diff --git a/claude_code/wrapper/main.go b/claude_code/wrapper/main.go
index 9bcb4f8..4dd1943 100644
--- a/claude_code/wrapper/main.go
+++ b/claude_code/wrapper/main.go
@@ -249,6 +249,10 @@ func cmdBuild(args []string) {
 		cmd = append(cmd, "--dangerously-skip-permissions")
 	}
 
+	// Stream-json output format: emits JSONL to stdout, including a final
+	// "result" message with token usage data for cost tracking.
+	cmd = append(cmd, "--output-format", "stream-json")
+
 	// Disallow Claude Code's native scheduling tools — StrawPot manages
 	// scheduling through its own orchestrator (denden).
 	cmd = append(cmd, "--disallowedTools", "CronCreate,CronDelete,CronList")
diff --git a/claude_code/wrapper/main_test.go b/claude_code/wrapper/main_test.go
index e5e4593..334760a 100644
--- a/claude_code/wrapper/main_test.go
+++ b/claude_code/wrapper/main_test.go
@@ -364,6 +364,25 @@ func TestCmdBuild_DangerouslySkipPermissions_Disabled(t *testing.T) {
 	}
 }
 
+func TestCmdBuild_StreamJsonOutputFormat(t *testing.T) {
+	tmpDir := t.TempDir()
+	wsDir := filepath.Join(tmpDir, "workspace")
+
+	args := []string{
+		"--agent-workspace-dir", wsDir,
+	}
+
+	output := captureBuildOutput(t, args)
+
+	var result map[string]interface{}
+	if err := json.Unmarshal(output, &result); err != nil {
+		t.Fatalf("Failed to parse JSON output: %v", err)
+	}
+
+	cmd := result["cmd"].([]interface{})
+	assertSequence(t, cmd, "--output-format", "stream-json")
+}
+
 func TestCmdBuild_DisallowedSchedulingTools(t *testing.T) {
 	tmpDir := t.TempDir()
 	wsDir := filepath.Join(tmpDir, "workspace")