fix: consolidate provider behaviour + fix multi-turn provider corruption

apps/harness/lib/harness/providers/claude_session.ex

@@ -17,7 +17,6 @@ defmodule Harness.Providers.ClaudeSession do
   @behaviour Harness.Providers.ProviderBehaviour
 
   use GenServer, restart: :temporary
-  @behaviour Harness.ProviderSession
 
   alias Harness.Event
 
@@ -88,6 +87,7 @@ defmodule Harness.Providers.ClaudeSession do
     GenServer.stop(pid, :normal)
   end
 
+  @impl Harness.Providers.ProviderBehaviour
   def wait_for_ready(_pid, _timeout \\ 30_000) do
     # Unlike CodexSession which starts a persistent process in init,
     # ClaudeSession spawns the CLI process lazily on each send_turn.

apps/harness/lib/harness/providers/codex_session.ex

@@ -17,7 +17,6 @@ defmodule Harness.Providers.CodexSession do
   @behaviour Harness.Providers.ProviderBehaviour
 
   use GenServer, restart: :temporary
-  @behaviour Harness.ProviderSession
 
   alias Harness.JsonRpc
   alias Harness.Event
@@ -151,6 +150,7 @@ defmodule Harness.Providers.CodexSession do
     GenServer.stop(pid, :normal)
   end
 
+  @impl Harness.Providers.ProviderBehaviour
   def wait_for_ready(pid, timeout \\ 30_000) do
     GenServer.call(pid, :wait_for_ready, timeout)
   end
@@ -197,22 +197,14 @@ defmodule Harness.Providers.CodexSession do
   def handle_info(:initialize, state) do
     {id, state} = next_request_id(state)
 
-    codex_opts = get_in(state.params, ["providerOptions", "codex"]) || %{}
-    experimental_api = Map.get(codex_opts, "experimentalApi", false)
-
-    capabilities =
-      if experimental_api do
-        %{"experimentalApi" => true}
-      else
-        %{}
-      end
-
     initialize_params = %{
       "clientInfo" => %{
         "name" => "t3-harness",
         "version" => "0.1.0"
       },
-      "capabilities" => capabilities
+      "capabilities" => %{
+        "experimentalApi" => true
+      }
     }
 
     state = send_rpc_request(state, id, "initialize", initialize_params)

apps/harness/lib/harness/providers/cursor_session.ex

@@ -11,7 +11,6 @@ defmodule Harness.Providers.CursorSession do
   @behaviour Harness.Providers.ProviderBehaviour
 
   use GenServer, restart: :temporary
-  @behaviour Harness.ProviderSession
 
   alias Harness.Event
 
@@ -82,6 +81,7 @@ defmodule Harness.Providers.CursorSession do
     GenServer.stop(pid, :normal)
   end
 
+  @impl Harness.Providers.ProviderBehaviour
   def wait_for_ready(_pid, _timeout \\ 30_000) do
     # Cursor is ready immediately — spawns process on send_turn, not in init.
     :ok

apps/harness/lib/harness/providers/mock_session.ex

@@ -11,8 +11,8 @@ defmodule Harness.Providers.MockSession do
     - deltaSizeKb: size of each delta in KB (default: 1)
     - delayMs: delay between deltas in ms (default: 10)
   """
+  @behaviour Harness.Providers.ProviderBehaviour
   use GenServer, restart: :temporary
-  @behaviour Harness.ProviderSession
 
   alias Harness.JsonRpc
   alias Harness.Event
@@ -36,6 +36,7 @@ defmodule Harness.Providers.MockSession do
 
   @request_timeout 30_000
 
+  @impl Harness.Providers.ProviderBehaviour
   def start_link(opts) do
     thread_id = Map.fetch!(opts, :thread_id)
 
@@ -44,17 +45,27 @@ defmodule Harness.Providers.MockSession do
     )
   end
 
+  @impl Harness.Providers.ProviderBehaviour
   def send_turn(pid, params), do: GenServer.call(pid, {:send_turn, params}, 60_000)
+  @impl Harness.Providers.ProviderBehaviour
   def interrupt_turn(pid, _tid, _turn_id), do: GenServer.call(pid, :interrupt_turn)
+  @impl Harness.Providers.ProviderBehaviour
   def respond_to_approval(_, _, _), do: :ok
+  @impl Harness.Providers.ProviderBehaviour
   def respond_to_user_input(_, _, _), do: :ok
+  @impl Harness.Providers.ProviderBehaviour
   def read_thread(_, _), do: {:ok, %{}}
+  @impl Harness.Providers.ProviderBehaviour
   def rollback_thread(_, _, _), do: {:ok, %{}}
 
+  @impl Harness.Providers.ProviderBehaviour
   def wait_for_ready(pid, timeout \\ 30_000) do
     GenServer.call(pid, :wait_for_ready, timeout)
   end
 
+  @impl Harness.Providers.ProviderBehaviour
+  def stop(pid), do: GenServer.stop(pid)
+
   @impl true
   def init(opts) do
     state = %__MODULE__{

apps/harness/lib/harness/providers/opencode_session.ex

@@ -38,7 +38,6 @@ defmodule Harness.Providers.OpenCodeSession do
   @behaviour Harness.Providers.ProviderBehaviour
 
   use GenServer, restart: :temporary
-  @behaviour Harness.ProviderSession
 
   alias Harness.Event
 
@@ -118,6 +117,7 @@ defmodule Harness.Providers.OpenCodeSession do
     GenServer.stop(pid, :normal)
   end
 
+  @impl Harness.Providers.ProviderBehaviour
   def wait_for_ready(pid, timeout \\ 30_000) do
     GenServer.call(pid, :wait_for_ready, timeout)
   end

apps/web/src/store.ts

@@ -193,7 +193,12 @@ function toLegacySessionStatus(
 }
 
 function toLegacyProvider(providerName: string | null): ProviderKind {
-  if (providerName === "codex" || providerName === "claudeAgent") {
+  if (
+    providerName === "codex" ||
+    providerName === "claudeAgent" ||
+    providerName === "cursor" ||
+    providerName === "opencode"
+  ) {
     return providerName;
   }
   return "codex";