fix: recover parent sessions during bootstrap

Preserves referenced parents when child sessions arrive before roots
Avoids publishing orphan-only bootstrap snapshots
Adds tests for bootstrap session merging

packages/ui/src/sync/DOCUMENTATION.md

@@ -61,6 +61,10 @@ Examples:
 - per-directory session/message bootstrap
 - session/message/part SSE updates
 
+Directory bootstrap must publish a closed session hierarchy: when a child is
+returned before the roots query catches up during cold startup, retain or
+recover its referenced parent instead of exposing an orphan-only snapshot.
+
 ### Global session list
 
 Use `useGlobalSessionsStore` when the UI needs a **shared global session cache**.

packages/ui/src/sync/reconnect-recovery.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, test } from "bun:test"
 import type { Message, Part, SessionStatus } from "@opencode-ai/sdk/v2/client"
 import type { Session } from "@opencode-ai/sdk/v2"
-import { getReconnectCandidateSessionIds } from "./reconnect-recovery"
+import { getReconnectCandidateSessionIds, mergeBootstrapSessions } from "./reconnect-recovery"
 
 function createSession(id: string, overrides: Partial<Session> = {}): Session {
   return {
@@ -88,3 +88,26 @@ describe("getReconnectCandidateSessionIds", () => {
     }).sort()).not.toContain("active")
   })
 })
+
+describe("mergeBootstrapSessions", () => {
+  test("recovers a referenced parent when the roots response is temporarily empty", () => {
+    const parent = createSession("parent")
+    const child = createSession("child", { parentID: "parent" })
+
+    expect(mergeBootstrapSessions([], [child], [parent])).toEqual({
+      sessions: [child, parent],
+      rootCount: 1,
+    })
+  })
+
+  test("recovers referenced parents from the broader response without retaining stale roots", () => {
+    const parent = createSession("parent")
+    const stale = createSession("stale")
+    const child = createSession("child", { parentID: "parent" })
+
+    expect(mergeBootstrapSessions([], [parent, child], [stale])).toEqual({
+      sessions: [child, parent],
+      rootCount: 1,
+    })
+  })
+})

packages/ui/src/sync/reconnect-recovery.ts

@@ -19,6 +19,46 @@ type ReconnectCandidateOptions = {
   viewedSession?: ViewedSessionMaterializationTarget | null
 }
 
+export function mergeBootstrapSessions(
+  rootSessions: Session[],
+  allSessions: Session[],
+  existingSessions: Session[],
+): { sessions: Session[]; rootCount: number } {
+  const rootIds = new Set(rootSessions.map((session) => session.id))
+  const sessionsById = new Map(existingSessions.map((session) => [session.id, session]))
+  for (const session of allSessions) sessionsById.set(session.id, session)
+  for (const session of rootSessions) sessionsById.set(session.id, session)
+
+  const includedIds = new Set(rootIds)
+  const pendingParentIds: string[] = []
+  for (const session of allSessions) {
+    const parentId = (session as Session & { parentID?: string | null }).parentID
+    if (!parentId) continue
+    includedIds.add(session.id)
+    pendingParentIds.push(parentId)
+  }
+
+  while (pendingParentIds.length > 0) {
+    const parentId = pendingParentIds.pop()
+    if (!parentId || includedIds.has(parentId)) continue
+    const parent = sessionsById.get(parentId)
+    if (!parent) continue
+    includedIds.add(parentId)
+    const ancestorId = (parent as Session & { parentID?: string | null }).parentID
+    if (ancestorId) pendingParentIds.push(ancestorId)
+  }
+
+  const sessions = [...includedIds]
+    .map((id) => sessionsById.get(id))
+    .filter((session): session is Session => Boolean(session))
+    .sort((a, b) => (a.id < b.id ? -1 : a.id > b.id ? 1 : 0))
+  const rootCount = sessions.reduce((count, session) => (
+    (session as Session & { parentID?: string | null }).parentID ? count : count + 1
+  ), 0)
+
+  return { sessions, rootCount }
+}
+
 export function getReconnectCandidateSessionIds(state: ReconnectMaterializationState, options?: ReconnectCandidateOptions) {
   const ids = new Set<string>()
 

packages/ui/src/sync/sync-context.tsx

@@ -27,7 +27,7 @@ import { setSyncRefs, getAllSyncSessions } from "./sync-refs"
 import { stripMessageDiffSnapshots, stripSessionDiffSnapshots } from "./sanitize"
 import { applySessionEventToGlobalSessions } from "./session-event-router"
 import { syncDebug } from "./debug"
-import { getReconnectCandidateSessionIds } from "./reconnect-recovery"
+import { getReconnectCandidateSessionIds, mergeBootstrapSessions } from "./reconnect-recovery"
 import { opencodeClient } from "@/lib/opencode/client"
 import { usePermissionStore } from "@/stores/permissionStore"
 import { processVSCodePermissionAutoAccept } from "./vscode-permission-auto-accept"
@@ -1780,24 +1780,22 @@ export function SyncProvider(props: {
                 // Child load is best-effort; fall back to roots only.
               }
 
-              // Merge: keep root sessions from the first query (for accurate
-              // sessionTotal), plus any child sessions from the broader query.
-              const rootIds = new Set(rootSessions.map((s: { id: string }) => s.id))
-              const childSessions = allSessions.filter((s: { id: string; parentID?: string | null }) => s?.id && !rootIds.has(s.id) && s.parentID)
-
-              const sessions = rootSessions.concat(childSessions)
+              // A cold OpenCode process can briefly return children before its
+              // roots query catches up. Recover referenced parents from the
+              // broader response or cache instead of publishing orphan rows.
+              const currentSessions = store.getState().session
+              const { sessions, rootCount } = mergeBootstrapSessions(rootSessions, allSessions, currentSessions)
               // Race guard: if the list came back empty but event pipeline
               // already populated the store, don't clobber. OpenCode can
               // answer HTTP with empty sessions while WS delivers session
               // events for the same data (disk warmup race on app launch).
-              const currentSessions = store.getState().session
               if (sessions.length === 0 && currentSessions.length > 0) {
                 console.warn(
                   `[bootstrap] experimental.session.list returned empty for ${dir}; preserving ${currentSessions.length} existing sessions`,
                 )
                 return
               }
-              store.setState({ session: sessions, sessionTotal: rootSessions.length, limit: Math.max(sessions.length, 50) })
+              store.setState({ session: sessions, sessionTotal: rootCount, limit: Math.max(sessions.length, 50) })
               ingestDirectoryStateIntoRoutingIndex(routingIndex, directory, store.getState())
             }),
           })