diff --git a/BUILD.md b/BUILD.md
index 7455d0e..7283288 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -84,11 +84,13 @@ CLI flags (applied before the first load/generate):
     planet.cfg   human-editable key=value config of every PlanetConfig parameter;
                  auto-created on first run, reload live with F2. Range-checked on
                  load; an invalid file reverts to safe defaults (not overwritten).
-    planet.save  binary snapshot (versioned, currently v17: +geography/atlas; v16
-                 +event log; v15 +stateful
-                 volcanoes; v13 +Live World clock rate; v12 +step-back history
-                 (~40 frames, so a load can rewind storms); v11 +weather systems/storms;
-                 v10 +weather fields; v9 +moons; v8 +Live World clock; v7 +biota): seed + config + full planet state; F5
+    planet.save  binary snapshot (versioned, currently v22: +diplomacy; v21
+                 +conflict/wars; v20 +settlements; v19 +ecoregions; v18
+                 +geography salt; v17 +geography/atlas; v16 +event log; v15
+                 +stateful volcanoes; v13 +Live World clock rate; v12
+                 +step-back history (~40 frames, so a load can rewind storms);
+                 v11 +weather systems/storms; v10 +weather fields; v9 +moons;
+                 v8 +Live World clock; v7 +biota): seed + config + full planet state; F5
                  writes it, F9 reloads and resumes deterministically. As of v6
                  the config is stored as a self-describing key=value block (like
                  planet.cfg), so adding/removing config fields no longer breaks saves
diff --git a/src/render/Viewer.cpp b/src/render/Viewer.cpp
index 4207e30..91596b3 100644
--- a/src/render/Viewer.cpp
+++ b/src/render/Viewer.cpp
@@ -5,6 +5,8 @@
 #include <cmath>
 #include <cstring>
 #include <fstream>
+#include <set>
+#include <utility>
 
 namespace {
     const char* weatherEventName(const WeatherSystem& ws, const Planet& p) {
@@ -17,6 +19,42 @@ namespace {
     int eventSeverityForWeather(const WeatherSystem& ws, const Planet& p) {
         return (ws.tropical && ws.strength >= p.cfg.weatherHurricaneStr) ? 2 : (ws.tropical ? 1 : 0);
     }
+    bool validFrameWar(const War& w, int settlementCount) {
+        return w.attacker >= 0 && w.attacker < settlementCount
+            && w.defender >= 0 && w.defender < settlementCount
+            && w.attacker != w.defender
+            && w.battles >= 0
+            && std::isfinite(w.warscore);
+    }
+    bool sanitizeFrameDiplomacy(std::vector<DiploTie>& ties, int settlementCount) {
+        std::set<std::pair<int, int>> seen;
+        for (DiploTie& t : ties) {
+            if (t.a < 0 || t.a >= settlementCount || t.b < 0 || t.b >= settlementCount || t.a == t.b)
+                return false;
+            if (t.a > t.b) std::swap(t.a, t.b);
+            if (!seen.insert({t.a, t.b}).second) return false;
+            if (!std::isfinite(t.attitude)) return false;
+            t.attitude = std::clamp(t.attitude, -1.0, 1.0);
+            if ((uint8_t)t.kind > (uint8_t)DiploKind::Rival) t.kind = DiploKind::Neutral;
+        }
+        return true;
+    }
+    bool validateFrameCivState(WeatherSnapshot& w, size_t currentSettlements) {
+        if (w.settlementPop.size() > currentSettlements) return false;
+        for (double p : w.settlementPop) if (!std::isfinite(p)) return false;
+        const int settlementCount = (int)w.settlementPop.size();
