🤖 Use runtime.normalizePath() for DRY in validateNoRedundantPrefix

Instead of manually normalizing paths with string operations, leverage the
runtime's existing normalizePath() method for consistent path handling.
This reduces duplication and ensures we handle paths the same way the
runtime does.

Changes:
- Use runtime.normalizePath(".", cwd) to normalize the working directory
- Keeps manual trailing slash cleanup for absolute paths (can't use
  normalizePath directly since it's designed for relative path resolution)
- Update documentation to reflect use of runtime method
- Remove underscore prefix from runtime param (now used)

_Generated with `cmux`_

Author: ammar-agent

src/services/tools/fileCommon.ts

@@ -53,36 +53,41 @@ export function validateFileSize(stats: FileStat): { error: string } | null {
  * Returns an error object if the path contains the cwd prefix, null if valid.
  * This helps save tokens by encouraging relative paths.
  *
- * Works for both local and SSH runtimes by using simple string matching
- * for absolute paths instead of Node's path module (which only handles local paths).
+ * Works for both local and SSH runtimes by using runtime.normalizePath()
+ * for consistent path handling across different runtime types.
  *
  * @param filePath - The file path to validate
  * @param cwd - The working directory
- * @param runtime - The runtime (unused, kept for consistency)
+ * @param runtime - The runtime to use for path normalization
  * @returns Error object if redundant prefix found, null if valid
  */
 export function validateNoRedundantPrefix(
   filePath: string,
   cwd: string,
-  _runtime: Runtime
+  runtime: Runtime
 ): { error: string } | null {
   // Only check absolute paths (start with /) - relative paths are fine
   // This works for both local and SSH since both use Unix-style paths
   if (!filePath.startsWith("/")) {
     return null;
   }
 
-  // Normalize both paths: remove trailing slashes for consistent comparison
+  // Use runtime's normalizePath to ensure consistent handling across local and SSH
+  // Normalize the cwd to get canonical form (removes trailing slashes, etc.)
+  const normalizedCwd = runtime.normalizePath(".", cwd);
+
+  // For absolute paths, we can't use normalizePath directly (it resolves relative paths)
+  // so just clean up trailing slashes manually
   const normalizedPath = filePath.replace(/\/+$/, "");
-  const normalizedCwd = cwd.replace(/\/+$/, "");
+  const cleanCwd = normalizedCwd.replace(/\/+$/, "");
 
   // Check if the absolute path starts with the cwd
   // Use startsWith + check for path separator to avoid partial matches
   // e.g., /workspace/project should match /workspace/project/src but not /workspace/project2
-  if (normalizedPath === normalizedCwd || normalizedPath.startsWith(normalizedCwd + "/")) {
+  if (normalizedPath === cleanCwd || normalizedPath.startsWith(cleanCwd + "/")) {
     // Calculate what the relative path would be
     const relativePath =
-      normalizedPath === normalizedCwd ? "." : normalizedPath.substring(normalizedCwd.length + 1);
+      normalizedPath === cleanCwd ? "." : normalizedPath.substring(cleanCwd.length + 1);
     return {
       error: `Redundant path prefix detected. The path '${filePath}' contains the workspace directory. Please use relative paths to save tokens: '${relativePath}'`,
     };