diff --git a/changelog.d/fixes/6634-6634-testmasking-selfref.md b/changelog.d/fixes/6634-6634-testmasking-selfref.md
new file mode 100644
index 0000000000..2982803f5a
--- /dev/null
+++ b/changelog.d/fixes/6634-6634-testmasking-selfref.md
@@ -0,0 +1 @@
+- fix(ci): exclude check-test-masking.test.ts's own tautology fixtures from the diff-based test-masking gate and recognize `✗` in validate-release-green's failure-line detector (#6634)
diff --git a/scripts/check/check-test-masking.mjs b/scripts/check/check-test-masking.mjs
index 3b5bf0e350..96f67e9d0b 100644
--- a/scripts/check/check-test-masking.mjs
+++ b/scripts/check/check-test-masking.mjs
@@ -319,6 +319,26 @@ export function partitionDeletedRenamed(nameStatusOutput) {
  * Os campos de skip e extTaut são opcionais (default 0) para compatibilidade
  * com chamadas legadas que só passam baseAsserts/headAsserts/baseTaut/headTaut.
  */
+/**
+ * (#6634) `check-test-masking.test.ts` legitimately embeds tautology-pattern string
+ * literals (`assert.ok(true)`, `expect(true).toBe(true)`, `assert.equal(1,1)`) as
+ * FIXTURES to exercise `countBareTautologies()`/`scanBareTautologies()` (#6404). The
+ * diff-based tautology counters (`countTautologies()`/`countExtendedTautologies()`)
+ * are dumb regex scans of raw source text with no awareness that a literal sits
+ * inside a fixture string rather than real assertion code, so any new fixture line
+ * self-trips a HARD "new tautology" flag on the gate's own regression-test file.
+ * Mirrors the exclusion `scanBareTautologies()` already applies for the same reason.
+ *
+ * The exclusion covers the whole `check-test-masking*` gate self-test family — not
+ * just `check-test-masking.test.ts` but sibling regression files such as
+ * `check-test-masking-selfref-6634.test.ts`, which likewise embed tautology-pattern
+ * literals as fixtures/documentation to prove this gate's own behavior.
+ */
+const SELF_TEST_FIXTURE_RE = /(^|\/)check-test-masking(-[\w-]+)?\.test\.tsx?$/;
+function isSelfTestFixtureFile(file) {
+  return SELF_TEST_FIXTURE_RE.test(file);
+}
+
 export function evaluateMasking(perFile, assertReductionAllowlist = new Set()) {
   const flags = [];
   for (const f of perFile) {
@@ -326,6 +346,7 @@ export function evaluateMasking(perFile, assertReductionAllowlist = new Set()) {
     const headSkips = f.headSkips ?? 0;
     const baseExtTaut = f.baseExtTaut ?? 0;
     const headExtTaut = f.headExtTaut ?? 0;
+    const isSelfTestFixture = isSelfTestFixtureFile(f.file);
 
     // The net-assert-REDUCTION signal can be allowlisted per file when the reduction is a
     // verified-legitimate refactor/field-removal (config/quality/test-masking-allowlist.json).
@@ -334,13 +355,13 @@ export function evaluateMasking(perFile, assertReductionAllowlist = new Set()) {
       flags.push(
         `${f.file}: asserts ${f.baseAsserts} → ${f.headAsserts} (REMOÇÃO de ${f.baseAsserts - f.headAsserts} — enfraquecimento?)`
       );
-    if (f.headTaut > f.baseTaut)
+    if (!isSelfTestFixture && f.headTaut > f.baseTaut)
       flags.push(`${f.file}: nova(s) ${f.headTaut - f.baseTaut} tautologia(s) assert.ok(true)`);
     if (headSkips > baseSkips)
       flags.push(
         `${f.file}: ${headSkips - baseSkips} novo(s) .skip/.todo/.only (asserts silenciados sem remoção)`
       );
-    if (headExtTaut > baseExtTaut)
+    if (!isSelfTestFixture && headExtTaut > baseExtTaut)
       flags.push(
         `${f.file}: nova(s) ${headExtTaut - baseExtTaut} tautologia(s) estendida(s) (expect(true).toBe(true) / assert.equal(1,1))`
       );
@@ -374,7 +395,7 @@ export function scanBareTautologies(testFiles, readFile) {
   const read = readFile || ((f) => fs.readFileSync(f, "utf8"));
   const flags = [];
   for (const file of testFiles || []) {
-    if (file.endsWith("check-test-masking.test.ts")) continue;
+    if (isSelfTestFixtureFile(file)) continue;
     let src;
     try {
       src = read(file);
diff --git a/scripts/quality/validate-release-green.mjs b/scripts/quality/validate-release-green.mjs
index aecc88734a..db0933ed67 100644
--- a/scripts/quality/validate-release-green.mjs
+++ b/scripts/quality/validate-release-green.mjs
@@ -96,7 +96,9 @@ export function firstFailureLine(out) {
     .split("\n")
     .map((l) => l.trim())
     .filter(Boolean);
-  const hit = lines.find((l) => /✖|not ok|AssertionError|error TS|FAIL|Error:|REGRESS/i.test(l));
+  const hit = lines.find((l) =>
+    /✖|✗|not ok|AssertionError|error TS|FAIL|Error:|REGRESS/i.test(l)
+  );
   return (hit || lines[lines.length - 1] || "failed").slice(0, 200);
 }
 
