diff --git a/news/changelog-1.9.md b/news/changelog-1.9.md
index 36d010ecdb..16cb2cb0da 100644
--- a/news/changelog-1.9.md
+++ b/news/changelog-1.9.md
@@ -83,6 +83,7 @@ All changes included in 1.9:
 - ([#13954](https://github.com/quarto-dev/quarto-cli/issues/13954)): Add support for Typst book projects via format extensions. Quarto now bundles the `orange-book` extension which provides a textbook-style format with chapter numbering, cross-references, and professional styling. Book projects with `format: typst` automatically use this extension.
 - ([#13978](https://github.com/quarto-dev/quarto-cli/pull/13978)): Keep term and description together in definition lists to avoid breaking across pages. (author: @mcanouil)
 - ([#13878](https://github.com/quarto-dev/quarto-cli/issues/13878)): Typst now uses Pandoc's skylighting for syntax highlighting by default (consistent with other formats). Use `syntax-highlighting: idiomatic` to opt-in to Typst's native syntax highlighting instead.
+- ([#14126](https://github.com/quarto-dev/quarto-cli/issues/14126)): Fix Skylighting code blocks in Typst lacking full-width background, padding, and border radius. Temporarily overrides the Pandoc-generated `Skylighting` Typst function to add `width: 100%`, `inset: 8pt`, and `radius: 2pt` to the block call, matching the styling of native code blocks. Brand `monospace-block.background-color` also now correctly applies to Skylighting output. This override will be removed once the fix is upstreamed to Skylighting.
 
 ### `pdf`
 
diff --git a/src/resources/filters/quarto-post/typst-brand-yaml.lua b/src/resources/filters/quarto-post/typst-brand-yaml.lua
index e23639c86a..f5394c6217 100644
--- a/src/resources/filters/quarto-post/typst-brand-yaml.lua
+++ b/src/resources/filters/quarto-post/typst-brand-yaml.lua
@@ -56,6 +56,31 @@ function render_typst_brand_yaml()
     return '"' .. value .. '"'
   end
 
+  -- Generate a replacement #let Skylighting() function with proper block styling.
+  -- The default Pandoc-generated version only uses block(fill: bgcolor, blocks)
+  -- which lacks width, inset, and radius (issue #14126).
+  local function emit_skylighting_override(bgcolor, lineNumberColor)
+    local lineNumberFill = ''
+    if lineNumberColor and type(lineNumberColor) == 'string' then
+      lineNumberFill = 'fill: rgb("' .. lineNumberColor .. '"), '
+    end
+    quarto.doc.include_text('in-header', table.concat({
+      '#let Skylighting(fill: none, number: false, start: 1, sourcelines) = {\n',
+      '   let blocks = []\n',
+      '   let lnum = start - 1\n',
+      '   let bgcolor = ', bgcolor, '\n',
+      '   for ln in sourcelines {\n',
+      '     if number {\n',
+      '       lnum = lnum + 1\n',
+      '       blocks = blocks + box(width: if start + sourcelines.len() > 999 { 30pt } else { 24pt }, text(', lineNumberFill, '[ #lnum ]))\n',
+      '     }\n',
+      '     blocks = blocks + ln + EndLine()\n',
+      '   }\n',
+      '   block(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks)\n',
+      '}\n',
+    }))
+  end
+
   return {
     Pandoc = function(pandoc0)
       local brand = param('brand')
@@ -228,6 +253,27 @@ function render_typst_brand_yaml()
           end
         end
 
+        -- When Skylighting is active, Pandoc emits #Skylighting() calls instead
+        -- of raw code blocks, so #show raw.where(block: true) rules above don't
+        -- apply. Override the Skylighting function to include proper block styling.
+        -- Use brand background-color if set, otherwise fall back to theme bgcolor.
