diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad32c7b..b8cc9a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,10 +2,14 @@
 
 All notable changes to kalshi-sdk will be documented in this file.
 
-## Unreleased
+## 2.2.0 — 2026-05-19
 
 Response-side spec drift hardening stack (#157). Backfills the remaining
-v3.18.0 / v0.14 fields and promotes additive drift to a hard CI failure.
+v3.18.0 OpenAPI / v0.14 AsyncAPI fields across REST and WebSocket response
+models (65 new optional fields across 16 models), promotes additive
+drift from warning to hard CI failure, and lands a high-signal bugfix
+for the subaccount-number request constraint that was rejecting valid
+server-assigned values.
 
 ### Added
 
diff --git a/CLAUDE.md b/CLAUDE.md
index 19c5c5b..2286d35 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -134,7 +134,7 @@ All work — bugs, enhancements, polish, spec drift — is tracked in **GitHub I
 on `TexasCoding/kalshi-python-sdk`. Use the `gh` CLI or the GitHub UI; do not add
 markdown trackers (TODOS/BACKLOG) back to the repo.
 
-- Active milestone: post-v2.0 (after the audit-driven hardening wave that shipped v2.0.0)
+- Active milestone: post-v2.2 (after the response-side spec drift hardening stack that shipped v2.2.0)
 - Labels in use: `bug`, `enhancement`, `documentation`, `polish`, `breaking`, `spec-drift`, `testing`, `infra`, `ws`, `cli`
 - `ROADMAP.md` — short pointer to the active milestone
 - `CHANGELOG.md` — release-facing history; updated per release
diff --git a/ROADMAP.md b/ROADMAP.md
index 9b6916d..8c99886 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -4,6 +4,18 @@
 
 See `CHANGELOG.md` for full release history.
 
+- **v2.2.0 (2026-05-19)** — response-side spec drift hardening (`#157`).
+  65 new optional fields backfilled across 16 REST + WS response models
+  for OpenAPI v3.18.0 / AsyncAPI v0.14 (`Market`, `Order`, `Fill`,
+  `Event`, `EventMetadata`, `Settlement`, `Trade`, `IncentiveProgram`,
+  `RFQ`, `Quote`, `OrderGroup` + 3 group responses, plus 11 WS payloads
+  including the new `*_ts_ms` Unix-ms timestamps and
+  `outcome_side` / `book_side` direction encoding). Promoted additive
+  drift from warn → hard fail in CI so the next missed field surfaces
+  loudly. Relaxed the request-side `le=32` cap on six subaccount fields
+  (demo allocates above 32). Registered `ErrorPayload` in
+  `WS_CONTRACT_MAP`; applied `extra="allow"` to all WS envelope and
+  helper classes to match the payload policy from `#143`.
 - **v2.1.0 (2026-05-18)** — OpenAPI sync v3.13.0 → v3.18.0 (`#155`). V2
   event-market orders family (`create_v2` / `amend_v2` / `decrease_v2` /
   `cancel_v2` + batched variants on `/portfolio/events/orders/*`),
@@ -47,20 +59,21 @@ See `CHANGELOG.md` for full release history.
 
 Not scoped. Carry-overs from v2.1 and v2.0 audit backlog:
 
-- **Response-side spec drift detection.** v2.1 contract tests cover request
-  bodies (`TestRequestBodyDrift`) but not response models, which is how
-  `Balance.balance_dollars` slipped through 5 rounds of review. Add a
-  `RESPONSE_MODEL_MAP` + walker that asserts spec-required fields exist on
-  the SDK model.
-
-- Apply `extra="allow"` policy to WS envelope models (`kalshi/ws/models/`)
-  to mirror the response-model uniformity from `#114`.
-- `MessageQueue._buffer = collections.deque(maxlen=maxsize+1)` for
+- **`MessageQueue._buffer = collections.deque(maxlen=maxsize+1)`** for
   defense-in-depth (#106 F-P-15 / F-R-02).
-- `_to_decimal_dollars` / `_to_decimal_fp` consolidation (#106 F-N-09 +
-  the follow-up noted in #140).
-- WS UX foot-guns: auto-start recv loop when no `subscribe_*` was called,
-  resubscribe-time data-frame stashing (#106 F-P-16 / F-R-13).
+- **`_to_decimal_dollars` / `_to_decimal_fp` consolidation** (#106
+  F-N-09 + the follow-up noted in #140).
+- **WS UX foot-guns**: auto-start recv loop when no `subscribe_*` was
+  called, resubscribe-time data-frame stashing (#106 F-P-16 / F-R-13).
+- **Map remaining REST sub-models / V2 family / internal containers**
+  (~42 entries) into `CONTRACT_MAP` and promote
+  `test_contract_map_completeness` (REST) to hard-fail. WS side already
+  hard-fails as of v2.2.0; the REST side stays warn-only until the
+  mapping work lands.
+- **Required-but-Optional drift policy decision** (~204 entries on
+  `test_required_drift` / `test_ws_required_drift`). Currently warn-only;
+  promote to fail behind either an allowlist or a tightening pass that
+  drops `None` defaults on fields the server reliably sends.
 
 Pick from `gh issue list` and the deferred items in `#106` opportunistically.
 
diff --git a/kalshi/__init__.py b/kalshi/__init__.py
index 5c5a968..acffd99 100644
--- a/kalshi/__init__.py
+++ b/kalshi/__init__.py
@@ -318,4 +318,4 @@
     "Withdrawal",
 ]
 
-__version__ = "2.1.0"
+__version__ = "2.2.0"
diff --git a/pyproject.toml b/pyproject.toml
index 22e95a4..dd1dd32 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "kalshi-sdk"
-version = "2.1.0"
+version = "2.2.0"
 description = "A professional Python SDK for the Kalshi prediction markets API"
 readme = "README.md"
 license = { text = "MIT" }