107 lines
4.3 KiB
Markdown
107 lines
4.3 KiB
Markdown
# OpenAI-Compatible Chat Integration
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## Purpose
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This document defines the outbound HTTP behavior implemented by Promptkit's
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internal OpenAI-compatible model client. The
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[internal model-client document](../internal/llm.md) owns implementation flow,
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errors, and test ownership. The root Promptkit engine uses this client by
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default unless a consumer injects another implementation. The
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[framework format reference](../formats.md) owns the profile and prompt values
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that produce these outbound settings.
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## Endpoint And Method
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Generation sends an HTTP `POST` with `Content-Type: application/json`.
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Before the client is called, the engine resolves framework, backend, profile,
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and request values into one execution target. A non-empty endpoint from that
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target overrides the client's configured base URL. After trailing slashes are
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removed, `/chat/completions` is appended. Generation fails before sending when
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neither source supplies an endpoint.
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The target's backend ID is routing metadata for prepared values, results, and
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injected clients. The built-in client does not derive the URL from that ID and
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does not serialize it in the provider request.
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## Authentication
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A non-empty API key supplied directly on the execution target takes
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precedence. Otherwise, when an API-key environment-variable name is supplied,
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the client reads that variable and requires a non-empty value. The selected
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key is sent as `Authorization: Bearer <key>`. No authorization header is sent
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when neither mechanism is configured.
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The target contains the already resolved environment-variable name: an
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explicit request override takes precedence over profile metadata, which takes
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precedence over the backend default. Only the name reaches prepared metadata;
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the environment value is read just before the provider call and is never added
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to the JSON body.
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## Request Body
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The request body always contains `model` and `messages`. The execution
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target's model takes precedence over the client's configured model, and one
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must be available.
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Each ordinary message contains its `role` and string `content`. A
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cache-controlled message instead uses a text content block containing `type`,
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`text`, and `cache_control`; an empty cache-control TTL is omitted.
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The effective direct or prompt-rendered session ID is trimmed, limited to 256
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Unicode code points, and sent when nonempty as top-level `session_id`. It is
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never also sent as a session header.
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The client conditionally includes:
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- `temperature`, `max_tokens`, and `top_p` when non-zero or explicitly
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present;
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- non-empty `service_tier` and effective `reasoning_effort`; an explicitly
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disabled reasoning setting is empty and therefore omitted; and
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- `response_format` for JSON Schema structured output, including its name,
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strict flag, and schema document.
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The engine resolves backend, profile, and request extra-parameter maps by
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whole-map replacement rather than key merging. The resulting effective map is
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then merged directly into the top-level body after JSON serialization is
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verified. Empty keys and collisions with these reserved fields are rejected
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before any provider call:
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- `model`
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- `session_id`
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- `messages`
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- `temperature`
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- `max_tokens`
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- `top_p`
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- `service_tier`
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- `reasoning_effort`
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- `response_format`
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`backend_id`, `api_key_env`, and resolved credential values are not provider
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request fields.
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## Response Handling
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Any 2xx response is decoded as an OpenAI-compatible chat response. The client
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returns the first choice's non-empty message content and maps prompt,
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completion, total, cached, and cache-write token counts.
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Invalid JSON, absent choices, and empty first-choice content are malformed
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responses. For a non-2xx status, the error includes the status code but never
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the provider response body.
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## Timeout And Cancellation
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Timeouts are layered:
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- the caller context remains the outer cancellation boundary;
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- a positive generation timeout adds a request context deadline;
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- zero adds no generation-specific deadline;
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- a negative generation timeout is invalid; and
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- the cloned `http.Client` supplies the whole-request transport cap, retaining
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a positive supplied-client timeout or applying the configured/default
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timeout when the supplied value is not positive.
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The earliest applicable caller, generation, or transport deadline controls the
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request. Constructing the internal client does not mutate a supplied
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`http.Client`.
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