STT deferral stand
+**for YouTube**. STT deferral superseded **for user-supplied audio only** by ADR-033; the
+YouTube audio-download rejection is unchanged.
 
 **Context.** YouTube's Data API does not expose transcripts. Options: official captions
 (clean, limited coverage) vs. audio download + local Whisper (broad coverage, ToS-grey,
@@ -1314,6 +1316,191 @@ roll back. No schema, no structural change.
 
 ---
 
+## ADR-033 — Upload audio, get a private Swedish transcript, discuss it (user-supplied STT)
+
+**Status:** Proposed (2026-10-01). **Decider: Mathias — pending.** Issue #33 (audio-only subset of
+#28). **Supersedes ADR-007's speech-to-text deferral for user-supplied audio only.** The
+YouTube audio-download rejection in ADR-007 **stands untouched**. Builds on ADR-012 (isolation),
+ADR-018 (single replica), ADR-021 (**the constraint**), ADR-022 (endpoint chain), ADR-025
+(honest status), ADR-027 (chat). ADR-014 item 4 ("Whisper reconsideration is a future ADR,
+gated on caption data") is a different question — whether to transcribe YouTube videos with no
+captions — and this ADR does not answer it. Measurements: `docs/research/audio-length-ceiling-2026-10-01.md`.
+
+**Context.** The maintainer has a concrete need: a Swedish Teams voice-only export, 30–90
+minutes, to upload and then *discuss* (what was decided, what is open, who owes what). Every
+piece exists — a Whisper endpoint on the gateway (infra#274), chat-with-transcript (ADR-027) —
+and nothing connects them.
+
+ADR-007 deferred STT for three reasons: yt-dlp fragility, ToS-grey scraping, and GPU contention
+with the JEPA PoC. Upload-STT shares **none** of them: the user owns the file, nothing is
+scraped, there is no caption rate gate, and the contention moved from koala to iguana. What it
+does share is landing Whisper in the codebase, which ADR-007 deferred — so a new ADR is required,
+and ADR-017's process note records the one time a guardrail-reversing change shipped without one.
+
+**The constraint that shapes everything.** ADR-021 made `transcripts` a shared, **non-RLS**
+table on the explicit grounds that it holds only public caption content and nothing
+user-identifying. A recorded internal meeting is the opposite: private third-party content owned
+by one user. The existing isolation test asserts `transcripts` *is* non-RLS, so a naive reuse
+would leak across tenants **and pass CI green**.
+
+**What was measured, not argued** (research doc above):
+- **No transcription ceiling up to 90 minutes.** One 174 MB request through the LiteLLM NodePort
+  took 440 s (~12× realtime). The first failure is the public ingress `llm-api.d-ma.be`
+  returning `413` above roughly 8–10 MB (~5 min of WAV) — not whisper, and not a Metal OOM.
+  The 8:20 failure recorded in #33 is consistent with that cap.
+- **`response_format=srt` survives LiteLLM, wrapped** in a JSON envelope (`{"text": "<srt>"}`).
+- **The two backends differ.** `iguana/kb-whisper` returns whole-second segments;
+  `berget/kb-whisper` returns sub-second times and a different `language` token.
+- **The existing chat path truncates at 18,000 chars (~22 min of speech), keeping the head.**
+  #33 assumed chat "retrieves rather than generates" and so has no length ceiling. It does
+  not retrieve; it stuffs the transcript into the prompt and cuts the tail.
+
+**Unknowns, stated.** Real-speech accuracy; compressed-input behaviour; concurrent long jobs on
+iguana; whether the models chat offers can hold an hour of Swedish (~50 k chars); and the Metal
+OOM, deliberately not provoked.
+
+**Decision.**
+
+1. **Audio only; transcript is the only thing kept.** An authenticated user uploads an audio
+   file; Tapir transcribes it and stores the transcript. The audio itself is deleted after
+   transcription (temp file, removed in a `defer`, swept at start-up) — no custody problem to
+   solve, and nothing to hand to #31. Video is rejected with a message naming #28. YouTube
+   audio-download stays rejected. No public/anonymous upload (ADR-008).
