diff --git a/scripts/test-parallel-memory.mjs b/scripts/test-parallel-memory.mjs
index 211dc12b42d..3bf9eca4049 100644
--- a/scripts/test-parallel-memory.mjs
+++ b/scripts/test-parallel-memory.mjs
@@ -7,13 +7,14 @@ const ANSI_ESCAPE_PATTERN = new RegExp(
   `${ESCAPE}(?:\\][^${BELL}]*(?:${BELL}|${ESCAPE}\\\\)|\\[[0-?]*[ -/]*[@-~]|[@-Z\\\\-_])`,
   "g",
 );
+const GITHUB_ACTIONS_LOG_PREFIX_PATTERN = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?Z\s+/u;
 
 const COMPLETED_TEST_FILE_LINE_PATTERN =
   /(?<file>(?:src|extensions|test|ui)\/\S+?\.(?:live\.test|e2e\.test|test)\.ts)\s+\(.*\)\s+(?<duration>\d+(?:\.\d+)?)(?<unit>ms|s)\s*$/;
 const MEMORY_TRACE_SUMMARY_PATTERN =
-  /^\[test-parallel\]\[mem\] summary (?<lane>\S+) files=(?<files>\d+) peak=(?<peak>[0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB)) totalDelta=(?<totalDelta>[+-][0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB)) peakAt=(?<peakAt>\S+) top=(?<top>.*)$/u;
+  /^\[test-parallel\]\[mem\] summary (?<lane>\S+) files=(?<files>\d+) peak=(?<peak>[0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB)) totalDelta=(?<totalDelta>[+-]?[0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB)) peakAt=(?<peakAt>\S+) top=(?<top>.*)$/u;
 const MEMORY_TRACE_TOP_ENTRY_PATTERN =
-  /^(?<file>(?:src|extensions|test|ui)\/\S+?\.(?:live\.test|e2e\.test|test)\.ts):(?<delta>[+-][0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB))$/u;
+  /^(?<file>(?:src|extensions|test|ui)\/\S+?\.(?:live\.test|e2e\.test|test)\.ts):(?<delta>[+-]?[0-9]+(?:\.[0-9]+)?(?:GiB|MiB|KiB))$/u;
 
 const PS_COLUMNS = ["pid=", "ppid=", "rss=", "comm="];
 
@@ -44,9 +45,14 @@ function stripAnsi(text) {
   return text.replaceAll(ANSI_ESCAPE_PATTERN, "");
 }
 
+function normalizeLogLine(line) {
+  return line.replace(GITHUB_ACTIONS_LOG_PREFIX_PATTERN, "");
+}
+
 export function parseCompletedTestFileLines(text) {
   return stripAnsi(text)
     .split(/\r?\n/u)
+    .map((line) => normalizeLogLine(line))
     .map((line) => {
       const match = line.match(COMPLETED_TEST_FILE_LINE_PATTERN);
       if (!match?.groups) {
@@ -63,6 +69,7 @@ export function parseCompletedTestFileLines(text) {
 export function parseMemoryTraceSummaryLines(text) {
   return stripAnsi(text)
     .split(/\r?\n/u)
+    .map((line) => normalizeLogLine(line))
     .map((line) => {
       const match = line.match(MEMORY_TRACE_SUMMARY_PATTERN);
       if (!match?.groups) {
diff --git a/scripts/test-update-memory-hotspots.mjs b/scripts/test-update-memory-hotspots.mjs
index 8fb2d400d16..2abbf2b2d02 100644
--- a/scripts/test-update-memory-hotspots.mjs
+++ b/scripts/test-update-memory-hotspots.mjs
@@ -57,6 +57,40 @@ function parseArgs(argv) {
   return args;
 }
 
