From 7419a536ad6857165b28b9b545a62d5916f696d2 Mon Sep 17 00:00:00 2001 From: tin-berri Date: Thu, 10 Sep 2026 19:18:25 -0700 Subject: [PATCH] fix(auto-router): omit Claude Code system text from classifier (#40655) Co-authored-by: Claude Code --- .../complexity_router/README.md | 7 + .../complexity_router/complexity_router.py | 15 ++- .../complexity_router/config.py | 14 +- .../router_strategy/test_complexity_router.py | 127 ++++++++++++++++++ 4 files changed, 154 insertions(+), 9 deletions(-) diff --git a/litellm/router_strategy/complexity_router/README.md b/litellm/router_strategy/complexity_router/README.md index 38dfd143cbc..1a4764c291e 100644 --- a/litellm/router_strategy/complexity_router/README.md +++ b/litellm/router_strategy/complexity_router/README.md @@ -455,6 +455,13 @@ If 2+ reasoning markers are detected in the user message, the request is promote Reasoning markers in the system prompt do **not** trigger the reasoning override. This prevents system prompts like "Think step by step before answering" from forcing all requests to the reasoning tier. +For requests identified by a `claude-cli/` or `claude-code/` user agent, the LLM classifier omits caller system +text to avoid classifying environment, agent, and skill catalogs. The current ask, configured prior-turn context, +and trajectory signal remain unchanged. The routed completion still receives the original system text. This +also excludes genuine task constraints supplied only in Claude Code system messages. Other clients keep the +existing system-context behavior. The browser routing preview has no client-identity field and retains that +generic behavior; use the real client when checking Claude Code routing. + ### Harness Reminder Blocks Agent harnesses inject their own context into the conversation as ordinary message text. That text is plumbing, not something a human asked for, so the router strips complete reminder blocks before classifying and picking a tier. A turn that is nothing but a reminder block strips to empty and is skipped, and the router falls back to the last real ask instead diff --git a/litellm/router_strategy/complexity_router/complexity_router.py b/litellm/router_strategy/complexity_router/complexity_router.py index a748bb5df27..7519f4c5156 100644 --- a/litellm/router_strategy/complexity_router/complexity_router.py +++ b/litellm/router_strategy/complexity_router/complexity_router.py @@ -48,6 +48,7 @@ from litellm.litellm_core_utils.prompt_templates.common_utils import ( request_contains_image_content, ) from litellm.litellm_core_utils.sensitive_data_masker import mask_credentials_in_payload +from litellm.llms.anthropic.common_utils import is_claude_code_user_agent from litellm.llms.base_llm.base_utils import type_to_response_format_param from litellm.router_strategy.adaptive_router.classifier import classify_prompt from litellm.router_strategy.complexity_router.tier_predictor import ( @@ -1993,8 +1994,7 @@ class ComplexityRouter(CustomLogger): Args: prompt: The current user ask text (already extracted as the real human ask, not tool results) - system_prompt: The caller's system prompt (task constraints), always included so later - turns never lose it + system_prompt: Caller task constraints, omitted from classification for Claude Code requests request_kwargs: Request metadata for spend attribution messages: Full message history for extracting prior turns and the trajectory signal """ @@ -2027,9 +2027,18 @@ class ComplexityRouter(CustomLogger): ) encrypted_task: Final = _encrypted_classifier_task(request_kwargs, marker_pairs) + caller_system_prompt: Final = ( + None + if any( + is_claude_code_user_agent(user_agent) + for metadata in (self._iter_metadata_dicts(request_kwargs) if request_kwargs is not None else ()) + if isinstance(user_agent := metadata.get("user_agent"), str) + ) + else system_prompt + ) user_payload: Final = self._build_classifier_user_payload( prompt="The delegated task in the following agent_message." if encrypted_task is not None else prompt, - system_prompt=system_prompt, + system_prompt=caller_system_prompt, prior_turns=prior_turns, messages=messages, has_prior_conversation=has_prior_conversation, diff --git a/litellm/router_strategy/complexity_router/config.py