fix(runtime): deliver the history-compact instruction as a trailing user message

[ggbdpq]

Summary

Fixes the root cause of #4634: the history summarizer delivered SUMMARIZATION_SYSTEM_PROMPT as provider instructions (system role). Agentic coding models such as kimi-coding-plan / k3-256k ignore that shape and keep answering the conversation, so every fold failed open with malformed_summary_missing_section, and the distinct system prompt also forfeited the main loop's prefix cache for every discarded summarizer call.

The instruction now rides as the request's trailing user message — the request already ended with one for chat-template models (#4559); generateSummary appends a single user message combining the sectioned prompt (or its shorten/repair variant) with the existing summary request, and AiSdkGenerateTextOptions drops the now-unused instructions field.

Scope: direction 1 from the issue. Of the contributing defects listed there, the missing output cap is already fixed on current main by #4653 (DEFAULT_HISTORY_COMPACT_MAX_OUTPUT_TOKENS, landed 09-03, after the reporter's build); extending the failure circuit to provider_error/output_length and bounding the summarizer input budget remain open follow-ups best split into their own issues.

Verification

Claim	Command	Result
Targeted suites green	npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/runtime run build, then node --test on history-compact-summarizer / effective-history-compaction / mid-turn-capacity-backend dist tests	139 tests, 139 pass, 0 fail
Red-green: the new test fails without the fix	git stash push -- packages/runtime/src/history-compact-summarizer.ts, rebuild, rerun the summarizer suite	53 tests, 3 fail (the new trailing-instruction test + the two variant-prompt captures); restored → 53/53 pass
New regression test	delivers the summarization instruction as the trailing user message (#4634)	asserts no instructions field reaches generateText and the final user message carries both the sectioned prompt and the summary request
Format	npm run format:check	exit 0, 1,942 files clean
License headers	npm run check:asf-headers	both changed files pass

AI use

Implemented with ZCode (GLM-5.3-Flash): read the issue's reproduction data, traced the summarizer request shape in packages/runtime/src/history-compact-summarizer.ts, and made the minimal request-shape change with a red-green regression test. The commit carries the Generated-by trailer.

Checklist

• Root-cause fix in the shared summarizer builder; no per-provider branching requested by the issue
• Regression test fails on the old code (verified via stash/rebuild)
• Test style follows the existing file (node:test + assert/strict, issue number in the test name)
• No new dependencies; docs unchanged

[hqhq1025]

Reviewed exact head 903aac5ae22ac823724b3cc47ba83a90b342e54f.

No P0-P3 findings.

The change consistently removes the separate system-role instructions field and appends the full sectioned summarization prompt plus the existing summary request as the final user message for the initial call, output-limit retry, and malformed-summary repair. Rolling checkpoints still prepend the previous summary and replay only newly folded events. I also exercised the real AI SDK lowering with a mock language model: the provider-facing prompt retained the original conversation followed by one final user instruction and contained no system message.

Validation completed: Core, Storage, and Runtime builds; 139 focused compaction tests; full Runtime suite (3,201 passed, 13 skipped, 0 failed); repository lint, format, and ASF header checks; git diff --check; clean exact-main merge; and the hosted test check on this exact head.

Residual limitation: I did not call the live k3-256k endpoint, so provider-specific behavior is supported by the issue reproduction rather than independently re-run here.

Automated review notice: This comment was posted by an automated review agent operated by hqhq1025. It is not an independent human review and does not replace one.

[Astro-Han]

Thanks for the change. Approving exact head 903aac5ae22ac823724b3cc47ba83a90b342e54f following the completed review and Astro-Han’s explicit acceptance of this merge batch. Current checks pass and no review threads remain unresolved.

Some coding models ignored system-role compaction instructions and failed to produce a valid summary. Move the shared initial, shorten and repair instruction into the existing trailing user message, retaining output validation, budgets and checkpoint ownership. No persisted-data migration; cache benefit is not independently established.

AI assistance: Codex performed the review and final-state verification; Astro-Han authorized approval and merge.

中文

感谢改动。基于已完成的审查和 Astro-Han 对本批次的明确认可，批准当前精确 head；检查通过，讨论已结清。此前说明的验证边界与后续事项保持不变。本次由 Codex 执行审查和状态核对，Astro-Han 授权批准与合并。