[skybleak333]

What:

• Bug Fix
• New Feature

Description:

Adds POST /v1/responses/input_tokens, which counts the input tokens of a request without creating a response. It takes the same parameters as responses()->create() and answers with {"object": "response.input_tokens", "input_tokens": 11} (token counting guide). Useful to check a long conversation against the context window, or to estimate the cost, before sending it.

$response = $client->responses()->inputTokens()->count([
    'model' => 'gpt-5',
    'input' => 'Tell me a joke.',
]);

$response->inputTokens; // 11

The naming follows the official SDKs (client.responses.input_tokens.count() in Python, client.responses.inputTokens.count() in Node) and the conversations()->items() sub-resource here: ResponsesInputTokens with its contract, InputTokenCountResponse with a fake fixture, ResponsesInputTokensTestResource for ClientFake, and a README section. The full suite, Pint and PHPStan pass.

[iBotPeaches]

Never used this. Will test it for real and report back.