feat: unify worker lifecycle restore semantics

crates/agen/examples/engine_cancel_demo.rs

@@ -4,7 +4,7 @@
 
 use agen::llm_client::scheme::{Scheme, anthropic::AnthropicScheme};
 use agen::llm_client::transport::{HttpTransport, ResolvedAuth};
-use agen::{Engine, EngineRunExit, StopReason};
+use agen::{Engine, EngineRunExit, RunInterruptionReason};
 use std::time::Duration;
 
 #[tokio::main]
@@ -51,7 +51,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         EngineRunExit::Finished => println!("✅ Task completed normally"),
         EngineRunExit::Paused => println!("⏸️  Task paused"),
         EngineRunExit::Yielded => println!("↩️  Task yielded"),
-        EngineRunExit::Interrupted(StopReason::LimitReached) => {
+        EngineRunExit::Interrupted(RunInterruptionReason::LimitReached) => {
             println!("🔒 Turn limit reached")
         }
         EngineRunExit::Interrupted(reason) => println!("❌ Task interrupted: {reason:?}"),

crates/agen/examples/engine_cli.rs

@@ -39,7 +39,7 @@ use tracing::info;
 use tracing_subscriber::EnvFilter;
 
 use agen::{
-    Engine, EngineRunExit, StopReason,
+    Engine, EngineRunExit, RunInterruptionReason,
     interceptor::{Interceptor, PostToolAction, ToolResultInfo},
     llm_client::{
         LlmClient,
@@ -478,7 +478,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     // One-shot mode
     if let Some(prompt) = args.prompt {
         let output = engine.run(&mut history, &prompt).await;
-        if let EngineRunExit::Interrupted(StopReason::Unexpected(error)) = output.result {
+        if let EngineRunExit::Interrupted(RunInterruptionReason::Unexpected(error)) = output.result
+        {
             eprintln!("\n❌ Error: {error}");
         }
 
@@ -518,7 +519,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             break;
         }
 
-        if let EngineRunExit::Interrupted(StopReason::Unexpected(error)) =
+        if let EngineRunExit::Interrupted(RunInterruptionReason::Unexpected(error)) =
             locked.run(&mut history, input).await
         {
             eprintln!("\n❌ Error: {error}");

crates/agen/src/engine.rs

@@ -147,12 +147,12 @@ pub enum EngineRunExit {
     Finished,
     Paused,
     Yielded,
-    Interrupted(StopReason),
+    Interrupted(RunInterruptionReason),
 }
 
 /// A typed reason why an engine run could not finish normally.
 #[derive(Debug)]
-pub enum StopReason {
+pub enum RunInterruptionReason {
     LimitReached,
     ContextWindowExceeded,
     Cancelled,
@@ -165,13 +165,15 @@ impl From<Result<EngineResult, EngineError>> for EngineRunExit {
             Ok(EngineResult::Finished) => Self::Finished,
             Ok(EngineResult::Paused) => Self::Paused,
             Ok(EngineResult::Yielded) => Self::Yielded,
-            Ok(EngineResult::LimitReached) => Self::Interrupted(StopReason::LimitReached),
-            Err(EngineError::Client(ClientError::ContextWindowExceeded)) => {
-                Self::Interrupted(StopReason::ContextWindowExceeded)
+            Ok(EngineResult::LimitReached) => {
+                Self::Interrupted(RunInterruptionReason::LimitReached)
             }
-            Err(EngineError::Cancelled) => Self::Interrupted(StopReason::Cancelled),
+            Err(EngineError::Client(ClientError::ContextWindowExceeded)) => {
+                Self::Interrupted(RunInterruptionReason::ContextWindowExceeded)
+            }
+            Err(EngineError::Cancelled) => Self::Interrupted(RunInterruptionReason::Cancelled),
             Err(EngineError::PauseRequested) => Self::Paused,
-            Err(error) => Self::Interrupted(StopReason::Unexpected(error)),
+            Err(error) => Self::Interrupted(RunInterruptionReason::Unexpected(error)),
         }
     }
 }

