chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/packages/coding-agent/examples/extensions/jev-router.ts

@@ -0,0 +1,113 @@
+/**
+ * Jev router - a virtual model that plans on a strong model and implements on a cheap one.
+ *
+ * Registers `jev/auto`, which routes between three OpenAI Codex models:
+ *
+ * - Planning: GPT-5.6 Sol for complex work, GPT-5.6 Terra otherwise. The Jev classifier rates the
+ *   first user message; planning stays on the chosen model.
+ * - Implementation: GPT-5.6 Luna.
+ *
+ * The planning model explores, plans, and makes the first edit. After the first successful `edit`
+ * or `write` tool call, the next request of the same turn goes to Luna, and the session stays
+ * there. A session therefore switches models once and accepts a single prompt-cache miss.
+ *
+ * The phase is router state: Pi stores it on the session branch, so it follows the session tree
+ * and survives compaction. The selected thinking level passes through as the reasoning effort of
+ * the chosen model. Requests outside the agent loop, such as compaction summaries, go to Luna.
+ *
+ * Requires TypeSafe credentials (TYPESAFE_API_KEY) and an OpenAI Codex login.
+ * Usage: pi -e ./jev-router.ts --model jev/auto
+ */
+
+import type { Message } from "@earendil-works/pi-ai";
+import type { ExtensionAPI, ExtensionContext, ModelRoute, ModelRouteRequest } from "@earendil-works/pi-coding-agent";
+
+const PROVIDER = "openai-codex";
+const SOL = "gpt-5.6-sol";
+const TERRA = "gpt-5.6-terra";
+const LUNA = "gpt-5.6-luna";
+
+/** Tools whose successful result means implementation has started. */
+const EDIT_TOOLS = new Set(["edit", "write"]);
+
+interface JevState {
+	phase: "planning" | "implementation";
+	/** OpenAI Codex model for this phase. */
+	model: string;
+}
+
+type JevRequest = ModelRouteRequest<JevState>;
+
+function routeTo(request: JevRequest, ctx: ExtensionContext, id: string, state?: JevState): ModelRoute<JevState> {
+	const model = ctx.modelRegistry.find(PROVIDER, id);
+	if (!model) throw new Error(`Model ${PROVIDER}/${id} is not in the catalog`);
+	return { model, thinkingLevel: request.thinkingLevel, state };
+}
+
+function lastUserText(messages: readonly Message[]): string {
+	const content = messages.filter((message) => message.role === "user").at(-1)?.content ?? "";
+	if (typeof content === "string") return content;
+	return content.flatMap((block) => (block.type === "text" ? [block.text] : [])).join("\n");
+}
+
+/** Whether a tool call since the last user message edited a file successfully. */
+function editedThisTurn(messages: readonly Message[]): boolean {
+	const lastUser = messages.findLastIndex((message) => message.role === "user");
+	return messages
+		.slice(lastUser + 1)
+		.some((message) => message.role === "toolResult" && EDIT_TOOLS.has(message.toolName) && !message.isError);
+}
+
+/** Planning model for a new session: Sol for complex work, Terra otherwise or when Jev is unavailable. */
+async function choosePlanningModel(request: JevRequest, ctx: ExtensionContext): Promise<string> {
+	// Keep a planning model the session already uses, so switching to jev/auto costs no cache miss.
+	const previous = request.previous?.model;
+	if (previous?.provider === PROVIDER && (previous.id === SOL || previous.id === TERRA)) return previous.id;
+
+	const jev = ctx.modelRegistry.findOfType("classifier", "typesafe", "jev-latest");
+	if (!jev) return TERRA;
+	const result = await ctx.modelRegistry.classify(
+		jev,
+		{
+			state: { prompt: lastUserText(request.messages).slice(0, 16_000) },
+			questions: {
+				complexity: {
+					type: "choice",
+					instructions: "How demanding is the software engineering work requested in `prompt`?",
+					criteria: {
+						standard: "Ordinary features, fixes, reviews, or questions",
+						complex: "Subtle design, cross-cutting changes, or hard debugging",
+					},
+				},
+			},
+		},
+		{ signal: request.signal },
+	);
+	const answer = result.stopReason === "stop" ? result.answers.complexity : undefined;
+	return answer?.type === "choice" && (answer.probabilities.complex ?? 0) >= 0.5 ? SOL : TERRA;
+}
+
+export default function (pi: ExtensionAPI) {
+	pi.registerVirtualModel<JevState>({
+		provider: "jev",
+		id: "auto",
+		name: "Auto (Jev)",
+		thinkingLevels: ["low", "medium", "high", "xhigh"],
+		// Shared by all three models; shown before the first response.
+		contextWindow: 272_000,
+		maxTokens: 128_000,
+		async route(request, ctx) {
+			if (request.reason === "direct") return routeTo(request, ctx, LUNA);
+			const state = request.state;
+			if (!state) {
+				const model = await choosePlanningModel(request, ctx);
+				return routeTo(request, ctx, model, { phase: "planning", model });
+			}
+			// The planning model made the first edit: hand the rest of the work to Luna.
+			if (state.phase === "planning" && editedThisTurn(request.messages)) {
+				return routeTo(request, ctx, LUNA, { phase: "implementation", model: LUNA });
+			}
+			return routeTo(request, ctx, state.model);
+		},
+	});
+}