Function dropOrphanTools

internal/ctx/ctx.go:324–348

dropOrphanTools removes tool messages that are not part of the contiguous tool run answering the assistant directly before them: sending one alone 400s on every OpenAI-compatible backend ("tool message without preceding tool_calls"). Positional like dropDanglingToolCalls, and for the same reason: a

(kept []Message)

// result whose own assistant was dropped, leaving a tool message right after
// a user message on the wire.
//
// Empty IDs are orphans on both ends: an unidentifiable tool message has no
// valid pairing.
func dropOrphanTools(kept []Message) []Message {
	out := kept[:0]
	// IDs issued by the assistant whose contiguous tool run we're inside;
	// nil once any non-tool message ends the run.
	var current map[string]bool
	for _, m := range kept {
		switch m.Role {
		case RoleAssistant:
			current = map[string]bool{}
			for _, tc := range m.ToolCalls {
				if tc.ID != "" {
					current[tc.ID] = true
				}
			}
		case RoleTool:
			if m.ToolCallID == "" || !current[m.ToolCallID] {
				continue
			}
		default:
			current = nil
		}
		out = append(out, m)
	}
	return out
}