perf(tooling): reach a fully populated sidebar in both profilers

Idle and streaming cost both depend on how much of the sidebar is mounted, so
the scenario setup is now shared. --expand-projects seeds the persisted collapse
state; --expand-sessions clicks every "Show more sessions" control, which
cannot be seeded because pagination is component state. Both run before the
measured window, so it stays input-free. Session expansion must run after the
sidebar has populated, not straight after the load event, or the controls do
not exist yet.

Also replaces a spread push over collected trace events, which overflowed the
call stack once a populated sidebar produced chunks of hundreds of thousands of
events, and the equivalent spread in the heap-maximum calculation.

scripts/perf/scenario.mjs

@@ -0,0 +1,44 @@
+/**
+ * Scenario setup shared by the idle and streaming profilers.
+ *
+ * Idle and streaming cost both depend on how much of the sidebar is mounted,
+ * so both commands need the same way to reach a heavily populated sidebar.
+ * Setup always runs before the measured window.
+ */
+
+import { evaluateValue, wait } from "./cdp.mjs"
+
+/**
+ * Expands every project. The sidebar persists the ids of collapsed projects,
+ * so an empty list expands everything. Requires a reload to take effect.
+ */
+export const expandProjects = async (client) => {
+  await evaluateValue(client, `localStorage.setItem("oc.sessions.projectCollapse", "[]")`)
+}
+
+/**
+ * Clicks every "Show more sessions" control until none remain.
+ *
+ * Session list pagination is component state, so unlike project collapse it
+ * cannot be seeded through storage. The controls only exist once the sidebar
+ * has populated, so call this after the page has settled, never straight after
+ * the load event.
+ *
+ * Matching is a case-insensitive substring test, which assumes the English UI
+ * locale; a non-English locale expands nothing and reports zero.
+ */
+export const expandSessionLists = async (client, { passes = 40, settleMs = 400 } = {}) => {
+  let totalClicked = 0
+  for (let pass = 0; pass < passes; pass += 1) {
+    const clicked = await evaluateValue(client, `(() => {
+      const controls = [...document.querySelectorAll("button")]
+        .filter((button) => (button.textContent ?? "").toLowerCase().includes("show more"))
+      for (const control of controls) control.click()
+      return controls.length
+    })()`)
+    if (!clicked) break
+    totalClicked += clicked
+    await wait(settleMs)
+  }
+  return totalClicked
+}

scripts/profile-idle.mjs

@@ -29,6 +29,7 @@ import process from "node:process"
 import { CdpClient, createPageTarget, evaluateValue, launchChrome, reservePort, resolveChrome, wait } from "./perf/cdp.mjs"
 import { buildIdleProbeSource, IDLE_PROBE_GLOBAL } from "./perf/idle-probe.mjs"
 import { summarizeCpuProfile } from "./perf/cpu-profile.mjs"
+import { expandProjects, expandSessionLists } from "./perf/scenario.mjs"
 import { growthPerSecond, metricMap, round } from "./perf/metrics.mjs"
 
 const HELP = `Usage: bun run profile:idle -- [options]
@@ -42,6 +43,10 @@ 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-sessions        Click every "Show more sessions" control until the
+                           sidebar has no collapsed session lists left, so all
+                           session rows are mounted. Clicks happen before the
+                           recording window, which stays input-free.
   --expand-projects        Expand every project in the sidebar before
                            recording, which mounts a row per worktree and
                            session directory
@@ -74,6 +79,7 @@ const parseArgs = (argv) => {
     thenTab: null,
     panels: [],
     expandProjects: false,
+    expandSessions: false,
     duration: 30,
     settle: 15,
     output: null,
@@ -99,6 +105,7 @@ const parseArgs = (argv) => {
     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 === "--expand-sessions") options.expandSessions = 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])
@@ -243,7 +250,7 @@ const buildSummary = ({ options, before, after, samples, cpu, probe, elapsedSeco
       frames: Number(after.Frames ?? 0),
       heapStartMb: round(heapSamples.at(0) ?? 0),
       heapEndMb: round(heapSamples.at(-1) ?? 0),
-      heapMaxMb: round(Math.max(0, ...heapSamples)),
+      heapMaxMb: round(heapSamples.reduce((max, value) => Math.max(max, value), 0)),
       heapGrowthMbPerSecond: growthPerSecond(samples, "jsHeapUsedMb"),
     },
     cpuProfile: cpu,
@@ -357,10 +364,7 @@ const main = async () => {
     await loaded
 
     if (options.expandProjects) {
-      // The sidebar persists the ids of collapsed projects, so an empty list
+      await expandProjects(client)
-      // 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.")
     }
 
@@ -374,18 +378,9 @@ const main = async () => {
     console.log(`Loaded ${options.url}; settling for ${options.settle}s before recording.`)
     await wait(options.settle * 1000)
 
