feat(sdk): chat.headStart handover for customAgent and createSession#3963
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chat.headStart previously handed the warm step-1 response over only to chat.agent. Now chat.customAgent (via conversation.consumeHandover) and chat.createSession (via turn.handover) consume it too, and a resumed tool round merges into the handed-over assistant instead of throwing or duplicating it. Also adds triggerConfig support to chat.headStart() and chat.openSession() so the handover-prepare run inherits tags, queue, and other session run options. Co-authored-by: saasjesus <armin@chatarmin.com>
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…3964) ## Summary `chat.headStart` now works with the `chat.customAgent` and `chat.createSession` backends (not just `chat.agent`), and takes a `triggerConfig` option. These docs cover both. The Fast starts guide gets a "Handover with custom agents" section showing how each backend consumes the handover (`consumeHandover` returning `{ isFinal, skipped }` for custom agents, `turn.handover` for createSession), including threading `originalMessages` so a resumed tool round merges into the handed-over assistant. The `chat.headStart` API section documents `triggerConfig` (tags, queue, machine, and the rest) on the auto-triggered run. The reference picks up `ChatTurn.handover`, `turn.complete()` with no source, `chat.waitForHandover`, and a new `HeadStartHandlerOptions` table. Docs for the SDK changes in [#3963](#3963).
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## Summary 7 improvements. ## Improvements - `@trigger.dev/sdk` now bundles the Trigger.dev agent skills and a curated snapshot of the docs those skills reference. The skills that `trigger skills` installs into your coding agent read this content from node_modules, so the guidance your AI assistant follows is pinned to the SDK version installed in your project and stays current across upgrades instead of going stale until the next reinstall. ([#3937](#3937)) - Running a CLI command like `dev`, `deploy`, `preview`, or `update` before initializing a project no longer crashes with a raw `Cannot find matching package.json` stack trace. The CLI now detects the missing project and points you to `npx trigger.dev@latest init` instead. ([#3929](#3929)) - The agent skills installed by `trigger skills` are now namespaced with a `trigger-` prefix (e.g. `trigger-authoring-tasks`, `trigger-getting-started`) so they don't collide with unrelated skills in your coding agent's skills directory. Adds a `trigger-cost-savings` skill for auditing and reducing compute spend (right-sizing machines, `maxDuration`, batching, debounce), and `@trigger.dev/sdk` now bundles the full Trigger.dev documentation so your agent can read the complete, version-pinned reference directly from node_modules. ([#3970](#3970)) - The run span API response now includes `cachedCost` and `cacheCreationCost` on the `ai` object, alongside the existing `inputCost` / `outputCost` / `totalCost`. `inputCost` reflects only the non-cached input, so these fields let you reconstruct the full cost breakdown for prompt-cached calls. ([#3958](#3958)) - `chat.headStart` now works with the `chat.customAgent` and `chat.createSession` backends, not only `chat.agent`. The warm step-1 response hands over to your loop the same way it does for a managed agent. ([#3963](#3963)) In a `chat.customAgent` loop, consume the handover on turn 0: ```ts const conversation = new chat.MessageAccumulator(); const { isFinal, skipped } = await conversation.consumeHandover({ payload }); if (skipped) return; // warm handler aborted, so exit without a turn if (isFinal) { await chat.writeTurnComplete(); // step 1 is the response, no streamText } else { const result = streamText({ model, messages: conversation.modelMessages, tools }); // Pass originalMessages so the handed-over tool round merges into the // step-1 assistant instead of starting a new message. const response = await chat.pipeAndCapture(result, { originalMessages: conversation.uiMessages, }); if (response) await conversation.addResponse(response); } ``` With `chat.createSession`, the iterator surfaces it as `turn.handover`; call `turn.complete()` with no argument on a final handover. The lower-level `chat.waitForHandover()` and `accumulator.applyHandover()` are also exported for hand-rolled loops. - Cache your chat agent's system prompt with Anthropic prompt caching. `chat.toStreamTextOptions()` now emits the system prompt as a cacheable message when you opt in, so a large, stable system block is billed at cache-read rates on every turn instead of full price. ([#3952](#3952)) ```ts // at the streamText call site (Anthropic sugar) streamText({ ...chat.toStreamTextOptions({ cacheControl: { type: "ephemeral" } }), messages, }); // provider-agnostic equivalent chat.toStreamTextOptions({ systemProviderOptions: { anthropic: { cacheControl: { type: "ephemeral" } } }, }); // or where the prompt is defined chat.prompt.set(SYSTEM_PROMPT, { providerOptions: { anthropic: { cacheControl: { type: "ephemeral" } } }, }); ``` Without an option, `system` stays a plain string. Pairs with a `prepareMessages` cache breakpoint to cache the conversation prefix across turns too. - Three fixes for