sam sync throws "Build method missing" error on static nodejs modules

I am using nodejs and "sam sync". I have a layer with shared js code that doesn't need to be built. I am using ES Modules for imports.

While I have this working, any changes to my shared code module results in a "Build method missing in layer" error making quick iteration difficult.

SAM CLI, version 1.70.0

Directory structure:

layers-test/{template.yaml, samconfig.toml}
layers-test/hello-world/{app.js, package.json}
layers-test/shared-code/tools/{tools.js, package.json}
layers-test/shared-code/util/{util.js, package.json}
layers-test/shared-modules/{package.json, package-lock.json, node_modules/}

hello-world/app.js:

import pick from "lodash.pick";
import { utilFunction } from "/opt/util/util.js";
import { toolsFunction } from "/opt/tools/tools.js";

export const lambdaHandler = async (event, context) => {
 try {
 utilFunction();
 toolsFunction();
 console.log('rez:', pick({ a: 40, b: 30, c: 20 }, ['a', 'b']));
 return {
 'statusCode': 200,
 'body': JSON.stringify({
 message: 'hello world',
 })
 }
 } catch (err) {
 console.log(err);
 return err;
 }
};

shared-modules/package.json:

{
 "name": "shared-modules",
 "version": "1.0.0",
 "description": "",
 "dependencies": {
 "lodash.pick": "^4.4.0"
 }
}

shared-code/util/util.js:

export const utilFunction = () => {
 console.log('running utilFunction');
};

shared-code/util/package.json:

{
 "name": "util",
 "version": "1.0.0",
 "description": "",
 "main": "util.js",
 "type": "module"
}

template.yaml:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
 layers-test

 Sample SAM Template for layers-test

Globals:
 Function:
 Timeout: 3

Resources:
 HelloWorldFunction:
 Type: AWS::Serverless::Function
 Properties:
 CodeUri: hello-world/
 Handler: app.lambdaHandler
 Runtime: nodejs18.x
 Architectures:
 - x86_64
 Layers:
 - !Ref SharedModulesLayer
 - !Ref SharedCodeLayer
 Events:
 HelloWorld:
 Type: Api
 Properties:
 Path: /hello
 Method: get

 SharedModulesLayer:
 Type: AWS::Serverless::LayerVersion
 Properties:
 ContentUri: layers/shared-modules
 CompatibleRuntimes:
 - nodejs18.x
 Metadata:
 BuildMethod: nodejs18.x
 BuildArchitecture: x86_64
 SharedCodeLayer:
 Type: AWS::Serverless::LayerVersion
 Properties:
 ContentUri: layers/shared-code
 CompatibleRuntimes:
 - nodejs18.x

All of this code works, but with sam sync active, whenever I make changes to anything in shared-code/ I get the error:

Syncing Layer SharedCodeLayer...
Layer <samcli.lib.providers.sam_function_provider.SamFunctionProvider object at 0x7f19797b81d0> is missing BuildMethod Metadata.
Code sync encountered an error.
Traceback (most recent call last):
 File "samcli/lib/sync/sync_flow_executor.py", line 342, in _sync_flow_execute_wrapper
 File "samcli/lib/sync/sync_flow.py", line 310, in execute
 File "samcli/lib/sync/flows/layer_sync_flow.py", line 224, in gather_resources
 File "samcli/commands/build/build_context.py", line 523, in collect_build_resources
 File "samcli/commands/build/build_context.py", line 611, in _collect_single_buildable_layer
samcli.commands.build.exceptions.MissingBuildMethodException: Build method missing in layer SharedCodeLayer.

If I add:

 Metadata:
 BuildMethod: nodejs18.x
 BuildArchitecture: x86_64

to SharedCodeLayer then the imports no longer work. I get an error like:

Uncaught Exception {"errorType":"Error","errorMessage":"Cannot find module '/opt/util/util.js' imported from /var/task/app.js","code":"ERR_MODULE_NOT_FOUND","stack":["Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/opt/util/util.js' imported from /var/task/app.js"," at new NodeError (node:internal/errors:393:5)"," at finalizeResolution (node:internal/modules/esm/resolve:328:11)"," at moduleResolve (node:internal/modules/esm/resolve:965:10)"," at moduleResolveWithNodePath (node:internal/modules/esm/resolve:909:12)"," at defaultResolve (node:internal/modules/esm/resolve:1173:79)"," at nextResolve (node:internal/modules/esm/loader:163:28)"," at ESMLoader.resolve (node:internal/modules/esm/loader:841:30)"," at ESMLoader.getModuleJob (node:internal/modules/esm/loader:424:18)"," at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:76:40)"," at link (node:internal/modules/esm/module_job:75:36)"]}

Is there any way to make these imports work while avoiding the "Build method missing in layer" in error?