supercode-harness 0.4.3

//! Versioned public SDK contract shared by every Supercode surface.
//!
//! This module names the operations, capabilities, events, and errors that
//! transports project. CLI, JSON-RPC, HTTP, MCP, ACP, and language clients
//! may add correlation ids or wire metadata, but they must not define a
//! second execution contract or place those envelope fields in a session.

use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use serde_json::Value;
use std::path::Path;
use std::sync::Arc;

use crate::{
    Agent, Config, DiscoveryPage, DiscoveryQuery, Fidelity, HarnessCatalog, Result as CoreResult,
    Session, SessionDescriptor, SessionLocator,
};

/// Renderable prompt source configured on an SDK emulation component.
///
/// MCP implements this seam, but the SDK does not depend on MCP transport or
/// client types, so removing the MCP adapter leaves runtime semantics intact.
#[async_trait]
pub trait SdkPromptSource: Send + Sync {
    /// Render one prompt with its named arguments.
    async fn render(&self, args: std::collections::BTreeMap<String, String>) -> CoreResult<String>;
    /// Declared argument names in stable source order.
    fn arg_names(&self) -> &[String];
}

/// Current language-neutral SDK schema.
pub const SDK_SCHEMA_VERSION: &str = "supercode.sdk.v1";

/// Discover persisted sessions through the canonical SDK catalog owner.
pub fn discover_sessions(query: &DiscoveryQuery) -> CoreResult<Vec<SessionDescriptor>> {
    Ok(HarnessCatalog::new().discover(query)?)
}

/// Discover one persisted-session page with its opaque successor cursor.
pub fn discover_session_page(query: &DiscoveryQuery) -> CoreResult<DiscoveryPage> {
    Ok(HarnessCatalog::new().discover_page(query)?)
}

/// Load one durable locator through the canonical SDK catalog owner.
pub fn load_session(locator: &SessionLocator) -> CoreResult<Session> {
    Ok(HarnessCatalog::new().load(locator)?)
}

/// [`load_session`] at a declared fidelity.
///
/// Read-only surfaces pass [`Fidelity::Semantic`] so a transcript whose record
/// graph cannot be reconstructed exactly still renders, with the degradation
/// named in [`Session::load_residue`]. Continuation, transfer and export
/// callers keep the strict default of [`load_session`].
pub fn load_session_with_fidelity(
    locator: &SessionLocator,
    fidelity: Fidelity,
) -> CoreResult<Session> {
    Ok(HarnessCatalog::new().load_with_fidelity(locator, fidelity)?)
}

/// Load an explicit transcript/store path through the SDK import boundary.
/// An OpenCode selector is accepted only for its SQLite store.
pub fn load_session_path(path: &Path, opencode_session: Option<&str>) -> CoreResult<Session> {
    if opencode_session.is_some() {
        return Ok(Session::from_opencode_sqlite(path, opencode_session)?);
    }
    if let Some(session) = load_native_store_family(path)? {
        return Ok(session);
    }
    Ok(Session::load(path)?)
}

pub(crate) fn load_native_store_family(path: &Path) -> CoreResult<Option<Session>> {
    Ok(supercode_interchange::load_native_store_family(path)?)
}

/// SDK-owned emulation runtime component.
///
/// The wrapper makes ownership transfer explicit: public adapters receive an
/// SDK component, and [`crate::server::RpcEngine`] consumes that component as
/// the sole live-loop owner. It intentionally does not implement `Deref`:
/// model/tool-loop entry points stay unreachable outside the SDK/runtime
/// implementation boundary.
pub struct SdkAgent(Agent);

impl SdkAgent {
    pub(crate) fn from_agent(agent: Agent) -> Self {
        Self(agent)
    }

    pub(crate) fn inner(&self) -> &Agent {
        &self.0
    }

    pub(crate) fn inner_mut(&mut self) -> &mut Agent {
        &mut self.0
    }

    /// Read the resolved runtime configuration without acquiring loop ownership.
    pub fn config(&self) -> &Config {
        self.0.config()
    }

    /// Install the full-fidelity sidecar writer used by SDK persistence.
    pub fn set_recorder(&mut self, writer: crate::sidecar::SidecarWriter) {
        self.0.set_recorder(writer);
    }

