# TypeSafe Jev

Jev is a System One model from TypeSafe. ThinkThen asks it when you name no backend.

| Backend name | `typesafe` |
| --- | --- |
| Address | `https://api.typesafe.ai/v1` |
| Key variable | `TYPESAFE_API_KEY` |
| Default model | `jev-1.13.0` |

The default model is a pinned version. TypeSafe can move an alias to a new model, and the pinned version stays the same. Name another version with `--model` only when you mean to change the model behind a run.

On 2026-09-29, [TypeSafe's public site](https://typesafe.ai/) advertised Jev input at $42 per billion tokens. Check your account terms for the rate you will pay.

## Two ways to reach it

With no backend named, ThinkThen posts to the same address with the same model and reads the key from `THINKTHEN_API_KEY`. With `--backend typesafe`, it reads the key from `TYPESAFE_API_KEY`. Both reach the same model, and both share the answer cache.

*Jev answers yes. Sending the item back asks for a refund.*

```
question="Does the customer ask for a refund?"

printf '%s\n' "I want to send this back." |
thinkthen decide "$question" --backend typesafe
```

*Output*

```
true
```

*exit 0: yes*

*One request carries all three lines. The thanks is the only no.*

```
question="Does the customer ask for a refund?"

cat <<'EOF' |
Please refund my order. It arrived broken.
Thanks for the quick help yesterday!
I want to send this back.
EOF
thinkthen decide "$question" \
  --lines \
  --backend typesafe
```

*Output*

```
{"input":"Please refund my order. It arrived broken.","value":true}
{"input":"Thanks for the quick help yesterday!","value":false}
{"input":"I want to send this back.","value":true}
```

*exit 0: the run finished*

## Check it

`thinkthen check` sends four fixed questions and reports whether the backend answers each one the way ThinkThen needs. The plan shows where they would go.

*The check would post to TypeSafe's address with Jev's pinned model. The plan sends nothing.*

```
thinkthen check \
  --backend typesafe \
  --plan |
head -n 4
```

*Output*

```
url https://api.typesafe.ai/v1/systemone
provider systemone
model asked unspecified
model sent jev-1.13.0
```

*exit 0*

On 2026-09-26, thinkthen check on build b50e0425c asked jev-1.13.0 and exited 0, with 0 critical and 0 warning findings.[The record](https://github.com/botassembly/thinkthen/blob/main/sdlc/records/0160-build-the-answer-contract-holds.md) holds the run.

## From your language

Each page shows how its language names a backend.

- [Bash](/install/shell/#backends)
- [Python](/install/python/#backends)
- [TypeScript](/install/typescript/#backends)
- [Ruby](/install/ruby/#backends)
- [R](/install/r/#backends)
- [Rust](/install/rust/#backends)
- [C](/install/c/#backends)
- [C++](/install/cpp/#backends)
- [Objective-C](/install/objective-c/#backends)
- [COBOL](/install/cobol/#backends)
- [Ada](/install/ada/#backends)
- [Java](/install/java/#backends)
- [Kotlin](/install/kotlin/#backends)
- [Scala](/install/scala/#backends)
- [C#](/install/csharp/#backends)
- [Go](/install/go/#backends)
- [Swift](/install/swift/#backends)
- [Zig](/install/zig/#backends)
- [PHP](/install/php/#backends)
- [Dart](/install/dart/#backends)

[All backends](/install/backends/) · [Configuration](/install/configuration/)

On GitHub: [github.com/botassembly/thinkthen](https://github.com/botassembly/thinkthen)