diff --git a/.claude/skills/pm-dispatch/references/app-platform-boundary.md b/.claude/skills/pm-dispatch/references/app-platform-boundary.md
new file mode 100644
index 0000000000..38d7271442
--- /dev/null
+++ b/.claude/skills/pm-dispatch/references/app-platform-boundary.md
@@ -0,0 +1,66 @@
+# App or platform — which work belongs where
+
+Routed here from `AGENTS.md`. This boundary was decided ad hoc three times in one day, by
+three seats, each from scratch, and the three derivations differed. It is one rule, not new
+policy: the rule those decisions already followed, written down so it stops being re-derived.
+
+Lessons here are self-contained by the 2026-08-12 ruling — failure mode, discipline and
+boundary in the text, no issue number to dereference.
+
+## The deciding question
+
+**Could this be written by something that has only the metadata, and no knowledge of this
+company?**
+
+| Answer | Belongs in |
+|:--|:--|
+| **No** — it encodes the company's own judgement | the **metadata app**: a discount ceiling, who a case is assigned to, how won/lost is booked; its own objects, views and flows |
+| **Yes** — it only asks whether the metadata is self-consistent | the **platform**: reference integrity, translation coverage, view rosters, sharing-rule coverage, CRUD round-trips, RLS probes per declared position |
+| the subject is platform behaviour, the cost lands on the app | the **platform**, and it is a **gap** until it does — asserting what a hook does inside the platform's own sandbox is one |
+
+The second row is the one that pays. An app that hand-writes it is hand-writing a
+consistency proof the platform can derive once, for every app, and check on every build.
+
+## The second question, for a capability an app wants published
+
+**If a second app needed this, would it copy the implementation?** Yes ⇒ platform.
+
+One consumer is a **use**; two is a **contract**. A resolution wanted by four call sites
+inside a single package stays package-private on exactly this test — the home question gets
+decided when a second consumer is actually in hand, and a symbol that was never published
+can move without a major. ⛔ The dependency graph is not the test: check the real edges
+before claiming two packages cannot import each other, because three of six directed edges
+usually already exist.
+
+⛔ This question decides what a package **in this monorepo** exports. It is contributor
+guidance and must not ship to customers, who cannot act on it.
+
+## ⛔ Anti-pattern 1 — an app hand-copies a platform rule
+
+The copy diverges from the rule the build actually applies, so the app stays green while
+the platform refuses. The divergence is invisible until the two disagree, and then the
+app's own test suite is the thing arguing for the wrong answer.
+
+Measured twice. A card wanting the platform's hook-body lowering pass turned out to want
+half a command that already ships (`os build --strict-body`, which turns "bundled instead
+of lowered" into exit 1 — `packages/cli/src/commands/compile.ts`, of which `build` is an
+alias) and half an `os lint` rule that exists nowhere in the tree. One level up, the same
+shape ships a rule claiming "0 findings over the corpus" against a corpus that is not the
+app it names.
+
+⇒ Before hand-writing against platform behaviour, grep the CLI for the command that already
+does it, and confirm the rule you are citing exists.
+
+## ⛔ Anti-pattern 2 — a capability that under-delivers silently
+
+Worse than none. `os verify` once derived **zero** cases on a multi-package app and reported
+success. `packages/cli/src/commands/verify.ts` states the shape in its own header: *a
+verifier that under-verifies reports success it never established*.
+
+An app that meets one of these writes its own harness and never comes back — so the loss is
+permanent, and it is invisible, because the capability is still reporting green.
+
+**The order is therefore fixed: make the derived half trustworthy first, then take the
+hand-written half back.** Reversing it just deletes protection. The fix for the `os verify`
+case landed as an ordered pair — ledger the four losses first so the fix has something to be
+checked against, then close them — which is this rule executed.
diff --git a/AGENTS.md b/AGENTS.md
index a7159d951f..60bc7266f5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -758,7 +758,7 @@ their output is current; the wrapper reports that each run rather than staying s
 | `packages/adapters/**` | Integration Engineer | Framework bindings, zero business logic |
 | `packages/client*/**` | SDK Engineer | Public API, DX, type safety |
 | `apps/docs/**` | Docs Engineer | Fumadocs + Next.js, MDX |
-| `examples/**` | Example Author | Minimal, runnable, uses `defineStack` |
+| `examples/**` | Example Author | Minimal, runnable, uses `defineStack`. App or platform, on any tree: could this be written from the metadata alone, with no knowledge of this company? No ⇒ the app; yes ⇒ the platform, and a **gap** until it does — `.claude/skills/pm-dispatch/references/app-platform-boundary.md` |
 | `content/docs/**` | Technical Writer | Respect auto-gen boundaries |
 | `../objectui/**` (sibling repo) | Studio UI Engineer | React + Shadcn + Tailwind, dark mode default |
 
diff --git a/scripts/pm/check-skill-line-ratchet.mjs b/scripts/pm/check-skill-line-ratchet.mjs
index fbeb9bfb93..180e469559 100644
--- a/scripts/pm/check-skill-line-ratchet.mjs
+++ b/scripts/pm/check-skill-line-ratchet.mjs
@@ -664,6 +664,14 @@ export const CEILINGS = new Map([
   // convention as every entry above); it is a NEW file, so this is an added row
   // and no other row moves.
   ['.claude/skills/pm-dispatch/references/core-rules.md', 150],
+  // The app-vs-platform boundary — the deciding question (could this be written
+  // from the metadata alone, with no knowledge of this company?), the publication
+  // test (one consumer is a use, two is a contract) and the two anti-patterns.
+  // It is on-demand DETAIL by this header's own division of labour: AGENTS.md
+  // carries the one routing row, this file carries the rule and the measurement
+  // behind each clause. A NEW file, so this is not a raise and funds nothing —
+  // set at the landed line count, headroom 0, same convention as above.
+  ['.claude/skills/pm-dispatch/references/app-platform-boundary.md', 66],
   // Lane job descriptions (maintainer ruling 2026-08-19: per-lane PM job
   // descriptions move from seat-post prose into versioned skill references).
   // Set at landed line counts (headroom 0, same convention as above).
@@ -1036,6 +1044,7 @@ export const MAX_TABLE_ROW_BYTES = new Map([
   ['.claude/skills/pm-dispatch/references/true-green.md', 0],
   ['.claude/skills/pm-dispatch/references/compile-surfaces.md', 352],
   ['.claude/skills/pm-dispatch/references/core-rules.md', 0],
+  ['.claude/skills/pm-dispatch/references/app-platform-boundary.md', 219],
   ['.claude/skills/pm-dispatch/references/lanes/engine.md', 0],
   ['.claude/skills/pm-dispatch/references/lanes/services.md', 0],
   ['.claude/skills/pm-dispatch/references/lanes/cli.md', 0],