Fix bash overflow temp directory to use Runtime abstraction

The bash tool overflow feature writes large outputs to temp files when they
exceed display limits. The previous implementation broke with SSH runtimes
because temp directories were created using local filesystem operations
(fs.mkdirSync) but passed to runtime.writeFile() which needs runtime-appropriate
paths.

Changes:
- Renamed 'tempDir' to 'runtimeTempDir' throughout for clarity
- StreamManager.createTempDirForStream() now uses runtime.exec('mkdir -p')
- Stream cleanup now uses runtime.exec('rm -rf') for temp directory removal
- Pass Runtime parameter through startStream() to enable temp dir operations
- Store Runtime in WorkspaceStreamInfo for cleanup access
- Updated ToolConfiguration interface (tempDir -> runtimeTempDir)
- Updated all tests to use runtimeTempDir

This ensures temp directories are created and cleaned up in the correct
location (local for LocalRuntime, remote for SSHRuntime) while preserving
the existing cleanup guarantees when streams end.

Author: ammar-agent

src/services/aiService.ts

@@ -522,14 +522,17 @@ export class AIService extends EventEmitter {
 
       // Generate stream token and create temp directory for tools
       const streamToken = this.streamManager.generateStreamToken();
-      const tempDir = this.streamManager.createTempDirForStream(streamToken);
+      const runtimeTempDir = await this.streamManager.createTempDirForStream(
+        streamToken,
+        runtime
+      );
 
       // Get model-specific tools with workspace path (correct for local or remote)
       const allTools = await getToolsForModel(modelString, {
         cwd: workspacePath,
         runtime,
         secrets: secretsToRecord(projectSecrets),
-        tempDir,
+        runtimeTempDir,
       });
 
       // Apply tool policy to filter tools (if policy provided)
@@ -694,6 +697,7 @@ export class AIService extends EventEmitter {
         modelString,
         historySequence,
         systemMessage,
+        runtime,
         abortSignal,
         tools,
         {

src/services/streamManager.ts

@@ -31,6 +31,7 @@ import type { HistoryService } from "./historyService";
 import { AsyncMutex } from "@/utils/concurrency/asyncMutex";
 import type { ToolPolicy } from "@/utils/tools/toolPolicy";
 import { StreamingTokenTracker } from "@/utils/main/StreamingTokenTracker";
+import type { Runtime } from "@/runtime/Runtime";
 
 // Type definitions for stream parts with extended properties
 interface ReasoningDeltaPart {
@@ -107,7 +108,9 @@ interface WorkspaceStreamInfo {
   // Track background processing promise for guaranteed cleanup
   processingPromise: Promise<void>;
   // Temporary directory for tool outputs (auto-cleaned when stream ends)
-  tempDir: string;
+  runtimeTempDir: string;
+  // Runtime for temp directory cleanup
+  runtime: Runtime;
 }
 
 /**
@@ -242,11 +245,24 @@ export class StreamManager extends EventEmitter {
    * - Agent mistakes when copying/manipulating paths
    * - Harder to read in tool outputs
    * - Potential path length issues on some systems
+   * 
+   * Uses the Runtime abstraction so temp directories work for both local and SSH runtimes.
    */
-  public createTempDirForStream(streamToken: StreamToken): string {
-    const homeDir = os.homedir();
-    const tempDir = path.join(homeDir, ".cmux-tmp", streamToken);
-    fs.mkdirSync(tempDir, { recursive: true, mode: 0o700 });
+  public async createTempDirForStream(
+    streamToken: StreamToken,
+    runtime: Runtime
+  ): Promise<string> {
+    const tempDir = path.join("~", ".cmux-tmp", streamToken);
+    // Use runtime.exec() to create directory (works for both local and remote)
+    const result = await runtime.exec(`mkdir -p "${tempDir}"`, {
+      cwd: "~",
+      timeout: 10,
+    });
+    // Wait for command to complete
+    const exitCode = await result.exitCode;
+    if (exitCode !== 0) {
+      throw new Error(`Failed to create temp directory ${tempDir}: exit code ${exitCode}`);
+    }
     return tempDir;
   }
 
@@ -429,7 +445,8 @@ export class StreamManager extends EventEmitter {
   private createStreamAtomically(
     workspaceId: WorkspaceId,
     streamToken: StreamToken,
-    tempDir: string,
+    runtimeTempDir: string,
+    runtime: Runtime,
     messages: ModelMessage[],
     model: LanguageModel,
     modelString: string,
@@ -508,7 +525,8 @@ export class StreamManager extends EventEmitter {
       lastPartialWriteTime: 0, // Initialize to 0 to allow immediate first write
       partialWritePromise: undefined, // No write in flight initially
       processingPromise: Promise.resolve(), // Placeholder, overwritten in startStream
-      tempDir, // Stream-scoped temp directory for tool outputs
+      runtimeTempDir, // Stream-scoped temp directory for tool outputs
+      runtime, // Runtime for temp directory cleanup
     };
 
     // Atomically register the stream
@@ -961,13 +979,20 @@ export class StreamManager extends EventEmitter {
         streamInfo.partialWriteTimer = undefined;
       }
 
