diff --git a/docs/project/readable-codebase/README.md b/docs/project/readable-codebase/README.md
index b2447fd..8aa4961 100644
--- a/docs/project/readable-codebase/README.md
+++ b/docs/project/readable-codebase/README.md
@@ -192,8 +192,13 @@ Three rules when you write a ticket file, because the agent reads its ticket and
      files (they name the deleted method as the history of `done` work) and 22 gitignored
      abandoned worktrees. Satisfying it literally would have corrupted completed-ticket
      history.
+   - RD-11 asserted `git grep "machineRemoteData\|LoadLifecycle"` returns nothing, but the
+     replacement it mandates is named **`fromLoadLifecycle`** — which contains the old name as
+     a substring. The check can never pass. **When the new name contains the old one, anchor
+     on word boundaries**: `git grep -w machineRemoteData` and
+     `git grep -nE "(^|[^a-zA-Z])LoadLifecycle\b"`.
 
-   Three habits that prevent all four:
+   Four habits that prevent all five:
 
    - **Use `git grep`, not `grep -r`.** It searches tracked files only, so untracked and
      gitignored paths never pollute the result. Measured on this repo: `grep -r` finds 132
@@ -203,3 +208,20 @@ Three rules when you write a ticket file, because the agent reads its ticket and
      appear elsewhere.
    - **Keep the Files list consistent with the Acceptance commands.** If a command reaches a
      file the ticket says not to touch, one of the two is wrong.
+   - **Prefer a number over a prohibition for anything that must not change.** "Do not rename
+     `BriefStatus`" invites reasoning around it; "this count must still be 54, and if it moves,
+     revert rather than adjust the number" does not. RD-11 renamed tags across 19 files with a
+     wire contract in the same file — on the same line in one place — and the count held.
+
+## Troubleshooting
+
+**`dotnet test` fails with `SQLite Error 1: 'no such table: <X>'`.** Stale, gitignored
+`bigregister.db` artifacts from an old build. Found during RD-11, where a 0-byte file dated
+months earlier failed 6 backend tests on an otherwise clean tree. Delete all three and re-run:
+
+```bash
+rm -f backend/bigregister.db backend/src/BigRegister.Api/bigregister.db \
+      backend/tests/BigRegister.Tests/bin/Debug/net10.0/bigregister.db
+```
+
+These are build artifacts, not fixtures — removing them is always safe.