diff --git a/crates/irtt-client/src/client/tests/config.rs b/crates/irtt-client/src/client/tests/config.rs
index 76f9120..f7560e6 100644
--- a/crates/irtt-client/src/client/tests/config.rs
+++ b/crates/irtt-client/src/client/tests/config.rs
@@ -85,6 +85,54 @@ fn params_from_config_encodes_continuous_duration_as_zero() {
     assert_eq!(params_from_config(&config).unwrap().duration_ns, 0);
 }
 
+#[test]
+fn params_from_config_rejects_zero_finite_duration() {
+    let config = ClientConfig {
+        duration: Some(Duration::ZERO),
+        ..ClientConfig::default()
+    };
+    assert!(matches!(
+        params_from_config(&config),
+        Err(ClientError::InvalidConfig { reason })
+            if reason == "duration must be greater than zero; use None for continuous mode"
+    ));
+}
+
+#[test]
+fn params_from_config_rejects_zero_interval() {
+    let config = ClientConfig {
+        interval: Duration::ZERO,
+        ..ClientConfig::default()
+    };
+    assert!(matches!(
+        params_from_config(&config),
+        Err(ClientError::InvalidConfig { reason }) if reason == "interval must be greater than zero"
+    ));
+}
+
+#[test]
+fn params_from_config_rejects_nanosecond_encoding_overflow_as_invalid_config() {
+    let config = ClientConfig {
+        duration: Some(Duration::from_nanos(i64::MAX as u64) + Duration::from_nanos(1)),
+        ..ClientConfig::default()
+    };
+    assert!(matches!(
+        params_from_config(&config),
+        Err(ClientError::InvalidConfig { reason })
+            if reason == "duration is too large to encode as nanoseconds"
+    ));
+
+    let config = ClientConfig {
+        interval: Duration::from_nanos(i64::MAX as u64) + Duration::from_nanos(1),
+        ..ClientConfig::default()
+    };
+    assert!(matches!(
+        params_from_config(&config),
+        Err(ClientError::InvalidConfig { reason })
+            if reason == "interval is too large to encode as nanoseconds"
+    ));
+}
+
 #[test]
 fn params_from_config_accepts_max_dscp_codepoint() {
     let config = ClientConfig {
diff --git a/crates/irtt-client/src/client/tests/negotiation.rs b/crates/irtt-client/src/client/tests/negotiation.rs
index 337e76f..0a1d8cf 100644
--- a/crates/irtt-client/src/client/tests/negotiation.rs
+++ b/crates/irtt-client/src/client/tests/negotiation.rs
@@ -29,6 +29,82 @@ fn loose_negotiation_accepts_server_restricted_params() {
     assert!(validate_negotiated_params(&requested, &returned, NegotiationPolicy::Loose).is_ok());
 }
 
+#[test]
+fn loose_negotiation_rejects_non_positive_returned_interval() {
+    let config = ClientConfig::default();
+    let requested = params_from_config(&config).unwrap();
+
+    for interval_ns in [0, -1] {
+        let mut returned = requested.clone();
+        returned.interval_ns = interval_ns;
+        assert!(matches!(
+            validate_negotiated_params(&requested, &returned, NegotiationPolicy::Loose),
+            Err(ClientError::NegotiationRejected { reason })
+                if reason == "interval must be positive"
+        ));
+    }
+}
+
+#[test]
+fn loose_negotiation_accepts_documented_duration_combinations() {
+    let finite_config = ClientConfig::default();
+    let requested_finite = params_from_config(&finite_config).unwrap();
+
+    let returned_same_finite = requested_finite.clone();
+    assert!(validate_negotiated_params(
+        &requested_finite,
+        &returned_same_finite,
+        NegotiationPolicy::Loose
+    )
+    .is_ok());
+
+    let mut returned_shorter_finite = requested_finite.clone();
+    returned_shorter_finite.duration_ns /= 2;
+    assert!(validate_negotiated_params(
+        &requested_finite,
+        &returned_shorter_finite,
+        NegotiationPolicy::Loose
+    )
+    .is_ok());
+
+    let continuous_config = ClientConfig {
+        duration: None,
+        ..ClientConfig::default()
+    };
+    let requested_continuous = params_from_config(&continuous_config).unwrap();
+
+    let returned_continuous = requested_continuous.clone();
+    assert!(validate_negotiated_params(
+        &requested_continuous,
+        &returned_continuous,
+        NegotiationPolicy::Loose
+    )
+    .is_ok());
+
+    let mut returned_finite = requested_continuous.clone();
+    returned_finite.duration_ns = 1_000_000_000;
+    assert!(validate_negotiated_params(
+        &requested_continuous,
+        &returned_finite,
+        NegotiationPolicy::Loose
+    )
+    .is_ok());
+}
+
+#[test]
+fn loose_negotiation_rejects_finite_request_returned_continuous() {
+    let config = ClientConfig::default();
+    let requested = params_from_config(&config).unwrap();
+    let mut returned = requested.clone();
+    returned.duration_ns = 0;
+
+    assert!(matches!(
+        validate_negotiated_params(&requested, &returned, NegotiationPolicy::Loose),
+        Err(ClientError::NegotiationRejected { reason })
+            if reason == "server returned continuous duration for finite request"
+    ));
+}
+
 #[test]
 fn loose_negotiation_rejects_negative_returned_length() {
     let config = ClientConfig::default();