Claude Opus 5 - NC Bench

anthropic/claude-opus-5

Claude Opus 5

via OpenRouter

Release Date

Jul 24th, 2026

Context Size

Reasoning

Benchmark Cost

$29.51

Speed

52.9 tok/s

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	97	93	92	91	89	92%
Horror: alone in an eerie place at night Creative Writing Hallucination	93	93	92	92	90	92%
Literary fiction: old friends reunite Creative Writing Hallucination	91	89	88	86	85	88%
Mystery: examining a crime scene Creative Writing Hallucination	95	93	92	89	89	92%
Romance: separated couple reunites Creative Writing Hallucination	89	88	87	84	79	85%
Thriller: chase through city streets Creative Writing Hallucination	97	93	90	88	88	91%
Detailed Writing Rules						90.02%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	89	89	88	86	83	87%
Horror: alone in an eerie place at night Creative Writing Hallucination	93	89	88	88	87	89%
Literary fiction: old friends reunite Creative Writing Hallucination	84	83	82	80	75	81%
Mystery: examining a crime scene Creative Writing Hallucination	89	86	86	85	85	86%
Romance: separated couple reunites Creative Writing Hallucination	83	81	80	79	77	80%
Thriller: chase through city streets Creative Writing Hallucination	87	85	85	84	83	85%
genre						84.62%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	88	87	86	85	84	86%
Horror: alone in an eerie place at night Creative Writing Hallucination	93	88	87	83	77	85%
Literary fiction: old friends reunite Creative Writing Hallucination	86	86	84	84	79	84%
Mystery: examining a crime scene Creative Writing Hallucination	92	92	91	90	82	89%
Romance: separated couple reunites Creative Writing Hallucination	84	84	83	81	80	82%
Thriller: chase through city streets Creative Writing Hallucination	92	87	86	85	81	86%
Novelcrafter Default Prompt						85.56%
86.73%

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	99	99	97	96	98%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	100	100	97	97	97	98%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	95	95	95	95	94	95%
97.19%

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	32	31	13	10	10	10	8	8	8	8	14%
Long text (~1594 words), small codex (11 entries) Hallucination	35	13	13	13	10	10	10	10	10	10	13%
Short text (~524 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
basic entries											56.79%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	38	32	32	13	10	10	10	10	8	7	17%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	50	33	17	17	17	63%
Short text (~524 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
detailed entries											70.08%
63.44%

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	97	96	95	95	95	94	93	93	91	90	94%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	81	81	81	81	92%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	3	90%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
matrix											94.14%
tiers
5 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
10 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
20 codex entries Tooling Reasoning	96	96	96	96	96	96	96	92	92	92	95%
40 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
tiers											98.68%
96.41%

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	0	0	40%
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%
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%
94.55%

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	99	95	94	94	91	89	87	87	60	52	85%
Write 200 words with 50% dialogue Rule Following Utility	87	59	50	50	50	50	50	50	49	48	54%
Write 200 words with 90% dialogue Rule Following Utility	100	100	96	89	87	83	82	75	75	68	85%
dialogue-200											74.82%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	75	56	50	49	45	38	18	15	5	0	35%
Write 500 words with 50% dialogue Rule Following Utility	50	50	48	46	44	43	41	3	0	0	32%
Write 500 words with 70% dialogue Rule Following Utility	68	64	51	45	41	36	6	3	3	2	32%
dialogue-500											33.09%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
60.54%

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	100	100	100	97	99%
Character dialogue (German) in a story Language	100	100	100	100	100	100%
Character dialogue (Hindi) in a story Language	100	100	100	100	100	100%
Character dialogue (Italian) in a story Language	100	100	100	100	95	99%
Character dialogue (Spanish) in a story Language	100	100	100	100	94	99%
99.47%

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	96	93	91	91	82	95%
Write sentences with 10 words each Utility	100	100	98	98	98	96	96	95	88	77	95%
Write sentences with 20 words each Utility	96	96	84	80	80	80	76	69	69	51	78%
89.41%

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	0	0	0	0	0	0	0	0	0	10%
outline-count											70.00%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	100	100	50	50	50	50	50	75%
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	100	100%
pov-count											91.67%
80.83%

Relationship tree

Extracts a deterministic XML family and relationship tree from cumulative literary prose.

Scenario	#1	#2	#3	#4	#5	Total
Core relationship tree Tooling Reasoning Hallucination	98	96	96	73	71	87%
Family relationship tree Tooling Reasoning Hallucination	92	90	88	77	73	84%
85.31%

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	99	99	99	99	99	98	98	99%
Expand all contractions Text Editing	100	100	100	99	99	99	99	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	97	95	95	95	94	94	94	95%
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	99	99	99	99	99	99	99	99%
Generic Prompt								99.19%
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	99	99	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	100	99	99	98	98	98	98	99%
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								99.86%
99.52%

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	0	0	0	0	0	0	0	0	0	0	0%
Simple Rule Following	0	0	0	0	0	0	0	0	0	0	0%
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	0	90%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
58.00%

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	100	100	100	100	100%
50 sentence summary Utility	100	100	100	100	100	98	92	77	54	27	85%
sentences											96.97%
words
10 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 word summary Utility	100	98	98	98	98	98	92	77	77	77	92%
50 word summary Utility	100	100	100	100	98	98	98	92	92	54	93%
100 word summary Utility	100	77	54	54	54	54	9	2	2	0	40%
200 word summary Utility	77	54	9	0	0	0	0	0	0	0	14%
words											67.85%
86.47%