    /// Install the reversible provider-view reduction policy.
    pub fn set_reduction_policy(&mut self, policy: crate::reduce::ReductionPolicy) {
        self.0.set_reduction_policy(policy);
    }

    /// Inspect the current provider-view reduction policy.
    pub fn reduction_policy(&self) -> Option<&crate::reduce::ReductionPolicy> {
        self.0.reduction_policy()
    }

    /// Replace the reversible reduction log after an SDK-owned projection.
    pub fn set_reduction_log(&mut self, log: crate::reduce::ReductionLog) {
        self.0.set_reduction_log(log);
    }

    /// Inspect the reversible reduction log.
    pub fn reduction_log(&self) -> &crate::reduce::ReductionLog {
        self.0.reduction_log()
    }

    /// Prepare optional cleared-turn summary metadata without sending a turn.
    pub fn prepare_cleared_turns_summary(
        &self,
        messages: &[crate::ChatMessage],
        policy: &crate::reduce::ReductionPolicy,
        prior: &crate::reduce::ReductionLog,
    ) -> Option<crate::reduce::PreparedClearSummary> {
        self.0
            .prepare_cleared_turns_summary(messages, policy, prior)
    }

    /// Install a reduction span summarizer.
    pub fn set_span_summarizer(
        &mut self,
        summarizer: impl crate::reduce::summarize::SpanSummarizer + Send + Sync + 'static,
    ) {
        self.0.set_span_summarizer(summarizer);
    }

    /// Install the optional persisted-session title generator.
    pub fn set_session_titler(
        &mut self,
        titler: impl crate::session_title::SessionTitler + Send + Sync + 'static,
    ) {
        self.0.set_session_titler(titler);
    }

    /// Generate a title from canonical history when configured.
    pub fn auto_title(&self) -> Option<String> {
        self.0.auto_title()
    }

    /// Attach a session store for SDK-owned subagent persistence.
    pub fn set_subagent_store(
        &mut self,
        store: std::sync::Arc<crate::SessionStore>,
        session_name: impl Into<String>,
    ) {
        self.0.set_subagent_store(store, session_name);
    }

    /// Install restored Claude runtime state without activating a timer.
    pub fn set_claude_runtime_manifest(
        &mut self,
        manifest: crate::claude_runtime_state::ClaudeRuntimeManifest,
    ) {
        self.0.set_claude_runtime_manifest(manifest);
    }

    /// Inspect restored Claude runtime state.
    pub fn claude_runtime_manifest(
        &self,
    ) -> Option<&crate::claude_runtime_state::ClaudeRuntimeManifest> {
        self.0.claude_runtime_manifest()
    }

    /// Mutate Claude runtime state from the SDK scheduler/persistence driver.
    pub fn claude_runtime_manifest_mut(
        &mut self,
    ) -> Option<&mut crate::claude_runtime_state::ClaudeRuntimeManifest> {
        self.0.claude_runtime_manifest_mut()
    }

    /// Restore project-scoped Claude agent definitions after disk reload.
    pub fn restore_claude_project_agents(&mut self) -> CoreResult<usize> {
        self.0.restore_claude_project_agents()
    }

    /// Replace canonical history with a loaded normalized session.
    pub fn load_session(&mut self, session: Session) {
        self.0.load_session(session);
    }

    /// Load a Supercode transcript through the SDK component.
    pub fn load_transcript(&mut self, path: impl AsRef<Path>) -> CoreResult<()> {
        self.0.load_transcript(path)
    }

    /// Save the canonical transcript through the SDK component.
    pub fn save_transcript(&self, path: impl AsRef<Path>) -> CoreResult<()> {
        self.0.save_transcript(path)
    }

    /// Read canonical history at a quiescent boundary.
    pub fn history(&self) -> &[crate::ChatMessage] {
        self.0.history()
    }

    /// Rewind canonical history to a prior message boundary.
    pub fn rewind_to(&mut self, checkpoint: usize) {
        self.0.rewind_to(checkpoint);
    }

