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 rules/d-padmanabhan/agent-engineering-handbook/440-dockergit clone --depth 1 https://github.com/d-padmanabhan/agent-engineering-handbookWrote 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/rules/d-padmanabhan/agent-engineering-handbook/440-docker)<a href="https://agentmods.dev/rules/d-padmanabhan/agent-engineering-handbook/440-docker"><img src="https://agentmods.dev/badge/rules/d-padmanabhan/agent-engineering-handbook/440-docker.svg" alt="Measured on agentmods" 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 | $0.00000 | $0.00747 |
| Opus 5 | $0.00000 | $0.00374 |
| Sonnet 5 | $0.00000 | $0.00149 |
| Haiku 4.5 | $0.00000 | $0.00075 |
Grade A, and why
440-docker scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Docker and Container Gates
This rule contains only mandatory policy. Use the containers and orchestration skill (${HANDBOOK_ROOT}/skills/containers-orchestration/SKILL.md) and its Docker reference (${HANDBOOK_ROOT}/skills/containers-orchestration/references/docker.md) for procedures, examples, Compose patterns, and troubleshooting.
Reproducible Inputs
- Pin production base images and deployed images by immutable digest. A readable tag may accompany the digest.
- Do not use
latestor another mutable tag as a production deployment input. - Use lock files and deterministic package-manager commands. Do not resolve unconstrained dependencies during the image build.
- Keep build context narrow with
.dockerignore; exclude.git, local dependencies, test artifacts not required by the build, credentials, and environment files. - Never copy secrets into an image or pass secrets through
ARG,ENV, source files, or the build context. Use BuildKit secret mounts or the deployment platform's secret broker.
Runtime Security
- Run the final image as a specific non-root user.
- Use the smallest runtime image that satisfies compatibility and support requirements.
- Use multi-stage builds when compilers, package managers, headers, or build-time credentials are not required at runtime.
- Do not grant privileged mode, host namespaces, broad capabilities, or writable host paths without a documented, time-bounded exception.
- Prefer a read-only root filesystem and dropped Linux capabilities where the workload supports them.
- Include a meaningful health check when the runtime exposes a health signal; do not add a probe that only proves the process exists.
Build Cache Contract
- Order instructions by change frequency: stable toolchain and dependency manifests before frequently changing source.
- Copy dependency manifests and lock files before application source, install dependencies, then copy source.
- Treat intentional layers as cache boundaries. Do not collapse unrelated dependency, build, and source work merely to minimize layer count.
- Combine only logically coupled package-manager operations, such as index refresh, install, and cleanup.
- Use BuildKit cache mounts for performance where useful, but require the build to succeed with an empty or garbage-collected cache.
- Do not disable a package manager's cache while mounting that same cache directory.
- Verify cache reuse with repeated BuildKit builds. If Docker or BuildKit is unavailable, report that runtime reuse was not verified.
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.
- 3d ago First seen · 48 lines · 0 tokens per session scan A 56ad85f15c3c
440-docker is a cursor rule published in the GitHub repository d-padmanabhan/agent-engineering-handbook (16 stars, last pushed 4d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 747 tokens. 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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