Issue #44: implement Rust client session values errors and CLI

Issue #45: scaffold Python package

clients/rust/Cargo.lock

@@ -145,6 +145,16 @@ version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
+[[package]]
+name = "cc"
+version = "1.2.61"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d16d90359e986641506914ba71350897565610e87ce0ad9e6f28569db3dd5c6d"
+dependencies = [
+ "find-msvc-tools",
+ "shlex",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.4"
@@ -225,6 +235,12 @@ version = "2.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9f1f227452a390804cdb637b74a86990f2a7d7ba4b7d5693aac9b4dd6defd8d6"
 
+[[package]]
+name = "find-msvc-tools"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5baebc0774151f905a1a2cc41989300b1e6fbb29aff0ceffa1064fdd3088d582"
+
 [[package]]
 name = "fixedbitset"
 version = "0.5.7"
@@ -258,6 +274,17 @@ version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7e3450815272ef58cec6d564423f6e755e25379b217b0bc688e295ba24df6b1d"
 
+[[package]]
+name = "futures-macro"
+version = "0.3.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e835b70203e41293343137df5c0664546da5745f82ec9b84d40be8336958447b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "futures-sink"
 version = "0.3.32"
@@ -277,11 +304,23 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "389ca41296e6190b48053de0321d02a77f32f8a5d2461dd38762c0593805c6d6"
 dependencies = [
  "futures-core",
+ "futures-macro",
  "futures-task",
  "pin-project-lite",
  "slab",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff2abc00be7fca6ebc474524697ae276ad847ad0a6b3faa4bcb027e9a4614ad0"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.4.2"
@@ -537,11 +576,14 @@ checksum = "1d87ecb2933e8aeadb3e3a02b828fed80a7528047e68b4f424523a0981a3a084"
 name = "mxgateway-client"
 version = "0.1.0"
 dependencies = [
+ "futures-core",
+ "futures-util",
  "prost",
  "prost-types",
  "serde_json",
  "thiserror",
  "tokio",
+ "tokio-stream",
  "tonic",
  "tonic-build",
 ]
@@ -551,8 +593,11 @@ name = "mxgw-cli"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "futures-util",
  "mxgateway-client",
+ "serde",
  "serde_json",
+ "tokio",
 ]
 
 [[package]]
@@ -724,6 +769,20 @@ version = "0.8.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
 
+[[package]]
+name = "ring"
+version = "0.17.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4689e6c2294d81e88dc6261c768b63bc4fcdb852be6d1352498b114f61383b7"
+dependencies = [
+ "cc",
+ "cfg-if",
+ "getrandom 0.2.17",
+ "libc",
+ "untrusted",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "rustix"
 version = "1.1.4"
@@ -737,6 +796,41 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.23.39"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c2c118cb077cca2822033836dfb1b975355dfb784b5e8da48f7b6c5db74e60e"
+dependencies = [
+ "log",
+ "once_cell",
+ "ring",
+ "rustls-pki-types",
+ "rustls-webpki",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-pki-types"
+version = "1.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30a7197ae7eb376e574fe940d068c30fe0462554a3ddbe4eca7838e049c937a9"
+dependencies = [
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-webpki"
+version = "0.103.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "61c429a8649f110dddef65e2a5ad240f747e85f7758a6bccc7e5777bd33f756e"
+dependencies = [
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "semver"
 version = "1.0.28"
@@ -750,6 +844,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a8e94ea7f378bd32cbbd37198a4a91436180c5bb472411e48b5ec2e2124ae9e"
 dependencies = [
  "serde_core",
+ "serde_derive",
 ]
 
 [[package]]
@@ -785,6 +880,12 @@ dependencies = [
  "zmij",
 ]
 
+[[package]]
+name = "shlex"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -823,6 +924,12 @@ version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "syn"
 version = "2.0.117"
@@ -847,7 +954,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
 dependencies = [
  "fastrand",
- "getrandom",
+ "getrandom 0.4.2",
  "once_cell",
  "rustix",
  "windows-sys 0.61.2",
@@ -899,6 +1006,16 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "tokio-rustls"
+version = "0.26.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1729aa945f29d91ba541258c8df89027d5792d85a8841fb65e8bf0f4ede4ef61"
+dependencies = [
+ "rustls",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-stream"
 version = "0.1.18"
@@ -945,6 +1062,7 @@ dependencies = [
  "prost",
  "socket2 0.5.10",
  "tokio",
+ "tokio-rustls",
  "tokio-stream",
  "tower",
  "tower-layer",
@@ -1046,6 +1164,12 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
 
+[[package]]
+name = "untrusted"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"
+
 [[package]]
 name = "utf8parse"
 version = "0.2.2"
@@ -1301,6 +1425,12 @@ dependencies = [
  "wasmparser",
 ]
 
+[[package]]
+name = "zeroize"
+version = "1.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+
 [[package]]
 name = "zmij"
 version = "1.0.21"

clients/rust/Cargo.toml

@@ -16,24 +16,31 @@ publish = false
 
 [workspace.dependencies]
 clap = { version = "4.5.53", features = ["derive"] }
+futures-core = "0.3.31"
+futures-util = "0.3.31"
 prost = "0.13.5"
 prost-types = "0.13.5"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.145"
 thiserror = "2.0.17"
-tokio = { version = "1.48.0", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.48.0", features = ["macros", "rt-multi-thread", "sync", "time"] }
-tonic = { version = "0.13.1", features = ["transport"] }
+tokio-stream = { version = "0.1.17", features = ["net"] }
+tonic = { version = "0.13.1", features = ["transport", "tls-ring"] }
 tonic-build = "0.13.1"
 
 [dependencies]
+futures-core = { workspace = true }
+futures-util = { workspace = true }
 prost = { workspace = true }
 prost-types = { workspace = true }
 thiserror = { workspace = true }
+tokio = { workspace = true }
 tonic = { workspace = true }
 
 [dev-dependencies]
 serde_json = { workspace = true }
 tokio = { workspace = true }
+tokio-stream = { workspace = true }
 
 [build-dependencies]
 tonic-build = { workspace = true }

clients/rust/README.md

@@ -1,7 +1,8 @@
 # Rust Client Workspace
 
 The Rust client workspace contains the MXAccess Gateway client library, a
-test CLI, and scaffold tests for generated contract wiring. The library uses
+test CLI, and tests for generated contract wiring plus wrapper behavior. The
+library uses
 the shared protobuf inputs documented in
 `../../docs/client-proto-generation.md` so the Rust bindings compile against
 the same public gateway and worker contracts as the server.
@@ -31,6 +32,7 @@ Run the Rust workspace checks from `clients/rust`:
 cargo fmt --all --check
 cargo test --workspace
 cargo check --workspace
+cargo clippy --workspace --all-targets -- -D warnings
 ```
 
 The build script uses `protoc` from `PATH` or the Windows path recorded in
@@ -38,13 +40,48 @@ The build script uses `protoc` from `PATH` or the Windows path recorded in
 
 ## CLI
 
-The scaffold CLI exposes version information:
+The CLI exposes version, session, command, event stream, write, and smoke
+commands over the same client wrapper used by tests:
 
