diff --git a/backend/src/ee/services/audit-log/audit-log-types.ts b/backend/src/ee/services/audit-log/audit-log-types.ts
index d0d1bc06c..1b162ca16 100644
--- a/backend/src/ee/services/audit-log/audit-log-types.ts
+++ b/backend/src/ee/services/audit-log/audit-log-types.ts
@@ -2693,7 +2693,7 @@ interface SelectSubOrganizationEvent {
   metadata: {
     organizationId: string;
     organizationName: string;
-    parentOrganizationId: string;
+    rootOrganizationId: string;
   };
 }
 
diff --git a/backend/src/server/routes/v3/login-router.ts b/backend/src/server/routes/v3/login-router.ts
index 4dbf9ac0b..13b9b358c 100644
--- a/backend/src/server/routes/v3/login-router.ts
+++ b/backend/src/server/routes/v3/login-router.ts
@@ -43,10 +43,15 @@ export const registerLoginRouter = async (server: FastifyZodProvider) => {
       rateLimit: authRateLimit
     },
     schema: {
-      body: z.object({
-        organizationId: z.string().trim(),
-        userAgent: z.enum(["cli"]).optional()
-      }),
+      body: z
+        .object({
+          organizationId: z.string().trim().optional(),
+          subOrganizationId: z.string().trim().optional(),
+          userAgent: z.enum(["cli"]).optional()
+        })
+        .refine((body) => Boolean(body.organizationId || body.subOrganizationId), {
+          message: "organizationId or subOrganizationId is required"
+        }),
       response: {
         200: z.object({
           token: z.string(),
@@ -57,12 +62,25 @@ export const registerLoginRouter = async (server: FastifyZodProvider) => {
     },
     handler: async (req, res) => {
       const cfg = getConfig();
-      const tokens = await server.services.login.selectOrganization({
-        userAgent: req.body.userAgent ?? req.headers["user-agent"],
-        authJwtToken: req.headers.authorization,
-        organizationId: req.body.organizationId,
-        ipAddress: req.realIp
-      });
+      let tokens;
+
+      const targetOrgId = req.body.subOrganizationId ?? req.body.organizationId ?? "";
+
+      if (req.body.subOrganizationId) {
+        tokens = await server.services.login.selectSubOrganization({
+          userAgent: req.body.userAgent ?? req.headers["user-agent"],
+          authJwtToken: req.headers.authorization,
+          subOrganizationId: req.body.subOrganizationId,
+          ipAddress: req.realIp
+        });
+      } else {
+        tokens = await server.services.login.selectOrganization({
+          userAgent: req.body.userAgent ?? req.headers["user-agent"],
+          authJwtToken: req.headers.authorization,
+          organizationId: req.body.organizationId as string,
+          ipAddress: req.realIp
+        });
+      }
 
       if (tokens.isMfaEnabled) {
         return {
@@ -75,7 +93,7 @@ export const registerLoginRouter = async (server: FastifyZodProvider) => {
       const githubOauthAccessToken = req.cookies[INFISICAL_PROVIDER_GITHUB_ACCESS_TOKEN];
       if (githubOauthAccessToken) {
         await server.services.githubOrgSync
-          .syncUserGroups(req.body.organizationId, tokens.user.userId, githubOauthAccessToken)
+          .syncUserGroups(targetOrgId, tokens.user.userId, githubOauthAccessToken)
           .finally(() => {
             void res.setCookie(INFISICAL_PROVIDER_GITHUB_ACCESS_TOKEN, "", {
               httpOnly: true,
@@ -108,74 +126,6 @@ export const registerLoginRouter = async (server: FastifyZodProvider) => {
     }
   });
 
