diff --git a/logos/examples/tests/expectation_fail_fast_capture.rs b/logos/examples/tests/expectation_fail_fast_capture.rs
new file mode 100644
index 0000000..0b0be89
--- /dev/null
+++ b/logos/examples/tests/expectation_fail_fast_capture.rs
@@ -0,0 +1,65 @@
+use std::time::Duration;
+
+use anyhow::{Result, anyhow};
+use async_trait::async_trait;
+use lb_framework::{CoreBuilderExt as _, LbcEnv, LbcLocalDeployer, ScenarioBuilder};
+use testing_framework_core::scenario::{
+    Deployer, DynError, Expectation, RunContext, ScenarioError,
+};
+use tracing_subscriber::fmt::try_init;
+
+const FAIL_AFTER_CHECKS: usize = 2;
+
+struct FailFastDuringCaptureExpectation {
+    checks: usize,
+}
+
+impl Default for FailFastDuringCaptureExpectation {
+    fn default() -> Self {
+        Self { checks: 0 }
+    }
+}
+
+#[async_trait]
+impl Expectation<LbcEnv> for FailFastDuringCaptureExpectation {
+    fn name(&self) -> &str {
+        "fail_fast_during_capture"
+    }
+
+    async fn check_during_capture(&mut self, _ctx: &RunContext<LbcEnv>) -> Result<(), DynError> {
+        self.checks += 1;
+        if self.checks >= FAIL_AFTER_CHECKS {
+            return Err(format!(
+                "intentional fail-fast trigger after {} capture checks",
+                self.checks
+            )
+            .into());
+        }
+
+        Ok(())
+    }
+
+    async fn evaluate(&mut self, _ctx: &RunContext<LbcEnv>) -> Result<(), DynError> {
+        Ok(())
+    }
+}
+
+#[tokio::test]
+#[ignore = "requires local node binary and open ports"]
+async fn expectation_can_fail_fast_during_capture() -> Result<()> {
+    let _ = try_init();
+
+    let mut scenario = ScenarioBuilder::deployment_with(|topology| topology.with_node_count(1))
+        .with_run_duration(Duration::from_secs(30))
+        .with_expectation(FailFastDuringCaptureExpectation::default())
+        .build()?;
+
+    let deployer = LbcLocalDeployer::default();
+    let runner = deployer.deploy(&scenario).await?;
+
+    match runner.run(&mut scenario).await {
+        Err(ScenarioError::ExpectationFailedDuringCapture(_)) => Ok(()),
+        Err(other) => Err(anyhow!("unexpected scenario error: {other}")),
+        Ok(_) => Err(anyhow!("expected fail-fast capture error, run succeeded")),
+    }
+}
diff --git a/testing-framework/core/src/scenario/expectation.rs b/testing-framework/core/src/scenario/expectation.rs
index c304582..f70f011 100644
--- a/testing-framework/core/src/scenario/expectation.rs
+++ b/testing-framework/core/src/scenario/expectation.rs
@@ -19,5 +19,12 @@ pub trait Expectation<E: Application>: Send + Sync {
         Ok(())
     }
 
