feat: add ANTHROPIC_BASE_URL setting for custom API endpoints

.env.example

@@ -63,6 +63,12 @@ USE_SDK=true
 # Get your API key from: https://console.anthropic.com/
 ANTHROPIC_API_KEY=
 
+# Custom base URL for the Anthropic API (optional)
+# Use this to point the SDK at a proxy/enterprise endpoint or an
+# Anthropic-compatible provider endpoint. Leave empty for the default endpoint.
+# Example: https://your-proxy.example.com/anthropic
+ANTHROPIC_BASE_URL=
+
 # Path to Claude CLI executable (optional - will auto-detect if not specified)
 # Example: /usr/local/bin/claude or ~/.nvm/versions/node/v20.19.2/bin/claude
 CLAUDE_CLI_PATH=

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- **Custom Anthropic base URL**: New `ANTHROPIC_BASE_URL` setting points the Claude Code SDK at a proxy/enterprise endpoint or any Anthropic-compatible provider endpoint, preserving the existing SDK/session flow when unset.
+
 ## [1.6.0] - 2026-03-30
 
 ### Added

README.md

@@ -230,6 +230,7 @@ ALLOWED_USERS=123456789          # Comma-separated Telegram user IDs
 ```bash
 # Claude
 ANTHROPIC_API_KEY=sk-ant-...     # API key (optional if using CLI auth)
+ANTHROPIC_BASE_URL=...           # Custom API endpoint (optional, for proxy/enterprise or Anthropic-compatible endpoints)
 CLAUDE_MAX_COST_PER_USER=10.0    # Spending limit per user (USD)
 CLAUDE_TIMEOUT_SECONDS=300       # Operation timeout
 

docs/configuration.md

@@ -64,6 +64,9 @@ DISABLE_TOOL_VALIDATION=false
 # Authentication
 ANTHROPIC_API_KEY=sk-ant-api03-...    # Optional: API key for SDK (uses CLI auth if omitted)
 
+# Custom API endpoint (optional, for proxy/enterprise or Anthropic-compatible endpoints)
+ANTHROPIC_BASE_URL=https://your-proxy.example.com/anthropic    # Optional: custom base URL for Anthropic API
+
 # Maximum conversation turns before requiring new session
 CLAUDE_MAX_TURNS=10
 

src/claude/sdk_integration.py

@@ -258,6 +258,17 @@ def __init__(
         else:
             logger.info("No API key provided, using existing Claude CLI authentication")
 
+        # Configure a custom base URL (proxy/enterprise or Anthropic-compatible
+        # endpoint) when provided. The Claude Code SDK reads ANTHROPIC_BASE_URL
+        # from the environment, so the existing SDK/session flow is preserved.
+        if config.anthropic_base_url_str:
+            os.environ["ANTHROPIC_BASE_URL"] = config.anthropic_base_url_str
+            logger.info(
+                "Using custom Anthropic base URL for Claude SDK",
+            )
+        else:
+            os.environ.pop("ANTHROPIC_BASE_URL", None)
+
     def _is_retryable_error(self, exc: BaseException) -> bool:
         """Return True for transient errors that warrant a retry.
         asyncio.TimeoutError is intentional (user-configured timeout) — not retried.

src/config/settings.py

@@ -78,6 +78,13 @@ class Settings(BaseSettings):
         None,
         description="Anthropic API key for SDK (optional if CLI logged in)",
     )
+    anthropic_base_url: Optional[str] = Field(
+        None,
+        description=(
+            "Custom base URL for the Anthropic API (optional, for "
+            "proxy/enterprise or Anthropic-compatible endpoints)"
+        ),
+    )
     claude_model: Optional[str] = Field(
         None, description="Claude model to use (defaults to CLI default if unset)"
     )
@@ -535,6 +542,12 @@ def anthropic_api_key_str(self) -> Optional[str]:
             else None
         )
 
+    @property
+    def anthropic_base_url_str(self) -> Optional[str]:
+        """Get the custom Anthropic base URL as string, if configured."""
+        base_url = self.anthropic_base_url
+        return base_url.strip() if base_url else None
