diff --git a/extensions/whatsapp/src/auto-reply.web-auto-reply.connection-and-logging.e2e.test.ts b/extensions/whatsapp/src/auto-reply.web-auto-reply.connection-and-logging.e2e.test.ts
index 76a54a20d015..27923c93a5ca 100644
--- a/extensions/whatsapp/src/auto-reply.web-auto-reply.connection-and-logging.e2e.test.ts
+++ b/extensions/whatsapp/src/auto-reply.web-auto-reply.connection-and-logging.e2e.test.ts
@@ -141,7 +141,7 @@ describe("web auto-reply connection", () => {
 
   it("handles helper envelope timestamps with trimmed timezones (regression)", () => {
     const d = new Date("2025-01-01T00:00:00.000Z");
-    expect(formatEnvelopeTimestamp(d, " America/Los_Angeles ")).toBe("Tue 2024-12-31 16:00 PST");
+    expect(formatEnvelopeTimestamp(d, " America/Los_Angeles ")).toBe("Tue 2024-12-31 16:00:00 PST");
   });
 
   it("handles reconnect progress and max-attempt stop behavior", async () => {
diff --git a/src/auto-reply/envelope.test.ts b/src/auto-reply/envelope.test.ts
index d2c55a5fbba3..31ae8be2a232 100644
--- a/src/auto-reply/envelope.test.ts
+++ b/src/auto-reply/envelope.test.ts
@@ -10,7 +10,7 @@ import {
 describe("formatAgentEnvelope", () => {
   it("includes channel, from, ip, host, and timestamp", () => {
     withEnv({ TZ: "UTC" }, () => {
-      const ts = Date.UTC(2025, 0, 2, 3, 4); // 2025-01-02T03:04:00Z
+      const ts = Date.UTC(2025, 0, 2, 3, 4, 5); // 2025-01-02T03:04:05Z
       const body = formatAgentEnvelope({
         channel: "WebChat",
         from: "user1",
@@ -21,7 +21,7 @@ describe("formatAgentEnvelope", () => {
         body: "hello",
       });
 
-      expect(body).toBe("[WebChat user1 mac-mini 10.0.0.5 Thu 2025-01-02T03:04Z] hello");
+      expect(body).toBe("[WebChat user1 mac-mini 10.0.0.5 Thu 2025-01-02T03:04:05Z] hello");
     });
   });
 
@@ -39,7 +39,7 @@ describe("formatAgentEnvelope", () => {
 
   it("formats timestamps in UTC when configured", () => {
     withEnv({ TZ: "America/Los_Angeles" }, () => {
-      const ts = Date.UTC(2025, 0, 2, 3, 4); // 2025-01-02T03:04:00Z (19:04 PST)
+      const ts = Date.UTC(2025, 0, 2, 3, 4, 5); // 2025-01-02T03:04:05Z (19:04:05 PST)
       const body = formatAgentEnvelope({
         channel: "WebChat",
         timestamp: ts,
@@ -47,12 +47,12 @@ describe("formatAgentEnvelope", () => {
         body: "hello",
       });
 
-      expect(body).toBe("[WebChat Thu 2025-01-02T03:04Z] hello");
+      expect(body).toBe("[WebChat Thu 2025-01-02T03:04:05Z] hello");
     });
   });
 
   it("formats timestamps in user timezone when configured", () => {
-    const ts = Date.UTC(2025, 0, 2, 3, 4); // 2025-01-02T03:04:00Z (04:04 CET)
+    const ts = Date.UTC(2025, 0, 2, 3, 4, 5); // 2025-01-02T03:04:05Z (04:04:05 CET)
     const body = formatAgentEnvelope({
       channel: "WebChat",
       timestamp: ts,
@@ -60,7 +60,7 @@ describe("formatAgentEnvelope", () => {
       body: "hello",
     });
 
-    expect(body).toMatch(/\[WebChat Thu 2025-01-02 04:04 [^\]]+\] hello/);
+    expect(body).toMatch(/\[WebChat Thu 2025-01-02 04:04:05 [^\]]+\] hello/);
   });
 
   it("omits timestamps when configured", () => {
diff --git a/src/auto-reply/envelope.ts b/src/auto-reply/envelope.ts
index dc1d688eddfe..fbac44885a5e 100644
--- a/src/auto-reply/envelope.ts
+++ b/src/auto-reply/envelope.ts
@@ -142,10 +142,10 @@ export function formatEnvelopeTimestamp(
 
   const formatted =
     zone.mode === "utc"
-      ? formatUtcTimestamp(date)
+      ? formatUtcTimestamp(date, { displaySeconds: true })
       : zone.mode === "local"
-        ? formatZonedTimestamp(date)
-        : formatZonedTimestamp(date, { timeZone: zone.timeZone });
+        ? formatZonedTimestamp(date, { displaySeconds: true })
+        : formatZonedTimestamp(date, { timeZone: zone.timeZone, displaySeconds: true });
 
   if (!formatted) {
     return undefined;
diff --git a/src/plugin-sdk/test-helpers/envelope-timestamp.ts b/src/plugin-sdk/test-helpers/envelope-timestamp.ts
index bdbcf8a9e272..1c2add763d7e 100644
--- a/src/plugin-sdk/test-helpers/envelope-timestamp.ts
+++ b/src/plugin-sdk/test-helpers/envelope-timestamp.ts
@@ -27,14 +27,18 @@ export function formatEnvelopeTimestamp(date: Date, zone: EnvelopeTimestampZone
   })();
 
   if (normalized === "utc" || normalized === "gmt") {
-    const ts = formatUtcTimestamp(date);
+    const ts = formatUtcTimestamp(date, { displaySeconds: true });
     return weekday ? `${weekday} ${ts}` : ts;
   }
   if (normalized === "local" || normalized === "host") {
-    const ts = formatZonedTimestamp(date) ?? formatUtcTimestamp(date);
+    const ts =
+      formatZonedTimestamp(date, { displaySeconds: true }) ??
+      formatUtcTimestamp(date, { displaySeconds: true });
     return weekday ? `${weekday} ${ts}` : ts;
   }
-  const ts = formatZonedTimestamp(date, { timeZone: trimmedZone }) ?? formatUtcTimestamp(date);
+  const ts =
+    formatZonedTimestamp(date, { timeZone: trimmedZone, displaySeconds: true }) ??
+    formatUtcTimestamp(date, { displaySeconds: true });
   return weekday ? `${weekday} ${ts}` : ts;
 }