diff --git a/docs/development.md b/docs/development.md
index e017c6c8..657a0256 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -18,7 +18,7 @@ Use `npm run fix` for mechanical cleanup, review its diff, and run `npm run chec
 
 Use `npm run test:coverage` to identify source modules and branches that lack exercised behavior. It reports every authored TypeScript source file, including files not imported by tests, while excluding generated app-server bindings. Open `coverage/index.html` to inspect line-level gaps. Coverage is diagnostic and has no pass/fail threshold; prioritize user-visible behavior and state-transition invariants rather than raising the aggregate percentage.
 
-Use `npm run test:mutation` for an exploratory mutation test of the domain-owned logic under `src/domain/` and `src/features/chat/domain/`. Review surviving mutants individually instead of treating the aggregate score as a quality gate: add tests for meaningful behavior gaps, simplify equivalent or redundant code, and leave mutants alone when neither change improves the durable contract. The run ignores expensive module-initialization mutants, is intentionally manual, and writes its ignored HTML report to `reports/mutation/mutation.html`.
+Use `npm run test:mutation` for an exploratory mutation test of domain-owned logic, app-server protocol normalization, thread-stream event mapping, and the chat root reducer. Review surviving mutants individually instead of treating the aggregate score as a quality gate: add tests for meaningful behavior gaps, simplify equivalent or redundant code, and leave mutants alone when neither change improves the durable contract. The run ignores expensive module-initialization mutants, is intentionally manual, and writes its ignored HTML report to `reports/mutation/mutation.html`.
 
 ## Commit Messages
 
diff --git a/stryker.config.mjs b/stryker.config.mjs
index d6fbd8e8..02f11421 100644
--- a/stryker.config.mjs
+++ b/stryker.config.mjs
@@ -1,7 +1,13 @@
 export default {
   testRunner: "vitest",
   coverageAnalysis: "perTest",
-  mutate: ["src/domain/**/*.ts", "src/features/chat/domain/**/*.ts"],
+  mutate: [
+    "src/domain/**/*.ts",
+    "src/app-server/protocol/**/*.ts",
+    "src/features/chat/domain/**/*.ts",
+    "src/features/chat/app-server/mappers/thread-stream/**/*.ts",
+    "src/features/chat/application/state/root-reducer.ts",
+  ],
   ignoreStatic: true,
   incremental: true,
   reporters: ["clear-text", "progress", "html"],