feat(engine): surface upstream move-type counters and replay seek

Two unused-for-free upstream card_game/klondike features:

- GameState now exposes the granular KlondikeStats counters
  (move_to_foundation_count, move_to_tableau_count,
  move_from_foundation_count, flip_up_count) and the win modal shows a
  quiet per-move-type recap line built from them (e.g. "21 to
  foundation - 14 tableau moves - 9 flips")
- wasm ReplayPlayer gains seek(step): clamped jump to any position,
  rewinding via a stored copy of the recorded deal instead of reparsing
  the replay JSON; replay.js Prev now uses it

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,23 @@ project follows [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+## [0.43.3] — 2026-07-10
+
+### Fixed
+
+- **Replays are now self-contained (schema v4).** A replay stores the dealt
+  board itself via the upstream `card_game` session serializers instead of
+  re-dealing from the seed at playback time, so replays survive RNG and
+  upstream upgrades that change the seed→deal mapping — the failure that had
+  silently broken every stored replay. The web player and web game now
+  exchange the full payload through the wasm layer (the old JS path hardcoded
+  `schema_version: 2`, uploaded empty move lists, and corrupted u64 seeds via
+  `Math.round`), and the replay viewer reports unplayable old-format replays
+  in the caption instead of dying silently. Pre-v4 replays are rejected by a
+  version gate; local histories repopulate with new wins. (#170)
+- **Difficulty-mode wins can upload.** The server's replay `mode` validation
+  now accepts data-carrying `GameMode` variants (previously a 400). (#170)
+
 ## [0.42.0] — 2026-07-06
 
 ### Added

Cargo.lock

@@ -7333,6 +7333,7 @@ dependencies = [
  "proptest",
  "rand 0.10.1",
  "serde",
+ "serde_json",
  "thiserror 2.0.18",
 ]
 

solitaire_core/Cargo.toml

@@ -9,7 +9,8 @@ default = []
 test-support = []
 
 [dev-dependencies]
-proptest = "1"
+proptest   = "1"
+serde_json = { workspace = true }
 
 [dependencies]
 serde     = { workspace = true }

solitaire_core/src/game_state.rs

@@ -277,6 +277,90 @@ impl<'de> Deserialize<'de> for GameState {
     }
 }
 
+/// Self-contained recording of one deal plus every instruction applied to it.
+///
+/// Serialises via the upstream `card_game` [`Session`] serde, whose wire
+/// format is `{config, initial_state, instructions}` — the dealt board is
+/// stored **explicitly**, so playback never depends on the seed→deal mapping
+/// staying stable across RNG or upstream-crate upgrades. This is the payload
+/// replays must persist; a bare seed is only sufficient for the exact build
+/// that recorded it.
+#[derive(Debug, Clone)]
+pub struct SessionRecording(Session<Klondike>);
+
+impl SessionRecording {
+    /// Builds a recording by dealing a fresh board from `seed` and
+    /// force-applying `instructions` **without validation**.
+    ///
+    /// Fixture/test aid only — production recordings come from
+    /// [`GameState::recording`], whose history is valid by construction.
+    /// Invalid instructions are absorbed by the upstream session's
+    /// `Option`-based pile pops rather than rejected, so a recording built
+    /// here may not replay cleanly through
+    /// [`GameState::apply_instruction`]'s validation.
+    pub fn from_instructions_unchecked(
+        seed: u64,
+        draw_mode: DrawStockConfig,
+        instructions: impl IntoIterator<Item = KlondikeInstruction>,
+    ) -> Self {
+        let mut session = GameState::new_session(seed, draw_mode);
+        for instruction in instructions {
+            session.process_instruction(instruction);
+        }
+        Self(session)
+    }
+
+    /// The dealt board the recording starts from (before any instruction).
+    fn initial_state(&self) -> &Klondike {
+        self.0
+            .history()
+            .first()
+            .map(|snapshot| snapshot.state())
+            .unwrap_or_else(|| self.0.state().state())
+    }
+
+    /// Ordered instruction list, replayable via
+    /// [`GameState::apply_instruction`] against the game returned by
+    /// [`GameState::from_recording`].
+    pub fn instructions(&self) -> Vec<KlondikeInstruction> {
+        self.0
+            .history()
+            .iter()
+            .map(|snapshot| *snapshot.instruction())
+            .collect()
+    }
+
+    /// Number of recorded instructions.
+    pub fn len(&self) -> usize {
+        self.0.history().len()
+    }
+
+    /// `true` when no instructions have been recorded.
+    pub fn is_empty(&self) -> bool {
+        self.0.history().is_empty()
+    }
+}
+
+impl PartialEq for SessionRecording {
+    fn eq(&self, other: &Self) -> bool {
+        self.initial_state() == other.initial_state() && self.instructions() == other.instructions()
+    }
+}
+
+impl Eq for SessionRecording {}
+
+impl Serialize for SessionRecording {
+    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        self.0.serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for SessionRecording {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        Session::deserialize(deserializer).map(Self)
+    }
+}
+
 impl GameState {
     /// Creates a new Classic-mode game dealt from the given seed and draw mode.
     pub fn new(seed: u64, draw_mode: DrawStockConfig) -> Self {
@@ -296,6 +380,44 @@ impl GameState {
         }
     }
 
+    /// Snapshot of the live session for replay persistence: the dealt board
+    /// plus the forward instruction history (undone moves are absent — the
+    /// session pops them). Serialise the returned [`SessionRecording`] with
+    /// the upstream `card_game` serializers; rebuild playback with
+    /// [`Self::from_recording`].
+    pub fn recording(&self) -> SessionRecording {
+        SessionRecording(self.session.clone())
+    }
+
+    /// Rebuilds the initial-deal game plus the ordered instruction list from
+    /// a [`SessionRecording`].
+    ///
+    /// The board and the session config (including draw mode) come from the
+    /// recording itself, so playback is independent of the current build's
+    /// seed→deal mapping. `seed` and `mode` are presentation metadata carried
+    /// alongside the recording by the replay file. Step through the returned
+    /// instructions with [`Self::apply_instruction`], which re-validates each
+    /// one and fails gracefully on corrupt input.
+    pub fn from_recording(
+        recording: &SessionRecording,
+        seed: u64,
+        mode: GameMode,
+    ) -> (Self, Vec<KlondikeInstruction>) {
+        let game = Self {
+            mode,
+            elapsed_seconds: 0,
+            seed,
+            take_from_foundation: true,
+            session: Session::new(
+                recording.initial_state().clone(),
+                recording.0.config().clone(),
+            ),
+            #[cfg(feature = "test-support")]
+            test_pile_state: None,
+        };
+        (game, recording.instructions())
+    }
+
     /// Whether the player draws one or three cards from the stock per turn.
     /// Derived from the underlying session config (set once at deal time).
     pub fn draw_mode(&self) -> DrawStockConfig {
@@ -339,6 +461,32 @@ impl GameState {
         self.session.stats().stats().recycle_count()
     }
 
+    /// Number of cards moved onto foundations this game, read from the
+    /// upstream session stats. Cumulative like [`Self::recycle_count`] —
+    /// not rolled back on undo.
+    pub fn move_to_foundation_count(&self) -> u32 {
+        self.session.stats().stats().move_to_foundation_count()
+    }
+
+    /// Number of stacks moved onto tableaus (from stock or another tableau)
+    /// this game, read from the upstream session stats. Cumulative — not
+    /// rolled back on undo.
+    pub fn move_to_tableau_count(&self) -> u32 {
+        self.session.stats().stats().move_to_tableau_count()
+    }
+
+    /// Number of cards taken back off a foundation this game, read from the
+    /// upstream session stats. Cumulative — not rolled back on undo.
+    pub fn move_from_foundation_count(&self) -> u32 {
+        self.session.stats().stats().move_from_foundation_count()
+    }
+
+    /// Number of face-down cards revealed (flipped up) this game, read from
+    /// the upstream session stats. Cumulative — not rolled back on undo.
+    pub fn flip_up_count(&self) -> u32 {
+        self.session.stats().stats().flip_up_bonus_count()
+    }
+
     /// Total moves made this game (draws, recycles, and card moves), derived
     /// from the session's instruction history length.
     pub fn move_count(&self) -> u32 {
@@ -1512,4 +1660,77 @@ mod tests {
         assert!(easy.is_err());
         assert!(matches!(medium, Ok(Some(_))));
     }
+
+    /// Play a few real moves on a fresh deal and return the game.
+    fn game_with_some_moves(seed: u64) -> GameState {
+        let mut game = GameState::new(seed, DrawStockConfig::DrawOne);
+        for _ in 0..40 {
+            let instructions = game.possible_instructions();
+            let applied = instructions
+                .into_iter()
+                .find(|i| game.clone().apply_instruction(*i).is_ok())
+                .and_then(|i| game.apply_instruction(i).ok());
+            if applied.is_none() && game.draw().is_err() {
+                break;
+            }
+        }
+        assert!(
+            !game.instruction_history().is_empty(),
+            "test needs at least one recorded move"
+        );
+        game
+    }
+
+    #[test]
+    fn recording_round_trips_through_upstream_serde() {
+        let game = game_with_some_moves(51);
+        let recording = game.recording();
+        let json = serde_json::to_string(&recording).expect("serialize recording");
+        let restored: SessionRecording = serde_json::from_str(&json).expect("parse recording");
+        assert_eq!(recording, restored);
+        assert_eq!(recording.instructions(), game.instruction_history());
+    }
+
+    #[test]
+    fn from_recording_replays_to_identical_board_without_seed_dealing() {
+        let game = game_with_some_moves(145);
+        let recording = game.recording();
+        let json = serde_json::to_string(&recording).expect("serialize recording");
+        let restored: SessionRecording = serde_json::from_str(&json).expect("parse recording");
+
+        // Deliberately pass a DIFFERENT seed: the board must come from the
+        // recording, proving playback no longer depends on seed→deal mapping.
+        let (mut replayed, instructions) =
+            GameState::from_recording(&restored, 0xDEAD_BEEF, game.mode);
+        assert_eq!(replayed.draw_mode(), game.draw_mode());
+        for instruction in instructions {
+            replayed
+                .apply_instruction(instruction)
+                .expect("recorded instruction must replay cleanly");
+        }
+        for pile in [KlondikePile::Stock]
+            .into_iter()
+            .chain(crate::TABLEAUS.map(KlondikePile::Tableau))
+            .chain(crate::FOUNDATIONS.map(KlondikePile::Foundation))
+        {
+            assert_eq!(
+                replayed.pile(pile),
+                game.pile(pile),
+                "pile {pile:?} differs"
+            );
+        }
+        assert_eq!(replayed.waste_cards(), game.waste_cards());
+        assert_eq!(replayed.move_count(), game.move_count());
+    }
+
+    #[test]
+    fn from_recording_of_fresh_deal_returns_empty_instructions() {
+        let game = GameState::new(7, DrawStockConfig::DrawThree);
+        let recording = game.recording();
+        assert!(recording.is_empty());
+        let (replayed, instructions) = GameState::from_recording(&recording, 7, game.mode);
+        assert!(instructions.is_empty());
+        assert_eq!(replayed.stock_cards(), game.stock_cards());
+        assert_eq!(replayed.draw_mode(), DrawStockConfig::DrawThree);
+    }
 }

solitaire_core/src/lib.rs

@@ -20,7 +20,9 @@ pub use klondike::{
 
 // Solvability check API (delegates to `card_game::Session::solve`); replaces the
 // former `solitaire_data::solver` wrapper module.
-pub use game_state::{DEFAULT_SOLVE_MOVES_BUDGET, DEFAULT_SOLVE_STATES_BUDGET, SolveOutcome};
+pub use game_state::{
+    DEFAULT_SOLVE_MOVES_BUDGET, DEFAULT_SOLVE_STATES_BUDGET, SessionRecording, SolveOutcome,
+};
 
