cli: add --provider flag to kagent install

[tjorourke]

Problem

kagent install defaults silently to OpenAI and has no way to select a different provider via the CLI. Users installing with Anthropic, Ollama, or Azure OpenAI see this confusing error with no guidance:

OPENAI_API_KEY is not set
Please set the OPENAI_API_KEY environment variable

The actual mechanism (KAGENT_DEFAULT_MODEL_PROVIDER) is undocumented and not surfaced in --help.

Solution

Add a --provider flag to kagent install that sets the provider explicitly:

ANTHROPIC_API_KEY=sk-ant-... kagent install --provider anthropic --profile demo
OPENAI_API_KEY=sk-...        kagent install --provider openAI    --profile demo
kagent install --provider ollama --profile minimal

Changes

• InstallCfg — add Provider string field
• ValidProviders() — new helper returning the accepted provider values (openAI, anthropic, azureOpenAI, ollama) used for flag validation and shell completion
• applyProviderFlag() — validates the flag value and sets KAGENT_DEFAULT_MODEL_PROVIDER so GetModelProvider() picks it up
• main.go — wire --provider flag with shell completion
• Error messages — fix stale "If model provider is openai" comments; add a hint pointing to --provider and KAGENT_DEFAULT_MODEL_PROVIDER when the key is missing and no --provider was given

Before / After

Before:

$ ANTHROPIC_API_KEY=sk-ant-... kagent install --profile demo
OPENAI_API_KEY is not set
Please set the OPENAI_API_KEY environment variable

After:

$ ANTHROPIC_API_KEY=sk-ant-... kagent install --provider anthropic --profile demo
 Installing kagent [Anthropic] ...
kagent installed successfully

Or, if the user forgets the flag:

$ kagent install --profile demo
OPENAI_API_KEY is not set
Please set the OPENAI_API_KEY environment variable
Tip: use --provider to select a different LLM provider (e.g. --provider anthropic)
     or set KAGENT_DEFAULT_MODEL_PROVIDER=anthropic before running install

[Copilot]

Pull request overview

Adds an explicit LLM provider selection to kagent install so users can avoid the implicit OpenAI default and get clearer guidance when the required API key is missing.

Changes:

• Extend InstallCfg with Provider and apply it early to override KAGENT_DEFAULT_MODEL_PROVIDER.
• Add ValidProviders() + applyProviderFlag() helper to validate provider values and drive shell completion.
• Improve missing-API-key messaging with guidance toward --provider / KAGENT_DEFAULT_MODEL_PROVIDER.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
go/core/cli/internal/cli/agent/install.go	Applies --provider precedence and enhances missing API key error guidance.
go/core/cli/internal/cli/agent/const.go	Adds provider validation helpers and env var application for the new flag.
go/core/cli/cmd/kagent/main.go	Wires the new --provider flag and shell completion into kagent install.

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[iplay88keys]

I don't think we should be setting the env var here. We are already using Viper for our CLI, so we should be able to utilize viper.MustBindEnv when we read in the config. Something like:

// Config struct - add provider
  type Config struct {
    KAgentURL    string        `mapstructure:"kagent_url"`
    Namespace    string        `mapstructure:"namespace"`
    OutputFormat string        `mapstructure:"output_format"`
    Verbose      bool          `mapstructure:"verbose"`
    Timeout      time.Duration `mapstructure:"timeout"`
    Provider     string        `mapstructure:"provider"`
  }

// Init() - add defaults and env bindings alongside existing ones
  viper.SetDefault("provider", "openAI")

  viper.MustBindEnv("provider", "KAGENT_DEFAULT_MODEL_PROVIDER")