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Your log store holds the bytes your evidence commits to. Sanning never reads it, so its settings are yours to get right, and the SDK is built to tell you when they are not. This page covers the bucket. For what the store contains and how a reader resolves it, see Retain what you anchored.

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What the SDK does on first use

Before it writes a byte, the store checks the bucket once. There are two acceptable outcomes and a third the check exists to prevent.
unknown is not off. A credential missing s3:GetObjectLockConfiguration, or a 403 on HeadBucket, means the SDK cannot see the protection rather than that there is none. A guard that stands down where it cannot look guards nothing. Object Lock enabled is not the same as protected. With no default retention rule, objects in a lock-enabled bucket carry no retention and delete like any other, so that state is reported as unprotected, because it is. Setting days: 0 is a legitimate choice for a customer applying per-object retention themselves, and the readiness check says what it sees.
warn is the default and it is not a silent third outcome: the write goes ahead and is announced with the property named. refuse is the posture for a customer who would rather hold no evidence than hold evidence they cannot defend.

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The three credentials

Three roles, three policies. Replace BUCKET throughout.

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Provisioner, one time, not the agent

Creates the bucket with its protection. A human or a CI job runs this once and the agent never holds it. s3:CreateBucket is the permission that makes an unprotected-bucket mistake permanent, so it does not belong in a long-lived agent credential.
Set createBucket: false when a platform team or Terraform provisions the bucket instead. The protection check still runs: turning off creation does not turn off the reporting.

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Writer, the agent

Adds objects. It cannot read them back, cannot list them, cannot delete anything, and cannot create or reconfigure a bucket.
The second statement is wider than “adds objects and nothing else”, on purpose. A credential that literally adds objects and nothing else cannot run the readiness check at all: HeadBucket needs s3:ListBucket, and the two protection reads need their own actions. Under it the SDK reports unknown on every run, which is honest and useless, and under refuse it would never write.The three added actions are bucket-configuration reads. They disclose no object, no key and no byte; they answer only whether this bucket is versioned and locked. Granting them is what makes the guarantee checkable by the party who depends on it.To hold the literal minimum instead, set createBucket: false and storeProtection: "warn", verify the bucket once with the provisioner credential, and accept that the SDK will say it cannot see the protection. That is the true statement, and the reason unknown is a state at all.

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Reader, the pack-runner

Reads objects and nothing else. No write, no delete, no configuration. This is the credential that syncs the bucket down before you build a pack.
Note what no credential has: s3:DeleteObject. Nothing in this system deletes evidence, so nothing that touches the bucket is granted the ability to. Object Lock is the backstop for a credential that gets one anyway.

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Backends

Do not take this table as settled for your deployment. The SDK detects and reports, which is the only claim that survives a backend changing under you. Verify against a real bucket before you rely on it.

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Check without gating

checkProtection() in TypeScript, check_protection() in Python, returns the verdict and writes nothing. It names no bucket and no key, so it is safe to surface somewhere that must stay content-blind: a health endpoint, a readiness probe, a dashboard tile.