diff --git a/src/agents/pi-embedded-runner/run/attempt.ts b/src/agents/pi-embedded-runner/run/attempt.ts
index e83c3ae4a..067f085f3 100644
--- a/src/agents/pi-embedded-runner/run/attempt.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.ts
@@ -612,6 +612,8 @@ export async function runEmbeddedAttempt(
         onAssistantMessageStart: params.onAssistantMessageStart,
         onAgentEvent: params.onAgentEvent,
         enforceFinalTag: params.enforceFinalTag,
+        provider: params.provider,
+        modelId: params.modelId,
       });
 
       const {
diff --git a/src/agents/pi-embedded-subscribe.handlers.messages.ts b/src/agents/pi-embedded-subscribe.handlers.messages.ts
index 1f515e113..ed72a60da 100644
--- a/src/agents/pi-embedded-subscribe.handlers.messages.ts
+++ b/src/agents/pi-embedded-subscribe.handlers.messages.ts
@@ -165,6 +165,25 @@ export function handleMessageEnd(
   const assistantMessage = msg as AssistantMessage;
   promoteThinkingTagsToBlocks(assistantMessage);
 
+  // Normalize Moonshot thinking signatures on receipt (not on send)
+  // Moonshot via OpenRouter returns "reasoning" but expects "reasoning_content" on replay
+  if (
+    ctx.params.provider === "openrouter" &&
+    ctx.params.modelId?.startsWith("moonshotai/kimi-") &&
+    Array.isArray(assistantMessage.content)
+  ) {
+    for (const block of assistantMessage.content) {
+      if (
+        block &&
+        typeof block === "object" &&
+        (block as { type?: unknown }).type === "thinking" &&
+        (block as { thinkingSignature?: unknown }).thinkingSignature === "reasoning"
+      ) {
+        (block as { thinkingSignature: string }).thinkingSignature = "reasoning_content";
+      }
+    }
+  }
+
   const rawText = extractAssistantText(assistantMessage);
   appendRawStream({
     ts: Date.now(),
diff --git a/src/agents/pi-embedded-subscribe.types.ts b/src/agents/pi-embedded-subscribe.types.ts
index 766ff7f18..bcb7bf5bf 100644
--- a/src/agents/pi-embedded-subscribe.types.ts
+++ b/src/agents/pi-embedded-subscribe.types.ts
@@ -31,6 +31,10 @@ export type SubscribeEmbeddedPiSessionParams = {
   onAssistantMessageStart?: () => void | Promise<void>;
   onAgentEvent?: (evt: { stream: string; data: Record<string, unknown> }) => void | Promise<void>;
   enforceFinalTag?: boolean;
+  /** Provider ID for provider-specific message normalization */
+  provider?: string;
+  /** Model ID for model-specific message normalization */
+  modelId?: string;
 };
 
 export type { BlockReplyChunking } from "./pi-embedded-block-chunker.js";