ProxiedResponseError [FetchResponseError]: HTTP 200 response does not appear to originate from GitHub.

[yermulnik]

Cross-posting the github/copilot.vim#282 from copilot.vim repo as the issue seems to pertain to copilot-language-server.

copilot-language-server is throwing ProxiedResponseError error on initialization:

init log

[2026-05-08 21:43:29] <-! npm warn exec The following package was not found and will be installed: @github/copilot-language-server@1.483.0
[2026-05-08 21:43:31] [INFO] [ripgrep] Set GITHUB_COPILOT_RIPGREP_PATH_OVERRIDE=/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/bin/linux/x64/rg
[2026-05-08 21:43:31] [INFO] [lsp] GitHub Copilot Language Server 1.483.0 initialized
[2026-05-08 21:43:31] [INFO] [UndiciFetcher] HTTP settings changed; resetting Undici dispatchers. {
  proxy: 'none',
  noProxyCount: 0,
  proxyStrictSSL: true,
  hasProxyAuthorization: false,
  hasProxyKerberosServicePrincipal: false
}
[2026-05-08 21:43:31] [WARN] [default] Policy watcher not available - continuing without policy watching: Unsupported platform
[2026-05-08 21:43:31] [INFO] [certificates] Removed 2 expired certificates
[2026-05-08 21:43:31] [INFO] [UndiciFetcher] Root certificate set changed; resetting Undici dispatchers. { certificateCount: 289 }
[2026-05-08 21:43:31] [INFO] [certificates] Removed 2 expired certificates
[2026-05-08 21:43:31] [INFO] [certificates] Removed 2 expired certificates
[2026-05-08 21:43:31] [ERROR] [GithubAvailableEmbeddingTypes] Error fetching available embedding types ProxiedResponseError [FetchResponseError]: HTTP 200 response does not appear to originate from GitHub. Is a proxy or firewall intercepting this request? https://gh.io/copilot-firewall
    at apiFetch (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:1523:8592)
    at processTicksAndRejections (node:internal/process/task_queues:104:5)
    at GithubAvailableEmbeddingTypesManager.doGetAvailableTypes (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:21243)
    at GithubAvailableEmbeddingTypesManager.getAllAvailableTypes (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:20923)
    at GithubAvailableEmbeddingTypesManager.getPreferredType (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:21752)
    at WorkspaceChunkSearchService.tryInit (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2615:38351) {
  code: 'HTTP200'
}
[2026-05-08 21:43:32] [ERROR] [GithubAvailableEmbeddingTypes] Error fetching available embedding types ProxiedResponseError [FetchResponseError]: HTTP 200 response does not appear to originate from GitHub. Is a proxy or firewall intercepting this request? https://gh.io/copilot-firewall
    at apiFetch (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:1523:8592)
    at processTicksAndRejections (node:internal/process/task_queues:104:5)
    at GithubAvailableEmbeddingTypesManager.doGetAvailableTypes (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:21243)
    at /home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:21101
    at GithubAvailableEmbeddingTypesManager.getPreferredType (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2582:21752)
    at WorkspaceChunkSearchService.tryInit (/home/georgii/.npm/_npx/e9e522e871635100/node_modules/@github/copilot-language-server/dist/main.js:2615:38351) {
  code: 'HTTP200'
}
[2026-05-08 21:43:32] [INFO] [GithubAvailableEmbeddingTypes] Could not find any available embedding types. Error: requestFailed

This is happening with NodeJS 26.0.0 while there's no issues with NodeJS 25.9.0.

I'm testing from two independent machines from different networks where no mitm/proxy exist.

The let g:copilot_proxy_strict_ssl = v:false and NODE_TLS_REJECT_UNAUTHORIZED=0 don't help.

> curl -i https://copilot-proxy.githubusercontent.com/_ping
HTTP/2 200
content-security-policy: default-src 'none'; sandbox
content-type: application/json
strict-transport-security: max-age=31536000
content-length: 48
date: Fri, 08 May 2026 21:23:08 GMT
x-github-backend: Kubernetes
x-github-request-id: CCD6:33FDDA:96751:DD2BC:69FE543C

{"now":1778275388,"status":"ok","ns1":"200 OK"}

[antoniorodr]

Same error with NodeJS v22.17.0, using sidekick.nvim. I tried to clean the cache and log in again, but I am getting this error:

Request signIn failed with message: Response content-type is missing (status=200)