Name every test scratch directory the one collision-proof way

CLAUDE.md

@@ -34,6 +34,14 @@ and say so explicitly.
 `voro-core` requires tests; state-machine transitions and scheduler ordering are
 the highest-value targets. TUI code is tested where practical, not dogmatically.
 
+A test that needs a scratch directory names it one way, with `tempfile`:
+`tempfile::Builder::new().prefix("voro-<area>-").tempdir().unwrap().keep()`.
+Never build the name from the process id and a clock stamp — the clock does not
+advance a nanosecond at a time, so two threads reading inside one step read the
+same number and land on the same directory. `keep` leaves the directory behind
+deliberately, so a failing test's scratch state survives for inspection; nothing
+cleans the temp dir up yet.
+
 ## Git conventions
 
 - Feature branches, squash-merged to `main`. One logical change per PR.

Cargo.toml

@@ -17,6 +17,7 @@ toml = "0.8"
 toml_edit = "0.22"
 ratatui = { version = "0.30", features = ["unstable-rendered-line-info"] }
 uuid = { version = "1", features = ["v4"] }
+tempfile = "3"
 
 # The profile that 'dist' will build with
 [profile.dist]

crates/voro-core/Cargo.toml

@@ -18,3 +18,6 @@ thiserror.workspace = true
 toml.workspace = true
 toml_edit.workspace = true
 uuid.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/voro-core/src/config_edit.rs

@@ -253,14 +253,11 @@ mod tests {
 
     /// A unique scratch path per test, cleaned up by the caller.
     fn scratch(tag: &str) -> std::path::PathBuf {
-        std::env::temp_dir().join(format!(
-            "voro-config-edit-{tag}-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ))
+        tempfile::Builder::new()
+            .prefix(&format!("voro-config-edit-{tag}-"))
+            .tempdir()
+            .unwrap()
+            .keep()
     }
 
     #[test]

crates/voro-core/src/store.rs

@@ -2049,16 +2049,11 @@ mod schema_guard_tests {
 
     /// A unique scratch directory per test, cleaned up by the caller.
     fn scratch(tag: &str) -> PathBuf {
-        let dir = std::env::temp_dir().join(format!(
-            "voro-store-{tag}-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
-        std::fs::create_dir_all(&dir).unwrap();
-        dir
+        tempfile::Builder::new()
+            .prefix(&format!("voro-store-{tag}-"))
+            .tempdir()
+            .unwrap()
+            .keep()
     }
 
     #[test]
@@ -4869,9 +4864,12 @@ mod tests {
 
     /// A unique scratch database path under the OS temp dir.
     fn scratch_db() -> PathBuf {
-        static COUNTER: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
-        let n = COUNTER.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
-        std::env::temp_dir().join(format!("voro-dataversion-{}-{n}.db", std::process::id()))
+        tempfile::Builder::new()
+            .prefix("voro-dataversion-")
+            .tempdir()
+            .unwrap()
+            .keep()
+            .join("voro.db")
     }
 
     #[test]

crates/voro/Cargo.toml

@@ -14,3 +14,6 @@ categories = ["command-line-utilities"]
 voro-core = { path = "../voro-core", version = "0.1.0" }
 ratatui.workspace = true
 clap = { version = "4.6.1", features = ["derive"] }
+
+[dev-dependencies]
+tempfile.workspace = true

crates/voro/src/app.rs

@@ -4145,14 +4145,11 @@ mod tests {
     ) -> (Store, crate::dispatch::DispatchCtx, std::path::PathBuf) {
         use std::process::{Command, Stdio};
 
-        let root = std::env::temp_dir().join(format!(
-            "voro-app-{name}-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let root = tempfile::Builder::new()
+            .prefix(&format!("voro-app-{name}-"))
+            .tempdir()
+            .unwrap()
+            .keep();
         let project_path = root.join("project");
         std::fs::create_dir_all(&project_path).unwrap();
         let status = Command::new("git")
@@ -4189,14 +4186,11 @@ mod tests {
     fn resuming_a_task_with_a_live_session_spawns_no_continuation() {
         use std::process::{Command, Stdio};
 
