ADRs 0091 and 0092; issues 026 and 070 resolved; designs 18 and 24 amended

03-DESIGN/01-to-be/18-building-a-module.md

@@ -7,6 +7,7 @@ code:
   - mesh-catalog modules/builder
 updated: 2026-09-21
 decisions:
+  - 02-DECISIONS/0091-a-mount-is-declared-three-ways.md
   - 02-DECISIONS/0087-a-seeded-file-is-created-once.md
   - 02-DECISIONS/0040-what-a-module-is.md
   - 02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md
@@ -182,6 +183,16 @@ disagrees with it.
 | `computed` | marks a module the controller generates rather than an author writing |
 | `build.artifacts` | what it produces |
 
+**A container mounts only what the manifest declares**
+([ADR 0091](../../02-DECISIONS/0091-a-mount-is-declared-three-ways.md)). A bind mount the module
+never declared is created by the container runtime as root, so the module's owner and mode never
+reach its data and the rule that keeps data when a module goes away does not cover it. A path is
+declared in one of three ways, for the three things a path can be: the module's own (a directory
+or file resource, or where a secret, grant or contribution lands), the operator's (an `accesses`
+entry), or the machine's (a facility a declared capability grants — `container-runtime` grants its
+socket). *How it is checked:* the parser refuses an undeclared mount naming the path and the three
+remedies, and a test parses every manifest in the catalogue beside the checkout.
+
 ### What it builds
 
 | kind | is |