diff --git a/src/examples/headerProviderExample.ts b/src/examples/headerProviderExample.ts
new file mode 100644
index 0000000000..85968f4b9c
--- /dev/null
+++ b/src/examples/headerProviderExample.ts
@@ -0,0 +1,133 @@
+/**
+ * Example of how extensions can register header providers
+ * This file demonstrates the header registration API for extension developers
+ */
+import { headerRegistry } from '@/services/headerRegistry'
+import type {
+  HeaderMap,
+  HeaderProviderContext,
+  IHeaderProvider
+} from '@/types/headerTypes'
+
+/**
+ * Example 1: Simple static header provider
+ */
+class StaticHeaderProvider implements IHeaderProvider {
+  provideHeaders(_context: HeaderProviderContext): HeaderMap {
+    return {
+      'X-Extension-Name': 'my-extension',
+      'X-Extension-Version': '1.0.0'
+    }
+  }
+}
+
+/**
+ * Example 2: Dynamic header provider that adds headers based on the request
+ */
+class DynamicHeaderProvider implements IHeaderProvider {
+  async provideHeaders(context: HeaderProviderContext): Promise<HeaderMap> {
+    const headers: HeaderMap = {}
+
+    // Add different headers based on the URL
+    if (context.url.includes('/api/')) {
+      headers['X-API-Version'] = 'v2'
+    }
+
+    // Add headers based on request method
+    if (context.method === 'POST' || context.method === 'PUT') {
+      headers['X-Request-ID'] = () => crypto.randomUUID()
+    }
+
+    // Add timestamp header
+    headers['X-Timestamp'] = () => new Date().toISOString()
+
+    return headers
+  }
+}
+
+/**
+ * Example 3: Auth token provider
+ */
+class AuthTokenProvider implements IHeaderProvider {
+  private getToken(): string | null {
+    // This could retrieve a token from storage, state, etc.
+    return localStorage.getItem('auth-token')
+  }
+
+  provideHeaders(_context: HeaderProviderContext): HeaderMap {
+    const token = this.getToken()
+
+    if (token) {
+      return {
+        Authorization: `Bearer ${token}`
+      }
+    }
+
+    return {}
+  }
+}
+
+/**
+ * Example of how to register providers in an extension
+ */
+export function setupHeaderProviders() {
+  // Register a simple static provider
+  const staticRegistration = headerRegistry.registerHeaderProvider(
+    new StaticHeaderProvider()
+  )
+
+  // Register a dynamic provider with higher priority
+  const dynamicRegistration = headerRegistry.registerHeaderProvider(
+    new DynamicHeaderProvider(),
+    { priority: 10 }
+  )
+
+  // Register an auth provider that only applies to API endpoints
+  const authRegistration = headerRegistry.registerHeaderProvider(
+    new AuthTokenProvider(),
+    {
+      priority: 20, // Higher priority to override other auth headers
+      filter: (context) => context.url.includes('/api/')
+    }
+  )
+
+  // Return cleanup function for when extension is unloaded
+  return () => {
+    staticRegistration.dispose()
+    dynamicRegistration.dispose()
+    authRegistration.dispose()
+  }
+}
+
+/**
+ * Example of a provider that integrates with a cloud service
+ */
+export class CloudServiceHeaderProvider implements IHeaderProvider {
+  constructor(
+    private apiKey: string,
+    private workspaceId: string
+  ) {}
+
+  async provideHeaders(context: HeaderProviderContext): Promise<HeaderMap> {
+    // Only add headers for requests to the cloud service
+    if (!context.url.includes('cloud.comfyui.com')) {
+      return {}
+    }
+
+    return {
+      'X-API-Key': this.apiKey,
+      'X-Workspace-ID': this.workspaceId,
+      'X-Client-Version': '1.0.0',
+      'X-Session-ID': async () => {
+        // Could fetch or generate session ID asynchronously
+        const sessionId = await this.getOrCreateSessionId()
+        return sessionId
+      }
+    }
+  }
+
+  private async getOrCreateSessionId(): Promise<string> {
+    // Simulate async session creation
+    return 'session-' + Date.now()
+  }
+}
diff --git a/src/services/headerRegistry.ts b/src/services/headerRegistry.ts
new file mode 100644
