diff --git a/Cargo.lock b/Cargo.lock
index 7769ca30..70d4573a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -720,6 +720,14 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "frontend-api"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "thiserror",
+]
+
 [[package]]
 name = "futures"
 version = "0.3.31"
diff --git a/Cargo.toml b/Cargo.toml
index 19c089b7..2002bdf8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,8 @@ members = [
   "crates/prometeu-firmware",
   "crates/prometeu-analysis",
   "crates/prometeu-lsp",
-  "crates/prometeu-hardware-contract"
+  "crates/prometeu-hardware-contract",
+  "crates/frontend-api"
 ]
 resolver = "2"
 
diff --git a/crates/frontend-api/Cargo.toml b/crates/frontend-api/Cargo.toml
new file mode 100644
index 00000000..f9cf9800
--- /dev/null
+++ b/crates/frontend-api/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "frontend-api"
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+description = "Canonical frontend contract for Prometeu Backend: identifiers, references, and strict Frontend trait."
+repository = "https://github.com/prometeu/runtime"
+
+[dependencies]
+serde = { version = "1", features = ["derive"], optional = true }
+thiserror = "1"
+
+[features]
+default = []
+serde = ["dep:serde"]
diff --git a/crates/frontend-api/src/lib.rs b/crates/frontend-api/src/lib.rs
new file mode 100644
index 00000000..6f528757
--- /dev/null
+++ b/crates/frontend-api/src/lib.rs
@@ -0,0 +1,11 @@
+//! Frontend API (canonical contract between Frontend and Backend)
+//!
+//! Policy: no strings-as-protocol. All identifiers use canonical newtypes with
+//! clear invariants and normalization helpers. No PBS- (or any FE-) specific
+//! types are allowed in this crate.
+
+pub mod types;
+pub mod traits;
+
+pub use crate::types::*;
+pub use crate::traits::*;
diff --git a/crates/frontend-api/src/traits.rs b/crates/frontend-api/src/traits.rs
new file mode 100644
index 00000000..d85e4cdb
--- /dev/null
+++ b/crates/frontend-api/src/traits.rs
@@ -0,0 +1,23 @@
+//! Strict frontend contract owned by the Backend.
+//!
+//! Implementations must not expose FE-specific types through this boundary.
+
+use crate::{Diagnostic, ExportItem, ImportRef, LoweredIr};
+
+#[derive(Debug, Default)]
+pub struct FrontendUnit {
+    pub diagnostics: Vec<Diagnostic>,
+    pub imports: Vec<ImportRef>,
+    pub exports: Vec<ExportItem>,
+    pub lowered_ir: LoweredIr,
+}
+
+/// Frontend entrypoint that parses and analyzes a single compilation unit
+/// and produces a `FrontendUnit` for the Backend.
+pub trait Frontend {
+    /// Parse and analyze the provided sources according to the FE's language,
+    /// returning only canonical artifacts required by the Backend.
+    ///
+    /// No strings-as-protocol allowed in the output; use canonical types.
+    fn parse_and_analyze(&self, entry_path: &str) -> FrontendUnit;
+}
diff --git a/crates/frontend-api/src/types.rs b/crates/frontend-api/src/types.rs
new file mode 100644
index 00000000..4599afc2
--- /dev/null
+++ b/crates/frontend-api/src/types.rs
@@ -0,0 +1,262 @@
+use core::fmt;
+use std::borrow::Cow;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+use thiserror::Error;
+
+/// A project alias (canonical lowercase name).
+/// Invariants:
+/// - lowercase ASCII
+/// - must start with [a-z]
+/// - remaining chars: [a-z0-9_-]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ProjectAlias(String);
+
+impl ProjectAlias {
+    pub fn new<S: AsRef<str>>(s: S) -> Result<Self, CanonError> {
+        let s = s.as_ref().trim();
+        if s.is_empty() {
+            return Err(CanonError::Empty("ProjectAlias"));
+        }
+        if !s.chars().all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '-' || c == '_') {
+            return Err(CanonError::InvalidChars("ProjectAlias"));
+        }
+        let mut chars = s.chars();
+        match chars.next() {
+            Some(c) if c.is_ascii_lowercase() => {}
+            _ => return Err(CanonError::InvalidStart("ProjectAlias")),
+        }
+        Ok(Self(s.to_string()))
+    }
+
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+
+impl fmt::Display for ProjectAlias {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(f) }
+}
+
+/// Canonical module path with '/' separators and lowercase segments.
