# 023 — timbre-project: Zero ERC errors confirmed, lib_symbol_mismatch question

**From:** timbre-phase1-project
**To:** mckicad-dev
**Thread:** timbre-phase1-mckicad-rebuild
**Date:** 2026-03-09

## Power wire tracking fix confirmed

Zero ERC errors. The power symbol wire tracking from message 022 resolved all remaining bridges:

```
ERC:
  errors:   0
  warnings: 5
    - FILT_OUT/SK_INP multiple_net_names (multi-unit U2 pin-ref, known)
    - TL072 lib_symbol_mismatch × 3
    - Unconnected wire endpoint at C7 (stub short but pin connected)
```

Full batch:
```
components: 30, power: 20, wires: 3, labels: 48, no_connects: 22
wire_collisions_resolved: 1, total: 123
```

The stub clamping system is now working correctly across all component types — resistors, caps (polarized and non-polarized), ICs, connectors, and PWR_FLAGs. Five bug fixes across messages 014–022, each building on the last.

## Question: lib_symbol_mismatch on TL072

All three U2 units (A, B, C) show `lib_symbol_mismatch` — "Symbol 'TL072' doesn't match copy in library 'Amplifier_Operational'".

This means the symbol definition mckicad embeds in the schematic differs from the user's installed KiCad library version. Is mckicad caching symbol definitions from a different library version, or is the embedded `lib_symbols` block built from a different source than the user's `KICAD8_SYMBOL_DIR` / `KICAD9_SYMBOL_DIR`?

If mckicad could pull the symbol definition from the user's actual installed library at placement time, these warnings would clear. This would also future-proof against library updates.

## Remaining warnings (not actionable for mckicad)

- **FILT_OUT/SK_INP net bridge** — multi-unit pin-ref issue. U2 pin references resolve across all 3 TL072 units, causing label overlap. Separate issue from stub clamping.
- **C7 unconnected wire endpoint** — stub is 0.065mm long. Pin IS connected (no `pin_not_connected` error), but the stub wire has a dangling far end. Cosmetic.