feat(test): refactor the memory usage test to use metrics from CLI process instead of test runner (#25708)

memory-tests/baselines.json

@@ -1,55 +1,55 @@
 {
   "version": 1,
-  "updatedAt": "2026-04-10T15:36:04.547Z",
+  "updatedAt": "2026-04-20T18:04:59.671Z",
   "scenarios": {
     "multi-turn-conversation": {
-      "heapUsedBytes": 120082704,
+      "heapUsedMB": 68.8,
-      "heapTotalBytes": 177586176,
+      "heapTotalMB": 91.2,
-      "rssBytes": 269172736,
+      "rssMB": 215.4,
-      "externalBytes": 4304053,
+      "externalMB": 93.8,
-      "timestamp": "2026-04-10T15:35:17.603Z"
+      "timestamp": "2026-04-20T18:02:40.101Z"
     },
     "multi-function-call-repo-search": {
-      "heapUsedBytes": 104644984,
+      "heapUsedMB": 73.5,
-      "heapTotalBytes": 111575040,
+      "heapTotalMB": 93.1,
-      "rssBytes": 204079104,
+      "rssMB": 223.6,
-      "externalBytes": 4304053,
+      "externalMB": 97.7,
-      "timestamp": "2026-04-10T15:35:22.480Z"
+      "timestamp": "2026-04-20T18:02:42.032Z"
     },
     "idle-session-startup": {
-      "heapUsedBytes": 119813672,
+      "heapUsedMB": 69.8,
-      "heapTotalBytes": 177061888,
+      "heapTotalMB": 92.4,
-      "rssBytes": 267943936,
+      "rssMB": 217.4,
-      "externalBytes": 4304053,
+      "externalMB": 93.8,
-      "timestamp": "2026-04-10T15:35:08.035Z"
+      "timestamp": "2026-04-20T18:02:36.294Z"
     },
     "simple-prompt-response": {
-      "heapUsedBytes": 119722064,
+      "heapUsedMB": 69.5,
-      "heapTotalBytes": 177324032,
+      "heapTotalMB": 92.4,
-      "rssBytes": 268812288,
+      "rssMB": 216.1,
-      "externalBytes": 4304053,
+      "externalMB": 93.8,
-      "timestamp": "2026-04-10T15:35:12.770Z"
+      "timestamp": "2026-04-20T18:02:38.198Z"
     },
     "resume-large-chat-with-messages": {
-      "heapUsedBytes": 106545568,
+      "heapUsedMB": 887.1,
-      "heapTotalBytes": 111509504,
+      "heapTotalMB": 954.3,
-      "rssBytes": 202596352,
+      "rssMB": 1109.6,
-      "externalBytes": 4306101,
+      "externalMB": 103.2,
-      "timestamp": "2026-04-10T15:36:04.547Z"
+      "timestamp": "2026-04-20T18:04:59.671Z"
     },
     "resume-large-chat": {
-      "heapUsedBytes": 106513760,
+      "heapUsedMB": 885.6,
-      "heapTotalBytes": 111509504,
+      "heapTotalMB": 955.6,
-      "rssBytes": 202596352,
+      "rssMB": 1107.8,
-      "externalBytes": 4306101,
+      "externalMB": 110.5,
-      "timestamp": "2026-04-10T15:35:59.528Z"
+      "timestamp": "2026-04-20T18:04:06.526Z"
     },
     "large-chat": {
-      "heapUsedBytes": 106471568,
+      "heapUsedMB": 158.5,
-      "heapTotalBytes": 111509504,
+      "heapTotalMB": 193,
-      "rssBytes": 202596352,
+      "rssMB": 787.9,
-      "externalBytes": 4306101,
+      "externalMB": 104,
-      "timestamp": "2026-04-10T15:35:53.180Z"
+      "timestamp": "2026-04-20T18:03:12.486Z"
     }
   }
 }

memory-tests/memory-usage.test.ts

@@ -16,15 +16,21 @@ import {
   mkdirSync,
   rmSync,
 } from 'node:fs';
-import { randomUUID } from 'node:crypto';
+import { randomUUID, createHash } from 'node:crypto';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const BASELINES_PATH = join(__dirname, 'baselines.json');
 const UPDATE_BASELINES = process.env['UPDATE_MEMORY_BASELINES'] === 'true';
+function getProjectHash(projectRoot: string): string {
+  return createHash('sha256').update(projectRoot).digest('hex');
+}
 const TOLERANCE_PERCENT = 10;
 
