diff --git a/packages/ai/src/dialect/demotion.ts b/packages/ai/src/dialect/demotion.ts
index bf5ea07e1..f89b2218f 100644
--- a/packages/ai/src/dialect/demotion.ts
+++ b/packages/ai/src/dialect/demotion.ts
@@ -28,8 +28,9 @@ const CLAUDE_FABLE_ID = /(?:^|[./])claude[-.]fable(?:[-.]|$)/i;
 export function renderDemotedThinking(modelId: string, text: string): string {
 	if (!text) return "";
 	text = text.toWellFormed();
+	const canonicalId = bareModelId(modelId);
 	const dialect = preferredDialect(modelId);
-	if (CLAUDE_FABLE_ID.test(bareModelId(modelId))) return `_Hmm. ${text}_\n`;
+	if (CLAUDE_FABLE_ID.test(canonicalId)) return `_Hmm. ${text}_\n`;
 	if (dialect === "harmony" || dialect === "gemma") return `<think>\n${text}\n</think>\n`;
 	return `${getDialectDefinition(dialect).renderThinking(text)}\n`;
 }
diff --git a/packages/ai/test/anthropic-prior-turn-thinking.test.ts b/packages/ai/test/anthropic-prior-turn-thinking.test.ts
index 57f06d17f..10023131b 100644
--- a/packages/ai/test/anthropic-prior-turn-thinking.test.ts
+++ b/packages/ai/test/anthropic-prior-turn-thinking.test.ts
@@ -344,9 +344,7 @@ describe("Anthropic prior-turn thinking preservation (#2257, #2265)", () => {
 			if (!assistant) throw new Error("expected assistant wire message");
 			const blocks = assistant.content as WireBlock[];
 			const textBlocks = blocks.filter((b): b is WireTextBlock => b.type === "text");
-			expect(textBlocks.every(block => block.text !== renderDemotedThinking(modelCase.id, reasoning))).toBe(true);
-			expect(textBlocks.every(block => !block.text.startsWith("_Hmm."))).toBe(true);
-			expect(textBlocks.every(block => !block.text.includes("<thinking>"))).toBe(true);
+			expect(textBlocks).toHaveLength(0);
 			expect(blocks.find(b => b.type === "thinking")).toBeUndefined();
 			const toolUse = blocks.find(b => b.type === "tool_use") as WireToolUseBlock | undefined;
 			expect(toolUse?.id).toBe(toolCallId);