CoalBoard solo-vs-board results—strong-solo and weak-solo, mirrored (2026-07-03)

Measured: 2026-07-03 · CoalBoard v1.5.5 (the skill installed at run time) · two arms on two platforms: Claude Code / Opus 4.8 (strong solo) and Antigravity / Gemini 3.5 Flash (weak solo) · the 5 tasks.md error-not-allowed tasks, judge-run scoring per README.md.

TL;DR: Opus 4.8: solo 4/5 · board 5/5—a strong solo already catches the four reasoning traps; the board's irreducible win is T3, the version-sensitive fact (run-the-check beats training-stale memory). Gemini 3.5 Flash: solo ~4/15 (27%) · board 5/5—a weak solo misses reasoning traps too, so the board recovers ALL of them. The board's margin scales inversely with solo strength; T3 is the win at both ends. Board = solo + ground-truth execution, not an omniscient LLM.

The paired result

Base model (solo arm)	Solo	Board	Board's added value
Opus 4.8 (strong)	4/5 (T3 miss: committed stale Node 22, 0/3)	5/5	small—only T3, the external fact
Gemini 3.5 Flash (weak)	~4/15 (27%) (every task ≤1/3)	5/5	large—all four reasoning traps + T3

The single task the board wins regardless of base model is T3: no model reasons its way past a training-cutoff gap; only the board's RUN-the-check step (a live fetch—Node 24, EOL 2028-04-30, cited) does. On reasoning traps (T1 crypto / T2 compound / T4 race / T5 headings) the board's edge exists only where the solo model is weak.

Full runs (the raw, dated records)

• Claude Code (Opus 4.8), solo-vs-board: results/onoff-claude-code-2026-07-03.md—per-task table, K-runs, the honest "margin narrows as the base model strengthens" analysis, run log in results/onoff/.
• Antigravity (Gemini 3.5 Flash), solo-vs-board: results/antigravity-onoff-2026-07-03.md—per-task M/3 runs; golds independently re-verified (no fabrication).
• Earlier board-reliability runs (2026-06-19, weaker/mixed solo era): results/claude-code.md (board 10/10 vs un-primed solo ~13/20) · results/antigravity.md + results/antigravity-board-raw.md (AG solo 1/5 → board 4/5, incl. the live correlated-blind-spot demo). Kept as history; the 2026-07-03 pair above supersedes them as the current headline.

Honest scope

Small n (K=1–3 per cell, majority verdicts—a direction, not a rate). The Claude Code arm is same-family on both sides (Opus lenses share Opus blind spots—the correlated-blind-spot ceiling applies; the board's reasoning-trap coverage cannot exceed what its lenses can see). The T3 gold is time-varying—re-fetch nodejs.org / endoflife.date to re-score. A 5-task sample, not a guarantee: the board's honest claim stays bounded-cost + zero-breakage + improved correctness, never a defect-rate number.