azure-dev: Instructions file for GitHub Copilot

applyTo:

• cli/azd/extensions/**

• When accessing a Subscription from PromptSubscription(), always use Subscription.UserTenantId (user access tenant) for credential creation, NOT Subscription.TenantId (resource tenant). For multi-tenant/guest users these differ, and using TenantId causes authentication failures. The LookupTenant() API already returns the correct user access tenant.

• When adding or reviewing destructive extension commands, verify the service API contract and local cleanup behavior end-to-end: confirm whether the API supports the requested delete scope, handle empty successful delete responses, avoid redundant pre-checks that later operations already cover, and clean up any persisted local state such as conversation or session IDs. Use the resource identity persisted by deployment, including custom/adopted names, and respect ownership when deciding what to delete.

• Follow extension guidelines in: cli/azd/docs/extensions/extensions-style-guide.md. If the work violates any of these principles, include a link to the guide so the user can read it and get ahead of some of the problems.

• Reject explicitly supplied flags that cannot take effect. Use cmd.Flags().Changed("<flag>") so explicit empty values are validated rather than treated as omitted. Explicit selectors take precedence over persisted values and defaults. Name conflicting inputs in the error and use exterrors.Validation(exterrors.CodeConflictingArguments, message, suggestion) where available, otherwise follow the extension's validation-error pattern.

• Redact credentials from URLs before printing to terminal, logs, or error messages. URLs may carry credentials in the userinfo component (user:pass@host) or in the query string (SAS tokens, sig= parameters). Clear URL.User and drop RawQuery and Fragment before passing a URL to any output function, error message, or log call. redactURL in cli/azd/pkg/azdext/pagination.go and redactURLForDebug in cli/azd/extensions/azure.ai.training/pkg/client show the shape, but both only strip the query and fragment, so clear the userinfo as well. This applies to download URLs, clone URLs, registry addresses, and any URL stored in artifacts or uploaded CI outputs. Add a non-disclosure test that feeds a credential-bearing URL and asserts no sensitive portion appears in the output.

• Keep output on the injected writer when a command handler or helper receives one; do not bypass it with direct writes to os.Stdout or os.Stderr, including in debug and diagnostic paths. Extensions that do not expose a writer must follow their local AGENTS.md output conventions. See "Keep terminal output on the injected writer" in cli/azd/AGENTS.md.

• When behavior narrows, narrow the help text and doc comments with it.

• Validate locally checkable inputs and conflicts before authentication or mutations. Invalid inputs must leave project files and persisted environment values unchanged.

• Keep schema, decoding, request mapping, and runtime validation consistent for inline and $ref definitions. Reject unsupported fields instead of silently dropping authored configuration.