### T-08 · `_SOCKET_TIMEOUT` defined 6× — `constants.py` constant unused

**Where found:** `backend/app/utils/constants.py:16` (defines `FAIL2BAN_SOCKET_TIMEOUT_SECONDS = 5.0` but is never imported); `ban_service.py` (5.0), `jail_service.py` (10.0), `config_service.py` (10.0), `server_service.py` (10.0), `log_service.py` (10.0), `jail_config_service.py` (10.0), `config_file_utils.py` (10.0)

**Why this is needed:** `constants.py` has a module docstring saying "import from this module rather than hard-coding values" — and then nothing imports the socket timeout. The values also disagree: `ban_service` uses `5.0` while all others use `10.0`, creating silent inconsistency in timeout behaviour across endpoints.

**Goal:** One constant in `constants.py`, imported everywhere. Decide on a single default (or two named constants for fast/slow operations).

**What to do:**
1. In `constants.py`, define `FAIL2BAN_SOCKET_TIMEOUT_FAST: Final[float] = 5.0` (for health/metadata probes) and `FAIL2BAN_SOCKET_TIMEOUT: Final[float] = 10.0` (for command operations) — or a single value if appropriate.
2. Replace all local `_SOCKET_TIMEOUT` float literals with imports from `constants`.
3. Confirm `ban_service` should actually be `5.0` or `10.0` (intentional vs accidental discrepancy).

**Possible traps and issues:**
- Changing `ban_service` from 5.0 to 10.0 (or vice versa) changes observable timeout behaviour. Decide deliberately.
- `fail2ban_metadata_service.py` also has `socket_timeout: float = 5.0` hardcoded inline — include this in the sweep.

**Docs changes needed:** None.

**Doc references:** `backend/app/utils/constants.py`

---

### T-09 · `_since_unix` has two divergent implementations — latent window-boundary bug

**Where found:** `backend/app/services/ban_service.py:393` (uses `time.time()`, applies `_TIME_RANGE_SLACK_SECONDS = 60`); `backend/app/services/history_service.py:53` (uses `datetime.now(UTC).timestamp()`, no slack)

**Why this is needed:** The `ban_service` docstring explicitly explains why `time.time()` is used and why the 60-second slack is needed for consistency with fail2ban's timestamp storage. `history_service` quietly omits both, so history queries return a slightly different window boundary than ban queries for the same `TimeRange` parameter. Inconsistent windows cause "same data, different count" bugs in the UI.

**Goal:** Single `_since_unix` function in a shared utility module, with documented rationale, used by both services.

**What to do:**
1. Move `_since_unix` (with the `time.time()` + slack approach) to `app/utils/time_utils.py` (which already exists).
2. Delete both local implementations.
3. Import from `time_utils` in both services.
4. Decide consciously whether history queries should also use the slack (probably yes for consistency).

**Possible traps and issues:**
- Adding the 60-second slack to history queries may change row counts in tests that assert exact counts against seeded timestamps.
- Confirm `_TIME_RANGE_SLACK_SECONDS` belongs in `constants.py`.

**Docs changes needed:** `Docs/Backend-Development.md` — document the timestamp handling rationale.

**Doc references:** `backend/app/utils/time_utils.py`, `backend/app/utils/constants.py`

---

### T-10 · `get_geo_batch_lookup` is false injectability — module function pointer injection

**Where found:** `backend/app/dependencies.py` — `get_geo_batch_lookup()` returns `geo_service.lookup_batch` (a module-level function)

**Why this is needed:** The dependency provider exists to give the appearance of injectable geo lookup, but because `geo_service` uses module-level global state (T-04), tests that inject a different callable into routers still have the global cache active. The abstraction provides type-level indirection without runtime isolation.

**Goal:** Once T-04 is done (GeoCache as an object), inject the `GeoCache` instance and call methods on it directly. The `GeoBatchLookup` callable protocol becomes a method reference on the injected instance.

