Laufzeiten: die MCP-Bruecke ist auch ohne Starter in der Sandbox (#712)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Core/Runtimes/ClaudeCodeRuntime.cs

@@ -101,7 +101,7 @@ public sealed class ClaudeCodeRuntime(Func<ClaudeCodeSettings> settings) : IFore
             ["CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC"] = "1"
         };
 
-        var readOnly = new List<string>(config.ReadOnlyPaths);
+        var readOnly = new List<string>(config.ReadOnlyPaths.Concat(context.HelperPaths()));
         var directory = Path.GetDirectoryName(executable)!;
         if (!directory.StartsWith("/usr/", StringComparison.Ordinal))
             readOnly.Add(directory);

src/ClawdDotNet.Core/Runtimes/CommandRuntime.cs

@@ -25,7 +25,7 @@ public sealed class CommandRuntime : IForeignRuntime
         File.WriteAllText(Path.Combine(context.PrivateDirectory, ForeignRunContext.BriefingFileName), context.Briefing);
 
         var command = runtime.Command.Trim();
-        var readOnly = new List<string>();
+        var readOnly = new List<string>(context.HelperPaths());
         if (Path.IsPathRooted(command))
         {
             var directory = Path.GetDirectoryName(command)!;

src/ClawdDotNet.Core/Runtimes/ForeignRuntime.cs

@@ -56,6 +56,12 @@ public sealed record ForeignRunContext
         return mounts;
     }
 
+    /// <summary>
+    /// What must be visible read-only for the MCP bridge: the application. Mounted whenever
+    /// there is MCP — not only when the launcher runs, which needs network or secrets.
+    /// </summary>
+    public IReadOnlyList<string> HelperPaths() => HasMcp ? Helper!.ReadOnlyPaths : [];
+
     /// <summary>What a program in the sandbox needs to reach the MCP server itself.</summary>
     public IReadOnlyDictionary<string, string> McpEnvironment()
     {
@@ -72,6 +78,8 @@ public sealed record ForeignRunContext
             environment["CLAWD_MCP_SOCKET"] = McpSocketInSandbox;
             environment[Mcp.McpStdioBridge.TokenFileVariable] = Private + "/" + TokenFileName;
             environment["CLAWD_HELPER"] = Helper!.Executable;
+            foreach (var (key, value) in Helper.Environment)
+                environment[key] = value;
         }
         return environment;
     }

src/ClawdDotNet.Core/Sandbox/BwrapSandbox.cs

@@ -223,7 +223,7 @@ public sealed class BwrapSandbox : ISandboxRunner
         // #712: what the launcher needs — the helper itself, the proxy's socket, the secrets.
         if (request.NeedsLauncher && helper is not null)
         {
-            foreach (var path in helper.ReadOnlyPaths)
+            foreach (var path in helper.ReadOnlyPaths.Except(request.ReadOnlyPaths.Select(Path.GetFullPath)))
                 args.AddRange(["--ro-bind", path, path]);
             if (launch.EgressSocket is { } socket)
                 args.AddRange(["--bind", socket, SandboxPaths.EgressSocket]);

tests/ClawdDotNet.Core.Tests/Runtimes/ForeignRuntimeTests.cs

@@ -452,6 +452,20 @@ public sealed class ForeignRuntimeTests : IDisposable
         sandbox.Request.Environment["CLAWD_TASK_ID"].ShouldBe("t-7");
     }
 
+    [Fact]
+    public void With_mcp_the_bridge_is_there_even_without_the_launcher()
+    {
+        // No network, no secrets — no launcher. The command still calls $CLAWD_HELPER.
+        _agent.Runtime = new AgentRuntimeConfig { Kind = RuntimeKinds.Command, Command = "/bin/sh" };
+
+        var request = new CommandRuntime().Prepare(Context());
+
+        request.NeedsLauncher.ShouldBeFalse();
+        request.ReadOnlyPaths.ShouldContain("/opt/clawd");
+        request.Environment["CLAWD_HELPER"].ShouldBe("/opt/clawd/ClawdDotNet");
+        request.Environment["DOTNET_ROOT"].ShouldBe("/usr/lib/dotnet");
+    }
+
     [Fact]
     public async Task A_failing_command_is_a_failed_run_with_its_reason()
     {

tests/ClawdDotNet.Web.Tests/McpSocketTests.cs

@@ -170,7 +170,7 @@ public sealed class McpSocketTests : IDisposable
             """m1='{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"t","version":"1"}}}'""",
             """m2='{"jsonrpc":"2.0","id":2,"method":"tools/list"}'""",
             """m3='{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"Echo","arguments":{}}}'""",
-            """printf '%s\n' "$m1" "$m2" "$m3" | "$CLAWD_HELPER" --mcp-bridge --socket "$CLAWD_MCP_SOCKET" """,
+            """printf '%s\n' "$m1" "$m2" "$m3" | "$CLAWD_HELPER" --mcp-bridge --socket "$CLAWD_MCP_SOCKET" 2>&1""",
             "echo done > /work/result.txt");
         var agent = new AgentConfig
         {