refactor(core): extract global resource store into standalone container

Refactor `GlobalResources` from a type-erased `Arc<Mutex<HashMap<...>>>`
alias into a `GlobalResContainer` struct with per-resource mutexes.
This prevents nested `modify_res` calls from deadlocking, allows
independent containers to coexist, and keeps `Program`'s public
resource API unchanged.

3 files changed, 446 insertions, 73 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7cbe748..c7f0250 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -115,6 +115,20 @@ None
 
     These changes fix incorrect word-index computation and avoid sending empty option values to the underlying completion engine from PowerShell completions.
 
+10. **[`core:resources`]** Refactored the global resource storage from a single type-erased `Arc<Mutex<HashMap<...>>>` container into a standalone `GlobalResContainer` struct with per-resource mutexes.
+
+    Previously, `GlobalResources` was a type alias for `Arc<Mutex<HashMap<TypeId, Box<dyn Any + Sync + Send>>>>`, and the resource methods (`with_resource`, `modify_res`, `__modify_res_and_return_route`, `__extract_res_mut`, `__store_res`, `res`, `res_or_route`, `res_or_default`) were implemented directly on `Program`. Now:
+
+    - **`GlobalResContainer`** — A new public struct owning the resource map (`map: Mutex<HashMap<TypeId, Box<dyn Any + Send + Sync>>>`), with `new()` and `Default` impls. Each resource entry is stored as `Arc<Mutex<Arc<Res>>>` — the outer `Mutex` guards the entry itself (so a resource can be locked without holding the container lock), and the inner `Arc<Res>` is the shared immutable snapshot returned by `res()`.
+    - **Per-resource mutex** — The container lock is only held for the brief lookup/clone of the entry. This means two nested `modify_res` calls (e.g., two `&mut` resource parameters generated by `#[chain]`) lock _different_ mutexes and cannot deadlock against each other.
+    - **`Program` delegation** — All resource methods on `Program` now delegate to its internal `resources: GlobalResContainer` member, keeping the public `Program` resource API unchanged.
+    - **Generic helper methods** — `__modify_res_and_return_route<Res, C>` and `res_or_route<Res, C>` now take an explicit `C: ProgramCollect<Enum = C>` generic parameter (added separately on the container), with `Program`'s versions keeping the single-`Res` signature.
+    - **`__store_res` semantics** — If an entry already exists for the type and is a matching `Arc<Mutex<Arc<Res>>>`, the value is updated in place under the entry lock; otherwise (missing entry, type mismatch, or poisoned lock) the entry is replaced wholesale.
+
+    The container is standalone and not coupled to any `Program` instance or the global `this::<C>()` context, so any number of independent `GlobalResContainer`s can be created and used simultaneously.
+
+    _No behavioral changes for downstream code — `Program`'s public resource API (`with_resource`, `modify_res`, `res`, `res_or_route`, `res_or_default`) is unchanged, and the `&mut` resource injection syntax for `#[chain]` (sync and async) continues to work as before. A side benefit: nested resource modifications no longer risk deadlock._
+
 #### Optimizations:
 
 1. **[`pathf`]** Added `is_module` field to `AnalyzeItem` and a new constructor `AnalyzeItem::local_module(module, item_name)` which sets `is_module: true`. The `type_mapping_builder` now tracks whether an item is a module: when generating `type_using.rs`, module items produce `use path::to::module::*;` (glob import) instead of the standard `use path::to::TypeName;` direct import. Non-module items continue to use direct imports as before. The internal data structure changed from `Vec<(String, String)>` to `Vec<(String, String, bool)>` to carry the `is_module` flag through the pipeline.
diff --git a/mingling_core/src/asset/global_resource.rs b/mingling_core/src/asset/global_resource.rs
index f37edd0..07d0b5e 100644
--- a/mingling_core/src/asset/global_resource.rs
+++ b/mingling_core/src/asset/global_resource.rs
@@ -6,22 +6,64 @@ use std::{
 
 use crate::{ChainProcess, Program, ProgramCollect, this};
 
