ByteDance Seed 1.6 Flash

bytedance-seed/seed-1.6-flash

ByteDance Seed 1.6 Flash

via OpenRouter

Release Date

Dec 23rd, 2025

Context Size

256k

Reasoning

Yes

Benchmark Cost

$0.59

Speed

150.9 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	78	75	74	74	76%
Horror: alone in an eerie place at night Creative Writing Hallucination	83	80	78	76	76	79%
Literary fiction: old friends reunite Creative Writing Hallucination	87	85	84	83	79	84%
Mystery: examining a crime scene Creative Writing Hallucination	93	82	79	78	77	82%
Romance: separated couple reunites Creative Writing Hallucination	85	82	82	79	76	81%
Thriller: chase through city streets Creative Writing Hallucination	87	85	85	85	76	84%
Detailed Writing Rules						80.72%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	80	80	79	72	69	76%
Horror: alone in an eerie place at night Creative Writing Hallucination	83	80	78	76	74	78%
Literary fiction: old friends reunite Creative Writing Hallucination	88	83	82	81	78	83%
Mystery: examining a crime scene Creative Writing Hallucination	84	80	78	77	75	79%
Romance: separated couple reunites Creative Writing Hallucination	85	82	80	80	80	81%
Thriller: chase through city streets Creative Writing Hallucination	83	82	79	78	77	80%
genre						79.43%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	84	80	78	76	75	79%
Horror: alone in an eerie place at night Creative Writing Hallucination	87	81	80	79	79	81%
Literary fiction: old friends reunite Creative Writing Hallucination	86	85	81	79	75	81%
Mystery: examining a crime scene Creative Writing Hallucination	92	84	81	79	79	83%
Romance: separated couple reunites Creative Writing Hallucination	88	84	83	82	81	84%
Thriller: chase through city streets Creative Writing Hallucination	90	80	78	77	77	80%
Novelcrafter Default Prompt						81.34%
80.50%

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	92	85	84	83	83	85%
Medium: The Hollow (Inferred) Tooling Reasoning	94	91	87	87	85	89%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	91	84	82	79	71	82%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	93	91	85	83	80	87%
85.54%

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	25	93%
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	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											98.13%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	25	17	84%
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	100	100	100	100	100	100	100	25	93%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	100	100	25	13	84%
detailed entries											90.10%
94.11%

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	82	80	76	76	75	74	73	71	71	69	75%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	91	89	88	86	84	84	82	81	80	72	84%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	97	93	90	88	84	84	83	80	80	79	86%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	97	97	97	97	93	93	93	93	88	84	93%
matrix											84.40%
tiers
5 codex entries Tooling Reasoning	100	93	93	93	93	93	93	93	93	83	93%
10 codex entries Tooling Reasoning	100	94	94	94	94	94	94	94	92	89	94%
20 codex entries Tooling Reasoning	94	91	91	91	91	91	88	82	82	73	87%
40 codex entries Tooling Reasoning	93	93	93	90	90	87	87	84	76	72	87%
tiers											90.30%
87.35%

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	50	95%
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	50	50	90%
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	50	95%
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	50	50	90%
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%
89.17%

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	43	30	0	0	0	0	0	0	0	0	7%
Write 200 words with 50% dialogue Rule Following Utility	100	99	76	50	49	45	41	4	2	0	47%
Write 200 words with 90% dialogue Rule Following Utility	63	56	28	14	0	0	0	0	0	0	16%
dialogue-200											23.30%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	2	0	0	0	0	0	0	0	0	0	0%
Write 500 words with 50% dialogue Rule Following Utility	43	43	40	23	18	16	13	13	0	0	21%
Write 500 words with 70% dialogue Rule Following Utility	48	45	36	6	0	0	0	0	0	0	14%
dialogue-500											11.59%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	61	61	61	14	14	14	0	52%
22.42%

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	0	0	0	0	0	0%
Friend got new kittens (Tagalog) Language	100	100	100	100	0	80%
40.00%

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	90	96%
Character dialogue (German) in a story Language	100	100	100	80	80	92%
Character dialogue (Hindi) in a story Language	58	56	54	53	0	44%
Character dialogue (Italian) in a story Language	100	100	100	93	92	97%
Character dialogue (Spanish) in a story Language	94	93	89	89	50	83%
82.45%

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	96	91	91	89	87	85	72	60	87%
Write sentences with 10 words each Utility	100	100	100	100	95	94	83	77	76	3	83%
Write sentences with 20 words each Utility	100	100	100	100	100	100	87	83	78	75	92%
87.37%

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	0	90%
Count scenes Utility	100	100	100	100	100	100	100	100	100	0	90%
outline-count											93.33%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	100	100	100	100	100	100	100	100%
Count point of views for Jack Harper Utility	100	100	100	100	100	100	100	100	0	0	80%
Count point of views for Olivia Utility	100	100	100	100	0	0	0	0	0	0	40%
pov-count											73.33%
83.33%

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	72	96%
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	98	94	94	91	90	82	32	83%
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	96	99%
Multi-character gender swap: Priya(F)->Rohan(M), Mara unchanged Text Editing	99	99	99	99	99	99	72	95%
Passive voice → active voice Text Editing Hallucination	94	94	92	89	89	88	88	90%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	99	99	97	96	99%
Tense rewriting: past to present Text Editing	92	92	92	92	91	88	85	90%
Generic Prompt								94.79%
Specific Prompt
Avoid said/asked/replied/answered Text Editing	100	100	100	100	100	89	83	96%
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	93	92	92	92	86	23	83%
Expand all contractions Text Editing	100	99	98	98	98	96	88	97%
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	91	99%
Passive voice → active voice Text Editing Hallucination	93	93	91	88	88	83	78	88%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	99	96	99%
Tense rewriting: past to present Text Editing	99	97	96	95	93	93	93	95%
Specific Prompt								95.16%
94.97%

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	0	0	0	0	0	0	0	0	0	0	0%
0.00%

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	0	0	0	0	0	0	0	0	20%
Simple Rule Following	100	100	100	100	100	100	100	0	0	0	70%
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	0	0	80%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	0	0	0	70%
66.00%

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	98	98	92	0	89%
50 sentence summary Utility	100	98	9	9	9	0	0	0	0	0	23%
sentences											82.27%
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	0	0	0	0	0	0	0	30%
100 word summary Utility	27	0	0	0	0	0	0	0	0	0	3%
200 word summary Utility	9	0	0	0	0	0	0	0	0	0	1%
words											46.57%
72.63%