new test main with code directly (fixes)

docs/general/specs/14. Name Resolution and Module Linking Specification.md

@@ -71,7 +71,7 @@ The following inputs are already fixed elsewhere and must not be contradicted he
 - Imports target modules, not files.
 - Reserved stdlib project spaces are resolved only from the selected stdlib environment.
 - Only `pub` symbols may be imported from another module.
-- Reserved stdlib/interface modules may expose compile-time-only shells for both host-backed and VM-owned surfaces.
+- Reserved stdlib/interface modules may expose compile-time-only shells for both host-backed and VM-owned surfaces, and may expose service facades over non-public host owners.
 - Source-visible builtin names are resolved through imported builtin shell declarations rather than by hardcoded source spelling alone.
 - Canonical builtin identity and canonical intrinsic identity are governed by builtin metadata rather than by the imported PBS-visible declaration name alone.
 - Canonical host identity is governed by host metadata rather than by imported owner spelling alone.

docs/general/specs/18. Standard Library Surface Specification.md

@@ -53,6 +53,7 @@ The following inputs are already fixed elsewhere and must not be contradicted he
 
 - Reserved stdlib project spaces include `@sdk:*` and `@core:*`.
 - Stdlib interface modules are compile-time-only and loaded as PBS-like modules.
+- Stdlib interface modules may include service facades whose bodies delegate to reserved host owners; such bodies are source-surface ergonomics and not standalone runtime modules.
 - User code must import stdlib modules explicitly.
 - Canonical host identity comes from reserved host-binding metadata, not from source owner spelling.
 - VM-owned builtin type, builtin constant, and intrinsic surfaces may be exposed through reserved stdlib shells without transferring semantic ownership away from the VM.
@@ -149,7 +150,9 @@ shells.
 Rules:
 
 - host-backed stdlib surfaces use `declare host`,
+- host-backed stdlib modules may also expose `declare service` facades that call internal non-public host owners,
 - host-backed method signatures carry `Host(...)`,
+- internal low-level host owners can remain non-public via `mod` barrel visibility while higher-level services are exported with `pub`,
 - user code may import those host owners through ordinary stdlib module imports,
 - and lowering continues through canonical host identity, `SYSC`, `HOSTCALL`, loader resolution, and final `SYSCALL`.
 

docs/general/specs/20. IRBackend to IRVM Lowering Specification.md

@@ -56,7 +56,8 @@ Lowering from `IRBackend` to `IRVM` may start only when:
 2. required callsite categories (`CALL_FUNC`/`CALL_HOST`/`CALL_INTRINSIC`) are available,
 3. required canonical host/intrinsic metadata is available for admitted callsites,
 4. dependency-scoped fail-fast exclusions have already been applied at the `IRBackend` boundary,
-5. and target `vm_profile` is selected deterministically.
+5. frontend-declared `IRBackend.entryPointCallableName` is present and non-blank,
+6. and target `vm_profile` is selected deterministically.
 
 ## 6. IRVM Model Obligations
 
@@ -91,9 +92,10 @@ Control-flow lowering must satisfy:
 
 Function indexing must be deterministic:
 
-1. entrypoint function id is `0`,
+1. entrypoint callable is selected by exact name match against `IRBackend.entryPointCallableName`,
-2. remaining functions are ordered by `(module_key, callable_name, source_start)`,
+2. selected entrypoint function id is `0`,
-3. and identical admitted input graphs must produce identical function-id assignments.
+3. remaining functions are ordered by `(module_key, callable_name, source_start)`,
+4. and identical admitted input graphs must produce identical function-id assignments.
 
 ## 9. Callsite Lowering Obligations
 

docs/pbs/pull-requests/INDEX.md

@@ -132,3 +132,4 @@ Foco: eliminar os dois `partial` remanescentes na matriz backend antes de mover
 
 1. `PR-07.1-optimize-irvm-span-source-hook-preservation.md`
 2. `PR-07.2-pbs-callsite-category-no-textual-heuristics-regression.md`
+3. `PR-07.3-irvm-entrypoint-export-emission-for-runtime-loader.md`

docs/pbs/pull-requests/PR-07.3-irvm-entrypoint-export-emission-for-runtime-loader.md

@@ -0,0 +1,77 @@
+# PR-07.3 - IRVM Entrypoint Export Emission for Runtime Loader Compatibility
+
+## Briefing
+
+Hoje um cartridge pode compilar com `entrypoint: "frame"` no `manifest.json` e `pub fn frame()` no `mod.barrel`, mas ainda falhar em runtime com `EntrypointNotFound`.
+
+A causa observada e que o `program.pbx` pode ser emitido sem secao `exports` (section kind `4`), enquanto o loader resolve entrypoint nominal usando `program.exports`.
+
+## Motivation
+
+### Dor atual que esta PR resolve
+
+1. Build aparentemente valido, mas falha de bootstrap em runtime.
+2. Divergencia entre contrato de manifesto (`entrypoint` nominal) e artefato PBX emitido.
+3. Falta de evidencia automatizada para evitar regressao de exports no caminho `IRBackend -> IRVM -> Bytecode`.
+
+## Target
+
+Corrigir o pipeline backend para sempre emitir export nominal do entrypoint no PBX de preload, garantindo compatibilidade com o loader quando o `manifest.json` declara entrypoint por nome.
+
+## Dependencies
+
+Prerequisitos diretos:
+
+1. `PR-05.3` (politica deterministica de entrypoint no indice `0`).
+2. `PR-05.4` (coerencia unica entre IRVM e EmissionPlan).
+
+## Scope
+
+1. `LowerToIRVMService` deve preencher `EmissionPlan.exports` com o simbolo do entrypoint apontando para `func_idx = 0`.
+2. Adicionar regressao dedicada para garantir que `coherentEmissionPlan()` preserva export do entrypoint.
+3. Validar serializacao PBX com secao `exports` presente quando houver entrypoint nominal.
+4. Cobrir cenario de integracao onde `manifest.entrypoint = "frame"` inicializa VM sem `EntrypointNotFound`.
+
+## Non-Goals
+
+1. Nao exportar toda a superficie de funcoes executaveis neste passo.
+2. Nao alterar formato binario PBX alem da presenca correta da secao `exports`.
+3. Nao mudar semantica de resolucao por indice numerico de entrypoint.
+
+## Method
+
+### O que deve ser feito explicitamente
+
+1. No `LowerToIRVMService`, construir `BytecodeEmitter.EmissionPlan` com `exports` contendo, no minimo, `Export(entryPointCallableName, 0)`.
+2. Garantir determinismo do export do entrypoint a partir da mesma politica que fixa `func_id = 0`.
+3. Adicionar teste unitario em `LowerToIRVMServiceTest` para verificar export nominal do entrypoint no plano coerente.
+4. Adicionar teste de emissao/link para verificar secao `exports` no modulo serializado.
+5. Adicionar teste de integracao runtime-backed para falhar se regressar para `EntrypointNotFound` em cartridge com entrypoint nominal valido.
+
+## Acceptance Criteria
+
+1. Build de projeto PBS com entrypoint `frame` gera PBX com secao `exports`.
+2. O simbolo `frame` aponta para `func_idx = 0` no artefato emitido.
+3. Execucao de cartridge com `manifest.entrypoint = "frame"` nao falha por `EntrypointNotFound` quando o programa contem o entrypoint admitido.
+4. Rebuilds equivalentes produzem mapping de export deterministico.
+
+## Tests
+
+1. Novos testes de backend:
+   - `:prometeu-compiler:prometeu-build-pipeline:test`
+2. Reexecucao de compatibilidade runtime-backed:
+   - `:prometeu-compiler:prometeu-build-pipeline:test --tests *Runtime*`
+3. Smoke local recomendado:
+   - `./runtime/prometeu build .`
+   - `./runtime/prometeu run cartridge`
+
+## Affected Documents
+
+1. `docs/general/specs/15. Bytecode and PBX Mapping Specification.md`
+2. `docs/general/specs/20. IRBackend to IRVM Lowering Specification.md`
+3. `docs/pbs/specs/7. Cartridge Manifest and Runtime Capabilities Specification.md`
+4. `docs/general/specs/22. Backend Spec-to-Test Conformance Matrix.md`
+
+## Open Questions
+
+1. Em evolucao futura, devemos exportar apenas o entrypoint ou tambem funcoes explicitamente marcadas para linking externo?

docs/pbs/specs/13. Lowering IRBackend Specification.md

@@ -78,6 +78,7 @@ For each admitted source unit and callable in the current lowering slice, `IRBac
 4. source attribution anchor (`file + span`) for diagnostics and traceability,
 5. source-observable parse intent for statement/expression structure (including precedence/associativity outcome already fixed by AST shape).
 6. deterministic `requiredCapabilities` derived from admitted host-binding metadata for packer/runtime-manifest assistance.
+7. frontend-declared executable entrypoint callable name from `FrontendSpec` (`entryPointCallableName`) for backend handoff.
 
 Lowering must not collapse source categories in a way that erases required declaration/callable identity needed by downstream diagnostics or conformance assertions.
 
@@ -194,3 +195,13 @@ It does not replace:
 1. `docs/general/specs/20. IRBackend to IRVM Lowering Specification.md`,
 2. `docs/general/specs/21. IRVM Optimization Pipeline Specification.md`,
 3. or `docs/general/specs/15. Bytecode and PBX Mapping Specification.md`.
+
+### 12.7 FrontendSpec Entry Point Obligation
+
+For executable language frontends, `FrontendSpec` must declare one canonical entrypoint callable name (`entryPointCallableName`).
+
+At `IRBackend` emission time:
+
+1. frontend must copy this declaration into `IRBackend.entryPointCallableName`,
+2. value must be non-blank and deterministic for the same language/spec version,
+3. and backend stages must treat this field as authoritative for entrypoint selection instead of hardcoded language-agnostic names.

docs/pbs/specs/5. Manifest, Stdlib, and SDK Resolution Specification.md

@@ -19,7 +19,8 @@ This document is the authority for how the compiler discovers and loads:
 
 - ordinary project modules,
 - reserved stdlib modules such as `@sdk:gfx`,
-- and compile-time-only host-binding metadata attached to those reserved modules.
+- compile-time reserved metadata attached to those reserved modules,
+- and interface-only service facades that wrap host surfaces for source ergonomics.
 
 This document does not define runtime load behavior.
 PBX host-binding emission and loader-side syscall resolution are defined by the Host ABI Binding and Loader Resolution Specification.
@@ -445,7 +446,7 @@ The current PBS design direction is:
 6. The root project selects the effective stdlib line for the whole build.
 7. Dependency projects with a higher stdlib requirement than the root are rejected.
 8. Stdlib modules are loaded as PBS-like interface modules, not as ordinary dependencies.
-9. Interface modules are compile-time-only and do not emit executable bytecode.
+9. Interface modules are compile-time-only in packaging terms: they may carry declarative service facades with method bodies for source-level API ergonomics, but they still do not emit executable bytecode as standalone modules.
 10. `declare host` remains reserved to stdlib/toolchain interface modules.
 11. Reserved attributes such as `[Host(...)]` are compile-time metadata, not runtime objects.
 12. The compiler consumes `Host` metadata to produce runtime-facing host-binding artifacts defined elsewhere.

docs/pbs/specs/7. Cartridge Manifest and Runtime Capabilities Specification.md

@@ -63,7 +63,7 @@ The current manifest shape relevant to this document is:
   "title": "Example",
   "app_version": "1.0.0",
   "app_mode": "game",
-  "entrypoint": "main",
+  "entrypoint": "frame",
   "capabilities": ["gfx", "input"],
   "asset_table": [],
   "preload": []
@@ -75,6 +75,7 @@ Rules:
 - `magic` identifies a Prometeu cartridge manifest,
 - `cartridge_version` identifies the cartridge manifest format line,
 - `entrypoint` identifies the runtime entrypoint,
+- for PBS v1, `entrypoint` should align with frontend-declared callable (`frame`),
 - `capabilities` declares the cartridge's requested runtime capabilities,
 - `asset_table` and `preload` remain separate concerns.
 

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/PBSDefinitions.java

@@ -9,5 +9,6 @@ public class PBSDefinitions {
             .languageId("pbs")
             .allowedExtensions(ReadOnlySet.from("pbs", "barrel"))
             .sourceRoots(ReadOnlySet.from("src"))
+            .entryPointCallableName("frame")
             .build();
 }

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/PbsFrontendCompiler.java

@@ -120,10 +120,43 @@ public final class PbsFrontendCompiler {
             final String moduleKey,
             final HostAdmissionContext hostAdmissionContext,
             final NameTable nameTable) {
+        return compileParsedFile(
+                fileId,
+                ast,
+                diagnostics,
+                sourceKind,
+                moduleKey,
+                hostAdmissionContext,
+                nameTable,
+                ReadOnlyList.empty(),
+                ReadOnlyList.empty(),
+                IRReservedMetadata.empty());
+    }
+
+    public IRBackendFile compileParsedFile(
+            final FileId fileId,
+            final PbsAst.File ast,
+            final DiagnosticSink diagnostics,
+            final SourceKind sourceKind,
+            final String moduleKey,
+            final HostAdmissionContext hostAdmissionContext,
+            final NameTable nameTable,
+            final ReadOnlyList<PbsAst.TopDecl> supplementalTopDecls,
+            final ReadOnlyList<ImportedCallableSurface> importedCallables,
+            final IRReservedMetadata importedReservedMetadata) {
         final var effectiveNameTable = nameTable == null ? new NameTable() : nameTable;
+        final var effectiveSupplementalTopDecls = supplementalTopDecls == null
+                ? ReadOnlyList.<PbsAst.TopDecl>empty()
+                : supplementalTopDecls;
+        final var effectiveImportedCallables = importedCallables == null
+                ? ReadOnlyList.<ImportedCallableSurface>empty()
+                : importedCallables;
+        final var effectiveImportedReservedMetadata = importedReservedMetadata == null
+                ? IRReservedMetadata.empty()
+                : importedReservedMetadata;
         final var semanticsErrorBaseline = diagnostics.errorCount();
         new PbsDeclarationSemanticsValidator(effectiveNameTable).validate(ast, sourceKind, diagnostics);
-        flowSemanticsValidator.validate(ast, diagnostics);
+        flowSemanticsValidator.validate(ast, effectiveSupplementalTopDecls, diagnostics);
         if (diagnostics.errorCount() > semanticsErrorBaseline) {
             return IRBackendFile.empty(fileId);
         }
@@ -142,14 +175,22 @@ public final class PbsFrontendCompiler {
                 extractedReservedMetadata.builtinTypeSurfaces(),
                 extractedReservedMetadata.builtinConstSurfaces(),
                 requiredCapabilities);
+        final var effectiveReservedMetadata = mergeReservedMetadata(
+                reservedMetadata,
+                effectiveImportedReservedMetadata);
 
