fix(test): sandbox status can be 'ok' or 'warn' depending on kernel namespaces

The /sandbox status check returns 'ok' on systems with working user
namespaces and 'warn' on systems without them (#731). The test was
only accepting 'warn', which caused failures on systems with namespaces.
This changes the test to accept both values, matching the kernel's
actual sandbox support.

Fixes the failure: direct_resume_safe_slash_commands_route_to_local_json_actions_831

.envrc

@@ -0,0 +1 @@
+use flake

.github/workflows/rust-ci.yml

@@ -25,6 +25,8 @@ on:
       - tests/test_roadmap_helpers.py
       - docs/**
       - rust/**
+      - flake.nix
+      - .envrc
   pull_request:
     branches:
       - main
@@ -47,6 +49,8 @@ on:
       - tests/test_roadmap_helpers.py
       - docs/**
       - rust/**
+      - flake.nix
+      - .envrc
   workflow_dispatch:
 
 concurrency:

.gitignore

@@ -15,3 +15,7 @@ status-help.txt
 .port_sessions/
 # Local agent session state
 .gjc/
+# Nix build outputs and direnv
+.envrc.local
+result
+result-*

docs/nix-development.md

@@ -0,0 +1,203 @@
+# Nix flake development environment
+
+This repository includes a **`flake.nix`** for reproducible development environments on NixOS and systems with Nix installed.
+
+## Prerequisites
+
+- **Nix** (version 2.4 or later with flakes support enabled)
+- **direnv** (optional, for automatic environment loading via `.envrc`)
+
+To verify Nix is installed and flakes are enabled:
+
+```bash
+nix --version
+nix flake --help
+```
+
+If flakes are not enabled, add this to your `~/.config/nix/nix.conf`:
+
+```
+experimental-features = nix-command flakes
+```
+
+## Quick start
+
+### Enter the development environment
+
+**Option 1: Using `nix flake`** (without direnv)
+
+```bash
+nix flake update              # Update inputs (optional, pins nixpkgs)
+nix develop                    # Enter default dev shell
+nix develop .#full             # Enter full dev shell with extra tools
+exit                           # Leave the shell
+```
+
+**Option 2: Using direnv** (automatic on directory entry)
+
+```bash
+direnv allow                   # Trust the .envrc file (one-time setup)
+cd .                           # Direnv reloads the flake automatically
+```
+
+When you leave the repository directory, the environment is automatically unloaded.
+
+## Development shells
+
+The flake provides two development shells:
+
+### `default` (minimal)
+
+```bash
+nix develop
+```
+
+Includes:
+- Rust (stable, latest)
+- Rust source code (`rust-src`)
+- `cargo-edit` (dependency management helpers)
+- `cargo-expand` (macro expansion tool)
+- `cargo-watch` (file watcher for incremental builds)
+- Build tools: `pkg-config`, `openssl`, `git`, `ca-certificates`
+
+### `full` (with extra tooling)
+
+```bash
+nix develop .#full
+```
+
+Includes everything from `default` plus:
+- `clippy` (linter)
+- `rustfmt` (code formatter)
+- `mold` (fast linker)
+- `lldb` (debugger)
+
+## Building the claw binary
+
+### With the dev environment
