## Summary
Two ergonomic additions for custom chat-agent loops that own the turn
loop (`chat.customAgent`, `chat.createSession`, and the hand-rolled
primitives).
`chat.writeTurnComplete()` now resolves to `{ lastEventId }`, the resume
cursor for the start of the next turn. A custom loop can persist it
straight from the task instead of round-tripping it back from the client
after the turn ends. The value was already produced internally by the
turn-complete write; the public wrapper simply discarded it.
`chat.pipeAndCapture()` no longer throws when a stream is stopped or
fails. It now resolves to a `PipeAndCaptureResult` carrying any partial
`message` captured before the stop or failure, a typed `status`
(`"complete" | "aborted" | "error"`), and the `error` on failure.
Previously a failed stream threw and the partial was lost, and an abort
was captured only when the AI SDK happened to fire `onFinish` in time.
```ts
const { message, status, error } = await chat.pipeAndCapture(result, { signal });
if (message) conversation.addResponse(message);
if (status === "error") logger.error("turn failed", { error });
const { lastEventId } = await chat.writeTurnComplete();
await db.chats.update(chatId, { lastEventId });
```
## Design
`pipeAndCapture` wraps the pipe in a `try/catch` and classifies the
outcome from the abort signal (a stop drains the source stream cleanly
rather than throwing) versus a thrown error. It also races the
`onFinish` capture against a timeout so a hard stop that prevents
`onFinish` from firing can't hang the caller. This mirrors the capture
path `chat.agent` already uses internally.
The `finishReason` from `onFinish` is surfaced too, since it was already
captured on the built-in path.
The internal `turn.complete()` helper keeps its existing contract: it
still returns `UIMessage | undefined`, still throws on a genuine stream
failure, and still discards output on a full run cancel.
## Breaking change
`chat.pipeAndCapture` previously resolved to `UIMessage | undefined`.
Call sites now read `.message` off the result. This is a young,
low-level API; the docs examples are updated in this PR.
Removes the release-candidate framing from the docs for the 4.5 GA: the
`@rc` install caveats on the `skills` CLI command, and the AI Agents and
Prompts release-candidate banner (a shared snippet used across the
ai-chat and prompts pages) plus the `>=4.5.0-rc.0` compatibility pin in
the AI reference.
## Summary
Lands the full AI Agents documentation surface alongside the v4.5
release candidate of `@trigger.dev/sdk`. Covers `chat.agent` end to end
— defining agents, lifecycle hooks, the frontend transport, sub-agents,
recovery from cancel/crash/OOM, AI Prompts integration — and the
Sessions primitive that backs it.
## Coverage
- **Conceptual**: Overview, Quick Start, How it works.
- **Building agents**: Backend (`chat.agent` / `chat.createSession` /
raw primitives), Lifecycle hooks, Frontend transport, Server-side
`AgentChat`, Sessions reference, `chat.local` state primitive,
TypeScript types.
- **Features**: AI Prompts integration, Fast starts (Preload + Head
Start), Compaction, Pending Messages (steering), Background Injection
(`chat.inject` + `chat.defer`), Actions (undo / regenerate / edit),
Error handling.
- **Patterns (13)**: Sub-agents, Branching conversations, Code sandbox,
Database persistence, Persistence and replay, HITL, Tool result
auditing, Large payloads, Agent skills, OOM resilience, Recovery boot,
Trusted edge signals, Version upgrades.
- **Reference**: API Reference, Client Protocol (wire format), Testing
harness (`mockChatAgent`), MCP server tools, Upgrade guide, Changelog.
## Structure changes
- Top-level nav: AI → **Agents**, with sub-groups for *Building agents /
Features / Patterns / Reference*.
- New RC banner snippet on every page links to the supported AI SDK
versions table on the API Reference.
- All examples use Anthropic with `stopWhen: stepCountIs(15)`.
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Matt Aitken