Claude Haiku 4.5 vs Claude Sonnet 5
Which one, when — curated verdict, not a benchmark table
Sonnet 5 doubles Haiku’s card ($2/$10 vs $1/$5) and quintuples the context (1M vs 200K). Haiku remains the latency-and-price floor of the Claude line; the moment prompts outgrow 200K or need deeper reasoning, Sonnet is the natural landing.
Pricing
| Claude Haiku 4.5 | Claude Sonnet 5 | Δ | |
|---|---|---|---|
| Input / 1M tokens | $1 | $2 | 0.5× |
| Output / 1M tokens | $5 | $10 | 0.5× |
| Cache read / 1M tokens | $0.1 | $0.2 | 0.5× |
| Cache write | 1.25x (5m) / 2x (1h) | 1.25x (5m) / 2x (1h) | — |
Rates from the live catalog at build time; each model page carries the current card.
Where they sit — input price per 1M tokens across all 63 chat models on this billing unit (log scale)
Capabilities
| Claude Haiku 4.5 | Claude Sonnet 5 | |
|---|---|---|
| Tool use | yes | yes |
| Thinking control | configurable | configurable |
| Structured output | yes | yes |
| Prompt caching | explicit (you mark the prefix) | explicit (you mark the prefix) |
| Cache lifetime | 5m default, 1h option | 5m default, 1h option |
| Minimum cached prefix | 1024 tokens | 1024 tokens |
Specs
| Claude Haiku 4.5 | Claude Sonnet 5 | |
|---|---|---|
| Input modalities | text image | text image |
| Output modalities | text | text |
| Released | 2025-10-15 | 2026-06-30 |
| Knowledge cutoff | 2025-02 | 2026-01 |
| Context window | 200K | 1M |
| Max output | 64K | 128K |
| Thinking parameter |
|
|
| Accepted values | budget_tokens
"adaptive" returns 400 | thinking.type
effort
"enabled" returns 400 |
| Default | off, with no thinking unless the request sets it | thinking on (adaptive) effort
|
Specs are transcribed from each vendor’s documentation; a row a vendor does not publish is left out rather than inferred. Full sources: Claude Haiku 4.5 · Claude Sonnet 5
One prompt, both models — measured through the gateway
Claude Haiku 4.5 passed · 3 sentences
# Why Your LLM Bill Doubled Reasoning models like o1 and o3 process queries through extended chains of thought before responding, consuming 5-10x more tokens internally than standard models while also charging higher per-token rates. This means both your input token usage and per-unit costs increased simultaneously—a compounding effect that easily doubles overall spend. Unless you've significantly reduced queries to other models or have very selective reasoning deployment, the math makes a doubling entirely predictable.
out 106 tok latency 2.8 s
Claude Sonnet 5 passed · 3 sentences
Reasoning mode works by having the model generate extended internal "thinking" steps before producing its final answer, and since we're billed on total tokens, that hidden reasoning text adds significantly to what we pay for—even though you never see it in the output. This is different from simply getting longer visible responses; the model is essentially "showing its work" behind the scenes, and complex prompts can trigger thousands of extra reasoning tokens per request. The upside is improved accuracy on complex tasks, but if we want to control costs, we should selectively enable reasoning only for queries that truly need it, rather than applying it universally.
out 194 tok latency 4.3 s
Instruction following (exactly three sentences — countable), audience shaping (CFO register), and the hidden-thinking billing gap the token meters below expose.
Claude Haiku 4.5 passed · 8/8 cases
# Fixed Function ```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 best = max(best, cur) else: cur = 1 return best ``` # Bug Explanation The original function has two related bugs stemming from incorrect initialization and loop logic. First, `best` and `cur` start at 0, which causes single-element lists to incorrectly return 0 instead of 1—a run of one identical element should have length 1. Second, `cur` is reset to 0 (not 1) when a mismatch occurs, causing the next matching pair to be undercounted. More critically, if the longest run ends at the last index, `best` is only updated *during* the loop when a mismatch is encountered; if no mismatch follows the final run, `best` never captures it. […]
out 310 tok latency 4.0 s
Claude Sonnet 5 passed · 8/8 cases
## The Bug The function has two related off-by-one issues rooted in the same cause: `cur` and `best` are initialized to `0` instead of `1`, treating run lengths as the number of *matches* between adjacent elements rather than the number of *elements* in the run. This means a single-element input never enters the loop (since `range(1, 1)` is empty) and returns `0` instead of the correct answer of `1`. It also means that for any input, the run length is undercounted by exactly one — a run of 3 equal elements only produces 2 "match" increments, so `best` ends up as 2 instead of 3. The claim that it "misses runs that end at the last index" is actually a symptom of this same undercount: the logic does update `best` correctly on every iteration (including the last), but because it's counting matches instead of elements, the final reported value is always one less than the true longest run. […]
out 536 tok latency 7.1 s
Whether the fix is actually correct (runnable), explanation density, and token efficiency on a bounded task.
