diff --git a/backend/app/domain/unit_of_work.py b/backend/app/domain/unit_of_work.py
new file mode 100644
index 0000000..b93f2b9
--- /dev/null
+++ b/backend/app/domain/unit_of_work.py
@@ -0,0 +1,47 @@
+"""Unit of Work — wraps a SQLAlchemy session for explicit transaction control.
+
+Usage in routers::
+
+    with UnitOfWork(db) as uow:
+        service_a(db, ...)
+        service_b(db, ...)
+        uow.commit()          # single commit for the entire operation
+
+If an exception propagates, ``__exit__`` issues a rollback automatically.
+Services should **never** call ``db.commit()``; they use ``db.add()`` /
+``db.flush()`` to stage work and let the caller decide when to commit.
+"""
+
+from __future__ import annotations
+
+from sqlalchemy.orm import Session
+
+
+class UnitOfWork:
+    """Lightweight transaction wrapper around an existing SQLAlchemy session."""
+
+    def __init__(self, session: Session) -> None:
+        self._session = session
+
+    # -- context manager -----------------------------------------------------
+
+    def __enter__(self) -> "UnitOfWork":
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+        if exc_type is not None:
+            self.rollback()
+
+    # -- public API ----------------------------------------------------------
+
+    def commit(self) -> None:
+        """Flush pending changes and commit the transaction."""
+        self._session.commit()
+
+    def rollback(self) -> None:
+        """Roll back the current transaction."""
+        self._session.rollback()
+
+    def flush(self) -> None:
+        """Flush pending changes without committing (useful for getting IDs)."""
+        self._session.flush()
diff --git a/backend/app/routers/notifications.py b/backend/app/routers/notifications.py
index 5f25cd6..fa7d6b2 100644
--- a/backend/app/routers/notifications.py
+++ b/backend/app/routers/notifications.py
@@ -15,6 +15,7 @@ from sqlalchemy.orm import Session
 
 from app.database import get_db
 from app.dependencies.auth import get_current_user
+from app.domain.unit_of_work import UnitOfWork
 from app.models.notification import Notification
 from app.models.user import User
 from app.schemas.notification import NotificationOut, UnreadCountOut
@@ -78,12 +79,14 @@ def read_notification(
     current_user: User = Depends(get_current_user),
 ):
     """Mark a single notification as read."""
-    success = mark_as_read(db, notification_id, current_user.id)
-    if not success:
-        raise HTTPException(
-            status_code=status.HTTP_404_NOT_FOUND,
-            detail="Notification not found",
-        )
+    with UnitOfWork(db) as uow:
+        success = mark_as_read(db, notification_id, current_user.id)
+        if not success:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail="Notification not found",
+            )
+        uow.commit()
     notif = db.query(Notification).filter(Notification.id == notification_id).first()
     return notif
 
