Add CUA AgentHarness model switching

Author: rgarcia

docs/architecture.md

@@ -41,7 +41,7 @@ someone who wants to read the code, contribute, or fork.
   - provider payload transforms and protocol quirks (for example, Yutori tool serialization policy)
   - canonical CUA tool-definition exports
 - `@onkernel/cua-agent` owns browser execution orchestration:
-  - `CuaAgent` / `CuaHarness` class wiring around `pi-agent-core`
+  - `CuaAgent` / `CuaAgentHarness` class wiring around vendored pi agent core
   - executing canonical CUA tool calls against Kernel browsers
   - typed executor coverage and translator integration
 
@@ -66,7 +66,7 @@ Dev/test:
 └── @onkernel/ptywright           (PTY-backed TUI regression harness)
 
 External:
-├── @earendil-works/pi-agent-core   # Agent loop, tool execution, streaming, steering
+├── vendored pi agent core          # Agent loop, tool execution, streaming, steering
 │   └── @earendil-works/pi-ai       # Provider transport (OpenAI Responses, Anthropic Messages, Google GenAI)
 ├── @earendil-works/pi-coding-agent # bash / read / write / edit / grep / find / ls AgentTools + SessionManager + skills
 ├── @earendil-works/pi-tui          # Terminal, Editor, Image, differential renderer

package-lock.json

@@ -1,9 +1,9 @@
 # `@onkernel/cua-agent`
 
-Kernel browser computer-use classes built on
-[`@earendil-works/pi-agent-core`](https://github.com/earendil-works/pi/tree/main/packages/agent).
+Kernel browser computer-use classes built on vendored pi `Agent` and
+`AgentHarness` source.
 
-This package keeps pi-agent-core semantics intact and adds browser execution
+This package keeps pi agent semantics intact and adds browser execution
 plumbing for canonical CUA tools.
 
 ## Installation
@@ -33,12 +33,12 @@ const agent = new CuaAgent({
 await agent.prompt("Open news.ycombinator.com and summarize the top story.");
 ```
 
-## Quick Start (`CuaHarness`)
+## Quick Start (`CuaAgentHarness`)
 
 ```ts
-import { CuaHarness } from "@onkernel/cua-agent";
+import { CuaAgentHarness } from "@onkernel/cua-agent";
 
-const harness = new CuaHarness({
+const harness = new CuaAgentHarness({
   browser,
   client,
   model: "openai:gpt-5.5",
@@ -54,17 +54,15 @@ lifecycle events, custom streaming, and explicit prompt/continue/queue control.
 Reach for the harness shape when you want an app layer around the loop:
 session/transcript helpers, resource and prompt entry points, provider/auth
 hooks, active tool selection, compaction/tree workflows, and higher-level queue
-events. `CuaHarness` is the thin CUA version of that shape today: it installs
-CUA defaults, delegates runtime methods to the wrapped `Agent`, and adds
-`getTranscript()`.
+events. `CuaAgentHarness` extends pi `AgentHarness`, installs CUA defaults, and
+refreshes provider-specific runtime state when `setModel()` changes models.
 
 ## Core Concepts
 
 ### Class-First API
 
 - `CuaAgent extends Agent`
-- `CuaHarness` wraps a pi `Agent` with a harness-style constructor and
-  delegated runtime methods.
+- `CuaAgentHarness extends AgentHarness`
 
 Both classes mirror pi constructor shapes and behavior, with minimal additions:
 - `browser` (Kernel browser response)
@@ -84,6 +82,17 @@ If tools are omitted, the classes install canonical CUA computer tool executors
 using runtime specs from `@onkernel/cua-ai`. If tools are provided, they are
 used exactly.
 
+### Model Switching
+
+`CuaAgent` follows pi `Agent` semantics: assign `agent.state.model` to a
+concrete model or CUA model ref. CUA-owned tools and the default system prompt
+refresh with the new provider runtime.
+
+`CuaAgentHarness` follows pi `AgentHarness` semantics: call
+`await harness.setModel(model)`. The harness updates its model through pi's
+snapshot machinery and refreshes CUA-owned tools and default prompt state for
+the next provider request.
+
 ### Tool Composition
 
