2089 core engine (C89) on Linux and obsidian - prediction log.
Author: Claude Opus 5.5 (claude-opus-5-5). Series letter: C.
Written BEFORE writing the core or building anything. Format: ID [confidence] claim.

--- round 1, design decided (freestanding C89 core, 32-bit LCG, text save format) ---
C01 [0.55] The core compiles with gcc 11 -std=c89 -pedantic -Wall -Wextra with zero
     warnings on the first attempt.
C02 [0.35] The Python oracle agrees with the C core on 10,000 random games on the first
     run (no bug in either needing a fix).
C03 [0.85] The golden RNG/replay hashes computed on x86_64 Linux (64-bit long) match
     on obsidian (32-bit long, big-endian) without any code change.
C04 [0.60] /usr/vac/bin/c89 compiles the core and tests with no diagnostics at all.
C05 [0.50] gcc 2.95.3 -ansi -pedantic -Wall -W gives at least one warning that gcc 11 did not.
C06 [0.90] The core object built with -ffreestanding has no undefined symbols (no libc).
C07 [0.55] The core's text section is under 4 KB with xlc -O on obsidian.
C08 [0.60] The full test suite runs in under 2 s on the 604e (xlc -O).
C09 [0.30] The test suite finds at least one bug in my first draft of the core.
Mon Oct 19 02:20:52 PM MDT 2026

=== OUTCOMES (scored 2026-10-19) ===
C01 HIT      [0.55] zero warnings on the first compile, even with -Wconversion -Wshadow.
C02 HIT      [0.35] 10,000 games, 0 mismatches on the first run (21 min of Python).
C03 HIT      [0.85] GOLD_RNG 0x42F4184C and GOLD_GAMES 0xF986A2F1 identical with xlc and
     gcc 2.95.3 on obsidian.
C04 MISS     [0.60] no language diagnostics, but xlc -O prints an informational
     1500-030 (raise MAXMEM above 2048) for t89_load/t89_save and test_save.
C05 MISS     [0.50] gcc 2.95.3 -ansi -pedantic -Wall -W -Wconversion is silent too.
C06 HIT      [0.90] none at -O0/-O2/-O3/-Os.  But gcc 2.95.3 on AIX turned the struct
     assignment in t89_load into a memcpy call (fixed by copying fields).
C07 MISS     [0.55] 4,408 bytes of text (plus 252 of function descriptors).
C08 MISS     [0.60] five runs: 1.99, 2.00, 2.00, 2.00, 2.01 s.  Median 2.00, not under.
C09 MISS     [0.30] the tests found no bug in the core; the one fix the first runs
     needed was in the tests (the "other sizes" games used only 4 and 6).

Calibration:  <0.50: 1/2   0.50-0.79: 1/5   >=0.80: 2/2
Not predicted: gcc 2.95's memcpy for struct assignment; xlc and gcc both call AIX
millicode (__divus, __mull, ...), so "no undefined symbols" only holds for gcc on x86;
the 13 public names already happened to be unique in 6 case-blind characters.