diff --git a/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.spec.ts b/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.spec.ts
new file mode 100644
index 000000000..0d491b233
--- /dev/null
+++ b/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.spec.ts
@@ -0,0 +1,280 @@
+/* eslint-disable playwright/expect-expect -- These are Node assertion-based performance contract tests. */
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import {
+    captureRendererProcessRssSample,
+    createRendererProcessRssCapture,
+    type RendererProcessRssCapture,
+    type RendererProcessRssUnavailableReason,
+} from './renderer-process-rss-capture';
+
+const RENDERER_PID = 42;
+const RENDERER_CREATION_TIME = 1_721_234_567_890;
+
+interface MetricOverrides {
+    readonly creationTime?: unknown;
+    readonly pid?: unknown;
+    readonly type?: unknown;
+    readonly workingSetSize?: unknown;
+}
+
+function metric(overrides: MetricOverrides = {}): unknown {
+    return {
+        creationTime:
+            overrides.creationTime === undefined
+                ? RENDERER_CREATION_TIME
+                : overrides.creationTime,
+        memory: {
+            workingSetSize:
+                overrides.workingSetSize === undefined
+                    ? 1_234
+                    : overrides.workingSetSize,
+        },
+        pid: overrides.pid === undefined ? RENDERER_PID : overrides.pid,
+        type: overrides.type === undefined ? 'Tab' : overrides.type,
+    };
+}
+
+function assertUnavailable(
+    capture: RendererProcessRssCapture,
+    unavailableReason: RendererProcessRssUnavailableReason,
+    expected: {
+        readonly identity: RendererProcessRssCapture['identity'];
+        readonly missingSampleCount?: number;
+        readonly validSampleCount?: number;
+    }
+): void {
+    assert.deepEqual(capture, {
+        identity: expected.identity,
+        missingSampleCount: expected.missingSampleCount ?? 0,
+        peakRssBytes: null,
+        unavailableReason,
+        validSampleCount: expected.validSampleCount ?? 0,
+    });
+}
+
+test('binds only the exact BrowserWindow renderer identity and converts KiB to bytes once', () => {
+    const capture = createRendererProcessRssCapture(RENDERER_PID, [
+        metric({
+            creationTime: RENDERER_CREATION_TIME + 1,
+            pid: 900,
+            type: 'Renderer',
+            workingSetSize: 9_999_999,
+        }),
+        metric(),
+    ]);
+
+    assert.deepEqual(capture, {
+        identity: {
+            creationTime: RENDERER_CREATION_TIME,
+            pid: RENDERER_PID,
+        },
+        missingSampleCount: 0,
+        peakRssBytes: 1_263_616,
+        unavailableReason: null,
+        validSampleCount: 1,
+    });
+});
+
+test('accepts only exact Tab or Renderer process types and tracks the peak without mutating prior state', () => {
+    const initial = createRendererProcessRssCapture(RENDERER_PID, [
+        metric({ type: 'Tab', workingSetSize: 2_000 }),
+    ]);
+    const lower = captureRendererProcessRssSample(initial, RENDERER_PID, [
+        metric({ type: 'Renderer', workingSetSize: 1_500 }),
+        metric({
+            pid: 777,
+            type: 'Renderer',
+            workingSetSize: 8_000_000,
+        }),
+    ]);
+
+    assert.equal(initial.validSampleCount, 1);
+    assert.equal(initial.peakRssBytes, 2_048_000);
+    assert.deepEqual(lower, {
+        identity: {
+            creationTime: RENDERER_CREATION_TIME,
+            pid: RENDERER_PID,
+        },
+        missingSampleCount: 0,
+        peakRssBytes: 2_048_000,
+        unavailableReason: null,
+        validSampleCount: 2,
+    });
+
+    const higher = captureRendererProcessRssSample(lower, RENDERER_PID, [
+        metric({ workingSetSize: 2_500 }),
+    ]);
+    assert.equal(higher.peakRssBytes, 2_560_000);
+    assert.equal(higher.validSampleCount, 3);
+});
+
+test('fails closed when the BrowserWindow OS process id is invalid', () => {
+    for (const invalidPid of [0, -1, 1.5, Number.NaN, '42'] as const) {
