Make Chrome primer and authorization log prompt-cache friendly

- Contribute the primer as a structured prompt section instead of forcing systemPrompt.
- Log pi-chrome-tool-change as a rendered custom entry that is not sent to the model.

1 files changed, 52 insertions, 0 deletions

diff --git a/test-suite/unit/prompt-section.test.mjs b/test-suite/unit/prompt-section.test.mjs
new file mode 100644
index 0000000..b83f526
--- /dev/null
+++ b/test-suite/unit/prompt-section.test.mjs
@@ -0,0 +1,52 @@
+// The Chrome primer must be a structured prompt section, never a forced `systemPrompt` override.
+// A forced override makes pi collapse all system messages into a new leading prompt every run,
+// which busts the provider prompt cache.
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import vm from "node:vm";
+import { stripTypeScriptTypes } from "node:module";
+import { test } from "node:test";
+
+const source = fs.readFileSync(new URL("../../extensions/chrome-profile-bridge/index.ts", import.meta.url), "utf8");
+const from = source.indexOf('pi.on("before_agent_start",');
+const to = source.indexOf("// Shared handlers,", from);
+assert.ok(from >= 0 && to > from, "Missing before_agent_start section");
+const handlerSource = stripTypeScriptTypes(source.slice(from, to));
+
+function load({ registered = true, authorized = true } = {}) {
+	let handler;
+	const pi = { on: (name, fn) => { if (name === "before_agent_start") handler = fn; } };
+	vm.runInNewContext(`${handlerSource}`, {
+		pi,
+		chromeToolsRegistered: registered,
+		chromeControlAuthorized: () => authorized,
+	});
+	return handler;
+}
+
+test("authorized: adds primer section and does not force systemPrompt", () => {
+	const event = { systemPrompt: "base", systemPromptOptions: { sections: {} } };
+	const result = load()(event);
+	assert.equal(result, undefined);
+	const primer = event.systemPromptOptions.sections["chrome-profile-bridge"];
+	assert.match(primer, /^Chrome control is available/);
+	assert.doesNotMatch(primer, /<\/?chrome-profile-bridge>/, "pi wraps sections in their tag");
+});
+
+test("locked: removes primer section and does not force systemPrompt", () => {
+	const event = { systemPrompt: "base", systemPromptOptions: { sections: { "chrome-profile-bridge": "stale", other: "keep" } } };
+	assert.equal(load({ authorized: false })(event), undefined);
+	assert.deepEqual(event.systemPromptOptions.sections, { other: "keep" });
+});
+
+test("tools not registered: no primer", () => {
+	const event = { systemPrompt: "base", systemPromptOptions: { sections: {} } };
+	assert.equal(load({ registered: false })(event), undefined);
+	assert.deepEqual(event.systemPromptOptions.sections, {});
+});
+
+test("legacy pi without sections: appends only when authorized", () => {
+	assert.equal(load({ authorized: false })({ systemPrompt: "base" }), undefined);
+	const result = load()({ systemPrompt: "base" });
+	assert.match(result.systemPrompt, /^base\n<chrome-profile-bridge>\nChrome control is available[\s\S]*<\/chrome-profile-bridge>$/);
+});