fix(vllm): declare entry-stage engine_input_source in GLM-Image NIXL config

[GuanLuo]

Overview:

The GLM-Image AR→DiT NIXL disaggregation launch script
(examples/backends/vllm/launch/disagg_omni_glm_image_nixl.sh) cannot start on
vllm-omni v0.26.0rc1. The AR stage exits with code 1 and the frontend never
becomes ready:

RuntimeError: Orchestrator initialization failed: Missing key
engine_input_source (full_key: stage_args[0].engine_input_source)

Summary

Stage 0 of stage_configs/glm_image_nixl.yaml is the pipeline's entry stage and
omitted engine_input_source. That was valid through v0.25.0rc1, where
vllm-omni defaulted the field to []. Upstream removed the default in
v0.26.0rc1 (fb4dd41d, "[Refactor]: Remove unnecessary config getattr" #5199),
so stage metadata extraction now reads it unconditionally. The legacy
stage_args config format applies no schema defaults, so the field is simply
absent and the orchestrator thread dies during engine creation.

Stage 1 already declares engine_input_source: [0], which is why only the AR
half crashed. The SHM variant is unaffected because it consumes vllm-omni's own
packaged config in the stages format, whose parser supplies the default.

This declares the field explicitly as an empty list — the value upstream itself
supplied until v0.26.0rc1, and the one its deploy parser still produces for an
entry stage (a stage with empty input_sources).

Details:

Fixing the config rather than _stage_config_to_dict in stage_worker.py:
that file ships in the wheel and is on the path of every omni deployment,
including the SHM path that currently works, whereas this change touches one
example config. Re-adding in Dynamo a default upstream deliberately removed
would also diverge from the engine's contract.

Where should the reviewer start?

Single file, four added lines:
examples/backends/vllm/launch/stage_configs/glm_image_nixl.yaml

Validation

• Reproduced the original failure against a v0.26.0rc1 checkout, matching the
  reported ConfigAttributeError exactly including full_key and
  object_type; confirmed it no longer raises after this change.
• Verified the field survives Dynamo's whitelist copy into the synthesized
  single-stage config that is handed to AsyncOmni.
• pre-commit run --files examples/backends/vllm/launch/stage_configs/glm_image_nixl.yaml passes.
• Not yet validated: end-to-end image generation over NIXL on a two-GPU
  host. This config has no CI lane, and the AR stage previously died before any
  transfer occurred, so the NIXL data path has not executed on this pin.

Related Issues

🚫 This PR is NOT linked to an issue:

• Confirmed — no related issue

🤖 Generated with Claude Code

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Summary by CodeRabbit

• Bug Fixes
  • Updated the GLM image stage configuration to explicitly define an empty engine input source, improving configuration clarity and consistency.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

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📥 Commits

Reviewing files that changed from the base of the PR and between e322c8d and ec83ccf.

📒 Files selected for processing (1)

• examples/backends/vllm/launch/stage_configs/glm_image_nixl.yaml

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Walkthrough

The AR entry stage configuration now explicitly declares an empty engine_input_source instead of relying on schema defaults.

Changes

AR entry configuration

Layer / File(s)	Summary
Explicit engine input source examples/backends/vllm/launch/stage_configs/glm_image_nixl.yaml	The AR entry stage declares an empty engine_input_source.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the configuration fix for the GLM-Image NIXL entry stage.
Description check	✅ Passed	The description covers the required sections, explains the failure and fix, identifies the review location, and confirms no related issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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