diff --git a/docs/development/task-backlog.md b/docs/development/task-backlog.md
index 4de7aa9..e5d8a93 100644
--- a/docs/development/task-backlog.md
+++ b/docs/development/task-backlog.md
@@ -356,10 +356,10 @@ Status markers:
 
 **Tasks:**
 
-- [ ] Allow only configured safe commands.
-- [ ] Stream stdout and stderr events.
-- [ ] Reject arbitrary commands unless permission policy allows them.
-- [ ] Commit with message `feat: add safe shell runtime adapter`.
+- [x] Allow only configured safe commands.
+- [x] Stream stdout and stderr events.
+- [x] Reject arbitrary commands unless permission policy allows them.
+- [x] Commit with message `feat: add safe shell runtime adapter`.
 
 **Acceptance Criteria:**
 
diff --git a/packages/runtime-adapters/src/execution/shell-adapter.test.ts b/packages/runtime-adapters/src/execution/shell-adapter.test.ts
new file mode 100644
index 0000000..bdb4a09
--- /dev/null
+++ b/packages/runtime-adapters/src/execution/shell-adapter.test.ts
@@ -0,0 +1,128 @@
+import { describe, expect, it } from "vitest";
+
+import { createSafeShellAdapter } from "./shell-adapter.js";
+
+describe("createSafeShellAdapter", () => {
+  it("executes configured safe commands and streams stdout and stderr events", async () => {
+    const adapter = createSafeShellAdapter({
+      allowedCommands: ["echo hello"],
+      runCommand: async (command) => {
+        expect(command).toBe("echo hello");
+        return {
+          stdout: "hello",
+          stderr: "warn",
+          exitCode: 0,
+        };
+      },
+      now: () => "2026-05-29T00:00:00.000Z",
+    });
+
+    const result = await adapter.executeTask({
+      taskId: "task-1",
+      prompt: "echo hello",
+      workspaceRoot: "/tmp/agentdeck",
+    });
+
+    expect(result.status).toBe("completed");
+    expect(result.events).toEqual([
+      {
+        id: "task-1-stdout-1",
+        taskId: "task-1",
+        type: "task.stdout",
+        createdAt: "2026-05-29T00:00:00.000Z",
+        payload: { text: "hello" },
+      },
+      {
+        id: "task-1-stderr-1",
+        taskId: "task-1",
+        type: "task.stderr",
+        createdAt: "2026-05-29T00:00:00.000Z",
+        payload: { text: "warn" },
+      },
+      {
+        id: "task-1-completed",
+        taskId: "task-1",
+        type: "task.completed",
+        createdAt: "2026-05-29T00:00:00.000Z",
+        payload: { exitCode: 0 },
+      },
+    ]);
+  });
+
+  it("rejects arbitrary commands before execution unless policy allows them", async () => {
+    let executed = false;
+    const adapter = createSafeShellAdapter({
+      allowedCommands: ["echo hello"],
+      runCommand: async () => {
+        executed = true;
+        return {
+          stdout: "",
+          stderr: "",
+          exitCode: 0,
+        };
+      },
+      now: () => "2026-05-29T00:00:00.000Z",
+    });
+
+    const result = await adapter.executeTask({
+      taskId: "task-1",
+      prompt: "rm -rf /tmp/example",
+      workspaceRoot: "/tmp/agentdeck",
+    });
+
+    expect(executed).toBe(false);
+    expect(result.status).toBe("failed");
+    expect(result.events).toEqual([
+      {
+        id: "task-1-failed",
+        taskId: "task-1",
+        type: "task.failed",
+        createdAt: "2026-05-29T00:00:00.000Z",
+        payload: { message: 'Command "rm -rf /tmp/example" is not allowed.' },
+      },
+    ]);
+  });
+
+  it("allows arbitrary commands when permission policy explicitly allows them", async () => {
+    const adapter = createSafeShellAdapter({
+      allowedCommands: [],
+      allowArbitraryCommands: true,
+      runCommand: async () => ({
+        stdout: "ok",
+        stderr: "",
+        exitCode: 0,
+      }),
+      now: () => "2026-05-29T00:00:00.000Z",
+    });
+
+    const result = await adapter.executeTask({
+      taskId: "task-1",
+      prompt: "pwd",
+      workspaceRoot: "/tmp/agentdeck",
+    });
+
+    expect(result.status).toBe("completed");
+    expect(result.events.map((event) => event.type)).toEqual(["task.stdout", "task.completed"]);
+  });
+
+  it("reports non-zero command exits as failures", async () => {
+    const adapter = createSafeShellAdapter({
+      allowedCommands: ["false"],
+      runCommand: async () => ({
+        stdout: "",
+        stderr: "bad",
+        exitCode: 1,
+      }),
+      now: () => "2026-05-29T00:00:00.000Z",
+    });
+
+    const result = await adapter.executeTask({
+      taskId: "task-1",
+      prompt: "false",
+      workspaceRoot: "/tmp/agentdeck",
+    });
+
+    expect(result.status).toBe("failed");
+    expect(result.events.map((event) => event.type)).toEqual(["task.stderr", "task.failed"]);
+  });
+});
diff --git a/packages/runtime-adapters/src/execution/shell-adapter.ts b/packages/runtime-adapters/src/execution/shell-adapter.ts
