fix: alert again when a watch condition clears and reappears

apps/server/src/engine/service.ts

@@ -1062,6 +1062,11 @@ export class AgentService {
           : this.matchesPrice(text, Number(monitor.value));
     const previouslyMatched = Boolean(task.state.matched);
     const shouldNotify = matched && (monitor.condition === "change" || !previouslyMatched);
+    // A condition becoming true again is a new event, even with identical page text.
+    // Commit its sequence with the outcome so publication retries still deduplicate.
+    const alertSequence =
+      Number(task.state.alertSequence ?? 0) +
+      (shouldNotify && monitor.condition !== "change" ? 1 : 0);
     const nextCheckAt = new Date(Date.now() + monitor.intervalMinutes * 60000).toISOString();
     await ctx.guard();
     // Worker lease is checked before each publication; monitor control also invalidates that lease.
@@ -1101,12 +1106,16 @@ export class AgentService {
         lastHash: currentHash,
         resumingMonitor: false,
         matched,
+        alertSequence,
         failures: 0,
         notice: shouldNotify
           ? {
               title: monitor.title,
               body: `Condition met at ${observation.url}: ${text.slice(0, 240)}`,
-              key: `monitor:${monitor.id}:${currentHash}`,
+              key:
+                monitor.condition === "change"
+                  ? `monitor:${monitor.id}:${currentHash}`
+                  : `monitor:${monitor.id}:${alertSequence}:${currentHash}`,
             }
           : null,
       },

tests/monitor-recovery.test.ts

@@ -136,6 +136,54 @@ test("a page change stays alertable when the task outcome is lost after the base
   assert.match(found[0].body, /One table at 7 pm/);
 });
 
+for (const scenario of [
+  {
+    condition: "contains",
+    value: "available now",
+    pages: ["Sold out", "Available now", "Sold out", "Available now"],
+    expectedAlerts: 2,
+  },
+  {
+    condition: "price_below",
+    value: "50",
+    pages: ["Price: $80", "Price: $40", "Price: $80", "Price: $40"],
+    expectedAlerts: 2,
+  },
+]) {
+  test(`${scenario.condition} alerts on recurring changes while deduplicating outcome replay`, async () => {
+    const monitor = await read<Monitor>(
+      "/monitors",
+      {
+        title: `Recurring ${scenario.condition}`,
+        url: "sample://availability",
+        condition: scenario.condition,
+        value: scenario.value,
+        intervalMinutes: 1,
+      },
+      201,
+    );
+    const alerts = async () =>
+      (await read<AgentNotification[]>("/notifications")).filter(
+        (item) => item.taskId === monitor.taskId,
+      );
+    for (const text of scenario.pages) {
+      await read("/sample-page", { text });
+      await read(`/monitors/${monitor.id}/control`, { action: "check" });
+      await server.agent.worker.tick();
+      // A restart can publish the same saved notice again; that is not a new alert.
+      await maintain();
+      await maintain();
+    }
+    assert.equal((await alerts()).length, scenario.expectedAlerts);
+    for (let i = 0; i < 2; i++) {
+      await read(`/monitors/${monitor.id}/control`, { action: "check" });
+      await server.agent.worker.tick();
+    }
+    assert.equal((await alerts()).length, scenario.expectedAlerts, "unchanged pages stay quiet");
+    await read(`/monitors/${monitor.id}/control`, { action: "stop" });
+  });
+}
+
 test("resuming a monitor fails without activating it when the task transition does not commit", async () => {
   await read("/sample-page", { text: "No tables available" });
   const monitor = await createMonitor("Resume availability");