feat: enhance start node object value check

[fatelei]

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Summary

fix #30731

enhance start node object value check

Screenshots

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Screen.Recording.2026-01-08.at.16.41.06.mov

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint and make type-check (backend) and cd web && npx lint-staged (frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @fatelei, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the validation process for JSON object inputs within start nodes. It adds a crucial type check to ensure that after a value is parsed as JSON, it strictly conforms to the expected dictionary type. This enhancement improves data integrity by preventing malformed or incorrectly typed JSON values from proceeding through the workflow, addressing a potential edge case where non-object JSON could bypass initial parsing but cause issues later.

Highlights

• Enhanced JSON Object Validation: A new check has been introduced to explicitly verify that parsed JSON object inputs for start nodes are indeed dictionaries. This prevents non-object JSON types (like arrays, strings, numbers, booleans, or null) from being accepted when an object is expected, even if they are valid JSON.

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[gemini-code-assist]

Code Review

This pull request correctly enhances validation for JSON_OBJECT variables by ensuring the provided value is a dictionary. The change is a good improvement. However, this validation is only applied when a json_schema is present. It would be more robust to apply this check for all JSON_OBJECT variables, regardless of schema presence. Also, please ensure tests for this new logic are included, as they appear to be missing from the pull request despite being checked in the description.

[QuantumGhost]

LGTM