Claude Sonnet 5.5 vs gpt-oss-20b
Pricing, context window and real answers (September 2026)
Claude Sonnet 5.5 (Anthropic) and gpt-oss-20b (OpenAI), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 Claude Sonnet 5.5 |  gpt-oss-20b | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥357.4 | ¥5.04 |
| Output (per 1M tokens) | ¥1,787 | ¥23.52 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,251 | ¥17 |
| Context window | 1,000,000 tokens | 131,072 tokens |
| Release date | 9/28/2026 | 8/5/2025 |
| Input modalities | text, image, file | text |
| Throughput (p50) | — | — |
| Arena · overall | Unranked | #259 · ELO 1,318 |
| Arena · Japanese | Unranked | #184 · ELO 1,256 |
| Arena · coding | Unranked | #240 · ELO 1,369 |
Prices are FastMetal's yen rates before tax.
Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-09-25; category names mapped and ratings rounded by FastMetal.
Which should you pick?
- On price, gpt-oss-20b: ¥23.52 per 1M output tokens, 99% less than Claude Sonnet 5.5.
- For long documents, Claude Sonnet 5.5: a 1,000,000-token context window against 131,072 for gpt-oss-20b.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
Claude Sonnet 5.5
Let me go through the word letter by letter.
**strawberry**
| Position | Letter |
|---|---|
| 1 | s |
| 2 | t |
| 3 | **r** ← 1st |
| 4 | a |
| 5 | w |
| 6 | b |
| 7 | e |
| 8 | **r** ← 2nd |
| 9 | **r** ← 3rd |
| 10 | y |
**Step-by-step reasoning:**
1. I split the word into individual letters: s-t-r-a-w-b-e-r-r-y (10 letters total).
2. I checked each letter for 'r'.
3. The first 'r' is in position 3, in "str…".
4. The second and third 'r's are in positions 8 and 9, in the "…rry" ending.
**Answer: There are 3 r's in "strawberry".**
A common mistake is to see "berry" as having only one 'r' (or to treat the double-r as a single letter), which leads to the incorrect answer of 2.
3.1s332 output tokens
gpt-oss-20b
**Count of ‘r’ in “strawberry”: 3**
---
### Step‑by‑step reasoning
1. **Write out the word in individual letters**
```
s t r a w b e r r y
```
2. **Identify each ‘r’**
- The first ‘r’: appears after the “t” → **r**
- The second ‘r’: appears in the part “berry” → **r**
- The third ‘r’: the next letter after that → **r**
3. **Verify there are no more letters left**
The remaining letters are “b”, “e”, “y”, none of which are “r”.
4. **Count the identified ‘r’s**
1 (first) + 1 (second) + 1 (third) = **3**
---
### Quick recap
- Word: **strawberry**
- Letters containing “r”: positions 3, 8, and 9.
- Total count: **3**.
11.6s371 output tokens
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
Claude Sonnet 5.5
## Cause
`users` is `undefined` when the component renders, so `users.map(...)` throws. This happens when:
1. **The parent doesn't pass the prop**, or passes it under a different name (e.g. `<UserList data={x} />` or a typo like `user=`).
2. **The data loads asynchronously.** On the first render, the state or fetch result hasn't arrived yet.
3. **The value is wrong.** For example, the API returns `{ users: [...] }` and you passed the whole object, or you're reading a property that doesn't exist (`response.data.users` vs `response.users`).
## Fixes
### 1. Default value (simplest)
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{use…
6.7s824 output tokens
gpt-oss-20b
### Why does the error happen?
`users.map(...)` can only run when **`users` is an array**.
The stack trace shows that the crash happens on line 12 of `UserList.js`, which is the
exact spot where the code tries to call `.map`.
The value that is being passed to `UserList` (or the initial value that the parent
creates) is **`undefined`** (or it could be `null`/`{}`). When JavaScript tries to
read `users.map`, it throws:
```
TypeError: Cannot read properties of undefined (reading 'map')
```
Typical reasons for this are:
1. The parent component **didn’t pass the `users` prop** at all.
2. The parent passed it but the value was **`undefined` / `null`** because data
hasn’t been loaded ye…
11.4s1303 output tokens
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
Claude Sonnet 5.5
# Code Review
## Main Issues
### 1. Bare `except:` hides bugs (most important)
It catches everything, including `KeyboardInterrupt` and `SystemExit`. It also wraps your parsing logic, so a missing `"active"` key (`KeyError`) or bad JSON is treated as a network failure, retried 3 times with sleeps, and then silently becomes `[]`. Catch only `requests.RequestException`, and keep parsing outside the `try`.
### 2. Silent failure
Returning `[]` after all retries fails is indistinguishable from "the server returned no active items." Callers can't tell whether something went wrong. Raise an exception (or at least log) once retries are exhausted.
### 3. Retry logic
- It sleeps after the final at…
20.9s3003 output tokens
gpt-oss-20b
Below is a quick “code‑review” style list that touches the three axes you asked for – **readability**, **performance**, and **best practices**.
After the bullet‑list I’ll paste a refactored version that incorporates the most common fixes.
---
## 1. Readability
| Issue | Why it hurts | Quick fix |
|-------|--------------|-----------|
| **Imports inside the function** | Every call recompiles the import tables and makes the module’s top‑level slower. | Move `import requests` and `import time` to the module’s global header. |
| **Bare `except:`** | Catches *everything* (KeyboardInterrupt, SystemExit, MemoryError, etc.) and swallows useful tracebacks. | Catch only the expected network-relate…
24.6s2267 output tokens
Frequently asked questions
- Which is cheaper, Claude Sonnet 5.5 or gpt-oss-20b?
- Per 1M output tokens, Claude Sonnet 5.5 is ¥1,787 and gpt-oss-20b is ¥23.52 on FastMetal (yen, before tax), so gpt-oss-20b is cheaper.
- How do the context windows of Claude Sonnet 5.5 and gpt-oss-20b compare?
- Claude Sonnet 5.5 takes 1,000,000 tokens; gpt-oss-20b takes 131,072.
- Can I use Claude Sonnet 5.5 and gpt-oss-20b with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-sonnet-5-5" or "gpt-oss-20b" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call Claude Sonnet 5.5 and gpt-oss-20b from the browser chat and the API. No monthly fee.