Files
Joseph Doherty
ecc2389ca8
AclsTab Probe-this-permission — first of three #196 slices. New /clusters/{ClusterId}/draft/{GenerationId} ACLs-tab gains a probe card above the grant table so operators can ask the trie "if cn=X asks for permission Y on node Z, would it be granted, and which rows contributed?" without shell-ing into the DB. Service thinly wraps the same PermissionTrieBuilder + PermissionTrie.CollectMatches call path the Server's dispatch layer uses at request time, so a probe answer is by construction identical to what the live server would decide. New PermissionProbeService.ProbeAsync(generationId, ldapGroup, NodeScope, requiredFlags) — loads the target generation's NodeAcl rows filtered to the cluster (critical: without the cluster filter, cross-cluster grants leak into the probe which tested false-positive in the unit suite), builds a trie, CollectMatches against the supplied scope + [ldapGroup], ORs the matched-grant flags into Effective, compares to Required. Returns PermissionProbeResult(Granted, Required, Effective, Matches) — Matches carries LdapGroup + Scope + PermissionFlags per matched row so the UI can render the contribution chain. Zero side effects + no audit rows — a failing probe is a question, not a denial. AclsTab.razor gains the probe card at the top (before the New-grant form + grant table): six inputs for ldap group + every NodeScope level (NamespaceId → UnsAreaId → UnsLineId → EquipmentId → TagId — blank fields become null so the trie walks only as deep as the operator specified), a NodePermissions dropdown filtered to skip None, Probe button, green Granted / red Denied badge + Required/Effective bitmask display, and (when matches exist) a small table showing which LdapGroup matched at which level with which flags. Admin csproj adds ProjectReference to Core — the trie + NodeScope live there + were previously Server-only. Five new PermissionProbeServiceTests covering: cluster-level row grants a namespace-level read; no-group-match denies with empty Effective; matching group but insufficient flags (Browse+Read vs WriteOperate required) denies with correct Effective bitmask; cross-cluster grants stay isolated (c2's WriteOperate does NOT leak into c1's probe); generation isolation (gen1's Read-only does NOT let gen2's WriteOperate-requiring probe pass). Admin.Tests 92/92 passing (was 87, +5). Admin builds 0 errors. Remaining #196 slices — SignalR invalidation + draft-diff ACL section — ship in follow-up PRs so the review surface per PR stays tight.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
AclsTab Probe-this-permission — first of three #196 slices. New /clusters/{ClusterId}/draft/{GenerationId} ACLs-tab gains a probe card above the grant table so operators can ask the trie "if cn=X asks for permission Y on node Z, would it be granted, and which rows contributed?" without shell-ing into the DB. Service thinly wraps the same PermissionTrieBuilder + PermissionTrie.CollectMatches call path the Server's dispatch layer uses at request time, so a probe answer is by construction identical to what the live server would decide. New PermissionProbeService.ProbeAsync(generationId, ldapGroup, NodeScope, requiredFlags) — loads the target generation's NodeAcl rows filtered to the cluster (critical: without the cluster filter, cross-cluster grants leak into the probe which tested false-positive in the unit suite), builds a trie, CollectMatches against the supplied scope + [ldapGroup], ORs the matched-grant flags into Effective, compares to Required. Returns PermissionProbeResult(Granted, Required, Effective, Matches) — Matches carries LdapGroup + Scope + PermissionFlags per matched row so the UI can render the contribution chain. Zero side effects + no audit rows — a failing probe is a question, not a denial. AclsTab.razor gains the probe card at the top (before the New-grant form + grant table): six inputs for ldap group + every NodeScope level (NamespaceId → UnsAreaId → UnsLineId → EquipmentId → TagId — blank fields become null so the trie walks only as deep as the operator specified), a NodePermissions dropdown filtered to skip None, Probe button, green Granted / red Denied badge + Required/Effective bitmask display, and (when matches exist) a small table showing which LdapGroup matched at which level with which flags. Admin csproj adds ProjectReference to Core — the trie + NodeScope live there + were previously Server-only. Five new PermissionProbeServiceTests covering: cluster-level row grants a namespace-level read; no-group-match denies with empty Effective; matching group but insufficient flags (Browse+Read vs WriteOperate required) denies with correct Effective bitmask; cross-cluster grants stay isolated (c2's WriteOperate does NOT leak into c1's probe); generation isolation (gen1's Read-only does NOT let gen2's WriteOperate-requiring probe pass). Admin.Tests 92/92 passing (was 87, +5). Admin builds 0 errors. Remaining #196 slices — SignalR invalidation + draft-diff ACL section — ship in follow-up PRs so the review surface per PR stays tight.