diff --git a/tests/unit/check-test-masking-selfref-6634.test.ts b/tests/unit/check-test-masking-selfref-6634.test.ts
new file mode 100644
index 0000000000..6d91a2e7c2
--- /dev/null
+++ b/tests/unit/check-test-masking-selfref-6634.test.ts
@@ -0,0 +1,84 @@
+/**
+ * Regression test for issue #6634 ("release/v3.8.47 branch not green — nightly
+ * release-green found HARD failures"). The nightly's "Test-masking
+ * (weakened-assert guard)" HARD failure was a SELF-REFERENTIAL false positive:
+ * tests/unit/check-test-masking.test.ts legitimately embeds tautology-pattern
+ * string literals (e.g. `expect(true).toBe(true);`, `assert.equal(1, 1);`) as
+ * FIXTURES to exercise countBareTautologies()/scanBareTautologies() — the same
+ * literal text that the diff-based subcheck (evaluateMasking(), fed by
+ * countTautologies()/countExtendedTautologies()) treated as "new tautologies in
+ * the file itself" because those counters are dumb regex scans of raw source
+ * text, blind to "this is inside a fixture string, not real assertion code".
+ *
+ * scanBareTautologies() already special-cases this exact file
+ * (`if (file.endsWith("check-test-masking.test.ts")) continue;` in
+ * scripts/check/check-test-masking.mjs) for precisely this reason — this test
+ * asserts evaluateMasking() now applies the same exclusion for its diff-based
+ * tautology counters, using the real base(origin/main)/head(HEAD) diff of
+ * tests/unit/check-test-masking.test.ts.
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import { execFileSync } from "node:child_process";
+
+import {
+  countTautologies,
+  countExtendedTautologies,
+  evaluateMasking,
+} from "../../scripts/check/check-test-masking.mjs";
+
+const FILE = "tests/unit/check-test-masking.test.ts";
+
+function git(args: string[]): string {
+  return execFileSync("git", args, { encoding: "utf8" });
+}
+
+test("#6634: check-test-masking.test.ts's own tautology fixtures must not self-flag as weakening", () => {
+  // origin/main predates the #6404 fixtures (countBareTautologies/scanBareTautologies
+  // tests) that legitimately embed tautology-pattern literals as string fixtures.
+  const baseSrc = git(["show", "origin/main:" + FILE]);
+  const headSrc = git(["show", "HEAD:" + FILE]);
+
+  const perFile = [
+    {
+      file: FILE,
+      baseAsserts: 0, // irrelevant to this assertion — only tautology counters matter
+      headAsserts: 0,
+      baseTaut: countTautologies(baseSrc),
+      headTaut: countTautologies(headSrc),
+      baseExtTaut: countExtendedTautologies(baseSrc),
+      headExtTaut: countExtendedTautologies(headSrc),
+    },
+  ];
+
+  const flags = evaluateMasking(perFile, new Set());
+
+  assert.deepEqual(
+    flags,
+    [],
+    "check-test-masking.test.ts's own literal tautology fixtures (added for #6404) must be " +
+      "excluded from the diff-based weakening check the same way scanBareTautologies() already " +
+      "excludes this file from the absolute-floor scan — otherwise the gate's own regression " +
+      "test permanently self-flags as a HARD release-green failure whenever new fixtures are added."
+  );
+});
+
+test("#6634: unrelated files still get flagged for genuinely new tautologies (guard is file-scoped, not global)", () => {
+  const perFile = [
+    {
+      file: "tests/unit/some-other-file.test.ts",
+      baseAsserts: 5,
+      headAsserts: 5,
+      baseTaut: 0,
+      headTaut: 1,
+      baseExtTaut: 0,
+      headExtTaut: 1,
+    },
+  ];
+
+  const flags = evaluateMasking(perFile, new Set());
+
+  assert.equal(flags.length, 2, "a non-fixture file must still trip both tautology signals");
+  assert.match(flags[0], /nova\(s\) 1 tautologia\(s\) assert\.ok\(true\)/);
+  assert.match(flags[1], /nova\(s\) 1 tautologia\(s\) estendida/);
+});
diff --git a/tests/unit/check-test-masking.test.ts b/tests/unit/check-test-masking.test.ts
index 5581d88b15..5579bd1cf8 100644
--- a/tests/unit/check-test-masking.test.ts
+++ b/tests/unit/check-test-masking.test.ts
@@ -330,6 +330,21 @@ test("scanBareTautologies: excludes check-test-masking.test.ts itself", () => {
   assert.deepEqual(scanBareTautologies(files, read), []);
 });
 
+test("scanBareTautologies: excludes sibling gate self-test files (#6634 selfref regression)", () => {
+  // The gate's own regression files (e.g. check-test-masking-selfref-6634.test.ts)
+  // embed tautology-pattern literals as fixtures/documentation — the family-wide
+  // exclusion must cover them too, not only check-test-masking.test.ts itself.
+  const files = ["tests/unit/check-test-masking-selfref-6634.test.ts"];
+  const read = () => `assert.equal(1, 1);`;
+  assert.deepEqual(scanBareTautologies(files, read), []);
+});
+
+test("scanBareTautologies: a non-family file with the pattern is still flagged (exclusion is scoped)", () => {
+  const files = ["tests/unit/some-unrelated.test.ts"];
+  const read = () => `assert.equal(1, 1);`;
+  assert.equal(scanBareTautologies(files, read).length, 1);
+});
+
 test("scanBareTautologies: skips unreadable files instead of throwing", () => {
   const files = ["tests/unit/does-not-exist.test.ts"];
   const read = () => {