All notable changes to cpp-sdk are recorded here. Format follows Keep a Changelog; the project uses Semantic Versioning.

• Property::setValue(float) published nan, inf or -inf, which the float payload grammar does not allow. homie_format_float() and homie_format_double() now return false with an empty string for a NaN or infinity, and setValue() logs and keeps the previous value. (#27)

• test_homie_float_vectors: the 434 float32 vectors shared with python-sdk and rust-sdk.

• Property::setValue(float) publishes the shortest decimal that reads back as the same float, laid out like python-sdk's float text: 21.4, 40.0, 1e-05, 1e16 instead of 21.400000. The formatters are homie_format_float() and homie_format_double() in ebus/homie/homie_datatype.h. (#23)

• Breaking: EbusLink::setup(EbusLink::CONTROLLER) needs ebus_link_enable_controller() to have been called; without it the link logs and is disabled. Controller mode moves to link/src/link_controller.cpp, which only that call reaches, so a device that uses EbusLink no longer links the controller and its discovery table. On an ESP32-POE-ISO-16MB device with three device-mode links that saves 2,544 bytes of static RAM and 3,664 bytes of flash. (#20)

• ebus_link, a CMake target over ebus_homie (link/, doc/link.md): EbusLink copies up to three property values, local or remote, into a settable property, with a format, rounding, change detection, retry backoff, and the last good value kept on a retraction. In a device (EbusLink::DEVICE) it reads the root Device's properties, watches remote ones through the settable table and sets a local target with deliver_local_set(); in a controller (EbusLink::CONTROLLER) it reads the discovery cache, binds * in the device or node part once discovery has settled, refuses an ambiguous match, and commands the target only while it is ready. The logic comes from esp32-sdk's logic/link, by Doug Mendonça. ebus_core links it, PlatformIO builds link/src/, and a CI step compiles it with only its own and ebus_homie's include directories.
• Unity suites test_link_core and test_link_engine, which link ebus_link.
• --link SOURCES=>TARGET (with --link-format, --link-decimals, --link-interval-ms) for ebus-posix-device and ebus-posix-controller, and the end-to-end tests e2e_link and e2e_link_device.

• Property::has_value(), and for the controller's copy of a remote property Property::store_received() and Property::forget_value() (doc/core.md).
• controller_device_count() and controller_device_at(), which return a pointer into the controller's device table, so a caller need not copy every ControllerDevice with controller_list_device_info().

• A zero-length payload on a property topic (the retained value removed) set the controller's copy to false, 0 or 0.000000 by datatype. It now clears has_value() and leaves value() at the last payload.
• The controller's value() of a received property is the payload as published. It was reformatted by datatype, so a float 21.37 read back as 21.370001.

• ebus_homie, a CMake target (homie/, doc/core.md): the Homie model, /set dispatch, the controller, id and payload validation, the JSON helpers, HomieTransport, and the log and clock hooks. It depends on ebus_mqtt and ArduinoJson, not on ebus_discovery. A CI step compiles it with only its own, ebus_mqtt's and ArduinoJson's include directories. (#3)

• The Homie headers move to <ebus/homie/...>, and util/jsonUtils.h to <ebus/homie/jsonUtils.h>; <homie/...> and <util/jsonUtils.h> forward to them. include/homie/homie_limits.h also repeats the four base limits esp32-sdk's generator reads from it.
• ebus_core is an INTERFACE target that links ebus_mqtt, ebus_discovery and ebus_homie. The Homie suites link ebus_homie alone. PlatformIO still builds one library.

• ebus_discovery, a CMake target with no dependency (discovery/, doc/discovery.md): txt_build_ebus(), txt_build_device_info(), txt_build_http() and txt_build_log(), which build each advertised service's TXT record from one EbusIdentity into a fixed-size TxtRecord, with the keys and order of framework.md, ebus-service-discovery and esp32-sdk; MdnsBackend, the advertise, browse and resolve interface a port implements over its mDNS stack; broker_browse() and broker_reresolve(), esp32-sdk's broker selection over that interface; broker_service_type(). ebus_core links it. PlatformIO still builds one library.
• Unity suites test_discovery_txt and test_discovery_backend, which link ebus_discovery alone, and a CI step that compiles ebus_discovery with only its own include directory.
• Device::forgetDescriptionHash(): the next publish() of that device sends $description even if it is unchanged. A port calls it on every device before a recovery republish (doc/core.md); the no-op skip in notifyStructuralChange() stays. (#9)

• broker_discovery.h and mdns_strings.h move to ebus_discovery as <ebus/discovery/broker_discovery.h> and <ebus/discovery/mdns_strings.h>; <platform/broker_discovery.h> and <platform/mdns_strings.h> forward to them. Their suite is now test_discovery_broker. mdns_strings.h adds the full service types (MDNS_TYPE_*), broker_ca, hw_version, broker-host and each auth method value.

• The POSIX demo device republishes the whole tree, $description included, on every reconnect (was publishStateTree()), so a broker restarted without persistence describes it again. The reconnect end-to-end test checks that the root and child $description are retained after the restart.
• doc/mqtt.md listed esp32-sdk's MqttClientTransport as overriding the Property queue_publish(); it overrides the generic one.

• ebus_mqtt, a CMake target with no dependency (mqtt/, doc/mqtt.md): MqttTransport, the transport interface, whose queue_publish() takes a QoS and a completion callback (mqtt_publish_done_fn and a void* context); PublishHold, the disconnected-link rules, moved from the POSIX port; and mqtt_after_connect(), which runs the reconnect order (flush, re-subscribe, notify). ebus_core links it. PlatformIO still builds one library.
• Unity suites test_mqtt_publish_hold and test_mqtt_reconnect, which link ebus_mqtt alone, and a CI step that compiles ebus_mqtt with only its own include directory.

• HomieTransport derives from MqttTransport. Its queue_publish(..., Property* source) is no longer pure: it forwards to the generic overload with a callback that calls Property::queued_publish_done(). A port that overrides it, as esp32-sdk's does, builds unchanged; a new port overrides the generic overload instead.
• PublishHold sizes are EBUS_MQTT_HOLD_ENTRIES, EBUS_MQTT_HOLD_TOPIC_MAX and EBUS_MQTT_HOLD_PAYLOAD_MAX (were EBUS_POSIX_HOLD_ENTRIES and EBUS_POSIX_HOLD_PAYLOAD_MAX). It no longer logs; hold() returns EVICTED_OLDEST or DROPPED_TOO_LARGE and the port logs. Its header is <ebus/mqtt/publish_hold.h>.
• The POSIX port's PahoTransport overrides the generic queue_publish() and runs its connect through mqtt_after_connect().

• The portable core, split out of esp32-sdk's lib/ebus_core/ with its history: the Homie 5 Device, Node and Property model, /set dispatch and the settable table, the controller, id and payload validation, broker-discovery parsing, and the HomieTransport, log and clock interfaces a port implements.
• The POSIX port (ports/posix/): a HomieTransport over Eclipse Paho MQTT C, a demo device and controller, and end-to-end tests against mosquitto.
• The core's Unity suites, built and run with CMake and CTest.
• library.json, so a PlatformIO project can add the core with a lib_deps git URL.