TASK22224: modernize involvement and updatecase handlers

memory-bank/change-log.md

@@ -379,3 +379,49 @@ Validation:
 Follow-ups:
 
 - Optional next big slice: bring remaining proxy/message routes using raw axios promise chains (`createcaseinvolvement_api.js`, `createrepinvolvement_api.js`, `updatecase_api.js`) onto the same async/await + explicit contract pattern.
+
+---
+
+### CL-010: TASK22224 involvement/update route async contract hardening bundle
+
+date: 2026-03-23
+author: Cline
+scope: `pages/api/file/{createcaseinvolvement_api,createrepinvolvement_api,updatecase_api}.js`, `tests/phase21/file-handler-contract.test.cjs`
+type: change
+rationale: Execute the next requested slice by modernizing remaining relay-backed involvement/update handlers that still used axios promise chains and legacy dead imports.
+impact: Improves reliability/readability and preserves existing response contracts, including 412 "record exists" semantics for involvement creation flows.
+status: completed
+
+Summary:
+
+- `createcaseinvolvement_api.js`
+    - removed unused `CryptoJS` import
+    - refactored axios `.then/.catch` to explicit `try/catch`
+    - preserved conflict behavior: status 412 -> success `{ record: "exists" }`
+    - preserved failure contract: `CREATE_CASE_INVOLVEMENT_FAILED`
+- `createrepinvolvement_api.js`
+    - removed unused `CryptoJS` import
+    - refactored axios `.then/.catch` to explicit `try/catch`
+    - preserved conflict behavior: status 412 -> success `{ record: "exists" }`
+    - preserved failure contract: `CREATE_REP_INVOLVEMENT_FAILED`
+- `updatecase_api.js`
+    - removed unused `CryptoJS` import
+    - refactored axios `.then/.catch` to explicit `try/catch`
+    - preserved failure contract: `UPDATE_CASE_FAILED`
+- Phase21 tests expanded:
+    - createcaseinvolvement 412 conflict success contract
+    - createrepinvolvement dependency failure contract
+    - updatecase dependency failure contract
+
+Validation:
+
+- `node tests/phase21/file-handler-contract.test.cjs` -> pass (49/49)
+- `node tests/phase21/api-contract-slice1.test.cjs` -> pass
+    - helper: 4/4
+    - file-handler: 49/49
+    - email-handler: 12/12
+    - endpoint-handler: 149/149
+
+Follow-ups:
+
+- Optional: apply equivalent modernization to any remaining relay-backed handlers outside `pages/api/file/` that still use raw axios promise chains and have no explicit phase21 contract assertions.