diff --git a/biome.json b/biome.json
index ce1eb7a28d22e4..9b305aa059f7c1 100644
--- a/biome.json
+++ b/biome.json
@@ -121,7 +121,6 @@
             "noImgElement": "warn"
           },
           "suspicious": {
-            "noReactSpecificProps": "warn",
             "noDoubleEquals": "warn",
             "noAssignInExpressions": "warn",
             "noExplicitAny": "warn",
diff --git a/packages/features/auth/lib/next-auth-options.ts b/packages/features/auth/lib/next-auth-options.ts
index 449d17a7e9a82d..4ab888eed4d54d 100644
--- a/packages/features/auth/lib/next-auth-options.ts
+++ b/packages/features/auth/lib/next-auth-options.ts
@@ -284,6 +284,7 @@ type SamlIdpUser = {
   name: string;
   email_verified: boolean;
   profile: UserProfile;
+  samlTenant?: string;
 };
 
 if (IS_GOOGLE_LOGIN_ENABLED) {
@@ -349,7 +350,7 @@ if (isSAMLLoginEnabled) {
         locale: profile.locale,
         // Pass SAML tenant for domain authority checks in signIn callback
         samlTenant: profile.requested?.tenant,
-        ...(user ? { profile: user.allProfiles[0] } : {}),
+        ...(user && { profile: user.allProfiles[0] }),
       };
     },
     options: {
@@ -400,7 +401,7 @@ if (isSAMLLoginEnabled) {
           return null;
         }
 
-        const { id, firstName, lastName } = userInfo;
+        const { id, firstName, lastName, requested } = userInfo;
         const email = userInfo.email.toLowerCase();
         const userRepo = new UserRepository(prisma);
         let user = !email ? undefined : await userRepo.findByEmailAndIncludeProfilesAndPassword({ email });
@@ -440,6 +441,8 @@ if (isSAMLLoginEnabled) {
           name: `${firstName} ${lastName}`.trim(),
           email_verified: true,
           profile: userProfile,
+          // Pass SAML tenant for domain authority checks in signIn callback (IdP-initiated flow)
+          samlTenant: requested?.tenant,
         };
       },
     })
@@ -817,6 +820,19 @@ export const getOptions = ({
 
       log.debug("callbacks:signin", safeStringify(params));
 
