diff --git a/Cargo.toml b/Cargo.toml
index 9601b49..38455b2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ path = "src/main.rs"
 tokio = { version = "1.40", features = ["full"] }
 redis = { version = "0.27", features = ["tokio-comp", "streams"] }
 ort = { version = "2.0.0-rc.9", features = ["ndarray", "download-binaries"] }
-ndarray = "0.16"
+ndarray = "0.17"
 image = "0.25"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
@@ -25,6 +25,7 @@ base64 = "0.22"
 sqlx = { version = "0.8", features = ["runtime-tokio", "postgres", "chrono", "uuid"] }
 uuid = { version = "1", features = ["v4", "serde"] }
 chrono = { version = "0.4", features = ["serde"] }
+dotenvy = "0.15"
 
 [profile.release]
 opt-level = 3
diff --git a/src/inference/detector.rs b/src/inference/detector.rs
index cdcaa8f..4fa25fc 100644
--- a/src/inference/detector.rs
+++ b/src/inference/detector.rs
@@ -31,10 +31,18 @@ pub struct FailureDetector {
 
 impl FailureDetector {
     pub fn load(model_path: &str, input_size: u32, confidence_threshold: f32, intra_threads: usize) -> anyhow::Result<Arc<Self>> {
-        let session = Session::builder()?
-            .with_optimization_level(GraphOptimizationLevel::Level3)?
-            .with_intra_threads(intra_threads)?
-            .commit_from_file(model_path)?;
+        // ort's builder error types carry raw FFI pointers that aren't
+        // Send/Sync, so they can't flow through `?` into `anyhow::Result`
+        // directly (anyhow requires Send + Sync + 'static). Stringify at
+        // the boundary instead.
+        let session = Session::builder()
+            .map_err(|e| anyhow::anyhow!("failed to create ONNX Runtime session builder: {e}"))?
+            .with_optimization_level(GraphOptimizationLevel::Level3)
+            .map_err(|e| anyhow::anyhow!("failed to set graph optimization level: {e}"))?
+            .with_intra_threads(intra_threads)
+            .map_err(|e| anyhow::anyhow!("failed to set intra-op thread count: {e}"))?
+            .commit_from_file(model_path)
+            .map_err(|e| anyhow::anyhow!("failed to load ONNX model at {model_path}: {e}"))?;
 
         Ok(Arc::new(Self {
             session: Mutex::new(session),
@@ -50,7 +58,7 @@ impl FailureDetector {
         let input = Value::from_array(tensor)?;
 
         let mut session = self.session.lock().await;
-        let outputs = session.run(ort::inputs!["images" => input]?)?;
+        let outputs = session.run(ort::inputs!["images" => input])?;
 
         // Exported with NMS baked into the graph: output0 is [1, N, 6]
         // rows of (x1, y1, x2, y2, confidence, class_id) in input-pixel space.
diff --git a/src/inference/preprocess.rs b/src/inference/preprocess.rs
index 57f974c..124b1fb 100644
--- a/src/inference/preprocess.rs
+++ b/src/inference/preprocess.rs
@@ -1,4 +1,4 @@
-use image::{DynamicImage, GenericImageView};
+use image::DynamicImage;
 use ndarray::Array4;
 
 /// Resizes an RGB frame to a square `size x size` input tensor in CHW layout,
@@ -18,7 +18,3 @@ pub fn to_input_tensor(image: &DynamicImage, size: u32) -> Array4<f32> {
 
     tensor
 }
-
-pub fn frame_dimensions(image: &DynamicImage) -> (u32, u32) {
-    image.dimensions()
-}
diff --git a/src/main.rs b/src/main.rs
index 56ec210..71d8896 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -132,18 +132,8 @@ async fn process_entry(
     Ok(())
 }
 
+/// Loads `.env` if present; a missing file is fine (env vars may already be
+/// set by the process supervisor), so the error is deliberately ignored.
 fn dotenvy_load() {
-    if let Ok(contents) = std::fs::read_to_string(".env") {
-        for line in contents.lines() {
-            let line = line.trim();
-            if line.is_empty() || line.starts_with('#') {
-                continue;
-            }
-            if let Some((key, value)) = line.split_once('=') {
-                if std::env::var(key).is_err() {
-                    std::env::set_var(key, value);
-                }
-            }
-        }
-    }
+    let _ = dotenvy::dotenv();
 }