blacksmith

TL;DR. Blacksmith runs GitHub Actions jobs through managed continuous integration (CI) runners. CI automates build and test checks for code changes. Runners are machines that run these jobs. Caching stores build data for reuse. CI observability shows job performance and failures. Personal repositories cannot use the service.

Overview

Blacksmith runs GitHub Actions jobs on managed runners. It describes the service as cloud CI. CI automates build and test checks for code changes.

Aditya Jayaprakash, Aayush Shah, and Aditya Maru started Blacksmith in 2024 after meeting in Toronto. The three University of Waterloo graduates brought experience from the companies Cockroach Labs and Faire. Blacksmith says its founders discussed the idea over dinner. They experienced slow, costly CI at their former workplaces.

The company reports a 41-person team. Earlier research listed 95 Third Street, 2nd Floor as its San Francisco address. The current source check could not verify this address.

Blacksmith entered Y Combinator’s Winter 2024 batch. In May 2025, it announced a $3.5 million seed round. GV and Y Combinator led the round. In September 2025, it announced a $10 million Series A.

GV led the Series A. In October 2026, Blacksmith announced a Series C. Sequoia Capital led the round.

Premji Invest, Peak XV Partners, GV, and Y Combinator participated in the Series C. Blacksmith reported $125 million raised in total and a $1 billion valuation.

Its core product replaces GitHub-hosted runners with managed runners. Blacksmith adds caching and CI observability. Blacksmith says more than 10,000 companies use its service.

The company website is blacksmith.sh. Blacksmith also has documentation, a GitHub page, and an engineering blog.

Who's Behind It

Three University of Waterloo graduates founded Blacksmith in 2024. Aditya Jayaprakash is chief executive officer (CEO). Aayush Shah and Aditya Maru are co-founders. This review did not verify their current executive titles.

Blacksmith’s current company page reports a team of 41. It describes three founders with engineering backgrounds. The company page does not date its team-size figure. The public roster also names Jon Boyer as vice president of Sales. It gives no hire date or biography.

Blacksmith describes its team as “lean,” multidisciplinary, “talented,” and “hungry.” These are company-stated descriptors, not an independent culture assessment.

The company’s investor section names industry figures including Kelsey Hightower, Spencer Kimball, and Peter Mattis. It also names Kelvin Beachum, Tony Dong, Eli Brown, Theo Browne, and David Cramer. The page does not identify them as directors or advisors. Blacksmith’s seed announcement separately names Kimball, Mattis, and Brown among its individual investors.

Pricing & Business Model

Blacksmith sells CI runner capacity by the minute. It includes 3,000 free minutes monthly.

A virtual central processing unit (vCPU) provides processor capacity to a virtual machine.

x64 and ARM identify processor types.

Published rates are $0.004 per minute for Ubuntu x64 and $0.0025 for Ubuntu ARM. Windows x64 costs $0.008, and macOS M4 costs $0.08.

An x64 2-vCPU minute is one minute on an x64 runner with 2 vCPUs. The free allowance applies per organization and uses x64 2-vCPU minutes. Runner types share that allowance. The current source check did not establish their conversion rates.

Docker packages software and its dependencies as container images. Each image has layers, which are saved build steps. Docker layer caching reuses those layers. Sticky Disks save selected directories between jobs. A gigabyte (GB) measures data size.

Optional Docker layer caching and Sticky Disks cost $0.50 per GB monthly.

Blacksmith offers static Internet Protocol (IP) addresses. A static IP address does not change. Static IPs cost $100 per IP monthly.

A service-level agreement (SLA) is a written service commitment. Blacksmith’s enterprise offering adds a 99.9% SLA. It also adds 24/7 priority support and a dedicated Slack channel. It also adds onboarding and CI optimization support.

Blacksmith does not publish an enterprise price on its pricing page. The company estimates Ubuntu x64 customers can save 67% against GitHub-hosted runners. It bases this estimate on its stated per-minute discount and estimated faster runtime.

Blacksmith announced a $125 million total funding figure with its October 2026 Series C. Sequoia led that round at a $1 billion valuation.

Annual recurring revenue (ARR) is the yearly value of recurring subscription revenue. The company reports 17x ARR growth from January to October 2026. It reports weekly CI jobs rose from 5 million to more than 90 million. These are company-reported growth metrics. The announcement gives no absolute ARR figure.

Earlier research cited a $10 billion CI compute market estimate. This review could not verify that estimate.

