diff --git a/extensions/action/src/constants.ts b/extensions/action/src/constants.ts
index 9bafbf63..520e4a2b 100644
--- a/extensions/action/src/constants.ts
+++ b/extensions/action/src/constants.ts
@@ -1,17 +1 @@
-import {
-    INTERNAL,
-} from '@harlem/core';
-
-export const SENDER = 'extension:action';
-export const STATE_PROP = `${INTERNAL.prefix}actions` as const;
-
-export const MUTATIONS = {
-    init: 'extension:action:init',
-    register: 'extension:action:register',
-    incrementRunCount: 'extension:action:increment-run-count',
-    addInstance: 'extension:action:add-instance',
-    removeInstance: 'extension:action:remove-instance',
-    addError: 'extension:action:add-error',
-    clearErrors: 'extension:action:clear-errors',
-    resetState: 'extension:action:reset-state',
-} as const;
\ No newline at end of file
+export const SENDER = 'extension:action';
\ No newline at end of file
diff --git a/extensions/action/src/index.ts b/extensions/action/src/index.ts
index 96f3a2ba..12a79434 100644
--- a/extensions/action/src/index.ts
+++ b/extensions/action/src/index.ts
@@ -71,49 +71,41 @@ export default function actionExtension<TState extends BaseState>(options?: Part
     return (store: InternalStore<TState>) => {
         store.register('extensions', 'action', () => rootOptions);
 
+        const actionTasks = new Map<string, Set<Task<unknown>>>();
         const actionState = reactive(new Map<string, ActionState>());
 
-        function setActionState<TPayload = unknown, TResult = unknown>(name: string) {
+        function setActionState<TPayload = unknown>(name: string) {
             const state = {
                 runCount: 0,
-                tasks: new Set(),
                 instances: new Map(),
                 errors: new Map(),
-            } as ActionState<TPayload, TResult>;
+            } as ActionState<TPayload>;
 
             actionState.set(name, state);
 
             return state;
         }
 
-        function getActionState<TPayload = unknown, TResult = unknown>(name: string) {
-            return (actionState.get(name) || setActionState(name)) as ActionState<TPayload, TResult>;
-        }
-
-        function updateActionState(name: string, producer: (currentState: ActionState) => Partial<ActionState>) {
-            const currentState = actionState.get(name);
-
-            if (!currentState) {
-                return;
-            }
-
-            const newState = producer(currentState);
-
-            if (newState !== currentState) {
-                actionState.set(name, {
-                    ...currentState,
-                    ...newState,
-                });
-            }
+        function getActionState<TPayload = unknown>(name: string) {
+            return (actionState.get(name) || setActionState(name)) as ActionState<TPayload>;
         }
 
         function registerAction(name: string, options: Partial<ActionOptions<any>> = {}) {
             store.register('actions', name, () => options);
-            return setActionState(name);
+            setActionState(name);
+
+            const tasks = new Set<Task<unknown>>();
+            actionTasks.set(name, tasks);
+
+            return {
+                tasks,
+            };
         }
 
         function action<TPayload, TResult = void>(name: string, body: ActionBody<TState, TPayload, TResult>, options?: Partial<ActionOptions<TPayload>>): Action<TPayload, TResult> {
-            registerAction(name, options);
+            const {
+                tasks,
+            } = registerAction(name, options);
 
             const {
                 concurrent,
@@ -132,16 +124,13 @@ export default function actionExtension<TState extends BaseState>(options?: Part
             } as ActionOptions<TPayload>;
 
             const mutate = (mutator: Mutator<TState, undefined, void>) => store.write(name, SENDER, mutator);
-            const incrementRunCount = () => updateActionState(name, ({ runCount }) => ({
-                runCount: runCount + 1,
-            }));
+            const incrementRunCount = () => getActionState(name).runCount += 1;
 
             return ((payload: TPayload, controller?: AbortController) => {
                 const {
-                    tasks,
                     instances,
                     errors,
-                } = getActionState<TPayload, TResult>(name);
+                } = getActionState<TPayload>(name);
 
                 if (!concurrent || (typeIsFunction(concurrent) && !concurrent(payload, Array.from(instances.values())))) {
                     abortAction(name, 'New instance started on non-concurrent action');
@@ -264,11 +253,9 @@ export default function actionExtension<TState extends BaseState>(options?: Part
             ([] as string[])
                 .concat(name)
                 .forEach(name => {
-                    const {
-                        tasks,
-                    } = getActionState(name);
+                    const tasks = actionTasks.get(name);
 
