diff --git a/.changeset/social-carrots-melt.md b/.changeset/social-carrots-melt.md
new file mode 100644
index 00000000000..b3effe5a915
--- /dev/null
+++ b/.changeset/social-carrots-melt.md
@@ -0,0 +1,6 @@
+---
+'@clerk/backend': patch
+'@clerk/nextjs': patch
+---
+
+Resolve machine token property mixing in discriminated unions
\ No newline at end of file
diff --git a/packages/backend/src/index.ts b/packages/backend/src/index.ts
index eadfe571e51..2b33d227388 100644
--- a/packages/backend/src/index.ts
+++ b/packages/backend/src/index.ts
@@ -162,3 +162,4 @@ export type {
  * Auth objects
  */
 export type { AuthObject } from './tokens/authObjects';
+export type { SessionAuthObject, MachineAuthObject } from './tokens/types';
diff --git a/packages/backend/src/internal.ts b/packages/backend/src/internal.ts
index fc729046e19..4f176cc0489 100644
--- a/packages/backend/src/internal.ts
+++ b/packages/backend/src/internal.ts
@@ -12,8 +12,6 @@ export type {
   OrganizationSyncOptions,
   InferAuthObjectFromToken,
   InferAuthObjectFromTokenArray,
-  SessionAuthObject,
-  MachineAuthObject,
   GetAuthFn,
 } from './tokens/types';
 
diff --git a/packages/backend/src/tokens/__tests__/getAuth.test-d.ts b/packages/backend/src/tokens/__tests__/getAuth.test-d.ts
new file mode 100644
index 00000000000..ec38dc42ffc
--- /dev/null
+++ b/packages/backend/src/tokens/__tests__/getAuth.test-d.ts
@@ -0,0 +1,107 @@
+import { assertType, test } from 'vitest';
+
+import type { AuthObject } from '../authObjects';
+import type { GetAuthFn, MachineAuthObject, SessionAuthObject } from '../types';
+
+// Across our SDKs, we have a getAuth() function
+const getAuth: GetAuthFn<Request> = (_request: any, _options: any) => {
+  return {} as any;
+};
+
+test('infers the correct AuthObject type for each accepted token type', () => {
+  const request = new Request('https://example.com');
+
+  // Session token by default
+  assertType<SessionAuthObject>(getAuth(request));
+
+  // Individual token types
+  assertType<SessionAuthObject>(getAuth(request, { acceptsToken: 'session_token' }));
+  assertType<MachineAuthObject<'api_key'>>(getAuth(request, { acceptsToken: 'api_key' }));
+  assertType<MachineAuthObject<'machine_token'>>(getAuth(request, { acceptsToken: 'machine_token' }));
+  assertType<MachineAuthObject<'oauth_token'>>(getAuth(request, { acceptsToken: 'oauth_token' }));
+
+  // Array of token types
+  assertType<SessionAuthObject | MachineAuthObject<'machine_token'>>(
+    getAuth(request, { acceptsToken: ['session_token', 'machine_token'] }),
+  );
+  assertType<MachineAuthObject<'machine_token' | 'oauth_token'>>(
+    getAuth(request, { acceptsToken: ['machine_token', 'oauth_token'] }),
+  );
+
+  // Any token type
+  assertType<AuthObject>(getAuth(request, { acceptsToken: 'any' }));
+});
+
+test('verifies correct properties exist for each token type', () => {
+  const request = new Request('https://example.com');
+
+  // Session token should have userId
+  const sessionAuth = getAuth(request, { acceptsToken: 'session_token' });
+  assertType<string | null>(sessionAuth.userId);
+
+  // All machine tokens should have id and subject
+  const apiKeyAuth = getAuth(request, { acceptsToken: 'api_key' });
