Compare GitHub Actions runners and CI platforms: StarSling vs GitHub-hosted, Depot, Blacksmith, WarpBuild, and Buildkite
StarSling is AI-native CI for GitHub Actions: a drop-in runner replacement with AI agents that open optimization PRs. These pages put it side by side with the runner and build-acceleration tools teams evaluate.
The alternatives run jobs faster. Only StarSling also opens AI optimization PRs that improve the pipeline over time. Where the alternatives differ from each other is the runner families they publish and what they attach to the Docker build. Buildkite is in this table as a platform, not a runner: it replaces GitHub Actions rather than speeding it up.
For new accounts, AI-powered optimization PRs are only available to customers on paid plans and are not enabled by default.
| Tool | Faster runners | AI optimization PRs | Runner families | Docker builds | Primary focus |
|---|---|---|---|---|---|
| StarSling | Yes | Yes | Linux only: Ubuntu 24.04 | No separate build service: Docker builds run in your workflow on faster hardware, and the agents open PRs that fix the build and cache steps | Self-driving CI: fast runners plus agents that open optimization PRs to enforce best practices |
| GitHub-hosted | No | No | Linux, macOS, and Windows (hosted-runner reference, checked 2026-07-14) | Runs in your workflow on GitHub's shared hardware; layer caching only through BuildKit's GitHub Actions cache backend (type=gha), with no remote builder (checked 2026-07-14) | Default GitHub Actions runner infrastructure |
| Depot | Yes | No | Linux, macOS, and Windows (runner types (depot.dev/docs/github-actions/runner-types), checked 2026-07-14) | Remote BuildKit builders that run in the same private network as the runner (depot.dev/docs/github-actions/overview), each with a persistent NVMe layer cache (depot.dev/docs/container-builds/overview) (50 GB, expandable). Depot Cache (depot.dev/docs/cache/overview) is a distinct product, a remote cache for GitHub Actions, Bazel, Go, Gradle, Turborepo and more (checked 2026-07-14) | Container builds, Depot Cache (depot.dev/docs/cache/overview), GitHub Actions runners, and Depot CI (products (depot.dev/), checked 2026-07-14) |
| Blacksmith | Yes | No | Linux x64 and ARM and macOS, with Windows Server 2025 in public beta (instance types (docs.blacksmith.sh/blacksmith-runners/overview), checked 2026-07-14) | Docker layer caches kept on per-Dockerfile sticky disks (docs.blacksmith.sh/blacksmith-caching/docker-builds) that persist between runs, billed per GB-month (checked 2026-07-14) | Fast drop-in runners plus caching and build infrastructure; its docs list no agent that opens optimization PRs (checked 2026-07-14) |
| WarpBuild | Yes | No | Linux x64 and ARM64, macOS, and Windows (cloud runners (www.warpbuild.com/docs/ci/cloud-runners), checked 2026-07-14) | Remote "Docker builders" (www.warpbuild.com/docs/ci/docker-builders) with Buildx integration, each builder profile keeping a persistent layer cache, plus a WarpBuilds/cache (www.warpbuild.com/docs/ci/features/caching) action documented as a drop-in for actions/cache@v4 (checked 2026-07-14) | Fast drop-in runners plus a container-build service; its docs list no agent that opens optimization PRs (checked 2026-07-14) |
| Buildkite | No | No | Agents you host yourself, on-premises or in the cloud, with Buildkite-hosted agents also offered (Pipelines architecture (buildkite.com/docs/pipelines/architecture), checked 2026-07-31) | Remote Docker builders: docker build and Buildx commands on Buildkite-hosted agents are directed to dedicated external builder machines rather than built on the agent, a default Enterprise-plan feature (Remote Docker builders (buildkite.com/docs/agent/buildkite-hosted/linux/remote-docker-builders), checked 2026-07-31) | Hybrid CI/CD platform, not a runner swap: a SaaS control plane that handles orchestration while you bring the compute, with a fully hosted option too (Pipelines architecture (buildkite.com/docs/pipelines/architecture), checked 2026-07-31). See StarSling vs Buildkite |
Real results from StarSling customer workflows
These are StarSling's published customer measurements, not benchmark claims about Depot, Blacksmith, WarpBuild, or GitHub-hosted runners. Each result links to the case study that explains the measurement window, source method, and caveats.
lower compute cost per run on Partcl's heaviest CI jobs
faster test suites at Mastra
faster E2E tests at Better Auth
- Better Auth: after migration and three agent PRs, E2E went from 2m 22s to 1m 04s and CI went from 1m 40s to 1m 02s.
