Claude Opus 4.5 - NC Bench

anthropic/claude-opus-4.5

Claude Opus 4.5

via OpenRouter

Release Date

Nov 24th, 2025

Context Size

200k

Reasoning

Benchmark Cost

$23.48

Speed

49.4 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	86	85	85	85	74	83%
Horror: alone in an eerie place at night Creative Writing Hallucination	91	88	88	87	83	87%
Literary fiction: old friends reunite Creative Writing Hallucination	90	90	86	85	83	87%
Mystery: examining a crime scene Creative Writing Hallucination	88	87	85	82	81	85%
Romance: separated couple reunites Creative Writing Hallucination	93	86	86	85	84	87%
Thriller: chase through city streets Creative Writing Hallucination	89	88	88	86	84	87%
Detailed Writing Rules						85.90%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	83	75	70	68	66	72%
Horror: alone in an eerie place at night Creative Writing Hallucination	88	87	84	82	80	84%
Literary fiction: old friends reunite Creative Writing Hallucination	80	79	78	72	72	76%
Mystery: examining a crime scene Creative Writing Hallucination	82	80	77	77	75	78%
Romance: separated couple reunites Creative Writing Hallucination	83	81	80	80	74	80%
Thriller: chase through city streets Creative Writing Hallucination	80	80	79	79	75	79%
genre						78.12%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	82	81	80	77	74	79%
Horror: alone in an eerie place at night Creative Writing Hallucination	89	86	83	80	79	83%
Literary fiction: old friends reunite Creative Writing Hallucination	84	84	83	80	78	82%
Mystery: examining a crime scene Creative Writing Hallucination	84	81	79	79	76	80%
Romance: separated couple reunites Creative Writing Hallucination	81	80	80	79	77	80%
Thriller: chase through city streets Creative Writing Hallucination	85	84	81	81	79	82%
Novelcrafter Default Prompt						80.87%
81.63%

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	99	98	98	98	98	98%
Medium: The Hollow (Inferred) Tooling Reasoning	100	99	98	98	98	99%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	99	99	99	99	97	98%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	100	100	100	99	99	99%
98.56%

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	50	42	42	42	42	42	38	17	13	8	33%
Long text (~1594 words), small codex (11 entries) Hallucination	38	38	17	17	17	13	10	10	10	10	18%
Short text (~524 words), big codex (51 entries) Hallucination	100	25	25	25	25	25	25	25	25	25	33%
Short text (~524 words), small codex (11 entries) Hallucination	25	25	25	25	25	25	25	25	25	25	25%
basic entries											27.15%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	35	33	33	25	25	17	17	17	10	8	22%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	42	42	42	42	38	38	38	38	38	35	39%
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											65.23%
46.19%

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	97	96	96	96	96	95	95	95	93	96%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
matrix											98.94%
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	100	100	100	100	100	100	100	100	100	100	100%
40 codex entries Tooling Reasoning	100	100	100	100	100	97	97	97	97	97	98%
tiers											99.58%
99.26%

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	0	0	0	0	0	0	0	0	0	0	0%
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%
87.50%

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	100	100	100	99	99	98	97	89	82	96%
Write 200 words with 50% dialogue Rule Following Utility	99	95	93	79	67	49	48	48	47	45	67%
Write 200 words with 90% dialogue Rule Following Utility	96	95	93	93	92	91	63	60	49	49	78%
dialogue-200											80.45%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	94	54	52	51	50	49	49	49	43	30	52%
Write 500 words with 50% dialogue Rule Following Utility	63	53	50	49	49	43	37	21	1	0	37%
Write 500 words with 70% dialogue Rule Following Utility	45	45	45	7	7	2	2	1	0	0	15%
dialogue-500											34.75%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
63.66%

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	100	100%
Character dialogue (German) in a story Language	100	100	100	100	95	99%
Character dialogue (Hindi) in a story Language	100	100	100	100	95	99%
Character dialogue (Italian) in a story Language	100	100	100	100	93	99%
Character dialogue (Spanish) in a story Language	100	100	100	100	100	100%
99.31%

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	100	100	100	89	99%
Write sentences with 10 words each Utility	100	100	100	100	100	100	100	100	100	97	100%
Write sentences with 20 words each Utility	100	96	88	88	84	80	75	75	74	60	82%
93.59%

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	100	100	100	100	100	0	0	80%
outline-count											93.33%
pov-count
Count point of views for Jack and Olivia Utility	100	100	50	50	50	50	50	50	50	0	55%
Count point of views for Jack Harper Utility	100	100	100	100	100	100	100	0	0	0	70%
Count point of views for Olivia Utility	100	100	100	100	100	100	100	100	100	100	100%
pov-count											75.00%
84.17%

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	99	99	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	98	98	98	98	98	97	97	97%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	99	99	99	99	99	99	99	99%
Tense rewriting: past to present Text Editing	100	99	99	99	99	99	99	99%
Generic Prompt								99.38%
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	98	98	98	97	97	97	97	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								99.69%
99.54%

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	0	0	0	0	0	50%
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	100	100%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
70.00%

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	98	98	98	92	54	54	0	79%
sentences											95.88%
words
10 word summary Utility	100	100	100	100	100	100	98	98	98	98	99%
20 word summary Utility	100	100	100	100	98	98	98	98	92	54	94%
50 word summary Utility	100	100	100	100	100	100	100	100	92	92	98%
100 word summary Utility	100	100	100	100	100	100	100	98	98	77	97%
200 word summary Utility	100	77	9	0	0	0	0	0	0	0	19%
words											81.53%
91.31%