-/// A thread-safe, type-erased container for storing global resources keyed by their type.
+/// A standalone, thread-safe container for storing global resources keyed by their type.
 ///
-/// Use `Program::with_resource` to insert resources and `Program::res` to retrieve them.
-pub type GlobalResources = Arc<Mutex<HashMap<TypeId, Box<dyn Any + Sync + Send>>>>;
+/// This is the resource store behind [`Program`]'s resource API: every `Program`
+/// owns one of these containers and all of its resource operations delegate to it.
+///
+/// Unlike the resource API on [`Program`], this container is **not** coupled to a
+/// program instance nor to the global `this::<C>()` context, so any number of
+/// containers can be created and used at the same time — each with fully
+/// independent storage.
+///
+/// Each resource is stored behind its **own** [`Mutex`]. The container lock is
+/// only held for the brief lookup/clone of the entry, so two nested
+/// `modify_res` calls (e.g. two `&mut` resource parameters generated by
+/// `#[chain]`) lock **different** mutexes and cannot deadlock against each other.
+pub struct GlobalResContainer {
+    /// Thread-safe storage for resources, keyed by their `TypeId` and protected by a `Mutex`.
+    ///
+    /// Each entry is a `Box<dyn Any>` holding an `Arc<Mutex<Arc<Res>>>`: the outer
+    /// `Mutex` guards the entry itself (so a resource can be locked without
+    /// holding the container lock), and the inner `Arc<Res>` is the shared
+    /// immutable snapshot returned by `res()`.
+    map: Mutex<HashMap<TypeId, Box<dyn Any + Send + Sync>>>,
+}
+
+impl GlobalResContainer {
+    /// Creates an empty resource container.
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            map: Mutex::new(HashMap::new()),
+        }
+    }
+
+    /// Clones the per-resource entry out from under the container lock.
+    ///
+    /// The container lock is released as soon as the entry `Arc` is cloned,
+    /// so all subsequent operations lock only the resource's own mutex.
+    fn res_entry<Res: 'static>(&self) -> Option<Arc<Mutex<Arc<Res>>>> {
+        let guard = self.map.lock().ok()?;
+        let entry = guard
+            .get(&TypeId::of::<Res>())?
+            .as_ref()
+            .downcast_ref::<Arc<Mutex<Arc<Res>>>>()
+            .map(Arc::clone);
+        drop(guard);
+        entry
+    }
 
-impl<C> Program<C>
-where
-    C: ProgramCollect<Enum = C>,
-{
     /// Insert a resource of the given type, cloning the provided value into the store
     pub fn with_resource<Res: 'static + Send + Sync + ResourceMarker>(
         &mut self,
         res: Res,
     ) -> &mut Self {
-        if let Ok(mut guard) = self.resources.lock() {
-            guard.insert(TypeId::of::<Res>(), Box::new(Arc::new(res)));
+        if let Ok(mut guard) = self.map.lock() {
+            guard.insert(
+                TypeId::of::<Res>(),
+                Box::new(Arc::new(Mutex::new(Arc::new(res)))),
+            );
         }
         self
     }
@@ -32,95 +74,102 @@ where
         Res: 'static + Default + ResourceMarker + Send + Sync,
         Return: Default,
     {
-        let Ok(mut guard) = self.resources.lock() else {
+        let Some(entry) = self.res_entry::<Res>() else {
             return Return::default();
         };
-        if let Some(arc_res) = guard
-            .get_mut(&TypeId::of::<Res>())
-            .and_then(|a| a.downcast_mut::<Arc<Res>>())
-        {
-            let mut new_res = match Arc::try_unwrap(std::mem::take(arc_res)) {
-                Ok(val) => val,
-                Err(arc) => (*arc).__resource_marker_clone(),
-            };
-            let r = f(&mut new_res);
-            *arc_res = Arc::new(new_res);
-            return r;
-        }
-        Return::default()
+        let Ok(mut guard) = entry.lock() else {
+            return Return::default();
+        };
+        let mut new_res = match Arc::try_unwrap(std::mem::take(&mut *guard)) {
+            Ok(val) => val,
+            Err(arc) => (*arc).__resource_marker_clone(),
+        };
+        let r = f(&mut new_res);
+        *guard = Arc::new(new_res);
+        r
     }
 
