feat: add agent-managed forked side threads

apps/server/src/mcp/McpHttpServer.ts

@@ -22,6 +22,8 @@ import {
   PreviewSnapshotToolkit,
   PreviewStandardToolkit,
 } from "./toolkits/preview/tools.ts";
+import { ThreadToolkitHandlersLayerLive } from "./toolkits/threads/handlers.ts";
+import { ThreadToolkit } from "./toolkits/threads/tools.ts";
 
 const unauthorized = HttpServerResponse.jsonUnsafe(
   {
@@ -208,10 +210,17 @@ export const PreviewToolkitRegistrationLive = Layer.mergeAll(
   PreviewSnapshotRegistrationLive,
 );
 
+export const ThreadToolkitRegistrationLive = McpServer.toolkit(ThreadToolkit).pipe(
+  Layer.provide(ThreadToolkitHandlersLayerLive),
+);
+
 const McpTransportLive = McpServer.layerHttp({
   name: "T3 Code",
   version: packageJson.version,
   path: "/mcp",
 }).pipe(Layer.provide(McpAuthMiddlewareLive));
 
-export const layer = PreviewToolkitRegistrationLive.pipe(Layer.provideMerge(McpTransportLive));
+export const layer = Layer.mergeAll(
+  PreviewToolkitRegistrationLive,
+  ThreadToolkitRegistrationLive,
+).pipe(Layer.provideMerge(McpTransportLive));

apps/server/src/mcp/McpInvocationContext.test.ts

@@ -37,3 +37,26 @@ it.effect("reports the scoped credential context when preview capability is unav
     expect(error.message).toBe("MCP credential does not grant the preview capability.");
   });
 });
+
+it.effect("reports a missing thread coordination capability", () => {
+  const invocation: McpInvocationContext.McpInvocationScope = {
+    environmentId: EnvironmentId.make("environment-1"),
+    threadId: ThreadId.make("thread-1"),
+    providerSessionId: "provider-session-1",
+    providerInstanceId: ProviderInstanceId.make("codex"),
+    capabilities: new Set(["preview"]),
+    issuedAt: 1,
+    expiresAt: 2,
+  };
+
+  return Effect.gen(function* () {
+    const error = yield* McpInvocationContext.requireMcpCapability("threads").pipe(
+      Effect.provideService(McpInvocationContext.McpInvocationContext, invocation),
+      Effect.flip,
+    );
+
+    expect(error).toBeInstanceOf(PreviewAutomationUnavailableError);
+    expect(error.capability).toBe("threads");
+    expect(error.message).toBe("MCP credential does not grant the threads capability.");
+  });
+});

apps/server/src/mcp/McpInvocationContext.ts

@@ -7,7 +7,7 @@ import {
 import * as Context from "effect/Context";
 import * as Effect from "effect/Effect";
 
-export type McpCapability = "preview";
+export type McpCapability = "preview" | "threads";
 
 export interface McpInvocationScope {
   readonly environmentId: EnvironmentId;

apps/server/src/mcp/McpSessionRegistry.ts

@@ -114,7 +114,7 @@ const makeWithOptions = Effect.fn("McpSessionRegistry.make")(function* (
         threadId: ThreadId.make(request.threadId),
         providerSessionId,
         providerInstanceId: ProviderInstanceId.make(request.providerInstanceId),
-        capabilities: new Set(["preview"]),
+        capabilities: new Set(["preview", "threads"]),
         issuedAt,
         expiresAt,
       };

