Long chats stay fast; search in a chat; media overview

Performance (measured with 5,900 messages: open 9 s -> 0.7 s, typing 440 ms -> 25 ms)
- GET /sessions/{id}?limit=N loads the end of a chat (from the last summary
  on, at most N); /sessions/{id}/messages?before|after|around loads more
  (scrolling up stops at a summary unless asked). Without parameters the
  full history as before (terminal client).
- Chat view: memoised message list (typing, streaming and status changes no
  longer re-render the history), finished turns fold into "N steps · M files"
  with the answer visible, tool card bodies and summaries are built only when
  opened, scroll-to-bottom only when content changes.

Search: /sessions/{id}/search over the whole chat; a hit loads its part
(around) and marks the message, "back to the latest messages" returns.

Media: /sessions/{id}/media lists images, videos and audio of a chat and its
subagents (generated images, tool output, files written, media in answers,
attachments); ⋯ -> Media shows them with filters, a large view and a jump to
the message.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/api.rs

@@ -81,6 +81,9 @@ pub fn router(app: AppState) -> Router {
         .route("/sessions/{id}/tabs", get(session_tabs).put(put_file_tabs))
         .route("/sessions/{id}/export", get(export_session))
         .route("/blobs/{hash}", get(get_blob))
+        .route("/sessions/{id}/messages", get(session_messages))
+        .route("/sessions/{id}/search", get(search_in_session))
+        .route("/sessions/{id}/media", get(session_media))
         .route("/sessions/{id}", get(get_session).patch(update_session).delete(delete_session))
         .route("/sessions/{id}/prompt", post(prompt))
         .route("/sessions/{id}/abort", post(abort))
@@ -813,14 +816,81 @@ async fn export_session(Extension(user): Extension<User>, State(app): State<AppS
         .into_response())
 }
 
-async fn get_session(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>) -> ApiResult {
+#[derive(Deserialize)]
+struct WindowQ {
+    /// Only the end of the chat (from the last summary on, at most this many messages);
+    /// without it, all messages (terminal client).
+    limit: Option<i64>,
+    before: Option<String>,
+    after: Option<String>,
+    around: Option<String>,
+    /// Loading older messages stops at a summary (the history before it on request).
+    #[serde(default)]
+    stop_at_summary: bool,
+}
+
+impl WindowQ {
+    fn window(&self) -> Option<crate::store::MessageWindow> {
+        use crate::store::MessageWindow as W;
+        let limit = self.limit.unwrap_or(200).clamp(1, 1000);
+        Some(match (&self.before, &self.after, &self.around) {
+            (Some(id), _, _) => W::Before { id: id.clone(), limit, stop_at_summary: self.stop_at_summary },
+            (_, Some(id), _) => W::After { id: id.clone(), limit },
+            (_, _, Some(id)) => W::Around { id: id.clone(), limit },
+            _ if self.limit.is_some() => W::Tail { limit },
+            _ => return None,
+        })
+    }
+}
+
+async fn get_session(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>, Query(q): Query<WindowQ>) -> ApiResult {
     let s = readable(&app, &user, &id)?;
-    let messages = app.store.messages(&id)?;
     let busy = app.is_busy(&id);
     let can_write = app.access(&user, &id) == Access::Full;
     let queue = app.store.queue_list(&id)?;
     let step = app.with_runtime(&id, |r| r.step.clone());
-    Ok(Json(json!({"session": s, "messages": messages, "busy": busy, "can_write": can_write, "queue": queue, "step": step})))
+    let mut out = json!({"session": s, "busy": busy, "can_write": can_write, "queue": queue, "step": step});
+    match q.window() {
+        Some(w) => {
+            let (messages, older, newer) = app.store.messages_window(&id, &w)?;
+            out["messages"] = json!(messages);
+            out["has_older"] = json!(older);
+            out["has_newer"] = json!(newer);
+        }
+        None => out["messages"] = json!(app.store.messages(&id)?),
+    }
+    Ok(Json(out))
+}
+
+/// More messages of a chat: before / after / around a message.
+async fn session_messages(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>, Query(q): Query<WindowQ>) -> ApiResult {
+    readable(&app, &user, &id)?;
+    let w = q.window().ok_or_else(|| ApiError(StatusCode::BAD_REQUEST, "before, after, around or limit is required".into()))?;
+    let (messages, older, newer) = app.store.messages_window(&id, &w).map_err(|e| ApiError(StatusCode::NOT_FOUND, format!("{e:#}")))?;
+    Ok(Json(json!({"messages": messages, "has_older": older, "has_newer": newer})))
+}
+
+/// Images, videos and audio files shown in a chat (all of it, with subagents).
+async fn session_media(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>) -> ApiResult {
+    readable(&app, &user, &id)?;
+    let a = app.clone();
+    let items = tokio::task::spawn_blocking(move || crate::media::collect(&a, &id)).await.map_err(|e| ApiError(StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))??;
+    Ok(Json(json!(items)))
+}
+
+/// Search within one chat (all of it, not only the loaded part).
+async fn search_in_session(Extension(user): Extension<User>, State(app): State<AppState>, Path(id): Path<String>, Query(q): Query<SearchQ>) -> ApiResult {
+    readable(&app, &user, &id)?;
+    if q.q.trim().chars().count() < 2 {
+        return Ok(Json(json!([])));
+    }
+    let hits: Vec<Value> = app
+        .store
+        .search_messages(&id, q.q.trim(), 100)?
+        .into_iter()
+        .map(|(mid, role, at, snippet)| json!({"id": mid, "role": role, "created_at": at, "snippet": snippet}))
+        .collect();
+    Ok(Json(json!(hits)))
 }
 
