diff --git a/.github/workflows/quality.yml b/.github/workflows/quality.yml
index db9f273..2bd75b6 100644
--- a/.github/workflows/quality.yml
+++ b/.github/workflows/quality.yml
@@ -4,9 +4,10 @@ on:
   pull_request:
     branches:
       - main
+      - release-*
 
 jobs:
-  quality_pipeline_lint:
+  quality_pipeline_lint_and_typecheck:
     runs-on: ubuntu-24.04
     timeout-minutes: 5
 
@@ -25,6 +26,9 @@ jobs:
       - name: Lint
         run: npm run lint
 
+      - name: Type Check
+        run: npm run test-types
+
   quality_pipeline_nodejs:
     runs-on: ubuntu-24.04
     timeout-minutes: 5
@@ -68,6 +72,9 @@ jobs:
       - name: Install
         run: npm ci && npx playwright install --with-deps chromium
 
+      - name: Build
+        run: npm run build
+
       - name: Test
         run: npm run test:chromium
 
@@ -76,12 +83,6 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
 
-      - name: Archive logs
-        uses: actions/upload-artifact@v4
-        with:
-          name: chromium-logs
-          path: reports/logs/chromium-112.0.5615.29.log
-
   quality_pipeline_firefox:
     runs-on: ubuntu-24.04
     timeout-minutes: 5
@@ -98,14 +99,12 @@ jobs:
       - name: Install
         run: npm ci && npx playwright install --with-deps firefox
 
+      - name: Build
+        run: npm run build
+
       - name: Test
         run: npm run test:firefox
 
-      - name: Report coverage
-        uses: codecov/codecov-action@v5
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}
-
   quality_pipeline_webkit:
     runs-on: ubuntu-24.04
     timeout-minutes: 5
@@ -122,10 +121,8 @@ jobs:
       - name: Install
         run: npm ci && npx playwright install --with-deps webkit
 
+      - name: Build
+        run: npm run build
+
       - name: Test
         run: npm run test:webkit
-
-      - name: Report coverage
-        uses: codecov/codecov-action@v5
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}
diff --git a/.nvmrc b/.nvmrc
index 0a49261..5bf4400 100644
--- a/.nvmrc
+++ b/.nvmrc
@@ -1 +1 @@
-24.11.0
+24.15.0
diff --git a/ci/eslint.config.mjs b/ci/eslint.config.mjs
index af98e0d..6440f1b 100644
--- a/ci/eslint.config.mjs
+++ b/ci/eslint.config.mjs
@@ -1,29 +1,23 @@
-import globals from 'globals';
-import path from 'node:path';
-import { fileURLToPath } from 'node:url';
 import js from '@eslint/js';
-import { FlatCompat } from '@eslint/eslintrc';
-
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
-const compat = new FlatCompat({
-    baseDirectory: __dirname,
-    recommendedConfig: js.configs.recommended,
-    allConfig: js.configs.all
-});
+import { defineConfig } from 'eslint/config';
+import tseslint from 'typescript-eslint';
+import globals from 'globals';
 
-export default [...compat.extends('eslint:recommended'), {
-    languageOptions: {
-        globals: {
-            ...globals.browser,
-            ...globals.node
+export default defineConfig(
+    js.configs.recommended,
+    tseslint.configs.recommended,
+    {
+        languageOptions: {
+            globals: {
+                ...globals.browser,
+                ...globals.node
+            },
+            ecmaVersion: 'latest',
+            sourceType: 'module'
         },
-
-        ecmaVersion: 'latest',
-        sourceType: 'module'
-    },
-
-    rules: {
-        'no-shadow': 2
+        rules: {
+            'no-shadow': 'error',
+            semi: 'error'
+        }
     }
-}];
\ No newline at end of file
+);
\ No newline at end of file
diff --git a/ci/tools/build-utils.js b/ci/tools/build-utils.js
index a40da00..0b74622 100644
--- a/ci/tools/build-utils.js
+++ b/ci/tools/build-utils.js
@@ -1,87 +1,62 @@
 import path from 'node:path';
 import fs from 'node:fs/promises';
-
 import esbuild from 'esbuild';
-
 import { calcIntegrity } from './integrity-utils.js';
 import * as stdout from './stdout.js';
 
 const SRC_DIR = 'src';
 const DIST_DIR = 'dist';
+const MAIN_FILE = 'object-observer.ts';
+const ENTRY_POINT = path.join(SRC_DIR, MAIN_FILE);
 
 stdout.writeGreen('Starting the build...');
 stdout.writeNewline();
-stdout.writeNewline();
 
 try {
 	await cleanDistDir();
 	await buildESModule();
-	await buildCJSModule();
 	await buildCDNResources();
 } catch (e) {
 	console.error(e);
 }
 
-stdout.writeGreen('... build done');
+stdout.writeGreen('... done');
 stdout.writeNewline();
 stdout.writeNewline();
 
 async function cleanDistDir() {
-	stdout.write(`\tcleaning "dist"...`);
+	stdout.write(`- cleaning "dist"...`);
 
 	await fs.rm(DIST_DIR, { recursive: true, force: true });
 	await fs.mkdir(DIST_DIR);
 
-	stdout.writeGreen('\tOK');
+	stdout.writeGreen('\t\tOK');
 	stdout.writeNewline();
 }
 
 async function buildESModule() {
-	stdout.write('\tbuilding ESM resources...');
+	stdout.write('- building ESM resources...');
 
-	await fs.copyFile(path.join(SRC_DIR, 'object-observer.d.ts'), path.join(DIST_DIR, 'object-observer.d.ts'));
-	await fs.copyFile(path.join(SRC_DIR, 'object-observer.js'), path.join(DIST_DIR, 'object-observer.js'));
-	await esbuild.build({
-		entryPoints: [path.join(DIST_DIR, 'object-observer.js')],
+	const config = {
+		entryPoints: [ENTRY_POINT],
+		bundle: true,
 		outdir: DIST_DIR,
-		minify: true,
+		format: 'esm',
+		minify: false,
 		sourcemap: true,
-		sourcesContent: false,
-		outExtension: { '.js': '.min.js' }
-	});
-
-	stdout.writeGreen('\tOK');
-	stdout.writeNewline();
-}
-
-async function buildCJSModule() {
-	stdout.write('\tbuilding CJS resources...');
-
-	const baseConfig = {
-		entryPoints: [path.join(SRC_DIR, 'object-observer.js')],
-		outdir: path.join(DIST_DIR, 'cjs'),
-		format: 'cjs',
-		outExtension: { '.js': '.cjs' }
+		sourcesContent: false
 	};
-	await esbuild.build(baseConfig);
-	await esbuild.build({
-		...baseConfig,
-		entryPoints: [path.join(DIST_DIR, 'cjs', 'object-observer.cjs')],
-		minify: true,
-		sourcemap: true,
-		sourcesContent: false,
-		outExtension: { '.js': '.min.cjs' }
-	});
+	await esbuild.build(config);
+	await esbuild.build({ ...config, minify: true, outExtension: { '.js': '.min.js' } });
 
 	stdout.writeGreen('\tOK');
 	stdout.writeNewline();
 }
 
 async function buildCDNResources() {
-	stdout.write('\tbuilding CDN resources...');
+	stdout.write('- building CDN resources...');
 
 	const CDN_DIR = path.join(DIST_DIR, 'cdn');
-
 	await fs.mkdir(CDN_DIR);
 
 	const files = (await fs.readdir(DIST_DIR))
@@ -92,7 +67,6 @@ async function buildCDNResources() {
 	}
 
 	const sriMap = await calcIntegrity(CDN_DIR);
-
 	await fs.writeFile('sri.json', JSON.stringify(sriMap, null, '\t'), { encoding: 'utf-8' });
 
 	stdout.writeGreen('\tOK');
diff --git a/docs/architecture.md b/docs/architecture.md
new file mode 100644
index 0000000..7f0a594
--- /dev/null
+++ b/docs/architecture.md
@@ -0,0 +1,12 @@
+# Architecture
+
+```mermaid
+classDiagram
+    class ObservableBase {
+        
+    }
+
+    ObservableBase <|-- ObservableObject
+    ObservableBase <|-- ObservableArray
+    ObservableBase <|-- ObservableTypedArray
+```
\ No newline at end of file
diff --git a/docs/changelog.md b/docs/changelog.md
index ed63133..c799346 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -7,13 +7,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ## [7.0.0]
+### BREAKING CHANGE
+- [Issue no. 152](https://github.com/gullerya/object-observer/issues/152) - `Observable.observe` options API replaced:
+  - removed: `path`, `pathsOf`, `pathsFrom`
+  - added: `filters` — a non-empty array of `Filter` instances; multiple filters compose as logical AND
+  - `Filter` is now exported from the package entry; use its static factories (`exactPaths`, `pathsStartWith`, `directChildrenOf`, `custom`) to build filters
+  - migration: `{ path: 'a.b' }` → `{ filters: [Filter.exactPaths(['a.b'])] }`; `{ pathsOf: 'a' }` → `{ filters: [Filter.directChildrenOf('a')] }`; `{ pathsFrom: 'a' }` → `{ filters: [Filter.pathsStartWith('a')] }`
 ### Added
 - [Issue no. 149](https://github.com/gullerya/object-observer/issues/149) - added verifiers to prevent unallowed changes
-- [Issue no. 152](https://github.com/gullerya/object-observer/issues/152) - change the way filters are configured
+- `Filter.directChildrenOf(path)` factory — covers the previous `pathsOf` semantics, with a fixed sibling-prefix bug (`directChildrenOf('inner')` no longer matches `innerX.foo`)
+### Fixed
+- `npm test` script referenced a non-existent `.json` config; now points to the correct `.js` file
 ### Chore
 - updated dependencies
 - reorganized sources
 - updated build scripts
+- raised Node.js runtime to `24.15.0` (aligned with current LTS)
+- browser support matrix updated to "last 2 versions" of Chrome, Firefox, Edge, Safari
+- removed stale commented-out duplicate of the dispatch pipeline from `src/object-observer.ts`
 
