runtime

---
name: runtime
description: >
license: MIT
---

# CopilotKit Runtime

`@copilotkit/runtime` is the server half of CopilotKit: it accepts AG-UI protocol
requests, dispatches them to an `AbstractAgent` (built-in or external), runs the
stream through an `AgentRunner`, and responds as Server-Sent Events.

This SKILL.md is the **index**. Read the reference under `references/` that matches
your task — do not try to absorb the whole package from this file.

## Mental Model — the three dictionaries you hand to `CopilotRuntime`

```ts
new CopilotRuntime({
  agents, // Record<string, AbstractAgent>     — see wiring-external-agents or built-in-agent
  runner, // AgentRunner (optional)            — see agent-runners
  intelligence, // CopilotKitIntelligence (optional) — see intelligence-mode (auto-wires runner)
  mcpApps, // McpAppsConfig (optional)          — see wiring-mcp-apps-middleware
  a2ui, // A2UIConfig (optional)             — see packages/a2ui-renderer skill
  hooks, // { onRequest, onBeforeHandler }    — see middleware
  beforeRequestMiddleware,
  afterRequestMiddleware, // legacy — see middleware
  transcription, // TranscriptionService (optional)  — see transcription
});
```

You then mount it:

```ts
import { createCopilotRuntimeHandler } from "@copilotkit/runtime/v2";
const handler = createCopilotRuntimeHandler({
  runtime,
  basePath: "/api/copilotkit",
});
export default { fetch: handler };
```

## When to load which reference

| Task                                                                                                                                                                           | Reference                                                                                                                                                                                                                                                                                                                                          |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Mounting on any fetch-native server (Cloudflare Workers, Bun, Deno, Vercel Edge, Next.js App Router, React Router v7, TanStack Start) or delegating from Express/Node          | `references/setup-endpoint.md`                                                                                                                                                                                                                                                                                                                     |
| Auth / logging / rate-limit / request-scoped guards via `hooks.onRequest` / `hooks.onBeforeHandler` (preferred) or legacy `beforeRequestMiddleware` / `afterRequestMiddleware` | `references/middleware.md`                                                                                                                                                                                                                                                                                                                         |
| Choosing between `InMemoryAgentRunner`, `SqliteAgentRunner`, or a custom subclass — including thread-locking semantics and the runner/Intelligence mutual exclusion            | `references/agent-runners.md` (+ `-in-memory.md`, `-sqlite.md`, `-custom.md` for backend-specific detail)                                                                                                                                                                                                                                          |
| Enabling durable threads + realtime websocket via CopilotKit Intelligence (a **managed service**, not self-hostable)                                                           | `references/intelligence-mode.md`                                                                                                                                                                                                                                                                                                                  |
| Voice transcription — implementing a `TranscriptionService` subclass for the `/transcribe` endpoint                                                                            | `references/transcription.md`                                                                                                                                                                                                                                                                                                                      |
| Instantiating `BuiltInAgent` — Simple Mode (classic) or Factory Mode with TanStack AI (preferred AG-UI-compliant default), AI SDK, or custom factory                           | `references/built-in-agent.md` (+ `-factory-modes.md`, `-helper-utilities.md`, `-model-identifiers.md`)                                                                                                                                                                                                                                            |
| Defining server-side tools via `defineTool` for `BuiltInAgent.config.tools` (Simple Mode only)                                                                                 | `references/server-side-tools.md`                                                                                                                                                                                                                                                                                                                  |
| Wiring an external agent framework into `CopilotRuntime({ agents })`                                                                                                           | `references/wiring-external-agents.md` (index) + per-framework refs (`wiring-mastra.md`, `wiring-langgraph.md`, `wiring-crewai-crews.md`, `wiring-crewai-flows.md`, `wiring-pydantic-ai.md`, `wiring-adk.md`, `wiring-llamaindex.md`, `wiring-agno.md`, `wiring-aws-strands.md`, `wiring-ms-agent-framework.md`, `wiring-ag2.md`, `wiring-a2a.md`) |
| Wiring MCP Apps (runtime-level middleware, not an agent)                                                                                                                       | `references/wiring-mcp-apps-middleware.md`                                                                                                                                                                                                                                                                                                         |

## Invariants and gotchas (load-once, before any reference)

- `createCopilotRuntimeHandler` is the canonical primitive. `createCopilotExpressHandler` / `createCopilotHonoHandler` exist but are **avoid at all costs** — delegate from Express/Hono routes to the fetch primitive instead.
- `publicLicenseKey` is the canonical provider-side field. `publicApiKey` is a **deprecated alias** — expect to see it in legacy code, emit the canonical name in new code.
- Intelligence mode auto-wires `IntelligenceAgentRunner`. Passing both `runner` and `intelligence` to `CopilotRuntime` is rejected at construction.
- Intelligence mode targets the managed CopilotKit Intelligence service (`api.cloud.copilotkit.ai`) and is **not self-hostable**.
- `hooks.onRequest` runs **before** `beforeRequestMiddleware` (hook-based middleware wins for Response short-circuits). `beforeRequestMiddleware` runs **after** `hooks.onRequest` (see `fetch-handler.ts:136-147`).
- `identifyUser` (Intelligence) does **not** forward thrown `Response` objects — convert to 500. Gate auth rejection in `hooks.onRequest`, which does forward Responses.
- `agents__unsafe_dev_only` and `selfManagedAgents` are dev-only aliases of each other; do not reach for them in production. Either signals that the SPA is in dev mode.

## Reading order for a first-time reader

1. `setup-endpoint` — the primitive.
2. `built-in-agent` **or** pick one from `wiring-external-agents` — the agent.
3. `agent-runners` — production persistence choice.
4. Optional: `middleware`, `intelligence-mode`, `server-side-tools`, `transcription`.