diff --git a/apps/api/src/services/warehouse/web-analytics-parity.clickhouse.e2e.test.ts b/apps/api/src/services/warehouse/web-analytics-parity.clickhouse.e2e.test.ts
index f50a2d6ae..698c415fc 100644
--- a/apps/api/src/services/warehouse/web-analytics-parity.clickhouse.e2e.test.ts
+++ b/apps/api/src/services/warehouse/web-analytics-parity.clickhouse.e2e.test.ts
@@ -227,14 +227,23 @@ const seed = async (): Promise<void> => {
 		database,
 	)
 
-	const sessionRows = SEED_SESSIONS.map(
-		(row) =>
-			`(${quote(ORG_ID)}, ${quote(row.sessionId)}, ${quote(row.startTime)}, ${row.durationMs}, ${row.pageViews}, ${row.version}, ${quote(row.visitorId)}, ${row.visitorIsNew}, ${quote(row.referrerHost)}, ${quote(row.country)}, ${quote(row.deviceType)}, ${quote(row.browserName)}, ${quote(row.osName)}, ${quote(row.language)}, ${quote(row.utmSource)}, ${quote(row.host)}, ${quote(row.entryPath)}, ${quote(row.exitPath)})`,
-	).join(",\n")
-	await clickhouseExec(
-		`INSERT INTO session_replays (OrgId, SessionId, StartTime, DurationMs, PageViews, Version, VisitorId, VisitorIsNew, ReferrerHost, Country, DeviceType, BrowserName, OsName, Language, UtmSource, Host, EntryPath, ExitPath) VALUES\n${sessionRows}`,
-		database,
-	)
+	// One INSERT per version, with merges held off. `optimize_on_insert` is on by
+	// default, so a single block collapses a ReplacingMergeTree's duplicates
+	// before they are ever visible — seeding that way leaves this suite asserting
+	// over pre-deduplicated rows, which is the one state it exists to rule out.
+	await clickhouseExec(`SYSTEM STOP MERGES session_replays`, database)
+	for (const version of [...new Set(SEED_SESSIONS.map((row) => row.version))].sort()) {
+		const sessionRows = SEED_SESSIONS.filter((row) => row.version === version)
+			.map(
+				(row) =>
+					`(${quote(ORG_ID)}, ${quote(row.sessionId)}, ${quote(row.startTime)}, ${row.durationMs}, ${row.pageViews}, ${row.version}, ${quote(row.visitorId)}, ${row.visitorIsNew}, ${quote(row.referrerHost)}, ${quote(row.country)}, ${quote(row.deviceType)}, ${quote(row.browserName)}, ${quote(row.osName)}, ${quote(row.language)}, ${quote(row.utmSource)}, ${quote(row.host)}, ${quote(row.entryPath)}, ${quote(row.exitPath)})`,
+			)
+			.join(",\n")
+		await clickhouseExec(
+			`INSERT INTO session_replays (OrgId, SessionId, StartTime, DurationMs, PageViews, Version, VisitorId, VisitorIsNew, ReferrerHost, Country, DeviceType, BrowserName, OsName, Language, UtmSource, Host, EntryPath, ExitPath) VALUES\n${sessionRows}`,
+			database,
+		)
+	}
 }
 
 const runJson = async (sql: string): Promise<ReadonlyArray<Record<string, unknown>>> => {
@@ -420,6 +429,25 @@ describe.skipIf(!clickhouseE2eEnabled)("web analytics raw-vs-rollup parity", ()
 		assert.strictEqual(Number(drift[0]?.n), 0, "write-time URL parsing diverged from read-time")
 	})
 
+	/**
+	 * Parity is an equality between two sources, so it holds just as well when
+	 * both are wrong. `session_replays` is a `ReplacingMergeTree(Version)` and the
+	 * seed's s1/s2 carry an un-merged v1 (`PageViews = 0`) beside a v2 reporting
+	 * two page views: a `uniqIf(SessionId, PageViews <= 1)` matches on the v1 row
+	 * and calls every one of them a bounce.
