refactor(channels): add per-channel rate limiting and send retry with error classification

Define sentinel error types (ErrNotRunning, ErrRateLimit, ErrTemporary,
ErrSendFailed) so the Manager can classify Send failures and choose the
right retry strategy: permanent errors bail immediately, rate-limit
errors use a fixed 1s delay, and temporary/unknown errors use exponential
backoff (500ms→1s→2s, capped at 8s, up to 3 retries). A per-channel
token-bucket rate limiter (golang.org/x/time/rate) throttles outbound
sends before they hit the platform API.

go.mod

@@ -23,6 +23,7 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/time v0.14.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

go.sum

@@ -226,6 +226,8 @@ golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/time v0.12.0 h1:ScB/8o8olJvc+CQPWrK3fPZNfh7qgwCrY0zJmoEQLSE=
 golang.org/x/time v0.12.0/go.mod h1:CDIdPxbZBQxdj6cxyCIdrNogrJKMJ7pr37NYpMcMDSg=
+golang.org/x/time v0.14.0 h1:MRx4UaLrDotUKUdCIqzPC48t1Y9hANFKIRpNx+Te8PI=
+golang.org/x/time v0.14.0/go.mod h1:eL/Oa2bBBK0TkX57Fyni+NgnyQQN4LitPmob2Hjnqw4=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200619180055-7c47624df98f/go.mod h1:EkVYQZoAsY45+roYkvgYkIh4xh/qjgUK9TdY2XT94GE=

pkg/channels/errors.go

@@ -0,0 +1,21 @@
+package channels
+
+import "errors"
+
+var (
+	// ErrNotRunning indicates the channel is not running.
+	// Manager will not retry.
+	ErrNotRunning = errors.New("channel not running")
+
+	// ErrRateLimit indicates the platform returned a rate-limit response (e.g. HTTP 429).
+	// Manager will wait a fixed delay and retry.
+	ErrRateLimit = errors.New("rate limited")
+
+	// ErrTemporary indicates a transient failure (e.g. network timeout, 5xx).
+	// Manager will use exponential backoff and retry.
+	ErrTemporary = errors.New("temporary failure")
+
+	// ErrSendFailed indicates a permanent failure (e.g. invalid chat ID, 4xx non-429).
+	// Manager will not retry.
+	ErrSendFailed = errors.New("send failed")
+)

pkg/channels/errors_test.go

@@ -0,0 +1,56 @@
+package channels
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestErrorsIs(t *testing.T) {
+	wrapped := fmt.Errorf("telegram API: %w", ErrRateLimit)
+	if !errors.Is(wrapped, ErrRateLimit) {
+		t.Error("wrapped ErrRateLimit should match")
+	}
+	if errors.Is(wrapped, ErrTemporary) {
+		t.Error("wrapped ErrRateLimit should not match ErrTemporary")
+	}
+}
+
+func TestErrorsIsAllTypes(t *testing.T) {
+	sentinels := []error{ErrNotRunning, ErrRateLimit, ErrTemporary, ErrSendFailed}
+
+	for _, sentinel := range sentinels {
+		wrapped := fmt.Errorf("context: %w", sentinel)
+		if !errors.Is(wrapped, sentinel) {
+			t.Errorf("wrapped %v should match itself", sentinel)
+		}
+
+		// Verify it doesn't match other sentinel errors
+		for _, other := range sentinels {
+			if other == sentinel {
+				continue
+			}
+			if errors.Is(wrapped, other) {
+				t.Errorf("wrapped %v should not match %v", sentinel, other)
+			}
+		}
+	}
+}
+
+func TestErrorMessages(t *testing.T) {
+	tests := []struct {
+		err  error
+		want string
+	}{
+		{ErrNotRunning, "channel not running"},
+		{ErrRateLimit, "rate limited"},
+		{ErrTemporary, "temporary failure"},
+		{ErrSendFailed, "send failed"},
+	}
+
+	for _, tt := range tests {
+		if got := tt.err.Error(); got != tt.want {
+			t.Errorf("error message = %q, want %q", got, tt.want)
+		}
+	}
+}

pkg/channels/manager.go

@@ -8,8 +8,13 @@ package channels
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"math"
 	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
 
