diff --git a/apps/class-solid/src/lib/runner.ts b/apps/class-solid/src/lib/runner.ts
index bae7006..8a7f701 100644
--- a/apps/class-solid/src/lib/runner.ts
+++ b/apps/class-solid/src/lib/runner.ts
@@ -11,11 +11,9 @@ const asyncRunner = wrap<typeof runClass>(worker);
 
 export async function runClassAsync(config: Config): Promise<ClassOutput> {
   try {
-    const output = asyncRunner(config);
-    return output;
+    return await asyncRunner(config);
   } catch (error) {
     console.error({ config, error });
-    // TODO use toast to give feedback to the user
+    throw error;
   }
-  throw new Error("Model run failed");
 }
diff --git a/apps/class-solid/src/lib/store.ts b/apps/class-solid/src/lib/store.ts
index 190bc42..25a2552 100644
--- a/apps/class-solid/src/lib/store.ts
+++ b/apps/class-solid/src/lib/store.ts
@@ -8,6 +8,7 @@ import {
   mergeConfigurations,
   pruneConfig,
 } from "@classmodel/class/config_utils";
+import { showToast } from "~/components/ui/toast";
 import { decodeAppState } from "./encode";
 import { parseExperimentConfig } from "./experiment_config";
 import type { ExperimentConfig } from "./experiment_config";
@@ -38,9 +39,19 @@ export async function runExperiment(id: number) {
 
   // Run reference
   const referenceConfig = unwrap(exp.config.reference);
-  const newOutput = await runClassAsync(referenceConfig);
-
-  setExperiments(id, "output", "reference", newOutput);
+  try {
+    const newOutput = await runClassAsync(referenceConfig);
+    setExperiments(id, "output", "reference", newOutput);
+  } catch (error) {
+    showToast({
+      title: "Error running reference configuration",
+      description: `${(error as Error).message}; Please correct configuration and try again.`,
+      variant: "destructive",
+      duration: Number.POSITIVE_INFINITY,
+    });
+    setExperiments(id, "output", "running", false);
+    return;
+  }
 
   // Run permutations
   let permCounter = 0;
@@ -50,8 +61,19 @@ export async function runExperiment(id: number) {
       referenceConfig,
       permConfig,
     ) as Config;
-    const newOutput = await runClassAsync(combinedConfig);
-    setExperiments(id, "output", "permutations", permCounter, newOutput);
+    try {
+      const newOutput = await runClassAsync(combinedConfig);
+      setExperiments(id, "output", "permutations", permCounter, newOutput);
+    } catch (error) {
+      showToast({
+        title: `Error running permutation: ${permConfig.name}`,
+        description: `${(error as Error).message}. Please correct configuration and try again.`,
+        variant: "destructive",
+        duration: Number.POSITIVE_INFINITY,
+      });
+      setExperiments(id, "output", "running", false);
+      return;
+    }
     permCounter++;
   }
 
diff --git a/packages/class/src/runner.ts b/packages/class/src/runner.ts
index e3ca529..09910a3 100644
--- a/packages/class/src/runner.ts
+++ b/packages/class/src/runner.ts
@@ -41,6 +41,11 @@ export function runClass(config: Config, freq = 600): ClassOutput {
   // Initial time
   writeOutput();
 
+  // TODO remove when we see this error rendered
+  if (config.runtime === 42_000) {
+    throw new Error("Runtime cannot be 42_000 seconds.");
+  }
+
   // Update loop
   while (model.t <= config.runtime) {
     model.update();