b/litellm/router_strategy/complexity_router/config.py index fb7003c887c..1f1b5a5cc4b 100644 --- a/litellm/router_strategy/complexity_router/config.py +++ b/litellm/router_strategy/complexity_router/config.py @@ -971,9 +971,11 @@ class ComplexityRouterConfig(BaseModel): "classified against what it refers to. Counts turns of both roles when " "classifier_context_include_assistant_turns is enabled. These turns are sent to the classifier " "model, which may " - "be a different deployment or provider than the routed completion model; that call already " - "carries the current user ask and the caller's system prompt in full. Set to 0 to send neither " - "prior turns nor any conversation context beyond the current ask. Only applies when " + "be a different deployment or provider than the routed completion model; that call carries " + "the current user ask and, except for Claude Code requests, the extracted system-role text in full. " + "Claude Code system text is omitted to avoid classifying harness instructions; the routed " + "completion still receives it. Set to 0 to send neither prior turns nor " + "any conversation context beyond the current ask. Only applies when " "classifier_type is 'llm'." ), ) @@ -985,9 +987,9 @@ class ComplexityRouterConfig(BaseModel): "context window, per classification call. Turns are taken newest first and quoted whole " "while they fit, so a conversation small enough to quote entirely is never cut; once the " "budget runs out the older turns are dropped whole and only the turn straddling the " - "boundary is truncated, into whatever space is left. The current ask and the caller's " - "system prompt sit outside this budget and are always sent in full, as does the numbering " - "each quoted turn carries. A budget under 120 leaves no room to quote a turn and " + "boundary is truncated, into whatever space is left. The current ask and, except for Claude " + "Code requests, the extracted system-role text sit outside this budget and are sent in full, as does " + "the numbering each quoted turn carries. A budget under 120 leaves no room to quote a turn and " "suppresses the block; set classifier_context_window_size to 0 to turn context off " "deliberately. Only applies when classifier_type is 'llm'." ), diff --git a/tests/test_litellm/router_strategy/test_complexity_router.py b/tests/test_litellm/router_strategy/test_complexity_router.py index b8e728c44a9..dddaee71a63 100644 --- a/tests/test_litellm/router_strategy/test_complexity_router.py +++ b/tests/test_litellm/router_strategy/test_complexity_router.py @@ -2676,6 +2676,26 @@ class TestEncryptedTaskClassifier: assert "source-secret" not in json.dumps(call) assert "originating_request_masked" not in call["proxy_server_request"]["body"] + @pytest.mark.asyncio + async def test_claude_code_encrypted_task_omits_caller_instructions(self): + router, dependency = _native_classifier_router() + task: Final = _encrypted_agent_task() + request: Final = { + "input": [task], + "instructions": "CLAUDE_CODE_SYSTEM", + "litellm_metadata": {"user_agent": "claude-cli/2.1.233"}, + } + original: Final = deepcopy(request) + + result: Final = await router.async_pre_routing_hook(model="encrypted-router", request_kwargs=request) + + assert result.routing_decision["cause"] == "llm_classifier" + assert request == original + call: Final = dependency.aresponses.call_args.kwargs + assert call["instructions"] == classification_system_prompt(router.config.classifier_context_window_size) + assert "CLAUDE_CODE_SYSTEM" not in json.dumps(call["input"][:-1]) + assert call["input"][-1] == task + @pytest.mark.asyncio @pytest.mark.parametrize( "items", @@ -7994,6 +8014,113 @@ _CODEX_ENVELOPES: Final = ( class TestContextAwareClassifier: """Test the new classifier context window and trajectory signals.""" + @pytest.mark.asyncio + @pytest.mark.parametrize( + "request_metadata,forwards_system", + [ + ({"metadata": {"user_agent": "claude-cli/2.1.233"}}, False), + ({"litellm_metadata": {"user_agent": "claude-code/2.1.233"}}, False), + ({"metadata": {"user_agent": "curl/8.7.1"}}, True), + ({"litellm_metadata": {}}, True), + ( + {"metadata": {"user_agent": "claude-cli/2.1.233"}, "litellm_metadata": {"user_agent": "curl/8.7.1"}}, + False, + ), + ({"metadata": {"user_agent": "Claude-Code/2.1.233"}}, True), + ], + ) + async