github/copilot-sdk · error

failed to set auto tier

Error message

failed to set auto tier: %w

What it means

Session.SetAutoTier changes the Auto routing preference via s.RPC.Model.SwitchAutoTier without switching models. This error wraps any failure of that RPC — an invalid AutoTier value, a runtime that doesn't support auto-tier routing, or a transport failure.

Solutions

1. Confirm the AutoTier value is one supported by the running runtime version
2. Inspect the wrapped error for the runtime's rejection reason
3. Upgrade the runtime/CLI if auto-tier support was added later
4. Fall back to SetModel with an explicit model when auto-tier is unavailable

Example fix

// before
result, err := session.SetAutoTier(ctx, &AutoTierHigh)
// after
result, err := session.SetAutoTier(ctx, &AutoTierHigh)
if err != nil {
    log.Printf("set auto tier failed, falling back to explicit model: %v", err)
    err = session.SetModel(ctx, defaultModel, defaultProvider)
}

if autoTier != nil && *autoTier != "high" && *autoTier != "low" {
    return errors.New("unsupported auto tier value")
}

result, err := session.SetAutoTier(ctx, tier)
if err != nil {
    log.Printf("auto tier unavailable: %v — using explicit model", err)
    return session.SetModel(ctx, fallbackModel, fallbackProvider)
}

When it happens

Trigger: Calling Session.SetAutoTier(ctx, autoTier) when `Model.SwitchAutoTier` rejects the request (unsupported tier value, feature unavailable in the running runtime) or the transport fails.

Common situations: Passing an AutoTier constant not recognized by an older runtime; invoking auto-tier on a deployment where the routing feature is disabled; stale session after reconnect.

Understand the failure class

Background: "API request failed": what wrapped HTTP errors from external APIs mean and how to find the real cause — this error's family across 29 libraries.

Related errors

• failed to set model
• decode elicitation schema property
• failed to abort session
• failed to disconnect session
• failed to get events

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/ac2bcc8229f6de84. Report an issue: GitHub.

Appendix: source

Thrown at go/session.go:2041

// Only the most recent request survives: issuing a new request replaces any earlier one
// that has not yet been claimed by a turn.
//
// Pass nil to return to the provider's default Auto routing.
//
// Experimental: SetAutoTier is part of an experimental Auto routing surface and
// may change or be removed.
//
// Example:
//
//	tier := copilot.AutoTierIntelligence
//	result, err := session.SetAutoTier(context.Background(), &tier)
//	if err != nil {
//	    log.Printf("Failed to set auto tier: %v", err)
//	}
func (s *Session) SetAutoTier(ctx context.Context, autoTier *AutoTier) (*rpc.ModelSwitchAutoTierResult, error) {
	result, err := s.RPC.Model.SwitchAutoTier(ctx, &rpc.ModelSwitchAutoTierRequest{AutoTier: autoTier})
	if err != nil {
		return nil, fmt.Errorf("failed to set auto tier: %w", err)
	}

	return result, nil
}

type LogOptions struct {
	// Level sets the log severity. Valid values are [rpc.SessionLogLevelInfo] (default),
	// [rpc.SessionLogLevelWarning], and [rpc.SessionLogLevelError].
	Level rpc.SessionLogLevel
	// Ephemeral marks the message as transient so it is not persisted
	// to the session event log on disk. When nil the server decides the
	// default; set to a non-nil value to explicitly control persistence.
	Ephemeral *bool
}

// Log sends a log message to the session timeline.
// The message appears in the session event stream and is visible to SDK consumers
// and (for non-ephemeral messages) persisted to the session event log on disk.

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