 // Fake API key for tests using fake responses
-const TEST_ENV = { GEMINI_API_KEY: 'fake-memory-test-key' };
+const TEST_ENV = {
+  GEMINI_API_KEY: 'fake-memory-test-key',
+  GEMINI_MEMORY_MONITOR_INTERVAL: '100',
+};
 
 describe('Memory Usage Tests', () => {
   let harness: MemoryTestHarness;
@@ -56,6 +62,7 @@ describe('Memory Usage Tests', () => {
     });
 
     const result = await harness.runScenario(
+      rig,
       'idle-session-startup',
       async (recordSnapshot) => {
         await rig.run({
@@ -85,6 +92,7 @@ describe('Memory Usage Tests', () => {
     });
 
     const result = await harness.runScenario(
+      rig,
       'simple-prompt-response',
       async (recordSnapshot) => {
         await rig.run({
@@ -122,6 +130,7 @@ describe('Memory Usage Tests', () => {
     ];
 
     const result = await harness.runScenario(
+      rig,
       'multi-turn-conversation',
       async (recordSnapshot) => {
         // Run through all turns as a piped sequence
@@ -144,6 +153,9 @@ describe('Memory Usage Tests', () => {
       );
     } else {
       harness.assertWithinBaseline(result);
+      harness.assertMemoryReturnsToBaseline(result.snapshots, 20);
+      const { leaked, message } = harness.analyzeSnapshots(result.snapshots);
+      if (leaked) console.warn(`⚠ ${message}`);
     }
   });
 
@@ -168,6 +180,7 @@ describe('Memory Usage Tests', () => {
     );
 
     const result = await harness.runScenario(
+      rig,
       'multi-function-call-repo-search',
       async (recordSnapshot) => {
         await rig.run({
@@ -189,6 +202,7 @@ describe('Memory Usage Tests', () => {
       );
     } else {
       harness.assertWithinBaseline(result);
+      harness.assertMemoryReturnsToBaseline(result.snapshots, 20);
     }
   });
 
@@ -228,6 +242,7 @@ describe('Memory Usage Tests', () => {
       });
 
       const result = await harness.runScenario(
+        rig,
         'large-chat',
         async (recordSnapshot) => {
           await rig.run({
@@ -257,19 +272,21 @@ describe('Memory Usage Tests', () => {
       });
 
       const result = await harness.runScenario(
+        rig,
         'resume-large-chat',
         async (recordSnapshot) => {
           // Ensure the history file is linked
           const targetChatsDir = join(
-            rig.testDir!,
+            rig.homeDir!,
+            '.gemini',
             'tmp',
-            'test-project-hash',
+            getProjectHash(rig.testDir!),
             'chats',
           );
           mkdirSync(targetChatsDir, { recursive: true });
           const targetHistoryPath = join(
             targetChatsDir,
-            'large-chat-session.json',
+            'session-large-chat.json',
           );
           if (existsSync(targetHistoryPath)) rmSync(targetHistoryPath);
           copyFileSync(sharedHistoryPath, targetHistoryPath);
@@ -302,19 +319,21 @@ describe('Memory Usage Tests', () => {
       });
 