         final ReadOnlyList<IRFunction> functions = sourceKind == SourceKind.SDK_INTERFACE
                 ? ReadOnlyList.empty()
                 : lowerFunctions(fileId, ast);
         final var loweringErrorBaseline = diagnostics.errorCount();
-        final var executableLowering = sourceKind == SourceKind.SDK_INTERFACE
+        final var executableLowering = lowerExecutableFunctions(
-                ? new ExecutableLoweringResult(ReadOnlyList.empty(), ReadOnlyList.empty(), ReadOnlyList.empty())
+                fileId,
-                : lowerExecutableFunctions(fileId, ast, moduleKey, reservedMetadata, effectiveNameTable, diagnostics);
+                ast,
+                moduleKey,
+                effectiveReservedMetadata,
+                effectiveNameTable,
+                diagnostics,
+                effectiveImportedCallables);
         if (diagnostics.errorCount() > loweringErrorBaseline) {
             return IRBackendFile.empty(fileId);
         }
@@ -181,7 +222,8 @@ public final class PbsFrontendCompiler {
             final String moduleKey,
             final IRReservedMetadata reservedMetadata,
             final NameTable nameTable,
-            final DiagnosticSink diagnostics) {
+            final DiagnosticSink diagnostics,
+            final ReadOnlyList<ImportedCallableSurface> importedCallables) {
         final var normalizedModuleKey = moduleKey == null ? "" : moduleKey;
         final var hostByMethodName = new HashMap<NameId, List<IRReservedMetadata.HostMethodBinding>>();
         for (final var hostBinding : reservedMetadata.hostMethodBindings()) {
@@ -199,31 +241,49 @@ public final class PbsFrontendCompiler {
         }
         final var callableIdTable = new CallableTable();
         final var callableIdsByNameAndArity = new HashMap<CallableResolutionKey, List<CallableId>>();
-        final var callableIdByDeclaration = new HashMap<PbsAst.FunctionDecl, CallableId>();
+        final var callableIdByDeclaration = new HashMap<LowerableCallable, CallableId>();
         final var returnSlotsByCallableId = new HashMap<CallableId, Integer>();
         final var intrinsicIdTable = new IntrinsicTable();
         final var typeSurfaceTable = new TypeSurfaceTable();
         final var callableShapeTable = new CallableShapeTable();
-        for (final var declaredFn : ast.functions()) {
+        final var localCallables = collectLocalLowerableCallables(ast);
+        for (final var declaredCallable : localCallables) {
+            final var declaredFn = declaredCallable.functionDecl();
             final var callableShapeId = callableShapeId(declaredFn, typeSurfaceTable, callableShapeTable);
             final var callableId = callableIdTable.register(
                     normalizedModuleKey,
-                    declaredFn.name(),
+                    declaredCallable.callableName(),
                     declaredFn.parameters().size(),
                     callableShapeSurface(callableShapeId, typeSurfaceTable, callableShapeTable));
-            callableIdByDeclaration.put(declaredFn, callableId);
+            callableIdByDeclaration.put(declaredCallable, callableId);
             callableIdsByNameAndArity
                     .computeIfAbsent(
-                            new CallableResolutionKey(nameTable.register(declaredFn.name()), declaredFn.parameters().size()),
+                            new CallableResolutionKey(nameTable.register(declaredCallable.callableName()), declaredFn.parameters().size()),
                             ignored -> new ArrayList<>())
                     .add(callableId);
             final var retSlots = returnSlotsFor(declaredFn);
             returnSlotsByCallableId.put(callableId, retSlots);
         }
+        for (final var importedCallable : importedCallables) {
+            final var callableId = callableIdTable.register(
+                    importedCallable.moduleKey(),
+                    importedCallable.callableName(),
+                    importedCallable.arity(),
+                    importedCallable.shapeSurface());
+            callableIdsByNameAndArity
+                    .computeIfAbsent(
+                            new CallableResolutionKey(
+                                    nameTable.register(importedCallable.callableName()),
+                                    importedCallable.arity()),
+                            ignored -> new ArrayList<>())
+                    .add(callableId);
+            returnSlotsByCallableId.put(callableId, importedCallable.returnSlots());
+        }
 
-        final var executableFunctions = new ArrayList<IRBackendExecutableFunction>(ast.functions().size());
+        final var executableFunctions = new ArrayList<IRBackendExecutableFunction>(localCallables.size());
-        for (final var fn : ast.functions()) {
+        for (final var callable : localCallables) {
-            final var functionCallableId = callableIdByDeclaration.get(fn);
+            final var fn = callable.functionDecl();
+            final var functionCallableId = callableIdByDeclaration.get(callable);
             if (functionCallableId == null) {
                 continue;
             }
@@ -268,7 +328,7 @@ public final class PbsFrontendCompiler {
             executableFunctions.add(new IRBackendExecutableFunction(
                     fileId,
                     normalizedModuleKey,
-                    fn.name(),
+                    callable.callableName(),
                     functionCallableId,
                     start,
                     end,
@@ -300,6 +360,48 @@ public final class PbsFrontendCompiler {
         };
     }
 
+    private ReadOnlyList<LowerableCallable> collectLocalLowerableCallables(final PbsAst.File ast) {
+        final var callables = new ArrayList<LowerableCallable>();
+        for (final var functionDecl : ast.functions()) {
+            callables.add(new LowerableCallable(functionDecl.name(), functionDecl));
+        }
+        for (final var topDecl : ast.topDecls()) {
+            if (!(topDecl instanceof PbsAst.ServiceDecl serviceDecl)) {
+                continue;
+            }
+            for (final var method : serviceDecl.methods()) {
+                callables.add(new LowerableCallable(serviceDecl.name() + "." + method.name(), method));
+            }
+        }
+        return ReadOnlyList.wrap(callables);
+    }
+
+    private IRReservedMetadata mergeReservedMetadata(
+            final IRReservedMetadata primary,
+            final IRReservedMetadata imported) {
+        final var hostBindings = new ArrayList<IRReservedMetadata.HostMethodBinding>();
+        hostBindings.addAll(primary.hostMethodBindings().asList());
+        hostBindings.addAll(imported.hostMethodBindings().asList());
+
+        final var builtinTypeSurfaces = new ArrayList<IRReservedMetadata.BuiltinTypeSurface>();
+        builtinTypeSurfaces.addAll(primary.builtinTypeSurfaces().asList());
+        builtinTypeSurfaces.addAll(imported.builtinTypeSurfaces().asList());
+
+        final var builtinConstSurfaces = new ArrayList<IRReservedMetadata.BuiltinConstSurface>();
+        builtinConstSurfaces.addAll(primary.builtinConstSurfaces().asList());
+        builtinConstSurfaces.addAll(imported.builtinConstSurfaces().asList());
+
+        final var requiredCapabilities = new HashSet<String>();
+        requiredCapabilities.addAll(primary.requiredCapabilities().asList());
+        requiredCapabilities.addAll(imported.requiredCapabilities().asList());
+
+        return new IRReservedMetadata(
+                ReadOnlyList.wrap(hostBindings),
+                ReadOnlyList.wrap(builtinTypeSurfaces),
+                ReadOnlyList.wrap(builtinConstSurfaces),
+                ReadOnlyList.wrap(requiredCapabilities.stream().toList()));
+    }
+
     private CallableShapeId callableShapeId(
             final PbsAst.FunctionDecl functionDecl,
             final TypeSurfaceTable typeSurfaceTable,
@@ -315,6 +417,13 @@ public final class PbsFrontendCompiler {
         return callableShapeTable.register(ReadOnlyList.wrap(parameterSurfaceIds), outputSurfaceId);
     }
 
+    public String callableShapeSurfaceOf(final PbsAst.FunctionDecl functionDecl) {
+        final var typeSurfaceTable = new TypeSurfaceTable();
+        final var callableShapeTable = new CallableShapeTable();
+        final var callableShapeId = callableShapeId(functionDecl, typeSurfaceTable, callableShapeTable);
+        return callableShapeSurface(callableShapeId, typeSurfaceTable, callableShapeTable);
+    }
+
     private String callableShapeSurface(
             final CallableShapeId callableShapeId,
             final TypeSurfaceTable typeSurfaceTable,
@@ -600,10 +709,26 @@ public final class PbsFrontendCompiler {
             reportUnsupportedLowering("executable lowering requires resolvable callee identity", callExpr.span(), context);
             return;
         }
-        final var callableCandidates = context.callableIdsByNameAndArity().get(
+        final var callableCandidates = new ArrayList<CallableId>();
-                new CallableResolutionKey(calleeIdentity.nameId(), callExpr.arguments().size()));
+        final var primaryCallableCandidates = context.callableIdsByNameAndArity().get(
-        final var hostCandidates = context.hostByMethodName().getOrDefault(calleeIdentity.nameId(), List.of());
+                new CallableResolutionKey(calleeIdentity.primaryCallableNameId(), callExpr.arguments().size()));
-        final var intrinsicCandidates = context.intrinsicByMethodName().getOrDefault(calleeIdentity.nameId(), List.of());
+        if (primaryCallableCandidates != null) {
+            callableCandidates.addAll(primaryCallableCandidates);
+        }
+        if (calleeIdentity.secondaryCallableNameId() != null) {
+            final var secondaryCallableCandidates = context.callableIdsByNameAndArity().get(
+                    new CallableResolutionKey(calleeIdentity.secondaryCallableNameId(), callExpr.arguments().size()));
+            if (secondaryCallableCandidates != null) {
+                for (final var candidate : secondaryCallableCandidates) {
+                    if (!callableCandidates.contains(candidate)) {
+                        callableCandidates.add(candidate);
+                    }
+                }
+            }
+        }
+
+        final var hostCandidates = context.hostByMethodName().getOrDefault(calleeIdentity.memberNameId(), List.of());
+        final var intrinsicCandidates = context.intrinsicByMethodName().getOrDefault(calleeIdentity.memberNameId(), List.of());
 
         var categoryCount = 0;
         if (callableCandidates != null && !callableCandidates.isEmpty()) {
@@ -651,6 +776,7 @@ public final class PbsFrontendCompiler {
                 return;
             }
             final var intrinsic = intrinsicCandidates.getFirst();
+            final var effectiveArgSlots = intrinsic.argSlots() + implicitReceiverArgSlots(callExpr.callee());
             context.instructions().add(new IRBackendExecutableFunction.Instruction(
                     IRBackendExecutableFunction.InstructionKind.CALL_INTRINSIC,
                     "",
@@ -660,13 +786,13 @@ public final class PbsFrontendCompiler {
                             intrinsic.canonicalName(),
                             intrinsic.canonicalVersion(),
                             context.intrinsicIdTable().register(intrinsic.canonicalName(), intrinsic.canonicalVersion())),
-                    intrinsic.argSlots(),
+                    effectiveArgSlots,
                     intrinsic.retSlots(),
                     callExpr.span()));
             return;
         }
 
-        if (callableCandidates == null || callableCandidates.isEmpty()) {
+        if (callableCandidates.isEmpty()) {
             reportUnsupportedLowering("executable lowering requires resolvable callable identity", callExpr.span(), context);
             return;
         }
@@ -678,7 +804,7 @@ public final class PbsFrontendCompiler {
         context.instructions().add(new IRBackendExecutableFunction.Instruction(
                 IRBackendExecutableFunction.InstructionKind.CALL_FUNC,
                 context.moduleKey(),
-                calleeIdentity.displayName(),
+                calleeIdentity.primaryCallableDisplayName(),
                 calleeCallableId,
                 null,
                 null,
@@ -692,16 +818,71 @@ public final class PbsFrontendCompiler {
             final NameTable nameTable) {
         return switch (callee) {
             case PbsAst.IdentifierExpr identifierExpr ->
-                    new CalleeIdentity(nameTable.register(identifierExpr.name()), identifierExpr.name());
+                    new CalleeIdentity(
-            // Member access does not carry executable callsite identity in v1 lowering.
+                            nameTable.register(identifierExpr.name()),
-            case PbsAst.MemberExpr ignored -> null;
+                            identifierExpr.name(),
+                            null,
+                            "",
+                            nameTable.register(identifierExpr.name()));
+            case PbsAst.MemberExpr memberExpr -> {
+                final var memberName = memberExpr.memberName();
+                final var rootName = memberRootName(memberExpr.receiver());
+                final var qualified = rootName == null || rootName.isBlank()
+                        ? memberName
+                        : rootName + "." + memberName;
+                final NameId secondaryNameId;
+                final String secondaryDisplayName;
+                if (qualified.equals(memberName)) {
+                    secondaryNameId = null;
+                    secondaryDisplayName = "";
+                } else {
+                    secondaryNameId = nameTable.register(memberName);
+                    secondaryDisplayName = memberName;
+                }
+                yield new CalleeIdentity(
+                        nameTable.register(qualified),
+                        qualified,
+                        secondaryNameId,
+                        secondaryDisplayName,
+                        nameTable.register(memberName));
+            }
             case PbsAst.BindExpr bindExpr ->
-                    new CalleeIdentity(nameTable.register(bindExpr.functionName()), bindExpr.functionName());
+                    new CalleeIdentity(
+                            nameTable.register(bindExpr.functionName()),
+                            bindExpr.functionName(),
+                            null,
+                            "",
+                            nameTable.register(bindExpr.functionName()));
             case PbsAst.GroupExpr groupExpr -> resolveCalleeIdentity(groupExpr.expression(), nameTable);
             default -> null;
         };
     }
 
+    private String memberRootName(final PbsAst.Expression expression) {
+        return switch (expression) {
+            case PbsAst.IdentifierExpr identifierExpr -> identifierExpr.name();
+            case PbsAst.MemberExpr memberExpr -> memberRootName(memberExpr.receiver());
+            case PbsAst.CallExpr callExpr -> memberRootName(callExpr.callee());
+            case PbsAst.GroupExpr groupExpr -> memberRootName(groupExpr.expression());
+            default -> null;
+        };
+    }
+
+    private int implicitReceiverArgSlots(final PbsAst.Expression callee) {
+        if (!(callee instanceof PbsAst.MemberExpr memberExpr)) {
+            return 0;
+        }
+        return receiverProducesRuntimeValue(memberExpr.receiver()) ? 1 : 0;
+    }
+
+    private boolean receiverProducesRuntimeValue(final PbsAst.Expression receiver) {
+        return switch (receiver) {
+            case PbsAst.CallExpr ignored -> true;
+            case PbsAst.GroupExpr groupExpr -> receiverProducesRuntimeValue(groupExpr.expression());
+            default -> false;
+        };
+    }
+
     private void emitJump(
             final IRBackendExecutableFunction.InstructionKind jumpKind,
             final String targetLabel,
@@ -785,7 +966,8 @@ public final class PbsFrontendCompiler {
             switch (instruction.kind()) {
                 case CALL_FUNC -> outHeight += instruction.expectedRetSlots() == null ? 0 : instruction.expectedRetSlots();
                 case CALL_HOST -> outHeight += instruction.hostCall() == null ? 0 : instruction.hostCall().retSlots();
-                case CALL_INTRINSIC, HALT, LABEL, JMP, RET -> {
+                case CALL_INTRINSIC -> outHeight += instruction.expectedRetSlots() == null ? 0 : instruction.expectedRetSlots();
+                case HALT, LABEL, JMP, RET -> {
                 }
                 case JMP_IF_TRUE, JMP_IF_FALSE -> {
                     if (outHeight <= 0) {
@@ -947,14 +1129,30 @@ public final class PbsFrontendCompiler {
             ReadOnlyList<IntrinsicReference> intrinsicPool) {
     }
 
