diff --git a/packages/coding-agent/docs/refactor.md b/packages/coding-agent/docs/refactor.md
index a1206ef1..8dfd915f 100644
--- a/packages/coding-agent/docs/refactor.md
+++ b/packages/coding-agent/docs/refactor.md
@@ -1308,8 +1308,8 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 1. `npm run check` passes
 2. Manual test: RPC mode still works (if you have a way to test it)
 
-- [ ] Create `src/modes/rpc-mode.ts`
-- [ ] Verify with `npm run check`
+- [x] Create `src/modes/rpc-mode.ts`
+- [x] Verify with `npm run check`
 
 ---
 
diff --git a/packages/coding-agent/src/modes/rpc-mode.ts b/packages/coding-agent/src/modes/rpc-mode.ts
new file mode 100644
index 00000000..4986b903
--- /dev/null
+++ b/packages/coding-agent/src/modes/rpc-mode.ts
@@ -0,0 +1,84 @@
+/**
+ * RPC mode: Headless operation with JSON stdin/stdout protocol.
+ *
+ * Used for embedding the agent in other applications.
+ * Receives commands as JSON on stdin, outputs events as JSON on stdout.
+ */
+
+import * as readline from "readline";
+import type { AgentSession } from "../core/agent-session.js";
+
+/**
+ * Run in RPC mode.
+ * Listens for JSON commands on stdin, outputs events on stdout.
+ *
+ * Commands:
+ * - { type: "prompt", message: string, attachments?: Attachment[] }
+ * - { type: "abort" }
+ * - { type: "compact", customInstructions?: string }
+ * - { type: "bash", command: string }
+ *
+ * Events are output as JSON lines (same format as session manager).
+ */
+export async function runRpcMode(session: AgentSession): Promise<never> {
+	// Output all agent events as JSON
+	session.subscribe((event) => {
+		console.log(JSON.stringify(event));
+	});
+
+	// Listen for JSON input
+	const rl = readline.createInterface({
+		input: process.stdin,
+		output: process.stdout,
+		terminal: false,
+	});
+
+	rl.on("line", async (line: string) => {
+		try {
+			const input = JSON.parse(line);
+
+			switch (input.type) {
+				case "prompt":
+					if (input.message) {
+						await session.prompt(input.message, {
+							attachments: input.attachments,
+							expandSlashCommands: false, // RPC mode doesn't expand slash commands
+						});
+					}
+					break;
+
+				case "abort":
+					await session.abort();
+					break;
+
+				case "compact":
+					try {
+						const result = await session.compact(input.customInstructions);
+						console.log(JSON.stringify({ type: "compaction", ...result }));
+					} catch (error: any) {
+						console.log(JSON.stringify({ type: "error", error: `Compaction failed: ${error.message}` }));
+					}
+					break;
+
+				case "bash":
+					if (input.command) {
+						try {
+							const result = await session.executeBash(input.command);
+							console.log(JSON.stringify({ type: "bash_end", ...result }));
+						} catch (error: any) {
+							console.log(JSON.stringify({ type: "error", error: `Bash failed: ${error.message}` }));
+						}
+					}
+					break;
+
+				default:
+					console.log(JSON.stringify({ type: "error", error: `Unknown command: ${input.type}` }));
+			}
+		} catch (error: any) {
+			console.log(JSON.stringify({ type: "error", error: error.message }));
+		}
+	});
+
+	// Keep process alive forever
+	return new Promise(() => {});
+}