-  server.route({
-    method: "POST",
-    url: "/select-sub-organization",
-    config: {
-      rateLimit: authRateLimit
-    },
-    schema: {
-      body: z.object({
-        subOrganizationId: z.string().trim(),
-        userAgent: z.enum(["cli"]).optional()
-      }),
-      response: {
-        200: z.object({
-          token: z.string(),
-          isMfaEnabled: z.boolean(),
-          mfaMethod: z.string().optional(),
-          subOrganization: z
-            .object({
-              id: z.string(),
-              name: z.string(),
-              slug: z.string()
-            })
-            .optional()
-        })
-      }
-    },
-    handler: async (req, res) => {
-      const cfg = getConfig();
-      const result = await server.services.login.selectSubOrganization({
-        userAgent: req.body.userAgent ?? req.headers["user-agent"],
-        authJwtToken: req.headers.authorization,
-        subOrganizationId: req.body.subOrganizationId,
-        ipAddress: req.realIp
-      });
-
-      if (result.isMfaEnabled) {
-        return {
-          token: result.mfa as string,
-          isMfaEnabled: true,
-          mfaMethod: result.mfaMethod
-        };
-      }
-
-      void res.setCookie("jid", result.refresh, {
-        httpOnly: true,
-        path: "/",
-        sameSite: "strict",
-        secure: cfg.HTTPS_ENABLED
-      });
-
-      addAuthOriginDomainCookie(res);
-
-      void res.cookie("infisical-project-assume-privileges", "", {
-        httpOnly: true,
-        path: "/",
-        sameSite: "strict",
-        secure: cfg.HTTPS_ENABLED,
-        maxAge: 0
-      });
-
-      return {
-        token: result.access,
-        isMfaEnabled: false,
-        subOrganization: result.subOrganization
-      };
-    }
-  });
-
   server.route({
     method: "POST",
     url: "/login2",
diff --git a/backend/src/services/auth/auth-login-service.ts b/backend/src/services/auth/auth-login-service.ts
index aec271ec9..4c063e547 100644
--- a/backend/src/services/auth/auth-login-service.ts
+++ b/backend/src/services/auth/auth-login-service.ts
@@ -725,39 +725,58 @@ export const authLoginServiceFactory = ({
     authJwtToken = authJwtToken.replace("Bearer ", "");
 
     const decodedToken = crypto.jwt().verify(authJwtToken, cfg.AUTH_SECRET) as AuthModeJwtTokenPayload;
+
     if (!decodedToken.authMethod) throw new UnauthorizedError({ name: "Auth method not found on existing token" });
-    if (!decodedToken.organizationId)
-      throw new BadRequestError({ message: "No organization selected in current token" });
 
     const user = await userDAL.findUserEncKeyByUserId(decodedToken.userId);
     if (!user) throw new BadRequestError({ message: "User not found", name: "Find user from token" });
 
+    // Check user membership in the sub-organization
+    const userSubOrgMembership = await membershipUserDAL.findOne({
+      actorUserId: user.id,
+      scopeOrgId: subOrganizationId,
+      scope: AccessScope.Organization,
+      status: OrgMembershipStatus.Accepted
+    });
+
     // Fetch the sub-organization
     const subOrg = await orgDAL.findById(subOrganizationId);
-    if (!subOrg) {
-      throw new BadRequestError({ message: `Sub-organization with ID ${subOrganizationId} not found` });
-    }
 
-    // Verify this is actually a sub-organization of the current root org
-    if (subOrg.rootOrgId !== decodedToken.organizationId && subOrg.id !== decodedToken.organizationId) {
+    if (!userSubOrgMembership) {
       throw new ForbiddenRequestError({
-        message: "Sub-organization does not belong to the current organization"
+        message: `User does not have access to the sub-organization named ${subOrg.name}`
       });
     }
 
-    // Check user membership in the sub-organization
-    const orgMembership = await membershipUserDAL.findOne({
-      actorUserId: user.id,
-      scopeOrgId: subOrganizationId,
-      scope: AccessScope.Organization
-    });
+    const subOrgmembershipRole = await membershipRoleDAL.findOne({ membershipId: userSubOrgMembership.id });
 
-    if (!orgMembership) {
-      throw new ForbiddenRequestError({ message: "User is not a member of this sub-organization" });
+    // Check if authEnforced is true and the current auth method is not an enforced method
+    if (
+      subOrg.authEnforced &&
+      !isAuthMethodSaml(decodedToken.authMethod) &&
+      decodedToken.authMethod !== AuthMethod.OIDC &&
+      !(subOrg.bypassOrgAuthEnabled && subOrgmembershipRole.role === OrgMembershipRole.Admin)
+    ) {
+      throw new BadRequestError({
+        message: "Login with the auth method required by your organization."
+      });
     }
 
-    if (!orgMembership.isActive) {
-      throw new ForbiddenRequestError({ message: "User membership in sub-organization is inactive" });
+    if (subOrg.googleSsoAuthEnforced && decodedToken.authMethod !== AuthMethod.GOOGLE) {
+      const canBypass = subOrg.bypassOrgAuthEnabled && subOrgmembershipRole.role === OrgMembershipRole.Admin;
+
+      if (!canBypass) {
+        throw new ForbiddenRequestError({
+          message: "Google SSO is enforced for this organization. Please use Google SSO to login.",
+          error: "GoogleSsoEnforced"
+        });
+      }
+    }
+
+    if (decodedToken.authMethod === AuthMethod.GOOGLE) {
+      await orgDAL.updateById(subOrg.id, {
+        googleSsoAuthLastUsed: new Date()
+      });
     }
 
