diff --git a/crates/irtt-cli/src/lib.rs b/crates/irtt-cli/src/lib.rs
index f8e9687..57e4294 100644
--- a/crates/irtt-cli/src/lib.rs
+++ b/crates/irtt-cli/src/lib.rs
@@ -24,7 +24,7 @@ const MAX_UDP_PAYLOAD_LENGTH: u32 = 65_507;
 pub struct CliArgs {
     pub server: String,
 
-    #[arg(long, default_value = "10s", value_parser = parse_duration)]
+    #[arg(long, default_value = "10s", value_parser = parse_test_duration)]
     pub duration: Duration,
 
     #[arg(long, default_value = "1s", value_parser = parse_duration)]
@@ -50,7 +50,7 @@ impl CliArgs {
     pub fn to_client_config(&self) -> ClientConfig {
         ClientConfig {
             server_addr: self.server.clone(),
-            duration: Some(self.duration),
+            duration: (!self.is_continuous()).then_some(self.duration),
             interval: self.interval,
             length: self.length,
             received_stats: ReceivedStats::Both,
@@ -64,6 +64,10 @@ impl CliArgs {
             ..ClientConfig::default()
         }
     }
+
+    pub fn is_continuous(&self) -> bool {
+        self.duration == Duration::ZERO
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
@@ -137,6 +141,30 @@ pub fn parse_duration(input: &str) -> Result<Duration, String> {
     }
 }
 
+pub fn parse_test_duration(input: &str) -> Result<Duration, String> {
+    if input == "0" {
+        return Ok(Duration::ZERO);
+    }
+    let (number, unit) = split_duration(input)?;
+    let value: u64 = number
+        .parse()
+        .map_err(|_| format!("invalid duration value {input:?}"))?;
+    if value == 0 {
+        return Ok(Duration::ZERO);
+    }
+    match unit {
+        "ms" => Ok(Duration::from_millis(value)),
+        "s" => Ok(Duration::from_secs(value)),
+        "m" => value
+            .checked_mul(60)
+            .map(Duration::from_secs)
+            .ok_or_else(|| "duration is too large".to_owned()),
+        _ => Err(format!(
+            "unsupported duration unit {unit:?}; use ms, s, or m"
+        )),
+    }
+}
+
 fn split_duration(input: &str) -> Result<(&str, &str), String> {
     let split = input
         .find(|ch: char| !ch.is_ascii_digit())
@@ -581,6 +609,7 @@ mod tests {
         assert_eq!(config.length, 0);
         assert_eq!(config.stamp_at, StampAt::Both);
         assert_eq!(config.clock, Clock::Both);
+        assert!(!args.is_continuous());
     }
 
     #[test]
@@ -588,16 +617,29 @@ mod tests {
         assert_eq!(parse_duration("1ms").unwrap(), Duration::from_millis(1));
         assert_eq!(parse_duration("2s").unwrap(), Duration::from_secs(2));
         assert_eq!(parse_duration("3m").unwrap(), Duration::from_secs(180));
+        assert_eq!(parse_test_duration("0").unwrap(), Duration::ZERO);
+        assert_eq!(parse_test_duration("0s").unwrap(), Duration::ZERO);
+        assert_eq!(
+            parse_test_duration("1ms").unwrap(),
+            Duration::from_millis(1)
+        );
     }
 
     #[test]
     fn rejects_invalid_duration() {
-        assert!(parse(&["--duration", "0s", "127.0.0.1:2112"]).is_err());
         assert!(parse(&["--duration", "-1s", "127.0.0.1:2112"]).is_err());
         assert!(parse(&["--duration", "5", "127.0.0.1:2112"]).is_err());
         assert!(parse(&["--duration", "1h", "127.0.0.1:2112"]).is_err());
     }
 
+    #[test]
+    fn duration_zero_selects_continuous_config() {
+        let args = parse(&["--duration", "0", "127.0.0.1:2112"]).unwrap();
+        assert!(args.is_continuous());
+        assert_eq!(args.duration, Duration::ZERO);
+        assert_eq!(args.to_client_config().duration, None);
+    }
+
     #[test]
     fn rejects_invalid_interval() {
         assert!(parse(&["--interval", "0ms", "127.0.0.1:2112"]).is_err());
diff --git a/crates/irtt-client/src/client.rs b/crates/irtt-client/src/client.rs
index 4d1063c..0dc577f 100644
--- a/crates/irtt-client/src/client.rs
+++ b/crates/irtt-client/src/client.rs
@@ -1734,6 +1734,47 @@ mod tests {
         server.join();
     }
 
+    #[test]
+    fn continuous_duration_keeps_generating_send_deadlines() {
+        let params = Params {
+            protocol_version: 1,
+            duration_ns: 0,
+            interval_ns: 500_000_000,
+            received_stats: ReceivedStats::Both,
+            stamp_at: StampAt::Both,
+            clock: Clock::Both,
+            ..Params::default()
+        };
+        let server = silent_open_server(params);
+        let config = ClientConfig {
+            duration: None,
+            interval: Duration::from_millis(500),
+            socket_config: crate::SocketConfig {
+                recv_timeout: Some(Duration::from_millis(200)),
+                ..Default::default()
+            },
+            ..default_test_config(server.addr)
+        };
+        let mut client = Client::connect(config).unwrap();
+        assert_open_started(client.open(ClientTimestamp::now()).unwrap());
+
+        let start = client.session.as_ref().unwrap().start_mono;
+        let interval = Duration::from_millis(500);
+        for seq in 0..4 {
+            let now = ClientTimestamp {
+                mono: start + interval * seq,
+                wall: SystemTime::now(),
+            };
+            let events = client.send_probe_at(now).unwrap();
+            assert_eq!(events.len(), 1);
+            assert!(client.next_send_deadline().is_some());
+            assert!(!client.session.as_ref().unwrap().sending_done);
+        }
+
+        client.close(ClientTimestamp::now()).unwrap();
+        server.join();
+    }
+
     #[test]
     fn next_send_deadline_advances_by_interval() {
         let params = default_params();