+
+```bash
+nix develop
+cd rust
+cargo build -p rusty-claude-cli
+```
+
+### Directly with `nix build`
+
+```bash
+nix build .#claw          # Build the claw binary
+nix build                 # Same as .#claw (default package)
+```
+
+The compiled binary is symlinked to `./result/bin/claw`.
+
+## Running common tasks
+
+Once in the dev shell:
+
+```bash
+# Format code
+cd rust
+cargo fmt
+
+# Run clippy linter
+cargo clippy --workspace --all-targets -- -D warnings
+
+# Run all tests
+cargo test --workspace
+
+# Run tests for a specific crate
+cargo test -p rusty-claude-cli
+
+# Build with optimizations
+cargo build --release -p rusty-claude-cli
+```
+
+## Environment variables
+
+The flake automatically sets:
+
+- `RUSTUP_TOOLCHAIN=stable` — uses stable Rust from nixpkgs
+- Standard Rust build flags are inherited from the environment
+
+For development, the minimal dev shell includes a helpful message on entry:
+
+```
+Claw Code development environment
+Run 'cargo build -p rusty-claude-cli' to build the claw binary
+Run 'cargo test --workspace' to run tests
+Run 'scripts/fmt.sh' to format code
+```
+
+## Troubleshooting
+
+### `command not found: nix`
+
+Nix is not installed. Install it from [nixos.org/download.html](https://nixos.org/download.html).
+
+### `error: experimental Nix feature 'flakes' is disabled`
+
+Enable flakes in your Nix configuration (`~/.config/nix/nix.conf` or `/etc/nix/nix.conf`):
+
+```
+experimental-features = nix-command flakes
+```
+
+### `error: ... does not provide attribute 'claw'`
+
+The flake structure may have changed. Try updating:
+
+```bash
+nix flake update
+nix flake check
+```
+
+### Rebuilds are slow after updating dependencies
+
+Cargo will recompile dependencies if `Cargo.lock` changes. This is expected:
+
+```bash
+nix build --rebuild
+```
+
+### `cache lock file needs to be updated`
+
+The Cargo.lock in `rust/` needs to be committed. Run:
+
+```bash
+cd rust
+cargo generate-lockfile
+git add Cargo.lock
+git commit -m "update: Cargo.lock"
+```
+
+## Integration with other tools
+
+### IDE integration (VS Code, IntelliJ, etc.)
+
+Many IDEs can detect and use Nix environments. Direnv integration is recommended:
+
+1. Install the direnv extension
+2. Enable `direnv` shell integration in your IDE
+3. Run `direnv allow` in the repository
+
+Your IDE will automatically use the correct Rust toolchain and dependencies from the flake.
+
+### CI/CD
+
+For GitHub Actions, consider using [cachix/install-nix-action](https://github.com/cachix/install-nix-action) to set up Nix on the runner:
+
+```yaml
+- uses: cachix/install-nix-action@v18
+  with:
+    nix_path: nixpkgs=channel:nixos-unstable
+    extra_nix_config: "experimental-features = nix-command flakes"
+
+- run: nix develop -c cargo test --workspace
+```
+
+## More information
+
+- [NixOS flakes documentation](https://nixos.wiki/wiki/Flakes)
+- [Direnv documentation](https://direnv.net/)
+- [Rust on Nix](https://github.com/oxalica/rust-overlay)