index 0000000000..4db8379e99
--- /dev/null
+++ b/src/services/headerRegistry.ts
@@ -0,0 +1,129 @@
+import type {
+  HeaderMap,
+  HeaderProviderContext,
+  HeaderProviderOptions,
+  HeaderValue,
+  IHeaderProvider,
+  IHeaderProviderRegistration
+} from '@/types/headerTypes'
+
+/**
+ * Internal registration entry
+ */
+interface HeaderProviderEntry {
+  id: string
+  provider: IHeaderProvider
+  options: HeaderProviderOptions
+}
+
+/**
+ * Registry for HTTP header providers
+ * Follows VSCode extension patterns for registration and lifecycle
+ */
+class HeaderRegistry {
+  private providers: HeaderProviderEntry[] = []
+  private nextId = 1
+
+  /**
+   * Registers a header provider
+   * @param provider - The header provider implementation
+   * @param options - Registration options
+   * @returns Registration handle for disposal
+   */
+  registerHeaderProvider(
+    provider: IHeaderProvider,
+    options: HeaderProviderOptions = {}
+  ): IHeaderProviderRegistration {
+    const id = `header-provider-${this.nextId++}`
+
+    const entry: HeaderProviderEntry = {
+      id,
+      provider,
+      options: {
+        priority: options.priority ?? 0,
+        filter: options.filter
+      }
+    }
+
+    // Insert provider in priority order (higher priority = later in array)
+    const insertIndex = this.providers.findIndex(
+      (p) => (p.options.priority ?? 0) > (entry.options.priority ?? 0)
+    )
+    if (insertIndex === -1) {
+      this.providers.push(entry)
+    } else {
+      this.providers.splice(insertIndex, 0, entry)
+    }
+
+    // Return disposable handle
+    return {
+      id,
+      dispose: () => {
+        const index = this.providers.findIndex((p) => p.id === id)
+        if (index !== -1) {
+          this.providers.splice(index, 1)
+        }
+      }
+    }
+  }
+
+  /**
+   * Gets all headers for a request by combining all registered providers
+   * @param context - Request context
+   * @returns Combined headers from all providers
+   */
+  async getHeaders(context: HeaderProviderContext): Promise<HeaderMap> {
+    const result: HeaderMap = {}
+
+    // Process providers in order (lower priority first, so higher priority can override)
+    for (const entry of this.providers) {
+      // Check filter if provided
+      if (entry.options.filter && !entry.options.filter(context)) {
+        continue
+      }
+
+      try {
+        const headers = await entry.provider.provideHeaders(context)
+
+        // Merge headers, resolving any function values
+        for (const [key, value] of Object.entries(headers)) {
+          result[key] = await this.resolveHeaderValue(value)
+        }
+      } catch (error) {
+        console.error(`Error getting headers from provider ${entry.id}:`, error)
+        // Continue with other providers even if one fails
+      }
+    }
+
+    return result
+  }
+
+  /**
+   * Resolves a header value, handling functions
+   */
+  private async resolveHeaderValue(
+    value: HeaderValue
+  ): Promise<string | number | boolean> {
+    if (typeof value === 'function') {
+      return await value()
+    }
+    return value
+  }
+
+  /**
+   * Clears all registered providers
+   */
+  clear(): void {
+    this.providers = []
+  }
+
+  /**
+   * Gets the count of registered providers
+   */
+  get providerCount(): number {
+    return this.providers.length
+  }
+}
+
+// Export singleton instance
+export const headerRegistry = new HeaderRegistry()
diff --git a/src/services/networkClientAdapter.ts b/src/services/networkClientAdapter.ts
new file mode 100644
index 0000000000..2989f0ed0d
--- /dev/null
+++ b/src/services/networkClientAdapter.ts
@@ -0,0 +1,87 @@
+import type { AxiosInstance, AxiosRequestConfig } from 'axios'
+import axios from 'axios'
+
+import { headerRegistry } from '@/services/headerRegistry'
+import type { HeaderProviderContext } from '@/types/headerTypes'
+
+/**
+ * Creates an axios instance with automatic header injection from the registry
