The RNRX coma: tacks are scattered, not thrown

Automaton II froze for three turns of game four: pathDenial proposed
HANDFUL OF TACKS on a square four steps away, the engine refused the
cast every turn ("you must be adjacent to scatter tacks"), and the
refusal-fallback loop read as a coma. The denial planner now offers
tacks only at the caster's feet — and the walker learns tacks are a
floor hazard, so a bot no longer mines its own doorstep and strolls
straight into it (also RNRX, seq 194-195). The frozen ledger moment
replays cured; a regression pins the planner's proposals to
engine-accepted commands. 288 tests; 24 ledgers verified.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015RCWSTnb1KYTPyL4GmhGnF

packages/engine/src/automaton.ts

@@ -370,7 +370,12 @@ function pathDenial(view: GameView): Command | null {
         );
       }
       // Never brick the square the treasure needs to stay reachable on.
-      if (filler && cellKey(b) !== cellKey(goal) && cellCastable(cellKey(b))) {
+      // TACKS are scattered at the caster's feet ("you must be adjacent"),
+      // not thrown — offering a distant square wedges the whole brain on
+      // an eternally refused cast.
+      const fillerReaches = !filler || filler.cardId !== "handful-of-tacks" ||
+        Math.abs(b.x - me(view).position.x) + Math.abs(b.y - me(view).position.y) <= 1;
+      if (filler && fillerReaches && cellKey(b) !== cellKey(goal) && cellCastable(cellKey(b))) {
         consider(
           { type: "cast", instanceId: filler.instanceId, target: { kind: "cell", cell: b } },
           { avoidCell: cellKey(b) },
@@ -609,7 +614,7 @@ function pathToward(
         const hazard = view.squareContents[k]?.kind;
         if (!opts.throughHazards &&
             (hazard === "pit" || hazard === "ooze" || hazard === "thornbush" ||
-             hazard === "rosebush" || hazard === "slime")) continue;
+             hazard === "rosebush" || hazard === "slime" || hazard === "tacks")) continue;
         if (opts.avoidNearEnemies && nearEnemy(to)) continue;
         next.push(to);
       }

packages/engine/test/automaton.test.ts

@@ -922,3 +922,35 @@ describe("lessons from the human duels", () => {
     expect(cmd).toMatchObject({ type: "cast", instanceId: "LB" });
   });
 });
+
+describe("the denial planner offers only castable blocks", () => {
+  it("tacks at range are never proposed — the RNRX coma", () => {
+    // Room RNRX froze Automaton II for three turns: pathDenial proposed
+    // scattering tacks four squares away, the engine refused ("you must
+    // be adjacent"), and the refusal-fallback loop read as a coma.
+    let { state } = createGame({ playerIds: ["foe", "bot"], seed: 42, sets: ["basic", "expansion1"] });
+    while (state.turn.round < 2 || state.players[state.turn.activeIndex]!.id !== "bot") {
+      const r = applyCommand(state, actingSeat(state), { type: "endTurn", draw: 0 });
+      if (!r.ok) throw new Error(r.error);
+      state = r.state;
+    }
+    const bot = state.players.find((p) => p.id === "bot")!;
+    const foe = state.players.find((p) => p.id === "foe")!;
+    // The bot's floor gold with a raider closing on it, and only TACKS
+    // in hand to deny the road — from a stand-off distance.
+    const gold = state.treasures.find((t) => t.owner === "bot" && t.position)!;
+    foe.position = { ...gold.position! };
+    bot.position = { ...bot.home };
+    bot.hand = [{ cardId: "handful-of-tacks", instanceId: "HT" } as never];
+    for (let guard = 0; guard < 6; guard++) {
+      const cmd = automatonCommand(viewFor(state, "bot"), "hunter", "archmage");
+      if (!cmd) break;
+      const r = applyCommand(state, "bot", cmd);
+      // Whatever the brain proposes, the engine must accept it.
+      expect(r.ok, `refused: ${JSON.stringify(cmd)} — ${!r.ok ? r.error : ""}`).toBe(true);
+      if (!r.ok) break;
+      state = r.state;
+      if (cmd.type === "endTurn") break;
+    }
+  });
+});