merge: diagnostics and telemetry runtime

2026-07-26 16:42:31 +09:00
parent 2fa0baa577 5173b6c8d6
commit 3f634eb655
43 changed files with 1760 additions and 116 deletions
@@ -84,7 +84,8 @@
        { "script": "check:types:fixture:page-action", "expect": "fail" },
        { "script": "check:types:fixture:icon-button", "expect": "fail" },
        { "script": "check:types:fixture:i18n-key", "expect": "fail" },
-        { "script": "check:types:fixture:i18n-params", "expect": "fail" }
+        { "script": "check:types:fixture:i18n-params", "expect": "fail" },
+        { "script": "check:types:fixture:diagnostics", "expect": "fail" }
      ],
      "logPath": "artifacts/quality/check-types.txt",
      "evidence": ["artifacts/quality/check-types.txt"],
@@ -158,6 +159,8 @@
        { "script": "check:design-system:fixture", "expect": "fail" },
        { "script": "check:i18n", "expect": "pass" },
        { "script": "check:i18n:fixture", "expect": "fail" },
+        { "script": "check:diagnostics", "expect": "pass" },
+        { "script": "check:diagnostics:fixture", "expect": "fail" },
        { "script": "check:registries", "expect": "pass" },
        { "script": "check:registries:fixture", "expect": "fail" },
        { "script": "check:routes:fixture", "expect": "fail" }
@@ -169,6 +172,8 @@
        "artifacts/quality/design-system-fixture.json",
        "artifacts/quality/i18n.json",
        "artifacts/quality/i18n-fixture.json",
+        "artifacts/quality/diagnostics.json",
+        "artifacts/quality/diagnostics-fixture.json",
        "artifacts/quality/registries.json",
        "artifacts/quality/registry-fixture.json",
        "artifacts/quality/route-registry-fixture.json"
@@ -0,0 +1,97 @@
+# VD-07: Diagnostics와 telemetry exporter 경계
+
+- 상태: Accepted
+- 결정일: 2026-07-26
+- 적용 브랜치: `feature-frontend-diagnostics-telemetry-runtime`
+- 재검토: 실제 운영 sink, consent가 필요한 analytics 또는 분산 tracing provider가
+  선정될 때
+
+## 배경
+
+기존 telemetry registry와 best-effort HTTP queue는 있었지만 운영 진단 record와
+semantic event의 책임이 하나의 telemetry port에 섞여 있었다. boot, HTTP,
+cache, storage, route와 release failure의 선언도 실제 production producer와
+완전히 연결되지 않았다. 이 상태에서는 retry attempt마다 같은 사건을 발행하거나
+raw URL, query, request body와 오류 객체가 queue에 들어갈 위험이 있다.
+
+반면 skeleton 단계에는 실제 관측 vendor, endpoint의 운영 보안 정책, analytics
+consent와 보존 기간이 결정되지 않았다. 특정 SDK를 기본 번들에 설치하는 것은
+vendor 결정 전에는 안전한 기본값이 아니다.
+
+## 결정
+
+1. level 기반 운영 진단은 `DiagnosticsPort`, registry 기반 semantic event는
+   `TelemetryPort`로 분리한다. application은 두 port의 concrete adapter나
+   exporter SDK를 알지 못한다.
+2. diagnostics의 level, event ID와 context key는 닫힌 registry/allowlist다.
+   telemetry도 event별 required/optional attribute와 value policy를 적용한다.
+   등록되지 않은 event·context·고카디널리티 값은 전송하지 않는다.
+3. 기본 diagnostics adapter는 bounded in-memory evidence이고 telemetry는
+   설정이 없으면 true no-op이다. endpoint가 있을 때만 bounded oldest-drop
+   queue와 best-effort HTTP sink를 사용한다.
+4. raw path/URL/query/body/response/storage value, credential, cookie, email,
+   stack과 오류 객체 전체는 context에 넣지 않는다. route ID, operation ID,
+   correlation ID, release ID, error kind, status/attempt/duration bucket만
+   허용한다.
+5. HTTP logical execution은 success, retry recovery, terminal failure 또는
+   abort마다 `http.request.completed` diagnostics를 정확히 한 번 남긴다.
+   `api.request.failed` telemetry는 retry가 끝난 terminal non-abort failure에만
+   정확히 한 번 발행한다.
+6. `app.boot.failed`, `ui.render.failed`, `release.mismatch.detected`,
+   `telemetry.delivery.dropped`를 production path에 연결한다. cache와 storage
+   실패는 diagnostics로 기록하되 raw key/value를 기록하지 않는다.
+7. queue full, invalid event/context, serialization과 sink failure는 제한된
+   reason bucket으로 집계한다. drop observer의 failure는 다시 telemetry를
+   발행하지 않는 nonrecursive 경계다.
+8. diagnostics와 telemetry failure는 제품 흐름, HTTP 결과, route transition,
+   storage/cache fallback과 React error surface를 바꾸지 않는다.
+9. mount 전 bootstrap failure는 안전한 build/config/error kind만 별도 evidence로
+   만들며 untrusted error message, stack과 support 입력을 serialize하지 않는다.
+10. 실제 error reporter, RUM, analytics나 tracing SDK는 같은 port 뒤의 외부
+    adapter로만 추가한다. SDK type과 event API를 application/feature/presentation
+    public contract에 노출하지 않는다.
+
+## 실행 경계
+
+```text
+route/application/HTTP/cache/storage/bootstrap
+  -> typed DiagnosticsPort 또는 TelemetryPort
+  -> registry + allowlist + value policy
+  -> bounded memory/no-op 또는 best-effort HTTP adapter
+  -> 프로젝트가 선택한 외부 sink
+```
+
+- diagnostics contract: `src/contracts/diagnostics.ts`
+- telemetry contract: `src/contracts/telemetry.js`
+- application ports: `src/application/ports/diagnostics-port.ts`,
+  `telemetry-port.ts`
+- bounded diagnostics: `src/adapters/diagnostics/bounded-diagnostics.ts`
+- best-effort telemetry: `src/adapters/telemetry/best-effort-telemetry.js`
+- composition: `src/bootstrap/runtime-adapters.js`
+
+## 검증
+
+- `check:diagnostics`는 모든 registry event에 production producer가 있는지와
+  source의 direct console/sensitive context 우회를 검사한다.
+- negative source fixture는 direct console, unknown event와 raw context를 실제로
+  거절하며 TypeScript fixture는 잘못된 level/event ID를 거절한다.
+- unit test는 allowlist, hostile/circular error, bounded diagnostics, no-op,
+  queue full, sink/observer failure와 pre-mount boot evidence를 검증한다.
+- HTTP integration은 success, retry recovery, terminal failure와 abort의 producer
+  횟수, route/operation/correlation context와 요청 값 비노출을 검증한다.
+- cache/storage/release/application/runtime test는 각 production wiring과
+  diagnostics failure isolation을 검증한다.
+
+## 한계와 재검토 조건
+
+기본 adapter는 운영 log 검색, source map 연계, session replay, distributed span,
+analytics consent, sampling budget과 장기 보존을 제공하지 않는다. 실제 sink를
+선정할 때 데이터 처리 지역, 보존 기간, consent, CSP, source map 접근 제어,
+sampling과 비용 상한을 별도 결정해야 한다.
+
+## Rollback
+
+telemetry exporter는 runtime 설정을 끄거나 adapter wiring을 `noOpTelemetry`로
+바꾸어 독립적으로 제거할 수 있다. 이때도 `DiagnosticsPort`, registry,
+redaction/value policy, producer-count와 negative fixture는 유지한다. 외부 SDK
+문제로 application producer와 안전 계약을 함께 되돌리지 않는다.
@@ -33,14 +33,14 @@

 특히 다음은 선행 해결이 필요하다.

-RP-01~RP-08에서 TypeScript 도구 안전망, application runtime 주입,
+RP-01~RP-09에서 TypeScript 도구 안전망, application runtime 주입,
 query/mutation inbound adapter, HTTP 실행 계약과 executable route/release
 recovery 계약, 제거 가능한 reference 수직 슬라이스, form/page, design system과
-i18n 실행 경계는 구현됐다. 현재 선행 해결
+i18n 실행 경계와 diagnostics/telemetry production wiring은 구현됐다. 현재 선행 해결
 대상은 다음과 같다.

-1. diagnostics/telemetry 실제 producer 연결
-2. registry evidence, 공급망과 optional adapter recipe 심화 게이트
+1. registry evidence와 실제 compatibility diff
+2. 공급망과 optional adapter recipe 심화 게이트

 따라서 현재 상태를 “프론트 공통부가 모두 구현됐다”고 표현하면 범위가 과장된다.
 더 정확한 표현은 다음과 같다.
@@ -66,7 +66,7 @@ i18n 실행 경계는 구현됐다. 현재 선행 해결
 | 계층 의존 방향 | 부분 준비 | `.dependency-cruiser.cjs`, `src/application/ports` | inbound/outbound 명명과 `contracts` 소유권까지 집행 |
 | application facade | 준비됨 | typed input/output catalog, provider, production composition test | feature input use case를 contribution으로 확장 |
 | HTTP client | 준비됨 | path/search/body projection, runtime timeout/retry, abort/cleanup test | feature gateway 뒤에서 사용 |
-| retry | 준비됨 | HTTP 단일 소유, runtime max attempts, Query retry off | RP-09에서 telemetry 연결 |
+| retry | 준비됨 | HTTP 단일 소유, runtime max attempts, Query retry off, logical execution당 bounded diagnostics | terminal event 중복 방지 계약 유지 |
 | 오류 모델 | 부분 준비 | error registry와 normalization 존재 | typed discriminated union과 계층별 mapper |
 | 검증 | 준비됨 | runtime/API/route/form Zod parse 결과를 실행 경계에서 사용하고 domain invariant와 분리 | feature별 schema 소유권 유지 |
 | 인증 연동 | 준비됨/프로젝트 선택 | opaque auth owner와 demo seam 존재 | 인증 방식별 recipe; 기본 token 저장소는 추가하지 않음 |
@@ -81,8 +81,8 @@ i18n 실행 경계는 구현됐다. 현재 선행 해결
 | 아이콘 | 준비됨 | Lucide static vendor facade와 semantic icon/IconButton 접근성 계약 | 의미 icon 추가 시 bundle/접근성 기준 적용 |
 | 폼 | 준비됨 | Zod 기반 local facade, error summary/focus, 422 allowlist, dirty/pending/conflict 정책 | 복합 form 요구가 생기면 VD-04 조건으로 vendor adapter 평가 |
 | 국제화 | 준비됨 | 137-key typed catalog, locale provider, Intl formatter, safe fallback/alias, pseudo·RTL gate | 실제 locale·번역 승인은 프로젝트에서 연결 |
-| logging/diagnostics | 미제공 | telemetry port는 있으나 logger 없음 | redaction이 적용된 diagnostics/logging 경계 |
-| telemetry | 부분 준비 | registry, queue, redaction 존재 | HTTP·boot·cache·storage·route 사건에 실제 연결 |
+| logging/diagnostics | 준비됨 | 별도 `DiagnosticsPort`, 8-event registry, allowlist, bounded/no-op adapter와 production producer | 실제 프로젝트의 remote sink는 port 뒤에서 선택 |
+| telemetry | 준비됨/프로젝트 선택 | 5-event registry, bounded queue, redaction/value policy, boot·HTTP·render·release·drop producer | analytics/RUM/error vendor와 consent는 프로젝트에서 선택 |
 | 비동기 상태 불변식 | 준비됨 | 배타적 typed overlay, stale latch, 실제 retry/conflict action | reference 화면에서 전체 상태 전시 |
 | 단위·통합·E2E | 준비됨 | Vitest, RTL, MSW, Playwright 3엔진 | TS 테스트 검사, 실제 bootstrap 통합, 위험 시나리오 보강 |
 | UI 회귀 검증 | 미제공 | axe/reflow는 있으나 visual baseline 없음 | Storybook 또는 동급 workshop과 시각 회귀 |
@@ -217,11 +217,14 @@ guard → browser navigation adapter의 1회 reload로 연결됐다. 일반 rend
 failure는 이 경로에서 제외되고, 반복 실패·offline·malformed manifest·storage
 실패는 지원 표면으로 fail-closed된다.

-#### telemetry, registry, 공급망 gate의 실행 깊이가 부족하다
+#### RP-09에서 diagnostics/telemetry 실행 깊이 보강

-telemetry registry에는 여러 사건이 있지만 실제 production producer는 제한적이다.
-boot, API attempt/final failure, auth recovery, storage/cache degradation, release/chunk
-recovery를 registry 사건에 연결해야 한다.
+`DiagnosticsPort`와 `TelemetryPort`를 분리하고 boot, HTTP logical outcome,
+render, cache, storage, route, release mismatch와 delivery drop을 production
+producer에 연결했다. HTTP retry는 attempt별 terminal event를 발행하지 않고
+logical execution 종료 시 한 번만 bounded outcome을 남긴다. allowlist와
+value policy가 raw URL/query/body/storage value/error object를 거절하고 queue와
+sink failure는 nonrecursive drop evidence로 제한된다.

 registry/compatibility 검사는 다음까지 확장한다.

