bryan-hunter · Sep 8, 2026 · Sep 8, 2026 · Sep 8, 2026 · Sep 8, 2026
@@ -0,0 +1,5 @@
+---
+"eve": patch
+---
+
+Add opt-in `experimental.taskEventDelivery` for agents that orchestrate background work. Task notifications remain chronological, compaction restores task identities, and queued child requests are serviced between parent steps without requiring the parent to end its turn.
@@ -5,6 +5,18 @@ description: "Delegate work to root-agent copies or declared specialists with th
 
 eve supports two ways to delegate work: the root-only built-in `agent` tool, which starts or continues a copy of the root agent, and declared subagents, which are specialists with their own directories. Use a subagent to run independent work in parallel, narrow the available tools, or give a task to a specialist.
 
+## Agent-directed task delivery
+
+Set `experimental: { taskEventDelivery: true }` in the parent agent definition to let its instructions govern how it handles background results. This disables the default launch acknowledgement and cohort reporting instructions, and stops injecting the changing task inventory into model requests. Existing task receipts and notifications remain in conversation history; task ownership, cancellation, approvals, and notification delivery are unchanged.
+
+With this option, the runtime services queued child requests between parent model steps. The parent does not need to end its turn to start a child, but requests arriving during an in-flight model or tool step wait for a safe step boundary. User messages and task-result notifications still follow their normal turn-delivery policy.
+
+Tell the parent to continue useful work after delegation, consume results as they arrive, and distinguish finishing its current turn from completing the user's request. Background notification turns may intentionally deliver nothing when there is nothing new to report. Child sessions and structured-output sessions still require an output.
+
+After compaction, eve adds a point-in-time index of task IDs, names, and terminal or unsettled statuses. It does not duplicate result bodies or private executor credentials. The compaction summary retains relevant results and artifact paths. Keep large findings in shared artifacts and return their locations in task results. Later notifications supersede the recovery snapshot.
+
+The option defaults to off. It reduces changing prompt context but does not guarantee provider cache hits.
+
 ## The built-in `agent` tool
 
 The root session receives `agent` by default. The model calls it to delegate a task to a new copy of the root agent or continue an existing copy:

@@ -0,0 +1,13 @@
+import { z } from "zod";
+import { defineDynamic, defineTool } from "#public/tools/index.js";
+
+export default defineDynamic({
+  events: {
+    "session.started": () =>
+      defineTool({
+        description: "Read a report.",
+        inputSchema: z.object({ report: z.string() }),
+        execute: ({ report }) => ({ report }),
+      }),
+  },
+});
@@ -0,0 +1,6 @@
+import { defineAgent } from "#public/definitions/agent.js";
+
+export default defineAgent({
+  model: "openai/gpt-5.5",
+  description: "Inspect a report.",
+});
@@ -0,0 +1,8 @@
+import { z } from "zod";
+import { defineTool } from "#public/tools/index.js";
+
+export default defineTool({
+  description: "Read a report.",
+  inputSchema: z.object({ report: z.string() }),
+  execute: ({ report }) => ({ report }),
+});
@@ -0,0 +1,13 @@
+{
+  "kind": "eve-extension-capability-contract",
+  "capability": "dynamicTool",
+  "epoch": 30,
+  "sha256": "fc1240ef5a9d41023d6847bf856505a4e8ec9ac135e343b17677e4b413629c61",
+  "exports": [
+    "DynamicToolEntry",
+    "DynamicToolEvents",
+    "DynamicToolResult",
+    "DynamicToolSet",
+    "defineDynamic"
+  ]
+}
@@ -0,0 +1,20 @@
+{
+  "kind": "eve-extension-capability-contract",
+  "capability": "subagent",
+  "epoch": 10,
+  "sha256": "947460b56cab11573a22ee71731121356bde6073c46bc33c15a245e3ca476ec2",
+  "exports": [
+    "AgentCompactionDefinition",
+    "AgentDefinition",
+    "AgentModelDefinition",
+    "AgentStaticModelDefinition",
+    "DefinedAgent",
+    "DynamicLocalSubagentDefinition",
+    "DynamicSubagentDefinition",
+    "RemoteAgentDefinition",
+    "RemoteAgentDefinitionInput",
+    "defineAgent",
+    "defineDynamic",
+    "defineRemoteAgent"
+  ]
+}
@@ -0,0 +1,20 @@
+{
+  "kind": "eve-extension-capability-contract",
+  "capability": "tool",
+  "epoch": 31,
+  "sha256": "6e33c63a9a14307ea6456f75dc7c25eca93b99d45e980484a162ce583cdb5e60",
+  "exports": [
+    "defaultWebSearch",
+    "defineTool",
+    "defineWorkflowTool",
+    "disableTool",
+    "experimental_workflow",
+    "isDisabledToolSentinel",
+    "isExperimentalWorkflowToolDefinition",
+    "isWebSearchToolDefinition",
+    "toolOutput",
+    "toolOutputPart",
+    "toolResultFrom",
+    "webSearch"
+  ]
+}
@@ -22,8 +22,8 @@ interface ExtensionCapabilityContract {
 const EXTENSION_CAPABILITY_CONTRACTS = {
   extension: { current: 1, supported: [1], dropped: {} },
   tool: {
-    current: 30,
-    supported: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 28, 29, 30],
+    current: 31,
+    supported: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 28, 29, 30, 31],
     dropped: {
       14: "TaskExec.delegated was removed; migrate to workflow-backed background tools",
       15: "TaskExec replaces stageEffect with send",
@@ -42,8 +42,10 @@ const EXTENSION_CAPABILITY_CONTRACTS = {
     },
   },
   dynamicTool: {
-    current: 29,
-    supported: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 28, 29],
+    current: 30,
+    supported: [
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 28, 29, 30,
+    ],
     dropped: {
       21: "Message and reasoning append events now expose deltas instead of cumulative snapshots.",
       23: "TaskExec.delegated was removed; migrate to workflow-backed background tools",
@@ -68,8 +70,8 @@ const EXTENSION_CAPABILITY_CONTRACTS = {
     },
   },
   subagent: {
-    current: 9,
-    supported: [3, 4, 6, 7, 8, 9],
+    current: 10,
+    supported: [3, 4, 6, 7, 8, 9, 10],
     dropped: {
       1: "Persistent subagent sessions are now the default and the experimental opt-in was removed",
       2: "Persistent subagent sessions are now the default and the experimental opt-in was removed",

