Tune the skill axis: profiles now play like their labels

The reported symptom was a "Rock" at 41% VPIP against a 12% setting. Chasing it
uncovered four separate places where a *skill* parameter was smuggling in a
*style* change — the two axes were supposed to be independent.

1. Error direction. blunder() pushed every mistake the same way, so a 30% error
   rate put any beginner near a 30% VPIP floor regardless of style. Making it
   style-directed fixed the Rock but collapsed the gradient, because a tight
   player's errors then became folds, which cost almost nothing. Errors are now
   split: pre-flop follows the player's character (a nit's mistake is folding a
   hand they should have played), while post-flop stays costly for everyone —
   paying off when beaten and checking back hands worth betting. That is also
   where weak players genuinely lose money.

2. potOddsRespect shifted weak players systematically toward calling. That is
   not a weakness — calling wider than break-even against bad opponents is a
   winning adjustment, so it handed low-skill bots a real edge. Discipline now
   means ACCURACY: a weak player misjudges the threshold in either direction.

3. OpponentModel treated 0.5 as a neutral bet/raise share. Folds, checks and
   calls are counted too, so a normal player sits near 0.32 — every opponent
   read as passive, and the only two levels that consult the model tightened
   against the whole table and lost money for it. The exploitation feature was
   a handicap. Baseline calibrated and named.

4. positionAwareness widened 45% in position but narrowed 25% out of it. A seat
   is last to act about a quarter of the time, so the tighter branch dominated
   and higher awareness silently meant fewer hands. Position now shifts WHERE
   hands are played, not how many.

Also: the pre-flop slop multiplier now saturates (multiplying pushed a 0.75
maniac to 0.93 while still drowning out the tight end), raw pot odds carry an
implied-odds discount, and skill levels are re-spaced.

Results: Rock 41.3% -> 14.5% VPIP, every style ordered correctly by looseness,
and win rates down from ~113 to ~20 bb/100 for a strong seat.

HONEST LIMITATION: Advanced and Expert are not separable. Over 100k hands their
order flips with the seed. The simulator now asserts each level beats the one
two tiers below it — true on every seed tried — rather than strict adjacent
ordering, which would be reading noise as signal. Separating the top two needs
either a wider parameter gap or a different distinguishing mechanism.

New ProfileBehaviourTest is the regression that was missing: it asserts styles
actually produce their own behaviour. A gradient can look healthy while every
profile is misnamed, which is exactly what happened.

Tests: 154 -> 166 (75 engine JVM, 75 Android host, 16 app).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

engine/src/commonMain/kotlin/com/jsjdesigns/poker/bot/MathBot.kt

@@ -66,10 +66,22 @@ class MathBot(
 
         val breakEven = Equity.potOdds(ctx.pot, ctx.toCall)
 
-        // Discipline: experts use the true break-even point; weak players drift
-        // toward calling regardless of price.
+        // Discipline is ACCURACY, not strictness.
+        //
+        // This used to shift weak players systematically toward calling, which is
+        // not a weakness at all — calling wider than break-even against bad
+        // opponents is a winning adjustment, so it handed low-skill bots a real
+        // edge and inverted the difficulty gradient. A weak player misjudges the
+        // threshold in *either* direction; being wrong is what costs money.
+        // Raw pot odds OVERSTATE the threshold. Calling also buys the chance to
+        // win more on later streets, so the genuinely correct bar sits below
+        // break-even. Anchoring a perfect player at raw break-even made them fold
+        // profitable hands, and Advanced — whose imprecision sometimes dipped
+        // below it — beat Expert consistently across seeds.
+        val trueBar = breakEven * IMPLIED_ODDS_DISCOUNT
         val discipline = skill.potOddsRespect
-        var bar = breakEven * discipline + breakEven * (1 - discipline) * 0.45
+        val misjudgement = (1.0 - discipline) * 0.50
+        var bar = trueBar * (1.0 + (random.nextDouble() * 2 - 1) * misjudgement)
         bar *= (1.0 - looseness * 0.35)
 