+        assertUnavailable(
+            createRendererProcessRssCapture(invalidPid, [metric()]),
+            'renderer-os-pid-invalid',
+            { identity: null }
+        );
+    }
+});
+
+test('fails closed when the initial target metric is missing or ambiguous', () => {
+    assertUnavailable(
+        createRendererProcessRssCapture(RENDERER_PID, [
+            metric({ pid: 99, workingSetSize: 99_999 }),
+        ]),
+        'renderer-process-metric-missing-at-start',
+        {
+            identity: null,
+            missingSampleCount: 1,
+        }
+    );
+
+    assertUnavailable(
+        createRendererProcessRssCapture(RENDERER_PID, [
+            metric(),
+            metric({ type: 'Renderer', workingSetSize: 2_000 }),
+        ]),
+        'renderer-process-metric-ambiguous',
+        { identity: null }
+    );
+});
+
+test('fails closed for invalid initial type, creation time, or working set', () => {
+    const cases: ReadonlyArray<{
+        readonly metric: unknown;
+        readonly reason: RendererProcessRssUnavailableReason;
+    }> = [
+        {
+            metric: metric({ type: 'RendererHelper' }),
+            reason: 'renderer-process-metric-type-invalid',
+        },
+        {
+            metric: metric({ creationTime: '1721234567890' }),
+            reason: 'renderer-process-metric-creation-time-invalid',
+        },
+        {
+            metric: metric({ workingSetSize: Number.POSITIVE_INFINITY }),
+            reason: 'renderer-process-metric-working-set-invalid',
+        },
+        {
+            metric: metric({ workingSetSize: 0 }),
+            reason: 'renderer-process-metric-working-set-invalid',
+        },
+    ];
+
+    for (const testCase of cases) {
+        assertUnavailable(
+            createRendererProcessRssCapture(RENDERER_PID, [testCase.metric]),
+            testCase.reason,
+            { identity: null }
+        );
+    }
+});
+
+test('invalidates the capture when the bound renderer is missing and never recovers', () => {
+    const initial = createRendererProcessRssCapture(RENDERER_PID, [metric()]);
+    const missing = captureRendererProcessRssSample(initial, RENDERER_PID, [
+        metric({ pid: 700, workingSetSize: 9_999_999 }),
+    ]);
+
+    assertUnavailable(
+        missing,
+        'renderer-process-metric-missing-during-capture',
+        {
+            identity: initial.identity,
+            missingSampleCount: 1,
+            validSampleCount: 1,
+        }
+    );
+
+    const laterValid = captureRendererProcessRssSample(missing, RENDERER_PID, [
+        metric({ workingSetSize: 5_000 }),
+    ]);
+    assert.deepEqual(laterValid, missing);
+});
+
+test('invalidates the capture when the BrowserWindow or process metric identity changes', () => {
+    const initial = createRendererProcessRssCapture(RENDERER_PID, [metric()]);
+
+    assertUnavailable(
+        captureRendererProcessRssSample(initial, 43, [
+            metric({
+                creationTime: RENDERER_CREATION_TIME + 1,
+                pid: 43,
+            }),
+        ]),
+        'renderer-process-identity-changed',
+        {
+            identity: initial.identity,
+            validSampleCount: 1,
+        }
+    );
+
+    assertUnavailable(
+        captureRendererProcessRssSample(initial, RENDERER_PID, [
+            metric({ creationTime: RENDERER_CREATION_TIME + 1 }),
+        ]),
+        'renderer-process-identity-changed',
+        {
+            identity: initial.identity,
+            validSampleCount: 1,
+        }
+    );
+});
+
+test('fails closed for invalid or ambiguous metrics after binding', () => {
+    const initial = createRendererProcessRssCapture(RENDERER_PID, [metric()]);
+    const cases: ReadonlyArray<{
+        readonly metrics: readonly unknown[];
+        readonly reason: RendererProcessRssUnavailableReason;
+    }> = [
+        {
+            metrics: [metric(), metric({ type: 'Renderer' })],
+            reason: 'renderer-process-metric-ambiguous',
