diff --git a/specs/2_systems_s/architecture.md b/specs/2_systems_s/architecture.md
index 7a06a78..2484307 100644
--- a/specs/2_systems_s/architecture.md
+++ b/specs/2_systems_s/architecture.md
@@ -183,3 +183,27 @@ These will accumulate value into your system over years.
 
 Even inside your system, set up so the pieces talk to each other via API, rather than tight coupling so that modules can be upgraded, replaced, outsourced, etc. 
 
+## Code
+
+Stay Python-First For:
+
+AI pipelines
+agents
+orchestration
+APIs
+content processing
+ingestion
+automation
+research tooling
+
+Add Go/Rust Selectively For:
+
+high-performance services
+distributed networking
+edge infrastructure
+heavy concurrency
+secure execution sandboxes
+streaming systems
+future NetworkSIG infrastructure
+low-memory edge compute
+
diff --git a/specs/2_systems_s/external-software-tools-repos.md b/specs/2_systems_s/external-software-tools-repos.md
index ab3d781..9c653d1 100644
--- a/specs/2_systems_s/external-software-tools-repos.md
+++ b/specs/2_systems_s/external-software-tools-repos.md
@@ -136,6 +136,8 @@
 
 [Turbopuffer](#turbopuffer)
 
+[e2a](#e2a)
+
 ---
 
 This doc is a list I maintain of anything interesting to me that I find 
@@ -405,3 +407,12 @@ How lakebase architecture delivers 5x faster Postgres writes
 
 # **Turbopuffer**
 How to build a distributed queue in a single JSON file on object storage
+
+# **e2a**
+Authenticated email gateway for AI agents. Receive emails as webhooks or via WebSocket, send emails through an HTTP API, and verify the identity of every sender — humans and other agents alike.
+
+Authenticated transport — SPF/DKIM verified on inbound; HMAC-signed X-E2A-Auth-* headers on every delivery
+Two delivery modes — webhook (cloud agents) or WebSocket (local agents, no public URL needed)
+Outbound API — agents send to other agents (SMTP relay) or humans (upstream SMTP, e.g. SES, Resend)
+Human in the loop — opt-in approval gate that holds outbound mail until a reviewer approves via dashboard, magic-link email, or CLI
+CLI + SDKs — TypeScript and Python SDKs, plus a e2a CLI for everyday agent ops
\ No newline at end of file