AlarmSurfaceInvoker — wraps IAlarmSource.Subscribe/Unsubscribe/Acknowledge through CapabilityInvoker with multi-host fan-out. Closes alarm-surface slice of task #161 (Phase 6.1 Stream A); the Roslyn invoker-coverage analyzer is split into new task #200 because a DiagnosticAnalyzer project is genuinely its own scaffolding PR (Microsoft.CodeAnalysis.CSharp.Workspaces dep, netstandard2.0 target, Microsoft.CodeAnalysis.Testing harness, ProjectReference OutputItemType=Analyzer wiring, and four corner-case rules I want tests for before shipping). Ship this PR as the runtime guardrail + callable API; the analyzer lands next as the compile-time guardrail. New AlarmSurfaceInvoker class in Core.Resilience. Three methods mirror IAlarmSource's three mutating surfaces: SubscribeAsync (fan-out: group sourceNodeIds by IPerCallHostResolver.ResolveHost, one CapabilityInvoker.ExecuteAsync per host with DriverCapability.AlarmSubscribe so AlarmSubscribe's retry policy kicks in + returns one IAlarmSubscriptionHandle per host); UnsubscribeAsync (single-host, defaultHost); AcknowledgeAsync (fan-out: group AlarmAcknowledgeRequests by resolver-mapped host, run each host's batch through DriverCapability.AlarmAcknowledge which does NOT retry per decision #143 — alarm-ack is a write-shaped op that's not idempotent at the plant-floor level). Drivers without IPerCallHostResolver (Galaxy single MXAccess endpoint, OpcUaClient against one remote, etc.) fall back to defaultHost = DriverInstanceId so breaker + bulkhead keying still happens; drivers with it get one-dead-PLC-doesn't-poison-siblings isolation per decision #144. Single-host single-subscribe returns [handle] with length 1; empty sourceNodeIds fast-paths to [] without a driver call. Five new AlarmSurfaceInvokerTests covering: (a) empty list short-circuits — driver method never called; (b) single-host sub routes via default host — one driver call with full id list; (c) multi-host sub fans out to 2 distinct hosts for 3 src ids mapping to 2 plcs — one driver call per host; (d) Acknowledge does not retry on failure — call count stays at 1 even with exception; (e) Subscribe retries transient failures — call count reaches 3 with a 2-failures-then-success fake. Core.Tests resilience-builder suite 19/19 passing (was 14, +5); Core.Tests whole suite still green. Core project builds 0 errors. Task #200 captures the compile-time guardrail: Roslyn DiagnosticAnalyzer at src/ZB.MOM.WW.OtOpcUa.Analyzers that flags direct invocations of the eleven capability-interface methods inside the Server namespace when the call is NOT inside a CapabilityInvoker.ExecuteAsync/ExecuteWriteAsync/AlarmSurfaceInvoker.*Async lambda. That analyzer is the reason we keep paying the wrapping-class overhead for every new capability.