 ```powershell
 cargo run -p mxgw-cli -- version --json
+cargo run -p mxgw-cli -- open-session --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --json
+cargo run -p mxgw-cli -- register --session-id <session-id> --client-name mxgw-rust-cli --json
+cargo run -p mxgw-cli -- add-item --session-id <session-id> --server-handle 1 --item TestChildObject.TestInt --json
+cargo run -p mxgw-cli -- advise --session-id <session-id> --server-handle 1 --item-handle 1 --json
+cargo run -p mxgw-cli -- stream-events --session-id <session-id> --max-events 1 --json
+cargo run -p mxgw-cli -- write --session-id <session-id> --server-handle 1 --item-handle 1 --value-type int32 --value 123 --json
 ```
 
-Additional commands are implemented with the client/session wrapper work.
+Use `--tls`, `--ca-file`, and `--server-name-override` for TLS endpoints. The
+CLI reads the API key from `--api-key` or from `--api-key-env`, which defaults
+to `MXGATEWAY_API_KEY`. API keys are redacted by the library option and secret
+types.
+
+## Library Surface
+
+`ClientOptions` configures endpoint, API key, plaintext or TLS transport,
+timeouts, custom CA files, and server name override. `GatewayClient::connect`
+creates an authenticated `tonic` client and attaches `authorization: Bearer
+<api-key>` metadata to unary and streaming calls.
+
+`GatewayClient` exposes raw generated calls through `open_session_raw`,
+`close_session_raw`, `invoke_raw`, `stream_events`, and `raw_client`. The
+session helpers keep MXAccess handles visible:
+
+```rust
+let session = client.open_session(request).await?;
+let server_handle = session.register("mxgw-rust").await?;
+let item_handle = session.add_item(server_handle, "TestChildObject.TestInt").await?;
+session.advise(server_handle, item_handle).await?;
+let mut events = session.events().await?;
+session.close().await?;
+```
+
+`MxValue`, `MxArrayValue`, and `MxStatus` wrap generated protobuf messages while
+preserving the raw message for parity diagnostics. Command replies whose
+protocol status is not `PROTOCOL_STATUS_CODE_OK` become `Error::Command` and
+retain the raw `MxCommandReply`.
 
 ## Related Documentation
 

clients/rust/build.rs

@@ -19,7 +19,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     println!("cargo:rerun-if-changed={}", worker_proto.display());
 
     tonic_build::configure()
-        .build_server(false)
+        .build_server(true)
         .build_client(true)
         .file_descriptor_set_path(descriptor_path)
         .compile_protos(

clients/rust/crates/mxgw-cli/Cargo.toml

@@ -10,5 +10,8 @@ path = "src/main.rs"
 
 [dependencies]
 clap = { workspace = true }
+futures-util = { workspace = true }
 mxgateway-client = { path = "../.." }
+serde = { workspace = true }
 serde_json = { workspace = true }
+tokio = { workspace = true }

clients/rust/crates/mxgw-cli/src/main.rs

@@ -1,8 +1,20 @@
+use std::env;
+use std::path::PathBuf;
 use std::process::ExitCode;
+use std::time::Duration;
 
-use clap::{Parser, Subcommand};
+use clap::{Args, Parser, Subcommand, ValueEnum};
-use mxgateway_client::{CLIENT_VERSION, GATEWAY_PROTOCOL_VERSION, WORKER_PROTOCOL_VERSION};
+use futures_util::StreamExt;
+use mxgateway_client::generated::mxaccess_gateway::v1::{
+    CloseSessionRequest, MxCommand, MxCommandKind, MxCommandRequest, OpenSessionRequest,
+    PingCommand, StreamEventsRequest,
+};
+use mxgateway_client::{
+    ApiKey, ClientOptions, Error, GatewayClient, MxValue, CLIENT_VERSION, GATEWAY_PROTOCOL_VERSION,
+    WORKER_PROTOCOL_VERSION,
+};
 use serde_json::json;
+use serde_json::Value;
 
 #[derive(Debug, Parser)]
 #[command(name = "mxgw")]
@@ -18,30 +30,428 @@ enum Command {
         #[arg(long)]
         json: bool,
     },
+    Ping {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long, default_value = "ping")]
+        message: String,
+        #[arg(long)]
+        json: bool,
+    },
+    OpenSession {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long, default_value = "mxgw-rust-cli")]
+        client_name: String,
+        #[arg(long)]
+        json: bool,
+    },
+    CloseSession {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long)]
+        json: bool,
+    },
+    Register {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long, default_value = "mxgw-rust-cli")]
+        client_name: String,
+        #[arg(long)]
+        json: bool,
+    },
+    AddItem {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long)]
+        server_handle: i32,
+        #[arg(long)]
+        item: String,
+        #[arg(long)]
+        json: bool,
+    },
+    Advise {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long)]
+        server_handle: i32,
+        #[arg(long)]
+        item_handle: i32,
+        #[arg(long)]
+        json: bool,
+    },
+    StreamEvents {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long, default_value_t = 0)]
+        after_worker_sequence: u64,
+        #[arg(long, default_value_t = 1)]
+        max_events: usize,
+        #[arg(long)]
+        json: bool,
+    },
+    Write {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long)]
+        server_handle: i32,
+        #[arg(long)]
+        item_handle: i32,
+        #[arg(long, value_enum)]
+        value_type: CliValueType,
+        #[arg(long)]
+        value: String,
+        #[arg(long, default_value_t = 0)]
+        user_id: i32,
+        #[arg(long)]
+        json: bool,
+    },
+    Write2 {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        session_id: String,
+        #[arg(long)]
+        server_handle: i32,
+        #[arg(long)]
+        item_handle: i32,
+        #[arg(long, value_enum)]
+        value_type: CliValueType,
+        #[arg(long)]
+        value: String,
+        #[arg(long)]
+        timestamp: String,
+        #[arg(long, default_value_t = 0)]
+        user_id: i32,
+        #[arg(long)]
+        json: bool,
+    },
+    Smoke {
+        #[command(flatten)]
+        connection: ConnectionArgs,
+        #[arg(long)]
+        item: String,
+        #[arg(long, default_value = "mxgw-rust-smoke")]
+        client_name: String,
+        #[arg(long)]
+        json: bool,
+    },
 }
 
-fn main() -> ExitCode {
+#[derive(Debug, Args, Clone)]
+struct ConnectionArgs {
+    #[arg(long, default_value = "http://127.0.0.1:5000")]
+    endpoint: String,
+    #[arg(long)]
+    api_key: Option<String>,
+    #[arg(long, default_value = "MXGATEWAY_API_KEY")]
+    api_key_env: String,
+    #[arg(long)]
+    plaintext: bool,
+    #[arg(long)]
+    tls: bool,
+    #[arg(long)]
+    ca_file: Option<PathBuf>,
+    #[arg(long)]
+    server_name_override: Option<String>,
+    #[arg(long, default_value_t = 10)]
+    connect_timeout_seconds: u64,
+    #[arg(long, default_value_t = 30)]
+    call_timeout_seconds: u64,
+}
+
+impl ConnectionArgs {
+    fn options(&self) -> ClientOptions {
+        let mut options = ClientOptions::new(self.endpoint.clone())
+            .with_plaintext(!self.tls || self.plaintext)
+            .with_connect_timeout(Duration::from_secs(self.connect_timeout_seconds))
+            .with_call_timeout(Duration::from_secs(self.call_timeout_seconds));
+
+        if let Some(api_key) = self
+            .api_key
+            .clone()
+            .or_else(|| env::var(&self.api_key_env).ok())
+            .filter(|value| !value.is_empty())
+        {
+            options = options.with_api_key(ApiKey::new(api_key));
+        }
+        if let Some(ca_file) = &self.ca_file {
+            options = options.with_ca_file(ca_file);
+        }
+        if let Some(server_name_override) = &self.server_name_override {
+            options = options.with_server_name_override(server_name_override);
+        }
+
+        options
+    }
+}
+
+#[derive(Clone, Copy, Debug, ValueEnum)]
+enum CliValueType {
+    Bool,
+    Int32,
+    Int64,
+    Float,
+    Double,
+    String,
+}
+
+#[tokio::main]
+async fn main() -> ExitCode {
     let cli = Cli::parse();
-    run(cli);
+    match run(cli).await {
-    ExitCode::SUCCESS
+        Ok(()) => ExitCode::SUCCESS,
+        Err(error) => {
+            eprintln!("{error}");
+            ExitCode::FAILURE
+        }
+    }
 }
 
-fn run(cli: Cli) {
+async fn run(cli: Cli) -> Result<(), Error> {
     match cli.command {
         Command::Version { json } => print_version(json),
+        Command::Ping {
+            connection,
+            message,
+            json,
+        } => {
+            let client = connect(connection).await?;
+            let reply = client
+                .invoke(MxCommandRequest {
+                    client_correlation_id: "rust-cli-ping".to_owned(),
+                    command: Some(MxCommand {
+                        kind: MxCommandKind::Ping as i32,
+                        payload: Some(mxgateway_client::generated::mxaccess_gateway::v1::mx_command::Payload::Ping(
