TUIにThinkingを表示する実装

crates/llm-worker/src/callback.rs

@@ -7,8 +7,8 @@
 use std::marker::PhantomData;
 
 use crate::handler::{
-    Handler, Kind, TextBlockEvent, TextBlockKind, ToolUseBlockEvent, ToolUseBlockKind,
+    Handler, Kind, TextBlockEvent, TextBlockKind, ThinkingBlockEvent, ThinkingBlockKind,
-    ToolUseBlockStart,
+    ToolUseBlockEvent, ToolUseBlockKind, ToolUseBlockStart,
 };
 use crate::tool::ToolCall;
 
@@ -95,6 +95,81 @@ impl Handler<TextBlockKind> for ClosureTextBlockHandler {
     }
 }
 
+// =============================================================================
+// ThinkingBlock Closure Handler
+// =============================================================================
+
+/// Callback scope for a thinking block.
+///
+/// Mirrors `TextBlockScope`. Some providers (or some configurations)
+/// emit thinking metadata without plaintext deltas — in that case the
+/// block fires `Start` and `Stop` with no `Delta` in between, which is
+/// expected and not an error.
+pub struct ThinkingBlockScope {
+    pub(crate) on_delta: Option<Box<dyn FnMut(&str) + Send + Sync>>,
+    pub(crate) on_stop: Option<Box<dyn FnMut(&str) + Send + Sync>>,
+}
+
+impl ThinkingBlockScope {
+    fn new() -> Self {
+        Self {
+            on_delta: None,
+            on_stop: None,
+        }
+    }
+
+    /// Register a callback for each thinking text delta (streaming fragment).
+    pub fn on_delta(&mut self, f: impl FnMut(&str) + Send + Sync + 'static) {
+        self.on_delta = Some(Box::new(f));
+    }
+
+    /// Register a callback invoked when the block completes.
+    ///
+    /// Receives the full accumulated thinking text. May be empty when
+    /// the provider didn't emit any plaintext deltas.
+    pub fn on_stop(&mut self, f: impl FnMut(&str) + Send + Sync + 'static) {
+        self.on_stop = Some(Box::new(f));
+    }
+}
+
+#[derive(Default)]
+pub(crate) struct ThinkingBlockClosureState {
+    on_delta: Option<Box<dyn FnMut(&str) + Send + Sync>>,
+    on_stop: Option<Box<dyn FnMut(&str) + Send + Sync>>,
+    buffer: String,
+}
+
+pub(crate) struct ClosureThinkingBlockHandler {
+    pub(crate) setup: Box<dyn FnMut(&mut ThinkingBlockScope) + Send + Sync>,
+}
+
+impl Handler<ThinkingBlockKind> for ClosureThinkingBlockHandler {
+    type Scope = ThinkingBlockClosureState;
+
+    fn on_event(&mut self, scope: &mut Self::Scope, event: &ThinkingBlockEvent) {
+        match event {
+            ThinkingBlockEvent::Start(_) => {
+                scope.buffer.clear();
+                let mut builder = ThinkingBlockScope::new();
+                (self.setup)(&mut builder);
+                scope.on_delta = builder.on_delta;
+                scope.on_stop = builder.on_stop;
+            }
+            ThinkingBlockEvent::Delta(text) => {
+                scope.buffer.push_str(text);
+                if let Some(f) = &mut scope.on_delta {
+                    f(text);
+                }
+            }
+            ThinkingBlockEvent::Stop(_) => {
+                if let Some(f) = &mut scope.on_stop {
+                    f(&scope.buffer);
+                }
+            }
+        }
+    }
+}
+
 // =============================================================================
 // ToolUseBlock Closure Handler
 // =============================================================================

crates/llm-worker/src/lib.rs

@@ -53,7 +53,7 @@ pub mod tool;
 pub mod tool_server;
 pub mod usage_record;
 
