# Changelog
All notable changes to this project will be documented in this file.
## [0.10.0] - 2026-05-07
Spec-compliance and correctness sweep against MQTT 5.0 (OASIS), plus server/
client robustness fixes. EMQX interop suite (49 tests against a live broker)
remains 100% green; no public API changes.
### Changed (potentially breaking at the wire level — stricter spec compliance)
- **Default `protocol_version` is now `5`** (was `4`). Library is
marketed "MQTT 5.0" and v5 features (topic aliases, AUTH, properties,
reason codes) were silently dropped under the v3.1.1 default.
`MqttX.Client.connect(protocol_version: 4)` to opt in to v3.1.1.
- **Server now rejects unsupported protocol versions** with CONNACK
`0x84` (v5) / `0x01` (v3.x). Default allowlist `[3, 4, 5]` configurable
via `:supported_versions` in `transport_opts`.
### Fixed (codec — `MqttX.Packet.Codec` / `MqttX.Packet.Properties`)
- PUBLISH with QoS=3 rejected as Malformed Packet (§3.3.1.2)
- PUBLISH with DUP=1 + QoS=0 rejected (§3.3.1.1)
- CONNECT reserved bit must be 0 (§3.1.2.3); non-zero fixed-header flags rejected (§3.1.1)
- Will Flag=0 with non-zero Will QoS or Will Retain rejected (§3.1.2.6/7)
- Will QoS=3 rejected (§3.1.2.6)
- v3.x username flag=0 with password flag=1 rejected (§3.1.2.9)
- Empty SUBSCRIBE / UNSUBSCRIBE payload rejected as Protocol Error (§3.8.3 / §3.10.3)
- Subscription Options reserved bits non-zero, QoS=3, RH=3 rejected (§3.8.3.1)
- DISCONNECT and AUTH 1-byte forms (reason code only, no property length) accepted per §3.14.2.2.1 / §3.15.2.2.1
- UTF-8 strings now reject U+0000 (null) and U+D800–U+DFFF (surrogates) per §1.5.4
- Malformed CONNECT no longer crashes the codec with `MatchError`; surfaces `:malformed_packet`
- Invalid SUBACK/UNSUBACK reason bytes return `:malformed_packet` instead of crashing
- **Properties** — duplicate non-User-Property properties rejected as Protocol Error (§2.2.2.2)
- Property value-0 rejection: Subscription Identifier (§3.8.2.1.2), Receive Maximum (§3.1.2.11.3), Maximum Packet Size (§3.1.2.11.4)
- Boolean properties (Payload Format Indicator, Request Problem Information, Retain Available, etc.) reject non-0/1 byte values
- Maximum QoS rejects values > 2
- User-Property accumulation switched from O(n²) `++ [val]` to prepend + reverse-once
- Subscription-Identifier list switched from O(n²) `++ [val]` to prepend + reverse-once
### Fixed (topic — `MqttX.Topic`)
- `+`/`#` filters at the first level no longer match `$SYS/...`-style topics (§4.7.2)
- Topic length capped at 65535 bytes (§1.5.4)
- Shared subscription `$share/<group>/...` rejects `+` or `#` in ShareName (§4.8.2)
- `flatten/1` switched from O(n²) binary concat to iolist + `Enum.intersperse`
### Fixed (server — `MqttX.Transport.Handler` / `MqttX.Server.Router` / `MqttX.Server.RateLimiter`)
- **Outgoing QoS 1 retransmission on the server** (§4.4). Outbound QoS 1
PUBLISHes are now tracked in `pending_qos1_tx`; the existing periodic retry
timer re-sends with `DUP=true` after `qos2_retry_interval` ms, dropping
after `qos2_max_retries` attempts. PUBACK arrival clears the entry.
Previously QoS 1 outbound was fire-and-forget — a lost PUBACK silently
dropped the message.
- **Receive Maximum applies to QoS 1 inbound** as well as QoS 2 (§3.1.2.11.3).
Previously the limit was only checked for QoS 2; a client could fill the
flow-control window with un-PUBCOMP'd QoS 2 messages and then push QoS 1
publishes through unbounded. The handler now responds to a QoS 1 PUBLISH
exceeding the limit with `PUBACK` reason `0x93` (Receive Maximum exceeded).
QoS 2 excess continues to receive `PUBREC 0x93` (spec permits either
per-message ack or DISCONNECT).
