diff --git a/nix/hashes.json b/nix/hashes.json
index 29a102ae66..e60c498ffd 100644
--- a/nix/hashes.json
+++ b/nix/hashes.json
@@ -1,8 +1,8 @@
 {
   "nodeModules": {
     "x86_64-linux": "sha256-07XxcHLuToM4QfWVyaPLACxjPZ93ZM7gtpX2o08Lp18=",
-    "aarch64-linux": "sha256-E6lyYFApS1cw3jE7ISx5QZxDDJ9V3HU0ICYFdY+aIBw=",
+    "aarch64-linux": "sha256-0Im52dLeZ0ZtaPJr/U4m7+IRtOfziHNJI/Bu/V6cPho=",
     "aarch64-darwin": "sha256-U2UvE70nM0OI0VhIku8qnX+ptPbA+Q/y1BGXbFMcyt4=",
-    "x86_64-darwin": "sha256-LxBsYdq5AzInQJzF89taXvS2vigew5C5hjaIEH8rTb8="
+    "x86_64-darwin": "sha256-grPR/YBqYPEUBks4nQKYe6/9f+9N0Fk9l2L9J6ylWkc="
   }
 }
diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 9f2e0ba061..f6f8fe0a1b 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -526,7 +526,11 @@ export namespace MessageV2 {
                 state: "output-available",
                 toolCallId: part.callID,
                 input: part.state.input,
-                output: part.state.time.compacted ? "[Old tool result content cleared]" : part.state.output,
+                // For compacted results, use plain string so SDK serializes as text type
+                // For normal results, pass object so toModelOutput can convert attachments to media parts
+                output: part.state.time.compacted
+                  ? "[Old tool result content cleared]"
+                  : { output: part.state.output, attachments: part.state.attachments },
                 callProviderMetadata: part.metadata,
               })
             }
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 8327698fd5..50d8180a04 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -716,7 +716,10 @@ export namespace SessionPrompt {
           )
           return result
         },
-        toModelOutput(result) {
+        toModelOutput(result: string | { output: string; attachments?: MessageV2.FilePart[] }) {
+          // Handle compacted results (plain string)
+          if (typeof result === "string") return { type: "text", value: result }
+          if (!result.attachments?.length) return { type: "text", value: result.output }
           return {
             type: "text",
             value: result.output,
@@ -806,7 +809,10 @@ export namespace SessionPrompt {
           content: result.content, // directly return content to preserve ordering when outputting to model
         }
       }
-      item.toModelOutput = (result) => {
+      item.toModelOutput = (result: string | { output: string; attachments?: MessageV2.FilePart[] }) => {
+        // Handle compacted results (plain string)
+        if (typeof result === "string") return { type: "text", value: result }
+        if (!result.attachments?.length) return { type: "text", value: result.output }
         return {
           type: "text",
           value: result.output,
diff --git a/packages/opencode/test/session/message-v2.test.ts b/packages/opencode/test/session/message-v2.test.ts
index f069f6ba68..9caa0d8520 100644
--- a/packages/opencode/test/session/message-v2.test.ts
+++ b/packages/opencode/test/session/message-v2.test.ts
@@ -297,7 +297,23 @@ describe("session.message-v2.toModelMessage", () => {
             type: "tool-result",
             toolCallId: "call-1",
             toolName: "bash",
-            output: { type: "text", value: "ok" },
+            output: {
+              type: "json",
+              value: {
+                attachments: [
+                  {
+                    id: "file-1",
+                    sessionID: "session",
+                    messageID: "m-assistant",
+                    type: "file",
+                    mime: "image/png",
+                    filename: "attachment.png",
+                    url: "https://example.com/attachment.png",
+                  },
+                ],
+                output: "ok",
+              },
+            },
             providerOptions: { openai: { tool: "meta" } },
           },
         ],