+                            PingCommand { message },
+                        )),
+                    }),
+                    ..MxCommandRequest::default()
+                })
+                .await?;
+            print_command_reply("ping", &reply, json);
         }
+        Command::OpenSession {
+            connection,
+            client_name,
+            json,
+        } => {
+            let client = connect(connection).await?;
+            let reply = client
+                .open_session_raw(OpenSessionRequest {
+                    client_session_name: client_name,
+                    ..OpenSessionRequest::default()
+                })
+                .await?;
+            if json {
+                println!(
+                    "{}",
+                    json!({
+                        "sessionId": reply.session_id,
+                        "backendName": reply.backend_name,
+                        "gatewayProtocolVersion": reply.gateway_protocol_version,
+                        "workerProtocolVersion": reply.worker_protocol_version,
+                    })
+                );
+            } else {
+                println!("{}", reply.session_id);
+            }
+        }
+        Command::CloseSession {
+            connection,
+            session_id,
+            json,
+        } => {
+            let client = connect(connection).await?;
+            let reply = client
+                .close_session_raw(CloseSessionRequest {
+                    session_id,
+                    client_correlation_id: "rust-cli-close-session".to_owned(),
+                })
+                .await?;
+            if json {
+                println!("{}", json!({ "sessionId": reply.session_id }));
+            } else {
+                println!("closed {}", reply.session_id);
+            }
+        }
+        Command::Register {
+            connection,
+            session_id,
+            client_name,
+            json,
+        } => {
+            let session = session_for(connection, session_id).await?;
+            let server_handle = session.register(&client_name).await?;
+            print_handle("serverHandle", server_handle, json);
+        }
+        Command::AddItem {
+            connection,
+            session_id,
+            server_handle,
+            item,
+            json,
+        } => {
+            let session = session_for(connection, session_id).await?;
+            let item_handle = session.add_item(server_handle, &item).await?;
+            print_handle("itemHandle", item_handle, json);
+        }
+        Command::Advise {
+            connection,
+            session_id,
+            server_handle,
+            item_handle,
+            json,
+        } => {
+            let session = session_for(connection, session_id).await?;
+            session.advise(server_handle, item_handle).await?;
+            print_ok("advise", json);
+        }
+        Command::StreamEvents {
+            connection,
+            session_id,
+            after_worker_sequence,
+            max_events,
+            json,
+        } => {
+            let client = connect(connection).await?;
+            let mut stream = client
+                .stream_events(StreamEventsRequest {
+                    session_id,
+                    after_worker_sequence,
+                })
+                .await?;
+            let mut events = Vec::new();
+            while events.len() < max_events {
+                let Some(event) = stream.next().await else {
+                    break;
+                };
+                events.push(event?);
+            }
+            if json {
+                println!("{}", json!({ "eventCount": events.len() }));
+            } else {
+                for event in events {
+                    println!("{} {}", event.worker_sequence, event.family);
+                }
+            }
+        }
+        Command::Write {
+            connection,
+            session_id,
+            server_handle,
+            item_handle,
+            value_type,
+            value,
+            user_id,
+            json,
+        } => {
+            let session = session_for(connection, session_id).await?;
+            session
+                .write(
+                    server_handle,
+                    item_handle,
+                    parse_value(value_type, &value)?,
+                    user_id,
+                )
+                .await?;
+            print_ok("write", json);
+        }
+        Command::Write2 {
+            connection,
+            session_id,
+            server_handle,
+            item_handle,
+            value_type,
+            value,
+            timestamp,
+            user_id,
+            json,
+        } => {
+            let session = session_for(connection, session_id).await?;
+            session
+                .write2(
+                    server_handle,
+                    item_handle,
+                    parse_value(value_type, &value)?,
+                    MxValue::string(timestamp),
+                    user_id,
+                )
+                .await?;
+            print_ok("write2", json);
+        }
+        Command::Smoke {
+            connection,
+            item,
+            client_name,
+            json,
+        } => {
+            let client = connect(connection).await?;
+            let session = client
+                .open_session(OpenSessionRequest {
+                    client_session_name: client_name.clone(),
+                    ..OpenSessionRequest::default()
+                })
+                .await?;
+            let result = async {
+                let server_handle = session.register(&client_name).await?;
+                let item_handle = session.add_item(server_handle, &item).await?;
+                session.advise(server_handle, item_handle).await?;
+                Ok::<_, Error>((server_handle, item_handle))
+            }
+            .await;
+            let close_result = session.close().await;
+            let (server_handle, item_handle) = result?;
+            close_result?;
+            if json {
+                println!(
+                    "{}",
+                    json!({
+                        "sessionId": session.id(),
+                        "serverHandle": server_handle,
+                        "itemHandle": item_handle,
+                        "closed": true,
+                    })
+                );
+            } else {
+                println!(
+                    "session {} registered server {server_handle}, item {item_handle}, closed",
+                    session.id()
+                );
+            }
+        }
+    }
+
+    Ok(())
+}
+
+async fn connect(connection: ConnectionArgs) -> Result<GatewayClient, Error> {
+    GatewayClient::connect(connection.options()).await
+}
+
+async fn session_for(
+    connection: ConnectionArgs,
+    session_id: String,
+) -> Result<mxgateway_client::Session, Error> {
+    let client = connect(connection).await?;
+    Ok(client.session(session_id))
 }
 
 fn print_version(use_json: bool) {
     if use_json {
-        println!(
+        println!("{}", version_json());
-            "{}",
-            json!({
-                "clientVersion": CLIENT_VERSION,
-                "gatewayProtocolVersion": GATEWAY_PROTOCOL_VERSION,
-                "workerProtocolVersion": WORKER_PROTOCOL_VERSION,
-            })
-        );
         return;
     }
 
@@ -50,6 +460,73 @@ fn print_version(use_json: bool) {
     println!("worker protocol {WORKER_PROTOCOL_VERSION}");
 }
 
+fn version_json() -> Value {
+    json!({
+        "clientVersion": CLIENT_VERSION,
+        "gatewayProtocolVersion": GATEWAY_PROTOCOL_VERSION,
+        "workerProtocolVersion": WORKER_PROTOCOL_VERSION,
+    })
+}
+
+fn print_command_reply(
+    operation: &str,
+    reply: &mxgateway_client::generated::mxaccess_gateway::v1::MxCommandReply,
+    use_json: bool,
+) {
+    if use_json {
+        println!(
+            "{}",
+            json!({
+                "operation": operation,
+                "sessionId": reply.session_id,
+                "correlationId": reply.correlation_id,
+                "kind": reply.kind,
+            })
+        );
+    } else {
+        println!("{operation} completed");
+    }
+}
+
+fn print_handle(name: &str, handle: i32, use_json: bool) {
+    if use_json {
+        println!("{}", json!({ name: handle }));
+    } else {
+        println!("{handle}");
+    }
+}
+
+fn print_ok(operation: &str, use_json: bool) {
+    if use_json {
+        println!("{}", json!({ "operation": operation, "ok": true }));
+    } else {
+        println!("{operation} completed");
+    }
+}
+
+fn parse_value(value_type: CliValueType, value: &str) -> Result<MxValue, Error> {
+    let parsed = match value_type {
+        CliValueType::Bool => MxValue::bool(parse_cli_value(value)?),
