diff --git a/src/lib/constants.ts b/src/lib/constants.ts
index 101927de..4c0f4c85 100644
--- a/src/lib/constants.ts
+++ b/src/lib/constants.ts
@@ -15,7 +15,119 @@ if (typeof Deno !== 'undefined') {
   JS_ENV = 'node'
 }
 
-export const DEFAULT_HEADERS = { 'X-Client-Info': `supabase-js-${JS_ENV}/${version}` }
+export function getClientPlatform(): string | null {
+  // @ts-ignore
+  if (typeof process !== 'undefined' && process.platform) {
+    // @ts-ignore
+    const platform = process.platform
+    if (platform === 'darwin') return 'macOS'
+    if (platform === 'win32') return 'Windows'
+    if (platform === 'linux') return 'Linux'
+    if (platform === 'android') return 'Android'
+  }
+
+  // @ts-ignore
+  if (typeof navigator !== 'undefined') {
+    // Modern User-Agent Client Hints API
+    // @ts-ignore
+    if (navigator.userAgentData && navigator.userAgentData.platform) {
+      // @ts-ignore
+      const platform = navigator.userAgentData.platform
+      if (platform === 'macOS') return 'macOS'
+      if (platform === 'Windows') return 'Windows'
+      if (platform === 'Linux') return 'Linux'
+      if (platform === 'Android') return 'Android'
+      if (platform === 'iOS') return 'iOS'
+    }
+  }
+
+  return null
+}
+
+export function getClientPlatformVersion(): string | null {
+  // @ts-ignore
+  if (typeof process !== 'undefined' && process.version) {
+    // @ts-ignore
+    return process.version.slice(1)
+  }
+
+  // @ts-ignore
+  if (typeof navigator !== 'undefined') {
+    // Modern User-Agent Client Hints API
+    // @ts-ignore
+    if (navigator.userAgentData && navigator.userAgentData.platformVersion) {
+      // @ts-ignore
+      return navigator.userAgentData.platformVersion
+    }
+  }
+
+  return null
+}
+
+export function getClientRuntime(): string | null {
+  // @ts-ignore
+  if (typeof Deno !== 'undefined') {
+    return 'deno'
+  }
+  // @ts-ignore
+  if (typeof Bun !== 'undefined') {
+    return 'bun'
+  }
+  // @ts-ignore
+  if (typeof process !== 'undefined' && process.versions && process.versions.node) {
+    return 'node'
+  }
+  return null
+}
+
+export function getClientRuntimeVersion(): string | null {
+  // @ts-ignore
+  if (typeof Deno !== 'undefined' && Deno.version) {
+    // @ts-ignore
+    return Deno.version.deno
+  }
+  // @ts-ignore
+  if (typeof Bun !== 'undefined' && Bun.version) {
+    // @ts-ignore
+    return Bun.version
+  }
+  // @ts-ignore
+  if (typeof process !== 'undefined' && process.versions && process.versions.node) {
+    // @ts-ignore
+    return process.versions.node
+  }
+  return null
+}
+
+function buildHeaders() {
+  const headers: Record<string, string> = {
+    'X-Client-Info': `supabase-js-${JS_ENV}/${version}`,
+  }
+
+  const platform = getClientPlatform()
+  if (platform) {
+    headers['X-Supabase-Client-Platform'] = platform
+  }
+
+  const platformVersion = getClientPlatformVersion()
+  if (platformVersion) {
+    headers['X-Supabase-Client-Platform-Version'] = platformVersion
+  }
+
+  const runtime = getClientRuntime()
+  if (runtime) {
+    headers['X-Supabase-Client-Runtime'] = runtime
+  }
+
+  const runtimeVersion = getClientRuntimeVersion()
+  if (runtimeVersion) {
+    headers['X-Supabase-Client-Runtime-Version'] = runtimeVersion
+  }
+
+  return headers
+}
+
+export const DEFAULT_HEADERS = buildHeaders()
 
 export const DEFAULT_GLOBAL_OPTIONS = {
   headers: DEFAULT_HEADERS,
diff --git a/test/unit/constants.test.ts b/test/unit/constants.test.ts
index 814c75b8..558a36ab 100644
--- a/test/unit/constants.test.ts
+++ b/test/unit/constants.test.ts
@@ -1,4 +1,10 @@
-import { DEFAULT_HEADERS } from '../../src/lib/constants'
+import {
+  DEFAULT_HEADERS,
+  getClientPlatform,
+  getClientPlatformVersion,
+  getClientRuntime,
+  getClientRuntimeVersion,
+} from '../../src/lib/constants'
 import { version } from '../../src/lib/version'
 
