feat(coding-agent): emit session header in json print mode (#679)

Also mark sandbox extension ctx param as intentionally unused.

packages/coding-agent/CHANGELOG.md

@@ -10,6 +10,7 @@
 - `/scoped-models`: Alt+Up/Down to reorder enabled models. Order is preserved when saving with Ctrl+S and determines Ctrl+P cycling order. ([#676](https://github.com/badlogic/pi-mono/pull/676) by [@thomasmhr](https://github.com/thomasmhr))
 - Amazon Bedrock provider support (experimental, tested with Anthropic Claude models only) ([#494](https://github.com/badlogic/pi-mono/pull/494) by [@unexge](https://github.com/unexge))
 - Extension example: `sandbox/` for OS-level bash sandboxing using `@anthropic-ai/sandbox-runtime` with per-project config ([#673](https://github.com/badlogic/pi-mono/pull/673) by [@dannote](https://github.com/dannote))
+- Print mode JSON output now emits the session header as the first line.
 
 ## [0.44.0] - 2026-01-12
 

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

@@ -29,6 +29,12 @@ export interface PrintModeOptions {
  */
 export async function runPrintMode(session: AgentSession, options: PrintModeOptions): Promise<void> {
 	const { mode, messages = [], initialMessage, initialImages } = options;
+	if (mode === "json") {
+		const header = session.sessionManager.getHeader();
+		if (header) {
+			console.log(JSON.stringify(header));
+		}
+	}
 	// Set up extensions for print mode (no UI, no command context)
 	const extensionRunner = session.extensionRunner;
 	if (extensionRunner) {