diff --git a/Cargo.lock b/Cargo.lock
index aa36f4a..5ff049a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1647,6 +1647,7 @@ dependencies = [
  "irpc",
  "irpc-iroh",
  "n0-future 0.2.0",
+ "n0-watcher",
  "postcard",
  "rand 0.9.2",
  "rcan",
diff --git a/Cargo.toml b/Cargo.toml
index 9e394ba..2a037de 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ bytes = { version = "1.10.1", features = ["serde"] }
 postcard = { version = "1.1.3", features = ["use-std"] }
 futures-buffered = "0.2.12"
 tokio-util = "0.7.16"
+n0-watcher = "0.3.0"
 
 [dev-dependencies]
 tokio = { version = "1.45", features = ["macros", "rt", "rt-multi-thread"] }
diff --git a/src/simulation.rs b/src/simulation.rs
index 5498e78..bfd4447 100644
--- a/src/simulation.rs
+++ b/src/simulation.rs
@@ -9,20 +9,23 @@ use std::{
 
 use anyhow::{Context, Result};
 use bytes::Bytes;
-use iroh::{Endpoint, NodeAddr, NodeId, SecretKey};
+use iroh::{Endpoint, NodeAddr, NodeId, SecretKey, Watcher};
 use iroh_metrics::encoding::Encoder;
 use iroh_n0des::{
     Registry,
     simulation::proto::{ActiveTrace, NodeInfo, TraceClient, TraceInfo},
 };
 use n0_future::IterExt;
+use n0_watcher::Watchable;
 use proto::{GetTraceResponse, NodeInfoWithAddr, Scope};
 use serde::{Serialize, de::DeserializeOwned};
-use tokio::sync::Semaphore;
+use tokio::{sync::Semaphore, time::MissedTickBehavior};
 use tokio_util::sync::CancellationToken;
 use tracing::{Instrument, debug, error_span, info, warn};
 use uuid::Uuid;
 
+use crate::simulation::proto::CheckpointId;
+
 pub mod events;
 pub mod proto;
 pub mod trace;
@@ -36,6 +39,8 @@ pub const ENV_TRACE_SERVER: &str = "N0DES_TRACE_SERVER";
 /// Environment variable name for the simulation session ID.
 pub const ENV_TRACE_SESSION_ID: &str = "N0DES_SESSION_ID";
 
+const METRICS_INTERVAL: Duration = Duration::from_secs(1);
+
 type BoxedSetupFn<D> = Box<dyn 'static + Send + Sync + FnOnce() -> BoxFuture<'static, Result<D>>>;
 
 type BoxedSpawnFn<D> = Arc<
@@ -50,6 +55,7 @@ type BoxedRoundFn<D> = Arc<
         + Sync
         + for<'a> Fn(&'a mut BoxNode, &'a RoundContext<'a, D>) -> BoxFuture<'a, Result<bool>>,
 >;
+type RoundLabelFn<D> = Arc<dyn 'static + Send + Sync + for<'a> Fn(&'a D, u32) -> Option<String>>;
 
 type BoxedCheckFn<D> = Arc<dyn Fn(&BoxNode, &RoundContext<'_, D>) -> Result<()>>;
 
@@ -221,6 +227,10 @@ pub trait Spawn<D: SetupData = ()>: Node + 'static {
     where
         Self: Sized;
 
+    fn round_label(_setup_data: &D, _round: u32) -> Option<String> {
+        None
+    }
+
     /// Spawns a new instance as a dynamically-typed node.
     ///
     /// This calls `spawn` and boxes the result.
@@ -308,6 +318,10 @@ pub trait DynNode: Send + Any + 'static {
         None
     }
 
+    fn round_label(&self, _round: u32) -> Option<String> {
+        None
+    }
+
     /// Returns a reference to this node as `Any` for downcasting.
     fn as_any(&self) -> &dyn Any;
 
@@ -353,6 +367,7 @@ pub struct NodeBuilder<N, D> {
     phantom: PhantomData<N>,
     spawn_fn: BoxedSpawnFn<D>,
     round_fn: BoxedRoundFn<D>,
+    round_label_fn: RoundLabelFn<D>,
     check_fn: Option<BoxedCheckFn<D>>,
 }
 
@@ -360,6 +375,7 @@ pub struct NodeBuilder<N, D> {
 struct ErasedNodeBuilder<D> {
     spawn_fn: BoxedSpawnFn<D>,
     round_fn: BoxedRoundFn<D>,
+    round_label_fn: RoundLabelFn<D>,
     check_fn: Option<BoxedCheckFn<D>>,
 }
 
