Gemini 2.5 Flash - NC Bench

google/gemini-2.5-flash

Gemini 2.5 Flash

via OpenRouter

Release Date

Jun 17th, 2025

Context Size

Reasoning

Benchmark Cost

$1.61

Speed

150.0 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	82	78	78	74	72	77%
Horror: alone in an eerie place at night Creative Writing Hallucination	80	77	77	76	72	76%
Literary fiction: old friends reunite Creative Writing Hallucination	82	82	76	75	75	78%
Mystery: examining a crime scene Creative Writing Hallucination	83	81	78	78	75	79%
Romance: separated couple reunites Creative Writing Hallucination	85	85	81	77	75	81%
Thriller: chase through city streets Creative Writing Hallucination	82	81	81	81	79	81%
Detailed Writing Rules						78.65%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	79	73	71	70	70	73%
Horror: alone in an eerie place at night Creative Writing Hallucination	89	84	78	77	76	81%
Literary fiction: old friends reunite Creative Writing Hallucination	78	77	76	74	69	75%
Mystery: examining a crime scene Creative Writing Hallucination	81	78	76	76	74	77%
Romance: separated couple reunites Creative Writing Hallucination	80	80	73	72	69	75%
Thriller: chase through city streets Creative Writing Hallucination	88	86	85	79	68	81%
genre						76.85%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	75	74	74	71	70	73%
Horror: alone in an eerie place at night Creative Writing Hallucination	84	82	74	73	72	77%
Literary fiction: old friends reunite Creative Writing Hallucination	78	75	74	74	68	74%
Mystery: examining a crime scene Creative Writing Hallucination	82	81	81	77	73	79%
Romance: separated couple reunites Creative Writing Hallucination	78	77	76	75	71	75%
Thriller: chase through city streets Creative Writing Hallucination	86	83	79	79	68	79%
Novelcrafter Default Prompt						76.20%
77.23%

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	97	96	96	95	82	93%
Medium: The Hollow (Inferred) Tooling Reasoning	96	96	95	94	93	95%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	98	97	93	93	92	95%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	95	95	95	94	94	94%
94.24%

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	17	17	13	13	13	10	8	7	5	5	11%
Long text (~1594 words), small codex (11 entries) Hallucination	13	13	13	10	10	10	8	7	6	5	9%
Short text (~524 words), big codex (51 entries) Hallucination	29	25	17	17	13	13	13	10	10	8	15%
Short text (~524 words), small codex (11 entries) Hallucination	25	25	25	25	25	25	25	17	17	17	23%
basic entries											14.46%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	25	25	25	25	17	17	17	17	17	17	20%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	10	10	8	8	8	8	8	8	7	5	8%
Short text (~524 words), big codex (51 detailed entries) Hallucination	25	25	25	25	25	25	25	25	25	25	25%
Short text (~524 words), small codex (11 detailed entries) Hallucination	25	25	25	25	25	17	13	13	3	2	17%
detailed entries											17.60%
16.03%

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	91	91	90	88	88	88	85	83	82	80	87%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	96	96	94	93	93	89	89	85	85	82	90%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	97	97	93	88	88	87	83	83	83	75	87%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	97	97	97	97	97	97	97	97	97	97	97%
matrix											90.21%
tiers
5 codex entries Tooling Reasoning	100	93	93	93	93	93	93	93	83	83	92%
10 codex entries Tooling Reasoning	94	92	92	92	92	86	86	86	86	79	89%
20 codex entries Tooling Reasoning	100	92	92	92	92	92	92	92	92	92	93%
40 codex entries Tooling Reasoning	100	100	97	97	97	97	95	95	91	87	96%
tiers											92.39%
91.30%

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	0	0	0	0	0	0	0	0	0	0	0%
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%
83.33%

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	50	48	47	45	38	22	18	14	1	0	28%
Write 200 words with 50% dialogue Rule Following Utility	50	50	7	5	5	3	0	0	0	0	12%
Write 200 words with 90% dialogue Rule Following Utility	68	68	67	65	50	50	49	29	21	18	49%
dialogue-200											29.57%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	45	34	10	0	0	0	0	0	0	0	9%
Write 500 words with 50% dialogue Rule Following Utility	50	49	41	30	0	0	0	0	0	0	17%
Write 500 words with 70% dialogue Rule Following Utility	47	13	0	0	0	0	0	0	0	0	6%
dialogue-500											10.64%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	61	61	61	61	1	74%
27.86%

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	0	80%
Asking for directions (German) Language	100	100	100	100	0	80%
Friend got new kittens (German) Language	100	100	0	0	0	40%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
75.00%

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	94	99%
Character dialogue (German) in a story Language	100	100	100	100	100	100%
Character dialogue (Hindi) in a story Language	100	100	100	92	58	90%
Character dialogue (Italian) in a story Language	100	100	100	100	100	100%
Character dialogue (Spanish) in a story Language	100	100	100	100	93	99%
97.46%

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	98	98	95	93	93	92	88	84	64	40	84%
Write sentences with 10 words each Utility	69	62	62	54	52	50	45	41	27	14	48%
Write sentences with 20 words each Utility	0	0	0	0	0	0	0	0	0	0	0%
43.98%

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	0	0	0	0	0	0	0	0	0	0	0%
outline-count											66.67%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	50	50	50	50	50	50	0	60%
Count point of views for Jack Harper Utility	0	0	0	0	0	0	0	0	0	0	0%
Count point of views for Olivia Utility	100	100	100	100	0	0	0	0	0	0	40%
pov-count											33.33%
50.00%

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	98	60	94%
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	96	95	95	94	94	93	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	96	96	93	92	92	92	85	92%
Generic Prompt								97.87%
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	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	100	100	100	100%
Specific Prompt								99.65%
98.76%

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	0	0	0	0	60%
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	0	90%
88.00%

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	98	92	77	54	27	27	9	2	2	0	39%
20 sentence summary Utility	92	92	54	54	54	27	27	9	9	0	42%
50 sentence summary Utility	100	100	98	98	27	9	0	0	0	0	43%
sentences											64.79%
words
10 word summary Utility	100	100	100	100	100	98	92	92	92	77	95%
20 word summary Utility	98	92	92	77	77	77	54	27	27	9	63%
50 word summary Utility	0	0	0	0	0	0	0	0	0	0	0%
100 word summary Utility	100	100	100	92	9	0	0	0	0	0	40%
200 word summary Utility	77	0	0	0	0	0	0	0	0	0	8%
words											41.27%
63.87%