Model Profile · Round 01
Claude Opus 4.6
Anthropic · proprietary · 200K ctx
ReliableReliability runner-up. Top-2 on agency, complete failure-mode coverage.
Composite Score
88.1
/100 · canonical
Arena ELO (R1)
—
joined post-R01
Multi-Turn ELO (R2)
1568
±100 · n=40
Reliability Rank
#2
avg 2.9
▌ Section 02 · The Lede
What this model is for.
Opus 4.6 is the completist Anthropic option in Round 02 — every adversarial axis the benchmark tests has at least three sessions on it, where its successor 4.7 is still missing F3 (lore) and F8 (momentum) coverage. The numbers it does have are top tier: F2 POV/tense at 4.47 (highest in pool), F3 lore at 4.60 (highest in pool), and a fatal-flaw rate of 0.29 per session — half of Opus 4.7's. The trade-off is engagement: Opus 4.6 reads denser, sits at #2 on multi-turn ELO behind 4.7 (1568 vs 1627), and generates twice as slowly (20s vs 10s median). Round 02 holds it as the reliability runner-up at the same price.
▌ Section 03 · At a Glance
Cross-test position
Claude Opus 4.6 holds #2 in Multi-Turn, #2 in Rubric, #2 in Adversarial and #3 in Composite. Sits at #20 on Cost · Latency — the caveat to watch.
▌ Section 04 · Strength & Weakness
Where it shines. Where it stumbles.
▲ Strength
Top-2 on agency respect (4.55/5) — and complete failure-mode coverage where 4.7 is missing F3/F8 axes. Lowest fatal-flaw rate of any Opus model.
▼ Weakness
Highest phrase repetition in the Anthropic family (0.076 vs population 0.049). Slowest generation among the top-5 multi-turn finalists at 20s median.
▌ Section 05 · Failure Modes
Per-axis breakdown.
Six adversarial probes per session, twenty sessions per model, judged by Sonnet 4 against a fixed rubric. Higher score = the model handled the failure mode better. Bars below show the mean across sessions; the black tick marks the population mean (4.20). Right column shows mean and rank within the rp-bench pool.
F1 · Agency
Doesn't write your character's actions
#2
F2 · POV / Tense
Holds 2nd-person, present-tense narration
#1
F3 · Lore
Doesn't break worldbuilding
#1
F8 · Momentum
Pushes scene forward when user goes passive
#9
F12 · Instruction Drift
Keeps to the system prompt
#2
F13 · Context Attention
Holds character cards 50+ turns deep
#4
“Every axis tested. Slowest in the Opus family. A reliability profile you can trust, end-to-end.”
— Round 02 verdict · Completist pick
▌ Section 06 · Subjective Dimensions
Engagement · Voice · Collaboration.
All three dimensions scored 1–5 by Sonnet 4 LLM-judge across twenty 12-turn multi-turn sessions. The same battery feeds the failure-mode rubric above — these are the subjective half of that judgment.
▌ Section 07 · Behavioral Metrics
How it writes.
Quantitative signals from the same 20 multi-turn sessions, compared against the population mean across all 11 models.
Avg words / turn
534↑
pop avg 265 · +102%
Unique-word ratio
0.551↓
pop avg 0.655 · -16%
Repetition score
0.076↑
pop avg 0.049 · +55%
▌ Section 08 · Flaw Hunter
Adversarial probe score.
Score of 100 minus deductions across 22 fail-mode flag types on adversarial 12-turn sessions. Higher = fewer flaws caught. Population range across the round is 12.8–46.9.
▌ Score breakdown
Mean 40.9
Median 42.0
Fatal/sess 0.29
Major/sess 6.82
▌ Top flaws caught
purple_proserecycled_descriptionnarrating_emotions
▌ Section 09 · Sample Responses
Highest- and lowest-rated turns.
▌ Pending Round 02
Best- and worst-rated sample responses ship with the raw-vote endpoint in Round 02. When that lands, this section will surface the model’s highest- and lowest-scoring blind-arena turns side by side, scored on the same rubric the leaderboard uses.
▌ Round 01 verdict
Opus 4.6 is the model you pick when you need the full reliability matrix — every axis covered, every probe answered. It loses Round 02's headline ELO race to 4.7 by ~60 points, but the gap fits inside the confidence interval at this sample size. Pick 4.6 over 4.7 if F3 (lore) or F8 (momentum) coverage matters to you; pick 4.7 if you want the fastest top-tier generation.
▌ Section 10 · Compare & Drill
Stack it against another model.
Profile · Claude Opus 4.6 · Round 01