feat(sdk-api): add registerToken method to BitGoAPI

Adds a `registerToken(coinConfig, coinConstructor)` method to `BitGoAPI`
that delegates to `GlobalCoinFactory.registerToken`. Enables runtime
registration of AMS-sourced tokens without requiring statics library
updates. Method is idempotent and does not affect existing statics coins.

Closes CSHLD-89

Author: manas-at-bitgo

modules/sdk-api/src/bitgoAPI.ts

@@ -5,6 +5,7 @@ import {
   BitGoBase,
   BitGoRequest,
   CoinConstructor,
+  CoinFactory,
   common,
   DecryptKeysOptions,
   DecryptOptions,
@@ -1559,6 +1560,21 @@ export class BitGoAPI implements BitGoBase {
     GlobalCoinFactory.register(name, coin);
   }
 
+  /**
+   * Registers a token into GlobalCoinFactory's coin map and constructor map.
+   * Enables runtime registration of tokens sourced from AMS (not in statics).
+   * Idempotent: re-registering the same token does not throw.
+   *
+   * @param coinConfig - The static coin/token config object
+   * @param coinConstructor - The constructor function for the token class
+   */
+  public registerToken(
+    coinConfig: Parameters<CoinFactory['registerToken']>[0],
+    coinConstructor: CoinConstructor
+  ): void {
+    GlobalCoinFactory.registerToken(coinConfig, coinConstructor);
+  }
+
   /**
    * Get bitcoin market data
    *

modules/sdk-api/test/unit/bitgoAPI.ts

@@ -4,6 +4,7 @@ import { ProxyAgent } from 'proxy-agent';
 import * as sinon from 'sinon';
 import nock from 'nock';
 import type { IHmacAuthStrategy } from '@bitgo/sdk-hmac';
+import { GlobalCoinFactory, CoinConstructor } from '@bitgo/sdk-core';
 
 describe('Constructor', function () {
   describe('cookiesPropagationEnabled argument', function () {
@@ -794,4 +795,79 @@ describe('Constructor', function () {
       nock.cleanAll();
     });
   });
+
+  describe('registerToken', function () {
+    let bitgo: BitGoAPI;
+    let sandbox: sinon.SinonSandbox;
+
+    beforeEach(function () {
+      bitgo = new BitGoAPI({ env: 'custom', customRootURI: 'https://app.example.local' });
+      sandbox = sinon.createSandbox();
+    });
+
+    afterEach(function () {
+      sandbox.restore();
+    });
+
+    it('should call GlobalCoinFactory.registerToken and allow sdk.coin() to resolve the registered token', function () {
+      const mockCoinInstance = { type: 'test-ams-dynamic-token' } as any;
+      const mockConstructor = sandbox.stub().returns(mockCoinInstance) as unknown as CoinConstructor;
+      const mockCoinConfig = { name: 'test-ams-dynamic-token', id: 'test-ams-dynamic-token-id' } as any;
+
+      sandbox.stub(GlobalCoinFactory, 'registerToken');
+      sandbox.stub(GlobalCoinFactory, 'getInstance').callsFake((_bitgo, name) => {
+        if (name === 'test-ams-dynamic-token') {
+          return mockConstructor(_bitgo, mockCoinConfig);
+        }
+        throw new Error(`Unsupported coin: ${name}`);
+      });
+
+      bitgo.registerToken(mockCoinConfig, mockConstructor);
+
+      const coin = bitgo.coin('test-ams-dynamic-token');
+      coin.should.equal(mockCoinInstance);
+      (GlobalCoinFactory.registerToken as sinon.SinonStub)
+        .calledOnceWith(mockCoinConfig, mockConstructor)
+        .should.be.true();
+    });
+
+    it('should be idempotent — calling registerToken twice for same token does not throw', function () {
+      const mockCoinConfig = { name: 'test-ams-idempotent-token', id: 'test-ams-idempotent-token-id' } as any;
+      const mockConstructor = sandbox.stub() as unknown as CoinConstructor;
+      sandbox.stub(GlobalCoinFactory, 'registerToken');
+
+      (() => {
+        bitgo.registerToken(mockCoinConfig, mockConstructor);
+        bitgo.registerToken(mockCoinConfig, mockConstructor);
+      }).should.not.throw();
+
+      (GlobalCoinFactory.registerToken as sinon.SinonStub).callCount.should.equal(2);
+    });
+
+    it('should not affect existing statics coins after registerToken calls', function () {
+      const newCoinConfig = { name: 'test-ams-new-token', id: 'test-ams-new-token-id' } as any;
+      const newConstructor = sandbox.stub() as unknown as CoinConstructor;
+      const existingCoinInstance = { type: 'eth' } as any;
+      const existingConstructor = sandbox.stub().returns(existingCoinInstance) as unknown as CoinConstructor;
+
+      const registerTokenStub = sandbox.stub(GlobalCoinFactory, 'registerToken');
+      sandbox.stub(GlobalCoinFactory, 'getInstance').callsFake((_bitgo, name) => {
+        if (name === 'eth') {
+          return existingConstructor(_bitgo, undefined);
+        }
+        throw new Error(`Unsupported coin: ${name}`);
+      });
+
+      // Register a new AMS token
+      bitgo.registerToken(newCoinConfig, newConstructor);
+
+      // Existing statics coin should still resolve correctly
+      const ethCoin = bitgo.coin('eth');
+      ethCoin.should.equal(existingCoinInstance);
+
+      // registerToken was called only once (for the new token, not for eth)
+      registerTokenStub.calledOnce.should.be.true();
+      registerTokenStub.calledWith(newCoinConfig, newConstructor).should.be.true();
+    });
+  });
 });