@@ -99,5 +102,7 @@ def read_all_notifications(
     current_user: User = Depends(get_current_user),
 ):
     """Mark all notifications for the current user as read."""
-    count = mark_all_as_read(db, current_user.id)
+    with UnitOfWork(db) as uow:
+        count = mark_all_as_read(db, current_user.id)
+        uow.commit()
     return {"detail": f"Marked {count} notifications as read"}
diff --git a/backend/app/routers/tests.py b/backend/app/routers/tests.py
index 4ad1ca5..df96902 100644
--- a/backend/app/routers/tests.py
+++ b/backend/app/routers/tests.py
@@ -43,6 +43,7 @@ from app.schemas.test import (
     TestRemediationUpdate,
 )
 from app.schemas.test_template import TestTemplateInstantiate
+from app.domain.unit_of_work import UnitOfWork
 from app.services.audit_service import log_action
 from app.services.status_service import recalculate_technique_status
 from app.services.test_workflow_service import (
@@ -434,7 +435,9 @@ def start_execution(
 ):
     """Move a test from ``draft`` to ``red_executing``."""
     test = _get_test_or_404(db, test_id)
-    test = wf_start_execution(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_start_execution(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -452,7 +455,9 @@ def submit_red(
 ):
     """Red Team finalises — move from ``red_executing`` to ``blue_evaluating``."""
     test = _get_test_or_404(db, test_id)
-    test = wf_submit_red(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_submit_red(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -470,7 +475,9 @@ def submit_blue(
 ):
     """Blue Team finalises — move from ``blue_evaluating`` to ``in_review``."""
     test = _get_test_or_404(db, test_id)
-    test = wf_submit_blue(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_submit_blue(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -488,7 +495,9 @@ def pause_timer(
 ):
     """Pause the running timer for the current phase (red_executing or blue_evaluating)."""
     test = _get_test_or_404(db, test_id)
-    test = wf_pause_timer(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_pause_timer(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -506,7 +515,9 @@ def resume_timer(
 ):
     """Resume the paused timer for the current phase."""
     test = _get_test_or_404(db, test_id)
-    test = wf_resume_timer(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_resume_timer(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -525,16 +536,15 @@ def validate_red(
 ):
     """Red Lead approves or rejects the red side of a test."""
     test = _get_test_with_technique(db, test_id)
-    test = wf_validate_red(
-        db, test, current_user,
-        validation_status=payload.red_validation_status,
-        notes=payload.red_validation_notes,
-    )
-
-    # Recalculate technique status if test reached a terminal state
-    if test.state in (TestState.validated, TestState.rejected):
-        recalculate_technique_status(db, test.technique)
-
+    with UnitOfWork(db) as uow:
+        test = wf_validate_red(
+            db, test, current_user,
+            validation_status=payload.red_validation_status,
+            notes=payload.red_validation_notes,
+        )
+        if test.state in (TestState.validated, TestState.rejected):
+            recalculate_technique_status(db, test.technique)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -553,16 +563,15 @@ def validate_blue(
 ):
     """Blue Lead approves or rejects the blue side of a test."""
     test = _get_test_with_technique(db, test_id)
-    test = wf_validate_blue(
-        db, test, current_user,
-        validation_status=payload.blue_validation_status,
-        notes=payload.blue_validation_notes,
-    )
-
-    # Recalculate technique status if test reached a terminal state
-    if test.state in (TestState.validated, TestState.rejected):
-        recalculate_technique_status(db, test.technique)
-
+    with UnitOfWork(db) as uow:
+        test = wf_validate_blue(
+            db, test, current_user,
+            validation_status=payload.blue_validation_status,
+            notes=payload.blue_validation_notes,
+        )
+        if test.state in (TestState.validated, TestState.rejected):
+            recalculate_technique_status(db, test.technique)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -580,7 +589,9 @@ def reopen(
 ):
     """Reopen a rejected test, moving it back to ``draft``."""
     test = _get_test_or_404(db, test_id)
-    test = wf_reopen(db, test, current_user)
+    with UnitOfWork(db) as uow:
+        test = wf_reopen(db, test, current_user)
+        uow.commit()
     db.refresh(test)
     return test
 
@@ -610,25 +621,23 @@ def update_remediation(
     for field, value in update_data.items():
         setattr(test, field, value)
 
-    db.commit()
+    with UnitOfWork(db) as uow:
+        log_action(
+            db,
+            user_id=current_user.id,
+            action="update_remediation",
+            entity_type="test",
+            entity_id=test.id,
+            details={"updated_fields": list(update_data.keys())},
+        )
+
+        new_status = update_data.get("remediation_status")
+        if new_status == "completed" and old_remediation_status != "completed":
+            wf_handle_remediation(db, test, current_user)
+
+        uow.commit()
+
     db.refresh(test)
-
-    log_action(
-        db,
-        user_id=current_user.id,
-        action="update_remediation",
-        entity_type="test",
-        entity_id=test.id,
-        details={"updated_fields": list(update_data.keys())},
-    )
-
-    # Auto-create retest when remediation is marked completed
-    new_status = update_data.get("remediation_status")
-    if new_status == "completed" and old_remediation_status != "completed":
-        retest = wf_handle_remediation(db, test, current_user)
-        if retest:
-            db.refresh(test)
-
     return test
 
 
diff --git a/backend/app/services/notification_service.py b/backend/app/services/notification_service.py
index df7c83c..86d523f 100644
--- a/backend/app/services/notification_service.py
+++ b/backend/app/services/notification_service.py
@@ -2,6 +2,9 @@
 
 Provides helpers for generating notifications automatically when test
 state changes occur, plus CRUD for the notifications API.
+
+Functions in this module stage changes via ``db.add()`` / ``db.flush()``
+but do **not** commit.  The caller is responsible for committing.
 """
 
 import uuid
@@ -38,8 +41,7 @@ def create_notification(
         entity_id=entity_id,
     )
     db.add(notif)
-    db.commit()
-    db.refresh(notif)
+    db.flush()
     return notif
 
 
@@ -53,7 +55,6 @@ def mark_as_read(db: Session, notification_id: uuid.UUID, user_id: uuid.UUID) ->
     if notif is None:
         return False
     notif.read = True
-    db.commit()
     return True
 
