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AI evaluation & reliability

Know what changed before your agents ship.

We turn observed failure modes into versioned datasets, calibrated graders, and release gates, so model, prompt, retrieval, and tool changes can be tested before they reach users.

System architectureStacklane engineering
Analyze → Execute → Grade → Release
The engineering problem

A convincing answer can still be wrong.

A support agent cites an expired return policy. The response reads well, but the retrieved evidence, answer, and release decision need separate checks.

Example integration surface
  • Versioned datasets
  • Code assertions
  • LLM judges
  • Trace evaluation

Inside the system

From error analysis to a release decision.

Inspect each stage of a support-agent evaluation. The records below are illustrative artifacts, not benchmark results.

Execution model01 / 04
One dataset. Two system versions.Illustrative flowreference labels → gradersTest fixturesQuestionPolicy versionExpected resultBaseline runprompt-v11Candidate runprompt-v12same inputs + contextGrade outputs + tracesCode assertionsschema / citationsSemantic rubriccalibrate to expert labelsRelease gatePromoteHoldReviewed production failures → new cases

Swipe to inspect the full diagram →

support-cases.jsonlExample record
case_id
return-045
slice
stale_policy
expected
Outside 30-day window

Follow the architecture as you scroll, or select a layer.

01

Build cases from observed failures

Review traces with domain experts. Separate retrieval errors, unsupported answers, and incorrect tool use; label representative cases and keep a held-out set for regression testing.

Input
Traces, expert labels, business rules
Transform
Classify failures and version test cases
Output
Dataset with references and failure slices
Redacted trace samplesSeparate development and held-out cases
02

Compare the full system

Run baseline and candidate against the same dataset version and controlled context. Record retrieved documents, tool arguments, outputs, latency, and usage; repeat stochastic cases where needed.

Input
Dataset, baseline, candidate configuration
Transform
Run controlled comparisons and capture traces
Output
Versioned outputs and tool trajectories
Pinned prompt and retrieval versionsSandboxed tools with no external writes
03

Test the answer and its evidence

Use code for schemas, citations, and tool permissions. Use rubric-based judges for semantic quality, calibrate against expert labels, and investigate disagreements before trusting the grader.

Input
Outputs, references, traces, expert labels
Transform
Apply assertions and calibrate semantic graders
Output
Scores, failed assertions, review queue
Versioned rubric and judge configurationHeld-out grader calibration examples
04

Gate changes and close the loop

Compare results by failure slice against agreed gates. Block critical regressions; review sampled production traces and turn confirmed failures into new tests for the next release.

Input
Comparison results and production feedback
Transform
Apply release gates and triage failures
Output
CI decision and new regression cases
Critical failures block promotionReviewed feedback becomes versioned fixtures

Inspect the behavior

Find the failure behind the answer.

Synthetic support policy: unopened items can be returned within 30 calendar days of delivery. Switch cases to inspect the evidence and gate; these are fixtures, not measured evaluation results.

Illustrative system · Synthetic inputs
Input

An unopened item arrived 12 days ago. Can I return it?

Case: passed
Trace: passed
Grade: passed
Gate: passed
System decision

This fixture passes

The answer checks the unopened condition and cites the current 30-day policy. Release still depends on the complete regression suite and agreed gates.

Evidence
returns-v4 · 30-day window
Answer
Eligible: unopened, day 12
Assertion
Current citation + correct outcome

Verification specification

Define what passes.
Inspect what fails.

We turn expected behavior into repeatable tests and operating controls. Acceptance thresholds are agreed for your workflow, data, and the consequences of an error.

System propertyVerification methodRelease / operating condition

01Task success by failure slice

Measure cases meeting all required assertions, with denominators and separate results for stale evidence, missing context, and tool errors.

Agreed thresholds per slice; critical violations block release.

02Grader agreement and error analysis

Compare judge labels with held-out expert labels. Inspect false passes, false failures, and the traces behind disagreements.

An uncalibrated judge cannot be the sole release gate.

03Regression, latency, and cost

Compare baseline and candidate on the same cases; report repeated-run variability, p95 latency, and attributed cost per successful task.

Review regressions against agreed quality and operating budgets.

The handover

Engineering you
can build on.

A defined implementation, reviewable evidence, and an operating model your team can own.

How we work

Versioned evaluation suite

Failure taxonomy, representative fixtures, reference labels, dataset splits, and reproducible run configuration.

Calibrated grading and release gates

Code assertions, judge rubrics, expert calibration examples, trace comparisons, and CI checks.

Production feedback workflow

Sampling rules, review ownership, trace retention settings, and a path from confirmed failure to regression test.

Architecture decisions

Questions that
shape the build.

What does an evaluation actually measure?

It depends on the task. A retrieval system can be checked for whether it finds the required evidence; an agent for correct tool selection and task completion. We combine deterministic checks, human review, and calibrated model-based grading where useful, with latency and cost measured alongside quality.

Can you improve a system another team built?

Yes. We review the available code, datasets, traces, and deployment history, then establish a baseline. The assessment identifies changes your team can prioritize, and we can implement the agreed fixes within the existing architecture.

Let’s scope your next build.

Bring a workflow, a product brief, or an AI system that needs to ship.

Discuss your project