 #[derive(Deserialize)]

server/src/main.rs

@@ -22,6 +22,7 @@ mod lsp;
 mod mentions;
 mod metrics;
 mod mcp;
+mod media;
 mod permission;
 mod prompts;
 mod push;

server/src/media.rs

@@ -0,0 +1,200 @@
+//! Media overview of a chat: every image, video and audio file that was shown in it –
+//! generated images, images in tool results (screenshots), media files the agent wrote,
+//! media referenced in answers, and the user's own attachments. Includes subagents.
+
+use crate::app::App;
+use crate::types::{Message, Part, Role};
+use serde::Serialize;
+use serde_json::Value;
+use std::collections::HashSet;
+use std::path::{Path, PathBuf};
+
+#[derive(Debug, Serialize, PartialEq)]
+pub struct MediaItem {
+    /// "image", "video" or "audio".
+    pub kind: &'static str,
+    pub url: String,
+    pub name: String,
+    /// "generated", "tool", "written", "answer" or "upload".
+    pub source: &'static str,
+    pub created_at: i64,
+    /// Message to jump to (only for messages of the chat itself, not of subagents).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub message_id: Option<String>,
+}
+
+const IMAGE: &[&str] = &["png", "jpg", "jpeg", "gif", "webp", "svg", "bmp", "avif"];
+const VIDEO: &[&str] = &["mp4", "webm", "mov", "m4v", "ogv"];
+const AUDIO: &[&str] = &["mp3", "wav", "ogg", "oga", "m4a", "flac", "opus", "aac"];
+
+/// Kind of a media file by its extension.
+pub fn kind_of(path: &str) -> Option<&'static str> {
+    let ext = Path::new(path.split(['?', '#']).next().unwrap_or(path)).extension()?.to_str()?.to_ascii_lowercase();
+    if IMAGE.contains(&ext.as_str()) {
+        Some("image")
+    } else if VIDEO.contains(&ext.as_str()) {
+        Some("video")
+    } else if AUDIO.contains(&ext.as_str()) {
+        Some("audio")
+    } else {
+        None
+    }
+}
+
+fn kind_of_mime(mime: &str) -> &'static str {
+    if mime.starts_with("video/") {
+        "video"
+    } else if mime.starts_with("audio/") {
+        "audio"
+    } else {
+        "image"
+    }
+}
+
+/// Like JavaScript's encodeURIComponent.
+fn encode(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    for b in s.bytes() {
+        if b.is_ascii_alphanumeric() || b"-_.!~*'()".contains(&b) {
+            out.push(b as char);
+        } else {
+            out.push_str(&format!("%{b:02X}"));
+        }
+    }
+    out
+}
+
+/// Absolute, normalised path of `p` (relative to `cwd`).
+fn resolve(p: &str, cwd: &Path) -> PathBuf {
+    let joined = if p.starts_with('/') { PathBuf::from(p) } else { cwd.join(p) };
+    crate::tools::normalize(&joined)
+}
+
+/// Media file paths in a text: Markdown images/links and plain paths with a media extension.
+fn paths_in(text: &str) -> Vec<String> {
+    let mut out = Vec::new();
+    for token in text.split(|c: char| c.is_whitespace() || "()[]<>\"'`,;".contains(c)) {
+        let t = token.trim_end_matches(['.', ':', '!', '?']);
+        if t.is_empty() || t.contains("://") || t.starts_with("data:") {
+            continue;
+        }
+        if kind_of(t).is_some() && t.chars().any(|c| c == '/' || c == '.') {
+            out.push(t.to_string());
+        }
+    }
+    out
+}
+
+/// All media of a chat and its subagents, newest first.
+pub fn collect(app: &App, session_id: &str) -> anyhow::Result<Vec<MediaItem>> {
+    let mut sessions = vec![session_id.to_string()];
+    // Subagents (and theirs).
+    let mut i = 0;
+    while i < sessions.len() && sessions.len() < 500 {
+        let children = app.store.child_sessions(&sessions[i])?;
+        sessions.extend(children);
+        i += 1;
+    }
+    let mut out: Vec<MediaItem> = Vec::new();
+    let mut seen: HashSet<String> = HashSet::new();
+    let mut push = |item: MediaItem, out: &mut Vec<MediaItem>| {
+        if seen.insert(item.url.clone()) {
+            out.push(item);
+        }
+    };
+    for sid in &sessions {
+        let Some(session) = app.store.get_session(sid)? else { continue };
+        let cwd = PathBuf::from(&session.cwd);
+        let own = sid == session_id;
+        // Tool results are shown in the card of the call: jump to that message.
+        let mut call_msg: Option<String> = None;