-    if (options.thenTab) {
+    if (options.expandSessions) {
-      // Route changes normally come from clicks; driving history directly
+      const expanded = await expandSessionLists(client)
-      // reaches the same router path without generating input work inside the
+      console.log(`Expanded ${expanded} collapsed session lists; settling ${options.settle}s again.`)
-      // recorded window, and leaves already-mounted surfaces mounted.
-      await evaluateValue(client, `(() => {
-        const url = new URL(window.location.href)
-        url.searchParams.set("tab", ${JSON.stringify(options.thenTab)})
-        window.history.pushState({}, "", url.toString())
-        window.dispatchEvent(new PopStateEvent("popstate", { state: {} }))
-        return true
-      })()`)
-      console.log(`Navigated to tab "${options.thenTab}" without reloading; settling ${options.settle}s again.`)
       await wait(options.settle * 1000)
     }
 

scripts/profile-session.mjs

@@ -30,6 +30,7 @@ import { CdpClient, createPageTarget, evaluateValue, launchChrome, reservePort,
 import { buildIdleProbeSource, IDLE_PROBE_GLOBAL } from "./perf/idle-probe.mjs"
 import { summarizeCpuProfile } from "./perf/cpu-profile.mjs"
 import { growthPerSecond, metricMap, round, summarizeLongTasks, summarizeTraceEvents } from "./perf/metrics.mjs"
+import { expandProjects, expandSessionLists } from "./perf/scenario.mjs"
 
 const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..")
 const cliPath = join(repoRoot, "packages/web/bin/cli.js")
@@ -47,6 +48,9 @@ Options:
   --port <port>            OpenChamber CLI port (default: from --url)
   --dir <path>             Session directory (default: repository root)
   --session <id>           Reuse this session instead of creating one
+  --expand-projects        Expand every project in the sidebar before recording
+  --expand-sessions        Click every "Show more sessions" control before
+                           recording, so all session rows are mounted
   --view-session <id>      Display this session while the prompt streams into
                            another one. Measures what an idle session costs
                            while a different session is active in the
@@ -79,6 +83,8 @@ const parseArgs = (argv) => {
     dir: repoRoot,
     session: null,
     viewSession: null,
+    expandProjects: false,
+    expandSessions: false,
     prompt: DEFAULT_PROMPT,
     model: null,
     agent: null,
@@ -108,6 +114,8 @@ const parseArgs = (argv) => {
     else if (value === "--dir") options.dir = argv[++index]
     else if (value === "--session") options.session = argv[++index]
     else if (value === "--view-session") options.viewSession = argv[++index]
+    else if (value === "--expand-projects") options.expandProjects = true
+    else if (value === "--expand-sessions") options.expandSessions = true
     else if (value === "--prompt") options.prompt = argv[++index]
     else if (value === "--model") options.model = argv[++index]
     else if (value === "--agent") options.agent = argv[++index]
@@ -364,7 +372,11 @@ const main = async () => {
     })
 
     const traceEvents = []
-    const unsubscribeTrace = client.on("Tracing.dataCollected", ({ value }) => traceEvents.push(...(value ?? [])))
+    // A spread push overflows the call stack once a chunk carries hundreds of
+    // thousands of events, which a heavily populated sidebar easily produces.
+    const unsubscribeTrace = client.on("Tracing.dataCollected", ({ value }) => {
+      for (const event of value ?? []) traceEvents.push(event)
+    })
 
     let loaded = client.once("Page.loadEventFired", 60_000)
     await client.send("Page.navigate", { url: target.toString() })
@@ -375,6 +387,10 @@ const main = async () => {
       localStorage.setItem("openchamber_sync_perf", "1")
       localStorage.setItem("openchamber_stream_perf", "1")
     `)
+    if (options.expandProjects) {
+      await expandProjects(client)
+      console.log("Expanded every project in the sidebar.")
+    }
     loaded = client.once("Page.loadEventFired", 60_000)
     await client.send("Page.reload", { ignoreCache: false })
     await loaded
@@ -382,6 +398,12 @@ const main = async () => {
     console.log(`Opened the session; settling for ${options.settle}s.`)
     await wait(options.settle * 1000)
 
+    if (options.expandSessions) {
+      const expanded = await expandSessionLists(client)
+      console.log(`Expanded ${expanded} collapsed session lists; settling ${options.settle}s again.`)
+      await wait(options.settle * 1000)
+    }
+
     await evaluateValue(client, `globalThis[${JSON.stringify(IDLE_PROBE_GLOBAL)}]?.start()`)
     await evaluateValue(client, `window.__openchamberSyncPerformance?.reset()`)
     await evaluateValue(client, `window.__openchamberStreamPerformance?.setEnabled(true)`)
@@ -553,7 +575,7 @@ const main = async () => {
         listenerGrowth: delta("JSEventListeners"),
         heapStartMb: round(heapSamples.at(0) ?? 0),
         heapEndMb: round(heapSamples.at(-1) ?? 0),
-        heapMaxMb: round(Math.max(0, ...heapSamples)),
+        heapMaxMb: round(heapSamples.reduce((max, value) => Math.max(max, value), 0)),
         heapGrowthMbPerSecond: growthPerSecond(samples, "jsHeapUsedMb"),
       },
       frameLiveness,