diff --git a/Cargo.lock b/Cargo.lock
index 257dd49..2c62a43 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -287,6 +287,7 @@ dependencies = [
  "echo-debugserv",
  "echo-diceserv",
  "echo-example",
+ "echo-gameserv",
  "echo-groupserv",
  "echo-helpserv",
  "echo-hostserv",
@@ -366,6 +367,13 @@ dependencies = [
  "echo-api",
 ]
 
+[[package]]
+name = "echo-gameserv"
+version = "0.0.1"
+dependencies = [
+ "echo-api",
+]
+
 [[package]]
 name = "echo-groupserv"
 version = "0.0.1"
diff --git a/Cargo.toml b/Cargo.toml
index c9eca50..d6719c3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ members = [
     "modules/hostserv",
     "modules/operserv",
     "modules/diceserv",
+    "modules/gameserv",
     "modules/infoserv",
     "modules/reportserv",
     "modules/groupserv",
@@ -40,6 +41,7 @@ echo-statserv = { path = "modules/statserv" }
 echo-hostserv = { path = "modules/hostserv" }
 echo-operserv = { path = "modules/operserv" }
 echo-diceserv = { path = "modules/diceserv" }
+echo-gameserv = { path = "modules/gameserv" }
 echo-infoserv = { path = "modules/infoserv" }
 echo-reportserv = { path = "modules/reportserv" }
 echo-groupserv = { path = "modules/groupserv" }
diff --git a/modules/gameserv/Cargo.toml b/modules/gameserv/Cargo.toml
new file mode 100644
index 0000000..78bcb8c
--- /dev/null
+++ b/modules/gameserv/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "echo-gameserv"
+version = "0.0.1"
+edition = "2021"
+description = "GameServ: a server-authoritative referee for tic-tac-toe, Connect Four and chess, with a ranked ladder."
+
+[dependencies]
+echo-api = { path = "../../api" }
diff --git a/modules/gameserv/src/board.rs b/modules/gameserv/src/board.rs
new file mode 100644
index 0000000..217858a
--- /dev/null
+++ b/modules/gameserv/src/board.rs
@@ -0,0 +1,283 @@
+//! The referee: game state and the per-game rules for tic-tac-toe, Connect Four
+//! and chess. GameServ validates every move here and decides the winner, so a
+//! client can never cheat (the board never leaves the server except as a signed
+//! state line the web client only renders). Chess lives in `chess.rs`.
+
+use crate::chess;
+
+const TTT_LINES: [[usize; 3]; 8] = [
+    [0, 1, 2], [3, 4, 5], [6, 7, 8],
+    [0, 3, 6], [1, 4, 7], [2, 5, 8],
+    [0, 4, 8], [2, 4, 6],
+];
+pub const C4_W: usize = 7;
+pub const C4_H: usize = 6;
+
+// One live game. `acc_*` is the ranked identity (account name, or the nick for a
+// guest); `side_*` is the piece/colour each side plays. A = challenger, moves first.
+pub struct Game {
+    pub id: u64,
+    pub gtype: String,        // "ttt" | "c4" | "chess"
+    pub acc_a: String,
+    pub acc_b: String,
+    pub nick_a: String,
+    pub nick_b: String,
+    pub a_reg: bool,
+    pub b_reg: bool,
+    pub side_a: String,
+    pub side_b: String,
+    pub board: String,
+    pub turn: String,         // side to move
+    pub status: String,       // "pending" | "active" | "over"
+    pub result: String,       // "" | "<winner account>" | "draw"
+}
+
+// One (account, game type) ladder row. A player can be Gold at chess and Bronze
+// at Connect Four, so each type keeps its own record.
+#[derive(Default, Clone)]
+pub struct Stats {
+    pub wins: u32,
+    pub losses: u32,
+    pub draws: u32,
+    pub points: i32,
+}
+
+impl Stats {
+    pub fn rank(&self) -> &'static str {
+        if self.points >= 800 {
+            "Master"
+        } else if self.points >= 400 {
+            "Gold"
+        } else if self.points >= 150 {
+            "Silver"
+        } else {
+            "Bronze"
+        }
+    }
+}
+
+pub fn valid_type(t: &str) -> bool {
+    matches!(t, "ttt" | "c4" | "chess")
+}
+
+pub fn type_label(t: &str) -> &'static str {
+    match t {
+        "chess" => "Échecs",
+        "c4" => "Puissance 4",
+        "ttt" => "Morpion",
+        _ => "?",
+    }
+}
+
+// The two sides for a game type; the challenger takes the first, moves first.
+pub fn sides(gtype: &str) -> (&'static str, &'static str) {
+    match gtype {
+        "ttt" => ("X", "O"),
+        "c4" => ("R", "Y"),
+        _ => ("w", "b"),
+    }
+}
+
+pub fn init_board(gtype: &str) -> String {
+    match gtype {
+        "ttt" => " ".repeat(9),
+        "c4" => " ".repeat(C4_W * C4_H),
+        "chess" => chess::encode(&chess::initial()),
+        _ => String::new(),
+    }
+}
+
+// Apply `mv` for `side`; returns true iff it was legal and applied (mutating the
+// board and flipping the turn). Rejects out-of-turn and illegal moves.
+pub fn apply_move(g: &mut Game, side: &str, mv: &str) -> bool {
+    if g.turn != side {
+        return false;
+    }
+    let other = if side == g.side_a { g.side_b.clone() } else { g.side_a.clone() };
+    match g.gtype.as_str() {
+        "ttt" => {
+            let c: i32 = mv.parse().unwrap_or(-1);
+            let mut b = g.board.clone().into_bytes();
+            if !(0..=8).contains(&c) || b[c as usize] != b' ' {
+                return false;
+            }
+            b[c as usize] = side.as_bytes()[0];
+            g.board = String::from_utf8(b).unwrap_or_default();
+            g.turn = other;
+            true
+        }
+        "c4" => {
+            let col: i32 = mv.parse().unwrap_or(-1);
+            if col < 0 || col as usize >= C4_W {
+                return false;
+            }
+            let col = col as usize;
+            let mut b = g.board.clone().into_bytes();
+            for r in 0..C4_H {
+                // row 0 = bottom; the piece drops to the lowest empty cell.
+                let i = r * C4_W + col;
+                if b[i] == b' ' {
+                    b[i] = side.as_bytes()[0];
+                    g.board = String::from_utf8(b).unwrap_or_default();
+                    g.turn = other;
+                    return true;
+                }
+            }
+            false // column full
+        }
+        "chess" => {
+            let st = chess::decode(&g.board);
+            match chess::parse(&st, mv) {
+                Some(m) => {
+                    let ns = chess::apply(&st, &m);
+                    g.board = chess::encode(&ns);
+                    g.turn = (ns.turn as char).to_string();
+                    true
+                }
+                None => false,
+            }
+        }
+        _ => false,
+    }
+}
+
+// "" = ongoing, "draw", or the winning side string.