 // Spider rules (second `card_game::Game` implementation; engine UI is a
 // later phase — nothing outside solitaire_core consumes these yet).

solitaire_data/src/replay.rs

@@ -12,22 +12,24 @@
 //! carries any other version so older replays are silently dropped instead
 //! of crashing the loader.
 //!
-//! The recording is intentionally minimal — only the
-//! [`KlondikeInstruction`](solitaire_core::KlondikeInstruction) inputs that
-//! successfully advanced the game. `Undo` is **not** recorded: a replay
-//! represents the canonical path the player ultimately took to win, so
-//! backed-out missteps simply do not appear in the move list. The starting
-//! deal is not stored either — the [`seed`](Replay::seed) +
-//! [`draw_mode`](Replay::draw_mode) + [`mode`](Replay::mode) are sufficient
-//! for `GameState::new_with_mode` to rebuild the identical layout.
+//! The payload is a [`SessionRecording`](solitaire_core::SessionRecording):
+//! the upstream `card_game` session serialisation, which stores the dealt
+//! board **explicitly** plus the ordered instruction list. `Undo` is not
+//! recorded: a replay represents the canonical path the player ultimately
+//! took to win, so backed-out missteps simply do not appear (the session
+//! pops them from its history).
+//!
+//! Storing the deal (rather than re-dealing from [`seed`](Replay::seed) at
+//! playback time, as schemas ≤ v3 did) makes replays immune to seed→deal
+//! mapping drift across RNG or upstream-crate upgrades — the exact failure
+//! that silently broke every pre-upgrade replay. `seed`, `draw_mode`, and
+//! `mode` remain as presentation/indexing metadata only.
 //!
 //! Each recorded move is the player's atomic *input*, not its outcome.
 //! `KlondikeInstruction::RotateStock` covers every click on the stock pile;
 //! the engine resolves draw-vs-recycle deterministically from the current
 //! stock state during playback, so the same input always produces the same
-//! effect on the same starting deal. Runtime-only pile-position types are
-//! never serialised — the instruction itself serialises via its compact
-//! upstream serde representation.
+//! effect on the same starting deal.
 
 use std::fs;
 use std::io;
@@ -35,7 +37,7 @@ use std::path::{Path, PathBuf};
 
 use chrono::NaiveDate;
 use serde::{Deserialize, Serialize};
-use solitaire_core::{DrawStockConfig, KlondikeInstruction, game_state::GameMode};
+use solitaire_core::{DrawStockConfig, SessionRecording, game_state::GameMode};
 
 const LATEST_REPLAY_FILE_NAME: &str = "latest_replay.json";
 const REPLAY_HISTORY_FILE_NAME: &str = "replays.json";
@@ -77,13 +79,19 @@ fn history_schema_v0() -> u32 {
 ///   variants which carried the *outcome* of a stock interaction rather
 ///   than the player's atomic input.
 /// - v2: `Draw` + `Recycle` collapsed into a single `StockClick` variant.
-/// - v3 (current): the bespoke `ReplayMove` serde mirror was dropped. Moves
-///   are now stored directly as upstream
-///   [`KlondikeInstruction`](solitaire_core::KlondikeInstruction) (compact
-///   int serde); `StockClick` is now `RotateStock`. Pile-position types are
-///   runtime-only and are never serialised. v1/v2 files fail to deserialise
-///   and are discarded by the loader.
-pub const REPLAY_SCHEMA_VERSION: u32 = 3;
+/// - v3: the bespoke `ReplayMove` serde mirror was dropped. Moves
+///   were stored directly as upstream `KlondikeInstruction` (compact
+///   int serde); `StockClick` became `RotateStock`. Pile-position types are
+///   runtime-only and are never serialised. The starting deal was still
+///   rebuilt from the seed at playback time.
+/// - v4 (current): the bare `moves` list was replaced by a
+///   [`SessionRecording`](solitaire_core::SessionRecording) — the upstream
+///   `card_game` session serialisation carrying the dealt board explicitly
+///   plus the instruction list. Playback no longer re-deals from the seed,
+///   so replays survive RNG/upstream upgrades that change the seed→deal
+///   mapping (which invalidated every v3 replay). v1–v3 files fail the
+///   version gate and are discarded by the loader.
+pub const REPLAY_SCHEMA_VERSION: u32 = 4;
 
 /// Default value for [`Replay::schema_version`] when deserialising files
 /// that pre-date the field. Any value other than [`REPLAY_SCHEMA_VERSION`]
@@ -94,9 +102,10 @@ fn schema_v0() -> u32 {
 
 /// A complete recording of a single winning game.
 ///
-/// Replays are reconstructed by rebuilding a fresh
-/// `GameState::new_with_mode(seed, draw_mode, mode)` and applying the
-/// [`moves`](Self::moves) in order. The presentation fields
+/// Replays are reconstructed via
+/// `GameState::from_recording(&replay.recording, replay.seed, replay.mode)`,
+/// which rebuilds the recorded deal directly and returns the instruction
+/// list to step through. The presentation fields
 /// ([`time_seconds`](Self::time_seconds), [`final_score`](Self::final_score),
 /// [`recorded_at`](Self::recorded_at)) drive the Stats UI caption such as
 /// "Replay (2:14 win on 2026-05-02)".
@@ -105,8 +114,9 @@ pub struct Replay {
     /// Schema version. See [`REPLAY_SCHEMA_VERSION`].
     #[serde(default = "schema_v0")]
     pub schema_version: u32,
-    /// Seed used for the deal — replay rasterises the deck via
-    /// `GameState::new_with_mode(seed, draw_mode, mode)`.
+    /// Seed the recorded game was originally dealt from. Presentation /
+    /// indexing metadata only — playback rebuilds the board from
+    /// [`recording`](Self::recording), never by re-dealing this seed.
     pub seed: u64,
     /// Draw mode the recorded game was played in.
     pub draw_mode: DrawStockConfig,
@@ -119,11 +129,10 @@ pub struct Replay {
     pub final_score: i32,
     /// ISO-8601 date the win was recorded.
     pub recorded_at: NaiveDate,
-    /// Ordered move list. Each entry is the atomic
-    /// [`KlondikeInstruction`](solitaire_core::KlondikeInstruction) the player
-    /// issued, replayable against a fresh `GameState` constructed from the
-    /// seed via `GameState::apply_instruction`.
-    pub moves: Vec<KlondikeInstruction>,
+    /// The dealt board plus the ordered instruction list, serialised via the
+    /// upstream `card_game` session serializers. Self-contained: playback
+    /// needs nothing else to reproduce the game move-for-move.
+    pub recording: SessionRecording,
     /// Public share URL for this replay on the active sync backend, set
     /// by `sync_plugin::poll_replay_upload_result` when the upload
     /// task resolves. `None` when the player won on a local-only
@@ -133,11 +142,12 @@ pub struct Replay {
     /// [`REPLAY_SCHEMA_VERSION`].
     #[serde(default)]
     pub share_url: Option<String>,
-    /// Index into [`moves`](Self::moves) of the move that triggered
-    /// the win condition (i.e. completed the last foundation pile).
+    /// Index into the [`recording`](Self::recording)'s instruction list
+    /// of the move that triggered the win condition (i.e. completed the
+    /// last foundation pile).
     ///
     /// For replays recorded by the live engine this is always
-    /// `Some(moves.len() - 1)` because recording freezes on win — but
+    /// `Some(recording.len() - 1)` because recording freezes on win — but
     /// the field is stored explicitly so the playback UI can read it
     /// directly without re-deriving "the last move was the win" each
     /// time, and to leave room for future recording semantics that
@@ -172,7 +182,7 @@ impl Replay {
         time_seconds: u64,
         final_score: i32,
         recorded_at: NaiveDate,
-        moves: Vec<KlondikeInstruction>,
+        recording: SessionRecording,
     ) -> Self {
         Self {
             schema_version: REPLAY_SCHEMA_VERSION,
@@ -182,7 +192,7 @@ impl Replay {
             time_seconds,
             final_score,
             recorded_at,
-            moves,
+            recording,
             share_url: None,
             win_move_index: None,
         }
@@ -193,7 +203,7 @@ impl Replay {
     /// [`Replay::new`]:
     ///
     /// ```ignore
-    /// let replay = Replay::new(...).with_win_move_index(Some(recording.moves.len() - 1));
+    /// let replay = Replay::new(...).with_win_move_index(recording.len().checked_sub(1));
     /// ```
     ///
     /// `None` is a valid input — useful for tests that don't care about
@@ -430,7 +440,8 @@ pub fn migrate_legacy_latest_replay(latest_path: &Path, history_path: &Path) {
 mod tests {
     use super::*;
     use klondike::{
-        DstFoundation, DstTableau, Foundation, KlondikePile, KlondikePileStack, Tableau,
+        DstFoundation, DstTableau, Foundation, KlondikeInstruction, KlondikePile,
+        KlondikePileStack, Tableau,
     };
     use std::env;
 
@@ -447,18 +458,22 @@ mod tests {
             134,
             5_120,
             date,
-            vec![
-                KlondikeInstruction::RotateStock,
-                KlondikeInstruction::DstTableau(DstTableau {
-                    src: KlondikePileStack::Stock,
-                    tableau: Tableau::Tableau4,
-                }),
-                KlondikeInstruction::RotateStock,
-                KlondikeInstruction::DstFoundation(DstFoundation {
-                    src: KlondikePile::Tableau(Tableau::Tableau4),
-                    foundation: Foundation::Foundation1,
-                }),
-            ],
+            SessionRecording::from_instructions_unchecked(
+                12345,
+                DrawStockConfig::DrawThree,
+                [
+                    KlondikeInstruction::RotateStock,
+                    KlondikeInstruction::DstTableau(DstTableau {
+                        src: KlondikePileStack::Stock,
+                        tableau: Tableau::Tableau4,
+                    }),
+                    KlondikeInstruction::RotateStock,
+                    KlondikeInstruction::DstFoundation(DstFoundation {
+                        src: KlondikePile::Tableau(Tableau::Tableau4),
+                        foundation: Foundation::Foundation1,
+                    }),
+                ],
+            ),
         )
     }
 
@@ -518,25 +533,22 @@ mod tests {
     /// rolling history wiped on the v0.19.0 update.
     #[test]
     fn replay_loads_when_share_url_field_is_absent() {
-        let pre_v019_json = format!(
-            r#"{{
-                "schema_version": {schema},
-                "seed": 1,
-                "draw_mode": "DrawOne",
-                "mode": "Classic",
-                "time_seconds": 60,
-                "final_score": 100,
-                "recorded_at": "2025-01-01",
-                "moves": []
-            }}"#,
-            schema = REPLAY_SCHEMA_VERSION,
-        );
-        let parsed: Replay = serde_json::from_str(&pre_v019_json)
-            .expect("pre-v0.19.0 replay JSON must still deserialise");
+        // Build a current-schema JSON object, then strip the optional
+        // fields to simulate a file written before they existed.
+        let mut value = serde_json::to_value(sample_replay()).expect("serialise sample");
+        let obj = value.as_object_mut().expect("replay serialises as object");
+        obj.remove("share_url");
+        obj.remove("win_move_index");
+        let parsed: Replay = serde_json::from_value(value)
+            .expect("replay JSON without optional fields must still deserialise");
         assert!(
             parsed.share_url.is_none(),
             "missing share_url field must default to None",
         );
+        assert!(
+            parsed.win_move_index.is_none(),
+            "missing win_move_index field must default to None",
+        );
     }
 
