fix(sync): stop directory cache thrashing when a project is expanded

Expanding a project with more worktrees and sessions than MAX_DIR_STORES put
the sidebar into an endless request loop (#1472).

Every sidebar row calls ensureChild during render, but the pin that protects
the directory is only taken in an effect after commit. ensureChild marked the
directory and ran eviction synchronously, so directories that were actively
rendering looked unpinned and were disposed. The next render recreated them
with a loading status, which issued another bootstrap request, and the cycle
repeated for as long as the project stayed expanded.

Raising the limit only moves the cliff, so the limit is now a soft target
instead: a directory touched within a grace window is never an overflow
victim. A burst of live directories overflows the cache briefly rather than
thrashing, while idle-time eviction still bounds it. Eviction is also coalesced
into one deferred pass per tick, so a render that mounts many rows no longer
sorts and scans every directory once per row, and a whole commit's pin effects
settle before anything is considered for disposal. Releasing the final consumer
stays synchronous, since that is an explicit lifecycle edge.

The idle profiler gains --expand-projects to reach this state.

Not yet verified end to end: reproducing the loop needs many worktrees under
one project, which this development environment does not have.

packages/ui/src/sync/child-store.ts

@@ -1,6 +1,6 @@
 import { create, type StoreApi } from "zustand"
 import type { DirState, State } from "./types"
-import { INITIAL_STATE, MAX_DIR_STORES, DIR_IDLE_TTL_MS } from "./types"
+import { INITIAL_STATE, MAX_DIR_STORES, DIR_IDLE_TTL_MS, EVICTION_GRACE_MS } from "./types"
 import { pickDirectoriesToEvict, canDisposeDirectory, hasPendingBlockingRequests } from "./eviction"
 import { readDirCache, persistVcs, persistProjectMeta, persistIcon, persistSessions } from "./persist-cache"
 import { normalizePath } from "@/lib/pathNormalization"
@@ -250,6 +250,7 @@ export class ChildStoreManager {
   readonly children = new Map<string, StoreApi<DirectoryStore>>()
   private readonly lifecycle = new Map<string, DirState>()
   private readonly pins = new Map<string, number>()
+  private evictionScheduled = false
   private readonly disposers = new Map<string, () => void>()
   private readonly registrySubscribers = new Set<() => void>()
   private readonly bootstrapSubscribers = new Set<() => void>()
@@ -308,7 +309,25 @@ export class ChildStoreManager {
   mark(directory: string) {
     if (!directory) return
     this.lifecycle.set(directory, { lastAccessAt: Date.now() })
-    this.runEviction(directory)
+    this.scheduleEviction()
+  }
+
+  /**
+   * Coalesce eviction into one pass per tick.
+   *
+   * `ensureChild` runs during render, once per sidebar row, and used to sort
+   * and scan every directory synchronously on each call. Deferring the pass
+   * also lets a whole render commit — and with it every pin effect — settle
+   * before anything is considered for disposal.
+   */
+  private scheduleEviction() {
+    if (this.evictionScheduled || this.disposed) return
+    this.evictionScheduled = true
+    queueMicrotask(() => {
+      this.evictionScheduled = false
+      if (this.disposed) return
+      this.runEviction()
+    })
   }
 
   pin(directory: string) {
@@ -327,6 +346,8 @@ export class ChildStoreManager {
       return
     }
     this.pins.delete(normalizedDirectory)
+    // Releasing the final consumer is an explicit lifecycle edge, not a render-
+    // path access, so this pass stays synchronous.
     this.runEviction()
   }
 
@@ -621,6 +642,7 @@ export class ChildStoreManager {
       pins: new Set(stores.filter((d) => this.pinned(d))),
       max: MAX_DIR_STORES,
       ttl: DIR_IDLE_TTL_MS,
+      graceMs: EVICTION_GRACE_MS,
       now: Date.now(),
       hasPendingBlockingRequests: (dir) => this.hasPendingBlockingRequestsForDirectory(dir),
     }).filter((d) => d !== skip)

