diff --git a/backend/app/api/endpoints/auth.py b/backend/app/api/endpoints/auth.py
index 7f5e017f..7b8a1ae1 100644
--- a/backend/app/api/endpoints/auth.py
+++ b/backend/app/api/endpoints/auth.py
@@ -47,8 +47,16 @@ logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/auth", tags=["authentication"])
 
 
-async def _store_refresh_token(db: AsyncSession, refresh_token_str: str, user_id) -> None:
-    """Decode a refresh token JWT and store its hash in the database."""
+async def store_refresh_token(db: AsyncSession, refresh_token_str: str, user_id) -> None:
+    """Decode a refresh token JWT and store its hash in the database.
+
+    Module-public so OAuth callback endpoints (and any future token-issuing
+    surface) can register the JTI in the ``refresh_tokens`` table the same
+    way ``/auth/login`` does. Without this the first ``/auth/refresh`` call
+    will reject the token as "revoked" because no row exists.
+
+    Caller is responsible for committing the session.
+    """
     payload = decode_token(refresh_token_str)
     if payload and payload.get("jti"):
         token_record = RefreshToken(
@@ -320,7 +328,7 @@ async def login(
     refresh_token_str = create_refresh_token(data={"sub": str(user.id)})
 
     # Store refresh token hash in DB
-    await _store_refresh_token(db, refresh_token_str, user.id)
+    await store_refresh_token(db, refresh_token_str, user.id)
     await db.commit()
 
     return Token(
@@ -355,7 +363,7 @@ async def login_json(
     refresh_token_str = create_refresh_token(data={"sub": str(user.id)})
 
     # Store refresh token hash in DB
-    await _store_refresh_token(db, refresh_token_str, user.id)
+    await store_refresh_token(db, refresh_token_str, user.id)
     await db.commit()
 
     return Token(
@@ -413,7 +421,7 @@ async def refresh_token(
     new_refresh_token_str = create_refresh_token(data={"sub": str(user.id)})
 
     # Store new refresh token
-    await _store_refresh_token(db, new_refresh_token_str, user.id)
+    await store_refresh_token(db, new_refresh_token_str, user.id)
     await db.commit()
 
     return Token(
diff --git a/backend/app/api/endpoints/oauth.py b/backend/app/api/endpoints/oauth.py
index dcf49263..446c686f 100644
--- a/backend/app/api/endpoints/oauth.py
+++ b/backend/app/api/endpoints/oauth.py
@@ -7,6 +7,7 @@ from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.api.endpoints.auth import store_refresh_token
 from app.core.admin_database import get_admin_db
 from app.core.config import settings
 from app.core.security import create_access_token, create_refresh_token
@@ -186,9 +187,16 @@ async def google_callback(
         account_invite_code=payload.account_invite_code,
         invited_email=payload.invited_email,
     )
+    refresh_token_str = create_refresh_token({"sub": str(user.id)})
+    # Persist the refresh-token JTI so the first /auth/refresh call doesn't
+    # reject this token as "revoked" (the rotation logic requires a row to
+    # mark as used). _sign_in_or_register already committed; this needs a
+    # second commit.
+    await store_refresh_token(db, refresh_token_str, user.id)
+    await db.commit()
     return OAuthCallbackResponse(
         access_token=create_access_token({"sub": str(user.id)}),
-        refresh_token=create_refresh_token({"sub": str(user.id)}),
+        refresh_token=refresh_token_str,
         is_new_user=is_new,
     )
 