     /// Atomic-write contract — `.tmp` must not be left behind after
@@ -588,7 +600,11 @@ mod tests {
             60,
             id,
             date,
-            vec![KlondikeInstruction::RotateStock],
+            SessionRecording::from_instructions_unchecked(
+                id as u64,
+                DrawStockConfig::DrawOne,
+                [KlondikeInstruction::RotateStock],
+            ),
         )
     }
 
@@ -824,22 +840,14 @@ mod tests {
         let path = tmp_path("legacy_no_win_move_index");
         let _ = fs::remove_file(&path);
 
-        // Hand-rolled minimal current-schema replay JSON with no
-        // win_move_index field — the additive field must still default to None.
-        let no_field = format!(
-            r#"{{
-            "schema_version": {schema},
-            "seed": 1,
-            "draw_mode": "DrawOne",
-            "mode": "Classic",
-            "time_seconds": 60,
-            "final_score": 100,
-            "recorded_at": "2026-05-02",
-            "moves": []
-        }}"#,
-            schema = REPLAY_SCHEMA_VERSION,
-        );
-        fs::write(&path, no_field).expect("write fixture");
+        // Current-schema replay JSON with the win_move_index field stripped —
+        // the additive field must still default to None.
+        let mut value = serde_json::to_value(sample_replay()).expect("serialise sample");
+        value
+            .as_object_mut()
+            .expect("replay serialises as object")
+            .remove("win_move_index");
+        fs::write(&path, serde_json::to_string(&value).expect("to_string")).expect("write fixture");
 
         let loaded = load_latest_replay_from(&path).expect("load");
         assert_eq!(loaded.win_move_index, None);

solitaire_engine/src/achievement_plugin.rs

@@ -1343,7 +1343,9 @@ mod tests {
 
     use crate::replay_playback::ReplayPlaybackState;
     use chrono::NaiveDate;
-    use solitaire_core::{DrawStockConfig, KlondikeInstruction, game_state::GameMode};
+    use solitaire_core::{
+        DrawStockConfig, KlondikeInstruction, SessionRecording, game_state::GameMode,
+    };
     use solitaire_data::Replay;
 
     /// Headless app variant that injects a default `ReplayPlaybackState`
@@ -1364,7 +1366,11 @@ mod tests {
             10,
             100,
             NaiveDate::from_ymd_opt(2026, 5, 5).expect("valid date"),
-            vec![KlondikeInstruction::RotateStock],
+            SessionRecording::from_instructions_unchecked(
+                1,
+                DrawStockConfig::DrawOne,
+                [KlondikeInstruction::RotateStock],
+            ),
         )
     }
 
@@ -1408,12 +1414,8 @@ mod tests {
 
         // Frame 1: enter Playing. The observer's first sample sees
         // `last_was_playing = false` and `now_playing = true`.
-        *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Playing {
-            replay: dummy_replay(),
-            cursor: 0,
-            secs_to_next: 0.0,
-            paused: false,
-        };
+        *app.world_mut().resource_mut::<ReplayPlaybackState>() =
+            ReplayPlaybackState::playing(dummy_replay(), 0, 0.0, false);
         app.update();
         assert!(
             !cinephile_unlocked(&app),
@@ -1442,12 +1444,8 @@ mod tests {
     fn cinephile_does_not_unlock_on_stop_button_abort() {
         let mut app = cinephile_app();
 
-        *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Playing {
-            replay: dummy_replay(),
-            cursor: 0,
-            secs_to_next: 0.0,
-            paused: false,
-        };
+        *app.world_mut().resource_mut::<ReplayPlaybackState>() =
+            ReplayPlaybackState::playing(dummy_replay(), 0, 0.0, false);
         app.update();
 
         // Direct Playing → Inactive — the path the Stop button takes via
@@ -1473,12 +1471,8 @@ mod tests {
         let mut app = cinephile_app();
 
         // First completion cycle to unlock.
-        *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Playing {
-            replay: dummy_replay(),
-            cursor: 0,
-            secs_to_next: 0.0,
-            paused: false,
-        };
+        *app.world_mut().resource_mut::<ReplayPlaybackState>() =
+            ReplayPlaybackState::playing(dummy_replay(), 0, 0.0, false);
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Completed;
         app.update();
@@ -1496,12 +1490,8 @@ mod tests {
         // Second cycle: Inactive → Playing → Completed once more.
         *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Inactive;
         app.update();
-        *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Playing {
-            replay: dummy_replay(),
-            cursor: 0,
-            secs_to_next: 0.0,
-            paused: false,
-        };
+        *app.world_mut().resource_mut::<ReplayPlaybackState>() =
+            ReplayPlaybackState::playing(dummy_replay(), 0, 0.0, false);
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Completed;
         app.update();
@@ -1520,12 +1510,8 @@ mod tests {
     fn cinephile_fires_once_across_completed_linger() {
         let mut app = cinephile_app();
 
-        *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Playing {
-            replay: dummy_replay(),
-            cursor: 0,
-            secs_to_next: 0.0,
-            paused: false,
-        };
+        *app.world_mut().resource_mut::<ReplayPlaybackState>() =
+            ReplayPlaybackState::playing(dummy_replay(), 0, 0.0, false);
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() = ReplayPlaybackState::Completed;
         app.update();

solitaire_engine/src/game_plugin/mod.rs

@@ -1062,11 +1062,16 @@ pub fn record_replay_on_win(
         if recording.moves.is_empty() {
             continue;
         }
+        // The session itself is the authoritative recording: its history
+        // holds the dealt board plus the forward instruction list (undos
+        // already popped), and it serialises via the upstream card_game
+        // serializers so playback never re-deals from the seed.
+        let session_recording = game.0.recording();
         // Recording freezes on win, so the move that triggered the
         // win condition is the last one in the list. Storing the
         // index explicitly lets the playback UI read the WIN MOVE
         // position directly instead of re-deriving it on every render.
-        let win_move_index = recording.moves.len().checked_sub(1);
+        let win_move_index = session_recording.len().checked_sub(1);
         let replay = Replay::new(
             game.0.seed,
             game.0.draw_mode(),
@@ -1074,7 +1079,7 @@ pub fn record_replay_on_win(
             ev.time_seconds,
             ev.score,
             Utc::now().date_naive(),
-            recording.moves.clone(),
+            session_recording,
         )
         .with_win_move_index(win_move_index);
         let Some(p) = path.as_ref().and_then(|r| r.0.as_deref()) else {

solitaire_engine/src/game_plugin/tests.rs

@@ -853,17 +853,15 @@ fn replay_recording_freezes_into_replay_on_game_won() {
     let mut app = test_app(7654);
     app.insert_resource(ReplayPath(Some(path.clone())));
 
-    // Push two recorded instructions manually so we can verify they
-    // survive the freeze/save round-trip without having to drive a
-    // real win. Both are `RotateStock` — the only instruction
-    // constructible without the runtime-only `klondike` pile-stack
-    // types (which the engine intentionally does not depend on); the
-    // round-trip shape is identical for any instruction variant.
-    {
-        let mut recording = app.world_mut().resource_mut::<RecordingReplay>();
-        recording.moves.push(KlondikeInstruction::RotateStock);
-        recording.moves.push(KlondikeInstruction::RotateStock);
-    }
+    // Drive two real draws so the *session* history (the source the
+    // freeze now serialises from, via `GameState::recording()`) holds
+    // two instructions. `RotateStock` is the only instruction the
+    // engine can drive without the runtime-only `klondike` pile-stack
+    // types; the round-trip shape is identical for any variant.
+    app.world_mut().write_message(DrawRequestEvent);
+    app.update();
+    app.world_mut().write_message(DrawRequestEvent);
+    app.update();
 
     // Fire the win event the engine emits when the last foundation
     // completes — `record_replay_on_win` listens for it.
@@ -895,9 +893,15 @@ fn replay_recording_freezes_into_replay_on_game_won() {
         loaded.time_seconds, 250,
         "time_seconds must come from the win event"
     );
-    assert_eq!(loaded.moves.len(), 2, "every recorded move must round-trip");
-    assert!(matches!(loaded.moves[0], KlondikeInstruction::RotateStock));
-    assert!(matches!(loaded.moves[1], KlondikeInstruction::RotateStock));
+    let instructions = loaded.recording.instructions();
+    assert_eq!(instructions.len(), 2, "every recorded move must round-trip");
+    assert!(matches!(instructions[0], KlondikeInstruction::RotateStock));
+    assert!(matches!(instructions[1], KlondikeInstruction::RotateStock));
+    assert_eq!(
+        loaded.win_move_index,
+        Some(1),
+        "win move index must point at the last recorded instruction",
+    );
 
     #[cfg(not(target_arch = "wasm32"))]
     let _ = std::fs::remove_file(&path);

solitaire_engine/src/replay_overlay/format.rs

@@ -122,12 +122,8 @@ pub(crate) fn format_move_body(instruction: &KlondikeInstruction) -> String {
 /// `▌ MOVE LOG · COMPLETE` in `Completed`.
 pub(crate) fn format_move_log_header(state: &ReplayPlaybackState) -> String {
     match state {
-        ReplayPlaybackState::Playing { replay, cursor, .. } => {
-            format!(
-                "\u{258C} MOVE LOG \u{00B7} {}/{}",
-                cursor,
-                replay.moves.len()
-            )
+        ReplayPlaybackState::Playing { moves, cursor, .. } => {
+            format!("\u{258C} MOVE LOG \u{00B7} {}/{}", cursor, moves.len())
         }
         ReplayPlaybackState::Completed => "\u{258C} MOVE LOG \u{00B7} COMPLETE".to_string(),
         ReplayPlaybackState::Inactive => String::new(),
@@ -135,7 +131,7 @@ pub(crate) fn format_move_log_header(state: &ReplayPlaybackState) -> String {
 }
 
 /// Pure helper — formats the kth-most-recently-applied move's row
-/// text. `k = 1` is the active row (`replay.moves[cursor - 1]`,
+/// text. `k = 1` is the active row (`moves[cursor - 1]`,
 /// displayed as `"{cursor} │ {body}"`). `k = 2` is the row above
 /// that (`moves[cursor - 2]` displayed as `"{cursor - 1} │ {body}"`),
 /// and so on.
@@ -147,14 +143,14 @@ pub(crate) fn format_move_log_header(state: &ReplayPlaybackState) -> String {
 ///   for k=1 and k=2 only, k=3 returns empty).
 /// - The move list is shorter than expected (defensive guard).
 pub(crate) fn format_kth_recent_row(state: &ReplayPlaybackState, k: usize) -> String {
-    let ReplayPlaybackState::Playing { replay, cursor, .. } = state else {
+    let ReplayPlaybackState::Playing { moves, cursor, .. } = state else {
         return String::new();
     };
     if k == 0 || k > *cursor {
         return String::new();
     }
     let zero_idx = *cursor - k;
-    let Some(m) = replay.moves.get(zero_idx) else {
+    let Some(m) = moves.get(zero_idx) else {
         return String::new();
     };
     let display_idx = *cursor - k + 1;
@@ -162,7 +158,7 @@ pub(crate) fn format_kth_recent_row(state: &ReplayPlaybackState, k: usize) -> St
 }
 
