Lab #4690: @swamp/video: generate intro and bed music sized to the take (ElevenLabs first; Suno once its API is open)

Problem

The intro music and the bed are mp3 files picked by hand from a stock-music folder (music, bed on @swamp/video/media). Rendering the Slack integrations demo (2026-11-12) ran into three problems with that:

Intro cue point. The intro card plays about 5s of the track from second 0. Most stock tracks open with a quiet build, so the card got the build instead of the hit. The workaround was to find the onset by measuring RMS (a hard hit at 30.7s in luminewave-devil-time), ffmpeg-trim a copy (…cue-30.65s.mp3) and point music at it. The media settings have no option to start a track partway in.
Bed loops. With bedMode: full the bed runs the whole video. A 1:50 track loops about 3.5 times under a 6:35 video, and the loop point is audible. Even a 3:11 track loops twice.
Fit and taste. The first pick was "too Seinfeld" (slap-bass funk). Choosing a track meant guessing from file names, since the agent can't listen. Nothing ties the music's length or structure to the video's.

Proposal: `@swamp/video/music`

A behavior with a compose method that generates instrumental music sized to a specific take:

Intro sting: a hit on the first frame, sized to the intro card plus its fade, read from the render's intro length (introSeconds, or the hook offset when there's a cold open). No cue-point hunting and no trimmed copies.
Bed: exactly the output length (video-render durationSeconds), with a fade at the end, so it never loops. Ambient by default: no melody hook, no drums, sits under voice.
Data: writes the file paths plus provenance (provider, model, prompt or plan, seed, length, generation time, license or plan the output was made under) as versioned data. A recut that keeps the same length reuses the tracks. compose with a new seed or prompt regenerates one track.
Wiring: media music/bed take the generated paths (CEL from the music data, or a musicFrom input on video-edit/video-recut like cardsFrom).
Provider is a setting. API key from a vault.

Provider research (2026-11-12)

Suno: promising but not ready to build on

There is now an official API sign-in page at https://platform.suno.com ("Suno's music generation engine behind a simple REST API": songs, covers and mashups from a prompt). Docs, pricing and endpoints are only visible after signing in, so instrumental mode, exact length and extend are unconfirmed.
In July 2026 Suno opened partner-only early access via an intake form (Music Business Worldwide). In September, third-party reviews still couldn't confirm self-serve signup. Nothing shows consumer Pro/Premier credits working through the API.
Unofficial wrappers and resellers exist but break Suno's terms and break without warning. Not suitable for a published extension.
Licensing: paid plans (Pro $10/mo, Premier $30/mo) allow commercial and YouTube use; the free tier is personal use only. Rights reportedly persist after cancelling. Suno keeps a license to outputs. Content ID claims can still happen and are disputed with the license.
Registry: the only Suno-related extension, @alvagante/content-music, goes through the 1min.ai reseller and targets lyric songs. Not a fit.

ElevenLabs Music: best fit for a first provider

POST https://api.elevenlabs.io/v1/music:

music_length_ms from 3,000 to 600,000: exact length
force_instrumental: true: guaranteed no vocals
composition_plan: sections, each with its own duration (3–120s) and positive and negative styles. Lets one request ask for a hit then a hold for the sting, or an intro, body and fade-out for the bed.
seed (with composition plan) for repeatable results; models music_v1, music_v2, music_v2_5
Output up to mp3_48000_192 or PCM 48 kHz, matching the render's 48 kHz audio
Optional C2PA signing
Reported price about $0.15 per generated minute direct (third-party comparisons; verify). A sting plus a 6.5-minute bed would cost about $1 per take.

Others

Stable Audio 2.5/3.0: instrumental-oriented, up to 3 or 6 minutes per generation, about $0.20–0.26 per generation (reported).
Google Lyria: Lyria 2 via fal is about $0.10 per 30s; the RealTime API is instrumental-only over WebSocket. Reports conflict on whether Lyria 3 has an API. Output is SynthID-watermarked.

Open questions

ElevenLabs as the only provider at first, with Suno added once platform.suno.com's docs confirm instrumental mode and exact length? Or a provider interface from day one?
Where license provenance should surface: in video-describe output (YouTube description), in data only, or both.
Default prompts and styles per brand: should @swamp/video/brand supply a house sound (synthwave, to match the cards)?
Caching: key generated tracks on (provider, model, prompt or plan, seed, length) so recuts don't re-spend.
Content ID: whether to keep generated outputs registered or listed somewhere for disputes.

