Crate Layout

Fabric is organized as a Cargo workspace with 14 crates (13 libraries + 1 binary).

Crate Overview

Crate	Type	Purpose
`fabric-domain`	lib	Typed IDs (`JobId`, `RunId`, `WorkflowId`, etc.), shared models, errors, time utilities
`fabric-proto`	lib	Protobuf definitions and codegen (prost/tonic) — canonical Rust types, gRPC service stubs
`fabric-auth`	lib	JWT validation (Supabase HS256), API key hashing/verification (`fab_*` prefix), principal resolution, auth middleware
`fabric-tenancy`	lib	Organizations, teams, memberships, invitations repository layer
`fabric-policy`	lib	RBAC evaluation, effective permission computation, resource/action evaluation, `authz_guard`
`fabric-workflows`	lib	DAG definitions, validation (Kahn’s algorithm), runs, node models, context propagation
`fabric-executor`	lib/bin	Step claiming (`SELECT ... FOR UPDATE SKIP LOCKED`), node dispatch (Native/Tool/Provider/Wasm), retries, leases, worker loop
`fabric-events`	lib	Domain events, in-process broadcast, persistence, SSE/WebSocket/webhook delivery, audit logs
`fabric-assets`	lib	Asset metadata, S3/GCS/local object store abstraction, signed URLs
`fabric-providers`	lib	Provider abstraction, registry, routing — OpenAI, Anthropic, Ollama, Whisper, ComfyUI, ONNX, Candle, Echo
`fabric-storage`	lib	Persistence abstraction — Postgres (sqlx) + in-memory repos, unified `Store` enum, usage persistence
`fabric-api`	lib	axum routes, gRPC services, request/response envelopes, auth extraction, validation, jobs API, rate limiter, quotas
`fabric`	bin	Server binary with `serve` (control plane) and `executor` (execution plane) subcommands

Build Order

The crates build in dependency order:

1. fabric-proto          (protobuf codegen)
2. fabric-domain         (pure domain types)
3. fabric-auth           ─┐
   fabric-tenancy         │ (depend on domain + proto)
   fabric-workflows      ─┘
4. fabric-policy         (depends on tenancy + domain)
5. fabric-events         (depends on domain)
6. fabric-assets         (depends on domain)
7. fabric-providers      (depends on domain)
8. fabric-storage        (depends on all domain crates)
9. fabric-executor       (depends on workflows + providers + storage)
10. fabric-api           (depends on all lib crates)
11. fabric               (binary, depends on api + executor)

Key Dependencies

Shared Across Workspace

tokio — Async runtime
axum — HTTP framework (control plane)
tonic / prost — gRPC framework and protobuf codegen
sqlx — Async Postgres driver
serde — Serialization/deserialization
uuid — Canonical ID generation
time — Timestamp handling
tracing — Structured logging

Optional Features

onnx-runtime — Actual ONNX inference via ort
candle — HuggingFace model loading via Candle
wasm-runtime — Wasmtime plugin execution

Design Principles

Protobuf is canonical for message contracts — fabric-proto generates the types consumed by all other crates
Pure domain layer — fabric-domain has no I/O dependencies
Storage abstraction — All persistence goes through fabric-storage, which supports both Postgres and in-memory backends
Layered architecture — Each crate has a clear boundary and minimal dependencies