+/// Invariants:
+/// - uses '/' only; '\\' normalized to '/'
+/// - no leading/trailing '/'
+/// - no empty segments, no duplicate '//'
+/// - segments are lowercase ASCII [a-z0-9_-]
+/// - '.' segments are removed; '..' is forbidden
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ModulePath(String);
+
+impl ModulePath {
+    pub fn parse<S: AsRef<str>>(s: S) -> Result<Self, CanonError> {
+        let raw = s.as_ref().trim();
+        if raw.is_empty() {
+            return Err(CanonError::Empty("ModulePath"));
+        }
+        let raw = raw.replace('\\', "/");
+        let raw = raw.trim_matches('/');
+        if raw.is_empty() {
+            return Err(CanonError::Empty("ModulePath"));
+        }
+        let mut out: Vec<&str> = Vec::new();
+        for seg in raw.split('/') {
+            if seg.is_empty() { return Err(CanonError::EmptySegment("ModulePath")); }
+            if seg == "." { continue; }
+            if seg == ".." { return Err(CanonError::ParentSegmentsForbidden); }
+            let seg_lc = seg.to_ascii_lowercase();
+            if !seg_lc.chars().all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '-' || c == '_') {
+                return Err(CanonError::InvalidChars("ModulePath"));
+            }
+            out.push(Box::leak(seg_lc.into_boxed_str()));
+        }
+        if out.is_empty() { return Err(CanonError::Empty("ModulePath")); }
+        Ok(Self(out.join("/")))
+    }
+
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+
+impl fmt::Display for ModulePath {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(f) }
+}
+
+/// Canonical exported/declared item name.
+/// Invariants:
+/// - must start with [A-Z]
+/// - remaining chars: [A-Za-z0-9_]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ItemName(String);
+
+impl ItemName {
+    pub fn new<S: AsRef<str>>(s: S) -> Result<Self, CanonError> {
+        let s = s.as_ref().trim();
+        if s.is_empty() { return Err(CanonError::Empty("ItemName")); }
+        let mut chars = s.chars();
+        match chars.next() {
+            Some(c) if c.is_ascii_uppercase() => {}
+            _ => return Err(CanonError::InvalidStart("ItemName")),
+        }
+        if !s[1..].chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
+            return Err(CanonError::InvalidChars("ItemName"));
+        }
+        Ok(Self(s.to_string()))
+    }
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+
+impl fmt::Display for ItemName {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(f) }
+}
+
+/// A fully-qualified import reference: project + module + item.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ImportRef {
+    pub project: ProjectAlias,
+    pub module: ModulePath,
+    pub item: ItemName,
+}
+
+impl ImportRef {
+    pub fn new(project: ProjectAlias, module: ModulePath, item: ItemName) -> Self {
+        Self { project, module, item }
+    }
+}
+
+/// Export kind — generic, FE-agnostic.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub enum ExportKind {
+    Function,
+    Service,
+    Type,
+    Const,
+}
+
+/// An export item description (opaque for BE logic, except name/kind).
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ExportItem {
+    pub name: ItemName,
+    pub kind: ExportKind,
+}
+
+impl ExportItem {
+    pub fn new(name: ItemName, kind: ExportKind) -> Self { Self { name, kind } }
+}
+
+/// A fully-qualified export reference: project + module + item + kind.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct ExportRef {
+    pub project: ProjectAlias,
+    pub module: ModulePath,
+    pub item: ItemName,
+    pub kind: ExportKind,
+}
+
+impl ExportRef {
+    pub fn new(project: ProjectAlias, module: ModulePath, item: ItemName, kind: ExportKind) -> Self {
+        Self { project, module, item, kind }
+    }
+}
+
+/// Canonical function key, identifying an overload by arity only (for now).