+    private record LowerableCallable(
+            String callableName,
+            PbsAst.FunctionDecl functionDecl) {
+    }
+
     private record CallableResolutionKey(
             NameId callableNameId,
             int arity) {
     }
 
     private record CalleeIdentity(
-            NameId nameId,
+            NameId primaryCallableNameId,
-            String displayName) {
+            String primaryCallableDisplayName,
+            NameId secondaryCallableNameId,
+            String secondaryCallableDisplayName,
+            NameId memberNameId) {
+    }
+
+    public record ImportedCallableSurface(
+            String moduleKey,
+            String callableName,
+            int arity,
+            int returnSlots,
+            String shapeSurface) {
     }
 
     private static final class ExecutableLoweringAnalysisException extends RuntimeException {

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/metadata/PbsReservedMetadataExtractor.java

@@ -119,9 +119,10 @@ public final class PbsReservedMetadataExtractor {
                 continue;
             }
             final var intrinsicMetadata = intrinsicAttribute.get();
+            final var intrinsicName = stringArgument(intrinsicMetadata, "name").orElse(signature.name());
             intrinsics.add(new IRReservedMetadata.IntrinsicSurface(
                     signature.name(),
-                    stringArgument(intrinsicMetadata, "name").orElse(signature.name()),
+                    canonicalIntrinsicName(canonicalTypeName, intrinsicName),
                     longArgument(intrinsicMetadata, "version").orElse(canonicalVersion),
                     signature.parameters().size(),
                     switch (signature.returnKind()) {
@@ -215,6 +216,23 @@ public final class PbsReservedMetadataExtractor {
         return rawValue;
     }
 
+    private String canonicalIntrinsicName(
+            final String canonicalTypeName,
+            final String intrinsicName) {
+        final var normalizedTypeName = canonicalTypeName == null ? "" : canonicalTypeName.trim();
+        final var normalizedIntrinsicName = intrinsicName == null ? "" : intrinsicName.trim();
+        if (normalizedIntrinsicName.isBlank()) {
+            return normalizedTypeName;
+        }
+        if (normalizedIntrinsicName.contains(".")) {
+            return normalizedIntrinsicName;
+        }
+        if (normalizedTypeName.isBlank()) {
+            return normalizedIntrinsicName;
+        }
+        return normalizedTypeName + "." + normalizedIntrinsicName;
+    }
+
     private String typeSurfaceKey(final PbsAst.TypeRef typeRef) {
         if (typeRef == null) {
             return "unit";

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/parser/PbsExprParser.java

@@ -285,7 +285,7 @@ final class PbsExprParser {
             }
 
             if (cursor.match(PbsTokenKind.DOT)) {
-                final var member = consume(PbsTokenKind.IDENTIFIER, "Expected member name after '.'");
+                final var member = consumeMemberName("Expected member name after '.'");
                 expression = new PbsAst.MemberExpr(
                         expression,
                         member.lexeme(),
@@ -631,6 +631,18 @@ final class PbsExprParser {
         return token;
     }
 
+    private PbsToken consumeMemberName(final String message) {
+        if (cursor.check(PbsTokenKind.IDENTIFIER) || cursor.check(PbsTokenKind.ERROR)) {
+            return cursor.advance();
+        }
+        final var token = cursor.peek();
+        report(token, ParseErrors.E_PARSE_EXPECTED_TOKEN, message + ", found " + token.kind());
+        if (!cursor.isAtEnd()) {
+            return cursor.advance();
+        }
+        return token;
+    }
+
     private Span span(final long start, final long end) {
         return new Span(fileId, start, end);
     }

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/parser/PbsParser.java

@@ -730,7 +730,7 @@ public final class PbsParser {
     }
 
     private PbsAst.FunctionDecl parseFunctionLike(final PbsToken fnToken) {
-        final var name = consume(PbsTokenKind.IDENTIFIER, "Expected function name");
+        final var name = consumeCallableName("Expected function name");
         consume(PbsTokenKind.LEFT_PAREN, "Expected '(' after function name");
         final var parameters = parseParametersUntilRightParen();
         final var rightParen = consume(PbsTokenKind.RIGHT_PAREN, "Expected ')' after parameter list");
@@ -752,7 +752,7 @@ public final class PbsParser {
             final PbsToken fnToken,
             final boolean requireSemicolon,
             final ReadOnlyList<PbsAst.Attribute> attributes) {
-        final var name = consume(PbsTokenKind.IDENTIFIER, "Expected function name");
+        final var name = consumeCallableName("Expected function name");
         consume(PbsTokenKind.LEFT_PAREN, "Expected '(' after function name");
         final var parameters = parseParametersUntilRightParen();
         final var rightParen = consume(PbsTokenKind.RIGHT_PAREN, "Expected ')' after parameter list");
@@ -774,6 +774,18 @@ public final class PbsParser {
                 span(fnToken.start(), end));
     }
 
+    private PbsToken consumeCallableName(final String message) {
+        if (cursor.check(PbsTokenKind.IDENTIFIER) || cursor.check(PbsTokenKind.ERROR)) {
+            return cursor.advance();
+        }
+        final var token = cursor.peek();
+        report(token, ParseErrors.E_PARSE_EXPECTED_TOKEN, message + ", found " + token.kind());
+        if (!cursor.isAtEnd()) {
+            return cursor.advance();
+        }
+        return token;
+    }
+
     /**
      * Parses `declare callback` declaration.
      */

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/semantics/PbsDeclarationSemanticsValidator.java

@@ -88,12 +88,6 @@ public final class PbsDeclarationSemanticsValidator {
             if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
                 binder.registerType(serviceDecl.name(), serviceDecl.span(), "service");
                 binder.registerValue(serviceDecl.name(), serviceDecl.span(), "service singleton");
-                if (interfaceModule) {
-                    reportInterfaceNonDeclarativeDecl(
-                            serviceDecl.span(),
-                            "Interface modules must not declare executable service bodies",
-                            diagnostics);
-                }
                 validateServiceDeclaration(serviceDecl, binder, rules);
                 continue;
             }

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/semantics/PbsFlowBodyAnalyzer.java

@@ -21,7 +21,14 @@ final class PbsFlowBodyAnalyzer {
     }
 
     public void validate(final PbsAst.File ast, final DiagnosticSink diagnostics) {
-        final var model = Model.from(ast);
+        validate(ast, ReadOnlyList.empty(), diagnostics);
+    }
+
+    public void validate(
+            final PbsAst.File ast,
+            final ReadOnlyList<PbsAst.TopDecl> supplementalTopDecls,
+            final DiagnosticSink diagnostics) {
+        final var model = Model.from(ast, supplementalTopDecls);
 
         for (final var topDecl : ast.topDecls()) {
             if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/semantics/PbsFlowSemanticSupport.java

@@ -169,109 +169,209 @@ final class PbsFlowSemanticSupport {
         final Map<String, Set<String>> errors = new HashMap<>();
         final Map<String, TypeView> constTypes = new HashMap<>();
         final Map<String, TypeView> serviceSingletons = new HashMap<>();
+        final Set<String> knownStructNames = new HashSet<>();
+        final Set<String> knownServiceNames = new HashSet<>();
+        final Set<String> knownContractNames = new HashSet<>();
+        final Set<String> knownEnumNames = new HashSet<>();
+        final Set<String> knownErrorNames = new HashSet<>();
+        final Set<String> knownCallbackNames = new HashSet<>();
     
         static Model from(final PbsAst.File ast) {
+            return from(ast, ReadOnlyList.empty());
+        }
+
+        static Model from(
+                final PbsAst.File ast,
+                final ReadOnlyList<PbsAst.TopDecl> supplementalTopDecls) {
             final var model = new Model();
             for (final var topDecl : ast.topDecls()) {
-                if (topDecl instanceof PbsAst.StructDecl structDecl) {
+                model.registerKnownTopDecl(topDecl);
-                    final var fields = new HashMap<String, StructFieldInfo>();
+            }
-                    for (final var field : structDecl.fields()) {
+            for (final var topDecl : supplementalTopDecls) {
-                        fields.put(
+                model.registerKnownTopDecl(topDecl);
-                                field.name(),
+            }
-                                new StructFieldInfo(
+            for (final var topDecl : ast.topDecls()) {
-                                        model.typeFrom(field.typeRef()),
+                model.ingestTopDecl(topDecl);
-                                        field.isPublic(),
+            }
-                                        field.isMutable()));
+            for (final var topDecl : supplementalTopDecls) {
-                    }
+                model.ingestTopDecl(topDecl);
-                    final var methods = new HashMap<String, List<CallableSymbol>>();
-                    for (final var method : structDecl.methods()) {
-                        methods.computeIfAbsent(method.name(), ignored -> new ArrayList<>())
-                                .add(model.callableFrom(
-                                        method.name(),
-                                        method.parameters(),
-                                        method.returnKind(),
-                                        method.returnType(),
-                                        method.resultErrorType(),
-                                        method.span()));
-                    }
-                    model.structs.put(structDecl.name(), new StructInfo(fields, methods));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
-                    final var methods = new HashMap<String, List<CallableSymbol>>();
-                    for (final var method : serviceDecl.methods()) {
-                        methods.computeIfAbsent(method.name(), ignored -> new ArrayList<>())
-                                .add(model.callableFrom(
-                                        method.name(),
-                                        method.parameters(),
-                                        method.returnKind(),
-                                        method.returnType(),
-                                        method.resultErrorType(),
-                                        method.span()));
-                    }
-                    model.services.put(serviceDecl.name(), new ServiceInfo(methods));
-                    model.serviceSingletons.put(serviceDecl.name(), TypeView.service(serviceDecl.name()));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.ContractDecl contractDecl) {
-                    final var methods = new HashMap<String, List<CallableSymbol>>();
-                    for (final var signature : contractDecl.signatures()) {
-                        methods.computeIfAbsent(signature.name(), ignored -> new ArrayList<>())
-                                .add(model.callableFrom(
-                                        signature.name(),
-                                        signature.parameters(),
-                                        signature.returnKind(),
-                                        signature.returnType(),
-                                        signature.resultErrorType(),
-                                        signature.span()));
-                    }
-                    model.contracts.put(contractDecl.name(), new ContractInfo(methods));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {
-                    model.topLevelCallables.computeIfAbsent(functionDecl.name(), ignored -> new ArrayList<>())
-                            .add(model.callableFrom(
-                                    functionDecl.name(),
-                                    functionDecl.parameters(),
-                                    functionDecl.returnKind(),
-                                    functionDecl.returnType(),
-                                    functionDecl.resultErrorType(),
-                                    functionDecl.span()));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.CallbackDecl(
-                        String name, ReadOnlyList<PbsAst.Parameter> parameters, PbsAst.ReturnKind returnKind,
-                        PbsAst.TypeRef returnType, PbsAst.TypeRef resultErrorType, Span span
-                )) {
-                    final var symbol = model.callableFrom(
-                            name,
-                            parameters,
-                            returnKind,
-                            returnType,
-                            resultErrorType,
-                            span);
-                    model.callbacks.put(name, new CallbackSignature(symbol.inputTypes(), symbol.outputType()));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.EnumDecl enumDecl) {
-                    final var cases = new HashSet<String>();
-                    for (final var enumCase : enumDecl.cases()) {
-                        cases.add(enumCase.name());
-                    }
-                    model.enums.put(enumDecl.name(), cases);
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.ErrorDecl errorDecl) {
-                    model.errors.put(errorDecl.name(), new HashSet<>(errorDecl.cases().asList()));
-                    continue;
-                }
-                if (topDecl instanceof PbsAst.ConstDecl constDecl && constDecl.explicitType() != null) {
-                    model.constTypes.put(constDecl.name(), model.typeFrom(constDecl.explicitType()));
-                }
             }
             return model;
         }
 