    /// Append an SDK-assembled system note.
    pub fn append_system_note(&mut self, text: &str) {
        self.0.append_system_note(text);
    }

    /// Register one configured tool before transferring live-loop ownership.
    pub fn register_tool(&mut self, tool: impl crate::Tool + 'static) {
        self.0.register_tool(tool);
    }

    /// Register one MCP prompt source before transferring loop ownership.
    pub fn register_mcp_prompt(
        &mut self,
        command_name: impl Into<String>,
        source: impl SdkPromptSource + 'static,
    ) {
        self.0.register_mcp_prompt(command_name, source);
    }

    /// Inspect the exact next-request tool schemas for preflight measurement.
    pub fn tool_schemas(&self) -> Vec<crate::ToolSchema> {
        self.0.tool_schemas()
    }

    /// Arm the per-request context limit guard.
    pub fn set_context_limit(&mut self, limit: u64) {
        self.0.set_context_limit(limit);
    }

    /// Inspect the armed context limit.
    pub fn context_limit(&self) -> Option<u64> {
        self.0.context_limit()
    }

    /// Switch the next-request model at a quiescent boundary.
    pub fn set_model(&mut self, model: impl Into<String>) {
        self.0.set_model(model);
    }

    /// Whether a provider request has actually been issued.
    pub fn request_issued(&self) -> bool {
        self.0.request_issued()
    }

    /// Configured durable session name.
    pub fn session_name(&self) -> Option<&str> {
        self.0.session_name()
    }

    /// Whether persistence is enabled for this component.
    pub fn session_persist(&self) -> bool {
        self.0.session_persist()
    }

    /// Captured git provenance.
    pub fn git_metadata(&self) -> Option<&crate::git_metadata::GitMetadataRecord> {
        self.0.git_metadata()
    }

    /// Save captured git provenance.
    pub fn save_git_metadata(&self, store: &crate::SessionStore, name: &str) -> CoreResult<()> {
        self.0.save_git_metadata(store, name)
    }

    /// Number of non-system canonical messages.
    pub fn turn_count(&self) -> usize {
        self.0.turn_count()
    }

    /// Cumulative provider-reported output tokens.
    pub fn total_output_tokens(&self) -> u64 {
        self.0.total_output_tokens()
    }
}

impl From<Agent> for SdkAgent {
    fn from(agent: Agent) -> Self {
        Self::from_agent(agent)
    }
}

/// Construct the emulation component inside the SDK ownership boundary.
pub fn create_agent(config: Config) -> CoreResult<SdkAgent> {
    Agent::new(config).map(SdkAgent::from_agent)
}

/// Resume canonical history inside a fresh SDK-owned emulation component.
pub fn resume_agent(config: Config, session: Session) -> CoreResult<SdkAgent> {
    Agent::resume(config, session).map(SdkAgent::from_agent)
}

/// Submit one text turn through the SDK-owned emulation loop.
pub async fn submit_agent(agent: &mut SdkAgent, prompt: &str) -> CoreResult<String> {
    agent.0.send(prompt).await
}

/// Submit one multimodal turn through the SDK-owned emulation loop.
pub async fn submit_agent_with_images(
    agent: &mut SdkAgent,
    prompt: &str,
    image_urls: &[String],
) -> CoreResult<String> {
    agent.0.send_with_images(prompt, image_urls).await
}

/// One operation owned by the SDK facade.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum SdkOperation {
    /// Discover persisted sessions.
    Discover,
    /// Load one persisted session without modifying it.
    Load,
    /// Start a harness-native runtime.
    Start,
    /// Resume a harness-native persisted runtime.
    Resume,
    /// Send input to an SDK-owned runtime connection.
    Input,
    /// Poll canonical runtime events.
    Events,
    /// Interrupt the active turn.
    Interrupt,
    /// Queue guidance at the next model-loop boundary.
    Steer,
    /// Answer a typed runtime request.
    Respond,
    /// Export a loaded session through a native serializer.
    Export,
    /// Close an SDK-owned runtime connection.
    Close,
}

impl SdkOperation {
    /// Complete v1 operation inventory in stable declaration order.
    pub const ALL: [Self; 11] = [
        Self::Discover,
        Self::Load,
        Self::Start,
        Self::Resume,
        Self::Input,
        Self::Events,
        Self::Interrupt,
        Self::Steer,
        Self::Respond,
        Self::Export,
        Self::Close,
    ];