+    /// Optional periodic check used by fail-fast expectation mode.
+    ///
+    /// Default is a no-op so existing expectations stay end-of-run only.
+    async fn check_during_capture(&mut self, _ctx: &RunContext<E>) -> Result<(), DynError> {
+        Ok(())
+    }
+
     async fn evaluate(&mut self, ctx: &RunContext<E>) -> Result<(), DynError>;
 }
diff --git a/testing-framework/core/src/scenario/runtime/deployer.rs b/testing-framework/core/src/scenario/runtime/deployer.rs
index 0151327..d6ee181 100644
--- a/testing-framework/core/src/scenario/runtime/deployer.rs
+++ b/testing-framework/core/src/scenario/runtime/deployer.rs
@@ -10,6 +10,8 @@ pub enum ScenarioError {
     Workload(#[source] DynError),
     #[error("expectation capture failed: {0}")]
     ExpectationCapture(#[source] DynError),
+    #[error("expectation failed during capture: {0}")]
+    ExpectationFailedDuringCapture(#[source] DynError),
     #[error("expectations failed:\n{0}")]
     Expectations(#[source] DynError),
 }
diff --git a/testing-framework/core/src/scenario/runtime/runner.rs b/testing-framework/core/src/scenario/runtime/runner.rs
index c1502d0..bcc453b 100644
--- a/testing-framework/core/src/scenario/runtime/runner.rs
+++ b/testing-framework/core/src/scenario/runtime/runner.rs
@@ -1,14 +1,15 @@
 use std::{any::Any, future::Future, panic::AssertUnwindSafe, sync::Arc, time::Duration};
 
-use futures::{FutureExt as _, future};
+use futures::FutureExt as _;
 use tokio::{
     task::{JoinError, JoinSet},
-    time::{sleep, timeout},
+    time::{Interval, interval, sleep},
 };
+use tracing::{debug, info, warn};
 
 use super::deployer::ScenarioError;
 use crate::scenario::{
-    Application, DynError, Expectation, Scenario,
+    Application, DynError, Expectation, Scenario, Workload,
     runtime::context::{CleanupGuard, RunContext, RunHandle},
 };
 
@@ -17,6 +18,7 @@ type WorkloadOutcome = Result<(), DynError>;
 const MIN_NODE_CONTROL_COOLDOWN: Duration = Duration::from_secs(30);
 const DEFAULT_BLOCK_FEED_SETTLE_WAIT: Duration = Duration::from_secs(1);
 const MIN_BLOCK_FEED_SETTLE_WAIT: Duration = Duration::from_secs(2);
+const EXPECTATION_CAPTURE_CHECK_INTERVAL: Duration = Duration::from_secs(1);
 const UNKNOWN_PANIC: &str = "<unknown panic>";
 
 /// Represents a fully prepared environment capable of executing a scenario.
@@ -60,6 +62,16 @@ impl<E: Application> Runner<E> {
         Caps: Send + Sync,
     {
         let context = self.context();
+        let run_duration = scenario.duration();
+        let workloads = scenario.workloads().to_vec();
+        let expectation_count = scenario.expectations().len();
+
+        info!(
+            run_secs = run_duration.as_secs(),
+            workloads = workloads.len(),
+            expectations = expectation_count,
+            "runner starting scenario execution"
+        );
 
         self.run_step(Self::prepare_expectations(
             scenario.expectations_mut(),
@@ -67,8 +79,13 @@ impl<E: Application> Runner<E> {
         ))
         .await?;
 
-        self.run_step(Self::run_workloads(Arc::clone(&context), scenario))
-            .await?;
+        self.run_step(Self::run_workload_phase(
+            Arc::clone(&context),
+            &workloads,
+            run_duration,
+            scenario.expectations_mut(),
+        ))
+        .await?;
 
         Self::settle_before_expectations(context.as_ref()).await;
 
@@ -78,6 +95,8 @@ impl<E: Application> Runner<E> {
         ))
         .await?;
 
+        info!("runner finished scenario execution");
+
         Ok(self.into_run_handle())
     }
 
@@ -108,32 +127,46 @@ impl<E: Application> Runner<E> {
         Ok(())
     }
 
-    async fn run_workloads<Caps>(
+    async fn run_workload_phase(
         context: Arc<RunContext<E>>,
-        scenario: &Scenario<E, Caps>,
-    ) -> Result<(), ScenarioError>
-    where
-        Caps: Send + Sync,
-    {
-        if scenario.workloads().is_empty() {
-            return idle_until_duration(scenario.duration()).await;
+        workloads: &[Arc<dyn Workload<E>>],
+        duration: Duration,
+        expectations: &mut [Box<dyn Expectation<E>>],
+    ) -> Result<(), ScenarioError> {
+        info!(
+            workloads = workloads.len(),
+            run_secs = duration.as_secs(),
+            "runner workload phase started"
+        );
+
+        if workloads.is_empty() {
+            Self::run_idle_window_with_capture_checks(duration, expectations, context.as_ref())
+                .await?;
+
+            info!("runner workload phase completed (idle)");
+
+            return Ok(());
         }
 