+
+2. **Private store: a separate RLS-scoped table, `uploaded_transcripts`** (resolves #28's
+   decision 1). `user_id NOT NULL REFERENCES users ON DELETE CASCADE`, `ENABLE` + `FORCE ROW LEVEL
+   SECURITY`, the same `tapir.current_user_id` policy as every other user-owned table. It carries
+   the transcript text and its timestamped segments (re-transcribing 90 minutes costs ~7
+   minutes; discarding the timestamps is irreversible), `status`, the `endpoint` that served
+   it, `audio_seconds`, and a typed `error_kind`. **Not** a `user_id` column on `transcripts`
+   with a partial policy, even though that would reuse more code: ADR-021's exception is
+   precisely that *that table holds no private row*, the isolation test asserts it has no
+   `user_id`, and a partial policy would turn "single exception" into "single exception, with a
+   private lane inside it" — the shape under which a future query drops the policy clause and
+   leaks. Two tables keep both boundaries independently assertable.
+
+3. **The isolation test asserts both boundaries and the set.** (a) User A cannot read, update or
+   delete user B's uploaded transcript; no GUC set → deny-all. (b) `transcripts` is still
+   non-RLS with no `user_id`. (c) **The set of public-schema tables with row security off is
+   asserted exactly** — so a new table added without RLS fails CI instead of passing it. (c) is
+   new; the existing test only checks the named tables.
+
+4. **Validate by probing, reject clearly.** Format and duration cannot be read from a filename
+   or MIME type — a Teams "voice-only" recording is typically an `.mp4` container with no video
+   stream, which is indistinguishable from video by extension. The upload is probed
+   (`ffprobe`): accept any container with an audio stream and **no** video stream; reject video
+   with "video is #28"; reject unreadable files. Limits, all configurable, all rejected
+   synchronously with a specific message rather than by timeout: **200 MB** upload and
+   **90 minutes** duration. 90 minutes is *the longest length measured*, not a ceiling that was
+   found; raising it is a measurement, not an edit.
+
+5. **Transcode server-side, always, to 16 kHz mono PCM WAV** — even when the input already is,
+   rather than assuming. whisper-server's `--convert` is rejected (its `--tmp-dir` is created at
+   process start and rots under macOS periodic cleanup). The transcoder sits behind a port; the
+   tests use a fake. **This puts `ffmpeg` and `ffprobe` in the runtime image**, which is
+   distroless-static today. **Provisional: copy static ffmpeg/ffprobe binaries into the existing
+   distroless image** (no shell, no package manager retained). This is a heavy new dependency
+   and is **the maintainer's call** — see Open items.
+
+6. **Transcription adapter via the gateway, never the public hostname.** A `Transcriber` port;
+   the implementation calls `POST {TAPIR_GATEWAY_URL}/audio/transcriptions` where the gateway
+   URL is the in-cluster NodePort (`koala:30401/v1`). Primary `iguana/kb-whisper`, fallback
+   `berget/kb-whisper` (immune to iguana contention, which can wedge permanently — infra#273).
+   - **Fallback triggers on any primary failure** (transport error, timeout, non-2xx). It never
+     branches on the body: `{"error":"failed to process audio"}` has had at least five distinct
+     causes.
+   - **`response_format=verbose_json`**, normalised to one segment shape: times clamped to the
+     audio duration (the final segment can end past it), one language token. Not `srt`: the
+     envelope adds a parse step and iguana's segment timing is the same either way.
+   - **No chunking in v1.** Nothing failed to 90 minutes (measured). Chunk-and-stitch is the
+     answer *if* the cap is raised or smaller requests become necessary — see triggers.
+   - **The serving endpoint is recorded per row**, and surfaced, because the two backends
+     differ in timestamp granularity: which one served a transcript is a quality fact.
