The preflight trigger charged reasoning/reasoning_content on every assistant message while the tail-budget walks charged newest-turn-only (#73624), so reasoning-heavy codex_responses sessions fired compaction forever while the walk protected everything (middle_window_tokens=0, no_progress every turn, each attempt a full aux summarization).
Wire truth: the codex_responses input builder never ships the text thinking keys (encrypted codex_reasoning_items carry the chain and were already charged unconditionally by both sides), so the trigger overcounted reality; echo-back chat-completions families (DeepSeek/Kimi/MiMo thinking mode) replay stored reasoning_content on every turn, so there the walk undercounted. New single wire-truth predicate message_sanitization.stale_thinking_reaches_wire() now drives BOTH sides: trigger estimates exclude stale thinking on non-echo routes; tail/prune walks charge it on echo routes.
Also: reasoning/reasoning_content double-count fixed in both estimators (wire ships at most one; +53% overcount vs provider prompt_tokens per issue comment), and the commit-layer no_progress path now arms the structural no-op backoff so an unchanged-transcript compaction cannot re-fire every turn (defense in depth; overlaps the #96775 re-entry class).
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