# s5 — trace / measurement path

**Protected property:** from the surfaces a consumer can discover which verbs
persist per-cycle traces and reach a signal-quality measurement — the milestone's
own headline being "signal quality is measured in R".

## What the surfaces say
`aura --help`: "Traces: `sweep --real --trace` / `walkforward --real --trace`
record per-cycle taps under runs/, consumed by `aura chart` and `aura measure`."
`aura measure ic --help`: "Information Coefficient of a **signal** tap against
forward returns of a **price** tap" — requires `--signal <SIGNAL>` and
`--price <PRICE>`.

## What actually happens
- Discovery works: `runs families` lists the traced families; `measure ic`'s
  `<RUN>` is the member path **relative to** `runs/traces/`
  (`<family>/<instr-window>/<param-combo>`); the missing-tap error is clear and
  lists available taps. `measure ic` runs green on the persisted taps.
- **Dead-end for the intended inputs.** The only taps any surface-reachable verb
  persists are the closed presentation set `equity` / `exposure` / `r_equity`
  (`net_r_equity`) — execution-side R/pip curves, **not** the strategy's bias
  signal nor the instrument price. So `measure ic` can only be fed, e.g.,
  `--signal exposure --price equity`, which is not a signal-vs-price IC at all
  (result ≈ noise, 0.0019).
- **Declared taps are silently dropped.** `graph build --help` documents the op
  `tap` as *"declare a **recordable** tap on a wire"*. `tapped.oplist.json` (this
  dir) declares `tap bias.bias as signal` and `tap fast.value as price`, yet after
  `sweep --real --trace` the persisted set is still `["equity","exposure",
  "r_equity"]`; both `measure ic --signal signal` and `chart --tap signal` report
  the tap does not exist. There is no surface-documented path to persist a genuine
  signal or price tap, so `measure ic`'s stated contract is unreachable end-to-end.

## Evidence (verbatim)
```
$ aura measure ic --signal signal --price price <tapped-run>
aura: run '…' has no tap 'signal' (taps: ["equity", "exposure", "r_equity"])
$ aura chart 010f8afa-0 --tap signal
aura: no family member has a tap named 'signal'        (exit 0)
```