def test_claude_code_classifier_omits_harness_system_prompt( + self, + llm_classifier_config: dict[str, object], + request_metadata: dict[str, object], + forwards_system: bool, + ) -> None: + dependency: Final = MagicMock(acompletion=AsyncMock(return_value=_llm_response('{"tier": "COMPLEX"}'))) + router: Final = ComplexityRouter( + "test-complexity-router", + dependency, + { + **llm_classifier_config, + "classifier_context_include_assistant_turns": True, + }, + ) + messages: Final = [ + {"role": "user", "content": "Design the retry state machine"}, + {"role": "assistant", "content": "The design needs a lease and fencing token"}, + {"role": "user", "content": "Now prove it cannot livelock"}, + { + "role": "system", + "content": [{"type": "text", "text": "ENVIRONMENT_CATALOG\nAGENT_CATALOG\nSKILL_CATALOG"}], + }, + ] + top_level_system: Final = [{"type": "text", "text": "TOP_LEVEL_HARNESS_SYSTEM"}] + claude_kwargs: Final = { + "metadata": {"user_agent": "claude-cli/2.1.233"}, + "system": top_level_system, + "proxy_server_request": {"body": {"system": top_level_system}}, + } + compared_kwargs: Final = { + **request_metadata, + "system": top_level_system, + "proxy_server_request": {"body": {"system": top_level_system}}, + } + original_messages: Final = deepcopy(messages) + original_kwargs: Final = deepcopy((claude_kwargs, compared_kwargs)) + results: Final = ( + await router.async_pre_routing_hook("test-complexity-router", claude_kwargs, messages), + await router.async_pre_routing_hook("test-complexity-router", compared_kwargs, messages), + ) + + assert all(result is not None and result.routing_decision["cause"] == "llm_classifier" for result in results) + assert all(result is not None and result.messages == original_messages for result in results) + assert messages == original_messages + assert (claude_kwargs, compared_kwargs) == original_kwargs + calls: Final = tuple(call.kwargs["messages"] for call in dependency.acompletion.await_args_list) + assert calls[0][0]["content"] == calls[1][0]["content"] == classification_system_prompt( + router.config.classifier_context_window_size + ) + payloads: Final = (calls[0][1]["content"], calls[1][1]["content"]) + for payload, expected_system in zip(payloads, (False, forwards_system)): + assert payload.endswith("Classify this message:\nNow prove it cannot livelock") + assert ("ENVIRONMENT_CATALOG" in payload) is expected_system + assert ("AGENT_CATALOG" in payload) is expected_system + assert ("SKILL_CATALOG" in payload) is expected_system + assert "Design the retry state machine" in payload + assert "lease and fencing token" in payload + assert "TOP_LEVEL_HARNESS_SYSTEM" not in payload + assert "Conversation so far: ~35 tokens across the request" in payload + + @pytest.mark.asyncio + async def test_claude_code_first_turn_without_context_omits_harness_system_prompt( + self, llm_classifier_config: dict[str, object] + ) -> None: + dependency: Final = MagicMock(acompletion=AsyncMock(return_value=_llm_response('{"tier": "SIMPLE"}'))) + router: Final = ComplexityRouter( + "test-complexity-router", + dependency, + {**llm_classifier_config, "classifier_context_window_size": 0}, + ) + messages: Final = [ + {"role": "user", "content": "What is two plus two?"}, + { + "role": "system", + "content": [{"type": "text", "text": "ENVIRONMENT_CATALOG\nAGENT_CATALOG\nSKILL_CATALOG"}], + }, + ] + request_kwargs: Final = {"litellm_metadata": {"user_agent": "claude-code/2.1.233"}} + original: Final = deepcopy((messages, request_kwargs)) + + result: Final = await router.async_pre_routing_hook("test-complexity-router", request_kwargs, messages) + + assert result is not None and result.routing_decision["cause"] == "llm_classifier" + assert result.messages == messages == original[0] + assert request_kwargs == original[1] + classifier_messages: Final = dependency.acompletion.call_args.kwargs["messages"] + assert classifier_messages[0]["content"] == classification_system_prompt( + router.config.classifier_context_window_size + ) + assert classifier_messages[1]["content"].strip() == "Classify this message:\nWhat is two plus two?" + @pytest.mark.parametrize( "tail,expected", (