fix(cron): pass agent identity through delivery path (#16218) (#16242)

* fix(cron): pass agent identity through delivery path

Cron delivery messages now include agent identity (name, avatar) in
outbound messages. Identity fields are passed best-effort for Slack
(graceful fallback if chat:write.customize scope is missing).

Fixes #16218

* fix: fix Slack cron delivery identity (#16242) (thanks @robbyczgw-cla)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/slack/send.ts

@@ -33,8 +33,83 @@ type SlackSendOpts = {
   mediaUrl?: string;
   client?: WebClient;
   threadTs?: string;
+  username?: string;
+  icon_url?: string;
+  icon_emoji?: string;
 };
 
+function hasCustomIdentity(opts: SlackSendOpts): boolean {
+  return Boolean(opts.username || opts.icon_url || opts.icon_emoji);
+}
+
+function isSlackCustomizeScopeError(err: unknown): boolean {
+  if (!(err instanceof Error)) {
+    return false;
+  }
+  const maybeData = err as Error & {
+    data?: {
+      error?: string;
+      needed?: string;
+      response_metadata?: { scopes?: string[]; acceptedScopes?: string[] };
+    };
+  };
+  const code = maybeData.data?.error?.toLowerCase();
+  if (code !== "missing_scope") {
+    return false;
+  }
+  const needed = maybeData.data?.needed?.toLowerCase();
+  if (needed?.includes("chat:write.customize")) {
+    return true;
+  }
+  const scopes = [
+    ...(maybeData.data?.response_metadata?.scopes ?? []),
+    ...(maybeData.data?.response_metadata?.acceptedScopes ?? []),
+  ].map((scope) => scope.toLowerCase());
+  return scopes.includes("chat:write.customize");
+}
+
+async function postSlackMessageBestEffort(params: {
+  client: WebClient;
+  channelId: string;
+  text: string;
+  threadTs?: string;
+  opts: SlackSendOpts;
+}) {
+  const basePayload = {
+    channel: params.channelId,
+    text: params.text,
+    thread_ts: params.threadTs,
+  };
+  try {
+    // Slack Web API types model icon_url and icon_emoji as mutually exclusive.
+    // Build payloads in explicit branches so TS and runtime stay aligned.
+    if (params.opts.icon_url) {
+      return await params.client.chat.postMessage({
+        ...basePayload,
+        ...(params.opts.username ? { username: params.opts.username } : {}),
+        icon_url: params.opts.icon_url,
+      });
+    }
+    if (params.opts.icon_emoji) {
+      return await params.client.chat.postMessage({
+        ...basePayload,
+        ...(params.opts.username ? { username: params.opts.username } : {}),
+        icon_emoji: params.opts.icon_emoji,
+      });
+    }
+    return await params.client.chat.postMessage({
+      ...basePayload,
+      ...(params.opts.username ? { username: params.opts.username } : {}),
+    });
+  } catch (err) {
+    if (!hasCustomIdentity(params.opts) || !isSlackCustomizeScopeError(err)) {
+      throw err;
+    }
+    logVerbose("slack send: missing chat:write.customize, retrying without custom identity");
+    return params.client.chat.postMessage(basePayload);
+  }
+}
+
 export type SlackSendResult = {
   messageId: string;
   channelId: string;
@@ -182,19 +257,23 @@ export async function sendMessageSlack(
       maxBytes: mediaMaxBytes,
     });
     for (const chunk of rest) {
-      const response = await client.chat.postMessage({
-        channel: channelId,
+      const response = await postSlackMessageBestEffort({
+        client,
+        channelId,
         text: chunk,
-        thread_ts: opts.threadTs,
+        threadTs: opts.threadTs,
+        opts,
       });
       lastMessageId = response.ts ?? lastMessageId;
     }
   } else {
     for (const chunk of chunks.length ? chunks : [""]) {
-      const response = await client.chat.postMessage({
-        channel: channelId,
+      const response = await postSlackMessageBestEffort({
+        client,
+        channelId,
         text: chunk,
-        thread_ts: opts.threadTs,
+        threadTs: opts.threadTs,
+        opts,
       });
       lastMessageId = response.ts ?? lastMessageId;
     }