Who It's Built For

A 10-engineer finance startup is one documented Blacksmith customer. The company also names enterprise software teams among its users. Blacksmith says more than 10,000 companies use its service. Its core audience is software engineering teams running GitHub Actions. The evidence points to teams from startups through enterprise. It does not show a defined target company size or an individual-user market.

Software engineers and DevOps engineers use the service. DevOps combines software delivery and system operations. Highbeam is a finance artificial intelligence (AI) platform. Its chief technology officer (CTO) is one documented executive buyer.

Unit tests check individual code parts. Integration tests check how code parts work together. Deployment pipelines automate the steps that release code.

Teams use Blacksmith to:

• Make checks for proposed code changes, unit tests, integration tests, and deployment pipelines faster.

• Lower CI infrastructure costs as engineering teams and test workloads grow.

• Replace self-hosted runners and reduce work maintaining runner reliability.

• Run builds, including jobs that build container images, and handle spikes in CI demand.

• Scale test workloads as code output rises, including code from AI tools.

Published customer examples center on software companies and developer infrastructure. They also include finance technology and human resources (HR) and payroll platforms. Finch connects human resources information systems and payroll software through an application programming interface (API). These examples show industry variety, not a measured concentration in one industry. Blacksmith says its compute runs in U.S. and European data centers.

The reviewed sources do not identify a dominant customer region.

Traction and Market Position

Blacksmith says more than 10,000 companies use its service. Blacksmith reports weekly CI jobs rose from 5 million to more than 90 million from January to October 2026. It reports 17x ARR growth during that period. The company also reports $125 million in total funding and a $1 billion valuation after its October 2026 Series C.

Blacksmith focuses on running CI jobs. It serves teams that want faster GitHub Actions without replacing their workflow system. A workflow file defines the steps for a GitHub Actions job. Its runner label selects the machine type. Blacksmith says customers can switch by changing that label.

Blacksmith provides computing capacity for CI. It stores build data near runners for reuse.

Blacksmith claims no fixed limit on jobs that run at the same time. These are vendor claims.

Actual savings depend on each workload.

The closest alternatives address different needs. Depot also offers GitHub Actions runners. It also sells CI, container builds, a registry, and developer sandboxes. Container builds create container images. A registry stores container images. Developer sandboxes provide separate environments for tests.

Buildkite offers a broader CI platform. Source-control systems track changes to code. Buildkite supports multiple source-control systems. It suits teams that need custom pipelines or infrastructure control. Blacksmith fits best when teams prefer GitHub Actions. It also fits when runner speed or cost causes problems.

Growth and named customers such as Mercury and LangChain are positive signals. Rising CI demand, which Blacksmith links to AI coding tools, is another positive signal. Risks include dependence on GitHub workflows and the requirement for a GitHub organization. Competition from broader CI platforms and runner providers is another risk. Blacksmith also plans major compute expansion. Chiri identifies this expansion work as a risk.

Recommend Blacksmith for engineering organizations with heavy GitHub Actions usage, recurring build delays, or costly self-hosted runners. Test a typical workflow before you adopt Blacksmith. Blacksmith reports the public savings and speed claims. Its outlook depends on reliable capacity and growth beyond managed runners.

Adoption & Sentiment

Blacksmith previously reported more than 6,000 companies running CI on its platform. Its October 2026 announcement reports more than 10,000 companies. Blacksmith names Supabase, Clerk, Ashby, and Mercury as customers. It also reports 5% to 10% weekly growth in CI jobs since early 2026. These adoption figures are vendor-reported, not independently audited.

I could not verify a reliable current G2, Capterra, or TrustRadius rating or review count. Public feedback instead comes from Blacksmith customer stories, practitioner posts, and Hacker News discussions. Blacksmith’s customer page quotes Supabase’s API lead saying tests took half as long after a small workflow change. Blacksmith’s Ashby case study reports deployments that take half as long and 75% lower annual CI costs. It also reports thousands of jobs each week.

An engineering blog reports that one workflow fell from 10-11 minutes to 2-3 minutes after switching. Blacksmith sponsored Agentgateway, the author’s project. The author says the sponsorship did not require the blog post.

The clearest recent complaint concerns free-tier billing. In June 2026, one user reported receiving a $1,081.45 invoice. The user exceeded free usage without adding a card. The user said the overage warnings caused confusion. The user considered the service useful. The user expected to continue.

