Fix browser portal leaking to other tabs on Bonsplit tab switch - #2000

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Greptile Summary

This PR fixes a visual leak where portal-hosted WKWebViews from deselected browser panels remained visible above the newly selected tab when switching Bonsplit tabs in keepAllAlive mode. The root cause is that SwiftUI .opacity(0) hides elements at the SwiftUI layer but has no effect on AppKit-level portal views, so the browser portal of the deselected tab was never explicitly hidden.

The fix adds a small private helper hideBrowserPortalsForDeselectedTabs(inPane:selectedTabId:) that iterates tabs in the active pane, skips the newly-selected tab, and calls hideBrowserPortalView(source: "tabDeselected") on any BrowserPanels found among the remaining tabs. This helper is called at the right point in applyTabSelectionNow — after focusedPane/selectedTabId are resolved and the "unfocus all other panels" loop — ensuring portal visibility is synchronised with the tab selection state.

Key design properties of the fix:

• Correctly scoped to the focused pane: only tabs in the pane where the selection changed are affected; selected browser tabs in other split panes are untouched.
• Nil-safe: both panelIdFromSurfaceId and the as? BrowserPanel cast are guarded, so non-browser and uninitialized tabs are silently skipped.
• Re-show is handled by the existing SwiftUI path: once the pane's opacity flips back to 1, updateNSView sets desiredPortalVisibleInUI = true and re-shows the portal through BrowserWindowPortalRegistry.bind.
• No automated test added: given the test quality policy (no source-inspection or stub-based tests), a meaningful regression test would need a full E2E harness with live WKWebViews; the PR provides a manual test plan instead.

Confidence Score: 5/5

• The fix is minimal, well-scoped, and uses an established hide primitive already in use elsewhere in the codebase.
• Single-file change adding ~13 lines of straightforward logic. The helper is correctly scoped to the focused pane (doesn't disturb other panes' browser portals), all lookups are nil-guarded, the hide primitive (hideBrowserPortalView) is already exercised in the workspaceRetire path, and re-showing when switching back relies on the existing SwiftUI bind path. No logic errors, no missing edge-case handling, no regressions expected.
• No files require special attention.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant User
    participant Workspace
    participant BonsplitController
    participant BrowserPanel
    participant BrowserWindowPortalRegistry

    User->>Workspace: Switch tab (e.g. browser → terminal)
    Workspace->>BonsplitController: focusPane(pane) / selectTab(tabId)
    BonsplitController-->>Workspace: focusedPane, selectedTabId resolved

    Note over Workspace: Unfocus all other panels

    Workspace->>Workspace: hideBrowserPortalsForDeselectedTabs(inPane: focusedPane, selectedTabId:)
    loop for each non-selected tab in pane
        Workspace->>BrowserPanel: hideBrowserPortalView(source: "tabDeselected")
        BrowserPanel->>BrowserWindowPortalRegistry: hide(webView:, source:)
        BrowserWindowPortalRegistry->>BrowserWindowPortalRegistry: entry.visibleInUI = false
        BrowserWindowPortalRegistry->>BrowserWindowPortalRegistry: containerView.isHidden = true
    end

    Workspace->>Workspace: activatePanel(panel, …)

    Note over User: Switch back to browser tab
    User->>Workspace: Switch tab (terminal → browser)
    Workspace->>BonsplitController: selectTab(browserTabId)
    BonsplitController-->>Workspace: opacity(1) triggers SwiftUI re-render
    Workspace->>BrowserWindowPortalRegistry: bind(webView:, visibleInUI: true, …)
    BrowserWindowPortalRegistry->>BrowserWindowPortalRegistry: containerView.isHidden = false

_{Reviews (1): Last reviewed commit: "Fix browser portal leaking to other tabs..." | Re-trigger Greptile}

Thank you for the contribution!