- Mastra: agents opened fourteen PRs across sleeps, polling, Docker healthchecks, sharding, race fixes, and runner migration; Combined store Tests measured 29m 56s to 5m 06s in the post-migration window.
- Partcl: on a synthesis-bound CI workload, the agents shipped eight optimization PRs, cut heaviest-job compute cost 13x per run, and reduced p95 queue time from 9.5 minutes to 35 seconds.
StarSling vs GitHub Actions
GitHub Actions is the default CI for GitHub repositories, and GitHub-hosted runners (ubuntu-latest, ubuntu-24.04) are its standard runner infrastructure.
StarSling vs Depot for GitHub Actions
Depot builds a broad CI platform: accelerated container builds, a distributed remote cache, GitHub Actions runners, and its own CI engine.
StarSling vs Blacksmith runners for GitHub Actions
Blacksmith provides fast, drop-in GitHub Actions runners on better hardware, with runner families beyond Linux and build-infrastructure features such as caching.
StarSling vs WarpBuild
WarpBuild is a fast, drop-in GitHub Actions runner with a container-build service attached.
StarSling vs Buildkite
Buildkite is a CI/CD platform, not a runner swap.
Depot vs Blacksmith for GitHub Actions
Both replace GitHub-hosted runners without changing your workflows beyond the runs-on label, and both keep a Docker layer cache between runs, so the real difference is what each attaches to the build. Depot documents remote BuildKit builders that run in the same private network as the runner (depot.dev/docs/github-actions/overview), each with a persistent NVMe layer cache (depot.dev/docs/container-builds/overview) of 50 GB, expandable, plus Depot Cache (depot.dev/docs/cache/overview), a separate remote cache for GitHub Actions, Bazel, Go, Gradle, Turborepo and more. Blacksmith documents Docker layer caches held on per-Dockerfile sticky disks (docs.blacksmith.sh/blacksmith-caching/docker-builds) that persist between runs and are billed per GB-month. Both checked 2026-07-14.
The runner families differ too. Depot publishes Linux, macOS and Windows runner types (depot.dev/docs/github-actions/runner-types); Blacksmith publishes Linux x64 and ARM and macOS, with Windows Server 2025 in public beta (instance types (docs.blacksmith.sh/blacksmith-runners/overview)), both checked 2026-07-14. So the choice follows the bottleneck: if the slow part of the pipeline is docker build itself, the remote-builder model is what moves it; if the whole job is slow, a faster runner changes every step of it. Both make the pipeline you already have run faster. StarSling is the only vendor with AI agents that open optimization PRs against your workflows, so the pipeline itself gets better over time.
Which runner fits which bottleneck
Start from the part of the run that is actually slow. Time a few runs before switching anything: the bottleneck usually picks the tool.
- Jobs wait before they start. That is queue time, and it is a concurrency problem rather than a hardware one. Cut queue time on GitHub Actions covers how to measure it from the run trigger rather than from the job's own timestamps, which is where most measurements of it go wrong.
docker builddominates the run. A remote builder moves that build off the machine running the job. Depot, WarpBuild and Buildkite each document one, on the terms cited in the table above.- Install, test and package steps dominate. Every step runs on the runner, so this is the case a drop-in runner swap actually fixes: one
runs-onlabel, no workflow rewrite. - You need macOS or Windows. StarSling publishes Linux runners only. The runner-families column above names what each vendor publishes, with the vendor's own documentation and the date we checked it.
- You are leaving GitHub Actions altogether. That is a platform migration rather than a runner swap, and Buildkite is the entry in this table on that axis.
