NC Bench
Overview
About
Tests
Models
Model
Claude Opus 4.5
Test
N-Length Sentences
Scenario
Write sentences with 20 words each
Run ID
2026-02-08-01KGYX9GFYC37X5CV2B11TYW18
Model input
User/Human
Please write the opening scene of a murder mystery where each sentence has exactly 20 words. Please make sure that each sentence has the same length. Only return the opening itself.
Model response
Messages
Meta
AI
The grandfather clock struck midnight when Detective Sarah Chen arrived at the sprawling Victorian mansion on Blackwood Hill Road. Rain pelted the windows like tiny fists demanding entry, and thunder rumbled ominously across the dark September sky above. She stepped inside the foyer where a butler stood waiting, his face pale as fresh fallen winter snow. The body of wealthy industrialist Marcus Webb lay crumpled at the bottom of the grand marble staircase near flowers. His eyes stared blankly at the crystal chandelier above, and a thin trail of blood pooled beneath his head. Three family members huddled in the adjacent parlor, each one watching the others with barely concealed suspicion and obvious fear. Sarah pulled out her notebook and pen, knowing that someone in this house had committed the ultimate unforgivable sin. The killer was close, perhaps standing mere feet away, waiting to see if their terrible secret would remain hidden.
created_at
"2026-02-08T15:18:06.985244+00:00"
Sunday, February 8th, 2026 at 3:18:06 PM GMT+00:00
model
"anthropic/claude-4.5-opus-20251124"
app_id
182717
external_user
(null)
streamed
true
cancelled
false
latency
1838
moderation_latency
(null)
generation_time
7099
tokens_prompt
35
tokens_completion
182
native_tokens_prompt
44
native_tokens_completion
197
native_tokens_completion_images
(null)
native_tokens_reasoning
0
native_tokens_cached
0
num_media_prompt
(null)
num_input_audio_prompt
(null)
num_media_completion
0
num_search_results
(null)
origin
"https://ncbench.com/"
is_byok
false
finish_reason
"stop"
native_finish_reason
"stop"
usage
0.005145
router
(null)
provider_responses
0
id
"msg_019PEa8sKV35T8jRXK4CzC9d"
status
200
is_byok
false
latency
1838
endpoint_id
"be883404-eb42-4b2d-b6e4-c7daa3aa8d62"
provider_name
"Anthropic"
model_permaslug
"anthropic/claude-4.5-opus-20251124"
api_type
"completions"
id
"gen-1770563879-IzIy0YRRJSnk8JP0hBwe"
upstream_id
"msg_019PEa8sKV35T8jRXK4CzC9d"
total_cost
0.005145
cache_discount
(null)
upstream_inference_cost
0
provider_name
"Anthropic"
Evaluation details
Result
Evaluator
Details
Meta Data
59.6815%
Matches word count
n/a
neededClean
false
sentences
8
wordCounts
0
19
1
19
2
18
3
19
4
19
5
20
6
19
7
19