Harden configuration validation

internal/app/operator_session_init_test.go

@@ -0,0 +1,52 @@
+package app
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestSessionInitRejectsRenderedTemplateThatOmitsExpectedPreviousSession(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	pipelinePath, campaignPath, _ := writeValidConfigFiles(t, workspaceRoot)
+	campaignDir := filepath.Dir(campaignPath)
+	templatePath := filepath.Join(campaignDir, "session.template.yml")
+	template := `session_id: {{ session_id }}
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+`
+	if err := os.WriteFile(templatePath, []byte(template), 0o644); err != nil {
+		t.Fatalf("write session template: %v", err)
+	}
+	campaign := `campaign_id: sample-campaign
+session_template_file: session.template.yml
+inputs:
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+  players_file: ./players.yml
+  party_file: ./party.yml
+`
+	if err := os.WriteFile(campaignPath, []byte(campaign), 0o644); err != nil {
+		t.Fatalf("write campaign config: %v", err)
+	}
+
+	var out bytes.Buffer
+	err := SessionInit(context.Background(), []string{
+		"2026-05-03",
+		"--config", pipelinePath,
+		"--campaign-file", campaignPath,
+		"--output", filepath.Join(t.TempDir(), "session.yml"),
+		"--previous-session-id", "2026-04-26",
+	}, &out)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "unused template variable value(s): previous_session_id") {
+		t.Fatalf("SessionInit() error = %q, want missing previous-session template error", err.Error())
+	}
+}