fix(agent): Ollama の format に移植スキーマを渡し文法変換失敗を解消

[yusuke0610]

概要

ローカル Ollama 経路（LLM_LOCAL_OLLAMA=1）で Agent チャットが 502 になっていた不具合を修正する。

原因

OllamaClient が /api/chat の format に 生スキーマ（build_output_schema）を渡しており、その value.maxLength(2000) / suggestions.maxItems(4) を llama.cpp の JSON Schema → GBNF 文法変換が解釈できず、{"error":{"message":"Failed to initialize samplers: failed to parse grammar"}} の 400 を返していた。これが LLMError → 502 になっていた。

実機 curl で切り分け済み:

• oneOf のみ → 200（無罪）
• フルスキーマ → 400（failed to parse grammar）
• maxLength/maxItems を除去（to_portable_schema 相当）→ 200

変更内容

• ollama_client.py: format に to_portable_schema(output_schema, drop_additional_properties=False) を渡す（maxLength/maxItems 除去・oneOf→enum 平坦化）。Gemini/OpenAI と同じ移植スキーマ経路に揃える。
• output_schema.py: 「Ollama は maxLength を助言扱い／生スキーマをそのまま使う」という誤った前提のコメントを実態（数値制約で文法変換が壊れる）に修正。ロジックは無変更。
• tests/test_llm_clients.py: 回帰テスト追加。Ollama に投げる format に oneOf/maxLength/maxItems が残らず、field が enum に畳まれることを検証。

影響範囲

• 文字数上限の実強制は従来どおり chat_service._parse_response（二重防衛）が担うため品質は不変。
• Anthropic / Gemini / OpenAI 経路は無変更（to_portable_schema の本体は触らず、Ollama を相乗りさせただけ）。

検証

• make lint-backend: pass
• make test-backend: pass（633 passed）
• 実機: 移植スキーマ相当のペイロードが Ollama /api/chat で 200 を返すことを curl で確認

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved compatibility when sending structured responses to the AI service by converting schemas into a more portable format before requests are made.
  • Reduced failures caused by schema constraints that are not reliably supported by some model backends.

• Tests

  • Added coverage to verify the request payload uses the portable schema format and preserves allowed field values.

[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: e66b3fd4-1b6a-4524-843f-878ad8ae8aa1

📥 Commits

Reviewing files that changed from the base of the PR and between 395b512 and fa75ff1.

📒 Files selected for processing (3)

• backend/app/services/agent/llm/ollama_client.py
• backend/app/services/agent/output_schema.py
• backend/tests/test_llm_clients.py

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📝 Walkthrough

Walkthrough

OllamaClient.generate now applies to_portable_schema to output_schema before placing it in the Ollama /api/chat request's format field, removing JSON Schema keywords (oneOf, maxLength, maxItems) that break llama.cpp grammar conversion. Docstrings in both files are updated, and a new test verifies the transformed payload.

Changes

Ollama Portable Schema

Layer / File(s)	Summary
Schema transformation and docs backend/app/services/agent/llm/ollama_client.py, backend/app/services/agent/output_schema.py	OllamaClient imports and applies to_portable_schema(output_schema, drop_additional_properties=False) for the format payload field. Docstrings in both files clarify which providers use the portable schema and that length enforcement is delegated to _parse_response.
Payload verification test backend/tests/test_llm_clients.py	test_ollama_client_sends_portable_schema captures the outgoing request via a monkeypatched httpx.AsyncClient and asserts the format field contains no oneOf, maxLength, or maxItems, and that project.field is folded into an enum.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 Hop hop, the grammar's clear,
No maxLength to cause llama fear,
oneOf dropped, the schema neat,
Portable format, what a treat!
The rabbit cheers — constraints complete! 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Ollama の format に移植スキーマを渡して grammar 変換失敗を解消する内容で、変更の主旨を適切に表しています。
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/ollama-format-portable-schema

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