 ## [6.1.4] - 2025-02-14
 ### Chore
diff --git a/docs/filter-paths.md b/docs/filter-paths.md
deleted file mode 100644
index c4a170d..0000000
--- a/docs/filter-paths.md
+++ /dev/null
@@ -1,73 +0,0 @@
-# Filter paths options
-
-`Observable.observe(...)` allows `options` parameter, third one, optional.
-
-Some of the options are filtering ones, allowing to specify the changes of interest from within the observable graph. Here is a detailed description of those options.
-
-## __`pathsFrom`__
-
-Value expected to be a non-empty string representing a path, any changes of which and deeper will be delivered to the observer.
-> This option MAY NOT be used together with `path` option.
-
-<table>
-	<tr>
-		<td width="50%">
-			<img src="./filter-graphs/filter-paths-from.svg"/>
-		</td>
-		<td>
-			Given, that we have subscribed for the changes via:
-<pre><code>Observable.observe(o, callback, { pathsFrom: 'address' });</code></pre>
-			Following mutations <b>will</b> be delivered to the <code>callback</code>:
-<pre><code>o.address.street.apt = 5;
-o.address.city = 'DreamCity';
-o.address = {};</code></pre>
-			Following mutations <b>will not</b> be delivered to the <code>callback</code>:
-<pre><code>o.lastName = 'Joker';</code></pre>
-		</td>
-	</tr>
-</table>
-
-## __`pathsOf`__
-
-Value expected to be a string, which MAY be empty, representing a path. Changes to direct properties of which will be notified.
-
-<table>
-	<tr>
-		<td width="50%">
-			<img src="./filter-graphs/filter-paths-of.svg"/>
-		</td>
-		<td>
-			Given, that we have subscribed for the changes via:
-<pre><code>Observable.observe(o, callback, { pathsOf: 'address' });</code></pre>
-			Following mutations <b>will</b> be delivered to the <code>callback</code>:
-<pre><code>o.address.street = {};
-o.address.city = 'DreamCity';</code></pre>
-			Following mutations <b>will not</b> be delivered to the <code>callback</code>:
-<pre><code>o.lastName = 'Joker';
-o.address = {};
-o.address.street.apt = 5;</code></pre>
-		</td>
-	</tr>
-</table>
-
-## __`path`__
-
-Value expected to be a non-empty string, representing a specific path to observe. Only a changes of this exact path will be notified.
-
-<table>
-	<tr>
-		<td width="50%">
-			<img src="./filter-graphs/filter-paths.svg"/>
-		</td>
-		<td>
-			Given, that we have subscribed for the changes via:
-<pre><code>Observable.observe(o, callback, { path: 'address.street' });</code></pre>
-			Following mutations <b>will</b> be delivered to the <code>callback</code>:
-<pre><code>o.address.street = {};</code></pre>
-			Following mutations <b>will not</b> be delivered to the <code>callback</code>:
-<pre><code>o.lastName = 'Joker';
-o.address = {};
-o.address.street.apt = 5;</code></pre>
-		</td>
-	</tr>
-</table>
\ No newline at end of file
diff --git a/docs/filters.md b/docs/filters.md
new file mode 100644
index 0000000..6561f32
--- /dev/null
+++ b/docs/filters.md
@@ -0,0 +1,67 @@
+# Filters
+
+`Observable.observe(...)` accepts an optional third argument — an options object. The only currently supported option is `filters`: a non-empty array of `Filter` instances. Changes that survive **all** filters (logical AND) are delivered to the observer.
+
+```javascript
+import { Observable, Filter } from '@gullerya/object-observer';
+
+Observable.observe(obs, callback, {
+    filters: [Filter.directChildrenOf('address'), Filter.pathsStartWith('address.city')]
+});
+```
+
+`Filter` instances are created via static factory methods only; the constructor is private.
+
+## Factory methods
+
+### `Filter.exactPaths(paths: string[]): Filter`
+
+Delivers only changes whose path (as a dotted string) is an exact match for one of the provided paths. `paths` MUST be a non-empty array.
+
+```javascript
+Filter.exactPaths(['firstName', 'address.city'])
+```
+
+### `Filter.pathsStartWith(prefix: string): Filter`
+
+Delivers changes whose path string starts with `prefix`. `prefix` MUST be a non-empty string.
+
+```javascript
+Filter.pathsStartWith('address')
+//  matches 'address', 'address.city', 'address.extra.data', ...
+```
+
+### `Filter.directChildrenOf(path: string): Filter`
+
+Delivers changes whose path is a **direct child** of `path` (exactly one level deeper). `path` MUST be a string (may be empty — empty string means the root). REVERSE and SHUFFLE changes at `path` itself are also delivered, because they are semantically mutations of the container's children.
+
+```javascript
+Filter.directChildrenOf('address')
+//  matches 'address.city', 'address.block'  — but NOT 'address' or 'address.extra.data'
+
+Filter.directChildrenOf('')
+//  matches any top-level property change
+```
+
+### `Filter.custom(fn: (changes: Change[]) => Change[]): Filter`
+
+Wraps an arbitrary function. `fn` receives the (already-narrowed) array of `Change` objects and returns a filtered array. `fn` MUST be a function.
+
+```javascript
+Filter.custom(changes => changes.filter(c => c.type === 'update'))
+```
+
+## Composition
+
+When multiple filters are provided, they run in order and each narrows the result of the previous one. Equivalent to logical AND:
+
+```javascript
+//  direct children of 'a' AND whose path starts with 'a.x'
+//  → only changes to 'a.x'
+{ filters: [Filter.directChildrenOf('a'), Filter.pathsStartWith('a.x')] }
+```
+
+## Validation
+
+- `filters` (when provided) MUST be a non-empty array.
+- Every element MUST be a `Filter` instance — bare functions are rejected. Use `Filter.custom(fn)` to wrap a function.
diff --git a/docs/observable.md b/docs/observable.md
index 24faac8..4078c79 100644
--- a/docs/observable.md
+++ b/docs/observable.md
@@ -86,15 +86,9 @@ Observable.unobserve(observableAddress);
 ```
 
 ## Observation options
-If/When provided, `options` parameter MUST contain ONLY one of the properties below, no 'unknown' properties allowed.
+If/When provided, `options` MUST be an object. Unknown properties are rejected — incorrect observation options throw, to fail fast.
 
-In order to fail-fast and prevent unexpected mess down the hill, incorrect observation options will throw.
-
-- __`path`__ - non-empty string; specific path to observe, only a changes of this exact path will be notified; [details here](filter-paths.md)
-
-- __`pathsOf`__ - string, MAY be empty; direct properties of the specified path will be notified; [details here](filter-paths.md)
-
-- __`pathsFrom`__ - non-empty string, any changes from the specified path and deeper will be delivered to the observer; [details here](filter-paths.md)
+- __`filters`__ - non-empty array of `Filter` instances; changes that survive **all** filters (logical AND) are delivered to the observer; [details here](filters.md)
 
 ## `Change` instance properties
 
diff --git a/package-lock.json b/package-lock.json
index 0286cfa..0b24b31 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -17,21 +17,13 @@
 			],
 			"license": "ISC",
 			"devDependencies": {
-				"@eslint/eslintrc": "^3.3.1",
 				"@eslint/js": "^9.39.1",
-				"@gullerya/just-test": "^4.0.12",
+				"@gullerya/just-test": "^4.0.17",
 				"esbuild": "^0.27.0",
 				"eslint": "^9.39.1",
-				"globals": "^16.5.0"
-			}
-		},
-		"node_modules/@aashutoshrathi/word-wrap": {
-			"version": "1.2.6",
-			"resolved": "https://registry.npmjs.org/@aashutoshrathi/word-wrap/-/word-wrap-1.2.6.tgz",
-			"integrity": "sha512-1Yjs2SvM8TflER/OD3cOjhWWOZb58A2t7wpE2S9XfBYTiIl+XFhQG2bjy4Pu1I+EAlCNUzRDYDdFwFYUKvXcIA==",
-			"dev": true,
-			"engines": {
-				"node": ">=0.10.0"
+				"globals": "^16.5.0",
+				"typescript": "^5.9.3",
+				"typescript-eslint": "^8.48.0"
 			}
 		},
 		"node_modules/@esbuild/aix-ppc64": {
@@ -509,9 +501,9 @@
 			}
 		},
 		"node_modules/@eslint-community/regexpp": {
-			"version": "4.12.1",
-			"resolved": "https://registry.npmjs.org/@eslint-community/regexpp/-/regexpp-4.12.1.tgz",
-			"integrity": "sha512-CCZCDJuduB9OUkFkY2IgppNZMi2lBQgD2qzwXkEia16cge2pijY/aXi96CJMquDMn3nJdlPV1A5KrJEXwfLNzQ==",
+			"version": "4.12.2",
+			"resolved": "https://registry.npmjs.org/@eslint-community/regexpp/-/regexpp-4.12.2.tgz",
+			"integrity": "sha512-EriSTlt5OC9/7SXkRSCAhfSxxoSUgBm33OH+IkwbdpgoqsSsUg7y3uh+IICI/Qg4BBWr3U2i39RpmycbxMq4ew==",
 			"dev": true,
 			"license": "MIT",
 			"engines": {
@@ -533,17 +525,6 @@
 				"node": "^18.18.0 || ^20.9.0 || >=21.1.0"
 			}
 		},
-		"node_modules/@eslint/config-array/node_modules/brace-expansion": {
-			"version": "1.1.12",
-			"resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.12.tgz",
-			"integrity": "sha512-9T9UjW3r0UW5c1Q7GTwllptXwhvYmEzFhzMfZ9H7FQWt+uZePjZPjBP/W1ZEyZ1twGWom5/56TF4lPcqjnDHcg==",
-			"dev": true,
-			"license": "MIT",
-			"dependencies": {
-				"balanced-match": "^1.0.0",
-				"concat-map": "0.0.1"
-			}
-		},
 		"node_modules/@eslint/config-array/node_modules/minimatch": {
 			"version": "3.1.2",
 			"resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.1.2.tgz",
@@ -607,17 +588,6 @@
 				"url": "https://opencollective.com/eslint"
 			}
 		},
-		"node_modules/@eslint/eslintrc/node_modules/brace-expansion": {
-			"version": "1.1.11",
-			"resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.11.tgz",
-			"integrity": "sha512-iCuPHDFgrHX7H2vEI/5xpz07zSHB00TpugqhmYtVmMO6518mCuRMoOYFldEBl0g187ufozdaHgWKcYFb61qGiA==",
-			"dev": true,
-			"license": "MIT",
-			"dependencies": {
-				"balanced-match": "^1.0.0",
-				"concat-map": "0.0.1"
-			}
-		},
 		"node_modules/@eslint/eslintrc/node_modules/globals": {
 			"version": "14.0.0",
 			"resolved": "https://registry.npmjs.org/globals/-/globals-14.0.0.tgz",
@@ -682,23 +652,39 @@
 			}
 		},
 		"node_modules/@gullerya/just-test": {
-			"version": "4.0.12",
-			"resolved": "https://registry.npmjs.org/@gullerya/just-test/-/just-test-4.0.12.tgz",
-			"integrity": "sha512-jyTaatrblzhpySRaT6AT/ihxux3+np20YmLPIwsG2USJ/3MpbHSLOqxvUy0Yk8+GHktqr1ENL4PE+fvX1TvNCA==",
+			"version": "4.0.17",
+			"resolved": "https://registry.npmjs.org/@gullerya/just-test/-/just-test-4.0.17.tgz",
+			"integrity": "sha512-L9naPalogYi0aEQIodeSXuN/p+MGDd0z1WN89oVYdkJrquw2Sjfk14MXtSuNBz7FUvHw8Qwm1RdTi8keQNbyfg==",
 			"dev": true,
 			"license": "MIT",
 			"dependencies": {
 				"data-tier": "^3.6.6",
 				"data-tier-list": "^2.2.1",
-				"glob": "^11.0.3",
+				"glob": "^12.0.0",
 				"minimatch": "^10.1.1",
 				"playwright": "^1.56.1",
-				"rich-component": "^1.8.0"
+				"rich-component": "^1.8.0",
+				"typescript": "^5.9.3"
 			},
 			"funding": {
 				"url": "https://paypal.me/gullerya?locale.x=en_US"
 			}
 		},
+		"node_modules/@gullerya/object-observer": {
+			"version": "6.1.4",
+			"resolved": "https://registry.npmjs.org/@gullerya/object-observer/-/object-observer-6.1.4.tgz",
+			"integrity": "sha512-taINf8vEnq6iwXpX/tuOcXpT+3Y3H3Hqi9mH5v+DL/D52wYP8lc3OXgpxO8hb+UXwChEUw8n9Nz3Q/htRYl7Gg==",
+			"dev": true,
+			"funding": [
+				{
+					"url": "https://paypal.me/gullerya?locale.x=en_US"
+				},
+				{
+					"url": "https://tidelift.com/funding/github/npm/object-observer"
+				}
+			],
+			"license": "ISC"
+		},
 		"node_modules/@humanfs/core": {
 			"version": "0.19.1",
 			"resolved": "https://registry.npmjs.org/@humanfs/core/-/core-0.19.1.tgz",
@@ -710,38 +696,25 @@
 			}
 		},
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 		"node_modules/type-check": {
 			"version": "0.4.0",
 			"resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
 			"integrity": "sha512-XleUoc9uwGXqjWwXaUTZAmzMcFZ5858QA2vvx1Ur5xIcixXIP+8LnFDgRplU30us6teqdlskFfu+ae4K79Ooew==",
 			"dev": true,
+			"license": "MIT",
 			"dependencies": {
 				"prelude-ls": "^1.2.1"
 			},
@@ -2008,6 +2341,45 @@
 				"node": ">= 0.8.0"
 			}
 		},
+		"node_modules/typescript": {
+			"version": "5.9.3",
+			"resolved": "https://registry.npmjs.org/typescript/-/typescript-5.9.3.tgz",
+			"integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
+			"dev": true,
+			"license": "Apache-2.0",
+			"peer": true,
+			"bin": {
+				"tsc": "bin/tsc",
+				"tsserver": "bin/tsserver"
+			},
+			"engines": {
+				"node": ">=14.17"
+			}
+		},
+		"node_modules/typescript-eslint": {
+			"version": "8.48.0",
+			"resolved": "https://registry.npmjs.org/typescript-eslint/-/typescript-eslint-8.48.0.tgz",
+			"integrity": "sha512-fcKOvQD9GUn3Xw63EgiDqhvWJ5jsyZUaekl3KVpGsDJnN46WJTe3jWxtQP9lMZm1LJNkFLlTaWAxK2vUQR+cqw==",
+			"dev": true,
+			"license": "MIT",
+			"dependencies": {
+				"@typescript-eslint/eslint-plugin": "8.48.0",
+				"@typescript-eslint/parser": "8.48.0",
+				"@typescript-eslint/typescript-estree": "8.48.0",
+				"@typescript-eslint/utils": "8.48.0"
+			},
+			"engines": {
+				"node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+			},
+			"funding": {
+				"type": "opencollective",
+				"url": "https://opencollective.com/typescript-eslint"
+			},
+			"peerDependencies": {
+				"eslint": "^8.57.0 || ^9.0.0",
+				"typescript": ">=4.8.4 <6.0.0"
+			}
+		},
 		"node_modules/uri-js": {
 			"version": "4.4.1",
 			"resolved": "https://registry.npmjs.org/uri-js/-/uri-js-4.4.1.tgz",
@@ -2034,6 +2406,16 @@
 				"node": ">= 8"
 			}
 		},
+		"node_modules/word-wrap": {
+			"version": "1.2.5",
+			"resolved": "https://registry.npmjs.org/word-wrap/-/word-wrap-1.2.5.tgz",
+			"integrity": "sha512-BN22B5eaMMI9UMtjrGd5g5eCYPpCPDUy0FJXbYsaT5zYxjFOckS53SQDE3pWkVoWpHXVb3BrYcEN4Twa55B5cA==",
+			"dev": true,
+			"license": "MIT",
+			"engines": {
+				"node": ">=0.10.0"
+			}
+		},
 		"node_modules/wrap-ansi": {
 			"version": "8.1.0",
 			"resolved": "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-8.1.0.tgz",
@@ -2134,6 +2516,7 @@
 			"resolved": "https://registry.npmjs.org/yocto-queue/-/yocto-queue-0.1.0.tgz",
 			"integrity": "sha512-rVksvsnNCdJ/ohGc6xgPwyN8eheCxsiLM8mxuE/t/mOVqJewPuO1miLpTHQiRgTKCLexL4MeAFVagts7HmNZ2Q==",
 			"dev": true,
+			"license": "MIT",
 			"engines": {
 				"node": ">=10"
 			},
diff --git a/package.json b/package.json
index fd69d20..55d00e5 100644
--- a/package.json
+++ b/package.json
@@ -61,22 +61,24 @@
 	],
 	"scripts": {
 		"build": "node ./ci/tools/build-utils.js",
-		"lint": "eslint -c ./ci/eslint.config.mjs ./src/*.js ./tests/*.js ./ci/**/*.js",
-		"test": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-node.json",
-		"test:chromium": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-chromium.json",
-		"test:firefox": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-firefox.json",
-		"test:webkit": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-webkit.json",
-		"test:nodejs": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-node.json",
+		"lint": "eslint -c ./ci/eslint.config.mjs ./src/* ./tests/*.js ./ci/**/*.js",
+		"test-types": "tsc",
+		"test": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-node.js",
+		"test:chromium": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-chromium.js",
+		"test:firefox": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-firefox.js",
+		"test:webkit": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-webkit.js",
+		"test:nodejs": "node node_modules/@gullerya/just-test/bin/local-runner.js config_file=./tests/configs/tests-config-ci-node.js",
 		"version": "npm run build && git add --all",
 		"postversion": "git push && git push --tags"
 	},
 	"devDependencies": {
-		"@eslint/eslintrc": "^3.3.1",
 		"@eslint/js": "^9.39.1",
-		"@gullerya/just-test": "^4.0.12",
+		"@gullerya/just-test": "^4.0.17",
 		"esbuild": "^0.27.0",
 		"eslint": "^9.39.1",
-		"globals": "^16.5.0"
+		"globals": "^16.5.0",
+		"typescript": "^5.9.3",
+		"typescript-eslint": "^8.48.0"
 	},
 	"publishConfig": {
 		"access": "public"
diff --git a/readme.md b/readme.md
index 0bf08a5..1602404 100644
--- a/readme.md
+++ b/readme.md
@@ -14,26 +14,29 @@ Main aspects and features:
 - observation is 'deep', yielding changes from a __sub-graphs__ too
 - nested objects of the observable graph are observables too
 - changes delivered in a __synchronous__ way by default, __asynchronous__ delivery is optionally available as per `Observable` configuration; [more details here](docs/sync-async.md)
-- observed path may optionally be filtered as per `observer` configuration; [more details here](docs/filter-paths.md)
+- observed changes may optionally be filtered via the `Filter` class; [more details here](docs/filters.md)
 - original objects are __cloned__ while turned into `Observable`s
   - circular references are nullified in the clone
+- observed mutations on plain objects:
+  - property assignment (`obj.x = v`, `obj['x'] = v`)
+  - property deletion (`delete obj.x`)
 - __array__ specifics:
-  - generic object-like mutations supported
-  - intrinsic `Array` mutation methods supported: `pop`, `push`, `shift`, `unshift`, `reverse`, `sort`, `fill`, `splice`, `copyWithin`
-  - massive mutations delivered in a single callback, usually having an array of an atomic changes
+  - indexed assignment (`arr[i] = v`), `length` assignment, and `delete arr[i]` are observed (same traps as for plain objects)
+  - intrinsic `Array` mutation methods observed: `pop`, `push`, `shift`, `unshift`, `reverse`, `sort`, `fill`, `splice`, `copyWithin`
+  - massive mutations delivered in a single callback, usually as an array of atomic changes
 - __typed array__ specifics:
-  - generic object-like mutations supported
-  - intrinsic `TypedArray` mutation methods supported: `reverse`, `sort`, `fill`, `set`, `copyWithin`
-  - massive mutations delivered in a single callback, usually having an array of an atomic changes
+  - indexed assignment (`ta[i] = v`) is observed (same trap as for plain objects); `length` is fixed
+  - intrinsic `TypedArray` mutation methods observed: `reverse`, `sort`, `fill`, `set`, `copyWithin`
+  - massive mutations delivered in a single callback, usually as an array of atomic changes
 - intrinsic mutation methods of `Map`, `WeakMap`, `Set`, `WeakSet` (`set`, `delete`) etc __are not__ observed (see this [issue](https://github.com/gullerya/object-observer/issues/1) for more details)
 - following host objects (and their extensions) are __skipped__ from cloning / turning into observables: `Date`
 
 Supported:
-![CHROME](docs/browser-icons/chrome.png)<sub>71+</sub> |
-![FIREFOX](docs/browser-icons/firefox.png)<sub>65+</sub> |
-![EDGE](docs/browser-icons/edge-chromium.png)<sub>79+</sub> |
-![SAFARI](docs/browser-icons/safari-ios.png)<sub>12.1</sub> |
-![NODE JS](docs/browser-icons/nodejs.png) <sub>12.0.0+</sub>
+![CHROME](docs/browser-icons/chrome.png)<sub>last 2 versions</sub> |
+![FIREFOX](docs/browser-icons/firefox.png)<sub>last 2 versions</sub> |
+![EDGE](docs/browser-icons/edge-chromium.png)<sub>last 2 versions</sub> |
+![SAFARI](docs/browser-icons/safari-ios.png)<sub>last 2 versions</sub> |
+![NODE JS](docs/browser-icons/nodejs.png) <sub>24.15.0+</sub>
 
 Performance report can be found [here](docs/performance-report.md).
 
@@ -210,11 +213,13 @@ In cases of massive changes touching presumably the whole array I took a pessimi
 
 ##### Observation options
 
-`object-observer` allows to filter the events delivered to each callback/listener by an optional configuration object passed to the `observe` API.
+`object-observer` allows to filter the events delivered to each callback/listener via an optional `filters` array — each element MUST be a `Filter` instance. Multiple filters compose as logical AND (each filter narrows the result).
 
 > In the examples below assume that `callback = changes => {...}`.
 
 ```javascript
+import { Observable, Filter } from '@gullerya/object-observer';
+
 let user = {
         firstName: 'Aya',
         lastName: 'Guller',
@@ -229,29 +234,40 @@ let user = {
     },
     oUser = Observable.from(user);
 
-//  path
+//  exact paths
 //
-//  going to observe ONLY the changes of 'firstName'
-Observable.observe(oUser, callback, {path: 'firstName'});
+//  going to observe ONLY the changes of 'firstName' or 'address.city'
+Observable.observe(oUser, callback, { filters: [Filter.exactPaths(['firstName', 'address.city'])] });
 
-//  going to observe ONLY the changes of 'address.city'
-Observable.observe(oUser, callback, {path: 'address.city'});
+//  direct children of 'address' (city, street, block, extra) — and REVERSE/SHUFFLE at 'address'
+Observable.observe(oUser, callback, { filters: [Filter.directChildrenOf('address')] });
 
-//  pathsOf
-//
-//  going to observe the changes of 'address' own properties ('city', 'block') but not else
-Observable.observe(oUser, callback, {pathsOf: 'address'});
-//  here we'll be notified on changes of
-//    address.city
-//    address.extra
+//  all changes from 'address' and deeper
+Observable.observe(oUser, callback, { filters: [Filter.pathsStartWith('address')] });
 
