Appendix J: Exception Taxonomy and Operational Playbooks

Exceptions are not edge cases at enterprise scale. A Reconstruction-Grade program treats exception handling as an operational discipline.

Table 12. Exception reason code taxonomy

Reason Code	Meaning	Recommended Response
PermissionDenied	Access to target object not granted at time of collection.	Coordinate permission remediation; reprocess; record approvals.
ItemDeletedOrOutsideRetention	Target object no longer exists or is beyond retention bounds.	Document loss; preserve link evidence; capture secondary sources if any.
Throttling	Service limits triggered; requests slowed or denied.	Apply controlled backoff; scale concurrency; extend job windows.
TransientServiceError	Temporary fault (timeouts, 5xx, network).	Retry with backoff; monitor systemic outage patterns.
UnresolvableLink	Link could not be canonicalized to a stable object.	Preserve original reference; attempt alternate resolution methods; flag for review.
UnsupportedArtifact	Artifact type not yet supported by preservation pipeline.	Record as explicit limitation; define roadmap or alternate capture method.
Unknown	Unexpected failure with insufficient classification.	Capture full error context; triage; refine reason codes over time.

Operational note: exception rates should be reported per matter and per workload, with trends and remediation backlog tracked as a program metric.