attempt to make end webhooks replies to the start webhooks

Author: sarahsturgeon

web/src/index.ts

@@ -53,6 +53,7 @@ export class BaseSession extends Container<Env> {
   // In-memory only: on DO hibernation we lose geo/ISP fields in the end
   // embed, which is cosmetic — never a correctness concern.
   protected obsContext?: RequestContext;
+  private startMessageId?: string;
 
   private async fetchCapacitySnapshot(): Promise<CapacitySnapshot | undefined> {
     try {
@@ -107,7 +108,7 @@ export class BaseSession extends Container<Env> {
       this.obsContext = parseContext(request.headers.get(OBS_CONTEXT_HEADER));
       void (async () => {
         const capacity = await this.fetchCapacitySnapshot();
-        await notify.sessionStarted(this.env, {
+        this.startMessageId = await notify.sessionStarted(this.env, {
           sessionId,
           branch: this.branch,
           context: this.obsContext ?? { ip: "unknown" },
@@ -414,6 +415,7 @@ export class BaseSession extends Container<Env> {
         extensionGranted: this.extensionGranted,
         context: this.obsContext,
         capacity,
+        replyTo: this.startMessageId,
       });
     })();
   }

web/src/observability/embeds.ts

@@ -27,6 +27,7 @@ interface DiscordEmbed {
 
 export interface DiscordWebhookPayload {
   embeds: DiscordEmbed[];
+  message_reference?: { message_id: string };
 }
 
 const COLORS = {

web/src/observability/index.ts

@@ -23,7 +23,10 @@ export const notify = {
   sessionStarted: (env: Env, event: SessionStartedEvent) =>
     post(env, { embeds: [buildSessionStartedEmbed(event)] }),
   sessionEnded: (env: Env, event: SessionEndedEvent) =>
-    post(env, { embeds: [buildSessionEndedEmbed(event)] }),
+    post(env, {
+      embeds: [buildSessionEndedEmbed(event)],
+      ...(event.replyTo ? { message_reference: { message_id: event.replyTo } } : {}),
+    }),
   queueEntered: (env: Env, event: QueueEnteredEvent) =>
     post(env, { embeds: [buildQueueEnteredEmbed(event)] }),
   error: (env: Env, event: ErrorEvent) =>

web/src/observability/types.ts

@@ -46,6 +46,7 @@ export interface SessionEndedEvent {
   extensionGranted: boolean;
   context?: RequestContext;
   capacity?: CapacitySnapshot;
+  replyTo?: string;
 }
 
 export interface QueueEnteredEvent {

web/src/observability/webhook.ts

@@ -2,23 +2,26 @@ import type { DiscordWebhookPayload } from "./embeds";
 
 const WEBHOOK_TIMEOUT_MS = 3000;
 
-export async function post(env: { DISCORD_WEBHOOK_URL?: string }, payload: DiscordWebhookPayload): Promise<void> {
+// Fire-and-forget. No-op when the secret is unset. Never throws —
+// observability must not be able to break the request path.
+// Returns the Discord message ID when available (for threading replies).
+export async function post(env: { DISCORD_WEBHOOK_URL?: string }, payload: DiscordWebhookPayload): Promise<string | undefined> {
   const url = env.DISCORD_WEBHOOK_URL;
-  if (!url) return;
+  if (!url) return undefined;
 
   let body: string;
   try {
     body = JSON.stringify(payload);
   } catch (e) {
     console.error("[obs] webhook payload JSON.stringify failed:", e);
-    return;
+    return undefined;
   }
 
   const controller = new AbortController();
   const timeout = setTimeout(() => controller.abort(), WEBHOOK_TIMEOUT_MS);
 
   try {
-    const res = await fetch(url, {
+    const res = await fetch(`${url}?wait=true`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body,
@@ -29,7 +32,10 @@ export async function post(env: { DISCORD_WEBHOOK_URL?: string }, payload: Disco
       console.error(
         `[obs] webhook non-2xx: status=${res.status} statusText=${res.statusText} body=${resBody.slice(0, 300)}`,
       );
+      return undefined;
     }
+    const data = await res.json<{ id: string }>();
+    return data.id;
   } catch (e) {
     if (e instanceof Error && e.name === "AbortError") {
       console.error(`[obs] webhook timed out after ${WEBHOOK_TIMEOUT_MS}ms`);
@@ -38,6 +44,7 @@ export async function post(env: { DISCORD_WEBHOOK_URL?: string }, payload: Disco
       const msg = e instanceof Error ? e.message : String(e);
       console.error(`[obs] webhook post failed: ${name}: ${msg}`);
     }
+    return undefined;
   } finally {
     clearTimeout(timeout);
   }