flake.nix

@@ -0,0 +1,115 @@
+{
+  description = "claw-code: Claude Code CLI agent harness in Rust";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs {
+          inherit system overlays;
+        };
+
+        # Build inputs needed for Rust and the project
+        buildInputs = with pkgs; [
+          pkg-config
+          openssl
+          ca-certificates
+          git
+        ];
+
+        # Runtime inputs for the dev environment
+        nativeBuildInputs = with pkgs; [
+          (rust-bin.stable.latest.default.override {
+            extensions = [ "rust-src" ];
+            targets = [ ];
+          })
+          cargo-edit
+          cargo-expand
+          cargo-watch
+        ];
+
+        # Derivation to build the claw binary
+        clawBinary = pkgs.rustPlatform.buildRustPackage {
+          pname = "claw";
+          version = (builtins.fromTOML (builtins.readFile ./rust/Cargo.toml)).workspace.package.version;
+
+          src = ./rust;
+
+          # Hash of all the dependencies in Cargo.lock
+          # This needs to be updated when dependencies change
+          # Run: nix flake update
+          cargoLock = {
+            lockFile = ./rust/Cargo.lock;
+          };
+
+          cargoBuildFlags = [ "-p" "rusty-claude-cli" ];
+
+          buildInputs = buildInputs ++ (with pkgs; [
+            openssl
+          ]);
+
+          nativeBuildInputs = with pkgs; [
+            pkg-config
+          ];
+
+          meta = with pkgs.lib; {
+            description = "Claude Code CLI: agent harness with Rust implementation";
+            homepage = "https://github.com/ultraworkers/claw-code";
+            license = licenses.mit;
+            platforms = platforms.unix;
+          };
+        };
+
+      in
+      {
+        # Provide the claw binary as a package
+        packages.claw = clawBinary;
+        packages.default = clawBinary;
+
+        # Development shell for contributors
+        devShells.default = pkgs.mkShell {
+          name = "claw-dev";
+          inherit buildInputs nativeBuildInputs;
+
+          shellHook = ''
+            echo "Claw Code development environment"
+            echo "Run 'cargo build -p rusty-claude-cli' to build the claw binary"
+            echo "Run 'cargo test --workspace' to run tests"
+            echo "Run 'scripts/fmt.sh' to format code"
+          '';
+
+          # Make sure we have the right Rust toolchain
+          RUSTUP_TOOLCHAIN = "stable";
+        };
+
+        # Alternative shell with additional development tools
+        devShells.full = pkgs.mkShell {
+          name = "claw-dev-full";
+          inherit buildInputs nativeBuildInputs;
+
+          nativeBuildInputs = nativeBuildInputs ++ (with pkgs; [
+            clippy
+            rustfmt
+            mold
+            lldb
+          ]);
+
+          shellHook = ''
+            echo "Claw Code full development environment (with extra tools)"
+            echo "Available tools: clippy, rustfmt, mold (linker), lldb (debugger)"
+          '';
+
+          RUSTUP_TOOLCHAIN = "stable";
+        };
+      }
+    );
+}

rust/crates/commands/src/lib.rs

@@ -1131,6 +1131,9 @@ pub enum SlashCommand {
     SecurityReview,
     Keybindings,
     PrivacySettings,
+    Workspace {
+        path: Option<String>,
+    },
     Plan {
         mode: Option<String>,
     },
@@ -1272,6 +1275,7 @@ impl SlashCommand {
             Self::SecurityReview => "/security-review",
             Self::Keybindings => "/keybindings",
             Self::PrivacySettings => "/privacy-settings",
+            Self::Workspace { .. } => "/workspace",
             Self::Plan { .. } => "/plan",
             Self::Review { .. } => "/review",
             Self::Tasks { .. } => "/tasks",
@@ -1405,6 +1409,9 @@ pub fn validate_slash_command_input(
             validate_no_args(command, &args)?;
             SlashCommand::Setup
         }
+        "workspace" | "cwd" => SlashCommand::Workspace {
+            path: optional_single_arg(command, &args, "[path]")?,
+        },
         "login" | "logout" => {
             return Err(command_error(
                 "This auth flow was removed. Set ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN instead.",
@@ -5342,6 +5349,7 @@ pub fn handle_slash_command(
         | SlashCommand::Cost
         | SlashCommand::Resume { .. }
         | SlashCommand::Config { .. }
+        | SlashCommand::Workspace { .. }
         | SlashCommand::Mcp { .. }
         | SlashCommand::Memory
         | SlashCommand::Init
@@ -6119,6 +6127,24 @@ mod tests {
         assert_eq!(suggest_slash_commands("zzz", 3), Vec::<String>::new());
     }
 
