From 965cbb3f87ff060a0b7e8af3da8ab678980fe0d2 Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 13:27:28 +0800
Subject: [PATCH 01/10] fix(anthropic): strip Claude Code identity from system
 prompt for non-Claude providers

Claude Code prefixes its system prompt with "You are Claude Code,
Anthropic's official CLI for Claude.". When routed to a provider whose
Anthropic-compatible endpoint serves a different model (DeepSeek, MiniMax,
Tencent, OpenAI-like passthrough), that sentence is a false self-description
and should be dropped before sending upstream.

This adds a should_strip_claude_code_identity() gate alongside the existing
should_strip_billing_metadata() gate, plus a strip_claude_code_identity()
helper. The two gates stay distinct: the billing-header strip also fires for
Bedrock/Vertex/Azure, which still serve real Claude models, whereas the
identity strip only fires for non-Claude models.
---
 litellm/llms/anthropic/chat/transformation.py |  13 ++
 litellm/llms/anthropic/common_utils.py        |  22 ++++
 .../messages/transformation.py                |  59 +++++++++
 .../llms/deepseek/messages/transformation.py  |   3 +
 .../llms/minimax/messages/transformation.py   |   3 +
 .../openai_like/messages/transformation.py    |   3 +
 .../llms/tencent/messages/transformation.py   |   3 +
 .../test_anthropic_chat_transformation.py     | 114 ++++++++++++++++++
 .../anthropic/test_anthropic_common_utils.py  |  24 ++++
 9 files changed, 244 insertions(+)

diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index 1f90d375bc2..bbea06e2cfc 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -1685,6 +1685,19 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
         """
         return False
 
+    def should_strip_claude_code_identity(self) -> bool:
+        """
+        Whether to drop Claude Code's self-identification from the system prompt.
+
+        Distinct from ``should_strip_billing_metadata``: that drops the billing header on
+        every provider whose request shape rejects it, including Bedrock/Vertex/Azure, which
+        still serve *Claude* models. This only trips on providers whose
+        Anthropic-compatible endpoint serves a *different* model, where "You are Claude
+        Code" is a false self-description. The first-party config and the Claude-serving
+        providers keep it, so this stays False here.
+        """
+        return False
+
     def translate_system_message(self, messages: list[AllMessageValues]) -> list[AnthropicSystemMessageContent]:
         """
         Translate system message to anthropic format.
diff --git a/litellm/llms/anthropic/common_utils.py b/litellm/llms/anthropic/common_utils.py
index 98e2f6d5bde..8bd9c56d92e 100644
--- a/litellm/llms/anthropic/common_utils.py
+++ b/litellm/llms/anthropic/common_utils.py
@@ -77,6 +77,9 @@ _CLAUDE_CODE_OBJECT_LIST_ADAPTER: Final = TypeAdapter(list[object])
 _CLAUDE_CODE_USER_AGENT_PREFIXES: Final = ("claude-cli/", "claude-code/")
 
 
+_CLAUDE_CODE_IDENTITY: Final = "You are Claude Code, Anthropic's official CLI for Claude."
+
+
 def supports_anthropic_cache_control(model: str, custom_llm_provider: str | None) -> bool:
     from litellm.litellm_core_utils.get_llm_provider_logic import get_llm_provider
     from litellm.utils import supports_prompt_caching
@@ -98,6 +101,25 @@ def is_claude_code_user_agent(user_agent: str) -> bool:
     return user_agent.startswith(_CLAUDE_CODE_USER_AGENT_PREFIXES)
 
 
+def strip_claude_code_identity(text: str) -> str | None:
+    """Remove Claude Code's self-identification sentence from a single system text block.
+
+    Claude Code prefixes its system prompt with ``You are Claude Code, Anthropic's
+    official CLI for Claude.``. When that prompt is forwarded to a non-Claude model
+    (e.g. a DeepSeek-compatible or OpenAI-like Anthropic-compatible endpoint), the
+    sentence is a false self-description and should be dropped before sending
+    upstream. Returns ``None`` when the text was nothing but the identity sentence
+    (so callers can drop the whole block), otherwise the text with the sentence and
+    its framing whitespace removed.
+    """
+    stripped: Final = text.strip()
+    if stripped == _CLAUDE_CODE_IDENTITY:
+        return None
+    if stripped.startswith(_CLAUDE_CODE_IDENTITY):
+        return text.replace(_CLAUDE_CODE_IDENTITY, "", 1).lstrip("\n")
+    return text
+
+
 def _validated_claude_code_mapping(value: object) -> dict[object, object] | None:
     try:
         return _CLAUDE_CODE_OBJECT_MAPPING_ADAPTER.validate_python(value)
diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 5fa686b7560..641f7410126 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -25,6 +25,7 @@ from ...common_utils import (
     AnthropicModelInfo,
     optionally_handle_anthropic_oauth,
     strip_advisor_blocks_from_messages,
+    strip_claude_code_identity,
     strip_encrypted_reasoning_blocks_from_anthropic_messages,
 )
 from .mid_conversation_system import (
@@ -122,6 +123,56 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         """
         return False
 