 
@@ -64,7 +65,6 @@ def mark_all_as_read(db: Session, user_id: uuid.UUID) -> int:
         .filter(Notification.user_id == user_id, Notification.read == False)  # noqa: E712
         .update({"read": True})
     )
-    db.commit()
     return count
 
 
@@ -88,7 +88,6 @@ def cleanup_old_notifications(db: Session, days: int = 90) -> int:
         )
         .delete()
     )
-    db.commit()
     return count
 
 
diff --git a/backend/app/services/status_service.py b/backend/app/services/status_service.py
index 50962c2..6fe251d 100644
--- a/backend/app/services/status_service.py
+++ b/backend/app/services/status_service.py
@@ -4,6 +4,9 @@ based on the state and result of its associated tests.
 V2 rules account for dual Red/Blue validation and use
 ``detection_result`` (filled by Blue Team) instead of the legacy
 ``result`` field.
+
+This function mutates the technique but does **not** commit.
+The caller is responsible for committing the session.
 """
 
 from sqlalchemy.orm import Session
@@ -42,5 +45,3 @@ def recalculate_technique_status(db: Session, technique: Technique) -> None:
         technique.status_global = TechniqueStatus.partial
     else:
         technique.status_global = TechniqueStatus.in_progress
-
-    db.commit()
diff --git a/backend/app/services/test_workflow_service.py b/backend/app/services/test_workflow_service.py
index cd89eb9..4e3ead6 100644
--- a/backend/app/services/test_workflow_service.py
+++ b/backend/app/services/test_workflow_service.py
@@ -7,8 +7,9 @@ for each step in the test lifecycle:
                                                                   ↓
                                                            rejected → draft
 
-Every public function validates the transition, mutates the test, writes an
-audit-log entry, and commits the session.
+Every public function validates the transition, mutates the test, and writes
+an audit-log entry.  The caller (router) is responsible for committing the
+session via the Unit of Work pattern.
 """
 
 import logging
@@ -122,7 +123,6 @@ def start_execution(db: Session, test: Test, user: User) -> Test:
     )
     test.execution_date = now
     test.red_started_at = now
-    db.commit()
     return test
 
 
@@ -161,7 +161,6 @@ def submit_red_evidence(db: Session, test: Test, user: User) -> Test:
     # Start Blue Team timer
     test.blue_started_at = now
     test.blue_paused_seconds = 0
-    db.commit()
     return test
 
 
@@ -196,7 +195,6 @@ def submit_blue_evidence(db: Session, test: Test, user: User) -> Test:
         description=f"Blue Team evaluation: {test.name}",
     )
 
-    db.commit()
     return test
 
 
@@ -222,7 +220,6 @@ def pause_timer(db: Session, test: Test, user: User) -> Test:
         entity_id=test.id,
         details={"state": test.state.value},
     )
-    db.commit()
     return test
 
 
@@ -252,7 +249,6 @@ def resume_timer(db: Session, test: Test, user: User) -> Test:
         entity_id=test.id,
         details={"paused_seconds": paused_seconds, "state": test.state.value},
     )
-    db.commit()
     return test
 
 
@@ -421,14 +417,12 @@ def check_dual_validation(db: Session, test: Test) -> Test:
 
     if red_status == "rejected" or blue_status == "rejected":
         test.state = TestState.rejected
-        db.commit()
         try:
             notify_test_state_change(db, test, "rejected")
         except Exception as e:
             logger.warning("Notification failed for test %s (rejected): %s", test.id, e, exc_info=True)
     elif red_status == "approved" and blue_status == "approved":
         test.state = TestState.validated
-        db.commit()
         # Invalidate cached scores — a validation changes org-level numbers
         try:
             from app.services.score_cache import invalidate
@@ -439,10 +433,6 @@ def check_dual_validation(db: Session, test: Test) -> Test:
             notify_test_state_change(db, test, "validated")
         except Exception as e:
             logger.warning("Notification failed for test %s (validated): %s", test.id, e, exc_info=True)
-    else:
-        # One side hasn't voted yet — stay in_review, just flush
-        db.commit()
-
     return test
 
 
@@ -533,8 +523,7 @@ def handle_remediation_completed(db: Session, test: Test, user: User) -> Test |
             entity_id=retest.id,
         )
 
-    db.commit()
-    db.refresh(retest)
+    db.flush()
     return retest
 
 
@@ -599,5 +588,4 @@ def reopen_test(db: Session, test: Test, user: User) -> Test:
     test.red_paused_seconds = 0
     test.blue_paused_seconds = 0
 
-    db.commit()
     return test