diff --git a/idptoken/introspector.go b/idptoken/introspector.go
index 91899ef..f7676c4 100644
--- a/idptoken/introspector.go
+++ b/idptoken/introspector.go
@@ -489,7 +489,7 @@ func (i *Introspector) makeIntrospectFuncForToken(ctx context.Context, token str
 	if err != nil {
 		return i.getStaticIntrospectFuncOrError(fmt.Errorf("parse JWT header: %w", err))
 	}
-	if !checkIntrospectionRequiredByJWTHeader(jwtHeader) {
+	if !checkIntrospectionRequiredByJWTHeader(jwtHeader, i.scopeFilter) {
 		return nil, ErrTokenIntrospectionNotNeeded
 	}
 
@@ -745,9 +745,16 @@ func parserJWTHeader(b []byte) (map[string]interface{}, error) {
 }
 
 // checkIntrospectionRequiredByJWTHeader checks if introspection is required by JWT header.
-// Introspection is required by default.
-func checkIntrospectionRequiredByJWTHeader(jwtHeader map[string]interface{}) bool {
-	notRequiredIntrospection, ok := jwtHeader["nri"]
+// Introspection is required when BOTH conditions are true:
+// 1. nri field indicates introspection is required (nri absent/false/0)
+// 2. irn (Introspectable Resource Namespace) field contains list of Resource Namespaces matching the scopeFilter
+func checkIntrospectionRequiredByJWTHeader(jwtHeader map[string]interface{}, scopeFilter jwt.ScopeFilter) bool {
+	return introspectionRequiredByNRIField(jwtHeader) &&
+		introspectionRequiredByIRNField(jwtHeader, scopeFilter)
+}
+
+func introspectionRequiredByNRIField(jwtHeader map[string]interface{}) bool {
+	notRequiredIntrospection, ok := jwtHeader[idputil.JWTHeaderFieldNRI]
 	if !ok {
 		return true
 	}
@@ -766,6 +773,36 @@ func checkIntrospectionRequiredByJWTHeader(jwtHeader map[string]interface{}) boo
 	return true
 }
 
