Guide of Souls bug — Guide of Souls put counters on a creature without spending any energy

[matthewevans]

Reported in Discord: https://discord.com/channels/1485498006781427802/1504860099972436118/1504860099972436118

Thread: Guide of Souls bug
Cards: guide of souls
Parser status: fully_parsed
Extraction confidence: 0.90

Summary

Guide of Souls put counters on a creature without spending any energy

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_{report_id: discord:1504860099972436118:1504860099972436118:0 · discord: 1504860099972436118/1504860099972436118}

[matthewevans]

Dev acknowledgement captured from Discord thread: syrius replied "seen this one come up fairly often. will target. ty" (2026-05-15T14:58:53).

[matthewevans]

Triage investigation

Dev acknowledged in Discord (syrius: "seen this one come up fairly often. will target. ty").

Hypothesis: the reflexive trigger structure for "... may pay {E}{E}{E}. When you do, put two +1/+1 counters ..." isn't gating the reflexive trigger on payment success. Card data export shows two top-level triggers but the inner PayCost sub-ability + reflexive trigger relationship needs verification — the "When you do" payload may resolve unconditionally instead of being conditioned on the optional PayCost succeeding.

Starting points: crates/engine/src/parser/oracle_trigger.rs for the "When you do" parse path; crates/engine/src/game/effects/pay.rs for whether PayCost emits an event the reflexive trigger listens for, or whether the chain runs the sub-ability inline regardless.

Class scope: every "you may pay X. When you do, Y" card is affected (Smuggler's Copter–era energy designs, plus a host of newer enchantments). Fix as a building block.

[matthewevans]

Fixed in commit 193bbc8b9.

Root cause: evaluate_condition returned true unconditionally for AbilityCondition::WhenYouDo, so Guide of Souls' reflexive "When you do" sub-ability ran even when its embedded {E}{E}{E} energy cost was unpayable or declined. Per CR 603.12 a reflexive trigger fires based on whether the trigger event actually occurred — an unpayable cost is not an occurrence, so the old => true was rules-wrong (and the "always fires" comment was factually incorrect).

Fix: the WhenYouDo arm now evaluates false only when the parent effect is a cost-payment effect AND cost_payment_failed_flag is set. For every non-cost parent (BecomeCopy reflexives, copy/exile replacements) it stays unconditionally true — preserving that documented contract. Gating on the parent effect type rather than a bare flag read is what prevents suppressing those non-cost reflexives when the flag is left stale by an earlier effect.

Coverage: positive tests (reflexive runs when the cost is paid, skipped when unpayable) + a negative-control test proving a BecomeCopy-parented WhenYouDo still fires under a stale cost_payment_failed_flag. Isolated /review-impl: clean.