diff --git a/src/simulator/crates/mc-ai/src/tactical/production.rs b/src/simulator/crates/mc-ai/src/tactical/production.rs
index 8826869d..e216f75d 100644
--- a/src/simulator/crates/mc-ai/src/tactical/production.rs
+++ b/src/simulator/crates/mc-ai/src/tactical/production.rs
@@ -226,6 +226,7 @@ fn pick_for_city(
         player.race_id.as_deref(),
         &player.strategic_resources,
         unit_catalog,
+        &player.clan_id,
     ).unwrap_or(ids::WARRIOR);
     let early_mil_floor = if turn <= EARLY_MIL_FLOOR_CUTOFF_TURN {
         EARLY_MIL_FLOOR
@@ -362,6 +363,7 @@ fn pick_best_melee<'a>(
     race_id: Option<&str>,
     strategic_resources: &[String],
     catalog: &'a [super::state::TacticalUnitSpec],
+    clan_id: &str,
 ) -> Option<&'a str> {
     let is_ranged_specialty = |id: &str| -> bool {
         id.contains("archer") || id.contains("ranger") || id.contains("flying")
@@ -383,10 +385,29 @@ fn pick_best_melee<'a>(
             None => true,
             Some(res) => strategic_resources.iter().any(|r| r == res),
         })
-        .max_by(|a, b| a.tier.cmp(&b.tier).then_with(|| a.id.cmp(&b.id)))
+        // Score: clan_affinity weight (×100) + tier. Affinity matches dominate
+        // tier within the same eligibility band; ties broken by id sort order
+        // for determinism. Generic units (empty clan_affinity) score as
+        // neutral fallbacks, off-clan units fall to the bottom but remain
+        // selectable when nothing affinity-matched is buildable. (p1-37)
+        .max_by_key(|u| (clan_affinity_score(u, clan_id), u.tier, std::cmp::Reverse(u.id.clone())))
         .map(|u| u.id.as_str())
 }
 
+/// Returns 2 if the unit's clan_affinity contains the player's clan, 1 if the
+/// affinity list is empty (generic unit, neutral fallback), 0 otherwise
+/// (off-clan — still buildable but ranked below affinity matches and
+/// generics). p1-37.
+fn clan_affinity_score(unit: &super::state::TacticalUnitSpec, clan_id: &str) -> u32 {
+    if unit.clan_affinity.is_empty() {
+        1
+    } else if unit.clan_affinity.iter().any(|c| c == clan_id) {
+        2
+    } else {
+        0
+    }
+}
+
 fn classify_posture(
     threatened: bool,
     own_mil: u32,
@@ -560,6 +581,8 @@ mod tests {
             unit_type: unit_type.into(),
             requires_resource: None,
             race_required: None,
+            clan_affinity: vec![],
+            archetype: None,
         }
     }
 
@@ -574,13 +597,32 @@ mod tests {
             unit_type: unit_type.into(),
             requires_resource: resource.map(Into::into),
             race_required: race.map(Into::into),
+            clan_affinity: vec![],
+            archetype: None,
+        }
+    }
+
+    /// Test helper: builds a TacticalUnitSpec with explicit clan_affinity for
+    /// p1-37 tests.
+    fn unit_spec_clan(
+        id: &str, tier: u32, tech: Option<&str>, clan_affinity: Vec<&str>,
+    ) -> super::super::state::TacticalUnitSpec {
+        super::super::state::TacticalUnitSpec {
+            id: id.into(),
+            tier,
+            tech_required: tech.map(Into::into),
+            unit_type: "military".into(),
+            requires_resource: None,
+            race_required: None,
+            clan_affinity: clan_affinity.into_iter().map(String::from).collect(),
+            archetype: None,
         }
     }
 
     #[test]
     fn pick_best_melee_falls_back_to_none_on_empty_catalog() {
         let techs: Vec<String> = vec![];
-        assert_eq!(pick_best_melee(&techs, None, &[], &[]), None);
+        assert_eq!(pick_best_melee(&techs, None, &[], &[], "ironhold"), None);
     }
 