+   - **Berget is a cloud endpoint.** On fallback the audio of a private meeting leaves the
+     homelab. #33 asks for this fallback; it is configurable (`TAPIR_TRANSCRIBE_FALLBACK_MODEL`,
+     empty disables), recorded per row, and called out in Open items rather than defaulted
+     silently.
+   - Swedish only (`language=sv`). Language detection and routing (#28 decision 2) are not
+     touched.
+   - `-H 'Expect:'`, multipart field `file` — encoded in the adapter and its tests, not rediscovered.
+
+7. **Jobs run in-process, one at a time (ADR-018 stands).** Transcription is minutes (~7.5 min
+   for 90) but a single goroutine behind a one-slot semaphore: two simultaneous 90-minute jobs on
+   iguana were not measured, so concurrency is 1 until they are. No worker, no new deployable,
+   no second replica. Honest status per ADR-025: `queued → transcribing → done | failed`, polled
+   by the same `/status` pattern, every terminal state a rendered card, never a stuck spinner.
+   Audio is not retained, so a restart mid-job **cannot resume**: at start-up any
+   `queued`/`transcribing` row is marked `failed` with `error_kind = interrupted`, and the user
+   re-uploads. The single-replica assumption gains a second dependent (the semaphore is
+   process-local) and is recorded here.
+
+8. **Chat reuses `chat.Service`; it is not forked.** The uploaded-transcript chat handlers
+   look the row up through the RLS-scoped store, so a non-owner gets 404 by the same mechanism
+   as ADR-027's summary gate. ADR-027's decisions (ephemeral, switchable models, trust-the-model)
+   carry over unchanged. **One thing must differ:** the 18,000-char default cuts a one-hour
+   meeting to its first third, so uploaded transcripts take their own cap,
+   `TAPIR_MAX_UPLOADED_TRANSCRIPT_CHARS`. **Provisional default 120,000 chars (~2.4 h at
+   measured density)**, with the existing `Truncated` flag surfaced honestly. The default is a
+   guess until the chat slice measures what the offered models actually accept; it is not
+   evidence that they can.
+
+9. **Not decided here.** Rich `AVSNITT`/`ALTERNATIV` analysis (gated on #30 — `analyze_srt.py`
+   hardcodes `max_tokens: 6000`); video, keyframes, synced playback (#28); language detection;
+   per-transcript deletion UX (account deletion cascades; see Open items); retention of audio.
+
+**On the sequencing question #28 asks of itself** — *is this the thing that best serves the
+Stage-0 gate, or the most interesting thing to build?* Recorded answer: it proceeds **ahead of
+#32** (the demand test) as the maintainer's explicit, knowing call (#28, comment of 2026-10-01),
+on a concrete need rather than speculation. It is not a return-nudge (ADR-020/027): it adds
+nothing that prompts a user to come back, so it does not contaminate the unprompted-return signal
+ADR-016 measures. The honest risk is the one ADR-016 names: it is larger than anything ADR-020
+deferred. The scope cut — chat first, no rich analysis, no video — is what keeps it bounded.
+
+**Consequences.**
+- **Positive.** The user's request is met end to end with existing parts. ADR-021's exception stays
+  singular and now provably so. The measured ceiling removes chunking from v1. No audio is stored.
+- **Negative / watch.**
+  - Tapir's runtime image gains `ffmpeg`: a larger image and a new CVE surface to patch.
+  - iguana becomes load-bearing for a user-facing feature (#28 decision 3; infra#273 is still the
+    dependency that matters) — a Metal OOM now means *every upload fails over to berget*, i.e.
+    private audio leaving the homelab, silently unless the per-row endpoint is surfaced.
+  - A 90-minute job holds the single slot for ~7.5 minutes; a second user's upload queues behind it.
+  - Chat over a long transcript is bounded by model context, not by anything in Tapir.
+  - Tapir's own ingress body limit for a 200 MB upload is **unverified** (it lives in `infra`).