+    def should_strip_claude_code_identity(self) -> bool:
+        """
+        Whether to drop Claude Code's self-identification from the system prompt.
+
+        Distinct from ``should_strip_billing_metadata``: that drops the billing header on
+        every provider whose request shape rejects it, including Bedrock/Vertex/Azure, which
+        still serve *Claude* models. This only trips on providers whose
+        Anthropic-compatible endpoint serves a *different* model (DeepSeek, MiniMax,
+        Tencent, OpenAI-like passthrough), where "You are Claude Code" is a false
+        self-description. The first-party config keeps it.
+        """
+        return False
+
+    @staticmethod
+    def _strip_claude_code_identity_from_system(system_param):
+        """
+        Strip Claude Code's self-identification sentence from system parameter.
+
+        Args:
+            system_param: Can be a string or a list of system message content blocks
+
+        Returns:
+            System parameter with the identity sentence removed, or None if all content was removed
+        """
+        if isinstance(system_param, str):
+            return strip_claude_code_identity(system_param)
+        elif isinstance(system_param, list):
+            filtered_list: Final = []
+            for content_block in system_param:
+                if isinstance(content_block, dict):
+                    text = content_block.get("text", "")
+                    content_type = content_block.get("type", "")
+                    if content_type != "text":
+                        filtered_list.append(content_block)
+                        continue
+                    stripped_text: Final[str | None] = strip_claude_code_identity(text)
+                    if stripped_text is None:
+                        continue
+                    # Only copy the block when the text changed.
+                    if stripped_text == text:
+                        filtered_list.append(content_block)
+                    else:
+                        filtered_list.append({**content_block, "text": stripped_text})
+                else:
+                    # Keep non-dict items as-is
+                    filtered_list.append(content_block)
+            return filtered_list if len(filtered_list) > 0 else None
+        else:
+            return system_param
+
     @staticmethod
     def _filter_billing_headers_from_system(system_param):
         """
@@ -529,6 +580,14 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
             else:
                 anthropic_messages_optional_request_params.pop("system", None)
 
+        stripped_identity_system: Final = anthropic_messages_optional_request_params.get("system")
+        if self.should_strip_claude_code_identity() and stripped_identity_system is not None:
+            identity_filtered: Final = self._strip_claude_code_identity_from_system(stripped_identity_system)
+            if identity_filtered is not None and len(identity_filtered) > 0:
+                anthropic_messages_optional_request_params["system"] = identity_filtered
+            else:
+                anthropic_messages_optional_request_params.pop("system", None)
+
         # Transform context_management from OpenAI format to Anthropic format if needed
         context_management_param: Final = anthropic_messages_optional_request_params.get("context_management")
         if context_management_param is not None:
diff --git a/litellm/llms/deepseek/messages/transformation.py b/litellm/llms/deepseek/messages/transformation.py
index 8dd720c464a..d7d44d1cba2 100644
--- a/litellm/llms/deepseek/messages/transformation.py
+++ b/litellm/llms/deepseek/messages/transformation.py
@@ -29,6 +29,9 @@ class DeepSeekAnthropicMessagesConfig(AnthropicMessagesConfig):
     def should_strip_billing_metadata(self) -> bool:
         return True
 
+    def should_strip_claude_code_identity(self) -> bool:
+        return True
+
     @staticmethod
     def get_api_key(api_key: str | None = None) -> str | None:
         return api_key or get_secret_str("DEEPSEEK_API_KEY") or litellm.api_key
diff --git a/litellm/llms/minimax/messages/transformation.py b/litellm/llms/minimax/messages/transformation.py
index d4c24c65cfa..aaa5a46d73f 100644
--- a/litellm/llms/minimax/messages/transformation.py
+++ b/litellm/llms/minimax/messages/transformation.py
@@ -31,6 +31,9 @@ class MinimaxMessagesConfig(AnthropicMessagesConfig):
     def should_strip_billing_metadata(self) -> bool:
         return True
 
+    def should_strip_claude_code_identity(self) -> bool:
+        return True
+
     @staticmethod
     def get_api_key(api_key: str | None = None) -> str | None:
         """
diff --git a/litellm/llms/openai_like/messages/transformation.py b/litellm/llms/openai_like/messages/transformation.py
index bae190c88c0..28cd069e412 100644
--- a/litellm/llms/openai_like/messages/transformation.py
+++ b/litellm/llms/openai_like/messages/transformation.py
@@ -32,6 +32,9 @@ class OpenAILikeAnthropicMessagesConfig(AnthropicMessagesConfig):
         super().__init__()
         self._cache_control_ttl: Final = cache_control_ttl
 
+    def should_strip_claude_code_identity(self) -> bool:
+        return True
+
     def validate_anthropic_messages_environment(
         self,
         headers: dict[str, str],
diff --git a/litellm/llms/tencent/messages/transformation.py b/litellm/llms/tencent/messages/transformation.py
index f1d9ee966ff..1e8d7243083 100644
--- a/litellm/llms/tencent/messages/transformation.py
+++ b/litellm/llms/tencent/messages/transformation.py
@@ -30,6 +30,9 @@ class TencentAnthropicMessagesConfig(AnthropicMessagesConfig):
     def should_strip_billing_metadata(self) -> bool:
         return True
 