-//  pathsFrom
-//
-//  going to observe the changes from 'address' and deeper
-Observable.observe(oUser, callback, {pathsFrom: 'address'});
-//  here we'll be notified on changes of
-//    address
-//    address.city
-//    address.extra
-//    address.extra.data
+//  custom predicate
+Observable.observe(oUser, callback, { filters: [Filter.custom(cs => cs.filter(c => c.type === 'update'))] });
+```
+
+##### Validators
+
+`object-observer` allows to veto mutations before they are applied via an optional `validators` array supplied to `Observable.from`. Each element MUST be a `Validator` instance. Validators are attached at tree creation — they apply to the whole observable graph, not per observer.
+
+A validator receives the prospective `Change[]` (with rooted paths and the raw, un-observified new value) BEFORE the underlying target is mutated. Throwing from a validator aborts the mutation: the target is left unchanged and observers are not invoked. Multiple validators compose as logical AND with short-circuit — the first throw stops the chain.
+
+```javascript
+import { Observable, Validator } from '@gullerya/object-observer';
+
+const immutableMarker = Validator.custom(changes => {
+    for (const c of changes) {
+        if (c.oldValue === 'immutable') {
+            throw new Error(`change at '${c.pathAsString}' rejected: oldValue is immutable`);
+        }
+    }
+});
+
+const oo = Observable.from({ a: 'immutable' }, { validators: [immutableMarker] });
+oo.a = 'other';    //  throws; oo.a still === 'immutable'; no observer fired
 ```
+
+> Not yet supported: validators do not currently run for `Array.prototype.splice`, `Array.prototype.fill`, and `Array.prototype.copyWithin` (and their `TypedArray` counterparts where applicable). These mutations proceed as before without validator consultation. Support is planned for a subsequent release.
diff --git a/src/changes-processors/filters.ts b/src/changes-processors/filters.ts
new file mode 100644
index 0000000..38052eb
--- /dev/null
+++ b/src/changes-processors/filters.ts
@@ -0,0 +1,77 @@
+import { Change } from '../model/change.ts';
+import { REVERSE, SHUFFLE } from '../constants.ts';
+
+export type FilterFn = (changes: Change[]) => Change[];
+
+export class Filter {
+	static #privateCtorKey = Symbol('FilterPrivateConstructorKey');
+	#fn: FilterFn;
+
+	constructor(privateCtorKey, fn: FilterFn) {
+		if (privateCtorKey !== Filter.#privateCtorKey) {
+			throw new Error('Filter class cannot be instantiated directly; use provided factory methods');
+		}
+
+		this.#fn = fn;
+	}
+
+	get fn(): FilterFn { return this.#fn; }
+
+	static custom(fn: FilterFn): Filter {
+		if (typeof fn !== 'function') {
+			throw new Error('custom Filter requires a function as argument');
+		}
+		return new Filter(Filter.#privateCtorKey, fn);
+	}
+
+	static exactPaths(paths: string[]): Filter {
+		if (!Array.isArray(paths) || paths.length === 0) {
+			throw new Error('exactPaths Filter requires a non-empty array as argument');
+		}
+		const pathsSet = new Set(paths);
+		return new Filter(
+			Filter.#privateCtorKey,
+			changes => changes.filter(change => pathsSet.has(change.pathAsString))
+		);
+	}
+
+	static pathsStartWith(prefix: string): Filter {
+		if (typeof prefix !== 'string' || prefix === '') {
+			throw new Error('pathsStartWith Filter requires a non-empty string as argument');
+		}
+		return new Filter(
+			Filter.#privateCtorKey,
+			changes => changes.filter(change => change.pathAsString.startsWith(prefix))
+		);
+	}
+
+	//	direct children of the given path; an empty string represents the root.
+	//	REVERSE/SHUFFLE happening at the path itself are also included
+	//	(they are semantically mutations of the container's direct children).
+	static directChildrenOf(path: string): Filter {
+		if (typeof path !== 'string') {
+			throw new Error('directChildrenOf Filter requires a string as argument (MAY be empty)');
+		}
+		const segments = path.split('.').filter(Boolean);
+		const depth = segments.length;
+		const prefix = segments.join('.');
+		//	at depth N, a direct-child path is the first N segments of change.path
+		return new Filter(
+			Filter.#privateCtorKey,
+			changes => changes.filter(change => {
+				const cp = change.path;
+				const pl = cp.length;
+				if (pl === depth + 1) {
+					for (let i = 0; i < depth; i++) {
+						if (cp[i] !== segments[i]) { return false; }
+					}
+					return true;
+				}
+				if (pl === depth && (change.type === REVERSE || change.type === SHUFFLE)) {
+					return change.pathAsString === prefix;
+				}
+				return false;
+			})
+		);
+	}
+}
\ No newline at end of file
diff --git a/src/changes-processors/validators.ts b/src/changes-processors/validators.ts
new file mode 100644
index 0000000..1de0704
--- /dev/null
+++ b/src/changes-processors/validators.ts
@@ -0,0 +1,26 @@
+import { Change } from '../model/change.ts';
+
+export type ValidatorFn = (changes: Change[]) => void;
+
+export class Validator {
+	static #privateCtorKey = Symbol('ValidatorPrivateConstructorKey');
+
+	#validate: ValidatorFn;
+
+	constructor(privateCtorKey, fn: ValidatorFn) {
+		if (privateCtorKey !== Validator.#privateCtorKey) {
+			throw new Error('Validator class cannot be instantiated directly; use provided factory methods');
+		}
+
+		this.#validate = fn;
+	}
+
+	get validate(): ValidatorFn { return this.#validate; }
+
+	static custom(fn: ValidatorFn): Validator {
+		if (typeof fn !== 'function') {
+			throw new Error('custom Validator requires a function as argument');
+		}
+		return new Validator(Validator.#privateCtorKey, fn);
+	}
+}
diff --git a/src/constants.ts b/src/constants.ts
new file mode 100644
index 0000000..d5572f9
--- /dev/null
+++ b/src/constants.ts
@@ -0,0 +1,6 @@
+export const oMetaKey = Symbol.for('object-observer-meta-key-0');
+export const INSERT = 'insert';
+export const UPDATE = 'update';
+export const DELETE = 'delete';
+export const REVERSE = 'reverse';
+export const SHUFFLE = 'shuffle';
\ No newline at end of file
diff --git a/src/model/change.ts b/src/model/change.ts
new file mode 100644
index 0000000..7552cb5
--- /dev/null
+++ b/src/model/change.ts
@@ -0,0 +1,47 @@
+export class Change {
+    #type: string;
+    #path: Array<string | symbol | number>;
+    #value: unknown;
+    #oldValue: unknown;
+    #object: object;
+
+    #pathAsString: string;
+
+    constructor(type: string, path: Array<string | symbol | number>, value: unknown, oldValue: unknown, object: object) {
+        this.#type = type;
+        this.#path = path;
+        this.#value = value;
+        this.#oldValue = oldValue;
+        this.#object = object;
+    }
+
+    get type() {
+        return this.#type;
+    }
+
+    get path() {
+        return this.#path;
+    }
+
+    get value() {
+        return this.#value;
+    }
+
+    get oldValue() {
+        return this.#oldValue;
+    }
+
+    get object() {
+        return this.#object;
+    }
+
+    /**
+     * lazily computed string representation of the path
+     */
+    get pathAsString(): string {
+        if (this.#pathAsString === undefined) {
+            this.#pathAsString = this.#path.join('.');
+        }
+        return this.#pathAsString;
+    }
+}
\ No newline at end of file
diff --git a/src/object-observer.d.ts b/src/object-observer.d.ts
deleted file mode 100644
index fb7d010..0000000
--- a/src/object-observer.d.ts
+++ /dev/null
@@ -1,97 +0,0 @@
-export type ChangeType = 'insert' | 'update' | 'delete' | 'reverse' | 'shuffle';
-
-/**
- * `Observable` allows to observe any (deep) changes on its underlying object graph
- * 
- * - created by `from` static method, via cloning the target
- * - important: the type `T` is not preserved, beside its shape
- */
-export abstract class Observable {
-
-	/**
-	 * create Observable from the target
-	 * - target is cloned, remaining unchanged in itself
-	 * - important: the type `T` is NOT preserved, beside its shape
-	 *
-	 * @param target source, to create `Observable` from
-	 * @param options observable options
-	 */
-	static from<T>(target: T, options?: ObservableOptions): Observable & T;
-
-	/**
-	 * check input for being `Observable`
-	 * 
-	 * @param input any object to be checked as `Observable`
-	 */
-	static isObservable(input: unknown): boolean;
-
-	/**
-	 * add observer to handle the observable's changes
-	 * 
-	 * @param observable observable to set observer on
-	 * @param observer observer function / logic
-	 * @param options observation options
-	 */
-	static observe(observable: Observable, observer: Observer, options?: ObserverOptions): void;
-
-	/**
-	 * remove observer/s from observable
-	 * 
-	 * @param observable observable to remove observer/s from
-	 * @param observers 0 to many observers to remove; if none supplied, ALL observers will be removed
-	 */
-	static unobserve(observable: Observable, ...observers: Observer[]): void;
-}
-
-export interface ObservableOptions {
-	async: boolean;
-}
-
-export interface Observer {
-	(changes: Change[]): void;
-}
-
-export interface ObserverOptions {
-	path?: string,
-	pathsOf?: string,
-	pathsFrom?: string
-}
-
-export interface Change {
-	type: ChangeType;
-	path: string[];
-	value?: any;
-	oldValue?: any;
-	object: object;
-}
-
-/**
- * `ObjectObserver` provides observation functionality in a WebAPI-like flavor
- * - `observer` created first, with the provided observer function
- * - `observer` may then be used to observe different targets
- */
-export class ObjectObserver {
-
-	/**
-	 * sets up observer function and options
-	 * @param observer observation logic (function)
-	 * @param options  `ObservableOptions` will be applied to any `Observable` down the road
-	 */
-	constructor(observer: Observer, options?: ObservableOptions);
-
-	/**
-	 * create `Observable` from the target and starts observation
-	 * - important: the type `T` is NOT preserved, beside its shape
-	 * @param target  target to be observed, turned into `Observable` via cloning
-	 * @param options `ObserverOptions` options
-	 */
-	observe<T>(target: T, options?: ObserverOptions): Observable & T;
-
-	/**
-	 * un-observes the `Observable`, returning the original undelying plain object
-	 * @param target target to be un-observed
-	 */
-	unobserve(target: Observable): void;
-
-	disconnect(): void;
-}
diff --git a/src/object-observer.js b/src/object-observer.js
deleted file mode 100644
index b4c9221..0000000
--- a/src/object-observer.js
+++ /dev/null
@@ -1,713 +0,0 @@
-export { Observable, ObjectObserver };
-
-const
-	INSERT = 'insert',
-	UPDATE = 'update',
-	DELETE = 'delete',
-	REVERSE = 'reverse',
-	SHUFFLE = 'shuffle',
-	oMetaKey = Symbol.for('object-observer-meta-key-0'),
-	validObservableOptionKeys = { async: 1 },
-	processObserveOptions = options => {
-		if (!options || typeof options !== 'object') {
-			return null;
-		}
-
-		const result = {};
-		const invalidOptions = [];
-		for (const [optName, optVal] of Object.entries(options)) {
-			if (optName === 'path') {
-				if (typeof optVal !== 'string' || optVal === '') {
-					throw new Error('"path" option, if/when provided, MUST be a non-empty string');
-				}
-				result[optName] = optVal;
-			} else if (optName === 'pathsOf') {
-				if (options.path) {
-					throw new Error('"pathsOf" option MAY NOT be specified together with "path" option');
-				}
-				if (typeof optVal !== 'string') {
-					throw new Error('"pathsOf" option, if/when provided, MUST be a string (MAY be empty)');
-				}
-				result[optName] = options.pathsOf.split('.').filter(Boolean);
-			} else if (optName === 'pathsFrom') {
-				if (options.path || options.pathsOf) {
-					throw new Error('"pathsFrom" option MAY NOT be specified together with "path"/"pathsOf" option/s');
-				}
-				if (typeof optVal !== 'string' || optVal === '') {
-					throw new Error('"pathsFrom" option, if/when provided, MUST be a non-empty string');
-				}
-				result[optName] = optVal;
-			} else {
-				invalidOptions.push(optName);
-			}
-		}
-		if (invalidOptions.length) {
-			throw new Error(`'${invalidOptions.join(', ')}' is/are not a valid observer option/s`);
-		}
-		return result;
-	},
-	prepareObject = (source, oMeta, visited) => {
-		const target = {};
-		target[oMetaKey] = oMeta;
-		for (const key in source) {
-			target[key] = getObservedOf(source[key], key, oMeta, visited);
-		}
-		return target;
-	},
-	prepareArray = (source, oMeta, visited) => {
-		let l = source.length;
-		const target = new Array(l);
-		target[oMetaKey] = oMeta;
-		for (let i = 0; i < l; i++) {
-			target[i] = getObservedOf(source[i], i, oMeta, visited);
-		}
-		return target;
-	},
-	prepareTypedArray = (source, oMeta) => {
-		source[oMetaKey] = oMeta;
-		return source;
-	},
-	filterChanges = (options, changes) => {
-		if (options === null) {
-			return changes;
-		}
-
-		let result = changes;
-		if (options.path) {
-			const oPath = options.path;
-			result = changes.filter(change =>
-				change.path.join('.') === oPath
-			);
-		} else if (options.pathsOf) {
-			const oPathsOf = options.pathsOf;
-			const oPathsOfStr = oPathsOf.join('.');
-			result = changes.filter(change =>
-				(change.path.length === oPathsOf.length + 1 ||
-					(change.path.length === oPathsOf.length && (change.type === REVERSE || change.type === SHUFFLE))) &&
-				change.path.join('.').startsWith(oPathsOfStr)
-			);
-		} else if (options.pathsFrom) {
-			const oPathsFrom = options.pathsFrom;
-			result = changes.filter(change =>
-				change.path.join('.').startsWith(oPathsFrom)
-			);
-		}
-		return result;
-	},
-	callObserverSafe = (listener, changes) => {
-		try {
-			listener(changes);
-		} catch (e) {
-			console.error(`failed to notify listener ${listener} with ${changes}`, e);
-		}
-	},
-	callObserversFromMT = function callObserversFromMT() {
-		const batches = this.batches;
-		this.batches = [];
-		for (const [listener, changes] of batches) {
-			callObserverSafe(listener, changes);
-		}
-	},
-	callObservers = (oMeta, changes) => {
-		let currentObservable = oMeta;
-		let isAsync, observers, target, options, relevantChanges, i;
-		const l = changes.length;
-		do {
-			isAsync = currentObservable.options.async;
-			observers = currentObservable.observers;
-			i = observers.length;
-			while (i--) {
-				[target, options] = observers[i];
-				relevantChanges = filterChanges(options, changes);
-
-				if (relevantChanges.length) {
-					if (isAsync) {
-						//	this is the async dispatch handling
-						if (currentObservable.batches.length === 0) {
-							queueMicrotask(callObserversFromMT.bind(currentObservable));
-						}
-						let rb;
-						for (const b of currentObservable.batches) {
-							if (b[0] === target) {
-								rb = b;
-								break;
-							}
-						}
-						if (!rb) {
-							rb = [target, []];
-							currentObservable.batches.push(rb);
-						}
-						Array.prototype.push.apply(rb[1], relevantChanges);
-					} else {
-						//	this is the naive straight forward synchronous dispatch
-						callObserverSafe(target, relevantChanges);
-					}
-				}
-			}
-
-			//	cloning all the changes and notifying in context of parent
-			const parent = currentObservable.parent;
-			if (parent) {
-				for (let j = 0; j < l; j++) {
-					const change = changes[j];
-					changes[j] = new Change(
-						change.type,
-						[currentObservable.ownKey, ...change.path],
-						change.value,
-						change.oldValue,
-						change.object
-					);
-				}
-				currentObservable = parent;
-			} else {
-				currentObservable = null;
-			}
-		} while (currentObservable);
-	},
-	getObservedOf = (item, key, parent, visited) => {
-		if (visited !== undefined && visited.has(item)) {
-			return null;
-		} else if (typeof item !== 'object' || item === null) {
-			return item;
-		} else if (Array.isArray(item)) {
-			return new ArrayOMeta({ target: item, ownKey: key, parent: parent, visited }).proxy;
-		} else if (ArrayBuffer.isView(item)) {
-			return new TypedArrayOMeta({ target: item, ownKey: key, parent: parent }).proxy;
-		} else if (item instanceof Date) {
-			return item;
-		} else {
-			return new ObjectOMeta({ target: item, ownKey: key, parent: parent, visited }).proxy;
-		}
-	},
-	proxiedPop = function proxiedPop() {
-		const oMeta = this[oMetaKey],
-			target = oMeta.target,
-			poppedIndex = target.length - 1;
-
-		let popResult = target.pop();
-		if (popResult && typeof popResult === 'object') {
-			const tmpObserved = popResult[oMetaKey];
-			if (tmpObserved) {
-				popResult = tmpObserved.detach();
-			}
-		}
-
-		const changes = [new Change(DELETE, [poppedIndex], undefined, popResult, this)];
-		callObservers(oMeta, changes);
-
-		return popResult;
-	},
-	proxiedPush = function proxiedPush() {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			l = arguments.length,
-			pushContent = new Array(l),
-			initialLength = target.length;
-
-		for (let i = 0; i < l; i++) {
-			pushContent[i] = getObservedOf(arguments[i], initialLength + i, oMeta);
-		}
-		const pushResult = Reflect.apply(target.push, target, pushContent);
-
-		const changes = [];
-		for (let i = initialLength, j = target.length; i < j; i++) {