+
     @property
     def mistral_api_key_str(self) -> Optional[str]:
         """Get Mistral API key as string."""

tests/unit/test_claude/test_sdk_integration.py

@@ -157,6 +157,49 @@ async def test_sdk_manager_initialization_without_api_key(self, config):
             if original_api_key:
                 os.environ["ANTHROPIC_API_KEY"] = original_api_key
 
+    async def test_sdk_manager_initialization_with_base_url(self, tmp_path):
+        """Test SDK manager sets ANTHROPIC_BASE_URL when configured."""
+        from src.config.settings import Settings
+
+        config_with_base_url = Settings(
+            telegram_bot_token="test:token",
+            telegram_bot_username="testbot",
+            approved_directory=tmp_path,
+            anthropic_base_url="https://custom.example.com/anthropic",
+            claude_timeout_seconds=2,
+        )
+
+        original_base_url = os.environ.get("ANTHROPIC_BASE_URL")
+
+        try:
+            ClaudeSDKManager(config_with_base_url)
+
+            assert (
+                os.environ.get("ANTHROPIC_BASE_URL")
+                == "https://custom.example.com/anthropic"
+            )
+        finally:
+            if original_base_url:
+                os.environ["ANTHROPIC_BASE_URL"] = original_base_url
+            elif "ANTHROPIC_BASE_URL" in os.environ:
+                del os.environ["ANTHROPIC_BASE_URL"]
+
+    async def test_sdk_manager_initialization_without_base_url(self, config):
+        """Test SDK manager does not set ANTHROPIC_BASE_URL when not configured."""
+        original_base_url = os.environ.get("ANTHROPIC_BASE_URL")
+
+        try:
+            if "ANTHROPIC_BASE_URL" in os.environ:
+                del os.environ["ANTHROPIC_BASE_URL"]
+
+            ClaudeSDKManager(config)
+
+            assert config.anthropic_base_url_str is None
+            assert "ANTHROPIC_BASE_URL" not in os.environ
+        finally:
+            if original_base_url:
+                os.environ["ANTHROPIC_BASE_URL"] = original_base_url
+
     async def test_execute_command_success(self, sdk_manager):
         """Test successful command execution."""
         mock_factory = _mock_client_factory(

tests/unit/test_config.py

@@ -560,6 +560,40 @@ def test_computed_properties(tmp_path):
     assert sqlite_settings.database_path == Path("data/bot.db").resolve()
 
 
+def test_anthropic_base_url_property(tmp_path):
+    """Test the anthropic_base_url_str computed property."""
+    test_dir = tmp_path / "projects"
+    test_dir.mkdir()
+
+    # Defaults to None when not configured
+    unset_settings = Settings(
+        telegram_bot_token="test_token",
+        telegram_bot_username="test_bot",
+        approved_directory=str(test_dir),
+    )
+    assert unset_settings.anthropic_base_url_str is None
+
+    # Returns the configured base URL
+    set_settings = Settings(
+        telegram_bot_token="test_token",
+        telegram_bot_username="test_bot",
+        approved_directory=str(test_dir),
+        anthropic_base_url="https://custom.example.com/anthropic",
+    )
+    assert set_settings.anthropic_base_url_str == "https://custom.example.com/anthropic"
+
+    # Whitespace is trimmed
+    padded_settings = Settings(
+        telegram_bot_token="test_token",
+        telegram_bot_username="test_bot",
+        approved_directory=str(test_dir),
+        anthropic_base_url="  https://custom.example.com/anthropic  ",
+    )
+    assert (
+        padded_settings.anthropic_base_url_str == "https://custom.example.com/anthropic"
+    )
+
+
 def test_feature_flags():
     """Test feature flag system."""
     # Create test MCP config file with valid structure before creating settings