@@ -243,7 +246,7 @@ known vulnerability, license policy, SBOM/provenance를 pinned tool로 검사해
 - token → primitive → pattern → template로 이어지는 디자인 시스템
 - Lucide를 감싼 local icon registry와 `IconButton`
 - typed message key, locale provider, formatter, pseudo-locale/RTL smoke
- redacted structured diagnostics/logger와 telemetry wiring
+- RP-09에서 완료한 redacted structured diagnostics와 telemetry wiring 유지
 - Storybook 또는 동급 isolated UI workshop
 - Playwright visual baseline, shared MSW scenarios, built-dist E2E
 - React Hooks, JSX accessibility, TanStack Query 관련 lint
@@ -380,7 +383,8 @@ bootstrap → React TSX → tests 순서로 이동한다.

 - retry: `src/adapters/http/retry-policy.js`, 부분 준비
 - API client: `src/adapters/http/client.js`, 부분 준비
- logger: 없음. telemetry와 분리하거나 diagnostics port로 합치는 결정 필요
+- logger: `DiagnosticsPort`로 telemetry와 분리해 구현. closed event/level,
+  allowlist와 bounded/no-op adapter 제공
 - token manager: 의도적으로 없음. opaque external auth owner가 credential을 소유
 - error: `src/contracts/errors.js`와 HTTP normalization, 부분 준비
 - validation: runtime/API Zod는 존재, route/form/domain 분리는 미완성
@@ -723,6 +723,28 @@ render와 release 사건을 실제 producer에 연결한다.
 RP-09는 exporter를 제거하고 즉시 no-op adapter로 전환할 수 있어야 한다.
 diagnostics port와 redaction test는 유지한다.

+**구현 증거 (2026-07-26)**
+
+- VD-07에서 level/event 기반 `DiagnosticsPort`와 semantic `TelemetryPort`를
+  분리하고 bounded memory/no-op 또는 설정 기반 best-effort HTTP exporter를
+  채택했다.
+- diagnostics 8종과 telemetry 5종의 registry, context/attribute allowlist,
+  고카디널리티 value policy, timestamp와 status/attempt/duration/queue bucket을
+  구현했다.
+- boot, route, render, HTTP logical outcome, cache, storage, release mismatch와
+  telemetry drop을 production composition에 연결했다. HTTP는 success/recovery/
+  terminal/abort 각각 logical execution당 diagnostics 한 번, terminal
+  non-abort failure telemetry 한 번만 발행한다.
+- bounded oldest-drop queue, drop reason 집계, sink/observer failure 격리와
+  nonrecursive delivery evidence를 구현했다. exporter가 없으면 network와 queue
+  side effect가 없는 true no-op이다.
+- `check:diagnostics`, source negative fixture와 TypeScript negative fixture가
+  producer 누락, direct console, unknown event/context, raw URL/query/body/
+  credential 경계를 거절한다.
+- unit/integration test가 circular/hostile error, pre-mount boot, queue/sink
+  failure, no-op, cache/storage/release producer, success/retry recovery/terminal/
+  abort 횟수와 reference route/operation/correlation context를 검증한다.
+
 ### 10. `feature-frontend-test-registry-evidence-hardening`

 **목표**
@@ -779,22 +779,31 @@ Logger와 telemetry는 같은 것이 아니다.
 - Telemetry: registry에 정의된 semantic event와 metric
 - Error reporter: 예외 집계와 release correlation

-기본 `Logger` output port는 safe context만 받는다.
+VD-07에 따라 기본 구현은 임의 message 문자열을 받는 `Logger`가 아니라 닫힌
+event ID와 safe context만 받는 `DiagnosticsPort`다.

 ```ts
-export interface Logger {
-  debug(message: string, context?: SafeLogContext): void;
-  info(message: string, context?: SafeLogContext): void;
-  warn(message: string, context?: SafeLogContext): void;
-  error(message: string, context?: SafeLogContext): void;
+export interface DiagnosticsPort {
+  record(input: {
+    level: DiagnosticLevel;
+    eventId: DiagnosticEventId;
+    context?: DiagnosticContext;
+  }): void;
 }
 ```

-개발 환경에는 redacted console adapter, production에는 allowlist 기반
-remote adapter, 테스트에는 recording 또는 no-op adapter를 연결한다.
+기본 runtime에는 bounded in-memory diagnostics와 설정 기반 best-effort
+telemetry adapter, 테스트에는 recording 또는 no-op adapter를 연결한다.
+direct `console`은 redaction 경계를 우회하므로 source gate가 거절한다.
 민감정보 redaction은 각 호출자의 선의가 아니라 adapter와 contract에서
 강제한다.

+현재 production producer는 boot, logical HTTP outcome, cache, storage, route,
+render, release mismatch와 telemetry delivery drop을 포함한다. HTTP terminal
+telemetry는 모든 retry가 끝난 뒤 한 번만 발행하며 abort에는 발행하지 않는다.
+raw path/query/body/error 대신 route/operation/correlation ID와
+status/attempt/duration bucket만 전달한다.
+
 ## 16. Feature 경계와 removable reference feature

 Reference feature는 단순 UI fixture가 아니라 다음 경로를 모두 실행해야
@@ -1223,9 +1232,10 @@ contract와 실패 분기를 우선한다.
 - [ ] runtime timeout/retry 설정이 실제 HTTP transport에 반영된다.
 - [ ] QueryClient와 feature query bridge가 실제 route에서 동작한다.
 - [ ] session UI API와 credential attachment가 분리되어 있다.
- [ ] logger와 telemetry가 HTTP/render/storage/cache failure 경로에
+- [x] diagnostics와 telemetry가 HTTP/render/storage/cache failure 경로에
      연결된다.
- [ ] page lifecycle에서 필요한 telemetry flush/cleanup이 수행된다.
+- [x] `pagehide`에서 bounded telemetry queue를 flush하고 adapter `dispose`가
+      lifecycle listener를 정리한다.

 ### 26.3 HTTP와 validation

@@ -468,23 +468,31 @@ raw response body, stack, token, URL query, PII를 사용자 copy나 일반 log

 ### 7.3 diagnostics와 telemetry

-현재 telemetry event contract와 별도로 개발·진단용 structured logger가 필요하다.
-다음 두 설계 중 하나를 ADR로 결정한다.
-
-1. `DiagnosticsPort`가 log/event/span을 내부 method로 구분
-2. `LoggerPort`와 `TelemetryPort`를 분리
+VD-07에서 level/event 기반 `DiagnosticsPort`와 semantic
+`TelemetryPort`를 분리했다. diagnostics는 8개 event ID와 safe context
+allowlist를, telemetry는 event별 required/optional attribute와 value policy를
+사용한다.

 공통 요구:

 - log level과 event key는 닫힌 union
 - attribute allowlist와 중앙 redaction
- dev adapter는 console을 사용하되 동일 redaction 적용
- production adapter는 provider SDK를 감싸며 앱 코드는 SDK를 import하지 않음
+- 기본 adapter는 bounded memory/no-op이고 endpoint가 있을 때만 best-effort
+  HTTP queue를 사용
+- production provider SDK를 추가할 때도 port 뒤에서 감싸며 앱 코드는 SDK를
+  import하지 않음
 - 오류 객체 전체를 그대로 serialize하지 않음
 - trace ID/build ID/route ID/operation ID를 허용된 범위에서 연결
 - logging failure가 제품 flow를 실패시키지 않음
 - consent가 필요한 analytics와 essential diagnostics를 분리

+HTTP는 route/operation/correlation ID를 logical execution context로 생성하고
+success/recovered/failed/aborted 종료 시 diagnostics를 한 번만 기록한다.
+terminal non-abort failure만 telemetry를 한 번 발행한다. cache/storage와 boot
+producer는 raw key, value, message, stack을 버리고 error kind와 bounded
+operation만 남긴다. queue full과 sink failure는 제한된 reason bucket이며 drop
+observer가 실패해도 재귀 발행하지 않는다.
+
 ### 7.4 locale, message와 표시 값

 RP-08부터 locale은 presentation-owned React context다. server/application
@@ -410,6 +410,8 @@ Page / AsyncSurface / Form pattern
 - filter 순서가 달라도 canonical key가 같다.
 - route unmount 또는 superseded input에서 request를 abort한다.
 - aborted request는 terminal error나 telemetry failure로 오분류되지 않는다.
+- success와 retry recovery는 terminal failure telemetry를 만들지 않고,
+  exhausted retry는 logical execution당 한 번만 발행한다.
 - offline/paused와 loading을 구분한다.
 - 401 복구는 한 번만 수행한다.
 - 재로그인 후 허용된 operation만 다시 실행한다.
@@ -1283,7 +1285,8 @@ CI registry에 추가한다.
 - [ ] high-risk module branch 목표를 충족한다.
 - [ ] 신규 코드의 미검증 branch에 승인 없는 예외가 없다.
 - [ ] bundle/performance budget을 통과한다.
- [ ] telemetry/error output에 민감 정보가 없다.
+- [x] diagnostics/telemetry output의 allowlist, value policy와 negative fixture가
+      raw URL/query/body/storage value/error object를 거절한다.
 - [ ] 관련 gate와 evidence registry가 갱신되었다.

