7.10 agui: AG-UI 1.0 events and SSE encoder

// crates/agui/src/lib.rs   (depends on axum, serde, serde_json)
use serde::{Deserialize, Serialize};
use serde_json::Value;

#[derive(Debug, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct RunAgentInput {
    pub thread_id: String,
    pub run_id: String,
    #[serde(default)] pub state: Value,
    #[serde(default)] pub messages: Vec<Value>,
    #[serde(default)] pub tools: Vec<Value>,
    #[serde(default)] pub context: Vec<Value>,
    #[serde(default)] pub forwarded_props: Value,
    #[serde(default)] pub resume: Vec<ResumeEntry>,
    pub protocol_version: Option<String>,   // absent => pre-1.0 client
}
#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(rename_all = "camelCase")]
pub struct ResumeEntry { pub interrupt_id: String, pub status: String, pub payload: Option<Value> }

#[derive(Debug, Serialize, Clone)]
#[serde(rename_all = "camelCase")]
pub struct Interrupt {
    pub id: String, pub reason: String,
    #[serde(skip_serializing_if = "Option::is_none")] pub message: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")] pub response_schema: Option<Value>,
    #[serde(skip_serializing_if = "Option::is_none")] pub expires_at: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")] pub metadata: Option<Value>,
}
#[derive(Debug, Serialize, Clone)]
#[serde(tag = "type", rename_all = "lowercase")]
pub enum RunOutcome { Success, Interrupt { interrupts: Vec<Interrupt> } }

/// Absent fields are omitted, never null (AG-UI 1.0 rule).
#[derive(Debug, Serialize, Clone)]
#[serde(tag = "type", rename_all = "SCREAMING_SNAKE_CASE", rename_all_fields = "camelCase")]
pub enum Event {
    RunStarted { thread_id: String, run_id: String, #[serde(skip_serializing_if = "Option::is_none")] protocol_version: Option<String> },
    RunFinished { thread_id: String, run_id: String,
        #[serde(skip_serializing_if = "Option::is_none")] result: Option<Value>,
        #[serde(skip_serializing_if = "Option::is_none")] outcome: Option<RunOutcome> },
    RunError { message: String, #[serde(skip_serializing_if = "Option::is_none")] code: Option<String> },
    StepStarted { step_name: String },
    StepFinished { step_name: String },
    TextMessageStart { message_id: String, role: String },
    TextMessageContent { message_id: String, delta: String },
    TextMessageEnd { message_id: String },
    ToolCallStart { tool_call_id: String, tool_call_name: String, #[serde(skip_serializing_if = "Option::is_none")] parent_message_id: Option<String> },
    ToolCallArgs { tool_call_id: String, delta: String },
    ToolCallEnd { tool_call_id: String },
    ToolCallResult { message_id: String, tool_call_id: String, content: String },
    StateSnapshot { snapshot: Value },
    StateDelta { delta: Vec<Value> },          // RFC 6902 JSON Patch operations
    MessagesSnapshot { messages: Vec<Value> },
    Custom { name: String, value: Value },
}

pub fn supports_interrupt_outcome(input: &RunAgentInput) -> bool {
    input.protocol_version.as_deref()
        .is_some_and(|v| v.split('.').next().and_then(|m| m.parse::<u32>().ok()).unwrap_or(0) >= 1)
}

/// Axum SSE encoding: one `data:` line per JSON event.
pub fn to_sse(ev: &Event) -> axum::response::sse::Event {
    axum::response::sse::Event::default().data(serde_json::to_string(ev).expect("serializable"))
}

Once ag-ui PR #2778 publishes an ag-ui 1.0 crate, replace this module with a re-export. A conformance test checks the JSON against the AG-UI 1.0 schema.