diff --git a/src/lib/execution/execution-backend.ts b/src/lib/execution/execution-backend.ts
new file mode 100644
index 0000000..35e2ba8
--- /dev/null
+++ b/src/lib/execution/execution-backend.ts
@@ -0,0 +1,13 @@
+import type {
+  ExecutionBackendDescription,
+  ExecutionImmediateResult,
+  ExecutionQueuedResult,
+  ExecutionRequest,
+} from "@/lib/execution/types";
+
+export interface ExecutionBackend {
+  backendId: string;
+  canHandle(input: ExecutionRequest): Promise<boolean> | boolean;
+  execute(input: ExecutionRequest): Promise<ExecutionQueuedResult | ExecutionImmediateResult>;
+  describe(input: ExecutionRequest): Promise<ExecutionBackendDescription>;
+}
diff --git a/src/lib/execution/orchestration-backend.ts b/src/lib/execution/orchestration-backend.ts
new file mode 100644
index 0000000..aca6412
--- /dev/null
+++ b/src/lib/execution/orchestration-backend.ts
@@ -0,0 +1,4 @@
+export interface OrchestrationBackend {
+  backendId: string;
+  describe(): Promise<{ backendId: string; label: string }>;
+}
diff --git a/src/lib/execution/types.ts b/src/lib/execution/types.ts
new file mode 100644
index 0000000..56f44e2
--- /dev/null
+++ b/src/lib/execution/types.ts
@@ -0,0 +1,104 @@
+import type { ReasoningEffort } from "@/lib/boss-data";
+
+export type ExecutionRequestKind =
+  | "master_agent_reply"
+  | "thread_reply"
+  | "dispatch_execution"
+  | "attachment_analysis";
+
+export interface ExecutionRequest {
+  kind: ExecutionRequestKind;
+  projectId: string;
+  requestMessageId: string;
+  body: string;
+  requestedByAccount?: string;
+  requestedByLabel?: string;
+  taskId?: string;
+  targetThreadId?: string;
+  targetProjectId?: string;
+  modelOverride?: string;
+  reasoningEffortOverride?: ReasoningEffort;
+}
+
+export interface ExecutionQueuedResult {
+  status: "queued" | "running";
+  taskId: string;
+  backendId: string;
+  sessionId?: string;
+}
+
+export interface ExecutionImmediateCompletedResult {
+  status: "completed";
+  backendId: string;
+  output: string;
+}
+
+export interface ExecutionImmediateFailedResult {
+  status: "failed";
+  backendId: string;
+  error: string;
+}
+
+export type ExecutionImmediateResult =
+  | ExecutionImmediateCompletedResult
+  | ExecutionImmediateFailedResult;
+
+export interface ExecutionBackendDescription {
+  backendId: string;
+  label: string;
+  mode: "local" | "remote" | "api";
+}
+
+export function createExecutionRequest(input: ExecutionRequest): ExecutionRequest {
+  return {
+    kind: input.kind,
+    projectId: input.projectId,
+    requestMessageId: input.requestMessageId,
+    body: input.body,
+    requestedByAccount: input.requestedByAccount ?? undefined,
+    requestedByLabel: input.requestedByLabel ?? undefined,
+    taskId: input.taskId ?? undefined,
+    targetThreadId: input.targetThreadId ?? undefined,
+    targetProjectId: input.targetProjectId ?? undefined,
+    modelOverride: input.modelOverride ?? undefined,
+    reasoningEffortOverride: input.reasoningEffortOverride ?? undefined,
+  };
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null;
+}
+
+function hasStringProperty(value: Record<string, unknown>, key: string): boolean {
+  return typeof value[key] === "string" && value[key].length > 0;
+}
+
+export function isQueuedExecutionResult(value: unknown): value is ExecutionQueuedResult {
+  if (!isRecord(value)) {
+    return false;
+  }
+
+  if (value.status !== "queued" && value.status !== "running") {
+    return false;
+  }
+
+  return hasStringProperty(value, "taskId") && hasStringProperty(value, "backendId");
+}
+
+export function isImmediateExecutionResult(
+  value: unknown,
+): value is ExecutionImmediateResult {
+  if (!isRecord(value)) {
+    return false;
+  }
+
+  if (value.status === "completed") {
+    return hasStringProperty(value, "backendId") && hasStringProperty(value, "output");
+  }
+
+  if (value.status === "failed") {
+    return hasStringProperty(value, "backendId") && hasStringProperty(value, "error");
+  }
+
+  return false;
+}
diff --git a/tests/execution-foundation-contracts.test.ts b/tests/execution-foundation-contracts.test.ts
new file mode 100644
index 0000000..f030f2c
--- /dev/null
+++ b/tests/execution-foundation-contracts.test.ts
@@ -0,0 +1,76 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import type { ExecutionImmediateResult } from "@/lib/execution/types";
+import {
+  createExecutionRequest,
+  isImmediateExecutionResult,
+  isQueuedExecutionResult,
+} from "@/lib/execution/types";
+
+test("ExecutionRequest 工厂会生成稳定默认字段", () => {
+  const request = createExecutionRequest({
+    kind: "master_agent_reply",
+    projectId: "master-agent",
+    requestMessageId: "msg-1",
+    body: "你好",
+  });
+
+  assert.equal(request.kind, "master_agent_reply");
+  assert.equal(request.projectId, "master-agent");
+  assert.equal(request.requestMessageId, "msg-1");
+  assert.equal(request.body, "你好");
+  assert.equal(request.targetProjectId, undefined);
+  assert.equal(request.targetThreadId, undefined);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "requestedByAccount"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "requestedByLabel"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "taskId"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "targetProjectId"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "targetThreadId"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "modelOverride"), true);
+  assert.equal(Object.prototype.hasOwnProperty.call(request, "reasoningEffortOverride"), true);
+});
+
+test("ExecutionResult 类型守卫能区分 queued 与 immediate", () => {
+  const queued = {
+    status: "queued",
+    taskId: "task-1",
+    backendId: "master-codex-node",
+  };
+  const running = {
+    status: "running",
+    taskId: "task-2",
+    backendId: "master-codex-node",
+    sessionId: "session-1",
+  };
+  const completed: ExecutionImmediateResult = {
+    status: "completed",
+    backendId: "openai-api",
+    output: "done",
+  };
+  const failed: ExecutionImmediateResult = {
+    status: "failed",
+    backendId: "openai-api",
+    error: "boom",
+  };
+  const invalidCompleted = {
+    status: "completed",
+    backendId: "openai-api",
+  };
+  const invalidFailed = {
+    status: "failed",
+    backendId: "openai-api",
+  };
+
+  assert.equal(isQueuedExecutionResult(queued), true);
+  assert.equal(isQueuedExecutionResult(running), true);
+  assert.equal(isImmediateExecutionResult(queued), false);
+  assert.equal(isImmediateExecutionResult(running), false);
+  assert.equal(isQueuedExecutionResult(completed), false);
+  assert.equal(isImmediateExecutionResult(completed), true);
+  assert.equal(isQueuedExecutionResult(failed), false);
+  assert.equal(isImmediateExecutionResult(failed), true);
+  assert.equal(isImmediateExecutionResult(invalidCompleted), false);
+  assert.equal(isImmediateExecutionResult(invalidFailed), false);
+  assert.equal(isQueuedExecutionResult(null), false);
+  assert.equal(isImmediateExecutionResult(undefined), false);
+});