fix(hooks): adapt SessionStart acknowledgment language

[lifan-builds]

Summary

• preserve Trellis's one-shot SessionStart proof-of-load acknowledgment
• choose its language from the user message that triggers the first visible reply
• fall back to an explicitly established project communication language, then Trellis SessionStart ✓
• prevent the acknowledgment from changing the language of the remaining response
• apply byte-equivalent wording across shared hooks, Codex, OpenCode, and Pi while keeping Copilot notice-free
• preserve existing payload shapes, context timing, OpenCode persistence/deduplication, and Pi memoization

Why

The existing notice requires a fixed Chinese sentence. Because the notice is model-visible after startup, /clear, and compaction, it can steer an otherwise non-Chinese conversation into Chinese.

The acknowledgment was intentionally added as cross-platform proof that otherwise-hidden SessionStart context loaded, so this change keeps that observability instead of removing it. Language selection happens when the first visible reply is generated, when the triggering user message is normally available. No OS-locale or repository-content guessing is introduced.

Validation

• full pre-commit suite: 333 core tests passed (1 skipped), 1,389 CLI tests passed
• focused SessionStart/OpenCode/Pi tests: 396 passed
• ESLint passed
• TypeScript typecheck passed
• basedpyright passed with 0 errors (64 pre-existing unused re-export warnings)
• all four live notices verified byte-equivalent
• fixed-Chinese wording and Copilot exclusion audits passed
• git diff --check passed

Fixes #412

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added adaptive first-reply acknowledgments based on the user’s request language, with project-language and language-neutral fallbacks.
  • Session-start context now includes additional startup information while preserving one-time acknowledgment behavior.
  • Acknowledgments remain consistent with the response language and are not repeated during the session.

• Documentation

  • Updated platform integration guidance and validation requirements for adaptive acknowledgments.

• Tests

  • Expanded coverage for acknowledgment content, ordering, persistence, and suppression of duplicate context injections.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 561dd9c6-e862-4b44-b38e-397da2f9fbbd

📥 Commits

Reviewing files that changed from the base of the PR and between c6f85dc and d08d7b4.

📒 Files selected for processing (8)

• .trellis/spec/cli/backend/platform-integration.md
• packages/cli/src/templates/codex/hooks/session-start.py
• packages/cli/src/templates/opencode/lib/session-utils.js
• packages/cli/src/templates/pi/extensions/trellis/index.ts.txt
• packages/cli/src/templates/shared-hooks/session-start.py
• packages/cli/test/regression.test.ts
• packages/cli/test/templates/opencode.test.ts
• packages/cli/test/templates/pi.test.ts

---

📝 Walkthrough

Walkthrough

SessionStart first-reply notices no longer require Chinese. Specifications and platform templates now define adaptive language selection with a neutral fallback, while tests validate payload structure, notice content, ordering, and reinjection behavior.

Changes

Adaptive SessionStart acknowledgment

Layer / File(s)	Summary
Adaptive notice contract .trellis/spec/cli/backend/platform-integration.md	Defines request-language, project-language, and neutral-fallback selection, plus one-shot emission and Pi startup-context requirements.
Template notice propagation packages/cli/src/templates/{shared-hooks,codex/hooks,opencode/lib,pi/extensions}/...	Updates platform-specific FIRST_REPLY_NOTICE prompts with adaptive language rules, continuation behavior, and no-repeat constraints.
Behavior and payload validation packages/cli/test/regression.test.ts, packages/cli/test/templates/{opencode,pi}.test.ts	Validates adaptive notice content, payload shapes, ordering, negative language assertions, and suppression of history-based reinjection.

Estimated code review effort: 2 (Simple) | ~15 minutes

Possibly related PRs

• mindfold-ai/Trellis#363: Updates the related Pi before_agent_start notice and startup-context behavior.
• mindfold-ai/Trellis#368: Restructures Pi startup-context payload composition and related tests.
• mindfold-ai/Trellis#411: Adjusts SessionStart payload generation around additionalContext.

Suggested reviewers: taosu0216

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: making SessionStart acknowledgment language adaptive.
Linked Issues check	✅ Passed	The PR replaces the hard-coded Chinese SessionStart reply with adaptive language selection and a neutral fallback, matching #412.
Out of Scope Changes check	✅ Passed	The modified hooks and tests all support the SessionStart language-adaptation objective, with no unrelated changes evident.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[taosu0216]

Reviewed in depth: notice wording verified byte-equivalent across shared/Codex/OpenCode/Pi templates, Copilot stays notice-free, full CLI suite 1389/1389 green, no payload-shape regressions. Thanks for the careful fix!