    /// Canonical `harness.v1` method used by JSON transports, when the
    /// operation is request/response rather than a subscription poll.
    pub const fn method(self) -> Option<&'static str> {
        match self {
            Self::Discover => Some("harness.v1.sessions.discover"),
            Self::Load => Some("harness.v1.sessions.load"),
            Self::Start => Some("harness.v1.runtimes.start"),
            Self::Resume => Some("harness.v1.runtimes.resume"),
            Self::Input => Some("harness.v1.runtimes.send_input"),
            Self::Events => None,
            Self::Interrupt => Some("harness.v1.runtimes.interrupt"),
            Self::Steer => Some("harness.v1.runtimes.steer"),
            Self::Respond => Some("harness.v1.runtimes.respond"),
            Self::Export => Some("harness.v1.sessions.export"),
            Self::Close => Some("harness.v1.runtimes.close"),
        }
    }

    /// Resolve one canonical method without accepting transport aliases.
    pub fn from_method(method: &str) -> Option<Self> {
        Self::ALL
            .into_iter()
            .find(|operation| operation.method() == Some(method))
    }

    /// Stable action spelling used by capability and error projections.
    pub const fn action_name(self) -> &'static str {
        match self {
            Self::Discover => "discover",
            Self::Load => "load",
            Self::Start => "start",
            Self::Resume => "resume",
            Self::Input => "input",
            Self::Events => "events",
            Self::Interrupt => "interrupt",
            Self::Steer => "steer",
            Self::Respond => "respond",
            Self::Export => "export",
            Self::Close => "close",
        }
    }

    /// Resolve a stable action spelling.
    pub fn from_action_name(action: &str) -> Option<Self> {
        Self::ALL
            .into_iter()
            .find(|operation| operation.action_name() == action)
    }
}

/// One typed SDK request before a transport adds its envelope.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct SdkRequest {
    /// Requested SDK operation.
    pub operation: SdkOperation,
    /// Operation-specific language-neutral parameters.
    #[serde(default)]
    pub params: Value,
}

/// Stable machine-readable SDK failure categories.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum SdkErrorCode {
    /// No authenticated client context was supplied.
    Unauthenticated,
    /// The authenticated client lacks a required capability.
    Unauthorized,
    /// Another client owns control or no controller lease was claimed.
    ControllerRequired,
    /// The caller's controller lease expired before the mutation.
    LeaseExpired,
    /// Input did not satisfy the operation contract.
    InvalidArgument,
    /// The requested session, runtime, or request was not found.
    NotFound,
    /// A turn already owns the runtime.
    Busy,
    /// The selected adapter honestly does not implement the operation.
    UnsupportedAction,
    /// A runtime or provider operation failed.
    Execution,
    /// The transport closed or returned an invalid envelope.
    Transport,
}

/// Typed turn failure shared by local, HTTP, ACP, CLI, and language adapters.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
pub enum RuntimeSubmitError {
    /// Another turn already owns the runtime.
    #[error("a turn is already in progress")]
    Busy,
    /// The active turn was cancelled through the SDK runtime handle.
    #[error("turn interrupted")]
    Interrupted,
    /// The model/provider/tool loop failed.
    #[error("{0}")]
    Agent(String),
}