+        if (!w.settlementAllegiance.empty()) {
+            if ((int)w.settlementAllegiance.size() != settlementCount) return false;
+            for (int a : w.settlementAllegiance)
+                if (a < -1 || a >= settlementCount) return false;
+        }
+        std::set<std::pair<int, int>> warsSeen;
+        for (const War& war : w.wars) {
+            if (!validFrameWar(war, settlementCount)) return false;
+            if (!warsSeen.insert(std::minmax(war.attacker, war.defender)).second) return false;
+        }
+        return sanitizeFrameDiplomacy(w.diplomacy, settlementCount);
+    }
 }
 
 bool Viewer::init(int argc, char** argv) {
@@ -166,21 +204,21 @@ void Viewer::recolor() {
                            ? habitabilityColor(hab[i]) : Color{30, 42, 64, 255};   // ocean/ice: dim blue
                 break;
             case ColorMode::Territory: {
-                int ni = (i < (int)cnat.size()) ? cnat[i] : -1;
+                int ni = (i < cnat.size()) ? cnat[i] : -1;
                 if (ni >= 0) vcolors[i] = nationColor(ni);                         // owned: realm tint
                 else vcolors[i] = (planet.cells[i].elevation > planet.cfg.seaLevel) // wilderness land vs sea
                                 ? Color{60, 64, 58, 255} : Color{26, 34, 52, 255};
                 break;
             }
             case ColorMode::Culture: {
-                int ci = (i < (int)ccult.size()) ? ccult[i] : -1;
+                int ci = (i < ccult.size()) ? ccult[i] : -1;
                 if (ci >= 0) vcolors[i] = cultureColor(ci);                        // owned: culture tint
                 else vcolors[i] = (planet.cells[i].elevation > planet.cfg.seaLevel) // uncultured land vs sea
                                 ? Color{60, 64, 58, 255} : Color{26, 34, 52, 255};
                 break;
             }
             case ColorMode::Wealth: {
-                double w = (i < (int)cwealth.size()) ? cwealth[i] : 0.0;
+                double w = (i < cwealth.size()) ? cwealth[i] : 0.0;
                 if (w > 0.0) vcolors[i] = wealthColor(w / wealthMax);              // owned land: trade prosperity
                 else vcolors[i] = (planet.cells[i].elevation > planet.cfg.seaLevel) // wilderness land vs sea
                                 ? Color{40, 42, 46, 255} : Color{22, 30, 44, 255};
@@ -428,7 +466,9 @@ void Viewer::detectLiveEvents(const std::vector<WeatherSystem>& beforeStorms,
 // -> realm foundings, tier rises (to a kingdom/empire), and collapses (capital lost/absorbed).
 void Viewer::detectNationEvents(const std::vector<Nation>& before) {
     auto byCapital = [](const std::vector<Nation>& v, int cap) -> const Nation* {
-        for (const Nation& nn : v) if (nn.capital == cap) return &nn; return nullptr;
+        for (const Nation& nn : v)
+            if (nn.capital == cap) return &nn;
+        return nullptr;
     };
     for (const Nation& nat : planet.nationList()) {
         if (nat.capital < 0 || nat.capital >= (int)planet.settlements.size()) continue;
@@ -643,6 +683,7 @@ void Viewer::loadGame(const char* path) {
                     || !std::isfinite(v.activity) || !std::isfinite(v.baseElev)
                     || !std::isfinite(v.built) || !std::isfinite(v.timer)
                     || !std::isfinite(v.ashTimer) || !std::isfinite(v.ashCarry)) historyOk = false;
+            if (!validateFrameCivState(f.w, planet.settlements.size())) historyOk = false;