 /// Pure helper — formats the kth-NEXT move's row text. `k = 1`
-/// is the move that will apply next (`replay.moves[cursor]`,
+/// is the move that will apply next (`moves[cursor]`,
 /// displayed as `cursor + 1`); `k = 2` is the move after that,
 /// and so on.
 ///
@@ -174,14 +170,14 @@ pub(crate) fn format_kth_recent_row(state: &ReplayPlaybackState, k: usize) -> St
 ///   replay — late in the move list, the trailing next rows
 ///   stay empty).
 pub(crate) fn format_kth_next_row(state: &ReplayPlaybackState, k: usize) -> String {
-    let ReplayPlaybackState::Playing { replay, cursor, .. } = state else {
+    let ReplayPlaybackState::Playing { moves, cursor, .. } = state else {
         return String::new();
     };
     if k == 0 {
         return String::new();
     }
     let zero_idx = *cursor + k - 1;
-    let Some(m) = replay.moves.get(zero_idx) else {
+    let Some(m) = moves.get(zero_idx) else {
         return String::new();
     };
     let display_idx = *cursor + k;

solitaire_engine/src/replay_overlay/mod.rs

@@ -383,7 +383,7 @@ pub struct ReplayOverlayMoveLogPrevRow {
 /// Marker on a "next move" row below the active row. `offset`
 /// is the 1-based distance forward from the active row:
 /// `offset = 1` is the move that will apply next
-/// (`replay.moves[cursor]`, displayed as `cursor + 1`),
+/// (`moves[cursor]`, displayed as `cursor + 1`),
 /// `offset = 2` is the one after that, and so on. Up to
 /// [`MOVE_LOG_NEXT_ROWS`] rows render below the active row.
 ///
@@ -1258,11 +1258,11 @@ fn keybind_footer_hint_text() -> &'static str {
 /// `win_move_index >= total` (defensive — shouldn't happen) doesn't
 /// position the marker outside the track.
 fn win_move_marker_pct(state: &ReplayPlaybackState) -> Option<f32> {
-    let ReplayPlaybackState::Playing { replay, .. } = state else {
+    let ReplayPlaybackState::Playing { replay, moves, .. } = state else {
         return None;
     };
     let idx = replay.win_move_index?;
-    let total = replay.moves.len();
+    let total = moves.len();
     if total == 0 {
         return None;
     }

solitaire_engine/src/replay_overlay/tests.rs

@@ -1,7 +1,7 @@
 use super::*;
 use chrono::NaiveDate;
 use solitaire_core::{DrawStockConfig, game_state::GameMode};
-use solitaire_core::{Foundation, KlondikeInstruction, KlondikePile, Tableau};
+use solitaire_core::{Foundation, KlondikeInstruction, KlondikePile, SessionRecording, Tableau};
 use solitaire_core::{Rank, Suit};
 use solitaire_data::Replay;
 
@@ -17,9 +17,11 @@ fn synthetic_replay(move_count: usize) -> Replay {
         120,
         1_000,
         NaiveDate::from_ymd_opt(2026, 5, 2).expect("valid date"),
-        (0..move_count)
-            .map(|_| KlondikeInstruction::RotateStock)
-            .collect(),
+        SessionRecording::from_instructions_unchecked(
+            42,
+            DrawStockConfig::DrawOne,
+            (0..move_count).map(|_| KlondikeInstruction::RotateStock),
+        ),
     )
 }
 
@@ -93,12 +95,7 @@ fn overlay_spawns_when_playback_starts() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -117,12 +114,7 @@ fn overlay_progress_text_reflects_cursor() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 5, 0.5, false),
     );
     app.update();
 
@@ -138,12 +130,7 @@ fn overlay_stop_button_click_clears_playback() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(overlay_root_count(&mut app), 1);
@@ -195,12 +182,7 @@ fn floating_chip_spawns_and_despawns_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(5),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(5), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -232,12 +214,7 @@ fn overlay_despawns_when_playback_returns_to_inactive() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(3),
-            cursor: 1,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(3), 1, 0.5, false),
     );
     app.update();
     assert_eq!(overlay_root_count(&mut app), 1);
@@ -260,12 +237,7 @@ fn overlay_text_changes_on_completed() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(7),
-            cursor: 7,
-            secs_to_next: 0.0,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(7), 7, 0.0, false),
     );
     app.update();
     assert_eq!(banner_text(&mut app), "\u{258C} replay");
@@ -314,30 +286,30 @@ fn scrub_pct_covers_state_corners() {
     assert_eq!(scrub_pct(&ReplayPlaybackState::Inactive), 0.0);
     assert_eq!(scrub_pct(&ReplayPlaybackState::Completed), 100.0);
     assert_eq!(
-        scrub_pct(&ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        }),
+        scrub_pct(&ReplayPlaybackState::playing(
+            synthetic_replay(10),
+            0,
+            0.5,
+            false,
+        )),
         0.0,
     );
     assert_eq!(
-        scrub_pct(&ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        }),
+        scrub_pct(&ReplayPlaybackState::playing(
+            synthetic_replay(10),
+            5,
+            0.5,
+            false,
+        )),
         50.0,
     );
     assert_eq!(
-        scrub_pct(&ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 10,
-            secs_to_next: 0.5,
-            paused: false,
-        }),
+        scrub_pct(&ReplayPlaybackState::playing(
+            synthetic_replay(10),
+            10,
+            0.5,
+            false,
+        )),
         100.0,
     );
 }
@@ -367,12 +339,12 @@ fn format_game_caption_covers_state_corners() {
     // Mar = 31, Apr = 30, May 2 = 122). Synthetic_replay always
     // uses this date so the assertion is stable.
     assert_eq!(
-        format_game_caption(&ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        }),
+        format_game_caption(&ReplayPlaybackState::playing(
+            synthetic_replay(10),
+            5,
+            0.5,
+            false,
+        )),
         Some("GAME #2026-122".to_string()),
     );
 
@@ -381,12 +353,7 @@ fn format_game_caption_covers_state_corners() {
     let mut early_january = synthetic_replay(10);
     early_january.recorded_at = NaiveDate::from_ymd_opt(2026, 1, 5).expect("valid date");
     assert_eq!(
-        format_game_caption(&ReplayPlaybackState::Playing {
-            replay: early_january,
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        }),
+        format_game_caption(&ReplayPlaybackState::playing(early_january, 0, 0.5, false,)),
         Some("GAME #2026-005".to_string()),
     );
 }
@@ -399,12 +366,7 @@ fn overlay_game_caption_shows_replay_date() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(game_caption_text(&mut app), "GAME #2026-122");
@@ -431,12 +393,7 @@ fn overlay_scrub_fill_tracks_cursor() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8),
-            cursor: 2,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(8), 2, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -447,12 +404,7 @@ fn overlay_scrub_fill_tracks_cursor() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8),
-            cursor: 6,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(8), 6, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -497,12 +449,7 @@ fn win_move_marker_pct_is_none_for_completed() {
 fn win_move_marker_pct_is_none_when_replay_lacks_field() {
     // Synthetic replay constructor leaves win_move_index as None
     // (legacy / pre-`ab857bb` path).
-    let state = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 0,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state = ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false);
     assert_eq!(win_move_marker_pct(&state), None);
 }
 
@@ -511,12 +458,12 @@ fn win_move_marker_pct_is_some_at_correct_position() {
     // 10 moves, win at index 9 → marker sits at 90 % of the track.
     // Matches the recording semantic: cursor reaches the marker
     // exactly when the about-to-apply move IS the win move.
-    let state = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10).with_win_move_index(Some(9)),
-        cursor: 0,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state = ReplayPlaybackState::playing(
+        synthetic_replay(10).with_win_move_index(Some(9)),
+        0,
+        0.5,
+        false,
+    );
     assert_eq!(win_move_marker_pct(&state), Some(90.0));
 }
 
@@ -524,12 +471,12 @@ fn win_move_marker_pct_is_some_at_correct_position() {
 fn win_move_marker_pct_clamps_to_track_bounds() {
     // Defensive: if a malformed replay carried `win_move_index >=
     // total`, the marker must still sit on the track, not past it.
-    let state = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(5).with_win_move_index(Some(99)),
-        cursor: 0,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state = ReplayPlaybackState::playing(
+        synthetic_replay(5).with_win_move_index(Some(99)),
+        0,
+        0.5,
+        false,
+    );
     assert_eq!(win_move_marker_pct(&state), Some(100.0));
 }
 
@@ -538,12 +485,12 @@ fn marker_spawned_when_replay_has_win_move_index() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8).with_win_move_index(Some(7)),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(
+            synthetic_replay(8).with_win_move_index(Some(7)),
+            0,
+            0.5,
+            false,
+        ),
     );
     app.update();
     assert_eq!(
@@ -559,12 +506,7 @@ fn marker_not_spawned_when_replay_lacks_win_move_index() {
     // Default constructor → win_move_index: None (legacy replay).
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(8), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -579,12 +521,12 @@ fn marker_despawns_when_replay_state_returns_to_inactive() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8).with_win_move_index(Some(7)),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(
+            synthetic_replay(8).with_win_move_index(Some(7)),
+            0,
+            0.5,
+            false,
+        ),
     );
     app.update();
     assert_eq!(win_marker_count(&mut app), 1);
@@ -608,12 +550,12 @@ fn win_move_marker_carries_hc_background_marker() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8).with_win_move_index(Some(7)),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(
+            synthetic_replay(8).with_win_move_index(Some(7)),
+            0,
+            0.5,
+            false,
+        ),
     );
     app.update();
 
@@ -669,12 +611,7 @@ fn scrub_notches_spawn_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -693,12 +630,7 @@ fn scrub_notches_carry_high_contrast_background_marker() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -723,12 +655,7 @@ fn scrub_track_carries_high_contrast_background_marker() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -759,12 +686,7 @@ fn scrub_notches_despawn_with_overlay() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(scrub_notch_count(&mut app), 5);
@@ -821,12 +743,7 @@ fn scrub_notch_labels_spawn_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -844,12 +761,7 @@ fn scrub_notch_labels_carry_helper_strings() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -870,12 +782,7 @@ fn scrub_notch_labels_despawn_with_overlay() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(scrub_notch_label_count(&mut app), 5);
@@ -947,12 +854,7 @@ fn keybind_footer_spawns_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -970,12 +872,7 @@ fn keybind_footer_paints_helper_strings() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -999,12 +896,7 @@ fn keybind_footer_carries_high_contrast_border_marker() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
 
@@ -1025,12 +917,7 @@ fn keybind_footer_despawns_with_overlay() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(keybind_footer_count(&mut app), 1);
@@ -1054,12 +941,7 @@ fn scrub_notches_spawn_even_without_win_marker() {
     // Default constructor → win_move_index: None.
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(8), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1144,12 +1026,7 @@ fn format_move_body_handles_stock_cycle() {
 /// `Inactive` → empty.
 #[test]
 fn format_move_log_header_covers_state_branches() {
-    let playing = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 3,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let playing = ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false);
     assert_eq!(
         format_move_log_header(&playing),
         "\u{258C} MOVE LOG \u{00B7} 3/10"
@@ -1167,24 +1044,14 @@ fn format_move_log_header_covers_state_branches() {
 /// `replay.moves[N - 1]` and the row reads `"N | ..."`.
 #[test]
 fn format_active_move_row_handles_cursor_zero_and_positive() {
-    let cursor_zero = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 0,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let cursor_zero = ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false);
     assert_eq!(
         format_active_move_row(&cursor_zero),
         "",
         "cursor=0 means no move applied yet; row stays empty",
     );
 
