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Titanium Engine — Session State Handoff

Purpose: Carry context into a new chat without re-discovery.
Last updated: Jun 2026 — O1 pawn LUT is production (cold-start built; binary 2.8MB→1.0MB), perft d5/d6 gates added, gen13 ACE port landed (acev13/).

Where we are

Layer Status
Movegen Closed. Shift walls + O1Lookup pawns (production default — perft-proven fastest at d4/d5); shift/scalar retained as bench/test alts (docs/MOVEGEN.md).
Perft Gates exact. Bench d3 ~210–240M nps (Zobrist §A on main).
Search Pure ID negamax + aspiration + adaptive LMR + qsearch + TT + CAT v3 prune.
ACE v11 port (ace/, pathfix gen11_ghi) and v13 port (acev13/, ACEV13.html) — gen13 inlines certify_win.js, so the certificate solver runs (eval floor + last-wall refutation gate). CLI: --engine ace-v13[-ti].
Tables Pawn O1 tables built at cold start (movegen::o1::runtime, ~0.1s); embed-tables feature bakes them in for prewarmed builds. Binary 2.8MB→1.0MB.
Eval Path-distance + CAT; opening depth still shallow.

Movegen — do not grind further

Single-thread only. No GPU. No movegen multithreading.

Depth Nodes Notes
3 2_062_264 CI gate
4 247_569_030 Stress oracle
5 28_837_934_502 sub-12s, public record (PERFT5_STARTPOS)
6 3_257_436_276_501 full enumeration (PERFT6_STARTPOS)

Next perf wins are not movegen: L3 in wall-heavy search, eval cache — see docs/MOVEGEN-HANDOFF.md. §A (Zobrist/Undo) merged on main.

Architecture snapshot

engine/src/
├── core/board.rs          Board, Move, zobrist, make/unmake
├── movegen/
│   ├── legal.rs           legal moves, lazy WallTrialCtx, O1Lookup default
│   ├── pawn_bits.rs       pawn variants (bench/tests)
│   └── o1/
│       ├── lookup.rs      wall_masks(), shift L2/TOPO; pawn O1 LUT hot path
│       ├── gen/           table-compute (single source of truth, shared w/ emitter)
│       ├── runtime.rs     cold-start PawnTables + OnceLock tables() + prewarm()
│       └── embedded.rs    baked consts (only under `--features embed-tables`)
├── acev13/                gen13 ACE port (game/net/race/search/certify/session)
├── path/parallel.rs       u128 flood + bit theft (L3)
├── search/alphabeta.rs    ID negamax, LMR, CAT prune
└── util/perft.rs          perft_fast, bulk d1, timed d4 test

Regression commands

cd engine
cargo test --release
cargo test --release perft_depth4_matches_oracle -- --ignored --nocapture
cargo run --release --bin titanium -- perft 4
cargo run --release --bin titanium -- bench 3 10
cargo bench --bench perft_pawn_modes

Next priorities (Fable / search)

  1. Make/unmake + Zobrist — profile and slim Undo (see MOVEGEN-HANDOFF.md §A)
  2. Eval function — dual BFS distance, wall value, mobility
  3. Per-node BFS cache in search eval
  4. Completeness program — invariant hash collision hunt (batch oracle)
  5. Opening depth — LMR / replay validation

Video / docs index

Doc Content
MOVEGEN.md Production movegen (current)
MOVEGEN-HANDOFF.md Fable handoff
video/PERFT-BENCHMARKS.md Perft gates
video/PERFT-OPTIMIZATIONS.md Historical discovery log
video/11-search-hardening.md Negamax/CAT session