fix(tests): align run_agent expectations with current routing

[kshitijk4poor]

Summary

• make TestBuildApiKwargs explicitly target the current OpenRouter route/model combinations required for extra_body assertions
• make the Claude prompt-caching test explicitly use the OpenRouter base URL instead of relying on implicit defaults
• patch the streaming fallback test to mock the request-scoped OpenAI client factory introduced in the current run_agent.py path

Problem

While validating #4552, the broader tests/test_run_agent.py tests/test_run_agent_codex_responses.py -q run hit unrelated failures on current main in tests/test_run_agent.py:

• TestBuildApiKwargs::* expected extra_body on a fixture that no longer explicitly targeted an OpenRouter-compatible route/model
• TestInit.test_prompt_caching_claude_openrouter expected Claude-via-OpenRouter prompt caching without explicitly setting the OpenRouter base URL
• TestStreamingApiCall.test_api_exception_falls_back_to_non_streaming only patched agent.client, but the current implementation now creates request-scoped clients through _create_request_openai_client

These were test-drift issues, not production regressions in run_agent.py.

Fix

1. Make routing assumptions explicit in TestBuildApiKwargs

The extra_body assertions now set:

• agent.base_url = "https://openrouter.ai/api/v1"
• a reasoning-capable OpenRouter model where needed

This matches the current _build_api_kwargs() gates instead of relying on fixture defaults.

2. Make the Claude prompt-caching test explicitly OpenRouter

test_prompt_caching_claude_openrouter now passes the OpenRouter base URL directly, so it tests the intended path instead of an implicit default that has drifted.

3. Patch request-scoped client creation in the streaming fallback test

test_api_exception_falls_back_to_non_streaming now mocks _create_request_openai_client so both the streaming path and the non-streaming fallback use the same mocked client and raise the expected ConnectionError.

Test Results

Passed:

• python -m pytest tests/test_run_agent.py -q -k "TestBuildApiKwargs or test_prompt_caching_claude_openrouter or test_api_exception_falls_back_to_non_streaming"
• python -m pytest tests/test_run_agent.py tests/test_run_agent_codex_responses.py -q

This follow-up is intentionally test-only and separate from #4552.

[teknium1]

Thanks for the contribution, @kshitijk4poor!

Closing this as stale. The test tree was rearchitected in #5946 — tests are now under tests/run_agent/ as individual test files rather than a single tests/test_run_agent.py. The file this PR modifies no longer exists on main.

If you want to revisit this for the refactored code on current main, please open a new PR rebased on main targeting the current file layout. Your authorship will be preserved through cherry-pick if we salvage any of your work.