             if (historyOk) wxUndo.push_back(std::move(f));
         }
         if (!historyOk) { wxUndo.clear(); skippedHistory = true; }
diff --git a/src/sim/Planet.hpp b/src/sim/Planet.hpp
index e120b62..929d5da 100644
--- a/src/sim/Planet.hpp
+++ b/src/sim/Planet.hpp
@@ -288,6 +288,11 @@ private:
     uint32_t  rnd();
     double    rndf();             // [0,1)
     void      buildGeometry();    // build icosphere + per-cell unit/neighbors
+    bool      readStateImpl(std::istream& is, bool hasBiome, bool hasBiota,
+                            bool hasMoons, bool hasWeather, bool hasStorms,
+                            bool hasVolcanoes, bool hasStatefulVolcanoes, bool hasGeography,
+                            bool hasGeoSalt, bool hasEcoregions, bool hasSettlements,
+                            bool hasConflict, bool hasDiplo);
     void      clearDerivedState(); // clear geometry-dependent scratch/derived fields
     void      assignPlates();
     void      seedInitialRelief();
diff --git a/src/sim/PlanetCiv.cpp b/src/sim/PlanetCiv.cpp
index 1e5129f..deb358f 100644
--- a/src/sim/PlanetCiv.cpp
+++ b/src/sim/PlanetCiv.cpp
@@ -217,7 +217,7 @@ CivUpdate Planet::stepCivilization(double dtHours, double liveTime) {
         double siteQ = std::clamp(0.45 + cfg.civSiteVariety * ((coast ? 1.2 : 0.0) + riverQ), 0.3, 6.0);
 
         double cond = harvest * droughtFactor * coldFactor * floodFactor * ashFactor;
-        double prosp = (k < sProsperity.size()) ? sProsperity[k] : 0.0;      // civ Step 7: trade wealth boosts capacity
+        double prosp = ((size_t)k < sProsperity.size()) ? sProsperity[(size_t)k] : 0.0;      // civ Step 7: trade wealth boosts capacity
         double K = cfg.civMaxPopulation * hab * siteQ * cond * (1.0 + cfg.tradeProsperityWeight * prosp);
         sCivCond[k] = cond; sCivDrought[k] = drought;
 
diff --git a/src/sim/PlanetGeography.cpp b/src/sim/PlanetGeography.cpp
index 6a81257..a3d287f 100644
--- a/src/sim/PlanetGeography.cpp
+++ b/src/sim/PlanetGeography.cpp
@@ -277,7 +277,9 @@ std::string Planet::nameNewLand(int cell) {
     uint32_t seed = geoSeed + (uint32_t)(cell * 2654435761u)
                   + (uint32_t)geoFeatures.size() * 40503u;
     auto inUse = [&](const std::string& nm) {
-        for (const GeoFeature& f : geoFeatures) if (f.name == nm) return true; return false;
+        for (const GeoFeature& f : geoFeatures)
+            if (f.name == nm) return true;
+        return false;
     };
     std::string nm = namegen::makeName(seed, bank);
     for (int g = 0; inUse(nm) && g < 128; ++g) nm = namegen::makeName(seed += 0x9E3779B9u, bank);
diff --git a/src/sim/PlanetIO.cpp b/src/sim/PlanetIO.cpp
index 95d5936..3ed055d 100644
--- a/src/sim/PlanetIO.cpp
+++ b/src/sim/PlanetIO.cpp
@@ -8,6 +8,8 @@
 #include <fstream>
 #include <sstream>
 #include <limits>
+#include <set>
+#include <utility>
 
 // --- Config file (text) + save/load (binary) --------------------------------
 
@@ -368,6 +370,16 @@ std::string validateConfig(const PlanetConfig& cfg) {
         bad.push_back("volcanoDormantMinYears > volcanoDormantMaxYears");
     if (cfg.volcanoAshMinYears > cfg.volcanoAshMaxYears)
         bad.push_back("volcanoAshMinYears > volcanoAshMaxYears");
+    if (!(cfg.biomeIceTemp < cfg.biomeTundraTemp && cfg.biomeTundraTemp < cfg.biomeTaigaTemp))
+        bad.push_back("biome temperature thresholds must satisfy Ice < Tundra < Taiga");
+    if (cfg.biomeHillsElev >= cfg.biomeMountainElev)