+pub fn terminal(g: &Game) -> String {
+    match g.gtype.as_str() {
+        "ttt" => {
+            let b = g.board.as_bytes();
+            for ln in TTT_LINES {
+                let a = b[ln[0]];
+                if a != b' ' && a == b[ln[1]] && a == b[ln[2]] {
+                    return (a as char).to_string();
+                }
+            }
+            if g.board.contains(' ') { String::new() } else { "draw".into() }
+        }
+        "c4" => {
+            let b = g.board.as_bytes();
+            let dirs: [(i32, i32); 4] = [(1, 0), (0, 1), (1, 1), (1, -1)];
+            for c in 0..C4_W as i32 {
+                for r in 0..C4_H as i32 {
+                    let p = b[r as usize * C4_W + c as usize];
+                    if p == b' ' {
+                        continue;
+                    }
+                    for (dc, dr) in dirs {
+                        let (mut cc, mut rr) = (c, r);
+                        let mut ok = true;
+                        for _ in 0..4 {
+                            if cc < 0 || cc >= C4_W as i32 || rr < 0 || rr >= C4_H as i32
+                                || b[rr as usize * C4_W + cc as usize] != p
+                            {
+                                ok = false;
+                                break;
+                            }
+                            cc += dc;
+                            rr += dr;
+                        }
+                        if ok {
+                            return (p as char).to_string();
+                        }
+                    }
+                }
+            }
+            if g.board.contains(' ') { String::new() } else { "draw".into() }
+        }
+        "chess" => chess::over(&chess::decode(&g.board)),
+        _ => String::new(),
+    }
+}
+
+// The board rendered space-free for the wire: chess is already a comma-FEN;
+// ttt/c4 map empty cells ' ' -> '.'.
+pub fn encode_board(g: &Game) -> String {
+    if g.gtype == "chess" {
+        g.board.clone()
+    } else {
+        g.board.replace(' ', ".")
+    }
+}
+
+// IRCv3 message-tag value escaping. We build the state TAGMSG as a raw line, and
+// the serializer only strips CR/LF/NUL — so a space or ';' in the value would
+// corrupt the s2s line (it once caused a netsplit under Anope). Escape here.
+pub fn escape_tag(v: &str) -> String {
+    let mut out = String::with_capacity(v.len());
+    for c in v.chars() {
+        match c {
+            ';' => out.push_str("\\:"),
+            ' ' => out.push_str("\\s"),
+            '\\' => out.push_str("\\\\"),
+            '\r' => out.push_str("\\r"),
+            '\n' => out.push_str("\\n"),
+            _ => out.push(c),
+        }
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn game(gtype: &str) -> Game {
+        let (sa, sb) = sides(gtype);
+        Game {
+            id: 1, gtype: gtype.into(), acc_a: "a".into(), acc_b: "b".into(),
+            nick_a: "a".into(), nick_b: "b".into(), a_reg: true, b_reg: true,
+            side_a: sa.into(), side_b: sb.into(), board: init_board(gtype),
+            turn: sa.into(), status: "active".into(), result: String::new(),
+        }
+    }
+
+    #[test]
+    fn ttt_rejects_out_of_turn_and_occupied_and_detects_a_win() {
+        let mut g = game("ttt");
+        // O can't move first (X's turn); an out-of-range/occupied cell is rejected.
+        assert!(!apply_move(&mut g, "O", "0"), "not O's turn");
+        assert!(apply_move(&mut g, "X", "0"));
+        assert!(!apply_move(&mut g, "X", "0"), "cell taken");
+        assert!(!apply_move(&mut g, "O", "9"), "off board");
+        // X top row: 0,1,2 with O elsewhere.
+        apply_move(&mut g, "O", "3");
+        apply_move(&mut g, "X", "1");
+        apply_move(&mut g, "O", "4");
+        assert_eq!(terminal(&g), "");
+        assert!(apply_move(&mut g, "X", "2"));
+        assert_eq!(terminal(&g), "X", "top row wins");
+    }
+
+    #[test]
+    fn c4_drops_to_bottom_and_detects_vertical_win() {
+        let mut g = game("c4");
+        // R stacks column 3; Y answers in column 4. Four R vertically wins.
+        for _ in 0..3 {
+            assert!(apply_move(&mut g, "R", "3"));
+            assert_eq!(terminal(&g), "");
+            assert!(apply_move(&mut g, "Y", "4"));
+        }
+        assert!(apply_move(&mut g, "R", "3"));
+        assert_eq!(terminal(&g), "R", "four in a column wins");
+        // The pieces fell to the bottom of column 3 (rows 0..3).
+        assert_eq!(&g.board[3..4], "R");
+    }
+
+    #[test]
+    fn chess_plays_a_legal_move_and_rejects_an_illegal_one() {
+        let mut g = game("chess");
+        assert!(!apply_move(&mut g, "b", "e7e5"), "white to move");
+        assert!(apply_move(&mut g, "w", "e2e4"));
+        assert_eq!(g.turn, "b");
+        assert!(!apply_move(&mut g, "b", "e7e9"), "off board / illegal");
+        assert!(apply_move(&mut g, "b", "e7e5"));
+        assert_eq!(terminal(&g), "", "game ongoing");
+    }
+
+    #[test]
+    fn encode_board_is_space_free() {
+        let g = game("ttt");
+        assert!(!encode_board(&g).contains(' '), "ttt empty cells become dots");
+        assert_eq!(escape_tag("GS# 1 g=ttt"), "GS#\\s1\\sg=ttt");
+    }
+}
diff --git a/modules/gameserv/src/chess.rs b/modules/gameserv/src/chess.rs
new file mode 100644
index 0000000..ccda0aa
--- /dev/null
+++ b/modules/gameserv/src/chess.rs
@@ -0,0 +1,695 @@
+//! Self-contained chess engine for the GameServ referee.
+//!
+//! Pure-logic port of the perft-verified `gschess` C++ engine (no I/O, no
+//! external crates). Board is 64 bytes, index = rank*8 + file
+//! (a1=0, h1=7, a8=56, h8=63), `b' '` = empty, pieces `PNBRQK` (white) /
+//! `pnbrqk` (black). The wire form ([`encode`]/[`decode`]) is a comma-separated
+//! FEN so it carries no spaces: `"<rows>,<turn>,<castling>,<ep>"`.
+
+const EMPTY: u8 = b' ';
+
+#[inline]
+fn cf(s: i32) -> i32 {
+    s & 7
+}
+
+#[inline]
+fn cr(s: i32) -> i32 {
+    s >> 3
+}
+
+#[inline]
+fn csq(f: i32, r: i32) -> i32 {
+    r * 8 + f
+}
+
+/// Colour of a piece byte: `b'w'` for uppercase (white), `b'b'` otherwise.
+#[inline]
+fn ccolor(p: u8) -> u8 {
+    if p.is_ascii_uppercase() {
+        b'w'
+    } else {
+        b'b'
+    }
+}
+
+/// True if `p` is a non-empty piece owned by colour `c`.
