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Curtail

Guardrails for AI-Generated Code

Static tests check your code at rest. ReGrade®'s patented runtime-behavior comparison checks it in motion, catching regressions, vulnerabilities, and performance issues before they reach production.

Our Research

Joint study with AFRL

Published study

ReGrade® helps AI coding agents fix 152% more bugs.

Every model we tested fixed more bugs.

A joint study with the Air Force Research Laboratory, cleared for public release. 17 language models from 6 providers, and the median model fixed 152% more bugs at a median 42% lower LLM API cost per bug fixed.

The study supplied behavioral evidence in the agent's initial prompt.

See the evidence for this →

How it works

Compare behavior before you approve a release.

ReGrade catches regressions in HTTP APIs by comparing a new build with recorded behavior from the current version. See changes in responses and latency before release.

The example advances every five seconds. Select a step to explore it.

1

A sensor acts as a proxy in front of your application and records real HTTP traffic. Capture QA sessions, developer testing or existing automation to build a reusable baseline.

2

Replay the traffic against a new build and compare every response with the recorded responses. Profiles normalize rotating IDs, tokens and timestamps so meaningful differences remain.

3

Review deltas (response differences) by severity and label them as known or dropped. ReGrade also compares latency overall and per endpoint. Inspect results in the web UI, through the API or with MCP. In CI, unexplained deltas or latency regressions can block a merge.

Illustrative example, not a live run

GET /api/orders/42

Capture the request and response.

A QA session passes through the sensor to the current application.

QA trafficSensorCurrent build

Recorded response

200 OK
status: "paid"
updated_at: "10:00:00"

Reusable baseline

The request, response and timing are saved for replay against another build.

Response time: 120 ms

Use Cases

QA recordings

Record manual or scripted QA sessions once, then replay them against every new build. No test scripts to write or maintain.

Dev testing

Record traffic against current code, make a change or refactor, then replay locally. Catch unintended changes in behavior or speed before you push.

CI testing

Replay recordings against each merge request's build. The pipeline fails on unlabeled deltas or latency regressions, so reviewers see exactly what changed.

CI enterprise dashboard

See every project's health from its latest merged change and a recent trend. Statuses are red, amber, stale, green or grey, so leads can spot unexplained regressions and projects that haven't been tested lately.

Why ReGrade

Why teams use ReGrade

Three minutes on the problem it solves: catching the changes no test asserts, knowing a release holds up under load, and proving a refactor behaves like the code it replaced.

Want to watch one run start to finish? See the runnable demos. Each one has a repo you can clone.

Risks of AI Coding

The code is changing. The risks are growing.

66%

of survey respondents use AI coding assistants or coding agents at work

Stack Overflow 2026

1.7×

as many review issues per AI-co-authored PR as human-only PRs, across 470 PRs

CodeRabbit 2025

48%

of surveyed developers say they always check AI-assisted code before committing

Sonar 2026

46%

of enterprise survey respondents report AI-code failures in production

SmartBear 2026

Case study

CurtailLucihub

Lucihub® & Curtail ReGrade®

Azeem Mohammad at Lucihub

Lucihub now uses Curtail ReGrade to test each release – taking only ~20 minutes. Running ReGrade provides broad testing and caught an API change nobody had documented.

When Lucihub's engineers moved to AI-assisted coding, code shipped faster, and QA's manual impact analysis grew with it. In a four-week pilot, Curtail ReGrade with Claude Code put regression checks on 1,154 real API calls across five user roles, without anyone having to write a single test assertion.

In their words

"Since our team moved to AI-assisted coding, every deploy carried more change than QA could check by hand. ReGrade gave us a regression baseline across our API with no test assertions to write, and a release verdict in about 20 minutes, including an API change nobody had documented."
Azeem, Engineering Manager, Lucihub

Pilot: September 25 to October 20, 2026, on Lucihub's staging environment.

What tests miss

What testing and code review miss

Tests verify what you expect. ReGrade catches what you don't.

Slow before anyone complains

ReGrade compares P95 and P99 latency across versions, so a release that quietly got slower is a number you see on the merge request rather than a support ticket next week.

P95/P99 latency

Zero-Day Discovery

By comparing actual responses against a known-good baseline, ReGrade surfaces vulnerabilities that no test was written to find, because no one knew they existed.

Security case study

Give your agents evidence for repairs

ReGrade supplies behavioral findings to the coding agent so it can attempt repairs. Your engineers review the changes and decide which differences are acceptable.

Agent feedback

See how ReGrade compares with unit, contract, snapshot, DAST and manual testing

AI Integrations

Works with your AI coding tools via MCP (Model Context Protocol)

Workflows

It meets your team where they already work

MCP Server

Connect your coding agents through MCP so they can investigate behavioral differences and attempt repairs.

Merge Request Analysis

Automatically analyze candidate builds before merge. ReGrade comments appear alongside your code review with specific field-level findings.

Preview Before Deploy

Replay production traffic against your candidate version in a safe environment. Inspect differences on the requests you replay before approving a release.

Evaluation

Plan a ReGrade evaluation

Choose one service and compare a baseline with a candidate build. Discuss what changed, how your team will review findings, and what recording and replay will cost.