Gemini CLI on Windows: every git command fails with `fatal: unable to access 'NUL': Invalid argument` (Git for Windows 2.56.0 regression)

发生场景

Source(s): https://github.com/google-gemini/gemini-cli/issues/29614 (upstream: https://github.com/git-for-windows/git/issues/6449) Status: reported working by source, not reproduced by us.

问题

When Gemini CLI runs git status, git log, git diff or any other git command through its shell tool on Windows, git aborts immediately with the error above.

报错原文（已脱敏/规范化）

fatal: unable to access 'NUL': Invalid argument

适用环境

Windows, Gemini CLI 0.62.0, Git for Windows 2.56.0 (the first 2.56 build, git version 2.56.0.windows.1 (our inference)).

如何确认是这个问题

1. git --version → expect: git version 2.56.0.windows.1 (our inference).
2. our inference: reproduce outside Gemini CLI in cmd with set GIT_CONFIG_GLOBAL=NUL followed by git status → expect the same fatal error.

不是这个问题时 / 边界

fatal: unable to access 'https://...' errors (network, proxy or credentials) are different problems. our inference: other tools that set GIT_CONFIG_GLOBAL=NUL on Windows may hit the same regression, and the same Git update should apply.

根因

Gemini CLI sanitizes the environment for its shell tool and sets GIT_CONFIG_GLOBAL to NUL on Windows (to /dev/null elsewhere). Git for Windows 2.56.0 introduced a regression where checking access to NUL returns "Invalid argument", so git stops before running the command. A commenter linked the upstream Git for Windows issue.

修复步骤

1. Update Git for Windows to <ip> or later (as the thread writes it; our inference: git --version then shows 2.56.0.windows.2). → expect: the original poster and two commenters confirmed this resolves it in Gemini CLI.
2. If you can't update yet, go back to Git for Windows 2.55.5 (suggested by a commenter).

如何验证

Ask Gemini CLI to run git status → expect: normal git output, no unable to access 'NUL'.

试过没用的办法

none reported

风险提示

our note: don't patch the CLI's installed bundle files; they get overwritten on the next update.

验证范围

Git for Windows 2.56.0 (first build), Gemini CLI 0.62.x, October 2026.

何时失效

2.56.0.windows.1 (our inference) is no longer in use.