Improve an existing charm

Audit and upgrade a charm you have already written, adding tests, observability, and modern patterns.

When to use improve mode

Use --improve when you have an existing charm that needs:

• An audit against current best practices
• Missing unit or integration tests
• COS integration (traces, metrics, dashboards)
• Deprecated API replacements (e.g. Harness → Scenario)
• Operational readiness evaluation
• Preparation for Charmhub listing

Run the improvement

Point Cantrip at your existing charm directory:

$ cantrip --improve /path/to/my-existing-charm

Cantrip reads the existing code and configuration, then creates a plan of improvements. You will see a proposal in the chat listing what the agent intends to change. Confirm or adjust the plan before the agent begins work.

What the agent does

In improve mode the agent typically follows this sequence:

1. Audit — reads all charm files, runs charmlint, checks metadata, and evaluates against Operational Readiness Metrics.
2. Propose — presents a prioritised list of improvements with rationale.
3. Implement — after your confirmation, subagents work through the list: adding tests, wiring up observability, replacing deprecated patterns.
4. Redeploy and test — packs the updated charm, deploys it, and runs the new test suite.

Steering the improvements

You can guide the agent during the improvement process:

• "Focus on testing only" — skip other categories.
• "Don't touch the config options" — exclude specific areas.
• "Add backup and restore actions" — request specific enhancements beyond what the audit found.

Working with git

The agent commits at appropriate points during the improvement. Each commit is a self-contained change (e.g. "add COS integration", "replace Harness tests with Scenario"). You can review the commits afterwards and cherry-pick or squash as needed.