Blacksmith’s product representative acknowledged unclear billing communication. The representative offered to address the user’s overage. The user reported a credit offer. The user also reported revised pricing and overage copy. A separate July 2025 Hacker News user objected to per-minute billing for many short checks.

That user said 70-plus checks often ran for about 10 seconds. The user said minute-level billing made this workflow costly.

These anecdotes identify billing clarity and the cost of short jobs as adoption barriers. They do not establish broad review trends.

Security & Compliance

Firecracker software creates lightweight virtual machines called microVMs. Blacksmith runs each CI job in a disposable microVM. It destroys the microVM after the job completes. System and Organization Controls (SOC) 2 audits assess controls that protect data. Type II audits assess these controls over time. Blacksmith reports SOC 2 Type II compliance.

The General Data Protection Regulation (GDPR) is a European Union privacy law. Blacksmith reports GDPR compliance. ISO 27001 is a standard for information security management. Blacksmith says its hardware runs in ISO 27001 data centers.

A data processing agreement (DPA) defines duties for personal data. Earlier research cited a June 15, 2026 update. The current source check could not verify that date.

This review could not verify access to Blacksmith’s SOC 2 report. The security page describes encryption and audit records. Blacksmith reports quarterly penetration tests. Penetration tests check a system for security weaknesses.

Secrets are protected values, such as passwords or keys. Blacksmith’s security page says its integration cannot access secrets. The current source check could not verify the detailed GitHub app permissions. GitHub OAuth provides dashboard sign-in. OAuth lets an account authorize access to another service. A just-in-time runner token is a short-term credential for one job.

The token expires after one hour. Cached artifacts are saved build files. Blacksmith reports that cached artifacts remain encrypted, authenticated, audited, and isolated by organization.

Earlier research cited US and EU processing, negotiated region moves, and exclusions from AI training. It also cited AI features that start enabled and a setting to disable them. The current source check could not verify these privacy terms. Buyers must confirm current terms directly.

Earlier research cited deletion within 30 days and breach notice without unnecessary delay. The current source check could not verify these terms. Legal retention rules can affect deletion.

On July 21, 2026, Blacksmith reported a multi-hour control-plane outage. The control plane schedules and manages runners. The outage disrupted how the control plane sends jobs to runners. It also disrupted cache operations.

A webhook is an automatic event message. Redis stores data in memory. Blacksmith attributed the outage to repeated webhook messages and overloaded Redis.

Classification

Primary Category: AI DevOps Categories: AI DevOps, AI Infrastructure, AI Analytics Tags: github actions, ci/cd, managed runners, build caching, docker builds, ci observability, log search, test analytics, github integration, platform engineering, software development teams

Products & Features

Blacksmith speeds GitHub Actions with managed runners, shared build caches, and CI debugging tools. Earlier research described Testboxes as environments for local code changes inside real CI jobs. It also cited AI tool access. The current source check could not verify those capabilities.

Teams switch by changing a workflow’s runner label. Blacksmith offers Ubuntu x64 and ARM, macOS Apple Silicon, and Windows runners. A beta is a test release that is not final. Blacksmith lists Windows as public beta. GitHub Actions cache integrations use Blacksmith’s nearby cache.

Throughput is the data rate. MB/s means megabytes per second. Earlier research cited 400 MB/s throughput. The current source check could not verify this figure. Sticky Disks save selected directories between jobs. Docker layer caching reuses unchanged build layers.

Blacksmith’s homepage claims 40x faster Docker builds. The current source check could not verify the earlier 2x-to-40x customer range. Docker layer caching and Sticky Disks cost $0.50 per GB monthly.

Its web dashboard includes CI job, failure-rate, and cost analytics at no additional charge. Earlier research also cited cache analytics. The current source check could not verify cache analytics.

JUnit XML is a file format for test results. Test Analytics is a Blacksmith feature that reports test results. It parses JUnit XML files or test-like log output.

GitHub pull requests are proposed code changes. Test Analytics can post detected test failures as GitHub pull-request comments. The current source check did not establish the accuracy of log parsing.

The current source check could not verify Blacksmith’s earlier recommendation to use JUnit XML.

Testboxes is a Blacksmith product name. The Buildkite comparison describes Testboxes as an early beta. Earlier research cited Linux and macOS support, support services, and secrets. It also cited repeat commands in 1-3 seconds and standard CI pricing. The current source check could not verify these capabilities, timings, or prices.

A command-line interface (CLI) accepts text commands. Earlier research cited Blacksmith CLI features for logs, metrics, caches, and Testboxes. The current source check could not verify those features.