+        local highlightMethod = PANDOC_WRITER_OPTIONS.highlight_method
+        if monospaceBlock and next(monospaceBlock)
+            and type(highlightMethod) == 'table' then
+          local bgcolor = monospaceBlock['background-color']
+          if not bgcolor then
+            local themeBg = highlightMethod['background-color']
+            if type(themeBg) == 'string' then
+              bgcolor = 'rgb("' .. themeBg .. '")'
+            end
+          end
+          if bgcolor then
+            local lineNumberColor = type(highlightMethod['line-number-color']) == 'string'
+              and highlightMethod['line-number-color'] or nil
+            emit_skylighting_override(bgcolor, lineNumberColor)
+          end
+        end
+
         local link = _quarto.modules.brand.get_typography(brandMode, 'link')
         local primaryColor = _quarto.modules.brand.get_color(brandMode, 'primary')
         if link and next(link) or primaryColor then
@@ -250,6 +296,24 @@ function render_typst_brand_yaml()
           }))
         end
       end
+
+      -- Non-brand Skylighting override: even without a brand, the Pandoc-generated
+      -- Skylighting function lacks width/inset/radius. Override it using the
+      -- theme's own background color from PANDOC_WRITER_OPTIONS.highlight_method.
+      -- Skip if brand already emitted an override above.
+      local highlightMethod = PANDOC_WRITER_OPTIONS.highlight_method
+      local monospaceBlock = brand and brand.processedData
+        and _quarto.modules.brand.get_typography(brandMode, 'monospace-block')
+      local brandAlreadyOverrode = monospaceBlock and next(monospaceBlock)
+        and type(highlightMethod) == 'table'
+      if not brandAlreadyOverrode and type(highlightMethod) == 'table' then
+        local themeBg = highlightMethod['background-color']
+        if type(themeBg) == 'string' then
+          local lineNumberColor = type(highlightMethod['line-number-color']) == 'string'
+            and highlightMethod['line-number-color'] or nil
+          emit_skylighting_override('rgb("' .. themeBg .. '")', lineNumberColor)
+        end
+      end
     end,
     Meta = function(meta)
       local brand = param('brand')
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/_brand.yml
new file mode 100644
index 0000000000..a56e5aa3b4
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/_brand.yml
@@ -0,0 +1,10 @@
+color:
+  palette:
+    code-fg: "#2d3748"
+
+typography:
+  monospace-block:
+    color: code-fg
+    weight: 500
+    size: 10pt
+    line-height: 1.5
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/brand-monospace-block-no-bg.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/brand-monospace-block-no-bg.qmd
new file mode 100644
index 0000000000..3e6bf00c79
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block-no-bg/brand-monospace-block-no-bg.qmd
@@ -0,0 +1,33 @@
+---
+title: Brand Monospace Block without Background Color
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting is active (default)
+          - "#Skylighting"
+          - "#KeywordTok"
+          # Brand monospace-block text properties emitted as show rules
+          - '^#show raw\.where\(block: true\): set text\(weight: 500, size: 10pt, fill: rgb\("#2d3748"\), \)$'
+          - '^#show raw\.where\(block: true\): set par\(leading: 0\.75em\)$'
+          # Even without brand bg, Skylighting override uses theme bgcolor
+          # so that width/inset/radius are applied
+          - 'let bgcolor = rgb\("#f1f3f5"\)'
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+        # No brand background-color show rule (not configured)
+        - ['^#show raw\.where\(block: true\): set block\(fill:']
+---
+
+Brand sets monospace-block color, weight, size, and line-height but NOT
+background-color. The Skylighting override should still be emitted using
+the theme's background color so that code blocks get proper width/inset/radius.
