diff --git a/README.md b/README.md
index ab89df9..1d7f94a 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,7 @@ Output:
 
 ```json
 {
-  "cmd": ["claude", "-p", "fix the bug", "--system-prompt", "/path/to/workspace/prompt.md", "--model", "claude-opus-4-6", "--dangerously-skip-permissions", "--add-dir", "/path/to/workspace"],
+  "cmd": ["claude", "-p", "fix the bug", "--system-prompt-file", "/path/to/workspace/prompt.md", "--model", "claude-opus-4-6", "--dangerously-skip-permissions", "--add-dir", "/path/to/workspace"],
   "cwd": "/path/to/project"
 }
 ```
diff --git a/claude_code/wrapper/main.go b/claude_code/wrapper/main.go
index 108358c..5fabbfd 100644
--- a/claude_code/wrapper/main.go
+++ b/claude_code/wrapper/main.go
@@ -227,7 +227,7 @@ func cmdBuild(args []string) {
 		cmd = append(cmd, "-p", ba.Task)
 	}
 
-	cmd = append(cmd, "--system-prompt", promptFile)
+	cmd = append(cmd, "--system-prompt-file", promptFile)
 
 	if model, ok := config["model"].(string); ok && model != "" {
 		cmd = append(cmd, "--model", model)
diff --git a/claude_code/wrapper/main_test.go b/claude_code/wrapper/main_test.go
index 0bb2bab..2db67b9 100644
--- a/claude_code/wrapper/main_test.go
+++ b/claude_code/wrapper/main_test.go
@@ -97,7 +97,7 @@ func TestCmdBuild_MinimalArgs(t *testing.T) {
 	}
 
 	assertContains(t, cmd, "claude")
-	assertContains(t, cmd, "--system-prompt")
+	assertContains(t, cmd, "--system-prompt-file")
 	assertContains(t, cmd, "--add-dir")
 	assertContains(t, cmd, wsDir)