diff --git a/clients/js/src/utils.ts b/clients/js/src/utils.ts
index 6fb0747..2b6f33c 100644
--- a/clients/js/src/utils.ts
+++ b/clients/js/src/utils.ts
@@ -35,14 +35,8 @@ import {
 
 export const ACCOUNT_HEADER_LENGTH = 96;
 
-export const LOADER_V1_PROGRAM_ADDRESS =
-    'BPFLoader1111111111111111111111111111111111' as Address<'BPFLoader1111111111111111111111111111111111'>;
-export const LOADER_V2_PROGRAM_ADDRESS =
-    'BPFLoader2111111111111111111111111111111111' as Address<'BPFLoader2111111111111111111111111111111111'>;
 export const LOADER_V3_PROGRAM_ADDRESS =
     'BPFLoaderUpgradeab1e11111111111111111111111' as Address<'BPFLoaderUpgradeab1e11111111111111111111111'>;
-export const LOADER_V4_PROGRAM_ADDRESS =
-    'CoreBPFLoaderV41111111111111111111111111111' as Address<'CoreBPFLoaderV41111111111111111111111111111'>;
 
 export type MetadataInput = {
     payer: TransactionSigner;
@@ -127,17 +121,16 @@ export async function getProgramAuthority(
         throw Error('Program account must be executable');
     }
 
-    // Check all the loader programs.
-    switch (programAccount.programAddress) {
-        case LOADER_V1_PROGRAM_ADDRESS:
-        case LOADER_V2_PROGRAM_ADDRESS:
-            return { authority: program };
-        case LOADER_V3_PROGRAM_ADDRESS:
-            return await getProgramAuthorityForLoaderV3(rpc, programAccount);
-        case LOADER_V4_PROGRAM_ADDRESS:
-        default:
-            throw new Error('Unsupported loader program: ' + programAccount.programAddress);
+    // Loader v3 programs store their upgrade authority in a separate program
+    // data account.
+    if (programAccount.programAddress === LOADER_V3_PROGRAM_ADDRESS) {
+        return await getProgramAuthorityForLoaderV3(rpc, programAccount);
     }
+
+    // For any other owner (loader v1, v2, v4, the native loader, etc.), the
+    // on-chain program considers the program's own address to be its authority
+    // — i.e. the program keypair itself must sign to prove canonicity.
+    return { authority: program };
 }
 
 async function getProgramAuthorityForLoaderV3(rpc: Rpc<GetAccountInfoApi>, programAccount: EncodedAccount) {
diff --git a/clients/js/test/_setup.ts b/clients/js/test/_setup.ts
index ba6866d..c5280e5 100644
--- a/clients/js/test/_setup.ts
+++ b/clients/js/test/_setup.ts
@@ -3,6 +3,7 @@ import path from 'node:path';
 import { systemProgram } from '@solana-program/system';
 import {
     Address,
+    address,
     createClient,
     generateKeyPairSigner,
     getAddressEncoder,
@@ -10,6 +11,7 @@ import {
     getStructEncoder,
     getU32Encoder,
     getU64Encoder,
+    getUtf8Encoder,
     KeyPairSigner,
     lamports,
     Lamports,
@@ -133,3 +135,28 @@ export const createDeployedProgram = async (
 
     return [program.address, programData];
 };
+
+export const NATIVE_LOADER_PROGRAM_ADDRESS = address('NativeLoader1111111111111111111111111111111');
+
+/**
+ * Fabricates a native (built-in) program inside the LiteSVM instance — i.e. an
+ * executable account owned by the native loader, like `ComputeBudget111...`.
+ * The program is never actually invoked — only its account is read by the
+ * client for the canonicity check.
+ */
+export const createNativeProgram = async (client: TestClient): Promise<Address> => {
+    const program = await generateKeyPairSigner();
+    const data = getUtf8Encoder().encode('native_program');
+    const space = BigInt(data.length);
+
+    client.svm.setAccount({
+        address: program.address,
+        data,
+        executable: true,
+        lamports: lamports(client.svm.minimumBalanceForRentExemption(space)),
+        programAddress: NATIVE_LOADER_PROGRAM_ADDRESS,
+        space,
+    });
+
+    return program.address;
+};
diff --git a/clients/js/test/getProgramAuthority.test.ts b/clients/js/test/getProgramAuthority.test.ts
new file mode 100644
index 0000000..052a44f
--- /dev/null
+++ b/clients/js/test/getProgramAuthority.test.ts
@@ -0,0 +1,43 @@
+import { generateKeyPairSigner } from '@solana/kit';
+import { expect, it } from 'vitest';
+
+import { getProgramAuthority } from '../src';
+import { createDeployedProgram, createNativeProgram, createTestClient, generateKeyPairSignerWithSol } from './_setup';
+
+it('resolves the upgrade authority of a loader-v3 program', async () => {
+    // Given a program deployed with loader v3 and the following upgrade authority.
+    const client = await createTestClient();
+    const authority = await generateKeyPairSigner();
+    const [program, programData] = await createDeployedProgram(client, authority);
+
+    // When we get the program authority.
+    const result = await getProgramAuthority(client.rpc, program);
+
+    // Then we expect the upgrade authority and the program data account to be returned.
+    expect(result).toStrictEqual({ authority: authority.address, programData });
+});
+
+it('resolves the program itself as the authority of a native program', async () => {
+    // Given a native program — i.e. an executable account owned by the native loader.
+    const client = await createTestClient();
+    const program = await createNativeProgram(client);
+
+    // When we get the program authority.
+    const result = await getProgramAuthority(client.rpc, program);
+
+    // Then we expect the program's own address to be returned as the authority,
+    // mirroring the on-chain rule for programs not owned by loader v3.
+    expect(result).toStrictEqual({ authority: program });
+});
+
+it('fails for non-executable accounts', async () => {
+    // Given a plain, non-executable wallet account.
+    const client = await createTestClient();
+    const wallet = await generateKeyPairSignerWithSol(client);
+
+    // When we try to get its program authority.
+    const promise = getProgramAuthority(client.rpc, wallet.address);
+
+    // Then we expect an error to be thrown.
+    await expect(promise).rejects.toThrow('Program account must be executable');
+});