diff --git a/customize.sh b/customize.sh
index 35593a6..f9f034b 100755
--- a/customize.sh
+++ b/customize.sh
@@ -392,6 +392,7 @@ apt-get update
 DEBIAN_FRONTEND=noninteractive apt-get -y upgrade
 DEBIAN_FRONTEND=noninteractive apt-get -y install ${APT_PACKAGES_ESCAPED}
 curl -fsSL https://mise.run | MISE_INSTALL_PATH=\"$MISE_INSTALL_PATH\" MISE_VERSION=\"$MISE_VERSION\" sh
+\"$MISE_INSTALL_PATH\" use -g github:anomalyco/opencode
 mkdir -p /etc/profile.d
 cat > /etc/profile.d/mise.sh <<'MISEPROFILE'
 if [ -n \"\${BASH_VERSION:-}\" ] && [ -x \"$MISE_INSTALL_PATH\" ]; then
diff --git a/internal/daemon/imagebuild.go b/internal/daemon/imagebuild.go
index 2186cc3..51aec52 100644
--- a/internal/daemon/imagebuild.go
+++ b/internal/daemon/imagebuild.go
@@ -23,6 +23,7 @@ const (
 	defaultMiseVersion      = "v2025.12.0"
 	defaultMiseInstallPath  = "/usr/local/bin/mise"
 	defaultMiseActivateLine = `eval "$(/usr/local/bin/mise activate bash)"`
+	defaultOpenCodeTool     = "github:anomalyco/opencode"
 )
 
 type imageBuildSpec struct {
@@ -258,6 +259,7 @@ func buildModulesCommand(modulesBase string) string {
 
 func appendMiseSetup(script *bytes.Buffer) {
 	fmt.Fprintf(script, "curl -fsSL https://mise.run | MISE_INSTALL_PATH=%s MISE_VERSION=%s sh\n", shellQuote(defaultMiseInstallPath), shellQuote(defaultMiseVersion))
+	fmt.Fprintf(script, "%s use -g %s\n", shellQuote(defaultMiseInstallPath), shellQuote(defaultOpenCodeTool))
 	script.WriteString("mkdir -p /etc/profile.d\n")
 	script.WriteString("cat > /etc/profile.d/mise.sh <<'EOF'\n")
 	fmt.Fprintf(script, "if [ -n \"${BASH_VERSION:-}\" ] && [ -x %s ]; then\n", shellQuote(defaultMiseInstallPath))
diff --git a/internal/daemon/imagebuild_test.go b/internal/daemon/imagebuild_test.go
index 86b2733..56d404b 100644
--- a/internal/daemon/imagebuild_test.go
+++ b/internal/daemon/imagebuild_test.go
@@ -11,6 +11,7 @@ func TestBuildProvisionScriptInstallsAndActivatesMise(t *testing.T) {
 	script := buildProvisionScript("devbox", "1.1.1.1", []string{"git", "curl"}, false)
 	for _, snippet := range []string{
 		"curl -fsSL https://mise.run | MISE_INSTALL_PATH='/usr/local/bin/mise' MISE_VERSION='v2025.12.0' sh",
+		"'/usr/local/bin/mise' use -g 'github:anomalyco/opencode'",
 		"cat > /etc/profile.d/mise.sh <<'EOF'",
 		"if [ -n \"${BASH_VERSION:-}\" ] && [ -x '/usr/local/bin/mise' ]; then",
 		`eval "$(/usr/local/bin/mise activate bash)"`,