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name: holoscan-module-lifecycle description: "Develop external Holoscan Modules with the Holoscan CLI and use them in Holoscan applications: scaffold, test, Python bindings, DEB/WHEEL packaging, and clean-consumer proof." license: Apache-2.0 metadata: author: "Holoscan Team holoscan-team@nvidia.com" compatibility: "Holoscan CLI 5.x (verified with 5.0.0); Python 3.12–3.14; packaged template requires Holoscan SDK 5.0.0 or later" github-url: "https://github.com/nvidia-holoscan/holoscan-applications" tags: - holoscan - modules

Holoscan Module lifecycle

Purpose

Take a reusable Holoscan Module from layout and API contract through producer, consumer, and clean artifact-install proof. Use uv run holoscan in a standalone module, or holoscan in its activated pip environment.

A Holoscan Module extends holoscan::core with operators, resources, and helpers for a domain capability, plus examples and tests. Core modules ship with the SDK; external modules live in their own repositories, and applications, including those in nvidia-holoscan/holoscan-applications, consume their installed packages. This skill covers external Holoscan Module development and consumption. For SDK core-module implementation, follow the selected SDK checkout’s modules/DEVELOPER.md and module-specific guide; do not apply the external CLI template or packaging workflow to SDK core modules.

Inputs

Required: the API contract, workspace, identities, SDK floor, license, maintainer, package formats, and acceptance checks, from the request or an authoritative repository source. Optional: a consuming application. If consequential release metadata remains unknown, stop before scaffolding or packaging rather than guessing.

• a reusable producer/consumer API contract rather than an ordinary app;
• the user-provided standalone module repository, or the parent directory for a new one;
• language, module/operator/package identities, minimum SDK version, license, maintainer details, and requested package formats;
• the consuming application, if any, such as one in a holoscan-applications checkout;
• finite producer, consumer, and artifact acceptance checks.

First honor any request for planning only (for example, “do not run commands”); preserve that restriction when routing. Check the session’s available skill catalog for the destination skill. Route a concrete failing or wrong holoscan command to holoscan-app-debug-build-run. If the matching skill is unavailable, preserve the handoff context and name the skill to install instead of broadening this workflow. An ordinary application without a reusable module API is outside this skill; follow the target repository's own guidance, such as README.md and CONTRIBUTING.md in holoscan-applications.

Prerequisites

• For module concepts and producer and consumer walkthroughs, use the Holoscan Modules tutorials: create a module and use a module. Recheck their version-sensitive commands against the selected checkout and CLI contract. If they are unavailable, use the summary above, the bundled references, and the selected CLI’s packaged template and help; identify the unavailable tutorial and do not claim to have checked it.
• Always read the Holoscan CLI contract and Holoscan CLI configuration.
• Read module development for layout, naming, scaffold, metadata, implementation, build, and test scope.
• Read consumers and packaging when a consuming app, Python binding consumer, or binary artifact is in scope.

The module's own README.md, DEVELOPER.md, and AGENTS.md, a consuming checkout's guidance, local help, schemas, templates, tutorials, and nearby examples are the live technical authority where they do not conflict with user, system, or safety constraints.

Instructions

For a planning-only request, return the proposed workflow and proof requirements without executing commands or changing files. Otherwise continue below.

At any step, a failing effect-bearing CLI command ends this happy path; follow Troubleshooting with its exact context. Parse read-only diagnostic results and stop only when a failed capability is required by the module, consumer, packaging environment, or requested proof. For example, a failed Docker capability blocks a container build; an unavailable display need not block an explicitly headless consumer.