/// Typed failure returned by every SDK adapter and compatibility projection.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
pub enum SdkError {
    /// A runtime operation was attempted without authenticated client state.
    #[error("SDK runtime authentication required")]
    Unauthenticated,
    /// The authenticated client lacks a required runtime permission.
    #[error("SDK runtime permission `{permission}` is required")]
    Unauthorized {
        /// Stable permission spelling.
        permission: String,
    },
    /// Mutation requires the controller lease. When another client owns it,
    /// its opaque identity and deadline are included for deterministic retry.
    #[error("controller lease required")]
    ControllerRequired {
        /// Current controller, when known.
        holder: Option<String>,
        /// Current controller deadline, when known.
        expires_at_ms: Option<u64>,
    },
    /// This client previously controlled the runtime but its lease expired.
    #[error("controller lease expired")]
    LeaseExpired,
    /// Input did not satisfy an operation contract.
    #[error("invalid SDK argument for {operation:?}: {message}")]
    InvalidArgument {
        /// Operation being decoded.
        operation: SdkOperation,
        /// Validation detail.
        message: String,
    },
    /// A stable identity was not found.
    #[error("SDK target for {operation:?} was not found: {message}")]
    NotFound {
        /// Operation being executed.
        operation: SdkOperation,
        /// Lookup detail.
        message: String,
    },
    /// The active adapter does not implement the requested action.
    #[error("SDK action `{0}` is not supported by this runtime")]
    UnsupportedAction(&'static str),
    /// The requested catalog operation is absent or has no typed route.
    #[error("SDK operation `{0}` is not supported by this runtime")]
    UnsupportedOperation(String),
    /// A slow consumer fell behind the bounded live-event channel.
    #[error("SDK event stream lost {0} event(s); reattach for a fresh snapshot")]
    ReplayGap(u64),
    /// The runtime closed its event stream.
    #[error("SDK runtime event stream closed")]
    Closed,
    /// An authenticated remote transport failed or returned an invalid value.
    #[error("SDK transport failed: {0}")]
    Transport(String),
    /// No live request exists for the supplied response id.
    #[error("SDK request {0} is not pending")]
    UnknownRequest(u64),
    /// The response kind or value does not match the pending request.
    #[error("invalid SDK response: {0}")]
    InvalidResponse(String),
    /// The canonical runtime rejected or failed a turn.
    #[error(transparent)]
    Submit(#[from] RuntimeSubmitError),
    /// A session/runtime implementation failed after validation.
    #[error("SDK execution failed for {operation:?}: {message}")]
    Execution {
        /// Operation being executed.
        operation: SdkOperation,
        /// Implementation detail.
        message: String,
    },
}

impl SdkError {
    /// Construct a typed failure for an SDK operation.
    pub fn new(code: SdkErrorCode, operation: SdkOperation, message: impl Into<String>) -> Self {
        let message = message.into();
        match code {
            SdkErrorCode::Unauthenticated => Self::Unauthenticated,
            SdkErrorCode::Unauthorized => Self::Unauthorized {
                permission: message,
            },
            SdkErrorCode::ControllerRequired => Self::ControllerRequired {
                holder: None,
                expires_at_ms: None,
            },
            SdkErrorCode::LeaseExpired => Self::LeaseExpired,
            SdkErrorCode::InvalidArgument => Self::InvalidArgument { operation, message },
            SdkErrorCode::NotFound => Self::NotFound { operation, message },
            SdkErrorCode::Busy => Self::Submit(RuntimeSubmitError::Busy),
            SdkErrorCode::UnsupportedAction => Self::unsupported(operation),
            SdkErrorCode::Execution => Self::Execution { operation, message },
            SdkErrorCode::Transport => Self::Transport(message),
        }
    }

    /// Construct a named unsupported-action failure.
    pub fn unsupported(operation: SdkOperation) -> Self {
        Self::UnsupportedAction(operation.action_name())
    }

    /// Stable machine-readable category.
    pub fn code(&self) -> SdkErrorCode {
        match self {
            Self::Unauthenticated => SdkErrorCode::Unauthenticated,
            Self::Unauthorized { .. } => SdkErrorCode::Unauthorized,
            Self::ControllerRequired { .. } => SdkErrorCode::ControllerRequired,
            Self::LeaseExpired => SdkErrorCode::LeaseExpired,
            Self::InvalidArgument { .. } | Self::InvalidResponse(_) => {
                SdkErrorCode::InvalidArgument
            }
            Self::NotFound { .. } | Self::UnknownRequest(_) => SdkErrorCode::NotFound,
            Self::Submit(RuntimeSubmitError::Busy) => SdkErrorCode::Busy,
            Self::UnsupportedAction(_) | Self::UnsupportedOperation(_) => {
                SdkErrorCode::UnsupportedAction
            }
            Self::Transport(_) | Self::ReplayGap(_) | Self::Closed => SdkErrorCode::Transport,
            Self::Submit(_) | Self::Execution { .. } => SdkErrorCode::Execution,
        }
    }

