Claude Sonnet 4 - NC Bench

claude-sonnet-4-20250514

Claude Sonnet 4

via anthropic

Release Date

May 22nd, 2025

Context Size

200k

Reasoning

Benchmark Cost

$12.94

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	79	76	71	71	67	73%
Horror: alone in an eerie place at night Creative Writing Hallucination	95	90	87	83	80	87%
Literary fiction: old friends reunite Creative Writing Hallucination	93	89	86	86	86	88%
Mystery: examining a crime scene Creative Writing Hallucination	90	88	86	81	80	85%
Romance: separated couple reunites Creative Writing Hallucination	96	91	90	86	78	88%
Thriller: chase through city streets Creative Writing Hallucination	91	90	89	84	77	86%
Detailed Writing Rules						84.56%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	74	74	68	67	64	69%
Horror: alone in an eerie place at night Creative Writing Hallucination	81	80	78	76	75	78%
Literary fiction: old friends reunite Creative Writing Hallucination	85	81	79	78	78	80%
Mystery: examining a crime scene Creative Writing Hallucination	79	79	74	73	65	74%
Romance: separated couple reunites Creative Writing Hallucination	80	80	79	78	77	79%
Thriller: chase through city streets Creative Writing Hallucination	86	82	75	75	75	78%
genre						76.49%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	75	74	72	69	67	71%
Horror: alone in an eerie place at night Creative Writing Hallucination	83	81	77	77	75	79%
Literary fiction: old friends reunite Creative Writing Hallucination	88	86	80	79	72	81%
Mystery: examining a crime scene Creative Writing Hallucination	87	80	78	77	77	80%
Romance: separated couple reunites Creative Writing Hallucination	89	83	81	79	77	82%
Thriller: chase through city streets Creative Writing Hallucination	80	78	77	76	72	76%
Novelcrafter Default Prompt						78.21%
79.75%

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	97	96	95	94	96%
Medium: The Hollow (Inferred) Tooling Reasoning	96	95	95	95	95	95%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	98	96	96	96	96	97%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	99	99	99	99	99	99%
96.69%

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	35	33	17	10	10	8	8	8	20%
Long text (~1594 words), small codex (11 entries) Hallucination	50	42	42	42	42	38	35	17	17	13	34%
Short text (~524 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	50	42	42	17	75%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	50	25	25	25	25	17	57%
basic entries											46.35%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	42	13	13	13	13	13	13	13	13	10	15%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	100	50	42	38	38	17	13	13	13	10	33%
Short text (~524 words), big codex (51 detailed entries) Hallucination	100	100	100	17	13	13	10	10	10	10	38%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	100	100	17	17	17	17	17	17	50%
detailed entries											34.10%
40.23%

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	93	92	92	92	92	91	91	89	88	87	91%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	96	96	96	96	94	91	97%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	92	92	92	83	83	83	83	83	83	87%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
matrix											93.75%
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	92	92	92	92	92	92	92	92	88	88	92%
40 codex entries Tooling Reasoning	97	97	97	97	97	97	97	93	93	93	96%
tiers											96.82%
95.28%

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	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%
95.83%

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	95	95	95	94	92	92	83	72	60	53	83%
Write 200 words with 50% dialogue Rule Following Utility	71	53	45	23	20	7	5	1	0	0	23%
Write 200 words with 90% dialogue Rule Following Utility	49	28	21	19	19	19	19	18	18	18	23%
dialogue-200											42.89%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	82	50	49	42	17	9	8	0	0	0	26%
Write 500 words with 50% dialogue Rule Following Utility	48	47	45	23	15	4	4	1	0	0	19%
Write 500 words with 70% dialogue Rule Following Utility	50	6	3	1	0	0	0	0	0	0	6%
dialogue-500											16.78%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
39.86%

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	0	0	60%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
90.00%

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	93	91	97%
Character dialogue (German) in a story Language	100	100	100	93	93	97%
Character dialogue (Hindi) in a story Language	93	92	92	57	53	78%
Character dialogue (Italian) in a story Language	100	100	100	94	92	97%
Character dialogue (Spanish) in a story Language	100	100	93	92	86	94%
92.61%

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	97	97	93	92	91	86	96%
Write sentences with 10 words each Utility	100	100	100	100	100	97	90	88	74	69	92%
Write sentences with 20 words each Utility	91	78	76	72	66	49	32	17	12	3	50%
79.03%

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	100	100	100	50	50	50	50	0	70%
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											86.67%
90.00%

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	97	97	97	96	96	96	96	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	99	99	99	100%
Generic Prompt								99.55%
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	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	98	98	97	97	96	98%
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								99.77%
99.66%

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	100	100	100	100	100	100	100	100%
100.00%

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	98	98	98	98	9	90%
50 sentence summary Utility	100	92	77	27	9	0	0	0	0	0	31%
sentences											84.17%
words
10 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 word summary Utility	100	100	100	98	98	98	98	98	92	92	98%
50 word summary Utility	98	92	92	77	54	54	27	27	2	0	52%
100 word summary Utility	100	100	100	98	98	98	98	92	2	0	79%
200 word summary Utility	92	0	0	0	0	0	0	0	0	0	9%
words											67.59%
81.45%