Grok 4 Fast - NC Bench

x-ai/grok-4-fast

Grok 4 Fast

via OpenRouter

Release Date

Sep 19th, 2025

Context Size

Reasoning

Yes

Benchmark Cost

$0.77

Speed

166.2 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	79	76	75	74	72	75%
Horror: alone in an eerie place at night Creative Writing Hallucination	79	77	75	75	73	76%
Literary fiction: old friends reunite Creative Writing Hallucination	83	81	80	77	73	79%
Mystery: examining a crime scene Creative Writing Hallucination	75	75	72	68	68	72%
Romance: separated couple reunites Creative Writing Hallucination	81	80	78	78	76	79%
Thriller: chase through city streets Creative Writing Hallucination	80	79	78	78	77	78%
Detailed Writing Rules						76.43%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	73	73	72	71	68	71%
Horror: alone in an eerie place at night Creative Writing Hallucination	81	80	78	72	68	76%
Literary fiction: old friends reunite Creative Writing Hallucination	80	79	79	78	76	78%
Mystery: examining a crime scene Creative Writing Hallucination	82	82	75	74	69	76%
Romance: separated couple reunites Creative Writing Hallucination	82	80	79	79	74	79%
Thriller: chase through city streets Creative Writing Hallucination	84	83	75	74	67	77%
genre						76.25%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	77	77	73	71	70	74%
Horror: alone in an eerie place at night Creative Writing Hallucination	80	80	78	73	71	77%
Literary fiction: old friends reunite Creative Writing Hallucination	85	83	82	82	80	82%
Mystery: examining a crime scene Creative Writing Hallucination	81	80	75	73	72	76%
Romance: separated couple reunites Creative Writing Hallucination	82	79	79	78	77	79%
Thriller: chase through city streets Creative Writing Hallucination	84	81	78	75	71	78%
Novelcrafter Default Prompt						77.58%
76.75%

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	97	97	96	96	94	96%
Medium: The Hollow (Inferred) Tooling Reasoning	96	96	96	95	94	96%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	98	98	97	96	94	97%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	99	99	95	95	93	96%
96.09%

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	17	17	17	17	17	13	13	13	15%
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	25	25	25	25	25	25	17	47%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	25	25	17	77%
basic entries											59.69%
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	25	25	25	25	25	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	25	93%
detailed entries											86.87%
73.28%

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	100	100	99	97	96	95	94	92	91	90	96%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	98	98	98	96	96	96	96	96	96	93	97%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	100	95	95	93	92	92	92	87	83	93%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	97	97	99%
matrix											96.13%
tiers
5 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	91	99%
10 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	69	97%
20 codex entries Tooling Reasoning	100	97	97	97	97	96	94	94	94	3	87%
40 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
tiers											95.73%
95.93%

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	50	50	49	49	49	47	47	43	41	7	43%
Write 200 words with 50% dialogue Rule Following Utility	49	49	48	46	45	30	21	18	8	5	32%
Write 200 words with 90% dialogue Rule Following Utility	77	56	51	43	31	25	18	11	11	2	33%
dialogue-200											35.83%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	50	49	45	43	18	1	0	0	0	0	21%
Write 500 words with 50% dialogue Rule Following Utility	51	50	50	50	45	34	10	9	1	0	30%
Write 500 words with 70% dialogue Rule Following Utility	98	92	78	67	58	54	50	50	47	18	61%
dialogue-500											37.22%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
45.59%

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	0	0	0	40%
Friend got new kittens (German) Language	100	100	100	100	100	100%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
85.00%

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	91	88	96%
Character dialogue (German) in a story Language	100	100	91	89	86	93%
Character dialogue (Hindi) in a story Language	57	56	50	45	44	51%
Character dialogue (Italian) in a story Language	100	100	100	100	80	96%
Character dialogue (Spanish) in a story Language	100	100	89	70	70	86%
84.22%

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	89	78	78	78	78	78	70	70	67	53	74%
Write sentences with 10 words each Utility	97	93	92	90	87	84	72	68	48	39	77%
Write sentences with 20 words each Utility	33	23	15	8	7	1	0	0	0	0	9%
53.10%

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	0	0	80%
Count chapters Utility	100	100	100	100	0	0	0	0	0	0	40%
Count scenes Utility	100	100	100	100	100	100	100	0	0	0	70%
outline-count											63.33%
pov-count
Count point of views for Jack and Olivia Utility	100	50	50	50	0	0	0	0	0	0	25%
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	0	0	0	0	0	0	0	0	0	10%
pov-count											11.67%
37.50%

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	100	100	99	99	97	97	97	98%
Expand all contractions Text Editing	100	100	100	100	100	100	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	96	96	94	94	93	81	93%
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	97	96	93	91	89	89	93%
Generic Prompt								98.30%
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	99	99	97	99%
Expand all contractions Text Editing	100	100	100	100	100	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	100	100	100	100	100	100	100%
Passive voice → active voice Text Editing Hallucination	99	99	98	98	98	98	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	99	99	100%
Specific Prompt								99.64%
98.97%

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	0	0	0	0	60%
Simple Rule Following	100	100	100	100	100	100	100	100	0	0	80%
Simple (1-shot) 1-shot Rule Following	100	100	100	100	100	100	100	100	100	0	90%
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%
84.00%

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	98	98	100%
50 sentence summary Utility	100	100	100	100	100	0	0	0	0	0	50%
sentences											89.92%
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	92	99%
50 word summary Utility	100	100	100	98	98	98	98	92	77	54	92%
100 word summary Utility	100	100	98	92	92	92	77	77	27	9	77%
200 word summary Utility	98	77	27	9	2	0	0	0	0	0	21%
words											77.76%
87.57%