sidecar

sidecar is a skill for Claude Code, Codex from joshukraine/dotfiles. It costs 74 tokens per session (829 once invoked), scanned A, original, MIT.

A research-only mode for a coding session whose shared repository is being edited by another session. It allows reading, research, planning, temporary notes, and GitHub issue creation while forbidding tracked-file and Git changes.

In plain words
What is it for?
Investigating issues, researching documentation, drafting plans, keeping scratch notes, and creating GitHub issues without editing or committing repository files.
Why use it?
It prevents two coding sessions from overwriting each other's work or changing the same repository state.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/joshukraine/dotfiles/sidecar
Any agent
npx skills add joshukraine/dotfiles --skill sidecar
Clone the repo
git clone --depth 1 https://github.com/joshukraine/dotfiles

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for sidecar

README.md
[![agentmods](https://agentmods.dev/badge/skills/joshukraine/dotfiles/sidecar.svg)](https://agentmods.dev/skills/joshukraine/dotfiles/sidecar)
Your own site
<a href="https://agentmods.dev/skills/joshukraine/dotfiles/sidecar"><img src="https://agentmods.dev/badge/skills/joshukraine/dotfiles/sidecar.svg" alt="Measured on agentmods" height="20"></a>
Per session 74 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 829 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00074 $0.00829
Opus 5 $0.00037 $0.00415
Sonnet 5 $0.00015 $0.00166
Haiku 4.5 $0.00007 $0.00083

Measured 5d ago against content hash 52f02a24a9c1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

sidecar scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

claude/.claude/skills/sidecar/SKILL.md · 42 lines

How it starts

The opening of the file, as written. The whole thing — 42 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sidecar (research-only session)

You are a secondary session sharing a working directory with another Claude Code session that is actively editing code in the same repository. Your job here is research, planning, theory, discussion, and drafting — not implementation. The other session owns the working tree; you must not step on it.

Read-only operations, web/MCP research, and outward-facing actions that touch no local state are all fine. The only things that cause collisions are mutations to shared local state, so those are off-limits.

The one rule

Do not mutate shared local state. That state is exactly: tracked files in the working tree, and git's index/HEAD. Everything dangerous follows from those two; everything safe is safe because it touches neither.

Forbidden

  • Editing, creating, or deleting tracked files in the repository (no Edit, Write, or NotebookEdit on anything under version control). Code, config, docs — all off-limits.
  • Git state mutations: git add, git commit, git checkout / git switch, git branch, git stash, git reset, git restore, git rebase, git merge, git pull. These corrupt whatever the other session is doing with the index, working tree, or HEAD.
  • Creating branches or pull requests (they require branch + push, i.e. git mutation).
  • Installing dependencies, running formatters that rewrite files, or starting long-running servers — these mutate node_modules, lockfiles, the tree, or fixed ports the other session may rely on.

Allowed

  • Read anything — files, code, docs, history.
  • Read-only git: git log, git diff, git status, git show, git blame.
  • Web search / fetch, Context7, and MCP tools — research freely.
  • Write to the session scratchpad — your scratchpad directory is session-isolated (its own UUID'd path), so temp files never collide with the other session. Put all temp files there, never in the repo root (e.g. do not write .git_commit_msg to the repo root; that path is shared).
  • Create and comment on GitHub issues via gh — this is outward-facing but touches no local shared state. When an issue body needs a temp file, write it to the scratchpad, then gh issue create -F <scratchpad-path>.

Read the full file on GitHub · 42 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 42 lines · 74 tokens per session scan A 52f02a24a9c1

Subscribe to this mod's changes

sidecar is a skill published in the GitHub repository joshukraine/dotfiles (422 stars, last pushed 23d ago), licensed MIT. It adds 74 tokens to every session and 829 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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