diff --git a/Cargo.lock b/Cargo.lock
index 0d7e384..d4b5f49 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -22,7 +22,7 @@ checksum = "b4388bee8683e3d04af747c73422af53102d2bd24d9eadb6cbc100baef4b43f8"
 
 [[package]]
 name = "breadmon"
-version = "0.1.0"
+version = "0.1.1"
 dependencies = [
  "anyhow",
  "crossterm",
diff --git a/Cargo.toml b/Cargo.toml
index c914e08..4f6e0f8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "breadmon"
-version = "0.1.0"
+version = "0.1.1"
 edition = "2021"
 description = "TUI monitor manager for Hyprland"
 license = "MIT"
diff --git a/README.md b/README.md
index dc02fc7..a0d2396 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,8 @@ A terminal UI monitor manager for Hyprland. Lets you position, configure, and mi
 
 ## Requirements
 
-- Hyprland compositor (the `hyprctl` binary must be on `PATH`)
+- **[BOS (Bread OS)](https://git.breadway.dev/breadway/bos)'s patched Hyprland build.** Applying changes (the `a` key / Global keys "Apply") runs `hyprctl eval` with a `hl.monitor({...})` Lua call — a BOS-specific extension that does not exist on vanilla/upstream Hyprland. On a non-BOS Hyprland install, `hyprctl eval` itself is not a recognized request, and breadmon will fail to apply with an explicit error explaining this instead of the raw hyprctl response. Everything else in the TUI (viewing/arranging/saving profiles) works regardless; only the live-apply step needs BOS.
+- The `hyprctl` binary must be on `PATH`
 - Rust toolchain (to build from source)
 
 ## Build
diff --git a/src/monitor.rs b/src/monitor.rs
index ca047aa..37f3128 100644
--- a/src/monitor.rs
+++ b/src/monitor.rs
@@ -367,6 +367,15 @@ pub async fn apply_monitors(monitors: &[Monitor]) -> Result<()> {
 
         let stdout = String::from_utf8_lossy(&output.stdout).trim().to_owned();
         if stdout != "ok" {
+            if is_missing_eval_extension(&stdout) {
+                return Err(anyhow::anyhow!(
+                    "breadmon: `hyprctl eval` (and the `hl.monitor()` Lua extension it uses \
+                     to apply monitor changes) is not available on this compositor. \
+                     This feature requires BOS (Bread OS)'s patched Hyprland build — it \
+                     does not exist on vanilla/upstream Hyprland. See the breadmon README \
+                     for details. (raw hyprctl response: {stdout:?})"
+                ));
+            }
             return Err(anyhow::anyhow!("hyprctl: {}", stdout));
         }
     }
@@ -382,6 +391,37 @@ pub async fn apply_monitors(monitors: &[Monitor]) -> Result<()> {
     Ok(())
 }
 
+/// Vanilla/upstream Hyprland doesn't recognize the `eval` request at all
+/// (BOS's Hyprland fork adds it, along with the `hl.monitor()` Lua global
+/// used above), and responds with an "unknown request" style message rather
+/// than an error about `hl`. Detect that case so we can point the user at
+/// the actual cause instead of surfacing the raw hyprctl text.
+fn is_missing_eval_extension(hyprctl_stdout: &str) -> bool {
+    let s = hyprctl_stdout.to_lowercase();
+    s.contains("unknown request") || s.contains("unknown command")
+}
+
+#[cfg(test)]
+mod eval_extension_tests {
+    use super::is_missing_eval_extension;
+
+    #[test]
+    fn detects_unknown_request() {
+        assert!(is_missing_eval_extension("unknown request"));
+        assert!(is_missing_eval_extension("Unknown Request"));
+    }
+
+    #[test]
+    fn does_not_flag_lua_errors() {
+        // A real Lua/apply-time error from a BOS build should still surface
+        // as a normal hyprctl error, not the "requires BOS" message.
+        assert!(!is_missing_eval_extension(
+            "error: attempt to call a nil value"
+        ));
+        assert!(!is_missing_eval_extension("ok"));
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;