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Don't salvage an aborted prefill as a continuation endpoint under MTP (fixes HTTP 500 'published MTP checkpoint is not materializable') #4

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Merged
iamwavecut merged 2 commits into from
Oct 3, 2026
Merged

Don't salvage an aborted prefill as a continuation endpoint under MTP (fixes HTTP 500 'published MTP checkpoint is not materializable') #4

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7ea2715
qwen3_5: do not salvage an aborted prefill under MTP
hermes-pimentel Sep 29, 2026
064ca42
qwen3_5: refuse an MTP salvage exactly when the planner cannot reuse it
iamwavecut Oct 3, 2026
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7 changes: 7 additions & 0 deletions src/models/qwen3_5/program/transactions/commit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -732,6 +732,13 @@ bool ProgramImpl::salvage_continuation(SequenceState& state, RequestControl& req
state.dflash_context_frontier < frontier) {
return false;
}
// The next request reuses this endpoint under MTP only with the tail hidden state and the
// MTP KV up to frontier - 1 (request_plan.cpp). A prefill cut before its last chunk has no
// tail hidden state, so the conversation resumes from its last captured checkpoint.
if (speculative_backend == SpeculativeBackend::Mtp &&
(!state.tail_hidden_valid || state.mtp_kv_valid + 1 < frontier)) {
return false;
}
} else if (lifecycle == Lifecycle::Active || lifecycle == Lifecycle::Finishable) {
frontier = state.execution_frontier;
if (frontier < kSalvageMinFrontier || state.text_kv_valid != frontier) { return false; }
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