diff --git a/docs/v2/Galaxy.ParityMatrix.md b/docs/v2/Galaxy.ParityMatrix.md
new file mode 100644
index 0000000..c6d6de6
--- /dev/null
+++ b/docs/v2/Galaxy.ParityMatrix.md
@@ -0,0 +1,104 @@
+# Galaxy backend parity matrix
+
+This document tracks the scenario × result matrix that the
+`Driver.Galaxy.ParityTests` suite drives against both Galaxy backends —
+the legacy out-of-process **Galaxy.Host** (.NET 4.8 x86 + MXAccess COM,
+fronted by `GalaxyProxyDriver`) and the new in-process **mxgateway**
+backend (`GalaxyDriver`, .NET 10 + gRPC against `mxaccessgw`).
+
+Maintained alongside Phase 5 (PR 5.W). The Phase 7 default flip
+(PR 7.1) consumes this matrix as its go/no-go gate — every row must be
+either green or carry an explicit *accepted-delta* justification.
+
+## Reading the matrix
+
+- **Status: green** — the scenario asserts strict parity and passes
+  (or skips cleanly when the rig isn't up).
+- **Status: yellow** — soft pin only (count or shape parity, not value
+  parity) — acceptable when the underlying COM/gRPC stacks have known
+  divergences in raw payloads but the surface presented to the
+  DriverNodeManager is equivalent.
+- **Status: red** — divergence detected. Row carries a fix or a
+  follow-up task ID.
+
+## Scenarios
+
+| PR | Test class | Scenario | Status | Notes |
+|----|-----------|----------|--------|-------|
+| 5.2 | `BrowseAndReadParityTests` | Same variable set | green | symmetric set diff on full-reference set |
+| 5.2 | `BrowseAndReadParityTests` | Same DataType / SecurityClass / IsHistorized | green | per-attribute meta triple parity |
+| 5.2 | `BrowseAndReadParityTests` | Same StatusCode + value-CLR-type on a sampled read | yellow | raw values legitimately drift between two reads on a live Galaxy; we pin StatusCode + type, not value equality |
+| 5.3 | `SubscribeAndEventRateParityTests` | Subscribe returns a handle on each backend | green | symmetric Unsubscribe cleanup |
+| 5.3 | `SubscribeAndEventRateParityTests` | Event rate within ±50% over 3s | yellow | both backends fed by the same upstream MXAccess subscriptions; tolerance absorbs scheduler jitter |
+| 5.4 | `WriteByClassificationParityTests` | FreeAccess / Operate write StatusCode parity | green | both backends use plain Write |
+| 5.4 | `WriteByClassificationParityTests` | Configure / Tune routes via secured-write | green | both backends pick up SecurityClassification from DiscoverAsync |
+| 5.5 | `AlarmTransitionParityTests` | Same alarm-condition source-node-id set | green | + per-condition SourceName / InitialSeverity / InAlarmRef / DescAttrNameRef |
+| 5.5 | `AlarmTransitionParityTests` | IsAlarm-marked variable count parity | green | soft pin — count must match, doesn't have to be non-zero |
+| 5.6 | `HistoryReadParityTests` | Same historized attribute set | green | what HistoryRouter consumes when routing to the Wonderware sidecar |
+| 5.6 | `HistoryReadParityTests` | Neither backend implements `IHistoryProvider` | green | architectural pin from Phase 1 (PR 1.3) |
+| 5.7 | `ReconnectParityTests` | Reinitialize → both Healthy + reads succeed | green | recovery latency is *not* pinned (legacy: pipe + COM client; mxgw: re-Register gw session) |
+| 5.7 | `ReconnectParityTests` | Health diverges only when one side recovers | yellow | soft pin until a toxiproxy-style fault injector lands |
+| 5.8 | `ScanStateProbeParityTests` | Same per-platform host set | green | transport-entry names differ by design (legacy = Galaxy.Host process; mxgw = `MxAccess.ClientName`) and are excluded |
+| 5.8 | `ScanStateProbeParityTests` | Same `HostState` per overlapping platform | green | drives Discover, waits 1.5s for the probe-watcher push, then snapshots both |
+
+## Accepted deltas
+
+These are intentional differences between the two backends — the parity
+suite skips or tolerates them by design.
+
+1. **Transport-entry host name.** The legacy backend's
+   `IHostConnectivityProbe` surface includes a host entry named after
+   the Galaxy.Host process identity; the mxgw backend uses the
+   configured `MxAccess.ClientName`. The names differ, but both are
+   correct for their respective sessions — the parity test compares
+   only the platform-host subset.
+
+2. **Reconnect latency cadence.** Legacy reconnect roundtrips an OS
+   named pipe + an MxAccess COM client + a Galaxy.Host process restart
+   if the host died. The mxgw reconnect re-Registers the gateway session
+   over an existing gRPC channel. Sub-second vs multi-second recoveries
+   are both correct for their own paths; only the eventual `Healthy`
+   convergence is pinned.
+
+3. **Read-value drift.** A read sampled twice on a live Galaxy can
+   return different values legitimately. We pin `StatusCode` and
+   value-CLR-type equality, not value equality. Driving an explicit
+   write-then-read pin requires the parity rig to own a writable
+   sandbox attribute — out of scope for the current suite.
+
+4. **Event-rate variance.** Both backends consume the same upstream
+   MXAccess publish events but route them through different deserializers
+   (LMXProxyServer COM events vs gRPC `MxEvent` protos). Scheduler
+   jitter on either side can shift counts within a 3s window; we pin a
+   ±50% ratio, not strict equality.
+
+5. **Per-driver `IHistoryProvider` is gone.** Phase 1 (PR 1.3) lifted
+   history off the per-driver path onto the server-owned
+   `HistoryRouter`. Both Galaxy backends correctly *do not* surface
+   `IHistoryProvider` — the absence is itself a parity assertion.
+
+## Outstanding deltas
+
+None as of PR 5.W. Phase 7 (PR 7.1) flips the default to `mxgw` once
+this matrix is fully green on the dev parity rig.
+
+## Running the matrix
+
+```bash
+# Both backends must be reachable for any row to run; rows skip
+# cleanly when their backend is unavailable.
+dotnet test tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.ParityTests/
+```
+
+Environment overrides for the mxgw backend:
+
+| Variable | Default | Purpose |
+|----------|---------|---------|
+| `OTOPCUA_PARITY_GW_ENDPOINT` | `http://localhost:5120` | mxaccessgw gRPC endpoint |
+| `OTOPCUA_PARITY_GW_API_KEY` | `parity-suite-key` | API key handed to `MxGatewayClient` |
+| `OTOPCUA_PARITY_CLIENT_NAME` | `OtOpcUa-Parity` | `MxAccess.ClientName` for the session |
+
+The legacy backend reads ZB SQL on `localhost:1433` and spawns
+`OtOpcUa.Driver.Galaxy.Host.exe` from
+`src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/bin/Debug/net48/` — both
+must exist for the legacy half to resolve.