@@ -209,8 +217,15 @@ async def microsoft_callback(
         account_invite_code=payload.account_invite_code,
         invited_email=payload.invited_email,
     )
+    refresh_token_str = create_refresh_token({"sub": str(user.id)})
+    # Persist the refresh-token JTI so the first /auth/refresh call doesn't
+    # reject this token as "revoked" (the rotation logic requires a row to
+    # mark as used). _sign_in_or_register already committed; this needs a
+    # second commit.
+    await store_refresh_token(db, refresh_token_str, user.id)
+    await db.commit()
     return OAuthCallbackResponse(
         access_token=create_access_token({"sub": str(user.id)}),
-        refresh_token=create_refresh_token({"sub": str(user.id)}),
+        refresh_token=refresh_token_str,
         is_new_user=is_new,
     )
diff --git a/backend/tests/test_oauth_callbacks.py b/backend/tests/test_oauth_callbacks.py
index f31e1688..7c14c7b7 100644
--- a/backend/tests/test_oauth_callbacks.py
+++ b/backend/tests/test_oauth_callbacks.py
@@ -2,8 +2,10 @@ import uuid
 import pytest
 from unittest.mock import patch
 from sqlalchemy import select
+from app.core.security import decode_token, hash_token
 from app.models.user import User
 from app.models.oauth_identity import OAuthIdentity
+from app.models.refresh_token import RefreshToken
 from app.models.subscription import Subscription
 from app.services.oauth_providers import OAuthProfile
 
@@ -118,3 +120,77 @@ async def test_microsoft_callback_creates_user(client, test_db, monkeypatch):
         select(OAuthIdentity).where(OAuthIdentity.user_id == user.id)
     )).scalar_one()
     assert identity.provider == "microsoft"
+
+
+@pytest.mark.asyncio
+async def test_oauth_google_callback_stores_refresh_token_jti(
+    client, test_db, monkeypatch
+):
+    """A successful Google OAuth callback must persist the refresh-token JTI
+    in the refresh_tokens table — otherwise /auth/refresh rejects it."""
+    from app.core.config import settings
+    monkeypatch.setattr(settings, "GOOGLE_CLIENT_ID", "client_dummy")
+    monkeypatch.setattr(settings, "GOOGLE_CLIENT_SECRET", "secret_dummy")
+
+    profile = OAuthProfile(
+        provider_subject="google_subject_jti_test",
+        email="jtitest@example.com",
+        name="JTI Test",
+    )
+    with patch("app.api.endpoints.oauth.google_exchange_code", return_value=profile):
+        response = await client.post(
+            "/api/v1/auth/google/callback", json={"code": "auth_code_xyz"}
+        )
+    assert response.status_code == 200, response.json()
+    body = response.json()
+    refresh_token_str = body["refresh_token"]
+
+    payload = decode_token(refresh_token_str)
+    assert payload is not None
+    jti = payload["jti"]
+    token_hash = hash_token(jti)
+
+    user = (await test_db.execute(
+        select(User).where(User.email == "jtitest@example.com")
+    )).scalar_one()
+
+    stored = (await test_db.execute(
+        select(RefreshToken).where(RefreshToken.token_hash == token_hash)
+    )).scalar_one_or_none()
+    assert stored is not None, "OAuth callback did not persist refresh-token JTI"
+    assert stored.user_id == user.id
+    assert stored.revoked_at is None
+
+
+@pytest.mark.asyncio
+async def test_oauth_refresh_works_after_oauth_signup(
+    client, test_db, monkeypatch
+):
+    """End-to-end: OAuth callback issues a refresh token; calling /auth/refresh
+    with that token must succeed (not be rejected as revoked)."""
+    from app.core.config import settings
+    monkeypatch.setattr(settings, "GOOGLE_CLIENT_ID", "client_dummy")
+    monkeypatch.setattr(settings, "GOOGLE_CLIENT_SECRET", "secret_dummy")
+
+    profile = OAuthProfile(
+        provider_subject="google_subject_refresh_test",
+        email="refresh-after-oauth@example.com",
+        name="Refresh After OAuth",
+    )
+    with patch("app.api.endpoints.oauth.google_exchange_code", return_value=profile):
+        callback_resp = await client.post(
+            "/api/v1/auth/google/callback", json={"code": "auth_code_xyz"}
+        )
+    assert callback_resp.status_code == 200, callback_resp.json()
+    refresh_token_str = callback_resp.json()["refresh_token"]
+
+    refresh_resp = await client.post(
+        "/api/v1/auth/refresh",
+        headers={"Authorization": f"Bearer {refresh_token_str}"},
+    )
+    assert refresh_resp.status_code == 200, refresh_resp.json()
+    refreshed = refresh_resp.json()
+    assert refreshed["access_token"]
+    assert refreshed["refresh_token"]
+    # Token rotation: new refresh token differs from the original.
+    assert refreshed["refresh_token"] != refresh_token_str