diff --git a/.claude/rules/testing/smoke-all-tests.md b/.claude/rules/testing/smoke-all-tests.md
index ea80419bcdf..7900aaeb19b 100644
--- a/.claude/rules/testing/smoke-all-tests.md
+++ b/.claude/rules/testing/smoke-all-tests.md
@@ -119,6 +119,23 @@ _quarto:
 
 Valid OS values: `linux`, `darwin`, `windows`
 
+## Project Rendering (cross-file resolution)
+
+Each `_quarto.tests` block renders only its own input file (`quarto render <input> --to <format>`). In a multi-file project (book/website) that leaves cross-file references resolved at the project post-render stage (e.g. an appendix cross-reference pointing into another chapter) unresolved.
+
+Set `render-project: true` as a sibling of `tests:` (under `_quarto`) to render the whole project first:
+
+```yaml
+_quarto:
+  render-project: true
+  tests:
+    html:
+      ensureFileRegexMatches:
+        - ['>Whatever A<']
+```
+
+Gotcha: the project pre-render runs `quarto render <projectDir>` with **no `--to`**, so it builds only the formats **declared in `_quarto.yml`**. To test a format's cross-file output, that format must be declared in the project config — otherwise the pre-render skips it and the per-file render alone cannot resolve cross-file refs. Example: `tests/docs/smoke-all/2026/06/23/issue-11772` (book must declare `format: html` for the HTML appendix cross-reference test).
+
 ## Pattern Specificity
 
 Avoid patterns that match template boilerplate instead of document content:
diff --git a/llm-docs/testing-patterns.md b/llm-docs/testing-patterns.md
index 2ddcfa0c364..86968475b5f 100644
--- a/llm-docs/testing-patterns.md
+++ b/llm-docs/testing-patterns.md
@@ -394,6 +394,23 @@ Run test **without fix** first to verify it fails, then verify it passes with fi
 
 Smoke-all tests embed test specifications directly in `.qmd` files using `_quarto.tests` metadata. See `.claude/rules/testing/smoke-all-tests.md` for full documentation.
 
+### Project pre-render for cross-file resolution
+
+A `_quarto.tests` block renders only its own input file (`quarto render <input> --to <format>`). In a multi-file project (book/website), cross-file references that are resolved at the project post-render stage — e.g. an appendix cross-reference in one chapter pointing at another chapter — stay unresolved under a single-file render.
+
+Set `render-project: true` as a sibling of `tests:` to render the whole project first:
+
+```yaml
+_quarto:
+  render-project: true
+  tests:
+    html:
+      ensureFileRegexMatches:
+        - ['>Whatever A<']
+```
+
+The harness runs `quarto render <projectDir>` (in `smoke-all.test.ts`) before the per-file render. **Gotcha:** that pre-render has no `--to`, so it builds only the formats declared in `_quarto.yml`. To test a format's cross-file output, declare that format in the project config — otherwise the pre-render skips it and the per-file render alone cannot resolve cross-file references. Reference fixture: `tests/docs/smoke-all/2026/06/23/issue-11772` (the book declares `format: html` so the HTML appendix cross-reference resolves; the per-file HTML render then reuses the project crossref index).
+
 ### YAML String Escaping for Regex
 
 **Critical rule:** In YAML single-quoted strings, `'\('` and `"\\("` are equivalent - both produce a literal `\(` in the regex.
diff --git a/news/changelog-1.10.md b/news/changelog-1.10.md
index 7cf310f1b2b..50156fb6f3c 100644
--- a/news/changelog-1.10.md
+++ b/news/changelog-1.10.md
@@ -50,6 +50,10 @@ All changes included in 1.10:
 - ([#14562](https://github.com/quarto-dev/quarto-cli/issues/14562)): Fix a heading inside `content-hidden when-format="llms-txt"` (visible in HTML) losing its `<section>` wrapper and `id` in a website with `llms-txt` enabled, which broke its table-of-contents link, anchors, and cross-references.
 - ([#14563](https://github.com/quarto-dev/quarto-cli/issues/14563)): Fix a fatal error when a shortcode is used inside conditional content (e.g. `content-visible when-format="llms-txt"`) in a website with `llms-txt` enabled.
 
+### Books
+
+- ([#11772](https://github.com/quarto-dev/quarto-cli/issues/11772)): Fix `crossref.appendix-title` not being applied to appendix cross-references in PDF output. Appendix cross-references now use the configured title (e.g. `See Whatever A`) instead of always showing the default `Appendix` prefix.
+
 ## Commands
 
 ### `quarto preview`
diff --git a/src/project/types/book/book-crossrefs.ts b/src/project/types/book/book-crossrefs.ts
index 6b2d3fc6284..cc120e0f555 100644
--- a/src/project/types/book/book-crossrefs.ts
+++ b/src/project/types/book/book-crossrefs.ts
@@ -18,6 +18,8 @@ import {
 import { pathWithForwardSlashes } from "../../../core/path.ts";
 
 import {
+  kCrossref,
+  kCrossrefAppendixTitle,
   kCrossrefApxPrefix,
   kCrossrefChapterId,
   kCrossrefChapters,
@@ -37,7 +39,7 @@ import { WebsiteProjectOutputFile } from "../website/website.ts";
 import { inputTargetIndex } from "../../project-index.ts";
 import { bookConfigRenderItems } from "./book-config.ts";
 import { isMultiFileBookFormat } from "./book-shared.ts";
-import { Format } from "../../../config/types.ts";
+import { Format, Metadata } from "../../../config/types.ts";
 
