diff --git a/.env.example b/.env.example
index a7240d6..7b34f61 100644
--- a/.env.example
+++ b/.env.example
@@ -279,3 +279,8 @@ OPT_CREDIT_PRICE_BOOK=
 # explicit (never a silent fallback), the response reports `credits: null`, and
 # purchases stay disabled. Unset/`on` requires the price book + ledger.
 OPT_CREDITS_MODE=
+
+# Central Keycloak (SIAX Portal)
+KEYCLOAK_ISSUER=https://auth.portal.siax.dev/realms/portal
+KEYCLOAK_EXPECTED_AUDIENCE=account
+KEYCLOAK_AUTHORIZED_PARTY=siax-portal
diff --git a/src/auth/zitadel.ts b/src/auth/zitadel.ts
index 25b4e86..5184710 100644
--- a/src/auth/zitadel.ts
+++ b/src/auth/zitadel.ts
@@ -45,6 +45,7 @@
 
 import {
   createRemoteJWKSet,
+  decodeJwt,
   jwtVerify,
   type JWTPayload,
   type JWTVerifyGetKey,
@@ -53,6 +54,33 @@ import {
 /** Default fleet Zitadel issuer (OIDC). Overridable via ZITADEL_ISSUER. */
 export const DEFAULT_ZITADEL_ISSUER = 'https://id-customers.siax.io';
 
+/** Central Keycloak (SIAX Portal) trust; additive, unset keeps legacy behaviour. */
+export function keycloakIssuer(): string | undefined {
+  const raw = process.env.KEYCLOAK_ISSUER?.trim().replace(/\/+$/, '');
+  return raw && raw.length > 0 ? raw : undefined;
+}
+
+export function keycloakAudiences(): string[] {
+  const raw = process.env.KEYCLOAK_EXPECTED_AUDIENCE?.trim();
+  if (!raw) return ['account'];
+  const list = raw.split(',').map((s) => s.trim()).filter((s) => s.length > 0);
+  return list.length > 0 ? list : ['account'];
+}
+
+export function keycloakAuthorizedParty(): string | undefined {
+  const raw = process.env.KEYCLOAK_AUTHORIZED_PARTY?.trim();
+  return raw && raw.length > 0 ? raw : undefined;
+}
+
+function tokenIssuerUnsafe(token: string): string | undefined {
+  try {
+    const iss = decodeJwt(token).iss;
+    return typeof iss === 'string' ? iss : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
 /** Standard + custom claim paths tenant derivation reads, in precedence order. */
 export const ZITADEL_ORG_ID_CLAIM = 'urn:zitadel:iam:org:id';
 export const ZITADEL_RESOURCEOWNER_CLAIM = 'urn:zitadel:iam:user:resourceowner:id';
@@ -190,6 +218,31 @@ export async function verifyBearer(
   token: string,
   opts: VerifyBearerOptions = {},
 ): Promise<VerifiedPrincipal> {
+  // Central Keycloak (SIAX Portal) user tokens, routed by issuer.
+  const kcIssuer = keycloakIssuer();
+  if (kcIssuer !== undefined && tokenIssuerUnsafe(token) === kcIssuer) {
+    const resolver = opts.keyResolver ?? keyResolverOverride ?? (await getRemoteJwks(kcIssuer));
+    let payload: JWTPayload;
+    try {
+      ({ payload } = await jwtVerify(token, resolver, {
+        issuer: kcIssuer,
+        audience: keycloakAudiences(),
+      }));
+    } catch (err) {
+      throw new BearerVerificationError('keycloak_token_verification_failed', err);
+    }
+    const azp = typeof payload.azp === 'string' ? payload.azp : '';
+    const expectedAzp = keycloakAuthorizedParty();
+    if (expectedAzp !== undefined && azp !== expectedAzp) {
+      throw new BearerVerificationError('keycloak_azp_mismatch');
+    }
+    const sub = typeof payload.sub === 'string' ? payload.sub : undefined;
+    if (!sub) throw new BearerVerificationError('token_missing_sub');
+    const tenantId = deriveTenantId(payload, opts.tenantClaim ?? tenantClaimOverride());
+    if (!tenantId) throw new BearerVerificationError('token_missing_tenant_claim');
+    return { sub, tenantId, claims: payload };
+  }
+
   const issuer = opts.issuer ?? zitadelIssuer();
   const resolver = opts.keyResolver ?? keyResolverOverride ?? (await getRemoteJwks(issuer));