packages/ui/src/sync/eviction-thrash.test.ts

@@ -0,0 +1,110 @@
+import { describe, expect, test } from "bun:test"
+
+import { pickDirectoriesToEvict } from "./eviction"
+import { DIR_IDLE_TTL_MS, EVICTION_GRACE_MS, MAX_DIR_STORES } from "./types"
+
+/**
+ * Regression coverage for the sidebar cache-thrash loop (issue #1472).
+ *
+ * Expanding a project with many worktrees mounts a sidebar row per directory.
+ * Each row calls `ensureChild` during render, while the pin that protects it is
+ * only taken in an effect after commit. With more live directories than the
+ * store limit, overflow eviction therefore disposed directories that were
+ * actively being rendered; the next render recreated them with a `loading`
+ * status, which issued another bootstrap request, and the cycle repeated
+ * indefinitely.
+ *
+ * The fix treats the limit as a soft target: a directory touched within the
+ * grace window is never an overflow victim, so a burst of live directories
+ * overflows the cache briefly instead of thrashing. Idle directories stay
+ * evictable, which is what keeps the cache bounded.
+ */
+
+const buildState = (directories: string[], lastAccessAt: number) =>
+  new Map(directories.map((directory) => [directory, { lastAccessAt }]))
+
+const directories = (count: number, prefix = "/repo/worktree-") =>
+  Array.from({ length: count }, (_, index) => `${prefix}${index}`)
+
+describe("directory eviction under sidebar expansion", () => {
+  test("does not evict directories that are being accessed right now", () => {
+    const now = 1_000_000
+    const stores = directories(MAX_DIR_STORES + 25)
+
+    const evicted = pickDirectoriesToEvict({
+      stores,
+      state: buildState(stores, now),
+      pins: new Set(),
+      max: MAX_DIR_STORES,
+      ttl: DIR_IDLE_TTL_MS,
+      graceMs: EVICTION_GRACE_MS,
+      now,
+    })
+
+    expect(evicted).toEqual([])
+  })
+
+  test("still evicts overflow once directories fall outside the grace window", () => {
+    const now = 1_000_000
+    const live = directories(MAX_DIR_STORES, "/repo/live-")
+    const stale = directories(5, "/repo/stale-")
+    const state = new Map([
+      ...buildState(live, now),
+      ...buildState(stale, now - EVICTION_GRACE_MS - 1),
+    ])
+
+    const evicted = pickDirectoriesToEvict({
+      stores: [...live, ...stale],
+      state,
+      pins: new Set(),
+      max: MAX_DIR_STORES,
+      ttl: DIR_IDLE_TTL_MS,
+      graceMs: EVICTION_GRACE_MS,
+      now,
+    })
+
+    expect([...evicted].sort()).toEqual([...stale].sort())
+  })
+
+  test("still evicts directories idle past the TTL even inside the limit", () => {
+    const now = 1_000_000
+    const active = directories(3, "/repo/active-")
+    const abandoned = directories(2, "/repo/abandoned-")
+    const state = new Map([
+      ...buildState(active, now),
+      ...buildState(abandoned, now - DIR_IDLE_TTL_MS - 1),
+    ])
+
+    const evicted = pickDirectoriesToEvict({
+      stores: [...active, ...abandoned],
+      state,
+      pins: new Set(),
+      max: MAX_DIR_STORES,
+      ttl: DIR_IDLE_TTL_MS,
+      graceMs: EVICTION_GRACE_MS,
+      now,
+    })
+
+    expect([...evicted].sort()).toEqual([...abandoned].sort())
+  })
+
+  test("never evicts pinned or blocked directories regardless of overflow", () => {
+    const now = 1_000_000
+    const stores = directories(MAX_DIR_STORES + 10)
+    const stale = now - EVICTION_GRACE_MS - 1
+
+    const evicted = pickDirectoriesToEvict({
+      stores,
+      state: buildState(stores, stale),
+      pins: new Set([stores[0]]),
+      max: MAX_DIR_STORES,
+      ttl: DIR_IDLE_TTL_MS,
+      graceMs: EVICTION_GRACE_MS,
+      now,
+      hasPendingBlockingRequests: (directory) => directory === stores[1],
+    })
+
+    expect(evicted).not.toContain(stores[0])
+    expect(evicted).not.toContain(stores[1])
+  })
+})

