vdm/contracts/README.md

contracts/ — the wire contract

This directory is the interface between every lane. Owner: agent PROTO. Nobody else commits here. Everybody else generates from here.

contracts/
├── VERSION                     # protocol semver, e.g. 1.0.0
├── openrpc.json                # human-readable API doc (generated from schema/)
├── schema/
│   ├── envelope.schema.json    # JSON-RPC 2.0 envelope + our error codes
│   ├── types/                  # Task, Segment, Category, Queue, Settings, CaptureOffer…
│   ├── methods/                # one file per method: params + result
│   └── events/                 # one file per server→client notification
├── fixtures/                   # golden request/response pairs, replayed by conformance
└── codegen/
    ├── gen_cpp.py              # → core/generated/  (structs + to_json/from_json)
    └── gen_ts.py               # → extension/src/shared/protocol/ (types + client)

Rules

1. Generated code is committed. No lane may be blocked because it can't run Python.
2. Hand-editing generated files is a merge blocker. Fix the schema and regenerate.
3. Every method needs at least one fixture — a success case and, where meaningful, an error case. A method with no fixture is not done.
4. Versioning: adding an optional field or a new method → minor bump. Removing, renaming, retyping, or changing a default → major bump and a written migration note in docs/adr/. session.hello rejects a major mismatch with error -32001 and a message the GUI renders as "Velox needs updating".
5. Changes arrive as a PR to contracts/ alone, containing: schema edit + fixtures + regenerated code + VERSION bump. Lanes rebase onto it. This is the only synchronization point in the whole project — keep it cheap and frequent rather than big and rare.

Transport framing

Client	Transport	Framing
GUI, CLI	$XDG_RUNTIME_DIR/velox/velox.sock	newline-delimited JSON (NDJSON)
nmhost ← Firefox	stdio	4-byte little-endian length prefix (Firefox's format)
nmhost → daemon	same Unix socket	NDJSON
Extension (fallback)	ws://127.0.0.1:520xx	one JSON message per WS text frame

All four carry the same JSON-RPC 2.0 payloads. The framing differences stop at the transport layer; no method behaves differently depending on how it arrived — except that methods marked "privileged": true in the schema are refused over the WebSocket transport.

Method surface (v1.0.0 target — expand only via PR)

Session

Method	Params → Result
session.hello	{clientType, clientName, protocolVersion, token?} → {daemonVersion, protocolVersion, capabilities[], sessionId}
session.pair	{clientName, extensionId} → {token, expiresAt} (WS only; triggers user prompt)
session.subscribe	{events[]} → {ok}

Downloads

Method	Params → Result
download.probe	{url, headers?, cookies?, referrer?, userAgent?} → {filename, sizeBytes?, mime, resumable, effectiveUrl, suggestedCategoryId}
download.add	{url, headers?, cookies?, referrer?, userAgent?, filename?, saveDir?, categoryId?, segments?, bufferBytes?, startMode:"now"|"later"|"queue", queueId?, description?, checksum?} → {taskId, state}
download.addBatch	{items[], defaults} → {taskIds[]}
download.list	{filter?, sort?, offset?, limit?} → {total, items: TaskSummary[]}
download.get	{taskId} → TaskDetail (includes segments[])
download.start | .pause | .resume | .cancel	{taskIds[]} → {updated[]}
download.remove	{taskIds[], deleteFile:bool} → {removed[]}
download.update	{taskId, patch:{filename?, saveDir?, categoryId?, queueId?, description?, segments?, bufferBytes?}} → TaskSummary
download.refreshUrl	{taskId, url, headers?} → {ok} (IDM's "Refresh Download Address")

Organisation

category.list · category.upsert · category.remove · queue.list · queue.upsert · queue.start · queue.stop · queue.reorder · rules.list · rules.upsert · schedule.get · schedule.set

Settings & limits

settings.get {keys?} · settings.set {values} · limiter.get · limiter.set {globalBps?, enabled}

Browser integration

Method	Notes
capture.offer	{url, method, headers, cookies, contentType?, contentLength?, contentDisposition?, tabUrl, filename?} → {action:"take"|"ignore", taskId?, reason?} — must answer within 750 ms; the extension gives up and lets Firefox handle it otherwise
capture.getRules	Extension mirrors the daemon's monitored types so the two never disagree
media.listVariants	{manifestUrl, headers} → {variants:[{id,resolution,bitrate,codec,sizeEstimate}]}
media.addVariant	{manifestUrl, variantId, ...addParams} → {taskId}

Grabber

grabber.start {startUrl, depth, includePatterns[], excludePatterns[], fileTypes[]} → {jobId}; grabber.status {jobId}; grabber.harvest {jobId, select[]} → {taskIds[]}

Events (server → client notifications)

Event	Payload
event.task.added / .removed	{taskId, summary?}
event.task.state	{taskId, state, error?}
event.task.progress	Batched array, emitted at ≤4 Hz: [{taskId, downloaded, speedBps, etaSec, segments:[{i,completed,speedBps}]}]
event.speed.global	{downBps, activeCount}
event.auth.required	{taskId, host, realm, scheme}
event.notify	{level, title, body, taskId?}
event.settings.changed	{keys[]}
event.grabber.progress	{jobId, found, crawled, done}

Error codes

Code	Meaning
-32600/-32601/-32602/-32603	Standard JSON-RPC
-32001	Protocol major version mismatch
-32002	Not paired / invalid token
-32003	Method not permitted on this transport
-32010	Task not found
-32011	Invalid destination path (outside allowed roots, or not writable)
-32012	Disk full
-32013	Probe failed (with data.httpStatus)
-32014	Rate limited (pairing brute-force lockout)