- **Critical:** retained-publish packet IDs now come from `next_packet_id` instead of `:rand.uniform/1` — was colliding with the QoS sequence allocator and breaking ack matching
- Will message published exactly once on keepalive timeout / `handle_close` / `handle_error` (was double-publishing through two paths)
- DISCONNECT reason code 0x04 publishes the Will; other reason codes suppress it (§3.14.4) — previously the reason code was ignored
- Empty topic with un-mapped Topic Alias triggers DISCONNECT 0x94 (§3.3.4) — previously dispatched an empty-topic PUBLISH to the user handler
- Outbound oversize-drop rolls back the packet_id allocation (was leaking)
- Duplicate PUBREC after PUBREL no longer re-sends PUBREL (§4.3.3 fig 4.4)
- AUTH-before-CONNECT now sends DISCONNECT 0x82 instead of leaving the handler in a broken state (CONNACK with `protocol_version: nil`)
- Will Delay Interval timers (§3.1.3.2.2) now owned by a supervised `MqttX.Server.WillDelay` GenServer under the application supervisor; cancelled on same-`client_id` reconnect
- Rate-limiter ETS table now created with `read_concurrency: true`
### Fixed (client — `MqttX.Client.Connection`)
- **Critical:** retry-loop reducer arity bug fixed — was crashing with
`MatchError` once both `{:rx, _}` and `{:tx, _}` `pending_acks` entries
coexisted on the same connection
- `keepalive == 0` correctly disables the keepalive timer (was scheduling a
zero-millisecond tight loop)
- **PINGRESP timeout**: client now arms a deadline at `keepalive*1500ms` on
every PINGREQ; if PINGRESP doesn't arrive, the socket is torn down and
reconnect is scheduled. Half-dead brokers no longer require TCP teardown to
detect.
- `session_present` from CONNACK now surfaced to the handler in the
`:connected` event; warns on MQTT-3.2.2-2 violation (`clean_session=true`
but `session_present=true`)
- Server-initiated DISCONNECT now closes the socket immediately and schedules
reconnect (was waiting for `:tcp_closed` to land separately)
- AUTH continuation in `wait_for_connack` re-arms `set_socket_active/1` so
multi-step AUTH doesn't hang after the first packet
- AUTH packet property names corrected: `:auth_method` / `:auth_data` →
`:authentication_method` / `:authentication_data`
- `next_packet_id` skips IDs currently in `pending_acks` (§2.2.1)
- `schedule_reconnect` cancels any existing reconnect timer (no more stacked
timers when several disconnect events fire)
- `set_socket_active` guards against `nil` socket (server-disconnect race)
- Pending SUBACK/UNSUBACK callers monitored via `Process.monitor`; entry
dropped on `:DOWN` (was leaking after `GenServer.call` timeouts)
### Fixed (WebSocket client — `MqttX.Client.WebSocket`)
- `Sec-WebSocket-Accept` now validated as `Base64(SHA1(client_key + magic GUID))`
per RFC 6455 §4.1; status line strictly matched as `HTTP/1.x 101 …`
- `Sec-WebSocket-Protocol` echo checked (warn-only on missing — common with
MQTT brokers that nonetheless speak it correctly)
- FIN-bit fragmentation: opaque `frag_state` threaded across `decode_frames/2`
calls so multi-frame messages split across TCP reads reassemble correctly
- Frame masking switched from byte-by-byte recursion to `:crypto.exor/2`
against a pre-padded mask buffer (orders-of-magnitude faster on large
payloads)
### Added
- `MqttX.Session.ETSOwner` — a long-lived owner of the default
`:mqttx_sessions` ETS table under the application supervisor. Previously
the table was owned by whichever client first called
`MqttX.Session.ETSStore.init/1`, so all sessions were lost when that
process exited. The table is now created with `read_concurrency: true,
write_concurrency: true`.
- `MqttX.Server.WillDelay` — supervised GenServer that owns Will Delay
Interval timers across connection lifecycles, with per-`client_id`
cancellation.
- `:supported_versions` server transport option (default `[3, 4, 5]`).
### Documentation
- `AGENTS.md` — usage guide for AI coding assistants integrating MqttX into
projects: mental model (client vs broker), transport selection, idiomatic
patterns (receive-on-client, broker↔PubSub bridge, persistent sessions,
custom auth), and a curated list of mistakes commonly made (publishing
wildcards, confusing `handle_publish` with `handle_mqtt_event`, random
`client_id` per connect, default-to-QoS-2, `$SYS` exclusion). Shipped in
the hex package and rendered on hexdocs.