+        },
+        {
+            metrics: [metric({ type: 'RendererHelper' })],
+            reason: 'renderer-process-metric-type-invalid',
+        },
+        {
+            metrics: [metric({ creationTime: Number.NaN })],
+            reason: 'renderer-process-metric-creation-time-invalid',
+        },
+        {
+            metrics: [metric({ workingSetSize: -1 })],
+            reason: 'renderer-process-metric-working-set-invalid',
+        },
+    ];
+
+    for (const testCase of cases) {
+        assertUnavailable(
+            captureRendererProcessRssSample(
+                initial,
+                RENDERER_PID,
+                testCase.metrics
+            ),
+            testCase.reason,
+            {
+                identity: initial.identity,
+                validSampleCount: 1,
+            }
+        );
+    }
+});
+
+test('keeps invalid renderer PIDs sticky after binding', () => {
+    const initial = createRendererProcessRssCapture(RENDERER_PID, [metric()]);
+    const invalid = captureRendererProcessRssSample(initial, 0, [metric()]);
+
+    assertUnavailable(invalid, 'renderer-os-pid-invalid', {
+        identity: initial.identity,
+        validSampleCount: 1,
+    });
+    assert.deepEqual(
+        captureRendererProcessRssSample(invalid, RENDERER_PID, [metric()]),
+        invalid
+    );
+});
diff --git a/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.ts b/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.ts
new file mode 100644
index 000000000..bc2a09b8f
--- /dev/null
+++ b/apps/electron-backend-e2e/src/performance/renderer-process-rss-capture.ts
@@ -0,0 +1,199 @@
+export type RendererProcessRssUnavailableReason =
+    | 'renderer-os-pid-invalid'
+    | 'renderer-process-identity-changed'
+    | 'renderer-process-metric-ambiguous'
+    | 'renderer-process-metric-creation-time-invalid'
+    | 'renderer-process-metric-missing-at-start'
+    | 'renderer-process-metric-missing-during-capture'
+    | 'renderer-process-metric-type-invalid'
+    | 'renderer-process-metric-working-set-invalid';
+
+export interface RendererProcessIdentity {
+    readonly creationTime: number;
+    readonly pid: number;
+}
+
+export interface RendererProcessRssCapture {
+    readonly identity: RendererProcessIdentity | null;
+    readonly missingSampleCount: number;
+    readonly peakRssBytes: number | null;
+    readonly unavailableReason: RendererProcessRssUnavailableReason | null;
+    readonly validSampleCount: number;
+}
+
+type JsonRecord = Record<string, unknown>;
+
+const KIBIBYTE_BYTES = 1_024;
+const MAX_WORKING_SET_KIB = Math.floor(
+    Number.MAX_SAFE_INTEGER / KIBIBYTE_BYTES
+);
+
+function readRecord(value: unknown): JsonRecord | null {
+    return typeof value === 'object' && value !== null
+        ? (value as JsonRecord)
+        : null;
+}
+
+function isValidOsPid(value: unknown): value is number {
+    return Number.isSafeInteger(value) && Number(value) > 0;
+}
+
+function findPidCandidates(
+    processMetrics: readonly unknown[],
+    pid: number
+): JsonRecord[] {
+    return processMetrics
+        .map((metric) => readRecord(metric))
+        .filter(
+            (metric): metric is JsonRecord =>
+                metric !== null && metric['pid'] === pid
+        );
+}
+
+function readMetric(metric: JsonRecord):
+    | {
+          readonly creationTime: number;
+          readonly rssBytes: number;
+      }
+    | RendererProcessRssUnavailableReason {
+    if (metric['type'] !== 'Tab' && metric['type'] !== 'Renderer') {
+        return 'renderer-process-metric-type-invalid';
+    }
+
+    const creationTime = metric['creationTime'];
+    if (
+        typeof creationTime !== 'number' ||
+        !Number.isFinite(creationTime) ||
+        creationTime < 0
+    ) {
+        return 'renderer-process-metric-creation-time-invalid';
+    }
+
+    const memory = readRecord(metric['memory']);
+    const workingSetSize = memory?.['workingSetSize'];
+    if (
+        !Number.isSafeInteger(workingSetSize) ||