     /// Internal syntax for the `&mut MyResource` syntax of #[chain], do not use directly
     #[doc(hidden)]
-    pub fn __modify_res_and_return_route<Res>(
+    pub fn __modify_res_and_return_route<Res, C>(
         &self,
         f: impl FnOnce(&mut Res) -> ChainProcess<C>,
     ) -> ChainProcess<C>
     where
         Res: 'static + Default + ResourceMarker + Send + Sync,
+        C: ProgramCollect<Enum = C>,
     {
-        let Ok(mut guard) = self.resources.lock() else {
+        let Some(entry) = self.res_entry::<Res>() else {
             let mut default_res = Res::__resource_marker_default();
             return f(&mut default_res);
         };
-        if let Some(arc_res) = guard
-            .get_mut(&TypeId::of::<Res>())
-            .and_then(|a| a.downcast_mut::<Arc<Res>>())
-        {
-            let mut new_res = match Arc::try_unwrap(std::mem::take(arc_res)) {
-                Ok(val) => val,
-                Err(arc) => (*arc).__resource_marker_clone(),
-            };
-            let r = f(&mut new_res);
-            *arc_res = Arc::new(new_res);
-            r
-        } else {
+        let Ok(mut guard) = entry.lock() else {
             let mut default_res = Res::__resource_marker_default();
-            f(&mut default_res)
-        }
+            return f(&mut default_res);
+        };
+        let mut new_res = match Arc::try_unwrap(std::mem::take(&mut *guard)) {
+            Ok(val) => val,
+            Err(arc) => (*arc).__resource_marker_clone(),
+        };
+        let r = f(&mut new_res);
+        *guard = Arc::new(new_res);
+        r
     }
 
     /// Internal syntax for the `&mut MyResource` syntax of async #[chain], do not use directly.
     ///
-    /// Extracts a mutable resource from the global store (clone-out), returning an
+    /// Extracts a mutable resource from the store (clone-out), returning an
     /// owned value. The caller must call [`__store_res`] to write back modifications.
     #[doc(hidden)]
     #[must_use]
     pub fn __extract_res_mut<Res: 'static + Default + ResourceMarker + Send + Sync>(&self) -> Res {
-        let Ok(mut guard) = self.resources.lock() else {
+        let Some(entry) = self.res_entry::<Res>() else {
             return Res::__resource_marker_default();
         };
-        guard
-            .get_mut(&TypeId::of::<Res>())
-            .and_then(|a| a.downcast_mut::<Arc<Res>>())
-            .map_or_else(
-                Res::__resource_marker_default,
-                |arc_res| match Arc::try_unwrap(std::mem::take(arc_res)) {
-                    Ok(val) => val,
-                    Err(arc) => (*arc).__resource_marker_clone(),
-                },
-            )
+        let Ok(mut guard) = entry.lock() else {
+            return Res::__resource_marker_default();
+        };
+        match Arc::try_unwrap(std::mem::take(&mut *guard)) {
+            Ok(val) => val,
+            Err(arc) => (*arc).__resource_marker_clone(),
+        }
     }
 
