SCENEGOD/lanes/C-server.md

Lane C — Server: FastAPI, assets, scenes, render pipeline

You own: scenegod/server.py, web/render.js, scripts/*, requirements.txt, .gitignore. Milestone: M1.

C1. Scaffold (first commit)

• requirements.txt: fastapi, uvicorn. Nothing else.
• .gitignore: .env, assets/, scenes/, renders/, __pycache__/, *.pyc, .DS_Store.
• scenegod/server.py, single file (split only when it hurts — MESHGOD's server.py is one file at 800+ lines and fine). SCENEGOD_PORT 8020, bind 127.0.0.1 (env SCENEGOD_BIND to override later — not now).
• Statics: GET / → web/index.html with Cache-Control: no-store (MESHGOD stale-cache lesson); /web/* served with short cache. Use FastAPI FileResponse/StaticFiles, headers set explicitly for the HTML.

C2. Assets endpoints

• Roots from env with defaults: SCENEGOD_ASSETS=./assets, SCENEGOD_SCENES=./scenes, SCENEGOD_RENDERS=./renders (create scenes/ renders on boot; assets must exist — clear error if not).
• GET /assets/tree: walk assets/{characters,animations,props,backdrops,audio}. Group rigroom-library style: files sharing dir+stem = one entry with a formats list ({"name":"lady","path":"characters/pack01/lady.glb", "formats":["glb","fbx"]}). Extensions: glb/gltf/fbx/obj/bvh + jpg/png/webp (backdrops) + wav/mp3 (audio). Scan live, no index file, cache 5s.
• GET /assets/file?path=: resolve and enforce path.resolve().is_relative_to(ASSETS_ROOT) — reject .., absolute paths, symlink escapes (resolve first, then check). Correct content-types (model/gltf-binary, etc.). This guard pattern applies to every path-taking endpoint you ever add here (ship-check rule).
• Read /Users/johnking/Documents/MESHGOD/meshgod/library.py first — same idea, steal the grouping approach.

C3. Scenes CRUD

• GET /scenes → [{name, mtime, duration}]; GET /scenes/{name}; POST /scenes/{name} with JSON body. name slugified [a-z0-9-_], file scenes/{name}.json, atomic write (tmp + rename).
• Validate on save (stdlib, no jsonschema dep): version==1, entity ids unique, every track sorted by t, clip blocks non-overlapping per entity (fade overlap allowed), cameraCuts reference existing camera entities. Reject with a 422 listing every violation (agents and UI both rely on the messages).

C4. scripts/test_server.py (M1 gate)

Stdlib urllib + subprocess (uvicorn on a test port, tmp asset/scene dirs): asserts tree grouping, file streaming, traversal attempts → 4xx (?path=../../etc/hosts, absolute, URL-encoded ..), scene round-trip, validation failures (unsorted keys, dup ids). python3 scripts/test_server.py green = M1 code-done. Run with | lm -l 2.

C5. Render pipeline — M3, but design lands now (endpoints stubbed 501)

• Session model: POST /render/begin {name,fps,width,height} → {renderId} (uuid, dir renders/{id}/frames/). POST /render/{id}/frame/{n}: raw PNG body → frames/{n:06d}.png. POST /render/{id}/end {audio?} → spawn ffmpeg in a background thread: ffmpeg -framerate {fps} -i frames/%06d.png -c:v libx264 -pix_fmt yuv420p -crf 18 out.mp4 (audio inputs + -map/amix in M4). GET /render/{id}/status = queued|encoding|done|error(+log tail); GET /render/{id}/out.mp4. ffmpeg presence checked at boot (shutil.which), endpoint 503s w/ message if absent. Reap render dirs >48h old on boot.
• web/render.js (M3): exports draftRecord(stage, timeline) — canvas.captureStream(fps) + MediaRecorder while timeline.play()s, save webm; and finalRender(stage, timeline, opts) — resize canvas, loop timeline.step(f) → stage.renderActiveCamera() → canvas.toBlob('image/png') → POST frame (3-4 in flight, backpressure via await), then /end, poll status, download link. Deterministic: never uses wall-clock time.

C6. M4 (locked): audio, MODELBEAST, graft

• ffmpeg audio mux per scene JSON audio[].
• POST /mb/submit proxy re-implementing the contract in MESHGOD meshgod/ops.py (upload input to /api/assets first; token read from ~/Documents/backnforth/.env at request time, never logged; endpoint only active when SCENEGOD_MB=1).
• scripts/graft_limb.py headless Blender (pattern: MESHGOD scripts/glb2fbx.py): --body body.glb --limb hand.glb --bone mixamorig:RightHand → align limb root bone to target bone head, join armatures, parent-keep-offset, join meshes (weights survive), export. If the body armature ALREADY has the bones the limb provides → exit 2 with "bones exist; mitten weights — re-skin, don't graft". Never route output through any finish/decimate path (rig contract).

M1 acceptance (log it)

• uvicorn scenegod.server:app --port 8020 serves Lane A's page (or a placeholder index if A hasn't landed — don't block on them).
• test_server.py green; paste the summary line in your log.

ORCHESTRATOR UPDATES

(none yet — check back each session)