omnigraph/docs/user/server.md

HTTP Server (omnigraph-server)

Axum 0.8 + tokio + utoipa-generated OpenAPI. Two modes (v0.6.0+): single-graph (legacy) and multi-graph (MR-668). Mode is inferred from CLI args + config shape.

Modes

Single-graph mode (legacy)

omnigraph-server <URI> or omnigraph-server --target <name> --config omnigraph.yaml. Routes are flat — /snapshot, /read, /branches, etc. Behavior unchanged from v0.6.0.

Multi-graph mode (v0.6.0+)

omnigraph-server --config omnigraph.yaml with a non-empty graphs: map and no single-mode selector (no server.graph, no <URI>, no --target). The server opens every configured graph in parallel at startup (bounded concurrency = 4, fail-fast on the first open error). Routes are nested under /graphs/{graph_id}/.... Bare flat paths return 404 in multi mode.

Mode inference (four-rule matrix):

1. CLI positional <URI> → single
2. CLI --target <name> → single
3. server.graph in config → single
4. --config + non-empty graphs: + no single-mode selector → multi
5. otherwise → error with migration hint

Stored-query validation at startup

If a graph declares a queries: registry (see cli-reference), the server loads and type-checks every stored query against that graph's live schema at startup and refuses to boot if any query references a type or property the schema lacks — the same fail-loud posture as a malformed policy file, so schema drift surfaces at the deploy boundary rather than at invocation. Two MCP-exposed queries claiming the same tool name is likewise a boot error. Non-blocking advisories (e.g. an MCP-exposed query with a vector parameter an agent cannot supply) are logged. Validate offline before deploying with omnigraph queries validate. Discover the exposed queries as a typed tool catalog with GET /queries, and invoke one over HTTP with POST /queries/{name} (both below).

Endpoint inventory

Per-graph endpoints — same body shape across modes; URLs differ:

Method	Single-mode path	Multi-mode path	Auth	Action	Handler
GET	/healthz	/healthz	none	—	server_health
GET	/openapi.json	/openapi.json	none	—	server_openapi (strips security if auth disabled; in multi mode emits cluster paths with cluster_ operation-id prefix)
GET	/snapshot?branch=	/graphs/{id}/snapshot?branch=	bearer + read	snapshot of branch	server_snapshot
POST	/query	/graphs/{id}/query	bearer + read	inline read query (canonical; clean field names query/name; mutations → 400)	server_query
POST	/read	/graphs/{id}/read	bearer + read	deprecated alias of /query (legacy field names query_source/query_name, byte-stable response; carries Deprecation: true + Link: </query>; rel="successor-version")	server_read
POST	/export	/graphs/{id}/export	bearer + export	NDJSON stream	server_export
POST	/mutate	/graphs/{id}/mutate	bearer + change	mutation (canonical; query/name; accepts legacy query_source/query_name as serde aliases)	server_mutate
POST	/change	/graphs/{id}/change	bearer + change	deprecated alias of /mutate (carries Deprecation: true + Link: </mutate>; rel="successor-version")	server_change
GET	/queries	/graphs/{id}/queries	bearer + read	list the mcp.expose stored queries as a typed tool catalog	server_list_queries
POST	/queries/{name}	/graphs/{id}/queries/{name}	bearer + invoke_query (+ change for a stored mutation)	invoke a named query from the queries: registry; deny == 404	server_invoke_query
GET	/schema	/graphs/{id}/schema	bearer + read	get current .pg source	server_schema_get
POST	/schema/apply	/graphs/{id}/schema/apply	bearer + schema_apply (target=main)	migrate	server_schema_apply
POST	/ingest	/graphs/{id}/ingest	bearer + branch_create (if new) + change	bulk load	server_ingest (32 MB body limit)
GET	/branches	/graphs/{id}/branches	bearer + read	list branches	server_branch_list
POST	/branches	/graphs/{id}/branches	bearer + branch_create	create	server_branch_create
DELETE	/branches/{branch}	/graphs/{id}/branches/{branch}	bearer + branch_delete	delete	server_branch_delete
POST	/branches/merge	/graphs/{id}/branches/merge	bearer + branch_merge	merge source → target	server_branch_merge
GET	/commits?branch=	/graphs/{id}/commits?branch=	bearer + read	list	server_commit_list
GET	/commits/{commit_id}	/graphs/{id}/commits/{commit_id}	bearer + read	show	server_commit_show

