Shared language for asking engineers and data teams to transfer a prototype's data behavior. These terms distinguish the requested handoff from a query, a specification, or a conversation summary; they do not assert that any particular interface is already implemented.

Source-to-target mapping: The correspondence from material input fields to output fields, including renames, derivations, aggregations, and dropped fields. It explains how data changes, not merely where it was fetched. Avoid: Data map (without specifying the boundary and outputs)

Input/output interface contract: The agreed expectations for data sent across a named producer-to-consumer boundary and data returned or emitted, including relevant field meanings and constraints. Examples illustrate the contract but do not establish every constraint. Avoid: Schema (when the request also needs behavior and meaning)

Data processing rules: The relevant instructions for validating, transforming, filtering, and handling missing data and failures at a named boundary. State viewer-specific access enforcement separately from fields merely hidden in a UI. Avoid: Data handling (without naming the rules or boundary)

Evidence-backed reproduction handoff: A source-to-target mapping and interface contract together with processing rules, tested model and harness provenance, scripts, benchmark cases, and traceable evidence for rebuilding and evaluating a prototype in another harness. It is a starting point for reproduction, not proof that a different model will match. Avoid: Handoff (without saying whether it is for an engineer or for resuming a session)

Viewer slice: One selected viewer and output boundary documented and evaluated independently, with its visibility and access assumptions stated explicitly. It is not necessarily one implementation ticket. Avoid: Ticket slice (when referring to a viewer/data boundary)

Field-level lineage: The evidence trail from an output field back to the inputs and transformations that produced it. It supports a mapping but does not replace the interface contract or processing rules. Avoid: Data map (when only traceability is meant)

Source query: A query that retrieves or computes source data for part of a workflow. Include it as supporting evidence where relevant; it is not, by itself, the source-to-target mapping, output contract, or processing rules. Avoid: Data map (when only a query is being delivered)

Session handoff: A summary of current conversation or agent work so another agent can continue. It may point to a reproduction handoff but is not the durable engineering contract. Avoid: Reproduction handoff (when only transferring conversation context)

Ask for: “A source-to-target mapping, input/output interface contract, and data processing rules for [named boundary or viewer slice], with evidence for observed behavior—not just the source query.” For a benchmarked prototype, request an evidence-backed reproduction handoff as well. Mark consequential unverified details Assumed—confirm or Unknown rather than treating them as agreed behavior.