**What to do:**
1. Complete T-04 first.
2. Update `get_geo_batch_lookup` to retrieve `GeoCache` from `app.state` and return its `lookup_batch` method.
3. Or inject `GeoCache` directly and let routers call `.lookup_batch()` on it.

**Possible traps and issues:** Blocked on T-04.

**Docs changes needed:** None beyond T-04.

**Doc references:** `backend/app/dependencies.py`

---

### T-11 · Repositories injected as module references via `cast()` — structural type-safety gap

**Where found:** `backend/app/dependencies.py` — `get_session_repo()`, `get_blocklist_repo()`, `get_settings_repo()`, `get_import_log_repo()`, `get_history_archive_repo()`, `get_geo_cache_repo()`, `get_fail2ban_db_repo()` all return the module itself cast to the Protocol type.

**Why this is needed:** The `cast()` call is a signal that the type system is being overridden. Modules pass Protocol structural checks only because their top-level `async def` functions happen to match the Protocol method signatures. This is fragile — a module rename, a function rename, or an added required parameter will silently pass mypy but fail at runtime.

**Goal:** Repository modules become proper singleton instances, or the dependency providers are acknowledged as module-adapters with explicit documentation.

**What to do (option A — correct):**
1. Convert each repository module's functions into a class with the same method signatures.
2. Instantiate singletons at startup and store on `app.state` or as module-level instances.
3. Update dependency providers to return the instance without `cast()`.

**What to do (option B — minimal):**
1. Document in each `get_*_repo` provider why the module-as-Protocol pattern is intentional.
2. Add a CI check (or mypy plugin) that validates structural compatibility doesn't silently break.

**Possible traps and issues:**
- Option A is a significant refactor affecting all repository call sites.
- Option B risks the pattern silently breaking in future.

**Docs changes needed:** `Docs/Backend-Development.md` — document repository injection pattern and why it works.

**Doc references:** `Docs/Backend-Development.md`, `backend/app/repositories/protocols.py`

---

### T-12 · Apply `useListData` consistently across all data-fetching hooks

**Where found:** `frontend/src/hooks/useJailList.ts`, `useJailDetail.ts`, `useServerStatus.ts`, `useBanTrend.ts`, `useDashboardCountryData.ts` — all re-implement abort-controller / loading / error state manually. `useListData.ts` exists and is used by `useBlocklists`, `useJailConfigs`, `useActionList`, `useFilterList`.

**Why this is needed:** At least 5 hooks implement the same 40-line pattern. Any fix to the pattern (e.g. abort-guard in `.finally()`) must be applied to every copy independently. `useHistory` has a real bug because of this (see T-18).

**Goal:** All hooks that load a list and need refresh semantics use `useListData` or a shared base.

**What to do:**
1. Audit all hooks for the manual abort-controller pattern.
2. Refactor `useJailList` first (cleanest candidate — no mutations).
3. For hooks with side-effects beyond listing (e.g. `useJailDetail`), split into data hook + command hook (see T-13) and use `useListData` for the data half.
4. Extend `useListData` if needed to support `onSuccess` callbacks returning non-array data (e.g. `total`).

**Possible traps and issues:**
- `useListData` currently requires `selector: (response) → TItem[]`. Hooks that expose `total` alongside items need `onSuccess` to capture it — the `onSuccess` callback already exists in `UseListDataOptions`.
- `useServerStatus` has a polling interval and window-focus refetch that `useListData` does not support — may need a `usePolledData` variant or extension.

**Docs changes needed:** None.

**Doc references:** `frontend/src/hooks/useListData.ts`

---

### T-13 · Split `useJailDetail` — SRP violation (read state + write commands in one hook)

**Where found:** `frontend/src/hooks/useJailDetail.ts`

**Why this is needed:** The hook manages fetch state AND exposes 8 write operations (`start`, `stop`, `reload`, `setIdle`, `addIp`, `removeIp`, `toggleIgnoreSelf`, `load`). Read concerns and command concerns are independent. The consumer (`JailDetailPage`) passes them separately through props anyway, so the UI doesn't depend on them being co-located.

