fix(coding-agent): preserve run prompt during tool refresh

closes #6162

packages/coding-agent/test/suite/regressions/6162-extension-active-tools-next-turn.test.ts

@@ -0,0 +1,136 @@
+import { fauxAssistantMessage, fauxToolCall } from "@earendil-works/pi-ai";
+import { Type } from "typebox";
+import { describe, expect, it } from "vitest";
+import type { ExtensionFactory } from "../../../src/index.ts";
+import { createHarness } from "../harness.ts";
+
+describe("extension active tools next-turn refresh", () => {
+	it("applies pi.setActiveTools before the next provider request in the same run", async () => {
+		const extensionFactories: ExtensionFactory[] = [
+			(pi) => {
+				pi.registerTool({
+					name: "switch_tools",
+					label: "Switch Tools",
+					description: "Switch the active extension tool set",
+					promptSnippet: "Switch to the next extension tool",
+					parameters: Type.Object({}),
+					execute: async () => {
+						pi.setActiveTools(["after_switch"]);
+						return {
+							content: [{ type: "text", text: "switched" }],
+							details: {},
+						};
+					},
+				});
+
+				pi.registerTool({
+					name: "after_switch",
+					label: "After Switch",
+					description: "Tool that should be available after switching",
+					promptSnippet: "Run after the active tool set changes",
+					parameters: Type.Object({}),
+					execute: async () => ({
+						content: [{ type: "text", text: "after" }],
+						details: {},
+					}),
+				});
+			},
+		];
+		const harness = await createHarness({
+			extensionFactories,
+		});
+
+		try {
+			harness.session.setActiveToolsByName(["switch_tools"]);
+
+			const providerToolNames: string[][] = [];
+			harness.setResponses([
+				(context) => {
+					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
+					return fauxAssistantMessage(fauxToolCall("switch_tools", {}), { stopReason: "toolUse" });
+				},
+				(context) => {
+					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
+					return fauxAssistantMessage("done");
+				},
+			]);
+
+			expect(harness.session.getActiveToolNames()).toEqual(["switch_tools"]);
+
+			await harness.session.prompt("start");
+
+			expect(harness.session.getActiveToolNames()).toEqual(["after_switch"]);
+			expect(providerToolNames).toEqual([["switch_tools"], ["after_switch"]]);
+		} finally {
+			harness.cleanup();
+		}
+	});
+
+	it("preserves before_agent_start system prompt overrides when tools change mid-run", async () => {
+		const extensionFactories: ExtensionFactory[] = [
+			(pi) => {
+				pi.on("before_agent_start", async (event) => ({
+					systemPrompt: `${event.systemPrompt}\n\nkeep this run override`,
+				}));
+
+				pi.registerTool({
+					name: "switch_tools",
+					label: "Switch Tools",
+					description: "Switch the active extension tool set",
+					promptSnippet: "Switch to the next extension tool",
+					parameters: Type.Object({}),
+					execute: async () => {
+						pi.setActiveTools(["after_switch"]);
+						return {
+							content: [{ type: "text", text: "switched" }],
+							details: {},
+						};
+					},
+				});
+
+				pi.registerTool({
+					name: "after_switch",
+					label: "After Switch",
+					description: "Tool that should be available after switching",
+					promptSnippet: "Run after the active tool set changes",
+					parameters: Type.Object({}),
+					execute: async () => ({
+						content: [{ type: "text", text: "after" }],
+						details: {},
+					}),
+				});
+			},
+		];
+		const harness = await createHarness({
+			extensionFactories,
+		});
+
+		try {
+			harness.session.setActiveToolsByName(["switch_tools"]);
+
+			const providerSystemPrompts: string[] = [];
+			const providerToolNames: string[][] = [];
+			harness.setResponses([
+				(context) => {
+					providerSystemPrompts.push(context.systemPrompt ?? "");
+					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
+					return fauxAssistantMessage(fauxToolCall("switch_tools", {}), { stopReason: "toolUse" });
+				},
+				(context) => {
+					providerSystemPrompts.push(context.systemPrompt ?? "");
+					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
+					return fauxAssistantMessage("done");
+				},
+			]);
+
+			await harness.session.prompt("start");
+
+			expect(providerToolNames).toEqual([["switch_tools"], ["after_switch"]]);
+			expect(providerSystemPrompts).toHaveLength(2);
+			expect(providerSystemPrompts[0]).toContain("keep this run override");
+			expect(providerSystemPrompts[1]).toContain("keep this run override");
+		} finally {
+			harness.cleanup();
+		}
+	});
+});

packages/coding-agent/test/suite/regressions/extension-active-tools-next-turn.test.ts

@@ -1,68 +0,0 @@
-import { fauxAssistantMessage, fauxToolCall } from "@earendil-works/pi-ai";
-import { Type } from "typebox";
-import { describe, expect, it } from "vitest";
-import type { ExtensionFactory } from "../../../src/index.ts";
-import { createHarness } from "../harness.ts";
-
-describe("extension active tools next-turn refresh", () => {
-	it("applies pi.setActiveTools before the next provider request in the same run", async () => {
-		const extensionFactories: ExtensionFactory[] = [
-			(pi) => {
-				pi.registerTool({
-					name: "switch_tools",
-					label: "Switch Tools",
-					description: "Switch the active extension tool set",
-					promptSnippet: "Switch to the next extension tool",
-					parameters: Type.Object({}),
-					execute: async () => {
-						pi.setActiveTools(["after_switch"]);
-						return {
-							content: [{ type: "text", text: "switched" }],
-							details: {},
-						};
-					},
-				});
-
-				pi.registerTool({
-					name: "after_switch",
-					label: "After Switch",
-					description: "Tool that should be available after switching",
-					promptSnippet: "Run after the active tool set changes",
-					parameters: Type.Object({}),
-					execute: async () => ({
-						content: [{ type: "text", text: "after" }],
-						details: {},
-					}),
-				});
-			},
-		];
-		const harness = await createHarness({
-			extensionFactories,
-		});
-
-		try {
-			harness.session.setActiveToolsByName(["switch_tools"]);
-
-			const providerToolNames: string[][] = [];
-			harness.setResponses([
-				(context) => {
-					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
-					return fauxAssistantMessage(fauxToolCall("switch_tools", {}), { stopReason: "toolUse" });
-				},
-				(context) => {
-					providerToolNames.push((context.tools ?? []).map((tool) => tool.name).sort());
-					return fauxAssistantMessage("done");
-				},
-			]);
-
-			expect(harness.session.getActiveToolNames()).toEqual(["switch_tools"]);
-
-			await harness.session.prompt("start");
-
-			expect(harness.session.getActiveToolNames()).toEqual(["after_switch"]);
-			expect(providerToolNames).toEqual([["switch_tools"], ["after_switch"]]);
-		} finally {
-			harness.cleanup();
-		}
-	});
-});