Make the launch call

Recommendation: AI auto-substitutions, launch meeting 30 October

Decision: no-go for Monday 2 November. Go with conditions from 4 November for London, South East, Midlands and North West. Scotland stays on picker substitutions until it re-passes.

Criteria by region

Figures are recomputed from the daily rows. Treatment (T) and control (C) are pooled over the 28 days.

Baskets are means of daily averages. The differences are small and I have not tested them for significance, but the point estimate is positive everywhere.

Checking what people have said

• Head of Commercial. The pooled numbers are right: acceptance is 85.9% against 71.2% (+14.7 points), and refunds are 19.5 against 18.1 per 1,000 (+8%). But the pooled refund figure hides Scotland, which is failing badly. Four regions are 2–5% better than control on refunds.
• Head of Analytics. The £4 gap is real in the pooled data (£61.10 vs £65.15) but it is a mix effect, not a treatment effect. London, with the highest baskets (about £72), was 42% of control orders but only 18% of treatment orders. The Midlands and Scotland (about £53–56) were 18% of control but 42% of treatment. Within every region, treatment baskets are £0.24–£0.46 higher. Criterion 4 passes. The uneven split did not bias the regional comparisons.
• Ops director (Scotland). The data does not support "settling down". Before the supplier switch on 15 October, Scotland treatment was healthy (86.3% acceptance, 17.3 refunds per 1,000). From 15 October to 28 October, acceptance has been flat at 78–81%, and daily refunds have been 25–33 against a pre-switch level of 10–14. The cause is the open incident: the new supplier's pack sizes are mapped to the wrong product family, so the model makes wrong-size dairy substitutions. That is a catalogue defect with no fix date, not noise. Scotland control is unaffected.

Why the date moves

Criterion 3 fails in three regions. The three mismatches include a nut-allergy case and a coeliac case. The hard filter that prevents them deploys on 4 November. Until it is live, every region has the same exposure. North West and Scotland show zero only because none were reported, and the incidents come from customer complaints, so the true rate is unknown. I would not switch on a known allergen risk two days before the fix.

Waiting is cheap. The booking window opens on 9 November, not 2 November. Deploying the filter on 4 November and switching regions on 4–5 November leaves several days before the window. Only Scotland has no route to launch before then.

Conditions for the four regions

1. The filter deploys on 4 November and passes regression tests. Before any region goes live, it is tested in production against the three incident SKUs (gluten-free loaf, vegan cheese, nut-free bar) and the other attributes: vegetarian, halal and kosher. The London incident is still open with the filter "in review", so confirm the filter would have blocked it.
2. Regions are switched on region by region, North West and South East first, then London and the Midlands. This gives a day of live data before the larger volumes go on.
3. Any dietary or allergen mismatch after launch switches that region back to picker substitution immediately, pending review. That includes any mismatch in the first week.
4. Daily monitoring of acceptance (80% floor) and refunds (10% guardrail) per region against a small held-back control. Delegate the switch-on decision so it does not need another meeting.

Scotland

Keep Scotland on picker substitutions. Retest only after the catalogue re-map ships, on a small treatment share. It should show at least three consecutive days at 80% or better acceptance, and refunds within 10% of control, before it goes to full volume. Engineering has no date, so Scotland should not be in the Christmas plan and should be treated as upside.

Data notes

• North West treatment has three duplicated rows (8, 9 and 10 October), matching the open export-job incident. I removed them. This restores the intended 50% split, and the North West rates barely move either way.
• Incident logs are a floor on dietary failures, not a measure of them.
• This is 28 days of data in a low-volume region (Scotland control is about 265 orders a day). Even so, the Scotland gap is far outside noise.

AI auto-substitutions: launch recommendation

Oct 29, 2026 · @Martin Slaney · For the 30 October launch meeting

Recommendation

No-go for Monday 2 November in any region. The dietary hard filter isn't live until 4 November, and the test produced three allergen and dietary mismatches.

Go with conditions for London, South East, Midlands and North West from Thursday 5 November, once the filter is live and verified. That is still four days before the Christmas booking window opens on 9 November.

No-go for Scotland until the dairy catalogue re-map ships and a fresh week of test data passes the criteria.

Launch criteria by region

Figures are for 1–28 October from daily\_metrics.csv, with duplicate rows removed. T = treatment, C = control.

Why not 2 November

Criterion 3 requires zero dietary or allergen mismatches. Treatment had three, all rated high severity: a gluten-free loaf swapped for a standard one (the customer is coeliac), vegan cheese swapped for dairy cheddar (the customer complained on social media), and a nut-free multipack swapped for one containing hazelnuts, sent to a child with a nut allergy. The nut incident is still open. Control had none.

