diff --git a/src/pcap/PcapOutput.test.ts b/src/pcap/PcapOutput.test.ts
index fffaf0f4c7..3f0c0637f3 100644
--- a/src/pcap/PcapOutput.test.ts
+++ b/src/pcap/PcapOutput.test.ts
@@ -581,6 +581,25 @@ it("accepts exact machine packet counts and rejects scaled human counts", () =>
   );
 });
 
+it.each([
+  ["0", 0],
+  ["1.250 seconds", 1.25],
+  ["2 second", 2],
+  ["n/a", null],
+  ["-1 seconds", null],
+  [`${"9".repeat(309)} seconds`, null],
+] as const)(
+  "retains finite capinfos duration %s and preserves other metadata",
+  (duration, expected) => {
+    const metadata = parseCapinfosOutput(
+      `File type: pcap\nFile encapsulation: Ethernet\nNumber of packets: 2\nCapture duration: ${duration}\nPacket size limit: file hdr: 65535 bytes\n`,
+    );
+    expect(metadata.captureDurationSeconds).toBe(expected);
+    expect(metadata.packetCount).toBe(2);
+    expect(metadata.snapshotLength).toBe(65535);
+  },
+);
+
 it("excludes transport credentials without normalizing observed URL bytes", async () => {
   const result = await parseTsharkJsonOutput(
     capture([
diff --git a/src/pcap/PcapOutput.ts b/src/pcap/PcapOutput.ts
index 4ab714fd05..3b73f2dd45 100644
--- a/src/pcap/PcapOutput.ts
+++ b/src/pcap/PcapOutput.ts
@@ -104,6 +104,7 @@ export const parseCapinfosOutput = (stdout: string): CapinfosMetadata => {
     durationText === undefined
       ? null
       : /^(\d+(?:\.\d+)?)(?:\s+seconds?)?$/u.exec(durationText);
+  const durationSeconds = duration === null ? null : Number(duration[1]);
   const snapshot = /^file hdr:\s*(\d+) bytes$/u.exec(
     lines.get("Packet size limit") ?? "",
   );
@@ -121,7 +122,10 @@ export const parseCapinfosOutput = (stdout: string): CapinfosMetadata => {
     captureEnd: captureInstant(
       lines.get("Latest packet time") ?? lines.get("Last packet time"),
     ),
-    captureDurationSeconds: duration === null ? null : Number(duration[1]),
+    captureDurationSeconds:
+      durationSeconds !== null && Number.isFinite(durationSeconds)
+        ? durationSeconds
+        : null,
     snapshotLength:
       snapshotLength !== null &&
       Number.isSafeInteger(snapshotLength) &&