       const result = await harness.runScenario(
+        rig,
         'resume-large-chat-with-messages',
         async (recordSnapshot) => {
           // Ensure the history file is linked
           const targetChatsDir = join(
-            rig.testDir!,
+            rig.homeDir!,
+            '.gemini',
             'tmp',
-            'test-project-hash',
+            getProjectHash(rig.testDir!),
             'chats',
           );
           mkdirSync(targetChatsDir, { recursive: true });
           const targetHistoryPath = join(
             targetChatsDir,
-            'large-chat-session.json',
+            'session-large-chat.json',
           );
           if (existsSync(targetHistoryPath)) rmSync(targetHistoryPath);
           copyFileSync(sharedHistoryPath, targetHistoryPath);
@@ -457,6 +476,9 @@ async function generateSharedLargeChatData(tempDir: string) {
   // Generate responses for resumed chat
   const resumeResponsesStream = createWriteStream(resumeResponsesPath);
   for (let i = 0; i < 5; i++) {
+    // Doubling up on non-streaming responses to satisfy classifier and complexity checks
+    resumeResponsesStream.write(JSON.stringify(complexityResponse) + '\n');
+    resumeResponsesStream.write(JSON.stringify(summaryResponse) + '\n');
     resumeResponsesStream.write(JSON.stringify(complexityResponse) + '\n');
     resumeResponsesStream.write(
       JSON.stringify({

packages/test-utils/src/memory-baselines.ts

@@ -10,10 +10,10 @@ import { readFileSync, writeFileSync, existsSync } from 'node:fs';
  * Baseline entry for a single memory test scenario.
  */
 export interface MemoryBaseline {
-  heapUsedBytes: number;
+  heapUsedMB: number;
-  heapTotalBytes: number;
+  heapTotalMB: number;
-  rssBytes: number;
+  rssMB: number;
-  externalBytes: number;
+  externalMB: number;
   timestamp: string;
 }
 
@@ -61,18 +61,18 @@ export function updateBaseline(
   path: string,
   scenarioName: string,
   measured: {
-    heapUsedBytes: number;
+    heapUsedMB: number;
-    heapTotalBytes: number;
+    heapTotalMB: number;
-    rssBytes: number;
+    rssMB: number;
-    externalBytes: number;
+    externalMB: number;
   },
 ): void {
   const baselines = loadBaselines(path);
   baselines.scenarios[scenarioName] = {
-    heapUsedBytes: measured.heapUsedBytes,
+    heapUsedMB: measured.heapUsedMB,
-    heapTotalBytes: measured.heapTotalBytes,
+    heapTotalMB: measured.heapTotalMB,
-    rssBytes: measured.rssBytes,
+    rssMB: measured.rssMB,
-    externalBytes: measured.externalBytes,
+    externalMB: measured.externalMB,
     timestamp: new Date().toISOString(),
   };
   saveBaselines(path, baselines);

packages/test-utils/src/memory-test-harness.ts

@@ -4,10 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import v8 from 'node:v8';
-import { setTimeout as sleep } from 'node:timers/promises';
 import { loadBaselines, updateBaseline } from './memory-baselines.js';
 import type { MemoryBaseline, MemoryBaselineFile } from './memory-baselines.js';
+import type { TestRig } from './test-rig.js';
 
 /** Configuration for asciichart plot function. */
 interface PlotConfig {
@@ -28,9 +27,6 @@ export interface MemorySnapshot {
   heapTotal: number;
   rss: number;
   external: number;
-  arrayBuffers: number;
-  heapSizeLimit: number;
-  heapSpaces: any[];
 }
 
 /**
@@ -64,16 +60,13 @@ export interface MemoryTestHarnessOptions {
   gcDelayMs?: number;
   /** Number of samples to take for median calculation. Default: 3 */
   sampleCount?: number;
-  /** Pause in ms between samples. Default: 50 */
-  samplePauseMs?: number;
 }
 