Claude Haiku 4.5 passed · 5/5 fields, guidance null
```json { "company": "Meridian Robotics", "quarter": "Q3", "revenue_usd_m": 412, "growth_pct": 11, "guidance": null } ```
out 63 tok latency 1.6 s
Claude Sonnet 5 passed · 5/5 fields, guidance null
```json { "company": "Meridian Robotics", "quarter": "Q3", "revenue_usd_m": 412, "growth_pct": 11.5, "guidance": null } ```
out 348 tok latency 5.3 s
Schema obedience (no invented fields), hallucination pressure (guidance is explicitly withheld), and structured-output path differences.
Claude Haiku 4.5 passed · 123 words, 0 banned, 1 question
# Introducing Prompt Cache Across Providers We're excited to announce our latest API gateway feature: intelligent prompt caching that works across multiple AI providers. This powerful capability stores frequently used prompts and their contexts, dramatically reducing latency and API costs for your applications. By intelligently managing cached prompts across providers like OpenAI, Anthropic, and others, you can optimize your infrastructure without changing your code. Why wait for responses when cached results can be delivered instantly? The system automatically handles cache invalidation and updates, ensuring your applications always access current information while maintaining performance gains. With support for complex multi-turn conversations and dynamic content, this feature scales seamlessly with your business needs. […]
out 165 tok latency 3.0 s
Claude Sonnet 5 passed · 123 words, 0 banned, 1 question
## Introducing Cross-Provider Prompt Caching We're rolling out a new caching layer for our API gateway that works across every major LLM provider you connect through it. Instead of resending identical prompts and paying full price each time, the gateway recognizes repeated requests and serves cached responses in milliseconds—regardless of whether you're routing to OpenAI, Anthropic, or Google. What does this mean for your bill and your latency? Both drop, often significantly, especially for teams running high-volume, repetitive workloads like customer support bots or batch content generation. The cache is configurable per route, with adjustable TTLs and invalidation rules, so you stay in control of freshness versus cost. Available now for all Pro and Enterprise plans. Check your dashboard to enable it today.
out 259 tok latency 4.8 s
Constraint obedience (word budget, banned-word list, the single question), style fingerprint, and length control.
Switch between them with one line
Both ids are in every tab below — the highlighted pair of lines is the only edit. Same endpoint, same key, same request shape.
from openai import OpenAI
client = OpenAI(
base_url="https://synthorai.io/v1",
api_key="sk-syn-...",
)
resp = client.chat.completions.create(
model="claude-haiku-4-5",
# model="claude-sonnet-5", # uncomment this line, comment the one above
messages=[{"role": "user", "content": "Summarize this diff"}],
)
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-haiku-4-5",
// model: "claude-sonnet-5", // uncomment this line, comment the one above
messages: [{ role: "user", content: "Summarize this diff" }],
});
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-haiku-4-5",
# "model": "claude-sonnet-5", # uncomment this line, comment the one above
"messages": [{"role": "user", "content": "Hello"}]
}'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-haiku-4-5",
// Model: "claude-sonnet-5", // uncomment this line, comment the one above
Messages: []openai.ChatCompletionMessageParamUnion{
openai.UserMessage("Summarize this diff"),
},
})
fmt.Println(resp.Choices[0].Message.Content)
}import com.openai.client.OpenAIClient;
import com.openai.client.okhttp.OpenAIOkHttpClient;
import com.openai.models.chat.completions.*;
OpenAIClient client = OpenAIOkHttpClient.builder()
.baseUrl("https://synthorai.io/v1")
.apiKey("sk-syn-...")
.build();
ChatCompletion resp = client.chat().completions().create(
ChatCompletionCreateParams.builder()
.model("claude-haiku-4-5")
// .model("claude-sonnet-5") // uncomment this line, comment the one above
.addUserMessage("Summarize this diff")
.build());
System.out.println(resp.choices().get(0).message().content().orElse(""));FAQ
Which is cheaper, Claude Haiku 4.5 or Claude Sonnet 5?
Claude Haiku 4.5 is cheaper on input / 1m tokens ($1 vs $2, 2.0× apart). Other rows may point the other way — the table above carries the full card, and real cost depends on your mix.
Can I A/B test Claude Haiku 4.5 against Claude Sonnet 5 without two integrations?
Yes. Both are served through the same OpenAI-compatible endpoint with one API key — switching is a one-line model-string change, so you can route a fraction of traffic to each and compare bills directly.
Do Claude Haiku 4.5 and Claude Sonnet 5 support prompt caching?
Yes — both bill cached reads below their input rate, so warm-prefix workloads cost less than the list rates suggest. The exact cache-read rows are in the pricing table above.