 ## 19. 금지 패턴
@@ -76,6 +76,7 @@ export default [
      "artifacts/**",
      "tests/fixtures/typecheck/**",
      "tests/fixtures/architecture/forbidden/**",
+      "tests/fixtures/diagnostics/forbidden/**",
      "tests/fixtures/i18n/forbidden/**",
      "tests/fixtures/security/forbidden/**",
    ],
@@ -116,6 +117,25 @@ export default [
      "no-unused-vars": "off",
    },
  },
+  {
+    files: ["**/*.d.ts"],
+    languageOptions: {
+      ...commonLanguageOptions,
+      parser: babelParser,
+      parserOptions: {
+        requireConfigFile: false,
+        babelOptions: {
+          plugins: [
+            ["@babel/plugin-syntax-typescript", { dts: true }],
+          ],
+        },
+      },
+    },
+    rules: {
+      "no-undef": "off",
+      "no-unused-vars": "off",
+    },
+  },
  {
    files: ["**/*.tsx"],
    languageOptions: {
@@ -19,6 +19,8 @@
    "check:design-system:fixture": "node scripts/check-design-system.mjs --fixture",
    "check:i18n": "node scripts/check-i18n.mjs",
    "check:i18n:fixture": "node scripts/check-i18n.mjs --fixture",
+    "check:diagnostics": "node scripts/check-diagnostics.mjs",
+    "check:diagnostics:fixture": "node scripts/check-diagnostics.mjs --fixture",
    "check:types": "corepack pnpm check:types:app && corepack pnpm check:types:node && corepack pnpm check:types:test",
    "check:types:app": "tsc --project tsconfig.app.json",
    "check:types:node": "tsc --project tsconfig.node.json",
@@ -34,6 +36,7 @@
    "check:types:fixture:icon-button": "tsc --ignoreConfig --allowJs --checkJs --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler --jsx react-jsx tests/fixtures/typecheck/invalid-icon-button.tsx",
    "check:types:fixture:i18n-key": "tsc --ignoreConfig --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-message-key.ts",
    "check:types:fixture:i18n-params": "tsc --ignoreConfig --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-message-params.ts",
+    "check:types:fixture:diagnostics": "tsc --ignoreConfig --strict --noEmit --skipLibCheck --target ES2022 --module ESNext --moduleResolution Bundler tests/fixtures/typecheck/invalid-diagnostics-port.ts",
    "test:runtime-schema": "vitest run tests/runtime-schema --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/runtime-schema.xml --passWithNoTests",
    "test:unit": "vitest run tests/unit --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/unit.xml",
    "test:component": "vitest run tests/component --reporter=default --reporter=junit --outputFile.junit=artifacts/tests/component.xml",
@@ -0,0 +1,120 @@
+import { mkdir, readFile, readdir, writeFile } from "node:fs/promises";
+import path from "node:path";
+
+// @ts-expect-error Node 24 executes erasable TypeScript for this build-time gate.
+import { DIAGNOSTIC_EVENT_REGISTRY } from "../src/contracts/diagnostics.ts";
+import { TELEMETRY_REGISTRY } from "../src/contracts/telemetry.js";
+
+const fixtureMode = process.argv.includes("--fixture");
+const failures = [];
+const extensions = /\.(?:js|jsx|mjs|ts|tsx|mts)$/;
+
+/** @param {string} directory @returns {Promise<string[]>} */
+async function filesBelow(directory) {
+  const result = [];
+  for (const entry of await readdir(directory, { withFileTypes: true })) {
+    const target = path.join(directory, entry.name);
+    if (entry.isDirectory()) result.push(...(await filesBelow(target)));
+    else if (extensions.test(entry.name)) result.push(target);
+  }
+  return result;
+}
+
+const telemetryProducerFiles =
+  /** @type {Readonly<Record<string, string>>} */ ({
+  "app.boot.failed": "src/adapters/diagnostics/bounded-diagnostics.ts",
+  "api.request.failed": "src/adapters/http/client.js",
+  "ui.render.failed": "src/application/create-application.ts",
+  "release.mismatch.detected": "src/application/create-application.ts",
+  "telemetry.delivery.dropped":
+    "src/adapters/telemetry/best-effort-telemetry.js",
+  });
+const diagnosticProducerFiles =
+  /** @type {Readonly<Record<string, string>>} */ ({
+  "app.boot.failed": "src/adapters/diagnostics/bounded-diagnostics.ts",
+  "http.request.completed": "src/adapters/http/client.js",
+  "cache.operation.failed":
+    "src/adapters/query-cache/tanstack-query-cache.js",
+  "storage.operation.failed":
+    "src/adapters/storage/browser-storage-adapter.js",
+  "route.changed": "src/application/create-application.ts",
+  "ui.render.failed": "src/application/create-application.ts",
+  "release.mismatch.detected": "src/application/create-application.ts",
+  "telemetry.delivery.dropped": "src/bootstrap/runtime-adapters.js",
+  });
+
+if (!fixtureMode) {
+  for (const eventName of Object.keys(TELEMETRY_REGISTRY)) {
+    const producer = telemetryProducerFiles[eventName];
+    if (!producer) {
+      failures.push(`telemetry event has no declared producer: ${eventName}`);
+      continue;
+    }
+    const source = await readFile(producer, "utf8");
+    if (!source.includes(`"${eventName}"`)) {
+      failures.push(`telemetry producer is not executable: ${eventName}`);
+    }
+  }
+  for (const eventId of Object.keys(DIAGNOSTIC_EVENT_REGISTRY)) {
+    const producer = diagnosticProducerFiles[eventId];
+    if (!producer) {
+      failures.push(`diagnostic event has no declared producer: ${eventId}`);
+      continue;
+    }
+    const source = await readFile(producer, "utf8");
+    if (!source.includes(`"${eventId}"`)) {
+      failures.push(`diagnostic producer is not executable: ${eventId}`);
+    }
+  }
+}
+
+const sources = fixtureMode
+  ? await filesBelow("tests/fixtures/diagnostics/forbidden")
+  : await filesBelow("src");
+const sensitiveContext =
+  /\b(?:authorization|cookie|access_token|refresh_token|request_body|response_body|raw_url|query_string|email|user_name)\b/i;
+for (const file of sources) {
+  const source = await readFile(file, "utf8");
+  if (file.includes("contracts/telemetry.js")) continue;
+  if (source.includes("console.")) {
+    failures.push(`direct console diagnostics bypass in ${file}`);
+  }
+  const calls = source.match(
+    /(?:\.record\(\{|\.emit\()[\s\S]{0,700}?(?:\}\)|\}\);)/g,
+  ) ?? [];
+  if (calls.some((call) => sensitiveContext.test(call))) {
+    failures.push(`sensitive diagnostic or telemetry context in ${file}`);
+  }
+  if (
+    file.includes("tests/fixtures/diagnostics/forbidden") &&
+    source.includes("UNKNOWN_DIAGNOSTIC_EVENT")
+  ) {
+    failures.push(`unknown diagnostic event in ${file}`);
+  }
+}
+
+const report = {
+  schemaVersion: 1,
+  mode: fixtureMode ? "negative-fixture" : "source",
+  telemetryEventCount: Object.keys(TELEMETRY_REGISTRY).length,
+  diagnosticEventCount: Object.keys(DIAGNOSTIC_EVENT_REGISTRY).length,
+  checkedFiles: sources.length,
+  failures,
+  passed: failures.length === 0,
+};
+await mkdir("artifacts/quality", { recursive: true });
+await writeFile(
+  fixtureMode
+    ? "artifacts/quality/diagnostics-fixture.json"
+    : "artifacts/quality/diagnostics.json",
+  `${JSON.stringify(report, null, 2)}\n`,
+);
+if (failures.length > 0) {
+  process.stderr.write(
+    `Diagnostics contract failed:\n${failures.join("\n")}\n`,
+  );
+  process.exit(1);
+}
+process.stdout.write(
+  `Diagnostics contract: ${report.diagnosticEventCount} diagnostics and ${report.telemetryEventCount} telemetry producers PASS\n`,
+);
@@ -0,0 +1,102 @@
+import type { DiagnosticsPort } from "../../application/ports/diagnostics-port.js";
+import {
+  projectDiagnosticRecord,
+  safeErrorKind,
+  type DiagnosticRecord,
+  type DiagnosticRecordInput,
+} from "../../contracts/diagnostics.js";
+import { projectTelemetryEvent } from "../../contracts/telemetry.js";
+
+export const noOpDiagnostics: DiagnosticsPort = Object.freeze({
+  record() {},
+});
+
+export function createDiagnosticsAdapter(
+  options: Readonly<{
+    maxEntries?: number;
+    now?: () => number;
+    sink?: (record: DiagnosticRecord) => void;
+  }> = {},
+) {
+  const maxEntries = Math.max(1, options.maxEntries ?? 100);
+  const entries: DiagnosticRecord[] = [];
+  const droppedReasons = new Map<string, number>();
+
+  function drop(reason: string) {
+    droppedReasons.set(reason, (droppedReasons.get(reason) ?? 0) + 1);
+  }
+
+  function record(input: DiagnosticRecordInput) {
+    try {
+      const projected = projectDiagnosticRecord(input, options.now);
+      if (!projected.success) {
+        drop(projected.reason);
+        return;
+      }
+      if (entries.length >= maxEntries) {
+        entries.shift();
+        drop("queue-full");
+      }
+      entries.push(projected.record);
+      try {
+        options.sink?.(projected.record);
+      } catch {
+        drop("sink-failure");
+      }
+    } catch {
+      drop("serialization-failure");
+    }
+  }
+
+  return Object.freeze({
+    record,
+    entries: () => structuredClone(entries) as readonly DiagnosticRecord[],
+    dropped: () => Object.freeze(Object.fromEntries(droppedReasons)),
+  });
+}
+
+type BootSafeContext = Readonly<{
+  kind?: string;
+  buildId?: string;
+  configSchemaVersion?: string;
+  supportReference?: string;
+}>;
+
+let lastBootEvidence:
+  | Readonly<{
+      diagnostic: DiagnosticRecord | null;
+      telemetry: Readonly<Record<string, unknown>> | null;
+    }>
+  | undefined;
+
+export function recordBootFailure(
+  error: unknown,
+  safe: BootSafeContext,
+  now: () => number = Date.now,
+) {
+  const errorKind =
+    typeof safe.kind === "string" ? safe.kind : safeErrorKind(error);
+  const attributes = {
+    error_kind: errorKind,
+    build_id: safe.buildId ?? "unknown",
+    config_schema_version: safe.configSchemaVersion ?? "unknown",
+  };
+  const diagnostic = projectDiagnosticRecord(
+    {
+      level: "error",
+      eventId: "app.boot.failed",
+      context: attributes,
+    },
+    now,
+  );
+  const telemetry = projectTelemetryEvent("app.boot.failed", attributes, now);
+  lastBootEvidence = Object.freeze({
+    diagnostic: diagnostic.success ? diagnostic.record : null,
+    telemetry: telemetry.success ? telemetry.event : null,
+  });
+  return lastBootEvidence;
+}
+
+export function getLastBootEvidence() {
+  return lastBootEvidence ? structuredClone(lastBootEvidence) : undefined;
+}
@@ -14,6 +14,11 @@ import {
  validateOperationRequest,
 } from "./schema-registry.js";
 import { buildRequestTarget } from "./request-builder.js";
+import {
+  attemptBucket,
+  durationBucket,
+  statusGroup,
+} from "../../contracts/diagnostics.js";

 const noAuthSession =
  /** @type {import("../../application/ports/auth-session-port.js").AuthSessionPort} */ ({
@@ -54,7 +59,10 @@ const noAuthSession =
 *   timeoutMs?: number,
 *   maxRetryAttempts?: number,
 *   scheduler?: Scheduler,
- *   getOperation?: typeof getApiOperation
+ *   getOperation?: typeof getApiOperation,
+ *   diagnostics?: import("../../application/ports/diagnostics-port.js").DiagnosticsPort,
+ *   telemetry?: import("../../application/ports/telemetry-port.js").TelemetryPort,
+ *   correlationIdFactory?: () => string
 * }} dependencies
 */
 export function createHttpClient(dependencies) {
@@ -72,6 +80,11 @@ export function createHttpClient(dependencies) {
  const defaultTimeoutMs = dependencies.timeoutMs ?? 10_000;
  const maxRetryAttempts = dependencies.maxRetryAttempts ?? 2;
  const selectOperation = dependencies.getOperation ?? getApiOperation;
+  const diagnostics = dependencies.diagnostics;
+  const telemetry = dependencies.telemetry;
+  const correlationIdFactory =
+    dependencies.correlationIdFactory ??
+    (() => `request-${Math.floor(random() * 1_000_000).toString(36)}`);
  const scheduler =
    dependencies.scheduler ??
    /** @type {Scheduler} */ ({
@@ -91,7 +104,8 @@ export function createHttpClient(dependencies) {
   *   pathParams?: Record<string, string | number>,
   *   searchParams?: unknown,
 *   signal?: AbortSignal,
- *   idempotencyKey?: string
+ *   idempotencyKey?: string,
+ *   correlationId?: string
   * }} [legacyInput]
 * @returns {Promise<HttpResult>}
 */
@@ -106,9 +120,55 @@ export function createHttpClient(dependencies) {
            body: legacyInput.body,
            signal: legacyInput.signal,
            idempotencyKey: legacyInput.idempotencyKey,
+            correlationId: legacyInput.correlationId,
          }
        : request;
    const operation = selectOperation(input.operationId);
+    const startedAt = clock.now();
+    const correlationId = input.correlationId ?? correlationIdFactory();
+    /**
+     * @param {HttpResult} outcome
+     * @param {"success" | "recovered" | "failed" | "aborted"} outcomeKind
+     */
+    function finalize(outcome, outcomeKind) {
+      const error = outcome.ok ? undefined : outcome.error;
+      const context = {
+        route_id: input.routeId,
+        operation_id: input.operationId,
+        correlation_id: correlationId,
+        outcome: outcomeKind,
+        error_kind: error?.kind ?? "NONE",
+        http_status_group: statusGroup(error?.httpStatus),
+        attempt_count_bucket: attemptBucket(
+          error?.attemptCount ?? retryCount + 1,
+        ),
+        duration_bucket: durationBucket(clock.now() - startedAt),
+      };
+      try {
+        diagnostics?.record({
+          level: error ? "warn" : "info",
+          eventId: "http.request.completed",
+          context,
+        });
+      } catch {
+        // Diagnostics cannot change the HTTP result.
+      }
+      if (error && outcomeKind !== "aborted") {
+        try {
+          telemetry?.emit("api.request.failed", {
+            error_kind: context.error_kind,
+            http_status_group: context.http_status_group,
+            attempt_count_bucket: context.attempt_count_bucket,
+            route_id: context.route_id,
+            operation_id: context.operation_id,
+            duration_bucket: context.duration_bucket,
+          });
+        } catch {
+          // Telemetry cannot change the HTTP result.
+        }
+      }
+      return outcome;
+    }
    const logicalIdempotencyKey =
      operation.idempotency === "keyed"
        ? input.idempotencyKey ?? idempotencyKeyFactory()
@@ -126,28 +186,40 @@ export function createHttpClient(dependencies) {
        idempotencyKey: logicalIdempotencyKey,
      });

-      if (outcome.ok) return outcome;
+      if (outcome.ok) {
+        return finalize(
+          outcome,
+          retryCount > 0 || recoveryUsed ? "recovered" : "success",
+        );
+      }

      if (outcome.error.httpStatus === 401 && !recoveryUsed) {
        recoveryUsed = true;
-        const recovered = await recoverSession(authSession, operation, outcome.error);
-        if (!recovered.ok) return recovered;
+        const recovered = await recoverSession(
+          authSession,
+          operation,
+          outcome.error,
+        );
+        if (!recovered.ok) return finalize(recovered, "failed");
        if (operation.idempotency === "none") {
-          return {
-            ok: false,
-            error: {
-              ...outcome.error,
-              retryable: false,
-              action: "retry",
+          return finalize(
+            {
+              ok: false,
+              error: {
+                ...outcome.error,
+                retryable: false,
+                action: "retry",
+              },
            },
-          };
+            "failed",
+          );
        }
        continue;
      }

      if (outcome.error.httpStatus === 401 && recoveryUsed) {
        authSession.onUnauthenticated();
-        return outcome;
+        return finalize(outcome, "failed");
      }

      if (
@@ -158,7 +230,10 @@ export function createHttpClient(dependencies) {
          maxRetryAttempts,
        )
      ) {
-        return outcome;
+        return finalize(
+          outcome,
+          outcome.error.kind === "REQUEST_ABORTED" ? "aborted" : "failed",
+        );
      }

      const delay = retryDelay(outcome.error, retryCount, random, clock.now());
@@ -167,12 +242,15 @@ export function createHttpClient(dependencies) {
      try {
        await clock.sleep(delay, input.signal);
      } catch {
-        return {
-          ok: false,
-          error: failure("REQUEST_ABORTED", input.operationId, retryCount, {
-            code: "REQUEST_ABORTED",
-          }),
-        };
+        return finalize(
+          {
+            ok: false,
+            error: failure("REQUEST_ABORTED", input.operationId, retryCount, {
+              code: "REQUEST_ABORTED",
+            }),
+          },
+          "aborted",
+        );
      }
    }
  }
@@ -8,6 +8,7 @@ export type OperationRequestInput = Readonly<{
  body?: unknown;
  signal?: AbortSignal;
  idempotencyKey?: string;
+  correlationId?: string;
 }>;

 export type RequestTargetResult =
@@ -1,6 +1,7 @@
-import { QueryClient } from "@tanstack/react-query";
+import { MutationCache, QueryCache, QueryClient } from "@tanstack/react-query";

 import { createFailure } from "../../contracts/errors.js";
+import { safeErrorKind } from "../../contracts/diagnostics.js";

 export const QUERY_CACHE_DEFAULTS = Object.freeze({
  staleTime: 30_000,
@@ -11,8 +12,32 @@ export const QUERY_CACHE_DEFAULTS = Object.freeze({
  persistence: false,
 });