-        let mut workloads = Self::spawn_workloads(scenario, Arc::clone(&context));
-        Self::run_workload_window(&mut workloads, scenario.duration()).await?;
+        let mut running = Self::spawn_workloads(workloads, Arc::clone(&context));
+
+        Self::run_window_until_timeout(&mut running, duration, expectations, context.as_ref())
+            .await?;
 
         if let Some(cooldown) = nonzero_cooldown(Self::cooldown_duration(context.as_ref())) {
-            Self::run_workload_window(&mut workloads, cooldown).await?;
+            info!(
+                cooldown_secs = cooldown.as_secs(),
+                "runner cooldown window started"
+            );
+
+            Self::run_window_until_timeout(&mut running, cooldown, expectations, context.as_ref())
+                .await?;
         }
 
-        Self::drain_workloads(&mut workloads).await
-    }
+        Self::drain_workloads(&mut running).await?;
+
+        info!("runner workload phase completed");
 
-    async fn run_workload_window(
-        workloads: &mut JoinSet<WorkloadOutcome>,
-        duration: Duration,
-    ) -> Result<(), ScenarioError> {
-        let _completed = Self::drive_until_timer(workloads, duration).await?;
         Ok(())
     }
 
@@ -203,19 +236,16 @@ impl<E: Application> Runner<E> {
     }
 
     /// Spawn each workload in its own task.
-    fn spawn_workloads<Caps>(
-        scenario: &Scenario<E, Caps>,
+    fn spawn_workloads(
+        workloads: &[Arc<dyn Workload<E>>],
         context: Arc<RunContext<E>>,
-    ) -> JoinSet<WorkloadOutcome>
-    where
-        Caps: Send + Sync,
-    {
-        let mut workloads = JoinSet::new();
-        for workload in scenario.workloads() {
+    ) -> JoinSet<WorkloadOutcome> {
+        let mut running = JoinSet::new();
+        for workload in workloads {
             let workload = Arc::clone(workload);
             let ctx = Arc::clone(&context);
 
-            workloads.spawn(async move {
+            running.spawn(async move {
                 // Convert panics into workload errors so the runner can report
                 // them instead of aborting the process.
                 let outcome = AssertUnwindSafe(async { workload.start(ctx.as_ref()).await })
@@ -228,29 +258,87 @@ impl<E: Application> Runner<E> {
             });
         }
 
-        workloads
+        running
     }
 
     /// Drive workload tasks until timeout or failure.
-    async fn drive_until_timer(
+    async fn run_window_until_timeout(
         workloads: &mut JoinSet<WorkloadOutcome>,
         duration: Duration,
-    ) -> Result<bool, ScenarioError> {
-        let run_future = async {
-            while let Some(result) = workloads.join_next().await {
-                Self::map_join_result(result)?;
+        expectations: &mut [Box<dyn Expectation<E>>],
+        context: &RunContext<E>,
+    ) -> Result<(), ScenarioError> {
+        if duration.is_zero() {
+            return Ok(());
+        }
+
+        let timer = sleep(duration);
+        tokio::pin!(timer);
+        let mut capture_tick = capture_check_interval();
+
+        loop {
+            tokio::select! {
+                _ = &mut timer => return Ok(()),
+                _ = capture_tick.tick() => {
+                    Self::run_capture_checks(expectations, context).await?;
+                }
+                result = workloads.join_next(), if !workloads.is_empty() => {
+                    let Some(result) = result else {
+                        return Ok(());
+                    };
+
+                    Self::map_join_result(result)?;
+
+                    if workloads.is_empty() {
+                        return Ok(());
+                    }
+                }
             }
+        }
+    }
 
