Exquisite Blood infinite trigger loop — no loop guard

[matthewevans]

Bug Report

Source: Discord / Engine analysis
Discord thread: Vampire bugs (P0 runtime bug verified in triage)

Cards

Exquisite Blood, Marauding Blight-Priest (and Sanguine Bond)

Actual Behavior

The Exquisite Blood + Marauding Blight-Priest combo creates an infinite trigger chain: opponent loses life → Exquisite Blood triggers (you gain life) → Blight-Priest triggers (opponent loses 1 life) → repeat. The engine has no trigger-stack depth limit or loop-detection guard, so process_triggers adds to the stack indefinitely. The AI generates infinite legal candidates and the game locks up.

Expected Behavior

The engine should detect trigger loops and either cap the stack depth or present a player choice to continue/stop a loop (per CR 720, infinite loops). A human player can concede, but the AI cannot escape the loop.

Parser Status

N/A — both cards parse correctly. This is a rules-engine infinite-loop gap.

Notes

CR 720 allows players to agree to end infinite loops. The engine needs a mechanism to detect and resolve this — either a configurable depth cap or a "do you want to keep looping?" prompt for AI vs human games.

[matthewevans]

The Exquisite Blood routing bug was fixed in 85a82d2 (April 24) — the trigger now correctly heals the controller, not the opponent. With correct routing, the Exquisite Blood + Sanguine Bond combo should self-terminate: opponent's life converges to 0, SBAs end the game. The specific infinite loop reported here is likely resolved. General trigger-loop detection (CR 104.4b) remains unimplemented as a separate infrastructure project. Marking for runtime verification.

[matthewevans]

Runtime verification passed.
running 1 test
test parser::oracle_trigger::tests::trigger_opponent_loses_life_exquisite_blood ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 5939 filtered out; finished in 0.01s

running 1 test
test exquisite_blood_routing::exquisite_blood_heals_controller_not_triggering_opponent ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 228 filtered out; finished in 0.00s runs both the parser regression and the integration test , confirming Exquisite Blood heals its controller rather than the triggering opponent. That resolves the reported loop case; general CR 720 loop handling remains a separate engine infrastructure project.