Server-level management endpoints (v0.6.0+):

Method	Path	Auth	Action	Handler
GET	/graphs	bearer + graph_list on Server::"root"	list registered graphs	server_graphs_list (405 in single mode)

Stored-query catalog (GET /queries)

List the graph's mcp.expose stored queries as a typed tool catalog — enough for a client (e.g. an MCP server) to register each as a tool without fetching .gq source. Each entry: { name, tool_name, description, instruction, mutation, params }, where each param is { name, kind, item_kind?, vector_dim?, nullable }. kind is one of string | bool | int | bigint | float | date | datetime | blob | vector | list (decomposed so a consumer maps it with a closed switch, never re-parsing GQ type spelling). bigint (I64/U64), date, datetime, and blob are carried as JSON strings — a 64-bit integer loses precision as a JSON number, dates are ISO strings, and a blob is a URI string.

• Read-gated (works in default-deny mode). The catalog is graph-wide (branch-independent; read is authorized against main).
• mcp.expose defaults to true — declaring a query in queries: lists it; set mcp: { expose: false } to keep it HTTP/service-callable but hidden from the catalog.
• Not Cedar-filtered per query (yet). A caller with read but not invoke_query can list a query they can't invoke (which would 404). Closing that gap is future per-query authorization; for now the catalog is a discovery surface and invoke_query remains the invocation gate.

Stored-query invocation (POST /queries/{name})

Invoke a curated, server-side stored query by name — the source comes from the graph's queries: registry, so the client never sends .gq. Body (all fields optional): { "params": { … }, "branch": "main", "snapshot": null }, where params keys match the query's declared parameters. The response is the read envelope (ReadOutput) for a stored read or the mutation envelope (ChangeOutput) for a stored mutation — serialized untagged, so the wire shape is identical to /query / /mutate.

• Gate: invoke_query (per-graph, graph-scoped) at the boundary. A stored mutation is double-gated — it also passes the engine's change gate, so an actor with invoke_query but not change gets 403.
• Deny == unknown, for callers without invoke_query: for a caller lacking the grant, an invoke_query denial and an unknown query name return the same 404 (identical body), so the catalog can't be probed. A caller that holds invoke_query may still get the inner gate's 403 for an existing query it can't read/change (the double-gate, above) — so existence is visible to grant-holders by design.
• Requires an explicit policy grant when auth is on. In default-deny mode (bearer tokens but no policy.file), only read is permitted, so every /queries/{name} call returns 404 until an invoke_query rule is configured.
• A stored mutation cannot target a snapshot (400); a parameter type error is a structured 400 naming the parameter.

Adding and removing graphs (multi mode)

Runtime add/remove via API is not exposed in v0.6.0 — neither POST /graphs nor DELETE /graphs/{id} is implemented. Operators add or remove graphs by stopping the server, editing the graphs: map in omnigraph.yaml, then restarting. The server treats omnigraph.yaml as operator-owned configuration and never writes it.

A future release may introduce a managed registry (Lance-backed, catalog-style: reserve → init → publish with recovery sidecars) and re-expose runtime mutation on top of it.

Inline read queries (POST /query)

POST /query is the read-only, agent-friendly twin of POST /read. The request body uses clean field names that match the CLI -e flag and the GQ query keyword:

{
  "query":    "query find($n: String) { match { $p: Person { name: $n } } return { $p.name } }",
  "name":     "find",
  "params":   { "n": "Alice" },
  "branch":   "main",
  "snapshot": null
}

Response shape is identical to /read (ReadOutput). If the inline source contains mutations (insert / update / delete), the request is rejected with HTTP 400 and an error pointing the caller at POST /mutate — the read-only contract is enforced at the URL.

POST /mutate is the canonical mutation endpoint. It accepts the same clean field names (query, name); the legacy field names query_source and query_name continue to deserialize as serde aliases so existing clients keep working without changes.