+ * @param config - Base axios configuration
+ * @returns Axios instance with header injection
+ */
+export function createAxiosWithHeaders(
+  config?: AxiosRequestConfig
+): AxiosInstance {
+  const instance = axios.create(config)
+
+  // Add request interceptor to inject headers
+  instance.interceptors.request.use(
+    async (requestConfig) => {
+      // Build context for header providers
+      const context: HeaderProviderContext = {
+        url: requestConfig.url || '',
+        method: requestConfig.method || 'GET',
+        body: requestConfig.data,
+        config: requestConfig
+      }
+
+      // Get headers from registry
+      const registryHeaders = await headerRegistry.getHeaders(context)
+
+      // Merge with existing headers (registry headers take precedence)
+      for (const [key, value] of Object.entries(registryHeaders)) {
+        requestConfig.headers[key] = value
+      }
+
+      return requestConfig
+    },
+    (error) => {
+      return Promise.reject(error)
+    }
+  )
+
+  return instance
+}
+
+/**
+ * Wraps the native fetch API with header injection from the registry
+ * @param input - Request URL or Request object
+ * @param init - Request initialization options
+ * @returns Promise resolving to Response
+ */
+export async function fetchWithHeaders(
+  input: RequestInfo | URL,
+  init?: RequestInit
+): Promise<Response> {
+  // Extract URL and method for context
+  const url =
+    typeof input === 'string'
+      ? input
+      : input instanceof URL
+        ? input.toString()
+        : input.url
+  const method =
+    init?.method || (input instanceof Request ? input.method : 'GET')
+
+  // Build context for header providers
+  const context: HeaderProviderContext = {
+    url,
+    method,
+    body: init?.body
+  }
+
+  // Get headers from registry
+  const registryHeaders = await headerRegistry.getHeaders(context)
+
+  // Convert registry headers to Headers object format
+  const headers = new Headers(init?.headers)
+  for (const [key, value] of Object.entries(registryHeaders)) {
+    headers.set(key, String(value))
+  }
+
+  // Perform fetch with merged headers
+  return fetch(input, {
+    ...init,
+    headers
+  })
+}
diff --git a/src/types/headerTypes.ts b/src/types/headerTypes.ts
new file mode 100644
index 0000000000..f96312ee51
--- /dev/null
+++ b/src/types/headerTypes.ts
@@ -0,0 +1,61 @@
+import type { AxiosRequestConfig } from 'axios'
+
+/**
+ * Header value can be a string, number, boolean, or a function that returns one of these
+ */
+export type HeaderValue =
+  | string
+  | number
+  | boolean
+  | (() => string | number | boolean | Promise<string | number | boolean>)
+
+/**
+ * Header provider interface for extensions to implement
+ */
+export interface IHeaderProvider {
+  /**
+   * Provides headers for HTTP requests
+   * @param context - Request context containing URL and method
+   * @returns Headers to be added to the request
+   */
+  provideHeaders(context: HeaderProviderContext): HeaderMap | Promise<HeaderMap>
+}
+
+/**
+ * Context passed to header providers
+ */
+export interface HeaderProviderContext {
+  /** The URL being requested */
+  url: string
+  /** HTTP method */
+  method: string
+  /** Optional request body */
+  body?: any
+  /** Original request config if available */
+  config?: AxiosRequestConfig
+}
+
+/**
+ * Map of header names to values
+ */
+export type HeaderMap = Record<string, HeaderValue>
+
+/**
+ * Registration handle returned when registering a header provider
+ */
+export interface IHeaderProviderRegistration {
+  /** Unique ID for this registration */
+  id: string
+  /** Disposes of this registration */
+  dispose(): void
+}
+
+/**
+ * Options for registering a header provider
+ */
+export interface HeaderProviderOptions {
+  /** Priority for this provider (higher = runs later, can override earlier providers) */
+  priority?: number
+  /** Optional filter to limit which requests this provider applies to */
