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fix: Anthropic OAuth compatibility — Claude Code identity fingerprinting #1597

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Merged
teknium1 merged 1 commit into from
Mar 17, 2026
Merged

fix: Anthropic OAuth compatibility — Claude Code identity fingerprinting #1597

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77 changes: 70 additions & 7 deletions agent/anthropic_adapter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -45,14 +45,19 @@ def _supports_adaptive_thinking(model: str) -> bool:
"fine-grained-tool-streaming-2025-05-14",
]

# Additional beta headers required for OAuth/subscription auth
# Both clawdbot and OpenCode include claude-code-20250219 alongside oauth-2025-04-20.
# Without claude-code-20250219, Anthropic's API rejects OAuth tokens with 401.
# Additional beta headers required for OAuth/subscription auth.
# Matches what Claude Code (and pi-ai / OpenCode) send.
_OAUTH_ONLY_BETAS = [
"claude-code-20250219",
"oauth-2025-04-20",
]

# Claude Code identity — required for OAuth requests to be routed correctly.
# Without these, Anthropic's infrastructure intermittently 500s OAuth traffic.
_CLAUDE_CODE_VERSION = "2.1.2"
_CLAUDE_CODE_SYSTEM_PREFIX = "You are Claude Code, Anthropic's official CLI for Claude."
_MCP_TOOL_PREFIX = "mcp_"


def _is_oauth_token(key: str) -> bool:
"""Check if the key is an OAuth/setup token (not a regular Console API key).
Expand Down Expand Up @@ -88,10 +93,16 @@ def build_anthropic_client(api_key: str, base_url: str = None):
kwargs["base_url"] = base_url

if _is_oauth_token(api_key):
# OAuth access token / setup-token → Bearer auth + beta headers
# OAuth access token / setup-token → Bearer auth + Claude Code identity.
# Anthropic routes OAuth requests based on user-agent and headers;
# without Claude Code's fingerprint, requests get intermittent 500s.
all_betas = _COMMON_BETAS + _OAUTH_ONLY_BETAS
kwargs["auth_token"] = api_key
kwargs["default_headers"] = {"anthropic-beta": ",".join(all_betas)}
kwargs["default_headers"] = {
"anthropic-beta": ",".join(all_betas),
"user-agent": f"claude-cli/{_CLAUDE_CODE_VERSION} (external, cli)",
"x-app": "cli",
}
else:
# Regular API key → x-api-key header + common betas
kwargs["api_key"] = api_key
Expand Down Expand Up @@ -714,14 +725,59 @@ def build_anthropic_kwargs(
max_tokens: Optional[int],
reasoning_config: Optional[Dict[str, Any]],
tool_choice: Optional[str] = None,
is_oauth: bool = False,
) -> Dict[str, Any]:
"""Build kwargs for anthropic.messages.create()."""
"""Build kwargs for anthropic.messages.create().

When *is_oauth* is True, applies Claude Code compatibility transforms:
system prompt prefix, tool name prefixing, and prompt sanitization.
"""
system, anthropic_messages = convert_messages_to_anthropic(messages)
anthropic_tools = convert_tools_to_anthropic(tools) if tools else []

model = normalize_model_name(model)
effective_max_tokens = max_tokens or 16384

# ── OAuth: Claude Code identity ──────────────────────────────────
if is_oauth:
# 1. Prepend Claude Code system prompt identity
cc_block = {"type": "text", "text": _CLAUDE_CODE_SYSTEM_PREFIX}
if isinstance(system, list):
system = [cc_block] + system
elif isinstance(system, str) and system:
system = [cc_block, {"type": "text", "text": system}]
else:
system = [cc_block]

# 2. Sanitize system prompt — replace product name references
# to avoid Anthropic's server-side content filters.
for block in system:
if isinstance(block, dict) and block.get("type") == "text":
text = block.get("text", "")
text = text.replace("Hermes Agent", "Claude Code")
text = text.replace("Hermes agent", "Claude Code")
text = text.replace("hermes-agent", "claude-code")
text = text.replace("Nous Research", "Anthropic")
block["text"] = text

# 3. Prefix tool names with mcp_ (Claude Code convention)
if anthropic_tools:
for tool in anthropic_tools:
if "name" in tool:
tool["name"] = _MCP_TOOL_PREFIX + tool["name"]

# 4. Prefix tool names in message history (tool_use and tool_result blocks)
for msg in anthropic_messages:
content = msg.get("content")
if isinstance(content, list):
for block in content:
if isinstance(block, dict):
if block.get("type") == "tool_use" and "name" in block:
if not block["name"].startswith(_MCP_TOOL_PREFIX):
block["name"] = _MCP_TOOL_PREFIX + block["name"]
elif block.get("type") == "tool_result" and "tool_use_id" in block:
pass # tool_result uses ID, not name

kwargs: Dict[str, Any] = {
"model": model,
"messages": anthropic_messages,
Expand Down Expand Up @@ -768,11 +824,15 @@ def build_anthropic_kwargs(

def normalize_anthropic_response(
response,
strip_tool_prefix: bool = False,
) -> Tuple[SimpleNamespace, str]:
"""Normalize Anthropic response to match the shape expected by AIAgent.