     /// Internal syntax for the `&mut MyResource` syntax of async #[chain], do not use directly.
     ///
-    /// Stores a modified resource value back into the global store.
+    /// Stores a modified resource value back into the store.
     #[doc(hidden)]
     pub fn __store_res<Res: 'static + Send + Sync + ResourceMarker>(&self, val: Res) {
-        if let Ok(mut guard) = self.resources.lock() {
-            guard.insert(TypeId::of::<Res>(), Box::new(Arc::new(val)));
+        let Ok(mut guard) = self.map.lock() else {
+            return;
+        };
+        let Some(boxed_any) = guard.get_mut(&TypeId::of::<Res>()) else {
+            guard.insert(
+                TypeId::of::<Res>(),
+                Box::new(Arc::new(Mutex::new(Arc::new(val)))),
+            );
+            return;
+        };
+        if let Some(entry) = boxed_any.downcast_mut::<Arc<Mutex<Arc<Res>>>>()
+            && let Ok(mut entry_guard) = entry.lock()
+        {
+            *entry_guard = Arc::new(val);
+            return;
         }
+        // The entry exists but cannot be updated (type mismatch or poisoned
+        // lock): replace it wholesale.
+        guard.insert(
+            TypeId::of::<Res>(),
+            Box::new(Arc::new(Mutex::new(Arc::new(val)))),
+        );
     }
 
     /// Get an resources by type, returning `Res` if present
     #[must_use]
     pub fn res<Res: 'static + Send + Sync>(&self) -> Option<GlobalResource<Res>> {
-        let guard = self.resources.lock().ok()?;
-        let boxed_any = guard.get(&TypeId::of::<Res>())?;
-        let arc_res = boxed_any.as_ref().downcast_ref::<Arc<Res>>()?;
-        let result = GlobalResource::from(Arc::clone(arc_res));
-        drop(guard);
-        Some(result)
+        let entry = self.res_entry::<Res>()?;
+        let guard = entry.lock().ok()?;
+        Some(GlobalResource::from(Arc::clone(&*guard)))
     }
 
     /// Get a resource by type, returning `GlobalResource<Res>` if present.
@@ -130,10 +179,14 @@ where
     /// # Errors
     ///
     /// Returns `Err(route)` when the resource of type `Res` is not present in the store.
-    pub fn res_or_route<Res: 'static + Send + Sync>(
+    pub fn res_or_route<Res, C>(
         &self,
         route: ChainProcess<C>,
-    ) -> Result<GlobalResource<Res>, ChainProcess<C>> {
+    ) -> Result<GlobalResource<Res>, ChainProcess<C>>
+    where
+        Res: 'static + Send + Sync,
+        C: ProgramCollect<Enum = C>,
+    {
         self.res().map_or_else(|| Err(route), Ok)
     }
 
