Three test failures caused by the real langfuse SDK import being triggered
at test time:
1. test_langfuse_prompt_management.py: Both tests create LangfusePromptManagement()
which calls `import langfuse`. Since earlier TestLangfuseUsageDetails tests
remove sys.modules["langfuse"] via patch.dict teardown, the real langfuse
import runs and fails on Python 3.14 (pydantic v1 incompatibility).
Fix: add setup_method/teardown_method to mock sys.modules["langfuse"].
2. test_langfuse.py::test_max_langfuse_clients_limit: Same root cause — creates
LangFuseLogger() without mocking sys.modules["langfuse"].
Fix: wrap test body with patch.dict("sys.modules", {"langfuse": mock}).
3. test_langfuse_otel.py::test_extract_langfuse_metadata_with_header_enrichment:
Replaces sys.modules["litellm.integrations.langfuse.langfuse"] with a stub
without restoring it, causing patch() in later tests to target the stub
instead of the real module.
Fix: use monkeypatch.setitem() which auto-restores after the test.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
* Fix: Map Gemini cached_tokens to Langfuse cache_read_input_tokens
Fixes#18520
## Problem
Langfuse integration was not capturing cached tokens from Gemini models.
Gemini returns cached tokens in `usage.prompt_tokens_details.cached_tokens`,
but Langfuse only read from top-level `usage.cache_read_input_tokens`
(which only Anthropic populates).
## Solution
Updated langfuse.py to check both locations:
1. First check top-level cache_read_input_tokens (for Anthropic)
2. Then check prompt_tokens_details.cached_tokens (for Gemini, OpenAI, others)
This ensures all providers' cached tokens are properly reported to Langfuse.
## Changes
- Modified litellm/integrations/langfuse/langfuse.py (lines 742-761)
- Added 3 unit tests in tests/test_litellm/integrations/langfuse/test_gemini_cached_tokens.py
- All existing Langfuse tests still pass (11/11)
## Testing
- test_cached_tokens_extraction: Verifies Gemini cached_tokens extraction
- test_cached_tokens_not_present: Backward compatibility (no cached_tokens)
- test_cached_tokens_is_zero: Edge case when cached_tokens = 0
* Refactor: Extract cache token logic into helper function
Address review feedback from @officer47p
- Created _extract_cache_read_input_tokens() helper function
- Reduces code bloat in _log_langfuse_v2 method
- Improves testability and reusability
- All tests still passing (11/11)
