TX CCS: entity broadcast bug and missing historical parameters prevent microsimulation

[hua7450]

Summary

Texas Child Care Services (TX CCS) has 3 pre-existing bugs that prevent it from running in microsimulation. These only affect microsim (vectorized) — the API/JSON path (single-household, scalar) works fine.

Discovered while attempting to wire tx_ccs into the new child_care_subsidies federal aggregator (PR #7765).

Bug 1: Entity broadcast mismatch in tx_ccs_work_requirement_eligible

File: policyengine_us/variables/gov/states/tx/twc/ccs/eligibility/tx_ccs_work_requirement_eligible.py
Line 37: parent_meets_requirement = is_exempt | household_meets_work_requirement

• is_exempt is Person-level (from spm_unit.members on line 17-19)
• household_meets_work_requirement is SPMUnit-level (from spm_unit.sum() on line 25, then comparison on line 36)
• In microsim: (101384,) | (43134,) → ValueError: operands could not be broadcast together

Fix options:

Option A — use spm_unit.project():

household_meets_work_requirement = spm_unit.project(total_work_hours >= requirement)
parent_meets_requirement = is_exempt | household_meets_work_requirement

Option B — simplify to pure SPMUnit logic (equivalent):

household_meets = total_work_hours >= requirement
all_parents_exempt = spm_unit.sum(is_head_or_spouse & ~is_exempt) == 0
return household_meets | all_parents_exempt

Bug 2: Missing historical copay data

File: policyengine_us/parameters/gov/states/tx/twc/ccs/copay/rate/first_child.yaml

The bracket parameter only has values from 2024-10-01. When microsim calculates months before October 2024 (e.g., January 2024), fc.thresholds[0] returns IndexError: list index out of range because no brackets exist for that period.

Fix: Add historical bracket data for prior years.

Bug 3: Missing region parameter data

File: policyengine_us/parameters/gov/states/tx/twc/ccs/region/

The workforce board region parameter is not found for 2024-01-01:

ParameterNotFoundError: The parameter 'gov.states.tx.twc.ccs.region[panhandle]' was not found in the 2024-01-01 tax and benefit system.

Fix: Add historical region parameter data.

Why these weren't caught

TX CCS was never wired into any aggregator or microsim-tested variable chain. The microsim test only calculates household_net_income and decile variables — programs outside that dependency chain are never exercised in microsim.

Impact

• API/JSON (single household): No impact — scalar values broadcast correctly
• Microsimulation: TX CCS cannot be included in the child_care_subsidies aggregator until all 3 bugs are fixed

Acceptance Criteria

• Entity broadcast fix in tx_ccs_work_requirement_eligible.py
• Historical copay bracket data added to first_child.yaml
• Historical region parameter data added
• tx_ccs wired into STATE_CHILD_CARE_SUBSIDY_VARIABLES in child_care_subsidies.py
• Microsimulation passes with TX CCS included