NamedError hides data.message: Error.message is set to the tag name #31414

Description

NamedError — the base class for the serialized error union (ProviderAuthError, UnknownError, APIError, etc.) — sets Error.message to its own tag name. Its constructor calls super(name), so every instance ends up with Error.message === Error.name.

Because Cause.pretty and Error.prototype.toString() render an error as ${name}: ${message}, this comes out as ProviderAuthError: ProviderAuthError, and the real data.message is never shown.

Steps to reproduce

1. Construct any NamedError, e.g. new ProviderAuthError({ providerID, message: "invalid token" }).
2. Render it via Cause.pretty(Cause.fail(err)) or err.toString().
3. Observe "ProviderAuthError: ProviderAuthError" — the "invalid token" detail is hidden.

OpenCode version

dev (current)