+    def should_strip_claude_code_identity(self) -> bool:
+        return True
+
     @staticmethod
     def get_api_key(api_key: str | None = None) -> str | None:
         return api_key or get_secret_str("TENCENT_API_KEY") or litellm.api_key
diff --git a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
index 633dd1d9460..8806c297db6 100644
--- a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
+++ b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
@@ -5894,6 +5894,120 @@ def test_should_strip_billing_metadata_by_provider(
     assert config_cls().should_strip_billing_metadata() is expected_strip
 
 
+@pytest.mark.parametrize(
+    "module_path, class_name, expected_strip",
+    [
+        # First-party and Claude-serving providers keep the identity sentence: the
+        # model genuinely *is* Claude, even via Bedrock/Vertex/Azure.
+        ("litellm.llms.anthropic.chat.transformation", "AnthropicConfig", False),
+        (
+            "litellm.llms.anthropic.experimental_pass_through.messages.transformation",
+            "AnthropicMessagesConfig",
+            False,
+        ),
+        (
+            "litellm.llms.bedrock.claude_platform.transformation",
+            "BedrockClaudePlatformConfig",
+            False,
+        ),
+        (
+            "litellm.llms.vertex_ai.vertex_ai_partner_models.anthropic.transformation",
+            "VertexAIAnthropicConfig",
+            False,
+        ),
+        ("litellm.llms.azure_ai.anthropic.transformation", "AzureAnthropicConfig", False),
+        # Non-Claude Anthropic-compatible endpoints strip the false self-description.
+        ("litellm.llms.minimax.messages.transformation", "MinimaxMessagesConfig", True),
+        (
+            "litellm.llms.deepseek.messages.transformation",
+            "DeepSeekAnthropicMessagesConfig",
+            True,
+        ),
+        (
+            "litellm.llms.tencent.messages.transformation",
+            "TencentAnthropicMessagesConfig",
+            True,
+        ),
+    ],
+)
+def test_should_strip_claude_code_identity_by_provider(
+    module_path, class_name, expected_strip
+):
+    import importlib
+
+    config_cls = getattr(importlib.import_module(module_path), class_name)
+    assert config_cls().should_strip_claude_code_identity() is expected_strip
+
+
+def _system_with_identity_block(identity_sentence: str) -> list:
+    return [
+        {
+            "role": "system",
+            "content": [
+                # Claude Code sends the identity sentence as its own text block.
+                {"type": "text", "text": identity_sentence},
+                {"type": "text", "text": "real system prompt"},
+            ],
+        }
+    ]
+
+
+def test_messages_request_strips_claude_code_identity_for_minimax():
+    from litellm.llms.minimax.messages.transformation import MinimaxMessagesConfig
+    from litellm.types.router import GenericLiteLLMParams
+
+    config = MinimaxMessagesConfig()
+    assert config.should_strip_claude_code_identity() is True
+
+    optional_params = {
+        "max_tokens": 16,
+        "system": [
+            {"type": "text", "text": "You are Claude Code, Anthropic's official CLI for Claude."},
+            {"type": "text", "text": "real system prompt"},
+        ],
+    }
+    result = config.transform_anthropic_messages_request(
+        model="MiniMax-M2",
+        messages=[{"role": "user", "content": "hi"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    texts = [block["text"] for block in result.get("system", [])]
+    assert "You are Claude Code, Anthropic's official CLI for Claude." not in texts
+    assert "real system prompt" in texts
+
+
+def test_messages_request_keeps_claude_code_identity_for_first_party():
+    from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+        AnthropicMessagesConfig,
+    )
+    from litellm.types.router import GenericLiteLLMParams
+
+    config = AnthropicMessagesConfig()
+    assert config.should_strip_claude_code_identity() is False
+
+    optional_params = {
+        "max_tokens": 16,
+        "system": [
+            {"type": "text", "text": "You are Claude Code, Anthropic's official CLI for Claude."},
+            {"type": "text", "text": "real system prompt"},
+        ],
+    }
+    result = config.transform_anthropic_messages_request(
+        model="claude-3-5-sonnet-latest",
+        messages=[{"role": "user", "content": "hi"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    texts = [block["text"] for block in result.get("system", [])]
+    assert "You are Claude Code, Anthropic's official CLI for Claude." in texts
+    assert "real system prompt" in texts
+
+
 def test_namespace_tool_flat_nested_tools_are_extracted():
     """Codex sends nested tools in flat format {type, name, description, parameters} with no 'function' wrapper.
     These must be normalized and mapped without raising KeyError: 'function'."""
diff --git a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
index 945033c5cac..62a6753a482 100644
--- a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
+++ b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
@@ -53,6 +53,30 @@ def test_is_claude_code_one_shot_subagent_request(messages, system, expected):
     )
 
