diff --git a/developer/src/kmc-convert/src/converter-messages.ts b/developer/src/kmc-convert/src/converter-messages.ts
index 1d8aa5e70b..115315cc03 100644
--- a/developer/src/kmc-convert/src/converter-messages.ts
+++ b/developer/src/kmc-convert/src/converter-messages.ts
@@ -25,41 +25,40 @@ export class ConverterMessages {
   static ERROR_NoConverterFound = SevError | 0x0002;
   static Error_NoConverterFound = (o: { inputFilename: string, outputFilename: string; }) => m(
     this.ERROR_NoConverterFound,
-    `No converter is available that can convert from '${def(o.inputFilename)}' to '${def(o.outputFilename)}'.`
+    `No converter is available that can convert from '${def(o.inputFilename)}' to '${def(o.outputFilename)}'.`,
   );
 
   static ERROR_FileNotFound = SevError | 0x0003;
   static Error_FileNotFound = (o: { inputFilename: string; }) => m(
-    this.ERROR_FileNotFound, `Input filename '${def(o.inputFilename)}
-    ' does not exist or could not be loaded.`
+    this.ERROR_FileNotFound,
+    `Input filename '${def(o.inputFilename)} ' does not exist or could not be loaded.`,
   );
 
   static ERROR_UnableToRead = SevError | 0x0004;
   static Error_UnableToRead = (o: { inputFilename: string; }) => m(
-    this.ERROR_UnableToRead, `Input file '${def(o.inputFilename)}
-    ' could not be read.`
+    this.ERROR_UnableToRead,
+    `Input file '${def(o.inputFilename)} ' could not be read.`,
   );
 
   static ERROR_UnableToConvert = SevError | 0x0005;
   static Error_UnableToConvert = (o: { inputFilename: string; }) => m(
-    this.ERROR_UnableToConvert, `Input file '${def(o.inputFilename)}
-    ' could not be converted.`
+    this.ERROR_UnableToConvert,
+    `Input file '${def(o.inputFilename)} ' could not be converted.`,
   );
 
   static ERROR_UnableToWrite = SevError | 0x0006;
   static Error_UnableToWrite = (o: { outputFilename: string; }) => m(
-    this.ERROR_UnableToWrite, `Output file for '${def(o.outputFilename)}
-    ' could not be written.`
+    this.ERROR_UnableToWrite,
+    `Output file for '${def(o.outputFilename)} ' could not be written.`,
   );
 
   static ERROR_UnsupportedCharactersDetected = SevError | 0x0007;
   static Error_UnsupportedCharactersDetected = (o: { inputFilename: string, keymap_index: string, key: string, output: string; }) => m(
-    this.ERROR_UnsupportedCharactersDetected, `Input file ${def(o.inputFilename)} contains unsupported character ('${def(o.output)}') on key (${def(o.key)}) at keyMap index ${def(o.keymap_index)}`
+    this.ERROR_UnsupportedCharactersDetected,
+    `Input file ${def(o.inputFilename)} contains unsupported character ('${def(o.output)}') on key ( ${def(o.key)}) at keyMap index ${def(o.keymap_index)}`,
   );
 
   static ERROR_InvalidFile = SevError | 0x0008;
   static Error_InvalidFile = (o: { errorText: string; }) => m(
-    this.ERROR_InvalidFile, `The source file has an invalid structure: ${def(o.errorText)}`
-  );
-
+    this.ERROR_InvalidFile, `The source file has an invalid structure: ${def(o.errorText)}`);
 }
diff --git a/developer/src/kmc-convert/src/converter.ts b/developer/src/kmc-convert/src/converter.ts
index 2e9911073a..8335c052db 100644
--- a/developer/src/kmc-convert/src/converter.ts
+++ b/developer/src/kmc-convert/src/converter.ts
@@ -83,7 +83,8 @@ export class Converter implements KeymanCompiler {
     const converter = new ConverterClass(this.callbacks, converterOptions);
     const artifacts = await converter.run(inputFilename, outputFilename);
     // Note: any subsequent errors in conversion will have been reported by the converter
-    return artifacts ? { artifacts } : null;
+    //return artifacts ? { artifacts } : null;
+    return artifacts ?  artifacts : null;
   }
 