ab_server integration fixture — per-family profiles + documented CI-fetch contract. Closes task #180 (AB CIP follow-up — ab_server CI fixture). Replaces the prior hardcoded single-family fixture with a parametric AbServerProfile abstraction covering ControlLogix / CompactLogix / Micro800 / GuardLogix. Prebuilt-Windows-binary fetch is documented as a CI YAML step rather than fabricated C#-side, because SHA-pinned binary distribution is a CI workflow concern (libplctag owns releases, we pin a version + verify hash) not a test-framework concern. New AbServerProfile record + KnownProfiles static class at tests/.../AbServerProfile.cs. Four profiles: ControlLogix (widest coverage — DINT/REAL/BOOL/SINT/STRING atomic + DINT[16] array so the driver's @tags Symbol-Object decoder + array-bound path both get end-to-end coverage), CompactLogix (atomic subset — driver-side ConnectionSize quirk from PR 10 still applies since ab_server doesn't enforce the narrower limit), Micro800 (ab_server has no dedicated --plc micro800 mode — falls back to controllogix while driver-side path enforces empty routing + unconnected-only per PR 11; real Micro800 coverage requires a 2080 lab rig), GuardLogix (ab_server has no safety subsystem — profile emulates the _S-suffixed naming contract the driver's safety-ViewOnly classification reads in PR 12; real safety-lock behavior requires a 1756-L8xS physical rig). Each profile composes --plc + --tag args via BuildCliArgs(port) — pure string formatter so the composition logic is unit-testable without launching the simulator. AbServerFixture gains a ctor overload taking AbServerProfile + port (defaults back to ControlLogix on parameterless ctor so existing test suites keep compiling). Fixture's InitializeAsync hands the profile's CLI args to ProcessStartInfo.Arguments. New AbServerTheoryAttribute mirrors AbServerFactAttribute but extends TheoryAttribute so a single test can MemberData over KnownProfiles.All + cover all four families. AbCipReadSmokeTests converted from single-fact to theory parametrized over KnownProfiles.All — one row per family reads TestDINT + asserts Good status + Healthy driver state. Fixture lifecycle is explicit try/finally rather than await using because IAsyncLifetime.DisposeAsync returns ValueTask + xUnit's concrete IAsyncDisposable shim depends on xunit version; explicit beats implicit here. Eight new unit tests in AbServerProfileTests.cs (runs without the simulator so CI green even when the binary is absent): BuildCliArgs composes port + plc + tag flags in the documented order; empty seed-tag list still emits port + plc; SeedTag.ToCliSpec handles both 2-segment scalar + 3-segment array; KnownProfiles.ForFamily returns expected --plc arg for every family (verifies Micro800 + GuardLogix both fall back to controllogix); KnownProfiles.All covers every AbCipPlcFamily enum value (regression guard — adding a new family without a profile fails this test); ControlLogix seeds every atomic type the driver supports; GuardLogix seeds at least one _S-suffixed safety tag. Integration tests still skip cleanly when ab_server isn't on PATH. 11/11 unit tests passing in this project (8 new + 3 prior). Full Admin solution builds 0 errors. docs/v2/test-data-sources.md gets a new "CI fixture" subsection under §2.Gotchas with the exact GitHub Actions YAML step — fetch the pinned libplctag release, SHA256-verify against a pinned hash recorded in the repo's CI lockfile (drift = fail closed), extract, append to PATH. The C# harness stays PATH-driven so dev-box installs (cmake + make from source) work identically to CI.
