Avoid relying on the optional REST HTTP server

* Default local API server ports are now extracted from lmstudio-js
* The singular DEFAULT_API_HOST is no longer defined
* New public APIs to check API host validity
* New public APIs to scan for a valid local API host on default ports
* Omitting the API host now results in a dynamic scan for a valid
  local API host when enter the client instance context
* Attempting to access the client api_host field when it is
  still to be determined now raises an exception
* Synchronous session API is now also marked as private

Closes #141

Author: ncoghlan

sdk-schema/sync-sdk-schema.py

@@ -41,7 +41,9 @@
     PythonVersion,
 )
 
-_THIS_DIR = Path(__file__).parent
+
+_THIS_FILE = Path(__file__)
+_THIS_DIR = _THIS_FILE.parent
 _LMSJS_DIR = _THIS_DIR / "lmstudio-js"
 _EXPORTER_DIR = _LMSJS_DIR / "packages/lms-json-schema"
 _SCHEMA_DIR = _EXPORTER_DIR / "schemas"
@@ -51,6 +53,12 @@
 _TEMPLATE_DIR = _THIS_DIR / "_templates"
 _MODEL_DIR = _THIS_DIR.parent / "src/lmstudio/_sdk_models"
 _MODEL_PATH = _MODEL_DIR / "__init__.py"
+_LMSJS_PORTS_PATH = _LMSJS_DIR / "packages/lms-common/src/apiServerPorts.ts"
+_PY_PORTS_PATH = _THIS_DIR.parent / "src/lmstudio/_api_server_ports.py"
+
+GENERATED_SOURCE_HEADER = f"""\
+# Automatically generated by {_THIS_FILE.name}. DO NOT EDIT THIS FILE!
+""".splitlines()
 
 # The following schemas are not actually used anywhere,
 # so they're excluded to avoid any conflicts with automatically
@@ -630,13 +638,40 @@ def _generate_data_model_from_json_schema() -> None:
         if line.startswith("class"):
             break
     updated_source_lines[idx:idx] = lines_to_insert
+    # Insert auto-generated code header
+    updated_source_lines[0:0] = GENERATED_SOURCE_HEADER
     _MODEL_PATH.write_text("\n".join(updated_source_lines) + "\n")
 
 
+def _sync_default_port_list() -> None:
+    """Copy the list of default ports to check for the local API server."""
+    print("Extracting default port list...")
+    print(f"  Reading {_LMSJS_PORTS_PATH}")
+    lmsjs_source = _LMSJS_PORTS_PATH.read_text()
+    START_PORTS = "apiServerPorts = ["
+    END_PORTS = "];"
+    _, found, remaining_text = lmsjs_source.partition(START_PORTS)
+    if not found:
+        raise RuntimeError(f"Failed to find {START_PORTS} in {lmsjs_source}")
+    ports_text, suffix_found, _ = remaining_text.partition(END_PORTS)
+    if not suffix_found:
+        raise RuntimeError(f"Failed to find {END_PORTS} in {remaining_text}")
+    default_ports = [*map(int, ports_text.split(","))]
+    if not default_ports:
+        raise RuntimeError("Failed to extract any default ports")
+    py_source_lines = [
+        *GENERATED_SOURCE_HEADER,
+        f"default_api_ports = ({','.join(map(str, default_ports))})",
+    ]
+    print(f"  Writing {_PY_PORTS_PATH}")
+    _PY_PORTS_PATH.write_text("\n".join(py_source_lines) + "\n")
+
+
 def _main() -> None:
     if sys.argv[1:] == ["--regen-schema"] or not _SCHEMA_PATH.exists():
         _export_zod_schemas_to_json_schema()
     _generate_data_model_from_json_schema()
+    _sync_default_port_list()
     print("Running automatic formatter after data model code generation")
     subprocess.run(["tox", "-e", "format"])
 

src/lmstudio/_api_server_ports.py

@@ -0,0 +1,2 @@
+# Automatically generated by sync-sdk-schema.py. DO NOT EDIT THIS FILE!
+default_api_ports = (41343, 52993, 16141, 39414, 22931)

src/lmstudio/_sdk_models/__init__.py

@@ -1,3 +1,4 @@
+# Automatically generated by sync-sdk-schema.py. DO NOT EDIT THIS FILE!
 from __future__ import annotations
 from typing import Annotated, Any, ClassVar, Literal, Mapping, Sequence, TypedDict
 from msgspec import Meta, field

src/lmstudio/async_api.py

@@ -28,6 +28,8 @@
     TypeIs,
 )
 
