diff --git a/dist/index.d.ts b/dist/index.d.ts
index dd375d56616f0ee48e6a02265aea0c7eb3f14359..790ac870b2911dc1a3ede03e2c3dcae4364c0ede 100644
--- a/dist/index.d.ts
+++ b/dist/index.d.ts
@@ -26,6 +26,9 @@ declare class XFormatConverter extends BaseFormatConverter {
  */
 type XAccessToken = string | (() => Promise<string> | string);
 interface XAdapterConfig {
+    /** Paperclip owns durable branch identity and explicit publication. */
+    paperclipPostThreadId?: (post: XPost, event: XActivityEvent) => Promise<string | null>;
+    paperclipExplicitReplies?: boolean;
     /** Override the X API base URL. Defaults to X_API_BASE_URL or https://api.x.com. */
     apiBaseUrl?: string;
     /**
@@ -239,8 +242,8 @@ declare class XAdapter implements Adapter<XThreadId, XRawMessage> {
      */
     protected handleCrcChallenge(request: Request): Response;
     protected verifySignature(request: Request, body: string): boolean;
-    protected routeActivityEvent(event: XActivityEvent, options?: WebhookOptions): void;
-    protected handleIncomingPost(post: XPost, author: XUser | undefined, options?: WebhookOptions): void;
+    protected routeActivityEvent(event: XActivityEvent, options?: WebhookOptions): Promise<void>;
+    protected handleIncomingPost(post: XPost, author: XUser | undefined, options?: WebhookOptions, event?: XActivityEvent): Promise<void>;
     protected handleIncomingDm(dmEvent: XDmEvent, sender: XUser | undefined, options?: WebhookOptions): void;
     /**
      * The user id of the other party in a DM: the sender for inbound events,
diff --git a/dist/index.js b/dist/index.js
index fa4b8d4e95edcb3a510f36f5adf38fc7e17dafb1..94fef366008dae2e3aa8e3f0d4469f6410f568b3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -194,6 +194,8 @@ var XAdapter = class {
   constructor(config) {
     this.apiBaseUrl = config.apiBaseUrl ?? DEFAULT_API_BASE_URL;
     this.consumerSecret = config.consumerSecret;
+    this.paperclipPostThreadId = config.paperclipPostThreadId;
+    this.paperclipExplicitReplies = config.paperclipExplicitReplies;
     this.userAccessToken = config.userAccessToken;
     if (config.clientId && config.refreshToken) {
       this.oauth = {
@@ -275,7 +277,7 @@ var XAdapter = class {
       events = [envelope.data];
     }
     for (const event of events) {
-      this.routeActivityEvent(event, options);
+      await this.routeActivityEvent(event, options);
     }
     return new Response("OK", { status: 200 });
   }
@@ -292,7 +294,7 @@ var XAdapter = class {
     return Response.json({ response_token: `${SIGNATURE_PREFIX}${hash}` });
   }
   verifySignature(request, body) {
-    const signature = request.headers.get(SIGNATURE_HEADER);
+    const signature = request.headers.get("x-twitter-webhooks-signature-oauth2") ?? request.headers.get(SIGNATURE_HEADER);
     if (!signature?.startsWith(SIGNATURE_PREFIX)) {
       return false;
     }
@@ -309,16 +311,17 @@ var XAdapter = class {
       return false;
     }
   }
-  routeActivityEvent(event, options) {
+  async routeActivityEvent(event, options) {
     const users = event.includes?.users;
     switch (event.event_type) {
+      case "post.reply.create":
       case "post.mention.create": {
         const extracted = extractPost(event.payload, users);
         if (!extracted) {
           this.logger.warn("Unrecognized X mention payload shape");
           return;
         }
-        this.handleIncomingPost(extracted.post, extracted.author, options);
+        await this.handleIncomingPost(extracted.post, extracted.author, options, event);
         return;
       }
       case "dm.received":
@@ -339,22 +342,24 @@ var XAdapter = class {
         });
     }
   }
-  handleIncomingPost(post, author, options) {
+  async handleIncomingPost(post, author, options, event) {
     if (!this.chat) {
       return;
     }
-    const threadId = this.encodeThreadId({
+    const override = this.paperclipPostThreadId ? await this.paperclipPostThreadId(post, event) : undefined;
+    if (override === null) return;
+    const threadId = override ?? this.encodeThreadId({
       conversationId: post.conversation_id ?? post.id,
       kind: "post"
     });
-    this.replyTargets.set(threadId, post.id);
+    if (!this.paperclipExplicitReplies) this.replyTargets.set(threadId, post.id);
     const message = this.buildPostMessage(
       { author, kind: "post", post },
       threadId,
       { isMention: true }
     );
     this.cacheMessage(message);
-    this.chat.processMessage(this, threadId, message, options);
+    await this.chat.processMessage(this, threadId, message, options);
   }
   handleIncomingDm(dmEvent, sender, options) {
     const participant = this.otherParticipant(dmEvent);
@@ -392,6 +397,7 @@ var XAdapter = class {
    * uploaded via the chunked media endpoint and attached to the post.
    */
   async postMessage(threadId, message) {
+    if (this.paperclipExplicitReplies) throw new ValidationError("x", "Use the durable conversation-bound x_reply tool");
     const decoded = this.decodeThreadId(threadId);
     const text2 = this.renderOutbound(message);
     const mediaIds = await this.uploadAttachments(message, decoded.kind);
@@ -1398,6 +1404,8 @@ function createXAdapter(config) {
     );
   }
   return new XAdapter({
+    paperclipPostThreadId: config?.paperclipPostThreadId,
+    paperclipExplicitReplies: config?.paperclipExplicitReplies,
     apiBaseUrl: config?.apiBaseUrl ?? process.env.X_API_BASE_URL,
     clientId,
     clientSecret: config?.clientSecret ?? process.env.X_CLIENT_SECRET,