perf(slack): reduce message hot-path overhead

vincentkoc · vincentkoc · commit c0302512d4dd · 2026-05-06T22:27:49.000-07:00
(cherry picked from commit 9962328)
diff --git a/extensions/slack/src/monitor/message-handler/dispatch.ts b/extensions/slack/src/monitor/message-handler/dispatch.ts
@@ -109,7 +109,13 @@ const UNICODE_TO_SLACK: Record<string, string> = {
 };
 
 function toSlackEmojiName(emoji: string): string {
-  const trimmed = emoji.trim().replace(/^:+|:+$/g, "");
+  let trimmed = emoji.trim();
+  while (trimmed.startsWith(":")) {
+    trimmed = trimmed.slice(1);
+  }
+  while (trimmed.endsWith(":")) {
+    trimmed = trimmed.slice(0, -1);
+  }
   return UNICODE_TO_SLACK[trimmed] ?? trimmed;
 }
 
diff --git a/extensions/slack/src/monitor/message-handler/prepare-content.ts b/extensions/slack/src/monitor/message-handler/prepare-content.ts
@@ -262,29 +262,29 @@ export async function resolveSlackMessageContent(params: {
     threadStarter: params.threadStarter,
   });
 
-  const media =
+  const mediaPromise =
     ownFiles && ownFiles.length > 0
-      ? await (async () => {
-          const { resolveSlackMedia } = await loadSlackMediaModule();
-          return resolveSlackMedia({
+      ? loadSlackMediaModule().then(({ resolveSlackMedia }) =>
+          resolveSlackMedia({
             files: ownFiles,
             token: params.botToken,
             maxBytes: params.mediaMaxBytes,
-          });
-        })()
-      : null;
+          }),
+        )
+      : Promise.resolve(null);
 
-  const attachmentContent =
+  const attachmentContentPromise =
     params.message.attachments && params.message.attachments.length > 0
-      ? await (async () => {
-          const { resolveSlackAttachmentContent } = await loadSlackMediaModule();
-          return resolveSlackAttachmentContent({
+      ? loadSlackMediaModule().then(({ resolveSlackAttachmentContent }) =>
+          resolveSlackAttachmentContent({
             attachments: params.message.attachments,
             token: params.botToken,
             maxBytes: params.mediaMaxBytes,
-          });
-        })()
-      : null;
+          }),
+        )
+      : Promise.resolve(null);
+
+  const [media, attachmentContent] = await Promise.all([mediaPromise, attachmentContentPromise]);
 
   const mergedMedia = [...(media ?? []), ...(attachmentContent?.media ?? [])];
   const effectiveDirectMedia = mergedMedia.length > 0 ? mergedMedia : null;
diff --git a/extensions/slack/src/monitor/message-handler/prepare.ts b/extensions/slack/src/monitor/message-handler/prepare.ts
@@ -67,6 +67,8 @@ import { isSlackSubteamMentionForBot } from "./subteam-mentions.js";
 import type { PreparedSlackMessage } from "./types.js";
 
 const mentionRegexCache = new WeakMap<SlackMonitorContext, Map<string, RegExp[]>>();
+const SLACK_ANY_MENTION_RE = /<@[^>]+>|<!subteam\^[^>]+>/;
+const SLACK_SUBTEAM_MENTION_MARKER = "<!subteam^";
 
 function resolveCachedMentionRegexes(
   ctx: SlackMonitorContext,
@@ -286,17 +288,20 @@ export async function prepareSlackMessage(params: {
     return null;
   }
   const { senderId, allowFromLower } = authorization;
-  const hasAnyMention = /<@[^>]+>|<!subteam\^[^>]+>/.test(message.text ?? "");
+  const messageText = message.text ?? "";
+  const hasAnyMention = SLACK_ANY_MENTION_RE.test(messageText);
+  const hasSubteamMention = messageText.includes(SLACK_SUBTEAM_MENTION_MARKER);
   const explicitlyMentioned = Boolean(
     ctx.botUserId &&
-    (message.text?.includes(`<@${ctx.botUserId}>`) ||
-      (await isSlackSubteamMentionForBot({
-        client: ctx.app.client,
-        text: message.text,
-        botUserId: ctx.botUserId,
-        teamId: ctx.teamId,
-        log: logVerbose,
-      }))),
+    (messageText.includes(`<@${ctx.botUserId}>`) ||
+      (hasSubteamMention &&
+        (await isSlackSubteamMentionForBot({
+          client: ctx.app.client,
+          text: messageText,
+          botUserId: ctx.botUserId,
+          teamId: ctx.teamId,
+          log: logVerbose,
+        })))),
   );
   const seedTopLevelRoomThreadBySource =
     opts.source === "app_mention" || opts.wasMentioned === true || explicitlyMentioned;
@@ -315,7 +320,7 @@ export async function prepareSlackMessage(params: {
     opts.wasMentioned ??
     (!isDirectMessage &&
       matchesMentionWithExplicit({
-        text: message.text ?? "",
+        text: messageText,
         mentionRegexes,
         explicit: {
           hasAnyMention,
