Replace an AI model and test it on the same workflow

When replacing a model, examine the entire affected application flow. A new model identifier in the configuration is insufficient evidence on its own. Use an existing evaluation set and record the change you are actually comparing.

Record both configurations clearly

Document each variant’s model identifier, prompt version, supplied sources, tools and settings. If inputs, rules and processing stay the same, you can investigate the model change more directly. If the prompt, adapter or evaluation must also change, you are comparing two application configurations; do not attribute the difference solely to the model.

Microsoft describes comparing saved variants on the same cases and examining individual failures. The expected task decisions for your flow must be established before the comparison.

Make differences visible for each case

The following example is entirely fictional. An application should extract a project identifier from a message or request manual review. It does not grant project access. The field names are our own internal schema, not a provider API.

The table contains assumed outputs for illustration. It is not an executed model test. Case descriptions do not replace the versioned original inputs of a real comparison.

In the second case, the new variant picks a project despite the ambiguity. In the third, it violates the field contract. An aggregate assessment could conceal these different causes of error. Formally valid outputs must also be correct for the task.

Handle errors before further processing

OWASP recommends validating model outputs before passing them to downstream components. In the example, a missing required field must not proceed as a successful extraction. The application must reject the output or send it through the intended review path. A project field being present still does not authorise access.

Alongside task and format cases, check the languages actually needed, outages and retries. A single run does not establish a stable error frequency. If known errors are used to adjust the new variant, additional held-out cases are needed for an independent check.

Plan release and rollback together

Before release, define which errors prevent the switch and who assesses unresolved differences. In the table’s example, the premature project assignment from an ambiguous message and the missing required field must first be addressed.

Retain the previous application configuration and a verified rollback path. Clarify whether the previous model remains available and stored data stays compatible. After the switch, observe actual results from the affected flow; three illustrative cases do not establish general production readiness.

Sources

• Microsoft — Evaluate models, prompts, and agents

• OWASP 2025 — Improper Output Handling