+        bad.push_back("biomeHillsElev >= biomeMountainElev");
+    if (cfg.civAbandonPop >= cfg.civTownPop || cfg.civTownPop >= cfg.civCityPop)
+        bad.push_back("civilization population thresholds must satisfy Abandon < Town < City");
+    if (cfg.civSeedPopulation <= cfg.civAbandonPop)
+        bad.push_back("civSeedPopulation <= civAbandonPop");
+    if (!(cfg.diploRivalThreshold < cfg.diploNonAggThreshold && cfg.diploNonAggThreshold < cfg.diploAllyThreshold))
+        bad.push_back("diplomacy thresholds must satisfy Rival < NonAggression < Alliance");
 
     if (bad.empty()) return {};
     std::string msg = "Bad config:";
@@ -412,6 +424,34 @@ namespace {
     bool validBiomeByte(uint8_t b) {
         return b <= (uint8_t)Biome::Mountains;
     }
+    bool validWarRecord(const War& w, int settlementCount) {
+        return w.attacker >= 0 && w.attacker < settlementCount
+            && w.defender >= 0 && w.defender < settlementCount
+            && w.attacker != w.defender
+            && w.battles >= 0
+            && std::isfinite(w.warscore);
+    }
+    bool validateWars(std::vector<War>& wars, int settlementCount) {
+        std::set<std::pair<int, int>> seen;
+        for (const War& w : wars) {
+            if (!validWarRecord(w, settlementCount)) return false;
+            auto key = std::minmax(w.attacker, w.defender);
+            if (!seen.insert(key).second) return false;
+        }
+        return true;
+    }
+    bool sanitizeDiplo(std::vector<DiploTie>& ties, int settlementCount) {
+        std::set<std::pair<int, int>> seen;
+        for (DiploTie& t : ties) {
+            if (t.a < 0 || t.a >= settlementCount || t.b < 0 || t.b >= settlementCount || t.a == t.b)
+                return false;
+            if (t.a > t.b) std::swap(t.a, t.b);
+            if (!seen.insert({t.a, t.b}).second) return false;
+            if (!std::isfinite(t.attitude)) return false;
+            t.attitude = std::clamp(t.attitude, -1.0, 1.0);
+        }
+        return true;
+    }
 }
 
 // Full simulation state. Geometry (unit/neighbors) is NOT stored -- it is rebuilt
@@ -519,6 +559,20 @@ bool Planet::readState(std::istream& is, bool hasBiome, bool hasBiota, bool hasM
                        bool hasWeather, bool hasStorms, bool hasVolcanoes, bool hasStatefulVolcanoes,
                        bool hasGeography, bool hasGeoSalt, bool hasEcoregions, bool hasSettlements,
                        bool hasConflict, bool hasDiplo) {
+    Planet tmp;
+    tmp.drifting = drifting;       // readState never serialized this flag; preserve old caller-visible behavior.
+    if (!tmp.readStateImpl(is, hasBiome, hasBiota, hasMoons, hasWeather, hasStorms, hasVolcanoes,
+                           hasStatefulVolcanoes, hasGeography, hasGeoSalt, hasEcoregions,
+                           hasSettlements, hasConflict, hasDiplo))
+        return false;
+    *this = std::move(tmp);
+    return true;
+}
+
+bool Planet::readStateImpl(std::istream& is, bool hasBiome, bool hasBiota, bool hasMoons,
+                           bool hasWeather, bool hasStorms, bool hasVolcanoes, bool hasStatefulVolcanoes,
+                           bool hasGeography, bool hasGeoSalt, bool hasEcoregions, bool hasSettlements,
+                           bool hasConflict, bool hasDiplo) {
     // Save blocks are append-only by version. If a caller asks for an older prefix,
     // later blocks cannot exist in that stream even if the default arguments say otherwise.
