Double Texting

1What is Double Texting and why it matters

Double Texting(Double sending) means that the user sends a new message to the same thread before the current run is completed. In real chat applications, this situation is extremely common:

• The user adds information immediately after sending the message ("Wait, I want to change it...")
• Users get impatient with slow responses and send the same message repeatedly
• The user sent a new, higher priority request while the AI was still processing it

LangGraph Server passedmultitask_strategyParameters provide four strategies, allowing developers to choose the most appropriate concurrency processing method according to business scenarios.

2Overview of four strategies

3Strategy 1: Reject

The simplest strategy: Run 1 rejects all new requests, returning HTTP 409 Conflict.

import httpx

thread = await client.threads.create()
config = {"configurable": {"user_id": "Test"}}

# 启动 Run 1
run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Add a ToDo to follow-up with DI Repairs.")]},
    config=config,
)

# Run 2 使用 reject 策略 → 触发 HTTPStatusError 409
try:
    await client.runs.create(
        thread["thread_id"], "task_maistro",
        input={"messages": [HumanMessage(content="Add a ToDo to mount dresser to the wall.")]},
        config=config,
        multitask_strategy="reject",
    )
except httpx.HTTPStatusError as e:
    print("Failed to start concurrent run", e)

After Run 1 is completed normally, the thread status only contains the first ToDo (mount dresser is not added).

4Strategy 2: Enqueue (queuing)

Run 2 will not be rejected and will go into the waiting queue. After Run 1 is completed, the server automatically starts executing Run 2. Both runs will be executed and messages will not be lost.

thread = await client.threads.create()

# Run 1：立即开始
first_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Send Erik his t-shirt gift this weekend.")]},
    config=config,
)

# Run 2：进入队列，等待 Run 1 完成
second_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Get cash and pay nanny for 2 weeks. Do this by Friday.")]},
    config=config,
    multitask_strategy="enqueue",
)

# 等待 Run 2 完成（Run 1 → Run 2 串行执行）
await client.runs.join(thread["thread_id"], second_run["run_id"])

5Strategy Three: Interrupt

When Run 2 comes, Run 1 is paused after the current node has finished executing (it will not be killed immediately). The completed work of Run 1 is retained to PostgreSQL and the status becomesinterrupted;Run 2 starts execution immediately.

import asyncio

thread = await client.threads.create()

# Run 1 开始（查询 ToDo 摘要）
interrupted_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Give me a summary of my ToDos due tomorrow.")]},
    config=config,
)

# 等 1 秒让 Run 1 执行一部分节点
await asyncio.sleep(1)

# Run 2 使用 interrupt 策略 → Run 1 在当前节点结束后停止
second_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Never mind, create a ToDo to Order Ham for Thanksgiving by next Friday.")]},
    config=config,
    multitask_strategy="interrupt",
)

await client.runs.join(thread["thread_id"], second_run["run_id"])

# 确认 Run 1 状态
status = (await client.runs.get(thread["thread_id"], interrupted_run["run_id"]))["status"]
print(status)  # "interrupted"

6Strategy 4: Rollback

When Run 2 arrives, Run 1 is immediately stopped andDelete from database(Including all its status changes). Run 2 starts executing from the thread's last clean checkpoint, as if Run 1 never happened.

thread = await client.threads.create()

# Run 1：用户的原始意图
rolled_back_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Add a ToDo to call to make appointment at Yoga.")]},
    config=config,
)

# Run 2：用户改变了主意
second_run = await client.runs.create(
    thread["thread_id"], "task_maistro",
    input={"messages": [HumanMessage(content="Actually, add a ToDo to drop by Yoga in person on Sunday.")]},
    config=config,
    multitask_strategy="rollback",
)

await client.runs.join(thread["thread_id"], second_run["run_id"])

# 验证 Run 1 已被删除
try:
    await client.runs.get(thread["thread_id"], rolled_back_run["run_id"])
except httpx.HTTPStatusError:
    print("Original run was correctly deleted")  # ✓

7Four strategies comparison and selection guide