diff --git a/.github/scripts/mock-registry.py b/.github/scripts/mock-registry.py
new file mode 100644
index 0000000..034cc46
--- /dev/null
+++ b/.github/scripts/mock-registry.py
@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Mock keypackage/account registry for the chat-cli CI smoketest.
+
+On startup the client registers its keypackage and account bundle. Publishing the
+bundle first fetches any existing record, so the stub answers:
+
+  * POST /v0/keypackage, POST /v0/account -> 200 (accept the write)
+  * GET  (any)                            -> 404 (nothing published yet)
+
+A 404 is what a fresh account looks like, which the client reads as "no existing
+record". This validates nothing — it only unblocks the smoketest; protocol-level
+behavior is covered by the workspace tests.
+"""
+
+from http.server import BaseHTTPRequestHandler, HTTPServer
+
+
+class Handler(BaseHTTPRequestHandler):
+    # Match the client's HTTP/1.1 requests so reqwest frames the response body.
+    protocol_version = "HTTP/1.1"
+
+    def _drain(self):
+        # Consume the request body so the client's request completes cleanly.
+        length = int(self.headers.get("Content-Length", 0))
+        if length:
+            self.rfile.read(length)
+
+    def _reply(self, status):
+        self.send_response(status)
+        self.send_header("Content-Length", "0")
+        self.end_headers()
+
+    def do_POST(self):
+        self._drain()
+        self._reply(200)
+
+    def do_GET(self):
+        self._drain()
+        self._reply(404)
+
+    def log_message(self, *args):
+        pass
+
+
+if __name__ == "__main__":
+    HTTPServer(("127.0.0.1", 18080), Handler).serve_forever()
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 41a9bb5..3ec919f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -73,4 +73,15 @@ jobs:
       - name: Build chat-cli (logos-delivery)
         run: nix develop -c bash -c 'LOGOS_DELIVERY_LIB_DIR=./result/lib cargo build --release -p chat-cli'
       - name: Run chat-cli smoketest
-        run: nix develop -c ./target/release/chat-cli --name ci-test --smoketest
+        # The client registers against the keypackage/account registry on
+        # startup, so stand up a mock that accepts those calls. It runs on the
+        # system Python (no Nix needed); only chat-cli needs the dev shell.
+        run: |
+          python3 .github/scripts/mock-registry.py &
+          mock_pid=$!
+          trap 'kill "$mock_pid" 2>/dev/null || true' EXIT
+          for _ in $(seq 1 50); do
+            curl -s -o /dev/null http://127.0.0.1:18080/ && break
+            sleep 0.2
+          done
+          nix develop -c ./target/release/chat-cli --name ci-test --smoketest