feat: surface streamed thinking content as a Discord blockquote

src/acp/protocol.rs

@@ -59,9 +59,9 @@ impl std::fmt::Display for JsonRpcError {
 #[derive(Debug)]
 pub enum AcpEvent {
     Text(String),
-    Thinking,
-    ToolStart { title: String },
-    ToolDone { title: String, status: String },
+    Thinking(String),
+    ToolStart { id: String, title: String },
+    ToolDone { id: String, title: String, status: String },
     Status,
 }
 
@@ -70,25 +70,49 @@ pub fn classify_notification(msg: &JsonRpcMessage) -> Option<AcpEvent> {
     let update = params.get("update")?;
     let session_update = update.get("sessionUpdate")?.as_str()?;
 
+    // toolCallId is the stable identity across tool_call → tool_call_update
+    // events for the same tool invocation. claude-agent-acp emits the first
+    // event before the input fields are streamed in (so the title falls back
+    // to "Terminal" / "Edit" / etc.) and refines them in a later
+    // tool_call_update; without the id we can't tell those events belong to
+    // the same call and end up rendering placeholder + refined as two
+    // separate lines.
+    let tool_id = update
+        .get("toolCallId")
+        .and_then(|v| v.as_str())
+        .unwrap_or("")
+        .to_string();
+
     match session_update {
         "agent_message_chunk" => {
             let text = update.get("content")?.get("text")?.as_str()?;
             Some(AcpEvent::Text(text.to_string()))
         }
         "agent_thought_chunk" => {
-            Some(AcpEvent::Thinking)
+            // Extract the streamed thinking text. claude-agent-acp emits
+            // these as `{ content: { type: "text", text: "..." } }` (same
+            // shape as agent_message_chunk). If the field is missing we
+            // still emit Thinking with an empty string so the reactions
+            // controller still flips 🤔.
+            let text = update
+                .get("content")
+                .and_then(|c| c.get("text"))
+                .and_then(|v| v.as_str())
+                .unwrap_or("")
+                .to_string();
+            Some(AcpEvent::Thinking(text))
         }
         "tool_call" => {
             let title = update.get("title").and_then(|v| v.as_str()).unwrap_or("").to_string();
-            Some(AcpEvent::ToolStart { title })
+            Some(AcpEvent::ToolStart { id: tool_id, title })
         }
         "tool_call_update" => {
             let title = update.get("title").and_then(|v| v.as_str()).unwrap_or("").to_string();
             let status = update.get("status").and_then(|v| v.as_str()).unwrap_or("").to_string();
             if status == "completed" || status == "failed" {
-                Some(AcpEvent::ToolDone { title, status })
+                Some(AcpEvent::ToolDone { id: tool_id, title, status })
             } else {
-                Some(AcpEvent::ToolStart { title })
+                Some(AcpEvent::ToolStart { id: tool_id, title })
             }
         }
         "plan" => Some(AcpEvent::Status),

src/discord.rs

@@ -210,7 +210,18 @@ async fn stream_prompt(
             let (buf_tx, buf_rx) = watch::channel(initial);
 
             let mut text_buf = String::new();
-            let mut tool_lines: Vec<String> = Vec::new();
+            // Accumulated thinking content from agent_thought_chunk events.
+            // Rendered above tool_lines + text as a blockquote so users can
+            // see the bot's reasoning before / alongside its actions.
+            let mut thought_buf = String::new();
+            // Tool calls indexed by toolCallId. Vec preserves first-seen
+            // order. We store id + title + state separately so a ToolDone
+            // event that arrives without a refreshed title (claude-agent-acp's
+            // update events don't always re-send the title field) can still
+            // reuse the title we already learned from a prior
+            // tool_call_update — only the icon flips 🔧 → ✅ / ❌. Rendering
+            // happens on the fly in compose_display().
+            let mut tool_lines: Vec<ToolEntry> = Vec::new();
             let current_msg_id = msg_id;
 
