Sidecar is a terminal-based workspace for running AI coding agents alongside file trees, task issues, Git diffs, and Jira or GitHub resources in split panes. Developers use it to monitor agent sessions, inspect files and changes, manage workspaces, and handle tasks without leaving one shell. The catalogue entries extend or guide coding-agent workflows used with Sidecar.
Borrowing it
Nothing to install: this file belongs to marcus/sidecar. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/marcus/sidecar/main/AGENTS.mdgit clone --depth 1 https://github.com/marcus/sidecarWrote 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.
[](https://agentmods.dev/instructions/marcus/sidecar/agents-md)<a href="https://agentmods.dev/instructions/marcus/sidecar/agents-md"><img src="https://agentmods.dev/badge/instructions/marcus/sidecar/agents-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/marcus/sidecar/agents-md"><img src="https://agentmods.dev/badge/instructions/marcus/sidecar/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.04660 | $0.04660 |
| Opus 5.5 | $0.01864 | $0.01864 |
| Sonnet 5.5 | $0.00932 | $0.00932 |
| Haiku 4.5 | $0.00466 | $0.00466 |
Grade C, and why
sidecar AGENTS.md scanned grade C with 1 finding 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 22d 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- td-agent-instructions:start --> How it starts
The opening of the file, as written. The whole thing — 330 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Working with td
td keeps task context durable across sessions. In a new context, run td usage --new-session -q to see current work.
Use your judgment about how much tracking a task needs. For substantive work: td start <id>, record progress with td log, hand off with td handoff <id>, then td review <id>.
Closing needs a review. Say who did it (default trusted mode; delegated/strict allow only the first):
- independent session:
td approve <id> --reason "..." - a sub-agent:
td approve <id> --reviewed-by "<who>" - you:
td approve <id> --self-review --reason "..."
Prefer a reviewer with its own TD_CONTEXT_ID; never name one who did not review.
Run td usage or td <command> --help.
Markdown plans
When writing plans or other Markdown documents, do not insert hard line breaks to keep a column width — let paragraphs flow as single long lines. Hard-wrapped text renders poorly when the document is viewed at any width other than the one it was written for.
Commit completed work by default
Unless the user explicitly asks not to commit, create a focused commit once the requested work is complete, verified, and reviewed. Stage only files that belong to the task, preserve unrelated dirty or staged changes, and do not push unless the user asks.
Working inside a Sidecar shell
Run sidecar agents for what you can do from here, and use it. sidecar --agents and sidecar -a are equivalent aliases. The two that earn their keep every session: keep the shell's name describing your current task, and put a file or issue in front of the user rather than describing its path (sidecar open works from any context, not only a Sidecar shell). Never edit shells.json or rename tmux sessions directly.
The pane layout is readable and writable
Three verbs over one model, all acting on the surface showing this shell (or, with --sessions, the global Sessions surface), and none of them ever queues — a request whose destination is off screen declines with the reason instead of arriving late.
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.
- 22d ago Changed · +2 lines · +208 tokens per session 3ac99776c50b
- 1mo ago Changed · +16 lines · +398 tokens per session 959c83b6e4a9
- 1mo ago Changed · +32 lines · +1,076 tokens per session 2e075614dae3
- 1mo ago First seen · 280 lines · 2,978 tokens per session scan C bda4725fd78f
sidecar AGENTS.md is an instructions file published in the GitHub repository marcus/sidecar (1,091 stars, last pushed 18d ago), licensed MIT. It adds 4,660 tokens to every session, about $0.0186 per session on Opus 5.5. A static security scan graded it C with 1 finding (hidden instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.