The scheduled JWT bounce called PsychicMqttClient::disconnect(), which ends
with esp_mqtt_client_stop(). That ends the client task and returns its 6 KiB
stack to the heap at the moment the TLS teardown vacates two 16 KiB mbedTLS
record buffers, so the stack lands in that hole and the next handshake cannot
reuse it. On non-PSRAM boards the largest free block then ratchets down 16 KiB
at a time while total free heap stays flat.
Soak evidence from a Heltec V3 on 8d1a0eb3: 43 of 60 disconnects had no
preceding transport error, i.e. they were this proactive bounce rather than a
broker FIN, and two of the three max_alloc steps landed within 5 s of one.
Losing a whole TLS session later returned exactly 16,384 bytes of contiguity.
softDisconnect() closes the transport without the stop, so the task and its
stack stay put across the handshake. The bounce uses it plus reconnect(), and
falls back to connect() when the client really is stopped, since reconnect()
is a silent no-op in that state.
Also corrects a comment claiming the mbedTLS context survives a transport
close: only the esp-mqtt client object does.
(cherry picked from commit 10cf5cf48fb009e751e25b37fcc1f3d1256ddbbc)
agessaman
4c90db2199