Claude Opus 4 - NC Bench

claude-opus-4-20250514

Claude Opus 4

via anthropic

Release Date

May 22nd, 2025

Context Size

200k

Reasoning

Benchmark Cost

$69.41

Speed

–

Subcategories

Bad Writing Habits

Detects common prose quality anti-patterns in AI-generated creative writing, including passive voice, past progressive overuse, weak dialogue tags, filter words, purple prose, cliches, AI-ism words/adverbs/names, and more.

Scenario	#1	#2	#3	#4	#5	Total
Detailed Writing Rules
Fantasy: entering an ancient ruin Creative Writing Hallucination	91	87	85	79	77	84%
Horror: alone in an eerie place at night Creative Writing Hallucination	90	88	87	85	84	87%
Literary fiction: old friends reunite Creative Writing Hallucination	94	94	92	90	89	92%
Mystery: examining a crime scene Creative Writing Hallucination	92	91	89	86	85	88%
Romance: separated couple reunites Creative Writing Hallucination	94	89	86	85	85	88%
Thriller: chase through city streets Creative Writing Hallucination	91	89	88	85	78	86%
Detailed Writing Rules						87.49%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	78	77	73	73	69	74%
Horror: alone in an eerie place at night Creative Writing Hallucination	82	79	78	78	77	79%
Literary fiction: old friends reunite Creative Writing Hallucination	86	84	83	78	77	82%
Mystery: examining a crime scene Creative Writing Hallucination	85	85	84	83	77	83%
Romance: separated couple reunites Creative Writing Hallucination	88	86	84	82	82	85%
Thriller: chase through city streets Creative Writing Hallucination	87	85	80	78	76	81%
genre						80.54%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	80	78	78	77	72	77%
Horror: alone in an eerie place at night Creative Writing Hallucination	86	86	85	79	76	83%
Literary fiction: old friends reunite Creative Writing Hallucination	85	84	84	82	80	83%
Mystery: examining a crime scene Creative Writing Hallucination	85	85	81	81	80	82%
Romance: separated couple reunites Creative Writing Hallucination	89	87	86	86	82	86%
Thriller: chase through city streets Creative Writing Hallucination	89	85	84	83	82	85%
Novelcrafter Default Prompt						82.56%
83.53%

Codex Extraction

Evaluates a model's ability to extract structured codex entries (characters, locations, objects, lore) from prose passages and return them as well-formed XML.

Scenario	#1	#2	#3	#4	#5	Total
Long: The Spire of Echoes (Dense) Tooling Reasoning	98	98	98	98	98	98%
Medium: The Hollow (Inferred) Tooling Reasoning	99	98	97	96	96	97%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	98	97	97	97	97	97%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	100	100	100	99	98	99%
97.85%

Codex Red Herring (False Positive Detection)

Tests whether models correctly report "no violations" when a codex is fully consistent with the prose passage. Models that hallucinate false violations (false positives) fail. Uses a 2×2 matrix of text length × codex size, with bare and detailed-entry variants.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
basic entries
Long text (~1594 words), big codex (51 entries) Hallucination	38	35	31	13	13	10	8	8	8	5	17%
Long text (~1594 words), small codex (11 entries) Hallucination	50	50	42	42	42	38	13	13	13	10	31%
Short text (~524 words), big codex (51 entries) Hallucination	50	25	25	25	25	25	25	25	25	25	28%
Short text (~524 words), small codex (11 entries) Hallucination	25	25	25	17	17	17	17	17	13	13	18%
basic entries											23.40%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	50	42	38	35	13	13	13	10	10	7	23%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	50	42	42	38	38	38	17	13	13	7	29%
Short text (~524 words), big codex (51 detailed entries) Hallucination	100	50	50	50	17	17	17	17	17	13	35%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	25	25	25	17	17	17	17	17	36%
detailed entries											30.69%
27.04%

Codex Violation Detection

Detects factual inconsistencies between a story bible and prose passages. The model must output structured XML identifying each violation with paragraph number and substring.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
matrix
Large codex (40 entries), long passage (1,019 words) Tooling Reasoning	96	94	92	91	90	90	87	87	86	84	90%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	98	96	94	91	89	89	89	89	85	82	90%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	97	88	88	88	88	84	84	79	79	79	85%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	92	92	92	92	92	92	95%
matrix											90.11%
tiers
5 codex entries Tooling Reasoning	100	100	100	100	100	83	83	83	83	83	92%
10 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	92	99%
20 codex entries Tooling Reasoning	96	96	96	88	88	88	88	85	85	85	90%
40 codex entries Tooling Reasoning	100	100	97	92	92	92	92	88	84	83	92%
tiers											93.08%
91.59%

Data extraction

Extract key details from a given block of text.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
All valid emails Utility	100	100	100	100	100	100	100	100	100	100	100%
Contextual pronoun Utility	100	100	100	100	100	100	100	100	100	100	100%
Fruits excluding citrus Utility	100	100	100	100	100	100	100	100	100	100	100%
Future event time Reasoning	50	50	50	50	50	50	50	50	50	50	50%
Guess the pet Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Highest-rated movie Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Indirect birth year Reasoning	100	100	100	100	100	100	100	100	100	100	100%
What instrument does Lucy play? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
What's the color of the car? Utility	100	100	100	100	100	100	100	100	100	100	100%
What's the correct time? Reasoning	100	100	100	100	100	0	0	0	0	0	50%
Who's the sister? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Who's the tallest? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
91.67%

Dialogue tags

Various tasks related to dialogue tags in text.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
dialogue-200
Write 200 words with 10% dialogue Rule Following Utility	100	96	95	95	85	73	70	67	55	41	78%
Write 200 words with 50% dialogue Rule Following Utility	49	45	43	41	38	38	22	7	1	0	28%
Write 200 words with 90% dialogue Rule Following Utility	94	93	86	85	80	80	65	52	51	21	71%
dialogue-200											59.00%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	47	47	45	41	38	26	10	7	0	0	26%
Write 500 words with 50% dialogue Rule Following Utility	50	45	34	34	34	33	26	0	0	0	26%
Write 500 words with 70% dialogue Rule Following Utility	50	48	45	28	22	18	14	11	1	0	24%
dialogue-500											25.07%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
50.32%

Language Comprehension

Does the model understand more than just English?

