Pull Request Checklist

• Target branch: dev
• Description: Provided below.
• Changelog: Provided below.
• Documentation: No user-facing behavior changes requiring docs update.
• Dependencies: No new dependencies.
• Testing: Manually tested with gpt-image-1 model using transparent/opaque/auto background options.
• Agentic AI Code: This PR has been manually reviewed and tested by a human.
• Code review: Self-reviewed.
• Design & Architecture: Minimal change, follows existing pattern for optional API parameters.
• Git Hygiene: Single atomic commit.
• Title Prefix: fix:

Changelog Entry

Description

The OpenAI Image Edit API (gpt-image-1) supports a background parameter with values "transparent", "opaque", or "auto", but Open WebUI does not pass this parameter through. This means users cannot
control background transparency when editing images via the built-in tool.

Added

• background field to EditImageForm model ("transparent", "opaque", or "auto")
• background parameter to edit_image built-in tool function with docstring

Changed

• N/A

Deprecated

• N/A

Removed

• N/A

Fixed

• background parameter is now passed to the OpenAI Image Edit API when provided

Security

• N/A

Breaking Changes

• N/A

Additional Information

• Follows existing pattern: **({"background": form_data.background} if form_data.background else {}) same as other optional parameters like size, n
• Parameter is optional with default None, so no breaking change to existing behavior
• Reference: OpenAI Image Edit API docs

Screenshots or Videos

• N/A (API parameter passthrough, no UI change)

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