-export function createQueryClient() {
+/**
+ * @param {{diagnostics?: import("../../application/ports/diagnostics-port.js").DiagnosticsPort}} [dependencies]
+ */
+export function createQueryClient(dependencies = {}) {
+  /** @param {string} operation @param {unknown} error */
+  function report(operation, error) {
+    try {
+      dependencies.diagnostics?.record({
+        level: "warn",
+        eventId: "cache.operation.failed",
+        context: {
+          operation,
+          error_kind: safeErrorKind(error),
+        },
+      });
+    } catch {
+      // Query behavior remains independent from diagnostics.
+    }
+  }
  return new QueryClient({
+    queryCache: new QueryCache({
+      onError: (error) => report("query", error),
+    }),
+    mutationCache: new MutationCache({
+      onError: (error) => report("mutation", error),
+    }),
    defaultOptions: {
      queries: {
        staleTime: QUERY_CACHE_DEFAULTS.staleTime,
@@ -29,15 +54,16 @@ export function createQueryClient() {

 /**
 * @param {QueryClient} queryClient
+ * @param {{diagnostics?: import("../../application/ports/diagnostics-port.js").DiagnosticsPort}} [dependencies]
 * @returns {import("../../application/ports/query-cache-port.js").QueryCachePort}
 */
-export function createQueryCacheAdapter(queryClient) {
+export function createQueryCacheAdapter(queryClient, dependencies = {}) {
  return Object.freeze({
    read(key) {
      try {
        return { ok: true, value: queryClient.getQueryData(key) };
      } catch {
-        return cacheFailure("read", key);
+        return cacheFailure("read", key, dependencies.diagnostics);
      }
    },
    write(key, value) {
@@ -45,7 +71,7 @@ export function createQueryCacheAdapter(queryClient) {
        queryClient.setQueryData(key, structuredClone(value));
        return { ok: true };
      } catch {
-        return cacheFailure("write", key);
+        return cacheFailure("write", key, dependencies.diagnostics);
      }
    },
    async invalidate(namespace) {
@@ -53,15 +79,31 @@ export function createQueryCacheAdapter(queryClient) {
        await queryClient.invalidateQueries({ queryKey: namespace, exact: false });
        return { ok: true };
      } catch {
-        return cacheFailure("invalidate", namespace);
+        return cacheFailure("invalidate", namespace, dependencies.diagnostics);
      }
    },
  });
 }

-/** @param {string} phase @param {readonly unknown[]} key */
-function cacheFailure(phase, key) {
+/**
+ * @param {string} phase
+ * @param {readonly unknown[]} key
+ * @param {import("../../application/ports/diagnostics-port.js").DiagnosticsPort | undefined} diagnostics
+ */
+function cacheFailure(phase, key, diagnostics) {
  const namespace = typeof key[0] === "string" ? key[0] : "unknown";
+  try {
+    diagnostics?.record({
+      level: "warn",
+      eventId: "cache.operation.failed",
+      context: {
+        operation: phase,
+        error_kind: "QUERY_CACHE_FAILURE",
+      },
+    });
+  } catch {
+    // Cache behavior remains independent from diagnostics.
+  }
  return {
    ok: /** @type {false} */ (false),
    error: createFailure("QUERY_CACHE_FAILURE", "QUERY_CACHE", 0, {
@@ -5,7 +5,8 @@ import { getStorageDefinition } from "../../contracts/storage-keys.js";
 * @param {{
 *   localStorage?: Storage,
 *   sessionStorage?: Storage,
- *   now?: () => number
+ *   now?: () => number,
+ *   diagnostics?: import("../../application/ports/diagnostics-port.js").DiagnosticsPort
 * }} [dependencies]
 * @returns {import("../../application/ports/storage-port.js").StoragePort}
 */
@@ -26,7 +27,7 @@ export function createBrowserStorageAdapter(dependencies = {}) {
      try {
        definition = getStorageDefinition(logicalName);
      } catch {
-        return unavailable("read", logicalName);
+        return unavailable("read", logicalName, dependencies.diagnostics);
      }

      const backend = backendFor(definition.backend);
@@ -50,7 +51,7 @@ export function createBrowserStorageAdapter(dependencies = {}) {
        }
        return { ok: true, value: structuredClone(envelope.value) };
      } catch {
-        return unavailable("read", logicalName);
+        return unavailable("read", logicalName, dependencies.diagnostics);
      }
    },

@@ -59,7 +60,7 @@ export function createBrowserStorageAdapter(dependencies = {}) {
      try {
        definition = getStorageDefinition(logicalName);
      } catch {
-        return unavailable("write", logicalName);
+        return unavailable("write", logicalName, dependencies.diagnostics);
      }

      const expiresAt =
@@ -82,12 +83,24 @@ export function createBrowserStorageAdapter(dependencies = {}) {

        if (definition.quotaFallback === "memory") {
          memory.set(definition.physicalKey, structuredClone(value));
+          recordStorageFailure(
+            dependencies.diagnostics,
+            "write",
+            logicalName,
+            quota,
+          );
          return {
            ok: false,
            error: storageFailure(quota, "write", logicalName),
            fallback: "memory",
          };
        }
+        recordStorageFailure(
+          dependencies.diagnostics,
+          "write",
+          logicalName,
+          quota,
+        );
        return {
          ok: false,
          error: storageFailure(quota, "write", logicalName),
@@ -101,14 +114,14 @@ export function createBrowserStorageAdapter(dependencies = {}) {
      try {
        definition = getStorageDefinition(logicalName);
      } catch {
-        return unavailable("remove", logicalName);
+        return unavailable("remove", logicalName, dependencies.diagnostics);
      }
      try {
        backendFor(definition.backend)?.removeItem(definition.physicalKey);
        memory.delete(definition.physicalKey);
        return { ok: true };
      } catch {
-        return unavailable("remove", logicalName);
+        return unavailable("remove", logicalName, dependencies.diagnostics);
      }
    },
  });
@@ -128,10 +141,38 @@ function storageFailure(quota, phase, logicalName) {
  );
 }

-/** @param {string} phase @param {string} logicalName */
-function unavailable(phase, logicalName) {
+/**
+ * @param {string} phase
+ * @param {string} logicalName
+ * @param {import("../../application/ports/diagnostics-port.js").DiagnosticsPort | undefined} diagnostics
+ */
+function unavailable(phase, logicalName, diagnostics) {
+  recordStorageFailure(diagnostics, phase, logicalName, false);
  return {
    ok: /** @type {false} */ (false),
    error: storageFailure(false, phase, logicalName),
  };
 }
+
+/**
+ * @param {import("../../application/ports/diagnostics-port.js").DiagnosticsPort | undefined} diagnostics
+ * @param {string} phase
+ * @param {string} logicalName
+ * @param {boolean} quota
+ */
+function recordStorageFailure(diagnostics, phase, logicalName, quota) {
+  try {
+    diagnostics?.record({
+      level: "warn",
+      eventId: "storage.operation.failed",
+      context: {
+        operation: `${phase}:${logicalName}`,
+        error_kind: quota
+          ? "STORAGE_QUOTA_EXCEEDED"
+          : "STORAGE_UNAVAILABLE",
+      },
+    });
+  } catch {
+    // Storage behavior remains independent from diagnostics.
+  }
+}
@@ -1,7 +1,14 @@
 import { projectTelemetryEvent } from "../../contracts/telemetry.js";
+import { queueSizeBucket } from "../../contracts/diagnostics.js";

 export const noOpTelemetry = Object.freeze({
  emit: () => {},
+  flush: async () => {},
+  pendingCount: () => 0,
+  droppedCount: () => 0,
+  dropReasons: () => Object.freeze({}),
+  deliveryEvidence: () => null,
+  dispose: () => {},
 });

 /**
@@ -10,22 +17,20 @@ export const noOpTelemetry = Object.freeze({
 *   endpoint?: string,
 *   fetcher?: typeof fetch,
 *   maxQueue?: number,
- *   schedule?: (callback: () => void) => void
+ *   schedule?: (callback: () => void) => void,
+ *   now?: () => number,
+ *   onDrop?: (event: Readonly<Record<string, unknown>>) => void,
+ *   lifecycle?: Pick<EventTarget, "addEventListener" | "removeEventListener">
 * }} options
 */
 export function createTelemetryAdapter(options) {
  if (!options.enabled || !options.endpoint) {
-    return Object.freeze({
-      ...noOpTelemetry,
-      flush: async () => {},
-      pendingCount: () => 0,
-      droppedCount: () => 0,
-    });
+    return noOpTelemetry;
  }

  const endpoint = /** @type {string} */ (options.endpoint);
  const fetcher = options.fetcher ?? fetch;
-  const maxQueue = options.maxQueue ?? 100;
+  const maxQueue = Math.max(1, options.maxQueue ?? 100);
  const schedule = options.schedule ?? queueMicrotask;
  const queue =
    /** @type {Array<{eventName: string, attributes: Readonly<Record<string, unknown>>}>} */ (
@@ -34,18 +39,63 @@ export function createTelemetryAdapter(options) {
  let scheduled = false;
  let flushing = false;
  let dropped = 0;
+  const dropReasons = new Map();
+  let lastDeliveryEvidence =
+    /** @type {Readonly<Record<string, unknown>> | null} */ (null);
+  const lifecycle =
+    options.lifecycle ??
+    (typeof globalThis.addEventListener === "function" &&
+    typeof globalThis.removeEventListener === "function"
+      ? globalThis
+      : undefined);
+
+  /** @param {string} reason @param {number} count */
+  function recordDrop(reason, count = 1) {
+    const safeReason =
+      {
+        "queue-full": "queue-full",
+        "sink-failure": "sink-failure",
+        "serialization-failure": "serialization-failure",
+        "unknown-attributes": "invalid-context",
+        "invalid-attribute-value": "invalid-context",
+        "missing-required-attributes": "invalid-context",
+        "unregistered-event": "invalid-event",
+      }[reason] ?? "invalid-event";
+    dropped += count;
+    dropReasons.set(safeReason, (dropReasons.get(safeReason) ?? 0) + count);
+    const internal = projectTelemetryEvent(
+      "telemetry.delivery.dropped",
+      {
+        reason: safeReason,
+        queue_size_bucket: queueSizeBucket(queue.length),
+      },
+      options.now,
+    );
+    if (internal.success) {
+      lastDeliveryEvidence = internal.event;
+      try {
+        options.onDrop?.(internal.event);
+      } catch {
+        // Drop observers are deliberately nonrecursive.
+      }
+    }
+  }

  /** @param {string} eventName @param {Record<string, unknown>} attributes */
  function emit(eventName, attributes) {
-    const projected = projectTelemetryEvent(eventName, attributes);
+    const projected = projectTelemetryEvent(
+      eventName,
+      attributes,
+      options.now,
+    );
    if (!projected.success) {
-      dropped += 1;
+      recordDrop(projected.reason);
      return;
    }

    if (queue.length >= maxQueue) {
      queue.shift();
-      dropped += 1;
+      recordDrop("queue-full");
    }
    queue.push(projected.event);

@@ -69,19 +119,32 @@ export function createTelemetryAdapter(options) {
        body: JSON.stringify({ events: batch }),
        keepalive: true,
      });
-      if (!response.ok) dropped += batch.length;
+      if (!response.ok) recordDrop("sink-failure", batch.length);
    } catch {
-      dropped += batch.length;
+      recordDrop("sink-failure", batch.length);
    } finally {
      flushing = false;
    }
  }

+  const flushBeforePageExit = () => {
+    void flush();
+  };
+  lifecycle?.addEventListener("pagehide", flushBeforePageExit);
+
+  function dispose() {
+    lifecycle?.removeEventListener("pagehide", flushBeforePageExit);
+  }
+
  return Object.freeze({
    emit,
    flush,
    pendingCount: () => queue.length,
    droppedCount: () => dropped,
+    dropReasons: () => Object.freeze(Object.fromEntries(dropReasons)),
+    deliveryEvidence: () =>
+      lastDeliveryEvidence ? structuredClone(lastDeliveryEvidence) : null,
+    dispose,
  });
 }