-    let cursor_three = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 3,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let cursor_three = ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false);
     // synthetic_replay produces all StockClicks, so the body
     // is "stock cycle". The displayed index is 3 (cursor),
     // matching the most-recently-applied move at moves[2].
@@ -1208,12 +1075,7 @@ fn move_log_panel_spawns_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1232,12 +1094,7 @@ fn move_log_panel_header_paints_helper_string() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(8),
-            cursor: 2,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(8), 2, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1254,12 +1111,7 @@ fn move_log_active_row_repaints_on_cursor_advance() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1271,12 +1123,7 @@ fn move_log_active_row_repaints_on_cursor_advance() {
     // Advance cursor to 2 (most-recently-applied move is moves[1]).
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 2,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 2, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1292,12 +1139,7 @@ fn move_log_active_row_repaints_on_cursor_advance() {
 /// early in a replay don't paint stale text.
 #[test]
 fn format_kth_recent_row_handles_in_range_and_out_of_range() {
-    let state_at_three = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 3,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state_at_three = ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false);
     // k=1 → active (most recent applied). cursor=3 → display=3.
     assert_eq!(
         format_kth_recent_row(&state_at_three, 1),
@@ -1348,12 +1190,7 @@ fn move_log_prev_rows_spawn_with_panel() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 3,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1371,12 +1208,7 @@ fn move_log_prev_rows_paint_helper_strings_at_spawn() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 5, 0.5, false),
     );
     app.update();
 
@@ -1401,12 +1233,7 @@ fn move_log_prev_rows_repaint_on_cursor_advance() {
     // Start at cursor=2: offset 1 → k=2 → display=1, offset 2 → k=3 → empty (k > cursor).
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 2,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 2, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1422,12 +1249,7 @@ fn move_log_prev_rows_repaint_on_cursor_advance() {
     // Advance to cursor=5 — both offsets now have history.
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 5, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1465,12 +1287,7 @@ fn move_log_next_row_text_at_offset(app: &mut App, offset: u8) -> String {
 /// alongside in-range correctness.
 #[test]
 fn format_kth_next_row_handles_in_range_and_out_of_range() {
-    let state_at_three = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 3,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state_at_three = ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false);
     // k=1 → moves[3], display=4
     assert_eq!(
         format_kth_next_row(&state_at_three, 1),
@@ -1498,12 +1315,7 @@ fn move_log_next_rows_spawn_with_panel() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 3,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1520,12 +1332,7 @@ fn move_log_next_rows_paint_helper_strings_at_spawn() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 5,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 5, 0.5, false),
     );
     app.update();
 
@@ -1549,12 +1356,7 @@ fn move_log_next_rows_underfill_at_replay_end() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 9,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 9, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -1578,12 +1380,7 @@ fn active_row_wrapper_carries_accent_primary_background() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 3,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false),
     );
     app.update();
 
@@ -1621,12 +1418,7 @@ fn active_row_text_uses_high_contrast_color_for_highlight() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 3,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 3, 0.5, false),
     );
     app.update();
 
@@ -1647,24 +1439,14 @@ fn active_row_text_uses_high_contrast_color_for_highlight() {
 /// dropping it has to also update this test.
 #[test]
 fn active_row_format_includes_focus_prefix() {
-    let state = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 5,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let state = ReplayPlaybackState::playing(synthetic_replay(10), 5, 0.5, false);
     let row = format_active_move_row(&state);
     assert!(
         row.starts_with('\u{25B6}'),
         "active-row format must start with ▶ focus marker; got {row:?}",
     );
     // Cursor=0 still returns empty, never just the prefix.
-    let cursor_zero = ReplayPlaybackState::Playing {
-        replay: synthetic_replay(10),
-        cursor: 0,
-        secs_to_next: 0.5,
-        paused: false,
-    };
+    let cursor_zero = ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false);
     assert_eq!(
         format_active_move_row(&cursor_zero),
         "",
@@ -1679,12 +1461,7 @@ fn move_log_panel_despawns_with_overlay() {
     let mut app = headless_app();
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(10),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(10), 0, 0.5, false),
     );
     app.update();
     assert_eq!(move_log_panel_count(&mut app), 1);
@@ -1728,21 +1505,11 @@ fn unique_button<M: Component>(app: &mut App) -> Entity {
 }
 
 fn pressed_paused_state(replay_len: usize, cursor: usize) -> ReplayPlaybackState {
-    ReplayPlaybackState::Playing {
-        replay: synthetic_replay(replay_len),
-        cursor,
-        secs_to_next: 0.5,
-        paused: true,
-    }
+    ReplayPlaybackState::playing(synthetic_replay(replay_len), cursor, 0.5, true)
 }
 
 fn running_state(replay_len: usize, cursor: usize) -> ReplayPlaybackState {
-    ReplayPlaybackState::Playing {
-        replay: synthetic_replay(replay_len),
-        cursor,
-        secs_to_next: 0.5,
-        paused: false,
-    }
+    ReplayPlaybackState::playing(synthetic_replay(replay_len), cursor, 0.5, false)
 }
 
 #[test]
@@ -2191,12 +1958,7 @@ fn dim_layer_spawns_and_despawns_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(5),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(5), 0, 0.5, false),
     );
     app.update();
     assert_eq!(
@@ -2255,12 +2017,7 @@ fn mini_tableau_panel_spawns_and_despawns_with_overlay() {
 
     set_state(
         &mut app,
-        ReplayPlaybackState::Playing {
-            replay: synthetic_replay(5),
-            cursor: 0,
-            secs_to_next: 0.5,
-            paused: false,
-        },
+        ReplayPlaybackState::playing(synthetic_replay(5), 0, 0.5, false),
     );
     app.update();
     assert_eq!(

solitaire_engine/src/replay_overlay/update.rs

@@ -83,11 +83,11 @@ pub(crate) fn update_floating_progress_chip(
     // any). `cursor` is the index of the *next* move to apply, so
     // the most-recently-applied move sits at `cursor - 1`.
     let dest_pile = match state.as_ref() {
-        ReplayPlaybackState::Playing { replay, cursor, .. } if *cursor > 0 => {
+        ReplayPlaybackState::Playing { moves, cursor, .. } if *cursor > 0 => {
             // The destination pile is recoverable directly from the
             // instruction — no live state needed. `RotateStock` has no
             // destination (the chip hides over the stock pile).
-            match &replay.moves[cursor - 1] {
+            match &moves[cursor - 1] {
                 KlondikeInstruction::DstFoundation(dst) => {
                     Some(KlondikePile::Foundation(dst.foundation))
                 }

solitaire_engine/src/replay_playback.rs

@@ -1,11 +1,12 @@
 //! In-engine replay playback core.
 //!
 //! When the player clicks "Watch replay" on the Stats overlay, the live
-//! game state is reset to the deal seeded from the replay's `seed` /
-//! `mode` / `draw_mode`, and the engine ticks through `replay.moves` at a
-//! steady cadence — firing the canonical [`MoveRequestEvent`] /
-//! [`DrawRequestEvent`] for each one. The existing animation pipeline
-//! plays back identically to a live game.
+//! game state is reset to the recorded deal — rebuilt directly from
+//! `replay.recording` via `GameState::from_recording`, never by
+//! re-dealing the seed — and the engine ticks through the recording's
+//! instruction list at a steady cadence, firing the canonical
+//! [`MoveRequestEvent`] / [`DrawRequestEvent`] for each one. The
+//! existing animation pipeline plays back identically to a live game.
 //!
 //! ## Public surface
 //!
@@ -95,7 +96,7 @@ pub const REPLAY_COMPLETION_LINGER_SECS: f32 = 5.0;
 /// 3. The tick system [`tick_replay_playback`] advances `cursor` once
 ///    per [`REPLAY_MOVE_INTERVAL_SECS`] and fires the canonical event
 ///    for each [`KlondikeInstruction`].
-/// 4. When `cursor == replay.moves.len()`, the state transitions to
+/// 4. When `cursor == moves.len()`, the state transitions to
 ///    [`Completed`](Self::Completed). It lingers for
 ///    [`REPLAY_COMPLETION_LINGER_SECS`] (driven by
 ///    [`auto_clear_completed_replay`]) before returning to
@@ -109,14 +110,20 @@ pub enum ReplayPlaybackState {
     #[default]
     Inactive,
     /// A replay is currently being played back. The overlay reads
-    /// `replay.moves.len()` for the denominator of the progress
+    /// `moves.len()` for the denominator of the progress
     /// indicator and `cursor` for the numerator.
     Playing {
         /// The replay being played back. Owned so the state is the
         /// only place playback metadata lives — no separate resource
-        /// needed.
-        replay: Replay,
-        /// Index of the next move to apply, in `[0, replay.moves.len()]`.
+        /// needed. Boxed: the v4 recording embeds the dealt board and
+        /// would otherwise dwarf the other variants
+        /// (`clippy::large_enum_variant`).
+        replay: Box<Replay>,
+        /// Instruction list extracted once from `replay.recording` at
+        /// [`start_replay_playback`] time, so the per-frame tick indexes
+        /// a plain slice instead of re-walking the recording.
+        moves: Vec<KlondikeInstruction>,
+        /// Index of the next move to apply, in `[0, moves.len()]`.
         cursor: usize,
         /// Seconds remaining until the next move is dispatched.
         secs_to_next: f32,
@@ -138,6 +145,19 @@ pub enum ReplayPlaybackState {
 }
 
 impl ReplayPlaybackState {
+    /// Construct a [`Self::Playing`] state, extracting the instruction
+    /// list from `replay.recording` once up front.
+    pub fn playing(replay: Replay, cursor: usize, secs_to_next: f32, paused: bool) -> Self {
+        let moves = replay.recording.instructions();
+        Self::Playing {
+            replay: Box::new(replay),
+            moves,
+            cursor,
+            secs_to_next,
+            paused,
+        }
+    }
+
     /// Returns `true` when a replay is currently being played back.
     pub fn is_playing(&self) -> bool {
         matches!(self, Self::Playing { .. })
@@ -156,7 +176,7 @@ impl ReplayPlaybackState {
     /// the total is no longer available in `Completed`.
     pub fn progress(&self) -> Option<(usize, usize)> {
         match self {
-            Self::Playing { replay, cursor, .. } => Some((*cursor, replay.moves.len())),
+            Self::Playing { moves, cursor, .. } => Some((*cursor, moves.len())),
             Self::Inactive | Self::Completed => None,
         }
     }
@@ -191,7 +211,11 @@ pub fn start_replay_playback(
 ) {
     use solitaire_core::game_state::GameState;
 
-    let fresh = GameState::new_with_mode(replay.seed, replay.draw_mode, replay.mode);
+    // The recording carries the dealt board and the session config
+    // (including draw mode), so the fresh game is bit-identical to the
+    // recorded deal regardless of how the current build maps seeds to
+    // deals — `replay.seed` is presentation metadata only.
+    let (fresh, moves) = GameState::from_recording(&replay.recording, replay.seed, replay.mode);
     commands.insert_resource(GameStateResource(fresh));
 
