diff --git a/manifests/context-packs/skill-triggers@1.json b/manifests/context-packs/skill-triggers@1.json
index 56714dcf9..aeccbf4b1 100644
--- a/manifests/context-packs/skill-triggers@1.json
+++ b/manifests/context-packs/skill-triggers@1.json
@@ -10,7 +10,7 @@
     "id": "hand-seeded",
     "source": "manual-curation-pending-regeneration"
   },
-  "registryDigest": "55e9ce5724329ea6315394ed8969fc23d820f1163d82a9f3e1baef304e7ca30f",
+  "registryDigest": "3a5aa65956a41c77902b6e3287d8352f04a06e04343decec804d0a5e93e538f5",
   "schemaVersion": 1,
   "triggers": {
     "skill:agent-runtime-gateway-smoke-test": [
diff --git a/skills/continuous-learning-v2/hooks/observe.sh b/skills/continuous-learning-v2/hooks/observe.sh
index b9bc37bb9..ff0d3235f 100755
--- a/skills/continuous-learning-v2/hooks/observe.sh
+++ b/skills/continuous-learning-v2/hooks/observe.sh
@@ -586,22 +586,21 @@ touch "$ACTIVITY_FILE" 2>/dev/null || true
 should_signal=0
 
 _clv2_bump_signal_counter() {
+  counter=0
   if [ -f "$SIGNAL_COUNTER_FILE" ]; then
-    counter=$(cat "$SIGNAL_COUNTER_FILE" 2>/dev/null || echo 0)
-    # Guard against a corrupt counter file: a non-integer value would abort the
-    # hook under `set -e` at the arithmetic below.
-    case "$counter" in
-      ''|*[!0-9]*) counter=0 ;;
-    esac
-    counter=$((counter + 1))
-    if [ "$counter" -ge "$SIGNAL_EVERY_N" ]; then
-      should_signal=1
-      counter=0
-    fi
-    echo "$counter" > "$SIGNAL_COUNTER_FILE"
-  else
-    echo "1" > "$SIGNAL_COUNTER_FILE"
+    counter=$(head -c 20 "$SIGNAL_COUNTER_FILE" 2>/dev/null || echo 0)
   fi
+  # Bound parsing and avoid shell arithmetic overflow on corrupt local state.
+  case "$counter" in
+    ''|*[!0-9]*) counter=0 ;;
+  esac
+  if [ "${#counter}" -gt 18 ]; then counter=0; fi
+  counter=$((10#$counter + 1))
+  if [ "$counter" -ge "$SIGNAL_EVERY_N" ]; then
+    should_signal=1
+    counter=0
+  fi
+  echo "$counter" > "$SIGNAL_COUNTER_FILE"
 }
 
 if command -v flock >/dev/null 2>&1 && exec 8>"$SIGNAL_COUNTER_LOCK" 2>/dev/null; then
@@ -655,14 +654,14 @@ try:
                 time.sleep(0.02)
         try:
             with open(sys.argv[2], encoding="ascii") as source:
-                value = source.read().strip()
-            counter = int(value) if value and value.isascii() and value.isdigit() else 0
-            counter += 1
-            signal = int(counter >= int(sys.argv[3]))
-            if signal:
-                counter = 0
+                value = source.read(20).strip()
         except FileNotFoundError:
-            counter, signal = 1, 0
+            value = ""
+        counter = int(value) if 0 < len(value) <= 18 and value.isascii() and value.isdigit() else 0
+        counter += 1
+        signal = int(counter >= int(sys.argv[3]))
+        if signal:
+            counter = 0
         with open(sys.argv[2], "w", encoding="ascii") as target:
             target.write(str(counter) + "\n")
         print(signal)
diff --git a/tests/hooks/observe-signal-counter-race.test.js b/tests/hooks/observe-signal-counter-race.test.js
index c116a291d..fc63cc83a 100644
--- a/tests/hooks/observe-signal-counter-race.test.js
+++ b/tests/hooks/observe-signal-counter-race.test.js
@@ -269,6 +269,30 @@ async function runStrandedLock() {
   }
 }
 
+async function runCounterBoundary(initial, threshold, expected, forcePython) {
+  const { testDir, projectDir, testObserve } = buildSandbox();
+  try {
+    if (initial !== null) {
+      fs.writeFileSync(path.join(projectDir, '.observer-signal-counter'), initial);
+    }
+    const extraEnv = { ECC_OBSERVER_SIGNAL_EVERY_N: String(threshold) };
+    if (forcePython || !hasFlock) {
+      const bashEnv = path.join(testDir, 'no-flock.sh');
+      const fixture = forcePython
+        ? 'command() { if [ "$1" = "-v" ] && [ "$2" = "flock" ]; then return 1; fi; builtin command "$@"; }\n'
+        // Exercise the real shell counter on macOS with an inherited-fd OS
+        // lock fixture. Native GNU flock remains a Linux platform check.
+        : `flock() { python3 -c 'import fcntl,sys; fcntl.flock(int(sys.argv[-1]), fcntl.LOCK_UN if sys.argv[1] == "-u" else fcntl.LOCK_EX)' "$@"; }\n`;
+      fs.writeFileSync(bashEnv, fixture);
+      extraEnv.BASH_ENV = bashEnv;
+    }
+    await runObserve(testObserve, projectDir, extraEnv);
+    assert.strictEqual(readCounter(projectDir), expected);
+  } finally {
+    cleanupDir(testDir);
+  }
+}
+
 async function runKilledOwner() {
   const { testDir, projectDir, testObserve } = buildSandbox();
   let owner;
@@ -305,6 +329,17 @@ async function runKilledOwner() {
     await asyncTest('concurrent invocations never lose a counter increment', runConcurrent);
     await asyncTest('stranded mkdir lock cannot delay or freeze later observations', runStrandedLock);
     await asyncTest('busy lock skips safely and a killed owner releases it automatically', runKilledOwner);
+    for (const forcePython of [false, true]) {
+      const label = forcePython ? 'Python fallback' : hasFlock ? 'flock' : 'shell counter with OS-lock fixture';
+      await asyncTest(`${label} applies threshold one to a missing first counter`,
+        () => runCounterBoundary(null, 1, 0, forcePython));
+      await asyncTest(`${label} resets a malformed counter before incrementing`,
+        () => runCounterBoundary('invalid\n', 2, 1, forcePython));
+      await asyncTest(`${label} resets an oversized counter before incrementing`,
+        () => runCounterBoundary('9'.repeat(5000) + '\n', 2, 1, forcePython));
+      await asyncTest(`${label} parses leading-zero counters as decimal`,
+        () => runCounterBoundary('08\n', 20, 9, forcePython));
+    }
   } else {
     console.log('  - skipping shell-execution tests (requires non-Windows + python3)');
   }