feat: add fill-first routing strategy

internal/config/config.go

@@ -60,6 +60,9 @@ type Config struct {
 	// QuotaExceeded defines the behavior when a quota is exceeded.
 	QuotaExceeded QuotaExceeded `yaml:"quota-exceeded" json:"quota-exceeded"`
 
+	// Routing controls credential selection behavior.
+	Routing RoutingConfig `yaml:"routing" json:"routing"`
+
 	// WebsocketAuth enables or disables authentication for the WebSocket API.
 	WebsocketAuth bool `yaml:"ws-auth" json:"ws-auth"`
 
@@ -124,6 +127,13 @@ type QuotaExceeded struct {
 	SwitchPreviewModel bool `yaml:"switch-preview-model" json:"switch-preview-model"`
 }
 
+// RoutingConfig configures how credentials are selected for requests.
+type RoutingConfig struct {
+	// Strategy selects the credential selection strategy.
+	// Supported values: "fill-first" (default), "round-robin".
+	Strategy string `yaml:"strategy,omitempty" json:"strategy,omitempty"`
+}
+
 // AmpModelMapping defines a model name mapping for Amp CLI requests.
 // When Amp requests a model that isn't available locally, this mapping
 // allows routing to an alternative model that IS available.

sdk/cliproxy/auth/manager.go

@@ -120,7 +120,7 @@ type Manager struct {
 // NewManager constructs a manager with optional custom selector and hook.
 func NewManager(store Store, selector Selector, hook Hook) *Manager {
 	if selector == nil {
-		selector = &RoundRobinSelector{}
+		selector = &FillFirstSelector{}
 	}
 	if hook == nil {
 		hook = NoopHook{}

sdk/cliproxy/auth/selector.go

@@ -20,6 +20,11 @@ type RoundRobinSelector struct {
 	cursors map[string]int
 }
 
+// FillFirstSelector selects the first available credential (deterministic ordering).
+// This "burns" one account before moving to the next, which can help stagger
+// rolling-window subscription caps (e.g. chat message limits).
+type FillFirstSelector struct{}
+
 type blockReason int
 
 const (
@@ -98,20 +103,8 @@ func (e *modelCooldownError) Headers() http.Header {
 	return headers
 }
 
-// Pick selects the next available auth for the provider in a round-robin manner.
-func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, opts cliproxyexecutor.Options, auths []*Auth) (*Auth, error) {
-	_ = ctx
-	_ = opts
-	if len(auths) == 0 {
-		return nil, &Error{Code: "auth_not_found", Message: "no auth candidates"}
-	}
-	if s.cursors == nil {
-		s.cursors = make(map[string]int)
-	}
-	available := make([]*Auth, 0, len(auths))
-	now := time.Now()
-	cooldownCount := 0
-	var earliest time.Time
+func collectAvailable(auths []*Auth, model string, now time.Time) (available []*Auth, cooldownCount int, earliest time.Time) {
+	available = make([]*Auth, 0, len(auths))
 	for i := 0; i < len(auths); i++ {
 		candidate := auths[i]
 		blocked, reason, next := isAuthBlockedForModel(candidate, model, now)
@@ -126,6 +119,18 @@ func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, o
 			}
 		}
 	}
+	if len(available) > 1 {
+		sort.Slice(available, func(i, j int) bool { return available[i].ID < available[j].ID })
+	}
+	return available, cooldownCount, earliest
+}
+
+func getAvailableAuths(auths []*Auth, provider, model string, now time.Time) ([]*Auth, error) {
+	if len(auths) == 0 {
+		return nil, &Error{Code: "auth_not_found", Message: "no auth candidates"}
+	}
+
+	available, cooldownCount, earliest := collectAvailable(auths, model, now)
 	if len(available) == 0 {
 		if cooldownCount == len(auths) && !earliest.IsZero() {
 			resetIn := earliest.Sub(now)
@@ -136,9 +141,21 @@ func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, o
 		}
 		return nil, &Error{Code: "auth_unavailable", Message: "no auth available"}
 	}
-	// Make round-robin deterministic even if caller's candidate order is unstable.
-	if len(available) > 1 {
-		sort.Slice(available, func(i, j int) bool { return available[i].ID < available[j].ID })
+
+	return available, nil
+}
+
+// Pick selects the next available auth for the provider in a round-robin manner.
+func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, opts cliproxyexecutor.Options, auths []*Auth) (*Auth, error) {
+	_ = ctx
+	_ = opts
+	if s.cursors == nil {
+		s.cursors = make(map[string]int)
+	}
+	now := time.Now()
+	available, err := getAvailableAuths(auths, provider, model, now)
+	if err != nil {
+		return nil, err
 	}
 	key := provider + ":" + model
 	s.mu.Lock()
@@ -154,6 +171,18 @@ func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, o
 	return available[index%len(available)], nil
 }
 
+// Pick selects the first available auth for the provider in a deterministic manner.
+func (s *FillFirstSelector) Pick(ctx context.Context, provider, model string, opts cliproxyexecutor.Options, auths []*Auth) (*Auth, error) {
+	_ = ctx
+	_ = opts
+	now := time.Now()
+	available, err := getAvailableAuths(auths, provider, model, now)
+	if err != nil {
+		return nil, err
+	}
+	return available[0], nil
+}
+
 func isAuthBlockedForModel(auth *Auth, model string, now time.Time) (bool, blockReason, time.Time) {
 	if auth == nil {
 		return true, blockReasonOther, time.Time{}

sdk/cliproxy/builder.go

@@ -5,6 +5,7 @@ package cliproxy
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/api"
 	sdkaccess "github.com/router-for-me/CLIProxyAPI/v6/sdk/access"
@@ -197,7 +198,20 @@ func (b *Builder) Build() (*Service, error) {
 		if dirSetter, ok := tokenStore.(interface{ SetBaseDir(string) }); ok && b.cfg != nil {
 			dirSetter.SetBaseDir(b.cfg.AuthDir)
 		}
-		coreManager = coreauth.NewManager(tokenStore, nil, nil)
+
+		strategy := ""
+		if b.cfg != nil {
+			strategy = strings.ToLower(strings.TrimSpace(b.cfg.Routing.Strategy))
+		}
+		var selector coreauth.Selector
+		switch strategy {
+		case "round-robin", "roundrobin", "rr":
+			selector = &coreauth.RoundRobinSelector{}
+		default:
+			selector = &coreauth.FillFirstSelector{}
+		}
+
+		coreManager = coreauth.NewManager(tokenStore, selector, nil)
 	}
 	// Attach a default RoundTripper provider so providers can opt-in per-auth transports.
 	coreManager.SetRoundTripperProvider(newDefaultRoundTripperProvider())