+
+**Validation / resolution triggers** (each observable by someone other than the author):
+- *Chunking*: build it when the duration cap is raised above 90 min, or when a measured
+  request at the current cap fails with whisper-side (not ingress) errors.
+- *Berget-first*: if more than a quarter of uploads in any week are served by the fallback,
+  swap the primary/fallback order and revisit infra#273.
+- *Retrieval chat*: if the chat slice finds an offered model cannot answer a question whose
+  answer is in the last third of a 60-minute transcript, chunked retrieval replaces the larger cap.
+- *Worker*: if a transcription job ever degrades the reading UI, or Tapir runs more than one
+  replica, ADR-018 is revisited.
+- *The decision itself*: if the maintainer has not used the feature unprompted within the
+  ADR-016 window, it was the interesting thing, not the useful one — remove it.
+
+**Open items this ADR creates.**
+- **DECISION NEEDED — ffmpeg in the runtime image.** *Options:* (A) static ffmpeg/ffprobe copied
+  into distroless **(recommended — the only option that satisfies "accept m4a/mp3/opus/mp4,
+  validate duration, reject video"; pure-Go decoders cover wav/mp3 only)**; (B) accept WAV
+  only, convert client-side (fails "I just want to upload it"); (C) a transcode sidecar
+  (second deployable, ADR-018's reasoning against). *Blocks:* the Dockerfile slice, not the
+  tests, which use the port.
+- **DECISION NEEDED — berget fallback for private audio.** *Options:* (A) enabled by default as
+  #33 specifies, with the serving endpoint shown **(recommended, matches the issue)**; (B)
+  disabled by default, a failed iguana job fails honestly and the user retries. *Blocks:*
+  the production default only; the adapter ships either way.
+- Verify Tapir's ingress `proxy-body-size` against the 200 MB cap (`infra`).
+- Per-transcript deletion is not built; account deletion cascades. A private-content store
+  without a delete button is a gap worth a ticket, not a silent omission.
+
+**Reversibility.** Additive: one table (down-migration drops it), one adapter, one upload
+surface, one image change. Removing the upload route removes the feature; `transcripts`, `videos`
+and ADR-021 are untouched.
+
+---
+
 ## Rejected alternatives
 
 Approaches considered during the 2026-06-02 planning + grill session and **deliberately not
@@ -1338,6 +1525,9 @@ maps to the ADR that settles it.
 | Reverse the Dex-write invite flow (Google OIDC only) | Some intended Future-B users won't use Google; OIDC-only leaves them with no onboarding path — invite flow is load-bearing | ADR-017 |
 | k8s CronJob for scheduled discovery (vs in-process) | At Future-B scale the in-process scheduler is simpler to deploy; CronJob's failure-isolation benefit was weighed and traded away knowingly (revisit if >1 replica or load grows) | ADR-018 |
 | Cached-transcript-first onboarding burst (instant, zero-fetch picks) | Live pilot DB: ~3% cross-user video overlap, 0 cached-and-unsummarized, a new user's newest-20 are 20/20 uncached — newest-first and cached-first are structurally incompatible. Empty lever at pilot scale | ADR-028 |
+| Uploaded transcripts as a `user_id` column + partial RLS policy on `transcripts` | Turns ADR-021's single exception into an exception with a private lane inside it; the isolation test asserts `transcripts` has no `user_id`. A separate RLS table keeps both boundaries independently assertable | ADR-033 |
+| whisper-server `--convert` for server-side transcode | Its `--tmp-dir` is created at process start and rots under macOS periodic cleanup | ADR-033 |
+| Calling the public `llm-api.d-ma.be` from in-cluster Tapir | Its ingress returns 413 above ~8–10 MB (~5 min of WAV); the NodePort has no such cap | ADR-033 |
 
 If a future case genuinely reopens one of these, that's a new ADR superseding the relevant one —
 not a silent reversal.