+        private void registerKnownTopDecl(final PbsAst.TopDecl topDecl) {
+            if (topDecl instanceof PbsAst.StructDecl structDecl) {
+                knownStructNames.add(structDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.BuiltinTypeDecl builtinTypeDecl) {
+                knownStructNames.add(builtinTypeDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
+                knownServiceNames.add(serviceDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.HostDecl hostDecl) {
+                knownServiceNames.add(hostDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.ContractDecl contractDecl) {
+                knownContractNames.add(contractDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.EnumDecl enumDecl) {
+                knownEnumNames.add(enumDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.ErrorDecl errorDecl) {
+                knownErrorNames.add(errorDecl.name());
+                return;
+            }
+            if (topDecl instanceof PbsAst.CallbackDecl callbackDecl) {
+                knownCallbackNames.add(callbackDecl.name());
+            }
+        }
+
+        private void ingestTopDecl(final PbsAst.TopDecl topDecl) {
+            if (topDecl instanceof PbsAst.StructDecl structDecl) {
+                final var fields = new HashMap<String, StructFieldInfo>();
+                for (final var field : structDecl.fields()) {
+                    fields.put(
+                            field.name(),
+                            new StructFieldInfo(
+                                    typeFrom(field.typeRef()),
+                                    field.isPublic(),
+                                    field.isMutable()));
+                }
+                final var methods = new HashMap<String, List<CallableSymbol>>();
+                for (final var method : structDecl.methods()) {
+                    methods.computeIfAbsent(method.name(), ignored -> new ArrayList<>())
+                            .add(callableFrom(
+                                    method.name(),
+                                    method.parameters(),
+                                    method.returnKind(),
+                                    method.returnType(),
+                                    method.resultErrorType(),
+                                    method.span()));
+                }
+                structs.put(structDecl.name(), new StructInfo(fields, methods));
+                return;
+            }
+            if (topDecl instanceof PbsAst.BuiltinTypeDecl builtinTypeDecl) {
+                final var fields = new HashMap<String, StructFieldInfo>();
+                for (final var field : builtinTypeDecl.fields()) {
+                    fields.put(
+                            field.name(),
+                            new StructFieldInfo(
+                                    typeFrom(field.typeRef()),
+                                    true,
+                                    false));
+                }
+                final var methods = new HashMap<String, List<CallableSymbol>>();
+                for (final var signature : builtinTypeDecl.signatures()) {
+                    methods.computeIfAbsent(signature.name(), ignored -> new ArrayList<>())
+                            .add(callableFrom(
+                                    signature.name(),
+                                    signature.parameters(),
+                                    signature.returnKind(),
+                                    signature.returnType(),
+                                    signature.resultErrorType(),
+                                    signature.span()));
+                }
+                structs.put(builtinTypeDecl.name(), new StructInfo(fields, methods));
+                return;
+            }
+            if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
+                final var methods = new HashMap<String, List<CallableSymbol>>();
+                for (final var method : serviceDecl.methods()) {
+                    methods.computeIfAbsent(method.name(), ignored -> new ArrayList<>())
+                            .add(callableFrom(
+                                    method.name(),
+                                    method.parameters(),
+                                    method.returnKind(),
+                                    method.returnType(),
+                                    method.resultErrorType(),
+                                    method.span()));
+                }
+                services.put(serviceDecl.name(), new ServiceInfo(methods));
+                serviceSingletons.put(serviceDecl.name(), TypeView.service(serviceDecl.name()));
+                return;
+            }
+            if (topDecl instanceof PbsAst.HostDecl hostDecl) {
+                final var methods = new HashMap<String, List<CallableSymbol>>();
+                for (final var signature : hostDecl.signatures()) {
+                    methods.computeIfAbsent(signature.name(), ignored -> new ArrayList<>())
+                            .add(callableFrom(
+                                    signature.name(),
+                                    signature.parameters(),
+                                    signature.returnKind(),
+                                    signature.returnType(),
+                                    signature.resultErrorType(),
+                                    signature.span()));
+                }
+                // Host owners are value singletons with callable members, same access shape as services.
+                services.put(hostDecl.name(), new ServiceInfo(methods));
+                serviceSingletons.put(hostDecl.name(), TypeView.service(hostDecl.name()));
+                return;
+            }
+            if (topDecl instanceof PbsAst.ContractDecl contractDecl) {
+                final var methods = new HashMap<String, List<CallableSymbol>>();
+                for (final var signature : contractDecl.signatures()) {
+                    methods.computeIfAbsent(signature.name(), ignored -> new ArrayList<>())
+                            .add(callableFrom(
+                                    signature.name(),
+                                    signature.parameters(),
+                                    signature.returnKind(),
+                                    signature.returnType(),
+                                    signature.resultErrorType(),
+                                    signature.span()));
+                }
+                contracts.put(contractDecl.name(), new ContractInfo(methods));
+                return;
+            }
+            if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {
+                topLevelCallables.computeIfAbsent(functionDecl.name(), ignored -> new ArrayList<>())
+                        .add(callableFrom(
+                                functionDecl.name(),
+                                functionDecl.parameters(),
+                                functionDecl.returnKind(),
+                                functionDecl.returnType(),
+                                functionDecl.resultErrorType(),
+                                functionDecl.span()));
+                return;
+            }
+            if (topDecl instanceof PbsAst.CallbackDecl(
+                    String name, ReadOnlyList<PbsAst.Parameter> parameters, PbsAst.ReturnKind returnKind,
+                    PbsAst.TypeRef returnType, PbsAst.TypeRef resultErrorType, Span span
+            )) {
+                final var symbol = callableFrom(
+                        name,
+                        parameters,
+                        returnKind,
+                        returnType,
+                        resultErrorType,
+                        span);
+                callbacks.put(name, new CallbackSignature(symbol.inputTypes(), symbol.outputType()));
+                return;
+            }
+            if (topDecl instanceof PbsAst.EnumDecl enumDecl) {
+                final var cases = new HashSet<String>();
+                for (final var enumCase : enumDecl.cases()) {
+                    cases.add(enumCase.name());
+                }
+                enums.put(enumDecl.name(), cases);
+                return;
+            }
+            if (topDecl instanceof PbsAst.ErrorDecl errorDecl) {
+                errors.put(errorDecl.name(), new HashSet<>(errorDecl.cases().asList()));
+                return;
+            }
+            if (topDecl instanceof PbsAst.ConstDecl constDecl && constDecl.explicitType() != null) {
+                constTypes.put(constDecl.name(), typeFrom(constDecl.explicitType()));
+            }
+        }
+    
         private CallableSymbol callableFrom(
                 final String name,
                 final ReadOnlyList<PbsAst.Parameter> parameters,
@@ -324,25 +424,28 @@ final class PbsFlowSemanticSupport {
                     if ("str".equals(typeRef.name())) {
                         yield TypeView.str();
                     }
-                    if (structs.containsKey(typeRef.name())) {
+                    if (structs.containsKey(typeRef.name()) || knownStructNames.contains(typeRef.name())) {
                         yield TypeView.struct(typeRef.name());
                     }
-                    if (services.containsKey(typeRef.name())) {
+                    if (services.containsKey(typeRef.name()) || knownServiceNames.contains(typeRef.name())) {
                         yield TypeView.service(typeRef.name());
                     }
-                    if (contracts.containsKey(typeRef.name())) {
+                    if (contracts.containsKey(typeRef.name()) || knownContractNames.contains(typeRef.name())) {
                         yield TypeView.contract(typeRef.name());
                     }
-                    if (enums.containsKey(typeRef.name())) {
+                    if (enums.containsKey(typeRef.name()) || knownEnumNames.contains(typeRef.name())) {
                         yield TypeView.enumType(typeRef.name());
                     }
-                    if (errors.containsKey(typeRef.name())) {
+                    if (errors.containsKey(typeRef.name()) || knownErrorNames.contains(typeRef.name())) {
                         yield TypeView.error(typeRef.name());
                     }
                     final var callbackSignature = callbacks.get(typeRef.name());
                     if (callbackSignature != null) {
                         yield TypeView.callback(typeRef.name(), callbackSignature.inputTypes(), callbackSignature.outputType());
                     }
+                    if (knownCallbackNames.contains(typeRef.name())) {
+                        yield TypeView.callback(typeRef.name(), List.of(), TypeView.unknown());
+                    }
                     yield TypeView.unknown();
                 }
                 case OPTIONAL -> TypeView.optional(typeFrom(typeRef.inner()));

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/pbs/semantics/PbsFlowSemanticsValidator.java

@@ -2,11 +2,19 @@ package p.studio.compiler.pbs.semantics;
 
 import p.studio.compiler.pbs.ast.PbsAst;
 import p.studio.compiler.source.diagnostics.DiagnosticSink;
+import p.studio.utilities.structures.ReadOnlyList;
 
 public final class PbsFlowSemanticsValidator {
     private final PbsFlowBodyAnalyzer flowBodyAnalyzer = new PbsFlowBodyAnalyzer();
 
     public void validate(final PbsAst.File ast, final DiagnosticSink diagnostics) {
-        flowBodyAnalyzer.validate(ast, diagnostics);
+        flowBodyAnalyzer.validate(ast, ReadOnlyList.empty(), diagnostics);
+    }
+
+    public void validate(
+            final PbsAst.File ast,
+            final ReadOnlyList<PbsAst.TopDecl> supplementalTopDecls,
+            final DiagnosticSink diagnostics) {
+        flowBodyAnalyzer.validate(ast, supplementalTopDecls, diagnostics);
     }
 }

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/java/p/studio/compiler/services/PBSFrontendPhaseService.java

@@ -1,14 +1,17 @@
 package p.studio.compiler.services;
 
 import lombok.extern.slf4j.Slf4j;
+import p.studio.compiler.PBSDefinitions;
 import p.studio.compiler.messages.BuildingIssueSink;
 import p.studio.compiler.messages.FrontendPhaseContext;
 import p.studio.compiler.models.IRBackend;
+import p.studio.compiler.models.IRReservedMetadata;
 import p.studio.compiler.models.ProjectDescriptor;
 import p.studio.compiler.models.SourceHandle;
 import p.studio.compiler.models.SourceKind;
 import p.studio.compiler.pbs.PbsFrontendCompiler;
 import p.studio.compiler.pbs.ast.PbsAst;
+import p.studio.compiler.pbs.metadata.PbsReservedMetadataExtractor;
 import p.studio.compiler.pbs.lexer.PbsLexer;
 import p.studio.compiler.pbs.linking.PbsLinkErrors;
 import p.studio.compiler.pbs.linking.PbsModuleVisibilityValidator;
@@ -42,6 +45,7 @@ import java.util.Set;
 @Slf4j
 public class PBSFrontendPhaseService implements FrontendPhaseService {
     private final PbsFrontendCompiler frontendCompiler = new PbsFrontendCompiler();
+    private final PbsReservedMetadataExtractor reservedMetadataExtractor = new PbsReservedMetadataExtractor();
     private final PbsModuleVisibilityValidator moduleVisibilityValidator = new PbsModuleVisibilityValidator();
     private final StdlibEnvironmentResolver stdlibEnvironmentResolver;
     private final InterfaceModuleLoader interfaceModuleLoader;
@@ -154,6 +158,7 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
         moduleVisibilityValidator.validate(ReadOnlyList.wrap(modules), nameTable, diagnostics);
         markModulesWithLinkingErrors(diagnostics, moduleIdByFile, failedModuleIds);
         final var moduleDependencyGraph = buildModuleDependencyGraph(parsedSourceFiles, moduleTable);
+        final var importedSemanticContexts = buildImportedSemanticContexts(parsedSourceFiles, moduleTable);
 
         final var compiledSourceFiles = new ArrayList<CompiledSourceFile>(parsedSourceFiles.size());
         for (final var parsedSource : parsedSourceFiles) {
@@ -161,6 +166,9 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
             if (blockedModuleIds.contains(parsedSource.moduleId())) {
                 continue;
             }
+            final var importedSemanticContext = importedSemanticContexts.getOrDefault(
+                    parsedSource.fileId(),
+                    ImportedSemanticContext.empty());
             final var compileErrorBaseline = diagnostics.errorCount();
             final var irBackendFile = frontendCompiler.compileParsedFile(
                     parsedSource.fileId(),
@@ -169,7 +177,10 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
                     parsedSource.sourceKind(),
                     renderModuleKey(moduleTable, parsedSource.moduleId()),
                     ctx.hostAdmissionContext(),
-                    nameTable);
+                    nameTable,
+                    importedSemanticContext.supplementalTopDecls(),
+                    importedSemanticContext.importedCallables(),
+                    importedSemanticContext.importedReservedMetadata());
             if (diagnostics.errorCount() > compileErrorBaseline) {
                 failedModuleIds.add(parsedSource.moduleId());
             }
@@ -183,6 +194,7 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
             }
             irBackendAggregator.merge(compiledSource.irBackendFile());
         }
+        irBackendAggregator.entryPointCallableName(PBSDefinitions.PBS.getEntryPointCallableName());
 
         final var irBackend = irBackendAggregator.emit();
         logs.using(log).debug("PBS frontend lowered to IR BE:\n%s".formatted(irBackend));
@@ -358,6 +370,383 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
         return dependenciesByModule;
     }
 