packages/ui/src/sync/eviction.ts

@@ -26,6 +26,7 @@ export function hasPendingBlockingRequests(state: State | undefined): boolean {
 export function pickDirectoriesToEvict(input: EvictPlan) {
   const overflow = Math.max(0, input.stores.length - input.max)
   let pendingOverflow = overflow
+  const graceMs = input.graceMs ?? 0
   const sorted = input.stores
     .filter((dir) => !input.pins.has(dir))
     .filter((dir) => !input.hasPendingBlockingRequests?.(dir))
@@ -34,8 +35,14 @@ export function pickDirectoriesToEvict(input: EvictPlan) {
   const output: string[] = []
   for (const dir of sorted) {
     const last = input.state.get(dir)?.lastAccessAt ?? 0
-    const idle = input.now - last >= input.ttl
+    const age = input.now - last
+    const idle = age >= input.ttl
     if (!idle && pendingOverflow <= 0) continue
+    // A directory touched moments ago is almost certainly still mounted and
+    // merely waiting for its pin effect to run. Evicting it starts the
+    // recreate/bootstrap loop this grace window exists to prevent; going over
+    // the limit for a while is the cheaper failure.
+    if (!idle && age < graceMs) continue
     output.push(dir)
     if (pendingOverflow > 0) pendingOverflow -= 1
   }

packages/ui/src/sync/types.ts

@@ -96,6 +96,7 @@ export type EvictPlan = {
   pins: Set<string>
   max: number
   ttl: number
+  graceMs?: number
   now: number
   hasPendingBlockingRequests?: (directory: string) => boolean
 }
@@ -110,6 +111,18 @@ export type DisposeCheck = {
 }
 
 export const MAX_DIR_STORES = 30
+/**
+ * Directories touched within this window are never overflow-eviction victims.
+ *
+ * Sidebar rows call `ensureChild` during render but only take their pin in an
+ * effect after commit. Without a grace window, expanding a project with more
+ * worktrees than `MAX_DIR_STORES` evicted directories that were actively
+ * rendering, which recreated them, which issued another bootstrap request, in
+ * an endless loop (issue #1472). The limit is therefore a soft target: a burst
+ * of live directories overflows briefly rather than thrashing, and the cache is
+ * bounded by idle-time eviction instead.
+ */
+export const EVICTION_GRACE_MS = 30 * 1000
 export const DIR_IDLE_TTL_MS = 20 * 60 * 1000
 export const SESSION_CACHE_LIMIT = 40
 

scripts/profile-idle.mjs

@@ -42,6 +42,9 @@ Options:
   --then-tab <name>        After settling, navigate to this tab without a
                            reload, then record. Use it to measure what a
                            surface keeps doing after the user leaves it.
+  --expand-projects        Expand every project in the sidebar before
+                           recording, which mounts a row per worktree and
+                           session directory
   --panel <mode[=target]>  Open the context panel on this surface before
                            recording (chat, preview, terminal, git, pr, notes,
                            file, diff, plan, context, browser, walkthrough).
@@ -70,6 +73,7 @@ const parseArgs = (argv) => {
     tab: null,
     thenTab: null,
     panels: [],
+    expandProjects: false,
     duration: 30,
     settle: 15,
     output: null,
@@ -94,6 +98,7 @@ const parseArgs = (argv) => {
     else if (value === "--tab") options.tab = argv[++index]
     else if (value === "--then-tab") options.thenTab = argv[++index]
     else if (value === "--panel") options.panels.push(argv[++index])
+    else if (value === "--expand-projects") options.expandProjects = true
     else if (value === "--label") options.label = argv[++index]
     else if (value === "--duration") options.duration = Number(argv[++index])
     else if (value === "--settle") options.settle = Number(argv[++index])
@@ -351,8 +356,16 @@ const main = async () => {
     await client.send("Page.navigate", { url: options.url })
     await loaded
 
-    if (options.panels.length > 0) {
-      await seedContextPanel(client, options.panels, options.session)
+    if (options.expandProjects) {
+      // The sidebar persists the ids of collapsed projects, so an empty list
+      // expands everything. This is the state in issue #1472: one mounted
+      // directory-bound row per worktree and session.
+      await evaluateValue(client, `localStorage.setItem("oc.sessions.projectCollapse", "[]")`)
+      console.log("Expanded every project in the sidebar.")
+    }
+
+    if (options.panels.length > 0 || options.expandProjects) {
+      if (options.panels.length > 0) await seedContextPanel(client, options.panels, options.session)
       const reloaded = client.once("Page.loadEventFired", 60_000)
       await client.send("Page.reload", { ignoreCache: false })
       await reloaded