-        let root = std::env::temp_dir().join(format!(
-            "voro-app-resume-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let root = tempfile::Builder::new()
+            .prefix("voro-app-resume-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let project_path = root.join("project");
         std::fs::create_dir_all(&project_path).unwrap();
         let status = Command::new("git")
@@ -7334,15 +7328,11 @@ mod tests {
     /// decides whether that directory is a git repository at all, which is the
     /// whole of what the press-time gate reads (DESIGN.md §8).
     fn pr_ready_app(with_repo: bool) -> (App, i64, std::path::PathBuf) {
-        let dir = std::env::temp_dir().join(format!(
-            "voro-review-key-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
-        std::fs::create_dir_all(&dir).unwrap();
+        let dir = tempfile::Builder::new()
+            .prefix("voro-review-key-")
+            .tempdir()
+            .unwrap()
+            .keep();
         if with_repo {
             let status = std::process::Command::new("git")
                 .arg("-C")
@@ -7661,15 +7651,11 @@ mod tests {
     /// config and PATH.
     fn app_with_agents(agents_toml: &str) -> App {
         let mut app = app_with(&[TaskState::Ready]);
-        let dir = std::env::temp_dir().join(format!(
-            "voro-plan-key-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
-        std::fs::create_dir_all(&dir).unwrap();
+        let dir = tempfile::Builder::new()
+            .prefix("voro-plan-key-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let agents_path = dir.join("voro.toml");
         std::fs::write(&agents_path, agents_toml).unwrap();
         app.dispatch_ctx = crate::dispatch::DispatchCtx {

crates/voro/src/cli.rs

@@ -2601,14 +2601,11 @@ mod tests {
 
     #[test]
     fn agent_init_then_list_through_the_cli() {
-        let dir = std::env::temp_dir().join(format!(
-            "voro-cli-agents-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let dir = tempfile::Builder::new()
+            .prefix("voro-cli-agents-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let agents_path = dir.join("voro/voro.toml");
         let ctx = DispatchCtx {
             db_path: dir.join("voro.db"),
@@ -2653,14 +2650,11 @@ mod tests {
 
     #[test]
     fn viewer_add_remove_round_trip_through_the_cli() {
-        let dir = std::env::temp_dir().join(format!(
-            "voro-cli-viewers-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let dir = tempfile::Builder::new()
+            .prefix("voro-cli-viewers-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let agents_path = dir.join("voro/voro.toml");
         let ctx = DispatchCtx {
             db_path: dir.join("voro.db"),
@@ -3672,15 +3666,11 @@ mod tests {
     /// A throwaway checkout with no remotes — the shape of a first project
     /// (DESIGN.md §8), which advertises `open` rather than `pr`.
     fn remoteless_checkout(tag: &str) -> std::path::PathBuf {
-        let path = std::env::temp_dir().join(format!(
-            "voro-cli-{tag}-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
-        std::fs::create_dir_all(&path).unwrap();
+        let path = tempfile::Builder::new()
+            .prefix(&format!("voro-cli-{tag}-"))
+            .tempdir()
+            .unwrap()
+            .keep();
         git_in(&path, &["init", "-q"]);
         path
     }
@@ -4622,15 +4612,11 @@ mod tests {
     /// viewers. The default `ctx()` points at the developer's real config,
     /// which these tests must not depend on (or launch viewers from).
     fn ctx_with_toml(toml: &str) -> DispatchCtx {
-        let root = std::env::temp_dir().join(format!(
-            "voro-cli-viewer-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
-        std::fs::create_dir_all(&root).unwrap();
+        let root = tempfile::Builder::new()
+            .prefix("voro-cli-viewer-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let agents_path = root.join("voro.toml");
         std::fs::write(&agents_path, toml).unwrap();
         DispatchCtx {
@@ -5104,14 +5090,11 @@ mod tests {
     fn a_dead_dispatched_session_is_finalised_and_stalled_on_read() {
         use std::process::{Command, Stdio};
 
-        let root = std::env::temp_dir().join(format!(
-            "voro-cli-reconcile-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let root = tempfile::Builder::new()
+            .prefix("voro-cli-reconcile-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let project = root.join("project");
         std::fs::create_dir_all(&project).unwrap();
         let git = |args: &[&str]| {
@@ -5188,14 +5171,11 @@ mod tests {
     fn scratch_env(cmd: &str) -> (Store, DispatchCtx, std::path::PathBuf) {
         use std::process::{Command, Stdio};
 
-        let root = std::env::temp_dir().join(format!(
-            "voro-cli-answer-{}-{}",
-            std::process::id(),
-            std::time::SystemTime::now()
-                .duration_since(std::time::UNIX_EPOCH)
-                .unwrap()
-                .as_nanos()
-        ));
+        let root = tempfile::Builder::new()
+            .prefix("voro-cli-answer-")
+            .tempdir()
+            .unwrap()
+            .keep();
         let project = root.join("project");
         std::fs::create_dir_all(&project).unwrap();
         let status = Command::new("git")