+	 */
+	it("counts a bounce from the session's latest version, not any version", async () => {
+		const rows = await runJson(
+			CH.compileUnsafe(CH.webAnalyticsSummaryQuery({ useProductEvents: false }), window).sql,
+		)
+		const row = rows[0]
+		assert.isDefined(row, "summary returned no rows")
+		// s1 and s2 ended on two page views; only s3, still on its start row, is a
+		// bounce. s4 carries no VisitorId and is outside the measured population.
+		assert.strictEqual(Number(row?.identifiedSessions), 3)
+		assert.strictEqual(Number(row?.bouncedSessions), 1)
+	})
+
 	// A `for` loop, not `describe.each`: the latter OOMs tsc in this repo.
 	for (const query of QUERIES) {
 		for (const filterCase of FILTER_CASES) {
diff --git a/packages/query-engine/src/__sql_baseline__/catalog.sql b/packages/query-engine/src/__sql_baseline__/catalog.sql
index c07c7bb26..7338e2d27 100644
--- a/packages/query-engine/src/__sql_baseline__/catalog.sql
+++ b/packages/query-engine/src/__sql_baseline__/catalog.sql
@@ -5019,12 +5019,12 @@ SELECT
         ORDER BY bucket ASC
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsSummaryQuery:default  [74bf3d64]
+-- builder:web-analytics:webAnalyticsSummaryQuery:default  [9a0359fc]
 SELECT
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           uniqIf(SessionId, multiSearchAnyCaseInsensitive(UserAgent, ['GPTBot', 'OAI-SearchBot', 'ChatGPT-User', 'ClaudeBot', 'Claude-User', 'PerplexityBot', 'Google-Extended', 'Applebot-Extended', 'meta-externalagent', 'meta-webindexer', 'Bytespider', 'CCBot', 'Amazonbot', 'DuckAssistBot', 'Googlebot', 'GoogleOther', 'AdsBot-Google', 'Google-Read-Aloud', 'bingbot', 'YandexBot', 'Baiduspider', 'DuckDuckBot', 'Applebot', 'Sogou', 'SeznamBot', 'AhrefsSiteAudit', 'AhrefsBot', 'SemrushBot', 'DataForSeoBot', 'DotBot', 'MJ12bot', 'Barkrowler', 'Screaming Frog', 'facebookexternalhit', 'Twitterbot', 'LinkedInBot', 'Slackbot', 'Discordbot', 'TelegramBot', 'Pinterest', 'HubSpot Crawler', 'Stripebot', 'UptimeRobot', 'Pingdom', 'StatusCake', 'Headless', 'bot/', 'bot\x3B', 'bot)', 'crawler', 'spider', '+http'])) AS botSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
@@ -5034,12 +5034,12 @@ SELECT
           AND StartTime <= '2026-01-03 14:15:00'
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsSummaryQuery:default-rollup  [74bf3d64]
+-- builder:web-analytics:webAnalyticsSummaryQuery:default-rollup  [9a0359fc]
 SELECT
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           uniqIf(SessionId, multiSearchAnyCaseInsensitive(UserAgent, ['GPTBot', 'OAI-SearchBot', 'ChatGPT-User', 'ClaudeBot', 'Claude-User', 'PerplexityBot', 'Google-Extended', 'Applebot-Extended', 'meta-externalagent', 'meta-webindexer', 'Bytespider', 'CCBot', 'Amazonbot', 'DuckAssistBot', 'Googlebot', 'GoogleOther', 'AdsBot-Google', 'Google-Read-Aloud', 'bingbot', 'YandexBot', 'Baiduspider', 'DuckDuckBot', 'Applebot', 'Sogou', 'SeznamBot', 'AhrefsSiteAudit', 'AhrefsBot', 'SemrushBot', 'DataForSeoBot', 'DotBot', 'MJ12bot', 'Barkrowler', 'Screaming Frog', 'facebookexternalhit', 'Twitterbot', 'LinkedInBot', 'Slackbot', 'Discordbot', 'TelegramBot', 'Pinterest', 'HubSpot Crawler', 'Stripebot', 'UptimeRobot', 'Pingdom', 'StatusCake', 'Headless', 'bot/', 'bot\x3B', 'bot)', 'crawler', 'spider', '+http'])) AS botSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