+        CliValueType::Int32 => MxValue::int32(parse_cli_value(value)?),
+        CliValueType::Int64 => MxValue::int64(parse_cli_value(value)?),
+        CliValueType::Float => MxValue::float(parse_cli_value(value)?),
+        CliValueType::Double => MxValue::double(parse_cli_value(value)?),
+        CliValueType::String => MxValue::string(value),
+    };
+    Ok(parsed)
+}
+
+fn parse_cli_value<T>(value: &str) -> Result<T, Error>
+where
+    T: std::str::FromStr,
+    T::Err: std::fmt::Display,
+{
+    value.parse::<T>().map_err(|source| Error::InvalidArgument {
+        name: "value".to_owned(),
+        detail: source.to_string(),
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use clap::Parser;
@@ -61,4 +538,31 @@ mod tests {
         let parsed = Cli::try_parse_from(["mxgw", "version", "--json"]);
         assert!(parsed.is_ok());
     }
+
+    #[test]
+    fn parses_write_command() {
+        let parsed = Cli::try_parse_from([
+            "mxgw",
+            "write",
+            "--session-id",
+            "session-1",
+            "--server-handle",
+            "12",
+            "--item-handle",
+            "34",
+            "--value-type",
+            "int32",
+            "--value",
+            "123",
+        ]);
+        assert!(parsed.is_ok());
+    }
+
+    #[test]
+    fn version_json_output_has_protocol_versions() {
+        let value = super::version_json();
+
+        assert_eq!(value["gatewayProtocolVersion"], 1);
+        assert_eq!(value["workerProtocolVersion"], 1);
+    }
 }

clients/rust/src/auth.rs

@@ -1,5 +1,9 @@
 use std::fmt;
 
+use tonic::metadata::MetadataValue;
+use tonic::service::Interceptor;
+use tonic::{Request, Status};
+
 /// API key wrapper that avoids exposing raw credentials in formatted output.
 #[derive(Clone, Eq, PartialEq)]
 pub struct ApiKey(String);
@@ -28,3 +32,56 @@ impl fmt::Display for ApiKey {
         formatter.write_str("<redacted>")
     }
 }
+
+/// `tonic` interceptor that attaches gateway API key metadata.
+#[derive(Clone, Debug, Default)]
+pub struct AuthInterceptor {
+    api_key: Option<ApiKey>,
+}
+
+impl AuthInterceptor {
+    pub fn new(api_key: Option<ApiKey>) -> Self {
+        Self { api_key }
+    }
+}
+
+impl Interceptor for AuthInterceptor {
+    fn call(&mut self, mut request: Request<()>) -> Result<Request<()>, Status> {
+        if let Some(api_key) = &self.api_key {
+            let header_value = format!("Bearer {}", api_key.expose_secret())
+                .parse::<MetadataValue<_>>()
+                .map_err(|_| Status::unauthenticated("invalid API key metadata"))?;
+            request.metadata_mut().insert("authorization", header_value);
+        }
+
+        Ok(request)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use tonic::service::Interceptor;
+    use tonic::Request;
+
+    use super::{ApiKey, AuthInterceptor};
+
+    #[test]
+    fn api_key_debug_is_redacted() {
+        let key = ApiKey::new("mxgw_visible_secret");
+
+        assert_eq!(format!("{key:?}"), "ApiKey(\"<redacted>\")");
+        assert!(!format!("{key:?}").contains("visible_secret"));
+        assert_eq!(key.to_string(), "<redacted>");
+    }
+
+    #[test]
+    fn interceptor_attaches_bearer_metadata() {
+        let mut interceptor = AuthInterceptor::new(Some(ApiKey::new("mxgw_fixture_secret")));
+        let request = interceptor.call(Request::new(())).unwrap();
+
+        assert_eq!(
+            request.metadata().get("authorization").unwrap(),
+            "Bearer mxgw_fixture_secret"
+        );
+    }
+}

clients/rust/src/client.rs

@@ -1,30 +1,123 @@
-use tonic::transport::Channel;
+use std::fs;
 
-use crate::error::Error;
+use tonic::codegen::InterceptedService;
+use tonic::transport::{Certificate, Channel, ClientTlsConfig};
+use tonic::Request;
+
+use crate::auth::AuthInterceptor;
+use crate::error::{ensure_command_success, Error};
 use crate::generated::mxaccess_gateway::v1::mx_access_gateway_client::MxAccessGatewayClient;
+use crate::generated::mxaccess_gateway::v1::{
+    CloseSessionReply, CloseSessionRequest, MxCommandReply, MxCommandRequest, MxEvent,
+    OpenSessionReply, OpenSessionRequest, StreamEventsRequest,
+};
 use crate::options::ClientOptions;
+use crate::session::Session;
+
+pub type RawGatewayClient = MxAccessGatewayClient<InterceptedService<Channel, AuthInterceptor>>;
+pub type EventStream =
+    std::pin::Pin<Box<dyn futures_core::Stream<Item = Result<MxEvent, Error>> + Send + 'static>>;
 
 /// Thin owner for the generated gateway client.
+#[derive(Clone)]
 pub struct GatewayClient {
-    inner: MxAccessGatewayClient<Channel>,
+    inner: RawGatewayClient,
+    call_timeout: std::time::Duration,
 }
 
 impl GatewayClient {
     pub async fn connect(options: ClientOptions) -> Result<Self, Error> {
-        let endpoint = Channel::from_shared(options.endpoint().to_owned()).map_err(|source| {
+        let mut endpoint =
+            Channel::from_shared(options.endpoint().to_owned()).map_err(|source| {
                 Error::InvalidEndpoint {
                     endpoint: options.endpoint().to_owned(),
                     detail: source.to_string(),
                 }
             })?;
+        endpoint = endpoint.connect_timeout(options.connect_timeout());
+
+        if !options.plaintext() {
+            let mut tls = ClientTlsConfig::new();
+            if let Some(server_name) = options.server_name_override() {
+                tls = tls.domain_name(server_name.to_owned());
+            }
+            if let Some(ca_file) = options.ca_file() {
+                let certificate = fs::read(ca_file).map_err(|source| Error::InvalidEndpoint {
+                    endpoint: options.endpoint().to_owned(),
+                    detail: format!("failed to read CA file {}: {source}", ca_file.display()),
+                })?;
+                tls = tls.ca_certificate(Certificate::from_pem(certificate));
+            }
+            endpoint = endpoint.tls_config(tls)?;
+        }
+
         let channel = endpoint.connect().await?;
+        let interceptor = AuthInterceptor::new(options.api_key().cloned());
 
         Ok(Self {
-            inner: MxAccessGatewayClient::new(channel),
+            inner: MxAccessGatewayClient::with_interceptor(channel, interceptor),
+            call_timeout: options.call_timeout(),
         })
     }
 
-    pub fn into_inner(self) -> MxAccessGatewayClient<Channel> {
+    pub fn raw_client(&mut self) -> &mut RawGatewayClient {
+        &mut self.inner
+    }
+
+    pub fn into_inner(self) -> RawGatewayClient {
         self.inner
     }
+
+    pub fn session(&self, session_id: impl Into<String>) -> Session {
+        Session::new(session_id, self.clone())
+    }
+
+    pub async fn open_session_raw(
+        &self,
+        request: OpenSessionRequest,
+    ) -> Result<OpenSessionReply, Error> {
+        let mut client = self.inner.clone();
+        let response = client.open_session(self.unary_request(request)).await?;
+        Ok(response.into_inner())
+    }
+
+    pub async fn open_session(&self, request: OpenSessionRequest) -> Result<Session, Error> {
+        let reply = self.open_session_raw(request).await?;
+        Ok(Session::new(reply.session_id, self.clone()))
+    }
+
+    pub async fn close_session_raw(
+        &self,
+        request: CloseSessionRequest,
+    ) -> Result<CloseSessionReply, Error> {
+        let mut client = self.inner.clone();
+        let response = client.close_session(self.unary_request(request)).await?;
+        Ok(response.into_inner())
+    }
+
+    pub async fn invoke_raw(&self, request: MxCommandRequest) -> Result<MxCommandReply, Error> {
+        let mut client = self.inner.clone();
+        let response = client.invoke(self.unary_request(request)).await?;
+        Ok(response.into_inner())
+    }
+
+    pub async fn invoke(&self, request: MxCommandRequest) -> Result<MxCommandReply, Error> {
+        ensure_command_success(self.invoke_raw(request).await?)
+    }
+
+    pub async fn stream_events(&self, request: StreamEventsRequest) -> Result<EventStream, Error> {
+        let mut client = self.inner.clone();
+        let response = client.stream_events(self.unary_request(request)).await?;
+        let stream = futures_util::StreamExt::map(response.into_inner(), |result| {
+            result.map_err(Error::from)
+        });
+
+        Ok(Box::pin(stream))
+    }
+
+    fn unary_request<T>(&self, message: T) -> Request<T> {
+        let mut request = Request::new(message);
+        request.set_timeout(self.call_timeout);
+        request
+    }
 }

clients/rust/src/error.rs

@@ -1,13 +1,161 @@
 use thiserror::Error as ThisError;
+use tonic::Code;
+
+use crate::generated::mxaccess_gateway::v1::{MxCommandReply, ProtocolStatusCode};
 
 #[derive(Debug, ThisError)]
 pub enum Error {
     #[error("invalid gateway endpoint `{endpoint}`: {detail}")]