Deprecated names (/read, /change)

POST /read and POST /change are kept for back-compat indefinitely — they are byte-stable on the request side and otherwise behave identically to /query / /mutate. They are flagged as deprecated through three independent channels:

• OpenAPI: the operations carry deprecated: true in openapi.json, so every OpenAPI codegen (typescript-fetch, openapi-generator, oapi-codegen, …) emits a @deprecated marker on the generated SDK method.
• Response headers (RFC 9745): every response carries Deprecation: true.
• Response headers (RFC 8288): every response carries a Link header pointing at the canonical successor: Link: </query>; rel="successor-version" for /read, and Link: </mutate>; rel="successor-version" for /change. SDKs and HTTP proxies can pick the successor up automatically.

Migration is purely cosmetic on the client side — swap the URL path, leave the request body and response handling alone.

Streaming

Only /export streams (application/x-ndjson, MPSC channel + Body::from_stream). Everything else is buffered JSON.

Error model

Uniform ErrorOutput { error, code?, merge_conflicts[], manifest_conflict? } with code ∈ unauthorized | forbidden | bad_request | not_found | conflict | too_many_requests | internal. Merge conflicts attach structured MergeConflictOutput { table_key, row_id?, kind, message }.

manifest_conflict is set on publisher CAS rejections (HTTP 409): the caller's pre-write view of one table's manifest version was stale. ManifestConflictOutput { table_key, expected, actual } tells the client which table to refresh and retry. This is the conflict shape produced by concurrent /mutate (or its /change alias) or /ingest calls landing the same (table, branch) race.

HTTP status codes used: 200, 400, 401, 403, 404, 409, 429, 500.

Per-actor admission control

Disjoint (table, branch) writes from different actors now run concurrently, guarded only by the engine's per-(table, branch) write queue. To keep one heavy actor from exhausting shared capacity (Lance I/O, manifest churn, network), the server gates mutating handlers through a WorkloadController configured per-process from environment variables:

Env var	Default	Purpose
OMNIGRAPH_PER_ACTOR_INFLIGHT_MAX	16	Concurrent in-flight mutations per actor
OMNIGRAPH_PER_ACTOR_BYTES_MAX	4 GiB	In-flight estimated bytes per actor

When an actor exceeds its in-flight count or byte budget, the server returns HTTP 429 Too Many Requests with code: too_many_requests and a Retry-After header (seconds). The actor should back off; other actors are unaffected.

Cedar policy authorization runs before admission accounting so denied requests don't consume admission slots.

Today admission gates every mutating handler: /mutate (and its deprecated alias /change), /ingest, /branches/{create,delete,merge}, and /schema/apply. Read-only endpoints (/snapshot, /query, /read, /export, /branches GET, /commits, /schema GET) are not admission-gated.

Body limits

• Default: 1 MB
• /ingest: 32 MB

Auth model (bearer + SHA-256)

• Tokens are SHA-256 hashed on startup; plaintext is never persisted in memory.
• Constant-time comparison via subtle::ConstantTimeEq.
• Three sources, in precedence:
  1. OMNIGRAPH_SERVER_BEARER_TOKENS_AWS_SECRET — AWS Secrets Manager (build with --features aws)
  2. OMNIGRAPH_SERVER_BEARER_TOKENS_FILE or OMNIGRAPH_SERVER_BEARER_TOKENS_JSON — JSON {actor_id: token, …}
  3. OMNIGRAPH_SERVER_BEARER_TOKEN — single legacy token, actor default
• If no tokens are configured, startup refuses unless --unauthenticated or OMNIGRAPH_UNAUTHENTICATED=1 explicitly opts into open local-dev mode. A policy file without tokens is also rejected at startup. In open mode /openapi.json strips the security scheme.

See deployment.md for token-source operational details.

Tracing & observability

• tower_http::TraceLayer::new_for_http()
• Policy decisions logged at INFO level with actor, action, branch, decision, matched rule
• Startup logs: token source name, graph URI, bind address
• Graceful SIGINT shutdown

Not implemented (by design or "TBD")

• CORS — not configured; add tower_http::cors if needed.
• Rate limiting — per-actor admission control gates /mutate (alias /change), /ingest, /branches/{create,delete,merge}, /schema/apply (see "Per-actor admission control" above). No global rate limiter is configured; add tower_http::limit if a graph-wide cap is needed.
• Pagination — none (commits/branches return everything; export streams).
• Runtime graph add/remove — edit omnigraph.yaml and restart.