1. Preserve and orient. Record full HEAD, concise status, selected CLI version/environment, and discovery output. Preserve the checkout revision and unrelated work.
2. Choose the layout. Use a standalone holoscan-<name> repository with its own demo applications. holoscan-applications keeps applications only and directs reusable operators and Modules to independent repositories.
3. Fix identities before files. Keep display name, snake_case module/namespace, holoscan-<kebab-case> repository/package, and snake_case_op operator slug consistent.
4. Scaffold with the packaged template. Follow the uv-first creation sequence in the development reference, from a parent directory outside any application checkout. Preview and run the same non-interactive holoscan create command with explicit language (cpp, or cpp python to add Python bindings) and agreed metadata. Always specify --context holoscan_version=<agreed-sdk-floor> to override configured or template defaults; the template requires 5.0.0 or later, and its preview does not check that floor. Examples explicitly select 5.0.0; use the agreed SDK floor for the actual module. No launcher or holoscan-applications checkout is required. Preserve existing Git state; reject populated destinations. Inspect generated files and Git status before continuing.
5. Implement the smallest public contract. Validate metadata, expose one useful operator/API, add deterministic tests, and add a finite demo that consumes the same public surface as another project. Keep demo policy out of the reusable operator.
6. Build and test honestly. Preview and run container-first module and demo commands, passing --language cpp or --language python when a project declares both. The module's test runs its repository-wide suite; combine it with focused pytest or CTest targets and report the scope.
7. Prove a real consumer. An application consumes the installed package with find_package(holoscan-<name> CONFIG REQUIRED) and holoscan::<module_slug>. In holoscan-applications, a metadata dependency alone neither fetches nor builds the module; follow the application consumer procedure and do not change the shared root CMake without maintainer agreement. For Python bindings, import from the exact build tree or install the holoscan-<name>-python component into a task-owned prefix; follow the Python consumer cleanup procedure: record the interpreter, build directory, prefix, and installed paths, always remove the task-owned prefix after the consumer attempt, and verify it is absent. The packaged template stages no editable-import hooks, so do not substitute install --dev. If cleanup fails, stop using that environment and report incomplete cleanup; a missing debugging skill does not permit continuing to package or publish. Discard a task-owned disposable environment only under existing cleanup authorization; a shared environment needs the owner’s repair decision.
8. Package only after behavior proof. Preview and build the requested artifacts, inspect identity/metadata/dependencies/payload, and install each format in a clean artifact-only consumer with an import/link and finite smoke check. The packaged template produces a C++-only DEB and no wheel; request WHEEL only for a module whose own pyproject.toml builds one. For DEB, verify the declared holoscan Debian dependency in the consumer’s package database: a successful Python import or C++ build is insufficient. If it is absent, report DEB installation unverified and follow the DEB prerequisite guidance; do not force dependency checks or claim archive extraction proves installability.
9. Validate and hand off. Rerun producer and clean-consumer checks, git diff --check, and final status. In a dirty checkout, restrict auto-fixing lint to task paths; before a requested commit, validate the exact candidate change with the full lint required by that repository's guidance, in a clean disposable checkout. If the required commands cannot be determined, report lint unverified. Confirm no generated artifacts or install prefixes are staged. Do not commit, push, upload, publish, or release unless requested.

Troubleshooting

If a CLI command fails, stop the happy path and hand off its exact command, revision, dirty state, inputs, and observed result to holoscan-app-debug-build-run.

Examples

• Scaffold and package a reusable operator with clean-consumer proof: use this skill.
• Package an ordinary app or diagnose a failing build: route out of this skill.

Limitations

• Preserve unrelated work. Do not reset, clean, remove unrelated files, change host configuration, broaden privileges, commit, push, upload, publish, or release without authorization.
• Never prefix holoscan with sudo; obtain approval for holoscan setup, host packages, host-local execution, root containers, devices/capabilities, or permission changes.
• Keep build, data, install prefixes, and package output out of commits.
• Protect credentials, proprietary source, patient data, private media, and identifying metadata.
• Claim support, reproducibility, installability, performance, or safety only for the producer, artifacts, and clean-consumer evidence actually collected.

Output

Return layout and identities, public API/demo, metadata and registrations, preview and real command results, honest test scope, consumer proof, artifact identity/contents/install results, licensing and publication limits, and final worktree state.

For a planning-only request, return the proposed order, authoritative metadata sources, approval boundaries, and proof requirements without claiming results.