Kotlin/kotlin-agent-skills is a collection of packaged instructions, scripts, and resources that help coding agents handle projects written in Kotlin. It is for developers using Kotlin, with skills covering areas such as backend frameworks and build tooling. The catalogue entries are the individual Kotlin-focused skills distributed from the repository.
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 skills add Kotlin/kotlin-agent-skills --skill kotlin-tooling-immutable-collections-0-5-x-migrationgit clone --depth 1 https://github.com/Kotlin/kotlin-agent-skillsWrote 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/skills/kotlin/kotlin-agent-skills/kotlin-tooling-immutable-collections-0-5-x-migration)<a href="https://agentmods.dev/skills/kotlin/kotlin-agent-skills/kotlin-tooling-immutable-collections-0-5-x-migration"><img src="https://agentmods.dev/badge/skills/kotlin/kotlin-agent-skills/kotlin-tooling-immutable-collections-0-5-x-migration/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/kotlin/kotlin-agent-skills/kotlin-tooling-immutable-collections-0-5-x-migration"><img src="https://agentmods.dev/badge/skills/kotlin/kotlin-agent-skills/kotlin-tooling-immutable-collections-0-5-x-migration.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 5.1 | $0.00192 | $0.02415 |
| Opus 5 | $0.00096 | $0.01208 |
| Sonnet 5 | $0.00038 | $0.00483 |
| Haiku 4.5 | $0.00019 | $0.00242 |
Grade A, and why
kotlin-tooling-immutable-collections-0-5-x-migration 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 13d 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 — 173 lines — stays where its author put it; the contents beside it link to each section on GitHub.
kotlinx.collections.immutable 0.5.x Migration
The 0.5.x line renames every copy-returning method on the persistent collections to a
participial form (per [KEEP-0459]) and deprecates the old names at WARNING level with a
ReplaceWith hint. Migrating is a mechanical, binary-compatible, semantics-preserving
call-site rename — same parameters, order, and return type; only the name changes.
Drive it from the compiler: bump the version, recompile, and fix each deprecation warning —
the warning names the replacement. Source of truth: [0.5.0-MIGRATION.md].
When it applies
Check the version the project currently uses:
- 0.3.x or 0.4.x (any pre-0.5.0) → run the migration below.
- On 0.5.x but not the latest → set the version to the latest 0.5.x and stop. All 0.5.x releases share the same renames, so a within-line bump adds no new deprecations and needs no recompile.
- On the latest 0.5.x, or on 0.6.x and later → nothing to do.
Migration
1. Find the build command
Check README.md, CLAUDE.md, or AGENTS.md for how the project builds; if it isn't
written down, infer it from the build files — Gradle (./gradlew), Maven (mvn, or the
./mvnw wrapper), Bazel
(a bazel wrapper), or a custom script. Record the compile command (and the test command).
In a multi-module project you only need the modules that use the library, plus any you
change — not a whole-repo build.
2. Baseline compile
Compile on the current version and confirm it's green. If it doesn't build now, you can't tell post-migration errors from pre-existing ones — get a working compile command first.
3. Bump to the latest 0.5.x
Find where the version is pinned — grep -rn kotlinx-collections-immutable across the build
files finds it (version catalog, build script, gradle.properties, pom.xml, …) — and set
it to the latest 0.5.x on [Maven Central] (a -beta is fine). If the build pins artifact
hashes (e.g. gradle/verification-metadata.xml), update those too — the cheapest fix is to
copy the new artifact's checksum straight from the dependency-verification failure message
and add just that one entry, rather than regenerating the whole metadata file. The bump is
binary-compatible; old code keeps compiling with warnings. (If the dependency fails to
resolve with a Kotlin metadata-version error, the project's Kotlin is too old for the 0.5.x
artifact — bump Kotlin first.)
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.
- 13d ago First seen · 173 lines · 192 tokens per session scan A 7b161da34a28
kotlin-tooling-immutable-collections-0-5-x-migration is a skill published in the GitHub repository Kotlin/kotlin-agent-skills (1,044 stars, last pushed yesterday), licensed Apache-2.0. It adds 192 tokens to every session and 2,415 once invoked, about $0.0010 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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