Claude Opus 5 (Reasoning, Low)

anthropic/claude-opus-5

Claude Opus 5 (Reasoning, Low)

via OpenRouter

Release Date

Jul 24th, 2026

Context Size

Reasoning

Yes

Benchmark Cost

$43.27

Speed

65.1 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	95	93	92	92	91	93%
Horror: alone in an eerie place at night Creative Writing Hallucination	97	95	94	93	91	94%
Literary fiction: old friends reunite Creative Writing Hallucination	92	88	86	86	85	87%
Mystery: examining a crime scene Creative Writing Hallucination	97	95	93	91	89	93%
Romance: separated couple reunites Creative Writing Hallucination	89	88	88	87	86	88%
Thriller: chase through city streets Creative Writing Hallucination	96	95	95	90	89	93%
Detailed Writing Rules						91.21%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	90	87	85	84	82	86%
Horror: alone in an eerie place at night Creative Writing Hallucination	86	84	84	83	82	84%
Literary fiction: old friends reunite Creative Writing Hallucination	89	88	86	83	80	85%
Mystery: examining a crime scene Creative Writing Hallucination	92	87	84	82	81	85%
Romance: separated couple reunites Creative Writing Hallucination	87	84	82	80	77	82%
Thriller: chase through city streets Creative Writing Hallucination	89	86	86	85	84	86%
genre						84.64%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	89	88	86	85	84	86%
Horror: alone in an eerie place at night Creative Writing Hallucination	89	87	86	84	84	86%
Literary fiction: old friends reunite Creative Writing Hallucination	89	85	85	84	84	85%
Mystery: examining a crime scene Creative Writing Hallucination	92	90	90	89	87	90%
Romance: separated couple reunites Creative Writing Hallucination	84	84	83	81	79	82%
Thriller: chase through city streets Creative Writing Hallucination	91	87	87	85	85	87%
Novelcrafter Default Prompt						86.05%
87.30%

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	98	98	98	98	98	98%
Medium: The Hollow (Inferred) Tooling Reasoning	99	99	99	99	97	99%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	97	97	97	97	95	97%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	100	95	94	94	94	95%
97.15%

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	25	25	85%
Short text (~524 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
basic entries											96.25%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), big codex (51 detailed entries) Hallucination	100	100	25	25	25	25	25	25	25	25	40%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	100	25	25	25	25	25	25	25	48%
detailed entries											71.88%
84.06%

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	98	98	98	98	98	98	98	98	97	97	98%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	81	81	96%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	100	100	100	100	92	92	83	80	3	85%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
matrix											94.72%
tiers
5 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
10 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	92	99%
20 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	92	92	98%
40 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
tiers											99.42%
97.07%

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	50	50	90%
Fruits excluding citrus Utility	100	100	100	100	100	100	100	100	100	100	100%
Future event time Reasoning	50	50	50	50	50	50	50	50	50	50	50%
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%
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%
94.55%

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	98	98	98	97	97	97	96	87	54	92%
Write 200 words with 50% dialogue Rule Following Utility	96	96	55	50	50	50	50	49	49	48	59%
Write 200 words with 90% dialogue Rule Following Utility	100	98	98	92	76	76	76	76	74	71	84%
dialogue-200											78.40%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	92	81	63	50	50	48	43	35	22	8	49%
Write 500 words with 50% dialogue Rule Following Utility	50	50	50	50	49	49	41	0	0	0	34%
Write 500 words with 70% dialogue Rule Following Utility	79	53	50	49	45	43	26	23	19	7	39%
dialogue-500											40.80%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
65.37%

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	100	100	100	100%
Friend got new kittens (German) Language	100	100	100	100	100	100%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
100.00%

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	97	96	99%
Character dialogue (German) in a story Language	100	100	100	100	97	99%
Character dialogue (Hindi) in a story Language	100	100	100	100	100	100%
Character dialogue (Italian) in a story Language	100	100	100	97	97	99%
Character dialogue (Spanish) in a story Language	100	100	98	97	95	98%
98.92%

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	99	94	84	98%
Write sentences with 10 words each Utility	100	100	100	100	100	100	100	98	94	73	97%
Write sentences with 20 words each Utility	100	100	100	100	100	100	100	100	97	78	97%
97.23%

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	100	50	50	50	50	50	75%
Count point of views for Jack Harper Utility	100	100	100	0	0	0	0	0	0	0	30%
Count point of views for Olivia Utility	100	100	100	0	0	0	0	0	0	0	30%
pov-count											45.00%
72.50%

Relationship tree

Extracts a deterministic XML family and relationship tree from cumulative literary prose.

Scenario	#1	#2	#3	#4	#5	Total
Core relationship tree Tooling Reasoning Hallucination	100	98	98	98	97	98%
Family relationship tree Tooling Reasoning Hallucination	93	91	74	73	72	81%
89.52%

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	98	98	98	98	98	98	98%
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	96	96	96	92	92	92	95%
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	95	94	94	93	91	91	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	99	99	99	99	98	98	99%
Generic Prompt								98.31%
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	99	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	99	99	99	99	98	98	98	99%
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								99.82%
99.06%

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	0	0	0	0	0	0	0	0	0	10%
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	100	100%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
74.00%

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	100	100%
sentences											100.00%
words
10 word summary Utility	100	100	100	100	100	100	100	98	98	98	99%
20 word summary Utility	100	100	100	100	100	100	98	98	92	92	98%
50 word summary Utility	100	100	100	100	100	100	100	100	100	9	91%
100 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
200 word summary Utility	100	100	100	100	100	100	100	100	92	92	98%
words											97.38%
98.99%