diff --git a/src/app/api/quota/pools/[id]/route.ts b/src/app/api/quota/pools/[id]/route.ts
index d5bf6167b7..cac6216e47 100644
--- a/src/app/api/quota/pools/[id]/route.ts
+++ b/src/app/api/quota/pools/[id]/route.ts
@@ -65,19 +65,35 @@ export async function PATCH(request: Request, { params }: RouteParams): Promise<
       }
     }
 
+    // Combos must be reconciled when the pool's group OR connection set changes,
+    // since the qtSd/ combo name embeds <groupSlug>/<provider>. Each provider in a
+    // group is served by at most one pool, so removing this pool's CURRENT (old)
+    // group+provider combos BEFORE the update — then re-syncing AFTER — cleanly
+    // drops stale combos and mints the new ones, using the existing per-pool
+    // helpers. Without the pre-update removal, a group/provider switch would leave
+    // orphan qtSd/ combos a quota key still sees. Guarded + non-fatal.
+    const combosNeedResync =
+      body !== null &&
+      typeof body === "object" &&
+      ("connectionIds" in body || "groupId" in body);
+    if (combosNeedResync) {
+      try {
+        const { removeQuotaCombosForPool } = await import("@/lib/quota/quotaCombos");
+        await removeQuotaCombosForPool(id); // pool still has its OLD group/provider here
+      } catch {
+        // Guard: combo cleanup failure must never break pool update.
+      }
+    }
+
     const pool = updatePool(id, parsed.data);
     if (!pool) {
       return NextResponse.json(buildErrorBody(404, "Pool not found"), { status: 404 });
     }
 
-    // Re-sync quota combos when connectionIds was explicitly changed.
-    // updatePool already fires a guarded sync internally, but we add an explicit
-    // awaited sync here so the caller's response reflects the updated combo state.
-    // Mirrors the dynamic-import + non-fatal pattern from groups/[id]/route.ts PATCH.
-    if (body !== null && typeof body === "object" && "connectionIds" in body) {
+    if (combosNeedResync) {
       try {
         const { syncQuotaCombos } = await import("@/lib/quota/quotaCombos");
-        await syncQuotaCombos(id);
+        await syncQuotaCombos(id); // pool now has its NEW group/provider
       } catch {
         // Guard: combo-sync failure must never break pool update callers.
       }
diff --git a/tests/unit/quota-pool-update-full.test.ts b/tests/unit/quota-pool-update-full.test.ts
index 2d8aeabf77..1497b144b6 100644
--- a/tests/unit/quota-pool-update-full.test.ts
+++ b/tests/unit/quota-pool-update-full.test.ts
@@ -24,7 +24,9 @@ const poolsDb = await import("../../src/lib/db/quotaPools.ts");
 const providersDb = await import("../../src/lib/db/providers.ts");
 const combosDb = await import("../../src/lib/db/combos.ts");
 const { createGroup } = await import("../../src/lib/db/quotaGroups.ts");
-const { syncQuotaCombos } = await import("../../src/lib/quota/quotaCombos.ts");
+const { syncQuotaCombos, removeQuotaCombosForPool } = await import(
+  "../../src/lib/quota/quotaCombos.ts"
+);
 const { PoolUpdateSchema } = await import("../../src/shared/schemas/quota.ts");
 const { isQuotaModelName, parseQuotaModelName, quotaGroupSlug } = await import(
   "../../src/lib/quota/quotaModelNaming.ts"
@@ -178,6 +180,52 @@ test("updatePool with new connectionIds triggers combo re-sync (openrouter → b
   assert.deepEqual(reread.connectionIds, [idB], "pool.connectionIds must contain only baidu conn");
 });
 
+test("PATCH route sequence (remove→update→sync) prunes OLD-provider combos on switch", async () => {
+  const group = createGroup("RouteSwitchGroup");
+  const groupSlug = quotaGroupSlug(group.name);
+
+  const connA = await providersDb.createProviderConnection({
+    provider: "openrouter",
+    authType: "apikey",
+    name: "rt-or-conn",
+    apiKey: "sk-rt-or",
+  });
+  const idA = (connA as Record<string, unknown>).id as string;
+  const connB = await providersDb.createProviderConnection({
+    provider: "baidu",
+    authType: "apikey",
+    name: "rt-baidu-conn",
+    apiKey: "sk-rt-baidu",
+  });
+  const idB = (connB as Record<string, unknown>).id as string;
+
+  const pool = poolsDb.createPool({ connectionId: idA, name: "Route Switch", groupId: group.id });
+  await syncQuotaCombos(pool.id);
+  assert.ok(
+    (await listQuotaCombos()).some((c) => parseQuotaModelName(c.name)?.provider === "openrouter"),
+    "precondition: openrouter combos exist"
+  );
+
+  // Mirror the PATCH route's connection/group-change path exactly:
+  await removeQuotaCombosForPool(pool.id); // pool still has OLD (openrouter) provider here
+  poolsDb.updatePool(pool.id, { connectionIds: [idB] });
+  await syncQuotaCombos(pool.id); // pool now has NEW (baidu) provider
+
+  const after = await listQuotaCombos();
+  const orphans = after.filter((c) => {
+    const p = parseQuotaModelName(c.name);
+    return p?.groupSlug === groupSlug && p?.provider === "openrouter";
+  });
+  assert.equal(orphans.length, 0, `OLD openrouter combos must be pruned; found ${orphans.length}`);
+  assert.ok(
+    after.some((c) => {
+      const p = parseQuotaModelName(c.name);
+      return p?.groupSlug === groupSlug && p?.provider === "baidu";
+    }),
+    "NEW baidu combos must exist after the switch"
+  );
+});
+
 test("updatePool with groupId persists the new group assignment", () => {
   const groupA = createGroup("GroupAlpha");
   const groupB = createGroup("GroupBeta");