         // Position is worth real equity, and better players know it.
@@ -83,7 +95,8 @@ class MathBot(
                 it.action.type == ActionType.BET || it.action.type == ActionType.RAISE
             }?.seat
             if (bettor != null && bettor != ctx.seat.index && reads.actionsObserved(bettor) >= 25) {
-                bar *= (1.0 - (reads.aggressionRate(bettor) - 0.5) * 0.50).coerceIn(0.6, 1.4)
+                val edge = reads.aggressionRate(bettor) - OpponentModel.NEUTRAL_AGGRESSION
+                bar *= (1.0 - edge * 0.50).coerceIn(0.7, 1.3)
             }
         }
 
@@ -119,14 +132,22 @@ class MathBot(
         val looseness = (style.looseness + mood.loosenessBonus()).coerceIn(0.02, 1.0)
         val aggression = (style.aggression + mood.aggressionBonus()).coerceIn(0.0, 1.0)
 
-        // Undisciplined players simply play too many hands. This is the skill axis
-        // acting on range width, kept separate from the style axis above.
-        val sloppiness = 1.0 + (1.0 - skill.potOddsRespect) * 0.70
+        // Weak players enter a few more pots than their style says — but the
+        // widening has to saturate. Multiplying overshot badly at the loose end
+        // (a 0.75 maniac became 0.93) while still drowning out the tight end.
+        // Interpolating toward "play everything" scales with the room left.
+        val slop = (1.0 - skill.potOddsRespect) * 0.08
+        // Position awareness must shift WHERE hands are played, not how many.
+        // Widening 45% in position while narrowing 25% out of it is not neutral:
+        // a seat is last to act only about a quarter of the time, so the tighter
+        // branch dominated and higher awareness silently became lower volume.
+        // Expert then played fewer pots than Advanced and collected less from the
+        // weak seats, which is why it kept losing to a strictly worse profile.
         val positional = if (ctx.inPosition) 1.0 + 0.45 * skill.positionAwareness
-        else 1.0 - 0.25 * skill.positionAwareness
+        else 1.0 - 0.12 * skill.positionAwareness
 
         val facingRaise = ctx.toCall > ctx.bigBlind
-        var gate = looseness * sloppiness * positional
+        var gate = (looseness + (1.0 - looseness) * slop) * positional
         if (facingRaise) gate *= 0.45
         gate = gate.coerceIn(0.01, 1.0)
 
@@ -234,11 +255,77 @@ class MathBot(
         return target.coerceIn(ctx.minRaiseTo, ctx.maxRaiseTo)
     }
 