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
@@ -19,12 +24,28 @@ import (
 	"github.com/sipeed/picoclaw/pkg/utils"
 )
 
-const defaultChannelQueueSize = 100
+const (
+	defaultChannelQueueSize = 100
+	defaultRateLimit        = 10 // default 10 msg/s
+	maxRetries              = 3
+	rateLimitDelay          = 1 * time.Second
+	baseBackoff             = 500 * time.Millisecond
+	maxBackoff              = 8 * time.Second
+)
+
+// channelRateConfig maps channel name to per-second rate limit.
+var channelRateConfig = map[string]float64{
+	"telegram": 20,
+	"discord":  1,
+	"slack":    1,
+	"line":     10,
+}
 
 type channelWorker struct {
-	ch    Channel
+	ch      Channel
-	queue chan bus.OutboundMessage
+	queue   chan bus.OutboundMessage
-	done  chan struct{}
+	done    chan struct{}
+	limiter *rate.Limiter
 }
 
 type Manager struct {
@@ -83,11 +104,7 @@ func (m *Manager) initChannel(name, displayName string) {
 			}
 		}
 		m.channels[name] = ch
-		m.workers[name] = &channelWorker{
+		m.workers[name] = newChannelWorker(name, ch)
-			ch:    ch,
-			queue: make(chan bus.OutboundMessage, defaultChannelQueueSize),
-			done:  make(chan struct{}),
-		}
 		logger.InfoCF("channels", "Channel enabled successfully", map[string]any{
 			"channel": displayName,
 		})
@@ -227,6 +244,23 @@ func (m *Manager) StopAll(ctx context.Context) error {
 	return nil
 }
 
+// newChannelWorker creates a channelWorker with a rate limiter configured
+// for the given channel name.
+func newChannelWorker(name string, ch Channel) *channelWorker {
+	rateVal := float64(defaultRateLimit)
+	if r, ok := channelRateConfig[name]; ok {
+		rateVal = r
+	}
+	burst := int(math.Max(1, math.Ceil(rateVal/2)))
+
+	return &channelWorker{
+		ch:      ch,
+		queue:   make(chan bus.OutboundMessage, defaultChannelQueueSize),
+		done:    make(chan struct{}),
+		limiter: rate.NewLimiter(rate.Limit(rateVal), burst),
+	}
+}
+
 // runWorker processes outbound messages for a single channel, splitting
 // messages that exceed the channel's maximum message length.
 func (m *Manager) runWorker(ctx context.Context, name string, w *channelWorker) {
@@ -246,18 +280,10 @@ func (m *Manager) runWorker(ctx context.Context, name string, w *channelWorker)
 				for _, chunk := range chunks {
 					chunkMsg := msg
 					chunkMsg.Content = chunk
-					if err := w.ch.Send(ctx, chunkMsg); err != nil {
+					m.sendWithRetry(ctx, name, w, chunkMsg)
-						logger.ErrorCF("channels", "Error sending chunk", map[string]any{
-							"channel": name, "error": err.Error(),
-						})
-					}
 				}
 			} else {
-				if err := w.ch.Send(ctx, msg); err != nil {
+				m.sendWithRetry(ctx, name, w, msg)
-					logger.ErrorCF("channels", "Error sending message", map[string]any{
-						"channel": name, "error": err.Error(),
-					})
-				}
 			}
 		case <-ctx.Done():
 			return
@@ -265,6 +291,63 @@ func (m *Manager) runWorker(ctx context.Context, name string, w *channelWorker)
 	}
 }
 
