dagger/dagger · error

client %q already exists with different host service proxy c

Error message

client %q already exists with different host service proxy client %q

What it means

When an existing initialized client is reattached with a HostServiceProxyClientID that differs from the one already recorded, the server rejects the request. A client's host-service proxy binding must be stable; conflicting bindings would misroute host service traffic (e.g. secret socket access). An empty stored value is back-filled instead of erroring.

Source

Thrown at engine/server/session.go:1329

			return nil, nil, fmt.Errorf("client %q already exists with different secret token", clientID)
		}

		// for nested clients running the dagger cli, the session attachable
		// connection may not have all of the client metadata yet, so we
		// fill in some missing fields here that may be set later by the cli
		if client.clientMetadata.AllowedLLMModules == nil {
			client.clientMetadata.AllowedLLMModules = opts.AllowedLLMModules
		}
		if opts.LoadWorkspaceModules {
			client.clientMetadata.LoadWorkspaceModules = true
		}
		if opts.HostServiceProxyClientID != "" {
			switch client.hostServiceProxyClientID {
			case "":
				client.hostServiceProxyClientID = opts.HostServiceProxyClientID
			case opts.HostServiceProxyClientID:
			default:
				return nil, nil, fmt.Errorf("client %q already exists with different host service proxy client %q", clientID, client.hostServiceProxyClientID)
			}
		}
		if opts.SingleQuery {
			client.clientMetadata.SingleQuery = true
		}
		if client.clientMetadata.WorkspaceModuleScope == "" {
			client.clientMetadata.WorkspaceModuleScope = opts.WorkspaceModuleScope
		}
		if opts.SuppressCompatWorkspaceWarning {
			client.clientMetadata.SuppressCompatWorkspaceWarning = true
		}
		if client.clientMetadata.Workspace == nil && !client.workspaceLoaded {
			if workspaceRef, ok := workspaceRefFromClientMetadata(opts.ClientMetadata); ok {
				ref := workspaceRef
				client.clientMetadata.Workspace = &ref
			}
		}
		if client.clientMetadata.WorkspaceEnv == nil && !client.workspaceLoaded {

View on GitHub (pinned to 82ba2681db)

Solutions

1. Ensure each client ID consistently maps to one host-service proxy client
2. Use a distinct client ID for connections that use a different proxy
3. Check nested client metadata propagation so the original proxy client ID is preserved

Example fix

// before
reconnect(existingClientID, newProxyClientID)
// after
reconnect(newClientID, newProxyClientID)

// ensure proxy client ID is derived from the same client identity
if existingProxyID != "" && newProxyID != existingProxyID {
    clientID = newClientID() // use a fresh client ID for a different proxy
}

if strings.Contains(err.Error(), "different host service proxy client") {
    clientID = newClientID(); reconnect(clientID, proxyID)
}

When it happens

Trigger: Calling getOrInitClient for an existing client where opts.HostServiceProxyClientID is non-empty and != client.hostServiceProxyClientID (stored value also non-empty).

Common situations: A nested exec reuses a parent's client ID but carries its own proxy client ID; misconfigured proxy wiring in module function calls; replayed requests through a different proxy.

Related errors

• proxy conn pool failed: %w
• failed to get engine client: %w
• only the main client can call this function
• client path is required
• SDK name is required

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/57422af8da4c18b9. Report an issue: GitHub.