-			changes[i - initialLength] = new Change(INSERT, [i], target[i], undefined, this);
-		}
-		callObservers(oMeta, changes);
-
-		return pushResult;
-	},
-	proxiedShift = function proxiedShift() {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target;
-		let shiftResult, i, l, item, tmpObserved;
-
-		shiftResult = target.shift();
-		if (shiftResult && typeof shiftResult === 'object') {
-			tmpObserved = shiftResult[oMetaKey];
-			if (tmpObserved) {
-				shiftResult = tmpObserved.detach();
-			}
-		}
-
-		//	update indices of the remaining items
-		for (i = 0, l = target.length; i < l; i++) {
-			item = target[i];
-			if (item && typeof item === 'object') {
-				tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					tmpObserved.ownKey = i;
-				}
-			}
-		}
-
-		const changes = [new Change(DELETE, [0], undefined, shiftResult, this)];
-		callObservers(oMeta, changes);
-
-		return shiftResult;
-	},
-	proxiedUnshift = function proxiedUnshift() {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			al = arguments.length,
-			unshiftContent = new Array(al);
-
-		for (let i = 0; i < al; i++) {
-			unshiftContent[i] = getObservedOf(arguments[i], i, oMeta);
-		}
-		const unshiftResult = Reflect.apply(target.unshift, target, unshiftContent);
-
-		for (let i = 0, l = target.length, item; i < l; i++) {
-			item = target[i];
-			if (item && typeof item === 'object') {
-				const tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					tmpObserved.ownKey = i;
-				}
-			}
-		}
-
-		//	publish changes
-		const l = unshiftContent.length;
-		const changes = new Array(l);
-		for (let i = 0; i < l; i++) {
-			changes[i] = new Change(INSERT, [i], target[i], undefined, this);
-		}
-		callObservers(oMeta, changes);
-
-		return unshiftResult;
-	},
-	proxiedReverse = function proxiedReverse() {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target;
-		let i, l, item;
-
-		target.reverse();
-		for (i = 0, l = target.length; i < l; i++) {
-			item = target[i];
-			if (item && typeof item === 'object') {
-				const tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					tmpObserved.ownKey = i;
-				}
-			}
-		}
-
-		const changes = [new Change(REVERSE, [], undefined, undefined, this)];
-		callObservers(oMeta, changes);
-
-		return this;
-	},
-	proxiedSort = function proxiedSort(comparator) {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target;
-		let i, l, item;
-
-		target.sort(comparator);
-		for (i = 0, l = target.length; i < l; i++) {
-			item = target[i];
-			if (item && typeof item === 'object') {
-				const tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					tmpObserved.ownKey = i;
-				}
-			}
-		}
-
-		const changes = [new Change(SHUFFLE, [], undefined, undefined, this)];
-		callObservers(oMeta, changes);
-
-		return this;
-	},
-	proxiedFill = function proxiedFill(filVal, start, end) {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			changes = [],
-			tarLen = target.length,
-			prev = target.slice(0);
-		start = start === undefined ? 0 : (start < 0 ? Math.max(tarLen + start, 0) : Math.min(start, tarLen));
-		end = end === undefined ? tarLen : (end < 0 ? Math.max(tarLen + end, 0) : Math.min(end, tarLen));
-
-		if (start < tarLen && end > start) {
-			target.fill(filVal, start, end);
-
-			let tmpObserved;
-			for (let i = start, item, tmpTarget; i < end; i++) {
-				item = target[i];
-				target[i] = getObservedOf(item, i, oMeta);
-				if (i in prev) {
-					tmpTarget = prev[i];
-					if (tmpTarget && typeof tmpTarget === 'object') {
-						tmpObserved = tmpTarget[oMetaKey];
-						if (tmpObserved) {
-							tmpTarget = tmpObserved.detach();
-						}
-					}
-
-					changes.push(new Change(UPDATE, [i], target[i], tmpTarget, this));
-				} else {
-					changes.push(new Change(INSERT, [i], target[i], undefined, this));
-				}
-			}
-
-			callObservers(oMeta, changes);
-		}
-
-		return this;
-	},
-	proxiedCopyWithin = function proxiedCopyWithin(dest, start, end) {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			tarLen = target.length;
-		dest = dest < 0 ? Math.max(tarLen + dest, 0) : dest;
-		start = start === undefined ? 0 : (start < 0 ? Math.max(tarLen + start, 0) : Math.min(start, tarLen));
-		end = end === undefined ? tarLen : (end < 0 ? Math.max(tarLen + end, 0) : Math.min(end, tarLen));
-		const len = Math.min(end - start, tarLen - dest);
-
-		if (dest < tarLen && dest !== start && len > 0) {
-			const
-				prev = target.slice(0),
-				changes = [];
-
-			target.copyWithin(dest, start, end);
-
-			for (let i = dest, nItem, oItem, tmpObserved; i < dest + len; i++) {
-				//	update newly placed observables, if any
-				nItem = target[i];
-				if (nItem && typeof nItem === 'object') {
-					nItem = getObservedOf(nItem, i, oMeta);
-					target[i] = nItem;
-				}
-
-				//	detach overridden observables, if any
-				oItem = prev[i];
-				if (oItem && typeof oItem === 'object') {
-					tmpObserved = oItem[oMetaKey];
-					if (tmpObserved) {
-						oItem = tmpObserved.detach();
-					}
-				}
-
-				if (typeof nItem !== 'object' && nItem === oItem) {
-					continue;
-				}
-				changes.push(new Change(UPDATE, [i], nItem, oItem, this));
-			}
-
-			callObservers(oMeta, changes);
-		}
-
-		return this;
-	},
-	proxiedSplice = function proxiedSplice() {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			splLen = arguments.length,
-			spliceContent = new Array(splLen),
-			tarLen = target.length;
-
-		//	observify the newcomers
-		for (let i = 0; i < splLen; i++) {
-			spliceContent[i] = getObservedOf(arguments[i], i, oMeta);
-		}
-
-		//	calculate pointers
-		const
-			startIndex = splLen === 0 ? 0 : (spliceContent[0] < 0 ? tarLen + spliceContent[0] : spliceContent[0]),
-			removed = splLen < 2 ? tarLen - startIndex : spliceContent[1],
-			inserted = Math.max(splLen - 2, 0),
-			spliceResult = Reflect.apply(target.splice, target, spliceContent),
-			newTarLen = target.length;
-
-		//	reindex the paths
-		let tmpObserved;
-		for (let i = 0, item; i < newTarLen; i++) {
-			item = target[i];
-			if (item && typeof item === 'object') {
-				tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					tmpObserved.ownKey = i;
-				}
-			}
-		}
-
-		//	detach removed objects
-		let i, l, item;
-		for (i = 0, l = spliceResult.length; i < l; i++) {
-			item = spliceResult[i];
-			if (item && typeof item === 'object') {
-				tmpObserved = item[oMetaKey];
-				if (tmpObserved) {
-					spliceResult[i] = tmpObserved.detach();
-				}
-			}
-		}
-
-		const changes = [];
-		let index;
-		for (index = 0; index < removed; index++) {
-			if (index < inserted) {
-				changes.push(new Change(UPDATE, [startIndex + index], target[startIndex + index], spliceResult[index], this));
-			} else {
-				changes.push(new Change(DELETE, [startIndex + index], undefined, spliceResult[index], this));
-			}
-		}
-		for (; index < inserted; index++) {
-			changes.push(new Change(INSERT, [startIndex + index], target[startIndex + index], undefined, this));
-		}
-		callObservers(oMeta, changes);
-
-		return spliceResult;
-	},
-	proxiedTypedArraySet = function proxiedTypedArraySet(source, offset) {
-		const
-			oMeta = this[oMetaKey],
-			target = oMeta.target,
-			souLen = source.length,
-			prev = target.slice(0);
-		offset = offset || 0;
-
-		target.set(source, offset);
-		const changes = new Array(souLen);
-		for (let i = offset; i < (souLen + offset); i++) {
-			changes[i - offset] = new Change(UPDATE, [i], target[i], prev[i], this);
-		}
-
-		callObservers(oMeta, changes);
-	},
-	proxiedArrayMethods = {
-		pop: proxiedPop,
-		push: proxiedPush,
-		shift: proxiedShift,
-		unshift: proxiedUnshift,
-		reverse: proxiedReverse,
-		sort: proxiedSort,
-		fill: proxiedFill,
-		copyWithin: proxiedCopyWithin,
-		splice: proxiedSplice
-	},
-	proxiedTypedArrayMethods = {
-		reverse: proxiedReverse,
-		sort: proxiedSort,
-		fill: proxiedFill,
-		copyWithin: proxiedCopyWithin,
-		set: proxiedTypedArraySet
-	};
-
-class Change {
-	constructor(type, path, value, oldValue, object) {
-		this.type = type;
-		this.path = path;
-		this.value = value;
-		this.oldValue = oldValue;
-		this.object = object;
-	}
-}
-
-class OMetaBase {
-	constructor(properties, cloningFunction) {
-		const { target, parent, ownKey, visited = new Set() } = properties;
-		if (parent && ownKey !== undefined) {
-			this.parent = parent;
-			this.ownKey = ownKey;
-		} else {
-			this.parent = null;
-			this.ownKey = null;
-		}
-		visited.add(target);
-		const targetClone = cloningFunction(target, this, visited);
-		visited.delete(target);
-		this.observers = [];
-		this.revocable = Proxy.revocable(targetClone, this);
-		this.proxy = this.revocable.proxy;
-		this.target = targetClone;
-		this.options = this.processOptions(properties.options);
-		if (this.options.async) {
-			this.batches = [];
-		}
-	}
-
-	processOptions(options) {
-		if (options) {
-			if (typeof options !== 'object') {
-				throw new Error(`Observable options if/when provided, MAY only be an object, got '${options}'`);
-			}
-			const invalidOptions = Object.keys(options).filter(option => !(option in validObservableOptionKeys));
-			if (invalidOptions.length) {
-				throw new Error(`'${invalidOptions.join(', ')}' is/are not a valid Observable option/s`);
-			}
-			return Object.assign({}, options);
-		} else {
-			return {};
-		}
-	}
-
-	detach() {
-		this.parent = null;
-		return this.target;
-	}
-
-	set(target, key, value) {
-		let oldValue = target[key];
-
-		if (value !== oldValue) {
-			const newValue = getObservedOf(value, key, this);
-			target[key] = newValue;
-
-			if (oldValue && typeof oldValue === 'object') {
-				const tmpObserved = oldValue[oMetaKey];
-				if (tmpObserved) {
-					oldValue = tmpObserved.detach();
-				}
-			}
-
-			const changes = oldValue === undefined
-				? [new Change(INSERT, [key], newValue, undefined, this.proxy)]
-				: [new Change(UPDATE, [key], newValue, oldValue, this.proxy)];
-			callObservers(this, changes);
-		}
-
-		return true;
-	}
-
-	deleteProperty(target, key) {
-		let oldValue = target[key];
-
-		delete target[key];
-
-		if (oldValue && typeof oldValue === 'object') {
-			const tmpObserved = oldValue[oMetaKey];
-			if (tmpObserved) {
-				oldValue = tmpObserved.detach();
-			}
-		}
-
-		const changes = [new Change(DELETE, [key], undefined, oldValue, this.proxy)];
-		callObservers(this, changes);
-
-		return true;
-	}
-}
-
-class ObjectOMeta extends OMetaBase {
-	constructor(properties) {
-		super(properties, prepareObject);
-	}
-}
-
-class ArrayOMeta extends OMetaBase {
-	constructor(properties) {
-		super(properties, prepareArray);
-	}
-
-	get(target, key) {
-		return proxiedArrayMethods[key] || target[key];
-	}
-}
-
-class TypedArrayOMeta extends OMetaBase {
-	constructor(properties) {
-		super(properties, prepareTypedArray);
-	}
-
-	get(target, key) {
-		return proxiedTypedArrayMethods[key] || target[key];
-	}
-}
-
-const Observable = Object.freeze({
-	from: (target, options) => {
-		if (!target || typeof target !== 'object') {
-			throw new Error('observable MAY ONLY be created from a non-null object');
-		} else if (target[oMetaKey]) {
-			return target;
-		} else if (Array.isArray(target)) {
-			return new ArrayOMeta({ target: target, ownKey: null, parent: null, options: options }).proxy;
-		} else if (ArrayBuffer.isView(target)) {
-			return new TypedArrayOMeta({ target: target, ownKey: null, parent: null, options: options }).proxy;
-		} else if (target instanceof Date) {
-			throw new Error(`${target} found to be one of a non-observable types`);
-		} else {
-			return new ObjectOMeta({ target: target, ownKey: null, parent: null, options: options }).proxy;
-		}
-	},
-	isObservable: input => {
-		return !!(input && input[oMetaKey]);
-	},
-	observe: (observable, observer, options) => {
-		if (!Observable.isObservable(observable)) {
-			throw new Error(`invalid observable parameter`);
-		}
-		if (typeof observer !== 'function') {
-			throw new Error(`observer MUST be a function, got '${observer}'`);
-		}
-
-		const observers = observable[oMetaKey].observers;
-		if (!observers.some(o => o[0] === observer)) {
-			observers.push([observer, processObserveOptions(options)]);
-		} else {
-			console.warn('observer may be bound to an observable only once; will NOT rebind');
-		}
-	},
-	unobserve: (observable, ...observers) => {
-		if (!Observable.isObservable(observable)) {
-			throw new Error(`invalid observable parameter`);
-		}
-
-		const existingObs = observable[oMetaKey].observers;
-		let el = existingObs.length;
-		if (!el) {
-			return;
-		}
-
-		if (!observers.length) {
-			existingObs.splice(0);
-			return;
-		}
-
-		while (el) {
-			let i = observers.indexOf(existingObs[--el][0]);
-			if (i >= 0) {
-				existingObs.splice(el, 1);
-			}
-		}
-	}
-});
-
-class ObjectObserver {
-	#observer;
-	#targets;
-
-	constructor(observer) {
-		this.#observer = observer;
-		this.#targets = new Set();
-		Object.freeze(this);
-	}
-
-	observe(target, options) {
-		const r = Observable.from(target);
-		Observable.observe(r, this.#observer, options);
-		this.#targets.add(r);
-		return r;
-	}
-
-	unobserve(target) {
-		Observable.unobserve(target, this.#observer);
-		this.#targets.delete(target);
-	}
-
-	disconnect() {
-		for (const t of this.#targets) {
-			Observable.unobserve(t, this.#observer);
-		}
-		this.#targets.clear();
-	}
-}
diff --git a/src/object-observer.ts b/src/object-observer.ts
new file mode 100644
index 0000000..4e7d4ae
--- /dev/null
+++ b/src/object-observer.ts
@@ -0,0 +1,113 @@
+import { oMetaKey } from './constants.ts';
+import { getObservableFromRoot } from './observables/processors/proc-utils.ts';
+import { Filter, type FilterFn } from './changes-processors/filters.ts';
+import { Validator } from './changes-processors/validators.ts';
+
+export { Filter, Validator };
+
+const
+	processObserveOptions = options => {
+		if (!options || typeof options !== 'object') {
+			return null;
+		}
+
+		const result: { filters?: FilterFn[] } = {};
+		const invalidOptions = [];
+		for (const [optName, optVal] of Object.entries(options)) {
+			if (optName === 'filters') {
+				if (!Array.isArray(optVal) || optVal.length === 0) {
+					throw new Error('"filters" option, if/when provided, MUST be a non-empty array of Filter instances');
+				}
+				const fns: FilterFn[] = new Array(optVal.length);
+				for (let i = 0; i < optVal.length; i++) {
+					const f = optVal[i];
+					if (!(f instanceof Filter)) {
+						throw new Error('"filters" option, if/when provided, MUST be a non-empty array of Filter instances');
+					}
+					fns[i] = f.fn;
+				}
+				result.filters = fns;
+			} else {
+				invalidOptions.push(optName);
+			}
+		}
+		if (invalidOptions.length) {
+			throw new Error(`'${invalidOptions.join(', ')}' is/are not a valid observer option/s`);
+		}
+		return Object.keys(result).length === 0 ? null : result;
+	};
+
+export const Observable = Object.freeze({
+	from: getObservableFromRoot,
+	isObservable: input => {
+		return !!(input && input[oMetaKey]);
+	},
+	observe: (observable, observer, options) => {
+		if (!Observable.isObservable(observable)) {
+			throw new Error(`invalid observable parameter`);
+		}
+		if (typeof observer !== 'function') {
+			throw new Error(`observer MUST be a function, got '${observer}'`);
+		}
+
+		const observers = observable[oMetaKey].observers;
+		if (!observers.some(o => o[0] === observer)) {
+			observers.push([observer, processObserveOptions(options)]);
+		} else {
+			console.warn('observer may be bound to an observable only once; will NOT rebind');
+		}
+	},
+	unobserve: (observable, ...observers) => {
+		if (!Observable.isObservable(observable)) {
+			throw new Error(`invalid observable parameter`);
+		}
+
+		const existingObs = observable[oMetaKey].observers;
+		let el = existingObs.length;
+		if (!el) {
+			return;
+		}
+
+		if (!observers.length) {
+			existingObs.splice(0);
+			return;
+		}
+
+		while (el) {
+			const i = observers.indexOf(existingObs[--el][0]);
+			if (i >= 0) {
+				existingObs.splice(el, 1);
+			}
+		}
+	}
+});
+
+export class ObjectObserver {
+	#observer;
+	#targets;
+
+	constructor(observer) {
+		this.#observer = observer;
+		this.#targets = new Set();
+		Object.freeze(this);
+	}
+
+	observe(target, options) {
+		const r = Observable.from(target);
+		Observable.observe(r, this.#observer, options);
+		this.#targets.add(r);
+		return r;
+	}
+
+	unobserve(target) {
+		Observable.unobserve(target, this.#observer);
+		this.#targets.delete(target);
+	}
+
+	disconnect() {
+		for (const t of this.#targets) {
+			Observable.unobserve(t, this.#observer);
+		}
+		this.#targets.clear();
+	}
+}
diff --git a/src/observables/abstract-base.ts b/src/observables/abstract-base.ts
new file mode 100644
index 0000000..cdd1db2
--- /dev/null
+++ b/src/observables/abstract-base.ts
@@ -0,0 +1,93 @@
+import { Change } from '../model/change.ts';
+import { Validator } from '../changes-processors/validators.ts';
+import { proxiedDeleteProperty } from './methods/delete-property.ts';
+import { proxiedSet } from './methods/set.ts';
+
+const validObservableOptionKeys = { async: 1, validators: 1 };
