[PavelMakarchuk]

Summary

New lane uk-benefit-uprating: the CPI rate that sets the April 2027 uprating of most working-age benefits, and PolicyEngine-UK's benefit rates against every published April uprating. It gives a baseline check for the Autumn Budget 2026 question "will any working-age benefit be cut or uprated below CPI?".

• Claims (2):
  • ONS September 2026 CPI, 3.5% (D7G7, release of 21 October 2026).
  • OBR's March 2026 forecast for 2026 Q3, 2.08% (EFO detailed forecast tables, economy, Table 1.7). obr.uk refuses scripted fetches, so the workbook is a Wayback copy, with its sha256 recorded.
  • The ONS rate is an official outturn. It is staged as a claim by decision (2026-10-22), a departure from the boundary rule that ARCHITECTURE.md records, as for the Census STC claims (US state income tax collections for every state (Census STC) as baseline claims #176).
  • Both claims are consumed_as_target: PE-UK takes ONS September rates and OBR determinants as inputs, so a match checks the input, not model skill.
• Counterparts: pipeline/compute_uk_uprating_readback.py reads the parameter tree of policyengine-uk 2.147.2. There is no simulation and no dataset; data_bundle is parameter-tree. The protected UC health element comes from the model's own Universal Credit Act 2025 s. 4 floor.
• Results on other lanes' claims (15), by claim_id, with no edit to those claims: the 4 HM Treasury Budget 2025 upratings (uk-ab2025-official) and the 11 Resolution Foundation upratings (uk-thinktanks). These were the archived "uprating_april2026" family that produce_campaign_uk blocks; this lane answers them on a current engine instead.

Claim	Published	PE-UK 2.147.2
Working-age benefits, April 2026 (HMT, Sept 2025 CPI)	3.8%	3.80%
UC standard allowance, April 2026 (HMT "over 6%"; RF)	6.0% / 6.2%	6.19%
UC standard allowance, under 25s, April 2026 (RF)	6.8%	6.81%
UC health element, existing claimants, April 2026 (RF)	1.5%	1.54%
LHA, April 2026 (RF)	0%	0% (freeze)
UC standard allowance, April 2027 / 2028 / 2029 (RF forecasts)	3.1 / 2.9 / 2.9%	3.10 / 2.89 / 2.78%
CPI-linked working-age rates, April 2027, against ONS September 2026 CPI	3.5%	2.30%
the same, against OBR's 2026 Q3 forecast	2.08%	2.30%

Finding. PE-UK 2.147.2 raises CPI-linked working-age rates by 2.30% in April 2027. That is OBR's calendar-year 2026 CPI, because gov.benefit_uprating_cpi follows the lagged calendar-year index. The model's own September 2026 CPI is a 2.12% forecast, with no outturn entered. Both are below the 3.5% that ONS published. This is PolicyEngine/policyengine-uk#2533; PolicyEngine/policyengine-uk#2557 (open) moves the index to September CPI and enters 3.5%. After that release, running the read-back again moves these rows with one command.

Also: the new metric cpi_inflation_rate, kept apart from cpi_inflation_effect (what a policy does to the CPI), and the release label parameter-tree.

Test plan

• tests/test_uk_benefit_uprating.py:
  • raw hashes;
  • the extract equals the adapter output (needs openpyxl);
  • the ONS date is the London date, and a month that occurs twice is refused;
  • the claims;
  • the read-back's April 2026 legislated entries, and the April 2027 basket rise;
  • 4 HMT and 11 RF results in the built DB, and every HMT uprating claim is mapped.
• Rebuild from scratch and export: 13 new feed rows (export pins UK +13, total 5724 → 5737); the 4 HMT rows gain results.
• pytest tests/ (test_modal_uk_event deselected locally): the only failures are 58 failures and 3 errors in the UK replay and registry tests. They come from this machine's base Python environment (an old policyengine-uk that uv run can see), and the same 58 + 3 occur on a clean main checkout.
• ruff format --check; bun test src, bun run lint (the 2 existing warnings), bun run build.

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Project	Deployment	Actions	Updated
policyengine-scorecard	Ready	Preview	Oct 22, 2026 9:56pm UTC