server: enforce Pro-only for actual LLM settings changes; add robust tests mirroring frontend full-payload behavior

[amanape]

• This change is worth documenting at https://docs.all-hands.dev/
• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

End-user friendly description of the problem this fixes or functionality this introduces.

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Summarize what the PR does, explaining any non-trivial design decisions.

• Precise LLM change detection to avoid blocking language-only saves
• SaaS: call subscription validation only when LLM fields truly change
• Tests updated to patch correct target and add regression for full-payload save

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Link of any specific issues this addresses:

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To run this PR locally, use the following command:

GUI with Docker:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:4946d7d-nikolaik   --name openhands-app-4946d7d   docker.all-hands.dev/all-hands-ai/openhands:4946d7d

CLI with uvx:

uvx --python 3.12 --from git+https://github.com/All-Hands-AI/OpenHands@fix/llm-settings-validation-tdd openhands

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
openhands/server
settings_validation.py					58-92
Project Total

This report was generated by python-coverage-comment-action

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Last updated: Sep 26, 2025, 12:56:14 PM ET

[amanape]

Closed by #11170