diff --git a/.gitignore b/.gitignore
index 9dbd8bb..d075350 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@ infra/desi-explorer-infra
 api/target/
 .env
 .env.*
+*.env
diff --git a/api/Makefile b/api/Makefile
index 36d94a7..3de9787 100644
--- a/api/Makefile
+++ b/api/Makefile
@@ -4,6 +4,20 @@
 # `api-*` convenience targets).
 
 CARGO ?= cargo
+ROOT  := ..
+
+# Normalize API_ENV_FILE / API_DESI_DATA (given relative to the repo root) to
+# absolute paths so the API process can open them regardless of its working
+# directory. "override" is required because they are usually passed as
+# command-line/env vars, which would otherwise override any assignment here.
+define normalize_path
+ifdef $1
+ifneq ($(abspath $($1)),$($1))
+override $1 := $(abspath $(ROOT)/$($1))
+endif
+endif
+endef
+$(foreach v,API_ENV_FILE API_DESI_DATA,$(eval $(call normalize_path,$v)))
 
 .PHONY: help setup run build test check fmt clean
 
diff --git a/api/src/store.rs b/api/src/store.rs
index 8db1fa7..9220dcb 100644
--- a/api/src/store.rs
+++ b/api/src/store.rs
@@ -55,56 +55,3 @@ impl CatalogStore {
         })
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn load_parses_catalogs_and_objects() {
-        let json = r#"{
-            "catalogs": [
-                {"name":"edr","release":"EDR","description":"test","object_count":2}
-            ],
-            "objects": [
-                {"id":"o1","catalog":"edr","object_type":"GALAXY","ra":1.5,"dec":2.5,"redshift":0.8}
-            ]
-        }"#;
-
-        let dir = std::env::temp_dir().join(format!(
-            "desi_explorer_store_{}_{}",
-            std::process::id(),
-            line!()
-        ));
-        std::fs::create_dir_all(&dir).unwrap();
-        let path = dir.join("data.json");
-        std::fs::write(&path, json).unwrap();
-
-        let store = CatalogStore::load(&path).unwrap();
-        let _ = std::fs::remove_dir_all(&dir);
-
-        assert_eq!(store.catalogs.len(), 1);
-        assert_eq!(store.catalogs[0].name, "edr");
-        assert_eq!(store.catalogs[0].object_count, Some(2));
-        assert_eq!(store.objects.len(), 1);
-        assert_eq!(store.objects[0].id, "o1");
-        assert_eq!(store.objects[0].ra, 1.5);
-    }
-
-    #[test]
-    fn load_rejects_malformed_json() {
-        let dir = std::env::temp_dir().join(format!(
-            "desi_explorer_store_{}_{}",
-            std::process::id(),
-            line!()
-        ));
-        std::fs::create_dir_all(&dir).unwrap();
-        let path = dir.join("data.json");
-        std::fs::write(&path, "not json").unwrap();
-
-        let result = CatalogStore::load(&path);
-        let _ = std::fs::remove_dir_all(&dir);
-
-        assert!(result.is_err());
-    }
-}
diff --git a/api/tests/store.rs b/api/tests/store.rs
new file mode 100644
index 0000000..4954aaa
--- /dev/null
+++ b/api/tests/store.rs
@@ -0,0 +1,54 @@
+use desi_explorer_api::store::CatalogStore;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn load_parses_catalogs_and_objects() {
+        let json = r#"{
+            "catalogs": [
+                {"name":"edr","release":"EDR","description":"test","object_count":2}
+            ],
+            "objects": [
+                {"id":"o1","catalog":"edr","object_type":"GALAXY","ra":1.5,"dec":2.5,"redshift":0.8}
+            ]
+        }"#;
+
+        let dir = std::env::temp_dir().join(format!(
+            "desi_explorer_store_{}_{}",
+            std::process::id(),
+            line!()
+        ));
+        std::fs::create_dir_all(&dir).unwrap();
+        let path = dir.join("data.json");
+        std::fs::write(&path, json).unwrap();
+
+        let store = CatalogStore::load(&path).unwrap();
+        let _ = std::fs::remove_dir_all(&dir);
+
+        assert_eq!(store.catalogs.len(), 1);
+        assert_eq!(store.catalogs[0].name, "edr");
+        assert_eq!(store.catalogs[0].object_count, Some(2));
+        assert_eq!(store.objects.len(), 1);
+        assert_eq!(store.objects[0].id, "o1");
+        assert_eq!(store.objects[0].ra, 1.5);
+    }
+
+    #[test]
+    fn load_rejects_malformed_json() {
+        let dir = std::env::temp_dir().join(format!(
+            "desi_explorer_store_{}_{}",
+            std::process::id(),
+            line!()
+        ));
+        std::fs::create_dir_all(&dir).unwrap();
+        let path = dir.join("data.json");
+        std::fs::write(&path, "not json").unwrap();
+
+        let result = CatalogStore::load(&path);
+        let _ = std::fs::remove_dir_all(&dir);
+
+        assert!(result.is_err());
+    }
+}
diff --git a/gui/Makefile b/gui/Makefile
index 94dca55..a0c71a9 100644
--- a/gui/Makefile
+++ b/gui/Makefile
@@ -8,13 +8,28 @@
 # output dirs live at the repo root and are referenced through `$(ROOT)`.
 
