microsoft/aspire · error · InvalidOperationException

The connection string

Error message

The connection string '{ConnectionName}' contains both '{DeploymentKey}' and '{ModelKey}' keys. Either of these may be specified, but not both.

What it means

GetRequiredDeploymentName throws when the resolved connection string contains both a Deployment key and a Model key. The library cannot decide which identifier to target, so the connection string must contain exactly one of the two.

Solutions

Remove either the Deployment= or the Model= key from the connection string so only one remains
Standardize on Model= for OpenAI endpoints and Deployment= for Azure OpenAI endpoints
Keep the value in the config section instead if both notions are needed

Example fix

// before
"ConnectionStrings:openai": "Endpoint=https://api.openai.com;Key=sk-...;Deployment=gpt-4o;Model=gpt-4o"
// after
"ConnectionStrings:openai": "Endpoint=https://api.openai.com;Key=sk-...;Model=gpt-4o"

Defensive patterns

Strategy: validation

Validate before calling

var parts = new System.Data.Common.DbConnectionStringBuilder { ConnectionString = cs };
bool hasDeployment = parts.ContainsKey("Deployment");
bool hasModel = parts.ContainsKey("Model");
if (hasDeployment && hasModel)
    throw new InvalidOperationException("Connection string may contain Deployment or Model, not both.");

Try / catch

try
{
    builder.AddOpenAIClient("openai");
}
catch (InvalidOperationException ex) when (ex.Message.Contains("both 'Deployment' and 'Model'"))
{
    logger.LogError(ex, "OpenAI connection string has conflicting Deployment/Model keys.");
    throw;
}

Prevention

Standardize on Model= for OpenAI and Deployment= for Azure OpenAI
Validate connection strings with a config linter before deployment
Avoid merging connection-string fragments from multiple environments

When it happens

Trigger: Providing a connection string like "Endpoint=https://x;Key=k;Deployment=gpt4o;Model=gpt4o" to AddOpenAIClient and resolving a deployment name from it — both keys present simultaneously.

Common situations: Copy-pasting Azure OpenAI style strings (Deployment=) and OpenAI style strings (Model=) into one connection string; merging environment-specific connection strings; template concatenation accidentally including both keys.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/cd213ec83816573a. Report an issue: GitHub.

Appendix: source

Thrown at src/Components/Aspire.OpenAI/AspireOpenAIClientBuilder.cs:72

    /// </summary>
    public virtual string ConfigurationSectionName => ServiceKey is null ?
        AspireOpenAIExtensions.DefaultConfigSectionName :
        $"{AspireOpenAIExtensions.DefaultConfigSectionName}:{ServiceKey}";

    internal string GetRequiredDeploymentName()
    {
        string? deploymentName = null;

        var configuration = HostBuilder.Configuration;
        if (configuration.GetConnectionString(ConnectionName) is string connectionString)
        {
            // Some hosting solutions require named deployments, while others identify the target directly by model name.
            var connectionBuilder = new DbConnectionStringBuilder { ConnectionString = connectionString };
            var deploymentValue = ConnectionStringValue(connectionBuilder, DeploymentKey);
            var modelValue = ConnectionStringValue(connectionBuilder, ModelKey);
            if (deploymentValue is not null && modelValue is not null)
            {
                throw new InvalidOperationException(
                    $"The connection string '{ConnectionName}' contains both '{DeploymentKey}' and '{ModelKey}' keys. Either of these may be specified, but not both.");
            }

            deploymentName = deploymentValue ?? modelValue;
        }

        if (string.IsNullOrEmpty(deploymentName))
        {
            var configSection = configuration.GetSection(ConfigurationSectionName);
            deploymentName = configSection[DeploymentKey];
        }

        if (string.IsNullOrEmpty(deploymentName))
        {
            throw new InvalidOperationException($"The deployment could not be determined. Ensure a '{DeploymentKey}' or '{ModelKey}' value is provided in 'ConnectionStrings:{ConnectionName}', or specify a '{DeploymentKey}' in the '{ConfigurationSectionName}' configuration section, or specify a '{nameof(deploymentName)}' in the call.");
        }

        return deploymentName;

View on GitHub (pinned to 25830f84bd)