One link per file, in request order; every row is committed as pending before this answers.

Non-uuid id (title invalid_id, source.parameter id), or an undecodable body (title invalid_json) — which includes a caseEntityId that is not a uuid.

Missing CI-Subject-URN or CI-Request-Id, absent CI-Role header, or a subject URN not provisioned as a KYC user (title unauthenticated, source.header names the offending header).

The caller's roles do not satisfy this operation's role gate (title forbidden), or the caller is a tenant user whose tenant is not provisioned in KYC.NEXT (title tenant_not_provisioned, on any operation).

The resource does not exist — or belongs to another tenant, which is indistinguishable (title not_found).

The case is closed — lifecycle past active, or workflow done or cancelled — so its facts are frozen (title case_closed). Nothing is written and nothing is audited; a change goes through a new case (ADR-0023 R2). Step pages of a closed case carry an empty stepActions, so a client that renders from the plane never sends this.

One entry per violation (title validation_failed, source.pointer names the member): an empty data, a wrong type or a client-supplied id on an element, a blank, NUL-bearing or unsupported fileName, a contentType that is not the extension's, a sizeBytes outside 1 to the maximum, a blank displayName, or a caseEntityId that is not an entity of this case. Nothing is written and no session is opened. One known limit: a member of the wrong JSON type (a quoted number, a data that is not an array) is reported alone, with the pointer naming the member but not the element index, because the decoder keeps only the first type error; the remaining violations surface on the retry.

Unexpected server error (title internal_error).