apps/server/src/mcp/toolkits/threads/handlers.ts

@@ -0,0 +1,249 @@
+import {
+  CommandId,
+  MessageId,
+  ThreadId,
+  type OrchestrationThread,
+  type OrchestrationThreadShell,
+} from "@t3tools/contracts";
+import * as Cause from "effect/Cause";
+import * as Crypto from "effect/Crypto";
+import * as DateTime from "effect/DateTime";
+import * as Effect from "effect/Effect";
+import * as Option from "effect/Option";
+
+import * as McpInvocationContext from "../../McpInvocationContext.ts";
+import { OrchestrationEngineService } from "../../../orchestration/Services/OrchestrationEngine.ts";
+import { ProjectionSnapshotQuery } from "../../../orchestration/Services/ProjectionSnapshotQuery.ts";
+import { ThreadToolkit, ThreadToolError } from "./tools.ts";
+
+const asToolFailure = (operation: string) => (cause: Cause.Cause<unknown>) =>
+  Effect.fail(
+    new ThreadToolError({
+      operation,
+      detail: Cause.pretty(cause),
+    }),
+  );
+
+const runThreadOperation = <A, E, R>(
+  operation: string,
+  effect: Effect.Effect<A, E, R>,
+): Effect.Effect<A, ThreadToolError, R> => effect.pipe(Effect.catchCause(asToolFailure(operation)));
+
+const makeHandlers = Effect.gen(function* () {
+  const invocation = yield* McpInvocationContext.requireMcpCapability("threads");
+  const engine = yield* OrchestrationEngineService;
+  const query = yield* ProjectionSnapshotQuery;
+  const crypto = yield* Crypto.Crypto;
+
+  const newId = Effect.fn("ThreadToolkit.newId")(function* () {
+    return yield* crypto.randomUUIDv4.pipe(Effect.orDie);
+  });
+
+  const currentThread = Effect.fn("ThreadToolkit.currentThread")(function* () {
+    const thread = yield* query.getThreadDetailById(invocation.threadId);
+    if (Option.isNone(thread)) {
+      return yield* new ThreadToolError({
+        operation: "thread_current",
+        detail: `Current thread '${invocation.threadId}' was not found.`,
+      });
+    }
+    return thread.value;
+  });
+
+  const projectThread = Effect.fn("ThreadToolkit.projectThread")(function* (threadId: ThreadId) {
+    const [current, target] = yield* Effect.all([
+      currentThread(),
+      query.getThreadDetailById(threadId),
+    ]);
+    if (Option.isNone(target) || target.value.projectId !== current.projectId) {
+      return yield* new ThreadToolError({
+        operation: "thread_target",
+        detail: `Thread '${threadId}' is not an active thread in the current project.`,
+      });
+    }
+    return target.value;
+  });
+
+  const startTurn = Effect.fn("ThreadToolkit.startTurn")(function* (
+    thread: OrchestrationThread,
+    prompt: string,
+  ) {
+    const [commandUuid, messageUuid, createdAt] = yield* Effect.all([
+      newId(),
+      newId(),
+      DateTime.now.pipe(Effect.map(DateTime.formatIso)),
+    ]);
+    yield* engine.dispatch({
+      type: "thread.turn.start",
+      commandId: CommandId.make(commandUuid),
+      threadId: thread.id,
+      message: {
+        messageId: MessageId.make(messageUuid),
+        role: "user",
+        text: prompt,
+        attachments: [],
+      },
+      modelSelection: thread.modelSelection,
+      runtimeMode: thread.runtimeMode,
+      interactionMode: thread.interactionMode,
+      createdAt,
+    });
+  });
+
+  const resultFor = (thread: Pick<OrchestrationThread, "id" | "title">, turnStarted: boolean) => ({
+    threadId: thread.id,
+    title: thread.title,
+    turnStarted,
+  });
+
+  return {
+    thread_list: (input: { readonly includeArchived?: boolean | undefined }) =>
+      Effect.gen(function* () {
+        const current = yield* currentThread();
+        const snapshot = yield* query.getShellSnapshot();
+        return snapshot.threads
+          .filter(
+            (thread) =>
+              thread.projectId === current.projectId &&
+              (input.includeArchived === true || thread.archivedAt === null),
+          )
+          .map((thread: OrchestrationThreadShell) => ({
+            threadId: thread.id,
+            title: thread.title,
+            status: thread.session?.status ?? "idle",
+            createdAt: thread.createdAt,
+            ...(thread.forkedFrom?.threadId
+              ? { forkedFromThreadId: thread.forkedFrom.threadId }
+              : {}),
+            ...(thread.forkedFrom?.turnId ? { forkedFromTurnId: thread.forkedFrom.turnId } : {}),
+          }));
+      }),
+    thread_create: (input: {
+      readonly title?: string | undefined;
+      readonly prompt?: string | undefined;
+    }) =>
+      Effect.gen(function* () {
+        const current = yield* currentThread();
+        const [threadUuid, commandUuid, createdAt] = yield* Effect.all([
+          newId(),
+          newId(),
+          DateTime.now.pipe(Effect.map(DateTime.formatIso)),
+        ]);
+        const threadId = ThreadId.make(threadUuid);
+        const title = input.title ?? "New thread";
+        yield* engine.dispatch({
+          type: "thread.create",
+          commandId: CommandId.make(commandUuid),
+          threadId,
+          projectId: current.projectId,
+          title,
+          modelSelection: current.modelSelection,
+          runtimeMode: current.runtimeMode,
+          interactionMode: current.interactionMode,
