fix(core-tools): resolve defensive path resolution for at-reference files

[luisfelipe-alt]

Summary

This PR resolves a critical filesystem bug where filesystem tools (read_file, replace, write_file) fail with a "File not found" error when the model attempts to read or update a file that was initially referenced using the CLI's @ mention syntax (e.g., @policies/new-policies.txt).

This occurs because the CLI's prompt reconstruction and file attachment headers include the @ prefix, leading the model to believe the file path literally starts with @. This PR implements a defensive path resolution strategy that strips the leading @ only if the literal path does not exist but the stripped path does.

Details

We implemented a centralized, defensive path resolution utility to handle @ prefixes dynamically without breaking legitimate filesystem paths starting with @ (e.g., scoped directories such as node_modules/@google/):

1. Central Path Normalizer: Implemented resolveDefensiveToolPath in packages/core/src/utils/paths.ts. It checks if the literal path exists on disk first. If not, and the path starts with @, it strips the @ and checks if the stripped path exists.
2. ReadFileTool Integration: Applied resolveDefensiveToolPath in ReadFileToolInvocation constructor and validateToolParamValues in packages/core/src/tools/read-file.ts.
3. WriteFileTool Integration: Applied resolveDefensiveToolPath in WriteFileToolInvocation constructor, validateToolParamValues, and getCorrectedFileContent in packages/core/src/tools/write-file.ts.
4. EditTool / pathCorrector Integration: Applied resolveDefensiveToolPath at the beginning of correctPath in packages/core/src/utils/pathCorrector.ts.
5. Consolidated Test Suite: Created a new, consolidated test file packages/core/src/tools/at-reference-resolution.test.ts to verify successful path resolution and execution across all three tools.

Related Issues

How to Validate

1. Run the Consolidated Test Suite:

   npx vitest run packages/core/src/tools/at-reference-resolution.test.ts

   Expected Result: All 3 tests pass successfully, proving that ReadFileTool, WriteFileTool, and correctPath resolve @-prefixed paths correctly.

2. Run Existing Test Suites (Regression Check):

   npx vitest run packages/core/src/tools/read-file.test.ts packages/core/src/tools/write-file.test.ts packages/core/src/utils/pathCorrector.test.ts

   Expected Result: All 85 existing tests pass successfully, proving zero regressions.

3. Run Linting and Type Checking:

   npm run lint && npm run typecheck

   Expected Result: Zero linting or type checking errors.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[github-actions]

📊 PR Size: size/L

• Lines changed: 732
• Additions: +703
• Deletions: -29
• Files changed: 6

[github-actions]

🛑 Action Required: Evaluation Approval

Steering changes have been detected in this PR. To prevent regressions, a maintainer must approve the evaluation run before this PR can be merged.

Maintainers:

1. Go to the Workflow Run Summary.
2. Click the yellow 'Review deployments' button.
3. Select the 'eval-gate' environment and click 'Approve'.

Once approved, the evaluation results will be posted here automatically.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a bug where filesystem tools failed to locate files referenced with the '@' syntax. By implementing a centralized, defensive path resolution strategy, the system now intelligently attempts to resolve paths by stripping the '@' prefix if the literal path does not exist on disk, improving the robustness of file operations initiated by the model.

Highlights

• Defensive Path Resolution: Introduced resolveDefensiveToolPath to handle file paths that are incorrectly prefixed with '@' by the model, ensuring the system checks for the existence of the stripped path if the literal path is not found.
• Tool Integration: Updated ReadFileTool, WriteFileTool, and pathCorrector to utilize the new defensive path resolution logic, preventing 'File not found' errors for referenced files.
• Consolidated Testing: Added a new test suite at-reference-resolution.test.ts to verify consistent behavior across all affected tools when handling '@'-prefixed paths.

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[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution and sanitization for LLM-generated file paths by adding a new utility function resolveDefensiveToolPath that strips leading @ reference prefixes. This utility is integrated into ReadFileTool, WriteFileTool, and correctPath, and is accompanied by a new test suite. The review feedback highlights two key improvements: first, ensuring that the sanitized path in WriteFileTool is resolved to an absolute path before reading to prevent unsafe resolution relative to process.cwd(); second, enhancing resolveDefensiveToolPath to handle new file creation with an @ prefix by checking if the parent directory of the stripped path exists.

[gemini-code-assist]

Code Review

This pull request introduces a defensive path resolution utility, 'resolveDefensiveToolPath', to strip leading '@' reference prefixes from LLM-generated file paths, integrating it into 'ReadFileTool', 'WriteFileTool', and 'correctPath' along with a new test suite. The review feedback highlights two critical improvements: first, ensuring that 'getCorrectedFileContent' in 'write-file.ts' resolves the sanitized path to an absolute path to prevent path traversal vulnerabilities; second, updating 'resolveDefensiveToolPath' in 'paths.ts' to handle new file creation by checking if the parent directory of the stripped path exists when the file itself does not yet exist.

