Reuse a per-session context across chat exchanges - #223
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Every generation created a fresh llama_context and prefilled the full rendered conversation from token zero, so multi-turn chat cost grew with the square of the transcript and long conversations spent most of their time re-decoding history. Keep one context alive per session for plain chat generations. Each exchange tokenizes the rendered prompt, keeps the longest token prefix shared with the context's recorded state, removes diverged state with llama_memory_seq_rm, and decodes only the remainder. Backends that cannot rewind, such as recurrent models, fall back to clearing memory and decoding the full prompt, and appends need no rewind on any backend. The final prompt token is always re-decoded so sampling has fresh logits, generated tokens extend the recorded state as they decode, and any generation error discards the cached context. Structured generation, image prompts, and encoder models keep single-use contexts, and clearCachedContext lets consumers free the cached state under memory pressure. Adds a live test asserting prefix reuse on the second turn of a session. (cherry picked from commit 49a2acf)
This was referenced Sep 10, 2026
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@james-333i's #215, cherry-picked onto
mainwith his authorship intact. GitHub couldn't squash #215 after #213 and #214 landed because it rewrites lines those PRs added, so this PR carries the same commit on a branch based on the currentmain.Original description and review discussion: #215.