- `CONTRIBUTING.md` — repo orientation for contributors: layout, test
commands, known test-environment couplings, and the deferred TODO carried
over from the v0.9.0 spec sweep. `CLAUDE.md` is now a symlink to
`AGENTS.md` for tool compatibility.
- README "Common Patterns" section with worked examples for receiving
messages on the client (`handle_mqtt_event/3`), broadcasting from the
server via `handle_info/2`, and resuming MQTT 5.0 sessions with
`session_expiry_interval`.
- README "Common Pitfalls" section covering session-store / `clean_session`
interaction, server keepalive override, max-packet-size enforcement,
publish-vs-subscribe wildcard rules, and `$SYS` topic exclusion.
## [0.9.0] - 2026-03-30
### Added
- **Server keepalive override** (MQTT 5.0): Configurable `server_keep_alive` in `transport_opts` — server sends keepalive override in CONNACK and uses it for the keepalive timer when protocol version >= 5
- **`handle_connect/4` callback** (optional): New `handle_connect(client_id, credentials, connect_info, state)` callback that receives connection metadata (`protocol_version`, `keep_alive`) separately from credentials. Existing `handle_connect/3` continues to work unchanged — `handle_connect/4` takes precedence when defined
## [0.8.0] - 2026-03-11
### Added
- **Complete MQTT 5.0 Client Compliance**: Closed all remaining client-side spec gaps
- **server_keep_alive**: Client applies server's keepalive override from CONNACK (§3.2.2.3.14)
- **assigned_client_identifier**: Client adopts server-assigned client ID from CONNACK (§3.2.2.3.7)
- **maximum_packet_size**: Client enforces server's maximum packet size from CONNACK; oversized outgoing packets return `{:error, :packet_too_large}` (§3.2.2.3.6)
- **server_reference**: Client parses and logs server redirect on CONNACK rejection and server DISCONNECT (§3.2.2.3.18)
- **Enhanced AUTH**: Client handles multi-step AUTH exchange during and after CONNECT via `handle_auth/3` callback (§4.12)
- **EMQX Cloud Interop**: 49 automated interop tests against EMQX Cloud broker
- **SUBACK Reason Code Checking**: `subscribe/3` now returns `{:ok, [granted_qos]}` or `{:error, {:subscription_refused, acks}}` based on actual SUBACK response
- **Outgoing Topic Aliases** (MQTT 5.0): Client automatically assigns and reuses topic aliases for repeated publish topics, reducing bandwidth
- **DISCONNECT with Reason Code**: `disconnect/2` accepts `:reason_code` and `:properties` options for MQTT 5.0 graceful disconnect
- **WebSocket Client Transport**: Connect to brokers over WebSocket with `transport: :ws` or `transport: :wss` (RFC 6455 binary framing)
- **Reason String Surfacing**: Server reason strings from SUBACK, UNSUBACK, PUBACK, DISCONNECT are logged automatically
### Fixed
- Formatting issues across multiple files (CI compliance)
- Dialyzer `callback_type_mismatch` in WebSocket transport `close/1` (now returns `:ok` per behaviour spec)
- WebSocket frame decoder byte-alignment bug in `decode_one_frame` (mask_bit extraction)
## [0.7.0] - 2026-03-05
### Added
- **Full MQTT 3.1/3.1.1/5.0 Compliance**: Closed all remaining spec compliance gaps
- **Pre-CONNECT packet rejection**: Non-CONNECT/AUTH packets before CONNECT now trigger DISCONNECT 0x82 (Protocol Error) per spec
- **Topic alias validation**: Incoming topic aliases are validated against `topic_alias_maximum`; out-of-range aliases trigger DISCONNECT 0x94
- **MQTT 5.0 property forwarding**: Outgoing PUBLISH packets now forward properties (user_properties, content_type, correlation_data, etc.) from handler callbacks
- **CONNACK capability properties**: Server advertises `retain_available`, `wildcard_subscription_available`, and `subscription_identifier_available` in CONNACK for MQTT 5.0 connections
- **retain_handling support**: Subscription option `retain_handling: 2` suppresses retained message delivery on subscribe
- **no_local support**: `Router.match/3` and `Router.match_and_advance/3` accept optional `publisher` parameter to filter out subscriptions with `no_local: true`
- **Client server DISCONNECT handling**: Client now handles server-initiated DISCONNECT packets, notifying the handler with `{:server_disconnect, reason_code}`
- **QoS 2 Retransmission & DUP Handling** (Server): Periodic retry timer re-sends PUBREC/PUBLISH(dup)/PUBREL for stale in-flight QoS 2 messages; drops after configurable max retries. DUP incoming PUBLISH re-sends PUBREC without re-delivering.
