explain()

gates.explain("checkout-v2");
// {
//   flagKey: "checkout-v2",
//   value: true,
//   reason: "rollout_match",
//   ruleId: "rule_…",
//   bucket: 1873,
//   revision: 42,
//   source: "cache",
//   context: { platform: "ios", appVersion: "2.4.1", …, installationId: "inst_…", user: { id: "u_1" } },
//   audiences: { "pro-ios": [ … ] }
// }

explain() is synchronous and local, like flag(). It does not record exposure.

Fields

Field	Meaning
`value`	What `flag()` returns (without a fallback).
`reason`	One of the reasons below.
`ruleId`	The rule that decided, for `rule_match`, `rollout_match` and `rollout_miss`.
`bucket`	This identity’s bucket, 0…9999, for `rollout_match` and `rollout_miss`.
`revision`	The snapshot revision the decision used.
`source`	`"none"`, `"cache"` or `"remote"`.
`context`	The runtime context the rules were matched against, or `null` before the local read finished.
`audiences`	The audiences the decision could reference, from the same snapshot.

Reasons

Evaluation runs in this order and stops at the first answer:

Reason	When
`flag_missing`	The snapshot has no such flag, or the client has not finished its local read (`context` is `null`). Value `false`.
`disabled`	The flag is disabled. Value `false`, whatever the rules say.
`rule_match`	The first rule whose conditions all match has no percentage (or 100%). Value is the rule’s value.
`rollout_match`	That rule has a percentage and this identity’s bucket is below it. Value is the rule’s value.
`rollout_miss`	That rule has a percentage and the bucket is not below it. Value is the flag’s default.
`default`	No rule matched. Value is the flag’s default.

A rollout miss does not fall through to the next rule: “you are not in the 25%” is an answer, not an absence of one.