@@ -3,6 +3,7 @@ import type {
  ApplicationApi,
  ColorSchemePreference,
  RenderFailureReport,
+  RouteChangedReport,
 } from "./ports/in/application-api.js";
 import type { ApplicationOutputPorts } from "./ports/out/application-output-ports.js";
 import { decideChunkRecovery } from "./use-cases/decide-chunk-recovery.js";
@@ -43,7 +44,20 @@ export function createApplication(
  const diagnostics = Object.freeze({
    reportRenderFailure(report: RenderFailureReport) {
      try {
-        outputPorts.diagnostics.emit("ui.render.failed", {
+        outputPorts.diagnostics.record({
+          level: "error",
+          eventId: "ui.render.failed",
+          context: {
+            route_id: report.routeId,
+            build_id: report.buildId,
+            component_boundary: report.boundaryName,
+          },
+        });
+      } catch {
+        // Diagnostics are best-effort and cannot become an application failure.
+      }
+      try {
+        outputPorts.telemetry.emit("ui.render.failed", {
          route_id: report.routeId,
          build_id: report.buildId,
          component_boundary: report.boundaryName,
@@ -52,6 +66,20 @@ export function createApplication(
        // Diagnostics are best-effort and cannot become an application failure.
      }
    },
+    reportRouteChanged(report: RouteChangedReport) {
+      try {
+        outputPorts.diagnostics.record({
+          level: "info",
+          eventId: "route.changed",
+          context: {
+            route_id: report.routeId,
+            build_id: report.buildId,
+          },
+        });
+      } catch {
+        // Diagnostics are best-effort and cannot become navigation failure.
+      }
+    },
  });

  const runtime = Object.freeze({
@@ -74,6 +102,37 @@ export function createApplication(
      try {
        const current = await outputPorts.releaseInfo.getCurrent();
        const active = await outputPorts.releaseInfo.refresh();
+        if (
+          current.buildId !== active.buildId ||
+          current.releaseId !== active.releaseId
+        ) {
+          const mismatchKind =
+            current.buildId !== active.buildId
+              ? "BUILD_MISMATCH"
+              : "RELEASE_MISMATCH";
+          try {
+            outputPorts.diagnostics.record({
+              level: "warn",
+              eventId: "release.mismatch.detected",
+              context: {
+                build_id: current.buildId,
+                active_release_id: active.releaseId,
+                mismatch_kind: mismatchKind,
+              },
+            });
+          } catch {
+            // Recovery remains independent from diagnostics.
+          }
+          try {
+            outputPorts.telemetry.emit("release.mismatch.detected", {
+              build_id: current.buildId,
+              active_release_id: active.releaseId,
+              mismatch_kind: mismatchKind,
+            });
+          } catch {
+            // Recovery remains independent from telemetry.
+          }
+        }
        if (!active.routeChunks[input.chunkId]) {
          return {
            action: "support" as const,
@@ -0,0 +1,5 @@
+import type { DiagnosticRecordInput } from "../../contracts/diagnostics.js";
+
+export type DiagnosticsPort = Readonly<{
+  record(input: DiagnosticRecordInput): void;
+}>;
@@ -11,6 +11,11 @@ export type RenderFailureReport = Readonly<{
  boundaryName: "route" | "feature";
 }>;

+export type RouteChangedReport = Readonly<{
+  routeId: string;
+  buildId: string;
+}>;
+
 export type ReleaseSummary = Readonly<{
  buildId: string;
  releaseId: string;
@@ -34,6 +39,7 @@ export type ApplicationApi = Readonly<{
  }>;
  diagnostics: Readonly<{
    reportRenderFailure(report: RenderFailureReport): void;
+    reportRouteChanged(report: RouteChangedReport): void;
  }>;
  runtime: Readonly<{
    getReleaseSummary(): Promise<ReleaseSummary>;
@@ -2,6 +2,7 @@ import type { AuthSessionPort } from "../auth-session-port.js";
 import type { ReleaseInfoPort } from "../release-info-port.js";
 import type { StoragePort } from "../storage-port.js";
 import type { TelemetryPort } from "../telemetry-port.js";
+import type { DiagnosticsPort } from "../diagnostics-port.js";

 /**
 * Capabilities required by application use cases. Implementations live in
@@ -13,7 +14,8 @@ export type ApplicationOutputPorts = Readonly<{
    "getState" | "subscribe" | "beginSignIn" | "signOut" | "recover"
  >;
  preferences: StoragePort;
-  diagnostics: TelemetryPort;
+  diagnostics: DiagnosticsPort;
+  telemetry: TelemetryPort;
  releaseInfo: ReleaseInfoPort;
  navigation: Readonly<{ reload(): void }>;
 }>;
@@ -9,3 +9,4 @@ export type { QueryCachePort } from "../query-cache-port.js";
 export type { ReleaseInfoPort } from "../release-info-port.js";
 export type { StoragePort } from "../storage-port.js";
 export type { TelemetryPort } from "../telemetry-port.js";
+export type { DiagnosticsPort } from "../diagnostics-port.js";
@@ -1,5 +0,0 @@
-/**
- * @typedef {{ emit(eventName: string, attributes: Record<string, unknown>): void }} TelemetryPort
- */
-
-export {};
@@ -0,0 +1,10 @@
+import type { TelemetryEventName } from "../../contracts/telemetry.js";
+
+export type { TelemetryEventName };
+
+export type TelemetryPort = Readonly<{
+  emit(
+    eventName: TelemetryEventName,
+    attributes: Record<string, unknown>,
+  ): void;
+}>;
@@ -1,5 +1,6 @@
 import { createRoot } from "react-dom/client";

+import { recordBootFailure } from "../adapters/diagnostics/bounded-diagnostics.js";
 import { BootErrorShell } from "../presentation/boundaries/boot-error-shell.jsx";
 import { createRuntimeComposition } from "./create-runtime-composition.js";
 import { initializeColorScheme } from "./initialize-color-scheme.js";
@@ -27,6 +28,7 @@ async function boot() {
        ? error.safe
        : { supportReference: "boot:unknown" };

+    recordBootFailure(error, safe);
    root.render(<BootErrorShell {...safe} />);
  }
 }
@@ -4,6 +4,7 @@ import {
  createUnavailableSessionAdapter,
 } from "../adapters/auth/external-session-adapter.js";
 import { createHttpClient } from "../adapters/http/client.js";
+import { createDiagnosticsAdapter } from "../adapters/diagnostics/bounded-diagnostics.js";
 import {
  createQueryClient,
 } from "../adapters/query-cache/tanstack-query-cache.js";
@@ -53,6 +54,8 @@ function storageOrUndefined(value) {
 *   fetcher?: typeof fetch,
 *   clock?: import("../application/ports/clock-port.js").ClockPort,
 *   scheduler?: Parameters<typeof createHttpClient>[0]["scheduler"]
+ *   diagnostics?: Parameters<typeof createHttpClient>[0]["diagnostics"],
+ *   telemetry?: Parameters<typeof createHttpClient>[0]["telemetry"]
 * }} context
 */
 export function createRuntimeHttpClient(context, contract = {}) {
@@ -64,6 +67,8 @@ export function createRuntimeHttpClient(context, contract = {}) {
    fetcher: context.fetcher,
    clock: context.clock,
    scheduler: context.scheduler,
+    diagnostics: context.diagnostics,
+    telemetry: context.telemetry,
    ...contract,
  });
 }
@@ -86,15 +91,28 @@ export async function createRuntimeAdapters(context) {
      : externalOwner
        ? createExternalAuthSessionAdapter(externalOwner)
        : createUnavailableSessionAdapter();
-  const queryClient = createQueryClient();
-  const storage = createBrowserStorageAdapter({
-    localStorage: storageOrUndefined(host.localStorage),
-    sessionStorage: storageOrUndefined(host.sessionStorage),
-  });
+  const diagnostics = createDiagnosticsAdapter();
  const telemetry = createTelemetryAdapter({
    enabled: config.TELEMETRY_ENABLED,
    endpoint: config.TELEMETRY_ENDPOINT,
    fetcher: context.fetcher,
+    onDrop(event) {
+      const attributes =
+        event.attributes && typeof event.attributes === "object"
+          ? event.attributes
+          : {};
+      diagnostics.record({
+        level: "warn",
+        eventId: "telemetry.delivery.dropped",
+        context: /** @type {Record<string, unknown>} */ (attributes),
+      });
+    },
+  });
+  const queryClient = createQueryClient({ diagnostics });
+  const storage = createBrowserStorageAdapter({
+    localStorage: storageOrUndefined(host.localStorage),
+    sessionStorage: storageOrUndefined(host.sessionStorage),
+    diagnostics,
  });
  const releaseInfo = Object.freeze({
    async getCurrent() {
@@ -125,6 +143,8 @@ export async function createRuntimeAdapters(context) {
          runtime: context.runtime,
          authSession,
          fetcher: context.fetcher,
+          diagnostics,
+          telemetry,
        },
        contract,
      ),
@@ -134,7 +154,8 @@ export async function createRuntimeAdapters(context) {
    outputPorts: Object.freeze({
      session: authSession,
      preferences: storage,
-      diagnostics: telemetry,
+      diagnostics,
+      telemetry,
      releaseInfo,
      navigation,
    }),
@@ -0,0 +1,183 @@
+export const DIAGNOSTIC_LEVELS = Object.freeze([
+  "debug",
+  "info",
+  "warn",
+  "error",
+] as const);
+export type DiagnosticLevel = (typeof DIAGNOSTIC_LEVELS)[number];
+
+export const DIAGNOSTIC_EVENT_REGISTRY = Object.freeze({
+  "app.boot.failed": Object.freeze({ level: "error" }),
+  "http.request.completed": Object.freeze({ level: "info" }),
+  "cache.operation.failed": Object.freeze({ level: "warn" }),
+  "storage.operation.failed": Object.freeze({ level: "warn" }),
+  "route.changed": Object.freeze({ level: "info" }),
+  "ui.render.failed": Object.freeze({ level: "error" }),
+  "release.mismatch.detected": Object.freeze({ level: "warn" }),
+  "telemetry.delivery.dropped": Object.freeze({ level: "warn" }),
+});
+export type DiagnosticEventId = keyof typeof DIAGNOSTIC_EVENT_REGISTRY;
+
+export const DIAGNOSTIC_CONTEXT_ALLOWLIST = Object.freeze([
+  "app_version",
+  "build_id",
+  "release_id",
+  "active_release_id",
+  "config_schema_version",
+  "api_contract_version",
+  "route_id",
+  "operation_id",
+  "correlation_id",
+  "error_kind",
+  "outcome",
+  "http_status_group",
+  "attempt_count_bucket",
+  "duration_bucket",
+  "component_boundary",
+  "mismatch_kind",
+  "operation",
+  "reason",
+  "queue_size_bucket",
+] as const);
+export type DiagnosticContextKey =
+  (typeof DIAGNOSTIC_CONTEXT_ALLOWLIST)[number];
+export type DiagnosticContext = Readonly<
+  Partial<Record<DiagnosticContextKey, string | number | boolean>>
+>;
+
+export type DiagnosticRecordInput = Readonly<{
+  level: DiagnosticLevel;
+  eventId: DiagnosticEventId;
+  context?: Readonly<Record<string, unknown>>;
+}>;
+
+export type DiagnosticRecord = Readonly<{
+  level: DiagnosticLevel;
+  eventId: DiagnosticEventId;
+  timestamp: string;
+  context: DiagnosticContext;
+}>;
+
+const SAFE_VALUE = /^[A-Za-z0-9][A-Za-z0-9._:@/-]{0,63}$/;
+
+function projectDiagnosticRecordUnsafe(
+  input: DiagnosticRecordInput,
+  now: () => number = Date.now,
+):
+  | Readonly<{ success: true; record: DiagnosticRecord }>
+  | Readonly<{ success: false; reason: string }> {
+  if (!Object.hasOwn(DIAGNOSTIC_EVENT_REGISTRY, input.eventId)) {
+    return { success: false, reason: "unregistered-event" };
+  }
+  if (!DIAGNOSTIC_LEVELS.includes(input.level)) {
+    return { success: false, reason: "invalid-level" };
+  }
+  const contextEntries = Object.entries(input.context ?? {});
+  if (contextEntries.length > DIAGNOSTIC_CONTEXT_ALLOWLIST.length) {
+    return { success: false, reason: "invalid-context" };
+  }
+  const projected: Partial<
+    Record<DiagnosticContextKey, string | number | boolean>
+  > = {};
+  for (const [key, value] of contextEntries) {
+    if (
+      !DIAGNOSTIC_CONTEXT_ALLOWLIST.includes(key as DiagnosticContextKey)
+    ) {
+      return { success: false, reason: "unknown-context" };
+    }
+    if (typeof value === "string") {
+      if (!SAFE_VALUE.test(value)) {
+        return { success: false, reason: "invalid-context" };
+      }
+      projected[key as DiagnosticContextKey] = value;
+    } else if (typeof value === "number" && Number.isFinite(value)) {
+      projected[key as DiagnosticContextKey] = value;
+    } else if (typeof value === "boolean") {
+      projected[key as DiagnosticContextKey] = value;
+    } else {
+      return { success: false, reason: "invalid-context" };
+    }
+  }
+  let timestamp: string;
+  try {
+    timestamp = new Date(now()).toISOString();
+  } catch {
+    timestamp = new Date(0).toISOString();
+  }
+  return {
+    success: true,
+    record: Object.freeze({
+      level: input.level,
+      eventId: input.eventId,
+      timestamp,
+      context: Object.freeze(projected),
+    }),
+  };
+}
+
+export function projectDiagnosticRecord(
+  input: DiagnosticRecordInput,
+  now: () => number = Date.now,
+): ReturnType<typeof projectDiagnosticRecordUnsafe> {
+  try {
+    return projectDiagnosticRecordUnsafe(input, now);
+  } catch {
+    return { success: false, reason: "serialization-failure" };
+  }
+}
+
+export function safeErrorKind(error: unknown): string {
+  try {
+    if (error && typeof error === "object") {
+      const record = error as Readonly<Record<string, unknown>>;
+      if (
+        typeof record.kind === "string" &&
+        /^[A-Z][A-Z0-9_]{0,63}$/.test(record.kind)
+      ) {
+        return record.kind;
+      }
+      if (
+        typeof record.name === "string" &&
+        /^[A-Za-z][A-Za-z0-9]{0,63}$/.test(record.name)
+      ) {
+        const normalized = record.name
+          .replace(/([a-z0-9])([A-Z])/g, "$1_$2")
+          .toUpperCase();
+        return /^[A-Z][A-Z0-9_]{0,63}$/.test(normalized)
+          ? normalized
+          : "UNKNOWN_FAILURE";
+      }
+    }
+  } catch {
+    return "UNKNOWN_FAILURE";
+  }
+  return "UNKNOWN_FAILURE";
+}
+
+export function statusGroup(status: number | undefined): string {
+  return typeof status === "number" && Number.isFinite(status)
+    ? `${Math.max(0, Math.min(9, Math.floor(status / 100)))}xx`
+    : "none";
+}
+
+export function attemptBucket(attemptCount: number): string {
+  if (attemptCount <= 1) return "1";
+  if (attemptCount === 2) return "2";
+  if (attemptCount <= 4) return "3-4";
+  return "5+";
+}
+
+export function durationBucket(durationMs: number): string {
+  if (!Number.isFinite(durationMs) || durationMs < 0) return "unknown";
+  if (durationMs < 100) return "lt100ms";
+  if (durationMs < 500) return "100-499ms";
+  if (durationMs < 2_000) return "500-1999ms";
+  return "gte2000ms";
+}
+
+export function queueSizeBucket(size: number): string {
+  if (size <= 0) return "0";
+  if (size <= 10) return "1-10";
+  if (size <= 50) return "11-50";
+  return "51+";
+}
@@ -0,0 +1,36 @@
+export type TelemetryEventName =
+  | "app.boot.failed"
+  | "api.request.failed"
+  | "ui.render.failed"
+  | "release.mismatch.detected"
+  | "telemetry.delivery.dropped";
+
+export type TelemetryDefinition = Readonly<{
+  eventName: TelemetryEventName;
+  trigger: string;
+  requiredAttributes: readonly string[];
+  optionalAttributes: readonly string[];
+  forbiddenAttributes: readonly string[];
+  sampling: string;
+  delivery: "best-effort";
+}>;
+
+export type TelemetryEvent = Readonly<{
+  eventName: TelemetryEventName;
+  timestamp: string;
+  attributes: Readonly<Record<string, unknown>>;
+}>;
+
+export const TELEMETRY_ATTRIBUTE_ALLOWLIST: readonly string[];
+export const TELEMETRY_FORBIDDEN_ATTRIBUTES: readonly string[];
+export const TELEMETRY_REGISTRY: Readonly<
+  Record<TelemetryEventName, TelemetryDefinition>
+>;
+
+export function projectTelemetryEvent(
+  eventName: string,
+  attributes: Record<string, unknown>,
+  now?: () => number,
+):
+  | Readonly<{ success: true; event: TelemetryEvent }>
+  | Readonly<{ success: false; reason: string }>;
@@ -81,7 +81,7 @@ export const TELEMETRY_REGISTRY = Object.freeze({
    "http_status_group",
    "attempt_count_bucket",
    "route_id",
-  ]),
+  ], ["operation_id", "duration_bucket"]),
  "ui.render.failed": event("ui.render.failed", "React boundary catch", [
    "route_id",
    "build_id",
@@ -101,11 +101,44 @@ export const TELEMETRY_REGISTRY = Object.freeze({
  ),
 });

