fix: use local timestamps in agent envelope

src/auto-reply/envelope.test.ts

@@ -4,6 +4,9 @@ import { formatAgentEnvelope } from "./envelope.js";
 
 describe("formatAgentEnvelope", () => {
   it("includes surface, from, ip, host, and timestamp", () => {
+    const originalTz = process.env.TZ;
+    process.env.TZ = "UTC";
+
     const ts = Date.UTC(2025, 0, 2, 3, 4); // 2025-01-02T03:04:00Z
     const body = formatAgentEnvelope({
       surface: "WebChat",
@@ -13,8 +16,29 @@ describe("formatAgentEnvelope", () => {
       timestamp: ts,
       body: "hello",
     });
+
+    process.env.TZ = originalTz;
+
+    expect(body).toMatch(
+      /^\[WebChat user1 mac-mini 10\.0\.0\.5 2025-01-02T03:04\+00:00\{.+\}\] hello$/,
+    );
+  });
+
+  it("formats timestamps in local time (not UTC)", () => {
+    const originalTz = process.env.TZ;
+    process.env.TZ = "America/Los_Angeles";
+
+    const ts = Date.UTC(2025, 0, 2, 3, 4); // 2025-01-02T03:04:00Z
+    const body = formatAgentEnvelope({
+      surface: "WebChat",
+      timestamp: ts,
+      body: "hello",
+    });
+
+    process.env.TZ = originalTz;
+
     expect(body).toBe(
-      "[WebChat user1 mac-mini 10.0.0.5 2025-01-02 03:04] hello",
+      "[WebChat 2025-01-01T19:04-08:00{America/Los_Angeles}] hello",
     );
   });
 

src/auto-reply/envelope.ts

@@ -11,8 +11,26 @@ function formatTimestamp(ts?: number | Date): string | undefined {
   if (!ts) return undefined;
   const date = ts instanceof Date ? ts : new Date(ts);
   if (Number.isNaN(date.getTime())) return undefined;
-  // Compact ISO-like format with minutes precision.
-  return date.toISOString().slice(0, 16).replace("T", " ");
+
+  const yyyy = String(date.getFullYear()).padStart(4, "0");
+  const mm = String(date.getMonth() + 1).padStart(2, "0");
+  const dd = String(date.getDate()).padStart(2, "0");
+  const hh = String(date.getHours()).padStart(2, "0");
+  const min = String(date.getMinutes()).padStart(2, "0");
+
+  // getTimezoneOffset() is minutes *behind* UTC. Flip sign to get ISO offset.
+  const offsetMinutes = -date.getTimezoneOffset();
+  const sign = offsetMinutes >= 0 ? "+" : "-";
+  const absOffsetMinutes = Math.abs(offsetMinutes);
+  const offsetH = String(Math.floor(absOffsetMinutes / 60)).padStart(2, "0");
+  const offsetM = String(absOffsetMinutes % 60).padStart(2, "0");
+
+  const tz = Intl.DateTimeFormat().resolvedOptions().timeZone;
+  const tzSuffix = tz ? `{${tz}}` : "";
+
+  // Compact ISO-like *local* timestamp with minutes precision.
+  // Example: 2025-01-02T03:04-08:00{America/Los_Angeles}
+  return `${yyyy}-${mm}-${dd}T${hh}:${min}${sign}${offsetH}:${offsetM}${tzSuffix}`;
 }
 
 export function formatAgentEnvelope(params: AgentEnvelopeParams): string {