+  const machineTokenAuth = getAuth(request, { acceptsToken: 'machine_token' });
+  const oauthTokenAuth = getAuth(request, { acceptsToken: 'oauth_token' });
+
+  assertType<string | null>(apiKeyAuth.id);
+  assertType<string | null>(machineTokenAuth.id);
+  assertType<string | null>(oauthTokenAuth.id);
+  assertType<string | null>(apiKeyAuth.subject);
+  assertType<string | null>(machineTokenAuth.subject);
+  assertType<string | null>(oauthTokenAuth.subject);
+
+  // Only api_key and machine_token should have name and claims
+  assertType<string | null>(apiKeyAuth.name);
+  assertType<Record<string, any> | null>(apiKeyAuth.claims);
+
+  assertType<string | null>(machineTokenAuth.name);
+  assertType<Record<string, any> | null>(machineTokenAuth.claims);
+
+  // oauth_token should NOT have name and claims
+  // @ts-expect-error oauth_token does not have name property
+  void oauthTokenAuth.name;
+  // @ts-expect-error oauth_token does not have claims property
+  void oauthTokenAuth.claims;
+});
+
+test('verifies discriminated union works correctly with acceptsToken: any', () => {
+  const request = new Request('https://example.com');
+
+  const auth = getAuth(request, { acceptsToken: 'any' });
+
+  if (auth.tokenType === 'session_token') {
+    // Should be SessionAuthObject - has userId
+    assertType<string | null>(auth.userId);
+    // Should NOT have machine token properties
+    // @ts-expect-error session_token does not have id property
+    void auth.id;
+  } else if (auth.tokenType === 'api_key') {
+    // Should be AuthenticatedMachineObject<'api_key'> - has id, name, claims
+    assertType<string | null>(auth.id);
+    assertType<string | null>(auth.name);
+    assertType<Record<string, any> | null>(auth.claims);
+    // Should NOT have session token properties
+    // @ts-expect-error api_key does not have userId property
+    void auth.userId;
+  } else if (auth.tokenType === 'machine_token') {
+    // Should be AuthenticatedMachineObject<'machine_token'> - has id, name, claims
+    assertType<string | null>(auth.id);
+    assertType<string | null>(auth.name);
+    assertType<Record<string, any> | null>(auth.claims);
+    // Should NOT have session token properties
+    // @ts-expect-error machine_token does not have userId property
+    void auth.userId;
+  } else if (auth.tokenType === 'oauth_token') {
+    // Should be AuthenticatedMachineObject<'oauth_token'> - has id but NOT name/claims
+    assertType<string | null>(auth.id);
+    // Should NOT have name or claims
+    // @ts-expect-error oauth_token does not have name property
+    void auth.name;
+    // @ts-expect-error oauth_token does not have claims property
+    void auth.claims;
+    // Should NOT have session token properties
+    // @ts-expect-error oauth_token does not have userId property
+    void auth.userId;
+  }
+});
diff --git a/packages/backend/src/tokens/authObjects.ts b/packages/backend/src/tokens/authObjects.ts
index 97135c03865..410aef1e77d 100644
--- a/packages/backend/src/tokens/authObjects.ts
+++ b/packages/backend/src/tokens/authObjects.ts
@@ -104,29 +104,43 @@ type MachineObjectExtendedProperties<TAuthenticated extends boolean> = {
 
