diff --git a/tests/validate-architectures.test.mjs b/tests/validate-architectures.test.mjs
index 4c315e2e..a56398a3 100644
--- a/tests/validate-architectures.test.mjs
+++ b/tests/validate-architectures.test.mjs
@@ -182,3 +182,25 @@ test('rejects a sourceUrl carrying a password-only userinfo component', () => {
   assert.equal(result.status, 1);
   assert.match(result.stderr, /sourceUrl must be an https URL/);
 });
+
+// record.id doubles as the error label, so a record that is missing it falls
+// back to '<unknown>'. Line coverage cannot see that fallback: the rest of
+// each `path: record.id || '<unknown>'` line runs on every malformed record.
+// Both fallback sites fire for one id-less record, and the reported label is
+// what a maintainer reads to find the offending entry.
+test('labels an id-less record <unknown> in every error it raises', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    catalogFixture([{ title: 'Acme Platform', organization: 'Acme Corp' }]),
+  );
+  assert.equal(result.status, 1);
+  assert.match(
+    result.stderr,
+    /\[error\] <unknown>: missing id, title, or organization/,
+  );
+  assert.match(
+    result.stderr,
+    /\[error\] <unknown>: sourceUrl must be an https URL/,
+  );
+  assert.doesNotMatch(result.stderr, /\[error\] undefined:/);
+});
diff --git a/tests/validate-case-studies.test.mjs b/tests/validate-case-studies.test.mjs
index d68c3186..c6ca9ef5 100644
--- a/tests/validate-case-studies.test.mjs
+++ b/tests/validate-case-studies.test.mjs
@@ -259,3 +259,33 @@ test('rejects an entry missing industries entirely', () => {
   assert.equal(result.status, 1);
   assert.match(result.stderr, /industries must be an array/);
 });
+
+// The error label is `entry.id ?? entry.slug ?? 'unknown'`. Both fallback arms
+// sit mid-line, so line coverage reports them as run whenever a malformed
+// entry is validated at all; only an entry that actually omits `id` reaches
+// the slug arm, and only one omitting `slug` too reaches the literal.
+test('falls back to the slug when an entry has no id', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [{ ...validEntry, id: undefined }],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /\[error\] example-org: duplicate or missing id/);
+  assert.doesNotMatch(result.stderr, /\[error\] unknown:/);
+});
+
+test('falls back to "unknown" when an entry has neither id nor slug', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [{ ...validEntry, id: undefined, slug: undefined }],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /\[error\] unknown: duplicate or missing id/);
+  assert.doesNotMatch(result.stderr, /\[error\] undefined:/);
+});
diff --git a/tests/validate-launch-metrics.test.mjs b/tests/validate-launch-metrics.test.mjs
index 20715c2f..c760721d 100644
--- a/tests/validate-launch-metrics.test.mjs
+++ b/tests/validate-launch-metrics.test.mjs
@@ -334,3 +334,34 @@ test('rejects a signal sourceUrl carrying a password-only userinfo component', (
   assert.equal(result.status, 1);
   assert.match(result.stderr, /sourceUrl must not carry a userinfo component/);
 });
+
+// `data.signals || []` keeps a file with no signals key from throwing on
+// .length, so the count check reports it as a data problem instead of the
+// script dying with a TypeError. The `|| []` arm is invisible to line
+// coverage because the assignment line runs for every file.
+test('reports a missing signals key as a count failure, not a crash', () => {
+  const withoutSignals = { ...validData };
+  delete withoutSignals.signals;
+  const result = runScriptWithFixtures(SCRIPT, fixture(withoutSignals));
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /signals must define 3-5 signals, got 0/);
+  assert.doesNotMatch(result.stderr, /TypeError/);
+});
+
+// A signal with no id has no natural label, so every error it raises is
+// filed under '(missing id)' rather than the empty string `signal.id` would
+// otherwise contribute.
+test('labels an id-less signal "(missing id)" in every error it raises', () => {
+  const anonymous = { ...validSignal };
+  delete anonymous.id;
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({ ...validData, signals: [...validData.signals, anonymous] }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(
+    result.stderr,
+    /\[error\] \(missing id\): duplicate or missing signal id/,
+  );
+  assert.doesNotMatch(result.stderr, /\[error\] undefined:/);
+});
diff --git a/tests/validate-metrics.test.mjs b/tests/validate-metrics.test.mjs
index 84ef9504..52afd042 100644
--- a/tests/validate-metrics.test.mjs
+++ b/tests/validate-metrics.test.mjs
@@ -398,3 +398,16 @@ test('accepts a valid breakdown', () => {
   );
   assert.equal(result.status, 0, result.stderr);
 });
+
+// `data.metrics || []` lets the per-metric loop skip a file whose collector
+// never wrote a metrics array, so the failure reported is the one that caused
+// it rather than an iteration TypeError. The `|| []` arm sits mid-line, so
+// line coverage reports it as run on every valid file.
+test('reports a metrics-less file by its real failure, not an iteration crash', () => {
+  const truncated = { ...validData, generated: false };
+  delete truncated.metrics;
+  const result = runScriptWithFixtures(SCRIPT, metricsFixture(truncated));
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /generated must be true/);
+  assert.doesNotMatch(result.stderr, /TypeError/);
+});