    /// Operation associated with this failure when it is unambiguous.
    pub fn operation(&self) -> Option<SdkOperation> {
        match self {
            Self::InvalidArgument { operation, .. }
            | Self::NotFound { operation, .. }
            | Self::Execution { operation, .. } => Some(*operation),
            Self::UnsupportedAction(action) => SdkOperation::from_action_name(action),
            Self::Unauthenticated
            | Self::Unauthorized { .. }
            | Self::ControllerRequired { .. }
            | Self::LeaseExpired => None,
            Self::UnknownRequest(_) | Self::InvalidResponse(_) => Some(SdkOperation::Respond),
            Self::Submit(_) => Some(SdkOperation::Input),
            Self::UnsupportedOperation(_)
            | Self::ReplayGap(_)
            | Self::Closed
            | Self::Transport(_) => None,
        }
    }
}

/// Capability inventory for the complete v1 SDK, independent of transport.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct SdkCapabilities {
    /// Schema identifier governing this descriptor.
    pub schema_version: String,
    /// Operations understood by the facade. A concrete runtime may still
    /// return `unsupported_action` for a mechanically unavailable action.
    pub operations: Vec<SdkOperation>,
    /// Stable error categories clients must preserve by name.
    pub error_codes: Vec<SdkErrorCode>,
    /// Whether events preserve unknown native payloads losslessly.
    pub opaque_events: bool,
}

impl Default for SdkCapabilities {
    fn default() -> Self {
        Self {
            schema_version: SDK_SCHEMA_VERSION.into(),
            operations: SdkOperation::ALL.to_vec(),
            error_codes: vec![
                SdkErrorCode::Unauthenticated,
                SdkErrorCode::Unauthorized,
                SdkErrorCode::ControllerRequired,
                SdkErrorCode::LeaseExpired,
                SdkErrorCode::InvalidArgument,
                SdkErrorCode::NotFound,
                SdkErrorCode::Busy,
                SdkErrorCode::UnsupportedAction,
                SdkErrorCode::Execution,
                SdkErrorCode::Transport,
            ],
            opaque_events: true,
        }
    }
}

/// Canonical event before a wire transport adds subscription metadata.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct SdkEvent {
    /// Monotonic sequence scoped to the SDK runtime.
    pub sequence: u64,
    /// Normalized or native event kind.
    pub kind: String,
    /// Complete payload, including unknown fields.
    pub payload: Value,
}

impl SdkEvent {
    pub(crate) fn new(sequence: u64, payload: Value) -> Self {
        let kind = payload
            .get("type")
            .or_else(|| payload.get("method"))
            .and_then(Value::as_str)
            .unwrap_or("unknown")
            .to_string();
        Self {
            sequence,
            kind,
            payload,
        }
    }
}

/// One runtime event paired with its durable SDK identity.
///
/// A transport may add a connection or subscription id around this value,
/// but those routing fields never become part of [`SdkEvent`] or a session.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct SdkRuntimeEvent {
    /// Stable SDK session identity, never a transport-local connection id.
    pub session_id: String,
    /// Canonical event shared by local and remote runtime adapters.
    pub event: SdkEvent,
}