 
+@pytest.mark.parametrize(
+    "text,expected",
+    [
+        # Identity sentence alone -> drop the whole block.
+        ("You are Claude Code, Anthropic's official CLI for Claude.", None),
+        # Identity sentence followed by the rest of the system prompt -> keep the rest.
+        (
+            "You are Claude Code, Anthropic's official CLI for Claude.\nYou are an interactive agent.",
+            "You are an interactive agent.",
+        ),
+        # Leading/trailing whitespace around the bare sentence is treated as drop-only.
+        ("  You are Claude Code, Anthropic's official CLI for Claude.  ", None),
+        # Non-Claude-Code prompts are untouched.
+        ("You are a helpful assistant.", "You are a helpful assistant."),
+        # A sentence that merely mentions Claude Code is untouched.
+        ("You are Claude Code's helper.", "You are Claude Code's helper."),
+    ],
+)
+def test_strip_claude_code_identity(text, expected):
+    from litellm.llms.anthropic.common_utils import strip_claude_code_identity
+
+    assert strip_claude_code_identity(text) == expected
+
+
 class TestOptionallyHandleAnthropicOAuth:
     """Tests for optionally_handle_anthropic_oauth function."""
 

From 2eab418cf94739835a058fb70614602d6692788d Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 15:42:35 +0800
Subject: [PATCH 02/10] fix(anthropic): annotate return type of identity-strip
 staticmethod

Restores the ANN205 strict-rule budget: the new helper is a @staticmethod
and must carry a return annotation like its billing-header sibling gate.
---
 .../experimental_pass_through/messages/transformation.py        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 641f7410126..f754c558c87 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -137,7 +137,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         return False
 
     @staticmethod
-    def _strip_claude_code_identity_from_system(system_param):
+    def _strip_claude_code_identity_from_system(system_param) -> str | list | None:
         """
         Strip Claude Code's self-identification sentence from system parameter.
 

From defee9ad13cbb43a53e6977b64673d0dba60e642 Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 15:50:44 +0800
Subject: [PATCH 03/10] fix(anthropic): suppress LIT002 for identity-strip
 payload lists

The identity filter builds the filtered system list and its rewrite dict in
a loop, same as the sibling billing-header filter; mark both mutable-ok.
---
 .../experimental_pass_through/messages/transformation.py      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index f754c558c87..13acc0bd437 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -150,7 +150,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         if isinstance(system_param, str):
             return strip_claude_code_identity(system_param)
         elif isinstance(system_param, list):
-            filtered_list: Final = []
+            filtered_list: Final = []  # mutable-ok: API message payload
             for content_block in system_param:
                 if isinstance(content_block, dict):
                     text = content_block.get("text", "")
@@ -165,7 +165,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                     if stripped_text == text:
                         filtered_list.append(content_block)
                     else:
-                        filtered_list.append({**content_block, "text": stripped_text})
+                        filtered_list.append({**content_block, "text": stripped_text})  # mutable-ok: API message payload
                 else:
                     # Keep non-dict items as-is
                     filtered_list.append(content_block)

From d03238136cafd5e928b581a7f168d797693846be Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 15:54:26 +0800
Subject: [PATCH 04/10] style(anthropic): keep identity-strip rewrite
 ruff-format clean

---
 .../experimental_pass_through/messages/transformation.py     | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 13acc0bd437..2a31c6e7e04 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -163,9 +163,10 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                         continue
                     # Only copy the block when the text changed.
                     if stripped_text == text:
-                        filtered_list.append(content_block)
+                        next_block = content_block
                     else:
-                        filtered_list.append({**content_block, "text": stripped_text})  # mutable-ok: API message payload
+                        next_block = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
+                    filtered_list.append(next_block)
                 else:
                     # Keep non-dict items as-is
                     filtered_list.append(content_block)

From 31569619c9c1cbb54174c9880c030fc6836d67ff Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 16:03:50 +0800
Subject: [PATCH 05/10] fix(anthropic): avoid GeneralTypeIssues by
 single-assigning the rewrite block

---
 .../experimental_pass_through/messages/transformation.py    | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 2a31c6e7e04..c32a5412839 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -163,10 +163,10 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                         continue
                     # Only copy the block when the text changed.
                     if stripped_text == text:
-                        next_block = content_block
+                        filtered_list.append(content_block)
                     else:
-                        next_block = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
-                    filtered_list.append(next_block)
+                        rewritten: Final = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
+                        filtered_list.append(rewritten)
                 else:
                     # Keep non-dict items as-is
                     filtered_list.append(content_block)

From 2fc4f448b32f76beff0b2a59227efe1e78eae57c Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 16:17:22 +0800
Subject: [PATCH 06/10] fix(anthropic): drop Final on loop-locals in identity
 strip