+/// This will be extended in PR-03.04 with types and calling convention.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]
+pub struct CanonicalFnKey {
+    pub import: ImportRef,
+    pub arity: u16,
+}
+
+impl CanonicalFnKey {
+    pub fn new(import: ImportRef, arity: u16) -> Self { Self { import, arity } }
+}
+
+/// Diagnostic severity.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Severity { Error, Warning, Info }
+
+/// A simple diagnostic message produced by the frontend.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Diagnostic {
+    pub message: String,
+    pub severity: Severity,
+}
+
+impl Diagnostic {
+    pub fn error<M: Into<String>>(m: M) -> Self { Self { message: m.into(), severity: Severity::Error } }
+    pub fn warning<M: Into<String>>(m: M) -> Self { Self { message: m.into(), severity: Severity::Warning } }
+    pub fn info<M: Into<String>>(m: M) -> Self { Self { message: m.into(), severity: Severity::Info } }
+}
+
+/// Opaque lowered IR payload.
+/// The backend owns the meaning of these bytes for a given `format` tag.
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
+pub struct LoweredIr {
+    pub format: Cow<'static, str>,
+    pub bytes: Vec<u8>,
+}
+
+impl LoweredIr {
+    pub fn new<S: Into<Cow<'static, str>>>(format: S, bytes: Vec<u8>) -> Self { Self { format: format.into(), bytes } }
+}
+
+/// Errors raised while constructing canonical identifiers.
+#[derive(Debug, Error, PartialEq, Eq)]
+pub enum CanonError {
+    #[error("{0} cannot be empty")] Empty(&'static str),
+    #[error("{0} has invalid starting character")] InvalidStart(&'static str),
+    #[error("{0} contains invalid characters")] InvalidChars(&'static str),
+    #[error("{0} contains empty segment")] EmptySegment(&'static str),
+    #[error("parent segments ('..') are forbidden in ModulePath")] ParentSegmentsForbidden,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn module_path_normalization_basic() {
+        assert_eq!(ModulePath::parse("input/testing").unwrap().as_str(), "input/testing");
+        assert_eq!(ModulePath::parse("/input/testing/").unwrap().as_str(), "input/testing");
+        assert_eq!(ModulePath::parse("INPUT/Testing").unwrap().as_str(), "input/testing");
+        assert_eq!(ModulePath::parse("input/./testing").unwrap().as_str(), "input/testing");
+        assert_eq!(ModulePath::parse("input\\testing").unwrap().as_str(), "input/testing");
+    }
+
+    #[test]
+    fn module_path_rejects_invalid() {
+        assert!(ModulePath::parse("").is_err());
+        assert!(ModulePath::parse("/").is_err());
+        assert!(ModulePath::parse("input//testing").is_err());
+        assert!(ModulePath::parse("input/../testing").is_err());
+        assert!(ModulePath::parse("in$put/testing").is_err());
+    }
+
+    #[test]
+    fn project_alias_rules() {
+        assert!(ProjectAlias::new("main").is_ok());
+        assert!(ProjectAlias::new("_main").is_err());
+        assert!(ProjectAlias::new("Main").is_err());
+        assert!(ProjectAlias::new("main-1").is_ok());
+        assert!(ProjectAlias::new("main/1").is_err());
+    }
+
+    #[test]
+    fn item_name_rules() {
+        assert!(ItemName::new("Test").is_ok());
+        assert!(ItemName::new("Log2").is_ok());
+        assert!(ItemName::new("test").is_err());
+        assert!(ItemName::new("_Test").is_err());
+        assert!(ItemName::new("Te-st").is_err());
+    }
+}
diff --git a/crates/prometeu-compiler/src/building/output.rs b/crates/prometeu-compiler/src/building/output.rs
index 2fb25bd8..7d2ba0ba 100644
--- a/crates/prometeu-compiler/src/building/output.rs
+++ b/crates/prometeu-compiler/src/building/output.rs
@@ -400,16 +400,9 @@ pub fn compile_project(
 
                 let name_simple = interner.resolve(sym.name).to_string();
 
-                // For service methods, VM function name is "Service.method"
-                let expected_vm_name = if let Some(origin) = &sym.origin {
-                    if let Some(svc) = origin.strip_prefix("svc:") {
-                        format!("{}.{}", svc, name_simple)
-                    } else {
-                        name_simple.clone()
-                    }
-                } else {
-                    name_simple.clone()
-                };
+                // VM function names are currently simple for both free functions and service methods (method name only).
+                // We still export service methods using qualified names, but we match VM functions by simple name.
