• Dependency prune: dropped tuple (the Tuple2<NodeId, AttributeId> keys in the client's monitored-items bookkeeping are now Dart 3 records, same structural equality) and the unused collection dependency.
• Data-source reads carry a status code + source timestamp. Server.addDataSourceVariableNode gained onReadValue, a richer alternative to onRead (provide exactly one): it returns a DataSourceValue (value + statusCode + optional sourceTimestamp), letting a proxy serve e.g. its last-known value with Bad_NoCommunication while the backing device is down instead of silently reporting stale data as Good (a Bad status still carries the value, as OPC UA allows). On the client, Client.readValue(nodeId) (also on ClientApi/ClientIsolate) returns a DataValue — decoded value, operation statusCode (isGood/isUncertain/isBad), sourceTimestamp and serverTimestamp — and does NOT throw on a non-Good operation status; Client.read/ readAttribute keep their existing throw-on-non-Good behavior. Monitored items already surfaced a non-Good notification as a stream error event (the notification's value/timestamps are not delivered on the data stream); that behavior is unchanged and now documented — the error carries the decoded status. Also exported: statusCodeToString and the UA_STATUSCODE_BADNOCOMMUNICATION / BADNOTWRITABLE / BADUSERACCESSDENIED / BADINTERNALERROR constants.
• Typed status-code rejection for data-source writes. New UaStatusException(statusCode) (exported): a data-source onWrite that throws it answers the client with exactly that status code — e.g. Bad_NotWritable (0x803B0000) for a gate-denied write or Bad_UserAccessDenied (0x801F0000) — instead of the generic Bad_InternalError that any other throw still maps to. The read dispatcher honors it symmetrically (onRead/onReadValue throwing one fails the read with that code and no value). Client side, the code is now extractable: Client.write fails with a UaStatusException carrying the operation (or service) status instead of a formatted string, and a monitored-item stream's error event for a non-Good notification is a UaStatusException too (was a string; ClientIsolate still marshals stream/request errors as strings across the isolate boundary, so there the code survives only inside the message text).
• Server session/subscription statistics. New Server.statistics returns a ServerStatistics snapshot: the secure-channel counters (currentChannelCount, cumulatedChannelCount, rejected/timeout/abort/ purge) and session counters (currentSessionCount, cumulatedSessionCount, securityRejected/rejected/timeout/abort) from UA_Server_getStatistics(), plus currentSubscriptionCount, cumulatedSubscriptionCount and currentMonitoredItemCount (the sum of the per-subscription monitoredItemCounts) read from the NS0 server-diagnostics nodes. No native/CMake change was needed: UA_ENABLE_DIAGNOSTICS is ON by default in open62541 1.5.7 and was already part of this package's build — the subscription-side fields are typed nullable and come back null only on a build without those NS0 nodes. Regenerated the FFI bindings (additive) with UA_Server_getStatistics and the UA_ServerStatistics / UA_SecureChannelStatistics / UA_SessionStatistics / UA_ServerDiagnosticsSummaryDataType / UA_SubscriptionDiagnosticsDataType structs; test/verify_sizes_test.dart pins their layouts against the native type table.
• PubSub (OPC UA Part 14) support, UDP + UADP transport. The native build now enables UA_ENABLE_PUBSUB and UA_ENABLE_PUBSUB_INFORMATIONMODEL (bundled open62541 still v1.5.7; MQTT/SKS/raw-Ethernet transports stay off), and Server gained an idiomatic PubSub API. Publisher side: addPubSubConnection (UDP multicast/unicast URL + PubSubPublisherId), addPublishedDataSet, addDataSetField (publishes an existing variable node), addWriterGroup (publishing interval; UADP message settings default to sending PublisherId/GroupHeader/WriterGroupId/PayloadHeader so readers can match) and addDataSetWriter. Subscriber side (which in OPC UA also hangs off the server): addReaderGroup, addDataSetReader (matches publisherId/writerGroupId/dataSetWriterId and carries the DataSetMetaData built from DataSetFieldMeta entries) and setDataSetReaderTargetVariables (maps received fields positionally into local variable nodes). Components are created disabled; enableAllPubSubComponents / disableAllPubSubComponents drive the Part 14 state machine and the per-component states are readable via writerGroupState / dataSetWriterState / readerGroupState / dataSetReaderState (PubSubState). triggerWriterGroupPublish publishes on demand.
• Server.onValueChanged(nodeId): a broadcast stream of every value written to a variable node (client writes, Server.write, and PubSub DataSetReader deliveries into target variables), backed by open62541's after-write value notification — the idiomatic way to consume received PubSub values.
• NodeId now supports GUID identifiers (NodeId.fromGuid, isGuid(), guid, ns=X;g=... formatting). Needed because open62541 identifies DataSetFields by GUID NodeIds; previously NodeId.fromRaw threw on any GUID-typed id.
• Regenerated the FFI bindings with the PubSub API surface (UA_Server_addPubSubConnection, UA_Server_addPublishedDataSet, UA_Server_addDataSetField, UA_Server_addWriterGroup, UA_Server_addDataSetWriter, UA_Server_addReaderGroup, UA_Server_addDataSetReader, UA_Server_setDataSetReaderTargetVariables, enable/disable/state functions, and the PubSub config structs). test/verify_sizes_test.dart pins the grown UA_ServerConfig (now embeds UA_PubSubConfiguration) and the PubSub config struct layouts; UA_ClientConfig is unchanged.
• Not yet exposed: delta frames (keyFrameCount is plumbed but open62541's enableDeltaFrames server option is left off), metadata ConfigurationVersion handling, PubSub message security (SKS/security policies), MQTT/Ethernet transports, and standalone SubscribedDataSets.