+// sendWithRetry sends a message through the channel with rate limiting and
+// retry logic. It classifies errors to determine the retry strategy:
+//   - ErrNotRunning / ErrSendFailed: permanent, no retry
+//   - ErrRateLimit: fixed delay retry
+//   - ErrTemporary / unknown: exponential backoff retry
+func (m *Manager) sendWithRetry(ctx context.Context, name string, w *channelWorker, msg bus.OutboundMessage) {
+	// Rate limit: wait for token
+	if err := w.limiter.Wait(ctx); err != nil {
+		// ctx cancelled, shutting down
+		return
+	}
+
+	var lastErr error
+	for attempt := 0; attempt <= maxRetries; attempt++ {
+		lastErr = w.ch.Send(ctx, msg)
+		if lastErr == nil {
+			return
+		}
+
+		// Permanent failures — don't retry
+		if errors.Is(lastErr, ErrNotRunning) || errors.Is(lastErr, ErrSendFailed) {
+			break
+		}
+
+		// Last attempt exhausted — don't sleep
+		if attempt == maxRetries {
+			break
+		}
+
+		// Rate limit error — fixed delay
+		if errors.Is(lastErr, ErrRateLimit) {
+			select {
+			case <-time.After(rateLimitDelay):
+				continue
+			case <-ctx.Done():
+				return
+			}
+		}
+
+		// ErrTemporary or unknown error — exponential backoff
+		backoff := min(time.Duration(float64(baseBackoff)*math.Pow(2, float64(attempt))), maxBackoff)
+		select {
+		case <-time.After(backoff):
+		case <-ctx.Done():
+			return
+		}
+	}
+
+	// All retries exhausted or permanent failure
+	logger.ErrorCF("channels", "Send failed", map[string]any{
+		"channel": name,
+		"chat_id": msg.ChatID,
+		"error":   lastErr.Error(),
+		"retries": maxRetries,
+	})
+}
+
 func (m *Manager) dispatchOutbound(ctx context.Context) {
 	logger.InfoC("channels", "Outbound dispatcher started")
 
@@ -343,11 +426,7 @@ func (m *Manager) RegisterChannel(name string, channel Channel) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.channels[name] = channel
-	m.workers[name] = &channelWorker{
+	m.workers[name] = newChannelWorker(name, channel)
-		ch:    channel,
-		queue: make(chan bus.OutboundMessage, defaultChannelQueueSize),
-		done:  make(chan struct{}),
-	}
 }
 