Loop-bound Final declarations trip basedpyright's reportGeneralTypeIssues.
---
 .../experimental_pass_through/messages/transformation.py      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index c32a5412839..1f8b78fa08e 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -158,14 +158,14 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
                     if content_type != "text":
                         filtered_list.append(content_block)
                         continue
-                    stripped_text: Final[str | None] = strip_claude_code_identity(text)
+                    stripped_text = strip_claude_code_identity(text)
                     if stripped_text is None:
                         continue
                     # Only copy the block when the text changed.
                     if stripped_text == text:
                         filtered_list.append(content_block)
                     else:
-                        rewritten: Final = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
+                        rewritten = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
                         filtered_list.append(rewritten)
                 else:
                     # Keep non-dict items as-is

From bbbf53bec19eb0a8034d048147fa3013fb51fddd Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 17:04:45 +0800
Subject: [PATCH 07/10] fix(anthropic): strip Claude Code identity on
 Anthropic->OpenAI translation bridge

The identity-strip gate only ran on the Anthropic messages parse path,
so providers routed through the chat-completions translation bridge
(e.g. hosted_vllm/* with use_chat_completions_api) forwarded the Claude
Code system sentence verbatim to non-Claude models.

Promote strip_claude_code_identity_from_system to common_utils and call it
from translate_anthropic_to_openai so those providers are scrubbed too.
---
 litellm/llms/anthropic/common_utils.py        | 39 ++++++++++++++++++
 .../adapters/transformation.py                | 14 +++++++
 .../messages/transformation.py                | 29 +------------
 ...al_pass_through_adapters_transformation.py | 38 +++++++++++++++++
 .../anthropic/test_anthropic_common_utils.py  | 41 +++++++++++++++++++
 5 files changed, 134 insertions(+), 27 deletions(-)

diff --git a/litellm/llms/anthropic/common_utils.py b/litellm/llms/anthropic/common_utils.py
index 8bd9c56d92e..6d3180f47aa 100644
--- a/litellm/llms/anthropic/common_utils.py
+++ b/litellm/llms/anthropic/common_utils.py
@@ -120,6 +120,45 @@ def strip_claude_code_identity(text: str) -> str | None:
     return text
 
 
+def strip_claude_code_identity_from_system(system_param: str | list | None) -> str | list | None:
+    """Strip Claude Code's self-identification sentence from a full system parameter.
+
+    Unlike :func:`strip_claude_code_identity`, which operates on a single text
+    block, this handles the whole ``system`` value of an Anthropic Messages
+    request -- either a plain string or a list of system content blocks.
+    Non-text blocks are kept as-is; text blocks have the identity sentence
+    removed, and are dropped entirely when it was the only content.
+
+    Returns ``None`` when every block was dropped so callers can remove the whole
+    ``system`` parameter.
+    """
+    if isinstance(system_param, str):
+        return strip_claude_code_identity(system_param)
+    if isinstance(system_param, list):
+        filtered_list: Final = []  # mutable-ok: API message payload
+        for content_block in system_param:
+            if isinstance(content_block, dict):
+                text = content_block.get("text", "")
+                content_type = content_block.get("type", "")
+                if content_type != "text":
+                    filtered_list.append(content_block)
+                    continue
+                stripped_text = strip_claude_code_identity(text)
+                if stripped_text is None:
+                    continue
+                # Only copy the block when the text changed.
+                if stripped_text == text:
+                    filtered_list.append(content_block)
+                else:
+                    rewritten = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
+                    filtered_list.append(rewritten)
+            else:
+                # Keep non-dict items as-is.
+                filtered_list.append(content_block)
+        return filtered_list if len(filtered_list) > 0 else None
+    return system_param
+
+
 def _validated_claude_code_mapping(value: object) -> dict[object, object] | None:
     try:
         return _CLAUDE_CODE_OBJECT_MAPPING_ADAPTER.validate_python(value)
diff --git a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
index 1a85cf80bff..a0b5c0b3045 100644
--- a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
@@ -5,6 +5,7 @@ from collections.abc import AsyncIterator, Iterator, Mapping, Sequence
 from typing import TYPE_CHECKING, Any, Final, Literal, TypeAlias, TypeVar, cast
 
 import litellm
+from litellm.llms.anthropic.common_utils import strip_claude_code_identity_from_system
 from litellm.llms.anthropic.experimental_pass_through.utils import (
     is_reasoning_auto_summary_enabled,
     prompt_cache_key_from_user_id,
@@ -1212,6 +1213,19 @@ class LiteLLMAnthropicMessagesAdapter:
         new_messages: list[AllMessageValues] = []
         tool_name_mapping: dict[str, str] = {}
 
