diff --git a/src/adapter.rs b/src/adapter.rs
index 88f89969..6e72aedb 100644
--- a/src/adapter.rs
+++ b/src/adapter.rs
@@ -292,6 +292,7 @@ impl Adapter {
                             run.whence().oid(),
                             run.broker_run_id().clone(),
                             &url,
+                            false,
                         );
                     }
                 }
diff --git a/src/bin/cibtoolcmd/cob.rs b/src/bin/cibtoolcmd/cob.rs
index 201cfc32..c27fd51b 100644
--- a/src/bin/cibtoolcmd/cob.rs
+++ b/src/bin/cibtoolcmd/cob.rs
@@ -18,6 +18,10 @@ pub struct CobCmd {
 
     /// Create this many runs in job COB.
     n: usize,
+
+    /// Announce changes?
+    #[clap(long)]
+    announce: bool,
 }
 
 impl Leaf for CobCmd {
@@ -30,7 +34,7 @@ impl Leaf for CobCmd {
         for i in 0..self.n {
             println!("{i}");
             let mut known = known.lock().unwrap();
-            known.create_run(self.repo_id, self.oid, run_id.clone(), &url);
+            known.create_run(self.repo_id, self.oid, run_id.clone(), &url, self.announce);
         }
         Ok(())
     }
diff --git a/src/cob.rs b/src/cob.rs
index 1a100c5a..99b3e5d7 100644
--- a/src/cob.rs
+++ b/src/cob.rs
@@ -66,7 +66,7 @@ impl KnownJobCobs {
         match job_for_commit(&jobs, oid) {
             Err(JobError::NoJob(_)) => {
                 let job = jobs.create(oid, &signer).map_err(JobError::CreateJob)?;
-                announce(&self.profile, repo_id)?;
+                announce(&self.profile, repo_id, false)?;
                 logger::job_create(&repo_id, &oid, job.id());
                 Ok(*job.id())
             }
@@ -89,9 +89,16 @@ impl KnownJobCobs {
     /// Create a new run for an existing job. The run id should be the one
     /// assigned by the CI broker, not the one by the adapter. The log URL
     /// has to be the from the adapter.
-    pub fn create_run(&mut self, repo_id: RepoId, oid: Oid, run_id: RunId, url: &Url) {
+    pub fn create_run(
+        &mut self,
+        repo_id: RepoId,
+        oid: Oid,
+        run_id: RunId,
+        url: &Url,
+        announce: bool,
+    ) {
         if let Some(job_id) = self.create_job(repo_id, oid) {
-            if let Err(err) = self.fallible_create_run(job_id, repo_id, run_id, url) {
+            if let Err(err) = self.fallible_create_run(job_id, repo_id, run_id, url, announce) {
                 logger::job_failure(
                     "failed to add a run to a job COB",
                     &repo_id,
@@ -108,6 +115,7 @@ impl KnownJobCobs {
         repo_id: RepoId,
         run_id: RunId,
         url: &Url,
+        a: bool,
     ) -> Result<(), JobError> {
         let uuid = Uuid::from_str(run_id.as_str()).map_err(JobError::Uuid)?;
 
@@ -118,7 +126,8 @@ impl KnownJobCobs {
         let mut job = jobs.get_mut(&job_id).map_err(JobError::GetJobMut)?;
         job.run(uuid, url.clone(), &signer)
             .map_err(JobError::AddRun)?;
-        announce(&self.profile, repo_id)?;
+
+        announce(&self.profile, repo_id, a)?;
 
         logger::job_run_create(job_id, uuid);
         Ok(())
@@ -156,7 +165,7 @@ fn finish(repo_id: RepoId, oid: Oid, run_id: RunId, reason: Reason) -> Result<()
     let mut job = jobs.get_mut(&job_id).map_err(JobError::GetJobMut)?;
     job.finish(uuid, reason, &signer)
         .map_err(JobError::Finish)?;
-    announce(&profile, repo_id)?;
+    announce(&profile, repo_id, true)?;
 
     logger::job_run_finished(job_id, uuid, reason);
     Ok(())
@@ -189,34 +198,35 @@ fn job_for_commit<'a>(jobs: &Jobs<'a, Repository>, wanted: Oid) -> Result<JobId,
     Err(JobError::NoJob(wanted))
 }
 
-fn announce(profile: &Profile, repo_id: RepoId) -> Result<(), JobError> {
-    const TIMEOUT: Duration = Duration::from_millis(5000);
+fn announce(profile: &Profile, repo_id: RepoId, announce: bool) -> Result<(), JobError> {
+    if announce {
+        const TIMEOUT: Duration = Duration::from_millis(5000);
 
-    let mut node = Node::new(profile.home.socket());
+        let mut node = Node::new(profile.home.socket());
 
-    let (synced, unsynced) = node.seeds(repo_id).map_err(JobError::Seeds)?.iter().fold(
-        (BTreeSet::new(), BTreeSet::new()),
-        |(mut synced, mut unsynced), seed| {
-            if seed.is_synced() {
-                synced.insert(seed.nid);
-            } else {
-                unsynced.insert(seed.nid);
-            }
-            (synced, unsynced)
-        },
-    );
+        let (synced, unsynced) = node.seeds(repo_id).map_err(JobError::Seeds)?.iter().fold(
+            (BTreeSet::new(), BTreeSet::new()),
+            |(mut synced, mut unsynced), seed| {
+                if seed.is_synced() {
+                    synced.insert(seed.nid);
+                } else {
+                    unsynced.insert(seed.nid);
+                }
+                (synced, unsynced)
+            },
+        );
 
-    let announcer = Announcer::new(AnnouncerConfig::public(
-        *profile.id(),
-        ReplicationFactor::MustReach(1),
-        BTreeSet::new(),
-        synced,
-        unsynced,
-    ))
-    .map_err(|_| JobError::Announcer)?;
-
-    node.announce(repo_id, TIMEOUT, announcer, |_, _| ())
-        .map_err(JobError::Announce)?;
+        let announcer = Announcer::new(AnnouncerConfig::public(
+            *profile.id(),
+            ReplicationFactor::MustReach(1),
+            BTreeSet::new(),
+            synced,
+            unsynced,
+        ))
+        .map_err(|_| JobError::Announcer)?;
+        node.announce(repo_id, TIMEOUT, announcer, |_, _| ())
+            .map_err(JobError::Announce)?;
+    }
 
     Ok(())
 }