Fix ImageGeneratingChatClient duplicating preceding content and dropping following content#7622
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[WIP] Fix duplication and content drop in ImageGeneratingChatClient
Fix ImageGeneratingChatClient duplicating preceding content and dropping following content
Jul 13, 2026
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Pull request overview
Fixes a content-rewrite bug in ImageGeneratingChatClient where reverse iteration could duplicate earlier content items and drop later items when replacing image-generation function content.
Changes:
- Updated
ReplaceImageGenerationFunctionResultsto iterate forward so surrounding content is preserved and not duplicated/dropped. - Added regression tests for both non-streaming and streaming responses to validate content order and cardinality when image-generation content appears at the start/middle/end.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/Libraries/Microsoft.Extensions.AI/ChatCompletion/ImageGeneratingChatClient.cs | Switches replacement logic to forward iteration to preserve content order and prevent duplication/dropping. |
| test/Libraries/Microsoft.Extensions.AI.Tests/ChatCompletion/ImageGeneratingChatClientTests.cs | Adds regression coverage for surrounding-content preservation in both GetResponseAsync and GetStreamingResponseAsync. |
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
jozkee
approved these changes
Jul 13, 2026
jeffhandley
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Jul 13, 2026
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/backport to release/10.8 |
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Started backporting to release/10.8: https://github.com/dotnet/extensions/actions/runs/29286341323 |
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ReplaceImageGenerationFunctionResultsiterated in reverse, causing content items after an image-generation match to be silently dropped (visited whilenewContentswas null) and items before it to be duplicated (CopyListcaptured the prefix, then the reverse loop re-appended those same items).For a message with contents
[A, ImageGenFunctionCall, B], the old code produced[A, ImageGenerationToolCallContent, A]— droppingBand duplicatingA.Changes
ImageGeneratingChatClient.cs: ChangedReplaceImageGenerationFunctionResultsfrom reverse to forward iteration.CopyList(contents, i)now correctly captures only items before the replacement point; remaining items are appended naturally as the loop continues.ImageGeneratingChatClientTests.cs: Added regression tests for bothGetResponseAsyncandGetStreamingResponseAsynccovering image-generation content at the start, middle, and end of the content list with surrounding unrelated content items of mixed types (FunctionResultContent,UsageContent).