diff --git a/configs/commands.json b/configs/commands.json
deleted file mode 100644
index 00f8e95..0000000
--- a/configs/commands.json
+++ /dev/null
@@ -1,14 +0,0 @@
-{
-    "sh": {
-        "run": {
-            "engine": "docker",
-            "entry": "main.sh",
-            "steps": [
-                {
-                    "box": "alpine",
-                    "command": ["sh", "main.sh"]
-                }
-            ]
-        }
-    }
-}
diff --git a/configs/commands/sh.json b/configs/commands/sh.json
new file mode 100644
index 0000000..277fabe
--- /dev/null
+++ b/configs/commands/sh.json
@@ -0,0 +1,12 @@
+{
+    "run": {
+        "engine": "docker",
+        "entry": "main.sh",
+        "steps": [
+            {
+                "box": "alpine",
+                "command": ["sh", "main.sh"]
+            }
+        ]
+    }
+}
diff --git a/internal/config/load.go b/internal/config/load.go
index 789b963..ee5f76a 100644
--- a/internal/config/load.go
+++ b/internal/config/load.go
@@ -4,12 +4,15 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"strings"
+
+	"github.com/nalgeon/codapi/internal/fileio"
 )
 
 const (
-	configFilename   = "config.json"
-	boxesFilename    = "boxes.json"
-	commandsFilename = "commands.json"
+	configFilename  = "config.json"
+	boxesFilename   = "boxes.json"
+	commandsDirname = "commands"
 )
 
 // Read reads application config from JSON files.
@@ -24,7 +27,7 @@ func Read(path string) (*Config, error) {
 		return nil, err
 	}
 
-	cfg, err = ReadCommands(cfg, filepath.Join(path, commandsFilename))
+	cfg, err = ReadCommands(cfg, filepath.Join(path, commandsDirname))
 	if err != nil {
 		return nil, err
 	}
@@ -71,31 +74,36 @@ func ReadBoxes(cfg *Config, path string) (*Config, error) {
 
 // ReadCommands reads commands config from a JSON file.
 func ReadCommands(cfg *Config, path string) (*Config, error) {
-	data, err := os.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-
-	commands := make(map[string]SandboxCommands)
-	err = json.Unmarshal(data, &commands)
+	fnames, err := filepath.Glob(filepath.Join(path, "*.json"))
 	if err != nil {
 		return nil, err
 	}
 
-	for _, playCmds := range commands {
-		for _, cmd := range playCmds {
-			if cmd.Before != nil {
-				setStepDefaults(cmd.Before, cfg.Step)
-			}
-			for _, step := range cmd.Steps {
-				setStepDefaults(step, cfg.Step)
-			}
-			if cmd.After != nil {
-				setStepDefaults(cmd.After, cfg.Step)
-			}
+	cfg.Commands = make(map[string]SandboxCommands, len(fnames))
+	for _, fname := range fnames {
+		sandbox := strings.TrimSuffix(filepath.Base(fname), ".json")
+		commands, err := fileio.ReadJson[SandboxCommands](fname)
+		if err != nil {
+			break
 		}
+		setCommandDefaults(commands, cfg)
+		cfg.Commands[sandbox] = commands
 	}
 