+import httpx
+
 from httpx_ws import AsyncWebSocketSession
 
 from .sdk_api import (
@@ -1518,6 +1520,8 @@ def __init__(self, api_host: str | None = None) -> None:
     async def __aenter__(self) -> Self:
         # Handle reentrancy the same way files do:
         # allow nested use as a CM, but close on the first exit
+        with sdk_public_api():
+            await self._ensure_api_host_is_valid()
         if not self._sessions:
             rm = self._resources
             await rm.enter_async_context(self._task_manager)
@@ -1536,6 +1540,43 @@ async def aclose(self) -> None:
         """Close any started client sessions."""
         await self._resources.aclose()
 
+    @staticmethod
+    async def _query_probe_url(url: str) -> httpx.Response:
+        async with httpx.AsyncClient() as client:
+            return await client.get(url, timeout=1)
+
+    @classmethod
+    @sdk_public_api_async()
+    async def is_valid_api_host(cls, api_host: str) -> bool:
+        """Report whether the given API host is running an API server instance."""
+        probe_url = cls._get_probe_url(api_host)
+        try:
+            probe_response = await cls._query_probe_url(probe_url)
+        except (httpx.ConnectTimeout, httpx.ConnectError):
+            return False
+        return cls._check_probe_response(probe_response)
+
+    @classmethod
+    @sdk_public_api_async()
+    async def find_default_local_api_host(cls) -> str | None:
+        """Query local ports for a running API server instance."""
+        for api_host in cls._iter_default_api_hosts():
+            if await cls.is_valid_api_host(api_host):
+                return api_host
+        return None
+
+    async def _ensure_api_host_is_valid(self) -> None:
+        specified_api_host = self._api_host
+        if specified_api_host is None:
+            api_host = await self.find_default_local_api_host()
+        elif await self.is_valid_api_host(specified_api_host):
+            api_host = specified_api_host
+        else:
+            api_host = None
+        if api_host is None:
+            raise self._get_probe_failure_error(specified_api_host)
+        self._api_host = api_host
+
     def _get_session(self, cls: Type[TAsyncSession]) -> TAsyncSession:
         """Get the client session of the given type."""
         namespace = cls.API_NAMESPACE

src/lmstudio/json_api.py

@@ -43,9 +43,11 @@
     Self,
 )
 
+import httpx
 
 from msgspec import Struct, convert, defstruct, to_builtins
 
+from . import _api_server_ports
 from .sdk_api import (
     LMStudioError,
     LMStudioRuntimeError,
@@ -190,7 +192,6 @@
 T = TypeVar("T")
 TStruct = TypeVar("TStruct", bound=AnyLMStudioStruct)
 
-DEFAULT_API_HOST = "localhost:1234"
 DEFAULT_TTL = 60 * 60  # By default, leaves idle models loaded for an hour
 
 # Require a coroutine (not just any awaitable) for run_coroutine_threadsafe compatibility
@@ -1964,9 +1965,45 @@ class ClientBase:
 
     def __init__(self, api_host: str | None = None) -> None:
         """Initialize API client."""
-        self.api_host = api_host if api_host else DEFAULT_API_HOST
+        self._api_host = api_host
         self._auth_details = self._create_auth_message()
 
+    @property
+    def api_host(self) -> str:
+        api_host = self._api_host
+        if api_host is None:
+            raise LMStudioRuntimeError("Local API host port is not yet resolved.")
+        return api_host
+
+    _DEFAULT_API_PORTS = _api_server_ports.default_api_ports
+
+    @staticmethod
+    def _get_probe_url(api_host: str) -> str:
+        return f"http://{api_host}/lmstudio-greeting"
+
+    @classmethod
+    def _iter_default_api_hosts(cls) -> Iterable[str]:
+        for port in cls._DEFAULT_API_PORTS:
+            api_host = f"127.0.0.1:{port}"
+            yield api_host
+
+    @staticmethod
+    def _check_probe_response(response: httpx.Response) -> bool:
+        """Returns true if the probe response indicates a valid API server."""
+        if response.status_code != httpx.codes.OK:
+            return False
+        response_data = response.json()
+        # Valid probe response format: {"lmstudio":true}
+        return isinstance(response_data, dict) and response_data.get("lmstudio", False)
+
+    @staticmethod
+    def _get_probe_failure_error(api_host: str | None) -> LMStudioClientError:
+        if api_host is None:
+            api_host = "any default port"
+        problem = f"LM Studio is not reachable at {api_host}"
+        suggestion = "Is LM Studio running?"
+        return LMStudioClientError(f"{problem}. {suggestion}")
+
     @staticmethod
     def _format_auth_message(
         client_id: str | None = None, client_key: str | None = None