fix(server): decode URL-encoded static asset paths

[yashranaway]

Static requests use the URL pathname as a filesystem path without decoding it. Files containing spaces, Unicode, percent signs, or # therefore return the SPA fallback instead of the requested asset.

Decode the pathname once before the existing path validation and lookup. Malformed encodings are rejected, and decoded traversal and NUL paths remain blocked. GET and HEAD now resolve the same filenames.

Validation: the regression test fails on main and passes with this change; all 10 focused static-serving tests pass. Server typecheck and targeted lint pass, with existing warnings outside the changed lines.

Model: GPT-6
Harness: Codex in T3 Code

Summary by CodeRabbit

• Bug Fixes
  • Static files with URL-encoded names, including spaces, Unicode characters, percent signs, hash symbols, and dots, are now served correctly.
  • Malformed encoded paths now return a client error instead of being processed incorrectly.
  • Path traversal checks now correctly handle filenames beginning with double dots.
  • Requests for the root static path continue to serve the default index page.
• Tests
  • Added coverage for encoded filenames, traversal-like names, and corresponding GET/HEAD response metadata.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This is a narrowly scoped static-asset bug fix with focused regression coverage, but it changes decoding and traversal validation for user-controlled filesystem paths. That security-sensitive boundary warrants human review.

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📒 Files selected for processing (2)

• apps/server/src/http.ts
• apps/server/src/server.test.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• apps/server/src/server.test.ts
• apps/server/src/http.ts

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📝 Walkthrough

Walkthrough

Static file handling now decodes URL pathnames before resolution. Malformed encoding returns HTTP 400. Root requests serve /index.html. Traversal checks apply to leading .. path segments. Tests cover encoded filenames and GET and HEAD responses.

Changes

Static file path handling

Layer / File(s)	Summary
Decoded path resolution and validation apps/server/src/http.ts, apps/server/src/server.test.ts	The handler decodes static request paths, maps / to /index.html, rejects malformed encoding with HTTP 400, and checks leading .. path segments. Tests verify encoded filenames, GET and HEAD responses, and invalid targets.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to fd851

This change lets the static file server correctly resolve URL-encoded filenames (spaces, Unicode, percent signs, #) for GET and HEAD requests while still rejecting malformed encodings, path traversal, and NUL bytes. Review of the validation and containment logic did not surface a security or correctness gap, and the accompanying tests exercise the core new behavior, so this appears safe to merge.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: decoding URL-encoded static asset paths in the server.
Description check	✅ Passed	The description clearly explains what changed, why it changed, validation results, and the absence of UI changes. It omits the template headings and checklist, but it contains the required core inform…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
In `@apps/server/src/http.ts`:
- Around line 549-555: Update the static file path validation after
decodeURIComponent in the static request handling flow to reject
parent-directory segments only when ".." is followed by a path separator or the
end of the path, rather than rejecting filenames that merely begin with "..".
Preserve traversal protection and add coverage for a valid filename beginning
with "..".

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• apps/server/src/http.ts
• apps/server/src/server.test.ts

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