@@ -5049,12 +5049,12 @@ SELECT
           AND StartTime <= '2026-01-03 14:15:00'
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsSummaryQuery:filtered  [816bf9de]
+-- builder:web-analytics:webAnalyticsSummaryQuery:filtered  [7be4ede6]
 SELECT
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           uniqIf(SessionId, multiSearchAnyCaseInsensitive(UserAgent, ['GPTBot', 'OAI-SearchBot', 'ChatGPT-User', 'ClaudeBot', 'Claude-User', 'PerplexityBot', 'Google-Extended', 'Applebot-Extended', 'meta-externalagent', 'meta-webindexer', 'Bytespider', 'CCBot', 'Amazonbot', 'DuckAssistBot', 'Googlebot', 'GoogleOther', 'AdsBot-Google', 'Google-Read-Aloud', 'bingbot', 'YandexBot', 'Baiduspider', 'DuckDuckBot', 'Applebot', 'Sogou', 'SeznamBot', 'AhrefsSiteAudit', 'AhrefsBot', 'SemrushBot', 'DataForSeoBot', 'DotBot', 'MJ12bot', 'Barkrowler', 'Screaming Frog', 'facebookexternalhit', 'Twitterbot', 'LinkedInBot', 'Slackbot', 'Discordbot', 'TelegramBot', 'Pinterest', 'HubSpot Crawler', 'Stripebot', 'UptimeRobot', 'Pingdom', 'StatusCake', 'Headless', 'bot/', 'bot\x3B', 'bot)', 'crawler', 'spider', '+http'])) AS botSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
@@ -5093,12 +5093,12 @@ SELECT
         GROUP BY sessionId)
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsSummaryQuery:filtered-rollup  [7dc77773]
+-- builder:web-analytics:webAnalyticsSummaryQuery:filtered-rollup  [81474d1b]
 SELECT
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           uniqIf(SessionId, multiSearchAnyCaseInsensitive(UserAgent, ['GPTBot', 'OAI-SearchBot', 'ChatGPT-User', 'ClaudeBot', 'Claude-User', 'PerplexityBot', 'Google-Extended', 'Applebot-Extended', 'meta-externalagent', 'meta-webindexer', 'Bytespider', 'CCBot', 'Amazonbot', 'DuckAssistBot', 'Googlebot', 'GoogleOther', 'AdsBot-Google', 'Google-Read-Aloud', 'bingbot', 'YandexBot', 'Baiduspider', 'DuckDuckBot', 'Applebot', 'Sogou', 'SeznamBot', 'AhrefsSiteAudit', 'AhrefsBot', 'SemrushBot', 'DataForSeoBot', 'DotBot', 'MJ12bot', 'Barkrowler', 'Screaming Frog', 'facebookexternalhit', 'Twitterbot', 'LinkedInBot', 'Slackbot', 'Discordbot', 'TelegramBot', 'Pinterest', 'HubSpot Crawler', 'Stripebot', 'UptimeRobot', 'Pingdom', 'StatusCake', 'Headless', 'bot/', 'bot\x3B', 'bot)', 'crawler', 'spider', '+http'])) AS botSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
@@ -5137,13 +5137,13 @@ SELECT
         GROUP BY sessionId)
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsTimeseriesQuery:default  [bdbaa144]
+-- builder:web-analytics:webAnalyticsTimeseriesQuery:default  [7ac5c3d6]
 SELECT
           toStartOfInterval(StartTime, INTERVAL 3600 SECOND) AS bucket,
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
         FROM session_replays
@@ -5154,13 +5154,13 @@ SELECT
         ORDER BY bucket ASC
         FORMAT JSON
 
--- builder:web-analytics:webAnalyticsTimeseriesQuery:default-rollup  [bdbaa144]
+-- builder:web-analytics:webAnalyticsTimeseriesQuery:default-rollup  [7ac5c3d6]
