diff --git a/modules/sdk-api/src/bitgoAPI.ts b/modules/sdk-api/src/bitgoAPI.ts
index 126d5e5c31..6cd4478103 100644
--- a/modules/sdk-api/src/bitgoAPI.ts
+++ b/modules/sdk-api/src/bitgoAPI.ts
@@ -1449,9 +1449,11 @@ export class BitGoAPI implements BitGoBase {
       const authUrl = this.microservicesUrl('/api/auth/v1/accesstoken');
       const request = this.post(authUrl);
 
-      const strategyAuthenticated = this._hmacAuthStrategy.isAuthenticated?.() ?? false;
-      if (!this._ecdhXprv && !strategyAuthenticated) {
-        // No ECDH key and no authenticated HMAC strategy — fall back to V1 Bearer auth.
+      if (!this._ecdhXprv) {
+        // No ECDH key — server cannot encrypt the response token for us. Fall back to V1
+        // so the server returns the plaintext token directly. This covers SSO/enterprise
+        // users (Okta, Entra) who never receive ecdhXprv at login because they have no
+        // BitGo password. HMAC request signing is orthogonal and continues to work.
         request.forceV1Auth = true;
         debug('forcing v1 auth for adding access token using token %s', this._token?.substr(0, 8));
       }
@@ -1465,10 +1467,6 @@ export class BitGoAPI implements BitGoBase {
       // verify the authenticity of the server's response before proceeding any further
       await verifyResponseAsync(this, this._token, 'post', request, response, this._authVersion);
 
-      // When ecdhXprv is available, the server returns an ECDH-encrypted token that
-      // must be decrypted. When the HMAC strategy is authenticated but ecdhXprv is
-      // absent (e.g. SSO/WebCrypto users), the server includes the plain token
-      // directly in response.body.token — no decryption step needed.
       if (this._ecdhXprv) {
         const responseDetails = await this.handleTokenIssuance(response.body);
         response.body.token = responseDetails.token;
diff --git a/modules/sdk-api/test/unit/bitgoAPI.ts b/modules/sdk-api/test/unit/bitgoAPI.ts
index 68c6a2f750..1bf27abb8d 100644
--- a/modules/sdk-api/test/unit/bitgoAPI.ts
+++ b/modules/sdk-api/test/unit/bitgoAPI.ts
@@ -667,13 +667,16 @@ describe('Constructor', function () {
         duration: 3600,
       };
 
-      it('should use HMAC auth when ecdhXprv is absent but hmacAuthStrategy is authenticated', async function () {
+      it('should force V1 auth and return plain token when ecdhXprv is absent, even if hmacAuthStrategy is authenticated (SSO/enterprise users)', async function () {
+        // Regression test for WCN-1790 / ANT-963: HMAC request signing and ECDH response
+        // encryption are orthogonal. forceV1Auth tells the server to return a plaintext token
+        // instead of ECDH-encrypting it. It must be set whenever ecdhXprv is absent,
+        // regardless of whether the HMAC strategy is active.
         const { strategy } = makeStrategy({
           isAuthenticated: sinon.stub().returns(true),
         });
         const bitgo = new BitGoAPI({ env: 'custom', customRootURI: ROOT, hmacAuthStrategy: strategy });
-        // Do NOT set _ecdhXprv — simulates SSO/WebCrypto session
-        // Set a v2x token so the request goes through the v2 auth path
+        // Do NOT set _ecdhXprv — simulates SSO/enterprise session (Okta, Entra, etc.)
         bitgo.authenticateWithAccessToken({ accessToken: 'v2xstrategytoken' });
 
         const scope = nock(ROOT).post('/api/auth/v1/accesstoken').reply(200, {
@@ -684,13 +687,12 @@ describe('Constructor', function () {
         const result = await bitgo.addAccessToken(validParams);
 
         scope.isDone().should.be.true();
-        // forceV1Auth should NOT have been set, so no downgrade warning
-        (result as any).should.not.have.property('warning');
-        // The plain token from the response body should be returned directly
+        // forceV1Auth MUST be set — server returns plaintext token since we have no decryption key
+        (result as any).warning.should.match(/protocol downgrade/);
         result.token.should.equal('v2xnewplaintoken');
       });
 
-      it('should return plain token from response body when ecdhXprv is absent but strategyAuthenticated', async function () {
+      it('should not call handleTokenIssuance when ecdhXprv is absent', async function () {
         const handleTokenSpy = sinon.spy(BitGoAPI.prototype, 'handleTokenIssuance');
         const { strategy } = makeStrategy({
           isAuthenticated: sinon.stub().returns(true),
@@ -705,14 +707,14 @@ describe('Constructor', function () {
 
         const result = await bitgo.addAccessToken(validParams);
 
-        // handleTokenIssuance should NOT be called — no ECDH decryption needed
+        // handleTokenIssuance must not be called — no ecdhXprv to decrypt with
         handleTokenSpy.called.should.be.false();
         result.token.should.equal('v2xplaintoken');
 
         handleTokenSpy.restore();
       });
 
-      it('should still force V1 auth when neither ecdhXprv nor strategy is authenticated', async function () {
+      it('should force V1 auth when ecdhXprv is absent and strategy is not authenticated', async function () {
         const { strategy } = makeStrategy({
           isAuthenticated: sinon.stub().returns(false),
         });
@@ -726,13 +728,11 @@ describe('Constructor', function () {
 
         const result = await bitgo.addAccessToken(validParams);
 
-        // V1 auth path should add the downgrade warning
         (result as any).warning.should.match(/protocol downgrade/);
       });
 
-      it('should still force V1 auth when isAuthenticated is not defined on strategy', async function () {
+      it('should force V1 auth when isAuthenticated is not defined on strategy', async function () {
         const { strategy } = makeStrategy();
-        // strategy has no isAuthenticated method by default from makeStrategy
         const bitgo = new BitGoAPI({ env: 'custom', customRootURI: ROOT, hmacAuthStrategy: strategy });
         bitgo.authenticateWithAccessToken({ accessToken: 'v2xnoauthmethod' });