 /**
  * MemoryTestHarness provides infrastructure for running memory usage tests.
  *
  * It handles:
- * - Forcing V8 garbage collection to reduce noise
+ * - Extracting memory metrics from CLI process telemetry
- * - Taking V8 heap snapshots for accurate memory measurement
  * - Comparing against baselines with configurable tolerance
  * - Generating ASCII chart reports of memory trends
  */
@@ -81,88 +74,45 @@ export class MemoryTestHarness {
   private baselines: MemoryBaselineFile;
   private readonly baselinesPath: string;
   private readonly defaultTolerancePercent: number;
-  private readonly gcCycles: number;
-  private readonly gcDelayMs: number;
-  private readonly sampleCount: number;
-  private readonly samplePauseMs: number;
   private allResults: MemoryTestResult[] = [];
 
   constructor(options: MemoryTestHarnessOptions) {
     this.baselinesPath = options.baselinesPath;
     this.defaultTolerancePercent = options.defaultTolerancePercent ?? 10;
-    this.gcCycles = options.gcCycles ?? 3;
-    this.gcDelayMs = options.gcDelayMs ?? 100;
-    this.sampleCount = options.sampleCount ?? 3;
-    this.samplePauseMs = options.samplePauseMs ?? 50;
     this.baselines = loadBaselines(this.baselinesPath);
   }
 
   /**
-   * Force garbage collection multiple times and take a V8 heap snapshot.
+   * Extract memory snapshot from TestRig telemetry.
-   * Forces GC multiple times with delays to allow weak references and
-   * FinalizationRegistry callbacks to run, reducing measurement noise.
    */
-  async takeSnapshot(label: string = 'snapshot'): Promise<MemorySnapshot> {
+  async takeSnapshot(
-    await this.forceGC();
+    rig: TestRig,
-
+    label: string = 'snapshot',
-    const memUsage = process.memoryUsage();
+    strategy: 'peak' | 'last' = 'last',
-    const heapStats = v8.getHeapStatistics();
-
-    return {
-      timestamp: Date.now(),
-      label,
-      heapUsed: memUsage.heapUsed,
-      heapTotal: memUsage.heapTotal,
-      rss: memUsage.rss,
-      external: memUsage.external,
-      arrayBuffers: memUsage.arrayBuffers,
-      heapSizeLimit: heapStats.heap_size_limit,
-      heapSpaces: v8.getHeapSpaceStatistics(),
-    };
-  }
-
-  /**
-   * Take multiple snapshot samples and return the median to reduce noise.
-   */
-  async takeMedianSnapshot(
-    label: string = 'median',
-    count?: number,
   ): Promise<MemorySnapshot> {
-    const samples: MemorySnapshot[] = [];
+    const metrics = rig.readMemoryMetrics(strategy);
-    const numSamples = count ?? this.sampleCount;
-
-    for (let i = 0; i < numSamples; i++) {
-      samples.push(await this.takeSnapshot(`${label}_sample_${i}`));
-      if (i < numSamples - 1) {
-        await sleep(this.samplePauseMs);
-      }
-    }
-
-    // Sort by heapUsed and take the median
-    samples.sort((a, b) => a.heapUsed - b.heapUsed);
-    const medianIdx = Math.floor(samples.length / 2);
-    const median = samples[medianIdx]!;
 
     return {
-      ...median,
+      timestamp: metrics.timestamp,
       label,
-      timestamp: Date.now(),
+      heapUsed: metrics.heapUsed,
+      heapTotal: metrics.heapTotal,
+      rss: metrics.rss,
+      external: metrics.external,
     };
   }
 
   /**
    * Run a memory test scenario.
    *
-   * Takes before/after snapshots around the scenario function, collects
+   * @param rig - The TestRig instance running the CLI
-   * intermediate snapshots if the scenario provides them, and compares
-   * the result against the stored baseline.
-   *
    * @param name - Scenario name (must match baseline key)
    * @param fn - Async function that executes the scenario. Receives a
    *   `recordSnapshot` callback for recording intermediate snapshots.
    * @param tolerancePercent - Override default tolerance for this scenario
    */
   async runScenario(
+    rig: TestRig,
     name: string,
     fn: (
       recordSnapshot: (label: string) => Promise<MemorySnapshot>,
@@ -172,27 +122,49 @@ export class MemoryTestHarness {
     const tolerance = tolerancePercent ?? this.defaultTolerancePercent;
     const snapshots: MemorySnapshot[] = [];
 