AB CIP UDT Template Object shape reader. Closes the shape-reader half of task #179. CipTemplateObjectDecoder (pure-managed) parses the Read Template blob per Rockwell CIP Vol 1 + libplctag ab/cip.c handle_read_template_reply — 12-byte header (u16 member_count + u16 struct_handle + u32 instance_size + u32 member_def_size) followed by memberCount × 8-byte member blocks (u16 info with bit-15 struct flag + lower-12-bit type code matching the Symbol Object encoding, u16 array_size, u32 struct_offset) followed by semicolon-terminated strings (UDT name first, then one per member). ParseSemicolonTerminatedStrings handles the observed firmware variations — name;\0 vs name; delimiters, optional null/space padding after the semicolon, trailing-name-without-semicolon corner case. Struct-flag members decode as AbCipDataType.Structure; unknown atomic codes fall back to Structure so the shape remains valid even with unrecognised members. Zero member count + short buffer both return null; missing member names yield <member_N> placeholders. IAbCipTemplateReader + IAbCipTemplateReaderFactory abstraction — one call per template instance id returning the raw blob. LibplctagTemplateReader is the production implementation creating a libplctag Tag with name @udt/{templateId} + handing the buffer to the decoder. AbCipDriver ctor gains optional templateReaderFactory parameter (defaults to LibplctagTemplateReaderFactory) + new internal FetchUdtShapeAsync that — checks AbCipTemplateCache first, misses call the reader + decode + cache, template-read exceptions + decode failures return null so callers can fall back to declaration-driven fan-out without the whole discovery blowing up. OperationCanceledException rethrows for shutdown propagation. Unknown device host returns null without attempting a fetch. FlushOptionalCachesAsync empties the cache so a subsequent fetch re-reads. 16 new decoder tests — simple two-member UDT, struct-member flag → Structure, array member ArrayLength, 6-member mixed-type with correct offsets, unknown type code → Structure, zero member count → null, short buffer → null, missing member name → placeholder, ParseSemicolonTerminatedStrings theory across 5 shapes. 6 new AbCipFetchUdtShapeTests exercising the driver integration via reflection (method is internal) — happy-path decode + cache, different template ids get separate fetches, unknown device → null without reader creation, decode failure returns null + doesn't cache (next call retries), reader exception returns null, FlushOptionalCachesAsync clears the cache. Total AbCip unit tests now 211/211 passing (+19 from the @tags merge's 192); full solution builds 0 errors; other drivers untouched. Whole-UDT read optimization (single libplctag call returning the packed buffer + client-side member decode using the template offsets) is left as a follow-up — requires rethinking the per-tag read path + careful hardware validation; current per-member fan-out still works correctly, just with N round-trips instead of 1.
RMW pass 2 — AbCip BOOL-within-DINT + AbLegacy bit-within-word. Closes task #181. AbCip — AbCipDriver.WriteAsync now detects BOOL writes with a bit index + routes them through WriteBitInDIntAsync: strip the .N suffix to form the parent DINT tag path (via AbCipTagPath with BitIndex=null + ToLibplctagName), get/create a cached parent IAbCipTagRuntime via EnsureParentRuntimeAsync (distinct from the bit-selector tag runtime so read + write target the DINT directly), acquire a per-parent-name SemaphoreSlim, Read → Convert.ToInt32 the current DINT → (current | 1<<bit) or (current & ~(1<<bit)) → Write via EncodeValue(DInt, updated). Per-parent lock prevents concurrent writers to the same DINT from losing updates — parallels Modbus + FOCAS pass 1. DeviceState gains ParentRuntimes dict + GetRmwLock helper + _rmwLocks ConcurrentDictionary. DisposeHandles now walks ParentRuntimes too. LibplctagTagRuntime.EncodeValue's BOOL-with-bitIndex branch stays as a defensive throw (message updated to point at the new driver-level dispatch) so an accidental bypass fails loudly rather than silently clobbering the whole DINT. AbLegacy — identical pattern for PCCC N-file bit writes. AbLegacyDriver.WriteAsync detects Bit with bitIndex + PMC letter not in {B, I, O} (B-file + I/O use their own bit-addressable semantics so don't RMW at N-file word level), routes through WriteBitInWordAsync which uses Int16 for the parent word, creates + caches a parent runtime with the suffix-stripped N7:0 address, acquires per-parent lock, RMW. DeviceState extended the same way as AbCip (ParentRuntimes + GetRmwLock). LibplctagLegacyTagRuntime.EncodeValue Bit-with-bitIndex branch points at the driver dispatch. Tests — 5 new AbCipBoolInDIntRmwTests (bit set ORs + preserves, bit clear ANDs + preserves, 8-way concurrent writes to same parent compose to 0xFF, different-parent writes get separate runtimes, repeat bit writes reuse the parent runtime init-count 1 + write-count 2), 4 new AbLegacyBitRmwTests (bit set preserves, bit clear preserves 0xFFF7, 8-way concurrent 0xFF, repeat writes reuse parent). Two pre-existing tests flipped — AbCipDriverWriteTests.Bit_in_dint_write_returns_BadNotSupported + AbLegacyReadWriteTests.Bit_within_word_write_rejected_as_BadNotSupported both now assert Good instead of BadNotSupported, renamed to _now_succeeds_via_RMW. Total tests — AbCip 166/166, AbLegacy 96/96, full solution builds 0 errors; Modbus + FOCAS + TwinCAT + other drivers untouched. Task #181 done across all four libplctag-backed + non-libplctag drivers (Modbus BitInRegister + AbCip BOOL-in-DINT + AbLegacy N-file bit + FOCAS PMC Bit — all with per-parent-word serialisation).