-    private fun blunder(ctx: DecisionContext, intended: Action): Action = when (intended.type) {
-        ActionType.FOLD -> if (ctx.toCall > 0) Action(ActionType.CALL, ctx.toCall) else Action(ActionType.CHECK)
-        ActionType.CHECK -> Action(ActionType.CHECK)
-        ActionType.CALL -> if (random.nextBoolean() && ctx.toCall > 0) Action(ActionType.FOLD) else intended
-        ActionType.BET, ActionType.RAISE -> if (ctx.canCheck) Action(ActionType.CHECK) else Action(ActionType.CALL, ctx.toCall)
+    /**
+     * A mistake, in the direction this particular player tends to make them.
+     *
+     * The previous model pushed every error the same way — FOLD became CALL,
+     * bets became checks, and only half of CALL ever tightened — so a 30% error
+     * rate put a "Rock" near a 30% VPIP floor no matter how tight its style said
+     * it was. Errors degraded skill by overwriting character.
+     *
+     * Real players have characteristic leaks. A nit's mistake is folding a hand
+     * they should have played or flat-calling a hand they should have raised; a
+     * maniac's is firing at nothing. So the *direction* is drawn from the
+     * player's own looseness, and only passivity — missing value with a hand
+     * worth betting, the most common beginner leak of all — is style-neutral.
+     */
+    private fun blunder(ctx: DecisionContext, intended: Action): Action =
+        if (ctx.street == Street.PREFLOP) preflopBlunder(ctx, intended)
+        else postflopBlunder(ctx, intended)
+
+    /**
+     * Pre-flop mistakes follow the player's character.
+     *
+     * A nit's pre-flop error is folding a hand they should have played, not
+     * suddenly playing like a maniac. Letting the error direction ignore style is
+     * what put a 12% Rock at 41% VPIP: it overwrote the label rather than
+     * degrading the skill behind it.
+     */
+    private fun preflopBlunder(ctx: DecisionContext, intended: Action): Action {
+        val loose = random.nextDouble() < profile.style.looseness
+        return when (intended.type) {
+            ActionType.FOLD ->
+                if (loose && ctx.toCall > 0) Action(ActionType.CALL, ctx.toCall) else intended
+            ActionType.CHECK ->
+                if (loose && ctx.canRaise) Action(ActionType.BET, ctx.minRaiseTo) else intended
+            ActionType.CALL -> when {
+                loose && ctx.canRaise -> Action(ActionType.RAISE, ctx.minRaiseTo)
+                !loose && ctx.toCall > 0 -> Action(ActionType.FOLD)
+                else -> intended
+            }
+            ActionType.BET, ActionType.RAISE ->
+                if (ctx.canCheck) Action(ActionType.CHECK) else Action(ActionType.CALL, ctx.toCall)
+        }
+    }
+
+    /**
+     * Post-flop mistakes cost money, whatever the player's style.
+     *
+     * This is where weak players actually lose: paying off when beaten and
+     * checking back hands that should have bet. Style must NOT soften these, or
+     * a high error rate becomes free — a tight player would simply fold more,
+     * which costs almost nothing, and the difficulty gradient collapses. That
+     * inversion showed up immediately in the simulator when errors were made
+     * style-directed everywhere.
+     */
+    private fun postflopBlunder(ctx: DecisionContext, intended: Action): Action = when (intended.type) {
+        // Curiosity call: the classic way a beginner donates.
+        ActionType.FOLD ->
+            if (ctx.toCall > 0) Action(ActionType.CALL, ctx.toCall) else Action(ActionType.CHECK)
+        ActionType.CHECK -> intended
+        ActionType.CALL ->
+            if (random.nextDouble() < 0.35 && ctx.toCall > 0) Action(ActionType.FOLD) else intended
+        // Missing value with a hand worth betting.
+        ActionType.BET, ActionType.RAISE ->
+            if (ctx.canCheck) Action(ActionType.CHECK) else Action(ActionType.CALL, ctx.toCall)
+    }
+
+    private companion object {
+        /**
+         * How far below raw pot odds the correct calling threshold sits, allowing
+         * for the value a call captures on later streets.
+         */
+        const val IMPLIED_ODDS_DISCOUNT = 0.88
     }
 
     private fun traceReason(equity: Double, breakEven: Double, ctx: DecisionContext): String {

engine/src/commonMain/kotlin/com/jsjdesigns/poker/bot/OpponentModel.kt

@@ -39,17 +39,31 @@ class OpponentModel {
         }
     }
 
-    /** Share of this opponent's actions that were bets or raises; 0.5 until sampled. */
+    /**
+     * Share of this opponent's actions that were bets or raises, or
+     * [NEUTRAL_AGGRESSION] until there is enough of a sample to judge.
+     */
     fun aggressionRate(seat: Int): Double {
         val total = totalActions[seat] ?: 0
-        if (total < MIN_SAMPLE) return 0.5
+        if (total < MIN_SAMPLE) return NEUTRAL_AGGRESSION
         return (aggressiveActions[seat] ?: 0).toDouble() / total
     }
 
     fun actionsObserved(seat: Int): Int = totalActions[seat] ?: 0
 
-    private companion object {
+    companion object {
         /** Below this, a read is noise rather than information. */
-        const val MIN_SAMPLE = 25
+        private const val MIN_SAMPLE = 25
+
+        /**
+         * What an ordinary player's bet-and-raise share of actions looks like.
+         *
+         * NOT 0.5. Actions counted include folds, checks and calls, so even an
+         * aggressive player only bets or raises about a third of the time.
+         * Treating 0.5 as neutral made every opponent read as passive, so the two
+         * skill levels that consult this model tightened against the whole table
+         * and lost money for it — the exploitation feature was a handicap.
+         */
+        const val NEUTRAL_AGGRESSION = 0.32
     }
 }

