fix: align compaction cuts and native usage accounting

tests/pricing-transport.test.ts

@@ -0,0 +1,34 @@
+import assert from "node:assert/strict";
+import test, { after } from "node:test";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+const scratch = fs.mkdtempSync(path.join(os.tmpdir(), "lh-pricing-transport-"));
+process.env.LH_DATA_DIR = scratch;
+process.env.LH_AUTH_FILE = path.join(scratch, "empty-auth.json");
+fs.writeFileSync(process.env.LH_AUTH_FILE, "{}", { mode: 0o600 });
+const { chatStore } = await import("../src/store/chats.ts");
+const { GET } = await import("../app/api/chats/[id]/route.ts");
+const { sessionCost } = await import("../src/server/pricing.ts");
+after(() => fs.rmSync(scratch, { recursive: true, force: true }));
+
+test("chat GET supplies derived Pi costs without persisting dollars or changing native history", async () => {
+	const record = chatStore.createChat("price projection fixture");
+	chatStore.saveMessages(record.id, [{ id: "fixture-input", role: "user", content: "synthetic", timestamp: 1 }]);
+	const step = { inputTokens: 10_000, outputTokens: 1_000, cacheReadTokens: 70_000, cacheWriteTokens: 0, cacheWrite1hTokens: 0, reasoningTokens: 500 };
+	for (const [id, model] of [["api", "openrouter:openai/gpt-6.1-sol"], ["plan", "chatgpt:fixture"], ["unknown", "missing:fixture"]]) {
+		chatStore.appendTurnUsage(record.id, { id: id!, model: model!, messageId: "fixture-input", at: "fixture", steps: [step] });
+	}
+	const file = path.join(scratch, "chats", `${record.id}.json`);
+	const before = fs.readFileSync(file, "utf8");
+	const response = await GET(new Request(`http://localhost/api/chats/${record.id}`), { params: Promise.resolve({ id: record.id }) });
+	assert.equal(response.status, 200);
+	const body = await response.json();
+	assert.deepEqual(body.messages, chatStore.getChat(record.id)!.messages);
+	assert.deepEqual(body.pricing, sessionCost(chatStore.getChat(record.id)!));
+	assert.equal(body.pricing.cost, 0.037);
+	assert.equal(body.pricing.subscription, 1);
+	assert.equal(body.pricing.unpriced, 1);
+	assert.deepEqual(body.pricing.turnCosts, { api: 0.037, plan: null, unknown: null });
+	assert.equal(fs.readFileSync(file, "utf8"), before, "read-time estimates must never rewrite the usage log");
+});