diff --git a/frontend/src/lib/components/copilot/chat/flow/FlowAIChat.svelte b/frontend/src/lib/components/copilot/chat/flow/FlowAIChat.svelte
index 37db9a90ba..b2496bbcda 100644
--- a/frontend/src/lib/components/copilot/chat/flow/FlowAIChat.svelte
+++ b/frontend/src/lib/components/copilot/chat/flow/FlowAIChat.svelte
@@ -135,7 +135,8 @@
 			await acceptPendingFlowEditsIfEnabled()
 		},
 		getFlowInputsSchema: async () => {
-			return flowStore.val.schema ?? {}
+			const s = flowStore.val.schema ?? {}
+			return { type: 'object', properties: {}, required: [], ...s }
 		},
 
 		updateExprsToSet: (id: string, inputTransforms: Record<string, InputTransform>) => {
diff --git a/frontend/src/lib/components/copilot/chat/shared.ts b/frontend/src/lib/components/copilot/chat/shared.ts
index aecea1ddfc..ddbd7bdb32 100644
--- a/frontend/src/lib/components/copilot/chat/shared.ts
+++ b/frontend/src/lib/components/copilot/chat/shared.ts
@@ -936,7 +936,9 @@ export async function buildSchemaForTool(
 			throw new Error(`Invalid flow inputs schema: ${invalidProperties.join(', ')}`)
 		}
 
-		toolDef.function.parameters = { ...schema, additionalProperties: false }
+		// Anthropic requires input_schema.type to be present; flows with no inputs
+		// can produce a sparse schema (e.g. { order: [] }) lacking it.
+		toolDef.function.parameters = { type: 'object', ...schema, additionalProperties: false }
 
 		// recursively normalize provider-incompatible schema fragments
 		normalizeToolParameterSchema(toolDef.function.parameters)