+#[inline]
+fn cown(p: u8, c: u8) -> bool {
+    p != EMPTY && ccolor(p) == c
+}
+
+#[inline]
+fn upper(p: u8) -> u8 {
+    p.to_ascii_uppercase()
+}
+
+const KN: [(i32, i32); 8] = [
+    (1, 2),
+    (2, 1),
+    (2, -1),
+    (1, -2),
+    (-1, -2),
+    (-2, -1),
+    (-2, 1),
+    (-1, 2),
+];
+const KG: [(i32, i32); 8] = [
+    (1, 0),
+    (1, 1),
+    (0, 1),
+    (-1, 1),
+    (-1, 0),
+    (-1, -1),
+    (0, -1),
+    (1, -1),
+];
+const BD: [(i32, i32); 4] = [(1, 1), (-1, 1), (-1, -1), (1, -1)];
+const RD: [(i32, i32); 4] = [(1, 0), (-1, 0), (0, 1), (0, -1)];
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct Move {
+    pub from: usize,
+    pub to: usize,
+    /// 0 or `b'q'` / `b'r'` / `b'b'` / `b'n'`.
+    pub promo: u8,
+    /// en-passant capture
+    pub ep: bool,
+    /// pawn double-push
+    pub dbl: bool,
+    /// 0, `b'K'` or `b'Q'`
+    pub castle: u8,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct State {
+    /// 64 bytes, index = rank*8 + file.
+    pub board: [u8; 64],
+    /// `b'w'` or `b'b'`.
+    pub turn: u8,
+    /// White king-side castling right.
+    pub c_k: bool,
+    /// White queen-side castling right.
+    pub c_q: bool,
+    /// Black king-side castling right.
+    pub c_k_black: bool,
+    /// Black queen-side castling right.
+    pub c_q_black: bool,
+    /// En-passant target square, -1 = none.
+    pub ep: i32,
+}
+
+impl Default for State {
+    fn default() -> Self {
+        State {
+            board: [EMPTY; 64],
+            turn: b'w',
+            c_k: true,
+            c_q: true,
+            c_k_black: true,
+            c_q_black: true,
+            ep: -1,
+        }
+    }
+}
+
+pub fn initial() -> State {
+    let mut st = State::default();
+    let back = b"RNBQKBNR";
+    for f in 0..8 {
+        st.board[csq(f, 0) as usize] = back[f as usize];
+        st.board[csq(f, 1) as usize] = b'P';
+        st.board[csq(f, 6) as usize] = b'p';
+        st.board[csq(f, 7) as usize] = back[f as usize].to_ascii_lowercase();
+    }
+    st
+}
+
+/// True if square `target` is attacked by any piece of colour `by`.
+fn attacked(b: &[u8; 64], target: i32, by: u8) -> bool {
+    let tf = cf(target);
+    let tr = cr(target);
+    let pr = if by == b'w' { tr - 1 } else { tr + 1 };
+
+    // Pawn attacks (a pawn of colour `by` on `pr` attacking diagonally).
+    for df in [-1, 1] {
+        let f = tf + df;
+        if (0..8).contains(&f) && (0..8).contains(&pr) {
+            let p = b[csq(f, pr) as usize];
+            if p != EMPTY && ccolor(p) == by && upper(p) == b'P' {
+                return true;
+            }
+        }
+    }
+    // Knight attacks.
+    for (dx, dy) in KN {
+        let f = tf + dx;
+        let r = tr + dy;
+        if (0..8).contains(&f) && (0..8).contains(&r) {
+            let p = b[csq(f, r) as usize];
+            if p != EMPTY && ccolor(p) == by && upper(p) == b'N' {
+                return true;
+            }
+        }
+    }
+    // King attacks.
+    for (dx, dy) in KG {
+        let f = tf + dx;
+        let r = tr + dy;
+        if (0..8).contains(&f) && (0..8).contains(&r) {
+            let p = b[csq(f, r) as usize];
+            if p != EMPTY && ccolor(p) == by && upper(p) == b'K' {
+                return true;
+            }
+        }
+    }
+    // Bishop / queen (diagonal) attacks.
+    for (dx, dy) in BD {
+        let mut f = tf + dx;
+        let mut r = tr + dy;
+        while (0..8).contains(&f) && (0..8).contains(&r) {
+            let p = b[csq(f, r) as usize];
+            if p != EMPTY {
+                let u = upper(p);
+                if ccolor(p) == by && (u == b'B' || u == b'Q') {
+                    return true;
+                }
+                break;
+            }
+            f += dx;
+            r += dy;
+        }
+    }
+    // Rook / queen (orthogonal) attacks.
+    for (dx, dy) in RD {
+        let mut f = tf + dx;
+        let mut r = tr + dy;
+        while (0..8).contains(&f) && (0..8).contains(&r) {
+            let p = b[csq(f, r) as usize];
+            if p != EMPTY {
+                let u = upper(p);
+                if ccolor(p) == by && (u == b'R' || u == b'Q') {
+                    return true;
+                }
+                break;
+            }
+            f += dx;
+            r += dy;
+        }
+    }
+    false
+}
+
+fn king_sq(b: &[u8; 64], c: u8) -> i32 {
+    let k = if c == b'w' { b'K' } else { b'k' };
+    b.iter().position(|&p| p == k).map(|i| i as i32).unwrap_or(-1)
+}
+
+fn in_check(st: &State, c: u8) -> bool {
+    let by = if c == b'w' { b'b' } else { b'w' };
+    attacked(&st.board, king_sq(&st.board, c), by)
+}
+
+fn add_pawn(mv: &mut Vec<Move>, from: i32, to: i32, promo: bool, ep: bool, dbl: bool) {
+    if promo {
+        for pr in *b"qrbn" {
+            mv.push(Move {
+                from: from as usize,
+                to: to as usize,
+                promo: pr,
+                ..Move::default()
+            });
+        }
+    } else {
+        mv.push(Move {
+            from: from as usize,
+            to: to as usize,
+            ep,
+            dbl,
+            ..Move::default()
+        });
+    }
+}
+
+/// Pseudo-legal moves (may leave the mover's own king in check).