The fix is the dietary hard filter, which is merged and deploys on 4 November after regression tests. Launching on 2 November would put every order in every region onto the unfiltered model for two days. North West's zero is luck, because it runs the same model.

Strictly, all four "go" regions fail criterion 3 as it's written. I'm asking the meeting to accept the filter as the remedy, on condition that we show it would have blocked all three incidents. If the meeting won't accept that, the honest answer is no-go everywhere.

Waiting three days costs nothing for Christmas, because bookings don't open until 9 November.

What the summaries get wrong

Head of Commercial: "refunds within the guardrail overall." Pooled, treatment refunds are 7.9% above control (19.5 vs 18.1 per 1,000 orders), which is inside 10%. But the criterion applies to every region, and the pooled figure hides Scotland at +66%. In the other four regions, treatment refunds are below control. The 15-point acceptance lift is real in those four regions (+15.0 to +15.4 points). In Scotland it's +11.7 overall and falling.

Head of Analytics: "treatment baskets are £4 smaller." Pooled, the gap is £61.09 vs £65.15, but it comes from how orders were split, not from the feature. Treatment got 70% of orders in Midlands and Scotland, which have the smallest baskets (£52–56), and only 30% in London, which has the largest (£72). Within every region, treatment baskets are £0.21–£0.44 larger, so criterion 4 passes everywhere.

Ops director, Scotland: "it's settling down." It isn't. Before the supplier switch on 15 October, Scotland's treatment arm matched the other regions (86.3% acceptance, 17.3 refunds per 1,000 vs 18.6 in control). Since then, treatment refunds have run at 25–33 a day with no downward trend: 28.1 a day on average from 15 to 21 October and 28.7 from 22 to 28 October. Refund value per order has tripled, from £0.09 to £0.30. Scotland's control arm is unaffected at 17.8 per 1,000. So the problem is specific to the model reading a mis-mapped catalogue: pickers can see the real pack sizes, and the model can't. The re-map has no date.

Data quality

The North West treatment rows for 8, 9 and 10 October each appear twice, because the export job re-ran (the open incident from 7 October). I removed the duplicates. They don't change any verdict: North West acceptance moves from 86.2% to 86.3%.

Conditions for the 5 November go

1. The dietary filter deploys on 4 November and passes regression tests. We replay the three incident orders and confirm the filter blocks each of them.²
2. The London nut-allergen incident is closed with a root cause.
3. We switch on region by region and keep a 10% control holdout in each region through Christmas, so criteria 2 and 4 stay measurable.
4. Kill switch: any single dietary or allergen mismatch turns the region off, as does a treatment refund rate more than 10% above its holdout over a rolling 3 days.¹
5. Scotland: ship the catalogue re-map, then run 7 days of test and re-check the criteria. If it can't be ready by 9 November, Scotland takes Christmas orders with picker substitutions.

Recommendation: No-go for the all-region rollout on 2 November

Do not enable auto-substitutions anywhere on 2 November: the dietary hard filter is not scheduled to deploy until 4 November, so the zero-mismatch safety criterion is not yet protected. After deployment and validation, North West is the only region I’d consider enabling first, with conditions. Hold the other regions for the reasons below.

Figures are for 1–28 October; refund rates are per 1,000 orders. Basket averages are order-weighted within each region. I excluded the three exact duplicate North West treatment rows on 8, 9 and 10 October.

Conditions and rationale

• North West: After the hard filter deploys, pass regression tests across all six protected attributes (gluten-free, vegan, vegetarian, nut-free, halal and kosher); then enable regionally with close monitoring and a rollback switch. The export duplicates should also be fixed or guarded against before relying on daily reporting.
• London, South East and Midlands: Do not launch until the filter is deployed and the dietary-mismatch failures are investigated and validated as fixed. Their good acceptance, refund and basket figures do not offset a safety-criterion failure.
• Scotland: Hold until the supplier catalogue re-map is complete and verified, and a fresh test meets both acceptance and refund guardrails. The sharp rise in treatment refunds and lower acceptance coincide with the dairy supplier/catalogue change; the issue is open, with no completion date.

The pooled “£4 smaller” basket claim should not drive this decision: treatment exposure differed by region, and baskets vary substantially by region. Within each region, the treatment average is slightly higher in these data. Likewise, an overall acceptance or refund result cannot override region-level launch gates. The 9 November booking window is important, but it does not justify launching before the safety control is live.