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The tmax guard checks how much time remains in the OpenRTB tmax window before running any other gate. If the remaining budget falls below a configurable threshold, it returns skipped: true and — because the engine runs fail-fast — all subsequent gates are bypassed. This keeps your gate pipeline from doing meaningful work on a bid that has already missed its serve deadline.

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Usage

Place tmaxGuard first in every RTB gate list. It is the only gate designed to short-circuit the entire pipeline on deadline exhaustion.

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Options

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number
default:"15"
The minimum number of milliseconds that must remain in the tmax window for downstream gates to run. If the remaining budget is less than this value, the gate returns skipped: true. Defaults to 15.
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string
default:"rtb.tmax-guard"
Override the gate’s name in evaluation results and telemetry.

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Required context fields

The gate reads two fields from EvaluationContext. If either is absent, the gate passes through silently — it cannot enforce a deadline it cannot measure.
The gate computes elapsed time as Date.now() - startedAt at the moment it runs, then checks whether tmaxMs - elapsed < bufferMs.

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What “skipped” means

A skipped result is not a failure. The gate result looks like this:
Skipped gates do not penalise the agent’s reputation score. They signal that evaluation was intentionally bypassed, not that a problem was found.
Set bufferMs to match your engine’s timeout option. If your gate pipeline has a 15ms budget, a bufferMs of 15 ensures you never start evaluating a bid that cannot complete before the auction closes.

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When context fields are missing

If tmaxMs or startedAt is not a number on the context, the gate returns:
No error is thrown. The remaining gates run normally.
If you omit startedAt from the context, the tmax guard cannot protect you from deadline overruns. Always record Date.now() at the point the upstream bid request is received and pass it as startedAt.