diff --git a/claudetool/bash.go b/claudetool/bash.go
index 882dddf..b24e700 100644
--- a/claudetool/bash.go
+++ b/claudetool/bash.go
@@ -167,6 +167,9 @@
 	cmd.Dir = WorkingDir(ctx)
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 
+	// Set environment with SKETCH=1
+	cmd.Env = append(os.Environ(), "SKETCH=1")
+
 	var output bytes.Buffer
 	cmd.Stdin = nil
 	cmd.Stdout = &output
@@ -246,6 +249,9 @@
 	cmd.Dir = WorkingDir(ctx)
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 
+	// Set environment with SKETCH=1
+	cmd.Env = append(os.Environ(), "SKETCH=1")
+
 	// Open output files
 	stdout, err := os.Create(stdoutFile)
 	if err != nil {