+  filter?: (context: HeaderProviderContext) => boolean
+}
diff --git a/tests-ui/tests/services/headerRegistry.test.ts b/tests-ui/tests/services/headerRegistry.test.ts
new file mode 100644
index 0000000000..d9acc0cae9
--- /dev/null
+++ b/tests-ui/tests/services/headerRegistry.test.ts
@@ -0,0 +1,253 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { headerRegistry } from '@/services/headerRegistry'
+import type {
+  HeaderProviderContext,
+  IHeaderProvider
+} from '@/types/headerTypes'
+
+describe('headerRegistry', () => {
+  beforeEach(() => {
+    headerRegistry.clear()
+  })
+
+  describe('registerHeaderProvider', () => {
+    it('should register a header provider', () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Test': 'value' })
+      }
+
+      const registration = headerRegistry.registerHeaderProvider(provider)
+
+      expect(registration).toBeDefined()
+      expect(registration.id).toMatch(/^header-provider-\d+$/)
+      expect(headerRegistry.providerCount).toBe(1)
+    })
+
+    it('should return a disposable registration', () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn()
+      }
+
+      const registration = headerRegistry.registerHeaderProvider(provider)
+      expect(headerRegistry.providerCount).toBe(1)
+
+      registration.dispose()
+      expect(headerRegistry.providerCount).toBe(0)
+    })
+
+    it('should insert providers in priority order', async () => {
+      const provider1: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Priority': 'low' })
+      }
+      const provider2: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Priority': 'high' })
+      }
+      const provider3: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Priority': 'medium' })
+      }
+
+      headerRegistry.registerHeaderProvider(provider1, { priority: 1 })
+      headerRegistry.registerHeaderProvider(provider2, { priority: 10 })
+      headerRegistry.registerHeaderProvider(provider3, { priority: 5 })
+
+      const context: HeaderProviderContext = {
+        url: 'https://api.example.com',
+        method: 'GET'
+      }
+
+      const headers = await headerRegistry.getHeaders(context)
+
+      // Higher priority provider should override
+      expect(headers['X-Priority']).toBe('high')
+    })
+  })
+
+  describe('getHeaders', () => {
+    it('should combine headers from all providers', async () => {
+      const provider1: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Header-1': 'value1',
+          'X-Common': 'provider1'
+        })
+      }
+      const provider2: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Header-2': 'value2',
+          'X-Common': 'provider2'
+        })
+      }
+
+      headerRegistry.registerHeaderProvider(provider1, { priority: 1 })
+      headerRegistry.registerHeaderProvider(provider2, { priority: 2 })
+
+      const context: HeaderProviderContext = {
+        url: 'https://api.example.com',
+        method: 'GET'
+      }
+
+      const headers = await headerRegistry.getHeaders(context)
+
+      expect(headers).toEqual({
+        'X-Header-1': 'value1',
+        'X-Header-2': 'value2',
+        'X-Common': 'provider2' // Higher priority wins
+      })
+    })
+
+    it('should resolve function header values', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Static': 'static',
+          'X-Dynamic': () => 'dynamic',
+          'X-Async': async () => 'async-value'
+        })
+      }
+
+      headerRegistry.registerHeaderProvider(provider)
+
+      const context: HeaderProviderContext = {
+        url: 'https://api.example.com',
+        method: 'GET'
+      }
+
+      const headers = await headerRegistry.getHeaders(context)
+
+      expect(headers).toEqual({
+        'X-Static': 'static',
+        'X-Dynamic': 'dynamic',
+        'X-Async': 'async-value'
+      })
+    })
+
+    it('should handle async providers', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockImplementation(async () => {