+        for m in app.store.messages(sid)? {
+            collect_message(&m, &cwd, own, call_msg.as_deref(), &mut |item| push(item, &mut out));
+            if m.role == Role::Assistant {
+                call_msg = Some(m.id.clone());
+            }
+        }
+    }
+    // Generated images whose tool result was not found (e.g. removed by a rewind).
+    for img in app.store.images_of_sessions(&sessions)? {
+        push(
+            MediaItem { kind: "image", url: format!("/api/images/{}/file", img.id), name: file_name(&img.path), source: "generated", created_at: img.created_at, message_id: None },
+            &mut out,
+        );
+    }
+    // Names of generated images (their files).
+    let names: std::collections::HashMap<String, String> = app.store.images_of_sessions(&sessions)?.into_iter().map(|i| (format!("/api/images/{}/file", i.id), file_name(&i.path))).collect();
+    for item in &mut out {
+        if let Some(n) = names.get(&item.url) {
+            item.name = n.clone();
+        }
+    }
+    out.sort_by(|a, b| b.created_at.cmp(&a.created_at));
+    Ok(out)
+}
+
+fn file_name(p: &str) -> String {
+    Path::new(p).file_name().and_then(|n| n.to_str()).unwrap_or(p).to_string()
+}
+
+fn collect_message(m: &Message, cwd: &Path, own: bool, call_msg: Option<&str>, add: &mut dyn FnMut(MediaItem)) {
+    let mid = own.then(|| m.id.clone());
+    let result_mid = own.then(|| call_msg.unwrap_or(&m.id).to_string());
+    let at = m.created_at;
+    let file = |p: &str, source: &'static str| -> Option<MediaItem> {
+        let kind = kind_of(p)?;
+        let abs = resolve(p, cwd);
+        abs.is_file().then(|| MediaItem { kind, url: format!("/api/files/raw?path={}", encode(&abs.display().to_string())), name: file_name(p), source, created_at: at, message_id: mid.clone() })
+    };
+    for p in &m.parts {
+        match p {
+            Part::Image { image } if m.role == Role::User => {
+                if let Some(h) = &image.blob {
+                    add(MediaItem { kind: kind_of_mime(&image.media_type), url: format!("/api/blobs/{h}"), name: "image".into(), source: "upload", created_at: at, message_id: mid.clone() });
+                }
+            }
+            Part::ToolResult { images, meta, .. } => {
+                let ids: Vec<&str> = meta.as_ref().and_then(|v| v["image_ids"].as_array()).map(|a| a.iter().filter_map(Value::as_str).collect()).unwrap_or_default();
+                if !ids.is_empty() {
+                    for id in ids {
+                        add(MediaItem { kind: "image", url: format!("/api/images/{id}/file"), name: "image".into(), source: "generated", created_at: at, message_id: result_mid.clone() });
+                    }
+                } else {
+                    for img in images {
+                        if let Some(h) = &img.blob {
+                            add(MediaItem { kind: kind_of_mime(&img.media_type), url: format!("/api/blobs/{h}"), name: "screenshot".into(), source: "tool", created_at: at, message_id: result_mid.clone() });
+                        }
+                    }
+                }
+            }
+            Part::ToolCall { name, input, .. } if matches!(name.as_str(), "write" | "edit") => {
+                if let Some(item) = input["path"].as_str().and_then(|p| file(p, "written")) {
+                    add(item);
+                }
+            }
+            Part::Text { text } if m.role == Role::Assistant => {
+                for p in paths_in(text) {
+                    if let Some(item) = file(&p, "answer") {
+                        add(item);
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn kinds_paths_and_encoding() {
+        assert_eq!(kind_of("a/b.PNG"), Some("image"));
+        assert_eq!(kind_of("clip.mp4?v=1"), Some("video"));
+        assert_eq!(kind_of("song.flac"), Some("audio"));
+        assert_eq!(kind_of("main.rs"), None);
+        assert_eq!(paths_in("Saved to `art/final/hero.png` and ![x](shots/a.webp). See https://x.org/y.png"), vec!["art/final/hero.png", "shots/a.webp"]);
+        assert_eq!(encode("/w/ä b.png"), "%2Fw%2F%C3%A4%20b.png");
+    }
+}

