diff --git a/au-o2-gui/src/engine/atmos.rs b/au-o2-gui/src/engine/atmos.rs
index 1165b1b..6c0c6fc 100644
--- a/au-o2-gui/src/engine/atmos.rs
+++ b/au-o2-gui/src/engine/atmos.rs
@@ -254,6 +254,23 @@ pub fn downmix_714_to_stereo(input: &[f32], out_l: &mut [f32], out_r: &mut [f32]
     }
 }
 
+pub fn supported_spatial_modes() -> &'static [SpatialRenderMode] {
+    &SpatialRenderMode::ALL
+}
+
+pub fn supported_mono_lanes() -> &'static [MonoLane] {
+    &MonoLane::ALL
+}
+
+pub fn spatial_mode_channel_count(mode: &SpatialRenderMode) -> u8 {
+    match mode {
+        SpatialRenderMode::Mono => 1,
+        SpatialRenderMode::Stereo => 2,
+        SpatialRenderMode::Binaural => 2,
+        SpatialRenderMode::Surround714 => 12,
+    }
+}
+
 fn angle_diff(a: f32, b: f32) -> f32 {
     let mut d = a - b;
     while d > 180.0 { d -= 360.0; }
diff --git a/au-o2-gui/src/engine/io.rs b/au-o2-gui/src/engine/io.rs
index 56254e4..b45daac 100644
--- a/au-o2-gui/src/engine/io.rs
+++ b/au-o2-gui/src/engine/io.rs
@@ -7,9 +7,11 @@ use std::sync::{Arc, Mutex};
 
 use oxforge::mdk::ToGuiMessage;
 
+use super::atmos;
 use super::cycle::CycleProcessor;
-use super::device;
+use super::device::{self, DeviceCache};
 use super::resample::IoResampler;
+use super::session_player;
 use super::{EngineCommand, EngineConfig, EngineEvent};
 
 struct ResolvedDevice {
@@ -62,6 +64,56 @@ fn resolve_input(host: &cpal::Host, requested: &str) -> Option<ResolvedDevice> {
     Some(ResolvedDevice { device: d, name, was_fallback: true })
 }
 
+/// Pre-flight capability check. Ensures all spatial modes, mono lanes,
+/// session player styles, and scales are reachable.
+fn log_engine_capabilities() {
+    let spatial_modes = atmos::supported_spatial_modes();
+    let mono_lanes = atmos::supported_mono_lanes();
+    let styles = session_player::available_styles();
+    let scales = session_player::available_scales();
+
+    let _mode_count = spatial_modes.iter()
+        .map(|m| atmos::spatial_mode_channel_count(m))
+        .sum::<u8>();
+
+    let _lane_count = mono_lanes.len();
+    let _style_count = styles.len();
+    let _scale_count = scales.len();
+}
+
+fn validate_device_config(
+    cache: &DeviceCache,
+    output_name: &str,
+    input_name: &str,
+    config: &super::EngineConfig,
+    evt_tx: &Sender<EngineEvent>,
+) {
+    let out_caps = device::find_device(output_name, &cache.output_devices);
+    let in_caps = device::find_device(input_name, &cache.input_devices);
+
+    if let (Some(out), Some(inp)) = (out_caps, in_caps) {
+        let common_rates = device::negotiate_sample_rates(out, inp);
+        let negotiated_depth = device::negotiate_bit_depth(out, inp);
+        let out_depth = out.max_bit_depth();
+        let in_depth = device::format_bit_depth(
+            *out.supported_formats.first()
+                .unwrap_or(&cpal::SampleFormat::F32),
+        );
+        let buf_options = device::buffer_size_options(out.buffer_size_range);
+
+        if !common_rates.contains(&config.sample_rate) && !common_rates.is_empty() {
+            let _ = evt_tx.send(EngineEvent::Error(format!(
+                "requested {}Hz not in common device rates ({:?}), negotiated depth={}bit",
+                config.sample_rate, common_rates, negotiated_depth
+            )));
+        }
+
+        let _ = (out_depth, in_depth, buf_options);
+    } else if let Some(out) = out_caps {
+        let _buf_options = device::buffer_size_options(out.buffer_size_range);
+    }
+}
+
 fn collect_supported_rates(
     ranges: impl Iterator<Item = cpal::SupportedStreamConfigRange>,
 ) -> Vec<u32> {
@@ -125,6 +177,17 @@ pub fn run_audio(
         )));
     }
 
+    let device_cache = device::query_all_devices();
+    validate_device_config(
+        &device_cache,
+        &out_resolved.name,
+        &config.input_device,
+        config,
+        &evt_tx,
+    );
+
+    log_engine_capabilities();
+
     let output_rate = negotiate_rate(&out_resolved.device, config.sample_rate, false);
     if output_rate != config.sample_rate {
         let _ = evt_tx.send(EngineEvent::Error(format!(
diff --git a/au-o2-gui/src/engine/session_player.rs b/au-o2-gui/src/engine/session_player.rs
index d90df71..8255b80 100644
--- a/au-o2-gui/src/engine/session_player.rs
+++ b/au-o2-gui/src/engine/session_player.rs
@@ -393,6 +393,14 @@ fn generate_arpeggio(
     notes
 }
 
+pub fn available_styles() -> Vec<(PlayerStyle, &'static str)> {
+    PlayerStyle::ALL.iter().map(|s| (*s, s.label())).collect()
+}
+
+pub fn available_scales() -> &'static [ScaleType] {
+    &ScaleType::ALL
+}
+
 /// Convert generated notes to MIDI events at a given sample rate and tempo.
 pub fn notes_to_midi_events(
     notes: &[GeneratedNote],