+const SAFE_IDENTIFIER = /^[A-Za-z0-9][A-Za-z0-9._:@/-]{0,63}$/;
+const ATTRIBUTE_VALUE_POLICIES =
+  /** @type {Readonly<Record<string, (value: string) => boolean>>} */ (
+    Object.freeze({
+      route_id: (value) => /^[A-Z][A-Z0-9_]{0,63}$/.test(value),
+      operation_id: (value) => /^[A-Z][A-Z0-9_]{0,63}$/.test(value),
+      error_kind: (value) => /^[A-Z][A-Z0-9_]{0,63}$/.test(value),
+      http_status_group: (value) => /^(?:[1-5]xx|none)$/.test(value),
+      attempt_count_bucket: (value) => /^(?:1|2|3|3-4|5\+)$/.test(value),
+      duration_bucket: (value) =>
+        /^(?:lt100ms|100-499ms|500-1999ms|gte2000ms|unknown)$/.test(
+          value,
+        ),
+      component_boundary: (value) =>
+        /^(?:route|feature|boot)$/.test(value),
+      mismatch_kind: (value) => /^[A-Z][A-Z0-9_]{0,63}$/.test(value),
+      reason: (value) =>
+        /^(?:queue-full|sink-failure|invalid-event|invalid-context|serialization-failure)$/.test(
+          value,
+        ),
+      queue_size_bucket: (value) =>
+        /^(?:0|1-10|11-50|51\+)$/.test(value),
+    })
+  );
+
+/** @param {string} key @param {unknown} value */
+function validAttributeValue(key, value) {
+  if (typeof value !== "string") return false;
+  const policy = ATTRIBUTE_VALUE_POLICIES[key];
+  return policy ? policy(value) : SAFE_IDENTIFIER.test(value);
+}
+
 /**
 * @param {string} eventName
 * @param {Record<string, unknown>} attributes
+ * @param {() => number} [now]
 */
-export function projectTelemetryEvent(eventName, attributes) {
+function projectTelemetryEventUnsafe(eventName, attributes, now = Date.now) {
  const registry =
    /** @type {Record<string, (typeof TELEMETRY_REGISTRY)[keyof typeof TELEMETRY_REGISTRY]>} */ (
      TELEMETRY_REGISTRY
@@ -118,13 +151,47 @@ export function projectTelemetryEvent(eventName, attributes) {
    };
  }

+  const attributeKeys = Object.keys(attributes);
+  if (
+    attributeKeys.length >
+    TELEMETRY_ATTRIBUTE_ALLOWLIST.length +
+      TELEMETRY_FORBIDDEN_ATTRIBUTES.length
+  ) {
+    return {
+      success: /** @type {false} */ (false),
+      reason: "invalid-attribute-value",
+    };
+  }
+  const unknown = attributeKeys.filter(
+    (key) =>
+      !TELEMETRY_ATTRIBUTE_ALLOWLIST.includes(key) &&
+      !TELEMETRY_FORBIDDEN_ATTRIBUTES.includes(key),
+  );
+  if (unknown.length > 0) {
+    return {
+      success: /** @type {false} */ (false),
+      reason: "unknown-attributes",
+    };
+  }
  const projected = Object.fromEntries(
    Object.entries(attributes).filter(
-      ([key]) =>
+      ([key, value]) =>
        TELEMETRY_ATTRIBUTE_ALLOWLIST.includes(key) &&
-        !TELEMETRY_FORBIDDEN_ATTRIBUTES.includes(key),
+        !TELEMETRY_FORBIDDEN_ATTRIBUTES.includes(key) &&
+        validAttributeValue(key, value),
    ),
  );
+  const invalid = Object.entries(attributes).filter(
+    ([key, value]) =>
+      TELEMETRY_ATTRIBUTE_ALLOWLIST.includes(key) &&
+      !validAttributeValue(key, value),
+  );
+  if (invalid.length > 0) {
+    return {
+      success: /** @type {false} */ (false),
+      reason: "invalid-attribute-value",
+    };
+  }
  const missing = definition.requiredAttributes.filter(
    (key) => projected[key] === undefined,
  );
@@ -135,11 +202,34 @@ export function projectTelemetryEvent(eventName, attributes) {
    };
  }

+  let timestamp;
+  try {
+    timestamp = new Date(now()).toISOString();
+  } catch {
+    timestamp = new Date(0).toISOString();
+  }
  return {
    success: /** @type {true} */ (true),
    event: Object.freeze({
      eventName,
+      timestamp,
      attributes: Object.freeze(projected),
    }),
  };
 }
+
+/**
+ * @param {string} eventName
+ * @param {Record<string, unknown>} attributes
+ * @param {() => number} [now]
+ */
+export function projectTelemetryEvent(eventName, attributes, now = Date.now) {
+  try {
+    return projectTelemetryEventUnsafe(eventName, attributes, now);
+  } catch {
+    return {
+      success: /** @type {false} */ (false),
+      reason: "serialization-failure",
+    };
+  }
+}
@@ -341,6 +341,7 @@ export const Dialog = forwardRef<HTMLDialogElement, DialogProps>(
    const { message } = useLocale();
    const dialogRef = useRef<HTMLDialogElement | null>(null);
    const previousFocusRef = useRef<HTMLElement | null>(null);
+    const focusRestoreGenerationRef = useRef(0);
    const titleId = useId();
    const descriptionId = useId();
    useImperativeHandle(forwardedRef, () => dialogRef.current!, []);
@@ -348,6 +349,8 @@ export const Dialog = forwardRef<HTMLDialogElement, DialogProps>(
    useEffect(() => {
      const dialog = dialogRef.current;
      if (!dialog) return;
+      const generation = focusRestoreGenerationRef.current + 1;
+      focusRestoreGenerationRef.current = generation;

      if (open) {
        previousFocusRef.current =
@@ -371,9 +374,19 @@ export const Dialog = forwardRef<HTMLDialogElement, DialogProps>(
      }
      const previousFocus = previousFocusRef.current;
      previousFocusRef.current = null;
-      queueMicrotask(() => {
-        if (previousFocus?.isConnected) previousFocus.focus();
-      });
+      const restoreFocus = () => {
+        if (
+          focusRestoreGenerationRef.current === generation &&
+          previousFocus?.isConnected
+        ) {
+          previousFocus.focus();
+        }
+      };
+      if (typeof globalThis.requestAnimationFrame === "function") {
+        const frame = globalThis.requestAnimationFrame(restoreFocus);
+        return () => globalThis.cancelAnimationFrame(frame);
+      }
+      queueMicrotask(restoreFocus);
    }, [open]);

    return (
@@ -105,9 +105,16 @@ function InvalidRouteSurface({ code }: { code: string }) {
  );
 }

-function RouteLifecycle({ definition }: { definition: RouteDefinition }) {
+function RouteLifecycle({
+  definition,
+  buildId,
+}: {
+  definition: RouteDefinition;
+  buildId: string;
+}) {
  const location = useLocation();
  const { message, resolve } = useLocale();
+  const { diagnostics } = useApplication();
  useEffect(() => {
    document.title = message("route.documentTitle", {
      title: resolve(`route.${definition.routeId}.title`),
@@ -122,7 +129,19 @@ function RouteLifecycle({ definition }: { definition: RouteDefinition }) {
    } catch {
      // Non-browser test hosts may not implement scrolling.
    }
-  }, [definition, location.key, location.pathname, message, resolve]);
+    diagnostics.reportRouteChanged({
+      routeId: definition.routeId,
+      buildId,
+    });
+  }, [
+    buildId,
+    definition,
+    diagnostics,
+    location.key,
+    location.pathname,
+    message,
+    resolve,
+  ]);
  return null;
 }

