fix(startup): fall back to USERPROFILE when HOME is not set (Windows)

On Windows, HOME is often unset. The CLI crashed at startup with
'error: io error: HOME is not set' because three paths only checked
HOME:
- config_home_dir() in tools crate (config/settings loading)
- credentials_home_dir() in runtime crate (OAuth credentials)
- detect_broad_cwd() in CLI (CWD-is-home-dir check)
- skill lookup roots in tools crate

All now fall through to USERPROFILE when HOME is absent. Error message
updated to suggest USERPROFILE or CLAW_CONFIG_HOME on Windows.

Source: MaxDerVerpeilte in #claw-code (Windows user, 2026-04-10).

rust/crates/runtime/src/oauth.rs

@@ -335,7 +335,14 @@ fn credentials_home_dir() -> io::Result<PathBuf> {
         return Ok(PathBuf::from(path));
     }
     let home = std::env::var_os("HOME")
-        .ok_or_else(|| io::Error::new(io::ErrorKind::NotFound, "HOME is not set"))?;
+        .or_else(|| std::env::var_os("USERPROFILE"))
+        .ok_or_else(|| {
+            io::Error::new(
+                io::ErrorKind::NotFound,
+                "HOME is not set (on Windows, set USERPROFILE or HOME, \
+                 or use CLAW_CONFIG_HOME to point directly at the config directory)",
+            )
+        })?;
     Ok(PathBuf::from(home).join(".claw"))
 }
 

rust/crates/rusty-claude-cli/src/main.rs

@@ -3055,6 +3055,7 @@ fn detect_broad_cwd() -> Option<PathBuf> {
         return None;
     };
     let is_home = env::var_os("HOME")
+        .or_else(|| env::var_os("USERPROFILE"))
         .map(|h| PathBuf::from(h) == cwd)
         .unwrap_or(false);
     let is_root = cwd.parent().is_none();

rust/crates/tools/src/lib.rs

@@ -3066,7 +3066,7 @@ fn skill_lookup_roots() -> Vec<SkillLookupRoot> {
     if let Ok(codex_home) = std::env::var("CODEX_HOME") {
         push_prefixed_skill_lookup_roots(&mut roots, std::path::Path::new(&codex_home));
     }
-    if let Ok(home) = std::env::var("HOME") {
+    if let Ok(home) = std::env::var("HOME").or_else(|_| std::env::var("USERPROFILE")) {
         push_home_skill_lookup_roots(&mut roots, std::path::Path::new(&home));
     }
     if let Ok(claude_config_dir) = std::env::var("CLAUDE_CONFIG_DIR") {
@@ -4987,7 +4987,14 @@ fn config_home_dir() -> Result<PathBuf, String> {
     if let Ok(path) = std::env::var("CLAW_CONFIG_HOME") {
         return Ok(PathBuf::from(path));
     }
-    let home = std::env::var("HOME").map_err(|_| String::from("HOME is not set"))?;
+    let home = std::env::var("HOME")
+        .or_else(|_| std::env::var("USERPROFILE"))
+        .map_err(|_| {
+            String::from(
+                "HOME is not set (on Windows, set USERPROFILE or HOME, \
+                 or use CLAW_CONFIG_HOME to point directly at the config directory)",
+            )
+        })?;
     Ok(PathBuf::from(home).join(".claw"))
 }