+fn pseudo(st: &State) -> Vec<Move> {
+    let mut mv = Vec::new();
+    let c = st.turn;
+    let dir = if c == b'w' { 1 } else { -1 };
+    let start_rank = if c == b'w' { 1 } else { 6 };
+    let promo_rank = if c == b'w' { 7 } else { 0 };
+
+    for s in 0..64 {
+        let p = st.board[s as usize];
+        if p == EMPTY || ccolor(p) != c {
+            continue;
+        }
+        let f = cf(s);
+        let r = cr(s);
+        let t = upper(p);
+        if t == b'P' {
+            let r1 = r + dir;
+            if (0..8).contains(&r1) && st.board[csq(f, r1) as usize] == EMPTY {
+                add_pawn(&mut mv, s, csq(f, r1), r1 == promo_rank, false, false);
+                if r == start_rank && st.board[csq(f, r + 2 * dir) as usize] == EMPTY {
+                    add_pawn(&mut mv, s, csq(f, r + 2 * dir), false, false, true);
+                }
+            }
+            for df in [-1, 1] {
+                let cf2 = f + df;
+                let cr2 = r + dir;
+                if !(0..8).contains(&cf2) || !(0..8).contains(&cr2) {
+                    continue;
+                }
+                let to = csq(cf2, cr2);
+                let tp = st.board[to as usize];
+                if tp != EMPTY && ccolor(tp) != c {
+                    add_pawn(&mut mv, s, to, cr2 == promo_rank, false, false);
+                } else if to == st.ep {
+                    mv.push(Move {
+                        from: s as usize,
+                        to: to as usize,
+                        ep: true,
+                        ..Move::default()
+                    });
+                }
+            }
+        } else if t == b'N' {
+            for (dx, dy) in KN {
+                let cf2 = f + dx;
+                let cr2 = r + dy;
+                if !(0..8).contains(&cf2) || !(0..8).contains(&cr2) {
+                    continue;
+                }
+                let to = csq(cf2, cr2);
+                if !cown(st.board[to as usize], c) {
+                    mv.push(Move {
+                        from: s as usize,
+                        to: to as usize,
+                        ..Move::default()
+                    });
+                }
+            }
+        } else if t == b'K' {
+            for (dx, dy) in KG {
+                let cf2 = f + dx;
+                let cr2 = r + dy;
+                if !(0..8).contains(&cf2) || !(0..8).contains(&cr2) {
+                    continue;
+                }
+                let to = csq(cf2, cr2);
+                if !cown(st.board[to as usize], c) {
+                    mv.push(Move {
+                        from: s as usize,
+                        to: to as usize,
+                        ..Move::default()
+                    });
+                }
+            }
+            let enemy = if c == b'w' { b'b' } else { b'w' };
+            let rank = if c == b'w' { 0 } else { 7 };
+            let k_from = csq(4, rank);
+            if s == k_from && !attacked(&st.board, k_from, enemy) {
+                let kr = if c == b'w' { st.c_k } else { st.c_k_black };
+                let qr = if c == b'w' { st.c_q } else { st.c_q_black };
+                let rook = if c == b'w' { b'R' } else { b'r' };
+                if kr
+                    && st.board[csq(5, rank) as usize] == EMPTY
+                    && st.board[csq(6, rank) as usize] == EMPTY
+                    && st.board[csq(7, rank) as usize] == rook
+                    && !attacked(&st.board, csq(5, rank), enemy)
+                    && !attacked(&st.board, csq(6, rank), enemy)
+                {
+                    mv.push(Move {
+                        from: k_from as usize,
+                        to: csq(6, rank) as usize,
+                        castle: b'K',
+                        ..Move::default()
+                    });
+                }
+                if qr
+                    && st.board[csq(3, rank) as usize] == EMPTY
+                    && st.board[csq(2, rank) as usize] == EMPTY
+                    && st.board[csq(1, rank) as usize] == EMPTY
+                    && st.board[csq(0, rank) as usize] == rook
+                    && !attacked(&st.board, csq(3, rank), enemy)
+                    && !attacked(&st.board, csq(2, rank), enemy)
+                {
+                    mv.push(Move {
+                        from: k_from as usize,
+                        to: csq(2, rank) as usize,
+                        castle: b'Q',
+                        ..Move::default()
+                    });
+                }
+            }
+        } else {
+            // Sliding pieces: bishop (BD), rook (RD), queen (both).
+            let dirs: &[(i32, i32)] = match t {
+                b'B' => &BD,
+                b'R' => &RD,
+                _ => &[BD[0], BD[1], BD[2], BD[3], RD[0], RD[1], RD[2], RD[3]],
+            };
+            for &(dx, dy) in dirs {
+                let mut cf2 = f + dx;
+                let mut cr2 = r + dy;
+                while (0..8).contains(&cf2) && (0..8).contains(&cr2) {
+                    let to = csq(cf2, cr2);
+                    let tp = st.board[to as usize];
+                    if tp != EMPTY {
+                        if ccolor(tp) != c {
+                            mv.push(Move {
+                                from: s as usize,
+                                to: to as usize,
+                                ..Move::default()
+                            });
+                        }
+                        break;
+                    }
+                    mv.push(Move {
+                        from: s as usize,
+                        to: to as usize,
+                        ..Move::default()
+                    });
+                    cf2 += dx;
+                    cr2 += dy;
+                }
+            }
+        }
+    }
+    mv
+}
+
+pub fn apply(st: &State, m: &Move) -> State {
+    let mut n = st.clone();
+    let c = st.turn;
+    let dir = if c == b'w' { 1 } else { -1 };
+    let piece = n.board[m.from];
+    n.board[m.from] = EMPTY;
+
+    if m.ep {
+        // Remove the pawn captured en passant: same file as target, same rank
+        // as the moving pawn's origin.
+        n.board[csq(cf(m.to as i32), cr(m.from as i32)) as usize] = EMPTY;
+    }
+    if m.promo != 0 {
+        n.board[m.to] = if c == b'w' {
+            m.promo.to_ascii_uppercase()
+        } else {
+            m.promo
+        };
+    } else {
+        n.board[m.to] = piece;
+    }
+    if m.castle != 0 {
+        let rk = if c == b'w' { 0 } else { 7 };
+        let rook = if c == b'w' { b'R' } else { b'r' };
+        if m.castle == b'K' {
+            n.board[csq(7, rk) as usize] = EMPTY;
+            n.board[csq(5, rk) as usize] = rook;
+        } else {
+            n.board[csq(0, rk) as usize] = EMPTY;
+            n.board[csq(3, rk) as usize] = rook;
+        }
+    }
+
+    let pu = upper(piece);
+    if pu == b'K' {
+        if c == b'w' {
+            n.c_k = false;
+            n.c_q = false;
+        } else {
+            n.c_k_black = false;
+            n.c_q_black = false;
+        }
+    }
+    if piece == b'R' {
+        if m.from == csq(0, 0) as usize {
+            n.c_q = false;
+        }
+        if m.from == csq(7, 0) as usize {
+            n.c_k = false;
+        }
+    }
+    if piece == b'r' {
+        if m.from == csq(0, 7) as usize {
+            n.c_q_black = false;
+        }
+        if m.from == csq(7, 7) as usize {
+            n.c_k_black = false;
+        }
+    }
+    // Capturing a rook on its home square removes that castling right.
+    if m.to == csq(0, 0) as usize {
+        n.c_q = false;
+    }
+    if m.to == csq(7, 0) as usize {
+        n.c_k = false;
+    }
+    if m.to == csq(0, 7) as usize {
+        n.c_q_black = false;
+    }
+    if m.to == csq(7, 7) as usize {
+        n.c_k_black = false;
+    }
+
+    n.turn = if c == b'w' { b'b' } else { b'w' };
+    n.ep = if m.dbl {
+        csq(cf(m.from as i32), cr(m.from as i32) + dir)
+    } else {
+        -1
+    };
+    n
+}
+
+/// Fully legal moves: pseudo-legal filtered so the mover's king is not left
+/// attacked.
+pub fn legal(st: &State) -> Vec<Move> {
+    let c = st.turn;
+    let by = if c == b'w' { b'b' } else { b'w' };
+    pseudo(st)
+        .into_iter()
+        .filter(|m| {
+            let ns = apply(st, m);
+            !attacked(&ns.board, king_sq(&ns.board, c), by)
+        })
+        .collect()
+}
+
+/// `""` ongoing; `"draw"` for stalemate; or the winning side (`"w"`/`"b"`) on
+/// checkmate.