docs/research/audio-length-ceiling-2026-10-01.md

@@ -0,0 +1,110 @@
+# Audio length ceiling — measured before designing chunking (tapir#33, 2026-10-01)
+
+Question (#33, "the main technical risk"): at what recording length does Swedish
+transcription through the LiteLLM gateway first fail, and with what failure mode?
+Measured **before** any chunking design, with iguana not holding a large ollama model,
+so the result is the ceiling and not the Metal OOM of infra#273.
+
+## Answer
+
+**No transcription ceiling was found at or below 90 minutes.** A single request carrying
+90 minutes of 16 kHz mono PCM (174 MB) transcribed in one pass in 440 s. The first thing
+that actually fails is **not whisper**: it is the public gateway ingress, which rejects the
+upload with `413` at roughly 5.5 minutes of WAV.
+
+| Route | First failure | Failure mode |
+|---|---|---|
+| `https://llm-api.d-ma.be` (openresty ingress) | between 8.0 MB and 10.5 MB body (~4–5.5 min of WAV) | `413 Request Entity Too Large`, HTML body from `openresty`, returned instantly |
+| `http://koala:30401` (LiteLLM NodePort) → `iguana/kb-whisper` | **none up to 90 min / 174 MB** | — |
+| `http://koala:30401` → `berget/kb-whisper` | **none up to 22 min / 42 MB** (largest tried) | — |
+
+The ingress limit is the reason the 8:20 / 15 MB recording in #33 "failed repeatedly" and a
+30-second slice succeeded. That failure was attributed to a Metal OOM; at least in the
+size-dependent form described, a body-size cap explains it without one. (The OOM
+mechanism in infra#273 is separately real; this run did not provoke it.)
+
+The exact ingress cap was bracketed (8.0 MB passed, 10.5 MB failed), not read from the
+ingress configuration, which lives in `infra`. "About 10 MB" is an inference.
+
+## Method
+
+- **Audio.** No known-good Swedish recording is available that is safe to use: the only real
+  one (`IMG_1233.wav`) is the private `/bygge` recording (#31 custody still open) and was
+  deliberately not touched. Instead: macOS `say -v Alva` (Swedish) on iguana, a 1,171-char
+  five-paragraph meeting script → 82.5 s of 16 kHz mono PCM WAV (`ffmpeg -ar 16000 -ac 1`).
+  Concatenated ×4, ×8, ×16, ×32, ×44, ×66 with Python `wave` (the issue's own recipe).
+  Nothing here is a real transcript; none of it is committed.
+- **Request.** `POST /v1/audio/transcriptions`, multipart `file=`, `model=iguana/kb-whisper`,
+  `response_format=verbose_json`, `-H 'Expect:'` (per #33's traps), master key supplied only
+  through `op run` and never on argv.
+- **Confound control.** `ollama /api/ps` on iguana was read before every step. Resident:
+  nothing, or `nomic-embed-text` (0.37 GB). Never a large model.
+
+## Results (`iguana/kb-whisper`, NodePort)
+
+| Audio | WAV size | HTTP | Wall | Realtime factor | Segments | Chars |
+|---|---|---|---|---|---|---|
+| 0:30 | 0.96 MB | 200 | 2.8 s | 11× | — | — |
+| 2:30 / 3:20 / 4:10 | 4.8 / 6.4 / 8.0 MB | 200 (ingress) | 12.9 / 16.0 / 19.9 s | 12× | — | — |
+| 5:30 (×4) | 10.5 MB | **413 ingress**, 200 NodePort in 27 s | 27 s | 12× | 121 | 4,557 |
+| 11:00 (×8) | 21.1 MB | 200 | 53 s | 12× | 241 | 9,094 |
+| 22:00 (×16) | 42.3 MB | 200 | 105 s | 13× | 482 | 18,201 |
+| 44:01 (×32) | 84.5 MB | 200 | 209 s | 13× | 966 | 36,438 |
+| 60:32 (×44) | 116.2 MB | 200 | 291 s | 12× | 1,332 | 50,145 |
+| 90:48 (×66) | 174.3 MB | 200 | 440 s | 12× | 2,005 | 75,165 |
+
+- Throughput is flat at ~12× realtime. 90 minutes costs ~7.5 minutes of wall time. This is
+  a minutes-long job, not a request/response one (see ADR-033 on ADR-018).