 export async function bookCrossrefsPostRender(
   context: ProjectContext,
@@ -305,11 +307,21 @@ function formatCrossref(
   // if this is a section we need a prefix
   const refNumber = numberOption(entry.order, options, type);
   if (type === "sec" && !noPrefix) {
-    const prefix = (options[kCrossrefChapters] && isChapterRef(entry))
-      ? options[kCrossrefChaptersAppendix]
-        ? language[kCrossrefApxPrefix]
-        : language[kCrossrefChPrefix]
-      : language[kCrossrefSecPrefix];
+    let prefix;
+    if (options[kCrossrefChapters] && isChapterRef(entry)) {
+      if (options[kCrossrefChaptersAppendix]) {
+        // appendix cross-references prefer crossref.appendix-title (the same
+        // option that titles the appendix chapter heading) so the reference
+        // text matches the heading
+        const crossref = format.metadata?.[kCrossref] as Metadata | undefined;
+        prefix = (crossref?.[kCrossrefAppendixTitle] as string) ??
+          language[kCrossrefApxPrefix];
+      } else {
+        prefix = language[kCrossrefChPrefix];
+      }
+    } else {
+      prefix = language[kCrossrefSecPrefix];
+    }
     const crossref = prefix + " " + refNumber;
     return crossref;
   } else {
diff --git a/src/resources/filters/crossref/format.lua b/src/resources/filters/crossref/format.lua
index 6c6908b285b..7f5d7dfc0cf 100644
--- a/src/resources/filters/crossref/format.lua
+++ b/src/resources/filters/crossref/format.lua
@@ -77,6 +77,14 @@ function refPrefix(type, upper)
   end
   default = stringToInlines(default)
   local prefix = crossrefOption(opt, default)
+  -- appendix cross-references prefer crossref.appendix-title (the same option that
+  -- titles the appendix chapter heading) so the reference text matches the heading
+  if type == "apx" then
+    local appendixTitle = crossrefOption("appendix-title")
+    if appendixTitle ~= nil then
+      prefix = appendixTitle
+    end
+  end
   if upper then
     local el = pandoc.Plain(prefix)
     local firstStr = true
diff --git a/tests/docs/smoke-all/2026/06/23/issue-11772/.gitignore b/tests/docs/smoke-all/2026/06/23/issue-11772/.gitignore
new file mode 100644
index 00000000000..ad293093b07
--- /dev/null
+++ b/tests/docs/smoke-all/2026/06/23/issue-11772/.gitignore
@@ -0,0 +1,2 @@
+/.quarto/
+**/*.quarto_ipynb
diff --git a/tests/docs/smoke-all/2026/06/23/issue-11772/_quarto.yml b/tests/docs/smoke-all/2026/06/23/issue-11772/_quarto.yml
new file mode 100644
index 00000000000..a5929d6f7d7
--- /dev/null
+++ b/tests/docs/smoke-all/2026/06/23/issue-11772/_quarto.yml
@@ -0,0 +1,21 @@
+project:
+  type: book
+
+book:
+  title: "issue-11772"
+  author: "Norah Jones"
+  chapters:
+    - index.qmd
+    - intro.qmd
+  appendices:
+    - summary.qmd
+
+format:
+  html: default
+  pdf:
+    documentclass: scrreprt
+    keep-tex: true
+
+crossref:
+  appendix-title: "Whatever"
+  appendix-delim: ":"
diff --git a/tests/docs/smoke-all/2026/06/23/issue-11772/index.qmd b/tests/docs/smoke-all/2026/06/23/issue-11772/index.qmd
new file mode 100644
index 00000000000..726a6cad132
--- /dev/null
+++ b/tests/docs/smoke-all/2026/06/23/issue-11772/index.qmd
@@ -0,0 +1,19 @@
+---
+format:
+  pdf:
+    keep-tex: true
+_quarto:
+  tests:
+    pdf:
+      # crossref.appendix-title ("Whatever") must drive the appendix
+      # cross-reference prefix in PDF, like it does in HTML output.
+      # Currently the prefix falls back to the default "Appendix"
+      # (only language.crossref-apx-prefix is honored) — issue #11772.
+      ensureLatexFileRegexMatches:
+        - ['See Whatever~\\ref\{sec-summary\}']
+        - ['See Appendix~\\ref\{sec-summary\}']
+---
+
+# Preface {.unnumbered}
+
+This is a book testing crossref appendix options in PDF (issue #11772).
diff --git a/tests/docs/smoke-all/2026/06/23/issue-11772/intro.qmd b/tests/docs/smoke-all/2026/06/23/issue-11772/intro.qmd
new file mode 100644
index 00000000000..f55602f21e4
--- /dev/null
+++ b/tests/docs/smoke-all/2026/06/23/issue-11772/intro.qmd
@@ -0,0 +1,17 @@
+---
+_quarto:
+  render-project: true
+  tests:
+    html:
+      # crossref.appendix-title ("Whatever") must drive the appendix
+      # cross-reference prefix in HTML too. This cross-file reference from a
+      # numbered chapter is resolved by the book post-render step, which
+      # previously only honored language.crossref-apx-prefix — issue #11772.
+      ensureFileRegexMatches:
+        - ['>Whatever A<']
+        - ['>Appendix A<']
+---
+
+# Introduction
+
+See @sec-summary.
diff --git a/tests/docs/smoke-all/2026/06/23/issue-11772/summary.qmd b/tests/docs/smoke-all/2026/06/23/issue-11772/summary.qmd
new file mode 100644
index 00000000000..8e2c15d0532
--- /dev/null
+++ b/tests/docs/smoke-all/2026/06/23/issue-11772/summary.qmd
@@ -0,0 +1,3 @@
+# Summary {#sec-summary}
+
+In summary, this book has no content whatsoever.