Reverse Engineering Reveals Codex CLI Compaction is Just an LLM Summarization Call
a_karvonen · x · 2026-08-12
A developer has investigated how the open-source Codex CLI context compaction works, finding strong evidence that the process is simply an API call asking to "create a handoff summary of this conversation."
For non-Codex models, the CLI compacts context locally: an LLM summarizes the conversation using a specific compaction prompt. The resulting compacted context is then used in subsequent API calls.
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