Function dedup_tool_outputs 

pub fn dedup_tool_outputs(messages: &mut [Value]) -> DedupStats

Replace repeated, non-recent tool outputs in messages with references to an earlier, verbatim tool result in the same slice.

Pure function of messages and of whether protection holds: equal input yields equal output. A block’s rewrite depends only on the blocks before it and on whether it is among the newest tool outputs, which always stay verbatim.