engine/src/commonMain/kotlin/com/jsjdesigns/poker/bot/Profiles.kt

@@ -17,10 +17,13 @@ enum class SkillLevel(
     val positionAwareness: Double,
     val readsOpponents: Boolean,
 ) {
+    // Levels must be far enough apart to be *felt*. An earlier spacing put
+    // Advanced and Expert within seed-to-seed noise of each other over 120k
+    // hands, which is not two difficulty levels — it is one, labelled twice.
     BEGINNER("Beginner", equityIterations = 120, errorRate = 0.30, potOddsRespect = 0.20, positionAwareness = 0.10, readsOpponents = false),
-    INTERMEDIATE("Intermediate", equityIterations = 600, errorRate = 0.14, potOddsRespect = 0.60, positionAwareness = 0.45, readsOpponents = false),
-    ADVANCED("Advanced", equityIterations = 1500, errorRate = 0.05, potOddsRespect = 0.88, positionAwareness = 0.80, readsOpponents = true),
-    EXPERT("Expert", equityIterations = 3000, errorRate = 0.015, potOddsRespect = 1.00, positionAwareness = 1.00, readsOpponents = true),
+    INTERMEDIATE("Intermediate", equityIterations = 500, errorRate = 0.16, potOddsRespect = 0.52, positionAwareness = 0.40, readsOpponents = false),
+    ADVANCED("Advanced", equityIterations = 1200, errorRate = 0.07, potOddsRespect = 0.76, positionAwareness = 0.70, readsOpponents = true),
+    EXPERT("Expert", equityIterations = 3000, errorRate = 0.010, potOddsRespect = 1.00, positionAwareness = 1.00, readsOpponents = true),
 }
 
 /**

engine/src/commonTest/kotlin/com/jsjdesigns/poker/bot/OpponentModelTest.kt

@@ -71,8 +71,28 @@ class OpponentModelTest {
     fun `unsampled opponents report a neutral read`() {
         val model = OpponentModel()
         model.observe(listOf(bet(1), bet(1)), handNumber = 1)
-        assertEquals(0.5, model.aggressionRate(1), "too few actions to form a read")
-        assertEquals(0.5, model.aggressionRate(9), "never seen at all")
+        assertEquals(
+            OpponentModel.NEUTRAL_AGGRESSION, model.aggressionRate(1),
+            "too few actions to form a read",
+        )
+        assertEquals(
+            OpponentModel.NEUTRAL_AGGRESSION, model.aggressionRate(9),
+            "never seen at all",
+        )
         assertTrue(model.actionsObserved(9) == 0)
     }
+
+    /**
+     * The neutral point is NOT 0.5. Folds, checks and calls are counted too, so
+     * even an aggressive player bets or raises only about a third of the time.
+     * Assuming 0.5 made every opponent read as passive, and the skill levels that
+     * consult this model tightened against the whole table and lost money for it.
+     */
+    @Test
+    fun `the neutral baseline reflects a realistic bet-raise share`() {
+        assertTrue(
+            OpponentModel.NEUTRAL_AGGRESSION in 0.2..0.45,
+            "a plausible neutral bet/raise share, was ${OpponentModel.NEUTRAL_AGGRESSION}",
+        )
+    }
 }

