fix(restore): serialize missing workspace mounts

Restore-created workspaces previously mounted in parallel. Solid could invoke Virtua refs before document adoption, causing ResizeObserver initialization to throw after the workspace entered the UI but before its restore binding committed. The affected tabs then lost saved ordering, session selection, idle markers, scroll snapshots, and generation recovery.

Create missing workspaces sequentially while preserving parallel hydration for existing workspaces and SideCars. Budget the startup deadline per serialized workspace and bound failed-creation cleanup so one stalled cancellation cannot block later tabs.

Validated with a packaged Tauri release against a three-workspace snapshot, confirming exact tab order, active tab, per-workspace active sessions, idle markers, scroll snapshot counts, and generation recovery. Added focused regression coverage and ran UI typecheck and restore tests.

Author: pascalandr

packages/ui/src/lib/hooks/use-app-session-capture.test.ts

@@ -15,4 +15,10 @@ describe("app session capture listener readiness", () => {
     assert.ok(restore.indexOf("await capture.ready") < restore.indexOf("capture.start("))
   })
 
+  it("serializes missing workspace mounts during session restore", () => {
+    const restore = source("./use-app-session-restore.ts")
+    assert.match(restore, /for \(const group of groups\.values\(\)\) for \(const match of group\) await restoreWorkspace\(match\)/)
+    assert.doesNotMatch(restore, /Array\.from\(groups\.values\(\), async/)
+  })
+
 })

packages/ui/src/lib/hooks/use-app-session-restore.ts

@@ -34,15 +34,23 @@ const NO_SESSION_DRAFT_SESSION_ID = "__no_session_draft__"
 const INITIAL_LOAD_TIMEOUT_MS = 15_000
 const OPERATION_TIMEOUT_MS = 30_000
 const CREATE_TIMEOUT_MS = OPERATION_TIMEOUT_MS * 2
+const CLEANUP_TIMEOUT_MS = 5_000
 const MINIMUM_STARTUP_TIMEOUT_MS = 60_000
 function startupTimeout(snapshot: RestorableSessionState): number {
-  const counts = new Map<string, number>()
-  for (const tab of snapshot.tabs) if (tab.kind === "workspace") {
-    const path = normalizeWorkspacePath(tab.folder)
-    counts.set(path, (counts.get(path) ?? 0) + 1)
-  }
+  const workspaceCount = snapshot.tabs.filter((tab) => tab.kind === "workspace").length
   return Math.max(MINIMUM_STARTUP_TIMEOUT_MS,
-    INITIAL_LOAD_TIMEOUT_MS + Math.max(1, ...counts.values()) * CREATE_TIMEOUT_MS + 5_000)
+    INITIAL_LOAD_TIMEOUT_MS + Math.max(1, workspaceCount) * (CREATE_TIMEOUT_MS + CLEANUP_TIMEOUT_MS) + 5_000)
+}
+async function disposeFailedRestoreWorkspace(instanceId: string): Promise<void> {
+  const cleanup = disposeRestoreCreatedInstance(instanceId)
+  try {
+    await runAbortable(() => cleanup, {
+      timeoutMs: CLEANUP_TIMEOUT_MS,
+      message: `Timed out cleaning up restored workspace ${instanceId}`,
+    })
+  } catch (error) {
+    log.warn("Restore workspace cleanup continues in the background", { instanceId, error })
+  }
 }
 async function restoreWorkspaceState(
   instanceId: string,
@@ -171,8 +179,8 @@ async function restoreTabs(context: RestoreContext): Promise<void> {
         } catch (error) {
           if (!existingId && creation?.requestId) {
             capture.settleRestoredTab(match.tabIndex, getInstanceAppTabId(id), null)
-            await disposeRestoreCreatedInstance(id)
             if (created) createdId = null
+            await disposeFailedRestoreWorkspace(id)
           }
           throw error
         }
@@ -187,7 +195,7 @@ async function restoreTabs(context: RestoreContext): Promise<void> {
     } catch (error) {
       if (createdId) {
         capture.settleRestoredTab(match.tabIndex, getInstanceAppTabId(createdId), null)
-        await disposeRestoreCreatedInstance(createdId)
+        await disposeFailedRestoreWorkspace(createdId)
       }
       if (!signal.aborted) log.warn("Skipped workspace while restoring app session", { folder: tab.folder, error })
     }
@@ -208,11 +216,11 @@ async function restoreTabs(context: RestoreContext): Promise<void> {
       if (!signal.aborted) log.warn("Skipped SideCar while restoring app session", { sidecarId: tab.sidecarId, error })
     }
   }
-  await Promise.all([
-    ...existing.map(restoreWorkspace),
-    ...Array.from(groups.values(), async (group) => { for (const match of group) await restoreWorkspace(match) }),
-    ...sidecars,
-  ])
+  const restoreMissing = async () => {
+    // ponytail: serialize DOM-heavy workspace mounts; parallel mounts can initialize Virtua before document adoption.
+    for (const group of groups.values()) for (const match of group) await restoreWorkspace(match)
+  }
+  await Promise.all([...existing.map(restoreWorkspace), restoreMissing(), ...sidecars])
 }
 export function useAppSessionRestore(): void {
   const capture = useAppSessionCapture()