# serde-error-thiserror

## AUDIT (2026-01-31)
Pattern: SerdeError in stemedb-core/src/serde.rs uses manual `impl fmt::Display` and `impl std::error::Error` instead of `#[derive(thiserror::Error)]` like all other error types.
Found: 3 items to fix in 1 file (enum + Display impl + Error impl)

All 5 other error types in the workspace use thiserror:
- stemedb-storage/src/error.rs: StorageError
- stemedb-api/src/error.rs: ApiError
- stemedb-wal/src/error.rs: QuarantineError
- stemedb-query/src/error.rs: QueryError
- stemedb-ingest/src/error.rs: IngestError

## FIX (2026-01-31)
- [x] crates/stemedb-core/src/serde.rs:52-69 - Replaced manual `impl fmt::Display` + `impl std::error::Error` with `#[derive(Debug, Error)]` and `#[error(...)]` attributes. Removed `use std::fmt`, added `use thiserror::Error`.

## VERIFY (2026-01-31)
- grep for `impl fmt::Display for SerdeError`: 0 matches
- grep for `impl std::error::Error for SerdeError`: 0 matches
- grep for `#[derive.*Error.*]` on error enums: 6/6 use thiserror
- cargo build: OK
- cargo clippy: OK (0 warnings)
- cargo test: 158 passed, 0 failed

## ENFORCE (2026-01-31)
- Updated `ai-lookup/patterns/error-handling.md` with explicit rule: "NEVER use manual impl Display + impl Error — use thiserror derives"
- Listed all 6 error types confirming compliance

## COMPLETE
Before: 3 items (enum definition, Display impl, Error impl)
After: 0 manual impls remaining