     if (!hasBiota) { hasMoons = false; hasWeather = false; hasStorms = false; hasVolcanoes = false; }
@@ -759,6 +813,7 @@ bool Planet::readState(std::istream& is, bool hasBiome, bool hasBiota, bool hasM
             if (w.attacker < 0 || w.attacker >= (int)settlements.size()
                 || w.defender < 0 || w.defender >= (int)settlements.size()) return false;
         }
+        if (!validateWars(wars, (int)settlements.size())) return false;
         readPod(is, sWarRng); readPod(is, sWarNextId);
         if (!sWarRng) sWarRng = cfg.seed ? (cfg.seed ^ 0x5A7B0A11u) : 0x5A7B0A11u;
         if (!sWarNextId) sWarNextId = 1;
@@ -776,6 +831,7 @@ bool Planet::readState(std::istream& is, bool hasBiome, bool hasBiota, bool hasM
             if (t.a < 0 || t.a >= (int)settlements.size()
                 || t.b < 0 || t.b >= (int)settlements.size()) return false;
         }
+        if (!sanitizeDiplo(diplomacy, (int)settlements.size())) return false;
     }
     computeBiotaDensity();                  // derived density scalars for the colour views
     return (bool)is;
diff --git a/test_biota.cpp b/test_biota.cpp
index 82c09ef..75b0a3c 100644
--- a/test_biota.cpp
+++ b/test_biota.cpp
@@ -1,11 +1,11 @@
 // Headless logic test for the Biota stage (flora / fauna / funga). No display.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_biota.cpp src/sim/IcoSphere.cpp \
-//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp \
-//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp \
-//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_biota.cpp src/sim/IcoSphere.cpp
+//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp
+//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp
+//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp
 //       src/sim/PlanetIO.cpp -o /tmp/tb && /tmp/tb
 //
 // Verifies: density ranges, zero life under ice + marine flora/fauna present in the
@@ -95,8 +95,12 @@ int main() {
     const auto& B = p.biota();
     bool slotsOk = true, pointsOk = true, carnGated = true, iceEmpty = true, oceanFungaEmpty = true;
     bool anyMarineOrg = false;
-    auto cost = [&](const std::vector<Organism>& v) { int s = 0; const auto& AR = biotaArchetypes();
-        for (auto& o : v) s += pointCost(AR[o.archetype].size); return s; };
+    auto cost = [&](const std::vector<Organism>& v) {
+        int s = 0;
+        const auto& AR = biotaArchetypes();
+        for (auto& o : v) s += pointCost(AR[o.archetype].size);
+        return s;
+    };
     for (int i = 0; i < n; ++i) {
         const CellBiota& cb = B[i];
         if (p.cells[i].biome == Biome::Ice) {                       // ice (land or frozen sea): empty
diff --git a/test_civ.cpp b/test_civ.cpp
index 734fb0c..2cfe206 100644
--- a/test_civ.cpp
+++ b/test_civ.cpp
@@ -1,12 +1,12 @@
 // Headless test for civilization Step 2 (habitability + settlements). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_civ.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_civ.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
 //       src/sim/PlanetIO.cpp -o /tmp/tc && /tmp/tc
 //
 // Verifies: habitability range/zeros; placement spacing/cap/land + unique names; food-driven growth
diff --git a/test_colony.cpp b/test_colony.cpp
index a56327b..789b685 100644
--- a/test_colony.cpp
+++ b/test_colony.cpp
@@ -1,7 +1,7 @@
 // Headless test for civilization colonization (kingdoms found new settlements + islands). No display.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_colony.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       ... (the same source list as test_civ) ... src/sim/PlanetTrade.cpp src/sim/PlanetIO.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_colony.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       ... (the same source list as test_civ) ... src/sim/PlanetTrade.cpp src/sim/PlanetIO.cpp
 //       -o /tmp/tcol && /tmp/tcol
 //
 // Verifies: colonies are founded (the settlement count grows); a colony belongs to its founder's realm
diff --git a/test_conflict.cpp b/test_conflict.cpp
index 766d749..b315f65 100644
--- a/test_conflict.cpp
+++ b/test_conflict.cpp
@@ -1,13 +1,13 @@
 // Headless test for civilization Step 5 (conflict, war & shifting borders). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_conflict.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
-//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_conflict.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
+//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp
 //       src/sim/PlanetIO.cpp -o /tmp/twar && /tmp/twar
 //
 // Verifies: wars start between neighbouring realms; conquest sets allegiance so computeTerritory moves
@@ -146,6 +146,30 @@ int main() {
         r.computeTerritory();
         check(r.cellNation() == p2.cellNation(), "territory recomputed after load matches (allegiance honoured)");