server/src/store.rs

@@ -1,6 +1,6 @@
 //! SQLite persistence for sessions and messages.
 
-use crate::types::{ImageData, Message, Part, Session, now_ms};
+use crate::types::{ImageData, Message, Part, Role, Session, now_ms};
 use serde::Serialize;
 use serde_json::{Value, json};
 use anyhow::Result;
@@ -244,28 +244,7 @@ impl Store {
             let (sdata, mdata) = row?;
             let session: Session = serde_json::from_str(&sdata)?;
             // Snippet from the visible text of the matching message (not JSON keys).
-            let mut snippet = String::new();
-            if let Some(m) = mdata.and_then(|d| serde_json::from_str::<Message>(&d).ok()) {
-                for p in &m.parts {
-                    let text = match p {
-                        Part::Text { text } | Part::Summary { text, .. } | Part::Reasoning { text, .. } => text.as_str(),
-                        Part::ToolResult { content, .. } => content.as_str(),
-                        _ => continue,
-                    };
-                    if let Some(i) = text.to_lowercase().find(&needle) {
-                        let mut a = i.saturating_sub(60);
-                        while !text.is_char_boundary(a) {
-                            a -= 1;
-                        }
-                        let mut b = (i + needle.len() + 100).min(text.len());
-                        while !text.is_char_boundary(b) {
-                            b += 1;
-                        }
-                        snippet = format!("{}{}{}", if a > 0 { "…" } else { "" }, text[a..b].replace('\n', " "), if b < text.len() { "…" } else { "" });
-                        break;
-                    }
-                }
-            }
+            let snippet = mdata.and_then(|d| serde_json::from_str::<Message>(&d).ok()).and_then(|m| snippet_in(&m, &needle)).unwrap_or_default();
             if snippet.is_empty() && !session.title.to_lowercase().contains(&needle) {
                 continue; // matched only JSON structure (keys, ids)
             }
@@ -274,6 +253,121 @@ impl Store {
         Ok(out)
     }
 