+
+```python
+def hello():
+    x = 1 + 2
+    print(f"result: {x}")
+```
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/_brand.yml
new file mode 100644
index 0000000000..b2335f9f42
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/_brand.yml
@@ -0,0 +1,12 @@
+color:
+  palette:
+    code-bg: "#1e1e2e"
+    code-fg: "#cdd6f4"
+
+typography:
+  monospace-block:
+    color: code-fg
+    background-color: code-bg
+    size: 10pt
+    weight: 400
+    line-height: 1.6
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/brand-monospace-block.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/brand-monospace-block.qmd
new file mode 100644
index 0000000000..0af4184a34
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-block/brand-monospace-block.qmd
@@ -0,0 +1,34 @@
+---
+title: Brand Monospace Block with Skylighting
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting is active (default)
+          - "#Skylighting"
+          - "#KeywordTok"
+          # Brand monospace-block properties are emitted as show rules
+          # (still useful for idiomatic mode fallback)
+          - '^#show raw\.where\(block: true\): set text\(weight: 400, size: 10pt, fill: rgb\("#cdd6f4"\), \)$'
+          - '^#show raw\.where\(block: true\): set block\(fill: rgb\("#1e1e2e"\)\)$'
+          - '^#show raw\.where\(block: true\): set par\(leading: 0\.85em\)$'
+          # Quarto-generated Skylighting override with brand bg and proper block styling
+          - 'let bgcolor = rgb\("#1e1e2e"\)'
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+        # Should NOT have raw fenced blocks
+        - ["```python"]
+---
+
+Brand monospace-block options should apply to Skylighting code blocks.
+
+```python
+def hello():
+    x = 1 + 2
+    print(f"result: {x}")
+```
+
+Inline code like `hello()` should NOT get monospace-block styling.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/_brand.yml
new file mode 100644
index 0000000000..cdf5d53d08
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/_brand.yml
@@ -0,0 +1,19 @@
+color:
+  palette:
+    block-bg: "#f0f4f8"
+    block-fg: "#1a365d"
+    inline-bg: "#fed7d7"
+    inline-fg: "#9b2c2c"
+
+typography:
+  monospace-block:
+    color: block-fg
+    background-color: block-bg
+    size: 11pt
+    weight: 400
+    line-height: 1.5
+  monospace-inline:
+    color: inline-fg
+    background-color: inline-bg
+    weight: 600
+    size: 0.9rem
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/brand-monospace-idiomatic.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/brand-monospace-idiomatic.qmd
new file mode 100644
index 0000000000..61fdd2315f
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-idiomatic/brand-monospace-idiomatic.qmd
@@ -0,0 +1,38 @@
+---
+title: Brand Monospace with Idiomatic Highlighting
+format:
+  typst:
+    keep-typ: true
+    syntax-highlighting: idiomatic
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Idiomatic = native typst highlighting = raw fenced code blocks
+          - "```python"
+          # Brand monospace-block properties (these target raw.where(block: true)
+          # which DOES match native/idiomatic code blocks)
+          - '^#show raw\.where\(block: true\): set text\(weight: 400, size: 11pt, fill: rgb\("#1a365d"\), \)$'
+          - '^#show raw\.where\(block: true\): set block\(fill: rgb\("#f0f4f8"\)\)$'
+          - '^#show raw\.where\(block: true\): set par\(leading: 0\.75em\)$'
+          # Brand monospace-inline properties
+          - '^#show raw\.where\(block: false\): set text\(weight: 600, size: 0\.9em, fill: rgb\("#9b2c2c"\), \)$'
+          - '^#show raw\.where\(block: false\): content => highlight\(fill: rgb\("#fed7d7"\), content\)$'
+        # Should NOT have Skylighting tokens
+        - ["#Skylighting", "#KeywordTok"]
+---
+
+With idiomatic highlighting, brand monospace-block properties apply directly
+to `raw.where(block: true)` which matches native Typst code blocks.
+This is the baseline that "just works."
+
+Here's `inline code` with brand styling.
