[antonsoo]

Removing a tag relation deletes the shared query indexes even when a component relation with the same origin, key and target still exists. Removing the component while keeping the tag has the same problem. Saving and loading rebuilds those indexes, so it unexpectedly changes query results.

import pickle
from tcod.ecs import Registry

world = Registry()
actor, faction = world["actor"], world["faction"]
actor.relation_tags_many[int].add(faction)
actor.relation_components[int][faction] = 42
query = world.Q.all_of(relations=[(int, faction)])
before = actor in query
actor.relation_tags_many[int].remove(faction)
after = actor in query
restored = pickle.loads(pickle.dumps(world))
after_load = restored["actor"] in restored.Q.all_of(
    relations=[(int, restored["faction"])])
print(before, after, after_load)
print(actor.relation_components[int][faction])

Before: True False True, with component value 42 still present. After: True True True, with the same component value.

Retain the index entry while either backing relation still owns it. Once the final relation is removed, normal index cleanup and cache invalidation continue. The guard checks membership, so a zero-valued component also keeps its relationship.

Regression coverage checks both removal orders, named and type keys, all four relation query forms and final cleanup. Faction-transition workflows with inherited actors and save/load checkpoints match separate dictionary state after the fix. The full suite, strict mypy and project hooks pass; the existing two XPASS cases and pytest parameter-iterator warning remain unchanged. No query syntax, save format or performance claim changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.17%. Comparing base (e5f0292) to head (08d20ca).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #61   +/-   ##
=======================================
  Coverage   99.16%   99.17%           
=======================================
  Files           9        9           
  Lines         959      965    +6     
=======================================
+ Hits          951      957    +6     
  Misses          8        8           

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