diff --git a/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.ps1 b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.ps1
index 647dacfff91..6742b7ce574 100644
--- a/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.ps1
+++ b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.ps1
@@ -15,3 +15,8 @@ Get-ChildItem -Recurse -Include *.ts -Exclude *.d.ts | ForEach-Object {
 
 # build dts
 tsc --emitDeclarationOnly --outDir dist\dts
+
+# fail loudly if the dist is incomplete - a truncated dist ships a jar whose whole JS layer
+# fails at runtime (see eclipse-dirigible/dirigible#6339)
+node verify-dist.js
+if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
diff --git a/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.sh b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.sh
index 7eb0d81dfd3..ef6ac78d9e3 100755
--- a/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.sh
+++ b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/build-source.sh
@@ -13,3 +13,7 @@ esbuild $(find . -iname '*.ts' -not -iname '*.d.ts') --sourcemap=inline --outdir
 
 # build dts
 tsc --emitDeclarationOnly --outDir dist/dts
+
+# fail loudly if the dist is incomplete - a truncated dist ships a jar whose whole JS layer
+# fails at runtime (see eclipse-dirigible/dirigible#6339)
+node verify-dist.js
diff --git a/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/verify-dist.js b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/verify-dist.js
new file mode 100644
index 00000000000..328d0d69b71
--- /dev/null
+++ b/components/api/api-modules-javascript/src/main/resources/META-INF/dirigible/modules/verify-dist.js
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2010-2026 Eclipse Dirigible contributors
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v20.html
+ *
+ * SPDX-FileCopyrightText: Eclipse Dirigible contributors
+ * SPDX-License-Identifier: EPL-2.0
+ */
+// Post-bundling completeness check: every SDK module folder under src/ (one with an index.ts)
+// must have produced dist/esm/<module>/index.mjs and dist/cjs/<module>/index.js. A truncated
+// dist otherwise ships silently inside the jar and kills the ENTIRE JS layer at runtime with a
+// cryptic module-resolution error, far from the cause - see eclipse-dirigible/dirigible#6339.
+// Runs from the modules/ directory, right after the esbuild/tsc steps in build-source.sh/.ps1.
+const { existsSync, readdirSync, statSync } = require("fs");
+const { join } = require("path");
+
+const modules = readdirSync("src").filter((name) => {
+    try {
+        return statSync(join("src", name)).isDirectory() && existsSync(join("src", name, "index.ts"));
+    } catch (ignored) {
+        return false;
+    }
+});
+
+if (modules.length === 0) {
+    console.error("verify-dist: no SDK module folders found under src/ - wrong working directory?");
+    process.exit(1);
+}
+
+const missing = [];
+for (const name of modules) {
+    if (!existsSync(join("dist", "esm", name, "index.mjs"))) {
+        missing.push(`dist/esm/${name}/index.mjs`);
+    }
+    if (!existsSync(join("dist", "cjs", name, "index.js"))) {
+        missing.push(`dist/cjs/${name}/index.js`);
+    }
+}
+
+if (missing.length > 0) {
+    console.error(`verify-dist: the bundled SDK dist is INCOMPLETE - ${missing.length} missing output(s):`);
+    for (const entry of missing) {
+        console.error(`  ${entry}`);
+    }
+    console.error("A jar packaged from this state fails every '@aerokit/sdk/*' import at runtime");
+    console.error("(eclipse-dirigible/dirigible#6339). A concurrent build mutating this checkout is the");
+    console.error("usual cause - rebuild this module on its own and avoid parallel builds of one tree.");
+    process.exit(1);
+}
+
+console.log(`verify-dist: OK - ${modules.length} SDK modules present in dist/esm and dist/cjs.`);