fix: address second-round CodeRabbit review on PR #6

- network: scope remote_cache filename per target triple so a shared
  PVM_DIR (NFS, dotfile sync) cannot serve linux-x86_64 entries to an
  aarch64 host
- use_cmd, install: remove unsafe std::env::set_var of PATH and
  PVM_MULTISHELL_PATH; the wrapper sources env_file into the parent
  shell on exit, and set_var is unsound under the multi-threaded tokio
  runtime
- ls_remote: hoist 'prefix.' allocation outside retain so the predicate
  does not reallocate per element
- docs: fix GEMINI.md PVM_DIR default for macOS, env file naming, and
  the data-integrity guideline to point at std::fs::File locking
  (fs4 was dropped in an earlier commit)

Author: Fahl-Design

GEMINI.md

@@ -13,11 +13,11 @@ When running `git commit -m "..."` in the shell (like Zsh/Bash), backticks are i
 
 ## Project Architecture (The Map)
 ### Filesystem Hierarchy
-- **$PVM_DIR**: Root directory, defaults to `~/.local/share/pvm` on Linux/macOS.
+- **$PVM_DIR**: Root directory. Resolved via `dirs::data_local_dir()`, so defaults to `~/.local/share/pvm` on Linux and `~/Library/Application Support/pvm` on macOS.
 - **$PVM_DIR/versions/<version>**: Installation directory for specific PHP versions.
 - **$PVM_DIR/bin/pvm**: The `pvm` binary itself.
-- **$PVM_DIR/remote_cache.json**: 24-hour cache for remote version data.
-- **$PVM_DIR/.env**: The generated file containing active version exports.
+- **$PVM_DIR/remote_cache-<target-triple>.json**: 24-hour cache for the remote version index, scoped per target triple (e.g. `linux-x86_64`).
+- **$PVM_DIR/.env_update[_<shell-pid>]**: Short-lived files written per shell invocation; the shell wrapper sources them to mutate the parent shell's environment.
 
 ### Module Responsibilities
 - `src/cli.rs`: Command definitions using `clap`.
@@ -46,7 +46,7 @@ When running `git commit -m "..."` in the shell (like Zsh/Bash), backticks are i
 - **Interactivity:** Use `dialoguer` for menus and confirmations.
 - **Icons:** Use `colored` for status icons: `✓` (green), `✗` (red), `↻` (blue), `💡` (yellow).
 - **Async:** Use `tokio` for runtime and `reqwest` for all network I/O.
-- **Data Integrity:** Use `fs4` file locking when writing to `.env` or `remote_cache.json`.
+- **Data Integrity:** Use file locking (`std::fs::File::lock` / `lock_shared` / `unlock`, stable since Rust 1.89) when writing to env update files or the remote cache.
 
 ## Testing & Validation
 ### Testing Protocol

src/commands/install.rs

@@ -116,19 +116,9 @@ pub async fn execute_install(version: &str) -> Result<()> {
         let env_file = crate::fs::get_env_update_path(None)?;
         crate::fs::write_env_file_locked(&env_file, &format!("{}\n{}", export_str1, export_str2))?;
 
-        unsafe {
-            std::env::set_var(MULTISHELL_PATH_VAR, &bin_dir);
-            if let Some(path) = std::env::var_os("PATH") {
-                let mut new_path = std::ffi::OsString::new();
-                new_path.push(&bin_dir);
-                #[cfg(windows)]
-                new_path.push(";");
-                #[cfg(not(windows))]
-                new_path.push(":");
-                new_path.push(&path);
-                std::env::set_var("PATH", new_path);
-            }
-        }
+        // Note: process-global env is intentionally NOT mutated here. std::env::set_var
+        // is unsound in a multi-threaded tokio runtime, and the wrapper sources env_file
+        // into the parent shell on exit, so subsequent pvm invocations see the new PATH.
         println!("{} Switched to PHP {}", "✓".green(), v.bold());
     } else if !cli_selected {
         println!(

src/commands/ls_remote.rs

@@ -16,7 +16,8 @@ impl LsRemote {
         let mut versions_info = network::get_available_versions().await?;
 
         if let Some(prefix) = &self.version_prefix {
-            versions_info.retain(|(v, _)| v == prefix || v.starts_with(&format!("{}.", prefix)));
+            let prefix_dot = format!("{}.", prefix);
+            versions_info.retain(|(v, _)| v == prefix || v.starts_with(&prefix_dot));
         }
 
         if versions_info.is_empty() {

src/commands/use_cmd.rs

@@ -108,20 +108,9 @@ impl Use {
         let env_file = fs::get_env_update_path(None)?;
         fs::write_env_file_locked(&env_file, &format!("{}\n{}", export_str1, export_str2))?;
 
-        // Also update the current Rust binary's environment so spawned subs (or interactive loop) see it
-        unsafe {
-            std::env::set_var(MULTISHELL_PATH_VAR, &bin_dir);
-            if let Some(path) = std::env::var_os("PATH") {
-                let mut new_path = std::ffi::OsString::new();
-                new_path.push(&bin_dir);
-                #[cfg(windows)]
-                new_path.push(";");
-                #[cfg(not(windows))]
-                new_path.push(":");
-                new_path.push(&path);
-                std::env::set_var("PATH", new_path);
-            }
-        }
+        // Note: process-global env is intentionally NOT mutated here. std::env::set_var
+        // is unsound in a multi-threaded tokio runtime, and the wrapper sources env_file
+        // into the parent shell on exit, so subsequent pvm invocations see the new PATH.
 
         Ok(())
     }

src/network.rs

@@ -45,7 +45,14 @@ fn get_target_triple() -> Result<&'static str> {
 
 pub async fn get_available_versions() -> Result<Vec<(String, Vec<String>)>> {
     let pvm_dir = crate::fs::get_pvm_dir()?;
-    let cache_path = pvm_dir.join(REMOTE_CACHE_FILE);
+    let target = get_target_triple()?;
+    // Cache is filtered by target triple, so the filename must include it
+    // to prevent cross-arch reuse when $PVM_DIR is shared (e.g. via NFS).
+    let cache_path = pvm_dir.join(format!(
+        "{}-{}.json",
+        REMOTE_CACHE_FILE.trim_end_matches(".json"),
+        target
+    ));
 
     // 1. Try to load from valid cache
     if cache_path.exists()
@@ -96,7 +103,6 @@ pub async fn get_available_versions() -> Result<Vec<(String, Vec<String>)>> {
         .context("Failed to parse remote version JSON")?;
     spinner.finish_and_clear();
 
-    let target = get_target_triple()?;
     let suffix = format!("-{}.tar.gz", target);
 
     let mut versions_map: std::collections::HashMap<String, Vec<String>> =