Add Anthropic LLM support (#185)

* Add Anthropic LLM support

Signed-off-by: droctothorpe <mythicalsunlight@gmail.com>

* Update skypilot link

Signed-off-by: droctothorpe <mythicalsunlight@gmail.com>

* Handle anthropic base_url

Signed-off-by: droctothorpe <mythicalsunlight@gmail.com>

* Address ruff format finding

Signed-off-by: droctothorpe <mythicalsunlight@gmail.com>

---------

Signed-off-by: droctothorpe <mythicalsunlight@gmail.com>

packages/leann-core/src/leann/settings.py

@@ -9,6 +9,7 @@ from typing import Any
 # Default fallbacks to preserve current behaviour while keeping them in one place.
 _DEFAULT_OLLAMA_HOST = "http://localhost:11434"
 _DEFAULT_OPENAI_BASE_URL = "https://api.openai.com/v1"
+_DEFAULT_ANTHROPIC_BASE_URL = "https://api.anthropic.com"
 
 
 def _clean_url(value: str) -> str:
@@ -52,6 +53,23 @@ def resolve_openai_base_url(explicit: str | None = None) -> str:
     return _clean_url(_DEFAULT_OPENAI_BASE_URL)
 
 
+def resolve_anthropic_base_url(explicit: str | None = None) -> str:
+    """Resolve the base URL for Anthropic-compatible services."""
+
+    candidates = (
+        explicit,
+        os.getenv("LEANN_ANTHROPIC_BASE_URL"),
+        os.getenv("ANTHROPIC_BASE_URL"),
+        os.getenv("LOCAL_ANTHROPIC_BASE_URL"),
+    )
+
+    for candidate in candidates:
+        if candidate:
+            return _clean_url(candidate)
+
+    return _clean_url(_DEFAULT_ANTHROPIC_BASE_URL)
+
+
 def resolve_openai_api_key(explicit: str | None = None) -> str | None:
     """Resolve the API key for OpenAI-compatible services."""
 
@@ -61,6 +79,15 @@ def resolve_openai_api_key(explicit: str | None = None) -> str | None:
     return os.getenv("OPENAI_API_KEY")
 
 
+def resolve_anthropic_api_key(explicit: str | None = None) -> str | None:
+    """Resolve the API key for Anthropic services."""
+
+    if explicit:
+        return explicit
+
+    return os.getenv("ANTHROPIC_API_KEY")
+
+
 def encode_provider_options(options: dict[str, Any] | None) -> str | None:
     """Serialize provider options for child processes."""