+    private Map<FileId, ImportedSemanticContext> buildImportedSemanticContexts(
+            final ArrayList<ParsedSourceFile> parsedSourceFiles,
+            final ModuleTable moduleTable) {
+        final Map<ModuleId, ArrayList<ParsedSourceFile>> sourcesByModule = new HashMap<>();
+        for (final var parsedSource : parsedSourceFiles) {
+            sourcesByModule
+                    .computeIfAbsent(parsedSource.moduleId(), ignored -> new ArrayList<>())
+                    .add(parsedSource);
+        }
+
+        final Map<ModuleId, IRReservedMetadata> reservedMetadataByModule = new HashMap<>();
+        for (final var entry : sourcesByModule.entrySet()) {
+            var merged = IRReservedMetadata.empty();
+            for (final var source : entry.getValue()) {
+                final var extracted = reservedMetadataExtractor.extract(source.ast(), source.sourceKind());
+                merged = mergeReservedMetadata(merged, extracted);
+            }
+            reservedMetadataByModule.put(entry.getKey(), merged);
+        }
+        final Map<ModuleId, Map<String, ArrayList<PbsAst.TopDecl>>> topDeclsByNameByModule = new HashMap<>();
+        for (final var entry : sourcesByModule.entrySet()) {
+            topDeclsByNameByModule.put(entry.getKey(), indexTopDeclsByName(entry.getValue()));
+        }
+
+        final Map<FileId, ImportedSemanticContext> contexts = new HashMap<>();
+        for (final var parsedSource : parsedSourceFiles) {
+            final var supplementalTopDecls = new ArrayList<PbsAst.TopDecl>();
+            final var importedCallables = new ArrayList<PbsFrontendCompiler.ImportedCallableSurface>();
+            final var importedCallableKeys = new HashSet<String>();
+            final var supplementalKeys = new HashSet<String>();
+            var importedReservedMetadata = IRReservedMetadata.empty();
+
+            for (final var importDecl : parsedSource.ast().imports()) {
+                final var moduleRef = importDecl.moduleRef();
+                final var importedModuleId = moduleId(moduleTable, moduleRef.project(), moduleRef.pathSegments());
+                final var importedSources = sourcesByModule.get(importedModuleId);
+                if (importedSources == null || importedSources.isEmpty()) {
+                    continue;
+                }
+                final var importedTopDeclsByName = topDeclsByNameByModule.get(importedModuleId);
+                if (importedTopDeclsByName == null) {
+                    continue;
+                }
+                final var importedModuleKey = renderModuleKey(moduleTable, importedModuleId);
+                importedReservedMetadata = mergeReservedMetadata(
+                        importedReservedMetadata,
+                        reservedMetadataByModule.getOrDefault(importedModuleId, IRReservedMetadata.empty()));
+
+                for (final var importItem : importDecl.items()) {
+                    final var importName = importItem.name();
+                    final var localName = importItemLocalName(importItem);
+                    final var directDecls = importedTopDeclsByName.getOrDefault(importName, new ArrayList<>());
+                    for (final var topDecl : directDecls) {
+                        appendSupplementalTopDecl(topDecl, supplementalTopDecls, supplementalKeys);
+                        appendTypeDependencyDecls(topDecl, importedTopDeclsByName, supplementalTopDecls, supplementalKeys);
+                        if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
+                            for (final var method : serviceDecl.methods()) {
+                                appendImportedCallable(
+                                        importedCallables,
+                                        importedCallableKeys,
+                                        new PbsFrontendCompiler.ImportedCallableSurface(
+                                                importedModuleKey,
+                                                localName + "." + method.name(),
+                                                method.parameters().size(),
+                                                returnSlotsFor(method),
+                                                frontendCompiler.callableShapeSurfaceOf(method)));
+                            }
+                            continue;
+                        }
+                        if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {
+                            appendImportedCallable(
+                                    importedCallables,
+                                    importedCallableKeys,
+                                    new PbsFrontendCompiler.ImportedCallableSurface(
+                                            importedModuleKey,
+                                            localName,
+                                            functionDecl.parameters().size(),
+                                            returnSlotsFor(functionDecl),
+                                            frontendCompiler.callableShapeSurfaceOf(functionDecl)));
+                        }
+                    }
+                }
+            }
+
+            contexts.put(parsedSource.fileId(), new ImportedSemanticContext(
+                    ReadOnlyList.wrap(supplementalTopDecls),
+                    ReadOnlyList.wrap(importedCallables),
+                    importedReservedMetadata));
+        }
+        return contexts;
+    }
+
+    private Map<String, ArrayList<PbsAst.TopDecl>> indexTopDeclsByName(
+            final ArrayList<ParsedSourceFile> moduleSources) {
+        final Map<String, ArrayList<PbsAst.TopDecl>> index = new HashMap<>();
+        for (final var source : moduleSources) {
+            for (final var topDecl : source.ast().topDecls()) {
+                final var declName = topDeclName(topDecl);
+                if (declName == null || declName.isBlank()) {
+                    continue;
+                }
+                index.computeIfAbsent(declName, ignored -> new ArrayList<>()).add(topDecl);
+            }
+        }
+        return index;
+    }
+
+    private void appendTypeDependencyDecls(
+            final PbsAst.TopDecl rootDecl,
+            final Map<String, ArrayList<PbsAst.TopDecl>> topDeclsByName,
+            final ArrayList<PbsAst.TopDecl> supplementalTopDecls,
+            final Set<String> supplementalKeys) {
+        final var pendingTypeNames = new ArrayDeque<String>();
+        final var visitedTypeNames = new HashSet<String>();
+        collectReferencedTypeNames(rootDecl, pendingTypeNames);
+        while (!pendingTypeNames.isEmpty()) {
+            final var typeName = pendingTypeNames.removeFirst();
+            if (!visitedTypeNames.add(typeName)) {
+                continue;
+            }
+            final var candidates = topDeclsByName.get(typeName);
+            if (candidates == null) {
+                continue;
+            }
+            for (final var candidate : candidates) {
+                if (!isTypeDecl(candidate)) {
+                    continue;
+                }
+                appendSupplementalTopDecl(candidate, supplementalTopDecls, supplementalKeys);
+                collectReferencedTypeNames(candidate, pendingTypeNames);
+            }
+        }
+    }
+
+    private void collectReferencedTypeNames(
+            final PbsAst.TopDecl topDecl,
+            final ArrayDeque<String> sink) {
+        if (topDecl instanceof PbsAst.StructDecl structDecl) {
+            for (final var field : structDecl.fields()) {
+                collectReferencedTypeNames(field.typeRef(), sink);
+            }
+            for (final var method : structDecl.methods()) {
+                collectReferencedTypeNames(method, sink);
+            }
+            for (final var ctor : structDecl.ctors()) {
+                for (final var parameter : ctor.parameters()) {
+                    collectReferencedTypeNames(parameter.typeRef(), sink);
+                }
+            }
+            return;
+        }
+        if (topDecl instanceof PbsAst.BuiltinTypeDecl builtinTypeDecl) {
+            for (final var field : builtinTypeDecl.fields()) {
+                collectReferencedTypeNames(field.typeRef(), sink);
+            }
+            for (final var signature : builtinTypeDecl.signatures()) {
+                collectReferencedTypeNames(signature, sink);
+            }
+            return;
+        }
+        if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
+            for (final var method : serviceDecl.methods()) {
+                collectReferencedTypeNames(method, sink);
+            }
+            return;
+        }
+        if (topDecl instanceof PbsAst.HostDecl hostDecl) {
+            for (final var signature : hostDecl.signatures()) {
+                collectReferencedTypeNames(signature, sink);
+            }
+            return;
+        }
+        if (topDecl instanceof PbsAst.ContractDecl contractDecl) {
+            for (final var signature : contractDecl.signatures()) {
+                collectReferencedTypeNames(signature, sink);
+            }
+            return;
+        }
+        if (topDecl instanceof PbsAst.CallbackDecl callbackDecl) {
+            collectReferencedTypeNames(callbackDecl.parameters(), callbackDecl.returnType(), callbackDecl.resultErrorType(), sink);
+            return;
+        }
+        if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {
+            collectReferencedTypeNames(functionDecl, sink);
+            return;
+        }
+        if (topDecl instanceof PbsAst.ConstDecl constDecl && constDecl.explicitType() != null) {
+            collectReferencedTypeNames(constDecl.explicitType(), sink);
+        }
+    }
+
+    private void collectReferencedTypeNames(
+            final PbsAst.FunctionDecl functionDecl,
+            final ArrayDeque<String> sink) {
+        collectReferencedTypeNames(
+                functionDecl.parameters(),
+                functionDecl.returnType(),
+                functionDecl.resultErrorType(),
+                sink);
+    }
+
+    private void collectReferencedTypeNames(
+            final PbsAst.FunctionSignature functionSignature,
+            final ArrayDeque<String> sink) {
+        collectReferencedTypeNames(
+                functionSignature.parameters(),
+                functionSignature.returnType(),
+                functionSignature.resultErrorType(),
+                sink);
+    }
+
+    private void collectReferencedTypeNames(
+            final ReadOnlyList<PbsAst.Parameter> parameters,
+            final PbsAst.TypeRef returnType,
+            final PbsAst.TypeRef resultErrorType,
+            final ArrayDeque<String> sink) {
+        for (final var parameter : parameters) {
+            collectReferencedTypeNames(parameter.typeRef(), sink);
+        }
+        collectReferencedTypeNames(returnType, sink);
+        collectReferencedTypeNames(resultErrorType, sink);
+    }
+
+    private void collectReferencedTypeNames(
+            final PbsAst.TypeRef typeRef,
+            final ArrayDeque<String> sink) {
+        if (typeRef == null) {
+            return;
+        }
+        switch (typeRef.kind()) {
+            case SIMPLE -> {
+                final var simpleName = typeRef.name();
+                if (!isPrimitiveTypeName(simpleName)) {
+                    sink.addLast(simpleName);
+                }
+            }
+            case OPTIONAL, GROUP -> collectReferencedTypeNames(typeRef.inner(), sink);
+            case NAMED_TUPLE -> {
+                for (final var field : typeRef.fields()) {
+                    collectReferencedTypeNames(field.typeRef(), sink);
+                }
+            }
+            case UNIT, SELF, ERROR -> {
+            }
+        }
+    }
+
+    private boolean isPrimitiveTypeName(final String typeName) {
+        return "int".equals(typeName)
+                || "float".equals(typeName)
+                || "bool".equals(typeName)
+                || "str".equals(typeName)
+                || "unit".equals(typeName);
+    }
+
+    private boolean isTypeDecl(final PbsAst.TopDecl topDecl) {
+        return topDecl instanceof PbsAst.StructDecl
+                || topDecl instanceof PbsAst.BuiltinTypeDecl
+                || topDecl instanceof PbsAst.ServiceDecl
+                || topDecl instanceof PbsAst.HostDecl
+                || topDecl instanceof PbsAst.ContractDecl
+                || topDecl instanceof PbsAst.CallbackDecl
+                || topDecl instanceof PbsAst.EnumDecl
+                || topDecl instanceof PbsAst.ErrorDecl;
+    }
+
+    private void appendSupplementalTopDecl(
+            final PbsAst.TopDecl topDecl,
+            final ArrayList<PbsAst.TopDecl> supplementalTopDecls,
+            final Set<String> supplementalKeys) {
+        final var key = topDeclKey(topDecl);
+        if (key == null || key.isBlank()) {
+            return;
+        }
+        if (supplementalKeys.add(key)) {
+            supplementalTopDecls.add(topDecl);
+        }
+    }
+
+    private void appendImportedCallable(
+            final ArrayList<PbsFrontendCompiler.ImportedCallableSurface> importedCallables,
+            final Set<String> importedCallableKeys,
+            final PbsFrontendCompiler.ImportedCallableSurface importedCallableSurface) {
+        final var callableKey = importedCallableSurface.moduleKey()
+                + "#"
+                + importedCallableSurface.callableName()
+                + "#"
+                + importedCallableSurface.arity()
+                + "#"
+                + importedCallableSurface.shapeSurface();
+        if (importedCallableKeys.add(callableKey)) {
+            importedCallables.add(importedCallableSurface);
+        }
+    }
+
+    private String topDeclKey(final PbsAst.TopDecl topDecl) {
+        final var declName = topDeclName(topDecl);
+        if (declName == null || declName.isBlank()) {
+            return null;
+        }
+        return topDecl.getClass().getSimpleName() + ":" + declName;
+    }
+
+    private String topDeclName(final PbsAst.TopDecl topDecl) {
+        if (topDecl instanceof PbsAst.StructDecl structDecl) {
+            return structDecl.name();
+        }
+        if (topDecl instanceof PbsAst.BuiltinTypeDecl builtinTypeDecl) {
+            return builtinTypeDecl.name();
+        }
+        if (topDecl instanceof PbsAst.ConstDecl constDecl) {
+            return constDecl.name();
+        }
+        if (topDecl instanceof PbsAst.ServiceDecl serviceDecl) {
+            return serviceDecl.name();
+        }
+        if (topDecl instanceof PbsAst.HostDecl hostDecl) {
+            return hostDecl.name();
+        }
+        if (topDecl instanceof PbsAst.ContractDecl contractDecl) {
+            return contractDecl.name();
+        }
+        if (topDecl instanceof PbsAst.FunctionDecl functionDecl) {
+            return functionDecl.name();
+        }
+        if (topDecl instanceof PbsAst.CallbackDecl callbackDecl) {
+            return callbackDecl.name();
+        }
+        if (topDecl instanceof PbsAst.EnumDecl enumDecl) {
+            return enumDecl.name();
+        }
+        if (topDecl instanceof PbsAst.ErrorDecl errorDecl) {
+            return errorDecl.name();
+        }
+        return null;
+    }
+
+    private IRReservedMetadata mergeReservedMetadata(
+            final IRReservedMetadata left,
+            final IRReservedMetadata right) {
+        final var hostBindings = new ArrayList<IRReservedMetadata.HostMethodBinding>();
+        hostBindings.addAll(left.hostMethodBindings().asList());
+        hostBindings.addAll(right.hostMethodBindings().asList());
+
+        final var builtinTypeSurfaces = new ArrayList<IRReservedMetadata.BuiltinTypeSurface>();
+        builtinTypeSurfaces.addAll(left.builtinTypeSurfaces().asList());
+        builtinTypeSurfaces.addAll(right.builtinTypeSurfaces().asList());
+
+        final var builtinConstSurfaces = new ArrayList<IRReservedMetadata.BuiltinConstSurface>();
+        builtinConstSurfaces.addAll(left.builtinConstSurfaces().asList());
+        builtinConstSurfaces.addAll(right.builtinConstSurfaces().asList());
+
+        final var requiredCapabilities = new HashSet<String>();
+        requiredCapabilities.addAll(left.requiredCapabilities().asList());
+        requiredCapabilities.addAll(right.requiredCapabilities().asList());
+
+        return new IRReservedMetadata(
+                ReadOnlyList.wrap(hostBindings),
+                ReadOnlyList.wrap(builtinTypeSurfaces),
+                ReadOnlyList.wrap(builtinConstSurfaces),
+                ReadOnlyList.wrap(requiredCapabilities.stream().toList()));
+    }
+
+    private int returnSlotsFor(final PbsAst.FunctionDecl functionDecl) {
+        return switch (functionDecl.returnKind()) {
+            case INFERRED_UNIT, EXPLICIT_UNIT -> 0;
+            case PLAIN, RESULT -> 1;
+        };
+    }
+
+    private String importItemLocalName(final PbsAst.ImportItem importItem) {
+        if (importItem.alias() == null || importItem.alias().isBlank()) {
+            return importItem.name();
+        }
+        return importItem.alias();
+    }
+
     private Set<ModuleId> blockedModulesByDependency(
             final Set<ModuleId> failedModuleIds,
             final Map<ModuleId, Set<ModuleId>> dependenciesByModule) {
@@ -420,4 +809,13 @@ public class PBSFrontendPhaseService implements FrontendPhaseService {
             ModuleId moduleId,
             p.studio.compiler.models.IRBackendFile irBackendFile) {
     }
+
+    private record ImportedSemanticContext(
+            ReadOnlyList<PbsAst.TopDecl> supplementalTopDecls,
+            ReadOnlyList<PbsFrontendCompiler.ImportedCallableSurface> importedCallables,
+            IRReservedMetadata importedReservedMetadata) {
+        private static ImportedSemanticContext empty() {
+            return new ImportedSemanticContext(ReadOnlyList.empty(), ReadOnlyList.empty(), IRReservedMetadata.empty());
+        }
+    }
 }

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/resources/stdlib/1/sdk/log/main.pbs

@@ -0,0 +1,62 @@
+declare host LowLog {
+  [Host(module = "log", name = "write", version = 1)]
+  [Capability(name = "log")]
+  fn write(level: int, message: str) -> void;
+
+  [Host(module = "log", name = "write_tag", version = 1)]
+  [Capability(name = "log")]
+  fn write_tag(level: int, tag: int, message: str) -> void;
+}
+
+declare service Log
+{
+    fn trace(msg: str) -> void
+    {
+        LowLog.write(0, msg);
+    }
+
+    fn debug(msg: str) -> void
+    {
+        LowLog.write(1, msg);
+    }
+
+    fn info(msg: str) -> void
+    {
+        LowLog.write(2, msg);
+    }
+
+    fn warn(msg: str) -> void
+    {
+        LowLog.write(3, msg);
+    }
+
+    fn error(msg: str) -> void
+    {
+        LowLog.write(4, msg);
+    }
+
+    fn trace(tag: int, msg: str) -> void
+    {
+        LowLog.write_tag(0, tag, msg);
+    }
+
+    fn debug(tag: int, msg: str) -> void
+    {
+        LowLog.write_tag(1, tag, msg);
+    }
+
+    fn info(tag: int, msg: str) -> void
+    {
+        LowLog.write_tag(2, tag, msg);
+    }
+
+    fn warn(tag: int, msg: str) -> void
+    {
+        LowLog.write_tag(3, tag, msg);
+    }
+
+    fn error(tag: int, msg: str) -> void
+    {
+        LowLog.write_tag(4, tag, msg);
+    }
+}

prometeu-compiler/frontends/prometeu-frontend-pbs/src/main/resources/stdlib/1/sdk/log/mod.barrel

@@ -0,0 +1,2 @@
+mod host LowLog;
+pub service Log;

prometeu-compiler/frontends/prometeu-frontend-pbs/src/test/java/p/studio/compiler/pbs/PbsGateUSdkInterfaceConformanceTest.java

