别被"魔法"吓到，源码短得惊人。定义在 types.py:811，核心逻辑在 types.py:901-934：

# types.py:811 def interrupt(value: Any) -> Any:  （省略了长文档字符串）
# types.py:901 起：
from langgraph._internal._constants import (
    CONFIG_KEY_CHECKPOINT_NS, CONFIG_KEY_SCRATCHPAD, CONFIG_KEY_SEND, RESUME,
)
from langgraph.config import get_config
from langgraph.errors import GraphInterrupt

conf = get_config()["configurable"]
# track interrupt index
scratchpad = conf[CONFIG_KEY_SCRATCHPAD]        # ① 拿到"本次任务的便签本"
idx = scratchpad.interrupt_counter()            # ② 这是本节点里第几个 interrupt
# find previous resume values
if scratchpad.resume:                           # ③ 便签本里已有恢复值？（重跑时）
    if idx < len(scratchpad.resume):
        conf[CONFIG_KEY_SEND]([(RESUME, scratchpad.resume)])
        return scratchpad.resume[idx]           #    直接返回，不再暂停
# find current resume value
v = scratchpad.get_null_resume(True)            # ④ 有没有"这次刚喂进来的"恢复值
if v is not None:
    assert len(scratchpad.resume) == idx, (scratchpad.resume, idx)
    scratchpad.resume.append(v)
    conf[CONFIG_KEY_SEND]([(RESUME, scratchpad.resume)])
    return v                                     #    返回它，继续执行
# no resume value found
raise GraphInterrupt(                            # ⑤ 什么恢复值都没有 → 抛异常暂停
    (Interrupt.from_ns(value=value, ns=conf[CONFIG_KEY_CHECKPOINT_NS]),)
)

"暂停"没有黑魔法，就是 raise 一个特殊异常，让它一路往上冒。异常家谱在 errors.py:50-107：

# errors.py:50
class GraphBubbleUp(Exception):        # 所有"该往上冒、不算失败"的异常的爹
    pass

# errors.py:102
class GraphInterrupt(GraphBubbleUp):
    """Raised when a subgraph is interrupted, suppressed by the root graph.
    Never raised directly, or surfaced to the user."""
    def __init__(self, interrupts: Sequence[Interrupt] = ()) -> None:
        super().__init__(interrupts)   # 把 Interrupt 元组塞进 args[0]

异常冒到执行器（runner）这一层被接住。看 _runner.py:584-591 的 commit 逻辑：

# _runner.py:584
elif exception:
    if isinstance(exception, GraphInterrupt):
        # save interrupt to checkpointer
        if exception.args[0]:                              # ① 异常里带了 Interrupt
            writes = [(INTERRUPT, exception.args[0])]      # ② 造一条 INTERRUPT "写"
            if resumes := [w for w in task.writes if w[0] == RESUME]:
                writes.extend(resumes)                     # ③ 连带已有的 RESUME 写一起
            self.put_writes()(task.id, writes)             # ④ 存进 checkpointer
    elif isinstance(exception, GraphBubbleUp):
        pass                                                # 其他冒泡异常：放行，别当错
    else:
        task.writes.append((ERROR, exception))             # 真错误才记 ERROR

抛出去的货物是 Interrupt，定义在 types.py:533-578：

# types.py:533
@final
@dataclass(init=False, slots=True)
class Interrupt:
    value: Any     # 给客户端看的值，比如 "要删库?"
    id: str        # 中断的身份证，用来精确恢复

    # types.py:576
    @classmethod
    def from_ns(cls, value: Any, ns: str) -> Interrupt:
        return cls(value=value, id=xxh3_128_hexdigest(ns.encode()))

如果 GraphInterrupt 一路冒到用户面前，那就成崩溃了。所以在主循环退出时有个"消音器" _loop.py:1317-1339：

# _loop.py:1317
def _suppress_interrupt(self, exc_type, exc_value, traceback) -> bool | None:
    # persist current checkpoint and writes
    if self.durability == "exit" and (...):        # 退出模式：此时才落盘（D45）
        self._put_exit_delta_writes()
        self._put_checkpoint(self.checkpoint_metadata)
        self._put_pending_writes()
    # suppress interrupt
    if isinstance(exc_value, GraphInterrupt) and not self.is_nested:
        interrupt = exc_value
        interrupts = tuple(interrupt.args[0]) if interrupt.args else ()
        self._push_graph_lifecycle_event("interrupt", interrupts=interrupts)
        # ... 返回 True 表示"这个异常我处理了，别再往外抛"