     // Check MFA requirements for the sub-organization
@@ -797,8 +816,8 @@ export const authLoginServiceFactory = ({
       user,
       userAgent,
       ip: ipAddress,
-      organizationId: decodedToken.organizationId, // Keep root org ID
-      subOrganizationId, // Add sub-org ID
+      ...(subOrg.rootOrgId && { organizationId: subOrg.rootOrgId }),
+      subOrganizationId,
       isMfaVerified: decodedToken.isMfaVerified,
       mfaMethod: decodedToken.mfaMethod
     });
@@ -823,7 +842,7 @@ export const authLoginServiceFactory = ({
         metadata: {
           organizationId: subOrganizationId,
           organizationName: subOrg.name,
-          parentOrganizationId: decodedToken.organizationId
+          rootOrganizationId: subOrg.rootOrgId ?? ""
         }
       }
     });
@@ -831,12 +850,7 @@ export const authLoginServiceFactory = ({
     return {
       ...tokens,
       user,
-      isMfaEnabled: false,
-      subOrganization: {
-        id: subOrg.id,
-        name: subOrg.name,
-        slug: subOrg.slug
-      }
+      isMfaEnabled: false
     };
   };
 
diff --git a/frontend/src/hooks/api/auth/queries.tsx b/frontend/src/hooks/api/auth/queries.tsx
index be81612f2..bac8815ab 100644
--- a/frontend/src/hooks/api/auth/queries.tsx
+++ b/frontend/src/hooks/api/auth/queries.tsx
@@ -58,10 +58,17 @@ export const loginLDAPRedirect = async (loginLDAPDetails: LoginLDAPDTO) => {
   return data;
 };
 
-export const selectOrganization = async (data: {
-  organizationId: string;
-  userAgent?: UserAgentType;
-}) => {
+export type SelectOrganizationParams =
+  | {
+      organizationId: string;
+      userAgent?: UserAgentType;
+    }
+  | {
+      subOrganizationId: string;
+      userAgent?: UserAgentType;
+    };
+
+export const selectOrganization = async (data: SelectOrganizationParams) => {
   const { data: res } = await apiRequest.post<{
     token: string;
     isMfaEnabled: boolean;
@@ -73,7 +80,7 @@ export const selectOrganization = async (data: {
 export const useSelectOrganization = () => {
   const queryClient = useQueryClient();
   return useMutation({
-    mutationFn: async (details: { organizationId: string; userAgent?: UserAgentType }) => {
+    mutationFn: async (details: SelectOrganizationParams) => {
       const data = await selectOrganization(details);
 
       // If a custom user agent is set, then this session is meant for another consuming application, not the web application.
@@ -107,49 +114,6 @@ export const useSelectOrganization = () => {
   });
 };
 
-export const selectSubOrganization = async (data: {
-  subOrganizationId: string;
-  userAgent?: UserAgentType;
-}) => {
-  const { data: res } = await apiRequest.post<{
-    token: string;
-    isMfaEnabled: boolean;
-    mfaMethod?: MfaMethod;
-    subOrganization?: {
-      id: string;
-      name: string;
-      slug: string;
-    };
-  }>("/api/v3/auth/select-sub-organization", data);
-  return res;
-};
-
-export const useSelectSubOrganization = () => {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: async (details: { subOrganizationId: string; userAgent?: UserAgentType }) => {
-      const data = await selectSubOrganization(details);
-
-      // If a custom user agent is set, then this session is meant for another consuming application, not the web application.
-      if (!details.userAgent && !data.isMfaEnabled) {
-        SecurityClient.setToken(data.token);
-        SecurityClient.setProviderAuthToken("");
-      }
-
-      if (data.token && !data.isMfaEnabled) {
-        setAuthToken(data.token);
-      }
-
-      return data;
-    },
-    onSuccess: () => {
-      queryClient.invalidateQueries({
-        queryKey: [organizationKeys.getUserOrganizations, projectKeys.getAllUserProjects]
-      });
-    }
-  });
-};
-
 export const useLogin2 = () => {
   return useMutation({
     mutationFn: async (details: {
diff --git a/frontend/src/layouts/OrganizationLayout/components/NavBar/Navbar.tsx b/frontend/src/layouts/OrganizationLayout/components/NavBar/Navbar.tsx
index 42d0e92c0..c664f7aec 100644
--- a/frontend/src/layouts/OrganizationLayout/components/NavBar/Navbar.tsx
+++ b/frontend/src/layouts/OrganizationLayout/components/NavBar/Navbar.tsx
@@ -62,7 +62,11 @@ import {
   useGetOrgTrialUrl,
   useLogoutUser
 } from "@app/hooks/api";
-import { authKeys, selectOrganization, selectSubOrganization } from "@app/hooks/api/auth/queries";
+import {
+  authKeys,
+  selectOrganization,
+  type SelectOrganizationParams
+} from "@app/hooks/api/auth/queries";
 import { MfaMethod } from "@app/hooks/api/auth/types";
 import { getAuthToken } from "@app/hooks/api/reactQuery";
 import { Organization, SubscriptionPlan } from "@app/hooks/api/types";
@@ -191,12 +195,26 @@ export const Navbar = () => {
     }
   }, [subscription, isBillingPage, isModalIntrusive]);
 
