fix dolt panic and close mrEnv dbs on engine open error

driver.go

@@ -68,7 +68,12 @@ func openSqlEngine(ctx context.Context, cfg config.ReadWriteConfig, fs filesys.F
 	}
 
 	go emitUsageEvent(context.Background(), mrEnv)
-	return engine.NewSqlEngine(ctx, mrEnv, seCfg)
+	se, err := engine.NewSqlEngine(ctx, mrEnv, seCfg)
+	if err != nil {
+		mrEnv.Close(ctx)
+		return nil, err
+	}
+	return se, nil
 }
 
 // Open opens and returns a connection to the datasource referenced by the string provided using the options provided.

go.mod

@@ -4,7 +4,7 @@ go 1.25.6
 
 require (
 	github.com/cenkalti/backoff/v4 v4.2.1
-	github.com/dolthub/dolt/go v0.40.5-0.20260316195416-ff749ef50e2e
+	github.com/dolthub/dolt/go v0.40.5-0.20260316200056-24e549c548e1
 	github.com/dolthub/eventsapi_schema v0.0.0-20260310172945-37a9265ade69
 	github.com/dolthub/go-mysql-server v0.20.1-0.20260313230549-0986a7fcf0fe
 	github.com/dolthub/vitess v0.0.0-20260309181228-a99af9c518ab

go.sum

@@ -331,8 +331,8 @@ github.com/dolthub/aws-sdk-go-ini-parser v0.0.0-20250305001723-2821c37f6c12 h1:I
 github.com/dolthub/aws-sdk-go-ini-parser v0.0.0-20250305001723-2821c37f6c12/go.mod h1:rN7X8BHwkjPcfMQQ2QTAq/xM3leUSGLfb+1Js7Y6TVo=
 github.com/dolthub/dolt-mcp v0.3.4 h1:AyG5cw+fNWXDHXujtQnqUPZrpWtPg6FN6yYtjv1pP44=
 github.com/dolthub/dolt-mcp v0.3.4/go.mod h1:bCZ7KHvDYs+M0e+ySgmGiNvLhcwsN7bbf5YCyillLrk=
-github.com/dolthub/dolt/go v0.40.5-0.20260316195416-ff749ef50e2e h1:kTT/Kup+JQCwmsJpTv2T2X/JLEJY8TuQespI8iTItag=
-github.com/dolthub/dolt/go v0.40.5-0.20260316195416-ff749ef50e2e/go.mod h1:x0TL0LQX70EdjIcj+RdIxYqGAVRpZk3IXDrHG6NW9B8=
+github.com/dolthub/dolt/go v0.40.5-0.20260316200056-24e549c548e1 h1:dCEG+v2yaZUSyqkbG1YeHxsgt+l4fpc6+X6pmlJHXSU=
+github.com/dolthub/dolt/go v0.40.5-0.20260316200056-24e549c548e1/go.mod h1:x0TL0LQX70EdjIcj+RdIxYqGAVRpZk3IXDrHG6NW9B8=
 github.com/dolthub/eventsapi_schema v0.0.0-20260310172945-37a9265ade69 h1:JShhbqMw26nKx3pqqu/cFxOpzBkN+4elVhzuUfgDw2k=
 github.com/dolthub/eventsapi_schema v0.0.0-20260310172945-37a9265ade69/go.mod h1:SSLraQS/jGLYFgff3vuZ+JbVUct6vyEeMzjLBqWqoyM=
 github.com/dolthub/flatbuffers v1.13.0-dh.1 h1:OWJdaPep22N52O/0xsUevxJ6Qfw1M2txCjZPOdjXybE=

lock_contention_test.go

@@ -0,0 +1,98 @@
+// Copyright 2026 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package embedded
+
+import (
+	"context"
+	"database/sql"
+	"net/url"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/cenkalti/backoff/v4"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestMultiDBLockContention verifies that when one connection holds the write lock on a
+// subdirectory database, a second connection opening the parent directory (which discovers
+// and tries to open the same subdirectory) returns an error instead of panicking.
+func TestMultiDBLockContention(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping on Windows: file handle cleanup is racey with t.TempDir()")
+	}
+
+	metricsDisabled.Store(true)
+
+	rootDir, err := os.MkdirTemp("", "TestMultiDBLockContention")
+	require.NoError(t, err)
+	defer os.RemoveAll(rootDir)
+
+	ctx := context.Background()
+
+	baseQuery := url.Values{
+		"commitname":  []string{"test"},
+		"commitemail": []string{"test@test.com"},
+	}
+
+	// First, open the root directory and create a "first" database so that
+	// a .dolt directory exists at rootDir/first.
+	rootDSN := url.URL{Scheme: "file", Path: encodeDir(rootDir), RawQuery: baseQuery.Encode()}
+	rootCfg, err := ParseDSN(rootDSN.String())
+	require.NoError(t, err)
+	rootConnector, err := NewConnector(rootCfg)
+	require.NoError(t, err)
+	setupDB := sql.OpenDB(rootConnector)
+	conn, err := setupDB.Conn(ctx)
+	require.NoError(t, err)
+	_, err = conn.ExecContext(ctx, "CREATE DATABASE `firstdb`")
+	require.NoError(t, err)
+	require.NoError(t, conn.Close())
+	_ = rootConnector.Close()
+
+	// Now open the subdirectory database directly — this holds the journal/write lock.
+	subDir := filepath.Join(rootDir, "firstdb")
+	subDSN := url.URL{Scheme: "file", Path: encodeDir(subDir), RawQuery: baseQuery.Encode()}
+	subCfg, err := ParseDSN(subDSN.String())
+	require.NoError(t, err)
+	subConnector, err := NewConnector(subCfg)
+	require.NoError(t, err)
+	subDB := sql.OpenDB(subConnector)
+	require.NoError(t, subDB.PingContext(ctx))
+
+	// Now open the root directory again with a bounded backoff. It will discover
+	// the "firstdb" subdirectory and fail to acquire its lock. This must return an
+	// error, not panic.
+	rootCfg2, err := ParseDSN(rootDSN.String())
+	require.NoError(t, err)
+	bo := backoff.NewExponentialBackOff()
+	bo.MaxElapsedTime = 2 * time.Second
+	bo.MaxInterval = 100 * time.Millisecond
+	rootCfg2.BackOff = bo
+	rootConnector2, err := NewConnector(rootCfg2)
+	require.NoError(t, err)
+	rootDB2 := sql.OpenDB(rootConnector2)
+
+	err = rootDB2.PingContext(ctx)
+	assert.Error(t, err, "expected an error due to lock contention, not a panic")
+
+	rootDB2.Close()
+	_ = rootConnector2.Close()
+	subDB.Close()
+	_ = subConnector.Close()
+}