+    // Record initial snapshot
+    const beforeSnap = await this.takeSnapshot(rig, 'before');
+    snapshots.push(beforeSnap);
+
     // Record a callback for intermediate snapshots
     const recordSnapshot = async (label: string): Promise<MemorySnapshot> => {
-      const snap = await this.takeMedianSnapshot(label);
+      // Small delay to allow telemetry to flush if needed
+      await rig.waitForTelemetryReady();
+      const snap = await this.takeSnapshot(rig, label);
       snapshots.push(snap);
       return snap;
     };
 
-    // Before snapshot
-    const beforeSnap = await this.takeMedianSnapshot('before');
-    snapshots.push(beforeSnap);
-
     // Run the scenario
     await fn(recordSnapshot);
 
-    // After snapshot (median of multiple samples)
+    // Final wait for telemetry to ensure everything is flushed
-    const afterSnap = await this.takeMedianSnapshot('after');
+    await rig.waitForTelemetryReady();
+
+    // After snapshot
+    const afterSnap = await this.takeSnapshot(rig, 'after');
     snapshots.push(afterSnap);
 
-    // Calculate peak values
+    // Calculate peak values from ALL snapshots seen during the scenario
-    const peakHeapUsed = Math.max(...snapshots.map((s) => s.heapUsed));
+    const allSnapshots = rig.readAllMemorySnapshots();
-    const peakRss = Math.max(...snapshots.map((s) => s.rss));
+    const scenarioSnapshots = allSnapshots.filter(
+      (s) =>
+        s.timestamp >= beforeSnap.timestamp &&
+        s.timestamp <= afterSnap.timestamp,
+    );
+
+    const peakHeapUsed = Math.max(
+      ...scenarioSnapshots.map((s) => s.heapUsed),
+      ...snapshots.map((s) => s.heapUsed),
+    );
+    const peakRss = Math.max(
+      ...scenarioSnapshots.map((s) => s.rss),
+      ...snapshots.map((s) => s.rss),
+    );
+    const peakExternal = Math.max(
+      ...scenarioSnapshots.map((s) => s.external),
+      ...snapshots.map((s) => s.external),
+    );
 
     // Get baseline
     const baseline = this.baselines.scenarios[name];
@@ -202,15 +174,12 @@ export class MemoryTestHarness {
     let withinTolerance = true;
 
     if (baseline) {
+      const measuredMB = afterSnap.heapUsed / (1024 * 1024);
       deltaPercent =
-        ((afterSnap.heapUsed - baseline.heapUsedBytes) /
+        ((measuredMB - baseline.heapUsedMB) / baseline.heapUsedMB) * 100;
-          baseline.heapUsedBytes) *
-        100;
       withinTolerance = deltaPercent <= tolerance;
     }
 
-    const peakExternal = Math.max(...snapshots.map((s) => s.external));
-
     const result: MemoryTestResult = {
       scenarioName: name,
       snapshots,
@@ -248,16 +217,16 @@ export class MemoryTestHarness {
       return; // Don't fail if no baseline exists yet
     }
 
+    const measuredMB = result.finalHeapUsed / (1024 * 1024);
     const deltaPercent =
-      ((result.finalHeapUsed - result.baseline.heapUsedBytes) /
+      ((measuredMB - result.baseline.heapUsedMB) / result.baseline.heapUsedMB) *
-        result.baseline.heapUsedBytes) *
       100;
 
