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.
npx agentmods add skills/patelr3/agents/dev-containernpx skills add patelr3/agents --skill dev-containergit clone --depth 1 https://github.com/patelr3/agentsWhat 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 | $0.00063 | $0.02340 |
| Opus 5 | $0.00032 | $0.01170 |
| Sonnet 5 | $0.00013 | $0.00468 |
| Haiku 4.5 | $0.00006 | $0.00234 |
Grade A, and why
dev-container 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 267 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Dev Container Skill
Run work inside a dev container. This skill manages the full lifecycle: container build → AI tool execution → cleanup.
A sub-agent (Copilot, Claude, or AMP) runs inside the dev container to do the actual work. The parent session (you) manages the container lifecycle around it.
Inputs
When this skill is invoked, gather the following from the user or calling agent:
| Input | Required | Default | Description |
|---|---|---|---|
| Workspace folder | Yes | — | Path to the repo/worktree directory containing .devcontainer/ config |
| Prompt | No | — | Inline instructions for the sub-agent. Free-form text describing the work to do. |
| Plan file | No | — | Path to a file in the repo that describes the work (e.g., a PRD, a plan, a design doc). The sub-agent reads it and executes it. |
| Tool | No | copilot |
AI backend to run inside the container: copilot, claude, or amp. |
| Container name | No | Auto-derived from workspace | Name for the dev container instance. |
| Port offset | No | — | Integer for parallel port isolation (API = 3001 + N, Web = 3000 + N). |
| Auto-merge | No | true |
Whether to enable auto-merge on the created PR. |
| Create PR | No | true |
Whether to create a PR at the end. Set to false if the sub-agent handles PR creation itself. |
At least one of Prompt or Plan file must be provided. They can also be used together — the plan file provides the specification and the prompt provides additional context or instructions.
Execution Flow
Step 1: Resolve Inputs
Validate the workspace folder exists and contains a .devcontainer/ directory:
WORKSPACE_FOLDER="<workspace-folder>"
PROJECT_NAME="$(basename "$WORKSPACE_FOLDER")"
TOOL="<tool>" # copilot, claude, or amp — default: copilot
Auto-derive container name if not provided:
BRANCH_SUFFIX=$(cd "$WORKSPACE_FOLDER" && git rev-parse --abbrev-ref HEAD | sed 's|.*/||')
CONTAINER_NAME="${PROJECT_NAME}-${BRANCH_SUFFIX}"
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- yesterday First seen · 267 lines · 63 tokens per session scan A da662d5f5ac9
dev-container is a skill published in the GitHub repository patelr3/agents (2 stars, last pushed 4mo ago), licensed MIT. It adds 63 tokens to every session and 2,340 once invoked, about $0.0003 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 2026-08-31.
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