pig/ai/stop_reason

A normalized stop reason across all LLM providers.

Each provider maps its native finish/stop reason string to one of these variants. This gives the rest of the codebase a stable, provider-agnostic type to pattern-match on.

Inspired by pi’s StopReason type.

Types

StopReason

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A normalized stop reason across all providers.

pub type StopReason {
  Stop
  Length
  ToolUse
  Error
  Unknown(String)
}

Constructors

```
Stop
```
The model finished normally (e.g. OpenAI "stop", Anthropic "end_turn")
```
Length
```
The model hit a token/length limit (e.g. OpenAI "length", Anthropic "max_tokens")
```
ToolUse
```
The model requested tool execution (e.g. OpenAI "tool_calls", Anthropic "tool_use")
```
Error
```
The model stopped due to an error or content filter (e.g. OpenAI "content_filter")
```
Unknown(String)
```
An unrecognized value from the provider — preserved for forward compatibility

Values

decoder

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pub fn decoder() -> decode.Decoder(StopReason)

Decode a StopReason from a JSON string value.

from_openai

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pub fn from_openai(raw: String) -> StopReason

Map an OpenAI native finish_reason string to a StopReason.

OpenAI value	StopReason
`"stop"`	`Stop`
`"tool_calls"`	`ToolUse`
`"length"`	`Length`
`"content_filter"`	`Error`
anything else	`Unknown`

from_string

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pub fn from_string(s: String) -> StopReason

Parse a canonical string back into a StopReason.

Inverse of to_string for known variants. Unrecognized strings become Unknown.

to_json

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pub fn to_json(reason: StopReason) -> json.Json

Serialize a StopReason as a JSON string value.

to_string

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pub fn to_string(reason: StopReason) -> String

Convert a StopReason to its canonical string representation.

Used for JSONL serialization, telemetry, and display. Unknown values pass through the original provider string.