@@ -147,6 +200,93 @@ where
     }
 }
 
+impl Default for GlobalResContainer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<C> Program<C>
+where
+    C: ProgramCollect<Enum = C>,
+{
+    /// Insert a resource of the given type, cloning the provided value into the store
+    pub fn with_resource<Res: 'static + Send + Sync + ResourceMarker>(
+        &mut self,
+        res: Res,
+    ) -> &mut Self {
+        self.resources.with_resource(res);
+        self
+    }
+
+    /// Modify a resource by type, applying a closure to the resource if present
+    pub fn modify_res<Res, Return>(&self, f: impl FnOnce(&mut Res) -> Return) -> Return
+    where
+        Res: 'static + Default + ResourceMarker + Send + Sync,
+        Return: Default,
+    {
+        self.resources.modify_res(f)
+    }
+
+    /// Internal syntax for the `&mut MyResource` syntax of #[chain], do not use directly
+    #[doc(hidden)]
+    pub fn __modify_res_and_return_route<Res>(
+        &self,
+        f: impl FnOnce(&mut Res) -> ChainProcess<C>,
+    ) -> ChainProcess<C>
+    where
+        Res: 'static + Default + ResourceMarker + Send + Sync,
+    {
+        self.resources.__modify_res_and_return_route(f)
+    }
+
+    /// Internal syntax for the `&mut MyResource` syntax of async #[chain], do not use directly.
+    ///
+    /// Extracts a mutable resource from the global store (clone-out), returning an
+    /// owned value. The caller must call [`__store_res`] to write back modifications.
+    #[doc(hidden)]
+    #[must_use]
+    pub fn __extract_res_mut<Res: 'static + Default + ResourceMarker + Send + Sync>(&self) -> Res {
+        self.resources.__extract_res_mut()
+    }
+
+    /// Internal syntax for the `&mut MyResource` syntax of async #[chain], do not use directly.
+    ///
+    /// Stores a modified resource value back into the global store.
+    #[doc(hidden)]
+    pub fn __store_res<Res: 'static + Send + Sync + ResourceMarker>(&self, val: Res) {
+        self.resources.__store_res(val);
+    }
+
+    /// Get an resources by type, returning `Res` if present
+    #[must_use]
+    pub fn res<Res: 'static + Send + Sync>(&self) -> Option<GlobalResource<Res>> {
+        self.resources.res()
+    }
+
+    /// Get a resource by type, returning `GlobalResource<Res>` if present.
+    ///
+    /// If the resource is not present, returns the provided [`ChainProcess`] as an `Err`.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err(route)` when the resource of type `Res` is not present in the store.
+    pub fn res_or_route<Res: 'static + Send + Sync>(
+        &self,
+        route: ChainProcess<C>,
+    ) -> Result<GlobalResource<Res>, ChainProcess<C>> {
+        self.resources.res_or_route(route)
+    }
+
+    /// Get a resource by type, returning `GlobalResource<Res>` or inserting a default
+    #[must_use]
+    pub fn res_or_default<Res: 'static + Send + Sync + ResourceMarker>(
+        &self,
+    ) -> GlobalResource<Res> {
+        self.resources.res_or_default()
+    }
+}
+
 /// Global assets for storing Program global state information
 pub struct GlobalResource<ResType: 'static + Send + Sync> {
     res_arc: Arc<ResType>,
@@ -225,6 +365,8 @@ where
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::MockProgramCollect;
+    use crate::error::ChainProcessError;
 
     #[test]
     fn global_resource_new_and_deref() {
@@ -285,8 +427,229 @@ mod tests {
         );
     }
 
