feat(pi): add Codex fast mode extension

pi/extensions/openai-codex-fast/index.ts

@@ -0,0 +1,71 @@
+import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
+import {
+  FAST_STATE_ENTRY,
+  isCodexModel,
+  parseFastCommand,
+  patchFastPayload,
+  restoreFastMode,
+} from "./state.ts";
+
+export default function openaiCodexFast(pi: ExtensionAPI) {
+  let enabled = false;
+
+  function updateStatus(ctx: ExtensionContext, model = ctx.model): void {
+    if (!ctx.hasUI) return;
+    ctx.ui.setStatus(
+      FAST_STATE_ENTRY,
+      enabled && isCodexModel(model) ? "Codex fast: priority" : undefined,
+    );
+  }
+
+  function restore(ctx: ExtensionContext): void {
+    enabled = restoreFastMode(ctx.sessionManager.getBranch());
+    updateStatus(ctx);
+  }
+
+  pi.on("session_start", (_event, ctx) => restore(ctx));
+  pi.on("session_tree", (_event, ctx) => restore(ctx));
+  pi.on("model_select", (event, ctx) => updateStatus(ctx, event.model));
+
+  pi.on("before_provider_request", (event, ctx) =>
+    patchFastPayload({ enabled, model: ctx.model, payload: event.payload }),
+  );
+
+  pi.registerCommand("fast", {
+    description: "Toggle Codex priority service. Usage: /fast [on|off|status]. May increase usage.",
+    handler: async (args, ctx) => {
+      const command = parseFastCommand(args);
+      if (!command) {
+        ctx.ui.notify("Usage: /fast [on|off|status]", "warning");
+        return;
+      }
+      if (command === "status") {
+        const state = enabled
+          ? isCodexModel(ctx.model) ? "on, requesting priority service" : "on, inactive for this provider"
+          : "off, using provider defaults";
+        ctx.ui.notify(`Codex fast mode is ${state}.`, "info");
+        return;
+      }
+      if (!ctx.isIdle()) {
+        ctx.ui.notify("Wait for the current turn to finish before changing fast mode.", "warning");
+        return;
+      }
+      const next = command === "toggle" ? !enabled : command === "on";
+      if (next && !isCodexModel(ctx.model)) {
+        ctx.ui.notify("Fast mode requires the openai-codex provider and openai-codex-responses API.", "warning");
+        return;
+      }
+      if (next !== enabled) {
+        pi.appendEntry(FAST_STATE_ENTRY, { enabled: next });
+        enabled = next;
+      }
+      updateStatus(ctx);
+      ctx.ui.notify(
+        enabled
+          ? "Codex fast mode on. Requesting priority service; usage may increase. OpenAI controls availability."
+          : "Codex fast mode off. Using provider defaults.",
+        "info",
+      );
+    },
+  });
+}