From 5d4f8b36a66540feab4a9fc026e9a791ce1de580 Mon Sep 17 00:00:00 2001 From: Hamza Shah <87142882+Hamjaster@users.noreply.github.com> Date: Thu, 27 Aug 2026 03:33:56 +0500 Subject: [PATCH] fix(fireworks_ai): stop using the trace id as the session affinity key (#35754) get_fireworks_session_id fell back to litellm_trace_id when no session id was given. That id is generated per request (uuid4 when absent), so x-session-affinity carried a different value every time and Fireworks prompt caching never hit; cached_tokens stayed 0 across identical prompts. The None path the original change described was effectively unreachable because of it. Drop the fallback so affinity comes only from an id the caller actually supplied: litellm_session_id, session_id, or metadata.session_id. Callers who were relying on a trace id for affinity can pass litellm_session_id instead, which is stable across the requests they want grouped. Co-authored-by: mubashir1osmani --- litellm/llms/fireworks_ai/common_utils.py | 10 +++++-- .../test_fireworks_ai_chat_transformation.py | 28 +++++++++++++++++-- 2 files changed, 33 insertions(+), 5 deletions(-) diff --git a/litellm/llms/fireworks_ai/common_utils.py b/litellm/llms/fireworks_ai/common_utils.py index 8e35cfebc5b..8c306faa036 100644 --- a/litellm/llms/fireworks_ai/common_utils.py +++ b/litellm/llms/fireworks_ai/common_utils.py @@ -13,6 +13,13 @@ class FireworksAIException(BaseLLMException): def get_fireworks_session_id(litellm_params: dict) -> str | None: + """ + Session id to send as `x-session-affinity`, or None when the caller gave none. + + Deliberately does not fall back to `litellm_trace_id`: that is generated per + request (`str(uuid.uuid4())` when absent), so using it pins every request to a + different Fireworks node and prompt caching never hits. + """ params: Final = litellm_params for key in ("litellm_session_id", "session_id"): value = params.get(key) @@ -23,9 +30,6 @@ def get_fireworks_session_id(litellm_params: dict) -> str | None: value = metadata.get("session_id") if value: return str(value) - value = params.get("litellm_trace_id") - if value: - return str(value) return None diff --git a/tests/test_litellm/llms/fireworks_ai/chat/test_fireworks_ai_chat_transformation.py b/tests/test_litellm/llms/fireworks_ai/chat/test_fireworks_ai_chat_transformation.py index 63a749dab84..95ec183792d 100644 --- a/tests/test_litellm/llms/fireworks_ai/chat/test_fireworks_ai_chat_transformation.py +++ b/tests/test_litellm/llms/fireworks_ai/chat/test_fireworks_ai_chat_transformation.py @@ -73,7 +73,13 @@ def test_validate_environment_sets_session_affinity_from_session_id(): assert headers["x-session-affinity"] == "session-id-123" -def test_validate_environment_sets_session_affinity_from_trace_id(): +def test_validate_environment_ignores_trace_id_for_session_affinity(): + """A trace id must not become the session id. + + litellm_trace_id defaults to a fresh uuid4 per request, so pinning + x-session-affinity to it sent every request to a different Fireworks node and + prompt caching never hit (cached_tokens stayed 0 across identical prompts). + """ config = FireworksAIConfig() headers = config.validate_environment( @@ -85,7 +91,25 @@ def test_validate_environment_sets_session_affinity_from_trace_id(): api_key="test-key", ) - assert headers["x-session-affinity"] == "trace-id-123" + assert "x-session-affinity" not in headers + + +def test_validate_environment_prefers_session_id_over_trace_id(): + config = FireworksAIConfig() + + headers = config.validate_environment( + headers={}, + model="accounts/fireworks/models/test-model", + messages=[], + optional_params={}, + litellm_params={ + "litellm_session_id": "session-123", + "litellm_trace_id": "trace-id-123", + }, + api_key="test-key", + ) + + assert headers["x-session-affinity"] == "session-123" def test_validate_environment_does_not_set_session_affinity_without_session_id():