Claude Fable 5 vs Claude Opus 5
Qual usar, quando — veredito curado, não uma tabela de benchmark
A própria encruzilhada da Anthropic: Opus 5 a $5/$25 com pensamento adaptativo que você pode desativar, Fable 5 a $10/$50 onde o pensamento é estrutural e sempre ativo. Se a sua carga de trabalho se beneficia de desativar a deliberação em chamadas simples, o Opus 5 custa metade do preço e obedece; o Fable 5 é para trabalhos nos quais você nunca quer que o modelo pule o pensamento.
Preços
| Claude Fable 5 | Claude Opus 5 | Δ | |
|---|---|---|---|
| Entrada / 1M tokens | $10 | $5 | 2× |
| Saída / 1M tokens | $50 | $25 | 2× |
| Leitura de cache / 1M tokens | $1 | $0.5 | 2× |
| Escrita de cache | 1.25x (5m) / 2x (1h) | 1.25x (5m) / 2x (1h) | — |
Tarifas do catálogo em tempo real no momento do build; a página de cada modelo contém o cartão atual.
Onde eles se posicionam — preço de entrada por 1M tokens entre todos os 63 modelos de chat nesta unidade de cobrança (escala logarítmica)
Capacidades
| Claude Fable 5 | Claude Opus 5 | |
|---|---|---|
| Uso de ferramentas | sim | sim |
| Controle de raciocínio | sempre ativo | configurável |
| Saída estruturada | sim | sim |
| Cache de prompt | explícito (você marca o prefixo) | explícito (você marca o prefixo) |
| Tempo de vida do cache | 5m default, 1h option | 5m default, 1h option |
| Prefixo mínimo em cache | 1024 tokens | 1024 tokens |
Especificações
| Claude Fable 5 | Claude Opus 5 | |
|---|---|---|
| Modalidades de entrada | texto imagem | texto imagem |
| Modalidades de saída | texto | texto |
| Lançamento | 2026-06-09 | 2026-07-24 |
| Corte de conhecimento | 2026-01 | 2026-05 |
| Janela de contexto | 1M | 1M |
| Saída máxima | 128K | 128K |
| Parâmetro de raciocínio | output_config.effort (thinking.type is adaptive-only and needs no configuration) |
|
| Valores aceitos | effort
both "enabled" and "disabled" return 400 | thinking.type
effort
|
| Padrão | thinking always on (adaptive) effort
| thinking on effort
|
As especificações são transcritas da documentação de cada fornecedor; uma linha que um fornecedor não publica é omitida em vez de ser inferida. Fontes completas: Claude Fable 5 · Claude Opus 5
Um prompt, ambos os modelos — medidos pelo gateway
Claude Fable 5 passou · 3 sentences
When we enabled reasoning, the model began generating extensive internal "thinking" tokens before each answer, and those tokens are billed as output even though users never see them. Output tokens typically cost several times more than input tokens, so adding thousands of hidden reasoning tokens per request effectively multiplied our per-query cost. In short, we're paying for a much longer response behind the scenes in exchange for higher answer quality, and we can manage this by tuning reasoning effort levels or reserving reasoning mode for complex tasks only.
saída 228 tok latência 6.7 s
Claude Opus 5 passou · 3 sentences
When reasoning is enabled, the model generates a hidden chain of "thinking" tokens before it writes the visible answer, and those internal tokens are billed at the output rate even though no one ever sees them — commonly 3–10x more tokens than the response itself. Because output tokens are priced several times higher than input tokens, that added volume hits us at our most expensive rate, which is why the bill roughly doubled while our request count stayed flat. The spend is controllable: we can cap the reasoning budget per call, route only genuinely hard requests to reasoning mode and cheaper models for the rest, and track cost per successfully completed task rather than cost per token, since a single correct answer usually beats three cheap retries plus human cleanup.
saída 529 tok latência 9.0 s
Cumprimento da instrução (exatamente três frases — contáveis), ajuste ao público (registro de CFO), e a lacuna de cobrança do pensamento oculto que os medidores de tokens abaixo expõem.
