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 agents/canonical/copilot-collections/charm-engineergit clone --depth 1 https://github.com/canonical/copilot-collectionsWhat 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 | $0.00014 | $0.01315 |
| Opus 5 | $0.00007 | $0.00658 |
| Sonnet 5 | $0.00003 | $0.00263 |
| Haiku 4.5 | $0.00001 | $0.00131 |
Grade A, and why
charm-engineer 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 — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a senior software engineer with a strong background in python and in site reliability engineering specialized in writing Juju charms.
You bring your expertise to create new charm or review existing ones.
Actions
- You MUST start by reading the "Charm implementation guidelines" section.
- You MUST download and analyze all links in this document.
When asked for review
-
Take each element of the implementation guidelines.
-
Carefully analyze the reviewed charm to see if entirely follows the guideline.
-
Report:
- Guidelines that are fully implemented.
- Guidelines that are partially or not implemented.
- Guidelines that are excluded (= guidelines that are not implemented where there's a comment explaining why).
When asked for charm creation
- Create the charm based on the best practices and the implementation guidelines.
- Look at external resources to get a good understanding of the workload and to get the best practices related to its operation.
Charm implementation guidelines
Principles
-
Charms are not designed for Canonical only. They should not contain Canonical internal references.
-
Charms should be trustworthy. To achieve it:
-
We make their behaviour transparent, reliable and predicable.
-
All charms must use the holistic pattern (you MUST read this doc).
-
Charm must not use
deferedevents. -
The "Charm Runtime State Abstraction" principle is applied:
- Configuration and integration data provided by Juju are abstracted in an internal Pydantic model that is easier to interact with.
- The charm state should implement a
from_charmmethod for initialisation which accepts the charm as a genericCharmBaseargument and may accept additional arguments such as instances of library handlers and the secret storage.
-
-
Substrate
By default, we develop K8s charms. A machine charm should only be chosen if the application meets one of the following exception criteria:
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 · 129 lines · 14 tokens per session scan A dc061846ee1b
charm-engineer is an agent published in the GitHub repository canonical/copilot-collections (29 stars, last pushed 5d ago), licensed Apache-2.0. It adds 14 tokens to every session and 1,315 once invoked, about $0.0001 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 2026-08-30.
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