fix(app): handle Windows paths in frontend file URL encoding

[yudgnahk]

Fixes #12424 (comment: #12424 (comment))

Summary

Fixes bug introduced in PR #12424 where Windows users cannot mention files. The frontend's encodeFilePath() function doesn't handle Windows backslashes, causing invalid file:// URLs on Windows.

Root Cause

Frontend path encoding splits by / but Windows uses \. Paths like D:\dev\projects\opencode\README.md get encoded as D%3A%5Cdev%5Cprojects%5C... instead of /D:/dev/projects/..., resulting in invalid file:// URLs:

TypeError: "file://D%3A%5Cdev%5Cprojects%5Copencode/README.bs.md" cannot be parsed as a URL.

Solution

• Normalize Windows backslashes to forward slashes before encoding
• Add leading / for Windows absolute paths (D: → /D:)
• Preserve proper encoding for special characters (#, ?, %, spaces)
• Backend already uses pathToFileURL() correctly (fixed in fix: properly encode file URLs with special characters #12424)

Changes

Frontend Files (4 files)

• packages/app/src/context/file/path.ts - Updated encodeFilePath() to handle Windows backslashes
• packages/app/src/components/prompt-input/build-request-parts.ts - Updated duplicate encodeFilePath() function
• packages/app/src/context/file/path.test.ts - Added 34 new tests for Windows/Linux/macOS paths
• packages/app/src/components/prompt-input/build-request-parts.test.ts - Added 8 integration tests

Testing

✅ 46 tests pass, 0 fail - All unit and integration tests
✅ TypeScript clean - No type errors
✅ Windows paths: Tests exact bug scenario from @alexyaroshuk
✅ Cross-platform: Tests Windows (D:\path), Linux (/path), macOS paths
✅ Special chars: Tests #, ?, %, spaces in filenames
✅ Backward compatible: Normal paths produce identical output

Impact

Fixes:

• File mentioning with @ on Windows (reported by @alexyaroshuk)
• File URL construction for Windows absolute paths
• Cross-platform compatibility for path encoding

4 files changed, 149 insertions(+), 8 deletions(-)

Verification

@alexyaroshuk Can you verify this fixes the file mentioning issue on your Windows machine?

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[yudgnahk]

Related to #12424 comment by @alexyaroshuk
Hi Alex, could you pull this branch and help me test in your local, please?

I do not have the windows machine :D

[yudgnahk]

Hi @adamdotdevin, please help me review the PR before releasing the new version. I don't want to harm the windows version...

[alexyaroshuk]

Related to #12424 comment by @alexyaroshuk Hi Alex, could you pull this branch and help me test in your local, please?

I do not have the windows machine :D

Just tested - the bug is fixed in this pr.

[yudgnahk]

Just tested - the bug is fixed in this pr.

Thank you @alexyaroshuk!

[yudgnahk]

Hi @rekram1-node could you help me review this PR please? Thank you!