diff --git a/tests/ClawdDotNet.Web.Tests/McpSocketTests.cs b/tests/ClawdDotNet.Web.Tests/McpSocketTests.cs
index fb3e213..14cfcb2 100644
--- a/tests/ClawdDotNet.Web.Tests/McpSocketTests.cs
+++ b/tests/ClawdDotNet.Web.Tests/McpSocketTests.cs
@@ -186,6 +186,65 @@ public sealed class McpSocketTests : IDisposable
         outcome.Text.ShouldContain("added: result.txt");
     }
 
+    /// <summary>
+    /// #712: The Claude Code path in the real sandbox, with a stand-in for <c>claude</c> —
+    /// the real one does not run on the test machine, and a test has no key. The stand-in
+    /// checks what Claude Code would be given (arguments, key, home, MCP configuration),
+    /// reaches the API host through the proxy, calls the MCP server the way Claude Code
+    /// would (the command from mcp.json) and answers in stream-json.
+    /// </summary>
+    [ForeignRunFact]
+    public async Task The_claude_code_path_holds_together_in_the_real_sandbox()
+    {
+        await using var host = NewHost();
+        await using var web = InstanceHttpHost.TryStart(host, NullLoggerFactory.Instance);
+        web.ShouldNotBeNull();
+
+        var bin = Path.Combine(_root, "fake-claude");
+        Directory.CreateDirectory(bin);
+        var claude = Path.Combine(bin, "claude");
+        File.WriteAllText(claude, string.Join("\n",
+            "#!/bin/sh",
+            """case " $* " in *dangerously*) echo "bypass passed" >&2; exit 9;; esac""",
+            """[ -n "$ANTHROPIC_API_KEY" ] || { echo "no key" >&2; exit 8; }""",
+            """[ -w "$HOME/.claude/settings.json" ] || { echo "no home" >&2; exit 7; }""",
+            """prompt=$(cat)""",
+            """api=$(curl -sS -o /dev/null -w '%{http_code}' --max-time 20 https://api.anthropic.com/ 2>&1)""",
+            """cmd=$(sed -n 's/.*"command":"\([^"]*\)".*/\1/p' /run/agent/mcp.json)""",
+            """tools=$(printf '%s\n' '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | CLAWD_MCP_TOKEN_FILE=/run/agent/mcp-token "$cmd" --mcp-bridge --socket /run/mcp.sock 2>&1 | tr -d '"')""",
+            """echo "changed by claude" > /work/answer.txt""",
+            """printf '%s\n' '{"type":"system","subtype":"init","model":"claude-test"}'""",
+            """printf '{"type":"result","subtype":"success","is_error":false,"num_turns":1,"result":"prompt=%s api=%s tools=%s","total_cost_usd":0.01,"usage":{"input_tokens":10,"output_tokens":5}}\n' "$prompt" "$api" "$tools" """,
+            ""));
+        if (OperatingSystem.IsLinux())
+            File.SetUnixFileMode(claude, UnixFileMode.UserRead | UnixFileMode.UserWrite | UnixFileMode.UserExecute);
+
+        var sandbox = (Core.Sandbox.BwrapSandbox)Core.Sandbox.BwrapSandbox.Detect(NullLogger.Instance);
+        var helper = Core.Sandbox.SandboxHelper.For(ForeignRunFactAttribute.HelperPath!);
+        sandbox.Helper = helper;
+        var settings = new Core.Runtimes.ClaudeCodeSettings { Executable = claude, ApiKey = "sk-ant-fake" };
+        var runner = new Core.Runtimes.ForeignRunner(sandbox, [new Core.Runtimes.ClaudeCodeRuntime(() => settings)], host.Mcp,
+            InstanceEndpoint.McpSocketPath(host.InstancePath), helper, NullLogger.Instance);
+
+        var agentDir = Path.Combine(host.InstancePath, "Agents", "Agent-coder");
+        Directory.CreateDirectory(Path.Combine(agentDir, "Workspace"));
+        var agent = new AgentConfig
+        {
+            AgentId = "coder", AgentDir = agentDir, WorkspacePath = Path.Combine(agentDir, "Workspace"),
+            Runtime = new Core.Runtimes.AgentRuntimeConfig { Kind = "claude-code", TimeoutMinutes = 2 }
+        };
+
+        var outcome = await runner.RunAsync(new Core.Runtimes.ForeignRunRequest(agent, "run-cc", null, "brief", "fix it"), _ => { }, CancellationToken.None);
+
+        outcome.Status.ShouldBe(AgentRunStatus.Completed, outcome.Text);
+        outcome.Text!.ShouldContain("prompt=fix it");
+        outcome.Text.ShouldNotContain("api=000", customMessage: "the API host is reached through the proxy");
+        outcome.Text.ShouldContain("name:Echo");
+        outcome.Text.ShouldContain("added: answer.txt");
+        outcome.Model.ShouldBe("claude-test");
+        outcome.CostUsd.ShouldBe(0.01m);
+    }
+
     private sealed class EchoTool : IAgentTool
     {
         public string Name => "Echo";