 func (m *Manager) UnregisterChannel(name string) {

pkg/channels/manager_test.go

@@ -0,0 +1,418 @@
+package channels
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/sipeed/picoclaw/pkg/bus"
+)
+
+// mockChannel is a test double that delegates Send to a configurable function.
+type mockChannel struct {
+	BaseChannel
+	sendFn func(ctx context.Context, msg bus.OutboundMessage) error
+}
+
+func (m *mockChannel) Send(ctx context.Context, msg bus.OutboundMessage) error {
+	return m.sendFn(ctx, msg)
+}
+
+func (m *mockChannel) Start(ctx context.Context) error { return nil }
+func (m *mockChannel) Stop(ctx context.Context) error  { return nil }
+
+// newTestManager creates a minimal Manager suitable for unit tests.
+func newTestManager() *Manager {
+	return &Manager{
+		channels: make(map[string]Channel),
+		workers:  make(map[string]*channelWorker),
+	}
+}
+
+func TestSendWithRetry_Success(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			return nil
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	if callCount != 1 {
+		t.Fatalf("expected 1 Send call, got %d", callCount)
+	}
+}
+
+func TestSendWithRetry_TemporaryThenSuccess(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			if callCount <= 2 {
+				return fmt.Errorf("network error: %w", ErrTemporary)
+			}
+			return nil
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	if callCount != 3 {
+		t.Fatalf("expected 3 Send calls (2 failures + 1 success), got %d", callCount)
+	}
+}
+
+func TestSendWithRetry_PermanentFailure(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			return fmt.Errorf("bad chat ID: %w", ErrSendFailed)
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	if callCount != 1 {
+		t.Fatalf("expected 1 Send call (no retry for permanent failure), got %d", callCount)
+	}
+}
+
+func TestSendWithRetry_NotRunning(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			return ErrNotRunning
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	if callCount != 1 {
+		t.Fatalf("expected 1 Send call (no retry for ErrNotRunning), got %d", callCount)
+	}
+}
+
+func TestSendWithRetry_RateLimitRetry(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			if callCount == 1 {
+				return fmt.Errorf("429: %w", ErrRateLimit)
+			}
+			return nil
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	start := time.Now()
+	m.sendWithRetry(ctx, "test", w, msg)
+	elapsed := time.Since(start)
+
+	if callCount != 2 {
+		t.Fatalf("expected 2 Send calls (1 rate limit + 1 success), got %d", callCount)
+	}
+	// Should have waited at least rateLimitDelay (1s) but allow some slack
+	if elapsed < 900*time.Millisecond {
+		t.Fatalf("expected at least ~1s delay for rate limit retry, got %v", elapsed)
+	}
+}
+
+func TestSendWithRetry_MaxRetriesExhausted(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			return fmt.Errorf("timeout: %w", ErrTemporary)
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	expected := maxRetries + 1 // initial attempt + maxRetries retries
+	if callCount != expected {
+		t.Fatalf("expected %d Send calls, got %d", expected, callCount)
+	}
+}
+
+func TestSendWithRetry_UnknownError(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			if callCount == 1 {
+				return errors.New("random unexpected error")
+			}
+			return nil
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	if callCount != 2 {
+		t.Fatalf("expected 2 Send calls (unknown error treated as temporary), got %d", callCount)
+	}
+}
+
+func TestSendWithRetry_ContextCancelled(t *testing.T) {
+	m := newTestManager()
+	var callCount int
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callCount++
+			return fmt.Errorf("timeout: %w", ErrTemporary)
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	// Cancel context after first Send attempt returns
+	ch.sendFn = func(_ context.Context, _ bus.OutboundMessage) error {
+		callCount++
+		cancel()
+		return fmt.Errorf("timeout: %w", ErrTemporary)
+	}
+
+	m.sendWithRetry(ctx, "test", w, msg)
+
+	// Should have called Send once, then noticed ctx cancelled during backoff
+	if callCount != 1 {
+		t.Fatalf("expected 1 Send call before context cancellation, got %d", callCount)
+	}
+}
+
+func TestWorkerRateLimiter(t *testing.T) {