@@ -12,6 +12,17 @@ import {
 } from "#compiler/validate-artifact.js";
 
 describe("compiled agent manifest v48", () => {
+  it.each([undefined, false, true])(
+    "round-trips the task event delivery opt-in (%s)",
+    async (taskEventDelivery) => {
+      const { manifest } = await compileFromMemory({
+        model: "openai/gpt-5.4",
+        agent: { model: "openai/gpt-5.4", experimental: { taskEventDelivery } },
+      });
+      const parsed = compiledAgentManifestSchema.parse(JSON.parse(JSON.stringify(manifest)));
+      expect(parsed.config.experimental?.taskEventDelivery).toBe(taskEventDelivery);
+    },
+  );
   it("round-trips a real compiled graph through the serialized schema", async () => {
     const { manifest } = await compileFromMemory({
       limits: { maxTokenCostUsdPerSession: 1.5 },

@@ -610,6 +610,7 @@ const compiledAgentConfigBaseFields = {
   description: z.string().optional(),
   experimental: z
     .object({
+      taskEventDelivery: z.boolean().optional(),
       instrumentationProviders: z.boolean().optional(),
       workflow: compiledAgentWorkflowDefinitionSchema.optional(),
     })
@@ -1209,6 +1210,7 @@ function cloneCompiledAgentDefinition(config: CompiledAgentDefinition): Compiled
       config.experimental === undefined
         ? undefined
         : {
+            taskEventDelivery: config.experimental.taskEventDelivery,
             instrumentationProviders: config.experimental.instrumentationProviders,
             workflow:
               config.experimental.workflow === undefined

@@ -182,6 +182,10 @@ function normalizeExperimentalDefinition(
 
   const compiledExperimental: Mutable<NonNullable<CompiledAgentDefinition["experimental"]>> = {};
 
+  if (experimental.taskEventDelivery !== undefined) {
+    compiledExperimental.taskEventDelivery = experimental.taskEventDelivery;
+  }
+
   if (experimental.instrumentationProviders !== undefined) {
     compiledExperimental.instrumentationProviders = experimental.instrumentationProviders;
   }

@@ -50,7 +50,7 @@ describe("turn workflow wire migrations", () => {
     ).toEqual({
       capabilities: undefined,
       completionToken: "turn-token",
-      driverCapabilities: { cancelledTurnSettle: true, turnInbox: true },
+      driverCapabilities: { bufferedDeliveries: true, cancelledTurnSettle: true, turnInbox: true },
       mode: "conversation",
       stepInput: {
         input: delivery,

@@ -58,6 +58,7 @@ interface TurnWorkflowInputBase {
    */
   readonly driverCapabilities?: {
     readonly turnInbox?: true;
+    readonly bufferedDeliveries?: true;
     readonly cancelledTurnSettle?: true;
   };
   readonly mode: RunMode;
@@ -108,7 +109,7 @@ export function createTurnWorkflowInput(input: TurnWorkflowDispatchInput): TurnW
   return {
     capabilities: input.capabilities,
     completionToken: input.completionToken,
-    driverCapabilities: { cancelledTurnSettle: true, turnInbox: true },
+    driverCapabilities: { bufferedDeliveries: true, cancelledTurnSettle: true, turnInbox: true },
     initialCancellation: input.initialCancellation,
     initialStep: input.initialStep,
     mode: input.mode,

