can1357/oh-my-pi · error

Unsupported RPC session change command

Error message

Unsupported RPC session change command

What it means

handleRpcSessionChange dispatches RPC session-change commands (e.g. 'branch') via a switch. If the command's type is not one of the known session change operations, the switch falls through and the function throws 'Unsupported RPC session change command'. It is a protocol-level guard against unknown or newer command types sent to an older host.

Source

Thrown at packages/coding-agent/src/modes/rpc/rpc-mode.ts:494

			const options = command.parentSession ? { parentSession: command.parentSession } : undefined;
			const cancelled = !(await session.newSession(options));
			if (!cancelled) subagentRegistry?.clear();
			return { type: "new_session", data: { cancelled } };
		}

		case "switch_session": {
			const cancelled = !(await session.switchSession(command.sessionPath));
			if (!cancelled) subagentRegistry?.clear();
			return { type: "switch_session", data: { cancelled } };
		}

		case "branch": {
			const result = await session.branch(command.entryId);
			if (!result.cancelled) subagentRegistry?.clear();
			return { type: "branch", data: { text: result.selectedText, cancelled: result.cancelled } };
		}
	}
	throw new Error("Unsupported RPC session change command");
}

function normalizeHostToolDefinitions(tools: RpcHostToolDefinition[]): RpcHostToolDefinition[] {
	return tools.map((tool, index) => {
		const name = typeof tool.name === "string" ? tool.name.trim() : "";
		if (!name) {
			throw new Error(`Host tool at index ${index} must provide a non-empty name`);
		}
		const description = typeof tool.description === "string" ? tool.description.trim() : "";
		if (!description) {
			throw new Error(`Host tool "${name}" must provide a non-empty description`);
		}
		if (!tool.parameters || typeof tool.parameters !== "object" || Array.isArray(tool.parameters)) {
			throw new Error(`Host tool "${name}" must provide a JSON Schema object`);
		}
		const label = typeof tool.label === "string" && tool.label.trim() ? tool.label.trim() : name;
		return {
			name,

View on GitHub (pinned to 9690622007)

Solutions

1. Check the command name sent over RPC for typos and confirm it is one of the supported session change commands (e.g. 'branch').
2. Upgrade the omp host (or client) so both sides support the command type.
3. Wrap the RPC dispatch in a handler that maps unknown-command errors to a clean 'unsupported command' response for the client.

Example fix

// before
await rpc.request("session.change", { command: "braanch", entryId });
// after
await rpc.request("session.change", { command: "branch", entryId });

const SUPPORTED = new Set(["branch"]);
if (!SUPPORTED.has(command.type)) throw new Error(`Unsupported session change command: ${command.type}`);

function isSessionChangeCommand(cmd: string): cmd is "branch" {
  return cmd === "branch";
}

try {
  await rpc.sessionChange(command);
} catch (err) {
  if (err instanceof Error && err.message === "Unsupported RPC session change command") {
    // surface a clean unsupported-command response to the client
  } else throw err;
}

When it happens

Trigger: Sending an RPC request whose session-change command type is misspelled, not implemented in this version, or added by a newer client than the running host, so no case in the switch matches.

Common situations: Version skew between an RPC client SDK and the omp host (client sends a new command the host doesn't know); a typo in the command name in custom tooling or scripts driving the RPC interface.

Related errors

• Replacement text is not valid UTF-8: {err}
• invalid glob `{pattern}`: {error}
• RPC chunk received before protocol negotiation
• RPC protocol v2 negotiation failed
• RPC chunk exceeded the transport limit

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/e30c8962bdc2de53. Report an issue: GitHub.