diff --git a/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMLoweringErrorCode.java b/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMLoweringErrorCode.java
index f0a6cc34..b547a710 100644
--- a/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMLoweringErrorCode.java
+++ b/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMLoweringErrorCode.java
@@ -2,6 +2,8 @@ package p.studio.compiler.backend.irvm;
 
 public enum IRVMLoweringErrorCode {
     LOWER_IRVM_EMPTY_EXECUTABLE_INPUT,
+    LOWER_IRVM_ENTRYPOINT_MISSING,
+    LOWER_IRVM_ENTRYPOINT_AMBIGUOUS,
     LOWER_IRVM_MISSING_CALLEE,
     LOWER_IRVM_INVALID_INTRINSIC_ID,
     LOWER_IRVM_CALL_ARG_SLOTS_MISMATCH,
diff --git a/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/LowerToIRVMService.java b/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/LowerToIRVMService.java
index 5cfb7f8e..aacab4e9 100644
--- a/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/LowerToIRVMService.java
+++ b/prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/LowerToIRVMService.java
@@ -217,13 +217,20 @@ public class LowerToIRVMService {
             final ReadOnlyList<IRBackendExecutableFunction> functions) {
         final var sorted = new ArrayList<>(functions.asList());
         sorted.sort(FUNCTION_ORDER);
-        var entrypoint = sorted.getFirst();
-        for (final var candidate : sorted) {
-            if ("main".equals(candidate.callableName())) {
-                entrypoint = candidate;
-                break;
-            }
+        final var entrypoints = sorted.stream()
+                .filter(candidate -> "main".equals(candidate.callableName()))
+                .toList();
+        if (entrypoints.isEmpty()) {
+            throw new IRVMLoweringException(
+                    IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_MISSING,
+                    "missing entrypoint callable 'main'");
         }
+        if (entrypoints.size() > 1) {
+            throw new IRVMLoweringException(
+                    IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_AMBIGUOUS,
+                    "ambiguous entrypoint: found %d callables named 'main'".formatted(entrypoints.size()));
+        }
+        final var entrypoint = entrypoints.getFirst();
         final var ordered = new ArrayList<IRBackendExecutableFunction>(sorted.size());
         ordered.add(entrypoint);
         for (final var fn : sorted) {
diff --git a/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/LowerToIRVMServiceTest.java b/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/LowerToIRVMServiceTest.java
index 722f2871..cb70343f 100644
--- a/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/LowerToIRVMServiceTest.java
+++ b/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/LowerToIRVMServiceTest.java
@@ -130,6 +130,29 @@ class LowerToIRVMServiceTest {
         assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_MISSING_JUMP_TARGET, thrown.code());
     }
 
+    @Test
+    void lowerMustRejectWhenEntrypointIsMissing() {
+        final var backend = IRBackend.builder()
+                .executableFunctions(ReadOnlyList.from(
+                        fn("helper", "app", 10, ReadOnlyList.from(ret()))))
+                .build();
+
+        final var thrown = assertThrows(IRVMLoweringException.class, () -> new LowerToIRVMService().lower(backend));
+        assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_MISSING, thrown.code());
+    }
+
+    @Test
+    void lowerMustRejectWhenEntrypointIsAmbiguous() {
+        final var backend = IRBackend.builder()
+                .executableFunctions(ReadOnlyList.from(
+                        fn("main", "app", 10, ReadOnlyList.from(ret())),
+                        fn("main", "sdk", 11, ReadOnlyList.from(ret()))))
+                .build();
+
+        final var thrown = assertThrows(IRVMLoweringException.class, () -> new LowerToIRVMService().lower(backend));
+        assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_AMBIGUOUS, thrown.code());
+    }
+
     private static IRBackendExecutableFunction fn(
             final String name,
             final String moduleKey,