# Homebrew: Error: Failure while executing; `git fetch --force origin` exited with 128 / fatal: not in a git directory

**Code:** `Homebrew: Failed to update / fatal: unable to access` · **Category:** macOS · **Seen on:** macOS, Git

`brew update` couldn't fetch the Homebrew repositories — network, a broken git state or safe.directory problems.

## Meaning

Check connectivity and proxy first. If the tap repo is corrupted, reset it: `git -C $(brew --repository) fetch --force origin && git -C $(brew --repository) reset --hard origin/master`. "Not in a git directory" or "dubious ownership" means git ownership/safe.directory settings need fixing. Try `HOMEBREW_NO_AUTO_UPDATE=1` to skip updates temporarily.

## Common causes

- Network/proxy/VPN blocking GitHub
- Corrupted tap repositories
- Git safe.directory / ownership issue
- Disk full
- Homebrew API cache problems

## Quick fix

1. `brew update-reset`
2. Check network: `curl -I https://github.com`
3. `git config --global --add safe.directory $(brew --repository)`

## Detailed fix by platform

### macOS

1. `brew update-reset && brew doctor`

## How to diagnose

1. **Network** — GitHub reachable?
2. **Repo** — Healthy?
3. **Ownership** — Same user?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/macos/brew-update-failed)