Bernstein vs Google Gemini CLI: quick decision guide

Install both

npm install -g @google/gemini-cli

pipx install bernstein

Feature matrix

Adapter source: src/bernstein/adapters/gemini.py | Upstream homepage: github.com

Verifiable facts

The brief for this surface requires at least three facts that a reader can verify against a primary source. The list below is built from the bernstein adapter source and, when available, the upstream project's own pages.

1. Bernstein ships a Google Gemini CLI adapter at src/bernstein/adapters/gemini.py that wraps the upstream CLI as one of 42 routable agents. [source: bernstein adapter source, as of 2026-08-16]
2. Upstream install command, as recorded in the bernstein adapter, is "npm install -g @google/gemini-cli". [source: upstream docs, as of 2026-08-16]
3. Bernstein last verified its adapter against upstream @google/gemini-cli 0.40.x on 2026-05-05. [source: bernstein adapter source, as of 2026-05-05]
4. Google Gemini CLI is flagged parallel-safe in Bernstein's adapter contract, meaning multiple instances can run in separate git worktrees against the same goal. [source: bernstein adapter source, as of 2026-08-16]
5. Google Gemini CLI supports the Model Context Protocol per the bernstein adapter contract, so Bernstein can inject MCP servers into its session. [source: bernstein adapter source, as of 2026-08-16]
6. Google Gemini CLI is distributed under Google proprietary, per the operator-curated overlay in data/adapters-overlay.json. [source: upstream docs, as of 2026-08-16]

Where Google Gemini CLI fits in Bernstein

Bernstein registers Google Gemini CLI under the slug "gemini" and the registry name "gemini". The adapter source lives at src/bernstein/adapters/gemini.py in the bernstein repo and was last touched at build time 2026-08-16. The Google Gemini CLI adapter file is 361 lines and 13,591 bytes long, fingerprinted 8241cb35d741d169 (first 16 hex chars of SHA-256). Operators install Google Gemini CLI on a worker box with "npm install -g @google/gemini-cli" before Bernstein routes any task to it. No upstream GitHub repository is recorded in the bernstein adapter for Google Gemini CLI; refer to the upstream vendor's documentation when auditing. The Google Gemini CLI project's homepage at github.com is the primary source for upstream release notes. Bernstein last verified the Google Gemini CLI adapter against upstream @google/gemini-cli 0.40.x on 2026-05-05, recorded inline in the adapter source. Google Gemini CLI accepts MCP servers, so Bernstein injects the same MCP toolset it provides every other MCP-aware adapter. Google Gemini CLI is flagged parallel-safe, meaning multiple Bernstein workers can spawn it in separate git worktrees against the same goal without file collisions. Google Gemini CLI ships under Google proprietary per the operator-curated overlay; cross-check against the upstream LICENSE file before production use. Auth model for Google Gemini CLI is "GEMINI_API_KEY or Google AI Studio session", scoped per adapter so a leaked key never grants access to a different model family. Bernstein routes tasks to Google Gemini CLI when its pass rate on similar work clears the configured threshold, otherwise the deterministic Python scheduler picks a different adapter from the 40+ adapter catalog.

Adapter source excerpt

The module docstring of the Google Gemini CLI adapter, as it stands in the bernstein repo. Punctuation is normalised for the web; the wording is the author's. Length: 1738 characters.

Google Gemini / Antigravity CLI adapter. The upstream CLI is changing binary names ahead of a deprecation date: the legacy ``gemini`` binary stops serving free / AI Pro / Ultra subscribers on 2026-06-18; the replacement ``antigravity`` binary uses the same model set and the same ``--output-format`` semantics. Enterprise customers retain the legacy binary via paid API keys. The adapter is dual-binary aware. At spawn time it discovers which binary is on ``PATH`` using a deterministic cascade defined by ``_DISCOVERY_CASCADE``: 1. The operator override ``BERNSTEIN_GEMINI_BINARY`` wins when set (and must resolve on ``PATH``, regardless of ``strict`` mode). 2. Otherwise ``antigravity`` is preferred. 3. The legacy ``gemini`` binary is used as a fallback. 4. If neither resolves, behavior depends on the ``strict`` flag passed to :func:`resolve_google_cli_binary`: - ``strict=True`` (used by ``bernstein adapters check`` / doctor): the adapter raises :class:`BinaryNotInstalledError`. - ``strict=False`` (default, used by :meth:`GeminiAdapter.spawn`): the resolver returns the first cascade entry as a fallback, letting downstream :func:`subprocess.Popen` raise the natural ``FileNotFoundError`` on actual invocation. This matches the codex / aider adapter posture and keeps tests that mock ``subprocess`` from tripping on eager discovery. The adapter contract (flags, env-isolation allow-list, sandbox profile, rate-limit meter, network policy) is unchanged: only the binary name and the discovery step differ. Recommended models (identical on both binaries): ``gemini-3.1-pro`` (highest reasoning), ``gemini-3-flash`` (default in the Gemini app, Pro-grade reasoning at Flash speed), or ``gemini-3.1-flash-lite`` for the cheapest tier.

Adapter telemetry

When to pick which

FAQ