# Known Issues

## Concurrent mutation during chunked `/controller` response

**Status:** fixed: reads in step 2, edits in step 3; command replies still read the live model (below).
**Introduced:** 2026-04-19, alongside the chunked-response conversion of `/controller` (the original crash report was about `cbuf::resize` aborting `async_tcp`).
**Fixed:** 2026-10-16, steps 2 and 3 of [LOOP_QUEUE_PLAN.md](LOOP_QUEUE_PLAN.md).

### What it was

The chunked `/controller` response read `somfy.rooms`, `somfy.shades`, `somfy.groups` and `somfy.repeaters` on async_tcp a piece at a time as the client's TCP window opened, for hundreds of ms to seconds. Anything that changed them meanwhile could make the document contradict itself: a deleted shade in `shades` but not in a group's `linkedShades`, two positions for one shade, a linked shade skipped or written twice. `/discovery`, `/shades` and the other reads had the same exposure, only shorter.

All eight read routes (`/controller`, `/discovery`, `/rooms`, `/shades`, `/groups`, `/room`, `/shade`, `/group`) now stream a ModelSnapshot that `loop()` fills, so each document describes one moment ([ADR-0002](adr/0002-loop-task-is-the-only-writer-of-the-shade-model.md)). That is fix option (c), taken per read in a heap slot of about 5.6 KB.

### Edits (step 3)

The handlers that changed the shade model on the web server task (adding, saving and deleting rooms, shades and groups; linking remotes, repeaters and group members; `/setPaired`; the sort orders) now hand the edit to `loop()` through the LoopQueue, and every client learns the result from a `requestResult` socket event. So `/linkRemote` can no longer race a received frame for a linked remote's rolling code: both now change it on `loop()`, in the order they happen.

### Still open

- Command replies (`/shadeCommand`, `/tiltCommand`, `/unpairShade`, `/setRollingCode`, ...) still copy the one item they report from the live shade model on async_tcp, so a reply can show a value from the middle of a change. `/room`, `/shade`, `/group` and `/groupOptions` also check on the live model whether the item exists, because the status goes out before the snapshot is filled.
- The read routes would leave out an item that didn't fit their 3 KB unit; a test now proves none can, see [Oversized read items are left out](#oversized-read-items-are-left-out).

## Oversized read items are left out

**Status:** guarded by a test (fix option (b)). It can't happen with today's fields, and a change that would make it happen fails `test_snapshot_limits`.
**Location:** `SnapshotWriter::overflowed` in [src/ModelSnapshot.cpp](../src/ModelSnapshot.cpp); the unit is `SNAPSHOT_UNIT_SIZE` in [src/ModelSnapshot.h](../src/ModelSnapshot.h).

### Summary

Every read route builds each room, shade, group and linked shade into a 3 KB unit before sending it. When one doesn't fit, the writer logs an `ESP_LOGE` line, skips that item and carries on, so the document stays valid JSON. The client gets no sign that anything is missing: the item just isn't in the list. Before step 2 only `/controller` did this; `/discovery`, `/shades` and the rest grew their buffer instead.

`test_snapshot_limits` fills a snapshot with the largest possible items: 20-character names of control characters (each escaped to `\u00XX`), all 7 linked remotes, 32 members in every group, and the widest value of every number. It checks that every read document written with the real unit is identical to the same document written with an unlimited one. The largest items are a shade at 1,097 bytes, a linked shade at 345, a group at 333 and a room at 159, against 3,072. The log line stays as a backstop.

### Concrete failure modes

1. A shade is left out after a firmware change adds fields to it. It is missing from the config UI, and Home Assistant doesn't create an entity for it.
2. A group whose `linkedShades` entry doesn't fit loses that shade from its list.

### Fix options (pick one later)

- **(a) Fail loud.** Add a list of the skipped item ids to the end of the document, and show a warning in the UI.
- **(b) Check the size at build time.** Work out the worst case for each item from the field limits and `static_assert` that it fits the buffer, so a change that breaks it doesn't build.

### Related

- The same "lost without telling the client" problem as [Large websocket events are dropped](#large-websocket-events-are-dropped).

## Large websocket events are dropped

**Status:** open
**Location:** [`JsonSockEvent` in src/WResp.cpp](../src/WResp.cpp), buffer `g_response[MAX_SOCK_RESPONSE]` (2048 bytes) in [src/outputs/SocketEmitter.cpp](../src/outputs/SocketEmitter.cpp).