Document trusted telemetry endpoint and authentication semantics

Docs: vault manual says legacy vault type names are automatically mapped, but vault create and migrate refuse them

Docs: reaching swamp start and swamp dashboard from another machine (--host)

Team mode: a member's or serve's copy is never slow to become usable (recovery, serve boot, catch-up after idle or compaction, login reset) — cost proportional to change, never to datastore size

ABAC support in @swamp/aws-sm

Docs: automatic continuation of interrupted runs in swamp serve (autoContinue)

serve: let methods act on swamp-club as the user who started the run (on-behalf-of token exchange)

@swamp/video: generate intro and bed music sized to the take (ElevenLabs first; Suno once its API is open)

@swamp/video/obs: add the brand stage to an existing OBS scene, with the webcam ring and mask optional

Docs: show the guard result on guarded skipped lines in make-workflows-idempotent

swamp behavior type rename: move a behavior type's data, outputs and catalog rows to a new type name

swamp issue: choose the target collective and control issue visibility -- at filing time and afterward -- from the CLI (with a settable default)

Render <details>/<summary> in serve's report view

stagecraft DESIGN.md: say the stored-as-received check catches only a redacted secret, and --literal-inputs is what stops evaluation

Lazy loading: delete compile.ts --no-bundle once a Deno version bump has shipped bundled

stagecraft: dispatch prompts read injected products by latest record, not the version the run indexed

Respect dependency versions pinned with extension pull dep@version

Find a working-directory Swamp repo even with `SWAMP_SERVE_URL` in the environment

Scheduled flaky-test detection is failing

datastore setup extension over serve: resolve --config expressions with per-caller authorization

serve: add a fitness test so no serve route is added under the /hooks/ webhook route-file prefix

Audit OAuth client deletion

Collective-registered OAuth clients can't complete authorization_code: redirect URIs are stored as a JSON array string

software-factory: a work item whose slug extends another's reads the other's records

Extension versions: print one spelling in log output (drop the v prefix in list, outdated, update, search)

Ambient tags: set tags once per repo/worktree (env or .swamp), add them to every run and everything downstream, filter run history by tag

Allow editing recent feed submissions

No way to add or switch to password login on an account created with SSO

Native interactive report views in the dashboard, with scoped workflow refresh

Expose a manual_approval gate's decision identity (decidedBy) to workflow expressions

data query rejects CEL list macros: exists(c, ...) fails with Unknown field "c"

A workflow run keeps every step's resource contents in memory, so a large forEach fan-out can exhaust the heap

Image factory: golden GCE and Docker base images built on ops

swamp data get and data versions report Behavior not found for data whose behavior definition was deleted

Workflow-scoped data get reports the behavior id as modelName once the behavior definition is deleted

Slackwater: let customers build integrations that drive workflows securely and auditably

Container run inspection and isolation metadata for audited recovery tests

swamp serve: apply config changes without failed requests (full reload, vault-backed webhook secrets, harmless restarts)

stagecraft tracker: tidy up external relations (duplicate entries, id case, second lookup)

SWAMP_SERVER_TOKEN does not authenticate with --server, while --token and SWAMP_SERVER_TOKEN_FILE do

Terminal title should be conversation summary

@swamp/issue-lifecycle: collapse the verification_passed, post_attestation, link_pr sequence

@swamp/issue-lifecycle: one-call verification

audit: register legitimate non-swamp commands as approved bypasses

Let a serve:* collective key look up usernames, so a recreated swamp serve does not need oauth:manage at runtime

aws-sm vault: optional secret_prefix to scope secrets within an AWS account and region

swamp skill: add a workspace guide and routing-table entry

serve: a capability probe answered by a follower does not speak for the leader that handles the forwarded request

serve OAuth client reuse: remaining review findings from swamp-club#4264

serve: the cron-fire dedup claim has no deadline, so a hung control plane stalls every scheduled fire

Relationships

#4690 @swamp/video: generate intro and bed music sized to the take (ElevenLabs first; Suno once its API is open)