## Summary
Sending a chat message immediately after an action (for example an undo)
could make the message's response vanish from the UI. The transport
opened a response stream that closed on the *earlier* turn's completion
instead of waiting for the send's own turn. The agent still produced and
persisted the answer, so it reappeared on refresh. Same "disappearing
message" class as
[#4176](https://github.com/triggerdotdev/trigger.dev/pull/4176),
different cause.
## Fix
A send's response stream had no way to tell whether a `turn-complete`
belonged to its turn. `POST /realtime/v1/sessions/:id/in/append` now
returns the appended record's sequence number, and the transport skips
any turn-complete whose `session-in-event-id` (the agent's committed
`.in` cursor) is below that seq, closing only on its own turn. Older
webapps omit the seq, in which case the transport falls back to the
previous behavior, so the SDK and server can ship independently.
Because the fix spans the SDK and the server, both a webapp deploy and
an SDK release are needed for the full effect.
Verified end to end with the ai-chat reference app:
undo-then-immediate-send loses the follow-up's answer before the fix and
streams it inline after, with a revert-the-guard run reproducing the
loss on the same script. Unit tests cover the skip and the no-seq
fallback.
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
Accuracy fixes across the AI chat docs: drop the non-existent per-call
option from `transport.preload`, clarify that `onValidateMessages` only
fires on turns carrying incoming messages, soften the turn-complete
token-refresh wording (the header is optional), document the new
`onTurnComplete` `error` field and `finishReason`, and correct the
idle-timeout default to 30 seconds.
## Summary
Updates the AI chat docs to match the slim-wire + field-level merge
behavior shipped in #3719 and the precise `.in/append` cap +
CORS-readable 413 shipped in #3720. No behavior changes here — code is
correct in `main`; the docs were lagging on three patterns customers
copy out of the page.
## What changed
- **`hydrateMessages` examples upsert by id** (in `lifecycle-hooks.mdx`,
`patterns/database-persistence.mdx`, and
`patterns/persistence-and-replay.mdx`). The previous
`stored.push(newMsg)` pattern duplicated the assistant id on HITL
continuations and caused the LLM to receive a tool call with no
`arguments`. The new examples include the rationale inline.
- **`onValidateMessages` example filters to user messages**
(`lifecycle-hooks.mdx`). The previous example called
`validateUIMessages({ messages, tools })` directly, which now throws on
HITL slim wires (the AI SDK schema requires `input` on resolved tool
parts). New example shows the filter pattern, with a Warning callout
explaining why.
- **Merge contract description updated** (`lifecycle-hooks.mdx`). The
old wording said incoming messages are "auto-merged" / "replaced"; the
new description explains the actual field-level overlay (state advances
only).
- **Approval-responded wire example slimmed** (`client-protocol.mdx`).
Shows the minimum shape the agent reads — `state` + `approval` (or
`output` / `errorText` for HITL). Notes that the built-in transports
ship this slim shape by default and that fuller shapes are still
accepted.
- **`/in/append` 413 row and FAQ updated** (`client-protocol.mdx`,
`patterns/trusted-edge-signals.mdx`). Reflects the new precise S2 cap
and the CORS-readable 413.
- **New changelog entry** at the top of `changelog.mdx` covering all of
the above.
The historical `## 512 KiB ceiling removed` entry further down the
changelog is left as-is (it's a snapshot of the prior transition), and
the v4.5 upgrade-guide section is skipped — the merge contract is
backwards compatible.
## Test plan
- Mintlify dev preview renders cleanly with no broken anchors
- Linked references resolve (`/ai-chat/lifecycle-hooks#hydratemessages`,
`/ai-chat/lifecycle-hooks#onvalidatemessages`,
`/ai-chat/patterns/database-persistence#alternative-hydratemessages`,
`/ai-chat/client-protocol#step-3-send-messages-stops-and-actions`,
`/ai-chat/patterns/large-payloads`)
## 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>
Eric Allam