Leave room for the answer: ALEX2ESP_MAX_MESSAGE defaults to ALEX2ESP_MAX_DIRECTIVE + 1024

Both limits were 2047 bytes. An answer repeats the correlationToken of its directive, which is most of a large directive, and adds 140 to 170 bytes for every property. So a directive between about 1,750 and 2,047 bytes was accepted, the sketch acted on it, and the answer was refused: the lamp switched and Alexa reported a device that does not respond.

The limit for messages now follows the limit for directives unless it is set: 2047 + 1024 = 3071 bytes, room for six properties on top of the largest directive. Both defines moved to src/AlexaLimits.h, next to each other, with the relation in the comment. The limit also applies to the discovery object of a device, which may now be 3071 bytes.

For a sketch: a report between 2,048 and 3,071 bytes is sent, where it was refused with an error. A project that sets ALEX2ESP_MAX_MESSAGE keeps its value.

Measured with the bridge built for the host against a fake MQTT client (not in the repository), a TurnOn of 2,047 bytes answered with two properties:
  8ea7778      handler ran, send() false, "2374 bytes not sent, the limit is 2047"
  this commit  handler ran, send() true, 2,374 bytes published

Tests: test_largest_directive_can_be_answered puts a directive of ALEX2ESP_MAX_DIRECTIVE bytes through the receive buffer, builds the Response of a lamp to it and checks it against ALEX2ESP_MAX_MESSAGE, also with six properties. 33 host tests pass.

examples/basicLight.cpp for d1_mini, static RAM / flash in bytes: 34,116 / 336,757 -> 34,116 / 336,757, no warnings.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/Alex2ESP.h

@@ -21,16 +21,12 @@
 #include "AlexaBridgeLogic.h"
 #include "AlexaDevice.h"
 #include "AlexaInterface.h"
+#include "AlexaLimits.h"
 #include "AlexaLog.h"
 #include "AlexaTransport.h"
 #include "AlexaUtils.h"
 #include <deque>
 
-// Largest directive the bridge accepts, in bytes. Override with -DALEX2ESP_MAX_DIRECTIVE=<bytes> in build_flags.
-#ifndef ALEX2ESP_MAX_DIRECTIVE
-#define ALEX2ESP_MAX_DIRECTIVE 2047
-#endif
-
 enum class Alex2ESPState
 {
     UNINITIALIZED, // begin() has not been called