+	m := newTestManager()
+
+	var mu sync.Mutex
+	var sendTimes []time.Time
+
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			mu.Lock()
+			sendTimes = append(sendTimes, time.Now())
+			mu.Unlock()
+			return nil
+		},
+	}
+
+	// Create a worker with a low rate: 2 msg/s, burst 1
+	w := &channelWorker{
+		ch:      ch,
+		queue:   make(chan bus.OutboundMessage, 10),
+		done:    make(chan struct{}),
+		limiter: rate.NewLimiter(2, 1),
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go m.runWorker(ctx, "test", w)
+
+	// Enqueue 4 messages
+	for i := 0; i < 4; i++ {
+		w.queue <- bus.OutboundMessage{Channel: "test", ChatID: "1", Content: fmt.Sprintf("msg%d", i)}
+	}
+
+	// Wait enough time for all messages to be sent (4 msgs at 2/s = ~2s, give extra margin)
+	time.Sleep(3 * time.Second)
+
+	mu.Lock()
+	times := make([]time.Time, len(sendTimes))
+	copy(times, sendTimes)
+	mu.Unlock()
+
+	if len(times) != 4 {
+		t.Fatalf("expected 4 sends, got %d", len(times))
+	}
+
+	// Verify rate limiting: total duration should be at least 1s
+	// (first message immediate, then ~500ms between each subsequent one at 2/s)
+	totalDuration := times[len(times)-1].Sub(times[0])
+	if totalDuration < 1*time.Second {
+		t.Fatalf("expected total duration >= 1s for 4 msgs at 2/s rate, got %v", totalDuration)
+	}
+}
+
+func TestNewChannelWorker_DefaultRate(t *testing.T) {
+	ch := &mockChannel{}
+	w := newChannelWorker("unknown_channel", ch)
+
+	if w.limiter == nil {
+		t.Fatal("expected limiter to be non-nil")
+	}
+	if w.limiter.Limit() != rate.Limit(defaultRateLimit) {
+		t.Fatalf("expected rate limit %v, got %v", rate.Limit(defaultRateLimit), w.limiter.Limit())
+	}
+}
+
+func TestNewChannelWorker_ConfiguredRate(t *testing.T) {
+	ch := &mockChannel{}
+
+	for name, expectedRate := range channelRateConfig {
+		w := newChannelWorker(name, ch)
+		if w.limiter.Limit() != rate.Limit(expectedRate) {
+			t.Fatalf("channel %s: expected rate %v, got %v", name, expectedRate, w.limiter.Limit())
+		}
+	}
+}
+
+func TestRunWorker_MessageSplitting(t *testing.T) {
+	m := newTestManager()
+
+	var mu sync.Mutex
+	var received []string
+
+	ch := &mockChannelWithLength{
+		mockChannel: mockChannel{
+			sendFn: func(_ context.Context, msg bus.OutboundMessage) error {
+				mu.Lock()
+				received = append(received, msg.Content)
+				mu.Unlock()
+				return nil
+			},
+		},
+		maxLen: 5,
+	}
+
+	w := &channelWorker{
+		ch:      ch,
+		queue:   make(chan bus.OutboundMessage, 10),
+		done:    make(chan struct{}),
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go m.runWorker(ctx, "test", w)
+
+	// Send a message that should be split
+	w.queue <- bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello world"}
+
+	time.Sleep(100 * time.Millisecond)
+
+	mu.Lock()
+	count := len(received)
+	mu.Unlock()
+
+	if count < 2 {
+		t.Fatalf("expected message to be split into at least 2 chunks, got %d", count)
+	}
+}
+
+// mockChannelWithLength implements MessageLengthProvider.
+type mockChannelWithLength struct {
+	mockChannel
+	maxLen int
+}
+
+func (m *mockChannelWithLength) MaxMessageLength() int {
+	return m.maxLen
+}
+
+func TestSendWithRetry_ExponentialBackoff(t *testing.T) {
+	m := newTestManager()
+
+	var callTimes []time.Time
+	var callCount atomic.Int32
+	ch := &mockChannel{
+		sendFn: func(_ context.Context, _ bus.OutboundMessage) error {
+			callTimes = append(callTimes, time.Now())
+			callCount.Add(1)
+			return fmt.Errorf("timeout: %w", ErrTemporary)
+		},
+	}
+	w := &channelWorker{
+		ch:      ch,
+		limiter: rate.NewLimiter(rate.Inf, 1),
+	}
+
+	ctx := context.Background()
+	msg := bus.OutboundMessage{Channel: "test", ChatID: "1", Content: "hello"}
+
+	start := time.Now()
+	m.sendWithRetry(ctx, "test", w, msg)
+	totalElapsed := time.Since(start)
+
+	// With maxRetries=3: attempts at 0, ~500ms, ~1.5s, ~3.5s
+	// Total backoff: 500ms + 1s + 2s = 3.5s
+	// Allow some margin
+	if totalElapsed < 3*time.Second {
+		t.Fatalf("expected total elapsed >= 3s for exponential backoff, got %v", totalElapsed)
+	}
+
+	if int(callCount.Load()) != maxRetries+1 {
+		t.Fatalf("expected %d calls, got %d", maxRetries+1, callCount.Load())
+	}
+}