Struct HarnessOptions 

pub struct HarnessOptions { /* private fields */ }

Available on crate feature async-client only.

How to launch and configure a harness session.

This carries both halves of startup: the InputConfig written over stdio during the handshake, and the HarnessConfig sent as the first WebSocket frame. Most callers only touch the latter.

Implementations

impl HarnessOptions

pub fn new() -> Self

Default options: read-only built-in tools, no models, no workspace.

A workspace and at least one model still need setting — a harness with no model exits during initialize.

pub fn binary(self, path: impl Into<PathBuf>) -> Self

Overrides binary discovery with an explicit path.

pub fn storage_directory(self, path: impl Into<PathBuf>) -> Self

Where the harness persists conversation state between runs.

Leave unset for an ephemeral session.

pub fn workspace(self, directory: impl AsRef<Path>) -> Self

Adds a directory the agent is allowed to read and write.

pub fn model(self, model: ModelBuilder) -> Self

Adds a model. Call more than once to register several.

pub fn system_instructions(self, instructions: SystemInstructions) -> Self

Sets the system prompt, replacing the harness’s built-in identity.

pub fn cascade_id(self, id: impl Into<String>) -> Self

Resumes, or creates, a conversation by id.

pub fn continuation_mode( self, mode: HarnessConfigSessionContinuationMode, ) -> Self

Chooses how an existing cascade_id is treated.

pub fn tool(self, tool: Tool) -> Self

Declares a tool the client executes. The harness will send a crate::protocol::ToolCall and wait for a crate::protocol::ToolResponse.

pub fn harness_side_tools(self, tools: HarnessSideTools) -> Self

Replaces the set of tools that run inside the harness itself.

Defaults to HarnessSideTools::read_only. Use HarnessSideTools::all to add shell execution and file writes, or HarnessSideTools::none for an agent that only talks.

pub fn mcp_server(self, server: McpServerConfig) -> Self

Registers an MCP server for the harness to connect to.

pub fn hook(self, hook: LifecycleHook) -> Self

Subscribes to a lifecycle hook. The harness will block the turn on a crate::protocol::CallHookRequest until the client answers.

pub fn subagent(self, agent: CustomAgent) -> Self

Registers a named subagent the model can delegate to.

pub fn policy(self, policy: PolicyConfig) -> Self

Installs tool-permission rules evaluated inside the harness.

pub fn skills_path(self, path: impl AsRef<Path>) -> Self

Adds a directory of agent skills.

pub fn app_data_dir(self, path: impl AsRef<Path>) -> Self

Where generated artifacts and media are written.

pub fn env(self, key: impl Into<String>, value: impl Into<String>) -> Self

Sets an environment variable for the harness process.

pub fn harness_config(self, config: HarnessConfig) -> Self

Replaces the whole HarnessConfig, for settings this builder does not surface.

Anything set by earlier builder calls is discarded — including the default read-only tool set, so set HarnessConfig::harness_side_tools yourself if you want any.

pub fn config(&self) -> &HarnessConfig

The HarnessConfig as built so far.

Trait Implementations

impl Clone for HarnessOptions

fn clone(&self) -> HarnessOptions

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for HarnessOptions

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for HarnessOptions

fn default() -> Self

Returns the “default value” for a type.