crates/prometeu-compiler/src/building/linker.rs

@@ -237,14 +237,19 @@ impl Linker {
                 if let Some(local_func_idx) = meta.func_idx {
                     let global_func_idx = module_function_offsets.last().unwrap() + local_func_idx;
                     final_exports.insert(format!("{}:{}", key.module_path, key.symbol_name), global_func_idx);
+                    // Also provide short name for root module exports to facilitate entrypoint resolution
+                    if !final_exports.contains_key(&key.symbol_name) {
+                        final_exports.insert(key.symbol_name.clone(), global_func_idx);
+                    }
                 }
             }
         }
 
-        // v0: Fallback export for entrypoint `src/main/modules:frame` (root module)
-        if !final_exports.iter().any(|(name, _)| name.ends_with(":frame")) {
+        // v0: Fallback export for entrypoint `frame` (root module)
+        if !final_exports.iter().any(|(name, _)| name.ends_with(":frame") || name == "frame") {
             if let Some(&root_offset) = module_function_offsets.last() {
                 if let Some((idx, _)) = combined_function_names.iter().find(|(i, name)| *i >= root_offset && name == "frame") {
+                    final_exports.insert("frame".to_string(), *idx);
                     final_exports.insert("src/main/modules:frame".to_string(), *idx);
                 }
             }
@@ -274,9 +279,9 @@ mod tests {
     use std::collections::BTreeMap;
     use super::*;
     use crate::building::output::{ExportKey, ExportMetadata, ImportKey, ImportMetadata};
+    use crate::semantics::export_surface::ExportSurfaceKind;
     use crate::building::plan::BuildTarget;
     use crate::deps::resolver::ProjectId;
-    use crate::frontends::pbs::symbols::SymbolKind;
     use prometeu_bytecode::opcode::OpCode;
     use prometeu_bytecode::FunctionMeta;
 
@@ -294,7 +299,7 @@ mod tests {
         lib_exports.insert(ExportKey {
             module_path: "math".into(),
             symbol_name: "add".into(),
-            kind: SymbolKind::Function,
+            kind: ExportSurfaceKind::Service,
         }, ExportMetadata { func_idx: Some(0), is_host: false, ty: None });
 
         let lib_module = CompiledModule {

crates/prometeu-compiler/src/building/output.rs

@@ -12,6 +12,7 @@ use crate::frontends::pbs::resolver::{ModuleProvider, Resolver};
 use crate::frontends::pbs::symbols::{ModuleSymbols, Namespace, Symbol, SymbolKind, Visibility};
 use crate::frontends::pbs::typecheck::TypeChecker;
 use crate::frontends::pbs::types::PbsType;
+use crate::semantics::export_surface::ExportSurfaceKind;
 use crate::lowering::core_to_vm;
 use prometeu_bytecode::{ConstantPoolEntry, DebugInfo, FunctionMeta};
 use serde::{Deserialize, Serialize};
@@ -22,7 +23,7 @@ use std::path::Path;
 pub struct ExportKey {
     pub module_path: String,
     pub symbol_name: String,
-    pub kind: SymbolKind,
+    pub kind: ExportSurfaceKind,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -165,12 +166,17 @@ pub fn compile_project(
                     