RMW pass 1 — Modbus BitInRegister + FOCAS PMC Bit write paths. First half of task #181 — the two drivers where read-modify-write is a clean protocol-level insertion (Modbus FC03/FC06 round-trip + FOCAS pmc_rdpmcrng / pmc_wrpmcrng round-trip). Per-driver SemaphoreSlim registry keyed on the parent word address serialises concurrent bit writes so two writers targeting different bits in the same word don't lose one another's update. Modbus — ModbusDriver gains WriteBitInRegisterAsync + _rmwLocks ConcurrentDictionary. WriteOneAsync routes BitInRegister (HoldingRegisters region only) through RMW ahead of the normal encode path. Read uses FC03 Read Holding Registers for 1 register at tag.Address, bit-op on the returned ushort via (current | 1<<bit) for set / (current & ~(1<<bit)) for clear, write back via FC06 Write Single Register. Per-address lock prevents concurrent bit writes to the same register from racing. Rejects out-of-range bits (0-15) with InvalidOperationException. EncodeRegister's BitInRegister branch repurposed as a defensive guard — if a non-RMW caller ever reaches it, throw so an unintended bypass stays loud rather than silently clobbering. FOCAS — FwlibFocasClient gains WritePmcBitAsync + _rmwLocks keyed on {addrType}:{byteAddr}. Driver-layer WriteAsync routes Bit writes with a bitIndex through the new path; other Pmc writes still hit the direct pmc_wrpmcrng path. RMW uses cnc_rdpmcrng + Byte dataType to grab the parent byte, bit-op with (current | 1<<bit) or (current & ~(1<<bit)), cnc_wrpmcrng to write back. Rejects out-of-range bits (0-7, FOCAS PMC bytes are 8-bit) with InvalidOperationException. EncodePmcValue's Bit branch now treats a no-bitIndex case as whole-byte boolean (non-zero / zero); bitIndex-present writes never hit this path because they dispatch to WritePmcBitAsync upstream. Tests — 5 new ModbusBitRmwTests + 4 new FocasPmcBitRmwTests + 1 renamed pre-existing test each covering — bit set preserves other bits, bit clear preserves other bits, concurrent bit writes to same word/byte compose correctly (8-parallel stress), bit writes on different parent words proceed without contention (4-parallel), sequential bit sets compose into 0xFF after all 8. Fake PmcRmwFake in FOCAS tests simulates the PMC byte storage + surfaces it through the IFocasClient contract so the test asserts driver-level behavior without needing Fwlib32.dll. FwlibNativeHelperTests.EncodePmcValue_Bit_throws_NotSupported_for_RMW_gap replaced with EncodePmcValue_Bit_without_bit_index_writes_byte_boolean reflecting the new behavior. ModbusDataTypeTests.BitInRegister_write_is_not_supported_in_PR24 renamed to BitInRegister_EncodeRegister_still_rejects_direct_calls; the message assertion updated to match the new defensive message. Modbus tests now 182/182, FOCAS tests now 119/119; full solution builds 0 errors; AbCip/AbLegacy/TwinCAT untouched (those get their RMW pass in a follow-up since libplctag bit access may need a parallel parent-word handle). Task #181 stays pending until that second pass lands.