 ODIN         ?= odin
+GDB          ?= gdb
 ROOT         := ..
 BIN          := $(ROOT)/bin
 BINARY       := $(BIN)/desi_explorer
 ODIN_FLAGS   := -collection:lib=lib/local
 WASM_DEFINE  := RAYLIB_WASM_LIB=env.o
 
-.PHONY: help setup add-dep run build build-debug build-web test clean fmt
+# Normalize GUI_ENV_FILE (given relative to the repo root) to an absolute path
+# so the Odin process can open it regardless of its working directory.
+# "override" is required because GUI_ENV_FILE is usually set on the command
+# line (or passed as an env var to this sub-make), which would otherwise
+# override any assignment made here.
+ifdef GUI_ENV_FILE
+ifneq ($(abspath $(GUI_ENV_FILE)),$(GUI_ENV_FILE))
+override GUI_ENV_FILE := $(abspath $(ROOT)/$(GUI_ENV_FILE))
+endif
+endif
+# "override" on a command-line variable silently drops it from the recipe
+# environment; re-export it so the app can find its env file (run + gdb).
+export GUI_ENV_FILE
+
+.PHONY: help setup add-dep run build build-debug gdb build-web test clean fmt
 
 help: ## List available targets
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | \
@@ -41,6 +56,9 @@ build-debug: ## Debug build -> bin/desi_explorer
 	@mkdir -p lib/local $(BIN)
 	$(ODIN) build src $(ODIN_FLAGS) -o:none -debug -out:$(BINARY)
 
+gdb: build-debug ## Run the native app under gdb (type 'run', then 'bt' on a crash)
+	$(GDB) -q --args $(BINARY) $(ARGS)
+
 build-web: ## WebAssembly build -> build/web (needs emscripten)
 	@scripts/build_web.sh
 
diff --git a/gui/lib/local/dotenv/src/dotenv.odin b/gui/lib/local/dotenv/src/dotenv.odin
index 9480bef..047da75 100644
--- a/gui/lib/local/dotenv/src/dotenv.odin
+++ b/gui/lib/local/dotenv/src/dotenv.odin
@@ -12,10 +12,7 @@ import "core:strings"
 // double quotes. Real process environment variables take precedence over the
 // file. The returned map owns its keys/values; release it with destroy.
 @(private)
-parse :: proc(
-	src: string,
-	allocator := context.allocator,
-) -> map[string]string {
+parse :: proc(src: string, allocator := context.allocator) -> map[string]string {
 	result := make(map[string]string, allocator)
 
