From 1a1c0bd86a458409f9c92118311bd1119626d9dc Mon Sep 17 00:00:00 2001
From: chrarnoldus <12196001+chrarnoldus@users.noreply.github.com>
Date: Thu, 4 Jun 2026 10:45:51 +0000
Subject: [PATCH] fix(cli): narrow webfetch image rejection

Co-authored-by: kiloconnect[bot] <240665456+kiloconnect[bot]@users.noreply.github.com>
---
 .changeset/calm-icons-fetch.md               |  2 +-
 packages/opencode/src/tool/webfetch.ts       |  9 ++++-
 packages/opencode/src/util/media.ts          |  5 ++-
 packages/opencode/test/tool/webfetch.test.ts | 39 ++++++++++++++++++--
 4 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/.changeset/calm-icons-fetch.md b/.changeset/calm-icons-fetch.md
index 6717f429e35..69a84091136 100644
--- a/.changeset/calm-icons-fetch.md
+++ b/.changeset/calm-icons-fetch.md
@@ -2,4 +2,4 @@
 "@kilocode/cli": patch
 ---
 
-Prevent unsupported images fetched from the web from causing provider request errors.
+Prevent icon images fetched from the web from causing provider request errors.
diff --git a/packages/opencode/src/tool/webfetch.ts b/packages/opencode/src/tool/webfetch.ts
index dc2c2ad35d7..01279ad55de 100644
--- a/packages/opencode/src/tool/webfetch.ts
+++ b/packages/opencode/src/tool/webfetch.ts
@@ -126,10 +126,15 @@ export const WebFetchTool = Tool.define(
           }
 
           // kilocode_change start
-          if (mime.startsWith("image/") && mime !== "image/svg+xml") {
+          if (
+            mime.startsWith("image/") &&
+            !isImageAttachment(mime) &&
+            mime !== "image/svg+xml" &&
+            mime !== "image/vnd.fastbidsheet"
+          ) {
             return {
               title,
-              output: `Unsupported image format: ${mime}. Supported formats are JPEG, PNG, GIF, and WebP.`,
+              output: `Unsupported image format: ${mime}.`,
               metadata: {},
             }
           }
diff --git a/packages/opencode/src/util/media.ts b/packages/opencode/src/util/media.ts
index f90eb30ae4c..0e855821336 100644
--- a/packages/opencode/src/util/media.ts
+++ b/packages/opencode/src/util/media.ts
@@ -1,4 +1,5 @@
 const startsWith = (bytes: Uint8Array, prefix: number[]) => prefix.every((value, index) => bytes[index] === value)
+const icons = new Set(["image/vnd.microsoft.icon", "image/x-icon", "image/x-ico", "image/ico", "image/icon"]) // kilocode_change
 
 export function isPdfAttachment(mime: string) {
   return mime === "application/pdf"
@@ -8,9 +9,11 @@ export function isMedia(mime: string) {
   return mime.startsWith("image/") || isPdfAttachment(mime)
 }
 
+// kilocode_change start
 export function isImageAttachment(mime: string) {
-  return ["image/jpeg", "image/png", "image/gif", "image/webp"].includes(mime) // kilocode_change
+  return mime.startsWith("image/") && mime !== "image/svg+xml" && mime !== "image/vnd.fastbidsheet" && !icons.has(mime)
 }
+// kilocode_change end
 
 export function sniffAttachmentMime(bytes: Uint8Array, fallback: string) {
   if (startsWith(bytes, [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])) return "image/png"
diff --git a/packages/opencode/test/tool/webfetch.test.ts b/packages/opencode/test/tool/webfetch.test.ts
index 89d10881cfc..e7df83c4f7b 100644
--- a/packages/opencode/test/tool/webfetch.test.ts
+++ b/packages/opencode/test/tool/webfetch.test.ts
@@ -83,16 +83,49 @@ describe("tool.webfetch", () => {
   })
 
   // kilocode_change start
-  test("rejects unsupported image attachments", async () => {
+  test.each(["image/x-icon", "image/vnd.microsoft.icon"])("rejects %s attachments", async (mime) => {
     const bytes = new Uint8Array([0, 0, 1, 0])
     await withFetch(
-      () => new Response(bytes, { status: 200, headers: { "content-type": "image/x-icon" } }),
+      () => new Response(bytes, { status: 200, headers: { "content-type": mime } }),
       async (url) => {
         await WithInstance.provide({
           directory: projectRoot,
           fn: async () => {
             const result = await exec({ url: new URL("/favicon.ico", url).toString(), format: "markdown" })
-            expect(result.output).toContain("Unsupported image format: image/x-icon")
+            expect(result.output).toContain(`Unsupported image format: ${mime}`)
+            expect(result.attachments).toBeUndefined()
+          },
+        })
+      },
+    )
+  })
+
+  test("returns non-icon image responses as file attachments", async () => {
+    const bytes = new Uint8Array([0, 0, 0, 0])
+    await withFetch(
+      () => new Response(bytes, { status: 200, headers: { "content-type": "image/avif" } }),
+      async (url) => {
+        await WithInstance.provide({
+          directory: projectRoot,
+          fn: async () => {
+            const result = await exec({ url: new URL("/image.avif", url).toString(), format: "markdown" })
+            expect(result.output).toBe("Image fetched successfully")
+            expect(result.attachments?.[0].mime).toBe("image/avif")
+          },
+        })
+      },
+    )
+  })
+
+  test("keeps fastbidsheet responses as text output", async () => {
+    await withFetch(
+      () => new Response("sheet", { status: 200, headers: { "content-type": "image/vnd.fastbidsheet" } }),
+      async (url) => {
+        await WithInstance.provide({
+          directory: projectRoot,
+          fn: async () => {
+            const result = await exec({ url: new URL("/sheet", url).toString(), format: "text" })
+            expect(result.output).toBe("sheet")
             expect(result.attachments).toBeUndefined()
           },
         })