[Core] Retain structured configs through runtime startup (#6849)

Signed-off-by: maithilijoshi20 <97733343+maithilijoshi20@users.noreply.github.com>

tests/entrypoints/test_serve.py

@@ -7,10 +7,12 @@ from __future__ import annotations
 
 import argparse
 from types import SimpleNamespace
+from typing import Any
 
 import pytest
 from pytest_mock import MockerFixture
 
+from vllm_omni.config.omni_config import VllmOmniDiffusionStageConfig
 from vllm_omni.config.resolver import OmniConfigResolution
 from vllm_omni.entrypoints.cli.serve import (
     OmniServeCommand,
@@ -334,6 +336,26 @@ def test_parse_stage_overrides_invalid_json_raises() -> None:
     assert f"Got: {bad!r}" in message
 
 
+@pytest.mark.parametrize(
+    "payload",
+    ['{"abc": {}}', '{"-1": {}}', '{"1.5": {}}', '{"\uff10": {}}'],
+)
+def test_parse_stage_overrides_rejects_invalid_stage_ids(payload: str) -> None:
+    with pytest.raises(argparse.ArgumentTypeError, match="non-negative integer stage ids"):
+        _parse_stage_overrides(payload)
+
+
+def test_parse_stage_overrides_preserves_arbitrary_override_fields() -> None:
+    parsed = _parse_stage_overrides(
+        '{"0": {"extras": {"ltx2_use_conv_vae": true}, "kv_cache_dtype": "fp8", "typo_field_xyz": 1}}'
+    )
+    assert parsed["0"] == {
+        "extras": {"ltx2_use_conv_vae": True},
+        "kv_cache_dtype": "fp8",
+        "typo_field_xyz": 1,
+    }
+
+
 def test_parse_stage_overrides_rejects_non_dict_top_level() -> None:
     """Top-level must be a JSON object (dict). A list, scalar, or non-dict
     mapping is rejected with a ValueError naming ``--stage-overrides`` and
@@ -706,6 +728,77 @@ def test_run_headless_diffusion_registers_and_spawns_proc(mocker: MockerFixture)
     assert manager_kwargs["omni_replica_id"] == 0
 
 
+def test_run_headless_generic_diffusion_launches_structured_stage(mocker: MockerFixture) -> None:
+    """Headless resolution starts the typed stage through the real group launcher."""
+    from vllm_omni.engine import stage_engine_startup as startup_module
+
+    mocker.patch("vllm_omni.config.resolver.StageConfigFactory.create_from_model", return_value=None)
+    mocker.patch(
+        "vllm_omni.config.resolver._resolve_generic_diffusion_model_class",
+        return_value=(True, "FakeDiffusionPipeline"),
+    )
+    mocker.patch("vllm_omni.engine.stage_init_utils.prepare_engine_environment")
+    mocker.patch.object(startup_module.stage_init_utils, "load_omni_transfer_config_for_model", return_value=None)
+    mocker.patch.object(
+        startup_module.initialization,
+        "resolve_omni_kv_config_for_stage",
+        return_value=(None, None, None),
+    )
+    captured: dict[str, Any] = {}
+    od_config = SimpleNamespace()
+
+    def _build_diffusion_config(model, stage_config, metadata):
+        captured.update(model=model, stage_config=stage_config, metadata=metadata)
+        return od_config
+
+    def _launch_replica_group(**kwargs):
+        captured.update(group_kwargs=kwargs)
+        captured["manager"] = kwargs["launch_one"](0)
+
+    def _launch_replica(**kwargs):
+        captured.update(replica_kwargs=kwargs)
+        return SimpleNamespace(exitcode=None)
+
+    mocker.patch.object(startup_module.stage_init_utils, "build_diffusion_config", side_effect=_build_diffusion_config)
+    mocker.patch.object(startup_module, "launch_headless_replica_group", side_effect=_launch_replica_group)
+    mocker.patch.object(startup_module, "launch_headless_diffusion_replica", side_effect=_launch_replica)
+
+    explicit_keys = frozenset(
+        {
+            "model",
+            "stage_id",
+            "omni_master_address",
+            "omni_master_port",
+            "worker_backend",
+            "model_class_name",
+            "num_gpus",
+        }
+    )
+    args = _make_headless_args(
+        explicit_keys=explicit_keys,
+        model="generic-diffusion",
+        model_class_name="FakeDiffusionPipeline",
+        num_gpus=1,
+    )
+
+    run_headless(args)
+
+    stage = captured["stage_config"]
+    assert isinstance(stage, VllmOmniDiffusionStageConfig)
+    assert captured["metadata"].stage_type == "diffusion"
+    assert captured["metadata"].model_stage == "diffusion"
+    assert captured["model"] == "generic-diffusion"
+    assert captured["group_kwargs"]["stage_id"] == 0
+    assert captured["group_kwargs"]["omni_dp_size_local"] == 1
+    assert captured["group_kwargs"]["per_replica_devices"] == ["0"]
+    assert captured["replica_kwargs"]["stage_config"] is stage
+    assert captured["replica_kwargs"]["stage_id"] == 0
+    assert captured["replica_kwargs"]["omni_master_address"] == "127.0.0.1"
+    assert captured["replica_kwargs"]["omni_master_port"] == 26000
+    assert captured["replica_kwargs"]["od_config"] is od_config
+    assert stage.runtime_config.devices == "0"
+
+
 def test_run_headless_diffusion_raises_on_nonzero_proc_exit(mocker: MockerFixture) -> None:
     """A diffusion replica that exits with a non-zero code must surface as a
     RuntimeError from ``run_headless`` (the head needs the signal to roll