Scenario	#1	#2	#3	#4	#5	Total
Asking for directions (Dutch) Language	100	100	100	100	100	100%
Asking for directions (German) Language	100	100	100	100	100	100%
Friend got new kittens (German) Language	100	100	100	100	100	100%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
100.00%

Language Writing

Can the model generate text in different languages?

Scenario	#1	#2	#3	#4	#5	Total
Character dialogue (French) in a story Language	100	94	94	92	89	94%
Character dialogue (German) in a story Language	100	100	100	95	93	98%
Character dialogue (Hindi) in a story Language	78	55	50	47	42	54%
Character dialogue (Italian) in a story Language	94	93	92	92	85	91%
Character dialogue (Spanish) in a story Language	100	93	93	92	86	93%
86.02%

N-Length Sentences

Write sentences with exactly N words

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Write sentences with 5 words each Utility	100	100	100	100	100	100	97	95	94	93	98%
Write sentences with 10 words each Utility	100	100	100	100	100	100	100	100	100	88	99%
Write sentences with 20 words each Utility	83	75	70	66	66	61	61	61	56	53	65%
87.23%

Novel outline

Handle questions about the outline of a novel in various formats

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
outline-count
Count acts Utility	100	100	100	100	100	100	100	100	100	100	100%
Count chapters Utility	100	100	100	100	100	100	100	100	100	100	100%
Count scenes Utility	100	100	100	0	0	0	0	0	0	0	30%
outline-count											76.67%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	100	100	100	100	100	100	50	95%
Count point of views for Jack Harper Utility	100	100	100	100	100	100	100	100	100	100	100%
Count point of views for Olivia Utility	100	100	100	100	100	100	100	100	100	0	90%
pov-count											95.00%
85.83%

Text Replacement

Tests deterministic text transformations: renaming characters/locations, expanding contractions, tense rewriting, POV shifts, gender swaps, combined transformations, and word avoidance. Scored by checking each expected change independently.

Scenario	#1	#2	#3	#4	#5	#6	#7	Total
Generic Prompt
Avoid said/asked/replied/answered Text Editing	100	100	100	100	100	100	100	100%
Character rename: Elena->Mirabel, Gregor->Aldric Text Editing	100	100	100	100	100	100	100	100%
Combined: 3rd person past → 1st person present Text Editing	100	100	100	99	99	99	95	99%
Expand all contractions Text Editing	100	100	100	100	100	100	100	100%
Location rename: market square, outer ring, bridge, northern mines Text Editing	100	100	100	100	100	100	100	100%
Multi-character gender swap: Priya(F)->Rohan(M), Mara unchanged Text Editing	100	100	100	100	100	100	100	100%
Passive voice → active voice Text Editing Hallucination	96	96	95	95	94	94	77	92%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	100	100	100%
Tense rewriting: past to present Text Editing	97	96	96	96	96	96	95	96%
Generic Prompt								98.58%
Specific Prompt
Avoid said/asked/replied/answered Text Editing	100	100	100	100	100	100	100	100%
Character rename: Elena->Mirabel, Gregor->Aldric Text Editing	100	100	100	100	100	100	100	100%
Combined: 3rd person past → 1st person present Text Editing	100	100	100	100	100	100	100	100%
Expand all contractions Text Editing	100	100	100	100	100	100	100	100%
Location rename: market square, outer ring, bridge, northern mines Text Editing	100	100	100	100	100	100	100	100%
Multi-character gender swap: Priya(F)->Rohan(M), Mara unchanged Text Editing	100	100	100	100	100	100	100	100%
Passive voice → active voice Text Editing Hallucination	99	98	98	97	96	96	95	97%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	100	100	100%
Tense rewriting: past to present Text Editing	100	100	100	100	100	100	100	100%
Specific Prompt								99.67%
99.13%

Tool usage within Novelcrafter

Output messages that are related to tool usage within Novelcrafter

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Create alternate prose sections Tooling	100	100	100	100	100	100	100	100	100	100	100%
100.00%

Voice/dialogue sheets

Extract dialogue from given text as voice sheets.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Multiple speakers Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Simple Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Simple (1-shot) 1-shot Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Simple (5-shot) Few-shot Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Unattributed dialogue Rule Following	100	100	100	0	0	0	0	0	0	0	30%
86.00%

Write N of X

Write exactly N words/sentences/paragraphs...

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
paragraphs
1 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
3 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
5 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
paragraphs											100.00%
sentences
1 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
3 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
10 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 sentence summary Utility	100	100	100	100	100	100	98	92	77	77	95%
50 sentence summary Utility	54	9	2	0	0	0	0	0	0	0	6%
sentences											80.19%
words
10 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 word summary Utility	100	100	100	100	100	98	98	98	98	98	99%
50 word summary Utility	100	100	100	100	100	98	98	98	92	92	98%
100 word summary Utility	100	100	100	98	77	77	77	27	27	0	69%
200 word summary Utility	98	92	0	0	0	0	0	0	0	0	19%
words											76.92%
83.50%