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fix(tools): guard against unsupported image formats to prevent session deadlock #1095

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fix(tools): guard against unsupported image formats to prevent session deadlock #1095

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fix(tools): guard against unsupported image formats (webp/gif) to pre…
itxaiohanglover Jun 25, 2026
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itxaiohanglover Jun 26, 2026
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5 changes: 5 additions & 0 deletions .changeset/image-format-guard.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@moonshot-ai/kimi-code": patch
---

Guard against unsupported image formats to prevent crashes when processing WebP/GIF images.
16 changes: 16 additions & 0 deletions packages/agent-core/src/tools/builtin/file/read-media.ts
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Expand Up @@ -199,6 +199,22 @@ export class ReadMediaFileTool implements BuiltinTool<ReadMediaFileInput> {
'Tell the user to use a model with image input capability.',
};
}
// Guard against image formats the model endpoint may reject.
// Some providers (e.g. kimi-for-coding) accept PNG/JPEG but reject
// WebP/GIF, causing a 400 that bricks the session because the failed
// image stays in history and is re-sent on every turn.
if (fileType.kind === 'image' && (fileType.mimeType === 'image/webp' || fileType.mimeType === 'image/gif')) {
const supported = this.capabilities.supportedImageMimes ?? ['image/png', 'image/jpeg'];

@chatgpt-codex-connector chatgpt-codex-connector Bot Jun 25, 2026

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P1 Badge Add the MIME capability field before reading it

In the current @moonshot-ai/kosong contract, ModelCapability has no supportedImageMimes field, so this new access makes the package fail typechecking (Property 'supportedImageMimes' does not exist on type 'ModelCapability'). If the field is intended, it needs to be added to the shared capability type and populated by the capability providers; otherwise this guard cannot compile and release builds for agent-core are blocked.

Useful? React with 👍 / 👎.

if (!supported.includes(fileType.mimeType)) {
return {
isError: true,
output:
`The current model does not support ${fileType.mimeType} images. ` +
'Supported formats: ' + supported.join(', ') + '. ' +
'Convert the image to PNG or JPEG before reading it.',
};
}
}
if (fileType.kind === 'video' && !this.capabilities.video_in) {
return {
isError: true,
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