**Goal:** `useJailData(name)` for reading, `useJailCommands(name, onSuccess)` for mutations.

**What to do:**
1. Create `useJailData(name): { jail, ignoreList, ignoreSelf, loading, error, refresh }` using `useListData` or the abort-controller pattern.
2. Create `useJailCommands(name, onSuccess: () => void): { start, stop, reload, setIdle, addIp, removeIp, toggleIgnoreSelf }` — each command calls the API and then calls `onSuccess()` to trigger a refresh.
3. In `JailDetailPage`, call both hooks and pass results to child components.
4. Delete `useJailDetail.ts`.

**Possible traps and issues:**
- `JailDetailPage` destructures all properties from `useJailDetail` in a single line — update the destructuring.
- Commands currently call `load()` directly. The `onSuccess` callback pattern keeps them decoupled from the data hook's internals.

**Docs changes needed:** None.

**Doc references:** `frontend/src/hooks/useJailDetail.ts`, `frontend/src/pages/JailDetailPage.tsx`

---

### T-14 · Move jail detail sub-sections from `pages/jail/` to `components/jail/`

**Where found:** `frontend/src/pages/jail/` — `JailInfoSection`, `PatternsSection`, `BantimeEscalationSection`, `IgnoreListSection`, `jailDetailPageStyles.ts`. `BannedIpsSection` is in `frontend/src/components/jail/` (correct location).

**Why this is needed:** The project convention is `pages/` for route-level components and `components/` for reusable UI. Sub-sections are reusable UI building blocks, not route components. `BannedIpsSection` already lives in the right place. The inconsistency makes the directory structure misleading.

**Goal:** All `*Section` components for jail detail under `components/jail/`. `pages/jail/` deleted or contains only route-level entry points.

**What to do:**
1. Move `JailInfoSection`, `PatternsSection`, `BantimeEscalationSection`, `IgnoreListSection`, and `jailDetailPageStyles.ts` to `frontend/src/components/jail/`.
2. Update imports in `JailDetailPage.tsx`.
3. Remove empty `pages/jail/` directory.

**Possible traps and issues:**
- Confirm no other page imports from `pages/jail/` before deleting it.
- Update any path-based test imports.

**Docs changes needed:** `Docs/Web-Development.md` — document the `pages/` vs `components/` convention explicitly.

**Doc references:** `Docs/Web-Development.md`

---

### T-15 · Replace `window` event bus for session expiry with React context callback

**Where found:** `frontend/src/api/client.ts` — `window.dispatchEvent(new Event(SESSION_EXPIRED_EVENT))`; `frontend/src/providers/AuthProvider.tsx` — `window.addEventListener(SESSION_EXPIRED_EVENT, ...)`

**Why this is needed:** Using `window` as a side-channel bypasses React's component tree, breaks in non-browser environments (SSR, test environments without full JSDOM), and creates an invisible coupling between the API client and the auth provider. It also fires globally — any code anywhere that dispatches `bangui:session-expired` on window will trigger a logout, with no tracing possible.

**Goal:** The API client receives an `onUnauthorized` callback injected at the provider level, called directly instead of via a DOM event.

**What to do:**
1. Add an `onUnauthorized` callback to the API client (e.g. a module-level setter `setUnauthorizedHandler(fn)`).
2. In `AuthProvider`, call `setUnauthorizedHandler(handleSessionExpired)` on mount and reset it on unmount.
3. In `client.ts`, call the handler directly instead of `window.dispatchEvent`.
4. Remove `SESSION_EXPIRED_EVENT` string constant and the `window.addEventListener` in `AuthProvider`.

