diff --git a/src/main/java/com/clearfolio/viewer/auth/TenantContext.java b/src/main/java/com/clearfolio/viewer/auth/TenantContext.java
index 40b79f92..fdcb9710 100644
--- a/src/main/java/com/clearfolio/viewer/auth/TenantContext.java
+++ b/src/main/java/com/clearfolio/viewer/auth/TenantContext.java
@@ -65,10 +65,12 @@ public record TenantContext(String tenantId, String subjectId, Set<String> permi
      * @param tenantId tenant claim
      * @param subjectId subject claim
      * @param permissions permission claims
+     * @throws IllegalArgumentException when tenant or subject authority is absent
+     *         or control-corrupted
      */
     public TenantContext {
-        tenantId = sanitize(tenantId);
-        subjectId = sanitize(subjectId);
+        tenantId = requireAuthority(tenantId, "tenantId");
+        subjectId = requireAuthority(subjectId, "subjectId");
         permissions = permissions == null
                 ? Set.of()
                 : Collections.unmodifiableSet(new LinkedHashSet<>(permissions));
@@ -78,7 +80,7 @@ public record TenantContext(String tenantId, String subjectId, Set<String> permi
      * Builds a tenant context from request headers.
      *
      * @param headers request headers
-     * @return tenant context when required claims are present
+     * @return tenant context when required claims are present and control-safe
      */
     public static Optional<TenantContext> fromHeaders(HttpHeaders headers) {
         if (headers == null) {
@@ -115,27 +117,46 @@ public String canonicalPermissions() {
     }
 
     private static Set<String> permissionsOf(String raw) {
-        String normalized = sanitize(raw);
-        if (normalized == null) {
+        if (raw == null) {
             return Set.of();
         }
 
         LinkedHashSet<String> parsed = new LinkedHashSet<>();
-        Arrays.stream(normalized.split(","))
+        Arrays.stream(raw.split(","))
                 .map(TenantContext::sanitize)
                 .filter(value -> value != null)
                 .forEach(parsed::add);
         return parsed;
     }
 
-    private static String sanitize(String value) {
+    private static String requireAuthority(String value, String claimName) {
         if (value == null) {
+            throw new IllegalArgumentException(claimName + " is required");
+        }
+        if (value.codePoints().anyMatch(TenantContext::isDisallowedClaimCharacter)) {
+            throw new IllegalArgumentException(claimName + " must not contain control characters");
+        }
+        String sanitized = sanitize(value);
+        if (sanitized == null) {
+            throw new IllegalArgumentException(claimName + " is required");
+        }
+        return sanitized;
+    }
+
+    private static String sanitize(String value) {
+        if (value == null
+                || value.codePoints().anyMatch(TenantContext::isDisallowedClaimCharacter)) {
             return null;
         }
 
-        String sanitized = value
-                .replace("\u0000", "")
-                .strip();
+        String sanitized = value.strip();
         return sanitized.isEmpty() ? null : sanitized;
     }
+
+    private static boolean isDisallowedClaimCharacter(int codePoint) {
+        int characterType = Character.getType(codePoint);
+        return Character.isISOControl(codePoint)
+                || characterType == Character.LINE_SEPARATOR
+                || characterType == Character.PARAGRAPH_SEPARATOR;
+    }
 }
diff --git a/src/test/java/com/clearfolio/viewer/auth/TenantContextAuthorityInvariantTest.java b/src/test/java/com/clearfolio/viewer/auth/TenantContextAuthorityInvariantTest.java
new file mode 100644
index 00000000..204a04cc
--- /dev/null
+++ b/src/test/java/com/clearfolio/viewer/auth/TenantContextAuthorityInvariantTest.java
@@ -0,0 +1,101 @@
+package com.clearfolio.viewer.auth;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.http.HttpHeaders;
+
+/**
+ * Verifies that directly constructed and header-derived tenant contexts cannot
+ * carry absent or control-corrupted authority across service boundaries.
+ */
+class TenantContextAuthorityInvariantTest {
+
+    @Test
+    void constructorRejectsMissingTenantAuthority() {
+        IllegalArgumentException nullTenant = assertThrows(
+                IllegalArgumentException.class,
+                () -> new TenantContext(null, "subject-1", Set.of("job:read"))
+        );
+        IllegalArgumentException blankTenant = assertThrows(
+                IllegalArgumentException.class,
+                () -> new TenantContext("   ", "subject-1", Set.of("job:read"))
+        );
+
+        assertEquals("tenantId is required", nullTenant.getMessage());
+        assertEquals("tenantId is required", blankTenant.getMessage());
+    }
+
+    @Test
+    void constructorRejectsControlCorruptedTenantAuthority() {
+        for (String tenantId : List.of(
+                "tenant\u0000-a",
+                "tenant\n-a",
+                "tenant\u001B-a",
+                "tenant\u2028-a"
+        )) {
+            IllegalArgumentException exception = assertThrows(
+                    IllegalArgumentException.class,
+                    () -> new TenantContext(tenantId, "subject-1", Set.of("job:read"))
+            );
+
+            assertEquals("tenantId must not contain control characters", exception.getMessage());
+        }
+    }
+
+    @Test
+    void constructorRejectsMissingSubjectAuthority() {
+        IllegalArgumentException nullSubject = assertThrows(
+                IllegalArgumentException.class,
+                () -> new TenantContext("tenant-a", null, Set.of("job:read"))
+        );
+        IllegalArgumentException blankSubject = assertThrows(
+                IllegalArgumentException.class,
+                () -> new TenantContext("tenant-a", "   ", Set.of("job:read"))
+        );
+
+        assertEquals("subjectId is required", nullSubject.getMessage());
+        assertEquals("subjectId is required", blankSubject.getMessage());
+    }
+
+    @Test
+    void constructorRejectsControlCorruptedSubjectAuthority() {
+        for (String subjectId : List.of(
+                "subject\u0000-a",
+                "subject\t-a",
+                "subject\u007F-a",
+                "subject\u2029-a"
+        )) {
+            IllegalArgumentException exception = assertThrows(
+                    IllegalArgumentException.class,
+                    () -> new TenantContext("tenant-a", subjectId, Set.of("job:read"))
+            );
+
+            assertEquals("subjectId must not contain control characters", exception.getMessage());
+        }
+    }
+
+    @Test
+    void headerParsingRejectsControlCorruptedClaimsAndPermissions() {
+        HttpHeaders controlTenant = headers("tenant\n-a", "subject-a", "job:read");
+        HttpHeaders controlSubject = headers("tenant-a", "subject\u2028-a", "job:read");
+        HttpHeaders controlPermission = headers("tenant-a", "subject-a", "job:\u0000read");
+
+        assertTrue(TenantContext.fromHeaders(controlTenant).isEmpty());
+        assertTrue(TenantContext.fromHeaders(controlSubject).isEmpty());
+        assertTrue(TenantContext.fromHeaders(controlPermission).isEmpty());
+    }
+
+    private static HttpHeaders headers(String tenantId, String subjectId, String permissions) {
+        HttpHeaders headers = new HttpHeaders();
+        headers.set(TenantContext.TENANT_ID_HEADER, tenantId);
+        headers.set(TenantContext.SUBJECT_ID_HEADER, subjectId);
+        headers.set(TenantContext.PERMISSIONS_HEADER, permissions);
+        return headers;
+    }
+}