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/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",