+          await new Promise((resolve) => setTimeout(resolve, 10))
+          return { 'X-Async': 'resolved' }
+        })
+      }
+
+      headerRegistry.registerHeaderProvider(provider)
+
+      const context: HeaderProviderContext = {
+        url: 'https://api.example.com',
+        method: 'GET'
+      }
+
+      const headers = await headerRegistry.getHeaders(context)
+
+      expect(headers).toEqual({ 'X-Async': 'resolved' })
+    })
+
+    it('should apply filters when provided', async () => {
+      const provider1: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Api': 'api-header' })
+      }
+      const provider2: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Other': 'other-header' })
+      }
+
+      // Only apply to API URLs
+      headerRegistry.registerHeaderProvider(provider1, {
+        filter: (ctx) => ctx.url.includes('/api/')
+      })
+
+      // Apply to all URLs
+      headerRegistry.registerHeaderProvider(provider2)
+
+      const apiContext: HeaderProviderContext = {
+        url: 'https://example.com/api/users',
+        method: 'GET'
+      }
+
+      const otherContext: HeaderProviderContext = {
+        url: 'https://example.com/assets/image.png',
+        method: 'GET'
+      }
+
+      const apiHeaders = await headerRegistry.getHeaders(apiContext)
+      const otherHeaders = await headerRegistry.getHeaders(otherContext)
+
+      expect(apiHeaders).toEqual({
+        'X-Api': 'api-header',
+        'X-Other': 'other-header'
+      })
+
+      expect(otherHeaders).toEqual({
+        'X-Other': 'other-header'
+      })
+    })
+
+    it('should continue with other providers if one fails', async () => {
+      const provider1: IHeaderProvider = {
+        provideHeaders: vi.fn().mockRejectedValue(new Error('Provider error'))
+      }
+      const provider2: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({ 'X-Header': 'value' })
+      }
+
+      headerRegistry.registerHeaderProvider(provider1)
+      headerRegistry.registerHeaderProvider(provider2)
+
+      const context: HeaderProviderContext = {
+        url: 'https://api.example.com',
+        method: 'GET'
+      }
+
+      const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {})
+
+      const headers = await headerRegistry.getHeaders(context)
+
+      expect(headers).toEqual({ 'X-Header': 'value' })
+      expect(consoleSpy).toHaveBeenCalledWith(
+        expect.stringContaining('Error getting headers from provider'),
+        expect.any(Error)
+      )
+
+      consoleSpy.mockRestore()
+    })
+  })
+
+  describe('clear', () => {
+    it('should remove all providers', () => {
+      const provider1: IHeaderProvider = {
+        provideHeaders: vi.fn()
+      }
+      const provider2: IHeaderProvider = {
+        provideHeaders: vi.fn()
+      }
+
+      headerRegistry.registerHeaderProvider(provider1)
+      headerRegistry.registerHeaderProvider(provider2)
+
+      expect(headerRegistry.providerCount).toBe(2)
+
+      headerRegistry.clear()
+
+      expect(headerRegistry.providerCount).toBe(0)
+    })
+  })
+
+  describe('providerCount', () => {
+    it('should return the correct count of providers', () => {
+      expect(headerRegistry.providerCount).toBe(0)
+
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn()
+      }
+
+      const reg1 = headerRegistry.registerHeaderProvider(provider)
+      expect(headerRegistry.providerCount).toBe(1)
+
+      const reg2 = headerRegistry.registerHeaderProvider(provider)
+      expect(headerRegistry.providerCount).toBe(2)
+
+      reg1.dispose()
+      expect(headerRegistry.providerCount).toBe(1)
+
+      reg2.dispose()
+      expect(headerRegistry.providerCount).toBe(0)
+    })
+  })
+})
diff --git a/tests-ui/tests/services/networkClientAdapter.test.ts b/tests-ui/tests/services/networkClientAdapter.test.ts
new file mode 100644
index 0000000000..85c6bb7a99
--- /dev/null
+++ b/tests-ui/tests/services/networkClientAdapter.test.ts
@@ -0,0 +1,289 @@