+
+export interface ObservableOptions {
+    async?: boolean;
+    validators?: Array<Validator>;
+}
+export type ChangesProcessor = (changes: Change[]) => void;
+
+export abstract class ObservableBase implements ProxyHandler<object> {
+    #parent: ObservableBase | null;
+    ownKey: string | null;
+    #target: object;
+    #proxy: unknown;
+    // eslint-disable-next-line no-unused-private-class-members
+    #revoke: () => void;
+    #async: boolean = false;
+    batches = new Map<ChangesProcessor, Change[]>();
+
+    set;
+    deleteProperty;
+
+    #validators: Array<Validator> = [];
+    #observers: Array<ChangesProcessor> = [];
+
+    constructor(properties) {
+        this.set = proxiedSet;
+        this.deleteProperty = proxiedDeleteProperty;
+
+        const { target, parent, ownKey, options, visited = new Set() } = properties;
+        if (parent && ownKey !== undefined) {
+            this.#parent = parent;
+            this.ownKey = ownKey;
+        } else {
+            this.#parent = null;
+            this.ownKey = null;
+        }
+        visited.add(target);
+        this.#target = this.observedGraphProcessor(target, this, visited);
+        visited.delete(target);
+
+        const revocableProxy = Proxy.revocable(this.#target, this);
+        this.#proxy = revocableProxy.proxy;
+        this.#revoke = revocableProxy.revoke;
+        this.#processOptions(options);
+    }
+
+    detach() {
+        this.#parent = null;
+        return this.#target;
+    }
+
+    get parent(): ObservableBase | null { return this.#parent; }
+    get target(): object { return this.#target; }
+    get proxy(): unknown { return this.#proxy; }
+    get async(): boolean { return this.#async; }
+    get validators(): Array<Validator> { return this.#validators; }
+    get observers(): Array<ChangesProcessor> { return this.#observers; }
+
+    abstract observedGraphProcessor(source: object, observableWrapper: ObservableBase, visited: Set<unknown>): object;
+
+    #processOptions(options: ObservableOptions | undefined): void {
+        if (!options) {
+            return;
+        }
+
+        if (typeof options !== 'object') {
+            throw new Error(`Observable options if/when provided, MAY only be an object, got '${options}'`);
+        }
+        const invalidOptions = Object.keys(options).filter(option => !(option in validObservableOptionKeys));
+        if (invalidOptions.length) {
+            throw new Error(`'${invalidOptions.join(', ')}' is/are not a valid Observable option/s`);
+        }
+
+        this.#async = Boolean(options.async);
+
+        if (options.validators !== undefined) {
+            if (!Array.isArray(options.validators) || options.validators.length === 0) {
+                throw new Error('"validators" option, if/when provided, MUST be a non-empty array of Validator instances');
+            }
+            for (const v of options.validators) {
+                if (!(v instanceof Validator)) {
+                    throw new Error('"validators" option, if/when provided, MUST be a non-empty array of Validator instances');
+                }
+            }
+            this.#validators.push(...options.validators);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/observables/array.ts b/src/observables/array.ts
new file mode 100644
index 0000000..fed46be
--- /dev/null
+++ b/src/observables/array.ts
@@ -0,0 +1,41 @@
+import { ObservableBase } from './abstract-base.ts';
+import { getObservedOf } from './processors/proc-utils.ts';
+import { oMetaKey } from '../constants.ts';
+import proxiedCopyWithin from './methods/copy-within.ts';
+import proxiedFill from './methods/fill.ts';
+import proxiedPop from './methods/pop.ts';
+import proxiedPush from './methods/push.ts';
+import proxiedReverse from './methods/reverse.ts';
+import proxiedShift from './methods/shift.ts';
+import proxiedSort from './methods/sort.ts';
+import proxiedSplice from './methods/splice.ts';
+import proxiedUnshift from './methods/unshift.ts';
+
+const proxiedArrayMethods = {
+    copyWithin: proxiedCopyWithin,
+    fill: proxiedFill,
+    pop: proxiedPop,
+    push: proxiedPush,
+    reverse: proxiedReverse,
+    shift: proxiedShift,
+    sort: proxiedSort,
+    splice: proxiedSplice,
+    unshift: proxiedUnshift
+};
+
+export class ObservableArray extends ObservableBase {
+
+    get(target: object, key: string): unknown {
+        return proxiedArrayMethods[key] || target[key];
+    }
+
+    observedGraphProcessor(source: Array<unknown>, observableWrapper: ObservableBase, visited: Set<unknown>): Array<unknown> {
+        const arrayLength = source.length;
+        const target = new Array(arrayLength);
+        for (let i = 0; i < arrayLength; i++) {
+            target[i] = getObservedOf(source[i], i, observableWrapper, visited);
+        }
+        target[oMetaKey] = observableWrapper;
+        return target;
+    }
+}
\ No newline at end of file
diff --git a/src/observables/methods/copy-within.ts b/src/observables/methods/copy-within.ts
new file mode 100644
index 0000000..424a36d
--- /dev/null
+++ b/src/observables/methods/copy-within.ts
@@ -0,0 +1,41 @@
+import { Change } from '../../model/change.ts';
+import { UPDATE, oMetaKey } from '../../constants.ts';
+import { callObservers, detachIfObservable, getObservedOf } from '../processors/proc-utils.ts';
+
+export default function proxiedCopyWithin(dest, start, end) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const tarLen = target.length;
+	dest = dest < 0 ? Math.max(tarLen + dest, 0) : dest;
+	start = start === undefined ? 0 : (start < 0 ? Math.max(tarLen + start, 0) : Math.min(start, tarLen));
+	end = end === undefined ? tarLen : (end < 0 ? Math.max(tarLen + end, 0) : Math.min(end, tarLen));
+	const len = Math.min(end - start, tarLen - dest);
+
+	if (dest < tarLen && dest !== start && len > 0) {
+		const prev = target.slice(0);
+		const changes = [];
+
+		target.copyWithin(dest, start, end);
+
+		for (let i = dest; i < dest + len; i++) {
+			//	update newly placed observables, if any
+			let nItem = target[i];
+			if (nItem && typeof nItem === 'object') {
+				nItem = getObservedOf(nItem, i, oMeta);
+				target[i] = nItem;
+			}
+
+			//	detach overridden observables, if any
+			const oItem = detachIfObservable(prev[i]);
+
+			if (typeof nItem !== 'object' && nItem === oItem) {
+				continue;
+			}
+			changes.push(new Change(UPDATE, [i], nItem, oItem, this));
+		}
+
+		callObservers(oMeta, changes);
+	}
+
+	return this;
+};
diff --git a/src/observables/methods/delete-property.ts b/src/observables/methods/delete-property.ts
new file mode 100644
index 0000000..d88bc8f
--- /dev/null
+++ b/src/observables/methods/delete-property.ts
@@ -0,0 +1,18 @@
+import { Change } from '../../model/change.ts';
+import { DELETE } from '../../constants.ts';
+import { callObservers, detachIfObservable, runValidators } from '../processors/proc-utils.ts';
+
+export function proxiedDeleteProperty(target: object, key: string | symbol): boolean {
+	const prevValue = target[key];
+
+	const prospective = [new Change(DELETE, [key], undefined, prevValue, this.proxy)];
+	runValidators(this, prospective);
+
+	delete target[key];
+	const oldValue = detachIfObservable(prevValue);
+
+	const changes = [new Change(DELETE, [key], undefined, oldValue, this.proxy)];
+	callObservers(this, changes);
+
+	return true;
+};
diff --git a/src/observables/methods/fill.ts b/src/observables/methods/fill.ts
new file mode 100644
index 0000000..c3d3732
--- /dev/null
+++ b/src/observables/methods/fill.ts
@@ -0,0 +1,31 @@
+import { Change } from '../../model/change.ts';
+import { INSERT, UPDATE, oMetaKey } from '../../constants.ts';
+import { callObservers, detachIfObservable, getObservedOf } from '../processors/proc-utils.ts';
+
+export default function proxiedFill(filVal, start, end) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const changes = [];
+	const tarLen = target.length;
+	const prev = target.slice(0);
+	start = start === undefined ? 0 : (start < 0 ? Math.max(tarLen + start, 0) : Math.min(start, tarLen));
+	end = end === undefined ? tarLen : (end < 0 ? Math.max(tarLen + end, 0) : Math.min(end, tarLen));
+
+	if (start < tarLen && end > start) {
+		target.fill(filVal, start, end);
+
+		for (let i = start; i < end; i++) {
+			target[i] = getObservedOf(target[i], i, oMeta);
+			if (i in prev) {
+				const oldValue = detachIfObservable(prev[i]);
+				changes.push(new Change(UPDATE, [i], target[i], oldValue, this));
+			} else {
+				changes.push(new Change(INSERT, [i], target[i], undefined, this));
+			}
+		}
+
+		callObservers(oMeta, changes);
+	}
+
+	return this;
+};
diff --git a/src/observables/methods/pop.ts b/src/observables/methods/pop.ts
new file mode 100644
index 0000000..a7c9b38
--- /dev/null
+++ b/src/observables/methods/pop.ts
@@ -0,0 +1,20 @@
+import { Change } from '../../model/change.ts';
+import { DELETE, oMetaKey } from '../../constants.ts';
+import { callObservers, detachIfObservable, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedPop() {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const poppedIndex = target.length - 1;
+	const prevValue = target[poppedIndex];
+
+	const prospective = [new Change(DELETE, [poppedIndex], undefined, prevValue, this)];
+	runValidators(oMeta, prospective);
+
+	const popResult = detachIfObservable(target.pop());
+
+	const changes = [new Change(DELETE, [poppedIndex], undefined, popResult, this)];
+	callObservers(oMeta, changes);
+
+	return popResult;
+}
diff --git a/src/observables/methods/push.ts b/src/observables/methods/push.ts
new file mode 100644
index 0000000..58900d8
--- /dev/null
+++ b/src/observables/methods/push.ts
@@ -0,0 +1,30 @@
+import { Change } from '../../model/change.ts';
+import { INSERT, oMetaKey } from '../../constants.ts';
+import { callObservers, getObservedOf, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedPush(...pushItems: unknown[]) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const pushLen = pushItems.length;
+	const initialLength = target.length;
+
+	const prospective = new Array(pushLen);
+	for (let i = 0; i < pushLen; i++) {
+		prospective[i] = new Change(INSERT, [initialLength + i], pushItems[i], undefined, this);
+	}
+	runValidators(oMeta, prospective);
+
+	const pushContent = new Array(pushLen);
+	for (let i = 0; i < pushLen; i++) {
+		pushContent[i] = getObservedOf(pushItems[i], initialLength + i, oMeta);
+	}
+	const pushResult = Reflect.apply(target.push, target, pushContent);
+
+	const changes = new Array(pushLen);
+	for (let i = 0; i < pushLen; i++) {
+		changes[i] = new Change(INSERT, [initialLength + i], target[initialLength + i], undefined, this);
+	}
+	callObservers(oMeta, changes);
+
+	return pushResult;
+};
diff --git a/src/observables/methods/reverse.ts b/src/observables/methods/reverse.ts
new file mode 100644
index 0000000..6b1e580
--- /dev/null
+++ b/src/observables/methods/reverse.ts
@@ -0,0 +1,18 @@
+import { Change } from '../../model/change.ts';
+import { REVERSE, oMetaKey } from '../../constants.ts';
+import { callObservers, reindexObservableChildren, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedReverse() {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+
+	const changes = [new Change(REVERSE, [], undefined, undefined, this)];
+	runValidators(oMeta, changes);
+
+	target.reverse();
+	reindexObservableChildren(target);
+
+	callObservers(oMeta, changes);
+
+	return this;
+};
diff --git a/src/observables/methods/set.ts b/src/observables/methods/set.ts
new file mode 100644
index 0000000..9a04274
--- /dev/null
+++ b/src/observables/methods/set.ts
@@ -0,0 +1,27 @@
+import { Change } from '../../model/change.ts';
+import { INSERT, UPDATE } from '../../constants.ts';
+import { callObservers, detachIfObservable, getObservedOf, runValidators } from '../processors/proc-utils.ts';
+
+export function proxiedSet(target: object, key: string | symbol, value: unknown): boolean {
+	const prevValue = target[key];
+
+	if (value !== prevValue) {
+		//	build prospective change with raw (un-observified) new value so validators see what the caller wrote
+		const prospective = prevValue === undefined
+			? [new Change(INSERT, [key], value, undefined, this.proxy)]
+			: [new Change(UPDATE, [key], value, prevValue, this.proxy)];
+		runValidators(this, prospective);
+
+		const newValue = getObservedOf(value, key, this);
+		target[key] = newValue;
+
+		const oldValue = detachIfObservable(prevValue);
+
+		const changes = oldValue === undefined
+			? [new Change(INSERT, [key], newValue, undefined, this.proxy)]
+			: [new Change(UPDATE, [key], newValue, oldValue, this.proxy)];
+		callObservers(this, changes);
+	}
+
+	return true;
+};
diff --git a/src/observables/methods/shift.ts b/src/observables/methods/shift.ts
new file mode 100644
index 0000000..a944306
--- /dev/null
+++ b/src/observables/methods/shift.ts
@@ -0,0 +1,20 @@
+import { Change } from '../../model/change.ts';
+import { DELETE, oMetaKey } from '../../constants.ts';
+import { callObservers, detachIfObservable, reindexObservableChildren, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedShift() {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const prevValue = target[0];
+
+	const prospective = [new Change(DELETE, [0], undefined, prevValue, this)];
+	runValidators(oMeta, prospective);
+
+	const shiftResult = detachIfObservable(target.shift());
+	reindexObservableChildren(target);
+
+	const changes = [new Change(DELETE, [0], undefined, shiftResult, this)];
+	callObservers(oMeta, changes);
+
+	return shiftResult;
+};
diff --git a/src/observables/methods/sort.ts b/src/observables/methods/sort.ts
new file mode 100644
index 0000000..9782281
--- /dev/null
+++ b/src/observables/methods/sort.ts
@@ -0,0 +1,18 @@
+import { Change } from '../../model/change.ts';
+import { SHUFFLE, oMetaKey } from '../../constants.ts';
+import { callObservers, reindexObservableChildren, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedSort(comparator) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+
+	const changes = [new Change(SHUFFLE, [], undefined, undefined, this)];
+	runValidators(oMeta, changes);
+
+	target.sort(comparator);
+	reindexObservableChildren(target);
+
+	callObservers(oMeta, changes);
+
+	return this;
+};
diff --git a/src/observables/methods/splice.ts b/src/observables/methods/splice.ts
new file mode 100644
index 0000000..b5b2380
--- /dev/null
+++ b/src/observables/methods/splice.ts
@@ -0,0 +1,45 @@
+import { Change } from '../../model/change.ts';
+import { INSERT, DELETE, UPDATE, oMetaKey } from '../../constants.ts';
+import { callObservers, detachIfObservable, getObservedOf, reindexObservableChildren } from '../processors/proc-utils.ts';
+
+export default function proxiedSplice(...spliceItems: unknown[]) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const splLen = spliceItems.length;
+	const spliceContent = new Array(splLen);
+	const tarLen = target.length;
+
+	//	observify the newcomers
+	for (let i = 0; i < splLen; i++) {
+		spliceContent[i] = getObservedOf(spliceItems[i], i, oMeta);
+	}
+
+	//	calculate pointers
+	const startIndex = splLen === 0 ? 0 : (spliceContent[0] < 0 ? tarLen + spliceContent[0] : spliceContent[0]);
+	const removed = splLen < 2 ? tarLen - startIndex : spliceContent[1];
+	const inserted = Math.max(splLen - 2, 0);
+	const spliceResult: unknown[] = Reflect.apply(target.splice, target, spliceContent);
+
+	reindexObservableChildren(target);
+
+	//	detach removed objects
+	for (let i = 0, l = spliceResult.length; i < l; i++) {
+		spliceResult[i] = detachIfObservable(spliceResult[i]);
+	}
+
+	const changes = [];
+	let index;
+	for (index = 0; index < removed; index++) {
+		if (index < inserted) {
+			changes.push(new Change(UPDATE, [startIndex + index], target[startIndex + index], spliceResult[index], this));
+		} else {
+			changes.push(new Change(DELETE, [startIndex + index], undefined, spliceResult[index], this));
+		}
+	}
+	for (; index < inserted; index++) {
+		changes.push(new Change(INSERT, [startIndex + index], target[startIndex + index], undefined, this));
+	}
+	callObservers(oMeta, changes);
+
+	return spliceResult;
+};
diff --git a/src/observables/methods/typed-set.ts b/src/observables/methods/typed-set.ts
new file mode 100644
index 0000000..7b9b82a
--- /dev/null
+++ b/src/observables/methods/typed-set.ts
@@ -0,0 +1,28 @@
+import { Change } from '../../model/change.ts';
+import { UPDATE, oMetaKey } from '../../constants.ts';
+import { callObservers, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedTypedArraySet(source, offset) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const souLen = source.length;
+	offset = offset || 0;
+
+	if (souLen > 0) {
+		const prev = target.slice(offset, offset + souLen);
+
+		const prospective = new Array(souLen);
+		for (let i = 0; i < souLen; i++) {
+			prospective[i] = new Change(UPDATE, [offset + i], source[i], prev[i], this);
+		}
+		runValidators(oMeta, prospective);
+
+		target.set(source, offset);
+
+		const changes = new Array(souLen);
+		for (let i = 0; i < souLen; i++) {
