fix: populate cache_creation_tokens for cost-calc path (OpenRouter)

The previous fix correctly set _cache_creation_input_tokens (private field)
from prompt_tokens_details.cache_write_tokens, which unblocked the streaming
adapter and Langfuse logging paths.

However the cost calculator in llm_cost_calc/utils.py
(_parse_prompt_tokens_details, line 442) reads
prompt_tokens_details.cache_creation_tokens (the public wrapper field), not
the private attribute. The Anthropic native mapping already sets both fields;
the OpenRouter block was inconsistent in only setting the private one.

This commit adds _ptd.cache_creation_tokens = _writes so both paths see the
correct value, and extends the unit test to assert the public field is
populated (covering the cost-calculation path that was previously untested).

Made-with: Cursor

litellm/types/utils.py

@@ -1662,10 +1662,13 @@ class Usage(SafeAttributeModel, CompletionUsage):
         ## OPENROUTER / OPENAI FORMAT MAPPING ##
         # OpenRouter (and other OpenAI-compatible providers) return cache token counts
         # in prompt_tokens_details rather than as top-level Anthropic fields.
-        # Populate the private Anthropic-style fields from prompt_tokens_details when
-        # the explicit Anthropic params (cache_creation_input_tokens,
-        # cache_read_input_tokens) were not provided, so that downstream consumers
-        # (cost calculators, streaming adapters, logging hooks) see the correct values.
+        # Populate both the private Anthropic-style fields AND the public
+        # prompt_tokens_details fields from prompt_tokens_details when the explicit
+        # Anthropic params (cache_creation_input_tokens, cache_read_input_tokens)
+        # were not provided, so that ALL downstream consumers see the correct values:
+        #   - streaming adapter / Langfuse: reads _cache_*_input_tokens (private)
+        #   - cost calculator (_parse_prompt_tokens_details): reads
+        #       prompt_tokens_details.cache_creation_tokens (public field on wrapper)
         _ptd = getattr(self, "prompt_tokens_details", None)
         if _ptd is not None:
             if not self._cache_read_input_tokens:
@@ -1676,6 +1679,10 @@ class Usage(SafeAttributeModel, CompletionUsage):
                 _writes = getattr(_ptd, "cache_write_tokens", 0) or 0
                 if _writes > 0:
                     self._cache_creation_input_tokens = _writes
+                    # Also populate the public field that the cost calculator reads
+                    # (_parse_prompt_tokens_details reads cache_creation_tokens, not
+                    # the private _cache_creation_input_tokens attribute)
+                    _ptd.cache_creation_tokens = _writes
 
         for k, v in params.items():
             setattr(self, k, v)

tests/test_litellm/types/test_types_utils.py

@@ -323,10 +323,16 @@ def test_usage_openrouter_cache_tokens_from_prompt_tokens_details():
         ),
     )
 
-    # Private Anthropic-style fields must be populated from prompt_tokens_details
+    # Private Anthropic-style fields (streaming adapter / Langfuse path)
     assert usage._cache_read_input_tokens == 17000
     assert usage._cache_creation_input_tokens == 400
 
+    # Public prompt_tokens_details fields (cost-calculator path).
+    # _parse_prompt_tokens_details in llm_cost_calc/utils.py reads
+    # prompt_tokens_details.cache_creation_tokens — it must be populated too.
+    assert usage.prompt_tokens_details is not None
+    assert usage.prompt_tokens_details.cache_creation_tokens == 400  # cost-calc path
+
     # When Anthropic native params are provided they must take precedence over
     # prompt_tokens_details so existing callers are not broken.
     usage_native = Usage(
@@ -353,3 +359,5 @@ def test_usage_openrouter_cache_tokens_from_prompt_tokens_details():
     dumped = usage_no_writes.model_dump()
     ptd = dumped.get("prompt_tokens_details", {})
     assert "cache_write_tokens" not in ptd
+    # cache_creation_tokens should also be absent when no writes were reported
+    assert "cache_creation_tokens" not in ptd