+pub fn over(st: &State) -> String {
+    if !legal(st).is_empty() {
+        return String::new();
+    }
+    if in_check(st, st.turn) {
+        return if st.turn == b'w' { "b" } else { "w" }.to_string();
+    }
+    "draw".to_string()
+}
+
+fn name_sq(s: i32) -> String {
+    let mut r = String::new();
+    r.push((b'a' + cf(s) as u8) as char);
+    r.push((b'1' + cr(s) as u8) as char);
+    r
+}
+
+fn sq_name(n: &[u8]) -> i32 {
+    csq((n[0] - b'a') as i32, (n[1] - b'1') as i32)
+}
+
+/// Find the legal move matching a UCI string (`e2e4`, `e7e8q`). `None` if not
+/// legal.
+pub fn parse(st: &State, uci: &str) -> Option<Move> {
+    let bytes = uci.as_bytes();
+    if bytes.len() < 4 {
+        return None;
+    }
+    let from = sq_name(&bytes[0..2]) as usize;
+    let to = sq_name(&bytes[2..4]) as usize;
+    let promo = if bytes.len() > 4 {
+        bytes[4].to_ascii_lowercase()
+    } else {
+        0
+    };
+    legal(st)
+        .into_iter()
+        .find(|m| m.from == from && m.to == to && m.promo == promo)
+}
+
+/// Comma-separated FEN (no spaces) for the wire.
+pub fn encode(st: &State) -> String {
+    let mut rows = String::new();
+    for r in (0..8).rev() {
+        let mut e = 0;
+        let mut row = String::new();
+        for f in 0..8 {
+            let p = st.board[csq(f, r) as usize];
+            if p != EMPTY {
+                if e > 0 {
+                    row.push_str(&e.to_string());
+                    e = 0;
+                }
+                row.push(p as char);
+            } else {
+                e += 1;
+            }
+        }
+        if e > 0 {
+            row.push_str(&e.to_string());
+        }
+        if r < 7 {
+            rows.push('/');
+        }
+        rows.push_str(&row);
+    }
+    let mut cc = String::new();
+    if st.c_k {
+        cc.push('K');
+    }
+    if st.c_q {
+        cc.push('Q');
+    }
+    if st.c_k_black {
+        cc.push('k');
+    }
+    if st.c_q_black {
+        cc.push('q');
+    }
+    if cc.is_empty() {
+        cc.push('-');
+    }
+    let ep = if st.ep < 0 {
+        "-".to_string()
+    } else {
+        name_sq(st.ep)
+    };
+    format!("{},{},{},{}", rows, st.turn as char, cc, ep)
+}
+
+/// Inverse of [`encode`]. On malformed input (fewer than 4 comma parts) returns
+/// [`initial`].
+pub fn decode(enc: &str) -> State {
+    let mut st = State {
+        board: [EMPTY; 64],
+        turn: b'w',
+        c_k: false,
+        c_q: false,
+        c_k_black: false,
+        c_q_black: false,
+        ep: -1,
+    };
+
+    // Collect up to 4 comma-separated fields, mirroring the C++ manual scan:
+    // each step takes the segment up to the next comma, or the whole remainder
+    // when no comma is left.
+    let mut parts: Vec<&str> = Vec::new();
+    let mut pos = 0;
+    while parts.len() < 4 {
+        match enc[pos..].find(',') {
+            Some(rel) => {
+                let comma = pos + rel;
+                parts.push(&enc[pos..comma]);
+                pos = comma + 1;
+            }
+            None => {
+                parts.push(&enc[pos..]);
+                break;
+            }
+        }
+    }
+    if parts.len() < 4 {
+        return initial();
+    }
+
+    // Board.
+    let mut r: i32 = 7;
+    let mut f: i32 = 0;
+    for ch in parts[0].bytes() {
+        if ch == b'/' {
+            r -= 1;
+            f = 0;
+        } else if (b'1'..=b'8').contains(&ch) {
+            f += (ch - b'0') as i32;
+        } else {
+            if (0..8).contains(&r) && (0..8).contains(&f) {
+                st.board[csq(f, r) as usize] = ch;
+            }
+            f += 1;
+        }
+    }
+    st.turn = parts[1].bytes().next().unwrap_or(b'w');
+    for ch in parts[2].bytes() {
+        match ch {
+            b'K' => st.c_k = true,
+            b'Q' => st.c_q = true,
+            b'k' => st.c_k_black = true,
+            b'q' => st.c_q_black = true,
+            _ => {}
+        }
+    }
+    st.ep = if parts[3] == "-" || parts[3].is_empty() {
+        -1
+    } else {
+        sq_name(parts[3].as_bytes())
+    };
+    st
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn perft(st: &State, depth: u32) -> u64 {
+        if depth == 0 {
+            return 1;
+        }
+        let moves = legal(st);
+        if depth == 1 {
+            return moves.len() as u64;
+        }
+        moves.iter().map(|m| perft(&apply(st, m), depth - 1)).sum()
+    }
+
+    #[test]
+    fn perft_start_position() {
+        let st = initial();
+        assert_eq!(perft(&st, 1), 20);
+        assert_eq!(perft(&st, 2), 400);
+        assert_eq!(perft(&st, 3), 8902);
+        assert_eq!(perft(&st, 4), 197281);
+    }
+
+    #[test]
+    fn encode_initial() {
+        let enc = encode(&initial());
+        assert_eq!(
+            enc,
+            "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR,w,KQkq,-"
+        );
+    }
+
+    #[test]
+    fn encode_decode_roundtrip() {
+        let st = initial();
+        assert_eq!(decode(&encode(&st)), st);
+    }
+
+    #[test]
+    fn decode_malformed_returns_initial() {
+        assert_eq!(decode("garbage"), initial());
+        assert_eq!(decode("a,b,c"), initial());
+    }
+
+    #[test]
+    fn parse_and_apply_e2e4() {
+        let st = initial();
+        let m = parse(&st, "e2e4").expect("e2e4 legal");
+        assert!(m.dbl);
+        let ns = apply(&st, &m);
+        assert_eq!(ns.turn, b'b');
+        assert_eq!(ns.ep, csq(4, 2)); // e3
+        assert!(parse(&st, "e2e5").is_none());
+    }
+}
diff --git a/modules/gameserv/src/lib.rs b/modules/gameserv/src/lib.rs
new file mode 100644
index 0000000..4311e5f
--- /dev/null
+++ b/modules/gameserv/src/lib.rs
@@ -0,0 +1,397 @@
+//! GameServ — a server-authoritative referee for tic-tac-toe, Connect Four and
+//! chess, with a per-game ranked ladder. Every move is validated here and the
+//! winner decided by the server, so a client can never cheat (see the hard rule:
+//! games stay server-side). Players drive games entirely over `/msg GameServ`;
+//! the machine-readable board is pushed to each player on an invisible client-only
+//! TAGMSG (`+tchatou.fr/gs`) that only the web client renders — IRC clients see
+//! just the human notices.