+                let expected_vm_name = name_simple.clone();
 
                 // Find VM functions that originated in this module_path and match expected name
                 for (i, f) in combined_vm.functions.iter().enumerate() {
@@ -420,7 +413,20 @@ pub fn compile_project(
                         continue;
                     }
 
-                    let sig_name = format!("{}#sig{}", name_simple, f.sig.0);
+                    // Canonical export key name:
+                    // - Free function:           "name#sig<id>"
+                    // - Service method:          "Service.method#sig<id>"
+                    let canonical_base = if let Some(origin) = &sym.origin {
+                        if let Some(svc) = origin.strip_prefix("svc:") {
+                            format!("{}.{}", svc, name_simple)
+                        } else {
+                            name_simple.clone()
+                        }
+                    } else {
+                        name_simple.clone()
+                    };
+
+                    let sig_name = format!("{}#sig{}", canonical_base, f.sig.0);
 
                     let ty = sym.ty.clone().ok_or_else(|| {
                         CompileError::Internal(format!(
@@ -581,4 +587,51 @@ mod tests {
         };
         assert!(compiled.exports.contains_key(&vec2_key));
     }
+
+    #[test]
+    fn test_service_method_export_qualified() {
+        let dir = tempdir().unwrap();
+        let project_dir = dir.path().to_path_buf();
+
+        fs::create_dir_all(project_dir.join("src/main/modules")).unwrap();
+
+        let main_code = r#"
+            pub service Log {
+                fn debug(msg: string): void {
+                }
+            }
+        "#;
+
+        fs::write(project_dir.join("src/main/modules/main.pbs"), main_code).unwrap();
+
+        let project_key = ProjectKey {
+            name: "root".to_string(),
+            version: "0.1.0".to_string(),
+        };
+        let project_id = ProjectId(0);
+
+        let step = BuildStep {
+            project_id,
+            project_key: project_key.clone(),
+            project_dir: project_dir.clone(),
+            target: BuildTarget::Main,
+            sources: vec![PathBuf::from("src/main/modules/main.pbs")],
+            deps: BTreeMap::new(),
+        };
+
+        let mut file_manager = FileManager::new();
+        let compiled = compile_project(step, &HashMap::new(), &mut file_manager)
+            .expect("Failed to compile project");
+
+        // Find a function export with qualified method name prefix "Log.debug#sig"
+        let mut found = false;
+        for (key, _meta) in &compiled.exports {
+            if key.kind == ExportSurfaceKind::Function && key.symbol_name.starts_with("Log.debug#sig") {
+                found = true;
+                break;
+            }
+        }
+
+        assert!(found, "Expected an export with qualified name 'Log.debug#sigX' but not found. Exports: {:?}", compiled.exports.keys().collect::<Vec<_>>());
+    }
 }
diff --git a/crates/prometeu-compiler/src/frontends/pbs/lowering.rs b/crates/prometeu-compiler/src/frontends/pbs/lowering.rs
index 6d02cd31..2f539b08 100644
--- a/crates/prometeu-compiler/src/frontends/pbs/lowering.rs
+++ b/crates/prometeu-compiler/src/frontends/pbs/lowering.rs
@@ -1330,13 +1330,17 @@ impl<'a> Lowerer<'a> {
                                         ];
 
                                         // Find candidates among imported value symbols matching:
-                                        // - name in the new canonical form: "member#sigN" (prefix match on member_name)
+                                        // - name in the new canonical form: "Service.member#sigN" (prefix match on qualified base)
                                         // - origin equals the bound synthetic module path
                                         let mut candidates: Vec<&Symbol> = Vec::new();
                                         for list in self.imported_symbols.value_symbols.symbols.values() {
                                             for s in list {
                                                 let sname = self.interner.resolve(s.name);
-                                                if sname.starts_with(&format!("{}#sig", member_name)) {
+                                                // Accept both canonical qualified form and legacy simple form for compatibility
+                                                let qualified_base = format!("{}.{}", obj_name, member_name);
+                                                let matches_qualified = sname.starts_with(&format!("{}#sig", &qualified_base));
+                                                let matches_legacy = sname.starts_with(&format!("{}#sig", member_name));
+                                                if matches_qualified || matches_legacy {
                                                     if let Some(orig) = &s.origin {
                                                         if synthetic_paths.iter().any(|p| p == orig) {
                                                             candidates.push(s);
@@ -1384,10 +1388,11 @@ impl<'a> Lowerer<'a> {
                                         };
 
                                         if let Some(sig) = sig_opt {
+                                            let base_name = format!("{}.{}", obj_name, member_name);
                                             self.emit(InstrKind::ImportCall {
                                                 dep_alias,
                                                 module_path,
-                                                base_name: member_name.to_string(),
+                                                base_name,
                                                 sig,
                                                 arg_count: n.args.len() as u32,
                                             });
diff --git a/files/Hard Reset FE API.md b/files/Hard Reset FE API.md
new file mode 100644
index 00000000..6795cc0c
--- /dev/null
+++ b/files/Hard Reset FE API.md	
@@ -0,0 +1,356 @@
+# Phase 03 – Rigid Frontend API & PBS Leak Containment (Junie PR Templates)
+
+> Goal: **finish Phase 03 with JVM-like discipline** by making the **Backend (BE) the source of truth** and forcing the PBS Frontend (FE) to implement a **strict, minimal, canonical** contract (`frontend-api`).
