[guard.repo.rho.D8+] fifteen servers against one repo means you cannot know which build you are looking at

Ivan: from now on port 1360, nobody starts another server, and put it in
CLAUDE.md.

This is a CORRECTNESS rule, not housekeeping. Measured today: four builds of the
app were being served at once (8100, 8101, 1342, 1360) plus eleven staging
copies from screenshot runs. A server left listening by an EARLIER SESSION held
1344; the harness started its own, that died with "address already in use" into
/dev/null, and Chrome loaded the old staged app instead. Two full rounds of
verification screenshots were of a previous build while I read them as evidence
about the new one. Separately, a staging dir kept a stale dirac.js and several
rounds of diagnosis described code that was not running.

Both failures share the shape this repo keeps finding: the fallback renders
identically to the primary, so the defect arrives as a plausible screenshot
rather than an error.

Rule lives in CLAUDE.md with the reasoning; AGENTS.md carries a pointer so the
Codex-side agents hit it too. One home for the fact, one line for the index.

Author: ivanicu

AGENTS.md

@@ -4,6 +4,14 @@
 
 This file is the **source of truth for any agent** working in this repo. Read it before committing.
 
+> ## ⚠ ONE DEV SERVER: PORT 1360. DO NOT START ANOTHER.
+> `http://192.168.1.3:1360/` serves `build/dirac` on `0.0.0.0`. Rebuild with
+> `npm run build:dirac` and reload — do not spin up a second server on a second
+> port, not even for one screenshot. **Rules and the measured reason they exist:
+> `CLAUDE.md` in this directory.** (Short version: fifteen servers were running
+> against this repo at once, one of them left over from an earlier session, and
+> two rounds of verification screenshots turned out to be of a stale build.)
+
 ## Repository topology
 
 ```

CLAUDE.md

@@ -0,0 +1,54 @@
+# Project: dirac
+
+Repo law lives in `AGENTS.md` (co-equal, loaded by the Codex runtime). This file
+holds the rules a Claude session in this repo must follow, and right now it holds
+one.
+
+---
+
+## ⚠ ONE DEV SERVER: PORT 1360. DO NOT START ANOTHER.
+
+**Ivan, 2026-08-11, standing until he lifts it.**
+
+```
+http://192.168.1.3:1360/     LAN
+http://100.78.155.10:1360/   tailnet
+http://127.0.0.1:1360/       local
+```
+
+Serving `/home/ivan/dirac/build/dirac`, bound to `0.0.0.0` so every device on the
+LAN and the tailnet reaches the same build.
+
+**The rules, in force for every agent working in this repo:**
+
+1. **Do not start a new HTTP server.** Not on a different port, not "just for a
+   screenshot", not "temporarily". If you need to look at the app, rebuild with
+   `npm run build:dirac` and reload 1360 — it serves `build/dirac`, so a rebuild
+   is all it takes to see your change.
+2. **If 1360 is down**, restart it *on 1360*:
+   `cd /home/ivan/dirac/build/dirac && python3 -m http.server 1360 --bind 0.0.0.0 &`
+3. **Do not kill 1360.** Other agents and Ivan's other devices are on it.
+4. **A test harness that needs its own copy** (e.g. `scripts/shoot-fields.sh`,
+   which appends a driver to a staged copy) must stop its server when it exits.
+   The harness already does this; anything new must too.
+
+**Why this exists — it is not tidiness, it cost real work.** Fifteen HTTP servers
+were running against this repo at once: four different builds of the app on 8100,
+8101, 1342 and 1360, plus eleven staging copies from screenshot runs. Two
+consequences, both measured on 2026-08-11:
+
+- **A server from an EARLIER SESSION held port 1344.** The harness started a new
+  one, it died with "address already in use" into `/dev/null`, and Chrome
+  cheerfully loaded the *old* staged app. Two full rounds of verification
+  screenshots were of a previous build while being read as evidence about the new
+  one. A stale server is a fallback that hides the primary's death, and it fails
+  toward looking correct.
+- **Several rounds of diagnosis described code that was not running**, because a
+  staging directory kept an old `dirac.js`.
+
+So this is a correctness rule, not a housekeeping one: **more than one server
+against one repo means you cannot know which build you are looking at**, and the
+failure never announces itself — it hands you a plausible screenshot.
+
+**When a rule needs the port to change**, change it here first, then tell the
+other agents; do not fork onto a second port and sort it out later.