     // Initial `secs_to_next` uses the constant rather than reading
@@ -201,7 +225,8 @@ pub fn start_replay_playback(
     // unusually short setting; subsequent ticks read the live setting
     // every frame via [`tick_replay_playback`].
     **state = ReplayPlaybackState::Playing {
-        replay,
+        replay: Box::new(replay),
+        moves,
         cursor: 0,
         secs_to_next: REPLAY_MOVE_INTERVAL_SECS,
         paused: false,
@@ -256,7 +281,7 @@ pub fn step_replay_playback(
     draws_writer: &mut MessageWriter<DrawRequestEvent>,
 ) -> bool {
     let ReplayPlaybackState::Playing {
-        replay,
+        moves,
         cursor,
         paused: true,
         ..
@@ -264,10 +289,10 @@ pub fn step_replay_playback(
     else {
         return false;
     };
-    if *cursor >= replay.moves.len() {
+    if *cursor >= moves.len() {
         return false;
     }
-    let instruction = replay.moves[*cursor];
+    let instruction = moves[*cursor];
     dispatch_instruction(instruction, *cursor, game, moves_writer, draws_writer);
     *cursor += 1;
     true
@@ -362,7 +387,7 @@ pub fn step_backwards_replay_playback(
 /// Drains `secs_to_next` by `time.delta_secs()`. When the countdown
 /// expires, fires the canonical event for the move at `cursor`,
 /// increments `cursor`, and resets `secs_to_next`. When `cursor`
-/// reaches `replay.moves.len()`, transitions to
+/// reaches `moves.len()`, transitions to
 /// [`ReplayPlaybackState::Completed`].
 ///
 /// The advance loop is a `while`, not an `if`, so coarse time steps
@@ -384,10 +409,11 @@ fn tick_replay_playback(
     let mut transition_to_completed = false;
 
     if let ReplayPlaybackState::Playing {
-        replay,
+        moves,
         cursor,
         secs_to_next,
         paused,
+        ..
     } = state.as_mut()
     {
         // While paused, the cursor and the timer freeze together —
@@ -397,8 +423,8 @@ fn tick_replay_playback(
         // path.
         if !*paused {
             *secs_to_next -= dt;
-            while *secs_to_next <= 0.0 && *cursor < replay.moves.len() {
-                let instruction = replay.moves[*cursor];
+            while *secs_to_next <= 0.0 && *cursor < moves.len() {
+                let instruction = moves[*cursor];
                 dispatch_instruction(
                     instruction,
                     *cursor,
@@ -410,7 +436,7 @@ fn tick_replay_playback(
                 *secs_to_next += interval;
             }
 
-            if *cursor >= replay.moves.len() {
+            if *cursor >= moves.len() {
                 transition_to_completed = true;
             }
         }
@@ -562,8 +588,7 @@ mod tests {
     use crate::game_plugin::GamePlugin;
     use bevy::time::TimeUpdateStrategy;
     use chrono::NaiveDate;
-    use solitaire_core::KlondikeInstruction;
-    use solitaire_core::{DrawStockConfig, game_state::GameMode};
+    use solitaire_core::{DrawStockConfig, SessionRecording, game_state::GameMode};
     use std::time::Duration;
 
     /// Builds a headless `App` with `MinimalPlugins`, `GamePlugin`, and
@@ -612,11 +637,11 @@ mod tests {
             60,
             500,
             NaiveDate::from_ymd_opt(2026, 5, 5).expect("valid date"),
-            vec![
-                KlondikeInstruction::RotateStock,
-                KlondikeInstruction::RotateStock,
-                KlondikeInstruction::RotateStock,
-            ],
+            SessionRecording::from_instructions_unchecked(
+                12345,
+                DrawStockConfig::DrawOne,
+                [KlondikeInstruction::RotateStock; 3],
+            ),
         )
     }
 
@@ -673,11 +698,14 @@ mod tests {
         let state = app.world().resource::<ReplayPlaybackState>();
         match state {
             ReplayPlaybackState::Playing {
-                cursor, replay: r, ..
+                cursor,
+                replay: r,
+                moves,
+                ..
             } => {
                 assert_eq!(*cursor, 0);
                 assert_eq!(r.seed, replay.seed);
-                assert_eq!(r.moves.len(), 3);
+                assert_eq!(moves.len(), 3);
             }
             other => panic!("expected Playing, got {other:?}"),
         }
@@ -778,7 +806,11 @@ mod tests {
             10,
             100,
             NaiveDate::from_ymd_opt(2026, 5, 5).expect("valid date"),
-            vec![KlondikeInstruction::RotateStock],
+            SessionRecording::from_instructions_unchecked(
+                42,
+                DrawStockConfig::DrawOne,
+                [KlondikeInstruction::RotateStock],
+            ),
         );
         start_playback(&mut app, one_move);
         app.update();
@@ -887,7 +919,11 @@ mod tests {
                 10,
                 100,
                 NaiveDate::from_ymd_opt(2026, 5, 5).expect("valid date"),
-                vec![KlondikeInstruction::RotateStock; 10],
+                SessionRecording::from_instructions_unchecked(
+                    7,
+                    DrawStockConfig::DrawOne,
+                    [KlondikeInstruction::RotateStock; 10],
+                ),
             )
         }
 

solitaire_engine/src/stats_plugin.rs

@@ -1939,7 +1939,11 @@ mod tests {
             time_seconds,
             0,
             date,
-            vec![],
+            solitaire_core::SessionRecording::from_instructions_unchecked(
+                1,
+                solitaire_core::DrawStockConfig::DrawOne,
+                [],
+            ),
         );
         r.share_url = share_url;
         r

solitaire_engine/src/sync_plugin.rs

@@ -335,7 +335,11 @@ fn push_replay_on_win(
             ev.time_seconds,
             ev.score,
             Utc::now().date_naive(),
-            recording.moves.clone(),
+            // The live session is the authoritative recording; it
+            // serialises via the upstream card_game serializers so web
+            // playback rebuilds the exact deal instead of re-dealing
+            // the seed.
+            game.0.recording(),
         );
         let provider = provider.0.clone();
         let rt = rt.0.clone();
@@ -621,7 +625,11 @@ mod tests {
             60,
             500,
             chrono::NaiveDate::from_ymd_opt(2026, 5, 6).expect("valid date"),
-            vec![],
+            solitaire_core::SessionRecording::from_instructions_unchecked(
+                7,
+                DrawStockConfig::DrawOne,
+                [],
+            ),
         );
         let history = ReplayHistory {
             schema_version: solitaire_data::REPLAY_HISTORY_SCHEMA_VERSION,

solitaire_engine/src/win_summary_plugin.rs

@@ -18,7 +18,7 @@
 //! shake duration elapses.
 
 use bevy::prelude::*;
-use solitaire_core::game_state::GameMode;
+use solitaire_core::game_state::{GameMode, GameState};
 use solitaire_core::scoring::compute_time_bonus;
 use solitaire_data::AnimSpeed;
 
@@ -93,6 +93,40 @@ pub struct WinSummaryPending {
     /// score-breakdown reveal can format the mode-multiplier row
     /// (e.g. `Zen ×0.0`, `Classic ×1.0`).
     pub mode: GameMode,
+    /// Per-move-type recap of the winning game, e.g.
+    /// `"21 to foundation · 14 tableau moves · 9 flips · 1 recycle"`.
+    /// Built from the upstream session counters at win time; empty when
+    /// every counter is zero (synthesised test wins).
+    pub move_detail: String,
+}
+
+/// Formats the per-move-type recap line for the win modal from the
+/// upstream session counters. Zero-valued components are omitted so the
+/// line stays short; returns an empty string when nothing was counted
+/// (only possible for synthesised test wins).
+fn build_move_detail(game: &GameState) -> String {
+    let mut parts: Vec<String> = Vec::new();
+    let foundation = game.move_to_foundation_count();
+    if foundation > 0 {
+        parts.push(format!("{foundation} to foundation"));
+    }
+    let tableau = game.move_to_tableau_count();
+    if tableau > 0 {
+        parts.push(format!("{tableau} tableau moves"));
+    }
+    let flips = game.flip_up_count();
+    if flips > 0 {
+        parts.push(format!("{flips} flips"));
+    }
+    let recycles = game.recycle_count();
+    if recycles > 0 {
+        parts.push(format!("{recycles} recycles"));
+    }
+    let returns = game.move_from_foundation_count();
+    if returns > 0 {
+        parts.push(format!("{returns} foundation returns"));
+    }
+    parts.join(" \u{00B7} ")
 }
 
 /// Builds a human-readable XP breakdown string for the win modal.
@@ -492,6 +526,7 @@ fn cache_win_data(
         pending.challenge_level = challenge_level;
         pending.undo_count = game.0.undo_count();
         pending.mode = game.0.mode;
+        pending.move_detail = build_move_detail(&game.0);
 
         if is_new_record {
             toast.write(InfoToastEvent("New Record!".to_string()));
@@ -913,6 +948,18 @@ fn spawn_overlay(
                     ));
                 }
 
+                // Move-type recap (same quiet styling as the XP breakdown)
+                if !pending.move_detail.is_empty() {
+                    card.spawn((
+                        Text::new(pending.move_detail.clone()),
+                        TextFont {
+                            font_size: 15.0,
+                            ..default()
+                        },
+                        TextColor(TEXT_SECONDARY),
+                    ));
+                }
+
                 // Achievements unlocked this game — at most 3 shown explicitly;
                 // excess is summarised with "...and N more".
                 if !session.names.is_empty() {
@@ -1288,6 +1335,49 @@ mod tests {
         assert_eq!(p.mode, GameMode::Classic);
     }
 
+    #[test]
+    fn build_move_detail_fresh_game_is_empty() {
+        let game = GameState::new(42, solitaire_core::DrawStockConfig::DrawOne);
+        assert!(
+            build_move_detail(&game).is_empty(),
+            "no moves yet, so the recap line must be empty"
+        );
+    }
+
+    #[test]
+    fn build_move_detail_reports_played_move_types() {
+        use solitaire_core::KlondikeInstruction;
+        // Drive a real deal forward so the upstream counters accumulate:
+        // prefer foundation moves, then anything else, drawing as needed.
+        let mut game = GameState::new(42, solitaire_core::DrawStockConfig::DrawOne);
+        for _ in 0..80 {
+            let instructions = game.possible_instructions();
+            let next = instructions
+                .iter()
+                .copied()
+                .find(|i| matches!(i, KlondikeInstruction::DstFoundation(_)))
+                .or_else(|| instructions.into_iter().next());
+            match next {
+                Some(i) => {
+                    let _ = game.apply_instruction(i);
+                }
+                None => break,
+            }
+            if game.move_to_foundation_count() > 0 && game.move_to_tableau_count() > 0 {
+                break;
+            }
+        }
+        let detail = build_move_detail(&game);
+        assert!(
+            detail.contains("to foundation"),
+            "seed 42 reaches a foundation move within 80 plies; got: {detail}"
+        );
+        assert!(
+            !detail.contains("0 "),
+            "zero-valued components must be omitted; got: {detail}"
+        );
+    }
+
     #[test]
     fn build_xp_detail_slow_win_with_undo() {
         // 300s >= 120s → no speed bonus; undo used → no no-undo bonus.

solitaire_server/src/replays.rs

@@ -31,17 +31,37 @@ use crate::{AppState, error::AppError, middleware::AuthenticatedUser};
 const KNOWN_MODES: &[&str] = &["Classic", "Zen", "TimeAttack", "Challenge", "Difficulty"];
 const KNOWN_DRAW_MODES: &[&str] = &["DrawOne", "DrawThree"];
 
