What does Windows error code 215 (ERROR_NESTING_NOT_ALLOWED) mean?

ERROR_NESTING_NOT_ALLOWED

What ERROR_NESTING_NOT_ALLOWED means

A LoadModule-style operation was called recursively or from a context where nested module loading is prohibited. Older loader implementations restrict re-entrant loading. A module initialization routine that starts another load can violate loader serialization and produce this status.

Common causes

• Initialization code loads another module while the loader lock is held
• A plugin callback triggers recursive discovery
• Dependency resolution cycles back to a module already being initialized
• A hook or instrumentation layer performs loading inside a loader callback

How to investigate

1. Capture the full call stack at the nested load
2. Record the module initialization state and dependency chain
3. Detect cycles in plugin or dependency metadata
4. Move deferred initialization outside the loader callback and compare behavior

Developer guidance

Keep module entry points minimal. Defer plugin discovery, thread creation, IPC, and additional module loading until normal application initialization after the loader has released internal locks.

Administrator and support guidance

Disable recently added plugins or instrumentation one at a time to identify the component initiating recursive loading.

How this code differs from related results

ERROR_TOO_MANY_MODULES is a capacity problem; this code is an illegal loading order even with only a few modules.

References

• Microsoft: System error codes 0–499