Current listed compute rates include $0.004 per minute for Ubuntu x64 and $0.0025 for Ubuntu ARM. Windows x64 costs $0.008, and macOS M4 costs $0.08.

Blacksmith lists 3,000 free minutes monthly. Rates and offers can change.

Chiri Analysis

Chiri Score: 73/100

Verdict

Best for:

• Engineering organizations with heavy GitHub Actions usage and recurring build delays

• Teams replacing costly or hard-to-maintain self-hosted runners

• Teams with Docker-heavy builds that benefit from layer caching

• Startups through enterprises that want CI cost and failure analytics without extra tooling

• Teams with more test work from AI tools that write code

Not for:

• Developers working only in personal GitHub repositories

• Teams using CI systems other than GitHub Actions or non-GitHub source control

• Workflows with many short checks, where one user reported that per-minute billing raised costs

• Organizations that need verified guarantees about data locations. This review could not verify those guarantees.

• Buyers who need fully supported Windows runners now, since Windows is in public beta

Head-to-head

Frequently Asked Questions

Is Blacksmith SOC 2 compliant?

Blacksmith reports SOC 2 Type II and GDPR compliance. Chiri Atlas could not independently verify these claims. This review could not verify access to its SOC 2 report. Buyers should get that report before signing.

How much does Blacksmith cost?

Blacksmith bills runner capacity per minute on a pay-as-you-go basis. Listed rates are $0.004 per minute for Ubuntu x64 and $0.0025 for Ubuntu ARM. Windows x64 costs $0.008, and macOS M4 costs $0.08. It lists 3,000 free minutes monthly per organization. Chiri Atlas did not verify these rates. The rates can change.

Blacksmith does not publish enterprise pricing.

Who are Blacksmith's competitors?

Blacksmith's direct alternatives include GitHub-hosted runners, Depot, Buildkite, and self-hosted runners. Depot also offers GitHub Actions runners. It also sells container builds, a registry, and developer sandboxes. Buildkite is a broader CI platform that supports multiple source-control systems.

Is Blacksmith good for enterprise?

Blacksmith names enterprise customers and describes an enterprise offering. That offering reportedly includes a 99.9% service-level agreement (SLA), 24/7 priority support, and a dedicated Slack channel. Chiri Atlas did not verify these offering terms. On July 21, 2026, Blacksmith reported a multi-hour control-plane outage. Enterprises should test reliability and review the SLA directly.

How do teams switch to Blacksmith?

Teams change the runner label in their GitHub Actions workflow files. Blacksmith requires a GitHub organization. It does not support personal repositories. Vendor-reported speed and savings vary by workload. Teams should test a typical workflow first. They should measure its speed and cost.

Which operating systems does Blacksmith support?

Blacksmith provides Ubuntu runners on x64 and ARM. It also offers macOS on Apple Silicon. Windows runners are in public beta.

How does Blacksmith isolate CI jobs?

Blacksmith runs each CI job in a disposable Firecracker microVM. A microVM is a lightweight virtual machine. Blacksmith destroys the microVM after the job completes.

Are there billing risks with Blacksmith's free tier?

In June 2026, one user reported a $1,081.45 invoice. The user exceeded free usage without adding a card. Blacksmith acknowledged unclear billing communication. The user reported a credit offer. Another user said per-minute billing made many checks of about 10 seconds costly. These are individual anecdotes, not broad review trends.

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Chiri Atlas Research Desk (AI Tooling Analyst) reviewed this report on 2026-11-06.

Sources

• Blacksmith company page

• Y Combinator company profile

• Seed funding announcement

• Analytics announcement

• Series B announcement

• Series A reporting

• Series C announcement

• Blacksmith home page

• Blacksmith documentation

• Privacy policy

• Blacksmith GitHub profile

• Runner pricing

• Runner instance types

• Series B reporting

• Support terms

• Customer stories

• Highbeam customer story

• Finch customer story

• Buildkite comparison

• Runner quickstart

• Depot pricing

• Ashby customer story

• Hacker News discussion 44659566

• Hacker News discussion 46190267

• Engineering review with sponsorship disclosure

• Customer billing account

• Hacker News discussion 48468370

• Trust center

• Security page

• Data processing agreement

• GitHub app permissions

• July 21 outage report

• Subprocessor list

• CI dashboard documentation

• Test Analytics documentation

• Testboxes documentation

• Sticky Disks documentation

• Command-line interface documentation

• https://firecracker-microvm.github.io/