+          branch: current.branch,
+          worktreePath: current.worktreePath,
+          createdAt,
+        });
+        const created = { ...current, id: threadId, title };
+        if (input.prompt !== undefined) yield* startTurn(created, input.prompt);
+        return resultFor(created, input.prompt !== undefined);
+      }),
+    thread_fork: (input: {
+      readonly sourceThreadId?: ThreadId | undefined;
+      readonly sourceTurnId?: import("@t3tools/contracts").TurnId | undefined;
+      readonly title?: string | undefined;
+      readonly prompt?: string | undefined;
+    }) =>
+      Effect.gen(function* () {
+        const source = yield* projectThread(input.sourceThreadId ?? invocation.threadId);
+        const [threadUuid, commandUuid, createdAt] = yield* Effect.all([
+          newId(),
+          newId(),
+          DateTime.now.pipe(Effect.map(DateTime.formatIso)),
+        ]);
+        const threadId = ThreadId.make(threadUuid);
+        const title = input.title ?? `${source.title} (fork)`;
+        yield* engine.dispatch({
+          type: "thread.fork",
+          commandId: CommandId.make(commandUuid),
+          threadId,
+          sourceThreadId: source.id,
+          ...(input.sourceTurnId !== undefined ? { sourceTurnId: input.sourceTurnId } : {}),
+          title,
+          createdAt,
+        });
+        const forked = {
+          ...source,
+          id: threadId,
+          title,
+          forkedFrom: {
+            threadId: source.id,
+            turnId: input.sourceTurnId ?? source.latestTurn?.turnId ?? null,
+          },
+          session: null,
+        };
+        if (input.prompt !== undefined) yield* startTurn(forked, input.prompt);
+        return resultFor(forked, input.prompt !== undefined);
+      }),
+    thread_send: (input: { readonly threadId: ThreadId; readonly prompt: string }) =>
+      Effect.gen(function* () {
+        const target = yield* projectThread(input.threadId);
+        yield* startTurn(target, input.prompt);
+        return resultFor(target, true);
+      }),
+    thread_archive: (input: { readonly threadId: ThreadId }) =>
+      Effect.gen(function* () {
+        if (input.threadId === invocation.threadId) {
+          return yield* new ThreadToolError({
+            operation: "thread_archive",
+            detail: "The current agent thread cannot archive itself.",
+          });
+        }
+        yield* projectThread(input.threadId);
+        yield* engine.dispatch({
+          type: "thread.archive",
+          commandId: CommandId.make(yield* newId()),
+          threadId: input.threadId,
+        });
+        return null;
+      }),
+  };
+});
+
+export const ThreadToolkitHandlers = {
+  thread_list: (input: { readonly includeArchived?: boolean | undefined }) =>
+    runThreadOperation(
+      "thread_list",
+      makeHandlers.pipe(Effect.flatMap((handlers) => handlers.thread_list(input))),
+    ),
+  thread_create: (input: {
+    readonly title?: string | undefined;
+    readonly prompt?: string | undefined;
+  }) =>
+    runThreadOperation(
+      "thread_create",
+      makeHandlers.pipe(Effect.flatMap((handlers) => handlers.thread_create(input))),
+    ),
+  thread_fork: (input: {
+    readonly sourceThreadId?: ThreadId | undefined;
+    readonly sourceTurnId?: import("@t3tools/contracts").TurnId | undefined;
+    readonly title?: string | undefined;
+    readonly prompt?: string | undefined;
+  }) =>
+    runThreadOperation(
+      "thread_fork",
+      makeHandlers.pipe(Effect.flatMap((handlers) => handlers.thread_fork(input))),
+    ),
+  thread_send: (input: { readonly threadId: ThreadId; readonly prompt: string }) =>
+    runThreadOperation(
+      "thread_send",
+      makeHandlers.pipe(Effect.flatMap((handlers) => handlers.thread_send(input))),
+    ),
+  thread_archive: (input: { readonly threadId: ThreadId }) =>
+    runThreadOperation(
+      "thread_archive",
+      makeHandlers.pipe(Effect.flatMap((handlers) => handlers.thread_archive(input))),
+    ),
+} satisfies Parameters<typeof ThreadToolkit.toLayer>[0];
+
+export const ThreadToolkitHandlersLayerLive = ThreadToolkit.toLayer(ThreadToolkitHandlers);

apps/server/src/mcp/toolkits/threads/tools.test.ts

@@ -0,0 +1,26 @@
+import { expect, it } from "@effect/vitest";
+import { Tool } from "effect/unstable/ai";
+
+import { ThreadToolkit } from "./tools.ts";
+
+it("exports provider-compatible thread management schemas", () => {
+  expect(Object.keys(ThreadToolkit.tools).sort()).toEqual([
+    "thread_archive",
+    "thread_create",
+    "thread_fork",
+    "thread_list",
+    "thread_send",
+  ]);
+
+  for (const tool of Object.values(ThreadToolkit.tools)) {
+    const schema = Tool.getJsonSchema(tool) as {
+      readonly type?: unknown;
+      readonly anyOf?: unknown;
+      readonly oneOf?: unknown;
+    };
+    expect(tool.description?.length ?? 0).toBeGreaterThan(40);
+    expect(schema.type, `${tool.name} must export a top-level object schema`).toBe("object");
+    expect(schema.anyOf, `${tool.name} must not export a root anyOf`).toBeUndefined();
+    expect(schema.oneOf, `${tool.name} must not export a root oneOf`).toBeUndefined();
+  }
+});