Grok 4.20 - NC Bench

x-ai/grok-4.20

Grok 4.20

via OpenRouter

Release Date

Mar 31st, 2026

Context Size

Reasoning

Benchmark Cost

$2.88

Speed

69.4 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	84	82	81	80	80	81%
Horror: alone in an eerie place at night Creative Writing Hallucination	86	85	85	83	80	84%
Literary fiction: old friends reunite Creative Writing Hallucination	91	90	89	85	83	88%
Mystery: examining a crime scene Creative Writing Hallucination	91	89	84	84	83	86%
Romance: separated couple reunites Creative Writing Hallucination	90	89	89	87	81	87%
Thriller: chase through city streets Creative Writing Hallucination	91	87	86	84	81	86%
Detailed Writing Rules						85.32%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	83	81	80	78	76	80%
Horror: alone in an eerie place at night Creative Writing Hallucination	84	83	80	76	70	79%
Literary fiction: old friends reunite Creative Writing Hallucination	86	84	84	83	80	83%
Mystery: examining a crime scene Creative Writing Hallucination	85	84	81	81	78	82%
Romance: separated couple reunites Creative Writing Hallucination	82	82	80	77	74	79%
Thriller: chase through city streets Creative Writing Hallucination	87	81	80	79	77	81%
genre						80.53%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	85	81	80	76	68	78%
Horror: alone in an eerie place at night Creative Writing Hallucination	88	87	87	84	83	86%
Literary fiction: old friends reunite Creative Writing Hallucination	88	87	80	79	78	82%
Mystery: examining a crime scene Creative Writing Hallucination	89	86	85	80	77	83%
Romance: separated couple reunites Creative Writing Hallucination	89	88	86	86	79	86%
Thriller: chase through city streets Creative Writing Hallucination	86	86	84	79	78	83%
Novelcrafter Default Prompt						82.96%
82.94%

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	96	96%
Medium: The Hollow (Inferred) Tooling Reasoning	97	96	93	93	93	94%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	97	95	94	93	92	94%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	99	99	97	94	87	95%
95.04%

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	33	27	3	3	3	3	2	2	1	1	8%
Long text (~1594 words), small codex (11 entries) Hallucination	100	100	100	100	29	27	27	6	6	2	50%
Short text (~524 words), big codex (51 entries) Hallucination	25	17	17	17	17	13	10	8	3	2	13%
Short text (~524 words), small codex (11 entries) Hallucination	100	25	25	25	25	25	25	25	25	13	31%
basic entries											25.36%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	29	4	3	3	3	2	2	2	2	1	5%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	6	6	5	5	5	5	5	4	2	2	4%
Short text (~524 words), big codex (51 detailed entries) Hallucination	17	17	17	13	13	13	13	10	8	8	13%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	13	13	13	13	10	10	10	10	29%
detailed entries											12.73%
19.05%

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	84	81	80	77	77	75	75	75	69	66	76%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	97	97	97	97	97	93	93	93	89	85	94%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	87	87	83	83	83	81	80	79	76	76	82%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	92	92	92	92	92	96%
matrix											86.81%
tiers
5 codex entries Tooling Reasoning	100	91	84	83	76	76	76	69	69	63	79%
10 codex entries Tooling Reasoning	92	92	92	86	86	86	86	86	72	66	85%
20 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	97	97	99%
40 codex entries Tooling Reasoning	95	92	92	91	87	83	79	79	76	71	84%
tiers											86.79%
86.80%

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	50	95%
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	50	50	50	50	50	50	50	50	50	50	50%
What instrument does Lucy play? Reasoning	100	100	100	0	0	0	0	0	0	0	30%
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%
81.25%

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	50	49	41	18	11	2	0	0	27%
Write 200 words with 50% dialogue Rule Following Utility	50	50	50	50	50	50	50	50	43	34	48%
Write 200 words with 90% dialogue Rule Following Utility	91	68	66	64	64	64	52	32	28	18	55%
dialogue-200											43.11%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	50	50	43	41	14	14	3	1	1	0	22%
Write 500 words with 50% dialogue Rule Following Utility	50	49	49	2	0	0	0	0	0	0	15%
Write 500 words with 70% dialogue Rule Following Utility	58	49	48	43	26	18	4	1	0	0	25%
dialogue-500											20.41%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
41.51%

Language Comprehension

Does the model understand more than just English?

Scenario	#1	#2	#3	#4	#5	Total
Asking for directions (Dutch) Language	100	100	0	0	0	40%
Asking for directions (German) Language	100	100	0	0	0	40%
Friend got new kittens (German) Language	100	100	100	100	0	80%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
65.00%

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	100	100%
Character dialogue (Hindi) in a story Language	93	67	62	55	50	65%
Character dialogue (Italian) in a story Language	100	100	100	100	92	98%
Character dialogue (Spanish) in a story Language	100	100	100	100	100	100%
92.72%

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	98	98	97	97	96	82	82	65	91%
Write sentences with 10 words each Utility	95	87	84	84	77	73	63	57	53	49	72%
Write sentences with 20 words each Utility	47	42	34	11	0	0	0	0	0	0	14%
59.06%

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	0	0	0	45%
Count point of views for Jack Harper Utility	100	100	100	100	100	100	0	0	0	0	60%
Count point of views for Olivia Utility	100	100	0	0	0	0	0	0	0	0	20%
pov-count											41.67%
67.50%

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	92	92	92	91	91	91	88	91%
Expand all contractions Text Editing	100	99	99	99	99	99	99	99%
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	83	74	94%
Passive voice → active voice Text Editing Hallucination	94	94	93	92	92	91	91	93%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	100	94	99%
Tense rewriting: past to present Text Editing	96	96	96	96	95	95	95	96%
Generic Prompt								96.84%
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	99	99	99	99	98	98	98	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	98	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	99	100%
Specific Prompt								99.57%
98.21%

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	0	90%
90.00%

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	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	0	0	0	0	60%
72.00%

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	98	100%
50 sentence summary Utility	100	100	98	98	98	98	98	98	92	77	96%
sentences											99.17%
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	98	98	92	99%
50 word summary Utility	100	100	100	100	100	98	92	77	2	2	77%
100 word summary Utility	100	100	100	98	92	77	54	27	2	0	65%
200 word summary Utility	98	98	54	0	0	0	0	0	0	0	25%
words											73.20%
89.37%