+    /// A part of a session's messages for the chat view (long chats are not loaded at
+    /// once). Returns the messages (oldest first) and whether older / newer ones exist.
+    pub fn messages_window(&self, session_id: &str, w: &MessageWindow) -> Result<(Vec<Message>, bool, bool)> {
+        let conn = self.conn.lock().unwrap();
+        let seq_of = |id: &str| -> Result<i64> {
+            conn.query_row("SELECT seq FROM messages WHERE session_id = ?1 AND id = ?2", params![session_id, id], |r| r.get(0))
+                .optional()?
+                .ok_or_else(|| anyhow::anyhow!("message {id} not found"))
+        };
+        let (sql, a, limit): (&str, i64, i64) = match w {
+            // From the last summary (compaction) on, at most `limit`.
+            MessageWindow::Tail { limit } => {
+                let from: i64 = conn
+                    .query_row(
+                        "SELECT seq FROM messages WHERE session_id = ?1 AND data LIKE '%\"type\":\"summary\"%' ORDER BY seq DESC LIMIT 1",
+                        [session_id],
+                        |r| r.get(0),
+                    )
+                    .optional()?
+                    .unwrap_or(i64::MIN);
+                ("SELECT data FROM messages WHERE session_id = ?1 AND seq >= ?2 ORDER BY seq DESC LIMIT ?3", from, *limit)
+            }
+            // Scrolling up stops at a summary (compaction); the history before it on request.
+            MessageWindow::Before { id, limit, stop_at_summary } => {
+                let before = seq_of(id)?;
+                let summary: Option<i64> = if *stop_at_summary {
+                    conn.query_row(
+                        "SELECT seq FROM messages WHERE session_id = ?1 AND seq < ?2 AND data LIKE '%\"type\":\"summary\"%' ORDER BY seq DESC LIMIT 1",
+                        params![session_id, before],
+                        |r| r.get(0),
+                    )
+                    .optional()?
+                } else {
+                    None
+                };
+                match summary {
+                    Some(from) => {
+                        let mut stmt = conn.prepare("SELECT seq, data FROM messages WHERE session_id = ?1 AND seq >= ?2 AND seq < ?3 ORDER BY seq DESC LIMIT ?4")?;
+                        let mut rows: Vec<(i64, Message)> = Vec::new();
+                        for r in stmt.query_map(params![session_id, from, before, limit], |r| Ok((r.get::<_, i64>(0)?, r.get::<_, String>(1)?)))? {
+                            let (seq, data) = r?;
+                            rows.push((seq, serde_json::from_str(&data)?));
+                        }
+                        drop(stmt);
+                        return Self::finish_window(&conn, session_id, rows, false);
+                    }
+                    None => ("SELECT data FROM messages WHERE session_id = ?1 AND seq < ?2 ORDER BY seq DESC LIMIT ?3", before, *limit),
+                }
+            }
+            MessageWindow::After { id, limit } => ("SELECT data FROM messages WHERE session_id = ?1 AND seq > ?2 ORDER BY seq ASC LIMIT ?3", seq_of(id)?, *limit),
+            // The message and about half the limit before it.
+            MessageWindow::Around { id, limit } => {
+                let seq = seq_of(id)?;
+                let before: i64 = conn.query_row(
+                    "SELECT COALESCE(MIN(seq), ?2) FROM (SELECT seq FROM messages WHERE session_id = ?1 AND seq < ?2 ORDER BY seq DESC LIMIT ?3)",
+                    params![session_id, seq, limit / 2],
+                    |r| r.get(0),
+                )?;
+                ("SELECT data FROM messages WHERE session_id = ?1 AND seq >= ?2 ORDER BY seq ASC LIMIT ?3", before, *limit)
+            }
+        };
+        let mut rows: Vec<(i64, Message)> = Vec::new();
+        let mut stmt = conn.prepare(&sql.replace("SELECT data", "SELECT seq, data"))?;
+        for r in stmt.query_map(params![session_id, a, limit], |r| Ok((r.get::<_, i64>(0)?, r.get::<_, String>(1)?)))? {
+            let (seq, data) = r?;
+            rows.push((seq, serde_json::from_str(&data)?));
+        }
+        drop(stmt);
+        Self::finish_window(&conn, session_id, rows, matches!(w, MessageWindow::Tail { .. }))
+    }
+
+    /// Sort a window and tell whether older / newer messages exist around it.
+    fn finish_window(conn: &Connection, session_id: &str, mut rows: Vec<(i64, Message)>, tail: bool) -> Result<(Vec<Message>, bool, bool)> {
+        rows.sort_by_key(|(seq, _)| *seq);
+        let exists = |q: &str, seq: i64| -> Result<bool> { Ok(conn.prepare(q)?.exists(params![session_id, seq])?) };
+        let older = match rows.first() {
+            Some((first, _)) => exists("SELECT 1 FROM messages WHERE session_id = ?1 AND seq < ?2", *first)?,
+            None => tail && exists("SELECT 1 FROM messages WHERE session_id = ?1 AND seq > ?2", i64::MIN)?,
+        };
+        let newer = match rows.last() {
+            Some((last, _)) => exists("SELECT 1 FROM messages WHERE session_id = ?1 AND seq > ?2", *last)?,
+            None => false,
+        };
+        Ok((rows.into_iter().map(|(_, m)| m).collect(), older, newer))
+    }
+
+    /// Messages of one session containing `q` (case-insensitive), newest first:
+    /// (message id, role, created_at, snippet).
+    pub fn search_messages(&self, session_id: &str, q: &str, limit: usize) -> Result<Vec<(String, Role, i64, String)>> {
+        let needle = q.to_lowercase();
+        let like = format!("%{}%", q.replace('\\', "\\\\").replace('%', "\\%").replace('_', "\\_"));
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare("SELECT data FROM messages WHERE session_id = ?1 AND data LIKE ?2 ESCAPE '\\' ORDER BY seq DESC")?;
+        let mut out = Vec::new();
+        for r in stmt.query_map(params![session_id, like], |r| r.get::<_, String>(0))? {
+            let Ok(m) = serde_json::from_str::<Message>(&r?) else { continue };
+            // Only visible text counts (not JSON keys or ids).
+            if let Some(snippet) = snippet_in(&m, &needle) {
+                out.push((m.id.clone(), m.role, m.created_at, snippet));
+                if out.len() >= limit {
+                    break;
+                }
+            }
+        }
+        Ok(out)
+    }
+
+    /// Ids of the subagent sessions started by a session.
+    pub fn child_sessions(&self, id: &str) -> Result<Vec<String>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare("SELECT id FROM sessions WHERE parent_id = ?1")?;
+        let rows = stmt.query_map([id], |r| r.get(0))?.collect::<rusqlite::Result<Vec<String>>>()?;
+        Ok(rows)
+    }
+
     pub fn delete_session(&self, id: &str) -> Result<()> {
         let conn = self.conn.lock().unwrap();
         // Child sessions (subagents) go with their parent.
@@ -1045,6 +1139,17 @@ impl Store {
     }
 