-            Ok(())
-        };
+    async fn run_capture_checks(
+        expectations: &mut [Box<dyn Expectation<E>>],
+        context: &RunContext<E>,
+    ) -> Result<(), ScenarioError> {
+        let expectation_count = expectations.len();
 
-        match timeout(duration, run_future).await {
-            Ok(result) => {
-                result?;
-                Ok(true)
+        for expectation in expectations {
+            if let Err(source) = expectation.check_during_capture(context).await {
+                warn!(expectation = expectation.name(), %source, "expectation failed during capture");
+
+                return Err(capture_check_failure(expectation.name(), source));
             }
+        }
 
-            Err(_) => Ok(false),
+        debug!(
+            expectations = expectation_count,
+            "expectation capture check pass"
+        );
+
+        Ok(())
+    }
+
+    async fn run_idle_window_with_capture_checks(
+        duration: Duration,
+        expectations: &mut [Box<dyn Expectation<E>>],
+        context: &RunContext<E>,
+    ) -> Result<(), ScenarioError> {
+        if duration.is_zero() {
+            return Ok(());
+        }
+
+        let timer = sleep(duration);
+        tokio::pin!(timer);
+        let mut capture_tick = capture_check_interval();
+
+        loop {
+            tokio::select! {
+                _ = &mut timer => return Ok(()),
+                _ = capture_tick.tick() => {
+                    Self::run_capture_checks(expectations, context).await?;
+                }
+            }
         }
     }
 
@@ -274,19 +362,14 @@ impl<E: Application> Runner<E> {
     }
 }
 
-async fn idle_until_duration(duration: Duration) -> Result<(), ScenarioError> {
-    if duration.is_zero() {
-        return Ok(());
-    }
-
-    let _ = timeout(duration, async { future::pending::<()>().await }).await;
-    Ok(())
-}
-
 fn nonzero_cooldown(cooldown: Option<Duration>) -> Option<Duration> {
     cooldown.filter(|duration| !duration.is_zero())
 }
 
+fn capture_check_interval() -> Interval {
+    interval(EXPECTATION_CAPTURE_CHECK_INTERVAL)
+}
+
 fn panic_message(panic: Box<dyn Any + Send>) -> String {
     panic
         .downcast_ref::<&str>()
@@ -295,6 +378,10 @@ fn panic_message(panic: Box<dyn Any + Send>) -> String {
         .unwrap_or_else(|| UNKNOWN_PANIC.to_owned())
 }
 
+fn capture_check_failure(expectation: &str, source: DynError) -> ScenarioError {
+    ScenarioError::ExpectationFailedDuringCapture(format!("{expectation}: {source}").into())
+}
+
 fn expectation_failure_summary(failures: Vec<(String, DynError)>) -> String {
     failures
         .into_iter()
diff --git a/testing-framework/deployers/local/src/deployer.rs b/testing-framework/deployers/local/src/deployer.rs
index 972769d..536e13e 100644
--- a/testing-framework/deployers/local/src/deployer.rs
+++ b/testing-framework/deployers/local/src/deployer.rs
@@ -126,9 +126,9 @@ impl From<ScenarioError> for ProcessDeployerError {
     fn from(value: ScenarioError) -> Self {
         match value {
             ScenarioError::Workload(source) => Self::WorkloadFailed { source },
-            ScenarioError::ExpectationCapture(source) | ScenarioError::Expectations(source) => {
-                Self::ExpectationsFailed { source }
-            }
+            ScenarioError::ExpectationCapture(source)
+            | ScenarioError::ExpectationFailedDuringCapture(source)
+            | ScenarioError::Expectations(source) => Self::ExpectationsFailed { source },
         }
     }
 }