Middleware & Handler Patterns

Middleware

Aspect	Slack (Bolt)	Teams SDK v2
Global middleware	app.use(async (\{ next \}) => \{ ... await next(); \})	app.use(async (ctx) => \{ ... ctx.next(); \})
Chaining	Explicit await next() — omitting drops the event silently	Explicit ctx.next() — omitting stops the pipeline
Listener middleware	Passed as extra args to app.message(filter, middleware, handler)	No equivalent — use guard functions at handler start
Authorization	Custom middleware checking Slack user/workspace	Bot Framework JWT validation is automatic

Rating: GREEN — both have middleware, but Slack's is more granular.

Key Difference

Slack supports listener middleware — functions that run only for specific handlers. Teams has no equivalent. Convert listener middleware to guard conditions at the top of each handler:

// Slack: listener middleware
app.message(isAdmin, async ({ say }) => { await say("Admin action"); });

// Teams: guard function
app.on("message", async (ctx) => {
  if (!isAdmin(ctx.activity.from.id)) return;
  await ctx.send("Admin action");
});