diff --git a/codex-rs/core/src/shell.rs b/codex-rs/core/src/shell.rs
index 194371256..48c760d66 100644
--- a/codex-rs/core/src/shell.rs
+++ b/codex-rs/core/src/shell.rs
@@ -166,7 +166,7 @@ fn get_shell_path(
     shell_type: ShellType,
     provided_path: Option<&PathBuf>,
     binary_name: &str,
-    fallback_paths: Vec<&str>,
+    fallback_paths: &[&str],
 ) -> Option<PathBuf> {
     // If exact provided path exists, use it
     if provided_path.and_then(file_exists).is_some() {
@@ -197,8 +197,10 @@ fn get_shell_path(
     None
 }
 
+const ZSH_FALLBACK_PATHS: &[&str] = &["/bin/zsh"];
+
 fn get_zsh_shell(path: Option<&PathBuf>) -> Option<Shell> {
-    let shell_path = get_shell_path(ShellType::Zsh, path, "zsh", vec!["/bin/zsh"]);
+    let shell_path = get_shell_path(ShellType::Zsh, path, "zsh", ZSH_FALLBACK_PATHS);
 
     shell_path.map(|shell_path| Shell {
         shell_type: ShellType::Zsh,
@@ -207,8 +209,10 @@ fn get_zsh_shell(path: Option<&PathBuf>) -> Option<Shell> {
     })
 }
 
+const BASH_FALLBACK_PATHS: &[&str] = &["/bin/bash"];
+
 fn get_bash_shell(path: Option<&PathBuf>) -> Option<Shell> {
-    let shell_path = get_shell_path(ShellType::Bash, path, "bash", vec!["/bin/bash"]);
+    let shell_path = get_shell_path(ShellType::Bash, path, "bash", BASH_FALLBACK_PATHS);
 
     shell_path.map(|shell_path| Shell {
         shell_type: ShellType::Bash,
@@ -217,8 +221,10 @@ fn get_bash_shell(path: Option<&PathBuf>) -> Option<Shell> {
     })
 }
 
+const SH_FALLBACK_PATHS: &[&str] = &["/bin/sh"];
+
 fn get_sh_shell(path: Option<&PathBuf>) -> Option<Shell> {
-    let shell_path = get_shell_path(ShellType::Sh, path, "sh", vec!["/bin/sh"]);
+    let shell_path = get_shell_path(ShellType::Sh, path, "sh", SH_FALLBACK_PATHS);
 
     shell_path.map(|shell_path| Shell {
         shell_type: ShellType::Sh,
@@ -227,14 +233,32 @@ fn get_sh_shell(path: Option<&PathBuf>) -> Option<Shell> {
     })
 }
 
+// Note the `pwsh` and `powershell` fallback paths are where the respective
+// shells are commonly installed on GitHub Actions Windows runners, but may not
+// be present on all Windows machines:
+// https://docs.github.com/en/actions/tutorials/build-and-test-code/powershell
+
+#[cfg(windows)]
+const PWSH_FALLBACK_PATHS: &[&str] = &[r#"C:\Program Files\PowerShell\7\pwsh.exe"#];
+#[cfg(not(windows))]
+const PWSH_FALLBACK_PATHS: &[&str] = &["/usr/local/bin/pwsh"];
+
+#[cfg(windows)]
+const POWERSHELL_FALLBACK_PATHS: &[&str] =
+    &[r#"C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe"#];
+#[cfg(not(windows))]
+const POWERSHELL_FALLBACK_PATHS: &[&str] = &[];
+
 fn get_powershell_shell(path: Option<&PathBuf>) -> Option<Shell> {
-    let shell_path = get_shell_path(
-        ShellType::PowerShell,
-        path,
-        "pwsh",
-        vec!["/usr/local/bin/pwsh"],
-    )
-    .or_else(|| get_shell_path(ShellType::PowerShell, path, "powershell", vec![]));
+    let shell_path = get_shell_path(ShellType::PowerShell, path, "pwsh", PWSH_FALLBACK_PATHS)
+        .or_else(|| {
+            get_shell_path(
+                ShellType::PowerShell,
+                path,
+                "powershell",
+                POWERSHELL_FALLBACK_PATHS,
+            )
+        });
 
     shell_path.map(|shell_path| Shell {
         shell_type: ShellType::PowerShell,
@@ -244,7 +268,7 @@ fn get_powershell_shell(path: Option<&PathBuf>) -> Option<Shell> {
 }
 
 fn get_cmd_shell(path: Option<&PathBuf>) -> Option<Shell> {
-    let shell_path = get_shell_path(ShellType::Cmd, path, "cmd", vec![]);
+    let shell_path = get_shell_path(ShellType::Cmd, path, "cmd", &[]);
 
     shell_path.map(|shell_path| Shell {
         shell_type: ShellType::Cmd,