diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad46477413..0ddcc1d655 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
 ### 🔧 Bug Fixes
 
 - **fix(routing):** combo model substitution no longer forwards a client `thinking:{type:"disabled"}` to a target model that rejects it — when a combo/route swaps the upstream model (e.g. `claude-opus-4-8` → `claude-fable-5`), OmniRoute now strips the now-invalid `thinking.type:"disabled"` for models flagged `rejectsThinkingDisabled` (Fable 5 defaults to adaptive and rejects it), preventing the upstream 400 that silently broke Claude Code's internal title/name-generation calls. Models that accept `disabled` (opus/sonnet) are untouched. ([#3554](https://github.com/diegosouzapw/OmniRoute/issues/3554))
+- **fix(usage):** the budget dashboard can now save a budget with some limit fields left empty and clear all limits — `setBudgetSchema` used `.positive()` (rejecting the `0` the form sends for blank fields) plus a superRefine requiring at least one limit `> 0`, so saving with one field filled 400'd and clearing all limits was impossible. Limits now accept `0` (= "no limit for this period"; enforcement only kicks in above 0) and the cross-field minimum was removed; negatives are still rejected. ([#3537](https://github.com/diegosouzapw/OmniRoute/issues/3537))
 
 ---
 
diff --git a/src/shared/validation/schemas.ts b/src/shared/validation/schemas.ts
index 9579aaa1ea..edeaf5aac4 100644
--- a/src/shared/validation/schemas.ts
+++ b/src/shared/validation/schemas.ts
@@ -913,15 +913,13 @@ export const v1CountTokensSchema = z
 export const setBudgetSchema = z
   .object({
     apiKeyId: z.string().trim().min(1, "apiKeyId is required"),
-    dailyLimitUsd: z.coerce.number().positive("dailyLimitUsd must be greater than zero").optional(),
-    weeklyLimitUsd: z.coerce
-      .number()
-      .positive("weeklyLimitUsd must be greater than zero")
-      .optional(),
-    monthlyLimitUsd: z.coerce
-      .number()
-      .positive("monthlyLimitUsd must be greater than zero")
-      .optional(),
+    // #3537: a limit of 0 means "no limit for this period" (checkBudget only enforces when
+    // activeLimitUsd > 0). The dashboard sends 0 for unfilled fields, so 0 must be accepted —
+    // `.positive()` (rejects 0) used to 400 any save that left a field blank. Negatives are
+    // still rejected by `.min(0)`.
+    dailyLimitUsd: z.coerce.number().min(0, "dailyLimitUsd must be zero or greater").optional(),
+    weeklyLimitUsd: z.coerce.number().min(0, "weeklyLimitUsd must be zero or greater").optional(),
+    monthlyLimitUsd: z.coerce.number().min(0, "monthlyLimitUsd must be zero or greater").optional(),
     warningThreshold: z.coerce.number().min(0).max(1).optional(),
     resetInterval: z.enum(["daily", "weekly", "monthly"]).optional(),
     resetTime: z
@@ -929,19 +927,10 @@ export const setBudgetSchema = z
       .trim()
       .regex(/^\d{2}:\d{2}$/, "resetTime must be in HH:MM format")
       .optional(),
-  })
-  .superRefine((value, ctx) => {
-    const hasAnyLimit = [value.dailyLimitUsd, value.weeklyLimitUsd, value.monthlyLimitUsd].some(
-      (entry) => typeof entry === "number" && Number.isFinite(entry) && entry > 0
-    );
-    if (!hasAnyLimit) {
-      ctx.addIssue({
-        code: z.ZodIssueCode.custom,
-        message: "At least one budget limit must be provided",
-        path: ["dailyLimitUsd"],
-      });
-    }
   });
+// #3537: the previous superRefine required at least one limit > 0, which made it impossible to
+// clear all limits (save 0/0/0). Setting all limits to 0 is a valid "disable enforcement"
+// operation, so no cross-field minimum is imposed.
 
 export const setTokenLimitSchema = z
   .object({
diff --git a/tests/unit/budget-schema-empty-limits-3537.test.ts b/tests/unit/budget-schema-empty-limits-3537.test.ts
new file mode 100644
index 0000000000..4ac839e676
--- /dev/null
+++ b/tests/unit/budget-schema-empty-limits-3537.test.ts
@@ -0,0 +1,44 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { setBudgetSchema } from "../../src/shared/validation/schemas.ts";
+
+// Regression for #3537: the budget dashboard sends 0 for unfilled limit fields, but
+// `setBudgetSchema` used `.positive()` (rejects 0) + a superRefine requiring at least one
+// limit > 0. Result: saving a budget with only one field filled 400'd, and clearing all
+// limits was impossible. A limit of 0 means "no limit for this period" (checkBudget only
+// enforces when activeLimitUsd > 0), so 0/all-zero must be accepted.
+
+test("#3537 saving one limit with the others left at 0 succeeds (Bug 1)", () => {
+  const r = setBudgetSchema.safeParse({
+    apiKeyId: "key-1",
+    dailyLimitUsd: 5,
+    weeklyLimitUsd: 0,
+    monthlyLimitUsd: 0,
+  });
+  assert.equal(r.success, true, r.success ? "" : JSON.stringify(r.error?.issues));
+});
+
+test("#3537 clearing all limits to 0 succeeds (Bug 2 — disables enforcement)", () => {
+  const r = setBudgetSchema.safeParse({
+    apiKeyId: "key-1",
+    dailyLimitUsd: 0,
+    weeklyLimitUsd: 0,
+    monthlyLimitUsd: 0,
+  });
+  assert.equal(r.success, true, r.success ? "" : JSON.stringify(r.error?.issues));
+});
+
+test("#3537 a budget with no limit fields (only apiKeyId) is accepted as no-limit", () => {
+  const r = setBudgetSchema.safeParse({ apiKeyId: "key-1" });
+  assert.equal(r.success, true, r.success ? "" : JSON.stringify(r.error?.issues));
+});
+
+test("#3537 negative limits are still rejected", () => {
+  const r = setBudgetSchema.safeParse({ apiKeyId: "key-1", dailyLimitUsd: -3 });
+  assert.equal(r.success, false);
+});
+
+test("#3537 a normal positive limit still validates (regression)", () => {
+  const r = setBudgetSchema.safeParse({ apiKeyId: "key-1", monthlyLimitUsd: 500 });
+  assert.equal(r.success, true, r.success ? "" : JSON.stringify(r.error?.issues));
+});