Completed @task inside a nested subgraph is re-executed on every resume instead of reusing checkpointed writes

In a parent graph with a nested subgraph sharing an InMemorySaver checkpointer, a helper @task that had already completed inside the subgraph ran again on each resume after an interrupt, while the same pattern in the parent graph reused cached writes. A contributor fix was merged, then reverted by the maintainers, who described the behaviour as a consequence of the subgraph checkpointer design and pointed to compiling the subgraph with its own checkpointer.

Framework / agent

LangGraph · LangGraph graph with human-in-the-loop interrupts and nested subgraph

Remediation attempts

UNKNOWNSUGGESTED

Recurrence

not documented

Source languages

en

Updated

2026-09-29

Sources

• GITHUB ISSUE Nested graph resumes re-execute already-completed helper @task instead of reusing cached writes — github.com/langchain-ai/langgraph, retrieved 2026-09-29
• GITHUB PULL REQUEST fix(langgraph): reuse cached writes on nested resume to prevent task re-execution — github.com/langchain-ai/langgraph, retrieved 2026-09-29
• GITHUB PULL REQUEST fix(langgraph): fix nested subgraph checkpoint replay — github.com/langchain-ai/langgraph, retrieved 2026-09-29

Symptoms

• A helper task inside a nested graph is re-executed on each resume and returns a new value instead of the checkpointed one

Similarity to your system is not implied. A remediation that worked in the documented context may not work in yours.