feat: add lazy CLI extensions

architecture/cli.md

@@ -20,6 +20,33 @@ The CLI is built on Typer with lazy command loading to keep startup fast. Config
 
 `create_lazy_typer_group` and `_LazyCommand` stubs defer importing command modules until a command is actually invoked. This keeps `data-designer --help` fast — only the command names and descriptions are loaded eagerly; the full module (and its dependencies) loads on first use.
 
+The root group also discovers optional command groups from the `data_designer.cli`
+entry-point group. The entry-point name is the top-level command name. Its target
+must be a zero-argument callable that returns a `click.Command`, normally a Click
+group produced from a Typer application. Root help uses the providing
+distribution's `Summary` metadata and does not load the target.
+
+```toml
+[project.entry-points."data_designer.cli"]
+slurm = "data_designer.slurm.cli:create_cli"
+```
+
+Extension distributions must declare a compatible dependency on
+`data-designer`. Compatibility and the loaded object are validated only when the
+extension command is selected. The entry-point name is authoritative and is
+assigned to the returned command. Built-in command names are reserved. A
+built-in collision makes that command unavailable with a targeted error rather
+than allowing the extension to replace it. A duplicate extension name remains
+visible as unavailable in root help and fails deterministically without loading
+any conflicting target. Invalid extension names and discovery failures are
+reported as warnings without disabling built-in commands.
+
+The installed-wheel smoke test measures nine warm root-help subprocesses for a
+base-only environment and an environment with the Slurm extension. The accepted
+base median is at most one second, and the median overhead from installing the
+extension is at most 100 ms. It also verifies that root help does not import the
+extension or compatibility-checking modules.
+
 ### Layering Pattern (Setup Workflows)
 
 Config management commands (models, providers, MCP providers, tools) follow a consistent four-layer pattern:

packages/data-designer-slurm/pyproject.toml

@@ -19,6 +19,9 @@ classifiers = [
     "Programming Language :: Python :: 3.14",
 ]
 
+[project.entry-points."data_designer.cli"]
+slurm = "data_designer.slurm.cli:create_cli"
+
 [build-system]
 requires = ["hatchling", "uv-dynamic-versioning>=0.7.0"]
 build-backend = "hatchling.build"

packages/data-designer-slurm/src/data_designer/slurm/cli.py

@@ -0,0 +1,23 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+from __future__ import annotations
+
+import click
+import typer
+
+app = typer.Typer(
+    name="slurm",
+    help="Run Data Designer workloads on Slurm",
+    no_args_is_help=True,
+)
+
+
+@app.callback()
+def slurm_callback() -> None:
+    pass
+
+
+def create_cli() -> click.Command:
+    """Create the Slurm CLI group."""
+    return typer.main.get_command(app)

packages/data-designer-slurm/tests/test_package.py

@@ -3,6 +3,7 @@
 
 from __future__ import annotations
 
+import importlib.metadata
 from pathlib import Path
 
 import data_designer
@@ -20,3 +21,14 @@ def test_slurm_is_published_before_base_extra() -> None:
     publish_script = (REPO_ROOT / "scripts" / "publish.sh").read_text()
 
     assert publish_script.index('"packages/data-designer-slurm"') < publish_script.index('"packages/data-designer"')
+
+
+def test_slurm_registers_lazy_cli_extension() -> None:
+    entry_points = importlib.metadata.entry_points(group="data_designer.cli")
+    slurm_entry_point = next(
+        entry_point
+        for entry_point in entry_points
+        if entry_point.name == "slurm" and entry_point.dist.name == "data-designer-slurm"
+    )
+
+    assert slurm_entry_point.value == "data_designer.slurm.cli:create_cli"