+function mergeHotspotEntry(aggregated, file, value) {
+  if (!(Number.isFinite(value?.deltaKb) && value.deltaKb > 0)) {
+    return;
+  }
+  const normalizeSourceLabel = (source) => {
+    const separator = source.lastIndexOf(":");
+    if (separator === -1) {
+      return source.endsWith(".log") ? source.slice(0, -4) : source;
+    }
+    const name = source.slice(0, separator);
+    const lane = source.slice(separator + 1);
+    return `${name.endsWith(".log") ? name.slice(0, -4) : name}:${lane}`;
+  };
+  const nextSources = Array.isArray(value?.sources)
+    ? value.sources
+        .filter((source) => typeof source === "string" && source.length > 0)
+        .map(normalizeSourceLabel)
+    : [];
+  const previous = aggregated.get(file);
+  if (!previous) {
+    aggregated.set(file, {
+      deltaKb: Math.round(value.deltaKb),
+      sources: [...new Set(nextSources)],
+    });
+    return;
+  }
+  previous.deltaKb = Math.max(previous.deltaKb, Math.round(value.deltaKb));
+  for (const source of nextSources) {
+    if (!previous.sources.includes(source)) {
+      previous.sources.push(source);
+    }
+  }
+}
+
 const opts = parseArgs(process.argv.slice(2));
 
 if (opts.logs.length === 0) {
@@ -65,6 +99,14 @@ if (opts.logs.length === 0) {
 }
 
 const aggregated = new Map();
+try {
+  const existing = JSON.parse(fs.readFileSync(opts.out, "utf8"));
+  for (const [file, value] of Object.entries(existing.files ?? {})) {
+    mergeHotspotEntry(aggregated, file, value);
+  }
+} catch {
+  // Start from scratch when the output file does not exist yet.
+}
 for (const logPath of opts.logs) {
   const text = fs.readFileSync(logPath, "utf8");
   const summaries = parseMemoryTraceSummaryLines(text).filter(
@@ -75,19 +117,10 @@ for (const logPath of opts.logs) {
       if (record.deltaKb < opts.minDeltaKb) {
         continue;
       }
-      const nextSource = `${path.basename(logPath)}:${summary.lane}`;
-      const previous = aggregated.get(record.file);
-      if (!previous) {
-        aggregated.set(record.file, {
-          deltaKb: record.deltaKb,
-          sources: [nextSource],
-        });
-        continue;
-      }
-      previous.deltaKb = Math.max(previous.deltaKb, record.deltaKb);
-      if (!previous.sources.includes(nextSource)) {
-        previous.sources.push(nextSource);
-      }
+      mergeHotspotEntry(aggregated, record.file, {
+        deltaKb: record.deltaKb,
+        sources: [`${path.basename(logPath, path.extname(logPath))}:${summary.lane}`],
+      });
     }
   }
 }
diff --git a/test/scripts/test-parallel.test.ts b/test/scripts/test-parallel.test.ts
index d2418a77e93..0f4a91c85a4 100644
--- a/test/scripts/test-parallel.test.ts
+++ b/test/scripts/test-parallel.test.ts
@@ -84,7 +84,7 @@ describe("scripts/test-parallel memory trace parsing", () => {
   it("parses memory trace summary lines and hotspot deltas", () => {
     const summaries = parseMemoryTraceSummaryLines(
       [
-        "[test-parallel][mem] summary unit-fast files=360 peak=13.22GiB totalDelta=+6.69GiB peakAt=poll top=src/config/schema.help.quality.test.ts:+1.06GiB, src/infra/update-runner.test.ts:+463.6MiB",
+        "2026-03-20T04:32:18.7721466Z [test-parallel][mem] summary unit-fast files=360 peak=13.22GiB totalDelta=6.69GiB peakAt=poll top=src/config/schema.help.quality.test.ts:1.06GiB, src/infra/update-runner.test.ts:+463.6MiB",
       ].join("\n"),
     );
 
@@ -93,12 +93,12 @@ describe("scripts/test-parallel memory trace parsing", () => {
       lane: "unit-fast",
       files: 360,
       peakRssKb: parseMemoryValueKb("13.22GiB"),
-      totalDeltaKb: parseMemoryValueKb("+6.69GiB"),
+      totalDeltaKb: parseMemoryValueKb("6.69GiB"),
       peakAt: "poll",
       top: [
         {
           file: "src/config/schema.help.quality.test.ts",
-          deltaKb: parseMemoryValueKb("+1.06GiB"),
+          deltaKb: parseMemoryValueKb("1.06GiB"),
         },
         {
           file: "src/infra/update-runner.test.ts",