@@ -95,9 +95,10 @@ class PbsGateUSdkInterfaceConformanceTest {
                 import { Color } from @core:color;
                 import { Gfx } from @sdk:gfx;
                 import { Input, InputPad, InputButton } from @sdk:input;
+                import { Log } from @sdk:log;
 
                 declare contract Renderer {
-                  fn render(gfx: Gfx, color: Color, input: Input, pad: InputPad, button: InputButton) -> void;
+                  fn render(gfx: Gfx, color: Color, input: Input, pad: InputPad, button: InputButton, log: Log) -> void;
                 }
                 """,
                 "pub contract Renderer;",
@@ -113,9 +114,19 @@ class PbsGateUSdkInterfaceConformanceTest {
                 .anyMatch(t -> t.sourceTypeName().equals("Input") && t.canonicalTypeName().equals("input")));
         assertTrue(positive.irBackend().getReservedMetadata().builtinTypeSurfaces().stream()
                 .anyMatch(t -> t.sourceTypeName().equals("InputButton")
-                        && t.intrinsics().stream().anyMatch(i -> i.canonicalName().equals("hold"))));
+                        && t.intrinsics().stream().anyMatch(i -> i.canonicalName().equals("input.button.hold"))));
         assertTrue(positive.irBackend().getReservedMetadata().hostMethodBindings().stream()
                 .anyMatch(h -> h.ownerName().equals("Gfx")));
+        assertTrue(positive.irBackend().getReservedMetadata().hostMethodBindings().stream()
+                .anyMatch(h -> h.ownerName().equals("LowLog")
+                        && h.abiModule().equals("log")
+                        && h.abiMethod().equals("write")
+                        && h.abiVersion() == 1));
+        assertTrue(positive.irBackend().getReservedMetadata().hostMethodBindings().stream()
+                .anyMatch(h -> h.ownerName().equals("LowLog")
+                        && h.abiModule().equals("log")
+                        && h.abiMethod().equals("write_tag")
+                        && h.abiVersion() == 1));
 
         final var negative = compileWorkspaceModule(
                 tempDir.resolve("gate-u-reserved-import-negative"),
@@ -129,6 +140,19 @@ class PbsGateUSdkInterfaceConformanceTest {
         final var missingModule = firstDiagnostic(negative.diagnostics(),
                 d -> d.getCode().equals(PbsLinkErrors.E_LINK_IMPORT_MODULE_NOT_FOUND.name()));
         assertStableDiagnosticIdentity(missingModule, PbsLinkErrors.E_LINK_IMPORT_MODULE_NOT_FOUND.name(), DiagnosticPhase.LINKING);
+
+        final var lowLogNotPublic = compileWorkspaceModule(
+                tempDir.resolve("gate-u-reserved-import-lowlog-hidden"),
+                """
+                import { LowLog } from @sdk:log;
+                fn run() -> int { return 1; }
+                """,
+                "pub fn run() -> int;",
+                1,
+                d -> d.getCode().equals(PbsLinkErrors.E_LINK_IMPORT_SYMBOL_NOT_PUBLIC.name()));
+        final var notPublic = firstDiagnostic(lowLogNotPublic.diagnostics(),
+                d -> d.getCode().equals(PbsLinkErrors.E_LINK_IMPORT_SYMBOL_NOT_PUBLIC.name()));
+        assertStableDiagnosticIdentity(notPublic, PbsLinkErrors.E_LINK_IMPORT_SYMBOL_NOT_PUBLIC.name(), DiagnosticPhase.LINKING);
     }
 
     @Test

prometeu-compiler/frontends/prometeu-frontend-pbs/src/test/java/p/studio/compiler/pbs/parser/PbsParserTest.java

@@ -142,6 +142,31 @@ class PbsParserTest {
         assertTrue(diagnostics.stream().anyMatch(d -> d.getCode().equals(ParseErrors.E_PARSE_ATTRIBUTES_NOT_ALLOWED.name())));
     }
 
+    @Test
+    void shouldParseServiceAndMemberNamesUsingErrorKeyword() {
+        final var source = """
+            declare service Log {
+              fn error(msg: str) -> void { return; }
+              fn error(tag: int, msg: str) -> void { return; }
+            }
+
+            fn run() -> void {
+              Log.error("oops");
+              Log.error(7, "oops");
+              return;
+            }
+            """;
+        final var diagnostics = DiagnosticSink.empty();
+        final var fileId = new FileId(0);
+
+        final PbsAst.File ast = PbsParser.parse(PbsLexer.lex(source, fileId, diagnostics), fileId, diagnostics);
+
+        assertTrue(diagnostics.isEmpty(), "Parser should accept 'error' as callable/member name");
+        final var service = assertInstanceOf(PbsAst.ServiceDecl.class, ast.topDecls().getFirst());
+        assertEquals(2, service.methods().size());
+        assertEquals("error", service.methods().getFirst().name());
+    }
+
     @Test
     void shouldAcceptStructFieldTrailingComma() {
         final var source = "declare struct S(a: int,);";

prometeu-compiler/frontends/prometeu-frontend-pbs/src/test/java/p/studio/compiler/pbs/semantics/PbsInterfaceModuleSemanticsTest.java

@@ -81,10 +81,6 @@ class PbsInterfaceModuleSemanticsTest {
         final var source = """
                 fn run() -> int { return 1; }
 
-                declare service Game {
-                  fn tick() -> int { return 1; }
-                }
-
                 declare contract C { fn run() -> int; }
                 declare struct S(v: int);
                 implements C for S using s {
@@ -98,7 +94,30 @@ class PbsInterfaceModuleSemanticsTest {
         final var nonDeclarativeCount = diagnostics.stream()
                 .filter(d -> d.getCode().equals(PbsSemanticsErrors.E_SEM_INTERFACE_NON_DECLARATIVE_DECLARATION.name()))
                 .count();
-        assertTrue(nonDeclarativeCount >= 3);
+        assertTrue(nonDeclarativeCount >= 2);
+    }
+
+    @Test
+    void shouldAllowDeclarativeServiceFacadesInInterfaceModule() {
+        final var source = """
+                declare host LowLog {
+                  [Host(module = "log", name = "write", version = 1)]
+                  [Capability(name = "log")]
+                  fn write(level: int, message: str) -> void;
+                }
+
+                declare service Log {
+                  fn trace(message: str) -> void {
+                    LowLog.write(0, message);
+                  }
+                }
+                """;
+        final var diagnostics = DiagnosticSink.empty();
+
+        new PbsFrontendCompiler().compileFile(new FileId(3), source, diagnostics, SourceKind.SDK_INTERFACE);
+
+        assertFalse(diagnostics.stream().anyMatch(d ->
+                d.getCode().equals(PbsSemanticsErrors.E_SEM_INTERFACE_NON_DECLARATIVE_DECLARATION.name())));
     }
 
     @Test

prometeu-compiler/frontends/prometeu-frontend-pbs/src/test/java/p/studio/compiler/services/PBSFrontendPhaseServiceTest.java

@@ -181,6 +181,7 @@ class PBSFrontendPhaseServiceTest {
                 BuildingIssueSink.empty());
 
         assertTrue(diagnostics.isEmpty());
+        assertEquals("frame", irBackend.getEntryPointCallableName());
         assertEquals(2, irBackend.getFunctions().size());
     }
 
@@ -783,6 +784,89 @@ class PBSFrontendPhaseServiceTest {
         assertEquals("independent", irBackend.getFunctions().getFirst().name());
     }
 
+    @Test
+    void shouldResolveImportedBuiltinTypeChainsInExpressionFlowSemantics() throws IOException {
+        final var projectRoot = tempDir.resolve("project-builtin-chain");
+        final var sourceRoot = projectRoot.resolve("src");
+        Files.createDirectories(sourceRoot);
+
+        final var sourceFile = sourceRoot.resolve("main.pbs");
+        final var modBarrel = sourceRoot.resolve("mod.barrel");
+        Files.writeString(sourceFile, """
+                import { Log } from @sdk:log;
+                import { Input } from @sdk:input;
+
+                fn frame() -> void
+                {
+                    if (Input.pad().a().pressed())
+                    {
+                        Log.debug("Hello World!");
+                    }
+                }
+                """);
+        Files.writeString(modBarrel, "pub fn frame() -> void;");
+
+        final var projectTable = new ProjectTable();
+        final var fileTable = new FileTable(1);
+        final var projectId = projectTable.register(ProjectDescriptor.builder()
+                .rootPath(projectRoot)
+                .name("main")
+                .version("1.0.0")
+                .sourceRoots(ReadOnlyList.wrap(List.of(sourceRoot)))
+                .build());
+
+        registerFile(projectId, projectRoot, sourceFile, fileTable);
+        registerFile(projectId, projectRoot, modBarrel, fileTable);
+
+        final var ctx = new FrontendPhaseContext(
+                projectTable,
+                fileTable,
+                new BuildStack(ReadOnlyList.wrap(List.of(projectId))),
+                1);
+        final var diagnostics = DiagnosticSink.empty();
+
+        final var irBackend = new PBSFrontendPhaseService().compile(
+                ctx,
+                diagnostics,
+                LogAggregator.empty(),
+                BuildingIssueSink.empty());
+
+        assertTrue(diagnostics.stream().noneMatch(d ->
+                d.getCode().equals(PbsSemanticsErrors.E_SEM_INVALID_MEMBER_ACCESS.name())));
+        assertTrue(diagnostics.stream().noneMatch(d ->
+                d.getCode().equals(PbsSemanticsErrors.E_SEM_APPLY_NON_CALLABLE_TARGET.name())));
+        final var frameExecutableOptional = irBackend.getExecutableFunctions().stream()
+                .filter(function -> "frame".equals(function.callableName()))
+                .findFirst();
+        final var executableNames = irBackend.getExecutableFunctions().stream()
+                .map(function -> function.callableName() + "@" + function.moduleKey())
+                .toList();
+        assertTrue(
+                frameExecutableOptional.isPresent(),
+                "diagnostics="
+                        + diagnostics.stream().map(d -> d.getCode() + ":" + d.getMessage()).toList()
+                        + " executableNames="
+                        + executableNames);
+        final var frameExecutable = frameExecutableOptional.orElseThrow();
+        final var intrinsicCalls = frameExecutable.instructions().stream()
+                .filter(instruction ->
+                        instruction.kind() == p.studio.compiler.models.IRBackendExecutableFunction.InstructionKind.CALL_INTRINSIC)
+                .toList();
+        assertTrue(intrinsicCalls.stream().anyMatch(instruction -> Integer.valueOf(1).equals(instruction.expectedArgSlots())));
+        assertTrue(intrinsicCalls.stream().anyMatch(instruction ->
+                instruction.intrinsicCall() != null && "input.pad".equals(instruction.intrinsicCall().canonicalName())));
+        assertTrue(intrinsicCalls.stream().anyMatch(instruction ->
+                instruction.intrinsicCall() != null && "input.pad.a".equals(instruction.intrinsicCall().canonicalName())));
+        assertTrue(intrinsicCalls.stream().anyMatch(instruction ->
+                instruction.intrinsicCall() != null && "input.button.pressed".equals(instruction.intrinsicCall().canonicalName())));
+        assertTrue(
+                irBackend.getExecutableFunctions().stream().anyMatch(function -> "frame".equals(function.callableName())),
+                "diagnostics="
+                        + diagnostics.stream().map(d -> d.getCode() + ":" + d.getMessage()).toList()
+                        + " executableNames="
+                        + executableNames);
+    }
+
     private void registerFile(
             final ProjectId projectId,
             final Path projectRoot,

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMIntrinsicRegistry.java

@@ -0,0 +1,73 @@
+package p.studio.compiler.backend.irvm;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.OptionalInt;
+
+final class IRVMIntrinsicRegistry {
+    private static final Map<IntrinsicKey, Integer> FINAL_ID_BY_INTRINSIC = createRegistry();
+
+    private IRVMIntrinsicRegistry() {
+    }
+
+    static OptionalInt resolveFinalId(
+            final String canonicalName,
+            final long canonicalVersion) {
+        if (canonicalName == null || canonicalName.isBlank()) {
+            return OptionalInt.empty();
+        }
+        final var resolved = FINAL_ID_BY_INTRINSIC.get(new IntrinsicKey(canonicalName, canonicalVersion));
+        if (resolved == null) {
+            return OptionalInt.empty();
+        }
+        return OptionalInt.of(resolved);
+    }
+
+    private static Map<IntrinsicKey, Integer> createRegistry() {
+        final var registry = new HashMap<IntrinsicKey, Integer>();
+        register(registry, "vec2.dot", 1, 0x1000);
+        register(registry, "vec2.length", 1, 0x1001);
+
+        register(registry, "input.pad", 1, 0x2000);
+        register(registry, "input.touch", 1, 0x2001);
+
+        register(registry, "input.pad.up", 1, 0x2010);
+        register(registry, "input.pad.down", 1, 0x2011);
+        register(registry, "input.pad.left", 1, 0x2012);
+        register(registry, "input.pad.right", 1, 0x2013);
+        register(registry, "input.pad.a", 1, 0x2014);
+        register(registry, "input.pad.b", 1, 0x2015);
+        register(registry, "input.pad.x", 1, 0x2016);
+        register(registry, "input.pad.y", 1, 0x2017);
+        register(registry, "input.pad.l", 1, 0x2018);
+        register(registry, "input.pad.r", 1, 0x2019);
+        register(registry, "input.pad.start", 1, 0x201A);
+        register(registry, "input.pad.select", 1, 0x201B);
+
+        register(registry, "input.touch.button", 1, 0x2020);
+        register(registry, "input.touch.x", 1, 0x2021);
+        register(registry, "input.touch.y", 1, 0x2022);
+
+        register(registry, "input.button.pressed", 1, 0x2030);
+        register(registry, "input.button.released", 1, 0x2031);
+        register(registry, "input.button.down", 1, 0x2032);
+        register(registry, "input.button.hold", 1, 0x2033);
+        return Map.copyOf(registry);
+    }
+
+    private static void register(
+            final Map<IntrinsicKey, Integer> registry,
+            final String canonicalName,
+            final long canonicalVersion,
+            final int finalId) {
+        final var previous = registry.put(new IntrinsicKey(canonicalName, canonicalVersion), finalId);
+        if (previous != null && previous != finalId) {
+            throw new IllegalStateException("duplicate intrinsic registry identity: " + canonicalName + "@" + canonicalVersion);
+        }
+    }
+
+    private record IntrinsicKey(
+            String canonicalName,
+            long canonicalVersion) {
+    }
+}

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMLoweringErrorCode.java

@@ -2,6 +2,7 @@ package p.studio.compiler.backend.irvm;
 
 public enum IRVMLoweringErrorCode {
     LOWER_IRVM_EMPTY_EXECUTABLE_INPUT,
+    LOWER_IRVM_ENTRYPOINT_DECLARATION_MISSING,
     LOWER_IRVM_ENTRYPOINT_MISSING,
     LOWER_IRVM_ENTRYPOINT_AMBIGUOUS,
     LOWER_IRVM_MISSING_CALLEE,

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/IRVMValidator.java

@@ -173,7 +173,7 @@ public class IRVMValidator {
         if (inHeight < pops) {
             throw new IRVMValidationException(
                     IRVMValidationErrorCode.MARSHAL_VERIFY_PRECHECK_STACK_UNDERFLOW,
-                    "stack underflow",
+                    "stack underflow. need=%d have=%d".formatted(pops, inHeight),
                     functionIndex,
                     pc);
         }