+//!
+//! `board.rs` is the referee (rules + state); `chess.rs` is the chess engine.
+
+use std::collections::HashMap;
+
+use echo_api::{HelpEntry, NetAction, NetView, Sender, Service, ServiceCtx, Store};
+
+#[path = "chess.rs"]
+mod chess;
+#[path = "board.rs"]
+mod board;
+
+use board::{Game, Stats};
+
+// Cap concurrent games per identity so a flood of never-finished challenges
+// can't grow the map without bound (finished games are dropped immediately).
+const MAX_GAMES_PER_USER: usize = 5;
+const TYPES: [&str; 3] = ["chess", "c4", "ttt"];
+
+const BLURB: &str = "GameServ referees \x02tic-tac-toe\x02, \x02Connect Four\x02 and \x02chess\x02 — it checks every move and keeps a ranked ladder. Challenge someone, then take turns. Moves: ttt cell \x020-8\x02, c4 column \x020-6\x02, chess \x02UCI\x02 (e2e4).";
+
+const TOPICS: &[HelpEntry] = &[
+    HelpEntry { cmd: "CHALLENGE", summary: "challenge someone to a game", detail: "Syntax: \x02CHALLENGE <nick> <ttt|c4|chess>\x02\nChallenges a user. They accept with \x02ACCEPT\x02; you move first." },
+    HelpEntry { cmd: "ACCEPT", summary: "accept a challenge", detail: "Syntax: \x02ACCEPT [id]\x02\nAccepts a pending challenge (the most recent one if no id is given)." },
+    HelpEntry { cmd: "DECLINE", summary: "decline a challenge", detail: "Syntax: \x02DECLINE [id]\x02\nDeclines a pending challenge." },
+    HelpEntry { cmd: "MOVE", summary: "make a move", detail: "Syntax: \x02MOVE <id> <move>\x02\nMakes a move: ttt cell \x020-8\x02, c4 column \x020-6\x02, chess \x02UCI\x02 like e2e4 (e7e8q to promote)." },
+    HelpEntry { cmd: "RESIGN", summary: "resign a game", detail: "Syntax: \x02RESIGN <id>\x02\nResigns an active game; your opponent wins." },
+    HelpEntry { cmd: "GAMES", summary: "list your games", detail: "Syntax: \x02GAMES\x02\nLists your pending and active games with their ids." },
+    HelpEntry { cmd: "STATS", summary: "show ranked stats", detail: "Syntax: \x02STATS [nick]\x02\nShows a player's ranked record per game type (yours if no nick)." },
+    HelpEntry { cmd: "TOP", summary: "show the leaderboard", detail: "Syntax: \x02TOP [ttt|c4|chess]\x02\nShows the top ranked players for a game type (chess by default)." },
+];
+
+// account key (lowercased) -> that player's ladder across game types.
+type Ladder = HashMap<String, PlayerLadder>;
+
+#[derive(Default)]
+struct PlayerLadder {
+    display: String,
+    by_type: HashMap<String, Stats>,
+}
+
+pub struct GameServ {
+    pub uid: String,
+    games: HashMap<u64, Game>,
+    ladder: Ladder,
+    nextid: u64,
+}
+
+impl GameServ {
+    pub fn new(uid: String) -> Self {
+        Self { uid, games: HashMap::new(), ladder: Ladder::new(), nextid: 1 }
+    }
+
+    // A player's ranked identity: their account if registered, else their nick
+    // (guests play casually under their nick; ranked points need an account).
+    fn ident<'a>(from: &'a Sender) -> &'a str {
+        from.account.unwrap_or(from.nick)
+    }
+
+    // Get (creating if needed) a mutable ladder row, remembering the display name.
+    fn stat(&mut self, account: &str, gtype: &str) -> &mut Stats {
+        let pl = self.ladder.entry(account.to_lowercase()).or_default();
+        if pl.display.is_empty() {
+            pl.display = account.to_string();
+        }
+        pl.by_type.entry(gtype.to_string()).or_default()
+    }
+
+    fn do_challenge(&mut self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let (Some(&target), Some(&game)) = (args.get(1), args.get(2)) else {
+            ctx.notice(me, from.uid, "Syntax: CHALLENGE <nick> <ttt|c4|chess>");
+            return;
+        };
+        let gtype = game.to_lowercase();
+        if !board::valid_type(&gtype) {
+            ctx.notice(me, from.uid, "Unknown game. Available: \x02ttt\x02 (tic-tac-toe), \x02c4\x02 (Connect Four), \x02chess\x02.");
+            return;
+        }
+        let Some(tuid) = net.uid_by_nick(target).map(str::to_string) else {
+            ctx.notice(me, from.uid, format!("\x02{target}\x02 is not online."));
+            return;
+        };
+        if tuid == from.uid {
+            ctx.notice(me, from.uid, "You cannot challenge yourself.");
+            return;
+        }
+        let meid = Self::ident(from).to_string();
+        let mine = self.games.values().filter(|g| g.acc_a == meid || g.acc_b == meid).count();
+        if mine >= MAX_GAMES_PER_USER {
+            ctx.notice(me, from.uid, format!("You have too many games in progress (max {MAX_GAMES_PER_USER}). Finish or resign one first."));
+            return;
+        }
+        let target_acc = net.account_of(&tuid).map(str::to_string);
+        let (sa, sb) = board::sides(&gtype);
+        let id = self.nextid;
+        self.nextid += 1;
+        let g = Game {
+            id,
+            gtype: gtype.clone(),
+            acc_a: meid,
+            a_reg: from.account.is_some(),
+            acc_b: target_acc.clone().unwrap_or_else(|| target.to_string()),
+            b_reg: target_acc.is_some(),
+            nick_a: from.nick.to_string(),
+            nick_b: target.to_string(),
+            side_a: sa.to_string(),
+            side_b: sb.to_string(),
+            board: board::init_board(&gtype),
+            turn: sa.to_string(),
+            status: "pending".to_string(),
+            result: String::new(),
+        };
+        self.games.insert(id, g);
+        ctx.notice(me, from.uid, format!("Challenge \x02#{id}\x02 ({gtype}) sent to \x02{target}\x02."));
+        ctx.notice(me, &tuid, format!("{} challenges you to {gtype} (game #{id}). \x02/msg GameServ ACCEPT {id}\x02", from.nick));
+        let g = &self.games[&id];
+        push_one(g, 0, "pending", me, net, ctx); // challenger: waiting
+        push_one(g, 1, "offer", me, net, ctx); // target: can accept/decline
+    }
+
+    fn do_accept(&mut self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let meid = Self::ident(from).to_string();
+        let id = match args.get(1) {
+            Some(&s) => s.parse::<u64>().ok().filter(|id| self.games.get(id).is_some_and(|g| g.status == "pending" && g.acc_b == meid)),
+            None => self.games.iter().find(|(_, g)| g.status == "pending" && g.acc_b == meid).map(|(id, _)| *id),
+        };
+        let Some(id) = id else {
+            ctx.notice(me, from.uid, "No pending challenge to accept.");
+            return;
+        };
+        let g = self.games.get_mut(&id).unwrap();
+        g.status = "active".to_string();
+        g.nick_b = from.nick.to_string();
+        let side = g.side_b.clone();
+        ctx.notice(me, from.uid, format!("Game \x02#{id}\x02 started. You are \x02{side}\x02."));
+        push_state(&self.games[&id], me, net, ctx);
+    }
+
+    fn do_decline(&mut self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let meid = Self::ident(from).to_string();
+        let want: Option<u64> = args.get(1).and_then(|s| s.parse().ok());
+        let id = self.games.iter().find(|(id, g)| {
+            g.status == "pending" && g.acc_b == meid && want.is_none_or(|w| w == **id)
+        }).map(|(id, _)| *id);
+        let Some(id) = id else {
+            ctx.notice(me, from.uid, "No pending challenge to decline.");
+            return;
+        };
+        let g = self.games.remove(&id).unwrap();
+        if let Some(auid) = net.uid_by_nick(&g.nick_a).map(str::to_string) {
+            ctx.notice(me, &auid, format!("{} declined your challenge #{id}.", from.nick));
+        }
+        ctx.notice(me, from.uid, "Declined.");
+    }
+
+    fn do_move(&mut self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let (Some(&ids), Some(&mv)) = (args.get(1), args.get(2)) else {
+            ctx.notice(me, from.uid, "Syntax: MOVE <id> <move>");
+            return;
+        };
+        let id: u64 = ids.parse().unwrap_or(0);
+        let meid = Self::ident(from).to_string();
+        // Apply under a scoped mutable borrow, then release it before pushing.
