Release: backport publisher_domain withdrawal before 3.1.4

[bokelley]

Required 3.1.x repair

The immutable v3.1.3 artifacts contain the publisher_domain source change that was withdrawn on main by PR #5887 / commit 81cf467. The origin/3.1.x branch still lacks that withdrawal.

Before publishing any 3.1.4 release:

1. Create a branch from origin/3.1.x in a workspace whose target branch is 3.1.x.
2. Backport the withdrawal semantically (do not mutate the existing v3.1.3 artifact).
3. Rebuild latest/source release surfaces according to the 3.1 patch workflow.
4. Run schema, immutable-artifact, current storyboard, and 3.0 compatibility checks.
5. Open the PR against 3.1.x and publish 3.1.4 only after it merges.

This main-targeted workspace intentionally does not create cross-lineage PRs.

[bokelley]

Triage

Classification: Bug (release-line inconsistency — 3.1.x branch retains the publisher_domain source change that was declared withdrawn on main)
Bucket(s): spec / protocol (patch release management)
Status: ready-to-implement
Milestone: 3.1.0 (issue already set; implied target release: 3.1.4)

What the experts said:

• ad-tech-protocol-expert (synthesized): Backporting the withdrawal from PR revert(protocol): withdraw invalid publisher domain patch #5887 (81cf467) to 3.1.x is non-breaking for conformant consumers — 3.1.3 was declared withdrawn, so no conformant implementation should have adopted its publisher_domain filter. Publishing 3.1.4 from current 3.1.x HEAD would re-introduce a minor feature on a stable patch line, which violates the patch contract.
• adtech-product-expert (synthesized): The sequencing constraint is sound — 3.1.4 must not ship until the withdrawal merges on 3.1.x. Adopters pinned to the stable 3.1.x line expect no new fields in a GA patch; the current state leaves 3.1.x source inconsistent with what 3.1.3 was declared to mean.

My take: Clean prior-art diff in PR #5887; the withdrawal is mechanical. This main-targeted workspace can't open cross-lineage PRs, so this is a brief rather than a draft PR.

Implementation scope:

• Branch from origin/3.1.x (not main) — see .agents/shortcuts/cut-patch.md for the patch workflow
• Cherry-pick the withdrawal from PR revert(protocol): withdraw invalid publisher domain patch #5887 (81cf4675648e54a3a3aeca7f39318ad6def3ebe0) into the 3.1.x-targeted branch, excluding main-specific Version Packages state; retain only the publisher_domain schema removal, training-agent removal, and 3.1.3 withdrawn documentation
• Add a patch changeset for adcontextprotocol describing the withdrawal; do not mutate any existing dist/ artifact under 3.1.3/
• Run: schema validation, immutable-artifact check, current storyboard checks, and 3.0 compatibility checks
• Open the PR against 3.1.x; publish 3.1.4 only after it merges

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Triaged by Claude Code. Session: https://claude.ai/code/session_01BJNrozk8jfacbG6BQTbjQw

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