-                    if (tasks.size) {
+                    if (tasks?.size) {
                         tasks.forEach(task => {
                             task.abort(reason);
                             tasks.delete(task);
diff --git a/extensions/action/src/types.ts b/extensions/action/src/types.ts
index abb3d6af..129a0401 100644
--- a/extensions/action/src/types.ts
+++ b/extensions/action/src/types.ts
@@ -26,9 +26,8 @@ export interface ActionAbortStrategies {
     warn: ActionAbortStrategy;
 }
 
-export interface ActionState<TPayload = unknown, TResult = unknown> {
+export interface ActionState<TPayload = unknown> {
     runCount: number;
-    tasks: Set<Task<TResult>>;
     instances: Map<symbol, TPayload>;
     errors: Map<symbol, unknown>;
 }
diff --git a/extensions/action/test/actions.test.ts b/extensions/action/test/actions.test.ts
index 68d3211e..905e74e6 100644
--- a/extensions/action/test/actions.test.ts
+++ b/extensions/action/test/actions.test.ts
@@ -202,12 +202,19 @@ describe('Actions Extension', () => {
     });
 
     test('Handles concurrency', async () => {
+        expect.assertions(3);
+
         const {
             action,
         } = instance.store;
 
-        const concurrentAction = action('concurrent-action', async () => {});
-        const nonConcurrentAction = action('non-concurrent-action', async () => {}, {
+        const abortFn = vi.fn();
+
+        const concurrentAction = action('concurrent-action', async () => sleep(100));
+        const nonConcurrentAction = action('non-concurrent-action', async (_, __, ___, onAbort) => {
+            onAbort(abortFn);
+            return sleep(100);
+        }, {
             concurrent: false,
         });
 
@@ -234,6 +241,43 @@ describe('Actions Extension', () => {
 
         expect(hasConcurrentFailed).toBe(false);
         expect(hasNonConcurrentFailed).toBe(true);
+        expect(abortFn).toHaveBeenCalled();
+    });
+
+    test('Handles custom concurrency methods', async () => {
+        expect.assertions(2);
+
+        const {
+            action,
+        } = instance.store;
+
+        const customConcurrentAction = action('concurrent-action', async (payload: number) => sleep(100), {
+            concurrent: (payload, runningPayloads) => !runningPayloads.includes(payload),
+        });
+
+        let hasCustomConcurrentFailed = false;
+
+        try {
+            await Promise.all([
+                customConcurrentAction(1),
+                customConcurrentAction(2),
+            ]);
+        } catch {
+            hasCustomConcurrentFailed = true;
+        }
+
+        expect(hasCustomConcurrentFailed).toBe(false);
+
+        try {
+            await Promise.all([
+                customConcurrentAction(2),
+                customConcurrentAction(2),
+            ]);
+        } catch {
+            hasCustomConcurrentFailed = true;
+        }
+
+        expect(hasCustomConcurrentFailed).toBe(true);
     });
 
     test('Handles nested cancellation', async () => {
@@ -247,8 +291,8 @@ describe('Actions Extension', () => {
 
         const catchAssertion = vi.fn();
 
-        const childAction1 = action('child1', () => sleep(1000));
-        const childAction2 = action('child2', () => sleep(1000));
+        const childAction1 = action('child1', () => sleep(100));
+        const childAction2 = action('child2', () => sleep(100));
         const parentAction = action('parent', (_, __, controller) => Promise.all([
             childAction1(_, controller),
             childAction2(_, controller),