                     let sym = Symbol {
                         name: key.symbol_name.clone(),
-                        kind: key.kind.clone(),
-                        namespace: match key.kind {
-                            SymbolKind::Function | SymbolKind::Service => Namespace::Value,
-                            SymbolKind::Struct | SymbolKind::Contract | SymbolKind::ErrorType => Namespace::Type,
-                            _ => Namespace::Value,
+                        kind: match key.kind {
+                            ExportSurfaceKind::Service => SymbolKind::Service,
+                            ExportSurfaceKind::DeclareType => {
+                                match &meta.ty {
+                                    Some(PbsType::Contract(_)) => SymbolKind::Contract,
+                                    Some(PbsType::ErrorType(_)) => SymbolKind::ErrorType,
+                                    _ => SymbolKind::Struct,
+                                }
+                            }
                         },
+                        namespace: key.kind.namespace(),
                         visibility: Visibility::Pub,
                         ty: meta.ty.clone(),
                         is_host: meta.is_host,
@@ -245,31 +251,35 @@ pub fn compile_project(
     for (module_path, ms) in &module_symbols_map {
         for sym in ms.type_symbols.symbols.values() {
             if sym.visibility == Visibility::Pub {
-                exports.insert(ExportKey {
-                    module_path: module_path.clone(),
-                    symbol_name: sym.name.clone(),
-                    kind: sym.kind.clone(),
-                }, ExportMetadata { 
-                    func_idx: None,
-                    is_host: sym.is_host,
-                    ty: sym.ty.clone(),
-                });
+                if let Some(surface_kind) = ExportSurfaceKind::from_symbol_kind(sym.kind) {
+                    exports.insert(ExportKey {
+                        module_path: module_path.clone(),
+                        symbol_name: sym.name.clone(),
+                        kind: surface_kind,
+                    }, ExportMetadata { 
+                        func_idx: None,
+                        is_host: sym.is_host,
+                        ty: sym.ty.clone(),
+                    });
+                }
             }
         }
         for sym in ms.value_symbols.symbols.values() {
             if sym.visibility == Visibility::Pub {
-                // Find func_idx if it's a function or service
-                let func_idx = vm_module.functions.iter().position(|f| f.name == sym.name).map(|i| i as u32);
-                
-                exports.insert(ExportKey {
-                    module_path: module_path.clone(),
-                    symbol_name: sym.name.clone(),
-                    kind: sym.kind.clone(),
-                }, ExportMetadata { 
-                    func_idx,
-                    is_host: sym.is_host,
-                    ty: sym.ty.clone(),
-                });
+                if let Some(surface_kind) = ExportSurfaceKind::from_symbol_kind(sym.kind) {
+                    // Find func_idx if it's a function or service
+                    let func_idx = vm_module.functions.iter().position(|f| f.name == sym.name).map(|i| i as u32);
+                    
+                    exports.insert(ExportKey {
+                        module_path: module_path.clone(),
+                        symbol_name: sym.name.clone(),
+                        kind: surface_kind,
+                    }, ExportMetadata { 
+                        func_idx,
+                        is_host: sym.is_host,
+                        ty: sym.ty.clone(),
+                    });
+                }
             }
         }
     }
@@ -359,7 +369,7 @@ mod tests {
         let vec2_key = ExportKey {
             module_path: "src/main/modules".to_string(),
             symbol_name: "Vec2".to_string(),
-            kind: SymbolKind::Struct,
+            kind: ExportSurfaceKind::DeclareType,
         };
         assert!(compiled.exports.contains_key(&vec2_key));
         

crates/prometeu-compiler/src/frontends/pbs/ast.rs

@@ -62,7 +62,7 @@ pub struct ImportSpecNode {
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct ServiceDeclNode {
     pub span: Span,
-    pub vis: String, // "pub" | "mod"
+    pub vis: Option<String>, // "pub" | "mod"
     pub name: String,
     pub extends: Option<String>,
     pub members: Vec<Node>, // ServiceFnSig
@@ -86,7 +86,7 @@ pub struct ParamNode {
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct FnDeclNode {
     pub span: Span,
-    pub vis: String,
+    pub vis: Option<String>,
     pub name: String,
     pub params: Vec<ParamNode>,
     pub ret: Option<Box<Node>>,

crates/prometeu-compiler/src/frontends/pbs/collector.rs

@@ -1,6 +1,7 @@
 use crate::common::diagnostics::{Diagnostic, DiagnosticBundle, DiagnosticLevel};
 use crate::frontends::pbs::ast::*;
 use crate::frontends::pbs::symbols::*;
+use crate::semantics::export_surface::ExportSurfaceKind;
 
 pub struct SymbolCollector {
     type_symbols: SymbolTable,
@@ -40,11 +41,14 @@ impl SymbolCollector {
     }
 
     fn collect_fn(&mut self, decl: &FnDeclNode) {
-        let vis = match decl.vis.as_str() {
-            "pub" => Visibility::Pub,
-            "mod" => Visibility::Mod,
+        let vis = match decl.vis.as_deref() {
+            Some("pub") => Visibility::Pub,
+            Some("mod") => Visibility::Mod,
             _ => Visibility::FilePrivate,
         };
+        
+        self.check_export_eligibility(SymbolKind::Function, vis, decl.span);
+
         let symbol = Symbol {
             name: decl.name.clone(),
             kind: SymbolKind::Function,
@@ -59,11 +63,13 @@ impl SymbolCollector {
     }
 
