diff --git a/packages/test-support/llm-replay/src/index.ts b/packages/test-support/llm-replay/src/index.ts
index 103ff2d881..065b19a3e9 100644
--- a/packages/test-support/llm-replay/src/index.ts
+++ b/packages/test-support/llm-replay/src/index.ts
@@ -1151,6 +1151,13 @@ export interface Config {
 function validateConfiguredModels(providers: ReplayProviderConfig[] | undefined): void {
   for (const provider of providers ?? []) {
     for (const model of provider.models ?? []) {
+      if (model.floorReasoningEffort !== undefined
+        && !model.reasoningEfforts?.includes(model.floorReasoningEffort)) {
+        throw new Error(
+          `llm-replay: provider "${provider.id}" model "${model.id}" floorReasoningEffort `
+          + 'must appear in reasoningEfforts',
+        )
+      }
       const modalities: unknown = model.inputModalities
       if (modalities !== undefined && (!Array.isArray(modalities)
         || !modalities.every((modality: unknown) => modality === 'text' || modality === 'image'))) {
diff --git a/packages/test-support/llm-replay/tests/llm-replay.spec.ts b/packages/test-support/llm-replay/tests/llm-replay.spec.ts
index eeff300274..fef2eb23bc 100644
--- a/packages/test-support/llm-replay/tests/llm-replay.spec.ts
+++ b/packages/test-support/llm-replay/tests/llm-replay.spec.ts
@@ -2161,7 +2161,13 @@ describe('apply (the plugin entry)', () => {
     apply(ctx, {
       file,
       providers: [
-        { id: 'm', models: [{ id: 'm', inputModalities: ['image'] }, { id: 'text' }] },
+        {
+          id: 'm',
+          models: [
+            { id: 'm', inputModalities: ['image'], reasoningEfforts: ['low'], floorReasoningEffort: 'low' },
+            { id: 'text' },
+          ],
+        },
         { id: 'empty' },
       ],
       paceMs: 1,
@@ -2204,6 +2210,17 @@ describe('apply (the plugin entry)', () => {
     expect(ctx.llm.imageRequestPricing('deepseek', 'plain')).toBeUndefined()
   })
 
+  it.each([undefined, [], ['high']])('rejects a floor absent from configured efforts %s', (reasoningEfforts) => {
+    const ctx = new Context()
+    const model = {
+      id: 'm', floorReasoningEffort: 'low',
+      ...reasoningEfforts === undefined ? {} : { reasoningEfforts },
+    }
+    expect(() => { apply(ctx, { file, providers: [{ id: 'm', models: [model] }] }) }).toThrow(
+      'llm-replay: provider "m" model "m" floorReasoningEffort must appear in reasoningEfforts',
+    )
+  })
+
   it('rejects imageRequestTokens on a model without the image modality during load', () => {
     const ctx = new Context()
     const providers = [{ id: 'm', models: [{ id: 'm', imageRequestTokens: 384 }] }] as