diff --git a/charts/openab/templates/configmap.yaml b/charts/openab/templates/configmap.yaml
index ed729a0..fdd55f6 100644
--- a/charts/openab/templates/configmap.yaml
+++ b/charts/openab/templates/configmap.yaml
@@ -44,10 +44,10 @@ data:
     {{- end }}
     {{- /* allowUserMessages: controls whether the bot requires @mention in threads (Discord) */ -}}
     {{- if $cfg.discord.allowUserMessages }}
-    {{- if not (has $cfg.discord.allowUserMessages (list "involved" "mentions")) }}
-    {{- fail (printf "agents.%s.discord.allowUserMessages must be one of: involved, mentions — got: %s" $name $cfg.discord.allowUserMessages) }}
+    {{- if not (has $cfg.discord.allowUserMessages (list "involved" "mentions" "multibot-mentions")) }}
+    {{- fail (printf "agents.%s.discord.allowUserMessages must be one of: involved, mentions, multibot-mentions (use hyphen form, not underscore) — got: %s" $name $cfg.discord.allowUserMessages) }}
     {{- end }}
-    allow_user_messages = {{ $cfg.discord.allowUserMessages | toJson }}  {{- /* involved (default): respond in bot's threads without @mention | mentions: always require @mention */ -}}
+    allow_user_messages = {{ $cfg.discord.allowUserMessages | toJson }}  {{- /* involved (default): respond in bot's threads without @mention | mentions: always require @mention | multibot-mentions: require @mention only when another bot has posted in the thread */ -}}
     {{- end }}
     {{- end }}
 
@@ -77,10 +77,10 @@ data:
     trusted_bot_ids = {{ ($cfg.slack).trustedBotIds | toJson }}
     {{- end }}
     {{- if ($cfg.slack).allowUserMessages }}
-    {{- if not (has ($cfg.slack).allowUserMessages (list "involved" "mentions")) }}
-    {{- fail (printf "agents.%s.slack.allowUserMessages must be one of: involved, mentions — got: %s" $name ($cfg.slack).allowUserMessages) }}
+    {{- if not (has ($cfg.slack).allowUserMessages (list "involved" "mentions" "multibot-mentions")) }}
+    {{- fail (printf "agents.%s.slack.allowUserMessages must be one of: involved, mentions, multibot-mentions (use hyphen form, not underscore) — got: %s" $name ($cfg.slack).allowUserMessages) }}
     {{- end }}
-    allow_user_messages = {{ ($cfg.slack).allowUserMessages | toJson }}  {{- /* involved (default): respond in bot's threads without @mention | mentions: always require @mention */ -}}
+    allow_user_messages = {{ ($cfg.slack).allowUserMessages | toJson }}  {{- /* involved (default): respond in bot's threads without @mention | mentions: always require @mention | multibot-mentions: require @mention only when another bot has posted in the thread */ -}}
     {{- end }}
     {{- end }}
 
diff --git a/charts/openab/tests/configmap_test.yaml b/charts/openab/tests/configmap_test.yaml
index 3735caa..6af408c 100644
--- a/charts/openab/tests/configmap_test.yaml
+++ b/charts/openab/tests/configmap_test.yaml
@@ -57,3 +57,43 @@ tests:
       - matchRegex:
           path: data["config.toml"]
           pattern: 'allow_bot_messages = "off"'
+
+  - it: renders allow_user_messages = "involved"
+    set:
+      agents.kiro.discord.allowUserMessages: involved
+    asserts:
+      - matchRegex:
+          path: data["config.toml"]
+          pattern: 'allow_user_messages = "involved"'
+
+  - it: renders allow_user_messages = "mentions"
+    set:
+      agents.kiro.discord.allowUserMessages: mentions
+    asserts:
+      - matchRegex:
+          path: data["config.toml"]
+          pattern: 'allow_user_messages = "mentions"'
+
+  - it: renders allow_user_messages = "multibot-mentions"
+    set:
+      agents.kiro.discord.allowUserMessages: multibot-mentions
+    asserts:
+      - matchRegex:
+          path: data["config.toml"]
+          pattern: 'allow_user_messages = "multibot-mentions"'
+
+  - it: rejects invalid allowUserMessages value
+    set:
+      agents.kiro.discord.allowUserMessages: yolo
+    asserts:
+      - failedTemplate:
+          errorPattern: "must be one of: involved, mentions, multibot-mentions"
+
+  - it: renders slack allow_user_messages = "multibot-mentions"
+    set:
+      agents.kiro.slack.enabled: true
+      agents.kiro.slack.allowUserMessages: multibot-mentions
+    asserts:
+      - matchRegex:
+          path: data["config.toml"]
+          pattern: 'allow_user_messages = "multibot-mentions"'
diff --git a/charts/openab/values.yaml b/charts/openab/values.yaml
index 7488535..c7468a4 100644
--- a/charts/openab/values.yaml
+++ b/charts/openab/values.yaml
@@ -141,9 +141,12 @@ agents:
       allowBotMessages: "off"
       # trustedBotIds: Bot User IDs (U...) — find via Slack UI: click bot profile → Copy member ID
       trustedBotIds: []
-      # allowUserMessages: "involved" (default) | "mentions"
+      # allowUserMessages: "involved" (default) | "mentions" | "multibot-mentions"
       # "involved" = respond to thread follow-ups without @mention if bot has participated
       # "mentions" = always require @mention
+      # "multibot-mentions" = same as "involved" in single-bot threads; require @mention
+      #                      only when another bot has also posted in the thread
+      #                      (recommended for multi-bot deployments)
       allowUserMessages: "involved"
     workingDir: /home/agent
     env: {}