+
+```python
+def hello():
+    x = 1 + 2
+    print(f"result: {x}")
+```
+
+Both inline and block code should reflect brand styling.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/_brand.yml
new file mode 100644
index 0000000000..d6378b3b31
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/_brand.yml
@@ -0,0 +1,25 @@
+color:
+  palette:
+    mono-base-fg: "#2d3748"
+    block-bg: "#edf2f7"
+    inline-bg: "#fefcbf"
+
+typography:
+  fonts:
+    - source: google
+      family: Fira Code
+      weight: [300, 400, 700]
+  # Base monospace: family and weight inherited by both inline and block
+  monospace:
+    family: Fira Code
+    weight: 400
+    size: 0.85rem
+    color: mono-base-fg
+  # Block overrides only background-color; inherits family, weight, size, color
+  monospace-block:
+    background-color: block-bg
+    line-height: 1.5
+  # Inline overrides only background-color and weight; inherits family, size, color
+  monospace-inline:
+    background-color: inline-bg
+    weight: 700
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/brand-monospace-inheritance.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/brand-monospace-inheritance.qmd
new file mode 100644
index 0000000000..4df3e99795
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inheritance/brand-monospace-inheritance.qmd
@@ -0,0 +1,41 @@
+---
+title: Brand Monospace Inheritance with Skylighting
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting is active (default)
+          - "#Skylighting"
+          # Base monospace family applied via codefont
+          - 'codefont: \("Fira Code",\),$'
+          # monospace-block inherits color from base monospace, gets its own bg
+          - '^#show raw\.where\(block: true\): set text\(weight: 400, size: 0\.85em, fill: rgb\("#2d3748"\), \)$'
+          - '^#show raw\.where\(block: true\): set block\(fill: rgb\("#edf2f7"\)\)$'
+          - '^#show raw\.where\(block: true\): set par\(leading: 0\.75em\)$'
+          # Quarto Skylighting override with inherited brand bg
+          - 'let bgcolor = rgb\("#edf2f7"\)'
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+          # monospace-inline overrides weight to 700, inherits color, gets its own bg
+          - '^#show raw\.where\(block: false\): set text\(weight: 700, size: 0\.85em, fill: rgb\("#2d3748"\), \)$'
+          - '^#show raw\.where\(block: false\): content => highlight\(fill: rgb\("#fefcbf"\), content\)$'
+        - ["```python"]
+---
+
+This tests that `monospace` base properties are properly inherited by
+`monospace-block` and `monospace-inline`, with specific overrides taking
+precedence.
+
+Inline code: `hello()` and `x + y` should use bold weight (700) from
+monospace-inline override, with yellow background.
+
+```python
+# Block code inherits base weight (400) with blue-gray background
+def greet(name):
+    return f"Hello, {name}!"
+```
+
+More `inline()` code references.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/_brand.yml
new file mode 100644
index 0000000000..3439f1a88e
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/_brand.yml
@@ -0,0 +1,11 @@
+color:
+  palette:
+    inline-bg: "#fff3cd"
+    inline-fg: "#664d03"
+
+typography:
+  monospace-inline:
+    color: inline-fg
+    background-color: inline-bg
+    weight: 600
+    size: 0.85rem
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/brand-monospace-inline.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/brand-monospace-inline.qmd
new file mode 100644
index 0000000000..11c54d441d
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-inline/brand-monospace-inline.qmd
@@ -0,0 +1,28 @@
+---
+title: Brand Monospace Inline with Skylighting
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting is active for code blocks
+          - "#Skylighting"
+          # Brand monospace-inline properties are emitted
+          - '^#show raw\.where\(block: false\): set text\(weight: 600, size: 0\.85em, fill: rgb\("#664d03"\), \)$'
+          - '^#show raw\.where\(block: false\): content => highlight\(fill: rgb\("#fff3cd"\), content\)$'
+        # No monospace-block show rules (not configured)
+        - ['^#show raw\.where\(block: true\): set block\(fill:']
+---
+
+Inline code like `hello()` and `x + y` should get brand monospace-inline styling
+(background highlight, custom color, weight, size).
