docs(ai-chat): add the 4.5.0-rc.7 changelog entry

[ericallam]

Summary

Adds the 4.5.0-rc.7 entry to the AI chat changelog, covering the agent-facing changes in v4.5.0-rc.7:

• chat.headStart now works with the chat.customAgent and chat.createSession backends, not just chat.agent
• Opt-in Anthropic system-prompt caching via chat.toStreamTextOptions()
• Three custom-agent-loop fixes: continuation replay, mid-stream steering, and task-backed tools
• trigger skills follow-ups: trigger- namespacing, SDK-bundled docs, and a new cost-savings skill

Generic, non-agent rc.7 items (the CLI uninitialized-project error message, run-span cost fields) are intentionally left out to keep this changelog scoped to AI chat agents.

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Reviewing files that changed from the base of the PR and between c97d246 and fa8198e.

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• docs/ai-chat/changelog.mdx

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• GitHub Check: Analyze (javascript-typescript)

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docs/**/*.mdx

📄 CodeRabbit inference engine (docs/CLAUDE.md)

docs/**/*.mdx: MDX documentation pages must include frontmatter with title (required), description (required), and sidebarTitle (optional) in YAML format
Use Mintlify components for structured content: , , , , , , /, /
Always import from @trigger.dev/sdk in code examples (never from @trigger.dev/sdk/v3)
Code examples must be complete and runnable where possible
Use language tags in code fences: typescript, bash, json

Files:

• docs/ai-chat/changelog.mdx

🧠 Learnings (4)

📚 Learning: 2026-03-10T12:44:14.176Z

Learnt from: nicktrn
Repo: triggerdotdev/trigger.dev PR: 3200
File: docs/config/config-file.mdx:353-368
Timestamp: 2026-03-10T12:44:14.176Z
Learning: In the trigger.dev repo, docs PRs are often companions to implementation PRs. When reviewing docs PRs (MDX files under docs/), check the PR description for any companion/related PR references and verify that the documented features exist in those companion PRs before flagging missing implementations. This ensures docs stay in sync with code changes across related PRs.

Applied to files:

• docs/ai-chat/changelog.mdx

📚 Learning: 2026-04-30T20:30:29.458Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3226
File: docs/ai-chat/quick-start.mdx:13-13
Timestamp: 2026-04-30T20:30:29.458Z
Learning: In this repo’s documentation MDX files (`docs/**/*.mdx`), use `ts` and `tsx` (not `typescript`) as the code-fence language tags for TypeScript/TSX snippets. Do not flag `ts`/`tsx` code-fence language tags as incorrect in any docs MDX file, since this is the site-wide Mintlify-compatible convention.

Applied to files:

• docs/ai-chat/changelog.mdx

📚 Learning: 2026-06-16T13:14:09.440Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3964
File: docs/ai-chat/reference.mdx:482-482
Timestamp: 2026-06-16T13:14:09.440Z
Learning: When documenting or reviewing usage of `ChatTurn.complete(source?)` (in `packages/trigger-sdk/src/v3/ai.ts`), note that `source` is optional (`source?: UIMessageStreamable`). Calling `complete()` with no `source` is valid specifically for a final head-start handover (`handover.isFinal`), because the warm partial already contains the response. If examples or guidance omit `source`, ensure they are in this final-hand-over context so they remain correct.

Applied to files:

• docs/ai-chat/changelog.mdx

📚 Learning: 2026-06-16T13:14:14.382Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3964
File: docs/ai-chat/reference.mdx:478-478
Timestamp: 2026-06-16T13:14:14.382Z
Learning: When reviewing RC-gated `ai-chat` docs under `docs/ai-chat/`, don’t immediately flag missing SDK type fields or implementation details just because the field isn’t present on the docs branch yet. Instead, find and cross-check the companion implementation PR that’s intended to land alongside the docs PR, and only report missing/incorrect fields if they are also absent in the companion SDK/type changes.

Applied to files:

• docs/ai-chat/changelog.mdx

🔇 Additional comments (1)

docs/ai-chat/changelog.mdx (1)

7-80: LGTM!

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Walkthrough

A new changelog entry dated June 17, 2026 (v4.5.0-rc.7) is prepended to docs/ai-chat/changelog.mdx. The entry documents four areas: chat.headStart compatibility with custom agents and chat.createSession including warm-step handover behavior; Anthropic prompt caching opt-in via chat.toStreamTextOptions() with systemProviderOptions and chat.prompt.set(); custom agent loop fixes for continuation deduplication, in-flight response preservation during steering, and task-backed tool session reuse; and trigger-skill updates covering trigger- namespacing, SDK bundling of agent skills and referenced documentation, and a new trigger-cost-savings skill.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately summarizes the main change: adding a specific changelog entry for version 4.5.0-rc.7 to the AI chat documentation.
Description check	✅ Passed	The description includes relevant context and details about the changelog entry content, but is missing several template sections: the issue reference, checklist items, testing details, and screenshots section.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/ai-chat-changelog-rc7

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