fix: bedrock reasoning issue (#25303)

packages/opencode/src/session/message-v2.ts

@@ -938,10 +938,18 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
             })
         }
         if (part.type === "reasoning") {
+          if (differentModel) {
+            if (part.text.trim().length > 0)
+              assistantMessage.parts.push({
+                type: "text",
+                text: part.text,
+              })
+            continue
+          }
           assistantMessage.parts.push({
             type: "reasoning",
             text: part.text,
-            ...(differentModel ? {} : { providerMetadata: part.metadata }),
+            providerMetadata: part.metadata,
           })
         }
       }

packages/opencode/test/session/message-v2.test.ts

@@ -469,6 +469,13 @@ describe("session.message-v2.toModelMessage", () => {
           },
           {
             ...basePart(assistantID, "a2"),
+            type: "reasoning",
+            text: "thinking",
+            metadata: { openai: { reasoning: "meta" } },
+            time: { start: 0 },
+          },
+          {
+            ...basePart(assistantID, "a3"),
             type: "tool",
             callID: "call-1",
             tool: "bash",
@@ -495,6 +502,7 @@ describe("session.message-v2.toModelMessage", () => {
         role: "assistant",
         content: [
           { type: "text", text: "done" },
+          { type: "text", text: "thinking" },
           {
             type: "tool-call",
             toolCallId: "call-1",