Cesar Garcia 0e601d0bfe Fix: Map Gemini cached_tokens to Langfuse cache_read_input_tokens (#18614) ...

* 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)

2026-01-06 01:34:09 +05:30

..

test_gemini_cached_tokens.py

Fix: Map Gemini cached_tokens to Langfuse cache_read_input_tokens (#18614)

2026-01-06 01:34:09 +05:30

test_langfuse_prompt_management.py

fix: not working log_failure_event in langfuse

2025-12-19 16:54:57 +09:00