-    // Note: Tests for Program::with_resource, res(), res_or_route(), res_or_default(),
-    // and modify_res() require a concrete ProgramCollect implementation, which is
-    // complex and outside the scope of these unit tests.
-    // Those are better covered by integration tests.
+    #[test]
+    fn container_new_creates_empty_store() {
+        let container = GlobalResContainer::new();
+        assert!(container.res::<i32>().is_none());
+    }
+
+    #[test]
+    fn container_insert_then_res() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(42i32);
+        let res = container.res::<i32>();
+        assert_eq!(*res.unwrap(), 42);
+    }
+
+    #[test]
+    fn container_missing_res_returns_none() {
+        let container = GlobalResContainer::new();
+        assert!(container.res::<String>().is_none());
+    }
+
+    #[test]
+    fn container_res_or_default_creates_default() {
+        let container = GlobalResContainer::new();
+        assert_eq!(*container.res_or_default::<i32>(), 0);
+    }
+
+    #[test]
+    fn container_res_or_default_returns_existing() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(7i32);
+        assert_eq!(*container.res_or_default::<i32>(), 7);
+    }
+
+    #[test]
+    fn container_modify_res_updates_value() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(1i32);
+        let doubled = container.modify_res(|v: &mut i32| {
+            *v *= 2;
+            *v
+        });
+        assert_eq!(doubled, 2);
+        assert_eq!(*container.res::<i32>().unwrap(), 2);
+    }
+
+    #[test]
+    fn container_modify_res_missing_returns_default() {
+        let container = GlobalResContainer::new();
+        let value: i32 = container.modify_res(|v: &mut i32| *v);
+        assert_eq!(value, 0);
+    }
+
+    #[test]
+    fn container_modify_res_through_shared_reference() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(10i32);
+        let shared = &container;
+        shared.modify_res(|v: &mut i32| *v += 5);
+        assert_eq!(*container.res::<i32>().unwrap(), 15);
+    }
+
+    #[test]
+    fn container_modify_res_clones_when_shared() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(10i32);
+        // Hold a shared handle so `Arc::try_unwrap` fails and the resource is cloned out
+        let handle = container.res::<i32>().unwrap();
+        container.modify_res(|v: &mut i32| *v += 5);
+        assert_eq!(*container.res::<i32>().unwrap(), 15);
+        assert_eq!(*handle, 10);
+    }
+
+    #[test]
+    fn container_extract_res_mut_takes_value_out() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(3i32);
+        let extracted: i32 = container.__extract_res_mut();
+        assert_eq!(extracted, 3);
+        // The slot is reset to a default value after the extraction
+        assert_eq!(*container.res::<i32>().unwrap(), 0);
+    }
+
+    #[test]
+    fn container_extract_res_mut_clones_when_shared() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(3i32);
+        // Hold a shared handle so `Arc::try_unwrap` fails and the resource is cloned out
+        let _handle = container.res::<i32>().unwrap();
+        let extracted: i32 = container.__extract_res_mut();
+        assert_eq!(extracted, 3);
+        // The slot is reset to a default value after the extraction
+        assert_eq!(*container.res::<i32>().unwrap(), 0);
+    }
+
+    #[test]
+    fn container_store_res_inserts_value() {
+        let container = GlobalResContainer::new();
+        container.__store_res(8i32);
+        assert_eq!(*container.res::<i32>().unwrap(), 8);
+    }
+
+    #[test]
+    fn container_extract_store_roundtrip() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(7i32);
+        let value: i32 = container.__extract_res_mut();
+        container.__store_res(value + 1);
+        assert_eq!(*container.res::<i32>().unwrap(), 8);
+    }
+
+    #[test]
+    fn container_res_shared_handles_share_the_arc() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(String::from("hello"));
+        let handle_a = container.res::<String>().unwrap();
+        let handle_b = container.res::<String>().unwrap();
+        assert_eq!(*handle_a, "hello");
+        assert_eq!(*handle_b, "hello");
+        assert!(Arc::ptr_eq(&handle_a.res_arc, &handle_b.res_arc));
+    }
+
+    #[test]
+    fn container_res_or_route_missing_returns_route() {
+        let container = GlobalResContainer::new();
+        let route: ChainProcess<MockProgramCollect> =
+            ChainProcess::Err(ChainProcessError::Other("missing".into()));
+        let result = container.res_or_route::<i32, MockProgramCollect>(route);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn container_res_or_route_present_returns_resource() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(5i32);
