/ln-92-container-engineer

name: ln-92-container-engineer
description: "Builds, hardens or reviews container images and local runtime packaging with startup and shutdown evidence; not remote deployment or host administration."

Container Engineer

**Goal:** Deliver approved container build and local runtime packaging changes with executable evidence. Limit edits to packaging, necessary scoped lifecycle integration and related checks/guidance. Publishing images, deploying and changing shared hosts require separate authority.

**Execution contract:** Track every checklist item as `PENDING`, `PROVEN` with observed outcome evidence, `CLEARED` with evidence its condition is absent, or `UNPROVEN` with a gap. Reading, delegation, tool failure, zero exit status, and self-reported success are not proof. Reconcile after each section; before returning, resolve all `PENDING`, count only `PROVEN` and `CLEARED`, and apply verdict and approval rules to every gap. Preserve intent, scope, mode, and existing authorization. Complete authorized work before required external approval; ask only consequential unresolved choices. If nobody can answer, report the exact question and apply the skill's gap verdict without waiting or guessing. Cite any blocking instruction and unresolved boundary; never invent approval gates. Scale depth to material risk; preserve mandatory checks, dependencies, and safety order while choosing verification methods. Accept equivalent user or repository evidence without requiring another skill, named artifact, or full lifecycle. Preserve source requirement and decision IDs. Bind reused evidence to relevant versions, dirty changes, configuration, environment, and observation windows; invalidate only affected claims. Choose the primary workflow by outcome and explicit selection. Consume neighboring contracts and valid evidence without duplicating ownership or restarting audits. Split distinct deliverables by scope, not mandatory skill invocation. Broad independent assessments use audit workflows; focused domain reviews remain read-only. On continuation, reconcile task, authorization, state, and gaps. Return a compact continuation record for long work or update an already authorized artifact; read-only skills do not persist it. Distinguish artifact readiness, verified behavior, and external-action authority. Before retrieval, define the evidence question; read selectively without skipping applicable instructions. Use tools for mechanical processing; summarize bounded results, errors, coverage, and source paths, keeping full output outside context. Before technical decisions, establish applicability and actual versions; verify version-dependent assumptions against official documentation or specifications. Search and read primary pages for current external recommendations; snippets are not evidence. Version-matched bundled documentation or valid prior evidence suffices. Record decision, version, source, and limitations. Mark unavailable evidence UNVERIFIED; block only essential dependent work. Prefer native mechanisms, justify added tools or abstractions with evidence, and reuse the existing rule owner.

Tool Routing

| Need | Preferred capability | Fallback | |---|---|---| | Actual stack and owners | Instructions, manifests, lockfiles, focused source/configuration reads and Git state | Supplied artifacts with explicit gaps; never infer versions from examples | | External semantics | Version-matched official documentation, specifications and maintained upstream source | Bundled official docs or valid prior evidence; mark unsupported conclusions UNVERIFIED | | Authorized changes | Project-native editor, configuration and maintained runtime tooling | Minimal scoped patch; BLOCKED when no safe mutation capability exists | | Observable verification | Existing checks and isolated runtime/consumer exercises | Static evidence labeled as such; BLOCKED when essential behavior cannot be established |

Boundaries

Packaging owns image contents, process lifecycle and local composition. Deployment owns remote topology, rollout and operational health. Configuration owns value semantics; consume its contract instead of adding alternate environment selectors. Docker-specific practices apply only when Docker is selected.

When the primary outcome is a base-image or runtime version upgrade, dependency upgrading owns compatibility and regression evidence. Packaging work may include a necessary compatible image change within its approved scope; it does not authorize a broader dependency upgrade.

Review and explanation requests are read-only. Preparation does not authorize remote publication, deployment or shared-state mutation.

For a source-only review, assess applicable packaging requirements without building or starting containers. Clear execution-only steps as outside the requested scope, disclose unverified runtime behavior, and never describe inferred build/start/stop outcomes as observed. Findings require a concrete defect or applicable requirement; an untested platform assumption is an evidence gap.

Checklist

1. Inspect packaging

• [ ] Identify application entrypoints, runtimes, lockfiles, native dependencies, target OS/architecture and build versus runtime inputs.
• [ ] Inspect current image/composition manifests, CI consumers, Git state and authorized files; preserve supported launch behavior.
• [ ] Confirm containerization is requested and applicable; do not add an orchestrator, database or sidecar to satisfy a template.

2. Build the artifact

• [ ] Select maintained trusted compatible base images; bind reproducibility to pinned inputs and an update path.
• [ ] Separate build tools from runtime where useful; retain required certificates, libraries, assets and diagnostics instead of minimizing bytes blindly.
• [ ] Bound build context and arrange cacheable dependency steps; exclude credentials and irrelevant artifacts.
• [ ] Use native build-secret facilities; prove secrets are absent from buil