diff --git a/open-sse/services/usage.ts b/open-sse/services/usage.ts
index b3cbd2ee1344..dec18065ae30 100644
--- a/open-sse/services/usage.ts
+++ b/open-sse/services/usage.ts
@@ -56,6 +56,7 @@ import {
   toDisplayLabel,
   pickFirstNonEmptyString,
 } from "./usage/scalars.ts";
+import { type UsageQuota, parseResetTime, createQuotaFromUsage } from "./usage/quota.ts";
 
 // Quota / usage upstream URLs (overridable for testing or relays).
 const CROF_USAGE_URL = process.env.OMNIROUTE_CROF_USAGE_URL ?? "https://crof.ai/usage_api/";
@@ -133,29 +134,6 @@ const MINIMAX_USAGE_CONFIG = {
 } as const;
 
 type JsonRecord = Record<string, unknown>;
-type UsageQuota = {
-  used: number;
-  total: number;
-  remaining?: number;
-  remainingPercentage?: number;
-  resetAt: string | null;
-  unlimited: boolean;
-  /**
-   * True when the upstream provider reported the remaining fraction. False
-   * means the API didn't include the field and the 0 value here is a sentinel,
-   * NOT a confirmed-exhausted state. Antigravity-specific.
-   */
-  fractionReported?: boolean;
-  quotaSource?: "retrieveUserQuota" | "fetchAvailableModels" | "localUsageHistory";
-  displayName?: string;
-  details?: Array<{
-    name: string;
-    used: number;
-  }>;
-  currency?: string;
-  grantedBalance?: number;
-  toppedUpBalance?: number;
-};
 type UsageProviderConnection = JsonRecord & {
   id?: string;
   provider?: string;
@@ -277,25 +255,6 @@ function getClaudePlanLabel(...candidates: Array<string | null | undefined>): st
   return null;
 }
 
