[ananyaa-ms]

Describe your changes

Enable the existing capture-onnx-graph --extra_mb_options flag with --use_mobius_builder, forwarding model-specific options to mobius.build(extra_options=...).

• Parse comma-separated key=value settings into typed JSON values or strings, including null as None; reject malformed settings and duplicate keys.
• Expose MobiusBuilder.extra_options for pass configurations. Omit the build keyword when options are absent, preserving compatibility with older Mobius versions.
• Document fixed-capacity Gemma4 vision options and cover forwarding, validation, nullable values, and coexistence with accuracy overrides.

Release note: olive capture-onnx-graph --use_mobius_builder now accepts model-specific Mobius settings through --extra_mb_options, including fixed-capacity Gemma4 vision options.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.

(Optional) Issue link

N/A.

[Copilot]

🟢 Approval recommended

No active review issues were identified for the Mobius build-option changes.

No open issues 🎉

What changed in this PR

Adds model-specific Mobius build options to Olive’s ONNX capture CLI and pass configuration, while preserving existing Model Builder parsing and compatibility when options are absent.

Changes:

• Parse Mobius key=value options into JSON values or strings, including nullable values, and reject malformed entries and duplicate keys.
• Forward nonempty options to mobius.build(extra_options=...).
• Document fixed-capacity Gemma4 vision usage and add tests for forwarding, validation, and coexistence with accuracy overrides.

File	Description
test/​passes/​onnx/​test_mobius_model_builder.py	Tests pass-level forwarding, including nullable option values.
test/​cli/​test_cli.py	Tests CLI parsing, validation, accuracy overrides, and unchanged Model Builder parsing.
olive/​passes/​onnx/​mobius_model_builder.py	Adds optional extra_options configuration and forwards nonempty options.
olive/​cli/​capture_onnx.py	Adds typed Mobius option parsing and CLI integration.
docs/​source/​reference/​cli.rst	Documents option syntax and a Gemma4 fixed-capacity vision example.

_{Review effort: Balanced}