# Package `scriptorium`

Import path:

```go
import "gitea.maximumdirect.net/eric/scriptorium"
```

This is the canonical public Go contract for in-process prompt preparation and
execution. Prompt, profile, and schema file formats are defined in the
[configuration reference](../config.md).

## Engine Construction

`NewEngine(Config, ...Option)` constructs an engine. `Config` has these
fields:

| Field | Meaning |
| --- | --- |
| `PromptDir` | Prompt-definition directory, required unless a prompt source option is supplied. |
| `ProfileDir` | Optional custom profile directory over built-ins. |
| `SchemaDir` | Schema directory; empty uses `.`. |
| `Timeout` | Transport-wide safety cap for the built-in OpenAI-compatible client when `HTTPClient` is absent or has a non-positive timeout. A non-positive value uses the internal ten-minute default. |
| `HTTPClient` | Optional HTTP client for that built-in client. It is cloned; a positive `Timeout` on it is the transport cap and takes precedence over `Config.Timeout`. A non-positive client timeout is treated as unset. |

Nil options are ignored. Invalid construction, including
`WithLLMClient(nil)` and `WithArtifactReader(nil)`, returns an error matching
`ErrInvalidConfig`.

Profile and request `timeout_seconds` values select a per-generation-call
deadline independently of the transport cap. An explicit request override of
zero disables that generation deadline only. The complete interaction with the
caller context is defined in the
[OpenAI-compatible integration contract](../integrations/openai-compatible-chat.md#authentication-and-timeout).

Source options replace their matching directory source:

- prompts: `WithPromptFS(fsys, root)`, `WithPromptFile(path)`;
- profiles: `WithProfileFS(fsys, root)`, `WithProfileFile(path)`, and
  `WithProfiles(profiles...)`;
- schemas: `WithSchemaFS(fsys, root)`, `WithSchemaFile(path)`; and
- LLM client: `WithLLMClient(client)`; and
- artifact reader: `WithArtifactReader(reader)`.

`fs.FS` prompt-content and schema paths stay inside their configured roots.
Single-file prompt and profile sources are selected by their YAML `id`, not
their file names. `WithPromptFile` resolves relative `content_file` paths from
the prompt file's directory. `WithSchemaFile` exposes its schema by the schema
file's base name. In-memory profiles take precedence over an explicit or
directory-backed profile source, which in turn takes precedence over built-ins.
File and filesystem sources use the format and credential rules in the
[configuration reference](../config.md).

## Prepare And Run

`Prepare(ctx, request)` resolves the prompt, profile, input artifacts,
validation contract, and rendered messages without calling an LLM.
`Run(ctx, request)` performs that preparation, calls the configured client,
and validates generated content.

```go
engine, err := scriptorium.NewEngine(scriptorium.Config{
	PromptDir:  "./examples/prompts",
	ProfileDir: "./examples/profiles",
})
if err != nil {
	return err
}

prepared, err := engine.Prepare(ctx, scriptorium.RunRequest{
	PromptID: "generic.markdown_summary",
	Inputs: map[string]scriptorium.ArtifactRef{
		"transcript": scriptorium.File("./examples/fixtures/transcript.md"),
	},
})
if err != nil {
	return err
}
_ = prepared.Messages
```

The maintained package example is
[`examples/go-library/prepare`](../../examples/go-library/prepare).

`PreparedRun` exposes prompt, selected-profile, effective-model, output
contract, structured-output, input-hash, rendered-message, and timing
information. It does not include a resolved API key, model output, validation
result, or target-presence metadata.

`RunResult` adds run ID, artifact, raw output, validation, model metadata,
usage, and duration. Generated-content validation failures return a result with
`Validation.Status == ValidationFailed`; schema or validator runtime failures
return an error matching `ErrValidation`.

## Public Values

`ArtifactRef` has `Type`, `URI`, and `Body`; `Artifact` has `Name`,
`ContentType`, `Body`, `URI`, `Size`, and `Hash`. `ExecutionTarget` exposes the
effective endpoint, model, numeric settings, credential-environment name,
service tier, reasoning effort, and extra parameters. `ValidationResult`
contains status, mode, errors, schema path, repair attempts, and validity.

