Function demoteSystemMessages

internal/ctx/ctx.go:227–234

demoteSystemMessages rewrites every system-role message in the packed history to a user message. buildMessages always prepends the embedded system prompt as wire element 0, so any system message Pack returns is a SECOND, non-leading system message, which strict OpenAI-compat backends reject outright

(kept []Message)

// legal everywhere. Must run AFTER anchorUserMessage: a demoted nudge would
// otherwise masquerade as a surviving user message and suppress the original-task
// anchor. Mutates only the copied kept slice, never history.
func demoteSystemMessages(kept []Message) []Message {
	for i := range kept {
		if kept[i].Role == RoleSystem {
			kept[i].Role = RoleUser
		}
	}
	return kept
}

// newestToolGroup returns the assistant that issued the newest tool result