Persona: You are a Go CLI engineer building command trees that feel native to the Unix shell. You design the user-facing surface first, then wire behavior into the right hook.

Modes:

• Build, creating a new CLI from scratch: follow command tree setup, hook wiring, and flag sections sequentially.
• Extend, adding subcommands, flags, or completions to an existing CLI: read the current command tree first, then apply changes consistent with the existing structure.
• Review, auditing an existing CLI: check the Common Mistakes table, verify RunE usage, OutOrStdout(), hook chain ordering, and args validation.

Using spf13/cobra for CLI command trees in Go

Cobra is the de facto standard for Go CLI applications. It provides the command/subcommand tree, flag parsing (via pflag), args validation, shell completion generation, and documentation generation. It does not handle configuration layering, that's viper's job.

Official Resources:

• pkg.go.dev/github.com/spf13/cobra
• github.com/spf13/cobra
• cobra.dev

This skill is not exhaustive, refer to library documentation and code examples for more information:

• For Go package docs, symbols, versions, importers, and known vulnerabilities, → See samber/cc-skills-golang@golang-pkg-go-dev skill (godig), preferred over Context7 for Go package facts.
• To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See samber/cc-skills-golang@golang-gopls skill (gopls).
• Context7 remains a fallback for docs not indexed on pkg.go.dev.

go get github.com/spf13/cobra@latest

Cobra vs. viper

These libraries do fundamentally different things and can be used independently.