diff --git a/extension/llm/runner/io_manager/TARGETS b/extension/llm/runner/io_manager/TARGETS
new file mode 100644
index 00000000000..2341af9282f
--- /dev/null
+++ b/extension/llm/runner/io_manager/TARGETS
@@ -0,0 +1,8 @@
+# Any targets that should be shared between fbcode and xplat must be defined in
+# targets.bzl. This file can contain fbcode-only targets.
+
+load(":targets.bzl", "define_common_targets")
+
+oncall("executorch")
+
+define_common_targets()
diff --git a/extension/llm/runner/io_manager/io_manager.h b/extension/llm/runner/io_manager/io_manager.h
new file mode 100644
index 00000000000..0f6b1700ddf
--- /dev/null
+++ b/extension/llm/runner/io_manager/io_manager.h
@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <executorch/extension/tensor/tensor.h>
+#include <executorch/runtime/core/exec_aten/exec_aten.h>
+#include <executorch/runtime/executor/method.h>
+#include <executorch/runtime/executor/method_meta.h>
+
+namespace executorch {
+namespace extension {
+namespace llm {
+
+/**
+ * @brief Base class for managing input/output operations for LLM inference.
+ *
+ * IOManagerBase provides an interface for handling the input preparation and
+ * output processing for both prefill and decode phases of LLM inference.
+ * Derived classes must implement the virtual methods to provide specific IO
+ * management functionality.
+ */
+class ET_EXPERIMENTAL IOManagerBase {
+ public:
+  /**
+   * @brief Virtual destructor to allow proper cleanup in derived classes.
+   */
+  virtual ~IOManagerBase() = default;
+
+  /**
+   * @brief Initialize the IO manager with method metadata for prefill and
+   * decode operations.
+   *
+   * @param prefill_method The prefill method to initialize with.
+   * @param decode_method The decode method to initialize with.
+   */
+  ET_NODISCARD virtual runtime::Error init(
+      executorch::ET_RUNTIME_NAMESPACE::Method& prefill_method,
+      executorch::ET_RUNTIME_NAMESPACE::Method& decode_method) = 0;
+
+  /**
+   * @brief Reset the IO manager state.
+   *
+   * @param prefill_method The prefill method to reset with.
+   * @param decode_method The decode method to reset with.
+   */
+  ET_NODISCARD virtual runtime::Error reset(
+      executorch::ET_RUNTIME_NAMESPACE::Method& prefill_method,
+      executorch::ET_RUNTIME_NAMESPACE::Method& decode_method) = 0;
+
+  /**
+   * @brief Prepare inputs for the prefill phase of LLM inference.
+   *
+   * @param input The input tensor containing token IDs.
+   * @param start_pos The tensor containing the starting position of the current
+   * input within the context.
+   * @param prefill_method The prefill method to prepare inputs for.
+   * @return std::vector<executorch::runtime::EValue> Vector of prepared inputs
+   * for the prefill method.
+   */
+  virtual runtime::Result<std::vector<executorch::runtime::EValue>>
+  prepare_prefill(
+      const executorch::extension::TensorPtr& input,
+      const executorch::extension::TensorPtr& start_pos,
+      executorch::ET_RUNTIME_NAMESPACE::Method& prefill_method) = 0;
+
+  /**
+   * @brief Prepare inputs for the decode phase of LLM inference.
+   *
+   * @param input The input tensor containing token IDs.
+   * @param start_pos The tensor containing the starting position of the current
+   * input within the context.
+   * @param decode_method The decode method to prepare inputs for.
+   * @return std::vector<executorch::runtime::EValue> Vector of prepared inputs
+   * for the decode method.
+   */
+  virtual runtime::Result<std::vector<executorch::runtime::EValue>>
+  prepare_decode(
+      const executorch::extension::TensorPtr& input,
+      const executorch::extension::TensorPtr& start_pos,
+      executorch::ET_RUNTIME_NAMESPACE::Method& decode_method) = 0;
+
+  /**
+   * @brief Process and update internal state with outputs from the prefill
+   * phase.
+   *
+   * @param prefill_method The prefill method to update with outputs.
+   * @param model_outputs Vector of outputs from the prefill method execution.
+   */
+  ET_NODISCARD virtual runtime::Error update_prefill(
+      executorch::ET_RUNTIME_NAMESPACE::Method& prefill_method,
+      const std::vector<executorch::runtime::EValue>& model_outputs) = 0;
+
+  /**
+   * @brief Process and update internal state with outputs from the decode
+   * phase.
+   *
+   * @param decode_method The decode method to update with outputs.
+   * @param model_outputs Vector of outputs from the decode method execution.
+   */
+  ET_NODISCARD virtual runtime::Error update_decode(
+      const executorch::ET_RUNTIME_NAMESPACE::Method& decode_method,
+      const std::vector<executorch::runtime::EValue>& model_outputs) = 0;
+};
+
+} // namespace llm
+} // namespace extension
+} // namespace executorch
diff --git a/extension/llm/runner/io_manager/targets.bzl b/extension/llm/runner/io_manager/targets.bzl
new file mode 100644
index 00000000000..5081fa4d756
--- /dev/null
+++ b/extension/llm/runner/io_manager/targets.bzl
@@ -0,0 +1,22 @@
+load("@fbsource//xplat/executorch/build:runtime_wrapper.bzl", "runtime")
+
+def define_common_targets():
+    for aten in (True, False):
+        aten_suffix = "_aten" if aten else ""
+
+        # Interface for IOManager. No concrete impl from this dep.
+        runtime.cxx_library(
+            name = "io_manager" + aten_suffix,
+            exported_headers = [
+                "io_manager.h",
+            ],
+            deps = [
+                "//executorch/extension/module:module" + aten_suffix,
+                "//executorch/extension/tensor:tensor" + aten_suffix,
+                "//executorch/runtime/core/exec_aten:lib" + aten_suffix,
+                "//executorch/runtime/executor:program_no_prim_ops" + aten_suffix,
+            ],
+            visibility = [
+                "@EXECUTORCH_CLIENTS",
+            ],
+        )