     if (deltaPercent > tolerance) {
       throw new Error(
         `Memory regression detected for "${result.scenarioName}"!\n` +
           `  Measured:  ${formatMB(result.finalHeapUsed)} heap used\n` +
-          `  Baseline:  ${formatMB(result.baseline.heapUsedBytes)} heap used\n` +
+          `  Baseline:  ${result.baseline.heapUsedMB.toFixed(1)} MB heap used\n` +
           `  Delta:     ${deltaPercent.toFixed(1)}% (tolerance: ${tolerance}%)\n` +
           `  Peak heap: ${formatMB(result.peakHeapUsed)}\n` +
           `  Peak RSS:  ${formatMB(result.peakRss)}\n` +
@@ -270,20 +239,22 @@ export class MemoryTestHarness {
    * Update the baseline for a scenario with the current measured values.
    */
   updateScenarioBaseline(result: MemoryTestResult): void {
+    const lastSnapshot = result.snapshots[result.snapshots.length - 1];
     updateBaseline(this.baselinesPath, result.scenarioName, {
-      heapUsedBytes: result.finalHeapUsed,
+      heapUsedMB: Number((result.finalHeapUsed / (1024 * 1024)).toFixed(1)),
-      heapTotalBytes:
+      heapTotalMB: Number(
-        result.snapshots[result.snapshots.length - 1]?.heapTotal ?? 0,
+        ((lastSnapshot?.heapTotal ?? 0) / (1024 * 1024)).toFixed(1),
-      rssBytes: result.finalRss,
+      ),
-      externalBytes: result.finalExternal,
+      rssMB: Number((result.finalRss / (1024 * 1024)).toFixed(1)),
+      externalMB: Number((result.finalExternal / (1024 * 1024)).toFixed(1)),
     });
     // Reload baselines after update
     this.baselines = loadBaselines(this.baselinesPath);
   }
 
   /**
-   * Analyze snapshots to detect sustained leaks across 3 snapshots.
+   * Analyze snapshots to detect sustained leaks.
-   * A leak is flagged if growth is observed in both phases for any heap space.
+   * A leak is flagged if growth is observed in both phases.
    */
   analyzeSnapshots(
     snapshots: MemorySnapshot[],
@@ -297,55 +268,20 @@ export class MemoryTestHarness {
     const snap2 = snapshots[snapshots.length - 2];
     const snap3 = snapshots[snapshots.length - 1];
 
-    if (!snap1 || !snap2 || !snap3) {
+    const growth1 = snap2.heapUsed - snap1.heapUsed;
-      return { leaked: false, message: 'Missing snapshots' };
+    const growth2 = snap3.heapUsed - snap2.heapUsed;
-    }
 
-    const spaceNames = new Set<string>();
+    const leaked = growth1 > thresholdBytes && growth2 > thresholdBytes;
-    snap1.heapSpaces.forEach((s: any) => spaceNames.add(s.space_name));
+    let message = leaked
-    snap2.heapSpaces.forEach((s: any) => spaceNames.add(s.space_name));
+      ? `Memory bloat detected: sustained growth (${formatMB(growth1)} -> ${formatMB(growth2)})`
-    snap3.heapSpaces.forEach((s: any) => spaceNames.add(s.space_name));
+      : `No sustained growth detected above threshold.`;
 
-    let hasSustainedGrowth = false;
+    return { leaked, message };
-    const growthDetails: string[] = [];
-
-    for (const name of spaceNames) {
-      const size1 =
-        snap1.heapSpaces.find((s: any) => s.space_name === name)
-          ?.space_used_size ?? 0;
-      const size2 =
-        snap2.heapSpaces.find((s: any) => s.space_name === name)
-          ?.space_used_size ?? 0;
-      const size3 =
-        snap3.heapSpaces.find((s: any) => s.space_name === name)
-          ?.space_used_size ?? 0;
-
-      const growth1 = size2 - size1;
-      const growth2 = size3 - size2;
-
-      if (growth1 > thresholdBytes && growth2 > thresholdBytes) {
-        hasSustainedGrowth = true;
-        growthDetails.push(
-          `${name}: sustained growth (${formatMB(growth1)} -> ${formatMB(growth2)})`,
-        );
-      }
-    }
-
-    let message = '';
-    if (hasSustainedGrowth) {
-      message =
-        `Memory bloat detected in heap spaces:\n  ` +
-        growthDetails.join('\n  ');
-    } else {
-      message = `No sustained growth detected in any heap space above threshold.`;
-    }
-
-    return { leaked: hasSustainedGrowth, message };
   }
 
