fix(web): folder links outside the workspace open a file explorer

[chisewaguri]

Problem

Clicking a chat link to a folder outside the thread's workspace opens a file tab with an empty pane and Failed to read workspace file '<folder>' in '<workspace>'. Folder links inside the workspace already open the explorer (#10909, #12449), and file links outside it already open read-only (#9140). An outside folder is the one case left. FilePreviewPanel keeps the read error on purpose with isDirectory = file.isNotFile && !isHostFile.

Reproduce on Windows: in a thread whose workspace is C:\Users\me\project, have the agent link C:\Users\me\other\, then click the chip.

Fixes #15215.

Change

When a host path turns out to be a folder, the preview panel now roots the explorer at that folder instead of keeping the error. The server already lists entries for any existing root, so the change is client only.

Paths from that explorer stay absolute, because the thread still belongs to the original workspace. FileBrowserPanel takes an absolutePaths flag and resolves tree paths against its root before it opens a file, copies a mention, or starts a drag. fileTreeDragMention takes an optional resolvePath for the drag case.

Scope and approval

This fixes the bug reported in #15215, which is still awaiting triage. It is the change from #12800 by @shardmods, ported to current main. That PR was closed unmerged on 2026-10-02 after the V2 merge, with no review objection. #16427 is related but separate. It makes ../ file links resolve outside the workspace, and a ../ folder link would then reach this same code path.

Verification

Captured in an isolated web dev server on Windows at 1280 x 800, with the right panel opened on a folder outside the server workspace.

Before (main)	After

Selecting notes.md in that explorer opens it in its own tab, read-only, from its absolute path. The folder tab stays open.

• vp test run on fileTreeDragMention.test.ts, FilePreviewPanel.test.ts, terminal-links.test.ts and rightPanelStore.test.ts passed 133 tests. The drag test checks that mentions from an outside tree carry absolute paths while deselection still uses the tree's row paths. The joinWorkspacePath tests check that an entry named ~/child.ts stays under the explorer root.
• tsc --noEmit in apps/web reports no errors in the changed files. It does report 13 errors elsewhere on this Windows checkout, all in files this PR does not touch.
• vp fmt is clean. I could not run vp lint here because oxlint-tsgolint does not resolve on Windows.

Ported from #12800 by @shardmods, who is credited as co-author on the commit.

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📒 Files selected for processing (3)

• apps/web/src/components/files/FileBrowserPanel.tsx
• apps/web/src/terminal-links.test.ts
• apps/web/src/terminal-links.ts

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📝 Walkthrough

Walkthrough

Host directories now open in an explorer rooted at the selected directory. The explorer can resolve file-open and mention paths against its root. Drag-end deselection continues to use the original selected paths.

Changes

External directory previews

Layer / File(s)	Summary
Resolve explorer paths apps/web/src/terminal-links.ts, apps/web/src/terminal-links.test.ts, apps/web/src/components/files/FileBrowserPanel.tsx, apps/web/src/components/files/fileTreeDragMention.ts, apps/web/src/components/files/fileTreeDragMention.test.ts	joinWorkspacePath joins a root and relative path using platform-appropriate separators. FileBrowserPanel adds optional absolute-path resolution for mentions and file-open callbacks. The drag-mention controller accepts a path resolver, trims trailing slashes before conversion, and has a test for resolved mention paths and original-path deselection.
Configure host-directory explorer apps/web/src/components/files/FilePreviewPanel.tsx	Directory reads outside the workspace configure an explorer rooted at the selected directory. The explorer receives the directory basename as its project name, enables absolute paths, and clears the selected path.

Priority: ⬇️ Low

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

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to 65a07

Opening a child file switches to its preview, while the host-directory explorer remains available in its tab. No actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the problem, change, and verification in detail, but the scope section does not meet the template’s approval requirement. Issue #15215 is still awaiting triage, and the prior …	Link a triaged issue or a discussion with explicit maintainer approval of the direction and scope. If the change qualifies for the exemption, explain why it is a very small, focused fix of an obvious bug and why it does not need prior appro…

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	[#15215] FilePreviewPanel now treats host directories as directories and roots FileBrowserPanel at the host path. It clears the selected child path and uses the folder basename as the explorer nam…
Out of Scope Changes check	✅ Passed	The FileBrowserPanel path resolution and fileTreeDragMention changes support navigation and mention actions in the outside-workspace explorer required by [#15215]. joinWorkspacePath and its test…
Approvability	✅ Passed	The pull request changes six files, all under apps/web/src and limited to the explorer fix and tests. absolutePaths defaults to false; FilePreviewPanel enables it only when it opens an explore…
Title check	✅ Passed	The title clearly summarizes the main change: opening an explorer for folder links outside the workspace.

Full details: Description check

Explanation

The description explains the problem, change, and verification in detail, but the scope section does not meet the template’s approval requirement. Issue #15215 is still awaiting triage, and the prior PR’s closure without review objections is not explicit maintainer approval or a justification for the small, obvious-fix exemption.

Resolution

Link a triaged issue or a discussion with explicit maintainer approval of the direction and scope. If the change qualifies for the exemption, explain why it is a very small, focused fix of an obvious bug and why it does not need prior approval.

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Actionable comments posted: 1

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Inline comments:
Review comments at @apps/web/src/components/files/FilePreviewPanel.tsx:
- Around line 1068-1069: Update the host-directory root selection in
FilePreviewPanel so opening a child file retains the active host explorer root
instead of falling back to cwd. Reuse or preserve the existing explorer root
across file selections, and keep it until the user leaves the host-directory
explorer.

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📒 Files selected for processing (4)

• apps/web/src/components/files/FileBrowserPanel.tsx
• apps/web/src/components/files/FilePreviewPanel.tsx
• apps/web/src/components/files/fileTreeDragMention.test.ts
• apps/web/src/components/files/fileTreeDragMention.ts

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR changes external folder links to open a rooted file explorer and propagates absolute paths through selection, mentions, and drag-and-drop. An unresolved High-severity path-resolution issue affects entries beginning with ~/, so the new behavior needs human review.

Not approved because:

• 1 blocking correctness issue found at or above your repo's Minimum Blocking Severity

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[chisewaguri]

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@chisewaguri I’ll review the changes in #16716.

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