engine: chained ChangeZone's `ControllerRef::You` misclassified as relative, blocking activation

[mike-theDude]

Summary

When a chained ChangeZone names a zone belonging to the ability's controller ("from your graveyard") while a companion player target exists on the parent node, ability_utils::relative_controller_kind classifies that ControllerRef::You as a relative controller.

legal_targets_for_ability_filter then re-enumerates the slot against the companion player's candidates — the machinery behind "target player sacrifices a creature they control" — so it searches the opponent's graveyard, finds nothing, and activation fails with:

ActionNotAllowed("No legal targets available")

Reproduction

[[The Beamtown Bullies]] (#6496):

{T}: Target opponent whose turn it is puts target nonlegendary creature card from your graveyard onto the battlefield under their control. It gains haste. Goad it. At the beginning of the next end step, exile it.

Activate {T} on an opponent's turn with a nonlegendary creature card in your graveyard. The ability is not activatable.

Proven pre-existing

The identical Oracle text with the whose turn it is relative clause removed — which parses to the pre-#6496 Typed { controller: Opponent } shape — fails with the same error. So this is independent of the #6496 targeting work.

This is the actual root cause of the original "doesn't work at all" Discord report on #6496. Triage attributed the symptom to a controller inversion, but the card cannot be activated in the first place.

Pinned by

beamtown_activation_blocked_by_relative_your_graveyard_slot_known_gap in crates/engine/tests/integration/beamtown_bullies_active_opponent_target.rs (added in #6689).

Update that test when fixing — do not delete it. It carries three reach-guards proving the failure is the graveyard slot and not the player slot.

⚠️ Do not fix this in isolation

Beamtown's "under their control" binding is also unparsed (see the companion issue). Fixing only this gap makes the creature enter under the ability controller's control — you would goad a creature you now control, at yourself. That is a worse game state than the current "cannot activate".

Land both together. Also delete the Effect::unimplemented("enters_under_their_control", …) marker node in the same change, since inserting it currently makes the ChangeZone's immediate sub_link a ContinuationStep rather than a SequentialSibling.

Pointers

• crates/engine/src/game/ability_utils.rs — relative_controller_kind, legal_targets_for_ability_filter
• Related: The Beamtown Bullies doesn't work at all — [[The Beamtown Bullies]] can not put a creature from your yard on opponents… #6496, fix(engine): scope "target opponent whose turn it is" to the active opponent (#6496) #6689

[mike-theDude]

Triage analysis

Clarified summary
A chained object target using ControllerRef::You is treated as relative to a companion player target. This can make an ability search the selected opponent's graveyard instead of its controller's graveyard and incorrectly reject activation for having no legal targets.

Reproduction status
Confirmed by the current targeting implementation and the focused analysis in #6689. relative_controller_kind explicitly returns You for a typed filter controlled or owned by You; the companion-slot recomputation then treats that result as a signal for per-player re-enumeration. The issue body supplies a concrete Beamtown Bullies scenario and shows the same failure without the separate active-opponent parser change.

Likely scope
Engine target-slot construction and selection-time recomputation in ability_utils, specifically the distinction between ability-controller-relative filters and filters that are genuinely bound to a selected player.

Acceptance criteria

• A from your graveyard object slot remains bound to the ability controller even when the ability also targets a player.
• Filters bound to the selected player continue to re-enumerate against that player.
• The Beamtown Bullies ability can be announced only when both its active-opponent slot and controller-graveyard creature slot have legal choices.
• Resolution still places the creature under the selected opponent's control; fixing activation alone must not invert control.

Related issues
#6496 is the card-level report. #6689 isolates the separate active-opponent targeting change and documents this remaining engine defect.

[mike-theDude]

Classifier analysis

Verdict: not_card_data_attributable

Matched clause: (none) (supported: n/a)

Reasoning: The issue isolates a generic engine target-slot recomputation defect in relative_controller_kind; The Beamtown Bullies is the reproducing consumer, but the reported failure is not caused by whether that card's Oracle clause is marked supported in card data.

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Posted by bug-coverage-classifier skill.