Add Connecticut premium assistance (Covered Connecticut)

[DTrim99]

Summary

Closes #9226.

Adds the Covered Connecticut Program — Connecticut's state-funded premium wrap that pays the enrollee's residual benchmark silver-plan premium (after the federal APTC) down to $0 for Access Health CT enrollees at or below 175% of the federal poverty level who are eligible for the federal ACA premium tax credit.

Scope is the premium axis only (residual premium to $0) for plan year 2026. The program's separate cost-sharing, dental, and non-emergency medical transportation benefits are not modeled (see Not modeled), which is why the programs.yaml status is partial.

Authority: June Special Session, Public Act No. 21-2 (2021), §16.

Regulatory authority

The program is created by June Sp. Sess., Public Act No. 21-2 (2021), §16 (Senate Bill No. 1202) — session law, not codified as a standalone CGS section. Program text spans PDF pages 21–24 (#page=21 anchors the §16 body).

• §16(b) — establishes the Covered Connecticut program within the Office of Health Strategy.
• §16(b)(1) — directs OHS to "provide premium and cost-sharing subsidies that are sufficient to ensure fully subsidized coverage" (the residual-to-zero design).
• §16(b)(1)(B)(iv) — household income up to "one hundred seventy-five per cent of the federal poverty level" (fpl_limit = 1.75).
• §16(b)(1)(B)(ii) — enrollees must be "eligible for premium and cost-sharing subsidies for a qualified health plan" (federal APTC-eligible).
• §16(b)(1)(B)(iii) — ineligible for Medicaid because income exceeds Medicaid limits (inherited from the APTC gate).
• §16(b)(1)(B)(v) — coverage under the benchmark silver qualified health plan (modeled via slcsp).
• §16(d) — the subsidy is not counted as income for CT personal income tax (chapter 229); satisfied by construction (not added to ct_agi).

Operational references: CT DSS and Access Health CT Covered Connecticut program pages.

Eligibility

A tax unit is eligible when all three hold (ct_covered_connecticut_eligible, defined_for = StateCode.CT):

1. In effect — the in_effect parameter is true (2026-01-01 onward).
2. APTC-eligible — at least one member is federal-APTC-eligible: tax_unit.any(members("is_aca_ptc_eligible")). This embeds on-Marketplace enrollment, the MFS exclusion, and the federal required-contribution income test.
3. Income — aca_magi_fraction <= 1.75 (175% FPL).

Notes:

• No explicit lower FPL floor. The is_aca_ptc_eligible gate already excludes Medicaid/HUSKY-eligible people (~≤138% FPL for CT adults), so Covered Connecticut effectively covers the ~138–175% FPL band.
• No age gate. The statute limits eligibility to nonpregnant adults 18–64 (plus family-variant dependents ≤26), but the MAGI + APTC structure captures the population; matches the MD/VT sibling design.

Benefit calculation

Residual-to-zero premium (a 0% target-contribution case):

ct_covered_connecticut = max_(0, add(tax_unit, period, ["slcsp"]) - aca_ptc)

• slcsp (the benchmark second-lowest-cost silver plan premium) proxies the statutory benchmark; it is MONTH-period and annualized by summing 12 months via add(...).
• aca_ptc is the annual federal advance premium tax credit.
• Because aca_ptc <= slcsp for benchmark enrollees, the result is implicitly capped at slcsp and never negative — no separate cap term is needed. This is the VT premium-assistance formula with the CT target contribution set to 0%, so the reduction machinery collapses to the residual; it is implemented directly.
• The amount variable is gated by defined_for = "ct_covered_connecticut_eligible", so ineligible tax units return 0.

Requirements coverage

40/40 YAML tests pass; ruff format clean.

Requirement	Status	Covered by
REQ-1 in_effect gate	Done	ct_covered_connecticut_eligible.py, eligible cases
REQ-2 APTC-eligible (any member)	Done	ct_covered_connecticut_eligible.py
REQ-3 aca_magi_fraction <= 1.75	Done	eligible + boundary cases
REQ-4 Eligibility composition, defined_for CT	Done	ct_covered_connecticut_eligible.py
REQ-5 Residual max_(0, slcsp - aca_ptc)	Done	ct_covered_connecticut.py, amount cases
REQ-6 Amount gated on eligibility	Done	ct_covered_connecticut.py
REQ-7 Medicaid floor inherited	Documented	variable docstring
REQ-8 Silver benchmark via slcsp	Documented	variable docstring
REQ-9 No explicit age gate	Documented	variable docstring
REQ-10 Not CT-taxable (§16(d))	By construction	not added to ct_agi
REQ-11 fpl_limit.yaml = 1.75	Done	parameter
REQ-12 in_effect.yaml (false → 2026 true, open-ended)	Done	parameter
REQ-13 ct_covered_connecticut.py (float/TaxUnit/YEAR)	Done	variable
REQ-14 ct_covered_connecticut_eligible.py (bool/TaxUnit/YEAR/CT)	Done	variable
REQ-15 Tests: residual, >175%=0, not-APTC=0, pre-2026=0, boundary	Done	4 YAML test files
REQ-16 Wired into healthcare_benefit_value.adds	Done	healthcare_benefit_value.py + Case 7
REQ-17 programs.yaml entry (status partial)	Done	programs.yaml
REQ-18 Changelog fragment	Done	changelog.d/
REQ-19 make format	Done	ruff clean
REQ-20 Node gov/states/ct/dss/covered_connecticut/	Done	all artifacts

