From 6c284bb5c341b4fc45ec341e1545106ded15d9ef Mon Sep 17 00:00:00 2001
From: Christophe Dervieux <christophe.dervieux@gmail.com>
Date: Tue, 27 Jan 2026 21:47:06 +0100
Subject: [PATCH 1/3] test, ipynb - add a test for cross ref in ipynb

Also add a verify function for Ipynb cell content
---
 .../docs/smoke-all/2026/01/27/issue-13956.qmd | 23 +++++++++++++
 tests/smoke/smoke-all.test.ts                 |  2 ++
 tests/verify.ts                               | 34 +++++++++++++++++++
 3 files changed, 59 insertions(+)
 create mode 100644 tests/docs/smoke-all/2026/01/27/issue-13956.qmd

diff --git a/tests/docs/smoke-all/2026/01/27/issue-13956.qmd b/tests/docs/smoke-all/2026/01/27/issue-13956.qmd
new file mode 100644
index 0000000000..8de340633e
--- /dev/null
+++ b/tests/docs/smoke-all/2026/01/27/issue-13956.qmd
@@ -0,0 +1,23 @@
+---
+title: "Issue 13956"
+format: ipynb
+_quarto:
+  tests:
+    ipynb:
+      ensureIpynbCellMatches:
+        cellType: markdown
+        matches:
+          - 'Figure\s1'
+          - '#fig-test'
+          - 'quarto-xref'
+          - 'This should render without crashing'
+---
+
+Testing crash when using inline `#| label: fig-*` syntax with format: ipynb.
+
+```{python}
+#| label: fig-test
+print("This should render without crashing")
+```
+
+See @fig-test for the output.
diff --git a/tests/smoke/smoke-all.test.ts b/tests/smoke/smoke-all.test.ts
index b209c2a631..36650b9266 100644
--- a/tests/smoke/smoke-all.test.ts
+++ b/tests/smoke/smoke-all.test.ts
@@ -23,6 +23,7 @@ import {
   ensureDocxXpath,
   ensureFileRegexMatches,
   ensureHtmlElements,
+  ensureIpynbCellMatches,
   ensurePdfRegexMatches,
   ensurePdfTextPositions,
   ensurePdfMetadata,
@@ -181,6 +182,7 @@ function resolveTestSpecs(
     ensureHtmlElementContents,
     ensureHtmlElementCount,
     ensureFileRegexMatches,
+    ensureIpynbCellMatches,
     ensureLatexFileRegexMatches,
     ensureTypstFileRegexMatches,
     ensureDocxRegexMatches,
diff --git a/tests/verify.ts b/tests/verify.ts
index d4ae29ada7..ca9db28cc8 100644
--- a/tests/verify.ts
+++ b/tests/verify.ts
@@ -302,6 +302,40 @@ export const validJsonWithFields = (file: string, fields: Record<string, unknown
   }
 }
 
+export const ensureIpynbCellMatches = (
+  file: string,
+  options: {
+    cellType: "code" | "markdown";
+    matches?: (string | RegExp)[];
+    noMatches?: (string | RegExp)[];
+  }
+): Verify => {
+  const { cellType, matches = [], noMatches = [] } = options;
+  return {
+    name: `IPYNB ${file} has ${cellType} cells matching patterns`,
+    verify: async (_output: ExecuteOutput[]) => {
+      const jsonStr = Deno.readTextFileSync(file);
+      const notebook = JSON.parse(jsonStr);
+      // deno-lint-ignore no-explicit-any
+      const cells = notebook.cells.filter((c: any) => c.cell_type === cellType);
+      // deno-lint-ignore no-explicit-any
+      const content = cells.map((c: any) =>
+        Array.isArray(c.source) ? c.source.join("") : c.source
+      ).join("\n");
+
+      for (const m of matches) {
+        const regex = typeof m === "string" ? new RegExp(m) : m;
+        assert(regex.test(content), `Pattern ${m} not found in ${cellType} cells of ${file}`);
+      }
+      for (const m of noMatches) {
+        const regex = typeof m === "string" ? new RegExp(m) : m;
+        assert(!regex.test(content), `Pattern ${m} should not be in ${cellType} cells of ${file}`);
+      }
+      return Promise.resolve();
+    }
+  };
+};
+
 export const outputCreated = (
   input: string,
   to: string,

From a6d1cf23bc51ad2f195f8226d19201e6db043ae0 Mon Sep 17 00:00:00 2001
From: Christophe Dervieux <christophe.dervieux@gmail.com>
Date: Tue, 27 Jan 2026 22:04:07 +0100
Subject: [PATCH 2/3] Fix ipynb crash with inline figure labels

Wrap float.content with pandoc.Blocks() in the ipynb renderer to handle
content that arrives as a list instead of a typed Blocks element.

Fixes #13956
---
 src/resources/filters/customnodes/floatreftarget.lua | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/resources/filters/customnodes/floatreftarget.lua b/src/resources/filters/customnodes/floatreftarget.lua
index 38d8a70379..f1dffaf7e0 100644
--- a/src/resources/filters/customnodes/floatreftarget.lua
+++ b/src/resources/filters/customnodes/floatreftarget.lua
@@ -933,10 +933,9 @@ end, function(float)
       float.identifier)
   end
 
-  return pandoc.Div({
-    float.content,
-    pandoc.Para(quarto.utils.as_inlines(float.caption_long) or {}),
-  });
+  local blocks = pandoc.Blocks(float.content)
+  blocks:insert(pandoc.Para(quarto.utils.as_inlines(float.caption_long) or {}))
+  return pandoc.Div(blocks)
 end)
 
 -- this should really be "_quarto.format.isEmbedIpynb()" or something like that..

From 7cbfb86417a9d3fb686a3a748e9cfbc19d20b3ea Mon Sep 17 00:00:00 2001
From: Christophe Dervieux <christophe.dervieux@gmail.com>
Date: Tue, 27 Jan 2026 22:18:40 +0100
Subject: [PATCH 3/3] Add to changelog

---
 news/changelog-1.9.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/news/changelog-1.9.md b/news/changelog-1.9.md
index 441d8d590d..617aed79ee 100644
--- a/news/changelog-1.9.md
+++ b/news/changelog-1.9.md
@@ -74,6 +74,10 @@ All changes included in 1.9:
 
 - ([#13722](https://github.com/quarto-dev/quarto-cli/issues/13722)): Fix `light-content` / `dark-content` SCSS rules not included in Reveal.js format. (author: @mcanouil)
 
+### `ipynb`
+
+- ([#13956](https://github.com/quarto-dev/quarto-cli/issues/13956)): Fix crash when rendering to `ipynb` format with figure labels (`#| label: fig-*`) on cells for cross references.
+
 ## Projects
 
 - ([#13892](https://github.com/quarto-dev/quarto-cli/issues/13892)): Fix `output-dir: ./` deleting entire project directory. `output-dir` must be a subdirectory of the project directory and check is now better to avoid deleting the project itself when it revolves to the same path.