     }
+    {
+        Planet bad = p2;
+        bad.wars.clear();
+        War w; w.attacker = 0; w.defender = (int)bad.settlements.size() + 10;
+        bad.wars.push_back(w);
+        std::stringstream ss(std::ios::in | std::ios::out | std::ios::binary);
+        bad.writeState(ss);
+        Planet r;
+        check(!r.readState(ss, true, true, true, true, true, true, true, true, true, true, true, true),
+              "readState rejects active wars with invalid settlement endpoints");
+    }
+    if (p2.settlements.size() >= 2) {
+        Planet bad = p2;
+        bad.wars.clear();
+        War a; a.attacker = 0; a.defender = 1;
+        War b; b.attacker = 1; b.defender = 0;
+        bad.wars.push_back(a);
+        bad.wars.push_back(b);
+        std::stringstream ss(std::ios::in | std::ios::out | std::ios::binary);
+        bad.writeState(ss);
+        Planet r;
+        check(!r.readState(ss, true, true, true, true, true, true, true, true, true, true, true, true),
+              "readState rejects duplicate active wars for the same realm pair");
+    }
 
     std::printf("Conflict: step-back snapshot round-trip\n");
     {
diff --git a/test_culture.cpp b/test_culture.cpp
index 8b3042f..dcf95db 100644
--- a/test_culture.cpp
+++ b/test_culture.cpp
@@ -1,12 +1,12 @@
 // Headless test for civilization Step 4 (cultures, beliefs & governments). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_culture.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_culture.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
 //       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetIO.cpp -o /tmp/tc && /tmp/tc
 //
 // Verifies: one culture per inhabited continent; every living settlement has a culture; valid
diff --git a/test_diplomacy.cpp b/test_diplomacy.cpp
index 2a97139..2fd4743 100644
--- a/test_diplomacy.cpp
+++ b/test_diplomacy.cpp
@@ -1,13 +1,13 @@
 // Headless test for civilization Step 6 (diplomacy, alliances & coalitions). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_diplomacy.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
-//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_diplomacy.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
+//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp
 //       src/sim/PlanetIO.cpp -o /tmp/tdip && /tmp/tdip
 //
 // Verifies: alliances + rivalries form; allies never war on each other; coalitions form (allies join a
@@ -127,6 +127,32 @@ int main() {
         check(ok, "readState accepts the v22 stream");
         check(tiesEqual(r.diploList(), p.diploList()), "diplomacy survives save/load");
     }
+    {
+        Planet bad = p;
+        bad.diplomacy.clear();
+        DiploTie t; t.a = 0; t.b = (int)bad.settlements.size() + 10;
+        bad.diplomacy.push_back(t);
+        std::stringstream ss(std::ios::in | std::ios::out | std::ios::binary);
+        bad.writeState(ss);
+        Planet r;
+        check(!r.readState(ss, true, true, true, true, true, true, true, true, true, true, true, true, true),
+              "readState rejects diplomacy ties with invalid settlement endpoints");
+    }
+    if (p.settlements.size() >= 2) {
+        Planet odd = p;
+        odd.diplomacy.clear();
+        DiploTie t; t.a = 1; t.b = 0; t.attitude = 99.0; t.kind = (DiploKind)255;
+        odd.diplomacy.push_back(t);
+        std::stringstream ss(std::ios::in | std::ios::out | std::ios::binary);
+        odd.writeState(ss);
+        Planet r;
+        bool ok = r.readState(ss, true, true, true, true, true, true, true, true, true, true, true, true, true);
+        bool sanitized = ok && r.diploList().size() == 1
+                      && r.diploList()[0].a == 0 && r.diploList()[0].b == 1
+                      && std::fabs(r.diploList()[0].attitude - 1.0) < 1e-12
+                      && r.diploList()[0].kind == DiploKind::Neutral;
+        check(sanitized, "readState canonicalizes and clamps salvageable diplomacy ties");
+    }
 
     std::printf("Diplomacy: step-back snapshot round-trip\n");
     {
diff --git a/test_geography.cpp b/test_geography.cpp
index c7912d2..5430e0b 100644
--- a/test_geography.cpp
+++ b/test_geography.cpp
@@ -1,11 +1,11 @@
 // Headless test for the geography / atlas stage (named feature extraction + naming). No display.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_geography.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_geography.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
 //       src/sim/PlanetGeography.cpp src/sim/PlanetIO.cpp -o /tmp/tg && /tmp/tg
 //
 // Verifies: extraction (continents/oceans/ranges/rivers/lakes), per-cell membership consistency,
diff --git a/test_live.cpp b/test_live.cpp
index c67091b..a34697e 100644
--- a/test_live.cpp
+++ b/test_live.cpp
@@ -1,11 +1,11 @@
 // Headless test for the Live World stage (insolation + live seasonal temperature).