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/backend/irvm/LowerToIRVMService.java

@@ -42,7 +42,7 @@ public class LowerToIRVMService {
                     "IRBackend has no executable functions");
         }
 
-        final var ordered = orderFunctions(backend.getExecutableFunctions());
+        final var ordered = orderFunctions(backend);
         final var funcIdByCallableId = new HashMap<CallableId, Integer>();
         for (var i = 0; i < ordered.size(); i++) {
             final var fn = ordered.get(i);
@@ -145,9 +145,31 @@ public class LowerToIRVMService {
                                     IRVMLoweringErrorCode.LOWER_IRVM_INVALID_INTRINSIC_ID,
                                     "invalid intrinsic id: " + intrinsic.intrinsicId());
                         }
-                        instructions.add(new IRVMInstruction(IRVMOp.INTRINSIC, intrinsicIndex));
+                        final var canonicalIntrinsic = backend.getIntrinsicPool().get(intrinsicIndex);
+                        if (!canonicalIntrinsic.canonicalName().equals(intrinsic.canonicalName())
+                                || canonicalIntrinsic.canonicalVersion() != intrinsic.canonicalVersion()) {
+                            throw loweringError(
+                                    fn,
+                                    instr,
+                                    IRVMLoweringErrorCode.LOWER_IRVM_INVALID_INTRINSIC_ID,
+                                    "intrinsic identity mismatch between callsite and pool: call=%s@%d pool=%s@%d".formatted(
+                                            intrinsic.canonicalName(),
+                                            intrinsic.canonicalVersion(),
+                                            canonicalIntrinsic.canonicalName(),
+                                            canonicalIntrinsic.canonicalVersion()));
+                        }
+                        final var finalIntrinsicId = IRVMIntrinsicRegistry
+                                .resolveFinalId(canonicalIntrinsic.canonicalName(), canonicalIntrinsic.canonicalVersion())
+                                .orElseThrow(() -> loweringError(
+                                        fn,
+                                        instr,
+                                        IRVMLoweringErrorCode.LOWER_IRVM_INVALID_INTRINSIC_ID,
+                                        "unknown VM-owned intrinsic identity: %s@%d".formatted(
+                                                canonicalIntrinsic.canonicalName(),
+                                                canonicalIntrinsic.canonicalVersion())));
+                        instructions.add(new IRVMInstruction(IRVMOp.INTRINSIC, finalIntrinsicId));
                         operations.add(BytecodeEmitter.Operation.intrinsic(
-                                intrinsicIndex,
+                                finalIntrinsicId,
                                 instr.expectedArgSlots(),
                                 instr.expectedRetSlots(),
                                 sourceSpan));
@@ -231,22 +253,29 @@ public class LowerToIRVMService {
         return program;
     }
 
-    private ReadOnlyList<IRBackendExecutableFunction> orderFunctions(
+    private ReadOnlyList<IRBackendExecutableFunction> orderFunctions(final IRBackend backend) {
-            final ReadOnlyList<IRBackendExecutableFunction> functions) {
+        final var entryPointCallableName = backend.getEntryPointCallableName();
-        final var sorted = new ArrayList<>(functions.asList());
+        if (entryPointCallableName == null || entryPointCallableName.isBlank()) {
+            throw new IRVMLoweringException(
+                    IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_DECLARATION_MISSING,
+                    "frontend IRBackend entrypoint declaration is missing");
+        }
+        final var sorted = new ArrayList<>(backend.getExecutableFunctions().asList());
         sorted.sort(FUNCTION_ORDER);
         final var entrypoints = sorted.stream()
-                .filter(candidate -> "main".equals(candidate.callableName()))
+                .filter(candidate -> entryPointCallableName.equals(candidate.callableName()))
                 .toList();
         if (entrypoints.isEmpty()) {
             throw new IRVMLoweringException(
                     IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_MISSING,
-                    "missing entrypoint callable 'main'");
+                    "missing entrypoint callable '%s'".formatted(entryPointCallableName));
         }
         if (entrypoints.size() > 1) {
             throw new IRVMLoweringException(
                     IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_AMBIGUOUS,
-                    "ambiguous entrypoint: found %d callables named 'main'".formatted(entrypoints.size()));
+                    "ambiguous entrypoint: found %d callables named '%s'".formatted(
+                            entrypoints.size(),
+                            entryPointCallableName));
         }
         final var entrypoint = entrypoints.getFirst();
         final var ordered = new ArrayList<IRBackendExecutableFunction>(sorted.size());

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/models/BuilderPipelineContext.java

@@ -21,6 +21,7 @@ public class BuilderPipelineContext {
     public IRVMProgram optimizedIrvm;
     public BytecodeModule bytecodeModule;
     public byte[] bytecodeBytes;
+    public Path bytecodeArtifactPath;
 
     private BuilderPipelineContext(
             final BuilderPipelineConfig config,

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/workspaces/BuilderPipelineService.java

@@ -23,7 +23,8 @@ public class BuilderPipelineService {
                 new OptimizeIRVMPipelineStage(),
                 new EmitBytecodePipelineStage(),
                 new LinkBytecodePipelineStage(),
-                new VerifyBytecodePipelineStage()
+                new VerifyBytecodePipelineStage(),
+                new WriteBytecodeArtifactPipelineStage()
         );
         INSTANCE = new BuilderPipelineService(stages);
     }

prometeu-compiler/prometeu-build-pipeline/src/main/java/p/studio/compiler/workspaces/stages/WriteBytecodeArtifactPipelineStage.java

@@ -0,0 +1,72 @@
+package p.studio.compiler.workspaces.stages;
+
+import lombok.extern.slf4j.Slf4j;
+import p.studio.compiler.messages.BuildingIssueSink;
+import p.studio.compiler.models.BuilderPipelineContext;
+import p.studio.compiler.workspaces.PipelineStage;
+import p.studio.utilities.logs.LogAggregator;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.StandardOpenOption;
+
+@Slf4j
+public class WriteBytecodeArtifactPipelineStage implements PipelineStage {
+    private static final String OUTPUT_DIR = "build";
+    private static final String OUTPUT_FILE = "program.pbx";
+
+    @Override
+    public BuildingIssueSink run(final BuilderPipelineContext ctx, final LogAggregator logs) {
+        if (ctx.rootProjectPathCanon == null) {
+            return BuildingIssueSink.empty()
+                    .report(builder -> builder
+                            .error(true)
+                            .phase("BACKEND_WRITE_ARTIFACT")
+                            .code("MARSHAL_FORMAT_STAGE_INPUT_MISSING")
+                            .message("[BUILD]: root project path is missing before WriteBytecodeArtifact stage"));
+        }
+
+        final var bytes = resolveBytes(ctx);
+        if (bytes == null || bytes.length == 0) {
+            return BuildingIssueSink.empty()
+                    .report(builder -> builder
+                            .error(true)
+                            .phase("BACKEND_WRITE_ARTIFACT")
+                            .code("MARSHAL_FORMAT_STAGE_INPUT_MISSING")
+                            .message("[BUILD]: bytecode bytes are missing before WriteBytecodeArtifact stage"));
+        }
+
+        final var outputDir = ctx.rootProjectPathCanon.resolve(OUTPUT_DIR);
+        final var outputPath = outputDir.resolve(OUTPUT_FILE);
+        try {
+            Files.createDirectories(outputDir);
+            Files.write(
+                    outputPath,
+                    bytes,
+                    StandardOpenOption.CREATE,
+                    StandardOpenOption.TRUNCATE_EXISTING,
+                    StandardOpenOption.WRITE);
+            ctx.bytecodeArtifactPath = outputPath;
+            logs.using(log).info("[BUILD]: wrote bytecode artifact to " + outputPath);
+            return BuildingIssueSink.empty();
+        } catch (IOException e) {
+            return BuildingIssueSink.empty()
+                    .report(builder -> builder
+                            .error(true)
+                            .phase("BACKEND_WRITE_ARTIFACT")
+                            .code("MARSHAL_ARTIFACT_WRITE_FAILED")
+                            .message("[BUILD]: failed to write bytecode artifact: " + outputPath)
+                            .exception(e));
+        }
+    }
+
+    private byte[] resolveBytes(final BuilderPipelineContext ctx) {
+        if (ctx.bytecodeBytes != null && ctx.bytecodeBytes.length > 0) {
+            return ctx.bytecodeBytes;
+        }
+        if (ctx.bytecodeModule != null) {
+            return ctx.bytecodeModule.serialize();
+        }
+        return null;
+    }
+}

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/GoldenArtifactsTest.java

@@ -68,7 +68,7 @@ class GoldenArtifactsTest {
                                         "",
                                         "",
                                         null,
-                                        new IRBackendExecutableFunction.IntrinsicCallMetadata("core.color.pack", 1, new IntrinsicId(0)),
+                                        new IRBackendExecutableFunction.IntrinsicCallMetadata("input.pad", 1, new IntrinsicId(0)),
                                         0,
                                         0,
                                         Span.none()),
@@ -80,7 +80,7 @@ class GoldenArtifactsTest {
                                         null,
                                         Span.none())),
                         Span.none())))
-                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("core.color.pack", 1)))
+                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("input.pad", 1)))
                 .build();
     }
 

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/IRVMValidatorTest.java

@@ -204,7 +204,7 @@ class IRVMValidatorTest {
     }
 
     @Test
-    void validateProgramMustApplyHostcallStackEffectsFromMetadata() {
+    void validateProgramMustRejectHostcallWhenDeclaredArgsAreMissingOnStack() {
         final var module = new IRVMModule(
                 "core-v1",
                 ReadOnlyList.from(new IRVMFunction(

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/LowerToIRVMServiceTest.java

@@ -36,15 +36,34 @@ class LowerToIRVMServiceTest {
         assertEquals(0, lowered.module().functions().get(1).instructions().get(0).immediate());
     }
 
+    @Test
+    void lowerMustUseFrontendDeclaredEntrypointCallable() {
+        final var backend = IRBackend.builder()
+                .entryPointCallableName("frame")
+                .executableFunctions(ReadOnlyList.from(
+                        fn("aux", "app", 11, ReadOnlyList.from(
+                                callFunc("app", "frame", 10),
+                                ret())),
+                        fn("frame", "app", 10, ReadOnlyList.from(
+                                ret()))))
+                .build();
+
+        final var lowered = new LowerToIRVMService().lower(backend);
+
+        assertEquals("frame", lowered.module().functions().get(0).name());
+        assertEquals("aux", lowered.module().functions().get(1).name());
+        assertEquals(0, lowered.module().functions().get(1).instructions().get(0).immediate());
+    }
+
     @Test
     void lowerMustMapHostAndIntrinsicCallsites() {
         final var backend = IRBackend.builder()
                 .executableFunctions(ReadOnlyList.from(
                         fn("main", "app", 10, ReadOnlyList.from(
                                 callHost("gfx", "draw_pixel", 1, 0, 0),
-                                callIntrinsic("core.color.pack", 1, 0),
+                                callIntrinsic("input.pad", 1, 0),
                                 ret()))))
-                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("core.color.pack", 1)))
+                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("input.pad", 1)))
                 .build();
 
         final var lowered = new LowerToIRVMService().lower(backend);
@@ -52,7 +71,7 @@ class LowerToIRVMServiceTest {
         final var instructions = lowered.module().functions().getFirst().instructions();
         assertEquals(IRVMOp.HOSTCALL, instructions.get(0).op());
         assertEquals(IRVMOp.INTRINSIC, instructions.get(1).op());
-        assertEquals(0, instructions.get(1).immediate());
+        assertEquals(0x2000, instructions.get(1).immediate());
         final var emissionOps = lowered.emissionPlan().functions().getFirst().operations();
         assertEquals(p.studio.compiler.backend.bytecode.BytecodeEmitter.OperationKind.HOSTCALL, emissionOps.get(0).kind());
         assertEquals(p.studio.compiler.backend.bytecode.BytecodeEmitter.OperationKind.INTRINSIC, emissionOps.get(1).kind());
@@ -84,6 +103,21 @@ class LowerToIRVMServiceTest {
         assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_MISSING_CALLEE, thrown.code());
     }
 
+    @Test
+    void lowerMustRejectUnknownCanonicalIntrinsicIdentity() {
+        final var backend = IRBackend.builder()
+                .executableFunctions(ReadOnlyList.from(
+                        fn("main", "app", 10, ReadOnlyList.from(
+                                callIntrinsic("core.color.pack", 1, 0),
+                                ret()))))
+                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("core.color.pack", 1)))
+                .build();
+
+        final var thrown = assertThrows(IRVMLoweringException.class, () -> new LowerToIRVMService().lower(backend));
+        assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_INVALID_INTRINSIC_ID, thrown.code());
+        assertTrue(thrown.getMessage().contains("unknown VM-owned intrinsic identity"));
+    }
+
     @Test
     void lowerMustRejectCallArgSlotMismatch() {
         final var backend = IRBackend.builder()
@@ -141,6 +175,18 @@ class LowerToIRVMServiceTest {
         assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_MISSING, thrown.code());
     }
 
+    @Test
+    void lowerMustRejectWhenEntrypointDeclarationIsMissing() {
+        final var backend = IRBackend.builder()
+                .entryPointCallableName(" ")
+                .executableFunctions(ReadOnlyList.from(
+                        fn("main", "app", 10, ReadOnlyList.from(ret()))))
+                .build();
+
+        final var thrown = assertThrows(IRVMLoweringException.class, () -> new LowerToIRVMService().lower(backend));
+        assertEquals(IRVMLoweringErrorCode.LOWER_IRVM_ENTRYPOINT_DECLARATION_MISSING, thrown.code());
+    }
+
     @Test
     void lowerMustRejectWhenEntrypointIsAmbiguous() {
         final var backend = IRBackend.builder()

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/backend/irvm/OptimizeIRVMEquivalenceHarnessTest.java

@@ -31,9 +31,9 @@ class OptimizeIRVMEquivalenceHarnessTest {
                 .executableFunctions(ReadOnlyList.from(
                         fn("main", 1, ReadOnlyList.from(
                                 callHost("gfx", "draw_pixel", 1, 0, 0),
-                                callIntrinsic("core.color.pack", 1, 0, 0, 0),
+                                callIntrinsic("input.pad", 1, 0, 0, 0),
                                 ret()))))
-                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("core.color.pack", 1)))
+                .intrinsicPool(ReadOnlyList.from(new IntrinsicReference("input.pad", 1)))
                 .build();
 
         final var lowered = new LowerToIRVMService().lower(backend);

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/integration/BackendGateIIntegrationTest.java