+        let route: ChainProcess<MockProgramCollect> =
+            ChainProcess::Err(ChainProcessError::Other("missing".into()));
+        let Ok(resource) = container.res_or_route::<i32, MockProgramCollect>(route) else {
+            panic!("expected the resource to be present");
+        };
+        assert_eq!(*resource, 5);
+    }
+
+    #[test]
+    fn container_modify_res_and_return_route_works() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(1i32);
+        let route: ChainProcess<MockProgramCollect> =
+            container.__modify_res_and_return_route(|v: &mut i32| {
+                *v += 1;
+                ChainProcess::Err(ChainProcessError::Other("done".into()))
+            });
+        assert!(matches!(route, ChainProcess::Err(_)));
+        assert_eq!(*container.res::<i32>().unwrap(), 2);
+    }
+
+    #[test]
+    fn container_nested_modify_res_different_types_do_not_deadlock() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(1i32).with_resource("a".to_string());
+        // Two `&mut` injections nest `modify_res` calls; each resource has its
+        // own mutex, so the inner call must not deadlock against the outer one.
+        container.modify_res(|count: &mut i32| {
+            *count += 10;
+            container.modify_res(|text: &mut String| {
+                text.push('b');
+            });
+        });
+        assert_eq!(*container.res::<i32>().unwrap(), 11);
+        assert_eq!(*container.res::<String>().unwrap(), "ab");
+    }
+
+    #[test]
+    fn container_nested_modify_res_and_return_route_no_deadlock() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(1i32).with_resource("a".to_string());
+        let route: ChainProcess<MockProgramCollect> =
+            container.__modify_res_and_return_route(|count: &mut i32| {
+                *count += 10;
+                container.__modify_res_and_return_route(|text: &mut String| {
+                    text.push('b');
+                    ChainProcess::Err(ChainProcessError::Other("done".into()))
+                })
+            });
+        assert!(matches!(route, ChainProcess::Err(_)));
+        assert_eq!(*container.res::<i32>().unwrap(), 11);
+        assert_eq!(*container.res::<String>().unwrap(), "ab");
+    }
+
+    #[test]
+    fn container_res_inside_modify_of_another_resource() {
+        let mut container = GlobalResContainer::new();
+        container.with_resource(1i32).with_resource("a".to_string());
+        container.modify_res(|count: &mut i32| {
+            // Reading a different resource while holding this one's lock must
+            // not deadlock either.
+            assert_eq!(*container.res::<String>().unwrap(), "a");
+            *count += 10;
+        });
+        assert_eq!(*container.res::<i32>().unwrap(), 11);
+    }
+
+    #[test]
+    fn container_multiple_instances_are_independent() {
+        let mut first = GlobalResContainer::new();
+        let mut second = GlobalResContainer::new();
+        first.with_resource(1i32);
+        second.with_resource(2i32);
+        first.modify_res(|v: &mut i32| *v += 10);
+        assert_eq!(*first.res::<i32>().unwrap(), 11);
+        assert_eq!(*second.res::<i32>().unwrap(), 2);
+        // A resource present in one container is invisible to the other
+        assert!(first.res::<String>().is_none());
+        assert!(second.res::<String>().is_none());
+    }
+
+    #[test]
+    fn program_resource_methods_delegate_to_container() {
+        let mut program = crate::Program::<MockProgramCollect>::new_with_args(Vec::<String>::new());
+        program.with_resource(1i32);
+        assert_eq!(*program.res::<i32>().unwrap(), 1);
+        program.modify_res(|v: &mut i32| *v += 1);
+        assert_eq!(*program.res::<i32>().unwrap(), 2);
+        assert_eq!(*program.res_or_default::<i32>(), 2);
+        assert_eq!(*program.res_or_default::<String>(), "");
+    }
 }
diff --git a/mingling_core/src/program.rs b/mingling_core/src/program.rs
index 3c43cee..be8d85c 100644
--- a/mingling_core/src/program.rs
+++ b/mingling_core/src/program.rs
@@ -2,13 +2,9 @@
 use std::env;
 
 use crate::{
-    AnyOutput, GlobalResources, asset::dispatcher::Dispatcher, error::ChainProcessError,
+    AnyOutput, GlobalResContainer, asset::dispatcher::Dispatcher, error::ChainProcessError,
     hook::ProgramHook,
 };
-use std::{
-    collections::HashMap,
-    sync::{Arc, Mutex},
-};
 
 #[doc(hidden)]
 pub mod error;
@@ -81,7 +77,7 @@ where
 
     pub(crate) hooks: Vec<ProgramHook<C>>,
 
-    pub(crate) resources: GlobalResources,
+    pub(crate) resources: GlobalResContainer,
 }
 
 impl<C> Program<C>
@@ -124,7 +120,7 @@ where
 
             hooks: Vec::new(),
 
-            resources: Arc::new(Mutex::new(HashMap::new())),
+            resources: GlobalResContainer::new(),
         }
     }