Write run outputs and diagnostics

internal/core/diagnostics/run_dir_test.go

@@ -118,6 +118,24 @@ func TestWriteJSONArtifactWritesIndentedNewlineTerminatedJSON(t *testing.T) {
 	}
 }
 
+func TestWriteJSONArtifactLeavesNoTemporaryFiles(t *testing.T) {
+	runDir := newTestRunDirectory(t)
+
+	if err := runDir.WriteJSONArtifact("artifact.json", map[string]any{"value": "ok"}); err != nil {
+		t.Fatalf("WriteJSONArtifact: %v", err)
+	}
+
+	entries, err := os.ReadDir(runDir.Path())
+	if err != nil {
+		t.Fatalf("read run directory: %v", err)
+	}
+	for _, entry := range entries {
+		if strings.Contains(entry.Name(), ".tmp-") {
+			t.Fatalf("temporary diagnostics file remains after success: %s", entry.Name())
+		}
+	}
+}
+
 func TestWriteInvocationMetadataFillsMissingRunIDAndStartTime(t *testing.T) {
 	runDir := newTestRunDirectory(t)