diff --git a/crates/explicit/src/integrate.rs b/crates/explicit/src/integrate.rs
index 194aa14..7e8a866 100644
--- a/crates/explicit/src/integrate.rs
+++ b/crates/explicit/src/integrate.rs
@@ -363,6 +363,7 @@ pub fn solve_explicit(model: &Model, step: Option<&str>, limits: &Limits) -> Res
     loop {
         if increments.is_multiple_of(PROGRESS_EVERY) {
             fieldcraft_model::progress::count(t);
+            fieldcraft_model::progress::check()?;
         }
         if increments >= max_increments {
             completed = false;
diff --git a/crates/lbm/src/solve.rs b/crates/lbm/src/solve.rs
index fa508ad..52e9ba9 100644
--- a/crates/lbm/src/solve.rs
+++ b/crates/lbm/src/solve.rs
@@ -137,6 +137,7 @@ pub fn run(setup: &Setup, flow: &mut Flow, limits: &Limits) -> Result<FluidResul
     let mut next_frame = 1u64;
     fieldcraft_model::progress::stage("Fluid steps", Some(total as f64), "");
     for k in 1..=total {
+        fieldcraft_model::progress::check()?;
         flow.step()?;
         if k % 64 == 0 {
             fieldcraft_model::progress::count(k as f64);
diff --git a/crates/mesh/src/hex/mod.rs b/crates/mesh/src/hex/mod.rs
index 4babfb6..004bbe8 100644
--- a/crates/mesh/src/hex/mod.rs
+++ b/crates/mesh/src/hex/mod.rs
@@ -276,6 +276,7 @@ pub fn hex_mesh(surface: &BoundarySurface, faces: &[Option<Surface>], field: &dy
     };
     let mut reasons: Vec<String> = Vec::new();
     for &method in methods {
+        fieldcraft_model::progress::check()?;
         let mut last = None;
         match method {
             HexMethod::Extrude | HexMethod::Revolve => {
@@ -287,6 +288,7 @@ pub fn hex_mesh(surface: &BoundarySurface, faces: &[Option<Surface>], field: &dy
                     }
                 };
                 for setup in setups {
+                    fieldcraft_model::progress::check()?;
                     // The cross-section is laid out once per frame; refinement retries reuse it.
                     let prepared = match layered::prepare(&ctx, setup) {
                         Ok(p) => p,
@@ -364,6 +366,7 @@ fn candidate_setups(ctx: &Ctx, method: HexMethod) -> std::result::Result<Vec<lay
 fn with_refinement(ctx: &Ctx, method: HexMethod, run: impl Fn(u32) -> Result<Raw>) -> Result<HexMesh> {
     let mut last = Error::Failed("no attempt".into());
     for refine in 0..=MAX_REFINE {
+        fieldcraft_model::progress::check()?;
         match run(refine).and_then(|raw| finish(&Cells::one(ctx), raw, method)) {
             Ok(mesh) => return Ok(mesh),
             Err(e @ Error::Failed(_)) => last = e,
diff --git a/crates/mesh/src/octree/mod.rs b/crates/mesh/src/octree/mod.rs
index b4ecd32..f09c49d 100644
--- a/crates/mesh/src/octree/mod.rs
+++ b/crates/mesh/src/octree/mod.rs
@@ -251,6 +251,7 @@ pub fn octree_hex_mesh(surface: &BoundarySurface, field: &dyn SizeField, options
     let mut hints: Vec<P> = Vec::new();
     let mut retries: Vec<String> = Vec::new();
     for attempt in 0..options.attempts {
+        fieldcraft_model::progress::check()?;
         let cap = if attempt == 0 {
             options.max_elements
         } else {
diff --git a/crates/mesh/src/tet/improve.rs b/crates/mesh/src/tet/improve.rs
index 487e631..3557ffd 100644
--- a/crates/mesh/src/tet/improve.rs
+++ b/crates/mesh/src/tet/improve.rs
@@ -460,6 +460,7 @@ pub fn improve(cx: &mut TetComplex, ctx: &Context, o: &ImproveOptions) -> Result
         stats.passes += 1;
         fieldcraft_model::progress::stage("Improvement pass", Some(o.max_passes as f64), "");
         fieldcraft_model::progress::count(stats.passes as f64);
+        fieldcraft_model::progress::check()?;
         let before = match carried.take() {
             Some(b) => b,
             None => indicators(cx)?,
diff --git a/crates/mesh/src/tet/mod.rs b/crates/mesh/src/tet/mod.rs
index 4210b36..255e879 100644
--- a/crates/mesh/src/tet/mod.rs
+++ b/crates/mesh/src/tet/mod.rs
@@ -491,6 +491,7 @@ pub fn quality_mesh(surface: &BoundarySurface, cdt: &TetMesh, analytic: Vec<Opti
     progress::stage("Refinement round", Some(o.rounds as f64), "");
     for round in 0..o.rounds {
         progress::count((round + 1) as f64);
+        progress::check()?;
         let stats = refine::refine(&mut cx, &ctx, &ropt)?;
         let quiet = stats.interior + stats.boundary == 0;
         let stopped = stats.stopped.clone();
@@ -514,6 +515,7 @@ pub fn quality_mesh(surface: &BoundarySurface, cdt: &TetMesh, analytic: Vec<Opti
     }
     // Put the boundary vertices on the exact surfaces (the tessellation is within its chordal
     // tolerance of them).
