diff --git a/tests/integration/combo-matrix/quota-share.test.ts b/tests/integration/combo-matrix/quota-share.test.ts
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+// tests/integration/combo-matrix/quota-share.test.ts
+//
+// E2E matrix test for the INTERNAL quota-share routing strategy (DRR / deficit
+// round-robin over auto-minted qtSd/ pool combos).
+//
+// Drive path: handleChat → chatCore → handleComboChat (strategy "quota-share")
+//   → selectQuotaShareTarget (DRR + P2C + bucket-gating) → executor dispatch.
+//
+// Two tests:
+//   1. DRR fairness — 2 equal-weight connections, 6 requests; both must be
+//      selected and balanced, proving DRR ran end-to-end (not a single-winner
+//      or definition-order dispatch).
+//   2. Saturation deprioritization — one connection marked saturated via
+//      recordUsage (5h window); a single request must dispatch to the clean
+//      connection first, proving the bucket-gating gate runs through the real
+//      wire.
+//
+// Drive path chosen: Option A — direct `combosDb.createCombo({ strategy:
+// "quota-share", ... })`. The `handleComboChat` dispatch at combo.ts:1573
+// branches on `strategy === "quota-share"` verbatim; no qtSd/ pool plumbing is
+// required to reach `selectQuotaShareTarget`.
+//
+// The preferred target is always the SECOND one in the combo definition so that
+// a pass proves the selector actually reordered targets (same discipline as the
+// 17-strategy quota-aware.test.ts matrix).
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { createComboRoutingHarness } from "../_comboRoutingHarness.ts";
+
+const h = await createComboRoutingHarness("combo-quota-share");
+const { BaseExecutor, combosDb, handleChat, buildRequest, seedConnection, resetStorage } = h;
+
+// DRR + bucket state seams — import AFTER harness initialises the DB so the
+// module-level in-process singletons are already live.
+const { _clearDrrStateForTest } = await import(
+  "../../../open-sse/services/combo/quotaShareStrategy.ts"
+);
+const { recordUsage, _clearBucketsForTest } = await import(
+  "../../../src/lib/quota/accountBuckets.ts"
+);
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+function body(model: string, suffix = "") {
+  return {
+    model,
+    stream: false,
+    messages: [{ role: "user", content: `quota-share route${suffix}` }],
+  };
+}
+
+// ── Lifecycle ─────────────────────────────────────────────────────────────────
+
+test.beforeEach(async () => {
+  BaseExecutor.RETRY_CONFIG.delayMs = 0;
+  _clearDrrStateForTest();
+  _clearBucketsForTest();
+  await resetStorage();
+});
+
+test.afterEach(async () => {
+  BaseExecutor.RETRY_CONFIG.delayMs = h.originalRetryDelayMs;
+  _clearDrrStateForTest();
+  _clearBucketsForTest();
+  await resetStorage();
+});
+
+test.after(async () => {
+  _clearDrrStateForTest();
+  _clearBucketsForTest();
+  await h.cleanup();
+});
+
+// ── Strategy: quota-share — DRR fairness ─────────────────────────────────────
+//
+// Mechanism: DRR (deficit round robin, quantum = weight / totalWeight).
+//
+// Engineered state:
+//   openai (1st in definition)  — equal weight 100
+//   gemini (2nd in definition)  — equal weight 100
+//
+// With 2 equal-weight targets DRR alternates: openai, gemini, openai, gemini, …
+// Over 6 requests both must be selected at least 2 times (proven to be exactly
+// 3 each by the deterministic math, but asserting >= 2 avoids brittleness if
+// P2C ever nudges a tie differently). The assertion fails if the pipeline
+// pin-picks the first candidate on every call — i.e. if DRR is bypassed.
+test("DRR fairness: 2 equal-weight connections alternate across 6 requests through real pipeline", async () => {
+  const openaiConn = await seedConnection("openai", { apiKey: "sk-openai-qs-drr-1" });
+  const geminiConn = await seedConnection("gemini", { apiKey: "sk-gemini-qs-drr-1" });
+
+  await combosDb.createCombo({
+    name: "m-qs-drr",
+    strategy: "quota-share",
+    config: { maxRetries: 0, retryDelayMs: 0, stickyRoundRobinLimit: 1 },
+    models: [
+      // openai FIRST in definition
+      {
+        id: "qs-drr-openai",
+        kind: "model",
+        providerId: "openai",
+        model: "gpt-4o-mini",
+        connectionId: openaiConn.id,
+      },
+      // gemini SECOND in definition — DRR must pick it on alternate rounds
+      {
+        id: "qs-drr-gemini",
+        kind: "model",
+        providerId: "gemini",
+        model: "gemini-2.5-flash",
+        connectionId: geminiConn.id,
+      },
+    ],
+  });
+  h.installRecordingFetch();
+
+  // Use a unique message suffix per request so session stickiness (message-hash
+  // based) does not pin every call to the first-round winner.  In real traffic
+  // each conversation has distinct content; the DRR distributes across them.
