chromedevtools--chrome-devtools-mcp
Pedro Durek
6992106d1c
## Summary Extend the existing `emulate` tool with an `extraHTTPHeaders` parameter that calls Puppeteer's `page.setExtraHTTPHeaders()` (which uses CDP `Network.setExtraHTTPHeaders` under the hood). Closes #1175 ## Approach Per [feedback from @natorion](https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/1175#issuecomment-4097587153), this integrates into the existing `emulate` tool rather than adding a standalone tool. The `emulate` tool is already the central hub for page-level state modifications (userAgent, viewport, networkConditions, geolocation, colorScheme), and custom HTTP headers fit naturally alongside them. This also avoids increasing the MCP tool count and LLM token overhead. ## Changes - **`src/types.ts`** — Added `extraHTTPHeaders?: Record<string, string>` to `EmulationSettings` - **`src/tools/emulation.ts`** — Added `extraHTTPHeaders` as an optional zod parameter on the `emulate` tool - **`src/McpContext.ts`** — Added handler logic in the `emulate()` method: - Calls `page.setExtraHTTPHeaders()` when `extraHTTPHeaders` is provided - Clears from settings when an empty `{}` is passed - Preserves existing headers when the param is **omitted** (unlike other emulation settings that reset when omitted) — prevents `emulate({colorScheme: "dark"})` from accidentally clearing previously-set headers - **`tests/tools/emulation.test.ts`** — Added 5 test cases: 1. Sets extra headers on requests 2. Clears headers with `{}` 3. Headers persist across navigations 4. Does not affect other emulation settings 5. Reports correctly per-page (new page has no headers) ## Use Case This enables setting custom HTTP headers on **all** requests — including the initial document navigation and `<script>` tag loads — which `initScript` cannot do since it runs after the document is already fetched. ## Usage ```js // Set headers emulate({ extraHTTPHeaders: { "X-Custom": "value", "Authorization": "Bearer token" } }) // Clear headers emulate({ extraHTTPHeaders: {} }) // Combine with other emulation settings emulate({ extraHTTPHeaders: { "X-Branch": "feature-1" }, userAgent: "MyBot/1.0" }) ``` --------- Co-authored-by: Alex Rudenko <alexrudenko@chromium.org> Co-authored-by: Nicholas Roscino <nroscino@google.com>