- **Topic Aliases** (MQTT 5.0 Server): Incoming PUBLISH with `topic_alias` property resolved automatically. Server advertises `topic_alias_maximum` in CONNACK. Alias-only publishes (empty topic) look up stored mapping.
- **Flow Control / Receive Maximum** (MQTT 5.0 Server): Server enforces `receive_maximum` for incoming QoS 2 messages. Excess publishes receive PUBREC with reason code `0x93` (Receive Maximum exceeded). Server advertises `receive_maximum` in CONNACK.
- **Maximum Packet Size** (MQTT 5.0 Server): Configurable `max_packet_size` option. Oversized incoming packets trigger DISCONNECT with reason code `0x95` (Packet too large). Outgoing publishes exceeding client's `maximum_packet_size` are silently dropped. Server advertises `maximum_packet_size` in CONNACK when configured.
- **WebSocket Transport**: MQTT over WebSocket via Bandit, supporting all MQTT protocol features over `ws://` and `wss://` connections.
- **Mosquitto Validation Suite**: 104 automated tests against Mosquitto clients across TCP and WebSocket transports, covering all protocol versions and MQTT 5.0 features.
- **Handler tests**: 30+ new tests covering compliance features, QoS 2 full flow, DUP handling, retry timer, CONNACK properties, topic aliases, flow control, max packet size, and server-initiated DISCONNECT.
### Changed
- **Codec**: MQTT 5.0 PUBLISH with empty topic is now valid when `topic_alias` property is present (per MQTT 5.0 spec section 3.3.2.1)
- **QoS 2 pending entries**: `pending_qos2_rx` entries now include timestamps and retry counts; `pending_qos2_tx` entries are enriched maps with phase, packet, timestamp, and retry info
- **Router API**: `match/2` → `match/3` and `match_and_advance/2` → `match_and_advance/3` with optional `publisher` parameter (backward compatible, defaults to `nil`)
### Fixed
- Server PUBREL handler now correctly extracts packet/opts from both legacy 2-tuple and new 4-tuple `pending_qos2_rx` entries
## [0.6.1] - 2026-03-02
### Fixed
- Logo rendering on hexdocs.pm (use absolute URL for README image)
- CI: increased GenServer.stop timeout in client tests for slower runners
- CI: skip JSON payload tests on OTP < 27
- Removed accidentally committed mqttx-0.1.0 directory
## [0.6.0] - 2026-03-02
### Added
- **Connection Supervision**: `MqttX.Client.Supervisor` DynamicSupervisor for managed client connections
- `MqttX.Client.connect_supervised/1` starts connections under the supervisor with automatic crash recovery
- `MqttX.Client.list/0` lists all registered connections via `MqttX.ClientRegistry`
- `MqttX.Client.whereis/1` looks up connections by client_id
- Connections auto-register in `MqttX.ClientRegistry` on init
- **Rate Limiting**: Per-client connection and message rate limiting for MQTT servers
- `MqttX.Server.RateLimiter` module with ETS-based atomic counters
- Connection rate limiting (configurable max connections per interval)
- Per-client message rate limiting (configurable max messages per client per interval)
- MQTT 5.0 reason code `0x96` (message_rate_too_high) sent for rate-limited QoS 1+ publishes
- Integrated into both ThousandIsland and Ranch transport adapters
- Configured via `:rate_limit` option in `MqttX.Server.start_link/3`
- **Capacity Planning guide**: Device-per-vCPU sizing tables for IoT workloads (sleepy sensors through real-time streaming), instance sizing recommendations
- **Performance & Scaling guide**: Architecture decisions, trie router internals, VM/OS tuning, and deployment guidelines
- **Project Branding**: MqttX logo in README and hexdocs
- **EMQX interop test suite**: 49 tests against live EMQX broker covering MQTT 5.0 features
- **Server Keepalive Timeout**: Disconnects clients that stop sending packets within 1.5x `keep_alive` seconds (MQTT spec compliance)
- Automatic timer start after CONNACK, reset on every received packet
- Will message published on keepalive timeout (ungraceful disconnect)
- **Will Delay Interval** (MQTT 5.0): Delays will message publication by `will_delay_interval` seconds after ungraceful disconnect
- `will_delay_interval: 0` (or MQTT 3.1.1) publishes immediately (backward compatible)
- Will properties forwarded to handler
- **Session Expiry Timer** (MQTT 5.0): Fires `handle_session_expired/2` callback after `session_expiry_interval` seconds post-disconnect
- `0` = expire immediately, `0xFFFFFFFF` = never expire
- New optional `handle_session_expired/2` callback in `MqttX.Server` behaviour
- **Server-Initiated Disconnect**: Kick clients with MQTT 5.0 reason codes
- `MqttX.Server.disconnect/3` sends DISCONNECT and closes connection
- `{:disconnect, reason_code, state}` return type from `handle_publish`, `handle_subscribe`, `handle_unsubscribe`, `handle_info`
- Ranch transport now properly forwards `handle_info` messages to handler (was silently dropping them)
### Changed
- **Trie-based Topic Router**: Replaced O(N) linear scan with a trie data structure for O(L+K) topic matching — independent of total subscription count. Same public API.