+    #[test]
+    fn parses_workspace_slash_command_and_alias() {
+        let workspace = validate_slash_command_input("/workspace")
+            .expect("workspace should parse")
+            .expect("workspace should be a slash command");
+        assert_eq!(workspace, SlashCommand::Workspace { path: None });
+
+        let cwd = validate_slash_command_input("/cwd src")
+            .expect("cwd alias should parse")
+            .expect("cwd alias should be a slash command");
+        assert_eq!(
+            cwd,
+            SlashCommand::Workspace {
+                path: Some("src".to_string()),
+            }
+        );
+    }
+
     #[test]
     fn compacts_sessions_via_slash_command() {
         let mut session = Session::new();

rust/crates/rusty-claude-cli/src/main.rs

@@ -6715,6 +6715,49 @@ fn run_resume_command(
             message: Some(render_memory_report()?),
             json: Some(render_memory_json()?),
         }),
+        SlashCommand::Workspace { path } => {
+            let cwd_before = env::current_dir()?;
+            let workspace_root = session
+                .workspace_root()
+                .map(Path::to_path_buf)
+                .unwrap_or_else(|| cwd_before.clone());
+            let workspace_root = canonicalize_or_clone(&workspace_root);
+            let changed = if let Some(path) = path.as_deref() {
+                let requested_path = Path::new(path);
+                let resolved_path = if requested_path.is_absolute() {
+                    requested_path.to_path_buf()
+                } else {
+                    cwd_before.join(requested_path)
+                };
+                let resolved_path = canonicalize_or_clone(&resolved_path);
+                if !resolved_path.starts_with(&workspace_root) {
+                    return Err(format!(
+                        "workspace_change_outside_root: `{}` is outside the current workspace root `{}`.\nUse `claw --cwd {}` to start a new session there.",
+                        resolved_path.display(),
+                        workspace_root.display(),
+                        resolved_path.display(),
+                    )
+                    .into());
+                }
+                env::set_current_dir(&resolved_path)?;
+                true
+            } else {
+                false
+            };
+            let cwd_after = env::current_dir()?;
+            let message =
+                render_workspace_report(&cwd_after, &workspace_root, &session.session_id, changed);
+            Ok(ResumeCommandOutcome {
+                session: session.clone(),
+                message: Some(message),
+                json: Some(workspace_report_json(
+                    &cwd_after,
+                    &workspace_root,
+                    &session.session_id,
+                    changed,
+                )),
+            })
+        }
         SlashCommand::Init => {
             // #142: run the init once, then render both text + structured JSON
             // from the same InitReport so both surfaces stay in sync.
@@ -8216,6 +8259,7 @@ impl LiveCli {
                 Self::print_config(section.as_deref())?;
                 false
             }
+            SlashCommand::Workspace { path } => self.handle_workspace_command(path.as_deref())?,
             SlashCommand::Mcp { action, target } => {
                 let args = match (action.as_deref(), target.as_deref()) {
                     (None, None) => None,
@@ -8374,6 +8418,51 @@ impl LiveCli {
         );
     }
 
+    fn handle_workspace_command(
+        &mut self,
+        target: Option<&str>,
+    ) -> Result<bool, Box<dyn std::error::Error>> {
+        let current_dir = env::current_dir()?;
+        let workspace_root = self
+            .runtime
+            .session()
+            .workspace_root()
+            .map(Path::to_path_buf)
+            .unwrap_or_else(|| current_dir.clone());
+        let workspace_root = canonicalize_or_clone(&workspace_root);
+
+        if let Some(target) = target {
+            let requested_path = Path::new(target);
+            let resolved_path = if requested_path.is_absolute() {
+                requested_path.to_path_buf()
+            } else {
+                current_dir.join(requested_path)
+            };
+            let resolved_path = canonicalize_or_clone(&resolved_path);
+            if !resolved_path.starts_with(&workspace_root) {
+                return Err(format!(
+                    "workspace_change_outside_root: `{}` is outside the current workspace root `{}`.\nUse `claw --cwd {}` to start a new session there.",
+                    resolved_path.display(),
+                    workspace_root.display(),
+                    resolved_path.display(),
+                )
+                .into());
+            }
+            env::set_current_dir(&resolved_path)?;
+        }
+
+        println!(
+            "{}",
+            render_workspace_report(
+                &env::current_dir()?,
+                &workspace_root,
+                &self.session.id,
+                target.is_some(),
+            )
+        );
+        Ok(target.is_some())
+    }
+
     fn record_prompt_history(&mut self, prompt: &str) {
         let timestamp_ms = std::time::SystemTime::now()
             .duration_since(UNIX_EPOCH)
@@ -9214,6 +9303,41 @@ fn new_cli_session() -> Result<Session, Box<dyn std::error::Error>> {
     Ok(Session::new().with_workspace_root(env::current_dir()?))
 }
 