+import axios from 'axios'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { headerRegistry } from '@/services/headerRegistry'
+import {
+  createAxiosWithHeaders,
+  fetchWithHeaders
+} from '@/services/networkClientAdapter'
+import type { IHeaderProvider } from '@/types/headerTypes'
+
+// Mock axios
+vi.mock('axios')
+
+// Mock fetch globally
+const mockFetch = vi.fn()
+vi.stubGlobal('fetch', mockFetch)
+
+describe('networkClientAdapter', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    headerRegistry.clear()
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  describe('createAxiosWithHeaders', () => {
+    it('should create an axios instance with header injection', async () => {
+      // Setup mock axios instance
+      const mockInterceptors = {
+        request: {
+          use: vi.fn()
+        },
+        response: {
+          use: vi.fn()
+        }
+      }
+
+      const mockAxiosInstance = {
+        interceptors: mockInterceptors,
+        get: vi.fn(),
+        post: vi.fn()
+      }
+
+      vi.mocked(axios.create).mockReturnValue(mockAxiosInstance as any)
+
+      // Create instance
+      createAxiosWithHeaders({ baseURL: 'https://api.example.com' })
+
+      // Verify axios.create was called with config
+      expect(axios.create).toHaveBeenCalledWith({
+        baseURL: 'https://api.example.com'
+      })
+
+      // Verify interceptor was added
+      expect(mockInterceptors.request.use).toHaveBeenCalledWith(
+        expect.any(Function),
+        expect.any(Function)
+      )
+    })
+
+    it('should inject headers from registry on request', async () => {
+      // Setup header provider
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Custom-Header': 'custom-value'
+        })
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      // Setup mock axios
+      const mockInterceptors = {
+        request: {
+          use: vi.fn()
+        },
+        response: {
+          use: vi.fn()
+        }
+      }
+
+      const mockAxiosInstance = {
+        interceptors: mockInterceptors
+      }
+
+      vi.mocked(axios.create).mockReturnValue(mockAxiosInstance as any)
+
+      // Create instance
+      createAxiosWithHeaders()
+
+      // Get the interceptor function
+      const [interceptorFn] = mockInterceptors.request.use.mock.calls[0]
+
+      // Test the interceptor
+      const config = {
+        url: '/api/test',
+        method: 'POST',
+        data: { foo: 'bar' },
+        headers: {
+          'Content-Type': 'application/json'
+        }
+      }
+
+      const result = await interceptorFn(config)
+
+      // Verify provider was called with correct context
+      expect(provider.provideHeaders).toHaveBeenCalledWith({
+        url: '/api/test',
+        method: 'POST',
+        body: { foo: 'bar' },
+        config
+      })
+
+      // Verify headers were merged
+      expect(result.headers).toEqual({
+        'Content-Type': 'application/json',
+        'X-Custom-Header': 'custom-value'
+      })
+    })
+
+    it('should handle interceptor errors', async () => {
+      // Setup mock axios
+      const mockInterceptors = {
+        request: {
+          use: vi.fn()
+        },
+        response: {
+          use: vi.fn()
+        }
+      }
+
+      const mockAxiosInstance = {
+        interceptors: mockInterceptors
+      }
+
+      vi.mocked(axios.create).mockReturnValue(mockAxiosInstance as any)
+
+      // Create instance
+      createAxiosWithHeaders()
+
+      // Get the error handler
+      const [, errorHandler] = mockInterceptors.request.use.mock.calls[0]
+
+      // Test error handling
+      const error = new Error('Request error')
+      await expect(errorHandler(error)).rejects.toThrow('Request error')
+    })
+  })
+
+  describe('fetchWithHeaders', () => {
+    it('should inject headers from registry into fetch requests', async () => {
+      // Setup header provider
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Api-Key': 'test-key',