-      // Clean up stream temp directory
-      if (streamInfo.tempDir && fs.existsSync(streamInfo.tempDir)) {
+      // Clean up stream temp directory using runtime
+      if (streamInfo.runtimeTempDir) {
         try {
-          fs.rmSync(streamInfo.tempDir, { recursive: true, force: true });
-          log.debug(`Cleaned up temp dir: ${streamInfo.tempDir}`);
+          const result = await streamInfo.runtime.exec(
+            `rm -rf "${streamInfo.runtimeTempDir}"`,
+            {
+              cwd: "~",
+              timeout: 10,
+            }
+          );
+          await result.exitCode; // Wait for completion
+          log.debug(`Cleaned up temp dir: ${streamInfo.runtimeTempDir}`);
         } catch (error) {
-          log.error(`Failed to cleanup temp dir ${streamInfo.tempDir}:`, error);
+          log.error(`Failed to cleanup temp dir ${streamInfo.runtimeTempDir}:`, error);
           // Don't throw - cleanup is best-effort
         }
       }
@@ -1090,6 +1115,7 @@ export class StreamManager extends EventEmitter {
     modelString: string,
     historySequence: number,
     system: string,
+    runtime: Runtime,
     abortSignal?: AbortSignal,
     tools?: Record<string, Tool>,
     initialMetadata?: Partial<CmuxMetadata>,
@@ -1123,18 +1149,16 @@ export class StreamManager extends EventEmitter {
       // Step 2: Use provided stream token or generate a new one
       const streamToken = providedStreamToken ?? this.generateStreamToken();
 
-      // Step 3: Create temp directory for this stream
-      // If token was provided, temp dir might already exist - that's fine
-      const tempDir = path.join(os.homedir(), ".cmux-tmp", streamToken);
-      if (!fs.existsSync(tempDir)) {
-        fs.mkdirSync(tempDir, { recursive: true, mode: 0o700 });
-      }
+      // Step 3: Create temp directory for this stream using runtime
+      // If token was provided, temp dir might already exist - mkdir -p handles this
+      const runtimeTempDir = await this.createTempDirForStream(streamToken, runtime);
 
       // Step 4: Atomic stream creation and registration
       const streamInfo = this.createStreamAtomically(
         typedWorkspaceId,
         streamToken,
-        tempDir,
+        runtimeTempDir,
+        runtime,
         messages,
         model,
         modelString,

src/services/tools/bash.test.ts

@@ -23,7 +23,7 @@ function createTestBashTool(options?: { niceness?: number }) {
   const tool = createBashTool({
     cwd: process.cwd(),
     runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-    tempDir: tempDir.path,
+    runtimeTempDir: tempDir.path,
     ...options,
   });
 
@@ -165,7 +165,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
       overflow_policy: "truncate",
     });
 
@@ -204,7 +204,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
       overflow_policy: "truncate",
     });
 
@@ -236,7 +236,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
       overflow_policy: "truncate",
     });
 
@@ -272,7 +272,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: tempDir.path, // Use tempDir as cwd so we can verify file creation
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
       // overflow_policy not specified - should default to tmpfile
     });
 
@@ -306,7 +306,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate ~50KB of output (well over 16KB display limit, under 100KB file limit)
@@ -358,7 +358,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate ~150KB of output (exceeds 100KB file limit)
@@ -401,7 +401,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate output that exceeds display limit but not file limit
@@ -443,7 +443,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate a single line exceeding 1KB limit, then try to output more
@@ -483,7 +483,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate ~15KB of output (just under 16KB display limit)
@@ -513,7 +513,7 @@ describe("bash tool", () => {
     const tool = createBashTool({
       cwd: process.cwd(),
       runtime: createRuntime({ type: "local", srcBaseDir: "/tmp" }),
-      tempDir: tempDir.path,
+      runtimeTempDir: tempDir.path,
     });
 
     // Generate exactly 300 lines (hits line limit exactly)

src/services/tools/bash.ts

@@ -421,9 +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);
-                  // Write to .cmux/tmp directory relative to cwd for runtime-agnostic path
+                  // Write to runtime temp directory (managed by StreamManager)
                   // This works for both LocalRuntime (local path) and SSHRuntime (remote path)
-                  const overflowPath = path.join(config.cwd, ".cmux", "tmp", `bash-${fileId}.txt`);
+                  const overflowPath = path.join(config.runtimeTempDir, `bash-${fileId}.txt`);
                   const fullOutput = lines.join("\n");
 
                   // Use runtime.writeFile() for SSH support

src/utils/tools/tools.ts

@@ -22,8 +22,8 @@ export interface ToolConfiguration {
   secrets?: Record<string, string>;
   /** Process niceness level (optional, -20 to 19, lower = higher priority) */
   niceness?: number;
-  /** Temporary directory for tool outputs (required) */
-  tempDir: string;
+  /** Temporary directory for tool outputs in runtime's context (local or remote) */
+  runtimeTempDir: string;
   /** Overflow policy for bash tool output (optional, not exposed to AI) */
   overflow_policy?: "truncate" | "tmpfile";
 }