   /**
diff --git a/developer/src/kmc-convert/src/keylayout-to-kmn/keylayout-to-kmn-converter.ts b/developer/src/kmc-convert/src/keylayout-to-kmn/keylayout-to-kmn-converter.ts
index 0c4e9e0e0d..4e18cbc17b 100644
--- a/developer/src/kmc-convert/src/keylayout-to-kmn/keylayout-to-kmn-converter.ts
+++ b/developer/src/kmc-convert/src/keylayout-to-kmn/keylayout-to-kmn-converter.ts
@@ -7,19 +7,32 @@
  *
  */
 
-import { CompilerCallbacks, CompilerOptions } from "@keymanapp/developer-utils";
-import { ConverterToKmnArtifacts } from "../converter-artifacts.js";
+import { CompilerCallbacks, CompilerOptions, KeymanCompilerResult, } from "@keymanapp/developer-utils";
 import { KmnFileWriter } from './kmn-file-writer.js';
 import { KeylayoutFileReader } from './keylayout-file-reader.js';
 import { ConverterMessages } from '../converter-messages.js';
+import { ConverterArtifacts } from "../converter-artifacts.js";
+import { ConverterToKmnArtifacts } from "../converter-artifacts.js"
 import { KeylayoutXMLSourceFile } from '../../../common/web/utils/src/types/keylayout/keylayout-xml.js';
 
-/**
- * Object holding all important data for the conversion between
- * input (*.keylayout) format and output (*.kmn) format.
- * It contains input and output filenames, an array of all used modifiers
- * and all preprocessed key rules for up to 3 key/modifier combinations.
- */
+
+export interface ConverterResult extends KeymanCompilerResult {
+  /**
+   * Internal in-memory build artifacts from a successful compilation. Caller
+   * can write these to disk with {@link Converter.write}
+   */
+  artifacts: ConverterArtifacts;
+};
+
+export interface ConverterToKmnResult extends ConverterResult {
+  /**
+   * Internal in-memory build artifacts from a successful compilation. Caller
+   * can write these to disk with {@link Converter.write}
+   */
+  artifacts: ConverterToKmnArtifacts;
+};
+
+
 export interface convert_object {
   keylayout_filename: string,
   kmn_filename: string,
@@ -51,14 +64,15 @@ export class KeylayoutToKmnConverter {
    * @param  outputFilename the resulting keyman .kmn-file
    * @return null on success
    */
-  async run(inputFilename: string, outputFilename?: string): Promise<ConverterToKmnArtifacts> {
-
+  async run(inputFilename: string, outputFilename?: string): Promise<ConverterToKmnResult> {
 
     if (!inputFilename) {
       this.callbacks.reportMessage(ConverterMessages.Error_FileNotFound({ inputFilename }));
       return null;
     }
 
+    outputFilename = outputFilename ?? inputFilename.replace(/\.keylayout$/, '.kmn');
+
     const KeylayoutReader = new KeylayoutFileReader(this.callbacks/*, this.options*/);
     const jsonO: KeylayoutXMLSourceFile = KeylayoutReader.read(inputFilename);
 
@@ -76,8 +90,6 @@ export class KeylayoutToKmnConverter {
       return null;
     }
 
-    outputFilename = outputFilename ?? inputFilename.replace(/\.keylayout$/, '.kmn');
-
     const outArray: convert_object = await this.convert(jsonO, outputFilename);
     if (!outArray) {
       this.callbacks.reportMessage(ConverterMessages.Error_UnableToConvert({ inputFilename }));
@@ -86,15 +98,27 @@ export class KeylayoutToKmnConverter {
 
     const kmnFileWriter = new KmnFileWriter(this.callbacks, this.options);
 
-    const out_text_ok: boolean = kmnFileWriter.write(outArray);
+    // _S2 still write to file - will be removed later
+    const out_text_ok: boolean = kmnFileWriter.writeToFile(outArray);
     if (!out_text_ok) {
       this.callbacks.reportMessage(ConverterMessages.Error_UnableToWrite({ outputFilename }));
       return null;
     }
 