 // No display / raylib needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_live.cpp src/sim/IcoSphere.cpp \
-//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp \
-//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp \
-//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp src/sim/PlanetLive.cpp \
-//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp src/sim/PlanetFaunaGen.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_live.cpp src/sim/IcoSphere.cpp
+//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp
+//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp
+//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp src/sim/PlanetLive.cpp
+//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp src/sim/PlanetFaunaGen.cpp
 //       src/sim/PlanetFungiGen.cpp src/sim/PlanetIO.cpp -o /tmp/tl && /tmp/tl
 //
 // Verifies: insolation range; the sub-solar hemisphere is lit and the night side dark;
diff --git a/test_logic.cpp b/test_logic.cpp
index 43c2cc7..d97b280 100644
--- a/test_logic.cpp
+++ b/test_logic.cpp
@@ -1,8 +1,8 @@
 // Headless logic test for Phase 1 tectonics. No display / raylib needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_logic.cpp src/sim/IcoSphere.cpp \
-//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp \
-//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp src/sim/PlanetIO.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_logic.cpp src/sim/IcoSphere.cpp
+//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp
+//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp src/sim/PlanetIO.cpp
 //       -o /tmp/t && /tmp/t
 //
 // Verifies the invariants documented in CLAUDE.md so Planet::step() and the
@@ -234,6 +234,20 @@ int main() {
         finishManualState(badPlate);
         Planet rp;
         check(!rp.readState(badPlate), "readState() rejects invalid cell plate ids");
+
+        Planet victim; victim.generate(cfg);
+        const size_t beforeCells = victim.cells.size();
+        const int beforeSubdiv = victim.cfg.subdivisions;
+        const double beforeElev = victim.cells.empty() ? 0.0 : victim.cells[0].elevation;
+        std::stringstream badAfterBuild(std::ios::in | std::ios::out | std::ios::binary);
+        writeManualStatePrefix(badAfterBuild, "subdivisions = 0\nplateCount = 1\n", 77);
+        finishManualState(badAfterBuild);
+        bool rejected = !victim.readState(badAfterBuild);
+        bool unchanged = victim.cells.size() == beforeCells
+                      && victim.cfg.subdivisions == beforeSubdiv
+                      && !victim.cells.empty()
+                      && victim.cells[0].elevation == beforeElev;
+        check(rejected && unchanged, "failed readState() leaves the existing planet unchanged");
     }
 
     std::printf("\n%s (%d failure%s)\n",
diff --git a/test_nation.cpp b/test_nation.cpp
index 1f9257e..c51287e 100644
--- a/test_nation.cpp
+++ b/test_nation.cpp
@@ -1,12 +1,12 @@
 // Headless test for civilization Step 3 (territory & nations / realms). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_nation.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_nation.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
 //       src/sim/PlanetNation.cpp src/sim/PlanetIO.cpp -o /tmp/tn && /tmp/tn
 //
 // Verifies: territory ownership + wilderness; bigger cities own more; realm grouping (kingdom vs
diff --git a/test_ocean.cpp b/test_ocean.cpp
index 34ee9bc..b358b01 100644
--- a/test_ocean.cpp
+++ b/test_ocean.cpp
@@ -1,11 +1,11 @@
 // Headless test for the Live World ocean/sky stage (moons + tides). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_ocean.cpp src/sim/IcoSphere.cpp \