Claude Fable 5 passou · 8/8 cases
## Fixed code ```python def longest_run(xs): if not xs: return 0 best = cur = 1 for i in range(1, len(xs)): if xs[i] == xs[i - 1]: cur += 1 else: cur = 1 best = max(best, cur) return best ``` ## Explanation The original function counts **adjacent equal pairs** rather than **items in a run**: a run of length *n* contains only *n − 1* equal neighbor pairs, so every result is off by one — a single-element list yields 0 instead of 1, and `[1, 2, 2]` yields 1 instead of 2 (which callers perceive as "missing" the run at the end). The fix is to initialize both `cur` and `best` to 1 (any nonempty list has a run of at least length 1), reset `cur` to 1 rather than 0 when
saída 531 tok latência 12.5 s
Claude Opus 5 passou · 8/8 cases
## Fixed version ```python def longest_run(xs): if not xs: return 0 best = 1 cur = 1 for i in range(1, len(xs)): if xs[i] == xs[i - 1]: cur += 1 else: cur = 1 if cur > best: best = cur return best ``` ## The bug The counters were tracking the wrong quantity: `cur` counted *matching adjacent pairs* rather than *elements in the current run*, and both counters started at `0` instead of `1`. Since a run of length *n* contains only *n − 1* adjacent equal pairs, every result came back one too small — `[1, 1]` returned 1, `[3, 3, 3]` returned 2 — and a single-element list returned 0 because the loop body never executed and `best` kept its initial value of `0`. […]
saída 1094 tok latência 16.1 s
Se a correção é de fato certa (executável), a densidade da explicação, e a eficiência em tokens numa tarefa delimitada.
Claude Fable 5 passou · 5/5 fields, guidance null
```json { "company": "Meridian Robotics", "quarter": "Q3 (September quarter)", "revenue_usd_m": 412, "growth_pct": 11, "guidance": null } ``` Notes on interpretation: "up eleven and change" is rendered as 11 (the precise figure isn't stated), and guidance is null because it was explicitly withheld.
saída 192 tok latência 6.5 s
Claude Opus 5 passou · 5/5 fields, guidance "Withheld pending Q4 close"
```json { "company": "Meridian Robotics", "quarter": "Q3", "revenue_usd_m": 412, "growth_pct": 11, "guidance": "Withheld pending Q4 close" } ``` Notes on judgment calls: - **quarter**: "September quarter" is labeled Q3 because the text refers to an upcoming "Q4 close," implying a calendar-aligned fiscal year. No fiscal year is given. - **revenue_usd_m**: 412 is stated as constant-currency and hedged ("call it"), so it's approximate; the currency is not explicitly stated as USD. - **growth_pct**: "up eleven and change" means slightly more than 11, so 11 is a floor rather than an exact figure.
saída 539 tok latência 7.6 s
Obediência ao esquema (sem campos inventados), pressão de alucinação (guidance é explicitamente retida), e diferenças no caminho de saída estruturada.
Claude Fable 5 passou · 120 words, 0 banned, 1 question
**Introducing Cross-Provider Prompt Caching for our API Gateway** Starting today, your repeated prompts are cached once and reused across OpenAI, Anthropic, Google, and any other provider you route through the gateway. Instead of paying full token costs every time your application sends the same system prompt or context block, the gateway detects matching prefixes and serves cached results in milliseconds. Why keep spending money and latency on identical requests? Early adopters report cost reductions of up to 60 percent on high-volume workloads, along with faster median response times. Configuration is simple: enable caching in your dashboard, set a TTL, and choose which routes participate. Cache entries are encrypted at rest and never shared between accounts. Available now on all plans.
saída 1173 tok latência 18.2 s
Claude Opus 5 passou · 123 words, 0 banned, 1 question
**Cross-Provider Prompt Caching** We're introducing Cross-Provider Prompt Caching in the API Gateway. Repeated system prompts, long documents, and few-shot examples are stored once at the gateway layer and reused across OpenAI, Anthropic, Google, and self-hosted models. Instead of paying full input token costs on every request, your application sends a cache reference, and the gateway rehydrates the context before forwarding it downstream. Why does that matter? Teams running high-volume agents and retrieval pipelines typically see input token spend fall 40 to 70 percent, with median latency dropping by several hundred milliseconds. Caches are scoped per project, encrypted at rest, and invalidated automatically when a prompt template changes. Enable it with a single header, and see the docs for TTL tuning and per-route controls.
saída 1593 tok latência 19.1 s
Obediência às restrições (orçamento de palavras, lista de palavras proibidas, a única pergunta), impressão digital de estilo, e controle de comprimento.