[jiangdingqian33-debug]

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[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution to handle LLM-generated file paths prefixed with '@' (at-references). It adds the resolveDefensiveToolPath utility to strip leading '@' characters when appropriate, integrates this sanitization into ReadFileTool, WriteFileTool, and correctPath, and adds comprehensive unit tests. The review feedback points out a limitation in the path sanitization logic when handling nested subdirectories that do not exist yet, providing a robust solution to check the first segment of the path instead.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution to handle LLM-generated file paths prefixed with @ by stripping the prefix when resolving paths in ReadFileTool, WriteFileTool, and correctPath. It also adds a comprehensive test suite for this behavior. The review feedback highlights two important improvements: handling leading slashes after the @ prefix in resolveDefensiveToolPath to prevent absolute path resolution issues, and validating path access in getCorrectedFileContent to mitigate potential path traversal vulnerabilities.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution for LLM-generated file paths by stripping leading '@' or '@/' reference prefixes when necessary. This is implemented via a new helper function resolveDefensiveToolPath and integrated into ReadFileTool, WriteFileTool, and path correction utilities, along with a comprehensive test suite. The review feedback points out a potential issue in getCorrectedFileContent where calling resolveToRealPath outside of a try-catch block could throw synchronous errors (e.g., due to symlink loops) and cause unhandled promise rejections, recommending wrapping it in a try-catch block.

[luisfelipe-alt]

/gemini review

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution to strip user-facing reference prefixes (such as '@') from LLM-generated file paths in ReadFileTool, WriteFileTool, and path correction utilities, alongside consolidated tests. The review feedback highlights critical security improvements to resolve symbolic links to their real paths using resolveToRealPath before path access validation to prevent path traversal. Additionally, a correctness bug was identified in resolveDefensiveToolPath when resolving paths for nested subdirectories that do not yet exist, with suggestions to fix the logic and add a corresponding test case.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution and sanitization across file tools to handle reference prefixes (such as '@') and safely resolve real paths. It adds the resolveDefensiveToolPath utility and integrates it into ReadFileTool, WriteFileTool, and path correction logic, supported by a comprehensive test suite. The feedback highlights a potential crash in ReadFileTool's validation logic if resolveToRealPath throws an unhandled exception, suggesting wrapping it in a try-catch block to return a clean validation error.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution and sanitization for LLM-generated file paths by stripping user-facing reference prefixes (such as @) when appropriate. These changes are integrated into ReadFileTool, WriteFileTool, and path correction utilities, supported by a new suite of unit tests. The review feedback highlights that calls to resolveToRealPath in ReadFileTool (both in the invocation constructor and the parameter validation method) can throw unhandled exceptions, potentially crashing tool execution or validation. It is recommended to wrap these calls in try-catch blocks to handle resolution errors gracefully.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a defensive path resolution strategy (resolveDefensiveToolPath) to sanitize LLM-generated file paths by stripping leading @ reference prefixes. This sanitization is integrated into ReadFileTool, WriteFileTool, and path correction utilities, supported by a new test suite. The review feedback identifies two critical issues: a bug in resolveDefensiveToolPath that unconditionally strips @ and prevents the creation of new scoped directories or files starting with @, and an inconsistency in getCorrectedFileContent where plan paths are not resolved to their real paths using resolveToRealPath.

[galz10]

Code Review: PR 27943 (Fixing @ prefix resolution in filesystem tools)

Intent Summary: The PR aims to resolve a bug where filesystem tools (read_file, write_file, and replace/EditTool) fail when the model attempts to read or update a file referenced using the CLI's @ mention syntax. It introduces a central resolveDefensiveToolPath utility to strip the @ prefix if the literal path does not exist but the stripped path does.

🚨 Critical Concerns (P0/P1)

Action required before merging.

• packages/core/src/tools/edit.ts:499 & 1109: EditTool falls back to unsanitized paths when creating new files. The PR updates correctPath in pathCorrector.ts, but if a file doesn't exist yet (e.g. creating a new file via EditTool with an empty old_string), correctPath returns { success: false }. The EditToolInvocation constructor and validateToolParamValues then fall back to path.resolve(..., this.params.file_path) directly. This completely skips the defensive stripping of the @ prefix, causing new files to be incorrectly created in a literal @-prefixed directory.

      } else {
        const sanitizedPath = resolveDefensiveToolPath(
          this.params.file_path,
          this.config.getTargetDir(),
        );
        this.resolvedPath = path.resolve(
          this.config.getTargetDir(),
          sanitizedPath,
        );
      }
  

• packages/core/src/tools/edit.ts:1186: getModifyContext misses path sanitization. If the user manually edits the AI's proposed replacement on a file starting with @, getModifyContext tries to readTextFile(params.file_path). Since this doesn't run through correctPath or resolveDefensiveToolPath, it will fail to find the file and cause the edit flow to break.

        getCurrentContent: async (params: EditToolParams): Promise<string> => {
          try {
            const sanitizedPath = resolveDefensiveToolPath(params.file_path, this.config.getTargetDir());
            const resolvedPath = path.resolve(this.config.getTargetDir(), sanitizedPath);
            return await this.config.getFileSystemService().readTextFile(resolvedPath);
          ...
  

