Fix bash tool to use runtime-appropriate temp directory

- Changed overflow file path from config.tempDir to {cwd}/.cmux/tmp/
- This fixes SSH runtime support where config.tempDir was a local path
- Runtime.writeFile() expects runtime-appropriate paths (remote for SSH)
- Updated test to verify files are created in .cmux/tmp subdirectory

Author: ammar-agent

src/services/tools/bash.test.ts

@@ -3,6 +3,7 @@ import { createBashTool } from "./bash";
 import type { BashToolArgs, BashToolResult } from "@/types/tools";
 import { BASH_MAX_TOTAL_BYTES } from "@/constants/toolLimits";
 import * as fs from "fs";
+import * as path from "path";
 import { TestTempDir } from "./testHelpers";
 import { createRuntime } from "@/runtime/runtimeFactory";
 
@@ -269,7 +270,7 @@ describe("bash tool", () => {
   it("should use tmpfile policy by default when overflow_policy not specified", async () => {
     const tempDir = new TestTempDir("test-bash-default");
     const tool = createBashTool({
-      cwd: process.cwd(),
+      cwd: tempDir.path, // Use tempDir as cwd so we can verify file creation
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
       tempDir: tempDir.path,
       // overflow_policy not specified - should default to tmpfile
@@ -289,8 +290,10 @@ describe("bash tool", () => {
       expect(result.error).toContain("saved to");
       expect(result.error).not.toContain("[OUTPUT TRUNCATED");
 
-      // Verify temp file was created
-      const files = fs.readdirSync(tempDir.path);
+      // Verify temp file was created in .cmux/tmp subdirectory
+      const cmuxTmpDir = path.join(tempDir.path, ".cmux", "tmp");
+      expect(fs.existsSync(cmuxTmpDir)).toBe(true);
+      const files = fs.readdirSync(cmuxTmpDir);
       const bashFiles = files.filter((f) => f.startsWith("bash-"));
       expect(bashFiles.length).toBe(1);
     }

src/services/tools/bash.ts

@@ -421,7 +421,9 @@ export const createBashTool: ToolFactory = (config: ToolConfiguration) => {
                 try {
                   // Use 8 hex characters for short, memorable temp file IDs
                   const fileId = Math.random().toString(16).substring(2, 10);
-                  const overflowPath = path.join(config.tempDir, `bash-${fileId}.txt`);
+                  // Write to .cmux/tmp directory relative to cwd for runtime-agnostic path
+                  // This works for both LocalRuntime (local path) and SSHRuntime (remote path)
+                  const overflowPath = path.join(config.cwd, ".cmux", "tmp", `bash-${fileId}.txt`);
                   const fullOutput = lines.join("\n");
 
                   // Use runtime.writeFile() for SSH support