+      // Extract samlTenant from user (credentials/saml-idp) or profile (oauth/saml)
+      const getSamlTenant = (): string | undefined => {
+        // Primary: user.samlTenant is set in authorize/profile callbacks (type-safe via NextAuth User extension)
+        if (user.samlTenant) return user.samlTenant;
+
+        // Fallback for OAuth SAML: raw BoxyHQ profile contains requested.tenant
+        // (NextAuth adapter doesn't pass custom fields through)
+        if (account?.provider === "saml") {
+          return (profile as { requested?: { tenant?: string } } | undefined)?.requested?.tenant;
+        }
+        return undefined;
+      };
+
       if (account?.provider === "email") {
         return true;
       }
@@ -978,7 +994,7 @@ export const getOptions = ({
           ) {
             // Verify SAML IdP is authoritative before auto-merge
             if (idP === IdentityProvider.SAML) {
-              const samlTenant = (user as { samlTenant?: string }).samlTenant;
+              const samlTenant = getSamlTenant();
               const validation = await validateSamlAccountConversion(samlTenant, user.email, "SelfHosted→SAML");
               if (!validation.allowed) {
                 return validation.errorUrl;
@@ -1000,7 +1016,7 @@ export const getOptions = ({
           ) {
             // Verify SAML IdP is authoritative before claiming invited user
             if (idP === IdentityProvider.SAML) {
-              const samlTenant = (user as { samlTenant?: string }).samlTenant;
+              const samlTenant = getSamlTenant();
               const validation = await validateSamlAccountConversion(samlTenant, user.email, "Invite→SAML");
               if (!validation.allowed) {
                 return validation.errorUrl;
@@ -1038,7 +1054,7 @@ export const getOptions = ({
           ) {
             // Verify SAML IdP is authoritative before converting account
             if (idP === IdentityProvider.SAML) {
-              const samlTenant = (user as { samlTenant?: string }).samlTenant;
+              const samlTenant = getSamlTenant();
               const validation = await validateSamlAccountConversion(samlTenant, user.email, "CAL→SAML");
               if (!validation.allowed) {
                 return validation.errorUrl;
@@ -1072,7 +1088,7 @@ export const getOptions = ({
             idP === IdentityProvider.SAML
           ) {
             // Verify SAML IdP is authoritative before converting account
-            const samlTenant = (user as { samlTenant?: string }).samlTenant;
+            const samlTenant = getSamlTenant();
             const validation = await validateSamlAccountConversion(samlTenant, user.email, "Google→SAML");
             if (!validation.allowed) {
               return validation.errorUrl;
diff --git a/packages/features/auth/lib/samlAccountLinking.ts b/packages/features/auth/lib/samlAccountLinking.ts
index 5a5f3d45a8e94e..0e2a339e8a3a4d 100644
--- a/packages/features/auth/lib/samlAccountLinking.ts
+++ b/packages/features/auth/lib/samlAccountLinking.ts
@@ -1,12 +1,13 @@
 import { MembershipRepository } from "@calcom/features/membership/repositories/MembershipRepository";
 import { OrganizationSettingsRepository } from "@calcom/features/organizations/repositories/OrganizationSettingsRepository";
+import { HOSTED_CAL_FEATURES } from "@calcom/lib/constants";
 import logger from "@calcom/lib/logger";
 import { prisma } from "@calcom/prisma";
 import type { PrismaClient } from "@calcom/prisma";
 
 import { tenantPrefix } from "../../ee/sso/lib/saml";
 
-const log = logger.getSubLogger({ prefix: ["samlAccountLinking"] });
+const log: ReturnType<typeof logger.getSubLogger> = logger.getSubLogger({ prefix: ["samlAccountLinking"] });
 const SAML_NOT_AUTHORITATIVE_ERROR_URL = "/auth/error?error=saml-idp-not-authoritative";
 
 export function getTeamIdFromSamlTenant(tenant: string): number | null {
@@ -14,7 +15,10 @@ export function getTeamIdFromSamlTenant(tenant: string): number | null {
     return null;
   }
   const teamId = parseInt(tenant.replace(tenantPrefix, ""), 10);
-  return isNaN(teamId) ? null : teamId;
+  if (Number.isNaN(teamId)) {
+    return null;
+  }
+  return teamId;
 }
 
 /**
@@ -78,6 +82,15 @@ export async function validateSamlAccountConversion(
 
   const samlOrgTeamId = getTeamIdFromSamlTenant(samlTenant);
   if (!samlOrgTeamId) {
+    // For hosted Cal.com: tenant must be in "team-{id}" format for org SSO
+    // For self-hosted: allow non-org tenants (admin controls the setup)
+    if (HOSTED_CAL_FEATURES) {
+      log.warn(`Blocking ${conversionContext} conversion - invalid tenant format for hosted`, {
+        tenant: samlTenant,
+        emailDomain: email.split("@")[1],
+      });
+      return { allowed: false, errorUrl: SAML_NOT_AUTHORITATIVE_ERROR_URL };
+    }
     return { allowed: true };
   }
 
diff --git a/packages/types/next-auth.d.ts b/packages/types/next-auth.d.ts
index 769858fea7c88c..faaff924ae79aa 100644
--- a/packages/types/next-auth.d.ts
+++ b/packages/types/next-auth.d.ts
@@ -42,6 +42,7 @@ declare module "next-auth" {
     role?: PrismaUser["role"] | "INACTIVE_ADMIN";
     locale?: string | null;
     profile?: UserProfile;
+    samlTenant?: string;
   }
 }