Set a Drift Budget to Cap Acceptable Upgrade Drift

A drift budget converts your DriftScore into an enforceable rule: stay within the budget and the scan passes; exceed it and the scan fails. This is the building block for fitness functions and CI gates. This tutorial sets a budget locally before you take it to CI.

Prerequisites

• Vibgrate CLI installed (npm i -g @vibgrate/cli)
• Basic familiarity with the DriftScore (0-100)

Steps

1. Establish your current DriftScore

Run a bare scan to see where you stand today:

vg

Note the DriftScore so you can pick a realistic budget.

2. Choose a budget value

Pick a number your project can actually meet today, then plan to tighten it later. A budget should be achievable now so the gate is meaningful rather than perpetually red.

3. Run a scan with a drift budget

Apply the budget on a scan:

vg scan --drift-budget 60

The scan compares your drift against the budget and reports whether you are within it.

4. Interpret pass or fail

If drift is within budget the scan succeeds. If it exceeds the budget the scan fails with a non-zero exit code, which is exactly what makes it usable as a gate in scripts and pipelines.

5. Verify the gate

Deliberately set a strict budget to confirm the failure path, then relax it to confirm the pass path.

Verification

Run vg scan --drift-budget 60 and check the exit code. A passing scan exits zero; a budget breach exits non-zero. That exit code is what CI keys off of.

Next Steps

• Ratchet the budget down release by release to drive drift toward zero.
• Fail CI when new drift appears on top of a baseline.