+fn canonicalize_or_clone(path: &Path) -> PathBuf {
+    fs::canonicalize(path).unwrap_or_else(|_| path.to_path_buf())
+}
+
+fn render_workspace_report(
+    cwd: &Path,
+    workspace_root: &Path,
+    session_id: &str,
+    changed: bool,
+) -> String {
+    let action = if changed { "change" } else { "show" };
+    format!(
+        "Workspace\n  Action           {action}\n  Session          {session_id}\n  Workspace root   {}\n  Current directory {}",
+        workspace_root.display(),
+        cwd.display(),
+    )
+}
+
+fn workspace_report_json(
+    cwd: &Path,
+    workspace_root: &Path,
+    session_id: &str,
+    changed: bool,
+) -> Value {
+    serde_json::json!({
+        "kind": "workspace",
+        "action": if changed { "change" } else { "show" },
+        "status": "ok",
+        "session_id": session_id,
+        "workspace_root": workspace_root.display().to_string(),
+        "current_directory": cwd.display().to_string(),
+        "changed": changed,
+    })
+}
+
 fn create_managed_session_handle(
     session_id: &str,
 ) -> Result<SessionHandle, Box<dyn std::error::Error>> {

rust/crates/rusty-claude-cli/tests/output_format_contract.rs

@@ -441,6 +441,9 @@ fn status_and_sandbox_emit_json_when_requested() {
 
 // #831: direct resume-safe slash commands should use the same local CliAction
 // JSON surfaces as their bare subcommands, not interactive_only guidance.
+// Note: /sandbox status depends on kernel support for user namespaces.
+// On systems with working user namespaces the status is "ok".
+// On systems without user namespaces the status is "warn" (#731).
 #[test]
 fn direct_resume_safe_slash_commands_route_to_local_json_actions_831() {
     let root = unique_temp_dir("direct-resume-safe-slash-831");
@@ -451,11 +454,11 @@ fn direct_resume_safe_slash_commands_route_to_local_json_actions_831() {
         .output()
         .expect("git init should launch");
 
-    for (command, expected_kind, expected_status) in [
-        ("/version", "version", "ok"),
-        ("/sandbox", "sandbox", "warn"),
-        ("/diff", "diff", "ok"),
-        ("/status", "status", "ok"),
+    for (command, expected_kind, expected_statuses) in [
+        ("/version", "version", &["ok"][..]),
+        ("/sandbox", "sandbox", &["ok", "warn"][..]),
+        ("/diff", "diff", &["ok"][..]),
+        ("/status", "status", &["ok"][..]),
     ] {
         let output = run_claw(&root, &["--output-format", "json", command], &[]);
         assert!(
@@ -470,9 +473,9 @@ fn direct_resume_safe_slash_commands_route_to_local_json_actions_831() {
             .unwrap_or_else(|_| panic!("{command} must emit JSON (#831), got: {stdout:?}"));
 
         assert_eq!(parsed["kind"], expected_kind, "{command} kind: {parsed}");
-        assert_eq!(
-            parsed["status"], expected_status,
-            "{command} status: {parsed}"
+        assert!(
+            expected_statuses.contains(&parsed["status"].as_str().unwrap_or("")),
+            "{command} status must be one of {expected_statuses:?}: {parsed}"
         );
         assert_ne!(
             parsed["error_kind"], "interactive_only",