Phase 3 PR 40 — LiveStackSmokeTests: write-roundtrip + subscribe-receives-OnDataChange against the live Galaxy. Finishes LMX #5 by exercising the IWritable + ISubscribable capability paths end-to-end through the Proxy → OtOpcUaGalaxyHost service → MXAccess → real Galaxy.
Phase 1 Streams B–E scaffold + Phase 2 Streams A–C scaffold — 8 new projects with ~70 new tests, all green alongside the 494 v1 IntegrationTests baseline (parity preserved: no v1 tests broken; legacy OtOpcUa.Host untouched). Phase 1 finish: Configuration project (16 entities + 10 enums + DbContext + DesignTimeDbContextFactory + InitialSchema/StoredProcedures/AuthorizationGrants migrations — 8 procs including sp_PublishGeneration with MERGE on ExternalIdReservation per decision #124, sp_RollbackToGeneration cloning rows into a new published generation, sp_ValidateDraft with cross-cluster-namespace + EquipmentUuid-immutability + ZTag/SAPID reservation pre-flight, sp_ComputeGenerationDiff with CHECKSUM-based row signature — plus OtOpcUaNode/OtOpcUaAdmin SQL roles with EXECUTE grants scoped to per-principal-class proc sets and DENY UPDATE/DELETE/INSERT/SELECT on dbo schema); managed DraftValidator covering UNS segment regex, path length, EquipmentUuid immutability across generations, same-cluster namespace binding (decision #122), reservation pre-flight, EquipmentId derivation (decision #125), driver↔namespace compatibility — returning every failing rule in one pass; LiteDB local cache with round-trip + ring pruning + corruption-fast-fail; GenerationApplier with per-entity Added/Removed/Modified diff and dependency-ordered callbacks (namespace → driver → device → equipment → poll-group → tag, Removed before Added); Core project with GenericDriverNodeManager (scaffold for the Phase 2 Galaxy port) and DriverHost lifecycle registry; Server project using Microsoft.Extensions.Hosting BackgroundService replacing TopShelf, with NodeBootstrap that falls back to LiteDB cache when the central DB is unreachable (decision #79); Admin project scaffolded as Blazor Server with Bootstrap 5 sidebar layout, cookie auth, three admin roles (ConfigViewer/ConfigEditor/FleetAdmin), Cluster + Generation services fronting the stored procs. Phase 2 scaffold: Driver.Galaxy.Shared (netstandard2.0) with full MessagePack IPC contract surface — Hello version negotiation, Open/CloseSession, Heartbeat, DiscoverHierarchy + GalaxyObjectInfo/GalaxyAttributeInfo, Read/WriteValues, Subscribe/Unsubscribe/OnDataChange, AlarmSubscribe/Event/Ack, HistoryRead, HostConnectivityStatus, Recycle — plus length-prefixed framing (decision #28) with a 16 MiB cap and thread-safe FrameWriter/FrameReader; Driver.Galaxy.Host (net48) implementing the Tier C cross-cutting protections from driver-stability.md — strict PipeAcl (allow configured server SID only, explicit deny on LocalSystem + Administrators), PipeServer with caller-SID verification via pipe.RunAsClient + WindowsIdentity.GetCurrent and per-process shared-secret Hello, Galaxy-specific MemoryWatchdog (warn at max(1.5×baseline, +200 MB), soft-recycle at max(2×baseline, +200 MB), hard ceiling 1.5 GB, slope ≥5 MB/min over 30-min rolling window), RecyclePolicy (1 soft recycle per hour cap + 03:00 local daily scheduled), PostMortemMmf (1000-entry ring buffer in %ProgramData%\OtOpcUa\driver-postmortem\galaxy.mmf, survives hard crash, readable cross-process), MxAccessHandle : SafeHandle (ReleaseHandle loops Marshal.ReleaseComObject until refcount=0 then calls optional unregister callback), StaPump with