Decompose StateImpl class for tree-shaking (#35)

* perf(core): add benchmark suite

* refactor(core): decompose StateImpl class for tree-shaking

Replace monolithic StateImpl class with module-level functions and
a createState closure factory. Bundlers can now eliminate unused
exports — importing only `state` drops derive, select, lens and
all lens helpers (87.5% size reduction for state-only consumers).

* docs: update architecture docs for tree-shaking and closure factory

* perf(bench): add per-benchmark heap usage reporting

Measure heap delta per benchmark run using process.memoryUsage().heapUsed
with forced GC before each run for a clean baseline. Reports median heap
delta in KB alongside existing timing stats. Adds --expose-gc flag to the
benchmark npm script.

* chore(biome): bump schema to 2.3.14 and reorder file includes

* chore(deps): bump biome 2.3.14, @types/node 25.2.2, npm 11.9.0

* chore(assets): backport v2 SVG logo from epoch-2

Author: nerdalytics

.github/README.md

@@ -1,10 +1,10 @@
-# Beacon <img align="right" src="https://raw.githubusercontent.com/nerdalytics/beacon/refs/heads/trunk/assets/beacon-logo.svg" width="128px" alt="A stylized lighthouse beacon with golden light against a dark blue background, representing the reactive state library"/>
+# Beacon <img align="right" src="https://raw.githubusercontent.com/nerdalytics/beacon/refs/heads/trunk/assets/beacon-logo-v2.svg" width="128px" alt="A stylized lighthouse beacon with golden light against a dark blue background, representing the reactive state library"/>
 
 > Lightweight reactive state management for Node.js backends
 
 [![license:mit](https://flat.badgen.net/static/license/MIT/blue)](https://github.com/nerdalytics/beacon/blob/trunk/LICENSE)
 [![registry:npm:version](https://img.shields.io/npm/v/@nerdalytics/beacon.svg)](https://www.npmjs.com/package/@nerdalytics/beacon)
-[![Socket Badge](https://badge.socket.dev/npm/package/@nerdalytics/beacon/1000.2.5)](https://socket.dev/npm/package/@nerdalytics/beacon/overview/1000.2.5)
+[![Socket Badge](https://badge.socket.dev/npm/package/@nerdalytics/beacon/1000.3.0)](https://socket.dev/npm/package/@nerdalytics/beacon/overview/1000.3.0)
 
 [![tech:nodejs](https://img.shields.io/badge/Node%20js-339933?style=for-the-badge&logo=nodedotjs&logoColor=white)](https://nodejs.org/)
 [![language:typescript](https://img.shields.io/badge/TypeScript-007ACC?style=for-the-badge&logo=typescript&logoColor=white)](https://typescriptlang.org/)
@@ -58,6 +58,7 @@ A lightweight reactive state library for Node.js backends. Enables reactive stat
 - **Cycle handling** - Safely manages cyclic dependencies without crashing
 - **Infinite loop detection** - Automatically detects and prevents infinite update loops
 - **TypeScript-first** - Full TypeScript support with generics
+- **Tree-shakeable** - Module-level exports let bundlers eliminate unused code
 - **Lightweight** - Zero dependencies
 - **Node.js compatibility** - Works with Node.js LTS v20+ and v22+
 
@@ -444,9 +445,10 @@ Beacon follows these key principles:
 
 ## Architecture
 
-Beacon is built around a centralized reactivity system with fine-grained dependency tracking. Here's how it works:
+Beacon is built around module-level functions and a closure-based state factory with fine-grained dependency tracking. All exports are independent `const` declarations, so bundlers can tree-shake unused primitives. Here's how it works:
 
 - **Automatic Dependency Collection**: When a state is read inside an effect, Beacon automatically records this dependency
+- **Closure-based State**: Each `state()` call returns a closure over its value and subscriber set
 - **WeakMap-based Tracking**: Uses WeakMaps for automatic garbage collection
 - **Topological Updates**: Updates flow through the dependency graph in the correct order
 - **Memory-Efficient**: Designed for long-running Node.js processes
@@ -531,7 +533,7 @@ app.listen(3000);
 
 #### Can Beacon be used in browser applications?
 
-While Beacon is optimized for Node.js server-side applications, its core principles would work in browser environments. However, the library is specifically designed for backend use cases and hasn't been optimized for browser bundle sizes or DOM integration patterns.
+While Beacon is designed for Node.js server-side applications, it works in browser environments too. The library is fully tree-shakeable (`sideEffects: false`), so bundlers like esbuild, Rollup, and webpack will eliminate any primitives you don't import. It has not been optimized for DOM integration patterns.
 