             if reset {
@@ -267,23 +278,79 @@ async fn stream_prompt(
                                 // Reaction: back to thinking after tools
                             }
                             text_buf.push_str(&t);
-                            let _ = buf_tx.send(compose_display(&tool_lines, &text_buf));
+                            let _ = buf_tx.send(compose_display(&tool_lines, &thought_buf, &text_buf));
                         }
-                        AcpEvent::Thinking => {
+                        AcpEvent::Thinking(t) => {
                             reactions.set_thinking().await;
+                            if !t.is_empty() {
+                                // claude-agent-acp emits both `thinking`
+                                // (new block) and `thinking_delta`
+                                // (continuation) events as the same
+                                // `agent_thought_chunk` shape, so we can't
+                                // tell block boundaries from the protocol
+                                // alone. Heuristic: if the previous chunk
+                                // ended with sentence-ending punctuation
+                                // and the new one starts with a letter
+                                // (no leading whitespace), it's almost
+                                // certainly a new thinking block — insert
+                                // a paragraph break so they don't visually
+                                // run together as ".There's".
+                                if needs_thinking_separator(&thought_buf, &t) {
+                                    thought_buf.push_str("\n\n");
+                                }
+                                thought_buf.push_str(&t);
+                                let _ = buf_tx.send(compose_display(&tool_lines, &thought_buf, &text_buf));
+                            }
                         }
-                        AcpEvent::ToolStart { title, .. } if !title.is_empty() => {
+                        AcpEvent::ToolStart { id, title } if !title.is_empty() => {
                             reactions.set_tool(&title).await;
-                            tool_lines.push(format!("🔧 `{title}`..."));
-                            let _ = buf_tx.send(compose_display(&tool_lines, &text_buf));
+                            let title = sanitize_title(&title);
+                            // Dedupe by toolCallId: replace if we've already
+                            // seen this id, otherwise append a new entry.
+                            // claude-agent-acp emits a placeholder title
+                            // ("Terminal", "Edit", etc.) on the first event
+                            // and refines it via tool_call_update; without
+                            // dedup the placeholder and refined version
+                            // appear as two separate orphaned lines.
+                            if let Some(slot) = tool_lines.iter_mut().find(|e| e.id == id) {
+                                slot.title = title;
+                                slot.state = ToolState::Running;
+                            } else {
+                                tool_lines.push(ToolEntry {
+                                    id,
+                                    title,
+                                    state: ToolState::Running,
+                                });
+                            }
+                            let _ = buf_tx.send(compose_display(&tool_lines, &thought_buf, &text_buf));
                         }
-                        AcpEvent::ToolDone { title, status, .. } => {
+                        AcpEvent::ToolDone { id, title, status } => {
                             reactions.set_thinking().await;
-                            let icon = if status == "completed" { "✅" } else { "❌" };
-                            if let Some(line) = tool_lines.iter_mut().rev().find(|l| l.contains(&title)) {
-                                *line = format!("{icon} `{title}`");
+                            let new_state = if status == "completed" {
+                                ToolState::Completed
+                            } else {
+                                ToolState::Failed
+                            };
+                            // Find by id (the title is unreliable — substring
+                            // match against the placeholder "Terminal" would
+                            // never find the refined entry). Preserve the
+                            // existing title if the Done event omits it.
+                            if let Some(slot) = tool_lines.iter_mut().find(|e| e.id == id) {
+                                if !title.is_empty() {
+                                    slot.title = sanitize_title(&title);
+                                }
+                                slot.state = new_state;
+                            } else if !title.is_empty() {
+                                // Done arrived without a prior Start (rare
+                                // race) — record it so we still show
+                                // something.
+                                tool_lines.push(ToolEntry {
+                                    id,
+                                    title: sanitize_title(&title),
+                                    state: new_state,
+                                });
                             }
-                            let _ = buf_tx.send(compose_display(&tool_lines, &text_buf));
+                            let _ = buf_tx.send(compose_display(&tool_lines, &thought_buf, &text_buf));
                         }
                         _ => {}
                     }
@@ -295,7 +362,7 @@ async fn stream_prompt(
             let _ = edit_handle.await;
 
             // Final edit
-            let final_content = compose_display(&tool_lines, &text_buf);
+            let final_content = compose_display(&tool_lines, &thought_buf, &text_buf);
             let final_content = if final_content.is_empty() {
                 "_(no response)_".to_string()
             } else {
@@ -317,15 +384,84 @@ async fn stream_prompt(
     .await
 }
 
-fn compose_display(tool_lines: &[String], text: &str) -> String {
+/// Flatten a tool-call title into a single line that's safe to render
+/// inside Discord inline-code spans. Discord renders single-backtick
+/// code on a single line only, so multi-line shell commands (heredocs,
+/// `&&`-chained commands split across lines) appear truncated; we
+/// collapse newlines to ` ; ` and rewrite embedded backticks so they
+/// don't break the wrapping span.
+fn sanitize_title(title: &str) -> String {
+    title.replace('\r', "").replace('\n', " ; ").replace('`', "'")
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ToolState {
+    Running,
+    Completed,
+    Failed,
+}
+
+#[derive(Debug, Clone)]
+pub struct ToolEntry {
+    pub id: String,
+    pub title: String,
+    pub state: ToolState,
+}
+
+impl ToolEntry {
+    fn render(&self) -> String {
+        let icon = match self.state {
+            ToolState::Running => "🔧",
+            ToolState::Completed => "✅",
+            ToolState::Failed => "❌",
+        };
+        let suffix = if self.state == ToolState::Running { "..." } else { "" };
+        format!("{icon} `{}`{}", self.title, suffix)
+    }
+}
+
+/// Heuristic for detecting a thinking block boundary in a stream of
+/// `agent_thought_chunk` deltas. claude-agent-acp doesn't tag the first
+/// delta of a new block, so we infer it: if the previous chunk ended in
+/// sentence-ending punctuation (`. ! ? 。 ! ?`) and the new chunk starts
+/// with a letter (no leading whitespace), they're almost certainly two
+/// separate thoughts that need a paragraph break.
+fn needs_thinking_separator(prev: &str, new: &str) -> bool {
+    if prev.is_empty() || new.is_empty() {
+        return false;
+    }
+    let last = match prev.chars().last() {
+        Some(c) => c,
+        None => return false,
+    };
+    let first = match new.chars().next() {
+        Some(c) => c,
+        None => return false,
+    };
+    let sentence_end = matches!(last, '.' | '!' | '?' | '。' | '！' | '？');
+    let starts_word = first.is_alphabetic();
+    sentence_end && starts_word
+}
+
+fn compose_display(tool_lines: &[ToolEntry], thought: &str, text: &str) -> String {
     let mut out = String::new();
-    if !tool_lines.is_empty() {
-        for line in tool_lines {
+    let trimmed_thought = thought.trim();
+    if !trimmed_thought.is_empty() {
+        out.push_str("> 🤔 _Thinking_\n");
+        for line in trimmed_thought.lines() {
+            out.push_str("> ");
             out.push_str(line);
             out.push('\n');
         }
         out.push('\n');
     }
+    if !tool_lines.is_empty() {
+        for entry in tool_lines {
+            out.push_str(&entry.render());
+            out.push('\n');
+        }
+        out.push('\n');
+    }
     out.push_str(text.trim_end());
     out
 }