diff --git a/paper/index.qmd b/paper/index.qmd
index 89e7637..ff9426c 100644
--- a/paper/index.qmd
+++ b/paper/index.qmd
@@ -6,7 +6,7 @@ author:
     affiliations:
       - name: PolicyEngine
     email: max@policyengine.org
-date: 2026-09-10
+date: 2026-09-12
 date-format: long
 bibliography: ../bibliography/references.bib
 format:
@@ -820,14 +820,35 @@ standalone calculator, with year-specific national bases, housing shares,
 geographic indices, assignments, and source fingerprints. The pinned
 calculator includes PolicyEngine, Microcosm, and native Axiom adapters
 that consume these quantities through explicit contracts. Population
-sources supply native SPM membership
-and composition roles; tax-benefit models retain responsibility for
-resources, and the population system retains its weights. A change of
+sources supply native SPM membership and composition roles;
+tax-benefit models retain responsibility for resources, including
+ordinary income, program awards, and the housing-assistance cap, and the
+population system retains its weights. A change of
 rules engine does not require a second expenditure forecast. Runtime
 parity and release integration are separate checks from the statistical
 validity of the projection. The snapshot date does not reconstruct
 historical information sets or certify a public deployment.
 
+The resource conventions below are specified separately in the
+[PolicyEngine-US resource contract](https://github.com/PolicyEngine/policyengine-us/blob/7b2ef566aee52db17fe1d8ab5d0a744669802506/docs/spm.md).
+That contract is outside the calculator artifacts pinned above and does
+not reproduce or revise the preserved historical poverty sensitivity.
+In population applications, the threshold's housing portion limits the
+housing subsidy counted as an SPM resource. The accompanying resource
+specification sums modeled awards within a household, allocates the total
+to SPM units by member share, and applies each unit's cap after allocation,
+following Census's subsidy proration [@spmtechnical, p. 14]. It treats
+interview-time public or reduced-rent housing status as full-year
+assistance to a program family represented by the householder's SPM unit,
+because the survey does not identify that family. For units whose modeled
+award is positive before allocation, it allocates their tenant
+contributions by the same member shares; Census
+does not document this split, so it is a declared consistency assumption
+rather than verified production parity. Program eligibility and awards
+do not depend on the cap. These choices concern resource valuation and
+do not change the threshold estimates reported here. They do not revise
+the separately preserved historical poverty sensitivity.
+
 Tables regenerate from the recorded artifacts. The build checks their
 hashes before generating outputs in temporary storage and comparing the
 results with the saved tables and evaluation JSON. Archived tables no