   /**
    * Assert that memory returns to a baseline level after a peak.
-   * Useful for verifying that large tool outputs are not retained.
+   * Useful for verifying that large tool outputs or history are not retained.
    */
   assertMemoryReturnsToBaseline(
     snapshots: MemorySnapshot[],
@@ -355,26 +291,22 @@ export class MemoryTestHarness {
       throw new Error('Need at least 3 snapshots to check return to baseline');
     }
 
-    const baseline = snapshots[0]; // Assume first is baseline
+    // Find the first non-zero snapshot as baseline
-    const peak = snapshots.reduce(
+    const baseline = snapshots.find((s) => s.heapUsed > 0);
-      (max, s) => (s.heapUsed > max.heapUsed ? s : max),
+    if (!baseline) {
-      snapshots[0],
+      return; // No memory reported yet
-    );
-    const final = snapshots[snapshots.length - 1];
-
-    if (!baseline || !peak || !final) {
-      throw new Error('Missing snapshots for return to baseline check');
     }
 
+    const final = snapshots[snapshots.length - 1]!;
+
     const tolerance = baseline.heapUsed * (tolerancePercent / 100);
     const delta = final.heapUsed - baseline.heapUsed;
 
     if (delta > tolerance) {
       throw new Error(
         `Memory did not return to baseline!\n` +
-          `  Baseline: ${formatMB(baseline.heapUsed)}\n` +
+          `  Baseline: ${formatMB(baseline.heapUsed)} (${baseline.label})\n` +
-          `  Peak:     ${formatMB(peak.heapUsed)}\n` +
+          `  Final:    ${formatMB(final.heapUsed)} (${final.label})\n` +
-          `  Final:    ${formatMB(final.heapUsed)}\n` +
           `  Delta:    ${formatMB(delta)} (tolerance: ${formatMB(tolerance)})`,
       );
     }
@@ -397,7 +329,7 @@ export class MemoryTestHarness {
     for (const result of resultsToReport) {
       const measured = formatMB(result.finalHeapUsed);
       const baseline = result.baseline
-        ? formatMB(result.baseline.heapUsedBytes)
+        ? `${result.baseline.heapUsedMB.toFixed(1)} MB`
         : 'N/A';
       const delta = result.baseline
         ? `${result.deltaPercent >= 0 ? '+' : ''}${result.deltaPercent.toFixed(1)}%`
@@ -461,26 +393,6 @@ export class MemoryTestHarness {
     console.log(report);
     return report;
   }
-
-  /**
-   * Force V8 garbage collection.
-   * Runs multiple GC cycles with delays to allow weak references
-   * and FinalizationRegistry callbacks to run.
-   */
-  private async forceGC(): Promise<void> {
-    if (typeof globalThis.gc !== 'function') {
-      throw new Error(
-        'global.gc() not available. Run with --expose-gc for accurate measurements.',
-      );
-    }
-
-    for (let i = 0; i < this.gcCycles; i++) {
-      globalThis.gc();
-      if (i < this.gcCycles - 1) {
-        await sleep(this.gcDelayMs);
-      }
-    }
-  }
 }
 
 /**

packages/test-utils/src/test-rig.ts

@@ -1475,7 +1475,7 @@ export class TestRig {
   readMetric(metricName: string): TelemetryMetric | null {
     const logs = this._readAndParseTelemetryLog();
     for (const logData of logs) {
-      if (logData.scopeMetrics) {
+      if (logData && logData.scopeMetrics) {
         for (const scopeMetric of logData.scopeMetrics) {
           for (const metric of scopeMetric.metrics) {
             if (metric.descriptor.name === `gemini_cli.${metricName}`) {
@@ -1488,6 +1488,133 @@ export class TestRig {
     return null;
   }
 