-//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp \
-//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp \
-//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp src/sim/PlanetLive.cpp \
-//       src/sim/PlanetOcean.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/PlanetIO.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_ocean.cpp src/sim/IcoSphere.cpp
+//       src/sim/Planet.cpp src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp
+//       src/sim/PlanetErosion.cpp src/sim/PlanetHydrology.cpp
+//       src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp src/sim/PlanetLive.cpp
+//       src/sim/PlanetOcean.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/PlanetIO.cpp
 //       -o /tmp/to && /tmp/to
 //
 // Verifies: 1-3 moons generated deterministically; moon/sun directions are unit vectors that
diff --git a/test_trade.cpp b/test_trade.cpp
index 6751cff..86c7a63 100644
--- a/test_trade.cpp
+++ b/test_trade.cpp
@@ -1,13 +1,13 @@
 // Headless test for civilization Step 7 (trade & economy). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_trade.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
-//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp \
-//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp \
-//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_trade.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
+//       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/NameGen.cpp
+//       src/sim/PlanetGeography.cpp src/sim/PlanetEcoregions.cpp src/sim/PlanetCiv.cpp
+//       src/sim/PlanetNation.cpp src/sim/PlanetCulture.cpp src/sim/PlanetConflict.cpp
 //       src/sim/PlanetTrade.cpp src/sim/PlanetIO.cpp -o /tmp/ttr && /tmp/ttr
 //
 // Verifies: trade links form (coastal pairs over a longer sea range); hubs are richer than isolated
diff --git a/test_volcano.cpp b/test_volcano.cpp
index 40501c1..9bd6d90 100644
--- a/test_volcano.cpp
+++ b/test_volcano.cpp
@@ -1,11 +1,11 @@
 // Headless test for Live World volcanoes (stateful growth, dormancy, explosions, ash,
 // rewind snapshots and save/load). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_volcano.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_volcano.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetVolcano.cpp src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp
 //       src/sim/PlanetFaunaGen.cpp src/sim/PlanetFungiGen.cpp src/sim/PlanetIO.cpp -o /tmp/tv && /tmp/tv
 
 #include "Planet.hpp"
diff --git a/test_weather.cpp b/test_weather.cpp
index 72b71c1..9eab235 100644
--- a/test_weather.cpp
+++ b/test_weather.cpp
@@ -1,10 +1,10 @@
 // Headless test for the Live World weather cycle (humidity / cloud / rain). No display needed.
 //
-//   g++ -std=c++17 -O2 -Isrc/sim test_weather.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp \
-//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp \
-//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp \
-//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp \
-//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp src/sim/PlanetFaunaGen.cpp \
+//   g++ -std=c++17 -O2 -Isrc/sim test_weather.cpp src/sim/IcoSphere.cpp src/sim/Planet.cpp
+//       src/sim/PlanetTectonics.cpp src/sim/PlanetDrift.cpp src/sim/PlanetErosion.cpp
+//       src/sim/PlanetHydrology.cpp src/sim/PlanetBiomes.cpp src/sim/PlanetClimate.cpp
+//       src/sim/PlanetLive.cpp src/sim/PlanetOcean.cpp src/sim/PlanetWeather.cpp
+//       src/sim/PlanetBiota.cpp src/sim/PlanetFloraGen.cpp src/sim/PlanetFaunaGen.cpp
 //       src/sim/PlanetFungiGen.cpp src/sim/PlanetIO.cpp -o /tmp/tw && /tmp/tw
 //
 // Verifies: fields stay in range; oceans (the evaporation source) end up moister than land;