Overview — Project 7: Mosaic

Mosaic is the capstone platform. It exposes the evidence, harness, model, evaluation, storage, and policy capabilities built through the earlier products behind a CLI, HTTP API, and durable worker.

The goal is not maximum features. It is one complete vertical slice that can survive malformed input, cancellation, restart, duplicate delivery, overload, provider failure, and rollback.

Architecture

CLI / HTTP
    ↓ validated task
admission + policy
    ↓ durable run/job
worker ─▶ evidence ─▶ retrieval ─▶ harness ─▶ model/tools
    ↓ events/receipts/artifacts                 │
database + content-addressed store ◀────────────┘
    ↓
replay / eval / quality-cost-latency dashboard

The six days

Day	Build	Production proof
29	workspace composition and Axum boundary	one request reaches typed domain code
30	SQL state, leases, idempotency, artifacts	restart and duplicate delivery preserve one outcome
31	bounded uploads, queues, SSE, cancellation	overload degrades predictably
32	identity, tenant scope, quotas, injection defenses	cross-tenant and unauthorized effects fail closed
33	logs, metrics, traces, release identity	bad release is detected and reversible
34	container, health, shutdown, final drill	deploy, operate, recover, explain

Run the current service boundary:

cd rust/rust-ai-engineering
cargo run -q -p mosaic-api --bin mosaic-service

The service intentionally reports an unavailable model path until a configured adapter is connected. A placeholder success would teach the wrong operational lesson.

Start with Day 29 — Workspace and API →.