@@ -89,6 +89,7 @@ export interface DurableSession {
   readonly workflowMaxSubagents?: number;
   readonly agent: {
     readonly system: string;
+    readonly taskEventDelivery?: boolean;
   };
   readonly compaction?: {
     readonly lastKnownInputTokens?: number;

@@ -76,6 +76,24 @@ describe("createCompactionConfig", () => {
 });
 
 describe("createSession", () => {
+  it.each([undefined, false, true])(
+    "carries task event delivery through session hydration (%s)",
+    (taskEventDelivery) => {
+      const turnAgent = createTestTurnAgent({ taskEventDelivery });
+      const session = createSession({
+        continuationToken: "root-token",
+        sessionId: "sess-root",
+        turnAgent,
+      });
+      expect(session.agent.taskEventDelivery).toBe(taskEventDelivery);
+      expect(projectToDurableSession(session).agent.taskEventDelivery).toBe(taskEventDelivery);
+      const hydrated = hydrateDurableSession({
+        durable: projectToDurableSession(session),
+        turnAgent,
+      });
+      expect(hydrated.agent.taskEventDelivery).toBe(taskEventDelivery);
+    },
+  );
   it("creates a session with correct agent configuration", () => {
     const outputSchema = { properties: { title: { type: "string" } }, type: "object" } as const;
     const session = createSession({

@@ -125,6 +125,7 @@ function createSessionAgent(
   const base = {
     compactionModelReference: turnAgent.compactionModel,
     reasoning: turnAgent.reasoning,
+    taskEventDelivery: turnAgent.taskEventDelivery,
     system,
     tools,
   };
@@ -200,7 +201,7 @@ export function mintSubagentContinuationToken(suffix?: string): string {
  */
 export function projectToDurableSession(session: HarnessSession): DurableSession {
   const durable: {
-    agent: { system: string };
+    agent: DurableSession["agent"];
     compaction?: {
       lastKnownInputTokens?: number;
       lastKnownPromptMessageCount?: number;
@@ -216,7 +217,12 @@ export function projectToDurableSession(session: HarnessSession): DurableSession
     taskId?: string;
     workflowMaxSubagents?: number;
   } = {
-    agent: { system: session.agent.system },
+    agent: {
+      system: session.agent.system,
+      ...(session.agent.taskEventDelivery !== undefined
+        ? { taskEventDelivery: session.agent.taskEventDelivery }
+        : {}),
+    },
     continuationToken: session.continuationToken,
     history: session.history,
     sessionId: session.sessionId,

@@ -26,6 +26,7 @@ export type TurnControlPayload =
       readonly inboxToken: string;
       readonly kind: "turn-delivery-request";
       readonly requestId: string;
+      readonly bufferedOnly?: boolean;
     }
   | { readonly kind: "turn-delivery-accepted"; readonly requestId: string }
   | { readonly kind: "turn-delivery-cancelled"; readonly requestId: string };

@@ -39,6 +39,26 @@ describe("TurnControlReceiver", () => {
     createHookMock.mockReset();
   });
 
+  it("answers an empty between-step poll without consuming queued user messages", async () => {
+    installControlHook([
+      { ...deliveryRequest("poll-1"), bufferedOnly: true },
+      { kind: "turn-delivery-accepted", requestId: "poll-1" },
+      parkResult(),
+    ]);
+    const message: DeliverHookPayload = { kind: "deliver", payloads: [{ message: "follow-up" }] };
+    const buffered = [message];
+    await runReceiver(buffered);
+    expect(forwardTurnDeliveryStep).toHaveBeenCalledWith({
+      inboxToken: "turn-inbox",
+      payload: {
+        kind: "driver-delivery",
+        requestId: "poll-1",
+        delivery: { kind: "deliver", payloads: [] },
+      },
+    });
+    expect(buffered).toEqual([message]);
+  });
+
   it("forwards a buffered delivery and consumes it once the turn accepts", async () => {
     const delivery: DeliverHookPayload = {
       kind: "deliver",
@@ -318,7 +338,9 @@ function runReceiver(
   return receiver.waitForAction().finally(() => receiver.dispose());
 }
 
-function deliveryRequest(requestId: string): TurnControlPayload {
+function deliveryRequest(
+  requestId: string,
+): Extract<TurnControlPayload, { kind: "turn-delivery-request" }> {
   return {
     continuationToken: "http:test",
     inboxToken: "turn-inbox",

@@ -222,6 +222,10 @@ export class TurnControlReceiver {
     await this.commandInbox.rekeyContinuation(request.continuationToken);
 
     let delivery = this.takeInputResponseDelivery();
+    // A between-step poll must not park the model waiting for future input.
+    if (delivery === undefined && request.bufferedOnly === true) {
+      delivery = { kind: "deliver", payloads: [] };
+    }
     while (delivery === undefined) {
       const winner = await Promise.race([
         this.getControlPromise().then((value) => ({ kind: "control" as const, value })),