     InvalidEndpoint { endpoint: String, detail: String },
 
+    #[error("invalid argument `{name}`: {detail}")]
+    InvalidArgument { name: String, detail: String },
+
     #[error("gateway transport error: {0}")]
     Transport(#[from] tonic::transport::Error),
 
+    #[error("authentication failed: {message}")]
+    Authentication {
+        message: String,
+        #[source]
+        status: Box<tonic::Status>,
+    },
+
+    #[error("authorization failed: {message}")]
+    Authorization {
+        message: String,
+        #[source]
+        status: Box<tonic::Status>,
+    },
+
+    #[error("gateway call timed out: {message}")]
+    Timeout {
+        message: String,
+        #[source]
+        status: Box<tonic::Status>,
+    },
+
+    #[error("gateway call cancelled: {message}")]
+    Cancelled {
+        message: String,
+        #[source]
+        status: Box<tonic::Status>,
+    },
+
     #[error("gateway status error: {0}")]
-    Status(#[from] tonic::Status),
+    Status(Box<tonic::Status>),
+
+    #[error("gateway command failed: {0}")]
+    Command(#[from] Box<CommandError>),
+}
+
+#[derive(Clone, Debug)]
+pub struct CommandError {
+    reply: MxCommandReply,
+}
+
+impl CommandError {
+    pub fn new(reply: MxCommandReply) -> Self {
+        Self { reply }
+    }
+
+    pub fn reply(&self) -> &MxCommandReply {
+        &self.reply
+    }
+
+    pub fn into_reply(self) -> MxCommandReply {
+        self.reply
+    }
+}
+
+impl std::fmt::Display for CommandError {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let status = self.reply.protocol_status.as_ref();
+        let code = status
+            .and_then(|status| ProtocolStatusCode::try_from(status.code).ok())
+            .unwrap_or(ProtocolStatusCode::Unspecified);
+        let message = status.map(|status| status.message.as_str()).unwrap_or("");
+
+        if message.is_empty() {
+            write!(formatter, "{code:?}")
+        } else {
+            write!(formatter, "{code:?}: {message}")
+        }
+    }
+}
+
+impl std::error::Error for CommandError {}
+
+impl From<tonic::Status> for Error {
+    fn from(status: tonic::Status) -> Self {
+        let message = redact_credentials(status.message());
+        match status.code() {
+            Code::Unauthenticated => Self::Authentication {
+                message,
+                status: Box::new(status),
+            },
+            Code::PermissionDenied => Self::Authorization {
+                message,
+                status: Box::new(status),
+            },
+            Code::DeadlineExceeded => Self::Timeout {
+                message,
+                status: Box::new(status),
+            },
+            Code::Cancelled => Self::Cancelled {
+                message,
+                status: Box::new(status),
+            },
+            _ => Self::Status(Box::new(status)),
+        }
+    }
+}
+
+pub fn ensure_command_success(reply: MxCommandReply) -> Result<MxCommandReply, Error> {
+    let code = reply
+        .protocol_status
+        .as_ref()
+        .and_then(|status| ProtocolStatusCode::try_from(status.code).ok())
+        .unwrap_or(ProtocolStatusCode::Unspecified);
+
+    if code == ProtocolStatusCode::Ok {
+        Ok(reply)
+    } else {
+        Err(Box::new(CommandError::new(reply)).into())
+    }
+}
+
+fn redact_credentials(message: &str) -> String {
+    message
+        .split_whitespace()
+        .map(|part| {
+            if part.starts_with("mxgw_") || part.eq_ignore_ascii_case("bearer") {
+                "<redacted>"
+            } else {
+                part
+            }
+        })
+        .collect::<Vec<_>>()
+        .join(" ")
+}
+
+#[cfg(test)]
+mod tests {
+    use tonic::{Code, Status};
+
+    use super::Error;
+
+    #[test]
+    fn classifies_authentication_status() {
+        let error = Error::from(Status::new(
+            Code::Unauthenticated,
+            "invalid API key mxgw_visible_secret",
+        ));
+
+        let message = error.to_string();
+
+        assert!(matches!(error, Error::Authentication { .. }));
+        assert!(message.contains("<redacted>"));
+        assert!(!message.contains("visible_secret"));
+    }
 }

clients/rust/src/lib.rs

@@ -13,9 +13,10 @@ pub mod session;
 pub mod value;
 pub mod version;
 
-pub use auth::ApiKey;
+pub use auth::{ApiKey, AuthInterceptor};
-pub use client::GatewayClient;
+pub use client::{EventStream, GatewayClient};
-pub use error::Error;
+pub use error::{CommandError, Error};
 pub use options::ClientOptions;
 pub use session::Session;
+pub use value::{MxArrayProjection, MxArrayValue, MxStatus, MxValue, MxValueProjection};
 pub use version::{CLIENT_VERSION, GATEWAY_PROTOCOL_VERSION, WORKER_PROTOCOL_VERSION};

clients/rust/src/options.rs

@@ -1,4 +1,6 @@
 use std::fmt;
+use std::path::PathBuf;
+use std::time::Duration;
 
 use crate::auth::ApiKey;
 
@@ -7,6 +9,10 @@ pub struct ClientOptions {
     endpoint: String,
     api_key: Option<ApiKey>,
     plaintext: bool,
+    ca_file: Option<PathBuf>,
+    server_name_override: Option<String>,
+    connect_timeout: Duration,
+    call_timeout: Duration,
 }
 
 impl ClientOptions {
@@ -15,6 +21,10 @@ impl ClientOptions {
             endpoint: endpoint.into(),
             api_key: None,
             plaintext: true,
+            ca_file: None,
+            server_name_override: None,
+            connect_timeout: Duration::from_secs(10),
+            call_timeout: Duration::from_secs(30),
         }
     }
 
@@ -23,6 +33,31 @@ impl ClientOptions {
         self
     }
 
+    pub fn with_plaintext(mut self, plaintext: bool) -> Self {
+        self.plaintext = plaintext;
+        self
+    }
+
+    pub fn with_ca_file(mut self, ca_file: impl Into<PathBuf>) -> Self {
+        self.ca_file = Some(ca_file.into());
+        self
+    }
+
+    pub fn with_server_name_override(mut self, server_name_override: impl Into<String>) -> Self {
+        self.server_name_override = Some(server_name_override.into());
+        self
+    }
+
+    pub fn with_connect_timeout(mut self, connect_timeout: Duration) -> Self {
+        self.connect_timeout = connect_timeout;
+        self
+    }
+
+    pub fn with_call_timeout(mut self, call_timeout: Duration) -> Self {
+        self.call_timeout = call_timeout;
+        self
+    }
+
     pub fn endpoint(&self) -> &str {
         &self.endpoint
     }
@@ -34,6 +69,22 @@ impl ClientOptions {
     pub fn plaintext(&self) -> bool {
         self.plaintext
     }
+
+    pub fn ca_file(&self) -> Option<&PathBuf> {
+        self.ca_file.as_ref()
+    }
+
+    pub fn server_name_override(&self) -> Option<&str> {
+        self.server_name_override.as_deref()
+    }
+
+    pub fn connect_timeout(&self) -> Duration {
+        self.connect_timeout
+    }
+
+    pub fn call_timeout(&self) -> Duration {
+        self.call_timeout
+    }
 }
 
 impl Default for ClientOptions {
@@ -49,6 +100,27 @@ impl fmt::Debug for ClientOptions {
             .field("endpoint", &self.endpoint)
             .field("api_key", &self.api_key.as_ref().map(|_| "<redacted>"))
             .field("plaintext", &self.plaintext)
+            .field("ca_file", &self.ca_file)
+            .field("server_name_override", &self.server_name_override)
+            .field("connect_timeout", &self.connect_timeout)
+            .field("call_timeout", &self.call_timeout)
             .finish()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::ClientOptions;
+    use crate::auth::ApiKey;
+
+    #[test]
+    fn debug_redacts_api_key() {
+        let options =
+            ClientOptions::new("http://localhost:5000").with_api_key(ApiKey::new("mxgw_secret"));
+
+        let debug = format!("{options:?}");
+
+        assert!(debug.contains("<redacted>"));
+        assert!(!debug.contains("mxgw_secret"));
+    }
+}

clients/rust/src/session.rs

@@ -1,15 +1,234 @@
+use crate::client::{EventStream, GatewayClient};
+use crate::error::Error;
+use crate::generated::mxaccess_gateway::v1::mx_command::Payload;
+use crate::generated::mxaccess_gateway::v1::mx_command_reply;
+use crate::generated::mxaccess_gateway::v1::{
+    AddItem2Command, AddItemCommand, AdviseCommand, CloseSessionRequest, MxCommand, MxCommandKind,
+    MxCommandReply, MxCommandRequest, MxValue as ProtoMxValue, OpenSessionRequest, RegisterCommand,
+    StreamEventsRequest, Write2Command, WriteCommand,
+};
+use crate::value::MxValue;
+
 /// Session identifier returned by the gateway.
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone)]
 pub struct Session {
     id: String,
+    client: GatewayClient,
 }
 
 impl Session {
-    pub fn new(id: impl Into<String>) -> Self {
+    pub(crate) fn new(id: impl Into<String>, client: GatewayClient) -> Self {
-        Self { id: id.into() }
+        Self {
+            id: id.into(),
+            client,
+        }
     }
 
     pub fn id(&self) -> &str {
