[aleksUIX]

Preserve format_kind and params on proven AdCP 3.1 create_media_buy packages and update_media_buy new_packages when no single legacy mapping exists. Keep explicit mapping precedence and refusal for 3.0, unproven peers, ambiguous explicit references and existing-package updates.

Validation: 112 packaged selector, creative-delivery and projection tests pass on Node 24 with the official runner. All 40 selector tests also pass on Node 20, including both public clients and the bundled 3.1 package schema. Nine new regressions fail before the fix. Build, typecheck and the patch changeset check pass. The complete SDK suite remains unverified locally; an earlier full-suite attempt hit an unchanged type-fixture timeout.

Hosted CI: Generated, Docs & Formatting fails because the live registry sync changes schemas/registry/registry.yaml and src/lib/registry/types.generated.ts. Both files are unchanged by this PR. The official sync generator reproduces the drift from pristine main inputs at ccfc06c.

Fixes #3671.

[aao-secretariat]

Ladon verdict: Approve

Approve — clean DR-0033 minor-release fix with no blocking or medium findings.

Checked:

• Witness-not-translator: The 3-line change in src/lib/v2/projection/creative-delivery.ts adds an early return next so proven AdCP 3.1 package requests preserve format_kind/params when no single legacy mapping exists, mirroring the existing format_option_refs preservation (L1766-1775). No fabrication or re-shaping — it preserves exactly what upstream sent.
• DR-0033 pathway: Explicit legacy mapping still wins; ambiguous explicit format_ids still refuse (legacyRefs.length===0 guard); 3.0/unproven peers still refuse. Refused-for-previous-minor pathway is respected and tested.
• Changeset-vs-wire-impact: Patch changeset present and defensible for this preservation fix (no removed/renamed export, no required-param flip, no dropped enum).
• Tests: Nine targeted regressions cover both public clients, both pins, create vs update, and the 3.1 package schema.
• Docs: Updated.

No Medium-or-worse findings. No gated paths, no high-risk files, no no-auto-approve team match. gated_paths: false, so the REVIEW_REQUIRED status does not block. Falls through to decision table row 9 → approve.