feat(durable): expose models on ToolExecutionApi and HookApi

closes #10395

packages/durable/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- `ToolExecutionApi.models` and `HookApi.models`: the Harness's `models`, so tools and hooks can resolve models and make requests with the same catalog, credentials, and request transforms as generation ([#10395](https://github.com/earendil-works/pi/issues/10395)).
+
 ### Changed
 
 - Within one task invocation, `runtime.context()` reuses the range its previous read scanned and reads only entries committed since then, unless the head marker changed. A generation's request no longer rereads the whole transcript after its prepare, which roughly halves context reads per turn. The range is dropped when the invocation ends or sleeps.

packages/durable/docs/spec.md

@@ -2561,6 +2561,8 @@ type HookResult<T> = T | undefined | Promise<T | undefined>;
 interface HookApi extends DocumentReader {
   readonly taskId: TaskId;
   readonly conversationId: ConversationId;
+  /** `HarnessOptions.models`. */
+  readonly models: Models;
   memo<T extends JsonValue>(name: string, context: Context): Promise<T | undefined>;
   memo<T extends JsonValue>(name: string, candidate: T, context: Context): Promise<T>;
 }
@@ -2693,6 +2695,8 @@ interface ToolExecutionApi<TDetails extends JsonValue = JsonValue> extends Docum
   readonly registry: RegistrySnapshot;
   /** The calling conversation's agent, as the tool task's phase resolved it. */
   agent(context: Context): Promise<Agent>;
+  /** `HarnessOptions.models`: the catalog, credentials, and request transforms generation uses. */
+  readonly models: Models;
   /** Built by `HarnessOptions.env` for this call. */
   readonly env: ExecutionEnv | undefined;
   output(chunk: string | Uint8Array): void;

packages/durable/src/harness/tool.ts

@@ -190,6 +190,7 @@ async function run(
 		callId: call.id,
 		registry: runtime.registry,
 		agent: runtime.agent,
+		models: runtime.models,
 		output: (chunk, skipped) => {
 			assertLive();
 			if (reported.output.push(chunk, skipped)) progress.mark();

packages/durable/src/harness/types.ts

@@ -171,6 +171,8 @@ export interface ToolExecutionApi<TDetails extends JsonValue = JsonValue> extend
 	readonly registry: RegistrySnapshot;
 	/** The calling conversation's agent, as the tool task's phase resolved it. */
 	agent(context: Context): Promise<Agent>;
+	/** `HarnessOptions.models`: the catalog, credentials, and request transforms generation uses. */
+	readonly models: Models;
 	/** Built by `HarnessOptions.env` for this call; `undefined` without an environment. */
 	readonly env: ExecutionEnv | undefined;
 	/**
@@ -605,6 +607,8 @@ export interface Harness extends Session {
 export interface HookApi extends DocumentReader {
 	readonly taskId: TaskId;
 	readonly conversationId: ConversationId;
+	/** `HarnessOptions.models`. */
+	readonly models: Models;
 	memo<T extends JsonValue>(name: string, context: Context): Promise<T | undefined>;
 	memo<T extends JsonValue>(name: string, candidate: T, context: Context): Promise<T>;
 }

packages/durable/test/harness-tools.test.ts

@@ -111,6 +111,30 @@ describe("tool round", () => {
 		await harness.close(context);
 	});
 
+	// #10395
+	it("gives tools and hooks the Harness's models", async () => {
+		const setup = chatSetup();
+		const seen: unknown[] = [];
+		addTool(
+			setup.registry,
+			tool("echo", async (_args, api) => {
+				seen.push(api.models);
+				return { content: [] };
+			}),
+		);
+		addHooks(setup.registry, ToolTask, {
+			beforeTool: (_call, api) => {
+				seen.push(api.models);
+				return undefined;
+			},
+		});
+		const { harness, status } = await run(setup, [calls(["echo", {}, "c1"]), DONE]);
+		expect(status).toBe("done");
+		expect(seen).toEqual([setup.models, setup.models]);
+		expect(seen.every((models) => models === setup.models)).toBe(true);
+		await harness.close(context);
+	});
+
 	it("answers calls to tools the request did not offer without a task", async () => {
 		const setup = chatSetup();
 		addTool(