-fn validate_header(h: &ReplayHeader) -> Result<(), AppError> {
+/// Extract the mode label from the client's serde representation.
+///
+/// Unit `GameMode` variants serialise as plain strings (`"Classic"`),
+/// but data-carrying variants serialise as single-key objects
+/// (`{"Difficulty": "Easy"}`) — a plain-`String` field rejected those
+/// uploads with a 400 even though `"Difficulty"` sits in `KNOWN_MODES`.
+fn mode_label(mode: &serde_json::Value) -> Result<String, AppError> {
+    if let Some(s) = mode.as_str() {
+        return Ok(s.to_string());
+    }
+    if let Some(obj) = mode.as_object()
+        && obj.len() == 1
+        && let Some(key) = obj.keys().next()
+    {
+        return Ok(key.clone());
+    }
+    Err(AppError::BadRequest(format!(
+        "invalid mode '{mode}'; expected a mode string or single-variant object"
+    )))
+}
+
+fn validate_header(h: &ReplayHeader, mode: &str) -> Result<(), AppError> {
     if !KNOWN_DRAW_MODES.contains(&h.draw_mode.as_str()) {
         return Err(AppError::BadRequest(format!(
             "invalid draw_mode '{}'; expected one of {:?}",
             h.draw_mode, KNOWN_DRAW_MODES
         )));
     }
-    if !KNOWN_MODES.contains(&h.mode.as_str()) {
+    if !KNOWN_MODES.contains(&mode) {
         return Err(AppError::BadRequest(format!(
-            "invalid mode '{}'; expected one of {:?}",
-            h.mode, KNOWN_MODES
+            "invalid mode '{mode}'; expected one of {KNOWN_MODES:?}"
         )));
     }
     if h.time_seconds <= 0 || h.time_seconds > 86_400 {
@@ -72,7 +92,11 @@ fn validate_header(h: &ReplayHeader) -> Result<(), AppError> {
 struct ReplayHeader {
     seed: u64,
     draw_mode: String,
-    mode: String,
+    /// Kept as raw JSON: unit variants arrive as strings, data-carrying
+    /// variants (`GameMode::Difficulty(level)`) as single-key objects.
+    /// [`mode_label`] projects both onto the label stored in the `mode`
+    /// column.
+    mode: serde_json::Value,
     time_seconds: i64,
     final_score: i64,
     recorded_at: String,
@@ -126,7 +150,8 @@ pub async fn upload(
     let header: ReplayHeader = serde_json::from_value(payload.clone())
         .map_err(|e| AppError::BadRequest(format!("replay JSON missing fields: {e}")))?;
 
-    validate_header(&header)?;
+    let mode = mode_label(&header.mode)?;
+    validate_header(&header, &mode)?;
 
     let id = Uuid::new_v4().to_string();
     let received_at = Utc::now().to_rfc3339();
@@ -144,7 +169,7 @@ pub async fn upload(
         user.user_id,
         seed_i64,
         header.draw_mode,
-        header.mode,
+        mode,
         header.time_seconds,
         header.final_score,
         header.recorded_at,
@@ -158,7 +183,7 @@ pub async fn upload(
     // beats their existing best. Only classic mode counts for the leaderboard.
     // Use `received_at` (server-computed) rather than `header.recorded_at`
     // (client-supplied) so clients cannot spoof the timestamp.
-    if header.mode == "Classic" {
+    if mode == "Classic" {
         sqlx::query!(
             r#"UPDATE leaderboard
                SET best_score      = ?,

solitaire_server/web/game.js

@@ -445,33 +445,30 @@ function showWin(s) {
     submitReplay(s);
 }
 
-function buildReplayPayload(s) {
-    if (!game || !s) return null;
-    let moves;
+function buildReplayPayload() {
+    if (!game) return null;
+    // The wasm side assembles the entire schema-v4 payload (including the
+    // session recording and the u64 seed, which JS numbers can't hold);
+    // JS only supplies the wall-clock time and today's date.
     try {
-        moves = game.replay_moves();
-        if (!Array.isArray(moves) || moves.length === 0) return null;
+        const json = game.replay_export(
+            Math.max(1, elapsedSecs),
+            new Date().toISOString().slice(0, 10),
+        );
+        const payload = JSON.parse(json);
+        if (!Array.isArray(payload?.recording?.instructions)
+            || payload.recording.instructions.length === 0) return null;
+        return payload;
     } catch (e) {
         console.warn("fs: replay export failed", e);
         return null;
     }
-    return {
-        schema_version: 2,
-        seed: Math.round(game.seed()),
-        draw_mode: drawThree ? "DrawThree" : "DrawOne",
-        mode: "Classic",
-        time_seconds: Math.max(1, elapsedSecs),
-        final_score: s.score,
-        recorded_at: new Date().toISOString().slice(0, 10),
-        moves,
-        win_move_index: moves.length - 1,
-    };
 }
 
 async function submitReplay(s) {
     const token = localStorage.getItem('fs_token');
     if (!token || !game) return;
-    const payload = buildReplayPayload(s);
+    const payload = buildReplayPayload();
     if (!payload) return;
     try {
         await fetch('/api/replays', {
@@ -1029,7 +1026,7 @@ window.__FERROUS_DEBUG__ = {
     },
     replayPayload() {
         if (!game) return null;
-        return buildReplayPayload(snap ?? game.state());
+        return buildReplayPayload();
     },
     runAutoplay(options) {
         return runDebugAutoplay(options);

solitaire_server/web/play.html

@@ -159,16 +159,17 @@
 
             function buildReplayPayload() {
                 if (!game) return null;
+                // Schema v4: the wasm side assembles the full payload,
+                // including the session recording and the u64 seed.
                 try {
-                    const moves = game.replay_moves();
-                    if (!Array.isArray(moves) || moves.length === 0) return null;
-                    return {
-                        schema_version: 2,
-                        seed: Math.round(game.seed()),
-                        draw_mode: game.debug_snapshot()?.draw_mode ?? "DrawOne",
-                        mode: "Classic",
-                        moves,
-                    };
+                    const json = game.replay_export(
+                        1,
+                        new Date().toISOString().slice(0, 10),
+                    );
+                    const payload = JSON.parse(json);
+                    if (!Array.isArray(payload?.recording?.instructions)
+                        || payload.recording.instructions.length === 0) return null;
+                    return payload;
                 } catch { return null; }
             }
 

solitaire_server/web/replay.js

@@ -121,7 +121,18 @@ function resetPlayer() {
         playInterval = null;
         btnPlay.textContent = "▶ Play";
     }
-    player = new ReplayPlayer(replayJson);
+    // Old replays (schema < 4) are rejected by the wasm player with a
+    // descriptive error — surface it instead of leaving a dead board.
+    try {
+        player = new ReplayPlayer(replayJson);
+    } catch (e) {
+        captionEl.textContent = `Cannot play this replay: ${e}`;
+        btnStep.disabled = true;
+        btnPlay.disabled = true;
+        btnPrev.disabled = true;
+        btnRestart.disabled = true;
+        return;
+    }
     btnPrev.disabled = true;
     btnRestart.disabled = true;
     btnStep.disabled = false;
@@ -304,10 +315,9 @@ btnPlay.addEventListener("click", () => {
     }, STEP_INTERVAL_MS);
 });
 
-/// Step the player back one move. Re-creates the ReplayPlayer and fast-
-/// forwards to (step_idx - 1) without rendering intermediate frames, then
-/// renders once so the CSS transition animates each card to its previous
-/// position.
+/// Step the player back one move via the wasm-side seek (rewinds to the
+/// recorded deal and fast-forwards internally), then renders once so the
+/// CSS transition animates each card to its previous position.
 function stepBack() {
     if (!player || player.step_idx() === 0) return;
     if (playInterval) {
@@ -315,12 +325,7 @@ function stepBack() {
         playInterval = null;
         btnPlay.textContent = "▶ Play";
     }
-    const target = player.step_idx() - 1;
-    player = new ReplayPlayer(replayJson);
-    for (let i = 0; i < target; i++) {
-        player.step();
-    }
-    render(player.state());
+    render(player.seek(player.step_idx() - 1));
     btnPrev.disabled = player.step_idx() === 0;
     btnRestart.disabled = player.step_idx() === 0;
     btnStep.disabled = false;

solitaire_wasm/src/lib.rs

@@ -26,16 +26,21 @@ use solitaire_core::{
     DrawStockConfig,
     game_state::{GameMode, GameState},
 };
-use solitaire_core::{KlondikeInstruction, KlondikePile};
+use solitaire_core::{KlondikeInstruction, KlondikePile, SessionRecording};
 use wasm_bindgen::prelude::*;
 
-/// Mirrors `solitaire_data::Replay` v3.
+/// Replay schema version this player understands. Mirrors
+/// `solitaire_data::REPLAY_SCHEMA_VERSION`; the loader rejects any
+/// other version with a descriptive error instead of desyncing.
+pub const REPLAY_SCHEMA_VERSION: u32 = 4;
+
+/// Mirrors `solitaire_data::Replay` v4.
 ///
-/// `moves` is a list of upstream [`KlondikeInstruction`]s — the same
-/// move-currency `solitaire_core` persists. A stock click is
-/// `KlondikeInstruction::RotateStock`; a card move is a
-/// `DstFoundation` / `DstTableau` instruction. Pile-position types are
-/// runtime-only and intentionally not part of the wire format.
+/// `recording` is the upstream `card_game` session serialisation
+/// (`{config, initial_state, instructions}`): the dealt board is stored
+/// explicitly, so playback rebuilds the exact deal instead of re-dealing
+/// from `seed` — schemas ≤ v3 did the latter and silently broke whenever
+/// an RNG or upstream upgrade changed the seed→deal mapping.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Replay {
     #[serde(default)]
@@ -46,7 +51,9 @@ pub struct Replay {
     pub time_seconds: u64,
     pub final_score: i32,
     pub recorded_at: NaiveDate,
-    pub moves: Vec<KlondikeInstruction>,
+    pub recording: SessionRecording,
+    #[serde(default)]
+    pub win_move_index: Option<usize>,
 }
 
 /// JS-friendly snapshot of a `GameState` at a particular replay step.
@@ -103,6 +110,9 @@ impl From<&(Card, bool)> for CardSnapshot {
 #[wasm_bindgen]
 pub struct ReplayPlayer {
     game: GameState,
+    /// The recorded deal before any instruction, kept so [`Self::seek_native`]
+    /// can rewind without reparsing the replay JSON.
+    initial: GameState,
     moves: Vec<KlondikeInstruction>,
     step_idx: usize,
 }
@@ -125,14 +135,42 @@ impl ReplayPlayer {
     pub fn from_json(replay_json: &str) -> Result<Self, String> {
         let replay: Replay =
             serde_json::from_str(replay_json).map_err(|e| format!("invalid replay JSON: {e}"))?;
-        let game = GameState::new_with_mode(replay.seed, replay.draw_mode, replay.mode);
+        if replay.schema_version != REPLAY_SCHEMA_VERSION {
+            return Err(format!(
+                "unsupported replay schema_version {} (this player requires {}); \
+                 replays recorded by older clients cannot be replayed",
+                replay.schema_version, REPLAY_SCHEMA_VERSION
+            ));
+        }
+        // The recording carries the dealt board and session config, so the
+        // rebuilt game is bit-identical to the recorded deal no matter how
+        // the current build maps seeds to deals.
+        let (game, moves) = GameState::from_recording(&replay.recording, replay.seed, replay.mode);
         Ok(Self {
+            initial: game.clone(),
             game,
-            moves: replay.moves,
+            moves,
             step_idx: 0,
         })
     }
 
