diff --git a/.changeset/fix-lobby-party-type.md b/.changeset/fix-lobby-party-type.md
new file mode 100644
index 0000000..ac2a239
--- /dev/null
+++ b/.changeset/fix-lobby-party-type.md
@@ -0,0 +1,5 @@
+---
+"partyserver": patch
+---
+
+Add `lobby.className` to `onBeforeConnect`/`onBeforeRequest` callbacks, providing the Durable Object class name (e.g. `"MyAgent"`). The existing `lobby.party` field is now deprecated (it returns the kebab-case URL namespace) and will be changed to return the class name in the next major version.
diff --git a/package-lock.json b/package-lock.json
index b2ded74..4b623ee 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12235,7 +12235,7 @@
       "devDependencies": {
         "@cloudflare/workers-types": "^4.20251218.0",
         "hono": "^4.11.1",
-        "partyserver": "^0.1.4"
+        "partyserver": "^0.1.5"
       },
       "peerDependencies": {
         "@cloudflare/workers-types": "^4.20240729.0",
@@ -12327,7 +12327,7 @@
       "license": "ISC",
       "devDependencies": {
         "@cloudflare/workers-types": "^4.20251218.0",
-        "partyserver": "^0.1.4",
+        "partyserver": "^0.1.5",
         "partysocket": "^1.1.13"
       },
       "peerDependencies": {
@@ -12345,7 +12345,7 @@
       },
       "devDependencies": {
         "@cloudflare/workers-types": "^4.20251218.0",
-        "partyserver": "^0.1.4"
+        "partyserver": "^0.1.5"
       },
       "peerDependencies": {
         "@cloudflare/workers-types": "^4.20240729.0",
@@ -12367,7 +12367,7 @@
       "license": "ISC",
       "dependencies": {
         "cron-parser": "^5.4.0",
-        "partyserver": "^0.1.4"
+        "partyserver": "^0.1.5"
       }
     },
     "packages/y-partyserver": {
@@ -12382,7 +12382,7 @@
       "devDependencies": {
         "@cloudflare/workers-types": "^4.20251218.0",
         "@types/lodash.debounce": "^4.0.9",
-        "partyserver": "^0.1.4",
+        "partyserver": "^0.1.5",
         "ws": "^8.18.3",
         "yjs": "^13.6.28"
       },
diff --git a/packages/hono-party/package.json b/packages/hono-party/package.json
index a3f2433..d901a8e 100644
--- a/packages/hono-party/package.json
+++ b/packages/hono-party/package.json
@@ -37,6 +37,6 @@
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20251218.0",
     "hono": "^4.11.1",
-    "partyserver": "^0.1.4"
+    "partyserver": "^0.1.5"
   }
 }
diff --git a/packages/partyserver/src/index.ts b/packages/partyserver/src/index.ts
index a7a910c..17e7411 100644
--- a/packages/partyserver/src/index.ts
+++ b/packages/partyserver/src/index.ts
@@ -31,6 +31,9 @@ const serverMapCache = new WeakMap<
   Record<string, DurableObjectNamespace>
 >();
 