-  const handleOrgChange = async (orgId: string, onSuccess?: () => void | Promise<void>) => {
-    if (orgId === currentOrg.id) return;
+  const handleOrgSelection = async ({
+    organizationId,
+    subOrganizationId,
+    onSuccess
+  }: {
+    organizationId?: string;
+    subOrganizationId?: string;
+    onSuccess?: () => void | Promise<void>;
+  }) => {
+    if (!organizationId && !subOrganizationId) return;
 
-    const { token, isMfaEnabled, mfaMethod } = await selectOrganization({
-      organizationId: orgId
-    });
+    const targetId = subOrganizationId ?? organizationId;
+
+    if (targetId === currentOrg.id) return;
+
+    const selectionPayload: SelectOrganizationParams = subOrganizationId
+      ? { subOrganizationId }
+      : { organizationId: organizationId as string };
+
+    const { token, isMfaEnabled, mfaMethod } = await selectOrganization(selectionPayload);
 
     if (isMfaEnabled) {
       SecurityClient.setMfaToken(token);
@@ -205,7 +223,7 @@ export const Navbar = () => {
       }
       toggleShowMfa.on();
       setMfaSuccessCallback(() => async () => {
-        await handleOrgChange(orgId, onSuccess);
+        await handleOrgSelection({ organizationId, subOrganizationId, onSuccess });
       });
       return;
     }
@@ -216,7 +234,7 @@ export const Navbar = () => {
     queryClient.removeQueries({ queryKey: projectKeys.getAllUserProjects() });
 
     await router.invalidate();
-    await navigateUserToOrg(navigate, orgId);
+    await navigateUserToOrg(navigate, targetId);
     queryClient.removeQueries({ queryKey: subOrgQuery.queryKey });
 
     if (onSuccess) {
@@ -234,43 +252,12 @@ export const Navbar = () => {
     };
 
     if (currentOrg.id !== rootOrg.id) {
-      await handleOrgChange(rootOrg.id, navigateToBilling);
+      await handleOrgSelection({ organizationId: rootOrg.id, onSuccess: navigateToBilling });
     } else {
       await navigateToBilling();
     }
   };
 
-  const handleSubOrgChange = async (subOrgId: string) => {
-    if (subOrgId === currentOrg.id) return;
-
-    const { token, isMfaEnabled, mfaMethod } = await selectSubOrganization({
-      subOrganizationId: subOrgId
-    });
-
-    localStorage.setItem("orgData.id", subOrgId);
-
-    if (isMfaEnabled) {
-      SecurityClient.setMfaToken(token);
-      if (mfaMethod) {
-        setRequiredMfaMethod(mfaMethod);
-      }
-      toggleShowMfa.on();
-      setMfaSuccessCallback(() => () => handleSubOrgChange(subOrgId));
-      return;
-    }
-
-    SecurityClient.setToken(token);
-    SecurityClient.setProviderAuthToken("");
-
-    queryClient.removeQueries({ queryKey: authKeys.getAuthToken });
-    queryClient.removeQueries({ queryKey: projectKeys.getAllUserProjects() });
-    await router.invalidate();
-    navigate({
-      to: "/organizations/$orgId/projects",
-      params: { orgId: subOrgId }
-    });
-  };
-
   const { mutateAsync } = useGetOrgTrialUrl();
 
   const logout = useLogoutUser();
@@ -340,7 +327,7 @@ export const Navbar = () => {
       return;
     }
 
-    handleOrgChange(org?.id);
+    handleOrgSelection({ organizationId: org?.id });
   };
 
   return (
@@ -465,7 +452,7 @@ export const Navbar = () => {
                             </div>
                             {subOrganizations.map((subOrg) => (
                               <DropdownMenuItem
-                                onClick={() => handleSubOrgChange(subOrg.id)}
+                                onClick={() => handleOrgSelection({ subOrganizationId: subOrg.id })}
                                 className="cursor-pointer font-normal"
                                 key={subOrg.id}
                               >
@@ -563,7 +550,7 @@ export const Navbar = () => {
                     </div>
                     {subOrganizations.map((subOrg) => (
                       <DropdownMenuItem
-                        onClick={() => handleSubOrgChange(subOrg.id)}
+                        onClick={() => handleOrgSelection({ subOrganizationId: subOrg.id })}
                         className="cursor-pointer font-normal"
                         key={subOrg.id}
                       >