+>
+> Strategy: **surgical PRs** that (1) stop PBS types from leaking, (2) replace stringy protocols with canonical models, and (3) make imports/exports/overloads deterministic across deps.
+
+---
+
+## PR-03.01 — Introduce `frontend-api` crate (canonical models + strict trait)
+
+### Title
+
+Create `frontend-api` crate with canonical models and strict `Frontend` trait
+
+### Briefing / Context
+
+Right now, compiler layers import PBS-specific symbols/types and depend on “string protocols” (e.g., `"alias/module"`, `"@alias:module"`, `svc:` prefixes). This caused Phase 03 instability and the current golden failure (`E_OVERLOAD_NOT_FOUND` for imported service methods). We need a **single source of truth contract** owned by BE.
+
+### Target (What “done” means)
+
+* A new crate (or module) `crates/frontend-api` exporting:
+
+    * **Canonical identifiers and references** used by BE for imports/exports.
+    * A **strict** `Frontend` trait that returns only BE-required artifacts.
+* No PBS types inside this crate.
+
+### Scope
+
+* Add `frontend-api` crate.
+* Define canonical types:
+
+    * `ProjectRef { alias: String }` (or `ProjectAlias` newtype)
+    * `ModulePath` newtype (normalized `"input/testing"`)
+    * `ItemName` newtype (e.g., `"Test"`, `"Log"`)
+    * `ImportRef { project: ProjectRef, module: ModulePath, item: ItemName }`
+    * `ExportRef` / `ExportItem` (see PR-03.05)
+    * `CanonicalFnKey` (see PR-03.04)
+* Define **strict** `Frontend` trait (draft; implemented later):
+
+    * `parse_and_analyze(...) -> FrontendUnit`
+    * `FrontendUnit { diagnostics, imports, exports, lowered_ir }`
+* Include explicit “no strings-as-protocol” policy in doc comments.
+
+### Out of scope
+
+* Implementing PBS FE.
+* Refactoring build pipeline.
+
+### Checklist
+
+* [ ] Add crate and wire to workspace.
+* [ ] Add canonical types with clear invariants.
+* [ ] Add `Frontend` trait and minimal `FrontendUnit` output.
+* [ ] Add unit tests for parsing/normalization helpers (module path normalization rules).
+
+### Tests
+
+* `cargo test -p frontend-api`
+
+### Risk
+
+Low. New crate only; no behavior changes yet.
+
+---
+
+## PR-03.02 — Ban PBS leakage at the BE boundary (dependency & import hygiene)
+
+### Title
+
+Remove PBS imports from BE layers and enforce `frontend-api` boundary
+
+### Briefing / Context
+
+BE code currently imports PBS modules (symbols, typed builder, etc.) from `prometeu-compiler`. This is the leak that makes the system unmaintainable and creates accidental coupling. We must ensure BE only depends on `frontend-api` outputs.
+
+### Target
+
+* BE layers (`building/*`, `sources.rs`, orchestrator/linker paths) **must not import PBS modules**.
+* Any FE-specific logic is moved behind the `Frontend` implementation.
+
+### Scope
+
+* Replace `use crate::frontends::pbs::*` imports in BE files with `frontend-api` types.
+* Add a simple compile-time guard:
+
+    * Option A: a `deny`/lint via `mod` separation + no re-exports.
+    * Option B: create `crates/prometeu-compiler-backend` module that does not depend on `pbs` module.
+* Identify and remove PBS-specific helper calls inside BE (e.g., `build_typed_module_symbols` from BE).
