diff --git a/services/assistant-api/src/main/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimeProperties.kt b/services/assistant-api/src/main/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimeProperties.kt
index fa899df5..782d9a3b 100644
--- a/services/assistant-api/src/main/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimeProperties.kt
+++ b/services/assistant-api/src/main/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimeProperties.kt
@@ -73,4 +73,23 @@ data class AgentRuntimeProperties(
     // starting with the `gh` wrapper degrading to a no-op.
     val githubAppBearerSecret: String = "github-app",
     val githubAppBearerSecretKey: String = "token-bearer",
-)
+) {
+    init {
+        require(defaultMcpProfile in VALID_MCP_PROFILES) {
+            "agent-runtime.default-mcp-profile must be one of " +
+                VALID_MCP_PROFILES.joinToString(", ") +
+                "; got '$defaultMcpProfile'"
+        }
+    }
+
+    companion object {
+        val VALID_MCP_PROFILES: Set<String> =
+            setOf(
+                "minimal",
+                "frontend",
+                "cluster",
+                "code-intel",
+                "full-diagnostic",
+            )
+    }
+}
diff --git a/services/assistant-api/src/test/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimePropertiesBindingTest.kt b/services/assistant-api/src/test/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimePropertiesBindingTest.kt
index 53a9d536..e1014a24 100644
--- a/services/assistant-api/src/test/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimePropertiesBindingTest.kt
+++ b/services/assistant-api/src/test/kotlin/com/jorisjonkers/personalstack/assistant/config/AgentRuntimePropertiesBindingTest.kt
@@ -1,6 +1,7 @@
 package com.jorisjonkers.personalstack.assistant.config
 
 import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatThrownBy
 import org.junit.jupiter.api.Test
 import org.springframework.boot.context.properties.bind.Binder
 import org.springframework.boot.context.properties.source.MapConfigurationPropertySource
@@ -73,6 +74,32 @@ class AgentRuntimePropertiesBindingTest {
         assertThat(props.nodeSelector).containsKey("personal-stacknode")
     }
 
+    @Test
+    fun `default mcp profile accepts every declared runner profile`() {
+        AgentRuntimeProperties.VALID_MCP_PROFILES.forEach { profile ->
+            val props =
+                bind(
+                    base +
+                        mapOf("agent-runtime.default-mcp-profile" to profile),
+                )
+
+            assertThat(props.defaultMcpProfile).isEqualTo(profile)
+        }
+    }
+
+    @Test
+    fun `default mcp profile rejects unknown values`() {
+        assertThatThrownBy {
+            bind(
+                base +
+                    mapOf("agent-runtime.default-mcp-profile" to "frontned"),
+            )
+        }.rootCause()
+            .isInstanceOf(IllegalArgumentException::class.java)
+            .hasMessageContaining("agent-runtime.default-mcp-profile")
+            .hasMessageContaining("frontned")
+    }
+
     private fun bind(properties: Map<String, String>): AgentRuntimeProperties {
         val source = MapConfigurationPropertySource(properties)
         return Binder(source)