+
+```python
+def hello():
+    print("world")
+```
+
+Code blocks use Skylighting and should not be affected by monospace-inline settings.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/_brand.yml b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/_brand.yml
new file mode 100644
index 0000000000..9d7a1041f6
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/_brand.yml
@@ -0,0 +1,18 @@
+color:
+  palette:
+    block-bg: "#282a36"
+    block-fg: "#f8f8f2"
+    inline-bg: "#e8e0f0"
+    inline-fg: "#6c3483"
+
+typography:
+  monospace-block:
+    color: block-fg
+    background-color: block-bg
+    weight: 400
+    size: 9pt
+    line-height: 1.4
+  monospace-inline:
+    color: inline-fg
+    background-color: inline-bg
+    weight: 500
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/brand-monospace-with-theme.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/brand-monospace-with-theme.qmd
new file mode 100644
index 0000000000..e209b351b3
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/brand-monospace-with-theme/brand-monospace-with-theme.qmd
@@ -0,0 +1,41 @@
+---
+title: Brand Monospace with Explicit Theme
+format:
+  typst:
+    keep-typ: true
+    syntax-highlighting: espresso
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting with espresso theme
+          - "#Skylighting"
+          - "#KeywordTok"
+          # Brand monospace-block properties (show rules for idiomatic fallback)
+          - '^#show raw\.where\(block: true\): set text\(weight: 400, size: 9pt, fill: rgb\("#f8f8f2"\), \)$'
+          - '^#show raw\.where\(block: true\): set block\(fill: rgb\("#282a36"\)\)$'
+          - '^#show raw\.where\(block: true\): set par\(leading: 0\.65em\)$'
+          # Quarto Skylighting override uses brand bg (not espresso theme bg)
+          - 'let bgcolor = rgb\("#282a36"\)'
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+          # Brand monospace-inline properties
+          - '^#show raw\.where\(block: false\): set text\(weight: 500, fill: rgb\("#6c3483"\), \)$'
+          - '^#show raw\.where\(block: false\): content => highlight\(fill: rgb\("#e8e0f0"\), content\)$'
+        - ["```python"]
+---
+
+This tests that brand monospace options and an explicit syntax-highlighting theme
+can coexist. The theme controls token colors; the brand controls the block
+container styling.
+
+Here's some `inline code` with brand styling.
+
+```python
+def fibonacci(n):
+    if n <= 1:
+        return n
+    return fibonacci(n - 1) + fibonacci(n - 2)
+```
+
+And more `inline()` references.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-default.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-default.qmd
new file mode 100644
index 0000000000..144b1964e3
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-default.qmd
@@ -0,0 +1,34 @@
+---
+title: Skylighting Default Style
+format:
+  typst:
+    keep-typ: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Default highlighting uses Skylighting (arrow theme)
+          - "#Skylighting"
+          - "#KeywordTok"
+          - "#let EndLine"
+          # Quarto override with proper block styling and arrow theme bgcolor
+          - 'let bgcolor = rgb\("#f1f3f5"\)'
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+        - ["```python"]
+---
+
+Default Skylighting (no explicit theme, no brand). This tests the baseline
+behavior that code blocks should have proper styling.
+
+```python
+def hello():
+    print("world")
+```
+
+```r
+x <- 1 + 1
+print(x)
+```
+
+And some `inline code` that should use default styling.
diff --git a/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-line-numbers.qmd b/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-line-numbers.qmd
new file mode 100644
index 0000000000..af2fe7e9f3
--- /dev/null
+++ b/tests/docs/smoke-all/typst/syntax-highlighting/skylighting-line-numbers.qmd
@@ -0,0 +1,31 @@
+---
+title: Skylighting with Line Numbers
+format:
+  typst:
+    keep-typ: true
+    syntax-highlighting: tango
+    code-line-numbers: true
+_quarto:
+  tests:
+    typst:
+      ensureTypstFileRegexMatches:
+        -
+          # Skylighting with line numbering enabled
+          - '#Skylighting\(number: true'
+          - "#KeywordTok"
+          # Quarto override with proper block styling
+          - 'block\(fill: bgcolor, width: 100%, inset: 8pt, radius: 2pt, blocks\)'
+        - ["```python"]
+---
+
+Code blocks with line numbers should render properly with Skylighting.
+
+```python
+def fibonacci(n):
+    if n <= 1:
+        return n
+    a, b = 0, 1
+    for _ in range(n):
+        a, b = b, a + b
+    return a
+```