fix(files): resolve workspace paths and add sandboxed HTML preview

[chriswritescode-dev]

Problem

Opening a file from a message used the raw path from tool output, which could be workspace-absolute or repo-relative, and the file browser could not resolve it consistently. HTML files could not be previewed, raw files were served without isolation, and file references embedded in URLs were misdetected. Keyboard focus rings appeared on mouse clicks instead of keyboard navigation.

Changes

• Accept workspace-absolute paths in the file service and return repo-relative paths for file reads and directory listings.
• Serve raw file content with a Content-Security-Policy: sandbox allow-scripts header.
• Preview HTML files in a sandboxed iframe with a raw/rendered toggle and an open-in-new-tab action.
• Resolve file-click paths in the session view from the session directory and the repo local path.
• Detect absolute and html/htm file references while ignoring URL paths.
• Accept the legacy filePath input key and filediff metadata in file tool renders.
• Fix the file browser navigating into an initially selected directory before the base listing resolves.
• Use focus-visible rings across shared UI primitives.

Testing

• Backend: 66 focused tests passed.
• Frontend: 92 focused tests passed.

Summary by CodeRabbit

• New Features
  • HTML files can be previewed in a sandboxed view or opened in a new tab.
  • File links from messages and session views handle more path formats, including absolute paths and legacy file references.
• Bug Fixes
  • File browsers avoid showing outdated results when directory loads overlap and handle initial file or directory selections more reliably.
  • Raw HTML responses include a security policy that restricts their browser context.
• Style
  • Focus rings appear for keyboard-visible focus states across several controls.

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⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: 42002e5b-905e-40e3-aa9d-ec31e7862eba

📥 Commits

Reviewing files that changed from the base of the PR and between cd7d139 and 12eba50.

📒 Files selected for processing (4)

• frontend/src/components/file-browser/FileBrowser.tsx
• frontend/src/components/file-browser/FileBrowserSheet.test.tsx
• frontend/src/components/message/FileToolRender.tsx
• frontend/src/components/message/MessagePart.test.tsx

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📝 Walkthrough

Walkthrough

The changes update workspace file path handling and raw file responses, add HTML previews, adjust file navigation and directory loading, and change focus-ring styling on selected controls.

Changes

File interactions

Layer / File(s)	Summary
Workspace file access backend/src/services/files.ts, backend/test/services/files.test.ts	Absolute paths within the workspace are accepted. Results for absolute-path requests use workspace-relative paths. Tests cover in-workspace reads and paths outside the workspace.
HTML file previews backend/src/routes/files.ts, backend/test/routes/files.test.ts, frontend/src/components/file-browser/FilePreview.tsx, frontend/src/components/file-browser/FilePreview.test.tsx	Raw file responses include a CSP sandbox header. HTML previews use a sandboxed iframe, with controls to show raw text or open the file in a new tab.
Initial directory selection and loading frontend/src/components/file-browser/FileBrowser.tsx, frontend/src/components/file-browser/FileBrowserSheet.test.tsx	Directory load results and status updates apply only to the latest request. Initial directory selection loads that path; a test covers a delayed listing response.
File paths from tool messages and references frontend/src/components/message/*, frontend/src/lib/fileReferences.ts, frontend/src/lib/fileReferences.test.ts, frontend/src/pages/SessionDetail.tsx	File tool rendering accepts legacy input paths and diff metadata. File reference matching and session file-click handling resolve the described paths. Tests cover clickable paths and reference detection.

Focus styling

Layer / File(s)	Summary
Visible focus rings frontend/src/components/repo/AddRepoDialog.tsx, frontend/src/components/ui/{badge,dialog,select,sidebar}.tsx	The listed controls use focus-visible variants for their ring styling.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant User
  participant FilePreview
  participant SandboxedIframe
  participant filesRoute
  User->>FilePreview: Select HTML preview
  FilePreview->>SandboxedIframe: Set raw file URL and allow-scripts sandbox
  SandboxedIframe->>filesRoute: Request raw file
  filesRoute-->>SandboxedIframe: Return HTML with CSP sandbox header

Loading

Merge Risk: 🟡 Moderate · up to cd7d1

Resizing can return the file browser to its initial directory, and affected legacy file links and previews may not open. Resolve these navigation issues before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to cd7d1

File access remains behind sign-in and workspace path checks, while HTML previews and new-tab views use sandboxing. No new security issue was established, but the changed access and rendering contracts merit review.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — An authenticated file-request caller can address paths within the workspace base, including paths outside the repositories directory. The prior relative-path resolver also allowed access to such workspace siblings, so the changed absolute-path handling is not shown to expand that boundary.

Trust Boundaries and Controls

• observed — Session middleware rejects requests without a session before file-route dispatch; the raw-content service independently validates its filesystem path before reading.
• inferred — The iframe sandbox and raw-response CSP give rendered HTML an opaque origin despite allowing scripts; the new-tab link also prevents access to its opener.

Hardening Proposals

• proposed — If workspace configuration files require a narrower audience than repository files, define that authorization boundary explicitly rather than relying on path form. This addresses a pre-existing workspace-wide access policy, not an established new issue in this PR.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description clearly explains the problem, lists the main changes, and reports backend and frontend test results. It does not use the required Summary, Type of Change, or Checklist sections, and it…	Restructure the description using the repository template. Add a Summary section, select the applicable Type of Change checkbox, and complete the Checklist, including code style, TypeScript types, tests, pnpm lint, and pnpm typecheck.
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 19 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the primary changes: workspace path resolution and sandboxed HTML preview support.
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.

Full details: Description check

Explanation

The description clearly explains the problem, lists the main changes, and reports backend and frontend test results. It does not use the required Summary, Type of Change, or Checklist sections, and it does not state whether lint and typecheck passed.

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Actionable comments posted: 2

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @frontend/src/components/file-browser/FileBrowser.tsx:
- Around line 448-450: Update the effect containing the
initialFileData.isDirectory check so directory initialization runs only when the
initial selection changes, not when isMobile changes; keep mobile preview
behavior in a separate effect so viewport changes do not call
loadFiles(initialFileData.path) or reset navigation.

Review comments at @frontend/src/components/message/FileToolRender.tsx:
- Around line 144-145: Update the path-selection helper so it uses input.path
only when it is a nonempty string; otherwise, fall back to input.filePath and
return it only when it is a nonempty string. This preserves valid filePath
values when path is empty or invalid.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: eac746d7-a0ce-4e13-9a3a-770568586338

📥 Commits

Reviewing files that changed from the base of the PR and between 5bd688d and cd7d139.

📒 Files selected for processing (19)

• backend/src/routes/files.ts
• backend/src/services/files.ts
• backend/test/routes/files.test.ts
• backend/test/services/files.test.ts
• frontend/src/components/file-browser/FileBrowser.tsx
• frontend/src/components/file-browser/FileBrowserSheet.test.tsx
• frontend/src/components/file-browser/FilePreview.test.tsx
• frontend/src/components/file-browser/FilePreview.tsx
• frontend/src/components/message/FileToolRender.tsx
• frontend/src/components/message/MessagePart.test.tsx
• frontend/src/components/message/ToolCallPart.tsx
• frontend/src/components/repo/AddRepoDialog.tsx
• frontend/src/components/ui/badge.tsx
• frontend/src/components/ui/dialog.tsx
• frontend/src/components/ui/select.tsx
• frontend/src/components/ui/sidebar.tsx
• frontend/src/lib/fileReferences.test.ts
• frontend/src/lib/fileReferences.ts
• frontend/src/pages/SessionDetail.tsx

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