diff --git a/src/slack/monitor/message-handler/dispatch.ts b/src/slack/monitor/message-handler/dispatch.ts
index b9c88e3448..9147f6a7a1 100644
--- a/src/slack/monitor/message-handler/dispatch.ts
+++ b/src/slack/monitor/message-handler/dispatch.ts
@@ -199,6 +199,8 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
           channel: message.channel,
           threadTs: streamThreadTs,
           text,
+          teamId: ctx.teamId,
+          userId: message.user,
         });
         replyPlan.markSent();
         return;
diff --git a/src/slack/streaming.ts b/src/slack/streaming.ts
index f9e1ab6979..936fba79fe 100644
--- a/src/slack/streaming.ts
+++ b/src/slack/streaming.ts
@@ -36,6 +36,18 @@ export type StartSlackStreamParams = {
   threadTs: string;
   /** Optional initial markdown text to include in the stream start. */
   text?: string;
+  /**
+   * The team ID of the workspace this stream belongs to.
+   * Required by the Slack API for `chat.startStream` / `chat.stopStream`.
+   * Obtain from `auth.test` response (`team_id`).
+   */
+  teamId?: string;
+  /**
+   * The user ID of the message recipient (required for DM streaming).
+   * Without this, `chat.stopStream` fails with `missing_recipient_user_id`
+   * in direct message conversations.
+   */
+  userId?: string;
 };
 
 export type AppendSlackStreamParams = {
@@ -64,13 +76,17 @@ export type StopSlackStreamParams = {
 export async function startSlackStream(
   params: StartSlackStreamParams,
 ): Promise<SlackStreamSession> {
-  const { client, channel, threadTs, text } = params;
+  const { client, channel, threadTs, text, teamId, userId } = params;
 
-  logVerbose(`slack-stream: starting stream in ${channel} thread=${threadTs}`);
+  logVerbose(
+    `slack-stream: starting stream in ${channel} thread=${threadTs}${teamId ? ` team=${teamId}` : ""}${userId ? ` user=${userId}` : ""}`,
+  );
 
   const streamer = client.chatStream({
     channel,
     thread_ts: threadTs,
+    ...(teamId ? { recipient_team_id: teamId } : {}),
+    ...(userId ? { recipient_user_id: userId } : {}),
   });
 
   const session: SlackStreamSession = {