fix(server): keep regenerated titles on topic

[t3dotgg]

Regenerated titles can drift toward the latest assistant finding or operational follow-up, especially after the original request falls out of the recent context window.

This gives regeneration its own subject-selection guidance and keeps the opening user message inside the existing 8,000-character budget alongside the recent tail. Opening image context is retained too.

Testing

• vp test run apps/server/src/textGeneration/TextGenerationPrompts.test.ts apps/server/src/orchestration/Layers/ProviderCommandReactor.test.ts
• git diff --check
• Server typecheck attempted; currently fails on existing unrelated Effect and Bun typing errors across the package

Generated by GPT-5.6 Sol (high reasoning) through the Codex harness in T3 Code.

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Note

Low Risk
Localized server-side title regeneration and prompt text; behavior is covered by tests and does not touch auth, persistence, or provider session logic.

Overview
Regenerated thread titles were drifting toward the latest assistant finding or operational detail when long threads exceeded the title model’s context window.

Context assembly (formatThreadTitleContext in ProviderCommandReactor) now, when the 8,000-character budget is exceeded, pins the first USER section (up to 2,000 chars, with [First user message truncated] if needed), then [Earlier content truncated] and the recent message tail. Title-generation attachments prefer the first user message’s first image plus recent retained images (up to four, deduped).

Regeneration prompts (buildThreadTitlePrompt) use separate guidance and editorial rules: prioritize the user’s durable goal, don’t elevate a single assistant finding unless the user adopts it, and add afterRules examples (e.g. subagent-monitoring review vs. one Codex bug). First-turn title prompts are unchanged.

Tests cover long-thread pinning, attachment selection, and updated prompt expectations.

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Note

Fix thread title regeneration to stay on topic by pinning the first user message

• Updates buildThreadTitlePrompt in TextGenerationPrompts.ts with regeneration-specific instruction wording, guidance, and rules that direct the model to identify the durable thread subject from USER messages rather than promoting transient assistant findings.
• Updates formatThreadTitleContext in ProviderCommandReactor.ts so that when the context exceeds 8,000 chars, the first USER message section is pinned at the start (capped at 2,000 chars), followed by [Earlier content truncated] and the recent tail.
• Attachments for title generation now include the first user message's first attachment plus recent retained attachments, up to four total, excluding duplicates.
• Adds an afterRules field to PromptFromMessageInput so regeneration prompts can append worked examples (e.g. distinguishing a durable bug topic from a transient subagent-monitoring state) directly after the rules block.

^{Macroscope summarized 224145f.}

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR changes runtime behavior for thread title regeneration by modifying both the context construction (pinning first user message when truncated) and the LLM prompt guidance. While well-tested and self-contained, changes to how generated titles are produced warrant human review.

No code changes detected at 224145f. Prior analysis still applies.

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