diff --git a/plugin/index.ts b/plugin/index.ts
index 377b4b3..2e0fb47 100644
--- a/plugin/index.ts
+++ b/plugin/index.ts
@@ -82,6 +82,7 @@ function extractUntrustedConversationInfo(text: string): Record<string, unknown>
 function deriveDecisionInputFromPrompt(
   prompt: string,
   messageProvider?: string,
+  channelIdFromCtx?: string,
 ): {
   channel: string;
   channelId?: string;
@@ -91,11 +92,17 @@ function deriveDecisionInputFromPrompt(
 } {
   const conv = extractUntrustedConversationInfo(prompt) || {};
   const channel = (messageProvider || "").toLowerCase();
-  const channelId =
-    (typeof conv.channel_id === "string" && conv.channel_id) ||
-    (typeof conv.chat_id === "string" && conv.chat_id.startsWith("channel:")
-      ? conv.chat_id.slice("channel:".length)
-      : undefined);
+
+  // Priority: ctx.channelId > conv.chat_id > conv.channel_id
+  let channelId = channelIdFromCtx;
+  if (!channelId) {
+    channelId =
+      (typeof conv.chat_id === "string" && conv.chat_id.startsWith("channel:")
+        ? conv.chat_id.slice("channel:".length)
+        : typeof conv.channel_id === "string" && conv.channel_id) ||
+      undefined;
+  }
+
   const senderId =
     (typeof conv.sender_id === "string" && conv.sender_id) ||
     (typeof conv.sender === "string" && conv.sender) ||
@@ -576,7 +583,7 @@ export default {
         );
       }
 
-      const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider);
+      const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider, ctx.channelId);
       // Only proceed if: discord channel AND prompt contains untrusted metadata
       const hasConvMarker = prompt.includes("Conversation info (untrusted metadata):");
       if (live.discordOnly !== false && (!hasConvMarker || derived.channel !== "discord")) return;
@@ -712,7 +719,7 @@ export default {
         if (rec) sessionDecision.delete(key);
 
         const prompt = ((event as Record<string, unknown>).prompt as string) || "";
-        const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider);
+        const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider, ctx.channelId);
 
         const decision = evaluateDecision({
           config: live,
@@ -747,7 +754,7 @@ export default {
 
       // Resolve end symbols from config/policy for dynamic instruction
       const prompt = ((event as Record<string, unknown>).prompt as string) || "";
-      const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider);
+      const derived = deriveDecisionInputFromPrompt(prompt, ctx.messageProvider, ctx.channelId);
       const policy = resolvePolicy(live, derived.channelId, policyState.channelPolicies);
       const isGroupChat = derived.conv.is_group_chat === true || derived.conv.is_group_chat === "true";
       const instruction = buildEndMarkerInstruction(policy.endSymbols, isGroupChat);