+    progress::check()?;
     progress::stage("Snapping to the geometry", None, "");
     report.unsnapped = snap_to_geometry(&mut cx, &exact, true)?;
     let c = cx.compact()?;
diff --git a/crates/mesh/src/tet/refine.rs b/crates/mesh/src/tet/refine.rs
index 5d77dcc..ce44ee9 100644
--- a/crates/mesh/src/tet/refine.rs
+++ b/crates/mesh/src/tet/refine.rs
@@ -263,6 +263,10 @@ pub fn refine(cx: &mut TetComplex, ctx: &Context, o: &RefineOptions) -> Result<R
     while head < queue.len() {
         let t = queue.get(head).copied().unwrap_or(NONE);
         head += 1;
+        // A round can insert hundreds of thousands of vertices: stop between them when asked.
+        if head.is_multiple_of(1024) {
+            fieldcraft_model::progress::check()?;
+        }
         // Keep the queue's memory bounded: drop the processed prefix now and then.
         if head > 1 << 20 {
             queue.drain(..head);
diff --git a/crates/solver/src/analysis.rs b/crates/solver/src/analysis.rs
index 40722e1..3fee7e7 100644
--- a/crates/solver/src/analysis.rs
+++ b/crates/solver/src/analysis.rs
@@ -271,6 +271,7 @@ pub(crate) fn factor_error(e: FactorError, mesh: &Mesh, reduction: &Reduction) -
         }
         FactorError::OutOfMemory { entries } => Error::Limit(format!("not enough memory for the factorization ({entries} entries)")),
         FactorError::Internal(what) => Error::Internal(what),
+        FactorError::Cancelled => Error::Model(fieldcraft_model::Error::Cancelled),
         FactorError::NotPositiveDefinite { column } => {
             let at = reduction.eq_dof.get(column).map_or_else(|| "an unknown degree of freedom".to_string(), |d| mesh.describe_dof(*d));
             Error::Singular(format!(
diff --git a/crates/solver/src/cholesky.rs b/crates/solver/src/cholesky.rs
index 6b2bc73..11c0703 100644
--- a/crates/solver/src/cholesky.rs
+++ b/crates/solver/src/cholesky.rs
@@ -221,6 +221,8 @@ pub enum FactorError {
     OutOfMemory { entries: usize },
     /// A broken internal invariant (a bug), reported instead of a panic.
     Internal(String),
+    /// The command was cancelled ([`fieldcraft_model::progress`]) between supernodes.
+    Cancelled,
 }
 
 impl FactorError {
@@ -892,8 +894,17 @@ impl Symbolic {
             at = range.end;
         }
         let broken = std::sync::Mutex::new(None::<FactorError>);
+        // The pool's threads do not report: they ask the caller's progress whether to stop.
+        let progress = fieldcraft_model::progress::current();
+        let cancelled = || progress.as_ref().is_some_and(|p| p.is_cancelled());
         parallel::for_each_mut(&mut pieces, |_, (range, piece, failed)| {
             for j in range.clone() {
+                if cancelled() {
+                    if let Ok(mut b) = broken.lock() {
+                        b.get_or_insert(FactorError::Cancelled);
+                    }
+                    break;
+                }
                 let (done, own) = piece.split_at_mut(j - range.start);
                 let Some(own) = own.first_mut() else { break };
                 match supernode(&context, j, done, range.start, own) {
@@ -923,6 +934,9 @@ impl Symbolic {
             None => e,
         };
         for &j in &self.top {
+            if cancelled() {
+                return Err(FactorError::Cancelled);
+            }
             if earliest.as_ref().and_then(FactorError::column).is_some_and(|c| self.structure.cols(j).start > c) {
                 break;
             }
@@ -1078,6 +1092,14 @@ mod tests {
         }
         let e = Factor::new(&UpperColumns::from_symmetric(&dense_to_csr(&sing)), usize::MAX).unwrap_err();
         assert_eq!(e, FactorError::NotPositiveDefinite { column: n - 1 });
+        // A cancelled command stops between supernodes, in Cholesky and LDLᵀ alike.
