GPT-5 Nano - NC Bench

openai/gpt-5-nano

GPT-5 Nano

via OpenRouter

Release Date

Aug 7th, 2025

Context Size

400k

Reasoning

Yes

Benchmark Cost

$2.06

Speed

98.7 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	69	65	65	64	63	65%
Horror: alone in an eerie place at night Creative Writing Hallucination	72	67	66	65	62	66%
Literary fiction: old friends reunite Creative Writing Hallucination	77	71	70	69	67	71%
Mystery: examining a crime scene Creative Writing Hallucination	68	66	66	66	65	66%
Romance: separated couple reunites Creative Writing Hallucination	78	73	71	69	67	72%
Thriller: chase through city streets Creative Writing Hallucination	70	70	70	68	67	69%
Detailed Writing Rules						68.31%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	71	65	63	63	59	64%
Horror: alone in an eerie place at night Creative Writing Hallucination	72	66	66	65	60	66%
Literary fiction: old friends reunite Creative Writing Hallucination	70	67	66	65	63	66%
Mystery: examining a crime scene Creative Writing Hallucination	71	67	66	65	64	67%
Romance: separated couple reunites Creative Writing Hallucination	72	68	66	65	64	67%
Thriller: chase through city streets Creative Writing Hallucination	68	68	68	66	61	66%
genre						66.03%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	64	64	64	62	59	62%
Horror: alone in an eerie place at night Creative Writing Hallucination	64	62	62	61	60	62%
Literary fiction: old friends reunite Creative Writing Hallucination	83	81	79	71	66	76%
Mystery: examining a crime scene Creative Writing Hallucination	74	70	69	67	64	69%
Romance: separated couple reunites Creative Writing Hallucination	78	72	69	68	68	71%
Thriller: chase through city streets Creative Writing Hallucination	77	74	71	70	67	72%
Novelcrafter Default Prompt						68.67%
67.67%

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	95	94	93	87	85	90%
Medium: The Hollow (Inferred) Tooling Reasoning	96	96	95	94	94	95%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	93	92	91	87	87	90%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	95	92	89	87	84	89%
91.23%

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	100	100	100	100	100	100	100	100	100	100	100%
Long text (~1594 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	100	25	25	25	78%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	25	25	85%
basic entries											90.63%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	25	93%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	25	93%
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	25	93%
detailed entries											94.38%
92.50%

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	86	84	84	83	83	79	78	76	72	72	80%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	92	92	90	89	88	87	86	84	3	0	71%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	88	87	84	84	80	80	79	76	71	71	80%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	97	97	93	93	93	93	90	90	90	90	93%
matrix											80.87%
tiers
5 codex entries Tooling Reasoning	100	100	100	93	93	93	93	75	75	3	83%
10 codex entries Tooling Reasoning	100	100	94	86	86	86	86	86	86	86	90%
20 codex entries Tooling Reasoning	97	94	94	94	89	89	88	86	85	85	90%
40 codex entries Tooling Reasoning	97	95	93	87	84	84	84	84	83	75	87%
tiers											87.28%
84.08%

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	100	100	100	100	100	100	100	100	100	100	100%
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%
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	100	100	100	100	100	100	100	100	68	97%
Write 200 words with 50% dialogue Rule Following Utility	100	100	96	50	50	50	50	50	50	50	65%
Write 200 words with 90% dialogue Rule Following Utility	98	98	98	50	50	50	50	50	50	13	61%
dialogue-200											74.06%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	74	50	50	27	20	18	2	0	0	0	24%
Write 500 words with 50% dialogue Rule Following Utility	71	60	50	50	25	0	0	0	0	0	26%
Write 500 words with 70% dialogue Rule Following Utility	50	1	0	0	0	0	0	0	0	0	5%
dialogue-500											18.26%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	61	96%
53.29%

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	0	80%
Asking for directions (German) Language	100	100	0	0	0	40%
Friend got new kittens (German) Language	0	0	0	0	0	0%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
55.00%

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	93	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	100	100%
Character dialogue (Spanish) in a story Language	100	100	100	100	91	98%
99.35%

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	100	100%
Write sentences with 10 words each Utility	100	100	100	100	100	100	100	100	100	100	100%
Write sentences with 20 words each Utility	100	100	100	100	100	100	100	100	100	100	100%
100.00%

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	100	100	100%
outline-count											100.00%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	100	50	50	50	50	50	50	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	100	100%
pov-count											90.00%
95.00%

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	96	95	93	90	90	90	89	92%
Expand all contractions Text Editing	100	100	100	100	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	99	97	75	75	73	89%
Passive voice → active voice Text Editing Hallucination	77	76	75	71	66	63	62	70%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	99	96	99%
Tense rewriting: past to present Text Editing	93	89	89	89	89	85	82	88%
Generic Prompt								93.04%
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	99	99	99	98	97	96	98%
Expand all contractions Text Editing	100	100	100	100	99	99	98	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	99	99	95	95	95	95	97%
Passive voice → active voice Text Editing Hallucination	89	89	83	82	80	72	67	80%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	98	98	99%
Tense rewriting: past to present Text Editing	100	100	100	100	96	96	96	98%
Specific Prompt								97.01%
95.03%

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	0	0	0	0	0	0	40%
Simple (5-shot) Few-shot Rule Following	100	100	100	100	100	100	100	100	0	0	80%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
44.00%

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	100	100	100	100	0	90%
sentences											97.99%
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	100	100	100	100	100	100%
50 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
100 word summary Utility	100	100	100	100	100	100	100	100	100	98	100%
200 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
words											99.96%
99.21%