diff --git a/container/agent-runner/src/providers/claude.ts b/container/agent-runner/src/providers/claude.ts
index 2798bc20a..0653d6065 100644
--- a/container/agent-runner/src/providers/claude.ts
+++ b/container/agent-runner/src/providers/claude.ts
@@ -257,8 +257,12 @@ function transcriptRotateBytes(): number {
  * non-positive value) disables the age check; size alone then governs.
  */
 function transcriptRotateAgeMs(): number {
-  const days = Number(process.env.CLAUDE_TRANSCRIPT_ROTATE_AGE_DAYS);
-  return Number.isFinite(days) && days > 0 ? days * 86_400_000 : 14 * 86_400_000;
+  const raw = process.env.CLAUDE_TRANSCRIPT_ROTATE_AGE_DAYS;
+  if (raw === undefined || raw.trim() === '') return 14 * 86_400_000;
+  const days = Number(raw);
+  if (!Number.isFinite(days)) return 14 * 86_400_000;
+  // Explicit non-positive override disables the age check; size alone governs.
+  return days > 0 ? days * 86_400_000 : Infinity;
 }
 
 function claudeProjectsDir(): string {