+			changes[i] = new Change(UPDATE, [offset + i], target[offset + i], prev[i], this);
+		}
+		callObservers(oMeta, changes);
+	}
+};
diff --git a/src/observables/methods/unshift.ts b/src/observables/methods/unshift.ts
new file mode 100644
index 0000000..a10baaf
--- /dev/null
+++ b/src/observables/methods/unshift.ts
@@ -0,0 +1,31 @@
+import { Change } from '../../model/change.ts';
+import { INSERT, oMetaKey } from '../../constants.ts';
+import { callObservers, getObservedOf, reindexObservableChildren, runValidators } from '../processors/proc-utils.ts';
+
+export default function proxiedUnshift(...unshiftItems: unknown[]) {
+	const oMeta = this[oMetaKey];
+	const target = oMeta.target;
+	const unshiftLen = unshiftItems.length;
+
+	const prospective = new Array(unshiftLen);
+	for (let i = 0; i < unshiftLen; i++) {
+		prospective[i] = new Change(INSERT, [i], unshiftItems[i], undefined, this);
+	}
+	runValidators(oMeta, prospective);
+
+	const unshiftContent = new Array(unshiftLen);
+	for (let i = 0; i < unshiftLen; i++) {
+		unshiftContent[i] = getObservedOf(unshiftItems[i], i, oMeta);
+	}
+	const unshiftResult = Reflect.apply(target.unshift, target, unshiftContent);
+
+	reindexObservableChildren(target);
+
+	const changes = new Array(unshiftLen);
+	for (let i = 0; i < unshiftLen; i++) {
+		changes[i] = new Change(INSERT, [i], target[i], undefined, this);
+	}
+	callObservers(oMeta, changes);
+
+	return unshiftResult;
+};
diff --git a/src/observables/object.ts b/src/observables/object.ts
new file mode 100644
index 0000000..8e1f0c1
--- /dev/null
+++ b/src/observables/object.ts
@@ -0,0 +1,15 @@
+import { ObservableBase } from './abstract-base.ts';
+import { getObservedOf } from './processors/proc-utils.ts';
+import { oMetaKey } from '../constants.ts';
+
+export class ObservableObject extends ObservableBase {
+
+    observedGraphProcessor(source: object, observableWrapper: ObservableBase, visited: Set<unknown>): object {
+        const target = {};
+        target[oMetaKey] = observableWrapper;
+        for (const key in source) {
+            target[key] = getObservedOf(source[key], key, observableWrapper, visited);
+        }
+        return target;
+    }
+}
\ No newline at end of file
diff --git a/src/observables/processors/proc-utils.ts b/src/observables/processors/proc-utils.ts
new file mode 100644
index 0000000..4f0c621
--- /dev/null
+++ b/src/observables/processors/proc-utils.ts
@@ -0,0 +1,164 @@
+import { oMetaKey } from '../../constants.ts';
+import { Change } from '../../model/change.ts';
+import { ObservableBase } from '../abstract-base.ts';
+import { ObservableArray } from '../array.ts';
+import { ObservableObject } from '../object.ts';
+import { ObservableTypedArray } from '../typed-array.ts';
+
+export function getObservedOf(item: unknown, key: string | symbol | number, parent: object, visited?: Set<unknown>): unknown {
+	if (visited !== undefined && visited.has(item)) {
+		return null;
+	} else if (typeof item !== 'object' || item === null) {
+		return item;
+	} else if (Array.isArray(item)) {
+		return new ObservableArray({ target: item, ownKey: key, parent: parent, visited }).proxy;
+	} else if (ArrayBuffer.isView(item)) {
+		return new ObservableTypedArray({ target: item, ownKey: key, parent: parent }).proxy;
+	} else if (item instanceof Date) {
+		return item;
+	} else {
+		return new ObservableObject({ target: item, ownKey: key, parent: parent, visited }).proxy;
+	}
+};
+
+export function getObservableFromRoot(target: unknown, options = undefined): unknown {
+	if (!target || typeof target !== 'object') {
+		throw new Error('observable MAY ONLY be created from a non-null object');
+	} else if (target[oMetaKey]) {
+		return target;
+	} else if (Array.isArray(target)) {
+		return new ObservableArray({ target: target, ownKey: null, parent: null, options: options }).proxy;
+	} else if (ArrayBuffer.isView(target)) {
+		return new ObservableTypedArray({ target: target, ownKey: null, parent: null, options: options }).proxy;
+	} else if (target instanceof Date) {
+		throw new Error(`${target} found to be one of a non-observable types`);
+	} else {
+		return new ObservableObject({ target: target, ownKey: null, parent: null, options: options }).proxy;
+	}
+}
+
+//	re-assign ownKey for every observable child of target whose position has changed
+export function reindexObservableChildren(target: ArrayLike<unknown>, from = 0): void {
+	for (let i = from, l = target.length; i < l; i++) {
+		const item = target[i];
+		if (item && typeof item === 'object') {
+			const childMeta = item[oMetaKey];
+			if (childMeta) {
+				childMeta.ownKey = i;
+			}
+		}
+	}
+}
+
+//	if value is an observable, detach it and return the unwrapped target; otherwise return value as-is
+export function detachIfObservable(value: unknown): unknown {
+	if (value && typeof value === 'object') {
+		const childMeta = value[oMetaKey];
+		if (childMeta) {
+			return childMeta.detach();
+		}
+	}
+	return value;
+}
+
+//	invoke every Validator attached to the root of this observable tree.
+//	changes' paths are rebuilt relative to the root before being passed to validators.
+//	any validator throw propagates — mutation is aborted.
+export function runValidators(oMeta: ObservableBase, changes: Change[]): void {
+	//	find root + accumulate path prefix from this node up
+	const prefix: Array<string | symbol | number> = [];
+	let current: ObservableBase = oMeta;
+	while (current.parent) {
+		prefix.unshift(current.ownKey);
+		current = current.parent;
+	}
+	const validators = current.validators;
+	if (validators.length === 0) {
+		return;
+	}
+	const rooted = prefix.length === 0
+		? changes
+		: changes.map(c => new Change(c.type, [...prefix, ...c.path], c.value, c.oldValue, c.object));
+	for (let i = 0, l = validators.length; i < l; i++) {
+		validators[i].validate(rooted);
+	}
+}
+
+export function callObservers(oMeta: ObservableBase, changes: Change[]) {
+	let currentObservable: ObservableBase = oMeta;
+	let isAsync, observers, target, options, relevantChanges, i;
+	const l = changes.length;
+	do {
+		isAsync = currentObservable.async;
+		observers = currentObservable.observers;
+		i = observers.length;
+		while (i--) {
+			[target, options] = observers[i];
+			relevantChanges = filterChanges(options, changes);
+
+			if (relevantChanges.length) {
+				if (isAsync) {
+					//	this is the async dispatch handling
+					if (currentObservable.batches.size === 0) {
+						queueMicrotask(callObserversFromMT.bind(currentObservable));
+					}
+					let batch = currentObservable.batches.get(target);
+					if (!batch) {
+						batch = [];
+						currentObservable.batches.set(target, batch);
+					}
+					batch.push(...relevantChanges);
+				} else {
+					//	this is the naive straight forward synchronous dispatch
+					callObserverSafe(target, relevantChanges);
+				}
+			}
+		}
+
+		//	cloning all the changes and notifying in context of parent
+		const parent = currentObservable.parent;
+		if (parent) {
+			for (let j = 0; j < l; j++) {
+				const change = changes[j];
+				changes[j] = new Change(
+					change.type,
+					[currentObservable.ownKey, ...change.path],
+					change.value,
+					change.oldValue,
+					change.object
+				);
+			}
+			currentObservable = parent;
+		} else {
+			break;
+		}
+	} while (currentObservable);
+};
+
+function filterChanges(options, changes) {
+	if (options === null || !options.filters) {
+		return changes;
+	}
+	let result = changes;
+	const filters = options.filters;
+	for (let i = 0, l = filters.length; i < l && result.length; i++) {
+		result = filters[i](result);
+	}
+	return result;
+}
+
+function callObserverSafe(listener, changes) {
+	try {
+		listener(changes);
+	} catch (e) {
+		console.error(`failed to notify listener ${listener} with ${changes}`, e);
+	}
+}
+
+function callObserversFromMT() {
+	const batches = this.batches;
+	this.batches = new Map();
+	for (const [listener, changes] of batches) {
+		callObserverSafe(listener, changes);
+	}
+};
diff --git a/src/observables/typed-array.ts b/src/observables/typed-array.ts
new file mode 100644
index 0000000..ea2a215
--- /dev/null
+++ b/src/observables/typed-array.ts
@@ -0,0 +1,27 @@
+import { ObservableBase } from './abstract-base.ts';
+import { oMetaKey } from '../constants.ts';
+import proxiedCopyWithin from './methods/copy-within.ts';
+import proxiedFill from './methods/fill.ts';
+import proxiedReverse from './methods/reverse.ts';
+import proxiedSort from './methods/sort.ts';
+import proxiedTypedArraySet from './methods/typed-set.ts';
+
+const proxiedTypedArrayMethods = {
+    copyWithin: proxiedCopyWithin,
+    fill: proxiedFill,
+    reverse: proxiedReverse,
+    sort: proxiedSort,
+    set: proxiedTypedArraySet
+};
+
+export class ObservableTypedArray extends ObservableBase {
+
+    get(target: object, key: string): unknown {
+        return proxiedTypedArrayMethods[key] || target[key];
+    }
+
+    observedGraphProcessor(source: Array<unknown>, observableWrapper: ObservableBase): Array<unknown> {
+        source[oMetaKey] = observableWrapper;
+        return source;
+    }
+}
\ No newline at end of file
diff --git a/sri.json b/sri.json
index cb438c4..3847fb6 100644
--- a/sri.json
+++ b/sri.json
@@ -1,5 +1,6 @@
 {
-	"dist/cdn/object-observer.js": "sha512-Jc51tpJGoR6MHLupRabCfXEVroGC2M5QEH19brhsgJ42vJnsIBUgDg4CeaTES8jZfQTLwzPp5mjIXg64cdEzAg==",
-	"dist/cdn/object-observer.min.js": "sha512-jieNuEyCm4guZuELCk+tZ8ijFhxyw6cOhx4q8cimhqdNccson04GDZpGm5kISKIkI//xERXAep1bt5HWKLDDNw==",
-	"dist/cdn/object-observer.min.js.map": "sha512-oCCsAVsC1+BcyrA8KzysTfw0U1qH6HN3Z/HTzyBbJUc5aPRA4+W2Hp4HSwD2Z5CDbYyKFDKyle7YHLy0V8GA2Q=="
+	"dist/cdn/object-observer.js": "sha512-TnjrVURwBr0zoybWnQTulkNvVJOxMzU8IiieCsvgIVSwz7wLGA1EKcFZjY2YuDEwznxbkMitJpn4dsoy9KLqDw==",
+	"dist/cdn/object-observer.js.map": "sha512-LaT8o/h0SZFtigRnjmzr0sNnr/oc9lO0TFYOD15aOWNKIHLGVkvhqtT6yHvVY1ooVlwbSzaskl+mCkxRom/0Yw==",
+	"dist/cdn/object-observer.min.js": "sha512-jCjYwEoBCiXdQiwkvz6WJWc/e8gxf7ER2wIHOB1Fqf1L369D4z/KWsDgbBJgJ7efKthGHRb3fhZjRlRVTdKvcg==",
+	"dist/cdn/object-observer.min.js.map": "sha512-2u7DLjdVHcTVSqIQMSkwy25HHW2bI1YsqMg/Btv2lQJcnc677Cs6OaDcCXcXIASqxms8JvtHPunepABFr9XKJw=="
 }
\ No newline at end of file
diff --git a/tests/api-base.js b/tests/api-base.js
index 1d40e26..ae924dd 100644
--- a/tests/api-base.js
+++ b/tests/api-base.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('ensure Observable object has defined APIs', () => {
 	assert.equal(typeof Observable, 'object');
diff --git a/tests/api-changes.js b/tests/api-changes.js
index 5f14a3f..03876ef 100644
--- a/tests/api-changes.js
+++ b/tests/api-changes.js
@@ -1,13 +1,13 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 //	object
 //
 test('verify object - root - insert', () => {
 	let c;
 	const o = Observable.from({});
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.some = 'new';
 	assert.deepStrictEqual(c, { type: 'insert', path: ['some'], value: 'new', oldValue: undefined, object: o });
 });
@@ -15,7 +15,7 @@ test('verify object - root - insert', () => {
 test('verify object - deep - insert', () => {
 	let c;
 	const o = Observable.from({ a: {} });
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.a.some = 'new';
 	assert.deepStrictEqual(c, { type: 'insert', path: ['a', 'some'], value: 'new', oldValue: undefined, object: o.a });
 });
@@ -23,7 +23,7 @@ test('verify object - deep - insert', () => {
 test('verify object - root - update', () => {
 	let c;
 	const o = Observable.from({ p: 'old' });
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.p = 'new';
 	assert.deepStrictEqual(c, { type: 'update', path: ['p'], value: 'new', oldValue: 'old', object: o });
 });
@@ -31,7 +31,7 @@ test('verify object - root - update', () => {
 test('verify object - deep - update', () => {
 	let c;
 	const o = Observable.from({ a: { p: 'old' } });
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.a.p = 'new';
 	assert.deepStrictEqual(c, { type: 'update', path: ['a', 'p'], value: 'new', oldValue: 'old', object: o.a });
 });
@@ -39,7 +39,7 @@ test('verify object - deep - update', () => {
 test('verify object - root - delete', () => {
 	let c;
 	const o = Observable.from({ p: 'old' });
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	delete o.p;
 	assert.deepStrictEqual(c, { type: 'delete', path: ['p'], value: undefined, oldValue: 'old', object: o });
 });
@@ -47,7 +47,7 @@ test('verify object - root - delete', () => {
 test('verify object - deep - delete', () => {
 	let c;
 	const o = Observable.from({ a: { p: 'old' } });
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	delete o.a.p;
 	assert.deepStrictEqual(c, { type: 'delete', path: ['a', 'p'], value: undefined, oldValue: 'old', object: o.a });
 });
@@ -57,7 +57,7 @@ test('verify object - deep - delete', () => {
 test('verify array - root - insert', () => {
 	let c;
 	const o = Observable.from([]);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.push('new');
 	assert.deepStrictEqual(c, { type: 'insert', path: [0], value: 'new', oldValue: undefined, object: o });
 });
@@ -65,7 +65,7 @@ test('verify array - root - insert', () => {
 test('verify array - deep - insert', () => {
 	let c;
 	const o = Observable.from([[]]);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o[0].push('new');
 	assert.deepStrictEqual(c, { type: 'insert', path: [0, 0], value: 'new', oldValue: undefined, object: o[0] });
 });
@@ -73,7 +73,7 @@ test('verify array - deep - insert', () => {
 test('verify array - root - update', () => {
 	let c;
 	const o = Observable.from(['old']);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o[0] = 'new';
 	assert.deepStrictEqual(c, { type: 'update', path: ['0'], value: 'new', oldValue: 'old', object: o });
 });
@@ -81,7 +81,7 @@ test('verify array - root - update', () => {
 test('verify array - deep - update', () => {
 	let c;
 	const o = Observable.from([['old']]);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o[0][0] = 'new';
 	assert.deepStrictEqual(c, { type: 'update', path: [0, '0'], value: 'new', oldValue: 'old', object: o[0] });
 });
@@ -89,7 +89,7 @@ test('verify array - deep - update', () => {
 test('verify array - root - delete', () => {
 	let c;
 	const o = Observable.from(['old']);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o.pop();
 	assert.deepStrictEqual(c, { type: 'delete', path: [0], value: undefined, oldValue: 'old', object: o });
 });
@@ -97,7 +97,7 @@ test('verify array - root - delete', () => {
 test('verify array - deep - delete', () => {
 	let c;
 	const o = Observable.from([['old']]);
-	Observable.observe(o, cs => { c = cs[0]; })
+	Observable.observe(o, cs => { c = cs[0]; });
 	o[0].pop();
 	assert.deepStrictEqual(c, { type: 'delete', path: [0, 0], value: undefined, oldValue: 'old', object: o[0] });
 });
diff --git a/tests/browser-host-objects.js b/tests/browser-host-objects.js
index 4cf3c7b..44667f7 100644
--- a/tests/browser-host-objects.js
+++ b/tests/browser-host-objects.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('test DOMStringMap', () => {
 	const
diff --git a/tests/configs/tests-config-ci-chromium.js b/tests/configs/tests-config-ci-chromium.js
new file mode 100644
index 0000000..2fa403a
--- /dev/null
+++ b/tests/configs/tests-config-ci-chromium.js
@@ -0,0 +1,31 @@
+const config = {
+	environments: [
+		{
+			browser: {
+				type: 'chromium',
+				executors: {
+					type: 'iframe'
+				}
+			},
+			tests: {
+				ttl: 32000,
+				maxFail: 0,
+				maxSkip: 5,
+				include: [
+					'./tests/*'
+				],
+				exclude: [
+					'**/configs/**',
+					'**/*-performance-*.js'
+				]
+			},
+			coverage: {
+				include: [
+					'./src/**/*'
+				]
+			}
+		}
+	]
+}
+
+export default config;
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-chromium.json b/tests/configs/tests-config-ci-chromium.json
deleted file mode 100644
index e15d9fd..0000000
--- a/tests/configs/tests-config-ci-chromium.json
+++ /dev/null
@@ -1,28 +0,0 @@
-{
-	"environments": [
-		{
-			"browser": {
-				"type": "chromium",
-				"executors": {
-					"type": "iframe"
-				}
-			},
-			"tests": {
-				"ttl": 32000,
-				"maxFail": 0,
-				"maxSkip": 5,
-				"include": [
-					"./tests/*.js"
-				],
-				"exclude": [
-					"**/tests/*-performance-*.js"
-				]
-			},
-			"coverage": {
-				"include": [
-					"./src/**/*.js"
-				]
-			}
-		}
-	]
-}
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-firefox.js b/tests/configs/tests-config-ci-firefox.js
new file mode 100644
index 0000000..d6332db
--- /dev/null
+++ b/tests/configs/tests-config-ci-firefox.js
@@ -0,0 +1,26 @@
+const config = {
+	environments: [
+		{
+			browser: {
+				type: 'firefox',
+				executors: {
+					type: 'iframe'
+				}
+			},
+			tests: {
+				ttl: 32000,
+				maxFail: 0,
+				maxSkip: 5,
+				include: [
+					'./tests/*'
+				],
+				exclude: [
+					'**/configs/**',
+					'**/*-performance-*.js'
+				]
+			}
+		}
+	]
+};
+
+export default config;
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-firefox.json b/tests/configs/tests-config-ci-firefox.json
deleted file mode 100644
index 2b8e0b6..0000000
