# Brain


- **Get started**
- [Introduction](/brain/docs): A minimal and extensible agent server for building agent applications.
- [Quickstart](/brain/docs/quickstart): Start Brain on your machine, create a Pi session, and stream the reply with the TypeScript or Python SDK.
- [Architecture](/brain/docs/architecture): How Brain runs a session, stores and recovers it, and divides the work between components.

- **Build with Brain**
- Guides
  - [Session lifecycle](/brain/docs/guides/sessions): Create sessions, send messages, stream events, and interrupt, resume, or close a session.
  - [Authentication & tenants](/brain/docs/guides/authentication): Authenticate requests with bearer tokens, keep each tenant's sessions separate, and verify Brain's calls to your tools.
  - [Persistence & recovery](/brain/docs/guides/persistence): Configure background checkpoints across filesystem, S3, R2, and GCS, and hand off sessions between servers.
  - [Operations & observability](/brain/docs/guides/operations): Check health, set capacity limits, read logs and OpenTelemetry signals, and run Brain in a container.
  - [Platform examples](/brain/docs/guides/platforms): Single-owner deployment examples for Docker Compose, Fly.io, AWS ECS/Fargate, and Cloudflare R2 tool Workers.
- Tools
  - [Distributed tools](/brain/docs/tools): Give sessions tools that run in your own services, over HTTP, server-sent events, or MCP.
  - [MCP tools](/brain/docs/tools/mcp): Connect tools from a remote MCP server, with the same tenant checks, validation, and limits as HTTP tools.
  - [Local tools & approvals](/brain/docs/tools/local-tools): Run the example Go tool server with HTTP JSON echo, delegated session inspection, and SSE operator approvals.
  - [Sandboxes](/brain/docs/tools/sandboxes): Create, execute, inspect, and terminate remote Modal, E2B, and Daytona sandboxes over the HTTP tool protocol.
  - [Storage & web](/brain/docs/tools/resources): Run tenant-scoped S3/R2 text storage, public web fetch, and Brave/Tavily web search tools.
- SDKs
  - [Go application SDK](/brain/docs/sdks/application): Compose Brain with installed tools, resource authorization, credential keys, and harness factories.
  - [TypeScript SDK](/brain/docs/sdks/typescript): Create sessions, send messages, and stream events in Node.js 24+ with the TypeScript client.
  - [Python SDK](/brain/docs/sdks/python): Create sessions, send messages, and stream events with the zero-dependency Python 3.11+ client.

- **Reference**
- HTTP API
  - [HTTP API](/brain/docs/api): Endpoints, authentication, request rules, pagination, and streaming for the Brain HTTP API.
  - Endpoints
    - [List available tools](/brain/docs/api/generated/catalog)
    - [Register runtime tools](/brain/docs/api/generated/registerExecutor)
    - [Close a runtime executor](/brain/docs/api/generated/unregisterExecutor)
    - [Connect a runtime executor](/brain/docs/api/generated/executorCommands)
    - [Submit runtime progress or result](/brain/docs/api/generated/executorReply)
    - [Connect bidirectional runtime RPC](/brain/docs/api/generated/executorRPC)
    - [List sessions](/brain/docs/api/generated/list)
    - [Create a session](/brain/docs/api/generated/create)
    - [Get a session](/brain/docs/api/generated/get)
    - [Close a session](/brain/docs/api/generated/close)
    - [Read or stream events](/brain/docs/api/generated/events)
    - [Send input](/brain/docs/api/generated/send)
    - [Flush external state](/brain/docs/api/generated/flush)
    - [Restore a checkpoint](/brain/docs/api/generated/restore)
    - [Resume a session](/brain/docs/api/generated/resume)
    - [Read synchronization status](/brain/docs/api/generated/sync)
- Runtime reference
  - [Host configuration](/brain/docs/reference/configuration): Reference for brain.json fields, authentication tokens, harnesses, model providers, tools, resource limits, and external persistence.
  - [Events & streaming](/brain/docs/reference/events): Event envelope, payload schemas, SSE wire format, and cursor-based reconnection.
  - [Errors](/brain/docs/reference/errors): HTTP status codes, error envelopes, tool errors, and session error events.
  - [Models & providers](/brain/docs/reference/models): Select models, configure provider API keys, set reasoning effort, route through custom endpoints, and preserve prompt caches.
  - [Model catalog](/brain/docs/reference/model-catalog): Offline model IDs, transports, and context windows bundled in the pinned Pi runtime registry.
- Adapters
  - [Adapter overview](/brain/docs/adapters): Extend Brain with custom harness runners, external tool services, and persistence backends.
  - [Harness adapters](/brain/docs/adapters/harness): Implement a harness runner over Brain's Go interface or stdio JSON protocol.
  - [Persistence adapters](/brain/docs/adapters/persistence): Object storage and metadata indexing interfaces for background checkpoints.
  - [Go interfaces](/brain/docs/adapters/interfaces): Session, tool, database, harness, and checkpoint contracts generated from Go source.

- **Project**
- [Roadmap](/brain/docs/roadmap): What comes next for Brain, and how mature each part is today.
- [Development & verification](/brain/docs/development): Set up the workspace, run the verification suite, regenerate contracts, preview the docs site, and see how CI publishes releases.