     fn collect_service(&mut self, decl: &ServiceDeclNode) {
-        let vis = match decl.vis.as_str() {
-            "pub" => Visibility::Pub,
-            "mod" => Visibility::Mod,
-            _ => Visibility::FilePrivate, // Should not happen with valid parser
+        let vis = match decl.vis.as_deref() {
+            Some("pub") => Visibility::Pub,
+            _ => Visibility::Mod, // Defaults to Mod
         };
+
+        self.check_export_eligibility(SymbolKind::Service, vis, decl.span);
+
         let symbol = Symbol {
             name: decl.name.clone(),
             kind: SymbolKind::Service,
@@ -89,6 +95,9 @@ impl SymbolCollector {
             "error" => SymbolKind::ErrorType,
             _ => SymbolKind::Struct, // Default
         };
+
+        self.check_export_eligibility(kind.clone(), vis, decl.span);
+
         let symbol = Symbol {
             name: decl.name.clone(),
             kind,
@@ -148,4 +157,15 @@ impl SymbolCollector {
             span: Some(symbol.span),
         });
     }
+
+    fn check_export_eligibility(&mut self, kind: SymbolKind, vis: Visibility, span: crate::common::spans::Span) {
+        if let Err(msg) = ExportSurfaceKind::validate_visibility(kind, vis) {
+            self.diagnostics.push(Diagnostic {
+                level: DiagnosticLevel::Error,
+                code: Some("E_SEMANTIC_EXPORT_RESTRICTION".to_string()),
+                message: msg,
+                span: Some(span),
+            });
+        }
+    }
 }

crates/prometeu-compiler/src/frontends/pbs/parser.rs

@@ -154,7 +154,7 @@ impl Parser {
 
     fn parse_top_level_decl(&mut self) -> Result<Node, DiagnosticBundle> {
         match self.peek().kind {
-            TokenKind::Fn => self.parse_fn_decl("file".to_string()),
+            TokenKind::Fn => self.parse_fn_decl(None),
             TokenKind::Pub | TokenKind::Mod | TokenKind::Declare | TokenKind::Service => self.parse_decl(),
             TokenKind::Invalid(ref msg) => {
                 let code = if msg.contains("Unterminated string") {
@@ -181,23 +181,14 @@ impl Parser {
         };
 
         match self.peek().kind {
-            TokenKind::Service => self.parse_service_decl(vis.unwrap_or_else(|| "pub".to_string())),
+            TokenKind::Service => self.parse_service_decl(vis),
             TokenKind::Declare => self.parse_type_decl(vis),
-            TokenKind::Fn => {
-                let vis_str = vis.unwrap_or_else(|| "file".to_string());
-                if vis_str == "pub" {
-                    return Err(self.error_with_code(
-                        "Functions cannot be public. They are always mod or file-private.",
-                        Some("E_RESOLVE_VISIBILITY"),
-                    ));
-                }
-                self.parse_fn_decl(vis_str)
-            }
+            TokenKind::Fn => self.parse_fn_decl(vis),
             _ => Err(self.error("Expected 'service', 'declare', or 'fn'")),
         }
     }
 
-    fn parse_service_decl(&mut self, vis: String) -> Result<Node, DiagnosticBundle> {
+    fn parse_service_decl(&mut self, vis: Option<String>) -> Result<Node, DiagnosticBundle> {
         let start_span = self.consume(TokenKind::Service)?.span;
         let name = self.expect_identifier()?;
         let mut extends = None;
@@ -362,7 +353,7 @@ impl Parser {
         }))
     }
 
-    fn parse_fn_decl(&mut self, vis: String) -> Result<Node, DiagnosticBundle> {
+    fn parse_fn_decl(&mut self, vis: Option<String>) -> Result<Node, DiagnosticBundle> {
         let start_span = self.consume(TokenKind::Fn)?.span;
         let name = self.expect_identifier()?;
         let params = self.parse_param_list()?;
@@ -1181,7 +1172,7 @@ fn good() {}
         let mut parser = Parser::new(source, 0);
         let result = parser.parse_file().expect("mod fn should be allowed");
         if let Node::FnDecl(fn_decl) = &result.decls[0] {
-            assert_eq!(fn_decl.vis, "mod");
+            assert_eq!(fn_decl.vis, Some("mod".to_string()));
         } else {
             panic!("Expected FnDecl");
         }
@@ -1191,10 +1182,12 @@ fn good() {}
     fn test_parse_pub_fn() {
         let source = "pub fn test() {}";
         let mut parser = Parser::new(source, 0);
-        let result = parser.parse_file();
-        assert!(result.is_err(), "pub fn should be disallowed");
-        let err = result.unwrap_err();
-        assert!(err.diagnostics[0].message.contains("Functions cannot be public"));
+        let result = parser.parse_file().expect("pub fn should be allowed in parser");
+        if let Node::FnDecl(fn_decl) = &result.decls[0] {
+            assert_eq!(fn_decl.vis, Some("pub".to_string()));
+        } else {
+            panic!("Expected FnDecl");
+        }
     }
 