+        let term = {
+            let Some(g) = self.games.get_mut(&id) else {
+                ctx.notice(me, from.uid, "No active game with that id.");
+                return;
+            };
+            if g.status != "active" || (g.acc_a != meid && g.acc_b != meid) {
+                ctx.notice(me, from.uid, "No active game with that id.");
+                return;
+            }
+            let side = if g.acc_a == meid { g.side_a.clone() } else { g.side_b.clone() };
+            if g.acc_a == meid {
+                g.nick_a = from.nick.to_string();
+            } else {
+                g.nick_b = from.nick.to_string();
+            }
+            if !board::apply_move(g, &side, mv) {
+                ctx.notice(me, from.uid, "Illegal move (or not your turn).");
+                return;
+            }
+            board::terminal(g)
+        };
+        if term.is_empty() {
+            push_state(&self.games[&id], me, net, ctx);
+        } else {
+            self.finish(id, &term, me, net, ctx);
+        }
+    }
+
+    fn do_resign(&mut self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let Some(&ids) = args.get(1) else {
+            ctx.notice(me, from.uid, "Syntax: RESIGN <id>");
+            return;
+        };
+        let id: u64 = ids.parse().unwrap_or(0);
+        let meid = Self::ident(from).to_string();
+        let winner_side = match self.games.get(&id) {
+            Some(g) if g.status == "active" && (g.acc_a == meid || g.acc_b == meid) => {
+                if g.acc_a == meid { g.side_b.clone() } else { g.side_a.clone() }
+            }
+            _ => {
+                ctx.notice(me, from.uid, "No active game with that id.");
+                return;
+            }
+        };
+        ctx.notice(me, from.uid, format!("You resigned game #{id}."));
+        self.finish(id, &winner_side, me, net, ctx);
+    }
+
+    // End a game: record the result, update the ladder (only when BOTH players are
+    // registered — casual guest games leave the ladder untouched), push the final
+    // state + refreshed stats, and drop the game.
+    fn finish(&mut self, id: u64, winner_side: &str, me: &str, net: &dyn NetView, ctx: &mut ServiceCtx) {
+        let Some(mut g) = self.games.remove(&id) else { return };
+        g.status = "over".to_string();
+        let a_won = winner_side != "draw" && winner_side == g.side_a;
+        g.result = if winner_side == "draw" {
+            "draw".to_string()
+        } else if a_won {
+            g.acc_a.clone()
+        } else {
+            g.acc_b.clone()
+        };
+        if g.a_reg && g.b_reg {
+            if winner_side == "draw" {
+                self.stat(&g.acc_a, &g.gtype).draws += 1;
+                self.stat(&g.acc_b, &g.gtype).draws += 1;
+            } else {
+                let (wacc, lacc) = if a_won { (g.acc_a.clone(), g.acc_b.clone()) } else { (g.acc_b.clone(), g.acc_a.clone()) };
+                let w = self.stat(&wacc, &g.gtype);
+                w.wins += 1;
+                w.points += 10;
+                let l = self.stat(&lacc, &g.gtype);
+                l.losses += 1;
+                l.points = (l.points - 8).max(0);
+            }
+        }
+        push_state(&g, me, net, ctx);
+        if g.a_reg {
+            push_stats(&self.ladder, &g.acc_a, &g.nick_a, me, net, ctx);
+        }
+        if g.b_reg {
+            push_stats(&self.ladder, &g.acc_b, &g.nick_b, me, net, ctx);
+        }
+    }
+
+    fn do_games(&self, me: &str, from: &Sender, ctx: &mut ServiceCtx) {
+        let meid = Self::ident(from).to_string();
+        let mut ids: Vec<u64> = self.games.iter().filter(|(_, g)| g.acc_a == meid || g.acc_b == meid).map(|(id, _)| *id).collect();
+        ids.sort_unstable();
+        if ids.is_empty() {
+            ctx.notice(me, from.uid, "You have no games. Use \x02CHALLENGE <nick> <game>\x02.");
+            return;
+        }
+        for id in ids {
+            let g = &self.games[&id];
+            let opp = if g.acc_a == meid { &g.nick_b } else { &g.nick_a };
+            ctx.notice(me, from.uid, format!("#{}  {}  vs {}  [{}]", g.id, g.gtype, opp, g.status));
+        }
+    }
+
+    fn do_stats(&self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let who = if let Some(&t) = args.get(1) {
+            net.uid_by_nick(t).and_then(|u| net.account_of(u)).map(str::to_string).unwrap_or_else(|| t.to_string())
+        } else if let Some(a) = from.account {
+            a.to_string()
+        } else {
+            ctx.notice(me, from.uid, "Log in or specify a nick.");
+            return;
+        };
+        push_stats(&self.ladder, &who, from.nick, me, net, ctx); // machine lines for the UI
+        ctx.notice(me, from.uid, format!("\x02{who}\x02 — classement Jeux"));
+        let mut any = false;
+        let pl = self.ladder.get(&who.to_lowercase());
+        for ty in TYPES {
+            if let Some(s) = pl.and_then(|p| p.by_type.get(ty)) {
+                any = true;
+                ctx.notice(me, from.uid, format!(
+                    "  \x02{}\x02  \x02{}\x02 — {} pts ({}V {}D {}N)",
+                    board::type_label(ty), s.rank(), s.points, s.wins, s.losses, s.draws
+                ));
+            }
+        }
+        if !any {
+            ctx.notice(me, from.uid, "  (aucune partie classée pour l'instant)");
+        }
+    }
+
+    fn do_top(&self, me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView) {
+        let ty = args.get(1).map(|s| s.to_lowercase()).unwrap_or_else(|| "chess".to_string());
+        if !board::valid_type(&ty) {
+            ctx.notice(me, from.uid, "Unknown game. Use \x02TOP ttt|c4|chess\x02.");
+            return;
+        }
+        let mut all: Vec<(&str, &Stats)> = self.ladder.values()
+            .filter_map(|pl| pl.by_type.get(&ty).filter(|s| s.points > 0).map(|s| (pl.display.as_str(), s)))
+            .collect();
+        all.sort_by_key(|&(_, s)| std::cmp::Reverse(s.points));
+        push_tag(me, net, from.nick, &format!("GS$TOPSTART {ty}"), ctx);
+        if all.is_empty() {
+            ctx.notice(me, from.uid, format!("Classement \x02{}\x02 vide. Sois le premier à gagner !", board::type_label(&ty)));
+            return;
+        }
+        ctx.notice(me, from.uid, format!("\x02Classement {} :\x02", board::type_label(&ty)));
+        for (rank, (acc, s)) in all.iter().take(10).enumerate() {
+            let rank = rank + 1;
+            ctx.notice(me, from.uid, format!("{rank:2}. {acc:<16} {}  {} pts", s.rank(), s.points));
+            push_tag(me, net, from.nick, &format!("GS$TOPROW {ty} {rank} {acc} {} {}", s.rank(), s.points), ctx);
+        }
+    }
+}
+
+// ── web-sync pushes (free functions so they never borrow the GameServ state) ──
+
+// Client-only tag on a TAGMSG: invisible in chat, read only by the web client.