- The pipeline itself is the problem. No runner makes an unsharded test suite or a missing cache go away. StarSling's agents open pull requests that apply the GitHub Actions CI best practices, which is the column of this table only one row is marked in.
Which GitHub Actions runner is right for me?
If you want faster runs and a pipeline that keeps improving itself, StarSling combines fast drop-in runners with AI agents that open optimization PRs. If you only need raw runner speed, any fast-runner provider works; if your main bottleneck is Docker image builds, a build-acceleration tool like Depot fits.
Do these runners work with my existing GitHub Actions workflows?
Yes. StarSling and the other drop-in runners run your existing workflows; you switch by changing the runs-on label. StarSling's label is starsling-ubuntu-24.04.
What makes StarSling different from other fast runners?
StarSling adds AI agents that analyze your workflows, logs, and telemetry and open pull requests that optimize caching, dependency installs, parallelization, and test sharding, applying the GitHub Actions CI best practices an expert would by hand. Other runners make jobs faster; StarSling also improves the pipeline over time.
How does Buildkite compare to Depot for Docker builds?
Both move docker build off the machine running the job, but they sit at different layers. Buildkite is a hybrid CI/CD platform rather than a runner swap: a SaaS control plane that handles orchestration while you bring the compute, and on Buildkite-hosted agents docker build and Buildx commands are directed to dedicated external builder machines rather than built on the agent, a default Enterprise-plan feature (Remote Docker builders (buildkite.com/docs/agent/buildkite-hosted/linux/remote-docker-builders), checked 2026-07-31). Depot stays inside GitHub Actions and attaches remote BuildKit builders that run in the same private network as the runner (depot.dev/docs/github-actions/overview), each with a persistent NVMe layer cache (depot.dev/docs/container-builds/overview) (50 GB, expandable), checked 2026-07-14. So the practical question is whether you are replacing GitHub Actions or accelerating it. Neither opens optimization PRs against your workflow, which is the axis StarSling is on.
How does Buildkite compare to Blacksmith for CI runners?
They are not the same kind of product. Blacksmith is a drop-in GitHub Actions runner: you keep your existing workflows and change the runs-on label, and it publishes Linux x64 and ARM and macOS runner families with Windows Server 2025 in public beta (instance types (docs.blacksmith.sh/blacksmith-runners/overview)), keeping Docker layer caches on per-Dockerfile sticky disks (docs.blacksmith.sh/blacksmith-caching/docker-builds) that persist between runs, billed per GB-month, checked 2026-07-14. Buildkite replaces GitHub Actions rather than speeding it up: the compute is agents you host yourself, on-premises or in the cloud, with Buildkite-hosted agents also offered (Pipelines architecture (buildkite.com/docs/pipelines/architecture), checked 2026-07-31). If the goal is faster GitHub Actions runs without rewriting your pipelines, that is the runner comparison; if it is moving off GitHub Actions entirely, it is a platform migration. Neither opens optimization PRs against your workflow, which is the axis StarSling is on.
How does WarpBuild compare to Blacksmith?
Both are drop-in GitHub Actions runners, so the difference is the runner families each publishes and what each attaches to the Docker build. WarpBuild publishes Linux x64 and ARM64, macOS, and Windows (cloud runners (www.warpbuild.com/docs/ci/cloud-runners)) and pairs them with remote "Docker builders" (www.warpbuild.com/docs/ci/docker-builders) with Buildx integration, each builder profile keeping a persistent layer cache and building natively for amd64 and arm64, plus a WarpBuilds/cache (www.warpbuild.com/docs/ci/features/caching) action documented as a drop-in for actions/cache@v4. Blacksmith publishes Linux x64 and ARM and macOS runner families up to 32 vCPU on Linux, with Windows Server 2025 in public beta (instance types (docs.blacksmith.sh/blacksmith-runners/overview)), and keeps Docker layer caches on per-Dockerfile sticky disks (docs.blacksmith.sh/blacksmith-caching/docker-builds) that persist between runs, billed per GB-month. Both checked 2026-07-14. Neither vendor's docs list an agent that opens optimization PRs, which is the axis StarSling is on.
Last updated 2026-08-05