+// Maps kebab-case namespace -> original env binding name (e.g. "my-agent" -> "MyAgent")
+const bindingNameCache = new WeakMap<object, Record<string, string>>();
+
 /**
  * For a given server namespace, create a server with a name.
  */
@@ -87,8 +90,20 @@ function camelCaseToKebabCase(str: string): string {
   // Convert any remaining underscores to hyphens and remove trailing -'s
   return kebabified.replace(/_/g, "-").replace(/-$/, "");
 }
+export interface Lobby<Env = Cloudflare.Env> {
+  /**
+   * The kebab-case namespace from the URL path (e.g. `"my-agent"`).
+   * @deprecated Use `className` instead, which returns the Durable Object class name.
+   * In the next major version, `party` will return the class name instead of the kebab-case namespace.
+   */
+  party: string;
+  /** The Durable Object class name / env binding name (e.g. `"MyAgent"`). */
+  className: Extract<keyof Env, string>;
+  /** The room / instance name extracted from the URL. */
+  name: string;
+}
+
 export interface PartyServerOptions<
-  // biome-ignore lint/correctness/noUnusedVariables: it's ok, we'll remove this in the next major
   Env = Cloudflare.Env,
   Props = Record<string, unknown>
 > {
@@ -122,17 +137,11 @@ export interface PartyServerOptions<
   cors?: boolean | HeadersInit;
   onBeforeConnect?: (
     req: Request,
-    lobby: {
-      party: string;
-      name: string;
-    }
+    lobby: Lobby<Env>
   ) => Response | Request | void | Promise<Response | Request | void>;
   onBeforeRequest?: (
     req: Request,
-    lobby: {
-      party: string;
-      name: string;
-    }
+    lobby: Lobby<Env>
   ) =>
     | Response
     | Request
@@ -175,26 +184,28 @@ export async function routePartykitRequest<
   options?: PartyServerOptions<Env, Props>
 ): Promise<Response | null> {
   if (!serverMapCache.has(env)) {
-    serverMapCache.set(
-      env,
-      Object.entries(env).reduce((acc, [k, v]) => {
-        if (
-          v &&
-          typeof v === "object" &&
-          "idFromName" in v &&
-          typeof v.idFromName === "function"
-        ) {
-          Object.assign(acc, { [camelCaseToKebabCase(k)]: v });
-          return acc;
-        }
-        return acc;
-      }, {})
-    );
+    const namespaceMap: Record<string, DurableObjectNamespace> = {};
+    const bindingNames: Record<string, string> = {};
+    for (const [k, v] of Object.entries(env)) {
+      if (
+        v &&
+        typeof v === "object" &&
+        "idFromName" in v &&
+        typeof v.idFromName === "function"
+      ) {
+        const kebab = camelCaseToKebabCase(k);
+        namespaceMap[kebab] = v as DurableObjectNamespace;
+        bindingNames[kebab] = k;
+      }
+    }
+    serverMapCache.set(env, namespaceMap);
+    bindingNameCache.set(env, bindingNames);
   }
   const map = serverMapCache.get(env) as unknown as Record<
     string,
     DurableObjectNamespace<T>
   >;
+  const bindingNames = bindingNameCache.get(env) as Record<string, string>;
 
   const prefix = options?.prefix || "parties";
   const prefixParts = prefix.split("/");
@@ -271,12 +282,27 @@ Did you forget to add a durable object binding to the class ${namespace[0].toUpp
       req.headers.set("x-partykit-props", JSON.stringify(options?.props));
     }
 
+    const className = bindingNames[namespace] as Extract<keyof Env, string>;
+    let partyDeprecationWarned = false;
+    const lobby: Lobby<Env> = {
+      get party() {
+        if (!partyDeprecationWarned) {
+          partyDeprecationWarned = true;
+          console.warn(
+            'lobby.party is deprecated and currently returns the kebab-case namespace (e.g. "my-agent"). ' +
+              'Use lobby.className instead to get the Durable Object class name (e.g. "MyAgent"). ' +
+              "In the next major version, lobby.party will return the class name."
+          );
+        }
+        return namespace;
+      },
+      className,
+      name
+    };
+
     if (isWebSocket) {
       if (options?.onBeforeConnect) {
-        const reqOrRes = await options.onBeforeConnect(req, {
-          party: namespace,
-          name
-        });
+        const reqOrRes = await options.onBeforeConnect(req, lobby);
         if (reqOrRes instanceof Request) {
           req = reqOrRes;
         } else if (reqOrRes instanceof Response) {
@@ -285,10 +311,7 @@ Did you forget to add a durable object binding to the class ${namespace[0].toUpp
       }
     } else {
       if (options?.onBeforeRequest) {
-        const reqOrRes = await options.onBeforeRequest(req, {
-          party: namespace,
-          name
-        });
+        const reqOrRes = await options.onBeforeRequest(req, lobby);
         if (reqOrRes instanceof Request) {
           req = reqOrRes;
         } else if (reqOrRes instanceof Response) {
diff --git a/packages/partyserver/src/tests/index.test.ts b/packages/partyserver/src/tests/index.test.ts
index 1cf9a51..fd11183 100644
--- a/packages/partyserver/src/tests/index.test.ts
+++ b/packages/partyserver/src/tests/index.test.ts
@@ -150,6 +150,19 @@ describe("Server", () => {
     expect(response.headers.get("Location")).toBe("https://example3.com");
   });
 
