Agentic Development

Move your agent to a better stack, and know it still behaves.

Models, harnesses, and clouds keep improving, and the best stack for your agent today won’t be the best next quarter. VAIL probes your agent through its own endpoint, so you can compare its behavior on the current stack and a new one before you switch, and keep watching after.

Scan your agent What changes when you switch

Every layer under your agent will change

Staying portable is how you take advantage of better models, better tools, and better prices without being locked to one vendor. But each switch can change how the agent follows its instructions, and nothing errors when it does.

CURRENT STACK Agent endpoint same API Model in use Harness in use Cloud in use CANDIDATE STACK Agent endpoint same API Model newer release Harness better tools Cloud lower latency VAIL Agent Assurance same probes both stacks Compare rules that now break
The probes reach the agent through its endpoint, so the model, harness, and cloud behind it can all change. The same probes on both stacks show which rules now break.

  • The model

    A newer model reasons better but may follow your rules differently: a dropped step, a different tool choice, a shortcut it didn’t take before.

  • The harness

    A harness with better tools changes how tools are described, called, and retried, and the agent’s tool use changes with it.

  • The cloud or provider

    Moving for uptime, cost, or latency can change behavior even with the same model. Stability Arena measures these differences across inference providers.

How VAIL checks a switch

01Baseline
VAIL scans the agent’s definition, turns each rule into probes, and records how the agent behaves on its current stack.
02Compare
Point the same probes at the agent on the candidate stack. Any endpoint that takes a message and returns the agent’s reply works, whatever model, harness, or cloud is behind it.
03Review
Findings show which rules the agent now breaks or keeps only intermittently, each with its failure rate and latest failing example.
04Monitor
Keep the probes scheduled after the switch. A finding that fails again is marked regressed.

Across the agent’s life

  • Pre-deployment scan

    Find how an agent could go rogue before it ships.

    Agent Assurance

  • Continuous behavioral monitoring

    Probe live agents on a schedule to confirm they behave as intended and stay within policy.

    Agent Assurance

  • Stack independence

    Know your agent will hold up on a new model, harness, or cloud before you switch.

    Agent Assurance

Built for

Teams
Agent engineers, forward-deployed engineering teams, systems integrators, and platform product owners.
Requirements
An API endpoint for each stack you want to compare, and a written definition: instructions, system prompts, and tool schemas.
Deployment
No SDK, no trace access, and no customer data read. Managed, in your cloud, or air-gapped.

Research

All publications

Go further

Agent Assurance Find how agents can go rogue.

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