+- Segments per source repetition stay at 30.1–30.4 from ×4 to ×66, and segment times are
+  monotonic with `last_end` within 0.2 s of `duration`. No drift and no repetition-loop
+  hallucination appeared across 90 minutes. This is a weak check — the input is a repeated
+  loop and synthetic voice — not evidence of accuracy.
+- **Only `iguana/kb-whisper`'s `x4` run reported `last_end` 360.0 s against `duration`
+  330.2 s.** Whisper's final segment can end past the audio; clamp to `duration`.
+
+## Findings that change the design
+
+1. **Use the NodePort route, not the public hostname.** Tapir runs in-cluster beside the
+   gateway; `llm-api.d-ma.be` is the external door and has a body cap. #33 said "use the
+   gateway, never the host" and named the public URL; the gateway is right, that URL is not.
+   `TAPIR_GATEWAY_URL` already points at `koala:30401/v1`.
+2. **`response_format=srt` survives the LiteLLM hop, but wrapped.** The response is JSON
+   `{"text": "<the SRT>", "usage": …}`, not a bare SRT body — a client that parses the body
+   as SRT gets a parse error on `{`. #33 question 2 is answered: it passes through, inside
+   an envelope.
+3. **The two backends return different timestamp granularity.** `iguana/kb-whisper`
+   segments are **whole seconds** (`0→1`, `1→4`, `4→7`); `berget/kb-whisper` returns real
+   sub-second times (`0.051→1.192`) and a different `language` token (`swedish` vs `sv`).
+   `verbose_json` and the default JSON were byte-identical on iguana. An adapter that
+   falls back between the two must normalise both, and "which endpoint served this" is
+   a quality fact, not just a log line.
+4. **The existing chat path cannot answer about most of a long recording.** At
+   828 chars/min (this fixture; real speech is plausibly a little denser),
+   `TAPIR_MAX_TRANSCRIPT_CHARS`'s default of **18,000** is ~21.7 minutes. A 60-minute
+   transcript is 50 k chars, a 90-minute one 75 k. `chat.Service` truncates by keeping
+   the head (`internal/adapters/chat/chat.go`), so questions about the last two-thirds of
+   a one-hour meeting get an answer from a transcript that does not contain it. #33 says
+   chat "retrieves rather than generates" and therefore has no ceiling; it **stuffs and
+   truncates**, and its ceiling is the model context. See ADR-033.
+5. **Chunking is not needed for v1 on length.** Nothing failed up to 90 minutes. The
+   chunking-and-stitching recipe in #33 (offset timestamps, renumber cues, strip `\r`) is
+   not built. It stays the answer *if* a longer cap is wanted or the OOM mechanism forces
+   smaller requests — see ADR-033's resolution triggers.
+
+## What this did not measure
+
+- **Metal OOM under contention.** Deliberately avoided. A big resident ollama model
+  during a long transcription is still the known way to wedge iguana permanently.
+- **Real speech.** TTS is clean, single-voice, no crosstalk or room noise. WER and
+  speaker overlap in a Teams export are untested. Speed is probably representative;
+  accuracy is not claimed.
+- **Compressed input.** Only WAV was sent. Whether `m4a`/`mp3`/`opus` can reach whisper
+  without a server-side transcode is not established here (ADR-033 treats it as needing one).
+- **Concurrency.** One request at a time. Two simultaneous 90-minute jobs on iguana were
+  not tried.
+- **`berget/kb-whisper` beyond 22 min / 42 MB.** Enough to know the fallback is not
+  size-capped at meeting length for 22 minutes; not proven at 90.
+- **Time-of-day / other tenants.** One afternoon, one run per length.
+
+Scripts were throwaway shell/Python in a session scratchpad and are not committed; the
+method above reproduces them.