disallow to disable guard during focus

backend/app/api/routes_settings.py

@@ -38,13 +38,20 @@ def put_settings(session: DbSession, patch: dict[str, Any] = Body(...)) -> dict:
         # `exc.errors()` can carry exception objects in `ctx`, which JSON cannot
         # take; pydantic's own `json()` renders them as text.
         raise HTTPException(status_code=422, detail=json.loads(exc.json())) from exc
+    except blocker_service.GuardLocked as exc:
+        # 409, not 422: the body is valid, the current state refuses it. A plain
+        # string detail is what every client's error path already surfaces.
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
     return {"settings": settings_service.mask_secrets(updated.model_dump(mode="json"))}
 
 
 @router.post("/reset")
 def reset_settings(session: DbSession) -> dict:
     """Back to defaults, re-seeded from the environment."""
-    updated = settings_service.save_settings(session, settings_service.settings_from_env())
+    try:
+        updated = settings_service.reset_to_env(session)
+    except blocker_service.GuardLocked as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
     return {"settings": settings_service.mask_secrets(updated.model_dump(mode="json"))}
 
 

backend/app/services/blocker_service.py

@@ -187,12 +187,59 @@ def schedule_active(settings: AppSettings, moment: datetime | None = None) -> bo
     return False
 
 
+GUARD_LOCK_NOTE = "Finish or drop the interval to switch the focus guard off."
+"""Said in one voice: the 409 detail, and the `lock_reason` every client renders."""
+
+
+class GuardLocked(RuntimeError):
+    """Switching the guard off was refused because an interval is live."""
+
+
+def guard_locked(session: Session, settings: AppSettings) -> bool:
+    """The guard is on and an interval is live, so it may not be switched off.
+
+    Any kind, running or paused — `pomodoro.current_session` is exactly that. A
+    break is not an escape hatch and neither is pausing the clock.
+
+    Deliberately keyed off `blocker.enabled` rather than off `policy()["active"]`:
+    in `scheduled` mode outside every window nothing is being blocked right now,
+    and the guard still must not be quietly switched off before the window opens.
+    """
+    return settings.blocker.enabled and pomodoro.current_session(session) is not None
+
+
+def ensure_guard_not_switched_off(
+    session: Session, before: AppSettings, after: AppSettings
+) -> None:
+    """Refuse a settings write that would turn the guard off mid-interval.
+
+    Compares the two documents rather than reading the patch. The patch is a deep
+    merge of a shared object and arrives loosely typed — `{"enabled": "no"}`
+    coerces to `False`, so inspecting the raw keys would have to re-implement
+    pydantic to be right — and "did the stored value go from on to off" is the
+    only question that cannot be fooled. It also means an unrelated patch, a
+    full-document echo and a re-sent `enabled: false` all pass by construction.
+
+    Switching the guard *on* is never refused.
+    """
+    if not after.blocker.enabled and guard_locked(session, before):
+        raise GuardLocked(GUARD_LOCK_NOTE)
+
+
 def policy(session: Session, settings: AppSettings) -> dict[str, Any]:
-    """What the desktop app polls: should I block, and what."""
+    """What the desktop app polls: should I block, and what.
+
+    `active` and `locked` answer two different questions and do disagree: in
+    `scheduled` mode outside every window, nothing is blocked (`active` false)
+    while the guard is still locked on (`locked` true) because an interval runs.
+    """
     blocker = settings.blocker
     current = pomodoro.current_session(session)
     active = False
     reason = "disabled"
+    # The same rule as `guard_locked()`, reusing the row this function already
+    # fetched rather than querying twice — `test_blocker.py` pins the two together.
+    locked = blocker.enabled and current is not None
 
     if blocker.enabled:
         if blocker.mode == "always":
@@ -218,7 +265,8 @@ def policy(session: Session, settings: AppSettings) -> dict[str, Any]:
         "reason": reason,
         "mode": blocker.mode,
         "enabled": blocker.enabled,
-        "strict": blocker.strict,
+        "locked": locked,
+        "lock_reason": GUARD_LOCK_NOTE if locked else "",
         "redirect_ip": blocker.redirect_ip,
         "domains": expand_domains(settings) if active else [],
         "apps": [app.strip() for app in blocker.blocked_apps if app.strip()] if active else [],

backend/app/services/settings_service.py

@@ -20,7 +20,7 @@ from sqlalchemy.orm import Session
 
 from app.config import env_settings
 from app.models import SettingsRow
-from app.services import pomodoro
+from app.services import blocker_service, pomodoro
 from app.settings_schema import SECRET_FIELDS, SECRET_MASK, AppSettings
 
 _SETTINGS_ID = 1
@@ -192,10 +192,17 @@ def unmask_secrets(stored: dict[str, Any], incoming: dict[str, Any]) -> dict[str
 
 def apply_patch(session: Session, patch: dict[str, Any]) -> AppSettings:
     """Merge a partial settings document (as the UI sends it) and store it."""
-    current = load_settings(session).model_dump(mode="json")
+    stored = load_settings(session)
+    current = stored.model_dump(mode="json")
     patch = unmask_secrets(current, patch)
     merged = _merge(current, patch)
-    updated = save_settings(session, AppSettings.model_validate(merged))
+    candidate = AppSettings.model_validate(merged)
+
+    # Validate, then refuse, then write: a malformed patch stays a 422 rather
+    # than becoming a 409, and nothing is stored either way.
+    blocker_service.ensure_guard_not_switched_off(session, stored, candidate)
+
+    updated = save_settings(session, candidate)
 
     # A changed Focus/Short/Long minute (directly, or via a preset) resizes
     # whatever interval is already running or paused — see
@@ -203,3 +210,16 @@ def apply_patch(session: Session, patch: dict[str, Any]) -> AppSettings:
     # is simplest to always run it rather than detect which keys changed.
     pomodoro.rescale_current(session, updated)
     return updated
+
+
+def reset_to_env(session: Session) -> AppSettings:
+    """Back to the environment seed — refused if that would unguard a live interval.
+
+    `settings_from_env` never touches the `blocker` subtree, so a reset always
+    lands on the schema default `enabled = False`: without this check one POST
+    would switch the focus guard off mid-interval.
+    """
+    stored = load_settings(session)
+    fresh = settings_from_env()
+    blocker_service.ensure_guard_not_switched_off(session, stored, fresh)
+    return save_settings(session, fresh)

backend/app/settings_schema.py

@@ -204,8 +204,6 @@ class BlockerSettings(BaseModel):
     """Terminate a blocked app when it appears; otherwise only warn and log."""
 
     schedule: list[BlockWindow] = Field(default_factory=list)
-    strict: bool = False
-    """The desktop app refuses to switch blocking off while a work interval runs."""
 
     redirect_ip: str = "127.0.0.1"
     app_poll_seconds: int = Field(default=5, ge=1, le=60)