fix: federation client accepts self-signed TLS certificates

httpx.AsyncClient used default SSL verification, rejecting self-signed
certs from muxplex setup-tls. Remote HTTPS instances (e.g., setup-tls
with self-signed fallback) were unreachable — all federation requests
failed with CERTIFICATE_VERIFY_FAILED. Fix: verify=False on the
federation client. Bearer token auth still protects authorization.

muxplex/main.py

@@ -176,7 +176,14 @@ async def lifespan(app: FastAPI):
     except Exception:
         pass  # tmux not running at startup is OK; hook will be set on first poll
 
-    app.state.federation_client = httpx.AsyncClient(timeout=5.0, follow_redirects=False)
+    app.state.federation_client = httpx.AsyncClient(
+        timeout=5.0,
+        follow_redirects=False,
+        verify=False,  # nosec B501 — muxplex is a dev tool for LAN/Tailscale use;
+        # self-signed certs from `muxplex setup-tls` must be accepted for federation.
+        # Bearer token auth handles authorization. Users who need cert verification
+        # should use mkcert (CA-trusted) or Tailscale (LE-trusted) certs.
+    )
 
     yield
 

muxplex/tests/test_api.py

@@ -1583,6 +1583,32 @@ def test_federation_client_exists_on_app_state(monkeypatch):
     )
 
 
+def test_federation_client_disables_ssl_verification(monkeypatch):
+    """Federation httpx client must disable SSL verification for self-signed certs.
+
+    muxplex setup-tls can generate self-signed certificates. When a remote instance
+    uses such a cert, httpx's default SSL verification rejects it with
+    CERTIFICATE_VERIFY_FAILED, making the remote unreachable in federation.
+    The client must use verify=False so self-signed certs on LAN/Tailscale remotes
+    are accepted. Bearer token auth still protects authorization.
+    """
+    import ssl
+
+    monkeypatch.setenv("MUXPLEX_PASSWORD", "test-password")
+
+    with TestClient(app):
+        client = app.state.federation_client
+        # httpx.AsyncClient(verify=False) creates a transport whose SSL context
+        # has verify_mode=ssl.CERT_NONE (0). If verify=True (default), it would
+        # use CERT_REQUIRED (2).
+        ssl_context = client._transport._pool._ssl_context
+        assert ssl_context is not None, "federation_client SSL context must be present"
+        assert ssl_context.verify_mode == ssl.CERT_NONE, (
+            "federation_client must use verify=False (CERT_NONE) "
+            "to support self-signed certificates on remote instances"
+        )
+
+
 # ---------------------------------------------------------------------------
 # GET /api/federation/sessions (task-5)
 # ---------------------------------------------------------------------------