+  for (let i = 0; i < 6; i++) {
+    const r = await handleChat(buildRequest({ body: body("m-qs-drr", ` #${i}`) }));
+    assert.equal(r.status, 200, `request ${i + 1} must succeed`);
+  }
+
+  const seen = h.providersSeen();
+  assert.equal(seen.length, 6, "all 6 requests must reach an upstream provider");
+
+  const openaiCount = seen.filter((p) => p === "openai").length;
+  const geminiCount = seen.filter((p) => p === "gemini").length;
+
+  assert.ok(
+    openaiCount >= 2,
+    `DRR fairness: openai must be selected at least 2 times out of 6; got ${openaiCount}. ` +
+      `Full sequence: [${seen.join(", ")}]. If openai was never selected, DRR was bypassed.`
+  );
+  assert.ok(
+    geminiCount >= 2,
+    `DRR fairness: gemini must be selected at least 2 times out of 6; got ${geminiCount}. ` +
+      `Full sequence: [${seen.join(", ")}]. If gemini was never selected, DRR was bypassed.`
+  );
+});
+
+// ── Strategy: quota-share — saturation deprioritization ──────────────────────
+//
+// Mechanism: filterEligibleBySaturation (isBucketSaturated, 5h window).
+//
+// Engineered state:
+//   openai (1st in definition)  — 5h bucket seeded at 100 % usage via
+//                                  recordUsage → isBucketSaturated returns true
+//                                  → filterEligibleBySaturation demotes it
+//   gemini (2nd in definition)  — no bucket recorded → eligible (clean)
+//
+// Expected: gemini dispatched first despite being second in the combo
+// definition. Proves the bucket-gating runs through the real pipeline wire
+// (not merely unit-tested in isolation).
+test("saturation deprioritization: saturated connection demoted — clean second target dispatched first", async () => {
+  const openaiConn = await seedConnection("openai", { apiKey: "sk-openai-qs-sat-1" });
+  const geminiConn = await seedConnection("gemini", { apiKey: "sk-gemini-qs-sat-1" });
+
+  // Seed openai connection as saturated (5h window, 100 % usage, reset in 1 h).
+  // recordUsage writes the in-process _buckets store; isBucketSaturated reads it.
+  // The resetAt must be in the FUTURE so the lazy-reset guard keeps the entry live.
+  const futureResetAt = new Date(Date.now() + 3_600_000).toISOString();
+  recordUsage(openaiConn.id, "5h", 100, futureResetAt);
+
+  await combosDb.createCombo({
+    name: "m-qs-sat",
+    strategy: "quota-share",
+    config: { maxRetries: 0, retryDelayMs: 0, stickyRoundRobinLimit: 1 },
+    models: [
+      // openai FIRST in definition — must be demoted (5h bucket saturated)
+      {
+        id: "qs-sat-openai",
+        kind: "model",
+        providerId: "openai",
+        model: "gpt-4o-mini",
+        connectionId: openaiConn.id,
+      },
+      // gemini SECOND — must win (no saturation recorded → eligible)
+      {
+        id: "qs-sat-gemini",
+        kind: "model",
+        providerId: "gemini",
+        model: "gemini-2.5-flash",
+        connectionId: geminiConn.id,
+      },
+    ],
+  });
+  h.installRecordingFetch();
+
+  const r = await handleChat(buildRequest({ body: body("m-qs-sat") }));
+  assert.equal(r.status, 200, "request must succeed via clean gemini target");
+
+  const first = h.providersSeen()[0];
+  assert.equal(
+    first,
+    "gemini",
+    `saturation deprioritization: openai 5h bucket is at 100 % (saturated), so ` +
+      `filterEligibleBySaturation must demote it and dispatch gemini first despite it ` +
+      `being second in the combo definition. Got: ${first}`
+  );
+});