+        let p = fieldcraft_model::progress::Progress::new();
+        p.cancel();
+        fieldcraft_model::progress::scoped(Some(p), || {
+            let upper = UpperColumns::from_symmetric(&csr);
+            assert_eq!(Factor::new(&upper, usize::MAX).unwrap_err(), FactorError::Cancelled);
+            assert_eq!(crate::ldlt::LdltFactor::new(&upper, usize::MAX).unwrap_err(), FactorError::Cancelled);
+        });
         // Empty and 1 × 1 matrices.
         let empty = Csr { n: 0, ptr: vec![0], idx: vec![], val: vec![] };
         let f = Factor::new(&UpperColumns::from_symmetric(&empty), 10).unwrap();
diff --git a/crates/solver/src/eigen.rs b/crates/solver/src/eigen.rs
index 54e8ecf..fe3f61f 100644
--- a/crates/solver/src/eigen.rs
+++ b/crates/solver/src/eigen.rs
@@ -296,6 +296,7 @@ pub fn lanczos(op: &impl Operator, shift: f64, wanted: Wanted, block: usize, max
     let mut prev_b: Option<Vec<Vec<f64>>> = None;
     let mut next_check = (wanted.count + b).max(2 * b);
     loop {
+        fieldcraft_model::progress::check()?;
         let j0 = q.len();
         // W = Op Q_j.
         let mut w: Vec<Vec<f64>> = Vec::with_capacity(b);
diff --git a/crates/solver/src/heat.rs b/crates/solver/src/heat.rs
index 0558423..15ead21 100644
--- a/crates/solver/src/heat.rs
+++ b/crates/solver/src/heat.rs
@@ -308,6 +308,7 @@ fn factor(a: &Csr, limits: &Limits, mesh: &HeatMesh, eqs: &Reduction) -> Result<
         }
         FactorError::OutOfMemory { entries } => Error::Limit(format!("not enough memory for the factorization ({entries} entries)")),
         FactorError::Internal(what) => Error::Internal(what),
+        FactorError::Cancelled => Error::Model(fieldcraft_model::Error::Cancelled),
         FactorError::NotPositiveDefinite { column } | FactorError::Singular { column } => {
             let node = eqs.eq_dof.get(column).and_then(|d| mesh.layout.locate(*d)).map(|(slot, _)| slot);
             let label = node.and_then(|n| mesh.labels.get(n)).copied().unwrap_or(0);
@@ -434,6 +435,7 @@ fn run(model: &Model, resolved: &Resolved, step: &Step, limits: &Limits) -> Resu
             fieldcraft_model::progress::stage("Time increment", Some(steps as f64), "");
             for i in 1..=steps {
                 fieldcraft_model::progress::count((i - 1) as f64);
+                fieldcraft_model::progress::check()?;
                 b.mul(&t, &mut rhs);
                 for (r, fj) in rhs.iter_mut().zip(&f) {
                     *r += dt * fj;
diff --git a/crates/solver/src/nonlinear.rs b/crates/solver/src/nonlinear.rs
index 40d37ad..dd70adc 100644
--- a/crates/solver/src/nonlinear.rs
+++ b/crates/solver/src/nonlinear.rs
@@ -702,7 +702,11 @@ impl Run<'_> {
         let mut dq = rf.clone();
         let [kff] = red.reduce([&k])?;
         drop(k);
-        let Ok(chol) = factor_raw(&kff, self.limits) else { return Ok(None) };
+        let chol = match factor_raw(&kff, self.limits) {
+            Ok(chol) => chol,
+            Err(FactorError::Cancelled) => return Err(Failure::Fatal(fieldcraft_model::Error::Cancelled.into())),
+            Err(_) => return Ok(None),
+        };
         chol.solve(&mut dq)?;
         let energy = dot(&dq, &rf).abs();
         Ok(dq.iter().all(|v| v.is_finite()).then(|| (q0.iter().zip(&dq).map(|(a, d)| a + d).collect(), energy)))
@@ -744,6 +748,7 @@ impl Run<'_> {
         let mut flips = 0usize;
         let max_iterations = usize::try_from(self.settings.max_iterations).unwrap_or(usize::MAX);
         for _ in 0..max_iterations {
+            fieldcraft_model::progress::check().map_err(Error::from)?;
             // The round-off rule: nothing left to correct.
             if norm_inf(&r) <= ROUND_OFF * tol.force * self.scale() && self.force_floor.is_some() {
                 return Ok(Converged { q, evaluation: eval, energy: first_energy });
@@ -1234,6 +1239,7 @@ fn solve_on(model: &Model, step: &str, limits: &Limits, notes: Vec<String>) -> R
         fieldcraft_model::progress::stage("Load factor", Some(1.0), "");
         while t < 1.0 {
             fieldcraft_model::progress::count(lambda);
+            fieldcraft_model::progress::check()?;
             if history.increments.len() >= max_increments {
                 return Err(Error::Limit(format!(
                     "step `{}`: {} increments reached the step's cap at load factor {lambda:.6} (raise max_increments)",
@@ -1663,6 +1669,7 @@ fn arc_length(
     let mut last: Option<Evaluation> = None;
     let max_increments = usize::try_from(settings.max_increments).unwrap_or(usize::MAX);
     loop {
+        fieldcraft_model::progress::check()?;
         if history.increments.len() >= max_increments {
             warnings.push(format!(
                 "the arc-length step `{}` ended at its cap of {} increments, at load factor {lambda:.6}",