  (Note: Apply the same sanitization inside getProposedContent).

• packages/core/src/tools/at-reference-resolution.test.ts: Missing test coverage for EditTool logic changes. The PR adds coverage for ReadFileTool and WriteFileTool, but only tests correctPath in isolation rather than EditTool execution. Because of this, the critical fallback bug for new files in EditTool was missed. This is a P0 architecture violation of our test coverage rules. Please add integration tests for EditTool editing an existing @-prefixed file and creating a new @-prefixed file.

🧹 Refactoring & Nits (P2/P3)

Recommended improvements.

• packages/core/src/tools/write-file.ts:117: In getCorrectedFileContent, you correctly call resolveDefensiveToolPath, but resolving to a real path via resolveToRealPath before confirming fs.existsSync might behave unexpectedly for some symlink parent directory edge cases if the final file doesn't exist yet. The underlying robustRealpath logic does try to handle this gracefully, so no strict action is required, but something to keep an eye on.

📝 Metadata Review

Feedback on PR description or commit message clarity.

• The PR description is highly detailed and cleanly structures the intended changes across the tools. However, the claim that updating correctPath fully solves the problem for replace / EditTool is inaccurate. Correcting the description to include the fallback logic fixes in edit.ts will make it completely accurate.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces defensive path resolution and sanitization for LLM-generated file paths, specifically handling the stripping of user-facing reference prefixes like @. These changes are integrated across EditTool, ReadFileTool, WriteFileTool, and the path corrector utility, supported by a new consolidated test suite. The reviewer recommends updating the path resolution logic in EditTool.getProposedContent to consistently handle plan mode and path correction, ensuring alignment with the robust resolution patterns implemented in other parts of the codebase.

[luisfelipe-alt]

/gemini review

[gemini-code-assist]

Code Review

This pull request implements defensive path resolution and sanitization for LLM-generated file paths across EditTool, ReadFileTool, WriteFileTool, and pathCorrector, including handling of '@' reference prefixes and resolving paths to their real paths. It also adds a comprehensive test suite. The review feedback identifies a security vulnerability in EditTool.getModifyContext where file paths are read without workspace access validation, potentially allowing arbitrary file reads. The reviewer suggests validating the resolved path using validatePathAccess and wrapping resolveToRealPath in a try-catch block.

[gemini-code-assist]

The getModifyContext method in EditTool resolves and reads files from the filesystem without validating that the resolved path is within the allowed workspace directories. Since the params object is populated directly from LLM tool calls (which are driven by untrusted user/prompt input), an attacker can supply a path outside the workspace (e.g., /etc/passwd or ../../etc/passwd) to read arbitrary files from the host system. Additionally, the resolvePath helper function calls resolveToRealPath directly without try-catch blocks. resolveToRealPath can throw exceptions, leading to unhandled promise rejections or application crashes. To address these issues, validate the resolved path using this.config.validatePathAccess(resolved) inside resolvePath before returning it, and throw an error if validation fails. Also, wrap the call to resolveToRealPath in a try-catch block to gracefully handle potential filesystem resolution errors and fall back to the unresolved path.

    const resolvePath = (params: EditToolParams): string => {
      let resolved: string;
      let pathBeforeRealResolve: string;

      if (this.config.isPlanMode()) {
        pathBeforeRealResolve = resolveAndValidatePlanPath(
          params.file_path,
          this.config.storage.getPlansDir(),
          this.config.getProjectRoot(),
        );
      } else if (!path.isAbsolute(params.file_path)) {
        const result = correctPath(params.file_path, this.config);
        if (result.success) {
          pathBeforeRealResolve = result.correctedPath;
        } else {
          const sanitizedPath = resolveDefensiveToolPath(
            params.file_path,
            this.config.getTargetDir(),
          );
          pathBeforeRealResolve = path.resolve(this.config.getTargetDir(), sanitizedPath);
        }
      } else {
        pathBeforeRealResolve = params.file_path;
      }

      try {
        resolved = resolveToRealPath(pathBeforeRealResolve);
      } catch (e) {
        resolved = pathBeforeRealResolve;
      }

      const validationError = this.config.validatePathAccess(resolved);
      if (validationError) {
        throw new Error(validationError);
      }
      return resolved;
    };

References

1. Sanitize user-provided file paths used in file system operations to prevent path traversal vulnerabilities.
2. Ensure consistent path resolution by using a single, robust function (e.g., resolveToRealPath) for all related path validations, including internal validations in components like WorkspaceContext.