The exported constants define these serialized values:

- artifact types: `inline` and `file`;
- output formats: `text`, `markdown`, and `json`;
- validation modes: `none`, `basic`, `json`, and `json_schema`; and
- validation statuses: `passed`, `failed`, and `skipped`.

`TokenUsage` reports prompt, completion, total, cached, and cache-write token
counts. `RenderedPrompt`, `RenderedMessage`, `CacheControl`, and
`StructuredOutputSpec` are the public shapes used by injected LLM clients.

`ArtifactReader` implements
`Read(context.Context, ArtifactRef) (*Artifact, error)`. Supplying it through
`WithArtifactReader` replaces, rather than extends, the engine's default inline
and file reader for every input. Omitting the option retains that default;
`WithArtifactReader(nil)` makes engine construction fail with
`ErrInvalidConfig`.

Reader failures are surfaced as errors matching `ErrArtifactLoad` while
preserving the reader's original error identity for `errors.Is`. A `(nil, nil)`
reader response is also an artifact-load failure. Readers are responsible for
artifact metadata, although the engine assigns the input-map name when the
returned name is empty; readers should not retain or mutate caller values.

## Requests, Inputs, And Overrides

`RunRequest` fields are `PromptID`, `PromptVersion`, `ProfileID`,
`APIKey`, `Inputs`, `Vars`, `Execution`, `Validation`, and
`Metadata`.

Input helpers are:

- `File(path)` for a file-backed artifact;
- `Inline(body)` for inline content; and
- `InlineWithURI(uri, body)` for inline content with URI metadata.

Required declared inputs must be supplied. Template rendering must also resolve
every input name the prompt actually references. Extra entries in `Inputs`
are not rejected solely because they are undeclared.

`ExecutionTargetOverride` supplies endpoint, model, credential-environment,
service-tier, reasoning-effort, and extra-parameter overrides. Its numeric
fields (`Temperature`, `MaxTokens`, `TopP`, and `TimeoutSeconds`) are
pointers so explicit zero values are preserved. `OutputContract` supplies
`Format`, `ValidationMode`, `SchemaPath`, and `RepairAttempts`.

`ExtraParams` accepts JSON-compatible values: strings, booleans, finite
numbers, objects with string keys, arrays or slices, and nil. Unsupported
values, non-string map keys, non-finite floats, and cycles return
`ErrInvalidConfig` for profiles or `ErrInvalidRequest` for request
overrides.

## Profiles And Credentials

`OpenAICompatibleProfile(OpenAICompatibleProfileConfig)` creates an
in-memory `Profile`. Its public fields are `ID`, `Endpoint`, `Model`,
`Temperature`, `MaxTokens`, `TopP`, `TimeoutSeconds`, `ServiceTier`,
`ReasoningEffort`, `APIKeyRequired`, and `ExtraParams`.
`WithProfiles` rejects duplicate IDs in one call.

A direct `RunRequest.APIKey` is request-scoped and takes precedence over
`api_key_env` for the built-in client. It is excluded from JSON output and
from `PreparedRun` and `RunResult`. The package's `String` and
`GoString` methods report only whether a direct key is set. Do not use
reflection-based dumps of request structs, which can bypass that redaction.

## Injected LLM Clients

`LLMClient` implements:

```go
Generate(context.Context, GenerateRequest) (*GenerateResponse, error)
```

Injected clients receive the rendered prompt, effective execution target, numeric
target-presence metadata, optional structured-output specification, and direct
request API key. `GenerateResponse` returns content and `TokenUsage`.
Custom clients should avoid logging raw prompts or credentials.

## Errors

Public methods preserve these sentinel checks through `errors.Is`:

- `ErrInvalidConfig`
- `ErrInvalidRequest`
- `ErrPromptNotFound`
- `ErrProfileNotFound`
- `ErrProfileRequired`
- `ErrPromptLoad`
- `ErrProfileLoad`
- `ErrAPIKeyEnvMissing`
- `ErrArtifactLoad`
- `ErrPromptRender`
- `ErrLLMGenerate`
- `ErrValidation`

`ErrProfileRequired` and `ErrAPIKeyEnvMissing` each also match
`ErrInvalidRequest`, so callers can select either the broad request category or
the specific condition.

For the HTTP interface, see the [HTTP API reference](../api.md).