+        # Strip Claude Code's self-identification from the system prompt before
+        # translating to an OpenAI chat-completions request. This bridge only runs
+        # for non-Anthropic models (first-party servers take the native
+        # AnthropicMessagesConfig path), so "You are Claude Code" is always a
+        # false self-description here and must not reach the target model.
+        system_param: Final = anthropic_message_request.get("system")
+        if system_param is not None:
+            stripped_system = strip_claude_code_identity_from_system(system_param)
+            if stripped_system is None:
+                anthropic_message_request.pop("system", None)
+            elif stripped_system != system_param:
+                anthropic_message_request["system"] = stripped_system
+
         ## CONVERT ANTHROPIC MESSAGES TO OPENAI
         messages_list: Final[list[AllAnthropicPassThroughMessageValues]] = cast(
             list[AllAnthropicPassThroughMessageValues],
diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 1f8b78fa08e..58c5a185fef 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -25,7 +25,7 @@ from ...common_utils import (
     AnthropicModelInfo,
     optionally_handle_anthropic_oauth,
     strip_advisor_blocks_from_messages,
-    strip_claude_code_identity,
+    strip_claude_code_identity_from_system,
     strip_encrypted_reasoning_blocks_from_anthropic_messages,
 )
 from .mid_conversation_system import (
@@ -147,32 +147,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         Returns:
             System parameter with the identity sentence removed, or None if all content was removed
         """
-        if isinstance(system_param, str):
-            return strip_claude_code_identity(system_param)
-        elif isinstance(system_param, list):
-            filtered_list: Final = []  # mutable-ok: API message payload
-            for content_block in system_param:
-                if isinstance(content_block, dict):
-                    text = content_block.get("text", "")
-                    content_type = content_block.get("type", "")
-                    if content_type != "text":
-                        filtered_list.append(content_block)
-                        continue
-                    stripped_text = strip_claude_code_identity(text)
-                    if stripped_text is None:
-                        continue
-                    # Only copy the block when the text changed.
-                    if stripped_text == text:
-                        filtered_list.append(content_block)
-                    else:
-                        rewritten = {**content_block, "text": stripped_text}  # mutable-ok: API message payload
-                        filtered_list.append(rewritten)
-                else:
-                    # Keep non-dict items as-is
-                    filtered_list.append(content_block)
-            return filtered_list if len(filtered_list) > 0 else None
-        else:
-            return system_param
+        return strip_claude_code_identity_from_system(system_param)
 
     @staticmethod
     def _filter_billing_headers_from_system(system_param):
diff --git a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
index b9a82e3fc68..329849d35c4 100644
--- a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
+++ b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
@@ -2833,6 +2833,44 @@ def test_translate_completion_input_params_keeps_provider_native_tools():
     assert translated["tools"] == [{"googleMaps": {}}]
 
 
+CLAUDE_CODE_IDENTITY = "You are Claude Code, Anthropic's official CLI for Claude."
+
+
+@pytest.mark.parametrize(
+    "system,expected_system_content",
+    [
+        # Identity sentence alone -> the whole system message is dropped. The bridge
+        # only serves non-Anthropic models, so the first-party case is never here.
+        (CLAUDE_CODE_IDENTITY, None),
+        # Identity followed by the real prompt -> the real prompt survives.
+        (f"{CLAUDE_CODE_IDENTITY}\nYou are an interactive agent.", "You are an interactive agent."),
+        # Non-identity system prompt is passed through untouched.
+        ("You are a helpful assistant.", "You are a helpful assistant."),
+    ],
+)
+def test_translate_anthropic_to_openai_strips_claude_code_identity(system, expected_system_content):
+    """The chat-completions bridge must not forward Claude Code's self-identification upstream."""
+    from litellm.types.llms.anthropic import AnthropicMessagesRequest
+
+    adapter = LiteLLMAnthropicMessagesAdapter()
+    openai_request, _ = adapter.translate_anthropic_to_openai(
+        anthropic_message_request=AnthropicMessagesRequest(
+            model="hosted_vllm/kimi-k3",
+            max_tokens=1024,
+            messages=[{"role": "user", "content": "hi"}],
+            system=system,
+        ),
+        custom_llm_provider="hosted_vllm",
+    )
+
+    system_messages = [m for m in openai_request["messages"] if m["role"] == "system"]
+    if expected_system_content is None:
+        assert system_messages == []
+    else:
+        assert len(system_messages) == 1
+        assert system_messages[0]["content"] == expected_system_content
+
+
 def test_translate_openai_content_to_anthropic_reasoning_content_without_thinking_blocks():
     """
     Test that reasoning_content is converted to thinking block when thinking_blocks is not present.
diff --git a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
index 62a6753a482..5d1f92773e5 100644
--- a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
+++ b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
@@ -77,6 +77,47 @@ def test_strip_claude_code_identity(text, expected):
     assert strip_claude_code_identity(text) == expected
 
