diff --git a/src/simulator/crates/mc-player-api/tests/ai_self_play_first_contact.rs b/src/simulator/crates/mc-player-api/tests/ai_self_play_first_contact.rs
new file mode 100644
index 00000000..9967fc98
--- /dev/null
+++ b/src/simulator/crates/mc-player-api/tests/ai_self_play_first_contact.rs
@@ -0,0 +1,82 @@
+//! p3-17 / p3-16 — deterministic self-play first-contact via exploration.
+//!
+//! The original objectives asked for "measurable improvement in a hotseat
+//! self-play run: earlier first-contact". The sim is deterministic (fixed seed →
+//! identical outcome), so this is a reproducible cargo test, not an apricot-only
+//! smoke batch: two AI militarists start fogged-apart on a small map; once the
+//! frontier-seek exploration (p3-17) expands their footprints, one must come into
+//! view of the other within a bounded turn budget. First contact is the discovery
+//! feed p3-16's war-dec gate (`decide_diplomacy` only declares on a *discovered*
+//! rival) depends on — without exploration this never happened reliably.
+
+mod common;
+
+use common::{
+    add_player_militarist_inline, build_building_catalog, build_runtime_units_catalog,
+    build_unit_catalog, stamp_personality,
+};
+use mc_player_api::action::PlayerAction;
+use mc_player_api::{apply_action, project_tactical_with_vision};
+use mc_state::game_state::GameState;
+use mc_vision::{compute_vision, VisionCatalog};
+
+fn grassland_grid(w: i32, h: i32) -> mc_core::grid::GridState {
+    let mut g = mc_core::grid::GridState::new(w, h);
+    for t in &mut g.tiles {
+        t.biome_label_id = "grassland".into();
+    }
+    g
+}
+
+/// Has player `viewer` discovered any unit or city of any *other* player
+/// (fog-aware projection redacts the unseen)?
+fn has_first_contact(state: &GameState, viewer: u8) -> bool {
+    let vs = compute_vision(state, &VisionCatalog::default(), None);
+    let Some(pv) = vs.for_player(viewer) else {
+        return false;
+    };
+    let tac = project_tactical_with_vision(state, viewer, Some(pv));
+    tac.players
+        .iter()
+        .any(|p| p.index != viewer && (!p.units.is_empty() || !p.cities.is_empty()))
+}
+
+#[test]
+fn ai_self_play_makes_first_contact_via_exploration() {
+    let mut state = GameState::default();
+    state.turn = 1;
+    state.units_catalog = build_runtime_units_catalog();
+    // Slot 0 is a passive "human" that only EndTurns; slots 1 + 2 are AI driven
+    // by the dispatch EndTurn. Start them fogged-apart on a compact 12x12 map.
+    add_player_militarist_inline(&mut state, 2, 2);
+    add_player_militarist_inline(&mut state, 9, 2);
+    add_player_militarist_inline(&mut state, 5, 9);
+    stamp_personality(&mut state, 1, "blackhammer");
+    stamp_personality(&mut state, 2, "deepforge");
+    state.ai_unit_catalog = build_unit_catalog();
+    state.ai_building_catalog = build_building_catalog();
+    state.ai_difficulty_threshold_mult = 1.0;
+    state.grid = Some(grassland_grid(12, 12));
+
+    // Sanity: nobody has seen anyone else at game start (fog intact).
+    assert!(
+        !has_first_contact(&state, 1),
+        "slot 1 must start fogged — no enemy visible before exploration"
+    );
+
+    // Drive deterministic self-play. Slot-0 EndTurn runs the AI for slots 1 + 2.
+    let mut contact_turn: Option<u32> = None;
+    for turn in 1..=40u32 {
+        apply_action(&mut state, 0, &PlayerAction::EndTurn).expect("end turn dispatch");
+        if has_first_contact(&state, 1) || has_first_contact(&state, 2) {
+            contact_turn = Some(turn);
+            break;
+        }
+    }
+
+    assert!(
+        contact_turn.is_some(),
+        "AI frontier-seek exploration must produce first contact within 40 turns; \
+         got none — exploration regressed or the discovery feed is broken"
+    );
+}