Page 28 · SimLabs LLM Visual

Evals: Evaluation & Regression Verification

One of the most common illusions in LLM systems is "I just tried a few examples and it seems better." A truly reliable engineering process does not rely on gut feelings, but uses evaluation sets, thresholds, and version comparisons to continuously verify: what exactly did this change improve, and did it break anything elsewhere.

First define metrics Then run version comparisons Finally set thresholds to prevent regression

Switch evaluation sets to see how "pass" is determined

First select a task type, then adjust the thresholds. The page will instantly judge which versions can pass the line, and which ones, although higher in some metric, do not meet the overall deployment criteria.

Quality Threshold

This is the minimum quality score you are willing to accept. Below this threshold, the response quality is not stable enough.

Current Threshold 80

Safety Threshold

Set a minimum bar for safety metrics such as refusal accuracy and risk identification rate to avoid the system pursuing only "better answering" while ignoring risks.

Current Threshold 85

Latency Budget

Higher metrics are not always better. Online systems often also have a maximum acceptable latency; exceeding it also prevents direct deployment.

Max Latency 1800ms

Why Demo Trials Cannot Replace Evals

Too few samples

The few examples you manually test may happen to be those the model excels at, failing to cover the real online distribution.

Easily biased toward "amazing cases"

Humans easily remember a few brilliant successful outputs while ignoring infrequent but costly errors.

No unified threshold

Without preset thresholds, the team falls into debates of "I think it's fine" versus "I think it's not stable enough" every time.

Cannot detect regression

A change may improve one scenario while quietly degrading another. Without regression testing, it is hard to detect in time.

A Practical Evaluation Loop

1

Define tasks and metrics

First clarify what exactly to evaluate — accuracy, citation quality, safe refusal, or latency cost.

2

Prepare benchmark sets

Collect data covering real scenarios, avoiding looking only at a few pretty examples.

3

Version comparison

Compare every change against the baseline version, checking not only "did it get better" but also "did it get worse."

4

Set thresholds to block

Automatically block when key metrics fail to meet thresholds, preventing problematic versions from going live directly.

In a nutshell: The value of Evals is not just telling you "which version is better," but transforming "deploying based on gut feeling" into "deploying with evidence, thresholds, and regression protection."