+  readMemoryMetrics(strategy: 'peak' | 'last' = 'peak'): {
+    timestamp: number;
+    heapUsed: number;
+    heapTotal: number;
+    rss: number;
+    external: number;
+  } {
+    const snapshots = this._getMemorySnapshots();
+    if (snapshots.length === 0) {
+      return {
+        timestamp: Date.now(),
+        heapUsed: 0,
+        heapTotal: 0,
+        rss: 0,
+        external: 0,
+      };
+    }
+
+    if (strategy === 'last') {
+      const last = snapshots[snapshots.length - 1];
+      return {
+        timestamp: last.timestamp,
+        heapUsed: last.heapUsed,
+        heapTotal: last.heapTotal,
+        rss: last.rss,
+        external: last.external,
+      };
+    }
+
+    // Find the snapshot with the highest RSS
+    let peak = snapshots[0];
+    for (const snapshot of snapshots) {
+      if (snapshot.rss > peak.rss) {
+        peak = snapshot;
+      }
+    }
+
+    // Fallback: if we didn't find any RSS but found heap, use the max heap
+    if (peak.rss === 0) {
+      for (const snapshot of snapshots) {
+        if (snapshot.heapUsed > peak.heapUsed) {
+          peak = snapshot;
+        }
+      }
+    }
+
+    return {
+      timestamp: peak.timestamp,
+      heapUsed: peak.heapUsed,
+      heapTotal: peak.heapTotal,
+      rss: peak.rss,
+      external: peak.external,
+    };
+  }
+
+  readAllMemorySnapshots(): {
+    timestamp: number;
+    heapUsed: number;
+    heapTotal: number;
+    rss: number;
+    external: number;
+  }[] {
+    return this._getMemorySnapshots();
+  }
+
+  private _getMemorySnapshots(): {
+    timestamp: number;
+    heapUsed: number;
+    heapTotal: number;
+    rss: number;
+    external: number;
+  }[] {
+    const snapshots: Record<
+      string,
+      {
+        timestamp: number;
+        heapUsed: number;
+        heapTotal: number;
+        rss: number;
+        external: number;
+      }
+    > = {};
+
+    const logs = this._readAndParseTelemetryLog();
+    for (const logData of logs) {
+      if (logData && logData.scopeMetrics) {
+        for (const scopeMetric of logData.scopeMetrics) {
+          for (const metric of scopeMetric.metrics) {
+            if (metric.descriptor.name === 'gemini_cli.memory.usage') {
+              for (const dp of metric.dataPoints) {
+                const sessionId =
+                  (dp.attributes?.['session.id'] as string) || 'unknown';
+                const component =
+                  (dp.attributes?.['component'] as string) || 'unknown';
+                const seconds = dp.startTime?.[0] || 0;
+                const nanos = dp.startTime?.[1] || 0;
+                const timeKey = `${sessionId}-${component}-${seconds}-${nanos}`;
+
+                if (!snapshots[timeKey]) {
+                  snapshots[timeKey] = {
+                    timestamp: seconds * 1000 + Math.floor(nanos / 1000000),
+                    rss: 0,
+                    heapUsed: 0,
+                    heapTotal: 0,
+                    external: 0,
+                  };
+                }
+
+                const type = dp.attributes?.['memory_type'];
+                const value = dp.value?.max ?? dp.value?.sum ?? 0;
+
+                if (type === 'heap_used') snapshots[timeKey].heapUsed = value;
+                else if (type === 'heap_total')
+                  snapshots[timeKey].heapTotal = value;
+                else if (type === 'rss') snapshots[timeKey].rss = value;
+                else if (type === 'external')
+                  snapshots[timeKey].external = value;
+              }
+            }
+          }
+        }
+      }
+    }
+
+    return Object.values(snapshots).sort((a, b) => a.timestamp - b.timestamp);
+  }
+
   async runInteractive(options?: {
     args?: string | string[];
     approvalMode?: 'default' | 'auto_edit' | 'yolo' | 'plan';