 /**
  * @internal
+ *
+ * Uses `T extends any` to create a distributive conditional type.
+ * This ensures that union types like `'api_key' | 'oauth_token'` are processed
+ * individually, creating proper discriminated unions where each token type
+ * gets its own distinct properties (e.g., oauth_token won't have claims).
  */
-export type AuthenticatedMachineObject<T extends MachineTokenType = MachineTokenType> = {
-  id: string;
-  subject: string;
-  scopes: string[];
-  getToken: () => Promise<string>;
-  has: CheckAuthorizationFromSessionClaims;
-  debug: AuthObjectDebug;
-  tokenType: T;
-} & MachineObjectExtendedProperties<true>[T];
+export type AuthenticatedMachineObject<T extends MachineTokenType = MachineTokenType> = T extends any
+  ? {
+      id: string;
+      subject: string;
+      scopes: string[];
+      getToken: () => Promise<string>;
+      has: CheckAuthorizationFromSessionClaims;
+      debug: AuthObjectDebug;
+      tokenType: T;
+    } & MachineObjectExtendedProperties<true>[T]
+  : never;
 
 /**
  * @internal
+ *
+ * Uses `T extends any` to create a distributive conditional type.
+ * This ensures that union types like `'api_key' | 'oauth_token'` are processed
+ * individually, creating proper discriminated unions where each token type
+ * gets its own distinct properties (e.g., oauth_token won't have claims).
  */
-export type UnauthenticatedMachineObject<T extends MachineTokenType = MachineTokenType> = {
-  id: null;
-  subject: null;
-  scopes: null;
-  getToken: () => Promise<null>;
-  has: CheckAuthorizationFromSessionClaims;
-  debug: AuthObjectDebug;
-  tokenType: T;
-} & MachineObjectExtendedProperties<false>[T];
+export type UnauthenticatedMachineObject<T extends MachineTokenType = MachineTokenType> = T extends any
+  ? {
+      id: null;
+      subject: null;
+      scopes: null;
+      getToken: () => Promise<null>;
+      has: CheckAuthorizationFromSessionClaims;
+      debug: AuthObjectDebug;
+      tokenType: T;
+    } & MachineObjectExtendedProperties<false>[T]
+  : never;
 
 /**
  * @interface
@@ -243,7 +257,7 @@ export function authenticatedMachineObject<T extends MachineTokenType>(
         name: result.name,
         claims: result.claims,
         scopes: result.scopes,
-      };
+      } as unknown as AuthenticatedMachineObject<T>;
     }
     case TokenType.MachineToken: {
       const result = verificationResult as MachineToken;
@@ -253,7 +267,7 @@ export function authenticatedMachineObject<T extends MachineTokenType>(
         name: result.name,
         claims: result.claims,
         scopes: result.scopes,
-      };
+      } as unknown as AuthenticatedMachineObject<T>;
     }
     case TokenType.OAuthToken: {
       return {
@@ -290,7 +304,7 @@ export function unauthenticatedMachineObject<T extends MachineTokenType>(
         tokenType,
         name: null,
         claims: null,
-      };
+      } as unknown as UnauthenticatedMachineObject<T>;
     }
     case TokenType.MachineToken: {
       return {
@@ -298,7 +312,7 @@ export function unauthenticatedMachineObject<T extends MachineTokenType>(
         tokenType,
         name: null,
         claims: null,
-      };
+      } as unknown as UnauthenticatedMachineObject<T>;
     }
     case TokenType.OAuthToken: {
       return {
diff --git a/packages/backend/src/tokens/types.ts b/packages/backend/src/tokens/types.ts
index c87f1f3bc8b..badda7d18f3 100644
--- a/packages/backend/src/tokens/types.ts
+++ b/packages/backend/src/tokens/types.ts
@@ -163,8 +163,8 @@ export type InferAuthObjectFromTokenArray<
 > = SessionTokenType extends T[number]
   ? T[number] extends SessionTokenType
     ? SessionType
-    : SessionType | (MachineType & { tokenType: T[number] })
-  : MachineType & { tokenType: T[number] };
+    : SessionType | (MachineType & { tokenType: Exclude<T[number], SessionTokenType> })
+  : MachineType & { tokenType: Exclude<T[number], SessionTokenType> };
 
 /**
  * Infers auth object type from a single token type.
@@ -174,12 +174,12 @@ export type InferAuthObjectFromToken<
   T extends TokenType,
   SessionType extends AuthObject,
   MachineType extends AuthObject,
-> = T extends SessionTokenType ? SessionType : MachineType & { tokenType: T };
+> = T extends SessionTokenType ? SessionType : MachineType & { tokenType: Exclude<T, SessionTokenType> };
 
 export type SessionAuthObject = SignedInAuthObject | SignedOutAuthObject;
-export type MachineAuthObject<T extends TokenType> = (AuthenticatedMachineObject | UnauthenticatedMachineObject) & {
-  tokenType: T;
-};
+export type MachineAuthObject<T extends Exclude<TokenType, SessionTokenType>> = T extends any
+  ? AuthenticatedMachineObject<T> | UnauthenticatedMachineObject<T>
+  : never;
 
 type AuthOptions = PendingSessionOptions & { acceptsToken?: AuthenticateRequestOptions['acceptsToken'] };
 
@@ -199,7 +199,10 @@ export interface GetAuthFn<RequestType, ReturnsPromise extends boolean = false>
   <T extends TokenType[]>(
     req: RequestType,
     options: AuthOptions & { acceptsToken: T },
-  ): MaybePromise<InferAuthObjectFromTokenArray<T, SessionAuthObject, MachineAuthObject<T[number]>>, ReturnsPromise>;
+  ): MaybePromise<
+    InferAuthObjectFromTokenArray<T, SessionAuthObject, MachineAuthObject<Exclude<T[number], SessionTokenType>>>,
+    ReturnsPromise
+  >;
 
