Stockless 0.8.9 - new chess engine

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Stockless = Stockfish's stable C++ backbone + selectively ported Reckless ideas + a separate Stockless hybrid search policy.
Author: gaong5247-cmd

What's new?
October 20, 2026 | UCI name: Stockless v0.8.9 | Latest stable release

Stockless combines the pinned Stockfish search and NNUE framework with Stockless's threat-aware hybrid search policy. This release integrates the conservative, node-equivalent search-policy refactor and corrects the test arena's accidental default-option overrides. It is not a new Stockfish 19 binary or a claim of proven superiority over Stockfish 19.

Each ZIP contains license and third-party notices, a README, branding, the exact source commit, a SHA-256 checksum for the binary, and a JSON manifest. The default Stockfish NNUE networks are embedded by the pinned source build; they do not require a separately supplied weight file.

What's changed
UCI identity and package consistency: the engine handshake, branding manifest, package names, metadata and release tag all use v0.8.9.
Search-policy fast path: retain the existing per-node threat signal but move default Stockless policy arithmetic until after Stockfish's native shallow pruning, avoiding some calculations for moves the search already discards. Existing LMR decisions remain unchanged on the tested depth-12 bench positions, which searched 1,078,618 nodes in both the reference and candidate.
Overdrive compatibility: keep the earlier policy timing with optional desktop Overdrive, which may affect pruning decisions.
Correct match defaults: fix a duplicated test-script assignment that inadvertently launched Stockless with Aggression 112 and Overdrive ON. Correct defaults are Aggression 145 / Overdrive OFF.
Release/CI repairs: correct obsolete UCI identity checks and outdated v0.7.1 filenames in the multi-platform release workflow; verify Windows/Linux handshakes, ARM ABI, manifest entries, source commit, and hashes before publishing.
Testing and strength caveat
Under x86-64 AVX2, 1 search thread, Hash 32 MiB, 0.5+0.005 time control and the official Stockfish 8moves_v3 color-swapped opening suite:

Opponent Games W/D/L Candidate score Relative Elo, 95% interval
Prior Stockless base 512 105 / 318 / 89 51.562% +10.86 (-7.66 to +29.38)
Official Stockfish 19 256 35 / 182 / 39 49.219% -5.43 (-28.31 to +17.45)
A separate repetition gave 51.172% versus the prior Stockless base and 46.484% versus Stockfish 19. All confidence intervals include a no-difference result. These short matches do not establish a statistically confirmed Elo improvement or a Stockfish 19 win.

Several identical depth-limited CI throughput repeats varied from about -0.61% to +2.57%. No reproducible NPS gain has been established. The release does not include a claimed PGO strength improvement or the separate, experimental PR #22 lazy-threat-map patch.

Stockless 0.8.9 download   mirror


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