+fn push_tag(me: &str, net: &dyn NetView, nick: &str, payload: &str, ctx: &mut ServiceCtx) {
+    if let Some(uid) = net.uid_by_nick(nick) {
+        ctx.actions.push(NetAction::Raw(format!("@+tchatou.fr/gs={} :{} TAGMSG {}", board::escape_tag(payload), me, uid)));
+    }
+}
+
+// The GS# state line for one side (0 = A, 1 = B). `status_override` lets a
+// challenge show as "pending" to the challenger and "offer" to the target.
+fn push_one(g: &Game, s: usize, status_override: &str, me: &str, net: &dyn NetView, ctx: &mut ServiceCtx) {
+    let (nick, side, oppnick, myacc) = if s == 0 {
+        (&g.nick_a, &g.side_a, &g.nick_b, &g.acc_a)
+    } else {
+        (&g.nick_b, &g.side_b, &g.nick_a, &g.acc_b)
+    };
+    let status = if status_override.is_empty() { g.status.as_str() } else { status_override };
+    let res = if g.status == "over" {
+        if g.result == "draw" { "draw" } else if &g.result == myacc { "win" } else { "loss" }
+    } else {
+        "none"
+    };
+    let payload = format!(
+        "GS# {} g={} s={} t={} me={} opp={} st={} r={}",
+        g.id, g.gtype, board::encode_board(g), g.turn, side, oppnick, status, res
+    );
+    push_tag(me, net, nick, &payload, ctx);
+}
+
+fn push_state(g: &Game, me: &str, net: &dyn NetView, ctx: &mut ServiceCtx) {
+    push_one(g, 0, "", me, net, ctx);
+    push_one(g, 1, "", me, net, ctx);
+}
+
+// One GS$ stats line per game type (for the client's rank strip / profile badge).
+fn push_stats(ladder: &Ladder, account: &str, to_nick: &str, me: &str, net: &dyn NetView, ctx: &mut ServiceCtx) {
+    let pl = ladder.get(&account.to_lowercase());
+    for ty in TYPES {
+        let s = pl.and_then(|p| p.by_type.get(ty)).cloned().unwrap_or_default();
+        let payload = format!("GS$ {} {} r={} p={} w={} l={} d={}", account, ty, s.rank(), s.points, s.wins, s.losses, s.draws);
+        push_tag(me, net, to_nick, &payload, ctx);
+    }
+}
+
+impl Service for GameServ {
+    fn nick(&self) -> &str {
+        "GameServ"
+    }
+    fn uid(&self) -> &str {
+        &self.uid
+    }
+    fn gecos(&self) -> &str {
+        "Game Service"
+    }
+
+    fn help_topics(&self) -> (&'static str, &'static [HelpEntry]) {
+        (BLURB, TOPICS)
+    }
+
+    fn on_command(&mut self, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView, _store: &mut dyn Store) {
+        let me = self.uid.clone();
+        match args.first().map(|s| s.to_ascii_uppercase()).as_deref() {
+            Some("CHALLENGE") => self.do_challenge(&me, from, args, ctx, net),
+            Some("ACCEPT") => self.do_accept(&me, from, args, ctx, net),
+            Some("DECLINE") => self.do_decline(&me, from, args, ctx, net),
+            Some("MOVE") => self.do_move(&me, from, args, ctx, net),
+            Some("RESIGN") => self.do_resign(&me, from, args, ctx, net),
+            Some("GAMES") => self.do_games(&me, from, ctx),
+            Some("STATS") => self.do_stats(&me, from, args, ctx, net),
+            Some("TOP") => self.do_top(&me, from, args, ctx, net),
+            Some("HELP") | None => echo_api::help(&me, from, ctx, BLURB, TOPICS, args.get(1).copied()),
+            Some(other) => ctx.notice(&me, from.uid, format!("I don't know \x02{other}\x02. Try \x02HELP\x02.")),
+        }
+    }
+}
diff --git a/src/config.rs b/src/config.rs
index 5b9e773..5dacb5d 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -152,7 +152,7 @@ impl Default for Modules {
 fn default_services() -> Vec<String> {
     [
         "nickserv", "chanserv", "botserv", "hostserv", "memoserv", "operserv", "statserv",
-        "groupserv", "infoserv", "reportserv", "helpserv", "chanfix", "diceserv", "debugserv",
+        "groupserv", "infoserv", "reportserv", "helpserv", "chanfix", "diceserv", "gameserv", "debugserv",
     ]
     .iter()
     .map(|s| s.to_string())
diff --git a/src/main.rs b/src/main.rs
index 69edc1e..0831809 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,6 +24,7 @@ use echo_statserv::StatServ;
 use echo_hostserv::HostServ;
 use echo_operserv::OperServ;
 use echo_diceserv::DiceServ;
+use echo_gameserv::GameServ;
 use echo_infoserv::InfoServ;
 use echo_reportserv::ReportServ;
 use echo_groupserv::GroupServ;
@@ -132,6 +133,9 @@ async fn main() -> Result<()> {
             uid: format!("{}AAAAAI", cfg.server.sid),
         }));
     }
+    if enabled("gameserv") {
+        services.push(Box::new(GameServ::new(format!("{}AAAAAP", cfg.server.sid))));
+    }
     if enabled("infoserv") {
         services.push(Box::new(InfoServ {
             uid: format!("{}AAAAAJ", cfg.server.sid),