feat(auth): implement weighted provider rotation for improved scheduling fairness

sdk/cliproxy/auth/scheduler.go

@@ -293,12 +293,46 @@ func (s *authScheduler) pickMixed(ctx context.Context, providers []string, model
 	}
 
 	cursorKey := strings.Join(normalized, ",") + ":" + modelKey
-	start := 0
-	if len(normalized) > 0 {
-		start = s.mixedCursors[cursorKey] % len(normalized)
+	weights := make([]int, len(normalized))
+	segmentStarts := make([]int, len(normalized))
+	segmentEnds := make([]int, len(normalized))
+	totalWeight := 0
+	for providerIndex, shard := range candidateShards {
+		segmentStarts[providerIndex] = totalWeight
+		if shard != nil {
+			weights[providerIndex] = shard.readyCountAtPriorityLocked(false, bestPriority)
+		}
+		totalWeight += weights[providerIndex]
+		segmentEnds[providerIndex] = totalWeight
 	}
+	if totalWeight == 0 {
+		return nil, "", s.mixedUnavailableErrorLocked(normalized, model, tried)
+	}
+
+	startSlot := s.mixedCursors[cursorKey] % totalWeight
+	startProviderIndex := -1
+	for providerIndex := range normalized {
+		if weights[providerIndex] == 0 {
+			continue
+		}
+		if startSlot < segmentEnds[providerIndex] {
+			startProviderIndex = providerIndex
+			break
+		}
+	}
+	if startProviderIndex < 0 {
+		return nil, "", s.mixedUnavailableErrorLocked(normalized, model, tried)
+	}
+
+	slot := startSlot
 	for offset := 0; offset < len(normalized); offset++ {
-		providerIndex := (start + offset) % len(normalized)
+		providerIndex := (startProviderIndex + offset) % len(normalized)
+		if weights[providerIndex] == 0 {
+			continue
+		}
+		if providerIndex != startProviderIndex {
+			slot = segmentStarts[providerIndex]
+		}
 		providerKey := normalized[providerIndex]
 		shard := candidateShards[providerIndex]
 		if shard == nil {
@@ -308,7 +342,7 @@ func (s *authScheduler) pickMixed(ctx context.Context, providers []string, model
 		if picked == nil {
 			continue
 		}
-		s.mixedCursors[cursorKey] = providerIndex + 1
+		s.mixedCursors[cursorKey] = slot + 1
 		return picked, providerKey, nil
 	}
 	return nil, "", s.mixedUnavailableErrorLocked(normalized, model, tried)
@@ -704,6 +738,20 @@ func (m *modelScheduler) pickReadyAtPriorityLocked(preferWebsocket bool, priorit
 	return picked.auth
 }
 
+func (m *modelScheduler) readyCountAtPriorityLocked(preferWebsocket bool, priority int) int {
+	if m == nil {
+		return 0
+	}
+	bucket := m.readyByPriority[priority]
+	if bucket == nil {
+		return 0
+	}
+	if preferWebsocket && len(bucket.ws.flat) > 0 {
+		return len(bucket.ws.flat)
+	}
+	return len(bucket.all.flat)
+}
+
 // unavailableErrorLocked returns the correct unavailable or cooldown error for the shard.
 func (m *modelScheduler) unavailableErrorLocked(provider, model string, predicate func(*scheduledAuth) bool) error {
 	now := time.Now()

sdk/cliproxy/auth/scheduler_test.go

@@ -208,7 +208,7 @@ func TestSchedulerPick_CodexWebsocketPrefersWebsocketEnabledSubset(t *testing.T)
 	}
 }
 
-func TestSchedulerPick_MixedProvidersUsesProviderRotationOverReadyCandidates(t *testing.T) {
+func TestSchedulerPick_MixedProvidersUsesWeightedProviderRotationOverReadyCandidates(t *testing.T) {
 	t.Parallel()
 
 	scheduler := newSchedulerForTest(
@@ -218,8 +218,8 @@ func TestSchedulerPick_MixedProvidersUsesProviderRotationOverReadyCandidates(t *
 		&Auth{ID: "claude-a", Provider: "claude"},
 	)
 
-	wantProviders := []string{"gemini", "claude", "gemini", "claude"}
-	wantIDs := []string{"gemini-a", "claude-a", "gemini-b", "claude-a"}
+	wantProviders := []string{"gemini", "gemini", "claude", "gemini"}
+	wantIDs := []string{"gemini-a", "gemini-b", "claude-a", "gemini-a"}
 	for index := range wantProviders {
 		got, provider, errPick := scheduler.pickMixed(context.Background(), []string{"gemini", "claude"}, "", cliproxyexecutor.Options{}, nil)
 		if errPick != nil {
@@ -272,7 +272,7 @@ func TestSchedulerPick_MixedProvidersPrefersHighestPriorityTier(t *testing.T) {
 	}
 }
 
-func TestManager_PickNextMixed_UsesProviderRotationBeforeCredentialRotation(t *testing.T) {
+func TestManager_PickNextMixed_UsesWeightedProviderRotationBeforeCredentialRotation(t *testing.T) {
 	t.Parallel()
 
 	manager := NewManager(nil, &RoundRobinSelector{}, nil)
@@ -288,8 +288,8 @@ func TestManager_PickNextMixed_UsesProviderRotationBeforeCredentialRotation(t *t
 		t.Fatalf("Register(claude-a) error = %v", errRegister)
 	}
 
-	wantProviders := []string{"gemini", "claude", "gemini", "claude"}
-	wantIDs := []string{"gemini-a", "claude-a", "gemini-b", "claude-a"}
+	wantProviders := []string{"gemini", "gemini", "claude", "gemini"}
+	wantIDs := []string{"gemini-a", "gemini-b", "claude-a", "gemini-a"}
 	for index := range wantProviders {
 		got, _, provider, errPick := manager.pickNextMixed(context.Background(), []string{"gemini", "claude"}, "", cliproxyexecutor.Options{}, map[string]struct{}{})
 		if errPick != nil {
@@ -399,8 +399,8 @@ func TestManager_PickNextMixed_UsesSchedulerRotation(t *testing.T) {
 		t.Fatalf("Register(claude-a) error = %v", errRegister)
 	}
 
-	wantProviders := []string{"gemini", "claude", "gemini", "claude"}
-	wantIDs := []string{"gemini-a", "claude-a", "gemini-b", "claude-a"}
+	wantProviders := []string{"gemini", "gemini", "claude", "gemini"}
+	wantIDs := []string{"gemini-a", "gemini-b", "claude-a", "gemini-a"}
 	for index := range wantProviders {
 		got, _, provider, errPick := manager.pickNextMixed(context.Background(), []string{"gemini", "claude"}, "", cliproxyexecutor.Options{}, nil)
 		if errPick != nil {