refactor: dedupe gateway session guards and agent test fixtures

src/gateway/server-methods/agent.test.ts

@@ -113,6 +113,18 @@ function captureUpdatedMainEntry() {
   return () => capturedEntry;
 }
 
+function primeMainAgentRun(params?: { sessionId?: string; cfg?: Record<string, unknown> }) {
+  mockMainSessionEntry(
+    { sessionId: params?.sessionId ?? "existing-session-id" },
+    params?.cfg ?? {},
+  );
+  mocks.updateSessionStore.mockResolvedValue(undefined);
+  mocks.agentCommand.mockResolvedValue({
+    payloads: [{ text: "ok" }],
+    meta: { durationMs: 100 },
+  });
+}
+
 async function runMainAgent(message: string, idempotencyKey: string) {
   const respond = vi.fn();
   await invokeAgent(
@@ -210,20 +222,7 @@ describe("gateway agent handler", () => {
       },
     };
 
-    mocks.loadSessionEntry.mockReturnValue({
-      cfg: mocks.loadConfigReturn,
-      storePath: "/tmp/sessions.json",
-      entry: {
-        sessionId: "existing-session-id",
-        updatedAt: Date.now(),
-      },
-      canonicalKey: "agent:main:main",
-    });
-    mocks.updateSessionStore.mockResolvedValue(undefined);
-    mocks.agentCommand.mockResolvedValue({
-      payloads: [{ text: "ok" }],
-      meta: { durationMs: 100 },
-    });
+    primeMainAgentRun({ cfg: mocks.loadConfigReturn });
 
     await invokeAgent(
       {
@@ -326,20 +325,7 @@ describe("gateway agent handler", () => {
       },
     );
 
-    mocks.loadSessionEntry.mockReturnValue({
-      cfg: {},
-      storePath: "/tmp/sessions.json",
-      entry: {
-        sessionId: "reset-session-id",
-        updatedAt: Date.now(),
-      },
-      canonicalKey: "agent:main:main",
-    });
-    mocks.updateSessionStore.mockResolvedValue(undefined);
-    mocks.agentCommand.mockResolvedValue({
-      payloads: [{ text: "ok" }],
-      meta: { durationMs: 100 },
-    });
+    primeMainAgentRun({ sessionId: "reset-session-id" });
 
     await invokeAgent(
       {
@@ -359,6 +345,58 @@ describe("gateway agent handler", () => {
     expect(call?.sessionId).toBe("reset-session-id");
   });
 
+  it("uses /reset suffix as the post-reset message and still injects timestamp", async () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2026-01-29T01:30:00.000Z")); // Wed Jan 28, 8:30 PM EST
+    mocks.agentCommand.mockReset();
+    mocks.loadConfigReturn = {
+      agents: {
+        defaults: {
+          userTimezone: "America/New_York",
+        },
+      },
+    };
+    mocks.sessionsResetHandler.mockImplementation(
+      async (opts: {
+        params: { key: string; reason: string };
+        respond: (ok: boolean, payload?: unknown) => void;
+      }) => {
+        expect(opts.params.key).toBe("agent:main:main");
+        expect(opts.params.reason).toBe("reset");
+        opts.respond(true, {
+          ok: true,
+          key: "agent:main:main",
+          entry: { sessionId: "reset-session-id" },
+        });
+      },
+    );
+    mocks.sessionsResetHandler.mockClear();
+    primeMainAgentRun({
+      sessionId: "reset-session-id",
+      cfg: mocks.loadConfigReturn,
+    });
+
+    await invokeAgent(
+      {
+        message: "/reset check status",
+        sessionKey: "agent:main:main",
+        idempotencyKey: "test-idem-reset-suffix",
+      },
+      { reqId: "4b" },
+    );
+
+    await vi.waitFor(() => expect(mocks.agentCommand).toHaveBeenCalled());
+    expect(mocks.sessionsResetHandler).toHaveBeenCalledTimes(1);
+    const call = mocks.agentCommand.mock.calls.at(-1)?.[0] as
+      | { message?: string; sessionId?: string }
+      | undefined;
+    expect(call?.message).toBe("[Wed 2026-01-28 20:30 EST] check status");
+    expect(call?.sessionId).toBe("reset-session-id");
+
+    mocks.loadConfigReturn = {};
+    vi.useRealTimers();
+  });
+
   it("rejects malformed agent session keys early in agent handler", async () => {
     mocks.agentCommand.mockClear();
     const respond = await invokeAgent(