 ## License
 

README.md

@@ -1,10 +1,10 @@
-# Beacon <img align="right" src="https://raw.githubusercontent.com/nerdalytics/beacon/refs/heads/trunk/assets/beacon-logo.svg" width="128px" alt="A stylized lighthouse beacon with golden light against a dark blue background, representing the reactive state library"/>
+# Beacon <img align="right" src="https://raw.githubusercontent.com/nerdalytics/beacon/refs/heads/trunk/assets/beacon-logo-v2.svg" width="128px" alt="A stylized lighthouse beacon with golden light against a dark blue background, representing the reactive state library"/>
 
 > Lightweight reactive state management for Node.js backends
 
 [![license:mit](https://flat.badgen.net/static/license/MIT/blue)](https://github.com/nerdalytics/beacon/blob/trunk/LICENSE)
 [![registry:npm:version](https://img.shields.io/npm/v/@nerdalytics/beacon.svg)](https://www.npmjs.com/package/@nerdalytics/beacon)
-[![Socket Badge](https://badge.socket.dev/npm/package/@nerdalytics/beacon/1000.2.5)](https://socket.dev/npm/package/@nerdalytics/beacon/overview/1000.2.5)
+[![Socket Badge](https://badge.socket.dev/npm/package/@nerdalytics/beacon/1000.3.0)](https://socket.dev/npm/package/@nerdalytics/beacon/overview/1000.3.0)
 
 [![tech:nodejs](https://img.shields.io/badge/Node%20js-339933?style=for-the-badge&logo=nodedotjs&logoColor=white)](https://nodejs.org/)
 [![language:typescript](https://img.shields.io/badge/TypeScript-007ACC?style=for-the-badge&logo=typescript&logoColor=white)](https://typescriptlang.org/)

TECHNICAL_DETAILS.md

@@ -4,13 +4,15 @@ This document describes the internal implementation details of the Beacon librar
 
 ## Reactive System Architecture
 
-Beacon uses a fine-grained reactivity system with automatic dependency tracking. Here's how the core architecture works:
+Beacon uses a fine-grained reactivity system with automatic dependency tracking. The entire library lives in a single module (`src/index.ts`) as independent `const` function declarations sharing module-level reactive state. This design makes every export tree-shakeable — bundlers can eliminate any primitive a consumer doesn't import.
 
-1. **State Primitives**: Base reactive values that can be read and modified
+Here's how the core architecture works:
+
+1. **State Primitives**: Base reactive values created by a closure factory (`createState`)
 2. **Derived Values**: Computed values that depend on other reactive states
 3. **Effects**: Side effects that run when dependencies change
 4. **Batching**: Optimization for multiple state changes
-5. **Dependency Tracking**: Automatic tracking of dependencies
+5. **Dependency Tracking**: Automatic tracking via module-level WeakMaps
 6. **Selectors**: Targeted subscriptions to subsets of state objects
 
 ### Core API Components
@@ -27,13 +29,15 @@ Beacon's API consists of the following key functions:
 
 ### Dependency Tracking Mechanism
 
+Reactive state is coordinated through 10 module-level variables (5 mutable, 5 WeakMap/Set constants). Each `state()` call returns a closure that captures its own `value`, `subscribers` Set, and `stateId` Symbol, while reading and writing the shared module-level tracking structures.
+
 When an effect or derived state runs:
 
-1. The global `currentSubscriber` variable is set to the current effect
+1. The module-level `currentSubscriber` variable is set to the current effect
 2. Reading any state during execution registers the state as a dependency
 3. A bidirectional relationship is established:
-   - The state keeps track of its subscribers (effects that depend on it)
-   - The effect keeps track of its dependencies (states it depends on)
+   - The state's closure-scoped `subscribers` Set tracks which effects depend on it
+   - The module-level `subscriberDependencies` WeakMap tracks which subscriber sets each effect belongs to
 4. When a state changes, it notifies all its subscribers
 
 ## Cyclical Dependencies
@@ -262,11 +266,12 @@ This system ensures there are no memory leaks from lingering effect subscription
 
 Several optimizations make Beacon efficient:
 
-1. Set-based dependency tracking for fast operations
-2. Value equality checks to prevent unnecessary updates
-3. Specialized handling for small subscriber sets
+1. Closure-based state factory — eliminates class instantiation and method dispatch overhead
+2. Set-based dependency tracking for fast operations
+3. Value equality checks to prevent unnecessary updates
 4. Efficient batching to minimize effect executions
 5. WeakMap for subscriber dependencies to allow garbage collection
+6. Module-level `const` exports with `sideEffects: false` — enables tree-shaking of unused primitives
 
 ---
 

assets/beacon-logo-v2.svg

@@ -1,5 +1,5 @@
 {
-	"$schema": "https://biomejs.dev/schemas/2.3.13/schema.json",
+	"$schema": "https://biomejs.dev/schemas/2.3.14/schema.json",
 	"assist": {
 		"actions": {
 			"source": {
@@ -12,9 +12,9 @@
 	"files": {
 		"ignoreUnknown": true,
 		"includes": [
-			"**/*.ts",
+			"*.json",
 			"**/*.js",
-			"**/*.json",
+			"**/*.ts",
 			"!package-lock.json",
 			"!**/tests/template.test.ts",
 			"!**/dist/**/*",

biome.json

@@ -1,5 +1,5 @@
 {
-	"$schema": "https://nodejs.org/dist/v24.10.0/docs/node-config-schema.json",
+	"$schema": "https://nodejs.org/dist/v24.13.0/docs/node-config-schema.json",
 	"nodeOptions": {
 		"test-coverage-branches": 100,
 		"test-coverage-exclude": [