[robjtede]

Move only Lint / rustfmt (no matrix) from blacksmith-2vcpu-ubuntu-2404 to ubuntu-slim. Formatting does not compile the workspace. Keep the nightly toolchain, checks, and permissions unchanged.

Retain tests (MSRV/stable), Clippy feature combinations, docs, coverage, and release on existing runners because they compile, use Nix, or publish. Retain the disabled public API diff. Retain zizmor on ubuntu-latest: its pinned composite action runs Docker.

GitHub documents slim as a generally available public/private repository runner with 1 CPU, 5 GB RAM, 14 GB disk, and a 15-minute limit. It uses an unprivileged container; nested Docker and privileged kernel operations are unsupported. Its minimal software image does not list Rust; the existing setup action installs the required toolchain.

Sources: https://docs.github.com/en/actions/reference/runners/github-hosted-runners and https://github.com/actions/runner-images/blob/main/images/ubuntu-slim/ubuntu-slim-Readme.md

Measurement notes (execution = job completed_at minus started_at; queue time excluded):

Workflow/job	Runner	SHA	Run	Result	Seconds
Lint/rustfmt	blacksmith-2vcpu-ubuntu-2404	ef584a9	https://github.com/x52dev/confik/actions/runs/41551240258	success	16
Lint/rustfmt	blacksmith-2vcpu-ubuntu-2404	14d3fe6	https://github.com/x52dev/confik/actions/runs/41321236932	success	18
Lint/rustfmt	blacksmith-2vcpu-ubuntu-2404	82a6b89	https://github.com/x52dev/confik/actions/runs/41321233336	success	13

Historical baseline n=3, median 16 seconds. This is a Blacksmith baseline, not a GitHub standard-runner baseline. These are different commits; nightly version, provisioning and cache differences confound comparison. Baseline cache is enabled; hit states were not confirmed.

All slim samples use head 721dca42f90498689e8434106800b0b29050abc1, workflow Lint/job rustfmt (no matrix), runner ubuntu-slim, run https://github.com/x52dev/confik/actions/runs/41636789247:

Attempt	Job	Result	Seconds	Cache
1	https://github.com/x52dev/confik/actions/runs/41636789247/job/125919892532	success	51	Rust cache miss
2	https://github.com/x52dev/confik/actions/runs/41636789247/job/125921827969	success	31	Rust cache hit
3	https://github.com/x52dev/confik/actions/runs/41636789247/job/126037485846	success	30	Rust cache hit

Slim n=3, median 31 seconds; 100*(31/16-1) = +93.75% versus historical Blacksmith. All three installed nightly Rust afresh; toolchain setup dominates. Execution durations exclude queue time; queue durations were not measured. No same-code standard-runner comparison was performed. Do not interpret this as isolated CPU performance or include it in a controlled GitHub-standard-versus-slim aggregate.

Validation: passed nix develop -c prettier --check .github/workflows/lint.yml. CI workflow https://github.com/x52dev/confik/actions/runs/41636791900 and Lint workflow both completed successfully on the current head. All executed jobs passed. The disabled public-api-diff and CodeRabbit checks were skipped. Other Lint results in attempts 2/3 were carried forward, not new executed samples. No executed failures, timeouts, capacity cancellations or rerun API rejections were observed. No deployment or publishing workflow was triggered. No measurements remain pending. Marked ready for review after verifying overall workflow conclusions and individual checks; no merge performed.

Summary by CodeRabbit

• Chores
  • Updated the environment used for automated formatting checks. This change affects the project’s development workflow and does not change the app’s features or behavior.

[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

The rustfmt job in the lint workflow now runs on ubuntu-slim instead of blacksmith-2vcpu-ubuntu-2404.

Changes: Lint runner

Layer / File(s)	Summary
Update rustfmt runner .github/workflows/lint.yml	The rustfmt job runner changes to ubuntu-slim.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Merge Risk: Minimal · up to 721dc

The rustfmt runner change has no identified merge-blocking issue. Reported runs succeeded, with longer execution times than the previous runner.

Pre-merge checks: 4

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title "ci: use ubuntu-slim for rustfmt" matches the only code change: the non-matrix Lint / rustfmt job in .github/workflows/lint.yml moves from blacksmith-2vcpu-ubuntu-2404 to ubuntu-slim. It is …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title "ci: use ubuntu-slim for rustfmt" matches the only code change: the non-matrix Lint / rustfmt job in .github/workflows/lint.yml moves from blacksmith-2vcpu-ubuntu-2404 to ubuntu-slim. It is specific, short, and states the main change. The PR objectives confirm the scope, and the title does not claim changes beyond that job.

Finishing Touches

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Recent review info

Run configuration

• Source mode: Auto
• Repository: x52dev/confik
• Branch: ci/ubuntu-slim-assessment
• File: .coderabbit.yml
• Commit: 721dca4
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Advanced
• Run ID: 6ac90eaf-cade-4450-bbd7-1d6e28685a16

Commits

Reviewing files that changed from the base of the PR and between b37d91f and 721dca4.

Files selected for processing: 1

• .github/workflows/lint.yml

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