 test('it has the correct type of returning with the correct value', () => {
@@ -13,11 +19,90 @@ test('it has the correct type of returning with the correct value', () => {
   } else {
     JS_ENV = 'node'
   }
-  const expected = {
-    'X-Client-Info': `supabase-js-${JS_ENV}/${version}`,
-  }
-  expect(DEFAULT_HEADERS).toEqual(expected)
+
   expect(typeof DEFAULT_HEADERS).toBe('object')
   expect(typeof DEFAULT_HEADERS['X-Client-Info']).toBe('string')
-  expect(Object.keys(DEFAULT_HEADERS).length).toBe(1)
+  expect(DEFAULT_HEADERS['X-Client-Info']).toBe(`supabase-js-${JS_ENV}/${version}`)
+
+  // X-Client-Info should always be present
+  expect(DEFAULT_HEADERS).toHaveProperty('X-Client-Info')
+
+  // Other headers should only be present if they can be detected
+  Object.keys(DEFAULT_HEADERS).forEach((key) => {
+    expect(typeof DEFAULT_HEADERS[key]).toBe('string')
+    expect(DEFAULT_HEADERS[key].length).toBeGreaterThan(0)
+  })
+})
+
+describe('Client Platform Detection', () => {
+  test('getClientPlatform returns platform or null', () => {
+    const platform = getClientPlatform()
+    expect(platform === null || typeof platform === 'string').toBe(true)
+    if (platform) {
+      expect(platform.length).toBeGreaterThan(0)
+      expect(['macOS', 'Windows', 'Linux', 'iOS', 'Android'].includes(platform)).toBe(true)
+    }
+  })
+
+  test('getClientPlatformVersion returns version string or null', () => {
+    const version = getClientPlatformVersion()
+    expect(version === null || typeof version === 'string').toBe(true)
+    if (version) {
+      expect(version.length).toBeGreaterThan(0)
+    }
+  })
+})
+
+describe('Client Runtime Detection', () => {
+  test('getClientRuntime returns runtime or null', () => {
+    const runtime = getClientRuntime()
+    expect(runtime === null || typeof runtime === 'string').toBe(true)
+    if (runtime) {
+      expect(runtime.length).toBeGreaterThan(0)
+      expect(['node', 'deno', 'bun'].includes(runtime)).toBe(true)
+    }
+  })
+
+  test('getClientRuntimeVersion returns version string or null', () => {
+    const version = getClientRuntimeVersion()
+    expect(version === null || typeof version === 'string').toBe(true)
+    if (version) {
+      expect(version.length).toBeGreaterThan(0)
+    }
+  })
+})
+
+describe('Header Constants', () => {
+  test('X-Client-Info header format', () => {
+    const header = DEFAULT_HEADERS['X-Client-Info']
+    expect(header).toMatch(/^supabase-js-.+\/\d+\.\d+\.\d+/)
+  })
+
+  test('X-Client-Info is always present', () => {
+    expect(DEFAULT_HEADERS).toHaveProperty('X-Client-Info')
+  })
+
+  test('Optional headers are only present when detected', () => {
+    // Test that optional headers are either not present or have valid values
+    const optionalHeaders = [
+      'X-Supabase-Client-Platform',
+      'X-Supabase-Client-Platform-Version',
+      'X-Supabase-Client-Runtime',
+      'X-Supabase-Client-Runtime-Version',
+    ]
+
+    optionalHeaders.forEach((headerName) => {
+      if (DEFAULT_HEADERS[headerName]) {
+        expect(typeof DEFAULT_HEADERS[headerName]).toBe('string')
+        expect(DEFAULT_HEADERS[headerName].length).toBeGreaterThan(0)
+      }
+    })
+  })
+
+  test('All present headers are properly formatted', () => {
+    Object.values(DEFAULT_HEADERS).forEach((value) => {
+      expect(typeof value).toBe('string')
+      expect(value.length).toBeGreaterThan(0)
+    })
+  })
 })