Alterne entre eles com uma linha
Ambos os IDs estão em todas as abas abaixo — o par de linhas destacado é a única edição. Mesmo endpoint, mesma chave, mesmo formato de requisição.
from openai import OpenAI
client = OpenAI(
base_url="https://synthorai.io/v1",
api_key="sk-syn-...",
)
resp = client.chat.completions.create(
model="claude-fable-5",
# model="claude-opus-5", # descomente esta linha, comente a linha acima
messages=[{"role": "user", "content": "Summarize this diff"}],
reasoning_effort="medium",
)
print(resp.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://synthorai.io/v1",
apiKey: "sk-syn-...",
});
const resp = await client.chat.completions.create({
model: "claude-fable-5",
// model: "claude-opus-5", // descomente esta linha, comente a linha acima
messages: [{ role: "user", content: "Summarize this diff" }],
reasoning_effort: "medium",
});
console.log(resp.choices[0].message.content);curl https://synthorai.io/v1/chat/completions \
-H "Authorization: Bearer sk-syn-..." \
-H "Content-Type: application/json" \
-d '{
"model": "claude-fable-5",
# "model": "claude-opus-5", # descomente esta linha, comente a linha acima
"messages": [{"role": "user", "content": "Hello"}],
"reasoning_effort": "medium"
}'package main
import (
"context"
"fmt"
"github.com/openai/openai-go/v3"
"github.com/openai/openai-go/v3/option"
)
func main() {
client := openai.NewClient(
option.WithBaseURL("https://synthorai.io/v1"),
option.WithAPIKey("sk-syn-..."),
)
resp, _ := client.Chat.Completions.New(context.TODO(), openai.ChatCompletionNewParams{
Model: "claude-fable-5",
// Model: "claude-opus-5", // descomente esta linha, comente a linha acima
Messages: []openai.ChatCompletionMessageParamUnion{
openai.UserMessage("Summarize this diff"),
},
ReasoningEffort: openai.ReasoningEffortMedium,
})
fmt.Println(resp.Choices[0].Message.Content)
}import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.chat.completions.*;
import com.openai.models.ReasoningEffort;
OpenAIClient client = OpenAIOkHttpClient.builder()
.baseUrl("https://synthorai.io/v1")
.apiKey("sk-syn-...")
.build();
ChatCompletion resp = client.chat().completions().create(
ChatCompletionCreateParams.builder()
.model("claude-fable-5")
// .model("claude-opus-5") // descomente esta linha, comente a linha acima
.addUserMessage("Summarize this diff")
.reasoningEffort(ReasoningEffort.MEDIUM)
.build());
System.out.println(resp.choices().get(0).message().content().orElse(""));FAQ
Qual é mais barato, Claude Fable 5 ou Claude Opus 5?
Claude Opus 5 é mais barato em entrada / 1m tokens ($5 vs $10, com 2.0× de diferença). Outras linhas podem apontar para o outro lado — a tabela acima traz o quadro completo, e o custo real depende do seu mix.
Posso fazer um teste A/B de Claude Fable 5 contra Claude Opus 5 sem duas integrações?
Sim. Ambos são servidos pelo mesmo endpoint compatível com OpenAI com uma única chave de API — a troca é uma alteração de uma linha na string do modelo, de modo que você pode rotear uma fração do tráfego para cada um e comparar as faturas diretamente.
Claude Fable 5 e Claude Opus 5 suportam prompt caching?
Sim — ambos cobram leituras em cache abaixo da sua taxa de entrada, então cargas de trabalho com warm-prefix custam menos do que as taxas listadas sugerem. As linhas exatas de leitura em cache estão na tabela de preços acima.