Data lab to help improve models and evaluate agents
What we do
A model is only as good as what it learns from.
The next gains in AI won't come from more of the same data. They'll come from data that captures how specialists make decisions and how work really gets done. Coastside builds that data with vetted experts, scores it with rubrics you can trust, and proves it moved the numbers.
What we build:
Supervised Fine-Tuning (SFT)
Expert-written prompt and answer sets with the reasoning shown, so models learn not just the right answer but the path to it.
Reinforcement Learning + Rubrics
Hard tasks paired with detailed grading criteria written by domain experts, giving your RL pipeline a reward signal grounded in real expertise instead of guesswork.
Agent Environments (API / MCP)
Sandboxed, realistic environments where agents call tools, hit APIs, and complete multi-step jobs. Built for both training runs and evaluation.
Computer Use Trajectories
Real people completing tasks in browsers and desktop apps, captured step by step, so models learn to operate software the way a person does.
Audio & Voice Data
Accented, multilingual, and noisy real-world speech with multi-speaker diarization and verified transcripts. The data most providers don't have.
Evaluations & Benchmarks
Custom test sets that show exactly where a model or agent breaks, so you fix the right thing before your users find it.
How it works
From unclear failure to measurable gain, in four steps.
- 01
Tell us the goal
The capability you want to improve or the agent you need to trust.
- 02
We find the failures
Targeted evaluations and benchmarks built for your use case.
- 03
We build the data
Expert-created training data and RL environments aimed at those gaps.
- 04
We help you improve
Fine-tuning and re-evaluation until the numbers move.
Fine-tuning & RL as a service
We don't just hand you data. We help you use it.
Our team runs supervised and reinforcement fine-tuning on your model or an open-weight base, using the data and evals we built together, so improvements ship in weeks instead of quarters.
Talk to usFor enterprises
Your AI agent looks great in the demo. Does it work in production?
Most enterprise agents stall before production because no one can see where they fail. Coastside closes that gap end to end.
- Step 1
Diagnose
Custom benchmarks find exactly where agents break.
- Step 2
Benchmark
We measure reliability across real workflows, not just accuracy.
- Step 3
Supply data
Training data built for the specific gaps we find.
- Step 4
Fine-tune
We improve the model and re-test until it's ready to ship.
Mission
We're here to help build AI that's worth trusting, and to share what it makes possible.
We believe the best future with AI is one where its benefits reach everyone: an age of abundance where powerful, dependable AI helps people do more, in more fields, than ever before. That future doesn't arrive on hype. It's built on unglamorous work: better data, honest evaluation, and models that actually do what they promise. That's the work we do at Coastside.
Who we are
Built by a team that's been in AI safety since before ChatGPT.
Coastside is based in San Francisco. Our team has been building AI safety solutions since before ChatGPT and was among the first to discover prompt injection attacks and report them to OpenAI. Since then we've worked with frontier AI labs and some of the largest data providers in the industry, so we know what strong training data and honest evaluations look like from the inside.
Contact
Start a conversation.
We read every message and reply within one business day.