learnharness/app/api/settings/defaults/route.ts

/**
 * GET/PUT /api/settings/defaults — server persistence for the DEFAULT
 * settings: THE default model + thinking level + knowledge-context
 * budget. The new-session surfaces' controls (the home graph view's
 * topic dock and /chat/new) ARE the settings page for the default model
 * (owner, 2026-09-18): there is no baked-in default — BYOK first boot
 * renders "no model" until the user picks one, and the last choice IS
 * the default from then on. Both surfaces share ONE record; the file
 * lives at data/default-settings.json (config.DEFAULT_SETTINGS_FILE).
 *
 *   GET → 200 {settings} once saved, 200 null on first boot ("no model").
 *   PUT → 200 {settings} — the VALIDATED copy persisted verbatim. The exact
 *         per-chat contract (parseSettingsBody + the catalog gate): unknown
 *         provider/model or an unsupported thinking level is a 400 carrying
 *         the supported list, never a silent clamp.
 *
 * Per-session settings (PUT /api/chats/:id/settings) are a separate record
 * untouched by this — the default still rides along on session creation
 * exactly as before.
 */
import { readDefaultSettings, writeDefaultSettings, parseSettingsBody, validateChatSettings } from "@/src/server";

export const dynamic = "force-dynamic";

export async function GET() {
	return Response.json(readDefaultSettings());
}

export async function PUT(request: Request) {
	const body = await request.json().catch(() => null);
	const parsed = parseSettingsBody(body);
	if (!parsed.ok) return Response.json({ error: parsed.error }, { status: 400 });
	const verdict = validateChatSettings(parsed.settings);
	if (!verdict.ok) {
		return Response.json({ error: verdict.error, supported: verdict.supported }, { status: 400 });
	}
	writeDefaultSettings(parsed.settings);
	return Response.json({ settings: parsed.settings });
}