**Possible traps and issues:**
- The module-level handler setter is still global state — an alternative is to pass the handler as a parameter to `request()` via a context object, but that changes the API signature more significantly.
- Tests that mock `window.dispatchEvent` need updating.
- SSR / Vitest environments that already mock `window` may need adjustment.

**Docs changes needed:** None.

**Doc references:** `frontend/src/api/client.ts`, `frontend/src/providers/AuthProvider.tsx`

---

### T-16 · Centralise `PAGE_SIZE` frontend constants

**Where found:** `frontend/src/hooks/useBans.ts:14` (`PAGE_SIZE = 100`); `frontend/src/pages/HistoryPage.tsx:45` (`PAGE_SIZE = 50`)

**Why this is needed:** Page sizes can silently diverge from backend defaults. If the backend changes `_DEFAULT_PAGE_SIZE`, the frontend won't know. Having multiple files define the same concept differently is also misleading.

**Goal:** All pagination constants in `frontend/src/utils/constants.ts`.

**What to do:**
1. Add `BAN_PAGE_SIZE = 100`, `HISTORY_PAGE_SIZE = 50` to `frontend/src/utils/constants.ts` (create it if it doesn't exist).
2. Replace local `const PAGE_SIZE = ...` in each hook/page with imports.

**Possible traps and issues:** Trivial. Verify test snapshots don't hard-code the old inline constant.

**Docs changes needed:** None.

**Doc references:** `frontend/src/utils/constants.ts`

---

### T-17 · `useHistory` is missing abort-signal guards — stale state update bug

**Where found:** `frontend/src/hooks/useHistory.ts` — `.then()`, `.catch()`, `.finally()` callbacks update state without checking `abortRef.current.signal.aborted`

**Why this is needed:** Every other data-fetching hook in the codebase guards all state-update callbacks against aborted signals. `useHistory` does not. If the component unmounts mid-request, `setItems`, `setTotal`, `setLoading` will all fire on an unmounted component. In React 18 this is a no-op but it still indicates a broken invariant and `handleFetchError` could misclassify the abort as a real error (depends on whether `fetch` threw `AbortError` or the API module swallowed it).

**Goal:** All callbacks in `useHistory` check the abort signal before mutating state.

**What to do:**
1. Capture the controller in a local variable inside `load()` (already done: `abortRef.current = new AbortController()`).
2. In `.then()`: add `if (abortRef.current.signal.aborted) return;` before `setItems(...)`.
3. In `.catch()`: add the same guard before `handleFetchError(...)`.
4. In `.finally()`: add `if (!abortRef.current.signal.aborted)` before `setLoading(false)`.

**Possible traps and issues:**
- `abortRef.current` may have been replaced by a new controller before the callback fires. Capture the controller in a closure variable at the top of `load()`: `const controller = abortRef.current`.

**Docs changes needed:** None.

**Doc references:** `frontend/src/hooks/useHistory.ts`

---

### T-18 · Merge `useDashboardCountryData` and `useMapData` — near-identical hooks

**Where found:** `frontend/src/hooks/useDashboardCountryData.ts` and `frontend/src/hooks/useMapData.ts`

**Why this is needed:** Both hooks call `fetchBansByCountry`, maintain the same state shape (`countries`, `countryNames`, `bans`, `total`, `loading`, `error`), and implement the same abort-controller pattern. The only behavioural difference is that `useMapData` adds a 300ms debounce. Any bug fix must be applied to both.

**Goal:** A single `useBansByCountry` base hook; `useMapData` adds the debounce on top.

**What to do:**
1. Create `useBansByCountry(range, origin, source, countryCode?)` — the shared fetch logic without debounce.
2. Refactor `useDashboardCountryData` to wrap `useBansByCountry`.
3. Refactor `useMapData` to wrap `useBansByCountry` and add the debounce layer.
4. Keep the existing hook names as thin wrappers to preserve call sites.

**Possible traps and issues:**
- `useMapData` returns `{ data }` (the full response object) whereas `useDashboardCountryData` unpacks `countries`, `countryNames`, `bans`, `total`. Normalise the return shape before collapsing.
- Tests for each hook test them independently — update or merge.

