From 108e0cd6320dfece9e3fe07cceae6ae8d42f56d4 Mon Sep 17 00:00:00 2001
From: Bryan Helmkamp <bryan@brynary.com>
Date: Mon, 30 Mar 2026 17:49:04 -0400
Subject: [PATCH] Split agent processing into thinking and executing

---
 docs/reference/sdk.mdx                        |  2 +-
 lib/crates/fabro-agent/src/session.rs         | 27 +++++++++++++------
 lib/crates/fabro-agent/src/types.rs           |  4 +--
 lib/crates/fabro-cli/src/commands/run/logs.rs |  8 ++++--
 4 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/docs/reference/sdk.mdx b/docs/reference/sdk.mdx
index 50771c9ef..76d8bc302 100644
--- a/docs/reference/sdk.mdx
+++ b/docs/reference/sdk.mdx
@@ -86,7 +86,7 @@ pub fn new(
 
 | Method | Description |
 |---|---|
-| `state()` | Returns `SessionState`: `Idle`, `Processing`, `AwaitingInput`, or `Closed`. |
+| `state()` | Returns `SessionState`: `Idle`, `Thinking`, `Executing`, or `Closed`. |
 | `history()` | Returns the conversation as `&History` (a sequence of `Turn` values). |
 | `subscribe()` | Returns a broadcast receiver for `SessionEvent` values. |
 
diff --git a/lib/crates/fabro-agent/src/session.rs b/lib/crates/fabro-agent/src/session.rs
index 29b64280f..d01979e56 100644
--- a/lib/crates/fabro-agent/src/session.rs
+++ b/lib/crates/fabro-agent/src/session.rs
@@ -481,9 +481,12 @@ impl Session {
     /// cleanup as appropriate for each transition.
     ///
     /// Valid transitions (matches the Attractor spec):
-    /// - Idle → Processing
-    /// - Processing → Idle  (emits ProcessingEnd)
-    /// - Processing → Closed (emits SessionEnded)
+    /// - Idle → Thinking
+    /// - Thinking → Executing
+    /// - Thinking → Idle  (emits ProcessingEnd)
+    /// - Executing → Thinking
+    /// - Thinking → Closed (emits SessionEnded)
+    /// - Executing → Closed (emits SessionEnded)
     /// - Idle → Closed (emits SessionEnded)
     /// - any → Closed (abort/error — emits SessionEnded)
     fn transition(&mut self, to: SessionState) {
@@ -495,9 +498,13 @@ impl Session {
         debug_assert!(
             matches!(
                 (from, to),
-                (SessionState::Idle, SessionState::Processing)
-                    | (SessionState::Processing, SessionState::Idle)
-                    | (_, SessionState::Closed)
+                (
+                    SessionState::Idle | SessionState::Executing,
+                    SessionState::Thinking
+                ) | (
+                    SessionState::Thinking,
+                    SessionState::Executing | SessionState::Idle
+                ) | (_, SessionState::Closed)
             ),
             "Invalid session state transition: {from:?} -> {to:?}"
         );
@@ -513,7 +520,9 @@ impl Session {
                 .emit(self.id.clone(), AgentEvent::SessionEnded);
         }
 
-        if from == SessionState::Processing && to == SessionState::Idle {
+        if matches!(from, SessionState::Thinking | SessionState::Executing)
+            && to == SessionState::Idle
+        {
             self.event_emitter
                 .emit(self.id.clone(), AgentEvent::ProcessingEnd);
         }
@@ -608,7 +617,7 @@ impl Session {
             return Err(AgentError::SessionClosed);
         }
 
-        self.transition(SessionState::Processing);
+        self.transition(SessionState::Thinking);
 
         // Expand skill references in input
         let expanded = if self.skills.is_empty() {
@@ -845,6 +854,7 @@ impl Session {
             round_count += 1;
 
             // Execute tool calls (parallel or sequential based on provider)
+            self.transition(SessionState::Executing);
             let results = execute_tool_calls(
                 &tool_calls,
                 true,
@@ -881,6 +891,7 @@ impl Session {
 
             // Drain steering after tool execution
             self.drain_steering();
+            self.transition(SessionState::Thinking);
 
             // Loop detection
             if self.config.enable_loop_detection
diff --git a/lib/crates/fabro-agent/src/types.rs b/lib/crates/fabro-agent/src/types.rs
index d9bdc4ed4..d6fe2fb6a 100644
--- a/lib/crates/fabro-agent/src/types.rs
+++ b/lib/crates/fabro-agent/src/types.rs
@@ -84,8 +84,8 @@ impl Turn {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum SessionState {
     Idle,
-    Processing,
-    AwaitingInput,
+    Thinking,
+    Executing,
     Closed,
 }
 
diff --git a/lib/crates/fabro-cli/src/commands/run/logs.rs b/lib/crates/fabro-cli/src/commands/run/logs.rs
index 3c2a8c129..d8920655a 100644
--- a/lib/crates/fabro-cli/src/commands/run/logs.rs
+++ b/lib/crates/fabro-cli/src/commands/run/logs.rs
@@ -1,3 +1,4 @@
+use std::fmt::Write as _;
 use std::io::{self, BufRead, IsTerminal, Write};
 use std::path::Path;
 use std::time::Duration;
@@ -496,8 +497,11 @@ pub(crate) fn format_event_pretty(line: &str, styles: &Styles) -> Option<String>
                 duration,
             );
             if token_total > 0 {
-                line.push_str("  ");
-                line.push_str(&styles.dim.apply_to(format_tokens(token_total)).to_string());
+                let _ = write!(
+                    line,
+                    "  {}",
+                    styles.dim.apply_to(format_tokens(token_total))
+                );
             }
             Some(line)
         }