-    return null;
-  }
+    // write to object/ConverterToKmnResult
+    const out_Uint8: Uint8Array = kmnFileWriter.write(outArray);
+    const Result_toBeReturned: ConverterToKmnResult = {
+      artifacts: {
+        kmn: { data: out_Uint8, filename: outputFilename }
+      }
+    };
 
+    if (!out_Uint8) {
+      this.callbacks.reportMessage(ConverterMessages.Error_UnableToWrite({ outputFilename }));
+      return null;
+    }
+    return Result_toBeReturned;
+  }
 
   /**
    * @brief  member function to read filename and behaviour of a json object into a convert_object
diff --git a/developer/src/kmc-convert/src/keylayout-to-kmn/kmn-file-writer.ts b/developer/src/kmc-convert/src/keylayout-to-kmn/kmn-file-writer.ts
index b78f69fbcc..906be3538f 100644
--- a/developer/src/kmc-convert/src/keylayout-to-kmn/kmn-file-writer.ts
+++ b/developer/src/kmc-convert/src/keylayout-to-kmn/kmn-file-writer.ts
@@ -23,7 +23,7 @@ export class KmnFileWriter {
    * @param  outputfilename the file that will be written; if no outputfilename is given an outputfilename will be created from data_ukelele.keylayout_filename
    * @return true if data has been written; false if not
    */
-  public write(data_ukelele: convert_object): boolean {
+  public writeToFile(data_ukelele: convert_object): boolean {
 
     let data: string = "\n";
 
@@ -37,29 +37,12 @@ export class KmnFileWriter {
       this.callbacks.fs.writeFileSync(data_ukelele.kmn_filename, new TextEncoder().encode(data));
       return true;
     } catch (err) {
-      this.callbacks.reportMessage(ConverterMessages.Error_OutputFilenameIsRequired());
+      this.callbacks.reportMessage(ConverterMessages.Error_UnableToWrite({outputFilename: data_ukelele.kmn_filename}));
       return false;
     }
   }
 
-  public writeToString(data_ukelele: convert_object): string {
-    let data: string = "\n";
-
-    // add top part of kmn file: STORES
-    data += this.write_KmnFileHeader(data_ukelele);
-
-    // add bottom part of kmn file: RULES
-    data += this.writeData_Rules(data_ukelele);
-
-    try {
-      return data;
-    } catch (err) {
-      this.callbacks.reportMessage(ConverterMessages.Error_OutputFilenameIsRequired());
-      return null;
-    }
-  }
-
-  public writeToUint8Array(data_ukelele: convert_object): Uint8Array {
+  public write(data_ukelele: convert_object): Uint8Array {
     let data: string = "\n";
 
     // add top part of kmn file: STORES
@@ -71,7 +54,7 @@ export class KmnFileWriter {
     try {
       return new TextEncoder().encode(data);
     } catch (err) {
-      this.callbacks.reportMessage(ConverterMessages.Error_OutputFilenameIsRequired());
+      this.callbacks.reportMessage(ConverterMessages.Error_UnableToWrite({outputFilename: data_ukelele.kmn_filename}));
       return null;
     }
   }
diff --git a/developer/src/kmc-convert/test/kmn-file-writer.tests.ts b/developer/src/kmc-convert/test/kmn-file-writer.tests.ts
index 9474abc36c..5f47448c33 100644
--- a/developer/src/kmc-convert/test/kmn-file-writer.tests.ts
+++ b/developer/src/kmc-convert/test/kmn-file-writer.tests.ts
@@ -22,7 +22,7 @@ describe('KmnFileWriter', function () {
     compilerTestCallbacks.clear();
   });
 
-  describe("write() ", function () {
+  describe("writeToFile() ", function () {
     const inputFilename = makePathToFixture('../data/Test.keylayout');
     const sut = new KeylayoutToKmnConverter(compilerTestCallbacks, compilerTestOptions);
     const sut_r = new KeylayoutFileReader(compilerTestCallbacks);
@@ -35,59 +35,19 @@ describe('KmnFileWriter', function () {
     const read_unavailable = sut_r.read(inputFilename_unavailable);
     const converted_unavailable = sut.convert_bound.convert(read_unavailable, inputFilename_unavailable.replace(/\.keylayout$/, '.kmn'));
 