@@ -381,6 +397,7 @@ impl<N: Spawn<D>, D: SetupData> NodeBuilder<N, D> {
         round_fn: impl for<'a> AsyncCallback<'a, N, RoundContext<'a, D>, Result<bool>>,
     ) -> Self {
         let spawn_fn: BoxedSpawnFn<D> = Arc::new(N::spawn_dyn);
+        let round_label_fn: RoundLabelFn<D> = Arc::new(N::round_label);
         let round_fn: BoxedRoundFn<D> = Arc::new(move |node, context| {
             let node = node
                 .as_any_mut()
@@ -393,6 +410,7 @@ impl<N: Spawn<D>, D: SetupData> NodeBuilder<N, D> {
             spawn_fn,
             round_fn,
             check_fn: None,
+            round_label_fn,
         }
     }
 
@@ -424,6 +442,7 @@ impl<N: Spawn<D>, D: SetupData> NodeBuilder<N, D> {
             spawn_fn: self.spawn_fn,
             round_fn: self.round_fn,
             check_fn: self.check_fn,
+            round_label_fn: self.round_label_fn,
         }
     }
 }
@@ -434,9 +453,11 @@ struct SimNode<D> {
     idx: u32,
     round_fn: BoxedRoundFn<D>,
     check_fn: Option<BoxedCheckFn<D>>,
+    round_label_fn: RoundLabelFn<D>,
     round: u32,
     info: NodeInfo,
-    metrics_encoder: Encoder,
+    metrics: Arc<RwLock<Registry>>,
+    checkpoint_watcher: n0_watcher::Watchable<CheckpointId>,
     all_nodes: Vec<NodeInfoWithAddr>,
 }
 
@@ -477,7 +498,9 @@ impl<D: SetupData> SimNode<D> {
             round: 0,
             round_fn: builder.round_fn,
             check_fn: builder.check_fn,
-            metrics_encoder: Encoder::new(Arc::new(RwLock::new(registry))),
+            round_label_fn: builder.round_label_fn,
+            checkpoint_watcher: Watchable::new(0),
+            metrics: Arc::new(RwLock::new(registry)),
             all_nodes: Default::default(),
         };
 
@@ -496,6 +519,38 @@ impl<D: SetupData> SimNode<D> {
 
         info!(idx = self.idx, "start");
 
+        // Spawn a task to periodically put metrics.
+        if let Some(node_id) = self.node_id() {
+            let client = client.clone();
+            let mut watcher = self.checkpoint_watcher.watch();
+            let mut metrics_encoder = Encoder::new(self.metrics.clone());
+            tokio::task::spawn(
+                async move {
+                    let mut interval = tokio::time::interval(METRICS_INTERVAL);
+                    interval.set_missed_tick_behavior(MissedTickBehavior::Skip);
+                    loop {
+                        let checkpoint = tokio::select! {
+                            _ = interval.tick() => None,
+                            checkpoint = watcher.updated() => {
+                                match checkpoint {
+                                    Err(_) => break,
+                                    Ok(checkpoint) => Some(checkpoint)
+                                }
+                            }
+                        };
+                        if let Err(err) = client
+                            .put_metrics(node_id, checkpoint, metrics_encoder.export())
+                            .await
+                        {
+                            warn!(?err, "failed to put metrics, stop metrics task");
+                            break;
+                        }
+                    }
+                }
+                .instrument(error_span!("metrics")),
+            );
+        }
+
         let info = NodeInfoWithAddr {
             addr: self.my_addr().await,
             info: self.info.clone(),
@@ -535,7 +590,6 @@ impl<D: SetupData> SimNode<D> {
 
     #[tracing::instrument(name="round", skip_all, fields(round=self.round))]
     async fn run_round(&mut self, client: &ActiveTrace, setup_data: &D) -> Result<bool> {
-        info!("start round");
         let context = RoundContext {
             round: self.round,
             node_index: self.idx,
@@ -543,24 +597,28 @@ impl<D: SetupData> SimNode<D> {
             all_nodes: &self.all_nodes,
         };
 
+        let label = (self.round_label_fn)(setup_data, self.round)
+            .unwrap_or_else(|| format!("Round {}", self.round));
+
+        info!(%label, "start round");
+
         let result = (self.round_fn)(&mut self.node, &context)
             .await
             .context("round function failed");
 
+        info!(%label, "end round");
+
         let checkpoint = (context.round + 1) as u64;
-        let label = format!("Round {} end", context.round);
+        self.checkpoint_watcher.set(checkpoint).ok();
         client
             .put_checkpoint(checkpoint, Some(label), to_str_err(&result))
-            .await?;
-
-        // TODO(Frando): Couple metrics to node idx, not node id.
-        if let Some(node_id) = self.node_id() {
-            client
-                .put_metrics(node_id, Some(checkpoint), self.metrics_encoder.export())
-                .await?;
-        }
+            .await
+            .context("put checkpoint")?;
 
-        client.wait_checkpoint(checkpoint).await?;
+        client
+            .wait_checkpoint(checkpoint)
+            .await
+            .context("wait checkpoint")?;
 
         match result {
             Ok(out) => {