@@ -244,7 +263,7 @@ function RegisteredRoute({
  const content = (
    <RouteInputContext.Provider value={parsed.data}>
      <CanonicalRouteRedirect input={parsed.data} />
-      <RouteLifecycle definition={definition} />
+      <RouteLifecycle definition={definition} buildId={buildId} />
      <Suspense fallback={<RouteLoadingSurface definition={definition} />}>
        <ChunkRecoveryBoundary
          chunkId={definition.chunkId}
@@ -0,0 +1,67 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { createHttpClient } from "../../../src/adapters/http/client.js";
+import { createReferenceHttpGateway } from "../../../src/features/reference-feature/adapters/reference-http-gateway.js";
+import { createReferenceFeatureInput } from "../../../src/features/reference-feature/application/reference-feature-api.js";
+import { REFERENCE_FEATURE_CONTRACT } from "../../../src/features/reference-feature/contracts/reference-feature-contract.js";
+import { mapReferenceOperation } from "../../../src/features/reference-feature/contracts/reference-mapper.js";
+import {
+  validateReferencePayload,
+  validateReferenceRequest,
+} from "../../../src/features/reference-feature/contracts/reference-schemas.js";
+
+describe("reference feature diagnostics correlation", () => {
+  it("preserves route, operation and request correlation through the vertical path", async () => {
+    const record = vi.fn();
+    const operations =
+      REFERENCE_FEATURE_CONTRACT.apiOperations as Readonly<
+        Record<
+          string,
+          ReturnType<
+            NonNullable<Parameters<typeof createHttpClient>[0]["getOperation"]>
+          >
+        >
+      >;
+    const client = createHttpClient({
+      baseUrl: "https://api.test",
+      fetcher: async () =>
+        Response.json({
+          success: true,
+          data: [{ id: "reference-1", name: "Reference" }],
+          meta: { requestId: "safe-request", traceId: "safe-trace" },
+        }),
+      getOperation(operationId) {
+        const operation = operations[operationId];
+        if (!operation) throw new Error("Unregistered reference operation");
+        return operation;
+      },
+      validatePayload: validateReferencePayload,
+      validateRequest: validateReferenceRequest,
+      mapPayload: mapReferenceOperation,
+      correlationIdFactory: () => "reference-correlation",
+      diagnostics: { record },
+      scheduler: {
+        setTimeout: () => 1,
+        clearTimeout: () => {},
+      },
+    });
+    const application = createReferenceFeatureInput(
+      createReferenceHttpGateway(client),
+    );
+
+    await expect(
+      application.listResources({ limit: 20 }),
+    ).resolves.toMatchObject({ ok: true });
+    expect(record).toHaveBeenCalledOnce();
+    expect(record).toHaveBeenCalledWith({
+      level: "info",
+      eventId: "http.request.completed",
+      context: expect.objectContaining({
+        route_id: "REFERENCE_RESOURCE_LIST",
+        operation_id: "LIST_REFERENCE_RESOURCES",
+        correlation_id: "reference-correlation",
+        outcome: "success",
+      }),
+    });
+  });
+});
@@ -0,0 +1,3 @@
+export function leakToConsole(token: string) {
+  console.error("UNKNOWN_DIAGNOSTIC_EVENT", token);
+}
@@ -0,0 +1,8 @@
+export function leakSensitiveContext(telemetry: {
+  emit(eventName: string, context: Record<string, unknown>): void;
+}) {
+  telemetry.emit("api.request.failed", {
+    authorization: "Bearer secret",
+    request_body: { email: "private@example.test" },
+  });
+}
@@ -0,0 +1,11 @@
+import type { DiagnosticsPort } from "../../../src/application/ports/diagnostics-port.js";
+import type { TelemetryPort } from "../../../src/application/ports/telemetry-port.js";
+
+declare const diagnostics: DiagnosticsPort;
+declare const telemetry: TelemetryPort;
+
+diagnostics.record({
+  level: "fatal",
+  eventId: "UNKNOWN_DIAGNOSTIC_EVENT",
+});
+telemetry.emit("unknown.telemetry.event", {});
@@ -5,7 +5,8 @@ import { createApplication } from "../../src/application/create-application.js";
 * @param {{
 *   session?: import("../../src/application/ports/auth-session-port.js").AuthSessionPort,
 *   preferences?: import("../../src/application/ports/storage-port.js").StoragePort,
- *   diagnostics?: import("../../src/application/ports/telemetry-port.js").TelemetryPort,
+ *   diagnostics?: import("../../src/application/ports/diagnostics-port.js").DiagnosticsPort,
+ *   telemetry?: import("../../src/application/ports/telemetry-port.js").TelemetryPort,
 *   releaseInfo?: import("../../src/application/ports/release-info-port.js").ReleaseInfoPort,
 *   navigation?: { reload(): void },
 *   featureInputs?: Readonly<Record<string, unknown>>
@@ -22,7 +23,8 @@ export function createTestApplication(overrides = {}) {
          write: () => ({ ok: /** @type {const} */ (true) }),
          remove: () => ({ ok: /** @type {const} */ (true) }),
        },
-      diagnostics: overrides.diagnostics ?? { emit: () => {} },
+      diagnostics: overrides.diagnostics ?? { record: () => {} },
+      telemetry: overrides.telemetry ?? { emit: () => {} },
      releaseInfo:
        overrides.releaseInfo ??
        {
@@ -0,0 +1,193 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { createHttpClient } from "../../src/adapters/http/client.js";
+import type { DiagnosticRecordInput } from "../../src/contracts/diagnostics.js";
+import { TEST_HTTP_CONTRACT } from "../helpers/http-contract-fixture.js";
+
+function successResponse(data: unknown) {
+  return Response.json({
+    success: true,
+    data,
+    meta: { requestId: "request-1", traceId: "trace-1" },
+  });
+}
+
+function failureResponse(status: number) {
+  return Response.json(
+    {
+      success: false,
+      error: { code: "TEMPORARY" },
+      meta: { requestId: "request-1", traceId: "trace-1" },
+    },
+    { status },
+  );
+}
+
+type EmittedEvent = Readonly<{
+  eventName: string;
+  attributes: Readonly<Record<string, unknown>>;
+}>;
+
+function harness(fetcher: typeof fetch, maxRetryAttempts = 1) {
+  const records: DiagnosticRecordInput[] = [];
+  const emitted: EmittedEvent[] = [];
+  let currentTime = 0;
+  const client = createHttpClient({
+    ...TEST_HTTP_CONTRACT,
+    baseUrl: "https://api.test",
+    fetcher,
+    maxRetryAttempts,
+    clock: {
+      now: () => currentTime,
+      sleep: async () => {
+        currentTime += 150;
+      },
+    },
+    scheduler: {
+      setTimeout: () => 1,
+      clearTimeout: () => {},
+    },
+    correlationIdFactory: () => "correlation-fixed",
+    diagnostics: {
+      record(input) {
+        records.push(structuredClone(input));
+      },
+    },
+    telemetry: {
+      emit(eventName, attributes) {
+        emitted.push({
+          eventName,
+          attributes: structuredClone(attributes),
+        });
+      },
+    },
+  });
+  return { client, records, emitted };
+}
+
+describe("HTTP diagnostics and terminal telemetry", () => {
+  it("records one successful reference route outcome and no failure event", async () => {
+    const { client, records, emitted } = harness(
+      vi.fn(async () => successResponse([])),
+    );
+
+    await expect(
+      client.execute({
+        operationId: "LIST_ENTITIES",
+        routeId: "TEST_ROUTE",
+      }),
+    ).resolves.toMatchObject({ ok: true });
+
+    expect(records).toEqual([
+      {
+        level: "info",
+        eventId: "http.request.completed",
+        context: {
+          route_id: "TEST_ROUTE",
+          operation_id: "LIST_ENTITIES",
+          correlation_id: "correlation-fixed",
+          outcome: "success",
+          error_kind: "NONE",
+          http_status_group: "none",
+          attempt_count_bucket: "1",
+          duration_bucket: "lt100ms",
+        },
+      },
+    ]);
+    expect(emitted).toEqual([]);
+  });
+
+  it("summarizes retry recovery once without a terminal failure event", async () => {
+    const fetcher = vi
+      .fn<typeof fetch>()
+      .mockResolvedValueOnce(failureResponse(503))
+      .mockResolvedValueOnce(successResponse([]));
+    const { client, records, emitted } = harness(fetcher);
+
+    await expect(
+      client.execute({
+        operationId: "LIST_ENTITIES",
+        routeId: "TEST_ROUTE",
+      }),
+    ).resolves.toMatchObject({ ok: true });
+
+    expect(fetcher).toHaveBeenCalledTimes(2);
+    expect(records).toHaveLength(1);
+    expect(records[0]).toMatchObject({
+      eventId: "http.request.completed",
+      context: {
+        outcome: "recovered",
+        correlation_id: "correlation-fixed",
+        duration_bucket: "100-499ms",
+      },
+    });
+    expect(emitted).toEqual([]);
+  });
+
+  it("emits one bounded terminal failure after all attempts", async () => {
+    const fetcher = vi.fn(async () => failureResponse(503));
+    const { client, records, emitted } = harness(fetcher);
+
+    await expect(
+      client.execute({
+        operationId: "CREATE_ENTITY",
+        routeId: "TEST_ROUTE",
+        body: { name: "private user input" },
+        idempotencyKey: "private-idempotency-key",
+      }),
+    ).resolves.toMatchObject({
+      ok: false,
+      error: { kind: "SERVER_FAILURE" },
+    });
+
+    expect(fetcher).toHaveBeenCalledTimes(2);
+    expect(records).toHaveLength(1);
+    expect(emitted).toEqual([
+      {
+        eventName: "api.request.failed",
+        attributes: {
+          error_kind: "SERVER_FAILURE",
+          http_status_group: "5xx",
+          attempt_count_bucket: "2",
+          route_id: "TEST_ROUTE",
+          operation_id: "CREATE_ENTITY",
+          duration_bucket: "100-499ms",
+        },
+      },
+    ]);
+    expect(JSON.stringify({ records, emitted })).not.toMatch(
+      /private user input|private-idempotency-key/,
+    );
+  });
+
+  it("records navigation abort without failure telemetry", async () => {
+    const caller = new AbortController();
+    caller.abort("navigation");
+    const fetcher = vi.fn(async (request: RequestInfo | URL) => {
+      const signal = (request as Request).signal;
+      if (signal.aborted) throw new DOMException("aborted", "AbortError");
+      return successResponse([]);
+    });
+    const { client, records, emitted } = harness(
+      fetcher as unknown as typeof fetch,
+    );
+
+    await expect(
+      client.execute({
+        operationId: "LIST_ENTITIES",
+        routeId: "TEST_ROUTE",
+        signal: caller.signal,
+      }),
+    ).resolves.toMatchObject({
+      ok: false,
+      error: { kind: "REQUEST_ABORTED" },
+    });
+
+    expect(records).toHaveLength(1);
+    expect(records[0]).toMatchObject({
+      eventId: "http.request.completed",
+      context: { outcome: "aborted", error_kind: "REQUEST_ABORTED" },
+    });
+    expect(emitted).toEqual([]);
+  });
+});
@@ -36,6 +36,7 @@ describe("application input/output boundary", () => {
  it("uses fake output ports for preference, session, and safe diagnostics flows", () => {
    const write = vi.fn(() => ({ ok: true as const }));
    const emit = vi.fn();
+    const record = vi.fn();
    const ports = {
      session: {
        getState: () => "authenticated" as const,
@@ -49,7 +50,8 @@ describe("application input/output boundary", () => {
        write,
        remove: () => ({ ok: true as const }),
      },
-      diagnostics: { emit },
+      diagnostics: { record },
+      telemetry: { emit },
      releaseInfo: {
        getCurrent: async () => ({
          buildId: "build-a",
@@ -82,20 +84,43 @@ describe("application input/output boundary", () => {
      buildId: "build-a",
      boundaryName: "route",
    });
+    expect(record).toHaveBeenCalledWith({
+      level: "error",
+      eventId: "ui.render.failed",
+      context: {
+        route_id: "APP_HOME",
+        build_id: "build-a",
+        component_boundary: "route",
+      },
+    });
    expect(emit).toHaveBeenCalledWith("ui.render.failed", {
      route_id: "APP_HOME",
      build_id: "build-a",
      component_boundary: "route",
    });
+    application.diagnostics.reportRouteChanged({
+      routeId: "APP_HOME",
+      buildId: "build-a",
+    });
+    expect(record).toHaveBeenCalledWith({
+      level: "info",
+      eventId: "route.changed",
+      context: { route_id: "APP_HOME", build_id: "build-a" },
+    });
  });

  it("does not let a failing diagnostics output escape into presentation", () => {
    const application = createTestApplication({
      diagnostics: {
-        emit() {
+        record() {
          throw new Error("sink details");
        },
      },
+      telemetry: {
+        emit() {
+          throw new Error("telemetry details");
+        },
+      },
    });

    expect(() =>
@@ -3,6 +3,8 @@ import { describe, expect, it, vi } from "vitest";
 import { createApplication } from "../../src/application/create-application.js";
 import { createAnonymousSessionAdapter } from "../../src/adapters/auth/external-session-adapter.js";
 import type { StoragePort } from "../../src/application/ports/storage-port.js";
+import type { DiagnosticsPort } from "../../src/application/ports/diagnostics-port.js";
+import type { TelemetryPort } from "../../src/application/ports/telemetry-port.js";