 
+CLAUDE_CODE_IDENTITY = "You are Claude Code, Anthropic's official CLI for Claude."
+
+
+@pytest.mark.parametrize(
+    "system_param,expected",
+    [
+        # String form: identity sentence alone -> drop the whole system param.
+        (CLAUDE_CODE_IDENTITY, None),
+        # String form: identity followed by the real prompt -> keep the real prompt.
+        (f"{CLAUDE_CODE_IDENTITY}\nYou are an interactive agent.", "You are an interactive agent."),
+        # String form: non-identity text is untouched.
+        ("You are a helpful assistant.", "You are a helpful assistant."),
+        # List form: identity text block is dropped, non-text blocks and the
+        # surviving text block are preserved.
+        (
+            [
+                {"type": "text", "text": CLAUDE_CODE_IDENTITY},
+                {"type": "text", "text": "real system prompt"},
+            ],
+            [{"type": "text", "text": "real system prompt"}],
+        ),
+        # List form: identity-only text means every block is dropped.
+        ([{"type": "text", "text": CLAUDE_CODE_IDENTITY}], None),
+        # List form: non-text blocks survive identity stripping untouched.
+        (
+            [
+                {"type": "text", "text": CLAUDE_CODE_IDENTITY},
+                {"type": "text", "text": "real system prompt", "cache_control": {"type": "ephemeral"}},
+            ],
+            [{"type": "text", "text": "real system prompt", "cache_control": {"type": "ephemeral"}}],
+        ),
+    ],
+)
+def test_strip_claude_code_identity_from_system(system_param, expected):
+    from litellm.llms.anthropic.common_utils import (
+        strip_claude_code_identity_from_system,
+    )
+
+    assert strip_claude_code_identity_from_system(system_param) == expected
+
+
 class TestOptionallyHandleAnthropicOAuth:
     """Tests for optionally_handle_anthropic_oauth function."""
 

From 5f8c3f470764b2efcfd11fde2a0f46b9d9b01cbf Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Mon, 21 Sep 2026 18:08:17 +0800
Subject: [PATCH 08/10] test(anthropic): cover identity-strip drop and non-text
 block branches

Close the Codecov gaps on strip_claude_code_identity_from_system:
identity+content same-block rewrite, non-text blocks, non-dict list
items, non-str/non-list payload, and the identity-only system-pop path.
---
 .../test_anthropic_chat_transformation.py     | 23 +++++++++++++++++++
 .../anthropic/test_anthropic_common_utils.py  | 14 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
index 8806c297db6..da7836d80de 100644
--- a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
+++ b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
@@ -6565,3 +6565,26 @@ def test_eager_input_streaming_reaches_anthropic_request_tools():
 
     assert result["tools"][0]["eager_input_streaming"] is True
     assert result["tools"][0]["name"] == "write_file"
+
+
+def test_messages_request_strips_identity_only_system_for_minimax():
+    """Identity-only system drops the whole system param (pop path)."""
+    from litellm.llms.minimax.messages.transformation import MinimaxMessagesConfig
+    from litellm.types.router import GenericLiteLLMParams
+
+    config = MinimaxMessagesConfig()
+    optional_params = {
+        "max_tokens": 16,
+        "system": [
+            {"type": "text", "text": "You are Claude Code, Anthropic's official CLI for Claude."},
+        ],
+    }
+    result = config.transform_anthropic_messages_request(
+        model="MiniMax-M2",
+        messages=[{"role": "user", "content": "hi"}],
+        anthropic_messages_optional_request_params=optional_params,
+        litellm_params=GenericLiteLLMParams(),
+        headers={},
+    )
+
+    assert "system" not in result
diff --git a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
index 5d1f92773e5..0e30c4c868c 100644
--- a/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
+++ b/tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py
@@ -108,6 +108,20 @@ CLAUDE_CODE_IDENTITY = "You are Claude Code, Anthropic's official CLI for Claude
             ],
             [{"type": "text", "text": "real system prompt", "cache_control": {"type": "ephemeral"}}],
         ),
+        # List form: identity + real content in the same block -> rewritten block.
+        (
+            [{"type": "text", "text": f"{CLAUDE_CODE_IDENTITY}\nreal system prompt"}],
+            [{"type": "text", "text": "real system prompt"}],
+        ),
+        # List form: a non-text block (type "other") is kept as-is.
+        (
+            [{"type": "text", "text": CLAUDE_CODE_IDENTITY}, {"type": "other", "foo": "bar"}],
+            [{"type": "other", "foo": "bar"}],
+        ),
+        # List form: non-dict items are kept as-is.
+        ([{"type": "text", "text": CLAUDE_CODE_IDENTITY}, "loose item"], ["loose item"]),
+        # Non-string, non-list system payload is passed through untouched.
+        (None, None),
     ],
 )
 def test_strip_claude_code_identity_from_system(system_param, expected):

From b1d6264a033315ae73a1f8b9f9e27d8e2fb433d6 Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Fri, 25 Sep 2026 23:30:56 +0800
Subject: [PATCH 09/10] fix(anthropic): restore blank lines before
 requires_native_compaction_beta (ruff format)

---
 litellm/llms/anthropic/common_utils.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/litellm/llms/anthropic/common_utils.py b/litellm/llms/anthropic/common_utils.py
index 6e3ac69241e..27aed50720a 100644
--- a/litellm/llms/anthropic/common_utils.py
+++ b/litellm/llms/anthropic/common_utils.py
@@ -80,6 +80,8 @@ _CLAUDE_CODE_USER_AGENT_PREFIXES: Final = ("claude-cli/", "claude-code/")
 
 
 _CLAUDE_CODE_IDENTITY: Final = "You are Claude Code, Anthropic's official CLI for Claude."
+
+
 def requires_native_compaction_beta(
     custom_llm_provider: str,
     optional_params: Mapping[str, object],