   /**
    * @example
@@ -208,7 +211,10 @@ export interface GetAuthFn<RequestType, ReturnsPromise extends boolean = false>
   <T extends TokenType>(
     req: RequestType,
     options: AuthOptions & { acceptsToken: T },
-  ): MaybePromise<InferAuthObjectFromToken<T, SessionAuthObject, MachineAuthObject<T>>, ReturnsPromise>;
+  ): MaybePromise<
+    InferAuthObjectFromToken<T, SessionAuthObject, MachineAuthObject<Exclude<T, SessionTokenType>>>,
+    ReturnsPromise
+  >;
 
   /**
    * @example
diff --git a/packages/backend/vitest.config.mts b/packages/backend/vitest.config.mts
index c4904416012..c690ee913f2 100644
--- a/packages/backend/vitest.config.mts
+++ b/packages/backend/vitest.config.mts
@@ -3,6 +3,10 @@ import { defineConfig } from 'vitest/config';
 export default defineConfig({
   plugins: [],
   test: {
+    typecheck: {
+      enabled: true,
+      include: ['**/*.test.ts'],
+    },
     coverage: {
       provider: 'v8',
     },
diff --git a/packages/nextjs/src/app-router/server/auth.ts b/packages/nextjs/src/app-router/server/auth.ts
index 74ea1ff9051..ec5b151f7ee 100644
--- a/packages/nextjs/src/app-router/server/auth.ts
+++ b/packages/nextjs/src/app-router/server/auth.ts
@@ -1,11 +1,10 @@
-import type { AuthObject } from '@clerk/backend';
+import type { AuthObject, MachineAuthObject, SessionAuthObject } from '@clerk/backend';
 import type {
   AuthenticateRequestOptions,
   InferAuthObjectFromToken,
   InferAuthObjectFromTokenArray,
-  MachineAuthObject,
   RedirectFun,
-  SessionAuthObject,
+  SessionTokenType,
 } from '@clerk/backend/internal';
 import { constants, createClerkRequest, createRedirect, TokenType } from '@clerk/backend/internal';
 import type { PendingSessionOptions } from '@clerk/types';
@@ -56,7 +55,13 @@ export interface AuthFn<TRedirect = ReturnType<typeof redirect>> {
    */
   <T extends TokenType[]>(
     options: AuthOptions & { acceptsToken: T },
-  ): Promise<InferAuthObjectFromTokenArray<T, SessionAuthWithRedirect<TRedirect>, MachineAuthObject<T[number]>>>;
+  ): Promise<
+    InferAuthObjectFromTokenArray<
+      T,
+      SessionAuthWithRedirect<TRedirect>,
+      MachineAuthObject<Exclude<T[number], SessionTokenType>>
+    >
+  >;
 
   /**
    * @example
@@ -64,7 +69,9 @@ export interface AuthFn<TRedirect = ReturnType<typeof redirect>> {
    */
   <T extends TokenType>(
     options: AuthOptions & { acceptsToken: T },
-  ): Promise<InferAuthObjectFromToken<T, SessionAuthWithRedirect<TRedirect>, MachineAuthObject<T>>>;
+  ): Promise<
+    InferAuthObjectFromToken<T, SessionAuthWithRedirect<TRedirect>, MachineAuthObject<Exclude<T, SessionTokenType>>>
+  >;
 
   /**
    * @example
diff --git a/packages/nextjs/src/server/protect.ts b/packages/nextjs/src/server/protect.ts
index bdd73ce85ec..cfb0dea5628 100644
--- a/packages/nextjs/src/server/protect.ts
+++ b/packages/nextjs/src/server/protect.ts
@@ -73,6 +73,12 @@ export interface AuthProtect {
     options?: AuthProtectOptions & { token: T },
   ): Promise<InferAuthObjectFromTokenArray<T, SignedInAuthObject, AuthenticatedMachineObject>>;
 
+  /**
+   * @example
+   * auth.protect({ token: 'any' });
+   */
+  (options?: AuthProtectOptions & { token: 'any' }): Promise<SignedInAuthObject | AuthenticatedMachineObject>;
+
   /**
    * @example
    * auth.protect();