 type ReleaseFixture = {
  buildId: string;
@@ -40,12 +42,15 @@ function applicationWith(options: {
  storage?: StoragePort;
  refresh?: () => Promise<ReturnType<typeof release>>;
  reload?: () => void;
+  diagnostics?: DiagnosticsPort;
+  telemetry?: TelemetryPort;
 }) {
  const current = release("build-a", "release-a");
  return createApplication({
    session: createAnonymousSessionAdapter(),
    preferences: options.storage ?? memoryStorage(),
-    diagnostics: { emit: () => {} },
+    diagnostics: options.diagnostics ?? { record: () => {} },
+    telemetry: options.telemetry ?? { emit: () => {} },
    releaseInfo: {
      getCurrent: async () => current,
      refresh:
@@ -59,7 +64,13 @@ function applicationWith(options: {
 describe("production chunk recovery application input", () => {
  it("reloads exactly once for one active build/release pair", async () => {
    const reload = vi.fn();
-    const application = applicationWith({ reload });
+    const record = vi.fn<DiagnosticsPort["record"]>();
+    const emit = vi.fn<TelemetryPort["emit"]>();
+    const application = applicationWith({
+      reload,
+      diagnostics: { record },
+      telemetry: { emit },
+    });
    const input = {
      chunkId: "route-home",
      failureKind: "CHUNK_LOAD_FAILURE" as const,
@@ -69,6 +80,20 @@ describe("production chunk recovery application input", () => {
      action: "reload-once",
      releasePair: "build-a/release-a->build-b/release-b",
    });
+    expect(record).toHaveBeenCalledWith({
+      level: "warn",
+      eventId: "release.mismatch.detected",
+      context: {
+        build_id: "build-a",
+        active_release_id: "release-b",
+        mismatch_kind: "BUILD_MISMATCH",
+      },
+    });
+    expect(emit).toHaveBeenCalledWith("release.mismatch.detected", {
+      build_id: "build-a",
+      active_release_id: "release-b",
+      mismatch_kind: "BUILD_MISMATCH",
+    });
    await expect(application.recovery.recoverChunk(input)).resolves.toEqual({
      action: "support",
      reason: "reload-already-attempted",
@@ -0,0 +1,141 @@
+import { describe, expect, it, vi } from "vitest";
+
+import {
+  createDiagnosticsAdapter,
+  getLastBootEvidence,
+  noOpDiagnostics,
+  recordBootFailure,
+} from "../../src/adapters/diagnostics/bounded-diagnostics.js";
+import {
+  projectDiagnosticRecord,
+  safeErrorKind,
+} from "../../src/contracts/diagnostics.js";
+
+describe("structured diagnostics contract", () => {
+  it("projects only registered, bounded context with deterministic time", () => {
+    const projected = projectDiagnosticRecord(
+      {
+        level: "info",
+        eventId: "route.changed",
+        context: { route_id: "APP_HOME", build_id: "build-a" },
+      },
+      () => 0,
+    );
+
+    expect(projected).toEqual({
+      success: true,
+      record: {
+        level: "info",
+        eventId: "route.changed",
+        timestamp: "1970-01-01T00:00:00.000Z",
+        context: { route_id: "APP_HOME", build_id: "build-a" },
+      },
+    });
+    expect(
+      projectDiagnosticRecord({
+        level: "error",
+        eventId: "ui.render.failed",
+        context: { raw_url: "https://example.test/private?token=secret" },
+      }),
+    ).toEqual({ success: false, reason: "unknown-context" });
+    expect(
+      projectDiagnosticRecord({
+        level: "error",
+        eventId: "ui.render.failed",
+        context: { route_id: "private value with whitespace" },
+      }),
+    ).toEqual({ success: false, reason: "invalid-context" });
+  });
+
+  it("bounds evidence and isolates throwing sinks and hostile error objects", () => {
+    const sink = vi.fn(() => {
+      throw new Error("sink-secret");
+    });
+    const adapter = createDiagnosticsAdapter({
+      maxEntries: 1,
+      now: () => 0,
+      sink,
+    });
+    const circular: Record<string, unknown> = { name: "TypeError" };
+    circular.self = circular;
+    const hostile = new Proxy(
+      {},
+      {
+        get() {
+          throw new Error("private getter");
+        },
+        ownKeys() {
+          throw new Error("private keys");
+        },
+      },
+    );
+
+    expect(safeErrorKind(circular)).toBe("TYPE_ERROR");
+    expect(safeErrorKind(hostile)).toBe("UNKNOWN_FAILURE");
+    expect(
+      projectDiagnosticRecord({
+        level: "error",
+        eventId: "ui.render.failed",
+        context: hostile,
+      }),
+    ).toEqual({ success: false, reason: "serialization-failure" });
+    expect(() =>
+      adapter.record({
+        level: "info",
+        eventId: "route.changed",
+        context: { route_id: "APP_HOME" },
+      }),
+    ).not.toThrow();
+    adapter.record({
+      level: "warn",
+      eventId: "cache.operation.failed",
+      context: { operation: "query", error_kind: "UNKNOWN_FAILURE" },
+    });
+
+    expect(adapter.entries()).toHaveLength(1);
+    expect(adapter.entries()[0]?.eventId).toBe("cache.operation.failed");
+    expect(adapter.dropped()).toEqual({
+      "queue-full": 1,
+      "sink-failure": 2,
+    });
+    expect(JSON.stringify(adapter.entries())).not.toMatch(
+      /sink-secret|private getter/,
+    );
+  });
+
+  it("creates safe pre-mount boot evidence and supports a true no-op", () => {
+    const circular: Record<string, unknown> = {
+      name: "TypeError",
+      token: "credential-value",
+      stack: "private-stack",
+    };
+    circular.self = circular;
+
+    expect(() =>
+      recordBootFailure(
+        circular,
+        {
+          buildId: "build-a",
+          configSchemaVersion: "1",
+          supportReference: "support-private",
+        },
+        () => 0,
+      ),
+    ).not.toThrow();
+    const evidence = getLastBootEvidence();
+    expect(evidence?.diagnostic?.eventId).toBe("app.boot.failed");
+    expect(evidence?.telemetry).toMatchObject({
+      eventName: "app.boot.failed",
+      timestamp: "1970-01-01T00:00:00.000Z",
+    });
+    expect(JSON.stringify(evidence)).not.toMatch(
+      /credential-value|private-stack|support-private/,
+    );
+    expect(() =>
+      noOpDiagnostics.record({
+        level: "error",
+        eventId: "app.boot.failed",
+      }),
+    ).not.toThrow();
+  });
+});
@@ -52,7 +52,10 @@ describe("TanStack QueryCachePort adapter", () => {
  it("normalizes adapter exceptions without raw key data", async () => {
    const client = new QueryClient();
    vi.spyOn(client, "invalidateQueries").mockRejectedValue(new Error("secret-key"));
-    const adapter = createQueryCacheAdapter(client);
+    const record = vi.fn();
+    const adapter = createQueryCacheAdapter(client, {
+      diagnostics: { record },
+    });
    const result = await adapter.invalidate(["resource", "sensitive-filter"]);

    expect(result).toMatchObject({
@@ -60,5 +63,16 @@ describe("TanStack QueryCachePort adapter", () => {
      error: { kind: "QUERY_CACHE_FAILURE" },
    });
    expect(JSON.stringify(result)).not.toContain("sensitive-filter");
+    expect(record).toHaveBeenCalledWith({
+      level: "warn",
+      eventId: "cache.operation.failed",
+      context: {
+        operation: "invalidate",
+        error_kind: "QUERY_CACHE_FAILURE",
+      },
+    });
+    expect(JSON.stringify(record.mock.calls)).not.toMatch(
+      /sensitive-filter|secret-key/,
+    );
  });
 });
@@ -46,6 +46,9 @@ describe("runtime adapter composition", () => {
      releaseId: "release-a",
    });
    expect(adapters.infrastructure.queryClient).toBeDefined();
+    expect(adapters.outputPorts.diagnostics.record).toEqual(expect.any(Function));
+    expect(adapters.outputPorts.telemetry.emit).toEqual(expect.any(Function));
+    expect(adapters.outputPorts.telemetry.pendingCount()).toBe(0);
    expect(adapters).not.toHaveProperty("http");
    expect(adapters).not.toHaveProperty("storage");
  });
@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";

 import { createBrowserStorageAdapter } from "../../src/adapters/storage/browser-storage-adapter.js";
 import {
@@ -61,13 +61,27 @@ describe("storage registry", () => {

  it("falls back to memory when preference storage quota is exceeded", () => {
    const localStorage = createStorage({ quota: true });
-    const adapter = createBrowserStorageAdapter({ localStorage });
+    const record = vi.fn();
+    const adapter = createBrowserStorageAdapter({
+      localStorage,
+      diagnostics: { record },
+    });
    expect(adapter.write("COLOR_SCHEME", "dark")).toMatchObject({
      ok: false,
      fallback: "memory",
      error: { kind: "STORAGE_QUOTA_EXCEEDED" },
    });
    expect(adapter.read("COLOR_SCHEME")).toEqual({ ok: true, value: "dark" });
+    expect(record).toHaveBeenCalledOnce();
+    expect(record).toHaveBeenCalledWith({
+      level: "warn",
+      eventId: "storage.operation.failed",
+      context: {
+        operation: "write:COLOR_SCHEME",
+        error_kind: "STORAGE_QUOTA_EXCEEDED",
+      },
+    });
+    expect(JSON.stringify(record.mock.calls)).not.toContain("dark");
  });

  it("discards data from a previous schema version", () => {
@@ -33,15 +33,26 @@ describe("telemetry registry and redaction", () => {
    }
  });

-  it("uses a default-deny attribute projection", () => {
+  it("redacts forbidden attributes and rejects unknown context", () => {
    const projected = projectTelemetryEvent("api.request.failed", {
      ...validAttributes,
      raw_url: "https://api.test/path?token=secret",
-      unregistered: "private",
    });

    expect(projected.success).toBe(true);
-    expect(JSON.stringify(projected)).not.toMatch(/raw_url|token|secret|unregistered/);
+    expect(JSON.stringify(projected)).not.toMatch(/raw_url|token|secret/);
+    expect(
+      projectTelemetryEvent("api.request.failed", {
+        ...validAttributes,
+        unregistered: "private",
+      }),
+    ).toEqual({ success: false, reason: "unknown-attributes" });
+    expect(
+      projectTelemetryEvent("api.request.failed", {
+        ...validAttributes,
+        route_id: "/users/actual-user-id",
+      }),
+    ).toEqual({ success: false, reason: "invalid-attribute-value" });
  });

  it("validates traceparent without exposing invalid values", () => {
@@ -71,10 +82,18 @@ describe("best-effort telemetry adapter", () => {

    expect(adapter.pendingCount()).toBe(2);
    expect(adapter.droppedCount()).toBe(1);
+    expect(adapter.dropReasons()).toEqual({ "queue-full": 1 });
+    expect(adapter.deliveryEvidence()).toMatchObject({
+      eventName: "telemetry.delivery.dropped",
+      attributes: { reason: "queue-full", queue_size_bucket: "1-10" },
+    });
    expect(scheduled).toHaveLength(1);
  });

  it("degrades on sink failure without throwing or recursive events", async () => {
+    const onDrop = vi.fn(() => {
+      throw new Error("observer unavailable");
+    });
    const adapter = createTelemetryAdapter({
      enabled: true,
      endpoint: "https://telemetry.test/events",
@@ -82,13 +101,50 @@ describe("best-effort telemetry adapter", () => {
      fetcher: async () => {
        throw new Error("sink unavailable");
      },
+      onDrop,
    });
    expect(() => adapter.emit("api.request.failed", validAttributes)).not.toThrow();
    await expect(adapter.flush()).resolves.toBeUndefined();
    expect(adapter.droppedCount()).toBe(1);
+    expect(adapter.dropReasons()).toEqual({ "sink-failure": 1 });
+    expect(onDrop).toHaveBeenCalledOnce();
    expect(adapter.pendingCount()).toBe(0);
  });

+  it("never serializes circular or unbounded event context", () => {
+    const adapter = createTelemetryAdapter({
+      enabled: true,
+      endpoint: "https://telemetry.test/events",
+      schedule: () => {},
+    });
+    const circular = {};
+    circular.self = circular;
+    const hostile = new Proxy(
+      {},
+      {
+        ownKeys() {
+          throw new Error("private proxy value");
+        },
+      },
+    );
+
+    expect(() =>
+      adapter.emit("api.request.failed", {
+        ...validAttributes,
+        unregistered: circular,
+      }),
+    ).not.toThrow();
+    expect(adapter.pendingCount()).toBe(0);
+    expect(adapter.dropReasons()).toEqual({ "invalid-context": 1 });
+    expect(() =>
+      adapter.emit("api.request.failed", hostile),
+    ).not.toThrow();
+    expect(adapter.dropReasons()).toEqual({
+      "invalid-context": 1,
+      "serialization-failure": 1,
+    });
+  });
+
  it("performs no network or queue work when disabled", async () => {
    const fetcher = vi.fn();
    const adapter = createTelemetryAdapter({
@@ -102,4 +158,25 @@ describe("best-effort telemetry adapter", () => {
    expect(fetcher).not.toHaveBeenCalled();
    expect(adapter.pendingCount()).toBe(0);
  });
+
+  it("flushes on page exit and removes the lifecycle listener", async () => {
+    const lifecycle = new EventTarget();
+    const remove = vi.spyOn(lifecycle, "removeEventListener");
+    const fetcher = vi.fn(async () => new Response(null, { status: 204 }));
+    const adapter = createTelemetryAdapter({
+      enabled: true,
+      endpoint: "https://telemetry.test/events",
+      schedule: () => {},
+      lifecycle,
+      fetcher,
+    });
+    adapter.emit("api.request.failed", validAttributes);
+
+    lifecycle.dispatchEvent(new Event("pagehide"));
+    await vi.waitFor(() => expect(fetcher).toHaveBeenCalledOnce());
+    adapter.dispose();
+
+    expect(adapter.pendingCount()).toBe(0);
+    expect(remove).toHaveBeenCalledWith("pagehide", expect.any(Function));
+  });
 });