diff --git a/Data/Engine/Unit_Tests/test_tokens_api.py b/Data/Engine/Unit_Tests/test_tokens_api.py
index 09b6f8f6..6d7c1ea7 100644
--- a/Data/Engine/Unit_Tests/test_tokens_api.py
+++ b/Data/Engine/Unit_Tests/test_tokens_api.py
@@ -77,14 +77,16 @@ def test_refresh_token_success(engine_harness: EngineTestHarness) -> None:
     with sqlite3.connect(str(harness.db_path)) as conn:
         cur = conn.cursor()
         cur.execute(
-            "SELECT last_used_at, revoked_at FROM refresh_tokens WHERE guid = ?",
+            "SELECT last_used_at, revoked_at, expires_at FROM refresh_tokens WHERE guid = ?",
             (guid,),
         )
         row = cur.fetchone()
     assert row is not None
-    last_used_at, revoked_at = row
+    last_used_at, revoked_at, bumped_expires_at = row
     assert last_used_at is not None
     assert revoked_at is None
+    refreshed_expiry = datetime.fromisoformat(bumped_expires_at)
+    assert refreshed_expiry > now + timedelta(days=80)
 
 
 def test_refresh_token_requires_payload(engine_harness: EngineTestHarness) -> None:
diff --git a/Data/Engine/services/API/enrollment/routes.py b/Data/Engine/services/API/enrollment/routes.py
index 42688e06..df7ac424 100644
--- a/Data/Engine/services/API/enrollment/routes.py
+++ b/Data/Engine/services/API/enrollment/routes.py
@@ -312,9 +312,11 @@ def register(
         return hashlib.sha256(token.encode("utf-8")).hexdigest()
 
     def _issue_refresh_token(cur: sqlite3.Cursor, guid: str) -> Dict[str, Any]:
+        # Sliding window expiration; refreshed on each successful token refresh call.
+        REFRESH_TOKEN_TTL_DAYS = 90
         token = secrets.token_urlsafe(48)
         now = _now()
-        expires_at = now.replace(microsecond=0) + timedelta(days=30)
+        expires_at = now.replace(microsecond=0) + timedelta(days=REFRESH_TOKEN_TTL_DAYS)
         cur.execute(
             """
             INSERT INTO refresh_tokens (id, guid, token_hash, created_at, expires_at)
diff --git a/Data/Engine/services/API/tokens/routes.py b/Data/Engine/services/API/tokens/routes.py
index 784093b1..41863101 100644
--- a/Data/Engine/services/API/tokens/routes.py
+++ b/Data/Engine/services/API/tokens/routes.py
@@ -12,7 +12,7 @@ from __future__ import annotations
 
 import hashlib
 import sqlite3
-from datetime import datetime, timezone
+from datetime import datetime, timezone, timedelta
 from typing import Callable
 
 from flask import Blueprint, current_app, jsonify, request
@@ -28,6 +28,7 @@ def register(
     dpop_validator: DPoPValidator,
 ) -> None:
     blueprint = Blueprint("tokens", __name__)
+    REFRESH_TOKEN_TTL_DAYS = 90
 
     def _hash_token(token: str) -> str:
         return hashlib.sha256(token.encode("utf-8")).hexdigest()
@@ -70,7 +71,8 @@ def register(
                 return jsonify({"error": "refresh_token_revoked"}), 401
             if expires_at:
                 try:
-                    if _parse_iso(expires_at) <= datetime.now(tz=timezone.utc):
+                    parsed_expiry = _parse_iso(expires_at)
+                    if parsed_expiry <= datetime.now(tz=timezone.utc):
                         return jsonify({"error": "refresh_token_expired"}), 401
                 except Exception:
                     pass
@@ -124,10 +126,16 @@ def register(
                 """
                 UPDATE refresh_tokens
                    SET last_used_at = ?,
+                       expires_at = ?,
                        dpop_jkt = COALESCE(NULLIF(?, ''), dpop_jkt)
                  WHERE id = ?
                 """,
-                (_iso_now(), jkt, record_id),
+                (
+                    _iso_now(),
+                    _iso(datetime.now(tz=timezone.utc) + timedelta(days=REFRESH_TOKEN_TTL_DAYS)),
+                    jkt,
+                    record_id,
+                ),
             )
             conn.commit()
         finally: