fix(tui): filter terminal control sequence fragments from composer

Prevent leaked OSC/Kitty terminal control fragments from landing in composer input while preserving legitimate overlapping user text.

crates/tui/src/tui/app.rs

@@ -406,10 +406,23 @@ fn sanitize_api_key_text(text: &str) -> String {
 }
 
 fn strip_raw_mouse_report_runs(input: &str, cursor: usize) -> Option<(String, usize)> {
-    let chars: Vec<char> = input.chars().collect();
-    let mut output = String::with_capacity(input.len());
+    // First pass: strip the well-defined control-sequence fragment
+    // shapes that crossterm sometimes hands us as `Char(c)` keystrokes
+    // when its event reader is interrupted mid-sequence during dense
+    // streaming output (#1915). This covers OSC 8 hyperlink fragments
+    // (`]8;;URL`, including the closing `]8;;`) and Kitty keyboard
+    // protocol fragments (`[?…u`, `[>…u`, `[?u`).
+    let (after_fragments, after_fragments_cursor, fragments_changed) =
+        strip_control_sequence_fragments(input, cursor);
+
+    // Second pass: the existing run-based filter handles SGR mouse
+    // reports (`[<35;44;18M`) and the multi-terminator burst shape
+    // (`5;46;18M;48;18M`) introduced in e63a4ba4a. It operates on a
+    // narrow char set so it can't be confused with user-typed text.
+    let chars: Vec<char> = after_fragments.chars().collect();
+    let mut output = String::with_capacity(after_fragments.len());
     let mut new_cursor = 0usize;
-    let mut changed = false;
+    let mut changed = fragments_changed;
     let mut index = 0usize;
 
     while index < chars.len() {
@@ -433,7 +446,7 @@ fn strip_raw_mouse_report_runs(input: &str, cursor: usize) -> Option<(String, us
                 continue;
             }
             for (offset, ch) in run.iter().copied().enumerate() {
-                if start + offset < cursor {
+                if start + offset < after_fragments_cursor {
                     new_cursor += 1;
                 }
                 output.push(ch);
@@ -441,7 +454,7 @@ fn strip_raw_mouse_report_runs(input: &str, cursor: usize) -> Option<(String, us
             continue;
         }
 
-        if index < cursor {
+        if index < after_fragments_cursor {
             new_cursor += 1;
         }
         output.push(chars[index]);
@@ -566,6 +579,155 @@ fn looks_like_raw_mouse_report_fragment(run: &[char]) -> bool {
         && run.iter().any(|ch| matches!(ch, 'M' | 'm'))
 }
 
+/// Scan `input` for control-sequence fragment shapes (#1915) — OSC 8
+/// hyperlinks and Kitty keyboard protocol responses — and excise each
+/// match. Returns `(output, new_cursor, changed)`. Cursor positions
+/// inside an excised fragment are moved to the fragment's start.
+///
+/// The match shapes are deliberately narrow so legitimate text like
+/// `[is this ok?]` or a typed URL survives untouched:
+///
+/// - **OSC 8**: `(\x1b?)] 8 ; ...` consuming everything up to the
+///   first BEL (`\x07`), `\x1b\\`, lone `\\`, or the next `\x1b]8;`
+///   block — terminator characters are optional because crossterm may
+///   have already consumed them.
+/// - **Kitty CSI**: `(\x1b?) [ (? | > | =) ... u` — the `?`/`>`/`=`
+///   private-parameter prefix is what distinguishes a Kitty response
+///   from a user-typed `[…u` (which is exceedingly rare and would
+///   need an explicit private-parameter byte to be a real CSI).
+fn strip_control_sequence_fragments(input: &str, cursor: usize) -> (String, usize, bool) {
+    let chars: Vec<char> = input.chars().collect();
+    let mut output = String::with_capacity(input.len());
+    let mut new_cursor = 0usize;
+    let mut changed = false;
+    let mut index = 0usize;
+
+    while index < chars.len() {
+        if let Some(end) = match_osc8_fragment(&chars, index) {
+            // The excised span contributes nothing to `output`, so
+            // `new_cursor` simply doesn't tick for any of those
+            // characters. A cursor that was inside the span ends up at
+            // the fragment's start position in the rewritten input,
+            // which matches the existing run-stripper's behavior.
+            index = end;
+            changed = true;
+            continue;
+        }
+
+        if let Some(end) = match_kitty_csi_fragment(&chars, index) {
+            index = end;
+            changed = true;
+            continue;
+        }
+
+        if index < cursor {
+            new_cursor += 1;
+        }
+        output.push(chars[index]);
+        index += 1;
+    }
+
+    let cursor = new_cursor.min(char_count(&output));
+    (output, cursor, changed)
+}
+
+/// If an OSC 8 hyperlink fragment starts at `chars[start]`, return its
+/// end index (exclusive). The leading `ESC` is optional because
+/// crossterm's event parser often consumes it before reclassifying the
+/// tail as keystrokes.
+fn match_osc8_fragment(chars: &[char], start: usize) -> Option<usize> {
+    let body_start = if chars.get(start) == Some(&'\x1b')
+        && chars.get(start + 1) == Some(&']')
+        && chars.get(start + 2) == Some(&'8')
+        && chars.get(start + 3) == Some(&';')
+    {
+        start + 4
+    } else if chars.get(start) == Some(&']')
+        && chars.get(start + 1) == Some(&'8')
+        && chars.get(start + 2) == Some(&';')
+    {
+        start + 3
+    } else {
+        return None;
+    };
+
+    // After `]8;` we expect the OSC 8 payload: an optional second `;`
+    // (params separator), then the URL (or empty for the closing
+    // wrapper), then a terminator. We deliberately stop at the first
+    // ASCII whitespace so a typed `]8;` followed by real prose can't
+    // swallow the user's words — real OSC 8 URLs don't contain spaces.
+    let mut end = body_start;
+    while end < chars.len() {
+        let ch = chars[end];
+        // BEL terminator.
+        if ch == '\x07' {
+            return Some(end + 1);
+        }
+        // `ESC \\` string terminator (ST).
+        if ch == '\x1b' && chars.get(end + 1) == Some(&'\\') {
+            return Some(end + 2);
+        }
+        // Lone `\\` — crossterm sometimes delivers ST with the leading
+        // ESC already consumed, leaving just `\\` as a Char keystroke.
+        if ch == '\\' {
+            return Some(end + 1);
+        }
+        // Start of the next OSC 8 wrapper (closing `]8;;` glued to the
+        // body) — close the current fragment here so the next iteration
+        // matches that one separately.
+        if ch == '\x1b' && chars.get(end + 1) == Some(&']') {
+            return Some(end);
+        }
+        if ch == ']' && chars.get(end + 1) == Some(&'8') && chars.get(end + 2) == Some(&';') {
+            return Some(end);
+        }
+        if ch.is_whitespace() {
+            // We never crossed a terminator, so this isn't a real
+            // fragment — give up rather than eat user prose.
+            return None;
+        }
+        end += 1;
+    }
+
+    // Reached end of input without a terminator or whitespace. Treat as
+    // a fragment in flight (its tail will arrive on a later keystroke
+    // and get filtered then).
+    Some(end)
+}
+
+/// If a Kitty keyboard protocol CSI fragment starts at `chars[start]`,
+/// return its end index (exclusive). Shape: `(ESC)? [ (? | > | =)
+/// [0-9;:]* u`. The private-parameter byte (`?`, `>`, `=`) is what
+/// keeps this distinct from text the user might plausibly type.
+fn match_kitty_csi_fragment(chars: &[char], start: usize) -> Option<usize> {
+    let after_csi = if chars.get(start) == Some(&'\x1b') && chars.get(start + 1) == Some(&'[') {
+        start + 2
+    } else if chars.get(start) == Some(&'[') {
+        start + 1
+    } else {
+        return None;
+    };
+
+    let priv_byte = chars.get(after_csi)?;
+    if !matches!(priv_byte, '?' | '>' | '=') {
+        return None;
+    }
+
+    let mut end = after_csi + 1;
+    while end < chars.len() {
+        let ch = chars[end];
+        if ch == 'u' {
+            return Some(end + 1);
+        }
+        if ch.is_ascii_digit() || ch == ';' || ch == ':' {
+            end += 1;
+            continue;
+        }
+        return None;
+    }
+    None
+}
+
 const MAX_SUBMITTED_INPUT_CHARS: usize = 16_000;
 const MAX_DRAFT_HISTORY: usize = 50;
 