         &self.id
     }
+
+    pub async fn open(client: GatewayClient, client_session_name: &str) -> Result<Self, Error> {
+        client
+            .open_session(OpenSessionRequest {
+                client_session_name: client_session_name.to_owned(),
+                ..OpenSessionRequest::default()
+            })
+            .await
+    }
+
+    pub async fn close(&self) -> Result<(), Error> {
+        self.client
+            .close_session_raw(CloseSessionRequest {
+                session_id: self.id.clone(),
+                client_correlation_id: "rust-client-close-session".to_owned(),
+            })
+            .await?;
+        Ok(())
+    }
+
+    pub async fn register(&self, client_name: &str) -> Result<i32, Error> {
+        let reply = self
+            .invoke(
+                MxCommandKind::Register,
+                Payload::Register(RegisterCommand {
+                    client_name: client_name.to_owned(),
+                }),
+            )
+            .await?;
+
+        Ok(register_server_handle(&reply))
+    }
+
+    pub async fn add_item(&self, server_handle: i32, item_definition: &str) -> Result<i32, Error> {
+        let reply = self
+            .invoke(
+                MxCommandKind::AddItem,
+                Payload::AddItem(AddItemCommand {
+                    server_handle,
+                    item_definition: item_definition.to_owned(),
+                }),
+            )
+            .await?;
+
+        Ok(add_item_handle(&reply))
+    }
+
+    pub async fn add_item2(
+        &self,
+        server_handle: i32,
+        item_definition: &str,
+        item_context: &str,
+    ) -> Result<i32, Error> {
+        let reply = self
+            .invoke(
+                MxCommandKind::AddItem2,
+                Payload::AddItem2(AddItem2Command {
+                    server_handle,
+                    item_definition: item_definition.to_owned(),
+                    item_context: item_context.to_owned(),
+                }),
+            )
+            .await?;
+
+        Ok(add_item2_handle(&reply))
+    }
+
+    pub async fn advise(&self, server_handle: i32, item_handle: i32) -> Result<(), Error> {
+        self.invoke(
+            MxCommandKind::Advise,
+            Payload::Advise(AdviseCommand {
+                server_handle,
+                item_handle,
+            }),
+        )
+        .await?;
+        Ok(())
+    }
+
+    pub async fn write(
+        &self,
+        server_handle: i32,
+        item_handle: i32,
+        value: MxValue,
+        user_id: i32,
+    ) -> Result<(), Error> {
+        self.invoke(
+            MxCommandKind::Write,
+            Payload::Write(WriteCommand {
+                server_handle,
+                item_handle,
+                value: Some(value.into_proto()),
+                user_id,
+            }),
+        )
+        .await?;
+        Ok(())
+    }
+
+    pub async fn write2(
+        &self,
+        server_handle: i32,
+        item_handle: i32,
+        value: MxValue,
+        timestamp_value: MxValue,
+        user_id: i32,
+    ) -> Result<(), Error> {
+        self.invoke(
+            MxCommandKind::Write2,
+            Payload::Write2(Write2Command {
+                server_handle,
+                item_handle,
+                value: Some(value.into_proto()),
+                timestamp_value: Some(timestamp_value.into_proto()),
+                user_id,
+            }),
+        )
+        .await?;
+        Ok(())
+    }
+
+    pub async fn events(&self) -> Result<EventStream, Error> {
+        self.events_after(0).await
+    }
+
+    pub async fn events_after(&self, after_worker_sequence: u64) -> Result<EventStream, Error> {
+        self.client
+            .stream_events(StreamEventsRequest {
+                session_id: self.id.clone(),
+                after_worker_sequence,
+            })
+            .await
+    }
+
+    pub async fn invoke_raw(
+        &self,
+        kind: MxCommandKind,
+        payload: Payload,
+    ) -> Result<MxCommandReply, Error> {
+        self.client
+            .invoke_raw(self.command_request(kind, payload))
+            .await
+    }
+
+    pub async fn invoke(
+        &self,
+        kind: MxCommandKind,
+        payload: Payload,
+    ) -> Result<MxCommandReply, Error> {
+        self.client
+            .invoke(self.command_request(kind, payload))
+            .await
+    }
+
+    fn command_request(&self, kind: MxCommandKind, payload: Payload) -> MxCommandRequest {
+        MxCommandRequest {
+            session_id: self.id.clone(),
+            client_correlation_id: format!("rust-client-{}", kind.as_str_name()),
+            command: Some(MxCommand {
+                kind: kind as i32,
+                payload: Some(payload),
+            }),
+        }
+    }
+}
+
+fn register_server_handle(reply: &MxCommandReply) -> i32 {
+    match reply.payload.as_ref() {
+        Some(mx_command_reply::Payload::Register(register)) => register.server_handle,
+        _ => reply
+            .return_value
+            .as_ref()
+            .and_then(int32_reply_value)
+            .unwrap_or_default(),
+    }
+}
+
+fn add_item_handle(reply: &MxCommandReply) -> i32 {
+    match reply.payload.as_ref() {
+        Some(mx_command_reply::Payload::AddItem(add_item)) => add_item.item_handle,
+        _ => reply
+            .return_value
+            .as_ref()
+            .and_then(int32_reply_value)
+            .unwrap_or_default(),
+    }
+}
+
+fn add_item2_handle(reply: &MxCommandReply) -> i32 {
+    match reply.payload.as_ref() {
+        Some(mx_command_reply::Payload::AddItem2(add_item)) => add_item.item_handle,
+        _ => reply
+            .return_value
+            .as_ref()
+            .and_then(int32_reply_value)
+            .unwrap_or_default(),
+    }
+}
+
+fn int32_reply_value(value: &ProtoMxValue) -> Option<i32> {
+    match value.kind.as_ref()? {
+        crate::generated::mxaccess_gateway::v1::mx_value::Kind::Int32Value(value) => Some(*value),
+        _ => None,
+    }
 }

clients/rust/src/value.rs

@@ -1,9 +1,239 @@
-use crate::generated::mxaccess_gateway::v1::MxValue;
+use crate::generated::mxaccess_gateway::v1::mx_array::Values;
+use crate::generated::mxaccess_gateway::v1::mx_value::Kind;
+use crate::generated::mxaccess_gateway::v1::{
+    BoolArray, DoubleArray, FloatArray, Int32Array, Int64Array, MxArray, MxDataType,
+    MxStatusCategory, MxStatusProxy, MxStatusSource, MxValue as ProtoMxValue, RawArray,
+    StringArray, TimestampArray,
+};
 
-pub fn int32_value(value: i32) -> MxValue {
+#[derive(Clone, Debug, PartialEq)]
-    MxValue {
+pub struct MxValue {
-        data_type: crate::generated::mxaccess_gateway::v1::MxDataType::Integer as i32,
+    raw: ProtoMxValue,
-        kind: Some(crate::generated::mxaccess_gateway::v1::mx_value::Kind::Int32Value(value)),
+    projection: MxValueProjection,
-        ..MxValue::default()
+}
+
+impl MxValue {
+    pub fn from_proto(raw: ProtoMxValue) -> Self {
+        let projection = MxValueProjection::from_proto(&raw);
+        Self { raw, projection }
+    }
+
+    pub fn bool(value: bool) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::Boolean as i32,
+            variant_type: "VT_BOOL".to_owned(),
+            kind: Some(Kind::BoolValue(value)),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn int32(value: i32) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::Integer as i32,
+            variant_type: "VT_I4".to_owned(),
+            kind: Some(Kind::Int32Value(value)),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn int64(value: i64) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::Integer as i32,
+            variant_type: "VT_I8".to_owned(),
+            kind: Some(Kind::Int64Value(value)),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn float(value: f32) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::Float as i32,
+            variant_type: "VT_R4".to_owned(),
+            kind: Some(Kind::FloatValue(value)),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn double(value: f64) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::Double as i32,
+            variant_type: "VT_R8".to_owned(),
+            kind: Some(Kind::DoubleValue(value)),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn string(value: impl Into<String>) -> Self {
+        Self::from_proto(ProtoMxValue {
+            data_type: MxDataType::String as i32,
+            variant_type: "VT_BSTR".to_owned(),
+            kind: Some(Kind::StringValue(value.into())),
+            ..ProtoMxValue::default()
+        })
+    }
+
+    pub fn raw(&self) -> &ProtoMxValue {
+        &self.raw
+    }
+
+    pub fn projection(&self) -> &MxValueProjection {
+        &self.projection
+    }
+
+    pub fn into_proto(self) -> ProtoMxValue {
+        self.raw
+    }
+}
+
