StarCraft II Quarkus Agent — Drools Strategy Arrives
Date: 2026-04-07 Type: phase-update
What I was trying to achieve: the first real R&D integration
The whole point of this project is to use StarCraft II as a testbed for Drools, Quarkus Flow, and CaseHub. Every plugin so far has been hand-coded Java — good discipline, but not the experiment. Drools StrategyTask was the first real target: replace BasicStrategyTask with DRL rules.
What I believed going in: two hours of wiring, then the interesting part
The library research had this pinned. org.drools:drools-quarkus, BOM at 10.1.0, Rule Units for native-compatible AOT compilation. I expected the rules themselves to be where the work was.
That was not accurate.
Four things that bit us before the rules ran
I brought Claude in for the implementation. We added drools-quarkus, drools-bom, and drools-ruleunits-api to the pom.xml, wrote StrategyRuleUnit implements RuleUnitData, the DRL file, and DroolsStrategyTask. Compiled clean.
First Quarkus build error: [ERR 101] Line 21:18 no viable alternative at input ']'. The pattern $b: /builders[] — empty brackets — isn’t valid OOPath. You write /builders with no brackets at all for a no-constraint match. Empty brackets are a parse error.
That fixed, the next: type is a reserved keyword in DRL. Writing buildings[ type == BuildingType.GATEWAY ] fails because the parser sees a keyword, not a property accessor. Same for isComplete — Drools applies JavaBean convention, mapping isComplete() to property complete, not isComplete. The fix for both: this.method() explicitly. buildings[ this.type() == BuildingType.GATEWAY, this.isComplete() == true ].
Two down, two to go.
The CaseHub gap: nobody home all along
Running the Quarkus build with DEBUG logging revealed something that had been wrong since the first plugin was written:
Removed unused CLASS bean [..., qualifiers=[@Any, @CaseType("starcraft-game")], target=org.acme.starcraft.plugin.BasicStrategyTask]
Removed unused CLASS bean [..., qualifiers=[@Any, @CaseType("starcraft-game")], target=org.acme.starcraft.plugin.BasicEconomicsTask]
All four @CaseType plugin beans were being removed by Quarkus Arc’s dead-bean elimination. Nothing in the application was injecting them through CDI. TaskDefinitionRegistry was always empty. Every game tick called into CaseHub, CaseHub found no tasks, and returned immediately. The plugins had never actually run.
The fix: StarCraftTaskRegistrar is a startup bean that explicitly injects all four plugin seam interfaces. The injection keeps Arc from discarding the beans; the registrar then registers each with TaskDefinitionRegistry. CaseHub now runs the plugins.
The classloader wall
Moving to the test phase, plain JUnit hit this immediately:
NullPointerException: Cannot invoke "DataSource$Factory.createStore()"
because "DataSource$FactoryHolder.get()" is null
DataSource.createStore() is initialized by the Quarkus extension at build time. Without Quarkus context, the factory is null. Drools Rule Unit tests require @QuarkusTest.
Adding @QuarkusTest, Claude came back with ExceptionInInitializerError during startup, caused by ClassNotFoundException: org.acme.starcraft.agent.ResourceBudget. The generated StrategyRuleUnitRuleUnit_Bean static initializer calls drools-ruleunits-impl’s SimpleRuleUnitVariable, which scans every field type of StrategyRuleUnit and calls Class.forName() on each. The plain fields ResourceBudget budget and IntentQueue intentQueue — application classes — weren’t visible through the Drools classloader at that point.
The solution: DataStore<T> fields erase to DataStore at runtime — only the raw type gets loaded. DataStore<ResourceBudget> is safe; ResourceBudget budget is not. We redesigned StrategyRuleUnit to hold only JDK and Drools-known types as plain fields. Rules write string decisions to a List<String> — "GATEWAY", "CYBERNETICS_CORE", "STALKER:gw-0" — and DroolsStrategyTask.execute() reads them after fire() and handles budget and intent dispatch in Java.
The rules look like this:
rule "Build Gateway"
salience 100
when
/builders
not /buildings[ this.type() == BuildingType.GATEWAY ]
/buildings[ this.type() == BuildingType.PYLON, this.isComplete() == true ]
then
buildDecisions.add("GATEWAY");
end
Declarative conditions. Budget and intents stay in Java. The separation is clean and testable.
107 tests
The session started at 94 tests. It ended at 107, all passing. The 13 new tests are in DroolsStrategyTaskTest — @QuarkusTest, injecting the active StrategyTask bean, calling execute(CaseFile) directly with crafted CaseFiles. BasicStrategyTask stays as a plain class for direct-instantiation testing, making the Drools tests the integration layer and the Basic tests the logic layer.
Two garden entries came out of the session: GE-0053 for the DataSource.createStore() plain-JUnit trap, and GE-0056 for the DRL OOPath gotchas — empty brackets, the type keyword clash, and the isComplete property naming convention. Three problems, one fix: this.method() throughout.
Quarkus Flow EconomicsTask is next.