-	cfg.Commands = commands
 	return cfg, err
 }
+
+// setCommandDefaults applies global defaults to sandbox commands.
+func setCommandDefaults(commands SandboxCommands, cfg *Config) {
+	for _, cmd := range commands {
+		if cmd.Before != nil {
+			setStepDefaults(cmd.Before, cfg.Step)
+		}
+		for _, step := range cmd.Steps {
+			setStepDefaults(step, cfg.Step)
+		}
+		if cmd.After != nil {
+			setStepDefaults(cmd.After, cfg.Step)
+		}
+	}
+}
diff --git a/internal/config/testdata/commands.json b/internal/config/testdata/commands.json
deleted file mode 100644
index 0e425c3..0000000
--- a/internal/config/testdata/commands.json
+++ /dev/null
@@ -1,25 +0,0 @@
-{
-    "python": {
-        "run": {
-            "engine": "docker",
-            "entry": "main.py",
-            "steps": [
-                {
-                    "box": "python",
-                    "command": ["python", "main.py"]
-                }
-            ]
-        },
-        "test": {
-            "engine": "docker",
-            "entry": "test_main.py",
-            "steps": [
-                {
-                    "box": "python",
-                    "command": ["python", "-m", "unittest"],
-                    "noutput": 8192
-                }
-            ]
-        }
-    }
-}
diff --git a/internal/config/testdata/commands/python.json b/internal/config/testdata/commands/python.json
new file mode 100644
index 0000000..9adde23
--- /dev/null
+++ b/internal/config/testdata/commands/python.json
@@ -0,0 +1,23 @@
+{
+    "run": {
+        "engine": "docker",
+        "entry": "main.py",
+        "steps": [
+            {
+                "box": "python",
+                "command": ["python", "main.py"]
+            }
+        ]
+    },
+    "test": {
+        "engine": "docker",
+        "entry": "test_main.py",
+        "steps": [
+            {
+                "box": "python",
+                "command": ["python", "-m", "unittest"],
+                "noutput": 8192
+            }
+        ]
+    }
+}
diff --git a/internal/fileio/fileio.go b/internal/fileio/fileio.go
index 6c77a19..6b672cb 100644
--- a/internal/fileio/fileio.go
+++ b/internal/fileio/fileio.go
@@ -2,6 +2,7 @@
 package fileio
 
 import (
+	"encoding/json"
 	"io"
 	"os"
 	"path/filepath"
@@ -37,3 +38,17 @@ func CopyFiles(pattern string, dstDir string) error {
 
 	return nil
 }
+
+// ReadJson reads the file and decodes it from JSON.
+func ReadJson[T any](path string) (T, error) {
+	var obj T
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return obj, err
+	}
+	err = json.Unmarshal(data, &obj)
+	if err != nil {
+		return obj, err
+	}
+	return obj, err
+}
diff --git a/internal/fileio/fileio_test.go b/internal/fileio/fileio_test.go
index 8ac2f71..c4513ac 100644
--- a/internal/fileio/fileio_test.go
+++ b/internal/fileio/fileio_test.go
@@ -3,6 +3,7 @@ package fileio
 import (
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 )
 
@@ -54,3 +55,30 @@ func TestCopyFiles(t *testing.T) {
 		t.Errorf("unexpected file content: got %q, want %q", data, expected)
 	}
 }
+
+func TestReadJson(t *testing.T) {
+	type Person struct{ Name string }
+
+	t.Run("valid", func(t *testing.T) {
+		got, err := ReadJson[Person](filepath.Join("testdata", "valid.json"))
+		if err != nil {
+			t.Fatalf("unexpected error %v", err)
+		}
+		want := Person{"alice"}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("expected %v, got %v", want, got)
+		}
+	})
+	t.Run("invalid", func(t *testing.T) {
+		_, err := ReadJson[Person](filepath.Join("testdata", "invalid.json"))
+		if err == nil {
+			t.Fatal("expected error, got nil")
+		}
+	})
+	t.Run("does not exist", func(t *testing.T) {
+		_, err := ReadJson[Person](filepath.Join("testdata", "missing.json"))
+		if err == nil {
+			t.Fatal("expected error, got nil")
+		}
+	})
+}
diff --git a/internal/fileio/testdata/invalid.json b/internal/fileio/testdata/invalid.json
new file mode 100644
index 0000000..2bcad2f
--- /dev/null
+++ b/internal/fileio/testdata/invalid.json
@@ -0,0 +1 @@
+name: alice
diff --git a/internal/fileio/testdata/valid.json b/internal/fileio/testdata/valid.json
new file mode 100644
index 0000000..7185646
--- /dev/null
+++ b/internal/fileio/testdata/valid.json
@@ -0,0 +1,3 @@
+{
+    "name": "alice"
+}