fix(opencode): cap Retry-After hint at 24h for usage refresh backoff

backend/internal/service/opencode_go_usage.go

@@ -1000,8 +1000,17 @@ func decodeOpenCodeGoUsageSnapshot(extra map[string]any) *OpenCodeGoUsageSnapsho
 
 // nextOpenCodeGoUsageDelay computes the not-before delay for the next refresh:
 // interval * 2^min(failureCount-1, 6) capped at 24h, ±10% jitter capped at 5min,
-// never below a Retry-After hint or one minute.
+// never below a Retry-After hint or one minute. The hint is honored over the
+// local backoff but clamped to the same 24h ceiling: it arrives over a network
+// path we do not control (upstream CDN, account proxy), and an unbounded value
+// would freeze a group's auto refresh indefinitely.
 func nextOpenCodeGoUsageDelay(intervalMinutes, failureCount int, retryAfterDuration time.Duration) time.Duration {
+	if retryAfterDuration < 0 {
+		retryAfterDuration = 0
+	}
+	if retryAfterDuration > opencodeGoUsageMaxDelay {
+		retryAfterDuration = opencodeGoUsageMaxDelay
+	}
 	minimumDelay := retryAfterDuration
 	base := time.Duration(intervalMinutes) * time.Minute
 	if base < opencodeGoUsageMinIntervalMinutes*time.Minute {

backend/internal/service/opencode_go_usage_test.go

@@ -403,11 +403,39 @@ func TestNextOpenCodeGoUsageDelayBackoff(t *testing.T) {
 	delay = nextOpenCodeGoUsageDelay(15, 0, 2*time.Hour)
 	require.GreaterOrEqual(t, delay, 2*time.Hour)
 
+	// a hint beyond the 24h ceiling is clamped, never adopted verbatim
+	delay = nextOpenCodeGoUsageDelay(15, 0, 48*time.Hour)
+	require.GreaterOrEqual(t, delay, 23*time.Hour+55*time.Minute)
+	require.LessOrEqual(t, delay, 24*time.Hour+5*time.Minute)
+
 	// floor of one minute
 	delay = nextOpenCodeGoUsageDelay(5, 0, 0)
 	require.GreaterOrEqual(t, delay, time.Minute)
 }
 
+func TestOpenCodeGoUsageRefreshClampsHugeRetryAfter(t *testing.T) {
+	now := time.Now().UTC()
+	account := openCodeGoUsageAccount(7)
+	repo := &openCodeGoUsageTestRepo{accounts: map[int64]*Account{7: account}}
+	stub := &openCodeGoUsageHTTPStub{
+		status: http.StatusTooManyRequests,
+		header: http.Header{"Retry-After": []string{"99999999"}},
+	}
+	svc := newOpenCodeGoUsageTestService(t, repo, stub, &upstreamBillingProbeSettingRepo{})
+	svc.now = func() time.Time { return now }
+
+	state, err := svc.Refresh(context.Background(), 7)
+	require.NoError(t, err)
+	require.Equal(t, OpenCodeGoUsageStatusFailed, state.Snapshot.Status)
+	require.Equal(t, http.StatusTooManyRequests, state.Snapshot.HTTPStatus)
+	require.Equal(t, "http_error", state.Snapshot.LastError)
+
+	maxExpected := now.Add(24*time.Hour + 5*time.Minute)
+	minExpected := now.Add(23*time.Hour + 55*time.Minute)
+	require.True(t, state.Snapshot.NextRefreshAt.Before(maxExpected.Add(time.Second)))
+	require.True(t, state.Snapshot.NextRefreshAt.After(minExpected.Add(-time.Second)))
+}
+
 func TestOpenCodeGoUsageManualRefreshThrottle(t *testing.T) {
 	now := time.Now().UTC()
 	account := openCodeGoUsageAccount(7)