new file mode 100644
index 0000000..0dd87d0
--- /dev/null
+++ b/packages/runtime-adapters/src/execution/shell-adapter.ts
@@ -0,0 +1,159 @@
+import { runProbe } from "../probe/run-probe.js";
+import {
+  createRuntimeAdapterCapabilities,
+  type RuntimeAdapter,
+  type RuntimeTaskResult,
+} from "./runtime-adapter.js";
+import { createTaskEvent, type TaskEvent } from "./task-events.js";
+
+export interface ShellCommandResult {
+  readonly stdout: string;
+  readonly stderr: string;
+  readonly exitCode: number | null;
+}
+
+export interface SafeShellAdapterOptions {
+  readonly allowedCommands: readonly string[];
+  readonly allowArbitraryCommands?: boolean;
+  readonly runCommand?: (command: string, cwd: string) => Promise<ShellCommandResult>;
+  readonly now?: () => string;
+}
+
+export function createSafeShellAdapter(options: SafeShellAdapterOptions): RuntimeAdapter {
+  const now = options.now ?? (() => new Date().toISOString());
+  const allowedCommands = new Set(options.allowedCommands);
+
+  return {
+    id: "shell",
+    name: "Safe Shell",
+    runtimeType: "node",
+    async executeTask(request) {
+      const command = request.prompt.trim();
+      if (!options.allowArbitraryCommands && !allowedCommands.has(command)) {
+        return {
+          taskId: request.taskId,
+          status: "failed",
+          events: [
+            createTaskEvent({
+              id: `${request.taskId}-failed`,
+              taskId: request.taskId,
+              type: "task.failed",
+              createdAt: now(),
+              payload: {
+                message: `Command "${command}" is not allowed.`,
+              },
+            }),
+          ],
+        };
+      }
+
+      const commandResult = await (options.runCommand ?? runShellCommand)(
+        command,
+        request.workspaceRoot,
+      );
+      return createRuntimeTaskResult({
+        taskId: request.taskId,
+        commandResult,
+        now,
+      });
+    },
+    async cancelTask() {
+      return {
+        cancelled: false,
+        reason: "Safe shell commands are not cancellable after dispatch.",
+      };
+    },
+    getCapabilities() {
+      return createRuntimeAdapterCapabilities({
+        streaming: true,
+        tools: ["shell"],
+      });
+    },
+  };
+}
+
+async function runShellCommand(command: string, cwd: string): Promise<ShellCommandResult> {
+  const result = await runProbe(command, {
+    cwd,
+  });
+
+  return {
+    stdout: result.stdout,
+    stderr: result.stderr,
+    exitCode: result.exitCode,
+  };
+}
+
+function createRuntimeTaskResult(input: {
+  readonly taskId: string;
+  readonly commandResult: ShellCommandResult;
+  readonly now: () => string;
+}): RuntimeTaskResult {
+  const events: TaskEvent[] = [];
+
+  if (input.commandResult.stdout.length > 0) {
+    events.push(
+      createTaskEvent({
+        id: `${input.taskId}-stdout-1`,
+        taskId: input.taskId,
+        type: "task.stdout",
+        createdAt: input.now(),
+        payload: {
+          text: input.commandResult.stdout,
+        },
+      }),
+    );
+  }
+
+  if (input.commandResult.stderr.length > 0) {
+    events.push(
+      createTaskEvent({
+        id: `${input.taskId}-stderr-1`,
+        taskId: input.taskId,
+        type: "task.stderr",
+        createdAt: input.now(),
+        payload: {
+          text: input.commandResult.stderr,
+        },
+      }),
+    );
+  }
+
+  if (input.commandResult.exitCode === 0) {
+    events.push(
+      createTaskEvent({
+        id: `${input.taskId}-completed`,
+        taskId: input.taskId,
+        type: "task.completed",
+        createdAt: input.now(),
+        payload: {
+          exitCode: 0,
+        },
+      }),
+    );
+
+    return {
+      taskId: input.taskId,
+      status: "completed",
+      events,
+    };
+  }
+
+  events.push(
+    createTaskEvent({
+      id: `${input.taskId}-failed`,
+      taskId: input.taskId,
+      type: "task.failed",
+      createdAt: input.now(),
+      payload: {
+        message: `Command failed with exit code ${input.commandResult.exitCode ?? "unknown"}.`,
+      },
+    }),
+  );
+
+  return {
+    taskId: input.taskId,
+    status: "failed",
+    events,
+  };
+}
diff --git a/packages/runtime-adapters/src/index.ts b/packages/runtime-adapters/src/index.ts
index 3576c8a..0bcea5d 100644
--- a/packages/runtime-adapters/src/index.ts
+++ b/packages/runtime-adapters/src/index.ts
@@ -52,3 +52,6 @@ export type {
   TaskStdoutEvent,
   TaskToolEvent,
 } from "./execution/task-events.js";
+
+export { createSafeShellAdapter } from "./execution/shell-adapter.js";
+export type { SafeShellAdapterOptions, ShellCommandResult } from "./execution/shell-adapter.js";