-pub use callback::{TextBlockScope, ToolUseBlockScope};
+pub use callback::{TextBlockScope, ThinkingBlockScope, ToolUseBlockScope};
 pub use handler::ToolUseBlockStart;
 pub use interceptor::Interceptor;
 pub use message::{ContentPart, Item, Message, Role};

crates/llm-worker/src/worker.rs

@@ -8,8 +8,8 @@ use tracing::{debug, info, trace, warn};
 use crate::{
     Item,
     callback::{
-        ClosureMetaHandler, ClosureTextBlockHandler, ClosureToolUseBlockHandler, TextBlockScope,
+        ClosureMetaHandler, ClosureTextBlockHandler, ClosureThinkingBlockHandler,
-        ToolUseBlockScope,
+        ClosureToolUseBlockHandler, TextBlockScope, ThinkingBlockScope, ToolUseBlockScope,
     },
     handler::{ErrorKind, StatusKind, ToolUseBlockStart, UsageKind},
     interceptor::{
@@ -237,6 +237,21 @@ impl<C: LlmClient, S: WorkerState> Worker<C, S> {
         });
     }
 
+    /// Register a thinking block observer with scoped callbacks.
+    ///
+    /// Mirrors `on_text_block`. Some providers don't expose plaintext
+    /// reasoning content; in that case the block fires Start and Stop
+    /// with no Delta in between, and `on_stop` receives an empty string.
+    pub fn on_thinking_block(
+        &mut self,
+        setup: impl FnMut(&mut ThinkingBlockScope) + Send + Sync + 'static,
+    ) {
+        self.timeline
+            .on_thinking_block(ClosureThinkingBlockHandler {
+                setup: Box::new(setup),
+            });
+    }
+
     /// Register a tool use block observer with scoped callbacks.
     ///
     /// The setup closure receives `&ToolUseBlockStart` (containing `id` and `name`)

crates/pod/src/controller.rs

@@ -141,6 +141,26 @@ impl PodController {
                 });
             });
 
+            let tx = event_tx.clone();
+            worker.on_thinking_block(move |block| {
+                // Start fires unconditionally so the TUI can show
+                // "Thinking..." even when the provider doesn't emit
+                // plaintext deltas.
+                let _ = tx.send(Event::ThinkingStart);
+                let tx_d = tx.clone();
+                block.on_delta(move |text| {
+                    let _ = tx_d.send(Event::ThinkingDelta {
+                        text: text.to_owned(),
+                    });
+                });
+                let tx_s = tx.clone();
+                block.on_stop(move |text| {
+                    let _ = tx_s.send(Event::ThinkingDone {
+                        text: text.to_owned(),
+                    });
+                });
+            });
+
             let tx = event_tx.clone();
             worker.on_tool_use_block(move |start, block| {
                 let _ = tx.send(Event::ToolCallStart {

crates/protocol/src/lib.rs

@@ -178,6 +178,21 @@ pub enum Event {
     TextDone {
         text: String,
     },
+    /// A reasoning / thinking block has started.
+    ///
+    /// Always paired with a `ThinkingDone`. `ThinkingDelta` is optional:
+    /// some providers (or some configurations) emit thinking metadata
+    /// without plaintext, in which case Start → Done arrive with no
+    /// deltas in between. Multiple thinking blocks per turn are allowed.
+    ThinkingStart,
+    ThinkingDelta {
+        text: String,
+    },
+    /// Thinking block completed. `text` is the full accumulated body
+    /// (empty string when the provider didn't emit plaintext).
+    ThinkingDone {
+        text: String,
+    },
     ToolCallStart {
         id: String,
         name: String,
@@ -468,6 +483,34 @@ mod tests {
         assert_eq!(parsed["data"]["text"], "Hello");
     }
 