--- a/tests/configs/tests-config-ci-firefox.json
+++ /dev/null
@@ -1,29 +0,0 @@
-{
-	"environments": [
-		{
-			"browser": {
-				"type": "firefox",
-				"executors": {
-					"type": "iframe"
-				},
-				"importmap": {
-					"imports": {
-						"@gullerya/just-test": "/libs/@gullerya/just-test/bin/runner/just-test.js",
-						"@gullerya/just-test/assert": "/libs/@gullerya/just-test/bin/common/assert-utils.js"
-					}
-				}
-			},
-			"tests": {
-				"ttl": 32000,
-				"maxFail": 0,
-				"maxSkip": 5,
-				"include": [
-					"./tests/*.js"
-				],
-				"exclude": [
-					"**/tests/*-performance-*.js"
-				]
-			}
-		}
-	]
-}
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-node.js b/tests/configs/tests-config-ci-node.js
new file mode 100644
index 0000000..ec7fece
--- /dev/null
+++ b/tests/configs/tests-config-ci-node.js
@@ -0,0 +1,27 @@
+const config = {
+	environments: [
+		{
+			node: true,
+			tests: {
+				ttl: 32000,
+				maxFail: 0,
+				maxSkip: 5,
+				include: [
+					'./tests/*'
+				],
+				exclude: [
+					'**/configs/**',
+					'**/browser-host-objects.js',
+					'**/*-performance-*.js'
+				]
+			},
+			coverage: {
+				include: [
+					'./src/**/*'
+				]
+			}
+		}
+	]
+};
+
+export default config;
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-node.json b/tests/configs/tests-config-ci-node.json
deleted file mode 100644
index d87a427..0000000
--- a/tests/configs/tests-config-ci-node.json
+++ /dev/null
@@ -1,24 +0,0 @@
-{
-	"environments": [
-		{
-			"node": true,
-			"tests": {
-				"ttl": 32000,
-				"maxFail": 0,
-				"maxSkip": 5,
-				"include": [
-					"./tests/*.js"
-				],
-				"exclude": [
-					"**/tests/browser-host-objects.js",
-					"**/tests/*-performance-*.js"
-				]
-			},
-			"coverage": {
-				"include": [
-					"./src/**/*.js"
-				]
-			}
-		}
-	]
-}
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-webkit.js b/tests/configs/tests-config-ci-webkit.js
new file mode 100644
index 0000000..262ab8f
--- /dev/null
+++ b/tests/configs/tests-config-ci-webkit.js
@@ -0,0 +1,26 @@
+const config = {
+	environments: [
+		{
+			browser: {
+				type: 'webkit',
+				executors: {
+					type: 'iframe'
+				}
+			},
+			tests: {
+				ttl: 32000,
+				maxFail: 0,
+				maxSkip: 5,
+				include: [
+					'./tests/*'
+				],
+				exclude: [
+					'**/configs/**',
+					'**/*-performance-*.js'
+				]
+			}
+		}
+	]
+};
+
+export default config;
\ No newline at end of file
diff --git a/tests/configs/tests-config-ci-webkit.json b/tests/configs/tests-config-ci-webkit.json
deleted file mode 100644
index 4412d41..0000000
--- a/tests/configs/tests-config-ci-webkit.json
+++ /dev/null
@@ -1,29 +0,0 @@
-{
-	"environments": [
-		{
-			"browser": {
-				"type": "webkit",
-				"executors": {
-					"type": "iframe"
-				},
-				"importmap": {
-					"imports": {
-						"@gullerya/just-test": "/libs/@gullerya/just-test/bin/runner/just-test.js",
-						"@gullerya/just-test/assert": "/libs/@gullerya/just-test/bin/common/assert-utils.js"
-					}
-				}
-			},
-			"tests": {
-				"ttl": 32000,
-				"maxFail": 0,
-				"maxSkip": 5,
-				"include": [
-					"./tests/*.js"
-				],
-				"exclude": [
-					"**/tests/*-performance-*.js"
-				]
-			}
-		}
-	]
-}
\ No newline at end of file
diff --git a/tests/cross-instance.js b/tests/cross-instance.js
index 8ac2f2c..1cf226d 100644
--- a/tests/cross-instance.js
+++ b/tests/cross-instance.js
@@ -1,7 +1,7 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable as O1, ObjectObserver as OO1 } from '../src/object-observer.js?1';
-import { Observable as O2, ObjectObserver as OO2 } from '../src/object-observer.js?2';
+import { Observable as O1, ObjectObserver as OO1 } from '../src/object-observer.ts?key=1';
+import { Observable as O2, ObjectObserver as OO2 } from '../src/object-observer.ts?key=2';
 
 test('Observable.isObservable interoperable', () => {
 	assert.notEqual(O1, O2);
diff --git a/tests/filters.js b/tests/filters.js
new file mode 100644
index 0000000..4b7d243
--- /dev/null
+++ b/tests/filters.js
@@ -0,0 +1,84 @@
+import { test } from '@gullerya/just-test';
+import { assert } from '@gullerya/just-test/assert';
+import { Filter } from '../src/changes-processors/filters.ts';
+import { Change } from '../src/model/change.ts';
+
+test('test filters - ctor direct use forbidden', () => {
+	assert.throws(() => new Filter('some', (change) => change.prop !== 'skip'), 'Filter class cannot be instantiated directly', 'Filter class cannot be instantiated directly');
+});
+
+test('custom filter - positive cases', () => {
+	const filterLogic = changes => changes.filter(c => c.value !== null);
+	const f = Filter.custom(filterLogic);
+	assert.strictEqual(f.fn, filterLogic, 'Filter code is correct');
+});
+
+test('custom filter - negative cases', () => {
+	assert.throws(() => Filter.custom(null), 'custom Filter requires a function as argument');
+	assert.throws(() => Filter.custom('some'), 'custom Filter requires a function as argument');
+});
+
+test('exactPaths filter - positive cases', () => {
+	const f = Filter.exactPaths(['a', 'b.c']);
+	const changes = [
+		new Change('update', ['a'], 1, 0),
+		new Change('update', ['b', 'c'], 2, 0),
+		new Change('update', ['a', 'b', 'c'], 3, 0),
+		new Change('update', ['b', 'c', 'd'], 4, 0)
+	];
+	const filtered = f.fn(changes);
+	assert.strictEqual(filtered.length, 2);
+});
+
+test('exactPaths filter - negative cases', () => {
+	assert.throws(() => Filter.exactPaths(null), 'exactPaths Filter requires a non-empty array as argument');
+	assert.throws(() => Filter.exactPaths([]), 'exactPaths Filter requires a non-empty array as argument');
+});
+
+test('pathsStartWith filter - positive cases', () => {
+	const f = Filter.pathsStartWith('a.b');
+	const changes = [
+		new Change('update', ['a'], 1, 0),
+		new Change('update', ['a', 'b'], 2, 0),
+		new Change('update', ['a', 'c', 'c'], 3, 0),
+		new Change('update', ['a', 'b', 'c'], 4, 0)
+	];
+	const filtered = f.fn(changes);
+	assert.strictEqual(filtered.length, 2);
+});
+
+test('pathsStartWith filter - negative cases', () => {
+	assert.throws(() => Filter.pathsStartWith(null), 'pathsStartWith Filter requires a non-empty string as argument');
+	assert.throws(() => Filter.pathsStartWith([]), 'pathsStartWith Filter requires a non-empty string as argument');
+	assert.throws(() => Filter.pathsStartWith(''), 'pathsStartWith Filter requires a non-empty string as argument');
+});
+
+test('directChildrenOf filter - positive cases', () => {
+	const f = Filter.directChildrenOf('a');
+	const changes = [
+		new Change('update', ['a'], 1, 0),
+		new Change('update', ['a', 'b'], 2, 0),
+		new Change('update', ['a', 'b', 'c'], 3, 0),
+		new Change('update', ['a', 'c'], 4, 0),
+		new Change('update', ['aX', 'b'], 5, 0)
+	];
+	const filtered = f.fn(changes);
+	assert.strictEqual(filtered.length, 2);
+});
+
+test('directChildrenOf filter - empty path = root', () => {
+	const f = Filter.directChildrenOf('');
+	const changes = [
+		new Change('update', ['a'], 1, 0),
+		new Change('update', ['a', 'b'], 2, 0),
+		new Change('reverse', [], undefined, undefined),
+		new Change('shuffle', [], undefined, undefined)
+	];
+	const filtered = f.fn(changes);
+	assert.strictEqual(filtered.length, 3);
+});
+
+test('directChildrenOf filter - negative cases', () => {
+	assert.throws(() => Filter.directChildrenOf(null), 'directChildrenOf Filter requires a string as argument (MAY be empty)');
+	assert.throws(() => Filter.directChildrenOf(123), 'directChildrenOf Filter requires a string as argument (MAY be empty)');
+});
diff --git a/tests/listeners.js b/tests/listeners.js
index 44f1816..571af8a 100644
--- a/tests/listeners.js
+++ b/tests/listeners.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('test listeners invocation - single listener', () => {
 	const oo = Observable.from({});
diff --git a/tests/object-generics.js b/tests/object-generics.js
index 1a16bf6..4342010 100644
--- a/tests/object-generics.js
+++ b/tests/object-generics.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('Object.seal - further extensions should fail', () => {
 	const oo = Observable.from({ propA: 'a', propB: 'b' });
diff --git a/tests/object-observer-api.js b/tests/object-observer-api.js
index af054b6..b7044d2 100644
--- a/tests/object-observer-api.js
+++ b/tests/object-observer-api.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { ObjectObserver, Observable } from '../src/object-observer.js';
+import { ObjectObserver, Observable } from '../src/object-observer.ts';
 
 test('ensure ObjectObserver constructable', () => {
 	assert.isTrue(typeof ObjectObserver === 'function');
diff --git a/tests/object-observer-arrays-copy-within.js b/tests/object-observer-arrays-copy-within.js
index ac9febb..2c42755 100644
--- a/tests/object-observer-arrays-copy-within.js
+++ b/tests/object-observer-arrays-copy-within.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('array copyWithin - primitives', () => {
 	const
diff --git a/tests/object-observer-arrays-typed.js b/tests/object-observer-arrays-typed.js
index 45631ab..4fd0828 100644
--- a/tests/object-observer-arrays-typed.js
+++ b/tests/object-observer-arrays-typed.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('typed array reverse - Int8Array', () => {
 	const
diff --git a/tests/object-observer-arrays.js b/tests/object-observer-arrays.js
index 189f83f..6111c9e 100644
--- a/tests/object-observer-arrays.js
+++ b/tests/object-observer-arrays.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('array push - primitives', () => {
 	const
diff --git a/tests/object-observer-native-objects-to-skip.js b/tests/object-observer-native-objects-to-skip.js
index 62978fd..f428a84 100644
--- a/tests/object-observer-native-objects-to-skip.js
+++ b/tests/object-observer-native-objects-to-skip.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('creating observable from non-observable should throw an error', () => {
 	const objectsToTest = [
diff --git a/tests/object-observer-objects-async.js b/tests/object-observer-objects-async.js
index 0dc43e1..2d9c8d5 100644
--- a/tests/object-observer-objects-async.js
+++ b/tests/object-observer-objects-async.js
@@ -1,7 +1,7 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
 import { waitNextTask } from '@gullerya/just-test/timing';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('multiple continuous mutations', async () => {
 	const
diff --git a/tests/object-observer-objects-circular.js b/tests/object-observer-objects-circular.js
index 166c433..f2a5c61 100644
--- a/tests/object-observer-objects-circular.js
+++ b/tests/object-observer-objects-circular.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('subgraph object pointing to the top parent', () => {
 	const o = { prop: 'text' };
diff --git a/tests/object-observer-objects-same-refs.js b/tests/object-observer-objects-same-refs.js
index d68c50a..cd4226c 100644
--- a/tests/object-observer-objects-same-refs.js
+++ b/tests/object-observer-objects-same-refs.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('subgraph objects pointing to the same object few times', { skip: true }, () => {
 	const childObj = { prop: 'A' };
diff --git a/tests/object-observer-objects.js b/tests/object-observer-objects.js
index 4eb2e3b..729dfdd 100644
--- a/tests/object-observer-objects.js
+++ b/tests/object-observer-objects.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('creating observable leaves original object as is', () => {
 	const person = {
@@ -42,7 +42,7 @@ test('plain object operations', () => {
 		name: 'name',
 		age: 7,
 		address: null
-	}
+	};
 	const
 		events = [],
 		tmpAddress = { street: 'some' };
diff --git a/tests/object-observer-subgraphs.js b/tests/object-observer-subgraphs.js
index ff23b37..ba33009 100644
--- a/tests/object-observer-subgraphs.js
+++ b/tests/object-observer-subgraphs.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('inner object from observable should fire events as usual', () => {
 	const
diff --git a/tests/observable-nested.js b/tests/observable-nested.js
index 5ea291a..31c12b3 100644
--- a/tests/observable-nested.js
+++ b/tests/observable-nested.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('nested of observable should be observable too', () => {
 	const oo = Observable.from({
@@ -97,7 +97,7 @@ test('nested observable should handle errors', () => {
 				city: 'city'
 			}
 		}
-	})
+	});
 	const oou = Observable.from(oo.user);
 	assert.throws(
 		() => Observable.observe(oou, 'invalid observer'),
@@ -135,7 +135,7 @@ test('nested observable should provide correct path (relative to self)', () => {
 				city: 'city'
 			}
 		}
-	})
+	});
 	const
 		oou = Observable.from(oo.user),
 		ooua = Observable.from(oo.user.address),
diff --git a/tests/observe-specific-paths.js b/tests/observe-specific-paths.js
index 7dc81bf..f3fff4c 100644
--- a/tests/observe-specific-paths.js
+++ b/tests/observe-specific-paths.js
@@ -1,71 +1,39 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable, Filter } from '../src/object-observer.ts';
 
-test('baseline - negative - path not a string', () => {
+test('baseline - negative - filters not an array', () => {
 	const oo = Observable.from({});
 	assert.throws(
-		() => Observable.observe(oo, () => { }, { path: 4 }),
-		'"path" option, if/when provided, MUST be a non-empty string'
+		() => Observable.observe(oo, () => { }, { filters: 'nope' }),
+		'"filters" option, if/when provided, MUST be a non-empty array of Filter instances'
 	);
 });
 
-test('baseline - negative - path empty', () => {
+test('baseline - negative - filters empty array', () => {
 	const oo = Observable.from({});
 	assert.throws(
-		() => Observable.observe(oo, () => { }, { path: '' }),
-		'"path" option, if/when provided, MUST be a non-empty string'
+		() => Observable.observe(oo, () => { }, { filters: [] }),
+		'"filters" option, if/when provided, MUST be a non-empty array of Filter instances'
 	);
 });
 
-test('baseline - negative - pathsFrom not a string', () => {
+test('baseline - negative - filters contains non-Filter element', () => {
 	const oo = Observable.from({});
 	assert.throws(
-		() => Observable.observe(oo, () => { }, { pathsFrom: 4 }),
-		'"pathsFrom" option, if/when provided, MUST be a non-empty string'
+		() => Observable.observe(oo, () => { }, { filters: [Filter.exactPaths(['a']), 'bad'] }),
+		'"filters" option, if/when provided, MUST be a non-empty array of Filter instances'
 	);
 });
 
-test('baseline - negative - pathsFrom empty', () => {
+test('baseline - negative - foreign option', () => {
 	const oo = Observable.from({});
 	assert.throws(
-		() => Observable.observe(oo, () => { }, { pathsFrom: '' }),
-		'"pathsFrom" option, if/when provided, MUST be a non-empty string'
-	);
-});
-
-test('baseline - negative - no pathsFrom when path present', () => {
-	const oo = Observable.from({});
-	assert.throws(
-		() => Observable.observe(oo, () => { }, { path: 'some', pathsFrom: 'else' }),
-		'"pathsFrom" option MAY NOT be specified together with'
-	);
-});
-
-test('baseline - negative - no foreign options (pathFrom)', () => {
-	const oo = Observable.from({});
-	assert.throws(
-		() => Observable.observe(oo, () => { }, { pathFrom: 'something' }),
+		() => Observable.observe(oo, () => { }, { somethingElse: 'x' }),
 		'is/are not a valid observer option/s'
 	);
 });
 
-test('observe paths of - negative a', () => {
-	const oo = Observable.from({});
-	assert.throws(
-		() => Observable.observe(oo, () => { }, { pathsOf: 4 }),
-		'"pathsOf" option, if/when provided, MUST be a string (MAY be empty)'
-	);
-});
-
-test('observe paths of - negative b', () => {
-	const oo = Observable.from({});
-	assert.throws(
-		() => Observable.observe(oo, () => { }, { path: 'inner.prop', pathsOf: 'some.thing' }),
-		'"pathsOf" option MAY NOT be specified together with "path" option'
-	);
-});
-
 test('baseline - no options / empty options', () => {
 	const
 		oo = Observable.from({ inner: { prop: 'more' } }),
@@ -92,7 +60,7 @@ test('baseline - empty options is valid', () => {
 	Observable.unobserve(oo, observer);
 });
 
-test('observe specific path', () => {
+test('exactPaths filter - single path', () => {
 	const oo = Observable.from({ inner: { prop: 'more' } });
 	let callbackCalls = 0,
 		changesCounter = 0;
@@ -100,7 +68,7 @@ test('observe specific path', () => {
 	Observable.observe(oo, changes => {
 		callbackCalls++;
 		changesCounter += changes.length;
-	}, { path: 'inner' });
+	}, { filters: [Filter.exactPaths(['inner'])] });
 
 	oo.newProp = 'non-relevant';
 	oo.inner.other = 'non-relevant';
@@ -110,11 +78,11 @@ test('observe specific path', () => {
 	assert.strictEqual(callbackCalls, 1);
 });
 
-test('observe paths from .. and deeper', () => {
+test('pathsStartWith filter - path and deeper', () => {
 	const oo = Observable.from({ inner: { prop: 'more', nested: { text: 'text' } } });
 	let counter = 0;
 
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsFrom: 'inner.prop' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.pathsStartWith('inner.prop')] });
 	oo.nonRelevant = 'non-relevant';
 	oo.inner.also = 'non-relevant';
