diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 4b081b5b4..9f2e0ba06 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -1,14 +1,7 @@
 import { BusEvent } from "@/bus/bus-event"
 import z from "zod"
 import { NamedError } from "@opencode-ai/util/error"
-import {
-  APICallError,
-  convertToModelMessages,
-  LoadAPIKeyError,
-  type ModelMessage,
-  type UIMessage,
-  type ToolSet,
-} from "ai"
+import { APICallError, convertToModelMessages, LoadAPIKeyError, type ModelMessage, type UIMessage } from "ai"
 import { Identifier } from "../id/id"
 import { LSP } from "../lsp"
 import { Snapshot } from "@/snapshot"
@@ -439,7 +432,7 @@ export namespace MessageV2 {
   })
   export type WithParts = z.infer<typeof WithParts>
 
-  export function toModelMessage(input: WithParts[], options?: { tools?: ToolSet }): ModelMessage[] {
+  export function toModelMessage(input: WithParts[]): ModelMessage[] {
     const result: UIMessage[] = []
 
     for (const msg of input) {
@@ -510,14 +503,30 @@ export namespace MessageV2 {
             })
           if (part.type === "tool") {
             if (part.state.status === "completed") {
+              if (part.state.attachments?.length) {
+                result.push({
+                  id: Identifier.ascending("message"),
+                  role: "user",
+                  parts: [
+                    {
+                      type: "text",
+                      text: `Tool ${part.tool} returned an attachment:`,
+                    },
+                    ...part.state.attachments.map((attachment) => ({
+                      type: "file" as const,
+                      url: attachment.url,
+                      mediaType: attachment.mime,
+                      filename: attachment.filename,
+                    })),
+                  ],
+                })
+              }
               assistantMessage.parts.push({
                 type: ("tool-" + part.tool) as `tool-${string}`,
                 state: "output-available",
                 toolCallId: part.callID,
                 input: part.state.input,
-                output: part.state.time.compacted
-                  ? "[Old tool result content cleared]"
-                  : { output: part.state.output, attachments: part.state.attachments },
+                output: part.state.time.compacted ? "[Old tool result content cleared]" : part.state.output,
                 callProviderMetadata: part.metadata,
               })
             }
@@ -556,12 +565,7 @@ export namespace MessageV2 {
       }
     }
 
-    return convertToModelMessages(
-      result.filter((msg) => msg.parts.some((part) => part.type !== "step-start")),
-      {
-        tools: options?.tools,
-      },
-    )
+    return convertToModelMessages(result.filter((msg) => msg.parts.some((part) => part.type !== "step-start")))
   }
 
   export const stream = fn(Identifier.schema("session"), async function* (sessionID) {
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 663f5660f..8327698fd 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -597,7 +597,7 @@ export namespace SessionPrompt {
         sessionID,
         system: [...(await SystemPrompt.environment()), ...(await SystemPrompt.custom())],
         messages: [
-          ...MessageV2.toModelMessage(sessionMessages, { tools }),
+          ...MessageV2.toModelMessage(sessionMessages),
           ...(isLastStep
             ? [
                 {
@@ -716,18 +716,10 @@ export namespace SessionPrompt {
           )
           return result
         },
-        toModelOutput(result: { output: string; attachments?: MessageV2.FilePart[] }) {
-          if (!result.attachments?.length) return { type: "text", value: result.output }
+        toModelOutput(result) {
           return {
-            type: "content",
-            value: [
-              { type: "text", text: result.output },
-              ...result.attachments.map((a) => ({
-                type: "media" as const,
-                data: a.url.slice(a.url.indexOf(",") + 1),
-                mediaType: a.mime,
-              })),
-            ],
+            type: "text",
+            value: result.output,
           }
         },
       })
@@ -814,18 +806,10 @@ export namespace SessionPrompt {
           content: result.content, // directly return content to preserve ordering when outputting to model
         }
       }
-      item.toModelOutput = (result: { output: string; attachments?: MessageV2.FilePart[] }) => {
-        if (!result.attachments?.length) return { type: "text", value: result.output }
+      item.toModelOutput = (result) => {
         return {
-          type: "content",
-          value: [
-            { type: "text", text: result.output },
-            ...result.attachments.map((a) => ({
-              type: "media" as const,
-              data: a.url.slice(a.url.indexOf(",") + 1),
-              mediaType: a.mime,
-            })),
-          ],
+          type: "text",
+          value: result.output,
         }
       }
       tools[key] = item