# Capture-v1 libhft candidate: implementation and pending qualification 2026-10-17. Source checkpoint only. No compilation, native pair or timing grade is claimed for this candidate. While the final llfix timing-controller functional job waits behind existing exclusive queues and shared conformance, the [separate libhft profile](../../bench/llfix_reference/PROFILE_CAPTURE_LIBHFT.md) now implements the next functional candidate. Its three-file source checkpoint is `34c250c392fb5d31582cd119cdc63c8a9dbf5d0c`, preserved on `s/codex-llfix-capture-libhft-source-20261017-v1`. ## Policy finding Reading the actual bundled llfix1.0.7 archive at upstream `165cc999fa283a4ead17a7b935c5d3f850fec851` shows: - `fix_session.h` opens the sequence store before the conditional message-journal initialization. `max_serialised_file_size=0` does not disable sequence storage. - `electronic_trading/session/sequence_store.h` updates two32-bit values in a mapped file. Its cold save/destructor flushes the mapping. - libhft `NullStore` would omit that retained storage work. The candidate instead selects the production pro mmap store with `PersistMessages=N` and checkpoint durability; its production lifecycle saves zero-length sequence markers. The formats and hot-path work still differ: numeric overwrites versus committed empty records/index updates, and libhft prepares its marker before send. They are explicit implementation costs, not benchmark substitutes for the stores. No SDK implementation or source byte was changed to obtain this profile. ## Implementation The sender preserves the original2,048-entry application cache, reference values, millisecond times and two parties. Public production composition/send APIs use the real session, pro mmap lifecycle and production TCP socket. A transport decorator delegates the actual send/retry and observes its result with the exact unchanged ten-frame capture-v1 tap. No frame copies continue after that prefix. The unchanged source-qualified llfix receiver independently converts actual fields and groups, with contiguous owner and partitioned value folds. The controller requires bilateral capture, receiver warmup completion, actual native identities and all-thread17/16 placement, complete raw series and exact cold replay. Every production mmap record must have zero payload, contiguous sequence and a valid commit; actual inbound checkpoint, counts, cursor and64MiB file size must agree. No per-message flush is introduced. Final checkpoints happen outside measurement. An explicit Git-object materializer checks the SDK archive's complete regular file roster, modes/sizes and every Git blob before writing its fresh directory. It uses no checkout/index/ref mutation or enclosing private SDK fallback. The selected source pin is `a697b542bebca49f86a5b070fb1f29d48a675948`,215 files and21,365,232 bytes. The queued build reads those already available immutable objects on HP; it does not pull or alter the checkout used by another session. Four local controls pass, zero skips: archive substitutions/unsafe members, private-source refusal, corrupted/nonempty sequence markers, and full-width raw/plot-clamp agreement. Actual compilation and tiny/full functional execution are queued high-priority on HP under `isol`, shared work allowed. The prior waiting jobs and running conformance are unchanged. Original failures, if any, will be retained in their own attempt rather than overwritten. ## Open gates The planned compiler is Clang21/C++23, while the frozen llfix sender and receiver are GCC11/C++17. This is functional work, not a matched compiler comparison. Ordinary localhost proof also cannot qualify a physical Onload run. Compilation, actual tiny/full pairs and cold proof remain pending, followed by matching toolchain/physical/quiet qualification before any timing comparison. The llfix timing-controller v3 job remains queued; no new timing job, quiet preflight, compact latency result or CDF is created in this sitting. The pending whole-host HP quiet-window request remains unanswered. Stage2 adapters, shared clock/framework/build helpers, fullbench controllers, all older frozen inputs, installed data generations and host policy remain unchanged. Only HP was contacted. ## Later qualification in this sitting The [continuation](RECORD_2026-10-17_llfix-capture-common-toolchain.md) records the completed exact HP v3 controller and candidate-v1 functional qualifications. The pending status above describes this original implementation checkpoint; no timing or physical candidate grade is inferred.