crates/agen/src/lib.rs

@@ -22,7 +22,7 @@ pub use agen_macros::{description, tool, tool_registry};
 pub use callback::{TextBlockScope, ThinkingBlockScope, ToolUseBlockScope};
 pub use engine::{
     Engine, EngineConfig, EngineError, EngineResult, EngineRunExit, EngineRunOutput,
-    LlmRetryNotice, StopReason, ToolRegistryError,
+    LlmRetryNotice, RunInterruptionReason, ToolRegistryError,
 };
 pub use handler::ToolUseBlockStart;
 pub use history::{History, HistoryEntry};

crates/agen/tests/engine_state_test.rs

@@ -14,7 +14,7 @@ use agen::interceptor::{
 };
 use agen::llm_client::event::{Event, ResponseStatus, StatusEvent};
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
-use agen::{Engine, EngineError, EngineRunExit, History, StopReason};
+use agen::{Engine, EngineError, EngineRunExit, History, RunInterruptionReason};
 use async_trait::async_trait;
 use common::MockLlmClient;
 
@@ -205,7 +205,7 @@ async fn history_append_failure_stops_before_tool_execution() {
     let exit = engine.run(&mut history, "use the tool").await;
 
     assert!(
-        matches!(exit, EngineRunExit::Interrupted(StopReason::Unexpected(EngineError::HistoryAppend(ref message))) if message == "simulated ENOSPC")
+        matches!(exit, EngineRunExit::Interrupted(RunInterruptionReason::Unexpected(EngineError::HistoryAppend(ref message))) if message == "simulated ENOSPC")
     );
     assert_eq!(tool.call_count(), 0);
     assert_eq!(history.len(), 1);
@@ -730,7 +730,7 @@ async fn paused_tool_resume_does_not_reset_the_consumed_turn_budget() {
 
     assert!(matches!(
         engine.resume(&mut history).await,
-        EngineRunExit::Interrupted(StopReason::LimitReached)
+        EngineRunExit::Interrupted(RunInterruptionReason::LimitReached)
     ));
     assert_eq!(engine.turn_count(), 1);
     assert_eq!(engine.active_run_turn_count(), None);
@@ -785,7 +785,7 @@ async fn interceptor_continuation_consumes_the_logical_run_budget() {
 
     assert!(matches!(
         engine.run(&mut history, "start").await,
-        EngineRunExit::Interrupted(StopReason::LimitReached)
+        EngineRunExit::Interrupted(RunInterruptionReason::LimitReached)
     ));
     assert_eq!(engine.turn_count(), 1);
     assert_eq!(engine.llm_call_count(), 1);
@@ -803,7 +803,7 @@ async fn restored_active_run_budget_is_enforced_before_another_llm_call() {
 
     assert!(matches!(
         engine.resume(&mut history).await,
-        EngineRunExit::Interrupted(StopReason::LimitReached)
+        EngineRunExit::Interrupted(RunInterruptionReason::LimitReached)
     ));
     assert_eq!(engine.turn_count(), 7);
     assert_eq!(engine.llm_call_count(), 0);

crates/agen/tests/parallel_execution_test.rs

@@ -580,7 +580,7 @@ async fn cooperative_cancellation_commits_bounded_terminal_output() {
     );
     assert!(matches!(
         output.result,
-        agen::EngineRunExit::Interrupted(agen::StopReason::Cancelled)
+        agen::EngineRunExit::Interrupted(agen::RunInterruptionReason::Cancelled)
     ));
 }
 
@@ -1214,7 +1214,7 @@ async fn post_tool_abort_commits_confirmed_result_before_stopping_run() {
     );
     assert!(matches!(
         output.result,
-        agen::EngineRunExit::Interrupted(agen::StopReason::Unexpected(
+        agen::EngineRunExit::Interrupted(agen::RunInterruptionReason::Unexpected(
             agen::EngineError::Aborted(ref reason)
         )) if reason == "policy stopped the run"
     ));