fix(todo): prevented stale batch state replay

- Stopped asynchronous tool-result handling from overwriting newer todo state.
- Added an AgentSession regression for six exclusive completion calls.

Fixes #6148

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed parallel `todo done` calls losing completions when asynchronous session event handling replayed stale result snapshots over newer tool state ([#6148](https://github.com/can1357/oh-my-pi/issues/6148)).
+
 ## [17.0.6] - 2026-07-20
 
 - Fixed failed plan-mode exits leaving the session on the restored execution model while plan mode remained active and silently changing ambient `xd://` tool presentation; rollback now restores the plan model, thinking level, and exact top-level-versus-mounted tool partition so exit can be retried safely ([#6013](https://github.com/can1357/oh-my-pi/pull/6013)).

packages/coding-agent/src/session/agent-session.ts

@@ -4828,9 +4828,10 @@ export class AgentSession {
 				if (toolName === "edit" && editedPath) {
 					this.#invalidateFileCacheForPath(editedPath);
 				}
+				// TodoTool commits its state during execute. Replaying the result after
+				// awaited event fan-out can overwrite a newer call from the same batch.
 				const phases = details?.phases;
 				if (toolName === "todo" && !isError && details && Array.isArray(phases) && phases.every(isTodoPhase)) {
-					this.setTodoPhases(phases);
 					if (this.#isTodoInitResult(details, toolCallId)) {
 						this.#scheduleReplanTitleRefresh();
 					}

packages/coding-agent/test/agent-session-event-order.test.ts

@@ -16,6 +16,7 @@
 import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from "bun:test";
 import * as path from "node:path";
 import { Agent } from "@oh-my-pi/pi-agent-core";
+import type { ToolCall } from "@oh-my-pi/pi-ai";
 import { createMockModel } from "@oh-my-pi/pi-ai/providers/mock";
 import { getBundledModel } from "@oh-my-pi/pi-catalog/models";
 import { ModelRegistry } from "@oh-my-pi/pi-coding-agent/config/model-registry";
@@ -24,6 +25,7 @@ import type { ExtensionRunner } from "@oh-my-pi/pi-coding-agent/extensibility/ex
 import { AgentSession } from "@oh-my-pi/pi-coding-agent/session/agent-session";
 import { AuthStorage } from "@oh-my-pi/pi-coding-agent/session/auth-storage";
 import { SessionManager } from "@oh-my-pi/pi-coding-agent/session/session-manager";
+import { TodoTool } from "@oh-my-pi/pi-coding-agent/tools";
 import { TempDir } from "@oh-my-pi/pi-utils";
 
 describe("AgentSession subscriber event order", () => {
@@ -124,4 +126,69 @@ describe("AgentSession subscriber event order", () => {
 			expect(endIndex).toBeGreaterThan(startIndex);
 		}
 	});
+
+	it("preserves every completion from a batch of exclusive todo calls", async () => {
+		const model = getBundledModel("anthropic", "claude-sonnet-4-5");
+		if (!model) throw new Error("Expected bundled test model to exist");
+
+		const tasks = ["one", "two", "three", "four", "five", "six"];
+		const calls: ToolCall[] = tasks.map((task, index) => ({
+			type: "toolCall",
+			id: `todo-${index}`,
+			name: "todo",
+			arguments: { op: "done", task },
+		}));
+		const mock = createMockModel({
+			responses: [{ content: calls }, { content: ["Done"] }],
+		});
+		const settings = Settings.isolated({
+			"compaction.enabled": false,
+			"retry.enabled": false,
+			"tools.xdev": false,
+		});
+		settings.setModelRole("default", `${model.provider}/${model.id}`);
+		const todo = new TodoTool({
+			cwd: tempDir.path(),
+			hasUI: false,
+			getSessionFile: () => null,
+			getSessionSpawns: () => "*",
+			settings,
+			getTodoPhases: () => session?.getTodoPhases() ?? [],
+			setTodoPhases: phases => {
+				session?.setTodoPhases(phases);
+			},
+		});
+		const agent = new Agent({
+			getApiKey: agentModel => `${agentModel.provider}-test-key`,
+			initialState: {
+				model,
+				systemPrompt: ["Test"],
+				tools: [todo],
+				messages: [],
+			},
+			streamFn: (streamModel, context, options) => mock.stream(streamModel, context, options),
+		});
+		session = new AgentSession({
+			agent,
+			sessionManager: SessionManager.inMemory(),
+			settings,
+			modelRegistry,
+		});
+		session.setTodoPhases([
+			{
+				name: "Execution",
+				tasks: tasks.map((content, index) => ({
+					content,
+					status: index === 0 ? "in_progress" : "pending",
+				})),
+			},
+		]);
+
+		await session.prompt("Complete every task");
+		await session.waitForIdle();
+		const toolResults = agent.state.messages.filter(message => message.role === "toolResult");
+		expect(toolResults.map(result => result.toolName)).toEqual(tasks.map(() => "todo"));
+
+		expect(session.getTodoPhases()[0]?.tasks.map(task => task.status)).toEqual(tasks.map(() => "completed"));
+	});
 });