# Coolhand vs Arize

> Arize AX observes, evaluates, and — via its Alyx agent — proposes improvements you review inside the platform.
> Coolhand proposes them as an actual pull request against your repo. Here's where each one stops.

## What is Arize?

Arize AX is a managed AI engineering platform built around three pillars: Observe, Evaluate, and Improve. It
traces agent trajectories, runs online and offline evals (including real-time guardrails for prompt injection and
unsafe content), and supports datasets, experiments, and a prompt playground — all built on OpenInference, Arize's
own open standard on top of OpenTelemetry. Arize also ships a free, self-hostable sibling project called Phoenix.

Arize's own agent, **Alyx**, runs evals, debugs traces, and proposes prompt, config, or dataset changes as
review-and-accept cards inside Arize AX. Even with "Auto Accept" turned on, that only applies to in-platform
actions — Alyx doesn't modify your production code, open a pull request, or deploy anything to your repo.

## What Coolhand actually does

Coolhand watches your production AI agents continuously. When something breaks — a hard error, a quality
regression, a spike in cost — it diagnoses the root cause against your actual code, drafts the fix, and opens it
as a pull request in your repo. Nothing merges without a human reviewing it first. Alongside that, an open-source
skill audits your codebase for places to capture feedback that's already happening — edits, approvals,
corrections — instead of asking you to build a new annotation queue. Cost and quality dashboards then show whether
all of this is actually working, in dollars and quality-trend terms, not just "traces logged."

Where Coolhand excels: it's the only thing in this loop that turns a diagnosed problem into a reviewable code
change on its own, continuously and without per-issue manual triggering. It doesn't need an annotation team, a
dedicated eval engineer, or someone babysitting a dashboard — the loop runs in the background and only asks for
your attention when there's a PR to review.

That's the gap Arize leaves open: Alyx can propose a change, but only as a card you accept inside Arize — never a
commit in your repo. Coolhand closes that last mile and turns the diagnosis into an actual PR.

## Feature comparison

| Capability | Arize | Coolhand |
|---|---|---|
| Primary purpose | Observe, evaluate, and iteratively improve agents in-platform | Diagnose production issues and ship the fix as a PR |
| Tracing depth | Deep — agent trajectory tracing on the OpenInference/OTel standard | Request-level logs built for diagnosis, not a dedicated trace explorer |
| Evaluation | LLM-as-judge, Eval Hub, configurable-cadence online and offline evals, guardrails | Correctness and sentiment evaluators feeding the diagnosis loop |
| Human feedback | Manual annotation queues | Passive capture from your app's existing UI — no queue to build or staff |
| Opens a PR with a fix | No — Alyx proposes changes as in-platform cards; it never touches your repo, even with Auto Accept on | Yes — opens a real PR in your repo; you review and merge |
| Ingestion | 40+ frameworks via OpenInference/OpenTelemetry, plus OpenLLMetry auto-instrumentation | Ruby/Python/Node SDKs and provider proxies; no OpenTelemetry endpoint yet |
| Self-hostable server | Free open-source sibling (Phoenix); AX itself is SaaS or self-hosted on Enterprise | No — managed service only (SDKs, CLI, and widget are open source) |
| ROI reporting | Not a core focus; usage/eval dashboards instead | Cost-per-outcome and quality-trend dashboards built in |
| Pricing entry point | Free up to 25k spans/month, then $50/month Pro | Free up to 10M tokens/week |

## When you need both

Arize is a strong choice if your team wants deep, standards-based tracing (OpenInference/OpenTelemetry),
real-time guardrails, and a mature eval workflow — and Alyx genuinely speeds up the "what should we try next" part
of that loop. Where it stops is the boundary of the platform itself: every proposed change is a card you accept
inside Arize, not a commit in your version control. You need Coolhand once you want that loop to end in something
your team already knows how to review — a pull request, with a diff, in your existing repo and CI.

## How to use them together

Run Arize for its evaluation depth and guardrails, especially if you're already standardized on
OpenTelemetry/OpenInference instrumentation. Point Coolhand's SDKs at the same production traffic so it's
diagnosing in parallel. Use Arize's dashboards and Alyx's suggestions as additional signal when Coolhand proposes
a fix — agreement between them is a good sanity check before you merge. Arize keeps the evaluation and guardrail
layer sharp; Coolhand is what actually turns a diagnosed issue into a PR your team merges.

## Frequently asked questions

**Does Arize fix code or open pull requests?**
No. Arize's Alyx agent proposes prompt, config, and dataset changes as review-and-accept cards inside Arize AX.
Even with Auto Accept on, those actions stay in-platform — Alyx never modifies your code, opens a pull request, or
deploys to your repo. Coolhand opens the fix as a real PR in your repository.

**Is Coolhand a replacement for Arize?**
No. Arize is a deep, standards-based tracing and evaluation platform (built on OpenInference/OpenTelemetry) with
real-time guardrails. Coolhand doesn't replace that — many teams run both, with Coolhand turning a diagnosed issue
into a reviewable pull request.

**What's the difference between Coolhand and Arize?**
Arize observes and evaluates agents and proposes improvements you accept inside its own platform. Coolhand
diagnoses production issues against your actual code and ships the fix as a pull request you review and merge.

**Can I use Coolhand and Arize together?**
Yes. Point both at the same production traffic — Arize keeps the evaluation and guardrail layer sharp, and Coolhand
turns a diagnosed issue into a PR. Agreement between the two is a good sanity check before you merge.

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Source: [coolhandlabs.com/beyond-observability/arize](https://coolhandlabs.com/beyond-observability/arize)