diff --git a/backend/README.md b/backend/README.md
index a2423a5..9923935 100644
--- a/backend/README.md
+++ b/backend/README.md
@@ -15,7 +15,7 @@ status codes and error envelope are production-shaped.
 covers it, see `docker-compose.yml`) does **not** lose data. Delete the file to
 reset demo data back to empty, the same state a fresh clone starts from. This is
 a deliberate, right-sized choice for a POC (SQLite, no external DB service) — see
-the durable-persistence design note in `docs/project/backlog/`.
+`docs/project/backlog/WP-22-durable-persistence.md`.
 
 ## Run
 
diff --git a/backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs b/backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs
index 92d2ccd..9c3541d 100644
--- a/backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs
+++ b/backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs
@@ -151,9 +151,8 @@ public static class LetterHtml
   private static string EncLines(string s) => Enc(s).Replace("\n", "<br>");
 
   // Walks up from the running assembly's own directory (NOT the process cwd, which
-  // varies by how `dotnet run`/docker/tests invoke it — see the letter-preview-html design
-  // note in docs/project/backlog/) until
-  // it finds `public/letter.css`. docker-compose.yml bind-mounts `./public` under the
+  // varies by how `dotnet run`/docker/tests invoke it — see
+  // docs/project/backlog/WP-25-letter-preview-html.md) until it finds `public/letter.css`. docker-compose.yml bind-mounts `./public` under the
   // api container's `/src` for exactly this walk to resolve there too.
   private static string FindLetterCss()
   {
diff --git a/docs/project/readable-codebase/RD-19-ticket-refs-backend.md b/docs/project/readable-codebase/RD-19-ticket-refs-backend.md
index 519179c..5caba89 100644
--- a/docs/project/readable-codebase/RD-19-ticket-refs-backend.md
+++ b/docs/project/readable-codebase/RD-19-ticket-refs-backend.md
@@ -25,10 +25,22 @@ Strip the reference, keep the sentence. No behaviour changes.
 
 ## Decisions (pre-made, don't relitigate)
 
-1. **Nothing in `backend/` is exempt. Strip all 370.** Unlike the front end, no backend file
-   disables a check by naming the ticket that removes it — verified against
-   `pragma warning disable`, `Skip =`, `NoWarn` and `SuppressMessage`, none of which carries a
-   reference. Keep all 40 `ADR-000x` references; that count must not move.
+1. **Strip all 370 except two.** No backend file disables a check by naming the ticket that
+   removes it — verified against `pragma warning disable`, `Skip =`, `NoWarn` and
+   `SuppressMessage`, none of which carries a reference. Keep all 40 `ADR-000x` references; that
+   count must not move.
+
+   **Corrected after the ticket ran.** The original text said "nothing is exempt", and it was
+   wrong. Two references are part of a path to a document that still exists:
+
+   | Site                               | Reference                                           |
+   | ---------------------------------- | --------------------------------------------------- |
+   | `backend/README.md:18`             | `docs/project/backlog/WP-22-durable-persistence.md` |
+   | `Domain/Letters/LetterHtml.cs:153` | `docs/project/backlog/WP-25-letter-preview-html.md` |
+
+   RD-18 exempted this same class of reference (`a11y.mdx:68`). A path that resolves is a
+   pointer, not provenance. Stripping the number breaks the path, and describing the file in
+   prose instead makes the reader search for it.
 
 2. **`public/letter.css` and `LetterHtml.golden.html` change together, or the build goes red.**
    `LetterHtml.cs:161` finds `public/letter.css` at run time and **inlines it** into the
@@ -96,7 +108,14 @@ Measured against the tree before handover. `git grep -o … | wc -l` counts **oc
 `git grep -c` counts lines and would give a different, wrong number.
 
 ```bash
-git grep -oE "\b(WP|RB)-[0-9]+" -- backend public/letter.css | wc -l   # is 373 -> MUST be 0
+git grep -oE "\b(WP|RB)-[0-9]+" -- backend public/letter.css | wc -l   # is 373 -> MUST be 2
+```
+
+The two survivors are the document paths in decision 1:
+
+```bash
+git grep -oE "\b(WP|RB)-[0-9]+" -- backend/README.md \
+  backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs | wc -l    # MUST be 2
 ```
 
 The ADR references survive, and the sweep leaves no damaged prose:
diff --git a/docs/project/readable-codebase/README.md b/docs/project/readable-codebase/README.md
index 5da9302..1d2137f 100644
--- a/docs/project/readable-codebase/README.md
+++ b/docs/project/readable-codebase/README.md
@@ -198,6 +198,15 @@ Three rules when you write a ticket file, because the agent reads its ticket and
      on word boundaries**: `git grep -w machineRemoteData` and
      `git grep -nE "(^|[^a-zA-Z])LoadLifecycle\b"`.
 
+   - RD-19 asserted the backend sweep must reach **0** references, after RD-18 had established
+     that a reference inside a path to a document that still exists is a pointer, not
+     provenance, and exempted one. The supervisor did not run that check against `backend/`.
+     Two such paths existed. The target of 0 gave the agent no way to keep them, so it
+     described the two documents in prose instead — losing a path that resolved. Fixed
+     afterwards; the target is 2. **When a ticket repeats an earlier sweep, re-run the earlier
+     sweep's exemption check against the new scope.** An exemption is a property of the
+     content, not of the directory that happened to hold it first.
+
    Four habits that prevent all five:
 
    - **Use `git grep`, not `grep -r`.** It searches tracked files only, so untracked and