diff --git a/CLAUDE.md b/CLAUDE.md
index 581bf68..e9f1a65 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -136,6 +136,10 @@ Three-layer split; `JCA` is the single global namespace:
 - Unknown joker keys (from other mods) must keep scoring 0 — never index
   `JCA.db[key]` without a nil guard.
 - Display names go through `localize{type='name_text', set='Joker', ...}` with a
-  pcall + `center.name` fallback; anti-synergies are deliberately not modeled.
+  pcall + `center.name` fallback.
+- Anti-synergies never affect scores. Known traps are warning-only data:
+  `CLASHES` (pairwise, red "Clashes -" tooltip line vs owned jokers) and
+  `CAUTIONS` (per-joker, buy-area "Caution:" line) in `synergies.lua`, same
+  ~34-char blurb budget as `PAIRS`. Learning mode keeps warnings visible.
 - The UI hooks are the only untested-in-game surface; if a tooltip regression is
   reported, suspect the `aut.info` entry format first and check the lovely log.
diff --git a/main.lua b/main.lua
index 07b4afb..c0e0bc4 100644
--- a/main.lua
+++ b/main.lua
@@ -36,6 +36,13 @@ for _, p in ipairs(data.pairs) do
     JCA.pair_blurb[pair_key(p[1], p[2])] = p[3]
 end
 
+-- Known traps: warning-only, never part of the synergy score.
+JCA.clash_blurb = {}
+for _, p in ipairs(data.clashes or {}) do
+    JCA.clash_blurb[pair_key(p[1], p[2])] = p[3]
+end
+JCA.cautions = data.cautions or {}
+
 -- Scoring -------------------------------------------------------------------
 
 -- Synergy score between two joker center keys. 0 = no known synergy.
@@ -205,6 +212,7 @@ end
 local function tooltip_rows(card)
     -- Touch mode enlarges every advice row for phone screens (see config.lua).
     local S = JCA.config.touch_mode and 1.4 or 1
+    local key = card.config.center.key
     local partners, total = JCA.partners_for(card)
 
     local rows = {}
@@ -239,7 +247,6 @@ local function tooltip_rows(card)
         else
             text_row('Active combos with:')
         end
-        local key = card.config.center.key
         local shown = math.min(3, #partners)
         for i = 1, shown do
             local p = partners[i]
@@ -263,6 +270,26 @@ local function tooltip_rows(card)
             text_row('Strong pick for this build!', G.C.GREEN)
         end
     end
+    -- Anti-synergy warnings: known traps against the board you keep. These
+    -- never touch the score (learning mode keeps them too — they teach).
+    if G.jokers and G.jokers.cards then
+        for _, owned in ipairs(G.jokers.cards) do
+            if owned ~= card and owned.config.center.set == 'Joker' then
+                local warn = JCA.clash_blurb[pair_key(key, owned.config.center.key)]
+                if warn then
+                    rows[#rows + 1] = {
+                        {n = G.UIT.T, config = {
+                            text = 'Clashes - ' .. name_of(owned.config.center.key) .. ': ',
+                            colour = G.C.RED, scale = 0.3 * S}},
+                        {n = G.UIT.T, config = {text = warn,
+                            colour = G.C.UI.TEXT_DARK, scale = 0.3 * S}},
+                    }
+                end
+            end
+        end
+    end
+    local caution = in_buy_area(card) and JCA.cautions[key]
+    if caution then text_row('Caution: ' .. caution, G.C.RED) end
     rows.name = 'Combo Advisor'
     return rows
 end
diff --git a/synergies.lua b/synergies.lua
index 95d731d..eb8a76e 100644
--- a/synergies.lua
+++ b/synergies.lua
@@ -214,6 +214,25 @@ local PAIRS = {
     {'j_oops',          'j_lucky_cat',       'better odds, more Lucky payoffs'},
 }
 
+-- Known traps: pairs that actively hurt each other. Warning-only — they
+-- never subtract from the synergy score; the tooltip just flags them with
+-- a red "Clashes" line. Keep warnings under ~34 chars (one tooltip row).
+local CLASHES = {
+    {'j_ride_the_bus', 'j_pareidolia',  'every card counts as a face'},
+    {'j_vampire',      'j_steel_joker', 'drains the Steel it counts'},
+    {'j_vampire',      'j_lucky_cat',   'strips Lucky cards before they pay'},
+    {'j_smeared',      'j_flower_pot',  'merged suits cannot make all four'},
+}
+
+-- Per-joker cautions for the buy-area tooltip: the joker is fine on its
+-- own, but it interacts badly with a board you want to keep. Same length
+-- budget as clash warnings.
+local CAUTIONS = {
+    j_ceremonial = 'eats the joker to its right',
+    j_madness    = 'destroys a random joker each blind',
+    j_stencil    = 'xMult grows with EMPTY joker slots',
+}
+
 -- How to phrase a tag link in the tooltip, from the partner's perspective:
 -- `give` when the partner provides the tag, `want` when the partner consumes
 -- it, `both` for cluster tags where the pair simply shares the theme.
@@ -307,5 +326,5 @@ for _, entry in pairs(J) do
     entry.gives, entry.wants = g, w
 end
 
-return { jokers = J, pairs = PAIRS, tag_text = TAG_TEXT, tag_order = TAG_ORDER,
-    theme_info = THEME_INFO }
+return { jokers = J, pairs = PAIRS, clashes = CLASHES, cautions = CAUTIONS,
+    tag_text = TAG_TEXT, tag_order = TAG_ORDER, theme_info = THEME_INFO }