🤖 fix: surface script errors in LLM transform

- append script error output when present so Codex/LLMs can see failures
- cover failure path in transformScriptMessagesForLLM tests

_Generated with `mux`_

Change-Id: I72f2f4ab6b5c56f5dc6d1fdf50d14b08c2d148fb
Signed-off-by: Thomas Kosiewski <tk@coder.com>

Author: ThomasK33

.cmux/scripts/web_fetch

@@ -234,6 +234,14 @@ export function transformScriptMessagesForLLM(messages: MuxMessage[]): MuxMessag
       llmContent += `\nStdout/Stderr: (no output)`;
     }
 
+    // Surface script errors for Codex/LLM reviewers even when no output exists.
+    if ("error" in result) {
+      const trimmedError = result.error.trim();
+      if (trimmedError.length > 0) {
+        llmContent += `\nError:\n${trimmedError}`;
+      }
+    }
+
     // EXCLUDE MUX_OUTPUT and MUX_PROMPT from the LLM context for the script message itself.
     // MUX_PROMPT is sent as a separate user message by ChatInput, so including it here would be duplication.
     // MUX_OUTPUT is intended for user toasts, not LLM context.

src/browser/utils/messages/modelMessageTransform.ts

@@ -78,11 +78,49 @@ describe("transformScriptMessagesForLLM", () => {
     const textPart = result[0].parts[0];
     expect(textPart.type).toBe("text");
     if (textPart.type === "text") {
-      expect(textPart.text).toContain("Stdout/Stderr:\nstdout stuff");
       expect(textPart.text).not.toContain("MUX_OUTPUT");
       expect(textPart.text).not.toContain("User toast");
       expect(textPart.text).not.toContain("MUX_PROMPT");
       expect(textPart.text).not.toContain("Model prompt");
     }
   });
+
+  it("should surface error details when script fails without output", () => {
+    const scriptResult: BashToolResult = {
+      success: false,
+      exitCode: 2,
+      wall_duration_ms: 120,
+      error: "Permission denied",
+    };
+
+    const messages: MuxMessage[] = [
+      {
+        id: "script-error",
+        role: "user",
+        parts: [{ type: "text", text: "Executed script: /script fail" }],
+        metadata: {
+          muxMetadata: {
+            type: "script-execution",
+            id: "script-error",
+            historySequence: 0,
+            timestamp: 999,
+            command: "/script fail",
+            scriptName: "fail.sh",
+            args: [],
+            result: scriptResult,
+          },
+        },
+      },
+    ];
+
+    const result = transformScriptMessagesForLLM(messages);
+    expect(result).toHaveLength(1);
+    const textPart = result[0].parts[0];
+    expect(textPart.type).toBe("text");
+    if (textPart.type === "text") {
+      expect(textPart.text).toContain("Stdout/Stderr: (no output)");
+      expect(textPart.text).toContain("Error:");
+      expect(textPart.text).toContain("Permission denied");
+    }
+  });
 });