@@ -4679,6 +4841,112 @@ mod tests {
         assert_eq!(app.input, "Size 12;34M");
     }
 
+    // === Bug #1915: broader terminal control-sequence fragments leaking
+    // into the composer during dense streaming output. The narrow SGR
+    // mouse-report filter installed in e63a4ba4a covers `[<…M` style
+    // bursts, but not OSC 8 hyperlink fragments (`]8;;http…`) or Kitty
+    // keyboard protocol responses (`[?u`, `[>1u`). These can arrive when
+    // crossterm's event reader is mid-sequence and the unparsed tail is
+    // delivered as individual Char(c) keystrokes that land in the input.
+
+    #[test]
+    fn composer_strips_osc8_hyperlink_fragment() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+        app.insert_str("draft ");
+
+        // OSC 8 prefix with URL body but no terminator delivered yet —
+        // exactly what crossterm hands us if its event reader is
+        // interrupted mid-sequence and the leading ESC is consumed by the
+        // parser before the rest gets reclassified as Char(c).
+        app.insert_str("]8;;https://example.com");
+
+        assert_eq!(app.input, "draft ");
+        assert_eq!(app.cursor_position, "draft ".chars().count());
+    }
+
+    #[test]
+    fn composer_strips_closing_osc8_fragment() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+        app.insert_str("hello ");
+
+        // The closing wrapper `]8;;` (with a stray ST `\\` from a
+        // chopped escape) can arrive on its own when the parser ate
+        // the start of the sequence in a previous read but caught the
+        // tail as keystrokes.
+        app.insert_str("]8;;\\");
+
+        assert_eq!(app.input, "hello ");
+        assert_eq!(app.cursor_position, "hello ".chars().count());
+    }
+
+    #[test]
+    fn composer_strips_kitty_keyboard_protocol_fragment() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+        app.insert_str("ready ");
+
+        // Kitty keyboard protocol responses look like `\x1b[?1u`,
+        // `\x1b[>1u`, or `\x1b[?u`. With the ESC consumed, the tail
+        // shape is `[?…u` or `[>…u`.
+        app.insert_str("[?1u[>1u[?u");
+
+        assert_eq!(app.input, "ready ");
+        assert_eq!(app.cursor_position, "ready ".chars().count());
+    }
+
+    #[test]
+    fn composer_strips_mixed_control_sequence_burst() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+        app.insert_str("hi");
+
+        // Mixed dense burst combining all three fragment families
+        // described in #1915.
+        app.insert_str("[<35;44;18M]8;;https://example.com[?1u");
+
+        assert_eq!(app.input, "hi");
+        assert_eq!(app.cursor_position, 2);
+    }
+
+    #[test]
+    fn composer_keeps_legitimate_url_text_with_mouse_capture_enabled() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+
+        // URLs typed by the user must survive the filter — only
+        // recognized control-sequence shapes are stripped.
+        app.insert_str("see https://example.com/path?a=1&b=2 for info");
+
+        assert_eq!(app.input, "see https://example.com/path?a=1&b=2 for info");
+    }
+
+    #[test]
+    fn composer_keeps_legitimate_bracket_question_text() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+
+        // Text that uses brackets, question marks, and lowercase `u` —
+        // shapes that overlap Kitty fragments — must not be eaten.
+        app.insert_str("[is this ok?] sure");
+
+        assert_eq!(app.input, "[is this ok?] sure");
+    }
+
+    #[test]
+    fn composer_keeps_legitimate_closing_bracket_digit_text() {
+        let mut app = App::new(test_options(false), &Config::default());
+        app.use_mouse_capture = true;
+
+        // Plain `]8` followed by spaces and words must survive — only
+        // the OSC 8 shape `]8;` (with the mandatory `;` separator)
+        // should be treated as a fragment.
+        app.insert_str("array[]8 elements");
+
+        assert_eq!(app.input, "array[]8 elements");
+    }
+
     // initial_onboarding_state tests
     // These pin the logic that decides whether the TUI shows the
     // onboarding flow (Welcome → Language → ApiKey → …) or goes