 	oo.inner.prop = 'relevant';
@@ -123,10 +91,10 @@ test('observe paths from .. and deeper', () => {
 	assert.strictEqual(counter, 3);
 });
 
-test('observe paths of - inner case', () => {
+test('directChildrenOf filter - inner case', () => {
 	const oo = Observable.from({ inner: { prop: 'more', nested: { text: 'text' } } });
 	let counter = 0;
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsOf: 'inner.nested' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('inner.nested')] });
 	oo.nonRelevant = 'non-relevant';
 	oo.inner.also = 'non-relevant';
 	oo.inner.nested.text = 'relevant';
@@ -136,10 +104,10 @@ test('observe paths of - inner case', () => {
 	assert.strictEqual(counter, 2);
 });
 
-test('observe paths of - array - property of same depth updated', () => {
+test('directChildrenOf filter - array - property of same depth updated', () => {
 	const oo = Observable.from({ array: [1, 2, 3], prop: { inner: 'value' } });
 	let counter = 0;
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsOf: 'array' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('array')] });
 	oo.nonRelevant = 'non-relevant';
 	oo.prop.inner = 'non-relevant';
 	oo.prop = { newObj: { test: 'non-relevant' } };
@@ -149,10 +117,10 @@ test('observe paths of - array - property of same depth updated', () => {
 	assert.equal(counter, 2);
 });
 
-test('observe paths of - root case', () => {
+test('directChildrenOf filter - root case', () => {
 	const oo = Observable.from({ inner: { prop: 'more', nested: { text: 'text' } } });
 	let counter = 0;
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsOf: '' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('')] });
 	oo.relevant = 'relevant';
 	oo.inner.also = 'non-relevant';
 	oo.inner = { newObj: { test: 'relevant' } };
@@ -160,20 +128,58 @@ test('observe paths of - root case', () => {
 	assert.equal(counter, 2);
 });
 
-test('observe paths of - root case - array sort', () => {
+test('directChildrenOf filter - root case - array sort', () => {
 	const oo = Observable.from([1, 3, 2, 4, 9]);
 	let counter = 0;
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsOf: '' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('')] });
 	oo.sort();
 	assert.isTrue(oo[0] === 1 && oo[1] === 2 && oo[2] === 3 && oo[3] === 4 && oo[4] === 9);
 	assert.equal(counter, 1);
 });
 
-test('observe paths of - root case - array reverse', () => {
+test('directChildrenOf filter - root case - array reverse', () => {
 	const oo = Observable.from([1, 2, 3, 4, 9]);
 	let counter = 0;
-	Observable.observe(oo, changes => { counter += changes.length; }, { pathsOf: '' });
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('')] });
 	oo.reverse();
 	assert.isTrue(oo[0] === 9 && oo[1] === 4 && oo[2] === 3 && oo[3] === 2 && oo[4] === 1);
 	assert.equal(counter, 1);
 });
+
+test('multiple filters compose as AND', () => {
+	const oo = Observable.from({ a: { x: 1, y: 2 }, b: { x: 3 } });
+	let counter = 0;
+	//	direct children of 'a' AND under 'a.x'  →  only 'a.x' changes
+	Observable.observe(
+		oo,
+		changes => { counter += changes.length; },
+		{ filters: [Filter.directChildrenOf('a'), Filter.pathsStartWith('a.x')] }
+	);
+	oo.a.x = 10;	//	kept
+	oo.a.y = 20;	//	dropped (not under a.x)
+	oo.b.x = 30;	//	dropped (not direct child of a)
+	assert.strictEqual(counter, 1);
+});
+
+test('directChildrenOf filter - sibling-prefix is not a child', () => {
+	//	regression guard: path 'innerX.foo' should NOT be a direct child of 'inner'
+	const oo = Observable.from({ inner: { a: 1 }, innerX: { a: 1 } });
+	let counter = 0;
+	Observable.observe(oo, changes => { counter += changes.length; }, { filters: [Filter.directChildrenOf('inner')] });
+	oo.innerX.a = 2;	//	must NOT match
+	oo.inner.a = 2;		//	must match
+	assert.strictEqual(counter, 1);
+});
+
+test('custom filter via Filter.custom', () => {
+	const oo = Observable.from({ a: 1, b: 2 });
+	let counter = 0;
+	Observable.observe(
+		oo,
+		changes => { counter += changes.length; },
+		{ filters: [Filter.custom(cs => cs.filter(c => c.value > 10))] }
+	);
+	oo.a = 5;		//	dropped
+	oo.b = 20;		//	kept
+	assert.strictEqual(counter, 1);
+});
diff --git a/tests/reassignment-of-equals.js b/tests/reassignment-of-equals.js
index 6246f5a..9f4e619 100644
--- a/tests/reassignment-of-equals.js
+++ b/tests/reassignment-of-equals.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('boolean', () => {
 	const oo = Observable.from({ p: true });
diff --git a/tests/revokation.js b/tests/revokation.js
index f4cc0cf..37f79c2 100644
--- a/tests/revokation.js
+++ b/tests/revokation.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('test revokation of replaced objects - simple set', () => {
 	const og = Observable.from({
diff --git a/tests/unobserve.js b/tests/unobserve.js
index d74718a..458b227 100644
--- a/tests/unobserve.js
+++ b/tests/unobserve.js
@@ -1,6 +1,6 @@
 import { test } from '@gullerya/just-test';
 import { assert } from '@gullerya/just-test/assert';
-import { Observable } from '../src/object-observer.js';
+import { Observable } from '../src/object-observer.ts';
 
 test('test unobserve - single observer - explicit unobserve', () => {
 	const
diff --git a/tests/validators.js b/tests/validators.js
new file mode 100644
index 0000000..3a251bd
--- /dev/null
+++ b/tests/validators.js
@@ -0,0 +1,277 @@
+import { test } from '@gullerya/just-test';
+import { assert } from '@gullerya/just-test/assert';
+import { Observable, Validator } from '../src/object-observer.ts';
+import { Change } from '../src/model/change.ts';
+import { oMetaKey } from '../src/constants.ts';
+
+test('test validators - ctor direct use forbidden', () => {
+	assert.throws(() => new Validator('some', () => { }), 'Validator class cannot be instantiated directly');
+});
+
+test('custom validator - positive cases', () => {
+	const validatorLogic = () => { };
+	const v = Validator.custom(validatorLogic);
+	assert.strictEqual(v.validate, validatorLogic, 'Validator code is correct');
+});
+
+test('custom validator - negative cases', () => {
+	assert.throws(() => Validator.custom(null), 'custom Validator requires a function as argument');
+	assert.throws(() => Validator.custom('some'), 'custom Validator requires a function as argument');
+});
+
+test('custom validator - validate invokes passed fn - success path (no throw)', () => {
+	let called = 0;
+	const v = Validator.custom(changes => { called = changes.length; });
+	const changes = [new Change('update', ['a'], 1, 0), new Change('update', ['b'], 2, 0)];
+	v.validate(changes);
+	assert.strictEqual(called, 2);
+});
+
+test('custom validator - validate propagates throw', () => {
+	const v = Validator.custom(() => { throw new Error('rejected'); });
+	assert.throws(() => v.validate([new Change('update', ['a'], 1, 0)]), 'rejected');
+});
+
+test('custom validator - validate is read-only', () => {
+	const v = Validator.custom(() => { });
+	assert.throws(() => { v.validate = () => { }; });
+});
+
+test('Observable.from - validators option - negative - not an array', () => {
+	assert.throws(
+		() => Observable.from({}, { validators: 'nope' }),
+		'"validators" option, if/when provided, MUST be a non-empty array of Validator instances'
+	);
+});
+
+test('Observable.from - validators option - negative - number', () => {
+	assert.throws(
+		() => Observable.from({}, { validators: 42 }),
+		'"validators" option, if/when provided, MUST be a non-empty array of Validator instances'
+	);
+});
+
+test('Observable.from - validators option - negative - empty array', () => {
+	assert.throws(
+		() => Observable.from({}, { validators: [] }),
+		'"validators" option, if/when provided, MUST be a non-empty array of Validator instances'
+	);
+});
+
+test('Observable.from - validators option - negative - non-Validator element', () => {
+	assert.throws(
+		() => Observable.from({}, { validators: [Validator.custom(() => { }), 'bad'] }),
+		'"validators" option, if/when provided, MUST be a non-empty array of Validator instances'
+	);
+});
+
+test('Observable.from - validators option - negative - bare function rejected', () => {
+	assert.throws(
+		() => Observable.from({}, { validators: [() => { }] }),
+		'"validators" option, if/when provided, MUST be a non-empty array of Validator instances'
+	);
+});
+
+test('Observable.from - validators option - positive - stored on meta', () => {
+	const v1 = Validator.custom(() => { });
+	const v2 = Validator.custom(() => { });
+	const oo = Observable.from({}, { validators: [v1, v2] });
+	const stored = oo[oMetaKey].validators;
+	assert.strictEqual(stored.length, 2);
+	assert.strictEqual(stored[0], v1);
+	assert.strictEqual(stored[1], v2);
+});
+
+//	e2e: a single "immutable-marker" validator rejecting any change whose oldValue === 'immutable'
+const immutableMarker = Validator.custom(changes => {
+	for (const c of changes) {
+		if (c.oldValue === 'immutable') {
+			throw new Error(`change at '${c.pathAsString}' rejected: oldValue is immutable`);
+		}
+	}
+});
+
+test('e2e - set insert - no oldValue - allowed', () => {
+	const oo = Observable.from({}, { validators: [immutableMarker] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	oo.a = 'new';
+	assert.strictEqual(oo.a, 'new');
+	assert.strictEqual(observed, 1);
+});
+
+test('e2e - set update - oldValue not immutable - allowed', () => {
+	const oo = Observable.from({ a: 'mutable' }, { validators: [immutableMarker] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	oo.a = 'other';
+	assert.strictEqual(oo.a, 'other');
+	assert.strictEqual(observed, 1);
+});
+
+test('e2e - set update - oldValue is immutable - throws, target unchanged, no observer fired', () => {
+	const oo = Observable.from({ a: 'immutable' }, { validators: [immutableMarker] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => { oo.a = 'other'; }, `change at 'a' rejected`);
+	assert.strictEqual(oo.a, 'immutable');
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - delete - oldValue not immutable - allowed', () => {
+	const oo = Observable.from({ a: 'mutable' }, { validators: [immutableMarker] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	delete oo.a;
+	assert.isTrue(!('a' in oo));
+	assert.strictEqual(observed, 1);
+});
+
+test('e2e - delete - oldValue is immutable - throws, target unchanged, no observer fired', () => {
+	const oo = Observable.from({ a: 'immutable' }, { validators: [immutableMarker] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => { delete oo.a; }, `change at 'a' rejected`);
+	assert.strictEqual(oo.a, 'immutable');
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - change shape at validator - set insert', () => {
+	let seen = null;
+	const oo = Observable.from({}, {
+		validators: [Validator.custom(changes => { seen = changes; })]
+	});
+	oo.a = 42;
+	assert.strictEqual(seen.length, 1);
+	const c = seen[0];
+	assert.strictEqual(c.type, 'insert');
+	assert.deepStrictEqual(c.path, ['a']);
+	assert.strictEqual(c.value, 42);
+	assert.strictEqual(c.oldValue, undefined);
+	assert.strictEqual(c.object, oo);
+});
+
+test('e2e - change shape at validator - set update', () => {
+	let seen = null;
+	const oo = Observable.from({ a: 1 }, {
+		validators: [Validator.custom(changes => { seen = changes; })]
+	});
+	oo.a = 2;
+	assert.strictEqual(seen.length, 1);
+	const c = seen[0];
+	assert.strictEqual(c.type, 'update');
+	assert.deepStrictEqual(c.path, ['a']);
+	assert.strictEqual(c.value, 2);
+	assert.strictEqual(c.oldValue, 1);
+	assert.strictEqual(c.object, oo);
+});
+
+test('e2e - change shape at validator - delete', () => {
+	let seen = null;
+	const oo = Observable.from({ a: 1 }, {
+		validators: [Validator.custom(changes => { seen = changes; })]
+	});
+	delete oo.a;
+	assert.strictEqual(seen.length, 1);
+	const c = seen[0];
+	assert.strictEqual(c.type, 'delete');
+	assert.deepStrictEqual(c.path, ['a']);
+	assert.strictEqual(c.value, undefined);
+	assert.strictEqual(c.oldValue, 1);
+	assert.strictEqual(c.object, oo);
+});
+
+test('e2e - rooted path - mutation on nested observable - validator sees full path', () => {
+	let seen = null;
+	const oo = Observable.from({ outer: { inner: { x: 1 } } }, {
+		validators: [Validator.custom(changes => { seen = changes; })]
+	});
+	oo.outer.inner.x = 2;
+	assert.strictEqual(seen.length, 1);
+	assert.deepStrictEqual(seen[0].path, ['outer', 'inner', 'x']);
+});
+
+test('e2e - raw (un-wrapped) new value at validator', () => {
+	const raw = { k: 'v' };
+	let seen = null;
+	const oo = Observable.from({}, {
+		validators: [Validator.custom(changes => { seen = changes; })]
+	});
+	oo.a = raw;
+	assert.strictEqual(seen[0].value, raw);	//	exact same object identity, no proxy wrapping yet
+});
+
+test('e2e - multiple validators - first throws, second not called', () => {
+	let v2Calls = 0;
+	const v1 = Validator.custom(() => { throw new Error('v1 reject'); });
+	const v2 = Validator.custom(() => { v2Calls++; });
+	const oo = Observable.from({}, { validators: [v1, v2] });
+	assert.throws(() => { oo.a = 1; }, 'v1 reject');
+	assert.strictEqual(v2Calls, 0);
+});
+
+//	vetoing validator used across the array-method e2e tests below
+const vetoAll = Validator.custom(() => { throw new Error('rejected'); });
+
+test('e2e - array pop - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([1, 2, 3], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.pop(), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [1, 2, 3]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - array push - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([1, 2, 3], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.push(4, 5), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [1, 2, 3]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - array shift - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([1, 2, 3], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.shift(), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [1, 2, 3]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - array unshift - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([1, 2, 3], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.unshift(0), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [1, 2, 3]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - array reverse - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([1, 2, 3], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.reverse(), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [1, 2, 3]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - array sort - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from([3, 1, 2], { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.sort(), 'rejected');
+	assert.deepStrictEqual(Array.from(oo), [3, 1, 2]);
+	assert.strictEqual(observed, 0);
+});
+
+test('e2e - typed-array set - vetoed - target unchanged, no observer fired', () => {
+	const oo = Observable.from(new Int32Array([1, 2, 3, 4]), { validators: [vetoAll] });
+	let observed = 0;
+	Observable.observe(oo, changes => { observed += changes.length; });
+	assert.throws(() => oo.set([10, 20], 1), 'rejected');
+	assert.deepStrictEqual(oo, new Int32Array([1, 2, 3, 4]));
+	assert.strictEqual(observed, 0);
+});
diff --git a/tests/workers/perf-async-test-a.js b/tests/workers/perf-async-test-a.js
index e0d4162..0959261 100644
--- a/tests/workers/perf-async-test-a.js
+++ b/tests/workers/perf-async-test-a.js
@@ -1,4 +1,4 @@
-import { Observable } from '../../src/object-observer.js';
+import { Observable } from '../../src/object-observer.ts';
 
 export default async setup => {
 	const {
diff --git a/tests/workers/perf-async-test-b.js b/tests/workers/perf-async-test-b.js
index 3ad190d..41bb05e 100644
--- a/tests/workers/perf-async-test-b.js
+++ b/tests/workers/perf-async-test-b.js
@@ -1,4 +1,4 @@
-import { Observable } from '../../src/object-observer.js';
+import { Observable } from '../../src/object-observer.ts';
 
 export default async setup => {
 	const {
diff --git a/tests/workers/perf-sync-test-a.js b/tests/workers/perf-sync-test-a.js
index b12421b..b1a03a3 100644
--- a/tests/workers/perf-sync-test-a.js
+++ b/tests/workers/perf-sync-test-a.js
@@ -1,4 +1,4 @@
-import { Observable } from '../../src/object-observer.js';
+import { Observable } from '../../src/object-observer.ts';
 
 export default setup => {
 	const {
diff --git a/tests/workers/perf-sync-test-b.js b/tests/workers/perf-sync-test-b.js
index eb41e41..fe68c6b 100644
--- a/tests/workers/perf-sync-test-b.js
+++ b/tests/workers/perf-sync-test-b.js
@@ -1,4 +1,4 @@
-import { Observable } from '../../src/object-observer.js';
+import { Observable } from '../../src/object-observer.ts';
 
 export default setup => {
 	const {
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..6d27183
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,11 @@
+{
+    "compilerOptions": {
+        "strict": false,
+        "target": "es2024",
+        "noEmit": true,
+        "allowImportingTsExtensions": true,
+        "rewriteRelativeImportExtensions": true,
+        "verbatimModuleSyntax": true,
+        "erasableSyntaxOnly": true
+    }
+}
\ No newline at end of file