**Docs changes needed:** None.

**Doc references:** `frontend/src/hooks/useDashboardCountryData.ts`, `frontend/src/hooks/useMapData.ts`

---

### T-19 · Move `DashboardFilterProvider` — page-scoped provider in wrong directory

**Where found:** `frontend/src/providers/DashboardFilterProvider.tsx` — instantiated only inside `DashboardPage.tsx`

**Why this is needed:** The `providers/` directory implies app-wide providers (alongside `AuthProvider`, `ThemeProvider`, `TimezoneProvider`). `DashboardFilterProvider` wraps only `DashboardPageContent` and is not used anywhere else. Its placement implies reuse that doesn't exist, misleading future contributors about its scope.

**Goal:** Co-located with its only consumer.

**What to do:**
1. Move `DashboardFilterProvider.tsx` to `frontend/src/pages/` (alongside `DashboardPage.tsx`) or to `frontend/src/pages/dashboard/` if the page is split into a subdirectory.
2. Update imports in `DashboardPage.tsx` and any tests.

**Possible traps and issues:** Only `DashboardPage.tsx` imports it — confirm with grep before moving.

**Docs changes needed:** `Docs/Web-Development.md` — document what belongs in `providers/` (app-wide) vs co-located.

**Doc references:** `Docs/Web-Development.md`

---

### T-20 · Replace inline `style={{}}` objects with `makeStyles` classes

**Where found:** `frontend/src/pages/map/MapBansTable.tsx` (multiple), `pages/JailDetailPage.tsx`, `pages/HistoryPage.tsx`, `pages/history/IpDetailView.tsx`, `components/WorldMap.tsx`, `components/TopCountriesPieChart.tsx`, `components/TopCountriesBarChart.tsx`

**Why this is needed:** The project uses Fluent UI's `makeStyles` with atomic CSS caching. Inline `style={{}}` objects are allocated on every render, bypass the atomic CSS cache, and are inconsistent with the established pattern. Exceptions are acceptable only for truly dynamic values (e.g. tooltip `left`/`top` that change on mouse move) — static layout values must use `makeStyles`.

**Goal:** All static layout properties moved to `makeStyles`. Inline styles only for genuinely dynamic values.

**What to do:**
1. Audit each file listed above.
2. For static `display: flex`, `gap`, `margin`, `padding` — move to `makeStyles` in that component's style block.
3. Keep inline `style` only where the value is truly dynamic at runtime (e.g. `WorldMap` tooltip position, `TopCountriesBarChart` chart height).

**Possible traps and issues:**
- `MapBansTable.tsx` has several consecutive inline `style` objects for its pagination row — these can be collapsed into one named class.
- Some components use both `tokens.*` values and inline styles — ensure `makeStyles` is imported where it isn't already.

**Docs changes needed:** `Docs/Web-Development.md` — add styling rule: use `makeStyles` for all static styles; inline `style` only for runtime-dynamic values.

**Doc references:** `Docs/Web-Development.md`, Fluent UI v9 docs on `makeStyles`

---

### T-21 · `Fail2BanMetadataService` has inline socket timeout hardcoded

**Where found:** `backend/app/services/fail2ban_metadata_service.py:64` — `socket_timeout: float = 5.0`

**Why this is needed:** Part of the same constant duplication as T-08. This file doesn't use `_SOCKET_TIMEOUT` as a module constant — it hardcodes `5.0` inline as a local variable. Should use the constant from `constants.py` once T-08 is done.

**Goal:** After T-08, replace with `FAIL2BAN_SOCKET_TIMEOUT_FAST` import.

**What to do:** Covered by T-08 sweep.

**Possible traps and issues:** None — dependent on T-08.

**Docs changes needed:** None.

**Doc references:** `backend/app/services/fail2ban_metadata_service.py`