diff --git a/ffi/connectors.json b/ffi/connectors.json
new file mode 100644
index 00000000..7347d71a
--- /dev/null
+++ b/ffi/connectors.json
@@ -0,0 +1,22 @@
+{
+  "_spdx": "MPL-2.0",
+  "_note": "Golden source-of-truth for the hexadeca-connector wire contract. The Zig enum (ffi/zig/src/hexadeca.zig), the Idris2 ABI (src/abi/Types.idr), and the Rust client (clients/rust/hypatia-client/src/connector.rs) MUST all agree with this list, in this exact order; id is the C ABI wire id. Drift is guarded by test/hexadeca_contract_test.exs. Wire ordering is load-bearing -- do not renumber.",
+  "connectors": [
+    { "id": 0, "name": "grpc" },
+    { "id": 1, "name": "graphql" },
+    { "id": 2, "name": "rest" },
+    { "id": 3, "name": "flatbuffers" },
+    { "id": 4, "name": "bebop" },
+    { "id": 5, "name": "jsonrpc" },
+    { "id": 6, "name": "websocket" },
+    { "id": 7, "name": "mqtt" },
+    { "id": 8, "name": "trpc" },
+    { "id": 9, "name": "capnproto" },
+    { "id": 10, "name": "soap" },
+    { "id": 11, "name": "verisimdb-rest" },
+    { "id": 12, "name": "bsp" },
+    { "id": 13, "name": "scip" },
+    { "id": 14, "name": "ipfs" },
+    { "id": 15, "name": "arrow-flight" }
+  ]
+}
diff --git a/test/hexadeca_contract_test.exs b/test/hexadeca_contract_test.exs
new file mode 100644
index 00000000..b45b1905
--- /dev/null
+++ b/test/hexadeca_contract_test.exs
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: MPL-2.0
+defmodule Hypatia.HexadecaContractTest do
+  @moduledoc false
+  use ExUnit.Case, async: true
+
+  # Single-oracle drift guard for the hexadeca-connector wire contract.
+  #
+  # `ffi/connectors.json` is the golden source-of-truth for the 16-connector
+  # surface. The Zig enum, the Idris2 ABI, and the Rust client each mirror it;
+  # this test reads the golden plus all three source files and fails if any
+  # mirror drifts in name or order. Wire ordering is load-bearing
+  # (see ffi/zig/src/hexadeca.zig).
+
+  @root Path.expand("..", __DIR__)
+  @golden Path.join(@root, "ffi/connectors.json")
+
+  @sources [
+    {"Zig (hexadeca.zig)", Path.join(@root, "ffi/zig/src/hexadeca.zig"),
+     ~r/\.\w+\s*=>\s*"([a-z0-9-]+)"/},
+    {"Idris2 (Types.idr)", Path.join(@root, "src/abi/Types.idr"),
+     ~r/connectorName\s+\w+\s*=\s*"([a-z0-9-]+)"/},
+    {"Rust (connector.rs)", Path.join(@root, "clients/rust/hypatia-client/src/connector.rs"),
+     ~r/Connector::\w+\s*=>\s*"([a-z0-9-]+)"/}
+  ]
+
+  defp golden_connectors do
+    @golden |> File.read!() |> Jason.decode!() |> Map.fetch!("connectors")
+  end
+
+  defp names_in(path, regex) do
+    regex |> Regex.scan(File.read!(path)) |> Enum.map(fn [_, name] -> name end)
+  end
+
+  test "golden fixture lists the 16 connectors with sequential wire ids" do
+    conns = golden_connectors()
+    assert length(conns) == 16
+    assert Enum.map(conns, & &1["id"]) == Enum.to_list(0..15)
+  end
+
+  test "every language mirror matches the golden in name and order" do
+    golden_names = Enum.map(golden_connectors(), & &1["name"])
+
+    for {label, path, regex} <- @sources do
+      names = names_in(path, regex)
+
+      assert length(names) == 16,
+             "#{label}: expected 16 connector names, found #{length(names)}"
+
+      assert names == golden_names,
+             "#{label} drifted from ffi/connectors.json\n  golden: #{inspect(golden_names)}\n  found:  #{inspect(names)}"
+    end
+  end
+end