mcp: throttle async job poll requests

crates/crank-registry/src/migrations.rs

@@ -558,6 +558,7 @@ pub async fn apply_postgres(pool: &PgPool) -> Result<(), sqlx::Error> {
             result_json jsonb null,
             error_json jsonb null,
             expires_at timestamptz null,
+            last_poll_at timestamptz null,
             created_at timestamptz not null,
             updated_at timestamptz not null,
             finished_at timestamptz null
@@ -566,6 +567,10 @@ pub async fn apply_postgres(pool: &PgPool) -> Result<(), sqlx::Error> {
     .execute(pool)
     .await?;
 
+    query("alter table async_jobs add column if not exists last_poll_at timestamptz null")
+        .execute(pool)
+        .await?;
+
     query(
         "create index if not exists async_jobs_workspace_status_idx
          on async_jobs(workspace_id, status, updated_at desc)",

crates/crank-registry/src/postgres/mod.rs

@@ -556,6 +556,7 @@ fn map_async_job(row: &PgRow) -> Result<AsyncJobHandle, RegistryError> {
             .try_get::<Option<Json<Value>>, _>("error_json")?
             .map(|value| value.0),
         expires_at: row.try_get("expires_at")?,
+        last_poll_at: row.try_get("last_poll_at")?,
         created_at: row.try_get("created_at")?,
         updated_at: row.try_get("updated_at")?,
         finished_at: row.try_get("finished_at")?,
@@ -2171,6 +2172,15 @@ mod tests {
         let loaded = registry.get_async_job(&job.id).await.unwrap().unwrap();
         assert_eq!(loaded.status, JobStatus::Completed);
 
+        let touched = registry
+            .touch_async_job_poll(&job.id, &timestamp("2026-04-06T12:02:00Z"))
+            .await
+            .unwrap();
+        assert_eq!(
+            touched.last_poll_at,
+            Some(timestamp("2026-04-06T12:02:00Z"))
+        );
+
         let page = registry
             .list_async_jobs(AsyncJobFilter {
                 workspace_id: &test_workspace_id(),
@@ -2511,6 +2521,7 @@ mod tests {
             result: None,
             error: None,
             expires_at: Some(timestamp("2026-04-06T12:05:00Z")),
+            last_poll_at: None,
             created_at: timestamp("2026-04-06T12:00:00Z"),
             updated_at: timestamp("2026-04-06T12:00:00Z"),
             finished_at: None,

crates/crank-registry/src/postgres/stream.rs

@@ -302,12 +302,13 @@ impl PostgresRegistry {
                 result_json,
                 error_json,
                 expires_at,
+                last_poll_at,
                 created_at,
                 updated_at,
                 finished_at
              ) values (
                 $1, $2, $3, $4, $5, $6::jsonb, $7::jsonb, $8::jsonb, $9::timestamptz,
-                $10::timestamptz, $11::timestamptz, $12::timestamptz
+                $10::timestamptz, $11::timestamptz, $12::timestamptz, $13::timestamptz
              )",
         )
         .bind(request.job.id.as_str())
@@ -319,6 +320,7 @@ impl PostgresRegistry {
         .bind(request.job.result.clone().map(Json))
         .bind(request.job.error.clone().map(Json))
         .bind(request.job.expires_at)
+        .bind(request.job.last_poll_at)
         .bind(request.job.created_at)
         .bind(request.job.updated_at)
         .bind(request.job.finished_at)
@@ -343,6 +345,7 @@ impl PostgresRegistry {
                 result_json,
                 error_json,
                 expires_at as \"expires_at: OffsetDateTime\",
+                last_poll_at as \"last_poll_at: OffsetDateTime\",
                 created_at as \"created_at!: OffsetDateTime\",
                 updated_at as \"updated_at!: OffsetDateTime\",
                 finished_at as \"finished_at: OffsetDateTime\"
@@ -364,6 +367,7 @@ impl PostgresRegistry {
                 result: row.result_json,
                 error: row.error_json,
                 expires_at: row.expires_at,
+                last_poll_at: row.last_poll_at,
                 created_at: row.created_at,
                 updated_at: row.updated_at,
                 finished_at: row.finished_at,
@@ -383,9 +387,9 @@ impl PostgresRegistry {
                 set status = $3,
                     progress_json = $4::jsonb,
                     result_json = $5::jsonb,
-                    error_json = $6::jsonb,
-                    expires_at = coalesce($7::timestamptz, expires_at),
-                    updated_at = $8::timestamptz,
+                error_json = $6::jsonb,
+                expires_at = coalesce($7::timestamptz, expires_at),
+                updated_at = $8::timestamptz,
                     finished_at = case
                         when $9::timestamptz is null then finished_at
                         else $9::timestamptz
@@ -402,6 +406,7 @@ impl PostgresRegistry {
                 result_json,
                 error_json,
                 expires_at,
+                last_poll_at,
                 created_at,
                 updated_at,
                 finished_at",
@@ -436,6 +441,43 @@ impl PostgresRegistry {
         }
     }
 
+    pub async fn touch_async_job_poll(
+        &self,
+        id: &AsyncJobId,
+        now: &OffsetDateTime,
+    ) -> Result<AsyncJobHandle, RegistryError> {
+        let row = sqlx::query(
+            "update async_jobs
+                set last_poll_at = $2::timestamptz
+              where id = $1
+            returning
+                id,
+                workspace_id,
+                agent_id,
+                operation_id,
+                status,
+                progress_json,
+                result_json,
+                error_json,
+                expires_at,
+                last_poll_at,
+                created_at,
+                updated_at,
+                finished_at",
+        )
+        .bind(id.as_str())
+        .bind(now)
+        .fetch_optional(&self.pool)
+        .await?;
+
+        match row.as_ref() {
+            Some(row) => map_async_job(row),
+            None => Err(RegistryError::AsyncJobNotFound {
+                job_id: id.as_str().to_owned(),
+            }),
+        }
+    }
+
     pub async fn cancel_async_job(
         &self,
         id: &AsyncJobId,
@@ -492,6 +534,7 @@ impl PostgresRegistry {
                 result_json,
                 error_json,
                 expires_at as \"expires_at: OffsetDateTime\",
+                last_poll_at as \"last_poll_at: OffsetDateTime\",
                 created_at as \"created_at!: OffsetDateTime\",
                 updated_at as \"updated_at!: OffsetDateTime\",
                 finished_at as \"finished_at: OffsetDateTime\"
@@ -524,6 +567,7 @@ impl PostgresRegistry {
                     result: row.result_json,
                     error: row.error_json,
                     expires_at: row.expires_at,
+                    last_poll_at: row.last_poll_at,
                     created_at: row.created_at,
                     updated_at: row.updated_at,
                     finished_at: row.finished_at,