feat(coding-agent): add set_session_name RPC command (#1075)

- Add set_session_name command with empty name validation
- Expose sessionName in get_state response
- Add setSessionName() to AgentSession and RpcClient
- Document in docs/rpc.md

packages/coding-agent/docs/rpc.md

@@ -154,6 +154,7 @@ Response:
     "followUpMode": "one-at-a-time",
     "sessionFile": "/path/to/session.jsonl",
     "sessionId": "abc123",
+    "sessionName": "my-feature-work",
     "autoCompactionEnabled": true,
     "messageCount": 5,
     "pendingMessageCount": 0
@@ -161,7 +162,7 @@ Response:
 }
 ```
 
-The `model` field is a full [Model](#model) object or `null`.
+The `model` field is a full [Model](#model) object or `null`. The `sessionName` field is the display name set via `set_session_name`, or omitted if not set.
 
 #### get_messages
 
@@ -612,6 +613,25 @@ Response:
 
 Returns `{"text": null}` if no assistant messages exist.
 
+#### set_session_name
+
+Set a display name for the current session. The name appears in session listings and helps identify sessions.
+
+```json
+{"type": "set_session_name", "name": "my-feature-work"}
+```
+
+Response:
+```json
+{
+  "type": "response",
+  "command": "set_session_name",
+  "success": true
+}
+```
+
+The current session name is available via `get_state` in the `sessionName` field.
+
 ### Commands
 
 #### get_commands

packages/coding-agent/src/core/agent-session.ts

@@ -590,6 +590,11 @@ export class AgentSession {
 		return this.sessionManager.getSessionId();
 	}
 
+	/** Current session display name, if set */
+	get sessionName(): string | undefined {
+		return this.sessionManager.getSessionName();
+	}
+
 	/** Scoped models for cycling (from --models flag) */
 	get scopedModels(): ReadonlyArray<{ model: Model<any>; thinkingLevel: ThinkingLevel }> {
 		return this._scopedModels;
@@ -2181,6 +2186,13 @@ export class AgentSession {
 		return true;
 	}
 
+	/**
+	 * Set a display name for the current session.
+	 */
+	setSessionName(name: string): void {
+		this.sessionManager.appendSessionInfo(name);
+	}
+
 	/**
 	 * Create a fork from a specific entry.
 	 * Emits before_fork/fork session events to extensions.

packages/coding-agent/src/modes/rpc/rpc-client.ts

@@ -362,6 +362,13 @@ export class RpcClient {
 		return this.getData<{ text: string | null }>(response).text;
 	}
 
+	/**
+	 * Set the session display name.
+	 */
+	async setSessionName(name: string): Promise<void> {
+		await this.send({ type: "set_session_name", name });
+	}
+
 	/**
 	 * Get all messages in the session.
 	 */

packages/coding-agent/src/modes/rpc/rpc-mode.ts

@@ -349,6 +349,7 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 					followUpMode: session.followUpMode,
 					sessionFile: session.sessionFile,
 					sessionId: session.sessionId,
+					sessionName: session.sessionName,
 					autoCompactionEnabled: session.autoCompactionEnabled,
 					messageCount: session.messages.length,
 					pendingMessageCount: session.pendingMessageCount,
@@ -490,6 +491,15 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 				return success(id, "get_last_assistant_text", { text });
 			}
 
+			case "set_session_name": {
+				const name = command.name.trim();
+				if (!name) {
+					return error(id, "set_session_name", "Session name cannot be empty");
+				}
+				session.setSessionName(name);
+				return success(id, "set_session_name");
+			}
+
 			// =================================================================
 			// Messages
 			// =================================================================

packages/coding-agent/src/modes/rpc/rpc-types.ts

@@ -58,6 +58,7 @@ export type RpcCommand =
 	| { id?: string; type: "fork"; entryId: string }
 	| { id?: string; type: "get_fork_messages" }
 	| { id?: string; type: "get_last_assistant_text" }
+	| { id?: string; type: "set_session_name"; name: string }
 
 	// Messages
 	| { id?: string; type: "get_messages" }
@@ -96,6 +97,7 @@ export interface RpcSessionState {
 	followUpMode: "all" | "one-at-a-time";
 	sessionFile?: string;
 	sessionId: string;
+	sessionName?: string;
 	autoCompactionEnabled: boolean;
 	messageCount: number;
 	pendingMessageCount: number;
@@ -185,6 +187,7 @@ export type RpcResponse =
 			success: true;
 			data: { text: string | null };
 	  }
+	| { id?: string; type: "response"; command: "set_session_name"; success: true }
 
 	// Messages
 	| { id?: string; type: "response"; command: "get_messages"; success: true; data: { messages: AgentMessage[] } }

packages/coding-agent/test/rpc.test.ts

@@ -282,4 +282,37 @@ describe.skipIf(!process.env.ANTHROPIC_API_KEY && !process.env.ANTHROPIC_OAUTH_T
 		text = await client.getLastAssistantText();
 		expect(text).toContain("test123");
 	}, 90000);
+
+	test("should set and get session name", async () => {
+		await client.start();
+
+		// Initially undefined
+		let state = await client.getState();
+		expect(state.sessionName).toBeUndefined();
+
+		// Set name
+		await client.setSessionName("my-test-session");
+
+		// Verify via state
+		state = await client.getState();
+		expect(state.sessionName).toBe("my-test-session");
+
+		// Wait for file writes
+		await new Promise((resolve) => setTimeout(resolve, 200));
+
+		// Verify session_info entry in session file
+		const sessionsPath = join(sessionDir, "sessions");
+		const sessionDirs = readdirSync(sessionsPath);
+		const cwdSessionDir = join(sessionsPath, sessionDirs[0]);
+		const sessionFiles = readdirSync(cwdSessionDir).filter((f) => f.endsWith(".jsonl"));
+		const sessionContent = readFileSync(join(cwdSessionDir, sessionFiles[0]), "utf8");
+		const entries = sessionContent
+			.trim()
+			.split("\n")
+			.map((line) => JSON.parse(line));
+
+		const sessionInfoEntries = entries.filter((e: { type: string }) => e.type === "session_info");
+		expect(sessionInfoEntries.length).toBe(1);
+		expect(sessionInfoEntries[0].name).toBe("my-test-session");
+	}, 30000);
 });