- **iodata Encoding**: Socket sends use `Codec.encode_iodata/2` in all transports, avoiding binary copies on every packet
- **Empty-buffer fast path**: Skips binary concatenation when the TCP buffer is empty (common case)
- **Cached callback dispatch**: `function_exported?` computed once at connection init, not per message
- **Direct inflight counter**: O(1) flow control check instead of scanning pending_acks
- **Retained message delivery**: Exact topic subscriptions use O(1) ETS lookup instead of full table scan
### Fixed
- **Handler state lost on callbacks**: `notify_handler` now correctly returns updated handler state (was silently discarding it)
- **Missing retries field in pending_acks**: QoS 1/2 pending_acks entries now include `retries: 0` (prevented retry tracking)
- **Session not saved on socket close**: Session data now persists on unexpected TCP close/error, not just clean disconnect
- **Queued messages not delivered on reconnect**: Buffer is now processed after CONNACK for persistent sessions
- **Protobuf codec crash on non-protobuf structs**: Now returns `{:error, {:protobuf_encode_error, _}}` instead of raising
- **Protobuf codec crash on unknown module**: Now returns `{:error, {:unknown_message_module, module}}` instead of raising
- Removed dead outgoing topic alias code (`topic_to_alias`, `next_alias`) that was never functional
- `MqttX.version/0` now returns correct version string
- Guides now included in hex.pm docs
## [0.5.0] - 2026-01-15
### Added
- **Telemetry Integration**: Comprehensive `:telemetry` events for observability
- Client events: connect, disconnect, publish, subscribe, message
- Server events: client_connect, client_disconnect, publish, subscribe
- New `MqttX.Telemetry` module with helper functions
- **Shared Subscriptions** (MQTT 5.0): `$share/group/topic` pattern for load balancing
- Round-robin distribution across group members
- `Router.match_and_advance/2` for stateful distribution
- Automatic group cleanup when last member leaves
- **Topic Alias** (MQTT 5.0): Bandwidth reduction for repeated topics
- Client stores `topic_alias_maximum` from CONNACK
- Resolves incoming topic aliases automatically
- `alias_to_topic` map in connection state
- **Message Expiry** (MQTT 5.0): Respects `message_expiry_interval` property
- Retained messages stored with timestamp
- Expired messages skipped on delivery
- Remaining expiry sent in delivered messages
- **Flow Control** (MQTT 5.0): Enforces `receive_maximum` for backpressure
- Client tracks inflight QoS 1/2 message count
- Returns `{:error, :flow_control}` when limit reached
- Stores `receive_maximum` from CONNACK
- **Enhanced Auth** (MQTT 5.0): SASL-style authentication callback
- New `handle_auth/3` callback in `MqttX.Server` behaviour
- Default implementation returns error (not supported)
- **Request/Response** (MQTT 5.0): Helper for request/response pattern
- `MqttX.Client.request/4` function
- Passes `response_topic` and `correlation_data` properties
- `:properties` option in `publish/4`
### Changed
- Transport adapters store retained messages with expiry metadata (5-tuple ETS format)
- Client connection state includes topic alias and receive_maximum fields
## [0.4.0] - 2026-01-15
### Added
- **TLS/SSL Client Support**: Optional TLS via `:transport` option (`:tcp` or `:ssl`)
- `:ssl_opts` for SSL configuration (verify, cacerts, etc.)
