Ensure Ninja directory flag uses current_dir

.gitignore

@@ -1,3 +1,5 @@
 target/
 **/*.rs.bk
+**/*~
 .crush
+build.ninja

Cargo.toml

@@ -63,6 +63,7 @@ cucumber = "0.20.0"
 tokio = { version = "1", features = ["macros", "rt-multi-thread"], default-features = false }
 insta = { version = "1", features = ["yaml"] }
 tempfile = "3"
+serial_test = "3"
 
 [[test]]
 name = "cucumber"

docs/netsuke-design.md

@@ -1138,12 +1138,14 @@ The command construction will follow this pattern:
    `ninja` is available in the system's `PATH`.
 
 1. Arguments passed to Netsuke's own CLI will be translated and forwarded to
-   Ninja. For example, a `Netsuke build -C build/ my_target` command would
-   result in `Command::new("ninja").arg("-C").arg("build/").arg("my_target")`.
-   Flags like `-j` for parallelism will also be passed through.[^8]
+   Ninja. For example, a `Netsuke build my_target` command would result in
+   `Command::new("ninja").arg("my_target")`. Flags like `-j` for parallelism
+   will also be passed through.[^8]
 
 1. The working directory for the Ninja process will be set using
-   `.current_dir()` if the user provides a `-C` flag.
+   `.current_dir()`. When the user supplies a `-C` flag, Netsuke
+   canonicalises the path and applies it via `current_dir` rather than
+   forwarding the flag to Ninja.
 
 1. Standard I/O streams (`stdin`, `stdout`, `stderr`) will be configured using
    `.stdout(Stdio::piped())` and `.stderr(Stdio::piped())`.[^24] This allows
@@ -1418,10 +1420,10 @@ The CLI is implemented using clap's derive API in `src/cli.rs`. Clap's
 `default_value_t` attribute marks `Build` as the default subcommand, so
 invoking `netsuke` with no explicit command still triggers a build. CLI
 execution and dispatch live in `src/runner.rs`, keeping `main.rs` focused on
-parsing. The working directory flag uses `-C` to mirror Ninja's convention,
-ensuring command line arguments map directly onto the underlying build tool.
-Error scenarios are validated using clap's `ErrorKind` enumeration in unit
-tests and via Cucumber steps for behavioural coverage.
+parsing. The working directory flag mirrors Ninja's `-C` option but is resolved
+internally; Netsuke changes directory before spawning Ninja rather than
+forwarding the flag. Error scenarios are validated using clap's `ErrorKind`
+enumeration in unit tests and via Cucumber steps for behavioural coverage.
 
 ## Section 9: Implementation Roadmap and Strategic Recommendations
 

src/ast.rs

@@ -106,7 +106,7 @@ pub struct Rule {
 /// Exactly one variant must be provided for a rule or target. The fields are
 /// flattened in the manifest, so the presence of `command`, `script`, or `rule`
 /// determines the variant.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Serialize)]
 pub enum Recipe {
     /// A single shell command.
     Command { command: String },

src/runner.rs

@@ -125,7 +125,12 @@ fn redact_sensitive_args(args: &[String]) -> Vec<String> {
 pub fn run_ninja(program: &Path, cli: &Cli, targets: &[String]) -> io::Result<()> {
     let mut cmd = Command::new(program);
     if let Some(dir) = &cli.directory {
-        cmd.current_dir(dir).arg("-C").arg(dir);
+        // Resolve and canonicalise the directory so Ninja receives a stable
+        // absolute path. Using only `current_dir` avoids combining it with
+        // Ninja's own `-C` flag which would otherwise double-apply the
+        // directory and break relative paths.
+        let dir = fs::canonicalize(dir)?;
+        cmd.current_dir(dir);
     }
     if let Some(jobs) = cli.jobs {
         cmd.arg("-j").arg(jobs.to_string());

tests/ninja_snapshot_tests.rs

@@ -68,7 +68,7 @@ fn touch_manifest_ninja_validation() {
     let _ = ninja_cmd(&["-t", "targets", "all"]);
     let _ = ninja_cmd(&["-t", "query", "out/a"]);
 
-    let _ = ninja_cmd(&["-w", "dupbuild=err", "-d", "stats"]);
+    let _ = ninja_cmd(&["-w", "phonycycle=err", "-d", "stats"]);
     let second = ninja_cmd(&["-n", "-d", "explain", "-v"]);
     assert!(
         second.contains("no work to do"),