     /// Latest images; `user = None` lists everybody's (admins).
+    /// Generated images of these sessions.
+    pub fn images_of_sessions(&self, sessions: &[String]) -> Result<Vec<ImageRecord>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare(&format!("SELECT {IMAGE_COLS} FROM images WHERE session_id = ?1"))?;
+        let mut out = Vec::new();
+        for s in sessions {
+            out.extend(stmt.query_map([s], image_row)?.collect::<rusqlite::Result<Vec<_>>>()?);
+        }
+        Ok(out)
+    }
+
     pub fn images(&self, user: Option<&str>, limit: i64) -> Result<Vec<ImageRecord>> {
         let conn = self.conn.lock().unwrap();
         let mut stmt = conn.prepare(&format!(
@@ -1392,3 +1497,45 @@ pub struct PushSub {
     pub p256dh: String,
     pub auth: String,
 }
+
+/// Which messages of a session the chat view loads (see Store::messages_window).
+pub enum MessageWindow {
+    Tail { limit: i64 },
+    Before { id: String, limit: i64, stop_at_summary: bool },
+    After { id: String, limit: i64 },
+    Around { id: String, limit: i64 },
+}
+
+/// Text around the first occurrence of `needle` (lowercase) in the visible text of a
+/// message: its text, reasoning, summaries, tool calls and tool output.
+fn snippet_in(m: &Message, needle: &str) -> Option<String> {
+    for p in &m.parts {
+        let owned;
+        let text = match p {
+            Part::Text { text } | Part::Summary { text, .. } | Part::Reasoning { text, .. } => text.as_str(),
+            Part::ToolResult { content, .. } => content.as_str(),
+            Part::ToolCall { input, .. } => {
+                owned = input.to_string();
+                owned.as_str()
+            }
+            _ => continue,
+        };
+        let lower = text.to_lowercase();
+        // Lowercasing can change byte lengths (rare): then cut the lowercase text.
+        let (src, i) = match lower.find(needle) {
+            Some(i) if lower.len() == text.len() => (text, i),
+            Some(i) => (lower.as_str(), i),
+            None => continue,
+        };
+        let mut a = i.saturating_sub(60);
+        while !src.is_char_boundary(a) {
+            a -= 1;
+        }
+        let mut b = (i + needle.len() + 100).min(src.len());
+        while !src.is_char_boundary(b) {
+            b += 1;
+        }
+        return Some(format!("{}{}{}", if a > 0 { "…" } else { "" }, src[a..b].replace('\n', " "), if b < src.len() { "…" } else { "" }));
+    }
+    None
+}