+        Number(workingSetSize) <= 0 ||
+        Number(workingSetSize) > MAX_WORKING_SET_KIB
+    ) {
+        return 'renderer-process-metric-working-set-invalid';
+    }
+
+    return {
+        creationTime,
+        rssBytes: Number(workingSetSize) * KIBIBYTE_BYTES,
+    };
+}
+
+function unavailableCapture(
+    unavailableReason: RendererProcessRssUnavailableReason,
+    options: {
+        readonly identity?: RendererProcessIdentity | null;
+        readonly missingSampleCount?: number;
+        readonly validSampleCount?: number;
+    } = {}
+): RendererProcessRssCapture {
+    return Object.freeze({
+        identity: options.identity ?? null,
+        missingSampleCount: options.missingSampleCount ?? 0,
+        peakRssBytes: null,
+        unavailableReason,
+        validSampleCount: options.validSampleCount ?? 0,
+    });
+}
+
+function invalidateCapture(
+    capture: RendererProcessRssCapture,
+    unavailableReason: RendererProcessRssUnavailableReason,
+    missingSampleCount = capture.missingSampleCount
+): RendererProcessRssCapture {
+    return unavailableCapture(unavailableReason, {
+        identity: capture.identity,
+        missingSampleCount,
+        validSampleCount: capture.validSampleCount,
+    });
+}
+
+export function createRendererProcessRssCapture(
+    webContentsOsPid: unknown,
+    processMetrics: readonly unknown[]
+): RendererProcessRssCapture {
+    if (!isValidOsPid(webContentsOsPid)) {
+        return unavailableCapture('renderer-os-pid-invalid');
+    }
+
+    const candidates = findPidCandidates(processMetrics, webContentsOsPid);
+    if (candidates.length === 0) {
+        return unavailableCapture('renderer-process-metric-missing-at-start', {
+            missingSampleCount: 1,
+        });
+    }
+    if (candidates.length !== 1) {
+        return unavailableCapture('renderer-process-metric-ambiguous');
+    }
+
+    const metric = readMetric(candidates[0] as JsonRecord);
+    if (typeof metric === 'string') {
+        return unavailableCapture(metric);
+    }
+
+    return Object.freeze({
+        identity: Object.freeze({
+            creationTime: metric.creationTime,
+            pid: webContentsOsPid,
+        }),
+        missingSampleCount: 0,
+        peakRssBytes: metric.rssBytes,
+        unavailableReason: null,
+        validSampleCount: 1,
+    });
+}
+
+export function captureRendererProcessRssSample(
+    capture: RendererProcessRssCapture,
+    webContentsOsPid: unknown,
+    processMetrics: readonly unknown[]
+): RendererProcessRssCapture {
+    if (capture.unavailableReason !== null) {
+        return capture;
+    }
+    if (!isValidOsPid(webContentsOsPid)) {
+        return invalidateCapture(capture, 'renderer-os-pid-invalid');
+    }
+
+    const identity = capture.identity;
+    if (identity === null || webContentsOsPid !== identity.pid) {
+        return invalidateCapture(capture, 'renderer-process-identity-changed');
+    }
+
+    const candidates = findPidCandidates(processMetrics, webContentsOsPid);
+    if (candidates.length === 0) {
+        return invalidateCapture(
+            capture,
+            'renderer-process-metric-missing-during-capture',
+            capture.missingSampleCount + 1
+        );
+    }
+    if (candidates.length !== 1) {
+        return invalidateCapture(capture, 'renderer-process-metric-ambiguous');
+    }
+
+    const metric = readMetric(candidates[0] as JsonRecord);
+    if (typeof metric === 'string') {
+        return invalidateCapture(capture, metric);
+    }
+    if (metric.creationTime !== identity.creationTime) {
+        return invalidateCapture(capture, 'renderer-process-identity-changed');
+    }
+
+    return Object.freeze({
+        identity,
+        missingSampleCount: capture.missingSampleCount,
+        peakRssBytes: Math.max(
+            capture.peakRssBytes ?? metric.rssBytes,
+            metric.rssBytes
+        ),
+        unavailableReason: null,
+        validSampleCount: capture.validSampleCount + 1,
+    });
+}