@@ -145,9 +145,9 @@ class BackendGateIIntegrationTest {
     void gateI_validIntrinsicPath() {
         final var module = emitFromBackend(backendWithSingleFunction(
                 fn("main", ReadOnlyList.from(
-                        callIntrinsic("core.color.pack", 1, 0),
+                        callIntrinsic("input.pad", 1, 0),
                         ret())),
-                ReadOnlyList.from(new IntrinsicReference("core.color.pack", 1))));
+                ReadOnlyList.from(new IntrinsicReference("input.pad", 1))));
 
         final var check = compatibilityAdapter.check(module);
         assertEquals(CompatibilityError.NONE, check.error());

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/workspaces/BuilderPipelineServiceOrderTest.java

@@ -9,6 +9,7 @@ import p.studio.compiler.workspaces.stages.LowerToIRVMPipelineStage;
 import p.studio.compiler.workspaces.stages.OptimizeIRVMPipelineStage;
 import p.studio.compiler.workspaces.stages.ResolveDepsPipelineStage;
 import p.studio.compiler.workspaces.stages.VerifyBytecodePipelineStage;
+import p.studio.compiler.workspaces.stages.WriteBytecodeArtifactPipelineStage;
 
 import java.lang.reflect.Field;
 import java.util.List;
@@ -35,7 +36,8 @@ class BuilderPipelineServiceOrderTest {
                         OptimizeIRVMPipelineStage.class,
                         EmitBytecodePipelineStage.class,
                         LinkBytecodePipelineStage.class,
-                        VerifyBytecodePipelineStage.class),
+                        VerifyBytecodePipelineStage.class,
+                        WriteBytecodeArtifactPipelineStage.class),
                 stageTypes);
     }
 }

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/workspaces/stages/LowerToIRVMPipelineStageTest.java

@@ -141,4 +141,67 @@ class LowerToIRVMPipelineStageTest {
         assertEquals(12, firstIssue.getStart());
         assertEquals(24, firstIssue.getEnd());
     }
+
+    @Test
+    void runMustRejectCallWhenStackDoesNotProvideDeclaredArgs() {
+        final var ctx = BuilderPipelineContext.compilerContext(new BuilderPipelineConfig(false, "."));
+        ctx.irBackend = IRBackend.builder()
+                .executableFunctions(ReadOnlyList.from(
+                        new IRBackendExecutableFunction(
+                                new FileId(0),
+                                "app",
+                                "callee",
+                                new CallableId(2),
+                                0,
+                                10,
+                                1,
+                                0,
+                                0,
+                                1,
+                                ReadOnlyList.from(new IRBackendExecutableFunction.Instruction(
+                                        IRBackendExecutableFunction.InstructionKind.RET,
+                                        "",
+                                        "",
+                                        null,
+                                        null,
+                                        Span.none())),
+                                Span.none()),
+                        new IRBackendExecutableFunction(
+                                new FileId(0),
+                                "app",
+                                "main",
+                                new CallableId(1),
+                                0,
+                                10,
+                                0,
+                                0,
+                                0,
+                                1,
+                                ReadOnlyList.from(
+                                        new IRBackendExecutableFunction.Instruction(
+                                                IRBackendExecutableFunction.InstructionKind.CALL_FUNC,
+                                                "app",
+                                                "callee",
+                                                new CallableId(2),
+                                                null,
+                                                null,
+                                                1,
+                                                0,
+                                                Span.none()),
+                                        new IRBackendExecutableFunction.Instruction(
+                                                IRBackendExecutableFunction.InstructionKind.RET,
+                                                "",
+                                                "",
+                                                null,
+                                                null,
+                                                Span.none())),
+                                Span.none())))
+                .build();
+
+        final var issues = new LowerToIRVMPipelineStage().run(ctx, LogAggregator.empty());
+        final var firstIssue = issues.asCollection().iterator().next();
+
+        assertTrue(issues.hasErrors());
+        assertEquals("MARSHAL_VERIFY_PRECHECK_STACK_UNDERFLOW", firstIssue.getCode());
+    }
 }

prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/workspaces/stages/WriteBytecodeArtifactPipelineStageTest.java

@@ -0,0 +1,86 @@
+package p.studio.compiler.workspaces.stages;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import p.studio.compiler.backend.bytecode.BytecodeModule;
+import p.studio.compiler.messages.BuilderPipelineConfig;
+import p.studio.compiler.models.BuilderPipelineContext;
+import p.studio.utilities.logs.LogAggregator;
+import p.studio.utilities.structures.ReadOnlyList;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class WriteBytecodeArtifactPipelineStageTest {
+
+    @TempDir
+    Path tempDir;
+
+    @Test
+    void runMustFailWhenRootProjectPathIsMissing() {
+        final var ctx = BuilderPipelineContext.compilerContext(new BuilderPipelineConfig(false, "."));
+        ctx.bytecodeBytes = new byte[] { 0x01 };
+
+        final var issues = new WriteBytecodeArtifactPipelineStage().run(ctx, LogAggregator.empty());
+        final var firstIssue = issues.asCollection().iterator().next();
+
+        assertTrue(issues.hasErrors());
+        assertEquals("BACKEND_WRITE_ARTIFACT", firstIssue.getPhase());
+        assertEquals("MARSHAL_FORMAT_STAGE_INPUT_MISSING", firstIssue.getCode());
+    }
+
+    @Test
+    void runMustFailWhenBytecodeInputIsMissing() {
+        final var ctx = BuilderPipelineContext.compilerContext(new BuilderPipelineConfig(false, "."));
+        ctx.rootProjectPathCanon = tempDir;
+
+        final var issues = new WriteBytecodeArtifactPipelineStage().run(ctx, LogAggregator.empty());
+        final var firstIssue = issues.asCollection().iterator().next();
+
+        assertTrue(issues.hasErrors());
+        assertEquals("BACKEND_WRITE_ARTIFACT", firstIssue.getPhase());
+        assertEquals("MARSHAL_FORMAT_STAGE_INPUT_MISSING", firstIssue.getCode());
+    }
+
+    @Test
+    void runMustWriteBuildProgramPbxFromByteArray() throws Exception {
+        final var ctx = BuilderPipelineContext.compilerContext(new BuilderPipelineConfig(false, "."));
+        ctx.rootProjectPathCanon = tempDir;
+        ctx.bytecodeBytes = new byte[] { 0x50, 0x42, 0x58, 0x00 };
+
+        final var issues = new WriteBytecodeArtifactPipelineStage().run(ctx, LogAggregator.empty());
+        final var outputPath = tempDir.resolve("build").resolve("program.pbx");
+
+        assertFalse(issues.hasErrors());
+        assertTrue(Files.exists(outputPath));
+        assertArrayEquals(ctx.bytecodeBytes, Files.readAllBytes(outputPath));
+        assertEquals(outputPath, ctx.bytecodeArtifactPath);
+    }
+
+    @Test
+    void runMustWriteBuildProgramPbxFromModuleWhenByteArrayIsMissing() throws Exception {
+        final var ctx = BuilderPipelineContext.compilerContext(new BuilderPipelineConfig(false, "."));
+        ctx.rootProjectPathCanon = tempDir;
+        ctx.bytecodeModule = new BytecodeModule(
+                0,
+                ReadOnlyList.empty(),
+                ReadOnlyList.empty(),
+                new byte[] { (byte) 0x51, 0x00 },
+                null,
+                ReadOnlyList.empty(),
+                ReadOnlyList.empty());
+
+        final var issues = new WriteBytecodeArtifactPipelineStage().run(ctx, LogAggregator.empty());
+        final var outputPath = tempDir.resolve("build").resolve("program.pbx");
+
+        assertFalse(issues.hasErrors());
+        assertTrue(Files.exists(outputPath));
+        assertArrayEquals(ctx.bytecodeModule.serialize(), Files.readAllBytes(outputPath));
+        assertEquals(outputPath, ctx.bytecodeArtifactPath);
+    }
+}

prometeu-compiler/prometeu-build-pipeline/src/test/resources/golden/bytecode-module.hex

@@ -1 +1 @@
-504253000000000004000000000000000000000000000000000000000000000001000000500000001400000002000000640000000e00000003000000720000004400000005000000b60000001b00000001000000000000000e000000000000000000020071000000000072000000000051000300000000000000010000000000000000000000060000000100000000000000000000000c0000000100000000000000000000000100000000000000040000006d61696e0100000003006766780a00647261775f706978656c010000000000
+504253000000000004000000000000000000000000000000000000000000000001000000500000001400000002000000640000000e00000003000000720000004400000005000000b60000001b00000001000000000000000e000000000000000000020071000000000072000020000051000300000000000000010000000000000000000000060000000100000000000000000000000c0000000100000000000000000000000100000000000000040000006d61696e0100000003006766780a00647261775f706978656c010000000000

prometeu-compiler/prometeu-build-pipeline/src/test/resources/golden/irvm-program.txt

@@ -1,5 +1,5 @@
 profile=core-v1
 fn#0:main param=0 local=0 ret=0 max=2
   HOSTCALL imm=0
-  INTRINSIC imm=0
+  INTRINSIC imm=8192
   RET imm=-

prometeu-compiler/prometeu-compiler-core/src/main/java/p/studio/compiler/models/FrontendSpec.java

@@ -11,8 +11,10 @@ public class FrontendSpec {
     private final ReadOnlySet<String> allowedExtensions;
     private final ReadOnlySet<String> sourceRoots;
     private final boolean caseSensitive;
+    @Builder.Default
+    private final String entryPointCallableName = "main";
 
     public String toString() {
-        return String.format("FrontendSpec(language=%s)", languageId);
+        return String.format("FrontendSpec(language=%s, entryPoint=%s)", languageId, entryPointCallableName);
     }
 }

prometeu-compiler/prometeu-frontend-api/src/main/java/p/studio/compiler/models/IRBackend.java

@@ -16,6 +16,8 @@ import java.util.LinkedHashSet;
 @Builder
 @Getter
 public class IRBackend {
+    @Builder.Default
+    private final String entryPointCallableName = "main";
     @Builder.Default
     private final ReadOnlyList<IRFunction> functions = ReadOnlyList.empty();
     @Builder.Default
@@ -32,6 +34,7 @@ public class IRBackend {
     }
 
     public static final class IRBackendAggregator {
+        private String entryPointCallableName;
         private final ArrayList<IRFunction> functions = new ArrayList<>();
         private final ArrayList<IRBackendExecutableFunction> executableFunctions = new ArrayList<>();
         private final CallableTable callableTable = new CallableTable();
@@ -58,6 +61,13 @@ public class IRBackend {
             requiredCapabilities.addAll(metadata.requiredCapabilities().asList());
         }
 
+        public IRBackendAggregator entryPointCallableName(final String callableName) {
+            if (callableName != null && !callableName.isBlank()) {
+                entryPointCallableName = callableName;
+            }
+            return this;
+        }
+
         private CallableId[] reindexCallables(final ReadOnlyList<CallableSignatureRef> localCallableSignatures) {
             if (localCallableSignatures == null || localCallableSignatures.isEmpty()) {
                 return new CallableId[0];
@@ -170,6 +180,7 @@ public class IRBackend {
         public IRBackend emit() {
             return IRBackend
                     .builder()
+                    .entryPointCallableName(resolveEntryPointCallableName())
                     .functions(ReadOnlyList.wrap(functions))
                     .executableFunctions(ReadOnlyList.wrap(executableFunctions))
                     .callableSignatures(emitCallableSignatures())
@@ -181,12 +192,19 @@ public class IRBackend {
                             ReadOnlyList.wrap(requiredCapabilities.stream().toList())))
                     .build();
         }
+
+        private String resolveEntryPointCallableName() {
+            return entryPointCallableName == null || entryPointCallableName.isBlank()
+                    ? "main"
+                    : entryPointCallableName;
+        }
     }
 
     @Override
     public String toString() {
         final var sb = new StringBuilder();
-        sb.append("IRBackend{functions=").append(functions.size())
+        sb.append("IRBackend{entrypoint=").append(entryPointCallableName)
+                .append(", functions=").append(functions.size())
                 .append(", executableFunctions=").append(executableFunctions.size())
                 .append(", callableSignatures=").append(callableSignatures.size())
                 .append(", intrinsicPool=").append(intrinsicPool.size())

prometeu-compiler/prometeu-frontend-api/src/test/java/p/studio/compiler/models/IRBackendExecutableContractTest.java

@@ -177,11 +177,21 @@ class IRBackendExecutableContractTest {
         final var backend = aggregator.emit();
 
         assertEquals(2, backend.getExecutableFunctions().size());
+        assertEquals("main", backend.getEntryPointCallableName());
         assertEquals("entry", backend.getExecutableFunctions().get(0).callableName());
         assertEquals("aux", backend.getExecutableFunctions().get(1).callableName());
         assertEquals(2, backend.getCallableSignatures().size());
     }
 
+    @Test
+    void aggregatorMustEmitConfiguredEntrypointCallableName() {
+        final var aggregator = IRBackend.aggregator();
+        aggregator.entryPointCallableName("frame");
+
+        final var backend = aggregator.emit();
+        assertEquals("frame", backend.getEntryPointCallableName());
+    }
+
     @Test
     void aggregatorMustReindexIntrinsicsToBuildGlobalPool() {
         final var fileA = new IRBackendFile(

test-projects/main/cartridge/manifest.json

@@ -0,0 +1,10 @@
+{
+  "magic": "PMTU",
+  "cartridge_version": 1,
+  "app_id": 1,
+  "title": "Main Test",
+  "app_version": "0.1.0",
+  "app_mode": "Game",
+  "entrypoint": "0",
+  "capabilities": ["log"]
+}

test-projects/main/prometeu.json

@@ -4,9 +4,5 @@
   "language": "pbs",
   "stdlib": "1",
   "dependencies": [
-    {
-      "name": "dep1",
-      "version": "1.0.0"
-    }
   ]
 }

test-projects/main/run.sh

@@ -0,0 +1,6 @@
+#!/bin/zsh
+
+set -e
+
+cp build/program.pbx cartridge
+./runtime/prometeu run cartridge

test-projects/main/runtime

@@ -0,0 +1 @@
+../../../runtime/dist-staging/stable/prometeu-cli-aarch64-apple-darwin/

test-projects/main/src/main.pbs

@@ -0,0 +1,10 @@
+import { Log } from @sdk:log;
+import { Input } from @sdk:input;
+
+fn frame() -> void
+{
+    if (Input.pad().a().pressed())
+    {
+        Log.debug("Hello World!");
+    }
+}

test-projects/main/src/mod.barrel

@@ -0,0 +1 @@
+pub fn frame() -> void;

test-projects/main/src/module-a/mod.barrel

@@ -1 +0,0 @@
-module-a.barrel: content

test-projects/main/src/module-a/source-1.pbs

@@ -1,3 +0,0 @@
-fn a1()
-{
-}

test-projects/main/src/module-a/source-2.pbs

@@ -1,4 +0,0 @@
-fn a2(v1: int, v2: bounded): int
-{
-    return v1 + v2;
-}

test-projects/main/src/module-a/source-3.pbs

@@ -1,4 +0,0 @@
-fn a3(): int
-{
-    return 1;
-}