+  it("provides className with the Durable Object class name", async () => {
+    const ctx = createExecutionContext();
+    const request = new Request(
+      "http://example.com/parties/on-start-server/lobby-info"
+    );
+    const response = await worker.fetch(request, env, ctx);
+    expect(response.status).toBe(200);
+    expect(await response.json()).toEqual({
+      className: "OnStartServer",
+      name: "lobby-info"
+    });
+  });
+
   it("ignores foreign hibernated websockets when broadcasting", async () => {
     const ctx = createExecutionContext();
 
diff --git a/packages/partyserver/src/tests/worker.ts b/packages/partyserver/src/tests/worker.ts
index 95b74c6..35b929f 100644
--- a/packages/partyserver/src/tests/worker.ts
+++ b/packages/partyserver/src/tests/worker.ts
@@ -353,8 +353,8 @@ export default {
 
     return (
       (await routePartykitRequest(request, env, {
-        onBeforeConnect: async (_request, { party, name }) => {
-          if (party === "on-start-server") {
+        onBeforeConnect: async (_request, { className, name }) => {
+          if (className === "OnStartServer") {
             if (name === "is-error") {
               return new Response("Error", { status: 503 });
             } else if (name === "is-redirect") {
@@ -365,17 +365,23 @@ export default {
             }
           }
         },
-        onBeforeRequest: async (_request, { party, name }) => {
-          if (party === "on-start-server") {
-            if (name === "is-error") {
+        onBeforeRequest: async (_request, lobby) => {
+          if (lobby.className === "OnStartServer") {
+            if (lobby.name === "is-error") {
               return new Response("Error", { status: 504 });
-            } else if (name === "is-redirect") {
+            } else if (lobby.name === "is-redirect") {
               return new Response("Redirect", {
                 status: 302,
                 headers: { Location: "https://example3.com" }
               });
             }
           }
+          if (lobby.name === "lobby-info") {
+            return Response.json({
+              className: lobby.className,
+              name: lobby.name
+            });
+          }
         }
       })) || new Response("Not Found", { status: 404 })
     );
diff --git a/packages/partysub/package.json b/packages/partysub/package.json
index 099d20c..833d52d 100644
--- a/packages/partysub/package.json
+++ b/packages/partysub/package.json
@@ -46,7 +46,7 @@
   },
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20251218.0",
-    "partyserver": "^0.1.4",
+    "partyserver": "^0.1.5",
     "partysocket": "^1.1.13"
   }
 }
diff --git a/packages/partysync/package.json b/packages/partysync/package.json
index 2cf6edc..2a3b306 100644
--- a/packages/partysync/package.json
+++ b/packages/partysync/package.json
@@ -54,6 +54,6 @@
   },
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20251218.0",
-    "partyserver": "^0.1.4"
+    "partyserver": "^0.1.5"
   }
 }
diff --git a/packages/partywhen/package.json b/packages/partywhen/package.json
index cae5ac7..3906256b 100644
--- a/packages/partywhen/package.json
+++ b/packages/partywhen/package.json
@@ -29,6 +29,6 @@
   "description": "A library for scheduling and running tasks in Cloudflare Workers",
   "dependencies": {
     "cron-parser": "^5.4.0",
-    "partyserver": "^0.1.4"
+    "partyserver": "^0.1.5"
   }
 }
diff --git a/packages/y-partyserver/package.json b/packages/y-partyserver/package.json
index f775eb4..e83f5ad 100644
--- a/packages/y-partyserver/package.json
+++ b/packages/y-partyserver/package.json
@@ -53,7 +53,7 @@
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20251218.0",
     "@types/lodash.debounce": "^4.0.9",
-    "partyserver": "^0.1.4",
+    "partyserver": "^0.1.5",
     "ws": "^8.18.3",
     "yjs": "^13.6.28"
   }