CML
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    Variable CMCD_REQUEST_PROVENANCEConst

    CMCD_REQUEST_PROVENANCE: unique symbol = ...

    The customData key under which CmcdReporter.createRequestReport() stamps session provenance on every request it returns.

    The value is a frozen CmcdRequestProvenance record: sid names the session that issued the request, cid is the content id in effect when the request was issued, and data carries the request's per-call data as an encoded CMCD string. CmcdReporter.recordResponseReceived() reads the record to attribute a late response to its session and to rebuild the request-time report keys. Spread and Object.assign carry the record through ordinary request clones, but JSON.stringify and structured clone drop symbol-keyed properties: read the value before such a boundary and restore it afterward. The record itself survives JSON, and attribution is by the sid value rather than object identity, so a revived plain-object copy attributes exactly. A record naming a sid the reporter does not retain drops the response rather than relabeling it.

    Backed by the symbol registry so duplicated copies of this library in one bundle interoperate. The registry key is stable across versions.