Server Factory API

Singleton factory helpers for DCC MCP server instances. Eliminates the boilerplate threading lock + None check that every adapter would otherwise duplicate.

Exported symbols: create_dcc_server, get_server_instance, make_start_stop

create_dcc_server

create_dcc_server(
    *, instance_holder: list, lock: threading.Lock, server_class: type,
    port: int = 8765, register_builtins: bool = True,
    extra_skill_paths: list[str] | None = None,
    include_bundled: bool = True, enable_hot_reload: bool = False,
    hot_reload_env_var: str | None = None, **server_kwargs
) -> McpServerHandle

Create-or-return a singleton DCC MCP server and start it. Thread-safe.

Parameter	Type	Default	Description
instance_holder	list	(required)	Single-element list used as mutable reference
lock	threading.Lock	(required)	Module-level lock for thread safety
server_class	type	(required)	DccServerBase subclass to instantiate
port	int	8765	TCP port for the MCP HTTP server
register_builtins	bool	True	Call register_builtin_actions() after creation
extra_skill_paths	list[str] | None	None	Additional skill directories
include_bundled	bool	True	Include dcc-mcp-core bundled skills
enable_hot_reload	bool	False	Enable skill hot-reload
hot_reload_env_var	str | None	None	Env var for hot-reload override

make_start_stop

make_start_stop(server_class: type, hot_reload_env_var: str | None = None) -> tuple[Callable, Callable]

Generate a (start_server, stop_server) function pair for a DCC adapter. Zero-boilerplate.

from dcc_mcp_core import make_start_stop

start_server, stop_server = make_start_stop(
    MyDccServer,
    hot_reload_env_var="DCC_MCP_MYDCC_HOT_RELOAD",
)

get_server_instance

get_server_instance(instance_holder: list) -> server | None

Return the current singleton instance (or None if not started).

---

Embedded-host wiring (issues #521, #525)

Embedded DCC plugins (Maya, Houdini, Unreal Python, Blender) typically need two pieces of glue beyond the bare server:

1. A callable dispatcher that routes skill scripts onto the host's UI / main thread.
2. A declarative skill list so launch-on-startup is reproducible across sessions.

DccServerBase exposes register_inprocess_executor() and register_builtin_actions(minimal_mode=...) for exactly this:

from dcc_mcp_core import (
    DccServerBase, McpHttpConfig,
    InProcessCallableDispatcher, build_inprocess_executor,
    MinimalModeConfig,
)

class MayaDccServer(DccServerBase):
    @classmethod
    def dcc_name(cls) -> str: return "maya"

server = MayaDccServer(McpHttpConfig(port=8765))

# 1) Wire the in-process executor BEFORE registering builtins.
dispatcher = InProcessCallableDispatcher()    # or your Maya UI-thread subclass
server.register_inprocess_executor(build_inprocess_executor(dispatcher))

# 2) Pin the boot-time skill set declaratively.
server.register_builtin_actions(minimal_mode=MinimalModeConfig(
    skills=("scene_inspector", "render_queue"),
    deactivate_groups={"render_queue": ("submit",)},
    env_var_minimal="DCC_MCP_MAYA_MINIMAL",
))

server.start()

See Callable Dispatcher API for the full BaseDccCallableDispatcher / BaseDccCallableDispatcherFull / BaseDccPump contract and the MinimalModeConfig resolution order.