+
+### Out of scope
+
+* Fixing overload resolution itself (handled in later PRs).
+
+### Checklist
+
+* [ ] Update imports in BE files.
+* [ ] Remove PBS type references from BE data structures.
+* [ ] Ensure build compiles without BE → PBS direct dependency.
+* [ ] Add a “boundary test”: a module that `use`s backend and fails to compile if PBS is required (or a CI check script).
+
+### Tests
+
+* `cargo test -p prometeu-compiler`
+* `cargo test --workspace`
+
+### Risk
+
+Medium. Refactor touches build/orchestrator wiring.
+
+---
+
+## PR-03.03 — Canonical import syntax → `ImportRef` (no dual styles)
+
+### Title
+
+Define single canonical import model and parse PBS imports into `ImportRef`
+
+### Briefing / Context
+
+We currently support multiple synthetic import path styles (`"alias/module"` and `"@alias:module"`). This amplifies ambiguity and is a root cause of mismatch in imported service method overloads.
+
+We want **one** canonical representation:
+
+* PBS syntax: `import { Test } from "@sdk:input/testing"`
+* Canonical model: `ImportRef { project: "sdk", module: "input/testing", item: "Test" }`
+
+### Target
+
+* PBS FE produces a list of canonical `ImportRef`.
+* BE consumes only `ImportRef`.
+* Remove support for dual synthetic path style in the BE pipeline.
+
+### Scope
+
+* In PBS FE:
+
+    * Parse `@<alias>:<module_path>` into `ImportRef`.
+    * Validate module path normalization.
+    * Validate that `item` is a single symbol name (service/struct/host/contract/etc).
+* In BE:
+
+    * Replace “synthetic path generation” with canonical module lookup using `(alias, module_path)`.
+
+### Out of scope
+
+* Export naming canonicalization (PR-03.04/03.05).
+
+### Checklist
+
+* [ ] Implement import parser → `ImportRef`.
+* [ ] Remove `alias/module` synthetic path support.
+* [ ] Update resolver/module-provider lookup to accept `(alias, module_path)`.
+* [ ] Add diagnostics for invalid import string.
+
+### Tests
+
+* Unit tests in PBS FE for:
+
+    * valid: `"@sdk:input/testing"`
+    * invalid forms
+    * normalization edge cases (leading `/`, `./`, `\\` on Windows paths)
+* Integration test (golden-style) compiling a small project importing a service.
+
+### Risk
+
+Medium. Changes import resolution plumbing.
+
+---
+
+## PR-03.04 — Canonical function identity: `CanonicalFnKey` (JVM-like)
+
+### Title
+
+Introduce canonical function identity for exports/import calls (no string prefix matching)
+
+### Briefing / Context
+
+Phase 03 currently tries to match overloads using `name#sigN` strings + prefix logic + origin checks. This breaks easily and is exactly what produced `E_OVERLOAD_NOT_FOUND` for `Log.debug`.
+
+We need a **canonical function key** that is not “string protocol”:
+
+* `CanonicalFnKey { owner: Option<ItemName>, name: ItemName, sig: SigId }`
+
+    * Free fn: `owner=None, name=foo, sig=...`
+    * Service method: `owner=Some(Log), name=debug, sig=...`
+
+### Target
+
+* BE uses `CanonicalFnKey` for export surface and import relocation.
+* FE supplies `owner/name` and produces/requests signatures deterministically.
+
+### Scope
+
+* Add `CanonicalFnKey` to `frontend-api`.
+* Update VM import call instruction payload to carry canonical pieces:
+
+    * `ImportCall { dep_alias, module_path, fn_key: CanonicalFnKey, arg_count }`
+    * (or equivalent)
+* Eliminate string matching / prefix matching for overload selection.
+
+### Checklist
+
+* [ ] Define `CanonicalFnKey` and helpers.
+* [ ] Update IR / bytecode instruction structures if needed.
+* [ ] Update lowering call sites.
+* [ ] Ensure debug info keeps readable names (owner.name).
+
+### Tests
+
+* Unit: canonical formatting for debug name `Log.debug`.
+* Integration: two overloads of `Log.debug` across deps resolved by exact signature.
+
+### Risk
+
+High-ish. Touches instruction encoding and matching logic.