### Summary

Socket events are built into a fixed 2 KB static buffer. When a value doesn't fit, [`JsonSockEvent::_safecat`](../src/WResp.cpp) marks the event as overflowed, and `endEvent` logs an error and doesn't send it. Clients never see malformed JSON. The event is simply lost, and the client isn't told.

Unlike the `/controller` HTTP crash, this path does **not** abort — there is no growing cbuf and no `new[]` on the send path. Per-client frame allocations inside `AsyncWebSocket` are bounded by the 2 KB buffer size and have their own overflow guard (queue drop / client disconnect).

### Concrete failure modes

1. A single event serializing a fully-populated shade (~1.3–1.5 KB for a shade with all `SOMFY_MAX_LINKED_REMOTES` = 7 populated) gets close to the 2 KB limit. Any additional fields or long names push it over, and that shade's state update never reaches the clients.
2. Any event that loops over a collection (e.g. frequency-scan results in `Transceiver.cpp`, batch emits in `SomfyEvents.cpp`) can exceed 2 KB depending on size, with no indication to the client beyond the ESP-side `ESP_LOGE` line.

### Fix options (pick one later)

- **(a) Fail loud.** Send a small error event in place of the dropped one so the client knows to reload the state.
- **(b) Split large events across frames.** Use the socket.io ack/chunk pattern to send an event in multiple frames when it wouldn't fit. Requires matching client-side reassembly.
- **(c) Raise `MAX_SOCK_RESPONSE`.** Cheapest, but just pushes the limit — doesn't eliminate the failure mode.

### Related

- Not the same code path as the `/controller` crash. Solve independently.
- Worth grepping for `JsonSockEvent` usages that iterate collections (see references in `SomfyEvents.cpp`, `Transceiver.cpp`, `ESPNetwork.cpp`, `GitOTA.cpp`) to identify the most at-risk events.
- [Group reads emit events from the web server task](#group-reads-emit-events-from-the-web-server-task) (fixed): a second task writing the same buffer.

## Group reads emit events from the web server task

**Status:** fixed 2026-10-16, step 2 of [LOOP_QUEUE_PLAN.md](LOOP_QUEUE_PLAN.md) (fix option (a)). Read routes write from a ModelSnapshot, and the replies still written on async_tcp copy the group with `snapshotGroup()`, which works its flags out without changing the group or sending anything.
**Location:** `serializeGroupRef` in [src/entryPoints/Web.cpp](../src/entryPoints/Web.cpp) called `SomfyGroup::updateFlags()` in [src/SomfyGroup.cpp](../src/SomfyGroup.cpp).

### Summary

Serializing a group for an HTTP reply first calls `group->updateFlags()`. When the group's flags no longer match its shades', that writes `group->flags`, sends a `groupState` socket event and publishes the group's MQTT topics, all on the async_tcp task, while `loop()` sends events and publishes too.

Every socket event is formatted into the one static buffer `g_response` in [src/outputs/SocketEmitter.cpp](../src/outputs/SocketEmitter.cpp) through the one `JsonSockEvent` in `sockEmit`. Two tasks emitting at once write over each other's event. The MQTT client (PubSubClient) isn't safe to use from two tasks either.

Reached from every route that serializes a group: `/controller`, `/discovery`, `/groups`, `/group`, `/groupCommand`, `/addGroup`, `/saveGroup`, `/linkToGroup`, `/unlinkFromGroup` and others.

### Concrete failure modes

1. A `groupState` from a `/groups` request and a `shadeState` from `loop()` are formatted at the same time: clients receive garbled JSON, or an event with another event's fields.
2. The group's MQTT publish interleaves with one from `loop()` in the client's buffer, and the broker gets a broken packet or the connection drops.
3. `group->flags` is written on async_tcp while `loop()` updates the same group through `updateGroupFlags()`.

It needs a group whose flags are out of date at the moment a client reads it, for example right after a sensor frame changed a linked shade's sun or wind flags, so it is rare.

### Fix options

- **(a) Drop `updateFlags()` from the serializers.** `loop()` already keeps group flags current through `updateGroupFlags()`. This is part of step 2 of [LOOP_QUEUE_PLAN.md](LOOP_QUEUE_PLAN.md): reads come from a ModelSnapshot that `loop()` fills, and serializers only read.
- **(b) Only emit from `loop()`.** Covered by ADR-0002 once nothing outside `loop()` changes the shade model.

### Related

- [ADR-0002](adr/0002-loop-task-is-the-only-writer-of-the-shade-model.md): the loop task is the only writer of the shade model.
- [Large websocket events are dropped](#large-websocket-events-are-dropped): the same `g_response` buffer.