-    it('write() should return true (no error) if written', async function () {
-
-      const result = sut_w.write(converted);
+    it('writeToFile()() should return true (no error) if written', async function () {
+      const result = sut_w.writeToFile(converted);
       assert.isTrue(result);
     });
 
-    it('write() should return false if no inputfile', async function () {
-      const result = sut_w.write(converted_unavailable);
+    it('writeToFile()() should return false if no inputfile', async function () {
+      const result = sut_w.writeToFile(converted_unavailable);
       assert.isFalse(result);
     });
 
   });
 
-  describe("writeToString() ", function () {
-    const inputFilename = makePathToFixture('../data/Test.keylayout');
-    const sut = new KeylayoutToKmnConverter(compilerTestCallbacks, compilerTestOptions);
-    const sut_r = new KeylayoutFileReader(compilerTestCallbacks);
-    const sut_w = new KmnFileWriter(compilerTestCallbacks, compilerTestOptions);
-    const read = sut_r.read(inputFilename);
-    const converted = sut.convert_bound.convert(read, inputFilename.replace(/\.keylayout$/, '.kmn'));
-
-    const out_expected_first: string = "c ..................................................................................................................\n"
-      + "c ..................................................................................................................\n"
-      + "c Keyman keyboard generated by kmn-convert version: " + KEYMAN_VERSION.VERSION + "\n"
-      + "c from Ukelele file: ";
-
-    const out_expected_last: string = "\n"
-      + "c ..................................................................................................................\n"
-      + "c ..................................................................................................................\n"
-      + "\n"
-      + "store(&TARGETS) 'desktop'\n"
-      + "\n"
-      + "begin Unicode > use(main)\n\n"
-      + "group(main) using keys\n\n"
-      + "\n";
-
-    // empty convert_object from unavailable file name
-    const inputFilename_unavailable = makePathToFixture('../data/X.keylayout');
-    const read_unavailable = sut_r.read(inputFilename_unavailable);
-    const converted_unavailable = sut.convert_bound.convert(read_unavailable, inputFilename_unavailable.replace(/\.keylayout$/, '.kmn'));
-
-    it('writeToString() should return result', async function () {
-      const result = sut_w.writeToString(converted);
-      assert.isNotNull(result);
-    });
-
-    it('writeToString() should return header in case of missing inputfile', async function () {
-      const result = sut_w.writeToString(converted_unavailable);
-      assert.equal(result, ("\n" + out_expected_first + out_expected_last));
-    });
-  });
-
-  describe("writeToUint8Array() ", function () {
+  describe("write()() ", function () {
     const inputFilename = makePathToFixture('../data/Test.keylayout');
     const sut = new KeylayoutToKmnConverter(compilerTestCallbacks, compilerTestOptions);
     const sut_r = new KeylayoutFileReader(compilerTestCallbacks);
@@ -116,13 +76,14 @@ describe('KmnFileWriter', function () {
     const inputFilename_unavailable = makePathToFixture('../data/X.keylayout');
     const read_unavailable = sut_r.read(inputFilename_unavailable);
     const converted_unavailable = sut.convert_bound.convert(read_unavailable, inputFilename_unavailable.replace(/\.keylayout$/, '.kmn'));
-    it('writeToUint8Array() should return header in case of missing inputfile', async function () {
-      const result = sut_w.writeToUint8Array(converted_unavailable);
+
+    it('write()() should return header in case of missing inputfile', async function () {
+      const result = sut_w.write(converted_unavailable);
       assert.equal(new TextDecoder().decode(result), ("\n" + out_expected_first + out_expected_last));
     });
 
-    it('writeToUint8Array() should return result', async function () {
-      const result = sut_w.writeToUint8Array(converted);
+    it('write()() should return result', async function () {
+      const result = sut_w.write(converted);
       assert.isNotNull(result);
     });
   });