vak — a layered map of every component

Provider clients, streaming, model routing, and usage accounting. The one thing nearly every other crate depends on.

The policy engine every effect passes through before dispatch. Rules in, allow/deny/prompt out — the heart of "nothing acts without permission."

Outbound message transport with a durable outbox and templating — the wire chat gateways and notifications send over.

The append-only JSONL ledger: event types, contracts, receipts, and recall. Branching and compaction append rather than rewrite, so every session is reconstructable.

The built-in tool set plus the broker and sandbox boundary: filesystem, shell, search, and web, each brokered through the permission gate. Landlock enforces containment on Linux.

The layered configuration model — defaults through user, project, environment, and CLI — with unknown keys warning rather than failing startup.

Lifecycle hook dispatch — user-supplied extension points around agent events, themselves policy-gated.

The agent turn loop: goal tracking, steering, spend limits, a failure circuit-breaker, and stop policy. Where a session's model calls and tool dispatches are actually driven.

Model Context Protocol client and manager — external MCP servers surfaced as brokered tools, so extensions get the same gate as built-ins.

A SQLite FTS5 rebuildable index over the JSONL ledgers — full-text session search and recall that can always be regenerated from the source of truth.

The composed core the surfaces share: checkpoints, memory, worktrees, FinOps, routing, the Docker sandbox, skills, learning, tasks, transcripts, and the system prompt. This is the "one core."

Static, declarative multi-step flows — checked and run through the same agent and permission machinery as an interactive turn.

Deterministic and live evaluation harness — exercises the agent against fixtures or real providers, gated identically to production runs.

Service lifecycle management — installing and controlling vak as a durable background service (macOS LaunchAgent / Linux systemd user unit).

The headless surface: vak exec, plan, flow, eval, config dump, sessions, checkpoints, memory, and a doctor. Depends on nearly every crate.

Exposes the session, run, approval, transcript, diff, and steering contracts over HTTP/SSE, plus chat gateways (Slack, Discord, Telegram), an admin API, rate limiting, and a core pool.

The native client host: isolated worktrees, streaming chat, diff review, an editor, a PTY terminal, previews, side chats, and best-of-N comparison. Embeds the server contracts.

The desktop front end (package vak-ui): SolidJS + Vite, xterm.js terminal, Shiki syntax highlighting, and the chat, composer, and diff components.

The admin console front end, built on the same token set as the desktop UI so the two surfaces read as one product. Served by the server's admin API.

A menu-bar / system-tray companion for controlling the background service without a full window.