Add exec_service proto

Author: afq984

exec_service/BUILD.bazel

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+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+proto_library(
+    name = "exec_service_proto",
+    srcs = ["exec_service.proto"],
+)

exec_service/README.md

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+A service to execute commands.
+
+Intended to be run inside a sandbox, with a socket exposed.
+Connected from a MCP or built-in integration of a coding agent.

exec_service/exec_service.proto

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+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package exec_service;
+
+// A simple command execution service.
+service ExecService {
+  // Executes a command and streams the output until completion.
+  rpc RunCommand(StartCommandRequest) returns (stream ServerEvent);
+}
+
+message StartCommandRequest {
+  // The raw shell command to execute.
+  string command_line = 1;
+
+  // The directory to execute the command in.
+  string working_dir = 2;
+}
+
+message ServerEvent {
+  oneof event {
+    // Incremental stdout/stderr from the command.
+    bytes output = 1;
+
+    // Sent exactly once when the command finishes.
+    ExitInfo exited = 2;
+  }
+}
+
+message ExitInfo {
+  int32 exit_code = 1;
+  // Populated only if the system failed to execute the command at all.
+  string error_message = 2;
+}