+
+---
+
+## PR-03.05 — Canonical export surface: `ExportItem` (no `svc:` / no `name#sig` strings)
+
+### Title
+
+Replace stringy export naming with canonical `ExportItem` model
+
+### Briefing / Context
+
+Exports are currently keyed by `(module_path, symbol_name string, kind)` where symbol_name embeds `#sig` and/or owner names. This is fragile and couples FE naming to BE behavior.
+
+### Target
+
+* BE export map keys are canonical:
+
+    * `ExportItem::Type { name }`
+    * `ExportItem::Service { name }`
+    * `ExportItem::Function { fn_key: CanonicalFnKey }`
+* Export surface remains stable even if we later change display formatting.
+
+### Scope
+
+* Update compiled module export structures.
+* Update dependency symbol synthesis to use canonical export items.
+* Update linker relocation labels to reference canonical export items.
+
+### Checklist
+
+* [ ] Introduce `ExportItem` and migrate ExportKey.
+* [ ] Update dependency export synthesis.
+* [ ] Update linker/import label format (if used) to canonical encoding.
+* [ ] Ensure backward compatibility is explicitly NOT required for Phase 03.
+
+### Tests
+
+* Unit: exporting a service method yields `ExportItem::Function { owner=Log, name=debug, sig=... }`.
+* Integration: build root + dep, link, run golden.
+
+### Risk
+
+High. Touches serialization and linking labels.
+
+---
+
+## PR-03.06 — Deterministic overload resolution across deps (arity is not enough)
+
+### Title
+
+Implement deterministic overload selection using canonical signature matching
+
+### Briefing / Context
+
+We currently try to disambiguate overloads by arity as a fallback. That’s not sufficient (same arity, different types). For Phase 03 “professional grade”, overload resolution must be deterministic and match by full signature.
+
+### Target
+
+* Imported method call selects overload by:
+
+    1. resolve callee symbol → candidate set
+    2. typecheck args → determine expected param types
+    3. choose exact match
+    4. otherwise `E_OVERLOAD_NOT_FOUND` or `E_OVERLOAD_AMBIGUOUS` deterministically
+
+### Scope
+
+* PBS FE typechecker must provide enough info to compute signature selection.
+* Resolver must expose all overload candidates for an imported `ImportRef` item.
+* Lowering uses canonical fn key and selected `SigId`.
+
+### Checklist
+
+* [ ] Ensure imported service methods are actually present in imported symbol arena.
+* [ ] Ensure candidates include `(owner, name, sig)` not just `name`.
+* [ ] Implement exact-match algorithm.
+* [ ] Implement deterministic ambiguity ordering for diagnostics.
+
+### Tests
+
+* Add golden regression reproducing `Log.debug` failure:
+
+    * dep exports `service Log { debug(string) }`
+    * root imports `Log` and calls `Log.debug("x")`
+* Add tests for:
+
+    * ambiguous same signature
+    * not found
+
+### Risk
+
+Medium/High. Needs clean integration across resolver/typechecker/lowering.
+
+---
+
+## PR-03.07 — Phase 03 cleanup: remove legacy compatibility branches and document boundary
+
+### Title
+
+Remove legacy string protocol branches and document FE/BE boundary rules
+
+### Briefing / Context
+
+After canonical models are in place, we must delete compatibility code paths (`alias/module`, `svc:` prefixes, prefix matching, etc.) to prevent regressions.
+
+### Target
+
+* No legacy synthetic module path support.
+* No string prefix matching for overloads.
+* Documentation: “BE owns the contract; FE implements it.”
+
+### Scope
+
+* Delete dead code.
+* Add `docs/phase-03-frontend-api.md` (or in-crate docs) summarizing invariants.
+* Add CI/lints to prevent BE from importing PBS modules.
+
+### Checklist
+
+* [ ] Remove legacy branches.
+* [ ] Add boundary docs.
+* [ ] Add lint/CI guard.
+
+### Tests
+
+* Full workspace tests.
+* Golden tests.
+
+### Risk
+
+Low/Medium. Mostly deletion + docs, but could expose hidden dependencies.
+
+---
+
+# Notes / Operating Rules (for Junie)
+
+1. **BE is the source of truth**: `frontend-api` defines canonical models; FE conforms.
+2. **No string protocols** across layers. Strings may exist only as *display/debug*.
+3. **No FE implementation imports from other FE implementations**.
+4. **No BE imports PBS modules** (hard boundary).
+5. **Overload resolution is signature-based** (arity alone is not valid).