     #[test]
@@ -590,7 +632,7 @@ mod tests {
             unit_spec("pikeman", 2, Some("bronze_working"), "military"),
         ];
         let techs = vec!["mining".to_string()];
-        assert_eq!(pick_best_melee(&techs, None, &[], &catalog), Some("warrior"));
+        assert_eq!(pick_best_melee(&techs, None, &[], &catalog, "ironhold"), Some("warrior"));
     }
 
     #[test]
@@ -601,9 +643,9 @@ mod tests {
             unit_spec("cavalry", 3, Some("steelworking"), "military"),
         ];
         let techs = vec!["bronze_working".to_string()];
-        assert_eq!(pick_best_melee(&techs, None, &[], &catalog), Some("pikeman"));
+        assert_eq!(pick_best_melee(&techs, None, &[], &catalog, "ironhold"), Some("pikeman"));
         let techs2 = vec!["bronze_working".to_string(), "steelworking".to_string()];
-        assert_eq!(pick_best_melee(&techs2, None, &[], &catalog), Some("cavalry"));
+        assert_eq!(pick_best_melee(&techs2, None, &[], &catalog, "ironhold"), Some("cavalry"));
     }
 
     #[test]
@@ -613,7 +655,7 @@ mod tests {
             unit_spec("worker", 1, None, "worker"),
             unit_spec("founder", 1, None, "founder"),
         ];
-        assert_eq!(pick_best_melee(&[], None, &[], &catalog), Some("warrior"));
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "ironhold"), Some("warrior"));
     }
 
     #[test]
@@ -625,7 +667,7 @@ mod tests {
         ];
         let techs = vec!["bronze_working".to_string()];
         assert_eq!(
-            pick_best_melee(&techs, None, &[], &catalog),
+            pick_best_melee(&techs, None, &[], &catalog, "ironhold"),
             Some("pikeman"),
             "ranged specialists must be excluded"
         );
@@ -644,18 +686,71 @@ mod tests {
         ];
         let techs = vec!["bronze_working".to_string(), "steelworking".to_string()];
         assert_eq!(
-            pick_best_melee(&techs, None, &[], &catalog),
+            pick_best_melee(&techs, None, &[], &catalog, "ironhold"),
             Some("pikeman"),
             "cavalry blocked by missing iron_ore; pikeman is highest unblocked"
         );
         // When iron_ore becomes available, cavalry unlocks.
         let resources = vec!["iron_ore".to_string()];
         assert_eq!(
-            pick_best_melee(&techs, None, &resources, &catalog),
+            pick_best_melee(&techs, None, &resources, &catalog, "ironhold"),
             Some("cavalry"),
         );
     }
 