+    /// Jump to `step` (clamped to the move count): the board state after
+    /// `step` moves have been applied. Rewinds by resetting to the stored
+    /// initial deal, then fast-forwards — a few hundred instruction
+    /// applications, microseconds in practice.
+    pub fn seek_native(&mut self, step: usize) -> Result<StateSnapshot, MoveError> {
+        let target = step.min(self.moves.len());
+        if target < self.step_idx {
+            self.game = self.initial.clone();
+            self.step_idx = 0;
+        }
+        while self.step_idx < target {
+            self.game.apply_instruction(self.moves[self.step_idx])?;
+            self.step_idx += 1;
+        }
+        Ok(self.snapshot())
+    }
+
     /// Apply the next move. Returns `Ok(None)` once the list is exhausted.
     pub fn step_native(&mut self) -> Result<Option<StateSnapshot>, MoveError> {
         if self.step_idx >= self.moves.len() {
@@ -219,6 +257,25 @@ impl ReplayPlayer {
         }
     }
 
+    /// Jump directly to `step` moves applied (clamped to the move count)
+    /// and return the snapshot there. Backwards seeks rewind to the
+    /// recorded deal and fast-forward, so any position is O(replay length)
+    /// at worst — no JSON reparse, no intermediate renders.
+    ///
+    /// Throws `"replay_desync"` if a recorded move is illegal during the
+    /// fast-forward (corrupt recording).
+    pub fn seek(&mut self, step: usize) -> Result<JsValue, JsValue> {
+        match self.seek_native(step) {
+            Ok(snap) => {
+                serde_wasm_bindgen::to_value(&snap).map_err(|e| JsValue::from_str(&e.to_string()))
+            }
+            Err(e) => {
+                log_replay_move_error(&e);
+                Err(JsValue::from_str("replay_desync"))
+            }
+        }
+    }
+
     /// Total number of moves the replay contains.
     pub fn total_steps(&self) -> usize {
         self.moves.len()
@@ -510,6 +567,36 @@ impl SolitaireGame {
         self.game.instruction_history()
     }
 
+    /// Builds the complete schema-v4 replay upload payload for the live
+    /// game as a JSON string, ready to `POST /api/replays` verbatim.
+    ///
+    /// The JS layer must not assemble this payload itself: the recording
+    /// serialises through the upstream `card_game` serializers, and the
+    /// `u64` seed exceeds JS number precision (`Math.round(game.seed())`
+    /// silently corrupts it).
+    ///
+    /// `recorded_at` is an ISO-8601 date (`YYYY-MM-DD`); the browser
+    /// supplies it because the wasm build has no reliable local clock.
+    fn replay_export_native(&self, time_seconds: u64, recorded_at: &str) -> Result<String, String> {
+        let recorded_at: NaiveDate = recorded_at
+            .parse()
+            .map_err(|e| format!("invalid recorded_at date '{recorded_at}': {e}"))?;
+        let recording = self.game.recording();
+        let win_move_index = recording.len().checked_sub(1);
+        let replay = Replay {
+            schema_version: REPLAY_SCHEMA_VERSION,
+            seed: self.game.seed,
+            draw_mode: self.game.draw_mode(),
+            mode: self.game.mode,
+            time_seconds,
+            final_score: self.game.score(),
+            recorded_at,
+            recording,
+            win_move_index,
+        };
+        serde_json::to_string(&replay).map_err(|e| format!("replay serialisation failed: {e}"))
+    }
+
     fn debug_snapshot_native(&self) -> DebugSnapshot {
         let legal_moves = self.legal_moves_native();
         let invariants = invariant_report_for_game(&self.game, &legal_moves);
@@ -694,6 +781,17 @@ impl SolitaireGame {
         serde_wasm_bindgen::to_value(&moves).map_err(|e| JsValue::from_str(&e.to_string()))
     }
 
+    /// Complete schema-v4 replay payload for the live game, as a JSON
+    /// string ready to `POST /api/replays` verbatim. See
+    /// [`Self::replay_export_native`] for why JS must not assemble the
+    /// payload itself. `recorded_at` is an ISO-8601 `YYYY-MM-DD` date.
+    /// `time_seconds` is `u32` so JS can pass a plain number (a `u64`
+    /// would demand a `BigInt`).
+    pub fn replay_export(&self, time_seconds: u32, recorded_at: String) -> Result<String, JsValue> {
+        self.replay_export_native(u64::from(time_seconds), &recorded_at)
+            .map_err(|e| JsValue::from_str(&e))
+    }
+
     /// Returns all currently-legal debug moves as a JS array.
     ///
     /// Includes [`DebugMove::StockClick`] when stock interaction is legal.
@@ -897,44 +995,25 @@ mod tests {
             "progressed game must export a non-empty replay move list"
         );
 
-        let moves_json = match serde_json::to_value(&exported_moves) {
-            Ok(value) => value,
-            Err(err) => panic!("failed to serialise exported replay moves: {err}"),
-        };
-        assert!(
-            moves_json.is_array(),
-            "exported replay moves must serialise as a JSON array"
-        );
-
-        let parsed_back: Vec<KlondikeInstruction> = match serde_json::from_value(moves_json) {
-            Ok(parsed) => parsed,
-            Err(err) => {
-                panic!("failed to parse replay move JSON as KlondikeInstruction list: {err}")
-            }
-        };
-        assert_eq!(
-            parsed_back, exported_moves,
-            "replay move JSON must round-trip through KlondikeInstruction"
-        );
-
-        let recorded_at = match NaiveDate::from_ymd_opt(2026, 6, 1) {
-            Some(date) => date,
-            None => panic!("invalid recorded_at date in test"),
-        };
-        let replay = Replay {
-            schema_version: 3,
-            seed,
-            draw_mode,
-            mode: GameMode::Classic,
-            time_seconds: 120,
-            final_score: game.game.score(),
-            recorded_at,
-            moves: exported_moves,
-        };
-        let replay_json = match serde_json::to_string(&replay) {
+        let replay_json = match game.replay_export_native(120, "2026-06-01") {
             Ok(json) => json,
-            Err(err) => panic!("failed to serialise replay JSON: {err}"),
+            Err(err) => panic!("failed to export replay JSON: {err}"),
         };
+        let parsed: Replay = match serde_json::from_str(&replay_json) {
+            Ok(parsed) => parsed,
+            Err(err) => panic!("exported replay JSON must parse back as Replay: {err}"),
+        };
+        assert_eq!(parsed.schema_version, REPLAY_SCHEMA_VERSION);
+        assert_eq!(
+            parsed.recording.instructions(),
+            exported_moves,
+            "exported recording must carry the exact instruction history"
+        );
+        assert_eq!(
+            parsed.win_move_index,
+            Some(exported_moves.len() - 1),
+            "win_move_index must point at the last instruction"
+        );
 
         let mut player = match ReplayPlayer::from_json(&replay_json) {
             Ok(value) => value,
@@ -962,6 +1041,118 @@ mod tests {
         );
     }
 
+    /// Pre-v4 replays re-dealt from the seed at playback time — the exact
+    /// mechanism that broke when the seed→deal mapping changed. The player
+    /// must refuse them with a version error, never desync silently.
+    #[test]
+    fn replay_player_rejects_pre_v4_schema_versions() {
+        let v3_json = r#"{
+            "schema_version": 3,
+            "seed": 7,
+            "draw_mode": "DrawOne",
+            "mode": "Classic",
+            "time_seconds": 60,
+            "final_score": 100,
+            "recorded_at": "2026-05-01",
+            "recording": null,
+            "moves": []
+        }"#;
+        // v3 files carry `moves`, not `recording`; either way the version
+        // gate (or the missing field) must produce an error, not a player.
+        let err = match ReplayPlayer::from_json(v3_json) {
+            Err(err) => err,
+            Ok(_) => panic!("v3 replay must be rejected"),
+        };
+        assert!(
+            err.contains("schema_version") || err.contains("invalid replay JSON"),
+            "error must name the version/format problem, got: {err}"
+        );
+    }
+
+    /// The whole point of v4: playback rebuilds the deal from the
+    /// recording, so a replay stays correct even when the top-level
+    /// `seed` no longer maps to the same deal (RNG upgrades, or a
+    /// corrupted seed from the old JS `Math.round` path).
+    #[test]
+    fn replay_playback_ignores_seed_for_dealing() {
+        let game = SolitaireGame {
+            game: GameState::new_with_mode(51, DrawStockConfig::DrawOne, GameMode::Classic),
+        };
+        let replay_json = game
+            .replay_export_native(60, "2026-06-01")
+            .expect("export must succeed");
+        // Corrupt the seed field only — playback must be unaffected.
+        let mut value: serde_json::Value =
+            serde_json::from_str(&replay_json).expect("parse exported JSON");
+        value["seed"] = serde_json::Value::from(0_u64);
+        let corrupted = serde_json::to_string(&value).expect("reserialise");
+
+        let player = ReplayPlayer::from_json(&corrupted).expect("player must construct");
+        let original_deal = serde_json::to_string(&game.snap()).expect("serialise original deal");
+        let replayed_deal =
+            serde_json::to_string(&player.snapshot()).expect("serialise replayed deal");
+        // Compare the board projections (piles), not the GameState wrapper
+        // (whose serde includes the now-different seed metadata).
+        let orig: serde_json::Value = serde_json::from_str(&original_deal).expect("parse");
+        let repl: serde_json::Value = serde_json::from_str(&replayed_deal).expect("parse");
+        assert_eq!(
+            orig["tableaus"], repl["tableaus"],
+            "tableau deal must come from the recording, not the seed"
+        );
+        assert_eq!(orig["stock"], repl["stock"], "stock deal must match");
+    }
+
+    /// `seek` must land on exactly the state produced by stepping — both
+    /// forwards (fast-forward from the current position) and backwards
+    /// (rewind to the recorded deal, then fast-forward).
+    #[test]
+    fn seek_matches_stepping_in_both_directions() {
+        let mut game = SolitaireGame {
+            game: GameState::new_with_mode(51, DrawStockConfig::DrawOne, GameMode::Classic),
+        };
+        for _ in 0..24 {
+            let legal_moves = game.legal_moves_native();
+            if legal_moves.is_empty() {
+                break;
+            }
+            let idx = pick_move_index(&legal_moves).unwrap_or_default();
+            game.apply_legal_move_native(idx).expect("advance game");
+        }
+        let replay_json = game
+            .replay_export_native(60, "2026-07-10")
+            .expect("export replay");
+
+        let mut stepped = ReplayPlayer::from_json(&replay_json).expect("player A");
+        let mut seeker = ReplayPlayer::from_json(&replay_json).expect("player B");
+        let total = stepped.total_steps();
+        assert!(total >= 4, "test needs a few moves, got {total}");
+
+        // Forward: step A to k, seek B to k, compare snapshots.
+        let k = total / 2;
+        for _ in 0..k {
+            stepped.step_native().expect("step").expect("mid-replay");
+        }
+        let sought = seeker.seek_native(k).expect("seek forward");
+        assert_eq!(sought, stepped.snapshot(), "forward seek diverged at {k}");
+
+        // Backward: seek B to k - 2 and compare against a fresh stepper.
+        let back = k - 2;
+        let mut fresh = ReplayPlayer::from_json(&replay_json).expect("player C");
+        for _ in 0..back {
+            fresh.step_native().expect("step").expect("mid-replay");
+        }
+        let sought_back = seeker.seek_native(back).expect("seek backward");
+        assert_eq!(
+            sought_back,
+            fresh.snapshot(),
+            "backward seek diverged at {back}"
+        );
+
+        // Clamping: past-the-end seeks stop at the final state.
+        let end = seeker.seek_native(usize::MAX).expect("seek to end");
+        assert_eq!(end.step_idx, total);
+    }
+
     #[test]
     fn debug_api_autonomous_seed_batch_smoke() {
         for seed in 0_u64..128_u64 {