fix(core): sanitize parameterized log message bodies

cursoragent · claude · cursoragent · commit 5a6da5722e9c · 2026-04-13T12:33:21.000Z
Co-Authored-By: Codex 5.3 &lt;noreply@anthropic.com&gt;
diff --git a/packages/core/src/logs/internal.ts b/packages/core/src/logs/internal.ts
@@ -7,7 +7,7 @@ import { DEBUG_BUILD } from '../debug-build';
 import type { Integration } from '../types-hoist/integration';
 import type { Log, SerializedLog } from '../types-hoist/log';
 import { consoleSandbox, debug } from '../utils/debug-logger';
-import { isParameterizedString } from '../utils/is';
+import { isParameterizedString, isString } from '../utils/is';
 import { getCombinedScopeData } from '../utils/scopeData';
 import { _getSpanForScope } from '../utils/spanOnScope';
 import { timestampInSeconds } from '../utils/time';
@@ -162,7 +162,7 @@ export function _INTERNAL_captureLog(
   const serializedLog: SerializedLog = {
     timestamp,
     level,
-    body: typeof message === 'string' ? _INTERNAL_removeLoneSurrogates(message) : message,
+    body: isString(message) ? _INTERNAL_removeLoneSurrogates(String(message)) : message,
     trace_id: traceContext?.trace_id,
     severity_number: severityNumber ?? SEVERITY_TEXT_TO_SEVERITY_NUMBER[level],
     attributes: sanitizeLogAttributes({
diff --git a/packages/core/test/lib/logs/internal.test.ts b/packages/core/test/lib/logs/internal.test.ts
@@ -1280,6 +1280,18 @@ describe('_INTERNAL_captureLog', () => {
       expect(logBuffer?.[0]?.body).toBe('bad surrogate \uFFFD here');
     });
 
+    it('sanitizes lone surrogates in parameterized log message body', () => {
+      const options = getDefaultTestClientOptions({ dsn: PUBLIC_DSN, enableLogs: true });
+      const client = new TestClient(options);
+      const scope = new Scope();
+      scope.setClient(client);
+
+      _INTERNAL_captureLog({ level: 'error', message: fmt`bad surrogate ${'\uD800'} here` }, scope);
+
+      const logBuffer = _INTERNAL_getLogBuffer(client);
+      expect(logBuffer?.[0]?.body).toBe('bad surrogate \uFFFD here');
+    });
+
     it('sanitizes lone surrogates in log attribute values', () => {
       const options = getDefaultTestClientOptions({ dsn: PUBLIC_DSN, enableLogs: true });
       const client = new TestClient(options);