+    #[test]
+    fn event_thinking_roundtrip() {
+        for event in [
+            Event::ThinkingStart,
+            Event::ThinkingDelta {
+                text: "step 1".into(),
+            },
+            Event::ThinkingDone {
+                text: "step 1\nstep 2".into(),
+            },
+        ] {
+            let json = serde_json::to_string(&event).unwrap();
+            let decoded: Event = serde_json::from_str(&json).unwrap();
+            match (&event, &decoded) {
+                (Event::ThinkingStart, Event::ThinkingStart) => {}
+                (Event::ThinkingDelta { text: a }, Event::ThinkingDelta { text: b })
+                | (Event::ThinkingDone { text: a }, Event::ThinkingDone { text: b }) => {
+                    assert_eq!(a, b);
+                }
+                _ => panic!("variant mismatch: {event:?} vs {decoded:?}"),
+            }
+        }
+
+        let parsed: serde_json::Value =
+            serde_json::from_str(&serde_json::to_string(&Event::ThinkingStart).unwrap()).unwrap();
+        assert_eq!(parsed["event"], "thinking_start");
+    }
+
     #[test]
     fn event_run_end_format() {
         let event = Event::RunEnd {

crates/tui/src/app.rs

@@ -1,6 +1,10 @@
+use std::time::Instant;
+
 use protocol::{AlertLevel, AlertSource, Event, Method, RunResult, Segment};
 
-use crate::block::{Block, CompactEvent, ToolCallBlock, ToolCallState};
+use crate::block::{
+    Block, CompactEvent, ThinkingBlock, ThinkingState, ToolCallBlock, ToolCallState,
+};
 use crate::cache::FileCache;
 use crate::input::InputBuffer;
 use crate::scroll::Scroll;
@@ -111,9 +115,40 @@ impl App {
             Event::TextDone { .. } => {
                 self.assistant_streaming = false;
             }
+            Event::ThinkingStart => {
+                self.assistant_streaming = false;
+                self.blocks.push(Block::Thinking(ThinkingBlock {
+                    text: String::new(),
+                    state: ThinkingState::Streaming {
+                        started_at: Instant::now(),
+                    },
+                }));
+            }
+            Event::ThinkingDelta { text } => {
+                if let Some(b) = self.last_streaming_thinking_mut() {
+                    b.text.push_str(&text);
+                }
+            }
+            Event::ThinkingDone { text } => {
+                if let Some(b) = self.last_streaming_thinking_mut() {
+                    if b.text.is_empty() {
+                        b.text = text;
+                    }
+                    let elapsed = match &b.state {
+                        ThinkingState::Streaming { started_at } => {
+                            Some(started_at.elapsed().as_secs())
+                        }
+                        _ => None,
+                    };
+                    b.state = ThinkingState::Finished {
+                        elapsed_secs: elapsed,
+                    };
+                }
+            }
             Event::TurnEnd { .. } => {
                 self.assistant_streaming = false;
                 self.mark_orphan_tool_calls_incomplete();
+                self.mark_orphan_thinking_incomplete();
                 self.current_tool = None;
             }
             Event::ToolCallStart { id, name } => {
@@ -272,6 +307,39 @@ impl App {
         self.assistant_streaming = true;
     }
 
+    /// Walk the most recently pushed blocks looking for a thinking
+    /// block that's still in `Streaming`. Stops at the current
+    /// `TurnHeader` to avoid latching onto a thinking block from a
+    /// previous turn after it was somehow left dangling.
+    fn last_streaming_thinking_mut(&mut self) -> Option<&mut ThinkingBlock> {
+        for b in self.blocks.iter_mut().rev() {
+            match b {
+                Block::Thinking(t) if matches!(t.state, ThinkingState::Streaming { .. }) => {
+                    return Some(t);
+                }
+                Block::TurnHeader { .. } => return None,
+                _ => continue,
+            }
+        }
+        None
+    }
+
+    fn mark_orphan_thinking_incomplete(&mut self) {
+        for b in self.blocks.iter_mut().rev() {
+            match b {
+                Block::Thinking(t) => {
+                    if let ThinkingState::Streaming { started_at } = t.state {
+                        t.state = ThinkingState::Incomplete {
+                            elapsed_secs: Some(started_at.elapsed().as_secs()),
+                        };
+                    }
+                }
+                Block::TurnHeader { .. } => break,
+                _ => {}
+            }
+        }
+    }
+
     fn find_tool_call_mut(&mut self, id: &str) -> Option<&mut ToolCallBlock> {
         for b in self.blocks.iter_mut().rev() {
             if let Block::ToolCall(tc) = b
@@ -396,6 +464,26 @@ impl App {
                         edit_snapshot: None,
                     }));
                 }
+                "reasoning" => {
+                    let text = item["text"].as_str().unwrap_or("").to_owned();
+                    let body = if text.is_empty() {
+                        item["summary"]
+                            .as_array()
+                            .map(|arr| {
+                                arr.iter()
+                                    .filter_map(|v| v.as_str())
+                                    .collect::<Vec<_>>()
+                                    .join("\n")
+                            })
+                            .unwrap_or_default()
+                    } else {
+                        text
+                    };
+                    self.blocks.push(Block::Thinking(ThinkingBlock {
+                        text: body,
+                        state: ThinkingState::Finished { elapsed_secs: None },
+                    }));
+                }
                 "tool_result" => {
                     let id = item["call_id"].as_str().unwrap_or("").to_owned();
                     let summary = item["summary"].as_str().unwrap_or("").to_owned();