/// Canonical live-runtime contract owned by the SDK.
///
/// Frontend modules are projections of this trait. They may render events or
/// add transport envelopes, but they do not own a second model loop.
#[async_trait]
pub trait SdkRuntime: Send + Sync {
    /// Describe runtime identity, modules, commands, actions, and state.
    async fn describe(&self) -> Result<crate::frontend::FrontendRuntimeDescriptor, SdkError>;
    /// Atomically attach at the canonical history/live-event boundary.
    async fn attach(
        &self,
        history_limit: usize,
    ) -> Result<crate::frontend::FrontendAttachment, SdkError>;
    /// Atomically accept a new user turn and return once ownership is claimed.
    ///
    /// Exactly one simultaneous caller succeeds. The accepted turn continues
    /// on the SDK-owned runtime and publishes its result through the canonical
    /// event stream; a competing caller receives [`SdkErrorCode::Busy`]
    /// synchronously from this operation.
    async fn send_input(self: Arc<Self>, prompt: String) -> Result<(), SdkError>;
    /// Atomically accept a multimodal user turn and return once ownership is
    /// claimed. Implementations must preserve images natively or reject the
    /// action; silently folding them into text is never allowed.
    async fn send_input_with_images(
        self: Arc<Self>,
        prompt: String,
        image_urls: Vec<String>,
    ) -> Result<(), SdkError> {
        if image_urls.is_empty() {
            self.send_input(prompt).await
        } else {
            Err(SdkError::UnsupportedAction("send_input_attachments"))
        }
    }
    /// Submit a new user turn.
    async fn submit(&self, prompt: String) -> Result<String, SdkError>;
    /// Submit a new user turn with canonical multimodal image inputs.
    ///
    /// Frontends must pass only runtime-resolved URLs or data URIs here; the
    /// SDK runtime, not a remote display client, owns input interpretation.
    async fn submit_with_images(
        &self,
        prompt: String,
        image_urls: Vec<String>,
    ) -> Result<String, SdkError> {
        if image_urls.is_empty() {
            self.submit(prompt).await
        } else {
            Err(SdkError::UnsupportedAction("submit_attachments"))
        }
    }
    /// Interrupt an active turn.
    async fn interrupt(&self) -> Result<bool, SdkError>;
    /// Queue a steering instruction when supported.
    async fn steer(&self, prompt: String) -> Result<(), SdkError>;
    /// Answer a typed runtime request when supported.
    async fn respond(&self, response: crate::frontend::FrontendResponse) -> Result<(), SdkError>;
    /// Invoke one operation from the descriptor's explicit catalog.
    async fn invoke(
        &self,
        operation: crate::frontend::FrontendOperationInvocation,
    ) -> Result<crate::frontend::FrontendOperationResult, SdkError> {
        Err(SdkError::UnsupportedOperation(
            operation.operation_id().to_string(),
        ))
    }
    /// Read the one-controller/many-observer ownership state.
    async fn lease_snapshot(&self) -> Result<crate::RuntimeLeaseSnapshot, SdkError> {
        Err(SdkError::UnsupportedOperation("runtime.lease".into()))
    }
    /// Explicitly acquire the controller lease from another interactive
    /// client. Ordinary mutations never perform an implicit takeover.
    async fn take_control(&self) -> Result<crate::RuntimeLeaseSnapshot, SdkError> {
        Err(SdkError::UnsupportedOperation(
            "runtime.take_control".into(),
        ))
    }
    /// Refresh observer activity and a controller lease owned by this client.
    async fn heartbeat(&self) -> Result<crate::RuntimeLeaseSnapshot, SdkError> {
        Err(SdkError::UnsupportedOperation("runtime.heartbeat".into()))
    }
    /// Release this client's observer/controller state without stopping the
    /// runtime.
    async fn detach(&self) -> Result<crate::RuntimeLeaseSnapshot, SdkError> {
        Err(SdkError::UnsupportedOperation("runtime.detach".into()))
    }
    /// Explicitly close the SDK-owned runtime when the negotiated descriptor
    /// grants that owner-level action. Dropping an attachment is always a
    /// detach and never calls this operation implicitly.
    async fn close(&self) -> Result<(), SdkError> {
        Err(SdkError::unsupported(SdkOperation::Close))
    }
}

/// Stateful SDK facade consumed by public transport adapters.
#[async_trait]
pub trait SdkService: Send {
    /// Describe the versioned contract without invoking a runtime.
    fn capabilities(&self) -> SdkCapabilities {
        SdkCapabilities::default()
    }

    /// Execute one typed request. Transport correlation fields are not part
    /// of this API and therefore cannot contaminate canonical state.
    async fn execute(&mut self, request: SdkRequest) -> Result<Value, SdkError>;

    /// Poll canonical runtime events without a transport envelope.
    async fn events(&mut self) -> Result<Vec<SdkRuntimeEvent>, SdkError>;
}