responsiveness probe (BlockingCollection dispatcher for Phase 1 — real Win32 GetMessage/DispatchMessage pump slots in with the same semantics when the Galaxy code lift happens), IsExternalInit shim for init setters on .NET 4.8; Driver.Galaxy.Proxy (net10) implementing IDriver + ITagDiscovery forwarding over the IPC channel with MX data-type and security-classification mapping, plus Supervisor pieces — Backoff (5s → 15s → 60s capped, reset-on-stable-run), CircuitBreaker (3 crashes per 5 min opens; 1h → 4h → manual cooldown escalation; sticky alert doesn't auto-clear), HeartbeatMonitor (2s cadence, 3 consecutive misses = host dead per driver-stability.md). Infrastructure: docker SQL Server remapped to host port 14330 to coexist with the native MSSQL14 Galaxy ZB DB instance on 1433; NuGetAuditSuppress applied per-project for two System.Security.Cryptography.Xml advisories that only reach via EF Core Design with PrivateAssets=all (fix ships in 11.0.0-preview); .slnx gains 14 project registrations. Deferred with explicit TODOs in docs/v2/implementation/phase-2-partial-exit-evidence.md: Phase 1 Stream E Admin UI pages (Generations listing + draft-diff-publish, Equipment CRUD with OPC 40010 fields, UNS Areas/Lines tabs, ACLs + permission simulator, Generic JSON config editor, SignalR real-time, Release-Reservation + Merge-Equipment workflows, LDAP login page, AppServer smoke test per decision #142), Phase 2 Stream D (Galaxy MXAccess code lift out of legacy OtOpcUa.Host, dual-service installer, appsettings → DriverConfig migration script, legacy Host deletion — blocked by parity), Phase 2 Stream E (v1 IntegrationTests against v2 topology, Client.CLI walkthrough diff, four 2026-04-13 stability findings regression tests, adversarial review — requires live MXAccess runtime).
RMW pass 1 — Modbus BitInRegister + FOCAS PMC Bit write paths. First half of task #181 — the two drivers where read-modify-write is a clean protocol-level insertion (Modbus FC03/FC06 round-trip + FOCAS pmc_rdpmcrng / pmc_wrpmcrng round-trip). Per-driver SemaphoreSlim registry keyed on the parent word address serialises concurrent bit writes so two writers targeting different bits in the same word don't lose one another's update. Modbus — ModbusDriver gains WriteBitInRegisterAsync + _rmwLocks ConcurrentDictionary. WriteOneAsync routes BitInRegister (HoldingRegisters region only) through RMW ahead of the normal encode path. Read uses FC03 Read Holding Registers for 1 register at tag.Address, bit-op on the returned ushort via (current | 1<<bit) for set / (current & ~(1<<bit)) for clear, write back via FC06 Write Single Register. Per-address lock prevents concurrent bit writes to the same register from racing. Rejects out-of-range bits (0-15) with InvalidOperationException. EncodeRegister's BitInRegister branch repurposed as a defensive guard — if a non-RMW caller ever reaches it, throw so an unintended bypass stays loud rather than silently clobbering. FOCAS — FwlibFocasClient gains WritePmcBitAsync + _rmwLocks keyed on {addrType}:{byteAddr}. Driver-layer WriteAsync routes Bit writes with a bitIndex through the new path; other Pmc writes still hit the direct pmc_wrpmcrng path. RMW uses cnc_rdpmcrng + Byte dataType to grab the parent byte, bit-op with (current | 1<<bit) or (current & ~(1<<bit)), cnc_wrpmcrng to write back. Rejects out-of-range bits (0-7, FOCAS PMC bytes are 8-bit) with InvalidOperationException. EncodePmcValue's Bit branch now treats a no-bitIndex case as whole-byte boolean (non-zero / zero); bitIndex-present writes never hit this path because they dispatch to WritePmcBitAsync upstream. Tests — 5 new ModbusBitRmwTests + 4 new FocasPmcBitRmwTests + 1 renamed pre-existing test each covering — bit set preserves other bits, bit clear preserves other bits, concurrent bit writes to same word/byte compose correctly (8-parallel stress), bit writes on different parent words proceed without contention (4-parallel), sequential bit sets compose into 0xFF after all 8. Fake PmcRmwFake in FOCAS tests simulates the PMC byte storage + surfaces it through the IFocasClient contract so the test asserts driver-level behavior without needing Fwlib32.dll. FwlibNativeHelperTests.EncodePmcValue_Bit_throws_NotSupported_for_RMW_gap replaced with EncodePmcValue_Bit_without_bit_index_writes_byte_boolean reflecting the new behavior. ModbusDataTypeTests.BitInRegister_write_is_not_supported_in_PR24 renamed to BitInRegister_EncodeRegister_still_rejects_direct_calls; the message assertion updated to match the new defensive message. Modbus tests now 182/182, FOCAS tests now 119/119; full solution builds 0 errors; AbCip/AbLegacy/TwinCAT untouched (those get their RMW pass in a follow-up since libplctag bit access may need a parallel parent-word handle). Task #181 stays pending until that second pass lands.
TwinCAT follow-up — Symbol browser via AdsClient + SymbolLoaderFactory. Closes task #188. Adds ITwinCATClient.BrowseSymbolsAsync — IAsyncEnumerable yielding TwinCATDiscoveredSymbol (InstancePath + mapped TwinCATDataType + ReadOnly flag) from the target's flat symbol table. AdsTwinCATClient implementation uses SymbolLoaderFactory.Create(_client, new SymbolLoaderSettings(SymbolsLoadMode.Flat)) + iterates loader.Symbols, maps IEC 61131-3 type names (BOOL/SINT/INT/DINT/LINT/REAL/LREAL/STRING/WSTRING/TIME/DATE/DT/TOD + BYTE/WORD/DWORD/LWORD unsigned-word aliases) through MapSymbolTypeName, checks SymbolAccessRights.Write bit for writable vs read-only. Unsupported types (UDTs / function blocks / arrays / pointers) surface with DataType=null so callers can skip or recurse. TwinCATDriverOptions.EnableControllerBrowse — new bool, default false to preserve the strict-config path. When true, DiscoverAsync iterates each device's BrowseSymbolsAsync, filters via TwinCATSystemSymbolFilter (rejects TwinCAT_*, Constants.*, Mc_*, __*, Global_Version* prefixes + anything empty), skips null-DataType symbols, emits surviving symbols under a per-device Discovered/ sub-folder with InstancePath as both FullName + BrowseName + ReadOnly→ViewOnly/writable→Operate. Pre-declared tags from TwinCATDriverOptions.Tags always emit regardless. Browse failure is non-fatal — exception caught + swallowed, pre-declared tags stay in the address space, operators see the failure in driver health on next read. TwinCATSystemSymbolFilter static class mirrors AbCipSystemTagFilter's shape with TwinCAT-specific prefixes. Fake client updated — BrowseResults list for test setup + FireNotification-style single-invocation on each subscribe, ThrowOnBrowse flag for failure testing. 8 new unit tests — strict path emits only pre-declared when EnableControllerBrowse=false, browse enabled adds Discovered/ folder, filter rejects system prefixes, null-DataType symbols skipped, ReadOnly symbols surface ViewOnly, browse failure leaves pre-declared intact, SystemSymbolFilter theory (10 cases). Total TwinCAT unit tests now 110/110 passing (+17 from the native-notification merge's 93); full solution builds 0 errors; other drivers untouched.