+    // ── Clan affinity weighting (p1-37) ─────────────────────────────────
+
+    #[test]
+    fn clan_affinity_match_outranks_off_clan_at_same_tier() {
+        // Two T2 units, same eligibility. Berserker → blackhammer; defender →
+        // ironhold. A blackhammer player picks berserker; an ironhold player
+        // picks defender.
+        let catalog = [
+            unit_spec_clan("berserker", 2, None, vec!["blackhammer"]),
+            unit_spec_clan("defender",  2, None, vec!["ironhold"]),
+        ];
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "blackhammer"), Some("berserker"));
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "ironhold"),   Some("defender"));
+    }
+
+    #[test]
+    fn clan_affinity_off_clan_still_buildable_when_no_alternative() {
+        // Only one military unit available; even if its clan_affinity excludes
+        // the player's clan, it must still be picked (off-clan score 0 >= None).
+        let catalog = [
+            unit_spec_clan("doomsoul", 10, None, vec!["blackhammer"]),
+        ];
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "ironhold"), Some("doomsoul"));
+    }
+
+    #[test]
+    fn clan_affinity_generic_unit_neutral_fallback() {
+        // Generic warrior (empty clan_affinity) loses to clan-affinity match
+        // for the active clan, but beats off-clan units of the same tier.
+        let catalog = [
+            unit_spec_clan("warrior",  1, None, vec![]),                 // generic
+            unit_spec_clan("doomsoul", 1, None, vec!["blackhammer"]),    // matches blackhammer
+            unit_spec_clan("defender", 1, None, vec!["ironhold"]),       // matches ironhold
+        ];
+        // Blackhammer prefers their affinity match
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "blackhammer"), Some("doomsoul"));
+        // Goldvein has no match — falls to generic warrior over off-clan
+        // (warrior score=1, doomsoul score=0, defender score=0)
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "goldvein"), Some("warrior"));
+    }
+
+    #[test]
+    fn clan_affinity_higher_tier_match_beats_lower_tier_match() {
+        // T6 affinity match should beat T1 affinity match (within same affinity
+        // tier, sort by .tier).
+        let catalog = [
+            unit_spec_clan("shield_bearer",   1, None, vec!["ironhold"]),
+            unit_spec_clan("mountain_king",  10, None, vec!["ironhold", "deepforge"]),
+        ];
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "ironhold"),  Some("mountain_king"));
+        assert_eq!(pick_best_melee(&[], None, &[], &catalog, "deepforge"), Some("mountain_king"));
+    }
+
     #[test]
     fn pick_best_melee_skips_unit_when_race_mismatched() {
         // Berserker requires dwarf race. A human-race player with dwarf_heritage
@@ -665,10 +760,10 @@ mod tests {
             unit_spec_full("berserker", 2, Some("dwarf_heritage"), "military", None, Some("dwarf")),
         ];
         let techs = vec!["dwarf_heritage".to_string()];
-        assert_eq!(pick_best_melee(&techs, Some("human"), &[], &catalog), Some("warrior"));
-        assert_eq!(pick_best_melee(&techs, Some("dwarf"), &[], &catalog), Some("berserker"));
+        assert_eq!(pick_best_melee(&techs, Some("human"), &[], &catalog, "ironhold"), Some("warrior"));
+        assert_eq!(pick_best_melee(&techs, Some("dwarf"), &[], &catalog, "ironhold"), Some("berserker"));
         // No race id at all (pre-p0-39 fixture) → race-gated units filtered out.
-        assert_eq!(pick_best_melee(&techs, None, &[], &catalog), Some("warrior"));
+        assert_eq!(pick_best_melee(&techs, None, &[], &catalog, "ironhold"), Some("warrior"));
     }
 
     #[test]
diff --git a/src/simulator/crates/mc-ai/src/tactical/state.rs b/src/simulator/crates/mc-ai/src/tactical/state.rs
index 1792603c..d3a0586c 100644
--- a/src/simulator/crates/mc-ai/src/tactical/state.rs
+++ b/src/simulator/crates/mc-ai/src/tactical/state.rs
@@ -135,7 +135,12 @@ pub struct TacticalPlayerState {
 pub struct TacticalUnit {
     /// Engine-assigned unique id — matches `Action::MoveUnit::unit_id`.
     pub id: u32,
-    /// Unit kind id (e.g. `"warrior"`, `"settler"`, `"scout"`).
+    /// Unit kind id (e.g. `"warrior"`, `"founder"`, `"scout"`, or race-prefixed
+    /// like `"dwarf_warrior"`). Both generic and race-prefixed kinds coexist;
+    /// see `data/units/<id>.json` (generic) and `resources/units/<race>_<id>.json`
+    /// (race-specific). For founder detection prefer `is_founder()` over a
+    /// kind-string match — clan-themed founders like `"dwarf_tribe"` carry the
+    /// `can_found_city` flag and would be missed by string match.
     pub kind: String,
     /// Current axial `(col, row)` position.
     pub hex: (i32, i32),
@@ -199,6 +204,17 @@ pub struct TacticalUnitSpec {
     /// means no race restriction.
     #[serde(default)]
     pub race_required: Option<String>,
+    /// Clan IDs that prefer this unit (e.g. `["ironhold", "deepforge"]` for
+    /// `mountain_king`). Drives clan personality differentiation in the
+    /// production picker (p1-37). Empty vec = neutral / shared by all clans.
+    #[serde(default)]
+    pub clan_affinity: Vec<String>,
+    /// Archetype label mirroring `units/*.json::archetype`:
+    /// `"light_melee"` | `"heavy_melee"` | `"anti_cavalry"` | `"ranged"` |
+    /// `"siege"` | `"cavalry_walker"` | `"wild"` | `"civilian"`. `None` for
+    /// fixtures predating p1-34.
+    #[serde(default)]
+    pub archetype: Option<String>,
 }
 
 /// A city.