 SELECT
           toStartOfInterval(StartTime, INTERVAL 3600 SECOND) AS bucket,
           uniqIf(VisitorId, VisitorId != '') AS visitors,
           uniq(SessionId) AS sessions,
           uniqIf(SessionId, VisitorIsNew = 1) AS newSessions,
-          uniqIf(SessionId, (PageViews <= 1 AND VisitorId != '')) AS bouncedSessions,
+          uniqIf(SessionId, VisitorId != '') - uniqIf(SessionId, (PageViews > 1 AND VisitorId != '')) AS bouncedSessions,
           uniqIf(SessionId, VisitorId != '') AS identifiedSessions,
           round(ifNotFinite(avgIf(assumeNotNull(DurationMs), DurationMs > 0), 0)) AS avgDurationMs
         FROM session_replays
diff --git a/packages/query-engine/src/ch/queries/web-analytics.ts b/packages/query-engine/src/ch/queries/web-analytics.ts
index 033b8d5f3..aa0fa4841 100644
--- a/packages/query-engine/src/ch/queries/web-analytics.ts
+++ b/packages/query-engine/src/ch/queries/web-analytics.ts
@@ -496,6 +496,14 @@ export interface WebAnalyticsSummaryOutput {
  * Within that population `PageViews <= 1` rather than `= 1`, so a session whose
  * only row is still the v1 start row counts as a bounce instead of vanishing
  * from both sides of the ratio.
+ *
+ * It is counted as "identified, minus those with a page view above one" rather
+ * than directly, because `session_replays` is a `ReplacingMergeTree(Version)`
+ * whose v1 start row and v2 end row coexist until a merge. A direct
+ * `uniqIf(SessionId, PageViews <= 1)` matches a session if ANY visible version
+ * satisfies it, so every multi-page session was a bounce for as long as its
+ * start row survived — the same class of error the `avgDurationMs` predicate
+ * already guards against.
  */
 export function webAnalyticsSummaryQuery(
 	filters: WebAnalyticsFilters = {},
@@ -505,7 +513,9 @@ export function webAnalyticsSummaryQuery(
 			visitors: CH.uniqIf($.VisitorId, $.VisitorId.neq("")),
 			sessions: CH.uniq($.SessionId),
 			newSessions: CH.uniqIf($.SessionId, $.VisitorIsNew.eq(1)),
-			bouncedSessions: CH.uniqIf($.SessionId, $.PageViews.lte(1).and($.VisitorId.neq(""))),
+			bouncedSessions: CH.uniqIf($.SessionId, $.VisitorId.neq("")).sub(
+				CH.uniqIf($.SessionId, $.PageViews.gt(1).and($.VisitorId.neq(""))),
+			),
 			identifiedSessions: CH.uniqIf($.SessionId, $.VisitorId.neq("")),
 			botSessions: CH.uniqIf($.SessionId, isBotCond($.UserAgent)),
 			// avgIf over the ended rows only: the v1 row's DurationMs is NULL, and
@@ -614,7 +624,9 @@ export function webAnalyticsTimeseriesQuery(
 			visitors: CH.uniqIf($.VisitorId, $.VisitorId.neq("")),
 			sessions: CH.uniq($.SessionId),
 			newSessions: CH.uniqIf($.SessionId, $.VisitorIsNew.eq(1)),
-			bouncedSessions: CH.uniqIf($.SessionId, $.PageViews.lte(1).and($.VisitorId.neq(""))),
+			bouncedSessions: CH.uniqIf($.SessionId, $.VisitorId.neq("")).sub(
+				CH.uniqIf($.SessionId, $.PageViews.gt(1).and($.VisitorId.neq(""))),
+			),
 			identifiedSessions: CH.uniqIf($.SessionId, $.VisitorId.neq("")),
 			// avgIf over the ended rows only — same as the summary: the v1 row's
 			// DurationMs is NULL and would average in as a NULL.