[devin-ai-integration]

Summary

Adds hermetic unit tests for agentlab.llm.response_api and agentlab.llm.tracking. Two new files only, no src/ changes. Child 3/11 of the unit-test fan-out.

• tests/llm/test_response_api_unit.py: ToolCall/ToolCalls, the MessageBuilder base (to_markdown with tool calls, add_image_url, add_responded_tool_calls), and all three provider builders (prepare_message, handle_tool_call, content transforms, cache markers). Also APIPayload validation, tool_call_to_python_code, AgentlabAction, and the _call_api param mapping (tool_choice / force_call_tool / cache flags) plus _parse_response for OpenAIResponseModel, OpenAIChatCompletionModel and ClaudeResponseModel, and every *ModelArgs factory. The call_*_api_with_retries helpers are patched, so no HTTP calls are made.
• tests/llm/test_tracking_unit.py: LLMTracker; set_tracker nesting and restore-on-exception, plus a two-thread Barrier test showing thread-local trackers don't leak into each other; cost_tracker_decorator. All four get_pricing_* functions are covered: requests.get is mocked for OpenRouter, and the langchain/litellm tables are faked. Also covers _remove_version_suffix, the whole TrackAPIPricingMixin (pricing fallback chain, token extraction, __call__ stats), and table tests of effective cost: Anthropic cache read/write and OpenAI chat prompt_tokens_details vs responses input_tokens_details, using exact numbers and real SDK usage objects. The module-level langchain import fallbacks are covered by running a copy of the module.

Coverage (target modules)

module	before (whole suite on main)	after (new files only)
agentlab.llm.response_api	70%	99%
agentlab.llm.tracking	70%	99%

Lines still uncovered: response_api.py 426, 431 (pass bodies of abstract methods) and tracking.py 378-379 (an else that can't be reached because api_type is always "chatcompletion" or "response").

Tests: 169 collected (164 pass + 5 strict xfail). Both files together take about 5s. They pass serially, with -n 4, and in random order (pytest-randomly, several seeds, together with the existing tests/llm).

Source bugs found (tests are xfail(strict=True); src/ not modified)

1. get_effective_cost_from_antrophic_api reads usage.cache_input_tokens, but Anthropic names this field cache_read_input_tokens, so cache-read tokens are never billed.
2. On the same path, an anthropic.types.Usage leaves cache_creation_input_tokens/cache_read_input_tokens as None when caching isn't used. None * float then raises TypeError where the cost should be 0.
3. OpenAIChatCompletionModel._extract_thinking_content_from_response: tool-call-only responses have content=None, and it ends up as the literal string "None" in LLMOutput.think.
4. ClaudeResponseModel.filter_system_messages checks c.get("type") == "image", but builder content looks like {"image": ...}, so an image added to a system message with add_image is never rejected.
5. OpenAIChatCompletionModel.__init__ doesn't pass api_key to super(), so model.api_key is None even when a key was given (the client still gets it).

Run

uv run pytest tests/llm/test_response_api_unit.py tests/llm/test_tracking_unit.py -p no:cacheprovider -q        # add -n 4 for xdist
uv run --with pytest-cov pytest tests/llm/test_response_api_unit.py tests/llm/test_tracking_unit.py -p no:cacheprovider -q --cov=agentlab.llm.response_api --cov=agentlab.llm.tracking --cov-report=term-missing

Devin-Org: engineering

Link to Devin session: https://devin-gtm.devinenterprise.com/sessions/3d7d885106884ebe8bca1efe65c5bfa4
Open in Devin Desktop: https://devin-gtm.devinenterprise.com/desktop/session/3d7d885106884ebe8bca1efe65c5bfa4?variant=devin
Requested by: @danigrim

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.