 Use `createCuaComputerTools()` to compose your own tool list from canonical
@@ -105,4 +114,4 @@ const tools = [
 ```
 
 For full event semantics, steering, follow-up queues, and tool execution
-details, see the pi-agent-core README.
+details, see the pi agent core source vendored in this package.

packages/agent/README.md

@@ -1,6 +1,6 @@
 import Kernel from "@onkernel/sdk";
 import { requireCuaEnvApiKeyForModel, type CuaModelRef } from "@onkernel/cua-ai";
-import { CuaHarness } from "../src/index";
+import { CuaAgentHarness } from "../src/index";
 import { SCENARIOS } from "./shared/scenarios";
 
 const modelRef = (process.env.MODEL_REF as CuaModelRef | undefined) ?? "openai:gpt-5.5";
@@ -13,7 +13,7 @@ async function main(): Promise<void> {
 	const browser = await client.browsers.create({ stealth: true });
 
 	try {
-		const harness = new CuaHarness({
+		const harness = new CuaAgentHarness({
 			browser,
 			client,
 			model: modelRef,

packages/agent/examples/harness-openai-smoke.ts

@@ -1,6 +1,6 @@
 import Kernel from "@onkernel/sdk";
 import { requireCuaEnvApiKeyForModel, type CuaModelRef } from "@onkernel/cua-ai";
-import { CuaHarness } from "../src/index";
+import { CuaAgentHarness } from "../src/index";
 import { SCENARIOS } from "./shared/scenarios";
 
 const modelRef = (process.env.MODEL_REF as CuaModelRef | undefined) ?? "openai:gpt-5.5";
@@ -15,7 +15,7 @@ async function main(): Promise<void> {
 	const scenario = SCENARIOS.find((entry) => entry.name === scenarioName) ?? SCENARIOS[0]!;
 
 	try {
-		const harness = new CuaHarness({
+		const harness = new CuaAgentHarness({
 			browser,
 			client,
 			model: modelRef,

packages/agent/examples/harness-provider-matrix.ts

@@ -16,7 +16,9 @@
     "dist",
     "examples",
     "README.md",
-    "CHANGELOG.md"
+    "CHANGELOG.md",
+    "src/vendor/pi-agent-core/LICENSE",
+    "src/vendor/pi-agent-core/README.md"
   ],
   "scripts": {
     "build": "tsc -b",
@@ -26,10 +28,10 @@
     "test": "vitest --run"
   },
   "dependencies": {
-    "@earendil-works/pi-agent-core": "^0.74.0",
     "@earendil-works/pi-ai": "^0.74.0",
     "@onkernel/cua-ai": "0.1.0",
-    "@onkernel/sdk": "0.49.0"
+    "@onkernel/sdk": "0.49.0",
+    "typebox": "^1.1.38"
   },
   "devDependencies": {
     "vitest": "^3.2.4"

packages/agent/package.json

@@ -0,0 +1,55 @@
+import { mkdir, writeFile } from "node:fs/promises";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const PI_COMMIT = "40c05f55391663024a6a05ad33249b616a04e7a1";
+const FILES = [
+	"agent.ts",
+	"agent-loop.ts",
+	"harness/agent-harness.ts",
+	"harness/compaction/branch-summarization.ts",
+	"harness/compaction/compaction.ts",
+	"harness/compaction/utils.ts",
+	"harness/env/nodejs.ts",
+	"harness/execution-env.ts",
+	"harness/messages.ts",
+	"harness/prompt-templates.ts",
+	"harness/session/repo/jsonl.ts",
+	"harness/session/repo/memory.ts",
+	"harness/session/repo/shared.ts",
+	"harness/session/session.ts",
+	"harness/session/storage/jsonl.ts",
+	"harness/session/storage/memory.ts",
+	"harness/session/uuid.ts",
+	"harness/skills.ts",
+	"harness/system-prompt.ts",
+	"harness/types.ts",
+	"harness/utils/shell-output.ts",
+	"harness/utils/truncate.ts",
+	"index.ts",
+	"proxy.ts",
+	"types.ts",
+];
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const vendorRoot = join(__dirname, "../src/vendor/pi-agent-core");
+const repoRawBase = `https://raw.githubusercontent.com/badlogic/pi-mono/${PI_COMMIT}`;
+const rawBase = `${repoRawBase}/packages/agent/src`;
+
+for (const file of FILES) {
+	const response = await fetch(`${rawBase}/${file}`);
+	if (!response.ok) {
+		throw new Error(`Failed to fetch ${file}: ${response.status} ${response.statusText}`);
+	}
+	const outputPath = join(vendorRoot, file);
+	await mkdir(dirname(outputPath), { recursive: true });
+	await writeFile(outputPath, await response.text());
+	console.log(`vendored ${file}`);
+}
+
+const licenseResponse = await fetch(`${repoRawBase}/LICENSE`);
+if (!licenseResponse.ok) {
+	throw new Error(`Failed to fetch LICENSE: ${licenseResponse.status} ${licenseResponse.statusText}`);
+}
+await writeFile(join(vendorRoot, "LICENSE"), await licenseResponse.text());
+console.log("vendored LICENSE");