     #[test]

crates/prometeu-compiler/src/frontends/pbs/symbols.rs

@@ -3,14 +3,14 @@ use crate::frontends::pbs::types::PbsType;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub enum Visibility {
     FilePrivate,
     Mod,
     Pub,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, PartialOrd, Ord)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, PartialOrd, Ord)]
 pub enum SymbolKind {
     Function,
     Service,

crates/prometeu-compiler/src/lib.rs

@@ -48,6 +48,7 @@ pub mod manifest;
 pub mod deps;
 pub mod sources;
 pub mod building;
+pub mod semantics;
 
 use anyhow::Result;
 use clap::{Parser, Subcommand};

crates/prometeu-compiler/src/semantics/export_surface.rs

@@ -0,0 +1,40 @@
+use crate::frontends::pbs::symbols::{SymbolKind, Visibility};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+pub enum ExportSurfaceKind {
+    Service,
+    DeclareType, // struct, storage struct, type alias
+}
+
+impl ExportSurfaceKind {
+    pub fn from_symbol_kind(kind: SymbolKind) -> Option<Self> {
+        match kind {
+            SymbolKind::Service => Some(ExportSurfaceKind::Service),
+            SymbolKind::Struct | SymbolKind::Contract | SymbolKind::ErrorType => {
+                Some(ExportSurfaceKind::DeclareType)
+            }
+            SymbolKind::Function | SymbolKind::Local => None,
+        }
+    }
+
+    pub fn validate_visibility(kind: SymbolKind, vis: Visibility) -> Result<(), String> {
+        if vis == Visibility::Pub {
+            if Self::from_symbol_kind(kind).is_none() {
+                let kind_str = match kind {
+                    SymbolKind::Function => "Functions",
+                    _ => "This declaration",
+                };
+                return Err(format!("{} are not exportable in this version.", kind_str));
+            }
+        }
+        Ok(())
+    }
+
+    pub fn namespace(&self) -> crate::frontends::pbs::symbols::Namespace {
+        match self {
+            ExportSurfaceKind::Service => crate::frontends::pbs::symbols::Namespace::Type,
+            ExportSurfaceKind::DeclareType => crate::frontends::pbs::symbols::Namespace::Type,
+        }
+    }
+}

crates/prometeu-compiler/src/semantics/mod.rs

@@ -0,0 +1 @@
+pub mod export_surface;

crates/prometeu-compiler/tests/link_integration.rs

@@ -67,7 +67,7 @@ fn test_integration_test01_link() {
     
     let mut vm = VirtualMachine::default();
     // Use initialize to load the ROM; entrypoint must be numeric or empty (defaults to 0)
-    vm.initialize(unit.rom, "").expect("Failed to initialize VM");
+    vm.initialize(unit.rom, "frame").expect("Failed to initialize VM");
     
     let mut native = SimpleNative;
     let mut hw = SimpleHardware::new();

crates/prometeu-core/tests/heartbeat.rs

@@ -6,7 +6,6 @@ use prometeu_core::virtual_machine::{LogicalFrameEndingReason, VirtualMachine};
 use prometeu_core::Hardware;
 use std::fs;
 use std::path::Path;
-use prometeu_bytecode::BytecodeLoader;
 
 struct MockNative;
 impl NativeInterface for MockNative {
@@ -40,7 +39,6 @@ fn test_canonical_cartridge_heartbeat() {
     let pbc_bytes = fs::read(pbc_path).expect("Failed to read canonical PBC. Did you run the generation test?");
 
     // Determine entrypoint from the compiled module exports
-    let module = BytecodeLoader::load(&pbc_bytes).expect("Failed to parse PBC");
     let entry_symbol = "src/main/modules:frame";
     
     let mut vm = VirtualMachine::new(vec![], vec![]);

test-cartridges/canonical/golden/ast.json

@@ -641,7 +641,7 @@
         "start": 739,
         "end": 788
       },
-      "vis": "file",
+      "vis": null,
       "name": "add",
       "params": [
         {
@@ -743,7 +743,7 @@
         "start": 790,
         "end": 1180
       },
-      "vis": "file",
+      "vis": null,
       "name": "frame",
       "params": [],
       "ret": {