+// introspectionRequiredByIRNField checks if current scope filter requires an Access Policy that is only
+// visible after token introspection and listed in the "irn" JWT header. In that case introspection is mandatory.
+func introspectionRequiredByIRNField(jwtHeader map[string]any, scopeFilter jwt.ScopeFilter) bool {
+	if len(scopeFilter) == 0 {
+		return true
+	}
+	// Backward compatibility: "irn" JWT header can be absent.
+	introspectableRNs, ok := jwtHeader[idputil.JWTHeaderFieldIRN]
+	if !ok {
+		return true
+	}
+	var introspectableRNsArr []any
+	if introspectableRNsArr, ok = introspectableRNs.([]any); !ok || len(introspectableRNsArr) == 0 {
+		return false
+	}
+	for i := range scopeFilter {
+		sfRN := strings.TrimSpace(scopeFilter[i].ResourceNamespace)
+		for j := range introspectableRNsArr {
+			iRN, ok := introspectableRNsArr[j].(string)
+			if !ok {
+				continue
+			}
+			if strings.EqualFold(sfRN, strings.TrimSpace(iRN)) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 type IntrospectionCacheItem struct {
 	IntrospectionResult IntrospectionResult
 	CreatedAt           time.Time
diff --git a/idptoken/introspector_test.go b/idptoken/introspector_test.go
index 58fe14b..e21f5a1 100644
--- a/idptoken/introspector_test.go
+++ b/idptoken/introspector_test.go
@@ -81,6 +81,13 @@ func TestIntrospector_IntrospectToken(t *gotesting.T) {
 		Role:              "account_viewer",
 		ResourcePath:      "resource-" + uuid.NewString(),
 	}}
+	validJWTScopeEmptyRN := []jwt.AccessPolicy{
+		{
+			TenantUUID:        uuid.NewString(),
+			ResourceNamespace: "",
+			Role:              "account_viewer",
+			ResourcePath:      "resource-" + uuid.NewString(),
+		}}
 	validJWTRegClaims := jwtgo.RegisteredClaims{
 		Issuer:    httpIDPSrv.URL(),
 		Audience:  jwtgo.ClaimStrings{"https://rs.example.com"},
@@ -96,6 +103,16 @@ func TestIntrospector_IntrospectToken(t *gotesting.T) {
 	}, idptest.TestKeyID, idptest.GetTestRSAPrivateKey(), map[string]interface{}{"typ": idputil.JWTTypeAppAccessToken})
 	httpServerIntrospector.SetResultForToken(validJWTWithAppTyp, &idptoken.DefaultIntrospectionResult{Active: true,
 		TokenType: idputil.TokenTypeBearer, DefaultClaims: jwt.DefaultClaims{RegisteredClaims: validJWTRegClaims, Scope: validJWTScope}}, nil)
+	validJWTWithIntrospectableRNs := idptest.MustMakeTokenStringWithHeader(&jwt.DefaultClaims{
+		RegisteredClaims: validJWTRegClaims,
+	}, idptest.TestKeyID, idptest.GetTestRSAPrivateKey(), map[string]interface{}{idputil.JWTHeaderFieldIRN: []string{"account-server", ""}})
+	httpServerIntrospector.SetResultForToken(validJWTWithIntrospectableRNs, &idptoken.DefaultIntrospectionResult{Active: true,
+		TokenType: idputil.TokenTypeBearer, DefaultClaims: jwt.DefaultClaims{RegisteredClaims: validJWTRegClaims, Scope: validJWTScope}}, nil)
+	validJWTWithEmptyIntrospectableRNs := idptest.MustMakeTokenStringWithHeader(&jwt.DefaultClaims{
+		RegisteredClaims: validJWTRegClaims,
+	}, idptest.TestKeyID, idptest.GetTestRSAPrivateKey(), map[string]interface{}{idputil.JWTHeaderFieldIRN: []string{""}})
+	httpServerIntrospector.SetResultForToken(validJWTWithEmptyIntrospectableRNs, &idptoken.DefaultIntrospectionResult{Active: true,
+		TokenType: idputil.TokenTypeBearer, DefaultClaims: jwt.DefaultClaims{RegisteredClaims: validJWTRegClaims, Scope: validJWTScopeEmptyRN}}, nil)
 	grpcServerIntrospector.SetResultForToken(validJWT, &pb.IntrospectTokenResponse{
 		Active:    true,
 		TokenType: idputil.TokenTypeBearer,
@@ -317,6 +334,57 @@ func TestIntrospector_IntrospectToken(t *gotesting.T) {
 				require.ErrorIs(t, err, idptoken.ErrTokenIntrospectionNotNeeded)
 			},
 		},
+		{
+			name: "error, dynamic introspection endpoint, nri is false, but irn does not match scope filter",
+			introspectorOpts: idptoken.IntrospectorOpts{
+				ScopeFilter: []jwt.ScopeFilterAccessPolicy{{ResourceNamespace: "event-manager"}},
+			},
+			tokenToIntrospect: idptest.MustMakeTokenStringWithHeader(&jwt.DefaultClaims{
+				RegisteredClaims: jwtgo.RegisteredClaims{
+					Subject:   uuid.NewString(),
+					ID:        uuid.NewString(),
+					ExpiresAt: jwtgo.NewNumericDate(time.Now().Add(time.Hour)),
+				},
+			}, idptest.TestKeyID, idptest.GetTestRSAPrivateKey(), map[string]interface{}{"irn": "account-server"}),
+			checkError: func(t *gotesting.T, err error) {
+				require.ErrorIs(t, err, idptoken.ErrTokenIntrospectionNotNeeded)
+			},
+		},
+		{
+			name: "ok, dynamic introspection endpoint, nri is false, irn match scope filter",
+			introspectorOpts: idptoken.IntrospectorOpts{
+				ScopeFilter: []jwt.ScopeFilterAccessPolicy{{ResourceNamespace: "account-server"}},
+			},
+			tokenToIntrospect: validJWTWithIntrospectableRNs,
+			expectedResult: &idptoken.DefaultIntrospectionResult{
+				Active:        true,
+				TokenType:     idputil.TokenTypeBearer,
+				DefaultClaims: jwt.DefaultClaims{RegisteredClaims: validJWTRegClaims, Scope: validJWTScope},
+			},
+			expectedHTTPSrvCalled: true,
+			expectedHTTPFormVals: url.Values{
+				"token":              {validJWTWithIntrospectableRNs},
+				"scope_filter[0].rn": {"account-server"},
+			},
+		},
+		{
+			name: "ok, dynamic introspection endpoint, nri is false, irn match scope filter and contains empty string element",
+			introspectorOpts: idptoken.IntrospectorOpts{
+				ScopeFilter: []jwt.ScopeFilterAccessPolicy{{ResourceNamespace: "event-manager"}, {ResourceNamespace: ""}},
+			},
+			tokenToIntrospect: validJWTWithEmptyIntrospectableRNs,
+			expectedResult: &idptoken.DefaultIntrospectionResult{
+				Active:        true,
+				TokenType:     idputil.TokenTypeBearer,
+				DefaultClaims: jwt.DefaultClaims{RegisteredClaims: validJWTRegClaims, Scope: validJWTScopeEmptyRN},
+			},
+			expectedHTTPSrvCalled: true,
+			expectedHTTPFormVals: url.Values{
+				"token":              {validJWTWithEmptyIntrospectableRNs},
+				"scope_filter[0].rn": {"event-manager"},
+				"scope_filter[1].rn": {""},
+			},
+		},
 		{
 			name:                  "ok, dynamic introspection endpoint, introspected token is expired JWT",
 			tokenToIntrospect:     expiredJWT,
diff --git a/internal/idputil/idp_util.go b/internal/idputil/idp_util.go
index e891475..ef7eef0 100644
--- a/internal/idputil/idp_util.go
+++ b/internal/idputil/idp_util.go
@@ -24,6 +24,15 @@ const JWTTypeAccessToken = "at+jwt"
 
 const JWTTypeAppAccessToken = "application/at+jwt"
 
+// "irn" stands for "Introspectable Resource Namespace".
+// It contains array of Resource Namespaces for roles available after token introspection only.
+const JWTHeaderFieldIRN = "irn"
+
+// "nri" stands for "Not Required Introspection".
+// This header field is absent for all Hybrid tokens and set to 1 for non-hybrid tokens.
+// Important: the "nri" field (and related logic) is planned to be deprecated in favor of "irn" header field (PLTFRM-85633).
+const JWTHeaderFieldNRI = "nri"
+
 const TokenTypeBearer = "Bearer"
 
 const (