+          'X-Request-ID': '12345'
+        })
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      // Setup fetch mock
+      mockFetch.mockResolvedValue(new Response('OK'))
+
+      // Make request
+      await fetchWithHeaders('https://api.example.com/data', {
+        method: 'GET',
+        headers: {
+          Accept: 'application/json'
+        }
+      })
+
+      // Verify provider was called
+      expect(provider.provideHeaders).toHaveBeenCalledWith({
+        url: 'https://api.example.com/data',
+        method: 'GET',
+        body: undefined
+      })
+
+      // Verify fetch was called with merged headers
+      expect(mockFetch).toHaveBeenCalledWith(
+        'https://api.example.com/data',
+        expect.objectContaining({
+          method: 'GET',
+          headers: expect.any(Headers)
+        })
+      )
+
+      // Check the headers
+      const [, init] = mockFetch.mock.calls[0]
+      const headers = init.headers as Headers
+      expect(headers.get('Accept')).toBe('application/json')
+      expect(headers.get('X-Api-Key')).toBe('test-key')
+      expect(headers.get('X-Request-ID')).toBe('12345')
+    })
+
+    it('should handle URL objects', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({})
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      mockFetch.mockResolvedValue(new Response('OK'))
+
+      const url = new URL('https://api.example.com/test')
+      await fetchWithHeaders(url)
+
+      expect(provider.provideHeaders).toHaveBeenCalledWith({
+        url: 'https://api.example.com/test',
+        method: 'GET',
+        body: undefined
+      })
+    })
+
+    it('should handle Request objects', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Custom': 'value'
+        })
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      mockFetch.mockResolvedValue(new Response('OK'))
+
+      const request = new Request('https://api.example.com/test', {
+        method: 'POST',
+        body: JSON.stringify({ data: 'test' })
+      })
+
+      await fetchWithHeaders(request)
+
+      expect(provider.provideHeaders).toHaveBeenCalledWith({
+        url: 'https://api.example.com/test',
+        method: 'POST',
+        body: undefined // init.body is undefined when using Request object
+      })
+
+      // Verify headers were added
+      const [, init] = mockFetch.mock.calls[0]
+      const headers = init.headers as Headers
+      expect(headers.get('X-Custom')).toBe('value')
+    })
+
+    it('should convert header values to strings', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Number': 123,
+          'X-Boolean': true,
+          'X-String': 'test'
+        })
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      mockFetch.mockResolvedValue(new Response('OK'))
+
+      await fetchWithHeaders('https://api.example.com')
+
+      const [, init] = mockFetch.mock.calls[0]
+      const headers = init.headers as Headers
+      expect(headers.get('X-Number')).toBe('123')
+      expect(headers.get('X-Boolean')).toBe('true')
+      expect(headers.get('X-String')).toBe('test')
+    })
+
+    it('should preserve existing headers and let registry override', async () => {
+      const provider: IHeaderProvider = {
+        provideHeaders: vi.fn().mockReturnValue({
+          'X-Override': 'new-value',
+          'X-New': 'added'
+        })
+      }
+      headerRegistry.registerHeaderProvider(provider)
+
+      mockFetch.mockResolvedValue(new Response('OK'))
+
+      await fetchWithHeaders('https://api.example.com', {
+        headers: {
+          'X-Override': 'old-value',
+          'X-Existing': 'keep-me'
+        }
+      })
+
+      const [, init] = mockFetch.mock.calls[0]
+      const headers = init.headers as Headers
+      expect(headers.get('X-Override')).toBe('new-value') // Registry wins
+      expect(headers.get('X-Existing')).toBe('keep-me')
+      expect(headers.get('X-New')).toBe('added')
+    })
+  })
+})