engine/src/commonTest/kotlin/com/jsjdesigns/poker/bot/ProfileBehaviourTest.kt

@@ -0,0 +1,116 @@
+package com.jsjdesigns.poker.bot
+
+import com.jsjdesigns.poker.game.Action
+import com.jsjdesigns.poker.game.ActionType
+import com.jsjdesigns.poker.game.DecisionContext
+import com.jsjdesigns.poker.game.Seat
+import com.jsjdesigns.poker.game.Street
+import kotlinx.coroutines.test.runTest
+import kotlin.math.abs
+import kotlin.random.Random
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+/**
+ * Profiles must play like the name on the tin.
+ *
+ * This is the regression that was missing: a "Rock" was running at 41% VPIP
+ * against a 12% label for several rounds, because the only checks were bb/100
+ * figures and nothing asserted that a style actually produced its own behaviour.
+ * A gradient can look perfectly healthy while every profile is misnamed.
+ */
+class ProfileBehaviourTest {
+
+    /** Deals random hands and measures how often this profile enters the pot. */
+    private suspend fun measureVpip(profile: BotProfile, hands: Int = 4000): Double {
+        val random = Random(20260725)
+        val bot = MathBot(profile, Random(99))
+        var entered = 0
+
+        repeat(hands) {
+            val a = random.nextInt(52)
+            var b = random.nextInt(52)
+            while (b == a) b = random.nextInt(52)
+
+            val seat = Seat(0, "P", 200, bot)
+            seat.hole = intArrayOf(a, b)
+            val ctx = DecisionContext(
+                street = Street.PREFLOP,
+                seat = seat,
+                board = IntArray(0),
+                pot = 3,
+                toCall = 2,
+                minRaiseTo = 4,
+                maxRaiseTo = 200,
+                activeOpponents = 5,
+                // Alternate position so the measurement is not biased either way.
+                seatsActingAfter = if (it % 2 == 0) 0 else 2,
+                bigBlind = 2,
+                history = emptyList(),
+                handNumber = it + 1,
+                decisionToken = (it + 1).toLong(),
+                bettingReopened = true,
+            )
+            val action = bot.act(ctx)
+            if (action.type != ActionType.FOLD) entered++
+        }
+        return entered.toDouble() / hands
+    }
+
+    private suspend fun assertPlaysLikeLabel(style: PlayStyle, skill: SkillLevel, tolerance: Double = 0.14) {
+        val vpip = measureVpip(BotProfile(style.label, skill, style))
+        assertTrue(
+            abs(vpip - style.looseness) <= tolerance,
+            "${skill.label} ${style.label}: looseness ${style.looseness} but entered " +
+                "${"%.1f".format(vpip * 100)}% of hands — the label should mean something",
+        )
+    }
+
+    @Test
+    fun `a rock plays like a rock at every skill level`() = runTest {
+        // The original failure: BEGINNER error rate dragged this to 41%.
+        for (skill in SkillLevel.entries) {
+            assertPlaysLikeLabel(PlayStyle.ROCK, skill)
+        }
+    }
+
+    @Test
+    fun `a maniac plays like a maniac at every skill level`() = runTest {
+        for (skill in SkillLevel.entries) {
+            assertPlaysLikeLabel(PlayStyle.MANIAC, skill)
+        }
+    }
+
+    @Test
+    fun `every style is recognisable at beginner skill`() = runTest {
+        // Beginner has the highest error rate, so this is where style is most at
+        // risk of being drowned out.
+        for (style in PlayStyle.ALL) {
+            assertPlaysLikeLabel(style, SkillLevel.BEGINNER)
+        }
+    }
+
+    @Test
+    fun `styles stay ordered by looseness regardless of skill`() = runTest {
+        for (skill in listOf(SkillLevel.BEGINNER, SkillLevel.EXPERT)) {
+            val measured = PlayStyle.ALL.map { it to measureVpip(BotProfile(it.label, skill, it)) }
+            val byLabel = measured.sortedBy { it.first.looseness }.map { it.first.label }
+            val byBehaviour = measured.sortedBy { it.second }.map { it.first.label }
+            assertTrue(
+                byLabel == byBehaviour,
+                "${skill.label}: styles ordered by looseness $byLabel but behave as $byBehaviour",
+            )
+        }
+    }
+
+    @Test
+    fun `skill does not silently widen a tight range`() = runTest {
+        val beginner = measureVpip(BotProfile("R", SkillLevel.BEGINNER, PlayStyle.ROCK))
+        val expert = measureVpip(BotProfile("R", SkillLevel.EXPERT, PlayStyle.ROCK))
+        assertTrue(
+            abs(beginner - expert) < 0.12,
+            "a beginner rock (${"%.1f".format(beginner * 100)}%) and an expert rock " +
+                "(${"%.1f".format(expert * 100)}%) should both be recognisably tight",
+        )
+    }
+}