• Bounded-send fix (native build hook): patch open62541's TCP send path so a dead/half-open connection can no longer wedge the client forever. In TCP_sendWithConnection (arch/posix/eventloop_posix_tcp.c), when the OS send buffer fills against a peer that keeps the socket open but stops draining, UA_send returns EWOULDBLOCK and open62541 spins a poll(POLLOUT, 100ms) retry loop with no overall deadline; POLLOUT never arrives (and on Windows WSAPoll never reports POLLHUP/POLLERR for a peer gone without RST), so the call — made synchronously from UA_Client_run_iterate on the client isolate's single event-loop thread — never returns and freezes the whole isolate. The fix adds a monotonic wall-clock deadline (compile-time constant UA62541_DART_SEND_DEADLINE_MS, default 5000 ms): on timeout the send is treated as a dead connection and shuts down exactly like any other send error, so run_iterate returns, connectStatus goes bad, and the existing keepConnected supervisor reconnects — no isolate killed, no UA_Client leaked. The deadline is wall-clock and independent of what poll reports, so it fixes every platform including the Windows WSAPoll case. The change ships as a unified-diff patch file (hook/bounded_send_deadline.patch) that the build hook applies to the extracted open62541 source with a standard patch tool (git apply -p1, falling back to patch -p1); a missing patch file, a missing target file, or a non-zero exit from the patch tool fails the build loudly. Bundled open62541 is unchanged (still v1.5.7); this is a binding-only build change.

• ClientIsolate.keepConnected / stopKeepConnected / reconnectStream: the auto-reconnect supervisor introduced for Client in 1.5.7 is now available on the isolate client too, by delegating to the native client's supervisor inside the isolate. This matters because the isolate client is where a dead session is the most invisible: the caller-side runIterate() future only completes when native run_iterate returns non-GOOD, so a session that dies while iterate keeps reporting GOOD (seen in production: channel expiring mid-session-create, server FIN never surfacing) parks the caller forever with no error. With keepConnected the supervisor and its pump live inside the isolate, so recovery does not depend on any error ever reaching the caller. Starting it stops any caller-driven runIterate() loop — the supervisor owns the pump, same contract as Client.keepConnected.

• Bump bundled open62541 from v1.5.6 to v1.5.7.
  • Upstream v1.5.7 is a maintenance release focused on security hardening and stability: rejects custom DataType definitions that overflow memSize/membersSize, fixes a PubSub off-by-one heap-OOB read in getFieldMetaData, guards several server-side use-after-free / NULL-deref / recursion-depth issues, and tightens URI and certificate-subject handling in plugins. See https://github.com/open62541/open62541/releases/tag/v1.5.7.
  • Regenerated the amalgamated header (third_party/open62541/open62541_modified.h), the remove_bitfields.patch line offsets, and the ffigen bindings (lib/src/third_party/open62541.g.dart) against v1.5.7. Struct layouts are unchanged: UA_ClientConfig (888 bytes) and UA_DataType (96 bytes) match the previous release, so verify_sizes_test still passes.
• Hardened the native build hook (hook/build.dart): every third-party source archive is now fetched over HTTPS (scheme enforced in code) and verified against a pinned SHA-256 before use, failing the build loudly on mismatch.
• Prepared the package for pub.flutter-io.cn publishing: expanded the description, added homepage/issue_tracker metadata, raised the SDK floor to ^3.10.0 (native build hooks are stable from Dart 3.10), and added an example/.

Native-build feature set (built from source at install time via Dart native build hooks, downloading open62541 and mbedTLS 3.6.5 and building them with CMake):

• Enable OPC UA encryption through mbedTLS (SignAndEncrypt).
• Force little-endian IEEE 754 float encoding so subnormal Float/Double values round-trip correctly on all supported targets.
• Patch the client subscription handler so deleteCallback fires for every client-side subscription when the server reports BadNoSubscription (OPC UA Part 4, 5.13.5).
• Client APIs: connect/reconnect, browse and recursive tree browse, subscriptions and monitored items, secure connections with certificates.
• Server APIs: variable nodes, array and structure (custom type) nodes, data-type nodes, and variable monitoring streams.
• Supports Linux, macOS, Windows, Android and iOS.