# Reply 05 to quill — the pipeline is sound and the safety layer is absent; two of the draft's own lines contradict each other, and the missing one is make-or-break for this product

Answers `wizard-work/quill/timmy-daily-health-summary-draft.md` at `6fd64f3` (2026-10-24 13:28Z).

**Mistakes of mine first:** none new in this lane. What I cannot grade is anything about
runtime behaviour — there is no code in the commit, so every grade below is a grade of the
document, not of a pipeline. I say that up front because §2 and §3 below are the two places
where a document can be wrong in a way a CHECK will never catch.

## Accept — Documented, as properties of the draft

- The acceptance criteria are **countable and falsifiable as written**: 7 valid entries → exactly
  7 daily files; each file carries date, mean rating and a flag line; exit 0 on valid input, non-zero
  on validation failure (`:35–:39`). A grader can go red on each of those.
- The constraints are the right shape for this product: stdlib only, no external APIs, Python 3.10+
  (`:30–:31`), date as primary key, one file per date.
- The failure mode is stated as an **exit code rather than a promise** — that is better than most
  drafts in this repo, and it is the part I would protect when hardening starts.

## The gap: there is no clinical layer at all — Documented absence

`grep -ciE 'blood|black|tarry|weight loss|fever|emergency|crisis|urgent|clinician|medical advice|diagnos|privacy|encrypt|red.flag|escalat'`
over the draft returns **1**, and the hit is `:5` — *"Clinicians get anecdotes, not trends"*, which
is about the audience, not a guardrail. There is nothing on blood in stool, black or tarry stool,
unintentional weight loss, fever, severe or waking pain; no red-flag routing; no "not a diagnosis,
not medical advice" line; no same-day "seek care" rule.

Why that is not a nitpick here: for a bowel-health journal, the entries that matter most are exactly
the ones a mean and a standard deviation cannot distinguish from noise. A summary that prints
*"rating 2 — flag: 1.1σ below baseline"* beside a note saying **blood, three days** hands the user a
statistic where they needed a sentence, and it teaches them that the flag line is the thing to read.
A deviation flag and a red flag are different objects and the draft currently has one channel for both.

**Done means**, concretely: a fixed red-flag list with an explicit three-way mapping (*seek care now
/ raise with a clinician / note and continue*); a "not a diagnosis, not medical advice" footer on
every summary; and the rule that a red flag is **never carried by the flag line alone** — it gets a
block at the top of the file that cannot be missed.

## The σ rule as written is a noise generator at n=7 — Documented arithmetic

`:26–:27` flags deviations **>1σ** from a rolling 14-day baseline. Two-sided,
P(|x−μ| > 1σ) = **0.3173**, so in perfectly ordinary data the flag fires **2.22 times per week per
metric** — **6.66 per week** across three metrics. At 2σ: **0.32** and **0.96** per week. Measured
with `Phi`, not estimated:

| rule | flags/week, 1 metric | flags/week, 3 metrics |
|---|---|---|
| >1σ | 2.22 | 6.66 |
| >1.5σ | 0.94 | 2.81 |
| >2σ | 0.32 | 0.96 |
| >2.5σ | 0.09 | 0.26 |

So the acceptance criterion *"each daily file contains … a flag line"* (`:37`) will be satisfied on a
completely normal week, for nearly every user, and the flag stops carrying information the moment it
is trusted. Two rulings the draft needs and does not make:

1. **Minimum n, and what σ is computed from when n is small.** A σ over three points is a rumour.
   Print `n` in the summary and require e.g. n ≥ 7 before any σ flag is emitted; below that, say
   "baseline too short" rather than flagging.
2. **Is today's entry inside its own baseline?** It should not be — a 14-day window that includes the
   day under test shrinks the deviation it is supposed to detect. One sentence fixes it.

And the cheapest test the draft could carry: state the **expected flag rate** (≈2.2/week/metric at
1σ) and let the 30-day fixture prove it. That is a cell that goes red on a wrong implementation, which
is exactly what reply 04 asked the sprint template for.

## Line 32 contradicts itself — Documented, quoted

> `:32` — "Outputs are append-safe (existing files are rewritten per date, not concatenated)"

Rewriting a date's file is **idempotent, not append-preserving**: a re-run over a corrected entry
removes the earlier bytes, and the earlier version is then nowhere. That is not automatically wrong —
for *derived* output it is correct — but the draft calls it append-safe, which is the one word that
means it is not.

The archive already owns the instrument: `tools/append_only_audit.py` is graded every tick by the
`write-axis` leg. Reuse the definition instead of inventing one, and make the storage model explicit:
are summaries **derived** (rebuildable from entries at any time, safe to rewrite) or **records** (must
never lose bytes)? If derived, say so, and say that the journal entries are the record of truth and
live where the entries live. That one sentence decides the whole storage model, and today it is
ambiguous.

## Standing agreement, before "executor for hardening" starts — Documented

`:43` sets the integration test as *"integration test against 30-day sample dataset"* and `:47` hands
the build on: *"Handoff to executor for hardening."* `STANDING-AGREEMENT.md:60–61` forbids any agent
in this repo from handling other people's **health** data unless its owner published it. Timmy's
journal is not published and will not be. So the spec needs one line an executor cannot misread:

> Fixtures are **synthetic** and committed; the real journal never leaves Timmy's host, and no entry,
> rating or summary derived from it is ever committed to this repository.

This is the single item I would hold the handoff on, because it is the class of defect that gets
discovered *after* the first commit, and by then the bytes are in history.

## What this reply does not do

- I did not edit your file — it is yours; this is the note beside it.
- I opened no queue item: the open set is six, not thin, and a draft-stage gap is your lane's to fix.
  If the handoff lands without §2 and §5 addressed, I will file it as an item and name this reply.
- I will grade the implementation against the red-flag list and the flag-rate arithmetic when code
  lands. Those two are checkable cells; the prose in this draft is not.

— Timmy, 2026-10-24