+impl From<MxValue> for ProtoMxValue {
+    fn from(value: MxValue) -> Self {
+        value.into_proto()
+    }
+}
+
+impl From<ProtoMxValue> for MxValue {
+    fn from(value: ProtoMxValue) -> Self {
+        Self::from_proto(value)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum MxValueProjection {
+    Unset,
+    Null,
+    Bool(bool),
+    Int32(i32),
+    Int64(i64),
+    Float(f32),
+    Double(f64),
+    String(String),
+    Timestamp(prost_types::Timestamp),
+    Array(MxArrayValue),
+    Raw(Vec<u8>),
+}
+
+impl MxValueProjection {
+    fn from_proto(value: &ProtoMxValue) -> Self {
+        if value.is_null {
+            return Self::Null;
+        }
+
+        match value.kind.as_ref() {
+            Some(Kind::BoolValue(value)) => Self::Bool(*value),
+            Some(Kind::Int32Value(value)) => Self::Int32(*value),
+            Some(Kind::Int64Value(value)) => Self::Int64(*value),
+            Some(Kind::FloatValue(value)) => Self::Float(*value),
+            Some(Kind::DoubleValue(value)) => Self::Double(*value),
+            Some(Kind::StringValue(value)) => Self::String(value.clone()),
+            Some(Kind::TimestampValue(value)) => Self::Timestamp(*value),
+            Some(Kind::ArrayValue(value)) => Self::Array(MxArrayValue::from_proto(value.clone())),
+            Some(Kind::RawValue(value)) => Self::Raw(value.clone()),
+            None => Self::Unset,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct MxArrayValue {
+    raw: MxArray,
+    projection: MxArrayProjection,
+}
+
+impl MxArrayValue {
+    pub fn from_proto(raw: MxArray) -> Self {
+        let projection = MxArrayProjection::from_proto(&raw);
+        Self { raw, projection }
+    }
+
+    pub fn string(values: Vec<String>) -> Self {
+        Self::from_proto(MxArray {
+            element_data_type: MxDataType::String as i32,
+            variant_type: "VT_ARRAY|VT_BSTR".to_owned(),
+            dimensions: vec![values.len() as u32],
+            values: Some(Values::StringValues(StringArray { values })),
+            ..MxArray::default()
+        })
+    }
+
+    pub fn raw(&self) -> &MxArray {
+        &self.raw
+    }
+
+    pub fn projection(&self) -> &MxArrayProjection {
+        &self.projection
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum MxArrayProjection {
+    Unset,
+    Bool(Vec<bool>),
+    Int32(Vec<i32>),
+    Int64(Vec<i64>),
+    Float(Vec<f32>),
+    Double(Vec<f64>),
+    String(Vec<String>),
+    Timestamp(Vec<prost_types::Timestamp>),
+    Raw(Vec<Vec<u8>>),
+}
+
+impl MxArrayProjection {
+    fn from_proto(array: &MxArray) -> Self {
+        match array.values.as_ref() {
+            Some(Values::BoolValues(BoolArray { values })) => Self::Bool(values.clone()),
+            Some(Values::Int32Values(Int32Array { values })) => Self::Int32(values.clone()),
+            Some(Values::Int64Values(Int64Array { values })) => Self::Int64(values.clone()),
+            Some(Values::FloatValues(FloatArray { values })) => Self::Float(values.clone()),
+            Some(Values::DoubleValues(DoubleArray { values })) => Self::Double(values.clone()),
+            Some(Values::StringValues(StringArray { values })) => Self::String(values.clone()),
+            Some(Values::TimestampValues(TimestampArray { values })) => {
+                Self::Timestamp(values.clone())
+            }
+            Some(Values::RawValues(RawArray { values })) => Self::Raw(values.clone()),
+            None => Self::Unset,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct MxStatus {
+    raw: MxStatusProxy,
+}
+
+impl MxStatus {
+    pub fn from_proto(raw: MxStatusProxy) -> Self {
+        Self { raw }
+    }
+
+    pub fn raw(&self) -> &MxStatusProxy {
+        &self.raw
+    }
+
+    pub fn success(&self) -> i32 {
+        self.raw.success
+    }
+
+    pub fn category(&self) -> Option<MxStatusCategory> {
+        MxStatusCategory::try_from(self.raw.category).ok()
+    }
+
+    pub fn detected_by(&self) -> Option<MxStatusSource> {
+        MxStatusSource::try_from(self.raw.detected_by).ok()
+    }
+
+    pub fn detail(&self) -> i32 {
+        self.raw.detail
+    }
+
+    pub fn raw_category(&self) -> i32 {
+        self.raw.raw_category
+    }
+
+    pub fn raw_detected_by(&self) -> i32 {
+        self.raw.raw_detected_by
+    }
+
+    pub fn diagnostic_text(&self) -> &str {
+        &self.raw.diagnostic_text
     }
 }

clients/rust/tests/client_behavior.rs

@@ -0,0 +1,398 @@
+use std::pin::Pin;
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    Arc,
+};
+use std::task::{Context, Poll};
+use std::time::Duration;
+
+use futures_core::Stream;
+use futures_util::StreamExt;
+use mxgateway_client::generated::mxaccess_gateway::v1::mx_access_gateway_server::{
+    MxAccessGateway, MxAccessGatewayServer,
+};
+use mxgateway_client::generated::mxaccess_gateway::v1::mx_command_reply;
+use mxgateway_client::generated::mxaccess_gateway::v1::mx_value::Kind;
+use mxgateway_client::generated::mxaccess_gateway::v1::{
+    AddItemReply, CloseSessionReply, CloseSessionRequest, MxCommandKind, MxCommandReply,
+    MxDataType, MxEvent, MxEventFamily, MxStatusCategory, MxStatusProxy, MxStatusSource, MxValue,
+    OpenSessionReply, OpenSessionRequest, ProtocolStatus, ProtocolStatusCode, SessionState,
+    StreamEventsRequest,
+};
+use mxgateway_client::{
+    ApiKey, ClientOptions, CommandError, Error, GatewayClient, MxStatus, MxValue as ClientMxValue,
+    MxValueProjection,
+};
+use serde_json::Value;
+use tokio::net::TcpListener;
+use tokio::sync::{mpsc, Mutex};
+use tokio_stream::wrappers::{ReceiverStream, TcpListenerStream};
+use tonic::transport::Server;
+use tonic::{Request, Response, Status};
+
+#[tokio::test]
+async fn fake_server_receives_bearer_metadata_and_raw_client_is_reachable() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let mut client = GatewayClient::connect(
+        ClientOptions::new(endpoint).with_api_key(ApiKey::new("mxgw_fixture_secret")),
+    )
+    .await
+    .unwrap();
+
+    let _raw = client.raw_client();
+    let session = client
+        .open_session(OpenSessionRequest {
+            client_session_name: "rust-test".to_owned(),
+            ..OpenSessionRequest::default()
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(session.id(), "session-fixture");
+    assert_eq!(
+        state.authorization.lock().await.as_deref(),
+        Some("Bearer mxgw_fixture_secret")
+    );
+}
+
+#[tokio::test]
+async fn session_helpers_build_commands_and_preserve_command_errors() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let item_handle = session.add_item(12, "Plant.Area.Tag").await.unwrap();
+
+    assert_eq!(item_handle, 34);
+    let last_command = state.last_command_kind.lock().await;
+    assert_eq!(*last_command, Some(MxCommandKind::AddItem as i32));
+    drop(last_command);
+
+    let error = session
+        .write(12, 34, ClientMxValue::int32(123), 0)
+        .await
+        .unwrap_err();
+    let Error::Command(error) = error else {
+        panic!("write failure should preserve the raw command reply: {error:?}");
+    };
+    assert_eq!(
+        error.reply().protocol_status.as_ref().unwrap().code,
+        ProtocolStatusCode::MxaccessFailure as i32
+    );
+    assert_eq!(error.reply().hresult, Some(-2147220992));
+    assert_eq!(error.reply().statuses.len(), 2);
+}
+
+#[tokio::test]
+async fn event_stream_preserves_order_and_drop_cancels_server_stream() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+
+    let mut stream = client
+        .stream_events(StreamEventsRequest {
+            session_id: "session-fixture".to_owned(),
+            after_worker_sequence: 0,
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(stream.next().await.unwrap().unwrap().worker_sequence, 1);
+    assert_eq!(stream.next().await.unwrap().unwrap().worker_sequence, 2);
+
+    drop(stream);
+    for _ in 0..20 {
+        if state.stream_dropped.load(Ordering::SeqCst) {
+            return;
+        }
+        tokio::time::sleep(Duration::from_millis(25)).await;
+    }
+
+    assert!(state.stream_dropped.load(Ordering::SeqCst));
+}
+
+#[test]
+fn value_conversion_fixtures_keep_typed_projection_and_raw_metadata() {
+    let fixture = behavior_fixture("values/value-conversion-cases.json");
+    let cases = fixture["cases"].as_array().unwrap();
+
+    let int64_case = case_by_id(cases, "int64.large");
+    let int64_value = ClientMxValue::from_proto(MxValue {
+        data_type: MxDataType::Integer as i32,
+        variant_type: "VT_I8".to_owned(),
+        kind: Some(Kind::Int64Value(
+            int64_case["value"]["int64Value"]
+                .as_str()
+                .unwrap()
+                .parse()
+                .unwrap(),
+        )),
+        ..MxValue::default()
+    });
+    assert_eq!(
+        int64_value.projection(),
+        &MxValueProjection::Int64(9_223_372_036_854_770_000)
