Reliability & agents — security notes

​

Idempotency (nestrs-idempotency)

• Always scope keys by authenticated principal (IdempotencyOptions.scope) so tenants cannot replay another user’s response.
• Treat in-flight collisions as 409, not 200 — never execute the handler twice for the same key.
• TTL must bound store growth; defaults to 24h in-memory.

​

Webhooks (nestrs-webhooks)

• Secrets: prefer whsec_ Standard Webhooks encoding; never log raw secrets.
• Verify on the raw body before JSON parse.
• Outbound URLs from user input are SSRF-sensitive — validate allowlists at the application layer before dispatch.

​

Outbox (nestrs-outbox)

• Poison messages: after max_attempts, messages move to DLQ — alert on list_dead_letters.
• In-memory store is for tests/dev; production should set allow_in_memory: false once a durable adapter is wired.

​

AI tools (nestrs-ai)

• Agent tools must enforce the caller’s authz (guards / Ability) — never run privileged tools anonymously.
• FakeModel is for tests only; never configure it in production binaries.
• generate_object fails closed on invalid JSON or missing required schema fields.

​

Resilience (nestrs-resilience)

• Retry jitter is on by default to avoid thundering herds.
• Map Timeout → 504 and CircuitOpen → 503 + Retry-After at the HTTP boundary.

​

Mail (nestrs-mail)

• Template render must escape HTML by default.
• HTTP providers inherit SSRF rules — pin destinations; do not follow arbitrary redirect targets from user content.

​

Locks / workflows (nestrs-locks, nestrs-workflows)

• Lease TTL must be shorter than the worst-case work you are willing to duplicate after a crash; extend leases on long steps.
• Approval waits are durable state — treat resume tokens as capability secrets (do not log them).