diff --git a/AGENTS.md b/AGENTS.md
index 799fa4f9f59..59950ad22d5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -145,6 +145,13 @@
 - Formatting/linting via Oxlint and Oxfmt.
 - Never add `@ts-nocheck` and do not add inline lint suppressions by default. Fix root causes first; only keep a suppression when the code is intentionally correct, the rule cannot express that safely, and the comment explains why.
 - Do not disable `no-explicit-any`; prefer real types, `unknown`, or a narrow adapter/helper instead. Update Oxlint/Oxfmt config only when required.
+- Prefer `zod` or existing schema helpers at external boundaries such as config, webhook payloads, CLI/JSON output, persisted JSON, and third-party API responses.
+- Prefer discriminated unions when parameter shape changes runtime behavior.
+- Prefer `Result<T, E>`-style outcomes and closed error-code unions for recoverable runtime decisions.
+- Keep human-readable strings for logs, CLI output, and UI; do not use freeform strings as the source of truth for internal branching.
+- Avoid `?? 0`, empty-string, empty-object, or magic-string sentinels when they can change runtime meaning silently.
+- If introducing a new optional field or nullable semantic in core logic, prefer an explicit union or dedicated type when the value changes behavior.
+- New runtime control-flow code should not branch on `error: string` or `reason: string` when a closed code union would be reasonable.
 - Dynamic import guardrail: do not mix `await import("x")` and static `import ... from "x"` for the same module in production code paths. If you need lazy loading, create a dedicated `*.runtime.ts` boundary (that re-exports from `x`) and dynamically import that boundary from lazy callers only.
 - Dynamic import verification: after refactors that touch lazy-loading/module boundaries, run `pnpm build` and check for `[INEFFECTIVE_DYNAMIC_IMPORT]` warnings before submitting.
 - Extension SDK self-import guardrail: inside an extension package, do not import that same extension via `openclaw/plugin-sdk/<extension>` from production files. Route internal imports through a local barrel such as `./api.ts` or `./runtime-api.ts`, and keep the `plugin-sdk/<extension>` path as the external contract only.