Test files (40 cases total):

• ct_covered_connecticut_eligible.yaml — 9 cases
• ct_covered_connecticut.yaml — 13 cases
• integration.yaml — 11 cases, including two scenarios derived from raw income (no injected ACA inputs) at ~150% and ~160% FPL
• household/healthcare_benefit_value.yaml — 7 cases (Case 7 asserts flow-through)

Not modeled

The Covered Connecticut Program does more than the premium wrap. The following are a separate benefits axis, deliberately out of scope for this PR — hence programs.yaml status partial:

• Cost-sharing reduction to $0 — deductibles, copays, coinsurance, out-of-pocket max (§16(b)(1)/(2)).
• Dental benefits (§16(b)(2), on/after July 1, 2022).
• Non-emergency medical transportation (NEMT) (§16(b)(2)).

Also not modeled:

• The separate 2026 Connecticut Option / BHP program (2026 SB-3, within OPM; a ≤200% FPL band for households ineligible for Covered Connecticut, plus a 400–600% band). This is a distinct program — a candidate for a future PR — and does not change Covered Connecticut's 175% FPL ceiling.
• Enrollment / take-up mechanics, quarterly carrier reimbursement operations, §1332/§1115 waiver machinery, and advance-payment reconciliation. Modeled as a static benefit value.
• Explicit age gate (18–64 / 19–64) and the family-variant dependents-≤26 distinction.

Files added

changelog.d/
  ct-premium-assistance.added.md
policyengine_us/
  programs.yaml   (entry added)
  parameters/gov/states/ct/dss/covered_connecticut/
    fpl_limit.yaml
    in_effect.yaml
  variables/gov/states/ct/dss/covered_connecticut/
    ct_covered_connecticut.py
    ct_covered_connecticut_eligible.py
  variables/household/
    healthcare_benefit_value.py   ("ct_covered_connecticut" added to adds)
  tests/policy/baseline/gov/states/ct/dss/covered_connecticut/
    ct_covered_connecticut.yaml
    ct_covered_connecticut_eligible.yaml
    integration.yaml
  tests/policy/baseline/household/
    healthcare_benefit_value.yaml   (Case 7 added)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (63bcfc5) to head (15cdb86).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main     #9246    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
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  Files           12         3     -9     
  Lines          192        38   -154     
==========================================
- Hits           192        38   -154     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[DTrim99]

Review fixes applied (/review-program → /fix-pr)

Ran the full multi-agent local review — regulatory, references, code patterns, test coverage, and a sighted value-audit against June Sp. Sess. P.A. 21-2 (2021) §16 (the 790-page implementer, §16 on file pages 21–24) and the CT DSS Covered Connecticut page. Zero critical findings — the residual formula max_(0, slcsp − aca_ptc), the ≤175% FPL gate, the federal-APTC prerequisite, the no-minimum-floor rationale, and the §16(d) not-CT-taxable treatment are all correct and production-ready. Applied all should-address items and every suggestion:

References / documentation (the main theme)

• Retargeted the P.A. 21-2 anchors to the operative pages: in_effect and both variables now point to #page=22 (the "fully subsidized coverage" mandate §16(b)(1)), and the ct_covered_connecticut documentation's §16(d) not-taxable citation gets a #page=24 anchor. (fpl_limit's §16(b)(1)(B)(iv) #page=23 was already correct.)
• Clarified the in_effect comment: the program launched July 1 2021 (parents/caretakers) and July 1 2022 (all adults 18–64) — 2026-01-01 is the modeled verified-coverage-start floor, not the year it became standing. Added the CT DSS program page as a second reference to corroborate ongoing status, and repointed the fpl_limit DSS href off a navigation stub.
• programs.yaml agency "DSS (Access Health CT)" → State (sibling convention); made the statutory age-cohort scope choice (adults 18–64, dependents ≤26, parents/caretakers not separately gated) explicit in the eligible-variable docs; commented the defensive max_(0, …) floor.

Tests (all passing — 40+ CT cases)

• 1.7501 FPL epsilon just above the inclusive ceiling (→ ineligible), MFS-driven ineligibility via a real filing_status: SEPARATE (exercising the derived federal-PTC gate rather than injecting it), and an immigration-ineligible arm.
• A fully income-derived integration scenario that surfaced a real modeling nuance: at ~140% FPL a single CT adult derives into Medicaid (an expansion state), so is_aca_ptc_eligible is false and the residual is $0 — documented as the effective lower bound. A companion derived healthcare_benefit_value case at 150% FPL (above the Medicaid split) shows a genuine non-zero residual (988.84) flowing into net income.
• A 2027 carry-forward case and a negative-income case.

No value (fpl_limit 1.75, in_effect date), the residual formula, or the .any() idiom changed. Rebased onto current main.

Note: a GitHub Actions infrastructure incident earlier today ("Service Unavailable" on action downloads) caused unrelated transient job failures on some sibling branches; those are being re-run and are not code issues.

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