What does Windows error code 146 (ERROR_IS_SUBST_PATH) mean?

ERROR_IS_SUBST_PATH

What ERROR_IS_SUBST_PATH means

ERROR_IS_SUBST_PATH is a Win32 system result whose documented message is: “The path specified is being used in a substitute.” In practical troubleshooting, it belongs to path validation in legacy mapping code where the supplied path is already traversing a SUBST drive.

Typical causes

• configuration stores an alias rather than the canonical directory
• a logon script changes drive mappings before another tool validates paths
• the application does not expand substituted drive letters

How to investigate the result

1. resolve the first path component through current SUBST mappings
2. Compare behavior in a clean session without logon mappings
3. store both logical and canonical paths in diagnostics

Developer guidance

Canonicalize user-facing aliases at the boundary and apply mapping operations to the underlying path.

Administrator and support guidance

Identify which startup script creates the substitution and decide which component owns the alias. Avoid silently stacking mappings.

Example

A legacy mapping utility receives S:\Project as its target, discovers that S: is a SUBST drive, and returns this result.

How it differs from related results

It says the path uses a substituted drive; ERROR_IS_SUBSTED says a drive selected for an operation is itself substituted.

References

• Microsoft: System error codes 0–499