diff --git a/alembic/versions/0024_add_session_version.py b/alembic/versions/0024_add_session_version.py
new file mode 100644
index 0000000..f3a9356
--- /dev/null
+++ b/alembic/versions/0024_add_session_version.py
@@ -0,0 +1,16 @@
+"""Add session_version to users for session invalidation on credential change."""
+
+from alembic import op
+
+revision = "0024"
+down_revision = "0023"
+
+
+def upgrade() -> None:
+    op.execute(
+        "ALTER TABLE users ADD COLUMN IF NOT EXISTS session_version INTEGER NOT NULL DEFAULT 1"
+    )
+
+
+def downgrade() -> None:
+    op.execute("ALTER TABLE users DROP COLUMN IF EXISTS session_version")
diff --git a/src/fabledassistant/auth.py b/src/fabledassistant/auth.py
index cac2515..3006219 100644
--- a/src/fabledassistant/auth.py
+++ b/src/fabledassistant/auth.py
@@ -15,6 +15,9 @@ def _check_auth(f, required_role: str | None = None):
         if not user:
             session.clear()
             return jsonify({"error": "Authentication required"}), 401
+        if session.get("session_version") != user.session_version:
+            session.clear()
+            return jsonify({"error": "Session expired. Please log in again."}), 401
         if required_role and user.role != required_role:
             return jsonify({"error": "Admin access required"}), 403
         g.user = user
diff --git a/src/fabledassistant/models/user.py b/src/fabledassistant/models/user.py
index 7fc7133..2db482a 100644
--- a/src/fabledassistant/models/user.py
+++ b/src/fabledassistant/models/user.py
@@ -1,4 +1,4 @@
-from sqlalchemy import Index, Text
+from sqlalchemy import Index, Integer, Text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from fabledassistant.models import Base
@@ -14,6 +14,7 @@ class User(Base, CreatedAtMixin):
     password_hash: Mapped[str | None] = mapped_column(Text, nullable=True)
     oauth_sub: Mapped[str | None] = mapped_column(Text, unique=True, nullable=True)
     role: Mapped[str] = mapped_column(Text, nullable=False, default="user")
+    session_version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
 
     __table_args__ = (
         Index("ix_users_username", "username"),
diff --git a/src/fabledassistant/routes/auth.py b/src/fabledassistant/routes/auth.py
index 7b4ccaf..434e991 100644
--- a/src/fabledassistant/routes/auth.py
+++ b/src/fabledassistant/routes/auth.py
@@ -76,6 +76,7 @@ async def register():
         return jsonify({"error": "Username already taken"}), 409
 
     session["user_id"] = user.id
+    session["session_version"] = user.session_version
     await log_audit("register", user_id=user.id, username=user.username, ip_address=_client_ip())
     return jsonify(user.to_dict()), 201
 
@@ -106,6 +107,7 @@ async def login():
         return jsonify({"error": "Invalid username or password"}), 401
 
     session["user_id"] = user.id
+    session["session_version"] = user.session_version
     await log_audit("login", user_id=user.id, username=user.username, ip_address=_client_ip())
     asyncio.create_task(notify_security_event(
         user.id, "login",
@@ -150,10 +152,12 @@ async def update_password():
         return jsonify({"error": "New password must be at least 8 characters"}), 400
 
     uid = get_current_user_id()
-    success = await change_password(uid, current, new_pw)
-    if not success:
+    new_version = await change_password(uid, current, new_pw)
+    if new_version is None:
         return jsonify({"error": "Current password is incorrect"}), 403
 
+    # Keep the current session alive with the new version (other sessions are now invalidated)
+    session["session_version"] = new_version
     await log_audit("password_change", user_id=uid, username=g.user.username, ip_address=_client_ip())
     asyncio.create_task(notify_security_event(
         uid, "password_change",
@@ -279,6 +283,7 @@ async def register_with_invite():
         return jsonify({"error": "Invalid or expired invitation"}), 400
 
     session["user_id"] = user.id
+    session["session_version"] = user.session_version
     await log_audit(
         "register_with_invite",
         user_id=user.id,
@@ -346,5 +351,6 @@ async def oauth_callback():
 
     user = await find_or_create_oauth_user(sub, email, preferred_username)
     session["user_id"] = user.id
+    session["session_version"] = user.session_version
     await log_audit("oauth_login", user_id=user.id, username=user.username, ip_address=_client_ip())
     return redirect("/")
diff --git a/src/fabledassistant/services/auth.py b/src/fabledassistant/services/auth.py
index e290381..57f8beb 100644
--- a/src/fabledassistant/services/auth.py
+++ b/src/fabledassistant/services/auth.py
@@ -109,18 +109,19 @@ async def get_user_by_username(username: str) -> User | None:
         return result.scalars().first()
 
 
-async def change_password(user_id: int, current_password: str, new_password: str) -> bool:
-    """Change a user's password. Returns True on success, False if current password is wrong."""
+async def change_password(user_id: int, current_password: str, new_password: str) -> int | None:
+    """Change a user's password. Returns new session_version on success, None if current password is wrong."""
     async with async_session() as session:
         user = await session.get(User, user_id)
         if not user:
-            return False
+            return None
         if not verify_password(current_password, user.password_hash):
-            return False
+            return None
         user.password_hash = hash_password(new_password)
+        user.session_version += 1
         await session.commit()
         logger.info("Password changed for user %d (%s)", user_id, user.username)
-        return True
+        return user.session_version
 
 
 async def is_registration_open() -> bool:
@@ -249,6 +250,7 @@ async def reset_password_with_token(raw_token: str, new_password: str) -> int |
             return None
 
         user.password_hash = hash_password(new_password)
+        user.session_version += 1
         reset_token.used = True
         await session.commit()
 
diff --git a/summary.md b/summary.md
index d7ee859..78fa089 100644
--- a/summary.md
+++ b/summary.md
@@ -12,7 +12,21 @@
 >    Include file-level details in the commit body when the change is non-trivial.
 
 ## Last Updated
-2026-03-06 — DRY refactoring pass: TimestampMixin, route helpers, shared composables, ConfirmDialog, shared CSS.
+2026-03-06 — Session invalidation on credential change (password reset + password change).
+
+**Session invalidation on credential change:**
+- `models/user.py`: added `session_version: Mapped[int]` column (default 1). `Integer` import added.
+- `alembic/versions/0024_add_session_version.py`: migration adds `session_version INTEGER NOT NULL DEFAULT 1` to `users`.
+- `auth.py` (`_check_auth`): after loading user, checks `session["session_version"] == user.session_version`; mismatch → `session.clear()` + 401 "Session expired. Please log in again."
+- `services/auth.py`:
+  - `change_password` return type changed from `bool` to `int | None` (returns new `session_version` on success, `None` on failure). Increments `user.session_version` before commit.
+  - `reset_password_with_token`: increments `user.session_version` before commit (invalidates all live sessions on password reset).
+- `routes/auth.py`:
+  - `login`, `register`, `register_with_invite`, `oauth_callback`: now also set `session["session_version"] = user.session_version` alongside `session["user_id"]`.
+  - `update_password`: receives `new_version` from `change_password`; updates `session["session_version"] = new_version` so the current user's own session stays valid while all other sessions are invalidated.
+- **Effect:** All existing sessions will require re-login once after the migration runs (existing cookies lack `session_version`, so they'll mismatch `1`). Subsequent credential changes immediately evict all other active sessions.
+
+---
 
 **DRY refactoring pass (backend):**
 - `src/fabledassistant/models/base.py` (new): `TimestampMixin` (`created_at` + `updated_at`) and `CreatedAtMixin` (`created_at` only) — SQLAlchemy 2.0 `Mapped[]` mixins. Applied to all 10+ models (`Note`, `Project`, `Milestone`, `Conversation`, `Message`, `User`, `PushSubscription`, `TaskLog`, `NoteDraft`, `NoteVersion`), removing ~60 lines of duplicated column definitions.