Spin guard: derivative-work rule (AGENTS.md) + rationale (ai.md) — proactive external scan cites in commit msg; 2nd failed fix = STOP and research externally, never a 3rd guess

Project lesson cited (the 2026-08 web-box saga, 9 commits): browser sources are fixed canvases
per OBS convention — the 'gap' was a widget CSS glow, not a bug.

AGENTS.md

@@ -58,6 +58,17 @@ at a problem.
   (merged once in `App.xaml`; never duplicate per-window).
 - **Do not add comments unless the code needs them; do not expand the task queue
   on your own** — work only what the user queues.
+- **Derivative work / spin guard.** Every problem here is derivative — OBS, other
+  overlay tools, and the WPF/WebView2 ecosystems already solved it. Both sides are
+  mandatory, not advisory:
+  - **Proactive (new features):** before writing code, do a quick external scan
+    (websearch: how do OBS/CEV/overlay tools do this?) and cite the reference in the
+    commit message.
+  - **Spin guard (objectively triggered):** a SECOND failed remedy for the same
+    symptom = STOP. No third guess over the same code. Research the established
+    answer externally, cite its URL in the commit message AND in `MyMistakes.md`,
+    then code it. You do not know everything — repeated failure is a research
+    trigger, not a persistence trigger.
 - **Response style: no default planning template.** Do the work, then report
   what changed and what's next. No "Plans & Pitfalls", pros/cons tables, or
   step-by-step plans unless the user asks for a plan first (see `ai.md`).

HANDOFF.md

@@ -43,6 +43,11 @@ auto-fit sized to the crop (`ab29ec8`, reverted).
 
 ## Key facts / landmines
 
+- **Why the web-box saga spun (2026-08):** nine commits of in-head theorizing for a problem
+  OBS already solved (browser source = fixed canvas, box = user-sized, content clips at the
+  edge). The apparent gap was the widget's CSS glow, not a bug. → AGENTS.md now mandates
+  external research on the second failed fix and proactive scans for new features.
+
 - **App running locks `ytLive.exe`** → build fails MSB3027 until creator exits the app.
 - **Startup diagnostics:** unhandled exceptions + checkpoints go to `%APPDATA%\ytLlive\startup.log`
   (`Helpers/AppLog.cs`). On a silent startup crash, read that.

ai.md

@@ -14,6 +14,20 @@ Skip feature pitch, step-by-step implementation plans, pros/cons tables, and
 "potential pitfalls" sections unless the user explicitly asks for a plan first.
 A short diff-style summary beats a proposal document every time.
 
+## Derivative work (spin guard mandated in AGENTS.md)
+
+Nothing we build is novel — streaming/overlay/WebView2 problems were solved by
+OBS, CEV, and WPF ecosystems long before us. Two consequences:
+1. **Proactive:** new features start with a quick external scan, not head-first
+   design (citation goes in the commit message).
+2. **Objectively triggered spin guard:** a second failed fix for the same symptom
+   means STOP theorizing and research the established answer externally; there is
+   no unique bug in this repo that the wider ecosystem hasn't hit.
+This project's hard lesson: the web-source bounding saga (2026-08) burned 9
+commits rediscovering that a browser source is a *fixed canvas* — OBS keeps it at
+a stable page size, crops/hugs content via the box, and clips at the edge. The
+apparent "gap" that ended the saga was a widget's own CSS glow effect, not a bug.
+
 ## LAN infrastructure (192.168.50.x)
 
 All LAN credentials live in `CREDENTIALS.md` (gitignored). Server IPs and roles: