From c2af70cf732502ce446819f543ab39703aa5b670 Mon Sep 17 00:00:00 2001
From: artboy <80608452+itxaiohanglover@users.noreply.github.com>
Date: Thu, 25 Jun 2026 14:50:03 +0800
Subject: [PATCH 1/2] fix(tools): guard against unsupported image formats
 (webp/gif) to prevent session deadlock

Some model endpoints accept PNG/JPEG but reject WebP/GIF with 400.
The failed image stays in history and is re-sent every turn, bricking
the session permanently.

Fix: check if the model supports the image MIME type before sending.
If not, return a helpful error instead of sending the unsupported image.

Fixes #1082
---
 .../src/tools/builtin/file/read-media.ts         | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/packages/agent-core/src/tools/builtin/file/read-media.ts b/packages/agent-core/src/tools/builtin/file/read-media.ts
index f21886974..85bfe99dd 100644
--- a/packages/agent-core/src/tools/builtin/file/read-media.ts
+++ b/packages/agent-core/src/tools/builtin/file/read-media.ts
@@ -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'];
+        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,

From 7ed11f69707616c5da21009ce3f091f2469e4d2b Mon Sep 17 00:00:00 2001
From: itxaiohanglover <1531137510@qq.com>
Date: Fri, 26 Jun 2026 12:13:13 +0800
Subject: [PATCH 2/2] Add changeset

---
 .changeset/image-format-guard.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/image-format-guard.md

diff --git a/.changeset/image-format-guard.md b/.changeset/image-format-guard.md
new file mode 100644
index 000000000..837116b42
--- /dev/null
+++ b/.changeset/image-format-guard.md
@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+Guard against unsupported image formats to prevent crashes when processing WebP/GIF images.