feat(web): open diff files in external editor

[ipanasenko]

The diff header filename opens the file in T3 Code’s internal viewer, but the header has no explicit way to open that file in the configured external editor.

This adds an external-editor button beside the copy-path action from #2403. The filename keeps its internal-viewer behavior, while the new action resolves the workspace-relative path and routes through the same preferred-editor setting used by the top Open control.

Built with GPT-5.6 Sol in the T3 Code harness.

Note

Add "open in external editor" button to diff files in DiffPanel

• Adds a per-file editor button in the diff panel header that opens the file in a resolved remote editor URL or the preferred local editor.
• Introduces openDiffFileInEditor in diffFileActions.ts to resolve repo-relative diff paths against the active workspace before invoking the editor opener.
• Adds reusable DiffFileHeaderActionButton and DiffFileOpenInEditorButton components, and a diff-header button variant in button.tsx.
• Refactors the existing copy-path action to use the shared header button component.
• Behavioral Change: the button is disabled unless an active thread, working directory, and a resolved remote or local editor are all available; failed opens produce warnings.

^{Macroscope summarized 116a925.}

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Note

Low Risk
Scoped UI and path-resolution changes reusing existing editor and workspace helpers; no auth or data-handling changes.

Overview
Adds an Open in editor control next to the copy-path button on each diff file header, while filename clicks still open the in-app file viewer.

A shared DiffFileHeaderActionButton backs both header actions. openDiffFileInEditor resolves workspace paths (same rules as the primary diff action) and invokes the editor launcher without opening the right-panel viewer. DiffPanel centralizes launching in launchDiffFileInEditor, which uses remote editor URLs when available and otherwise the existing preferred local editor flow; the new button stays disabled until an editor can be resolved.

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Summary by CodeRabbit

• New Features

  • Open diff files directly in a configured editor.
  • Supports opening files from remote workspaces when available.
  • Added accessible tooltips and labels for diff file actions.

• Enhancements

  • Standardized diff header actions, including copying file paths.
  • Diff file paths are resolved against the active workspace before opening.

• Tests

  • Added coverage for opening repository-relative diff files in the editor.

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a new production workflow for opening diff files in local editors or remote editor deep links, including new UI components and environment-dependent launch behavior. Its external side effects and remote integration exceed a minor UI adjustment, so human review is appropriate.

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⚙️ Run configuration

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Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between f5081b0 and 116a925.

📒 Files selected for processing (2)

• apps/web/src/components/DiffFileHeaderActionButton.tsx
• apps/web/src/components/ui/button.tsx

🚧 Files skipped from review as they are similar to previous changes (1)

• apps/web/src/components/DiffFileHeaderActionButton.tsx

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📝 Walkthrough

Walkthrough

The change adds shared diff header action buttons, workspace path resolution, and remote or local editor launching in DiffPanel. The file header now includes an editor action alongside the existing copy action.

Changes

Diff editor actions

Layer / File(s)	Summary
Shared diff header actions apps/web/src/components/DiffFileHeaderActionButton.tsx, apps/web/src/components/DiffFileOpenInEditorButton.tsx, apps/web/src/components/DiffFilePathCopyButton.tsx, apps/web/src/components/ui/button.tsx	Adds the shared tooltip action button and diff-header variant. Adds the editor action and updates the copy action to use the shared component.
Workspace editor path resolution apps/web/src/diffFileActions.ts, apps/web/src/diffFileActions.test.ts	Adds openDiffFileInEditor, which resolves repository-relative paths against the active workspace. Tests validate the resolved editor path.
Diff panel editor integration apps/web/src/components/DiffPanel.tsx	Adds remote editor resolution, remote URL launching, local editor fallback, launch eligibility checks, and the editor action in the diff file header.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 116a9

This change adds an Open in editor control to diff headers while retaining existing viewer and fallback behavior. No concrete merge-blocking risk remains.

Sequence Diagram(s)

sequenceDiagram
  participant DiffPanel
  participant RemoteOpenResolution
  participant RemoteEditor
  participant LocalEditor
  DiffPanel->>RemoteOpenResolution: resolve editor mode and preferred editor
  alt remote links available
    DiffPanel->>RemoteEditor: build and open remote diff URL
  else local editor fallback
    DiffPanel->>LocalEditor: open resolved diff file path
  end

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Suggested reviewers: juliusmarminge, maria-rcks

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 7 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: opening diff files in an external editor.
Description check	✅ Passed	The description explains what changed and why, describes the UI behavior, and includes a screenshot. It omits the template headings and checklist, but the required substantive information is present.
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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Inline comments:
In `@apps/web/src/components/DiffFileHeaderActionButton.tsx`:
- Line 28: Update the button styling in DiffFileHeaderActionButton to use a
dedicated existing or newly defined button variant for this action, rather than
overriding ghost variant colors through className. Preserve the intended muted,
hover, pressed, and disabled appearance within the variant definition, then
remove the conflicting call-site color override.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 54abad2e-c50a-4f3c-a8f9-cf1ade43414d

📥 Commits

Reviewing files that changed from the base of the PR and between 1d1bf50 and f5081b0.

📒 Files selected for processing (6)

• apps/web/src/components/DiffFileHeaderActionButton.tsx
• apps/web/src/components/DiffFileOpenInEditorButton.tsx
• apps/web/src/components/DiffFilePathCopyButton.tsx
• apps/web/src/components/DiffPanel.tsx
• apps/web/src/diffFileActions.test.ts
• apps/web/src/diffFileActions.ts

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[juliusmarminge]

i'd prefer this being in a context menu on right clicking the header.

[ipanasenko]

Got it, on it!

[ipanasenko]

@juliusmarminge do you want both actions there (Copy + Open), or just Open?