io-harness 0.5.0

A Rust agent harness: run an AI agent from a typed task contract to a verified result. Provider-agnostic (OpenRouter, Anthropic, OpenAI), multi-file edits with grep/find over a workspace, budgets, retry, full trace, resumable runs, execution-based verification, and a layered permission policy with a human-approval gate. Embeddable in-process.
Documentation 
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//! The one error type the crate returns.

/// Errors io-harness can return from a run.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// A filesystem tool operation failed.
    #[error("filesystem error: {0}")]
    Io(#[from] std::io::Error),

    /// The state store (rusqlite) failed.
    #[error("state store error: {0}")]
    State(#[from] rusqlite::Error),

    /// The provider request or its streamed response failed.
    #[error("provider error: {0}")]
    Provider(String),

    /// Configuration was missing or invalid (e.g. no API key).
    #[error("configuration error: {0}")]
    Config(String),

    /// The permission policy refused the action. Typed separately from
    /// [`Error::Config`] so a refusal is distinguishable from a malfunction —
    /// a verification that was refused is not a verification that ran and
    /// failed, and the model is told the difference.
    #[error("refused by policy: {act} {target}{}", .rule.as_ref().map(|r| format!(" (rule {r} in layer {})", .layer.as_deref().unwrap_or("?"))).unwrap_or_default())]
    Refused {
        /// The action attempted.
        act: String,
        /// The path or binary it targeted.
        target: String,
        /// The glob that refused it, when a rule rather than a default did.
        rule: Option<String>,
        /// The layer that rule came from.
        layer: Option<String>,
    },
}

/// Crate result alias.
pub type Result<T> = std::result::Result<T, Error>;