crates/tui/src/block.rs

@@ -7,6 +7,8 @@
 
 #![allow(dead_code)] // Phase 5 will consume `output` in detail mode.
 
+use std::time::Instant;
+
 use protocol::{AlertLevel, AlertSource, Greeting, Segment};
 
 pub enum Block {
@@ -20,6 +22,7 @@ pub enum Block {
     AssistantText {
         text: String,
     },
+    Thinking(ThinkingBlock),
     ToolCall(ToolCallBlock),
     Alert {
         level: AlertLevel,
@@ -34,6 +37,25 @@ pub enum Block {
     },
 }
 
+pub struct ThinkingBlock {
+    /// Accumulated reasoning body. Empty for providers that emit only
+    /// metadata (no plaintext deltas).
+    pub text: String,
+    pub state: ThinkingState,
+}
+
+pub enum ThinkingState {
+    /// Live block: actively streaming. `started_at` is `None` only for
+    /// blocks materialised from `Event::History`, which never enter the
+    /// streaming state.
+    Streaming { started_at: Instant },
+    /// Block ended cleanly with `ThinkingDone`.
+    Finished { elapsed_secs: Option<u64> },
+    /// `TurnEnd` arrived before `ThinkingDone`. Elapsed time is frozen
+    /// at the last observed instant.
+    Incomplete { elapsed_secs: Option<u64> },
+}
+
 pub enum CompactEvent {
     Start,
     Done { new_session_id: uuid::Uuid },

crates/tui/src/ui.rs

@@ -23,7 +23,7 @@ use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 use protocol::{AlertLevel, Greeting, Segment};
 
 use crate::app::{App, alert_source_label, fmt_tokens};
-use crate::block::{Block, CompactEvent};
+use crate::block::{Block, CompactEvent, ThinkingBlock, ThinkingState};
 
 /// Display density for the history view.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -298,6 +298,7 @@ fn render_block_into(lines: &mut Vec<Line<'static>>, block: &Block, width: u16,
             Mode::Overview => push_overview_line(lines, text, width, MessageKind::Assistant, ""),
             _ => push_padded_lines(lines, text, MessageKind::Assistant),
         },
+        Block::Thinking(t) => render_thinking(lines, t, width, mode),
         // ToolCall is dispatched in `compute_history` via `tool::render_tool`
         // so it can consume multiple adjacent blocks (Read aggregation).
         Block::ToolCall(_) => unreachable!("ToolCall handled by compute_history"),
@@ -541,6 +542,97 @@ fn count_visual_rows(text: &str, width: u16) -> usize {
     total.max(1)
 }
 
