diff --git a/src/tui/tui.test.ts b/src/tui/tui.test.ts
index 9b46da66a99..2882cebcd64 100644
--- a/src/tui/tui.test.ts
+++ b/src/tui/tui.test.ts
@@ -74,6 +74,27 @@ describe("resolveTuiSessionKey", () => {
       }),
     ).toBe("agent:ops:incident");
   });
+
+  it("lowercases session keys with uppercase characters", () => {
+    // Uppercase in agent-prefixed form
+    expect(
+      resolveTuiSessionKey({
+        raw: "agent:main:Test1",
+        sessionScope: "global",
+        currentAgentId: "main",
+        sessionMainKey: "agent:main:main",
+      }),
+    ).toBe("agent:main:test1");
+    // Uppercase in bare form (prefixed by currentAgentId)
+    expect(
+      resolveTuiSessionKey({
+        raw: "Test1",
+        sessionScope: "global",
+        currentAgentId: "main",
+        sessionMainKey: "agent:main:main",
+      }),
+    ).toBe("agent:main:test1");
+  });
 });
 
 describe("resolveGatewayDisconnectState", () => {
diff --git a/src/tui/tui.ts b/src/tui/tui.ts
index 847245b3b67..fe365477d91 100644
--- a/src/tui/tui.ts
+++ b/src/tui/tui.ts
@@ -203,9 +203,9 @@ export function resolveTuiSessionKey(params: {
     return trimmed;
   }
   if (trimmed.startsWith("agent:")) {
-    return trimmed;
+    return trimmed.toLowerCase();
   }
-  return `agent:${params.currentAgentId}:${trimmed}`;
+  return `agent:${params.currentAgentId}:${trimmed.toLowerCase()}`;
 }
 
 export function resolveGatewayDisconnectState(reason?: string): {