 	it := src
@@ -54,18 +51,12 @@ parse :: proc(
 
 // parse_file reads a dotenv file from disk and parses it into a map. It
 // returns (nil, false) when the file cannot be read (e.g. it does not exist).
-parse_file :: proc(
-	filename: string,
-	allocator := context.allocator,
-) -> (
-	map[string]string,
-	bool,
-) {
+parse_file :: proc(filename: string, allocator := context.allocator) -> (map[string]string, bool) {
 	data, err := os.read_entire_file(filename, allocator)
 	if err != nil {
 		return nil, false
 	}
-	defer delete(data)
+	defer delete(data, allocator)
 
 	return parse(string(data), allocator), true
 }
@@ -86,8 +77,7 @@ destroy :: proc(env: map[string]string) {
 // case-insensitive, so API_URL maps onto api_url (or an `env:"API_URL"` tag).
 @(private)
 env_key_for_field :: proc(field: reflect.Struct_Field) -> string {
-	if tag_key, ok := reflect.struct_tag_lookup(field.tag, "env");
-	   ok && tag_key != "" {
+	if tag_key, ok := reflect.struct_tag_lookup(field.tag, "env"); ok && tag_key != "" {
 		return tag_key
 	}
 	return field.name
@@ -100,11 +90,7 @@ env_key_for_field :: proc(field: reflect.Struct_Field) -> string {
 // and floats with strconv.parse_f64. Keys missing from env leave the field
 // at its zero value. It returns false if a present value cannot be converted
 // to the field's type.
-decode :: proc(
-	env: map[string]string,
-	dest: ^$T,
-	allocator := context.allocator,
-) -> bool {
+decode :: proc(env: map[string]string, dest: ^$T, allocator := context.allocator) -> bool {
 	ti := reflect.type_info_base(type_info_of(T))
 	fields, ok := ti.variant.(runtime.Type_Info_Struct)
 	if !ok {
diff --git a/gui/src/config.odin b/gui/src/config.odin
index b6f06b7..1aa9ea4 100644
--- a/gui/src/config.odin
+++ b/gui/src/config.odin
@@ -11,10 +11,7 @@ get_config :: proc(env_file: ^string = nil) -> (^Config, ^Error) {
 	path := ".env"
 	if env_file != nil && env_file^ != "" {
 		path = env_file^
-	} else if from_env, ok := os.lookup_env(
-		"GUI_ENV_FILE",
-		context.temp_allocator,
-	); ok {
+	} else if from_env, ok := os.lookup_env("GUI_ENV_FILE", context.temp_allocator); ok {
 		path = from_env
 	}
 
@@ -39,9 +36,9 @@ get_config :: proc(env_file: ^string = nil) -> (^Config, ^Error) {
 	return c, nil
 }
 
-validate_config :: proc(c: ^Config) -> ^Error {
-	err := new(Error)
-	if c.api_url == "" do err.type = .Config; err.message = "'API_URL' is required"
-
+validate_config :: proc(c: ^Config) -> (err: ^Error) {
+	if c.api_url == "" {
+		err = &Error{.Config, "'API_URL' is required"}
+	}
 	return err
 }
diff --git a/gui/src/main.odin b/gui/src/main.odin
index 315b1cb..06213d8 100644
--- a/gui/src/main.odin
+++ b/gui/src/main.odin
@@ -1,7 +1,9 @@
 package main
 
+import "base:runtime"
 import "core:math"
 import "core:math/rand"
+import "core:os"
 import rl "vendor:raylib"
 
 WIDTH :: 1280
@@ -27,7 +29,9 @@ main :: proc() {
 
 	c: ^Config
 
-	if c, err := get_config(); err != nil {
+	s := os.get_env("GUI_ENV_FILE", context.temp_allocator)
+
+	if c, err := get_config(&s); err != nil {
 		panic(format_error(err))
 	}