- Default port 8883 for SSL connections
- **QoS 2 Complete Flow**: Full PUBREC/PUBREL/PUBCOMP handshake implementation
- Client tracks outgoing QoS 2 messages through all phases
- Client handles incoming QoS 2 messages correctly
- **Message Inflight Tracking**: Timer-based retry for unacknowledged QoS 1/2 messages
- Configurable `:retry_interval` option (default: 5000ms)
- Automatic retry with `dup: true` flag
- Max 3 retries before dropping message
- **Retained Messages**: Server stores and delivers retained messages
- ETS-based storage per server instance
- Delivered to new subscribers on SUBSCRIBE
- Empty payload clears retained message
- **Will Message Delivery**: Server publishes will message on ungraceful disconnect
- Stored from CONNECT packet
- Published when connection closes without DISCONNECT
- Supports retained will messages
- **Session Persistence**: Configurable session storage for `clean_session: false`
- `MqttX.Session.Store` behaviour for custom implementations
- `MqttX.Session.ETSStore` built-in in-memory store
- Saves/restores subscriptions, pending messages, packet IDs
### Changed
- Client connection state now tracks subscriptions for session persistence
- Transport adapters create ETS tables for retained messages
## [0.3.0] - 2026-01-15
### Added
- MQTT vs WebSocket JSON performance comparison in README
- Comprehensive API reference documentation in README
- New test files for improved coverage:
- `backoff_test.exs` - exponential backoff logic tests
- `properties_test.exs` - MQTT 5.0 properties encode/decode tests
- `client_test.exs` - client API tests
- `server_test.exs` - server behaviour and callback tests
- MQTT 5.0 packet tests (AUTH, DISCONNECT with reason codes, properties)
- MQTT 3.1 packet tests
- Edge case tests (empty payload, large payload, max packet ID, unicode topics)
### Changed
- Updated ThousandIsland dependency to `~> 1.4` (was `~> 1.0`)
- Updated Ranch dependency to `~> 2.2` (was `~> 2.1`)
- Updated Protox dependency to `~> 2.0` (was `>= 1.7.0`)
### Fixed
- Formatting issues in `thousand_island.ex`
- Protobuf payload codec updated for Protox 2.0 API changes (encode returns 3-tuple)
## [0.2.0] - 2026-01-15
### Added
- `handle_info/2` callback for MqttX.Server to handle custom messages (e.g., PubSub)
- Support for outgoing PUBLISH via `{:publish, topic, payload, state}` return value
- Enables bidirectional communication (server can push messages to connected clients)
## [0.1.6] - 2026-01-15
### Changed
- Broadened protox dependency to support both 1.x and 2.x (`>= 1.7.0`)
## [0.1.5] - 2026-01-15
### Added
- GitHub Actions CI workflow (tests on Elixir 1.17-1.19, OTP 27-28, dialyzer)
- Roadmap section in README
- Username/password example in client documentation
- Changelog link on hex.pm package page
- Hex.pm, Docs, and CI badges to README
### Changed
- Documentation landing page now shows README instead of module docs
### Fixed
- JSON payload codec now conditionally compiles only on OTP 27+
- Code formatting issues
- Version test no longer hardcodes version string
- Dialyzer false positives for defensive pattern matching
## [0.1.1] - 2026-01-15
### Added
- GitHub Actions CI workflow (tests, formatting, dialyzer)
- Roadmap section in README
- Username/password example in client documentation
- Changelog link on hex.pm package page
### Fixed
- JSON codec description now correctly references built-in Erlang/OTP 27+ module
## [0.1.0] - 2026-01-14
### Added
- Initial release
- MQTT packet codec supporting MQTT 3.1, 3.1.1, and 5.0
- All 15 MQTT packet types
- MQTT 5.0 properties support
- ThousandIsland transport adapter
- Ranch transport adapter
- MQTT Server behaviour with handler callbacks
- Topic router with wildcard support (+, #)
- MQTT Client with automatic reconnection
- JSON payload codec (via built-in Erlang/OTP 27+ JSON module)
- Protobuf payload codec (via Protox)
- Raw binary payload codec
- Comprehensive test suite
