diff --git a/apps/coder/src/schema.sql b/apps/coder/src/schema.sql
index 5bef50d..050c9fc 100644
--- a/apps/coder/src/schema.sql
+++ b/apps/coder/src/schema.sql
@@ -423,3 +423,7 @@ CREATE INDEX IF NOT EXISTS contestants_task_id_idx ON contestants(task_id);
 
 -- Cross-examination listing per battle.
 CREATE INDEX IF NOT EXISTS cross_examinations_battle_idx ON cross_examinations(battle_id);
+
+-- TokenScope: per-category token breakdown on arena contestants and tasks.
+ALTER TABLE contestants ADD COLUMN IF NOT EXISTS token_breakdown JSONB;
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS token_breakdown JSONB;
diff --git a/apps/coder/src/services/__tests__/arena-decisions.test.ts b/apps/coder/src/services/__tests__/arena-decisions.test.ts
index 176ba22..68ce2f1 100644
--- a/apps/coder/src/services/__tests__/arena-decisions.test.ts
+++ b/apps/coder/src/services/__tests__/arena-decisions.test.ts
@@ -162,6 +162,24 @@ describe('computeBenchmark', () => {
     expect(bench.durationMs).toBe(0);
     expect(bench.tokensPerSec).toBeNull();
   });
+
+  it('includes token breakdown when provided', () => {
+    const breakdown = {
+      system: 10,
+      user: 20,
+      assistant: 30,
+      tools: 40,
+      reasoning: 5,
+      total: 105,
+    };
+    const bench = computeBenchmark(t0, t1, 500, 'local', breakdown);
+    expect(bench.tokenBreakdown).toEqual(breakdown);
+  });
+
+  it('defaults token breakdown to null when omitted', () => {
+    const bench = computeBenchmark(t0, t1, 500, 'local');
+    expect(bench.tokenBreakdown).toBeNull();
+  });
 });
 
 // ─── sanitizeSlug ────────────────────────────────────────────────────────────
diff --git a/apps/coder/src/services/arena-decisions.ts b/apps/coder/src/services/arena-decisions.ts
index fd2d642..a1d081b 100644
--- a/apps/coder/src/services/arena-decisions.ts
+++ b/apps/coder/src/services/arena-decisions.ts
@@ -9,7 +9,7 @@
  * A contestant's status lifecycle:
  *   queued → running → done | error
  */
-import type { BattleType, ContestantLane } from '@boocode/contracts/arena';
+import type { BattleType, ContestantLane, TokenBreakdown } from '@boocode/contracts/arena';
 
 // ─── Lane classification ──────────────────────────────────────────────────────
 
@@ -73,6 +73,7 @@ export function isBattleComplete(contestants: readonly { status: string }[]): bo
 export interface Benchmark {
   durationMs: number;
   tokensPerSec: number | null;
+  tokenBreakdown: TokenBreakdown | null;
 }
 
 /**
@@ -86,13 +87,14 @@ export function computeBenchmark(
   endedAt: Date,
   costTokens: number | null,
   lane: ContestantLane,
+  tokenBreakdown: TokenBreakdown | null = null,
 ): Benchmark {
   const durationMs = Math.max(0, endedAt.getTime() - startedAt.getTime());
   const tokensPerSec =
     lane === 'local' && costTokens !== null && durationMs > 0
       ? (costTokens / durationMs) * 1000
       : null;
-  return { durationMs, tokensPerSec };
+  return { durationMs, tokensPerSec, tokenBreakdown };
 }
 
 // ─── Slug / path helpers ──────────────────────────────────────────────────────