custom agent loops (`chat.customAgent`, `chat.createSession`, and hand-rolled `MessageAccumulator` loops): ([#3936](#3936)) - Continuation runs no longer replay already-answered user messages into the first turn. The `.in` resume cursor is now seeded before any listener attaches (the same boot logic `chat.agent` uses), so a chat that continues after a cancel, crash, or upgrade only sees genuinely new messages. - Steering a hand-rolled loop mid-stream no longer wipes the in-flight assistant response. `chat.pipeAndCapture` now stamps a server-generated message id on the stream, so a `prepareStep` injection keeps the partial text instead of replacing the message. - Task-backed tools (`ai.toolExecute`) now work from custom agent loops: the parent's session is threaded to the child run, so child tasks can stream progress into the chat with `chat.stream.writer({ target: "root" })` instead of failing with "session handle is not initialized". <details> <summary>Raw changeset output</summary>⚠️ ⚠️ ⚠️ ⚠️ ⚠️ ⚠️ `main` is currently in **pre mode** so this branch has prereleases rather than normal releases. If you want to exit prereleases, run `changeset pre exit` on `main`.⚠️ ⚠️ ⚠️ ⚠️ ⚠️ ⚠️ # Releases ## @trigger.dev/build@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## trigger.dev@4.5.0-rc.7 ### Patch Changes - `@trigger.dev/sdk` now bundles the Trigger.dev agent skills and a curated snapshot of the docs those skills reference. The skills that `trigger skills` installs into your coding agent read this content from node_modules, so the guidance your AI assistant follows is pinned to the SDK version installed in your project and stays current across upgrades instead of going stale until the next reinstall. ([#3937](#3937)) - Running a CLI command like `dev`, `deploy`, `preview`, or `update` before initializing a project no longer crashes with a raw `Cannot find matching package.json` stack trace. The CLI now detects the missing project and points you to `npx trigger.dev@latest init` instead. ([#3929](#3929)) - The agent skills installed by `trigger skills` are now namespaced with a `trigger-` prefix (e.g. `trigger-authoring-tasks`, `trigger-getting-started`) so they don't collide with unrelated skills in your coding agent's skills directory. Adds a `trigger-cost-savings` skill for auditing and reducing compute spend (right-sizing machines, `maxDuration`, batching, debounce), and `@trigger.dev/sdk` now bundles the full Trigger.dev documentation so your agent can read the complete, version-pinned reference directly from node_modules. ([#3970](#3970)) - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` - `@trigger.dev/build@4.5.0-rc.7` - `@trigger.dev/schema-to-json@4.5.0-rc.7` ## @trigger.dev/core@4.5.0-rc.7 ### Patch Changes - The run span API response now includes `cachedCost` and `cacheCreationCost` on the `ai` object, alongside the existing `inputCost` / `outputCost` / `totalCost`. `inputCost` reflects only the non-cached input, so these fields let you reconstruct the full cost breakdown for prompt-cached calls. ([#3958](#3958)) ## @trigger.dev/python@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/sdk@4.5.0-rc.7` - `@trigger.dev/core@4.5.0-rc.7` - `@trigger.dev/build@4.5.0-rc.7` ## @trigger.dev/react-hooks@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## @trigger.dev/redis-worker@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## @trigger.dev/rsc@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## @trigger.dev/schema-to-json@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## @trigger.dev/sdk@4.5.0-rc.7 ### Patch Changes - `@trigger.dev/sdk` now bundles the Trigger.dev agent skills and a curated snapshot of the docs those skills reference. The skills that `trigger skills` installs into your coding agent read this content from node_modules, so the guidance your AI assistant follows is pinned to the SDK version installed in your project and stays current across upgrades instead of going stale until the next reinstall. ([#3937](#3937)) - `chat.headStart` now works with the `chat.customAgent` and `chat.createSession` backends, not only `chat.agent`. The warm step-1 response hands over to your loop the same way it does for a managed agent. ([#3963](#3963)) In a `chat.customAgent` loop, consume the handover on turn 0: ```ts const conversation = new chat.MessageAccumulator(); const { isFinal, skipped } = await conversation.consumeHandover({ payload }); if (skipped) return; // warm handler aborted, so exit without a turn if (isFinal) { await chat.writeTurnComplete(); // step 1 is the response, no streamText } else { const result = streamText({ model, messages: conversation.modelMessages, tools }); // Pass originalMessages so the handed-over tool round merges into the // step-1 assistant instead of starting a new message. const response = await chat.pipeAndCapture(result, { originalMessages: conversation.uiMessages, }); if (response) await conversation.addResponse(response); } ``` With `chat.createSession`, the iterator surfaces it as `turn.handover`; call `turn.complete()` with no argument on a final handover. The lower-level `chat.waitForHandover()` and `accumulator.applyHandover()` are also exported for hand-rolled loops. - Add `triggerConfig` support to `chat.headStart()` and `chat.openSession()`, so the auto-triggered handover-prepare run inherits tags, queue, machine, and other session trigger options the same way `chat.createStartSessionAction()` does. The `chat:{chatId}` tag is prepended automatically. ([#3963](#3963)) ```ts export const POST = chat.headStart({ agentId: "my-agent", triggerConfig: { tags: ["org:acme"], queue: "chat" }, run: async ({ chat }) => streamText({ ...chat.toStreamTextOptions(), model }), }); ``` Because the session is created once on the first head-start turn and is idempotent on the chat id, this is the only place to set those options for a head-start chat's lifetime. `chat.createStartSessionAction()` now also forwards `maxDuration`, `region`, and `lockToVersion` so both session entry points stay consistent. - Cache your chat agent's system prompt with Anthropic prompt caching. `chat.toStreamTextOptions()` now emits the system prompt as a cacheable message when you opt in, so a large, stable system block is billed at cache-read rates on every turn instead of full price. ([#3952](#3952)) ```ts // at the streamText call site (Anthropic sugar) streamText({ ...chat.toStreamTextOptions({ cacheControl: { type: "ephemeral" } }), messages, }); // provider-agnostic equivalent chat.toStreamTextOptions({ systemProviderOptions: { anthropic: { cacheControl: { type: "ephemeral" } } }, }); // or where the prompt is defined chat.prompt.set(SYSTEM_PROMPT, { providerOptions: { anthropic: { cacheControl: { type: "ephemeral" } } }, }); ``` Without an option, `system` stays a plain string. Pairs with a `prepareMessages` cache breakpoint to cache the conversation prefix across turns too. - Three fixes for custom agent loops (`chat.customAgent`, `chat.createSession`, and hand-rolled `MessageAccumulator` loops): ([#3936](#3936)) - Continuation runs no longer replay already-answered user messages into the first turn. The `.in` resume cursor is now seeded before any listener attaches (the same boot logic `chat.agent` uses), so a chat that continues after a cancel, crash, or upgrade only sees genuinely new messages. - Steering a hand-rolled loop mid-stream no longer wipes the in-flight assistant response. `chat.pipeAndCapture` now stamps a server-generated message id on the stream, so a `prepareStep` injection keeps the partial text instead of replacing the message. - Task-backed tools (`ai.toolExecute`) now work from custom agent loops: the parent's session is threaded to the child run, so child tasks can stream progress into the chat with `chat.stream.writer({ target: "root" })` instead of failing with "session handle is not initialized". - The agent skills installed by `trigger skills` are now namespaced with a `trigger-` prefix (e.g. `trigger-authoring-tasks`, `trigger-getting-started`) so they don't collide with unrelated skills in your coding agent's skills directory. Adds a `trigger-cost-savings` skill for auditing and reducing compute spend (right-sizing machines, `maxDuration`, batching, debounce), and `@trigger.dev/sdk` now bundles the full Trigger.dev documentation so your agent can read the complete, version-pinned reference directly from node_modules. ([#3970](#3970)) - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` ## @trigger.dev/plugins@4.5.0-rc.7 ### Patch Changes - Updated dependencies: - `@trigger.dev/core@4.5.0-rc.7` </details> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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Summary
chat.headStart(the warm step-1 fast path) previously handed its response over only tochat.agent. This extends handover to the other two backends:chat.customAgentconsumes it withconversation.consumeHandover({ payload })on turn 0, andchat.createSessionsurfaces it asturn.handover(callturn.complete()with no source to finalize a pure-text handover). The low-levelchat.waitForHandover()andaccumulator.applyHandover()are exported for hand-rolled loops.It also adds
triggerConfigtochat.headStart()andchat.openSession(), so the auto-triggered handover-prepare run inherits tags, queue, machine, and the other session run options the same waychat.createStartSessionAction()does. Thechat:{chatId}tag is prepended automatically. Because the session is created once on the first head-start turn (idempotent on the chat id), this is the only place those options can be set for a head-start chat's lifetime.Fix: tool-call resume
When the warm step-1 hands over a pending tool call (rather than pure text), the agent loop resumes that tool round. For it to merge cleanly the pipe threads the spliced partial as
originalMessages, so the resumed tool-output chunk attaches to the handed-over tool-call instead of throwingNo tool invocation found.MessageAccumulator.addResponsenow also dedups by id (replace-in-place), so the persisted history doesn't carry a duplicate assistant message when the resumed response reuses the partial's id.Incorporates the
triggerConfigwork from #3933 by @saasjesus, withcreateStartSessionActionextended to also forwardmaxDuration,region, andlockToVersionso the two session entry points stay consistent.Verified end-to-end against a local environment: handover (pure-text and tool-call) on both new backends, a
chat.agentregression pass, andtriggerConfigtags and queue landing on the run.