-function createQuotaFromUsage(
-  usedValue: unknown,
-  totalValue: unknown,
-  resetValue: unknown
-): UsageQuota {
-  const total = Math.max(0, toNumber(totalValue, 0));
-  const used = total > 0 ? Math.min(Math.max(0, toNumber(usedValue, 0)), total) : 0;
-  const remaining = total > 0 ? Math.max(total - used, 0) : 0;
-
-  return {
-    used,
-    total,
-    remaining,
-    remainingPercentage: total > 0 ? clampPercentage((remaining / total) * 100) : 0,
-    resetAt: parseResetTime(resetValue),
-    unlimited: false,
-  };
-}
-
 function getMiniMaxQuotaResetAt(
   model: JsonRecord,
   capturedAtMs: number,
@@ -1371,37 +1330,6 @@ export async function getUsageForProvider(
  * Parse reset date/time to ISO string
  * Handles multiple formats: Unix timestamp (ms), ISO date string, etc.
  */
-function parseResetTime(resetValue: unknown): string | null {
-  if (!resetValue) return null;
-
-  try {
-    let date: Date;
-    if (resetValue instanceof Date) {
-      date = resetValue;
-    } else if (typeof resetValue === "number") {
-      date = new Date(resetValue < 1e12 ? resetValue * 1000 : resetValue);
-    } else if (typeof resetValue === "string") {
-      // Numeric strings are Unix timestamps too (seconds or milliseconds).
-      // `new Date("1700000000")` otherwise returns Invalid Date.
-      if (/^\d+$/.test(resetValue)) {
-        const ts = Number(resetValue);
-        date = new Date(ts < 1e12 ? ts * 1000 : ts);
-      } else {
-        date = new Date(resetValue);
-      }
-    } else {
-      return null;
-    }
-
-    // Epoch-zero (1970-01-01) means no scheduled reset — treat as null
-    if (date.getTime() <= 0) return null;
-
-    return date.toISOString();
-  } catch (error) {
-    return null;
-  }
-}
-
 /**
  * GitHub Copilot Usage
  * Uses GitHub accessToken (not copilotToken) to call copilot_internal/user API
diff --git a/open-sse/services/usage/quota.ts b/open-sse/services/usage/quota.ts
new file mode 100644
index 000000000000..ce9642c902e3
--- /dev/null
+++ b/open-sse/services/usage/quota.ts
@@ -0,0 +1,85 @@
+/**
+ * usage/quota.ts — shared usage-quota shape + builders for the usage fetchers.
+ *
+ * Extracted from services/usage.ts (god-file decomposition): the `UsageQuota` value
+ * type every per-provider fetcher returns, plus the two pure builders that normalize
+ * upstream reset timestamps and assemble a quota from used/total counts. Depends only on
+ * the sibling scalar leaf — no network, no DB, no module state — so usage.ts and the
+ * per-provider fetcher leaves (MiniMax, GLM, …) import it without a cycle.
+ */
+
+import { toNumber, clampPercentage } from "./scalars.ts";
+
+export type UsageQuota = {
+  used: number;
+  total: number;
+  remaining?: number;
+  remainingPercentage?: number;
+  resetAt: string | null;
+  unlimited: boolean;
+  /**
+   * True when the upstream provider reported the remaining fraction. False
+   * means the API didn't include the field and the 0 value here is a sentinel,
+   * NOT a confirmed-exhausted state. Antigravity-specific.
+   */
+  fractionReported?: boolean;
+  quotaSource?: "retrieveUserQuota" | "fetchAvailableModels" | "localUsageHistory";
+  displayName?: string;
+  details?: Array<{
+    name: string;
+    used: number;
+  }>;
+  currency?: string;
+  grantedBalance?: number;
+  toppedUpBalance?: number;
+};
+
+export function parseResetTime(resetValue: unknown): string | null {
+  if (!resetValue) return null;
+
+  try {
+    let date: Date;
+    if (resetValue instanceof Date) {
+      date = resetValue;
+    } else if (typeof resetValue === "number") {
+      date = new Date(resetValue < 1e12 ? resetValue * 1000 : resetValue);
+    } else if (typeof resetValue === "string") {
+      // Numeric strings are Unix timestamps too (seconds or milliseconds).
+      // `new Date("1700000000")` otherwise returns Invalid Date.
+      if (/^\d+$/.test(resetValue)) {
+        const ts = Number(resetValue);
+        date = new Date(ts < 1e12 ? ts * 1000 : ts);
+      } else {
+        date = new Date(resetValue);
+      }
+    } else {
+      return null;
+    }
+
+    // Epoch-zero (1970-01-01) means no scheduled reset — treat as null
+    if (date.getTime() <= 0) return null;
+
+    return date.toISOString();
+  } catch {
+    return null;
+  }
+}
+
+export function createQuotaFromUsage(
+  usedValue: unknown,
+  totalValue: unknown,
+  resetValue: unknown
+): UsageQuota {
+  const total = Math.max(0, toNumber(totalValue, 0));
+  const used = total > 0 ? Math.min(Math.max(0, toNumber(usedValue, 0)), total) : 0;
+  const remaining = total > 0 ? Math.max(total - used, 0) : 0;
+
+  return {
+    used,
+    total,
+    remaining,
+    remainingPercentage: total > 0 ? clampPercentage((remaining / total) * 100) : 0,
+    resetAt: parseResetTime(resetValue),
+    unlimited: false,
+  };
+}
diff --git a/tests/unit/usage-quota-core-split.test.ts b/tests/unit/usage-quota-core-split.test.ts
new file mode 100644
index 000000000000..eb2197a5bfa4
--- /dev/null
+++ b/tests/unit/usage-quota-core-split.test.ts
@@ -0,0 +1,52 @@
+// Characterization of the services/usage.ts quota-core split (god-file decomposition): the shared
+// UsageQuota shape + the two pure builders (parseResetTime, createQuotaFromUsage) moved into
+// services/usage/quota.ts so the per-provider fetcher leaves can share them without a cycle.
+// Behavior-preserving move — these locks pin the timestamp normalization (sec vs ms, epoch-zero →
+// null, numeric strings) and the used/total → quota assembly (clamping, remaining %).
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+const Q = await import("../../open-sse/services/usage/quota.ts");
+
+test("parseResetTime normalizes seconds, millis, numeric strings; epoch-zero → null", () => {
+  // seconds (< 1e12) get *1000
+  assert.equal(Q.parseResetTime(1_700_000_000), new Date(1_700_000_000_000).toISOString());
+  // millis pass through
+  assert.equal(Q.parseResetTime(1_700_000_000_000), new Date(1_700_000_000_000).toISOString());
+  // numeric string as seconds
+  assert.equal(Q.parseResetTime("1700000000"), new Date(1_700_000_000_000).toISOString());
+  // ISO string passes through
+  assert.equal(Q.parseResetTime("2026-01-02T03:04:05.000Z"), "2026-01-02T03:04:05.000Z");
+  // epoch-zero / falsy / junk → null
+  assert.equal(Q.parseResetTime(0), null);
+  assert.equal(Q.parseResetTime(null), null);
+  assert.equal(Q.parseResetTime("not a date"), null);
+});
+
+test("createQuotaFromUsage clamps used to total and computes remaining %", () => {
+  const q = Q.createQuotaFromUsage(30, 100, null);
+  assert.equal(q.total, 100);
+  assert.equal(q.used, 30);
+  assert.equal(q.remaining, 70);
+  assert.equal(q.remainingPercentage, 70);
+  assert.equal(q.unlimited, false);
+  assert.equal(q.resetAt, null);
+
+  // used above total is clamped
+  const over = Q.createQuotaFromUsage(250, 100, null);
+  assert.equal(over.used, 100);
+  assert.equal(over.remaining, 0);
+  assert.equal(over.remainingPercentage, 0);
+
+  // total 0 → everything zeroed
+  const zero = Q.createQuotaFromUsage(5, 0, null);
+  assert.equal(zero.total, 0);
+  assert.equal(zero.used, 0);
+  assert.equal(zero.remaining, 0);
+  assert.equal(zero.remainingPercentage, 0);
+});
+
+test("createQuotaFromUsage threads the reset timestamp through parseResetTime", () => {
+  const q = Q.createQuotaFromUsage(1, 10, 1_700_000_000);
+  assert.equal(q.resetAt, new Date(1_700_000_000_000).toISOString());
+});