fix(config): skip writeback bootstrap on invalid env config

internal/config/config_test.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"encoding/base64"
+	"errors"
 	"os"
 	"strings"
 	"testing"
@@ -124,6 +125,35 @@ func TestEnvBackedStoreWritebackBootstrapsMissingConfigFile(t *testing.T) {
 	}
 }
 
+func TestEnvBackedStoreWritebackDoesNotBootstrapOnInvalidEnvJSON(t *testing.T) {
+	tmp, err := os.CreateTemp(t.TempDir(), "config-*.json")
+	if err != nil {
+		t.Fatalf("create temp config: %v", err)
+	}
+	path := tmp.Name()
+	_ = tmp.Close()
+	_ = os.Remove(path)
+
+	t.Setenv("DS2API_CONFIG_JSON", "{invalid-json")
+	t.Setenv("CONFIG_JSON", "")
+	t.Setenv("DS2API_CONFIG_PATH", path)
+	t.Setenv("DS2API_ENV_WRITEBACK", "1")
+
+	cfg, fromEnv, loadErr := loadConfig()
+	if loadErr == nil {
+		t.Fatalf("expected loadConfig error for invalid env json")
+	}
+	if !fromEnv {
+		t.Fatalf("expected fromEnv=true when parsing env config fails")
+	}
+	if len(cfg.Keys) != 0 || len(cfg.Accounts) != 0 {
+		t.Fatalf("expected empty config on parse failure, got keys=%d accounts=%d", len(cfg.Keys), len(cfg.Accounts))
+	}
+	if _, statErr := os.Stat(path); !errors.Is(statErr, os.ErrNotExist) {
+		t.Fatalf("expected no bootstrapped config file, stat err=%v", statErr)
+	}
+}
+
 func TestRuntimeTokenRefreshIntervalHoursDefaultsToSix(t *testing.T) {
 	t.Setenv("DS2API_CONFIG_JSON", `{
 		"keys":["k1"],

internal/config/store.go

@@ -47,6 +47,9 @@ func loadConfig() (Config, bool, error) {
 	}
 	if rawCfg != "" {
 		cfg, err := parseConfigString(rawCfg)
+		if err != nil {
+			return cfg, true, err
+		}
 		cfg.ClearAccountTokens()
 		cfg.DropInvalidAccounts()
 		if IsVercel() || !envWritebackEnabled() {