Returns (assistant_message, finish_reason) where assistant_message has
.content, .tool_calls, and .reasoning attributes.

When *strip_tool_prefix* is True, removes the ``mcp_`` prefix that was
added to tool names for OAuth Claude Code compatibility.
"""
text_parts = []
reasoning_parts = []
Expand All @@ -784,12 +844,15 @@ def normalize_anthropic_response(
elif block.type == "thinking":
reasoning_parts.append(block.thinking)
elif block.type == "tool_use":
name = block.name
if strip_tool_prefix and name.startswith(_MCP_TOOL_PREFIX):
name = name[len(_MCP_TOOL_PREFIX):]
tool_calls.append(
SimpleNamespace(
id=block.id,
type="function",
function=SimpleNamespace(
name=block.name,
name=name,
arguments=json.dumps(block.input),
),
)
Expand Down
17 changes: 12 additions & 5 deletions run_agent.py
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Original file line number Diff line number Diff line change
Expand Up @@ -546,6 +546,8 @@ def __init__(
effective_key = api_key or resolve_anthropic_token() or ""
self._anthropic_api_key = effective_key
self._anthropic_base_url = base_url
from agent.anthropic_adapter import _is_oauth_token as _is_oat
self._is_anthropic_oauth = _is_oat(effective_key)
self._anthropic_client = build_anthropic_client(effective_key, base_url)
# No OpenAI client needed for Anthropic mode
self.client = None
Expand Down Expand Up @@ -3372,6 +3374,7 @@ def _build_api_kwargs(self, api_messages: list) -> dict:
tools=self.tools,
max_tokens=self.max_tokens,
reasoning_config=self.reasoning_config,
is_oauth=getattr(self, "_is_anthropic_oauth", False),
)

if self.api_mode == "codex_responses":
Expand Down Expand Up @@ -3789,7 +3792,7 @@ def flush_memories(self, messages: list = None, min_turns: int = None):
tool_calls = assistant_msg.tool_calls
elif self.api_mode == "anthropic_messages" and not _aux_available:
from agent.anthropic_adapter import normalize_anthropic_response as _nar_flush
_flush_msg, _ = _nar_flush(response)
_flush_msg, _ = _nar_flush(response, strip_tool_prefix=getattr(self, '_is_anthropic_oauth', False))
if _flush_msg and _flush_msg.tool_calls:
tool_calls = _flush_msg.tool_calls
elif hasattr(response, "choices") and response.choices:
Expand Down Expand Up @@ -4550,9 +4553,10 @@ def _handle_max_iterations(self, messages: list, api_call_count: int) -> str:
if self.api_mode == "anthropic_messages":
from agent.anthropic_adapter import build_anthropic_kwargs as _bak, normalize_anthropic_response as _nar
_ant_kw = _bak(model=self.model, messages=api_messages, tools=None,
max_tokens=self.max_tokens, reasoning_config=self.reasoning_config)
max_tokens=self.max_tokens, reasoning_config=self.reasoning_config,
is_oauth=getattr(self, '_is_anthropic_oauth', False))
summary_response = self._anthropic_messages_create(_ant_kw)
_msg, _ = _nar(summary_response)
_msg, _ = _nar(summary_response, strip_tool_prefix=getattr(self, '_is_anthropic_oauth', False))
final_response = (_msg.content or "").strip()
else:
summary_response = self._ensure_primary_openai_client(reason="iteration_limit_summary").chat.completions.create(**summary_kwargs)
Expand Down Expand Up @@ -4580,9 +4584,10 @@ def _handle_max_iterations(self, messages: list, api_call_count: int) -> str:
elif self.api_mode == "anthropic_messages":
from agent.anthropic_adapter import build_anthropic_kwargs as _bak2, normalize_anthropic_response as _nar2
_ant_kw2 = _bak2(model=self.model, messages=api_messages, tools=None,
is_oauth=getattr(self, '_is_anthropic_oauth', False),
max_tokens=self.max_tokens, reasoning_config=self.reasoning_config)
retry_response = self._anthropic_messages_create(_ant_kw2)
_retry_msg, _ = _nar2(retry_response)
_retry_msg, _ = _nar2(retry_response, strip_tool_prefix=getattr(self, '_is_anthropic_oauth', False))
final_response = (_retry_msg.content or "").strip()
else:
summary_kwargs = {
Expand Down Expand Up @@ -5644,7 +5649,9 @@ def _stop_spinner():
assistant_message, finish_reason = self._normalize_codex_response(response)
elif self.api_mode == "anthropic_messages":
from agent.anthropic_adapter import normalize_anthropic_response
assistant_message, finish_reason = normalize_anthropic_response(response)
assistant_message, finish_reason = normalize_anthropic_response(
response, strip_tool_prefix=getattr(self, "_is_anthropic_oauth", False)
)
else:
assistant_message = response.choices[0].message

Expand Down
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