ESPSomfy-RTS/docs/KNOWN_ISSUES.md

Known Issues

Concurrent mutation during chunked /controller response

Status: fixed for the read routes; the web-task writers below are still open. 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, step 2 of 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). That is fix option (c), taken per read in a heap slot of about 5.6 KB.

Still open

• Command and edit replies (/shadeCommand, /saveShade, /linkRemote, ...) 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 and /group also check on the live model whether the item exists, because the status goes out before the snapshot is filled.

• Other handlers on the web server task still change the shade model that loop() owns (step 3 of the plan):

  • /addRoom, /saveRoom, /deleteRoom, /addShade, /saveShade, /deleteShade, /addGroup, /saveGroup and /deleteGroup add, change and remove rooms, shades and groups.
  • /linkRemote and /unlinkRemote change a shade's linked remotes. /linkRemote also sets a linked remote's rolling code, which loop() updates whenever it receives a frame from that remote: the last write wins, so a received frame can undo the code just set.
  • /linkToGroup and /unlinkFromGroup change a group's linked shades.
  • /setPaired sets paired.

  Shade requests (shade and group commands, set-My, unpair, /setPositions, /setRollingCode, and every MQTT command), a shades restore and /updateShadeConfig already go through the LoopQueue to loop().

• The read routes leave out an item that doesn't fit their 3 KB unit, see Oversized read items are left out.

Oversized read items are left out

Status: open Location: SnapshotWriter::overflowed in src/ModelSnapshot.cpp.

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.

A shade with every linked remote populated is about 1.5 KB today, so nothing overflows yet. It becomes a silent loss as soon as a change to the shade, room or group fields pushes an item past 3 KB.

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

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

Summary

Socket events are built into a fixed 2 KB static buffer. When a value doesn't fit, JsonSockEvent::_safecat 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 (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 (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 called SomfyGroup::updateFlags() in 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/Sockets.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: 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: the loop task is the only writer of the shade model.
• Large websocket events are dropped: the same g_response buffer.