From 49de19e6e349048532d13eed5a62306bc376363d Mon Sep 17 00:00:00 2001
From: Sangsiva <101570025+Sangsiva@users.noreply.github.com>
Date: Sat, 26 Sep 2026 00:20:56 +0800
Subject: [PATCH 10/10] fix(anthropic): don't mutate read-only requests and
 tighten system list typing

- copy the request before stripping the Claude Code identity so a read-only
  wire-body mapping (shadow evaluation) no longer raises TypeError on pop/assign
- annotate the system-list helper as list[object] instead of bare list
- drop a comment that restated the equality check it precedes
- add a regression test for the read-only request path
---
 litellm/llms/anthropic/common_utils.py        |  5 ++--
 .../adapters/transformation.py                | 12 ++++++----
 .../messages/transformation.py                |  2 +-
 ...al_pass_through_adapters_transformation.py | 24 +++++++++++++++++++
 4 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/litellm/llms/anthropic/common_utils.py b/litellm/llms/anthropic/common_utils.py
index 27aed50720a..a7b8ce2a0e1 100644
--- a/litellm/llms/anthropic/common_utils.py
+++ b/litellm/llms/anthropic/common_utils.py
@@ -143,7 +143,9 @@ def strip_claude_code_identity(text: str) -> str | None:
     return text
 
 
-def strip_claude_code_identity_from_system(system_param: str | list | None) -> str | list | None:
+def strip_claude_code_identity_from_system(
+    system_param: str | list[object] | None,
+) -> str | list[object] | None:
     """Strip Claude Code's self-identification sentence from a full system parameter.
 
     Unlike :func:`strip_claude_code_identity`, which operates on a single text
@@ -169,7 +171,6 @@ def strip_claude_code_identity_from_system(system_param: str | list | None) -> s
                 stripped_text = strip_claude_code_identity(text)
                 if stripped_text is None:
                     continue
-                # Only copy the block when the text changed.
                 if stripped_text == text:
                     filtered_list.append(content_block)
                 else:
diff --git a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
index a0be08c4bb9..bc3dc685539 100644
--- a/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py
@@ -1239,10 +1239,14 @@ class LiteLLMAnthropicMessagesAdapter:
         system_param: Final = anthropic_message_request.get("system")
         if system_param is not None:
             stripped_system = strip_claude_code_identity_from_system(system_param)
-            if stripped_system is None:
-                anthropic_message_request.pop("system", None)
-            elif stripped_system != system_param:
-                anthropic_message_request["system"] = stripped_system
+            if stripped_system is None or stripped_system != system_param:
+                # This adapter is also invoked with a read-only wire-body mapping
+                # (shadow evaluation); mutate a copy, never the caller's request.
+                anthropic_message_request = cast(AnthropicMessagesRequest, dict(anthropic_message_request))
+                if stripped_system is None:
+                    anthropic_message_request.pop("system", None)
+                else:
+                    anthropic_message_request["system"] = stripped_system
 
         ## CONVERT ANTHROPIC MESSAGES TO OPENAI
         messages_list: Final[list[AllAnthropicPassThroughMessageValues]] = cast(
diff --git a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
index 56bcd351ef0..f692194f0ad 100644
--- a/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/messages/transformation.py
@@ -143,7 +143,7 @@ class AnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         return False
 
     @staticmethod
-    def _strip_claude_code_identity_from_system(system_param) -> str | list | None:
+    def _strip_claude_code_identity_from_system(system_param: str | list[object] | None) -> str | list[object] | None:
         """
         Strip Claude Code's self-identification sentence from system parameter.
 
diff --git a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
index e99ae2358d6..b07f65088e0 100644
--- a/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
+++ b/tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py
@@ -2900,6 +2900,30 @@ def test_translate_anthropic_to_openai_strips_claude_code_identity(system, expec
         assert system_messages[0]["content"] == expected_system_content
 
 
+def test_translate_anthropic_to_openai_strips_claude_code_identity_read_only_request():
+    """Identity stripping must not mutate a read-only request (shadow evaluation passes a
+    MappingProxyType, so the adapter must copy before rewriting ``system``)."""
+    from types import MappingProxyType
+
+    adapter = LiteLLMAnthropicMessagesAdapter()
+    request = MappingProxyType(
+        {
+            "model": "hosted_vllm/kimi-k3",
+            "max_tokens": 1024,
+            "messages": [{"role": "user", "content": "hi"}],
+            "system": f"{CLAUDE_CODE_IDENTITY}\nYou are an interactive agent.",
+        }
+    )
+
+    openai_request, _ = adapter.translate_anthropic_to_openai(
+        anthropic_message_request=request,
+        custom_llm_provider="hosted_vllm",
+    )
+
+    system_messages = [m for m in openai_request["messages"] if m["role"] == "system"]
+    assert [m["content"] for m in system_messages] == ["You are an interactive agent."]
+
+
 def test_translate_openai_content_to_anthropic_reasoning_content_without_thinking_blocks():
     """
     Test that reasoning_content is converted to thinking block when thinking_blocks is not present.