+    );
+
+    let raw_case = case_by_id(cases, "raw-fallback.variant");
+    let raw_value = ClientMxValue::from_proto(MxValue {
+        data_type: MxDataType::Unknown as i32,
+        variant_type: "VT_RECORD".to_owned(),
+        raw_diagnostic: raw_case["value"]["rawDiagnostic"]
+            .as_str()
+            .unwrap()
+            .to_owned(),
+        raw_data_type: raw_case["value"]["rawDataType"].as_i64().unwrap() as i32,
+        kind: Some(Kind::RawValue(vec![1, 2, 3, 4, 5])),
+        ..MxValue::default()
+    });
+    assert_eq!(
+        raw_value.projection(),
+        &MxValueProjection::Raw(vec![1, 2, 3, 4, 5])
+    );
+    assert_eq!(raw_value.raw().raw_data_type, 32767);
+    assert!(raw_value.raw().raw_diagnostic.contains("No lossless"));
+}
+
+#[test]
+fn status_conversion_fixtures_preserve_raw_fields() {
+    let fixture = behavior_fixture("statuses/status-conversion-cases.json");
+    let cases = fixture["cases"].as_array().unwrap();
+    let raw_case = case_by_id(cases, "raw-unknown-category");
+    let status = MxStatus::from_proto(MxStatusProxy {
+        success: raw_case["status"]["success"].as_i64().unwrap() as i32,
+        category: MxStatusCategory::Unknown as i32,
+        detected_by: MxStatusSource::Unknown as i32,
+        detail: raw_case["status"]["detail"].as_i64().unwrap() as i32,
+        raw_category: raw_case["status"]["rawCategory"].as_i64().unwrap() as i32,
+        raw_detected_by: raw_case["status"]["rawDetectedBy"].as_i64().unwrap() as i32,
+        diagnostic_text: raw_case["status"]["diagnosticText"]
+            .as_str()
+            .unwrap()
+            .to_owned(),
+    });
+
+    assert_eq!(status.success(), 0);
+    assert_eq!(status.category(), Some(MxStatusCategory::Unknown));
+    assert_eq!(status.raw_category(), 99);
+    assert_eq!(status.raw_detected_by(), 77);
+    assert!(status.diagnostic_text().contains("preserved"));
+}
+
+#[test]
+fn authentication_and_authorization_statuses_are_distinct_and_redacted() {
+    let auth = Error::from(Status::unauthenticated(
+        "invalid API key mxgw_visible_secret",
+    ));
+    let denied = Error::from(Status::permission_denied("missing scope mxaccess.write"));
+
+    assert!(matches!(auth, Error::Authentication { .. }));
+    assert!(matches!(denied, Error::Authorization { .. }));
+    assert!(!auth.to_string().contains("visible_secret"));
+}
+
+#[test]
+fn command_error_display_keeps_raw_reply_accessible() {
+    let reply = mxaccess_failure_reply();
+    let error = CommandError::new(reply.clone());
+
+    assert_eq!(error.reply().hresult, Some(-2147220992));
+    assert!(error.to_string().contains("MxaccessFailure"));
+}
+
+#[derive(Default)]
+struct FakeState {
+    authorization: Mutex<Option<String>>,
+    last_command_kind: Mutex<Option<i32>>,
+    stream_dropped: Arc<AtomicBool>,
+}
+
+#[derive(Clone)]
+struct FakeGateway {
+    state: Arc<FakeState>,
+}
+
+#[tonic::async_trait]
+impl MxAccessGateway for FakeGateway {
+    async fn open_session(
+        &self,
+        request: Request<OpenSessionRequest>,
+    ) -> Result<Response<OpenSessionReply>, Status> {
+        *self.state.authorization.lock().await = request
+            .metadata()
+            .get("authorization")
+            .and_then(|value| value.to_str().ok())
+            .map(str::to_owned);
+
+        Ok(Response::new(OpenSessionReply {
+            session_id: "session-fixture".to_owned(),
+            backend_name: "fake".to_owned(),
+            worker_process_id: 1234,
+            worker_protocol_version: 1,
+            gateway_protocol_version: 1,
+            protocol_status: Some(ok_status("opened")),
+            ..OpenSessionReply::default()
+        }))
+    }
+
+    async fn close_session(
+        &self,
+        request: Request<CloseSessionRequest>,
+    ) -> Result<Response<CloseSessionReply>, Status> {
+        Ok(Response::new(CloseSessionReply {
+            session_id: request.into_inner().session_id,
+            final_state: SessionState::Closed as i32,
+            protocol_status: Some(ok_status("closed")),
+        }))
+    }
+
+    async fn invoke(
+        &self,
+        request: Request<mxgateway_client::generated::mxaccess_gateway::v1::MxCommandRequest>,
+    ) -> Result<Response<MxCommandReply>, Status> {
+        let request = request.into_inner();
+        let kind = request
+            .command
+            .as_ref()
+            .map(|command| command.kind)
+            .unwrap_or_default();
+        *self.state.last_command_kind.lock().await = Some(kind);
+
+        if kind == MxCommandKind::Write as i32 {
+            return Ok(Response::new(mxaccess_failure_reply()));
+        }
+
+        Ok(Response::new(MxCommandReply {
+            session_id: request.session_id,
+            correlation_id: "fake-correlation".to_owned(),
+            kind,
+            protocol_status: Some(ok_status("command ok")),
+            payload: Some(mx_command_reply::Payload::AddItem(AddItemReply {
+                item_handle: 34,
+            })),
+            ..MxCommandReply::default()
+        }))
+    }
+
+    type StreamEventsStream = DropAwareStream;
+
+    async fn stream_events(
+        &self,
+        _request: Request<StreamEventsRequest>,
+    ) -> Result<Response<Self::StreamEventsStream>, Status> {
+        let (sender, receiver) = mpsc::channel(4);
+        sender.send(Ok(event(1))).await.unwrap();
+        sender.send(Ok(event(2))).await.unwrap();
+
+        Ok(Response::new(DropAwareStream {
+            inner: ReceiverStream::new(receiver),
+            dropped: self.state.stream_dropped.clone(),
+        }))
+    }
+}
+
+struct DropAwareStream {
+    inner: ReceiverStream<Result<MxEvent, Status>>,
+    dropped: Arc<AtomicBool>,
+}
+
+impl Stream for DropAwareStream {
+    type Item = Result<MxEvent, Status>;
+
+    fn poll_next(mut self: Pin<&mut Self>, context: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        Pin::new(&mut self.inner).poll_next(context)
+    }
+}
+
+impl Drop for DropAwareStream {
+    fn drop(&mut self) {
+        self.dropped.store(true, Ordering::SeqCst);
+    }
+}
+
+async fn spawn_fake_gateway(state: Arc<FakeState>) -> String {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let address = listener.local_addr().unwrap();
+    let incoming = TcpListenerStream::new(listener);
+    let service = MxAccessGatewayServer::new(FakeGateway { state });
+    tokio::spawn(async move {
+        Server::builder()
+            .add_service(service)
+            .serve_with_incoming(incoming)
+            .await
+            .unwrap();
+    });
+
+    format!("http://{address}")
+}
+
+fn ok_status(message: &str) -> ProtocolStatus {
+    ProtocolStatus {
+        code: ProtocolStatusCode::Ok as i32,
+        message: message.to_owned(),
+    }
+}
+
+fn mxaccess_failure_reply() -> MxCommandReply {
+    MxCommandReply {
+        session_id: "session-fixture".to_owned(),
+        correlation_id: "gateway-correlation-write-1".to_owned(),
+        kind: MxCommandKind::Write as i32,
+        protocol_status: Some(ProtocolStatus {
+            code: ProtocolStatusCode::MxaccessFailure as i32,
+            message: "MXAccess rejected the write.".to_owned(),
+        }),
+        hresult: Some(-2147220992),
+        statuses: vec![
+            MxStatusProxy {
+                success: 0,
+                category: MxStatusCategory::SecurityError as i32,
+                detected_by: MxStatusSource::RespondingLmx as i32,
+                detail: 321,
+                raw_category: 8,
+                raw_detected_by: 3,
+                diagnostic_text: "Write denied by provider security.".to_owned(),
+            },
+            MxStatusProxy {
+                success: 0,
+                category: MxStatusCategory::OperationalError as i32,
+                detected_by: MxStatusSource::RespondingNmx as i32,
+                detail: 902,
+                raw_category: 7,
+                raw_detected_by: 5,
+                diagnostic_text: "Provider rejected the item state.".to_owned(),
+            },
+        ],
+        ..MxCommandReply::default()
+    }
+}
+
+fn event(sequence: u64) -> MxEvent {
+    MxEvent {
+        family: MxEventFamily::OnDataChange as i32,
+        session_id: "session-fixture".to_owned(),
+        worker_sequence: sequence,
+        ..MxEvent::default()
+    }
+}
+
+fn behavior_fixture(path: &str) -> Value {
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("../proto/fixtures/behavior")
+        .join(path);
+    let data = std::fs::read_to_string(&path).unwrap();
+    serde_json::from_str(&data).unwrap()
+}
+
+fn case_by_id<'a>(cases: &'a [Value], id: &str) -> &'a Value {
+    cases
+        .iter()
+        .find(|case| case["id"].as_str() == Some(id))
+        .unwrap_or_else(|| panic!("missing fixture case {id}"))
+}