+fn render_thinking(lines: &mut Vec<Line<'static>>, t: &ThinkingBlock, width: u16, mode: Mode) {
+    let header_style = kind_style(MessageKind::Thinking);
+    let body_style = Style::default().fg(Color::DarkGray);
+
+    let header = match &t.state {
+        ThinkingState::Streaming { started_at } => {
+            let secs = started_at.elapsed().as_secs();
+            format!("Thinking... ({})", fmt_elapsed(secs))
+        }
+        ThinkingState::Finished { elapsed_secs } => match elapsed_secs {
+            Some(s) => format!("Thought for {}", fmt_elapsed(*s)),
+            None => "Thought".to_owned(),
+        },
+        ThinkingState::Incomplete { elapsed_secs } => match elapsed_secs {
+            Some(s) => format!("Thinking interrupted ({})", fmt_elapsed(*s)),
+            None => "Thinking interrupted".to_owned(),
+        },
+    };
+
+    if matches!(mode, Mode::Overview) {
+        push_overview_line(lines, &header, width, MessageKind::Thinking, "");
+        return;
+    }
+
+    lines.push(Line::from(Span::styled(header, header_style)));
+
+    if t.text.is_empty() {
+        return;
+    }
+
+    match mode {
+        Mode::Detail => {
+            for raw in t.text.lines() {
+                lines.push(Line::from(vec![
+                    Span::styled("  ", body_style),
+                    Span::styled(raw.to_owned(), body_style),
+                ]));
+            }
+        }
+        Mode::Normal => {
+            // Streaming: show the *latest* tail to keep the cursor of
+            // attention near where new tokens are appearing. Finished:
+            // show the first line as a static preview — collapsing it
+            // entirely would lose the only context most users want
+            // ("what was it thinking about").
+            let preview = match &t.state {
+                ThinkingState::Streaming { .. } => trailing_line_preview(&t.text),
+                _ => first_line_preview(&t.text),
+            };
+            if !preview.is_empty() {
+                let budget = width.saturating_sub(2) as usize;
+                let truncated = truncate_with_ellipsis(&preview, budget);
+                lines.push(Line::from(vec![
+                    Span::styled("  ", body_style),
+                    Span::styled(truncated, body_style),
+                ]));
+            }
+        }
+        Mode::Overview => unreachable!("handled above"),
+    }
+}
+
+/// Last segment of `text` after the final newline (or the whole string
+/// if it has no newline). Used as the live "what is it thinking now"
+/// 1-liner.
+fn trailing_line_preview(text: &str) -> String {
+    text.rsplit_once('\n')
+        .map(|(_, tail)| tail)
+        .unwrap_or(text)
+        .trim_end()
+        .to_owned()
+}
+
+/// First non-empty line of `text`. Used as the static preview after a
+/// thinking block finishes, mirroring the "first line + (+N lines)"
+/// idiom of the overview mode.
+fn first_line_preview(text: &str) -> String {
+    text.lines()
+        .find(|l| !l.trim().is_empty())
+        .unwrap_or("")
+        .to_owned()
+}
+
+fn fmt_elapsed(secs: u64) -> String {
+    if secs < 60 {
+        format!("{secs}s")
+    } else {
+        format!("{}m{:02}s", secs / 60, secs % 60)
+    }
+}
+
 fn render_compact(lines: &mut Vec<Line<'static>>, evt: &CompactEvent, width: u16, mode: Mode) {
     let (text, kind) = match evt {
         CompactEvent::Start => ("[compact] starting".to_owned(), MessageKind::NoticeWarn),
@@ -745,6 +837,7 @@ pub enum MessageKind {
     TurnHeader,
     User,
     Assistant,
+    Thinking,
     TurnStats,
     NoticeWarn,
     NoticeError,
@@ -755,6 +848,9 @@ pub fn kind_style(kind: MessageKind) -> Style {
         MessageKind::TurnHeader => Style::default().fg(Color::DarkGray),
         MessageKind::User => Style::default().fg(Color::Green),
         MessageKind::Assistant => Style::default().fg(Color::White),
+        MessageKind::Thinking => Style::default()
+            .fg(Color::Magenta)
+            .add_modifier(Modifier::ITALIC),
         MessageKind::TurnStats => Style::default().fg(Color::DarkGray),
         MessageKind::NoticeWarn => Style::default()
             .fg(Color::Black)