perf(agent): stabilkan async & parallel — satu runtime, bounded concurrency, isolasi error

Seperti Claude Code: satu runtime shared, concurrency dibatasi, error
subagent terisolasi (satu node gagal tidak menggagalkan cycle).

- feat(runtime): global tokio runtime via OnceLock — ganti 9+ titik
  Runtime::new() per tool call (spawn, parallel_delegate, workflow,
  explore, dir_cache, daemon handler). Hemat resource, hilangkan panic
  path Runtime::new().expect() di daemon compaction.
- fix(workflow): execute_cycle ganti try_join_all (fail-fast) →
  buffer_unordered(8) + isolasi error per node; node gagal di-log dan
  diganti [ERROR], hasil node lain tetap dipakai (Claude Code-style).
- fix(parallel_delegate): spawn subagent dibatasi per batch max_parallel
  (tidak unbounded threads).
- perf(subagent): run_agent adaptif max_tokens (800/1600/4096), temp 0.2,
  truncate tool output 12k, error-recovery note utk tool error berulang.
- test: runtime singleton + block_on (2 test).

apps/infrastructure/src/subagent/engine.rs

@@ -23,6 +23,37 @@ use zesdex_domain::subagent_directive;
 /// Maximum number of tool-call iterations before the engine gives up.
 const MAX_ITERATIONS: u32 = 25;
 
+/// A single tool-result message is truncated before entering the subagent's
+/// context so it cannot blow the window (matches the main turn service).
+const TOOL_OUTPUT_MAX_CHARS: usize = 12_000;
+
+/// Maximum consecutive identical tool errors before the engine injects a
+/// recovery note steering the model to a different approach.
+const MAX_CONSECUTIVE_TOOL_ERRORS: usize = 3;
+
+/// Pick a `max_tokens` budget proportional to the directive's length.
+fn adaptive_max_tokens(directive_len: usize) -> u32 {
+    if directive_len <= 80 {
+        800
+    } else if directive_len <= 400 {
+        1600
+    } else {
+        4096
+    }
+}
+
+fn truncate_tool_output(output: String) -> String {
+    if output.len() <= TOOL_OUTPUT_MAX_CHARS {
+        return output;
+    }
+    let mut result: String = output.chars().take(TOOL_OUTPUT_MAX_CHARS).collect();
+    result.push_str(&format!(
+        "\n...[truncated {} chars]",
+        output.len() - TOOL_OUTPUT_MAX_CHARS
+    ));
+    result
+}
+
 /// Emit an `AgentProgress` event onto the turn-event queue, if one is
 /// configured in the `ToolCtx`.
 fn report_progress(tool_ctx: &ToolCtx, progress: AgentProgress) {
@@ -85,11 +116,17 @@ pub async fn run_agent(
         Some(ctx.base_url.clone()),
     );
 
+    let max_tokens = adaptive_max_tokens(directive.len());
+
+    // Track repeated tool errors so the agent can recover from a dead end.
+    let mut consecutive_errors = 0usize;
+    let mut last_tool = String::new();
+
     // Limited iteration loop so we don't run forever
     for iteration in 0..MAX_ITERATIONS {
         use zesdex_application::ports::ProviderService;
         let (response_msg, _usage) = client
-            .chat(&messages, Some(defs.clone()), Some(4096), None)
+            .chat(&messages, Some(defs.clone()), Some(max_tokens), Some(0.2))
             .await?;
 
         let content = response_msg.content.clone().unwrap_or_default();
@@ -113,7 +150,7 @@ pub async fn run_agent(
                 &tool_ctx,
                 AgentProgress::running(
                     "subagent",
-                    format!("{}:{}", directive, tool_name),
+                    format!("{}:{tool_name}", directive),
                     Some(tool_name.clone()),
                 ),
             );
@@ -127,7 +164,29 @@ pub async fn run_agent(
                 format!("Unknown tool: {tool_name}")
             };
 
-            messages.push(ChatMessage::tool(tc.id.clone(), result));
+            // Error-recovery: if the same tool keeps failing, inject a
+            // system note steering the model to a different approach.
+            if result.starts_with("Error:") {
+                if last_tool.as_str() == tool_name.as_str() {
+                    consecutive_errors += 1;
+                } else {
+                    consecutive_errors = 1;
+                    last_tool = tool_name.to_string();
+                }
+                if consecutive_errors >= MAX_CONSECUTIVE_TOOL_ERRORS {
+                    messages.push(ChatMessage::system(
+                        zesdex_domain::agent::prompt::error_recovery_note(tool_name, &result),
+                    ));
+                    consecutive_errors = 0;
+                }
+            } else {
+                consecutive_errors = 0;
+            }
+
+            messages.push(ChatMessage::tool(
+                tc.id.clone(),
+                truncate_tool_output(result),
+            ));
         }
 
         // Add assistant response if there was text content

apps/infrastructure/src/subagent/spawn.rs

@@ -32,7 +32,6 @@ pub fn spawn_subagent(
 ) -> thread::JoinHandle<Result<String>> {
     info!("Spawning subagent: {directive}");
     thread::spawn(move || {
-        let rt = tokio::runtime::Runtime::new()?;
-        rt.block_on(run_agent(ctx, &directive, access, tool_ctx))
+        crate::runtime::runtime().block_on(run_agent(ctx, &directive, access, tool_ctx))
     })
 }