diff --git a/src/hooks/start-work/start-work-hook.ts b/src/hooks/start-work/start-work-hook.ts
index 357f9552a..f916c2eae 100644
--- a/src/hooks/start-work/start-work-hook.ts
+++ b/src/hooks/start-work/start-work-hook.ts
@@ -85,12 +85,12 @@ export function createStartWorkHook(ctx: PluginInput) {
     const activeAgent = isAgentRegistered("atlas")
       ? "atlas"
       : "sisyphus"
-    const activeAgentDisplayName = getAgentDisplayName(activeAgent)
+    const activeAgentDisplayName = activeAgent === "atlas"
+      ? getAgentListDisplayName(activeAgent)
+      : getAgentDisplayName(activeAgent)
     updateSessionAgent(input.sessionID, activeAgent)
     if (output.message) {
-      // Use config key for agent field to avoid HTTP header validation issues
-      // Display names like "Atlas (Plan Executor)" contain parens that are invalid in headers
-      output.message["agent"] = activeAgent
+      output.message["agent"] = activeAgentDisplayName
     }
 
     const existingState = readBoulderState(ctx.directory)