fix(markdown): restore paragraph spacing in assistant messages

Wire the unused --markdown-paragraph-spacing token to .markdown-content p so
adjacent paragraphs no longer collapse into a single visual line (Tailwind
preflight had zeroed the default <p> margins).

The renderer wraps each block in a display:contents [data-md-block] element, so
the message-level last-child margin nullifiers target the wrapper, not the
paragraph. Drop the trailing margin on the last paragraph of the last block
directly so messages don't gain extra bottom space. Keep tool-card and
reasoning markdown compact.

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+- Chat: adjacent paragraphs in assistant messages now render with a visible gap instead of collapsing into a single visual line. Reasoning and tool-card markdown stay compact, and messages don't gain trailing space at the bottom.
+
 ## [1.13.1] - 2026-06-17
 
 - Chat: inline math delimiters no longer incorrectly treat currency amounts like `$50` as LaTeX math expressions — only `$$...$$` display math and `\(...\)` inline math are recognized.

packages/ui/src/index.css

@@ -938,6 +938,30 @@ html:not(.dark) .chat-scroll {
   line-height: inherit;
 }
 
+/* Restore paragraph block spacing inside markdown content. The
+   --markdown-paragraph-spacing token existed but was never wired, so Tailwind
+   preflight's zeroed <p> margins left adjacent paragraphs collapsed into one
+   visual line. */
+.markdown-content p {
+  margin: 0 0 var(--markdown-paragraph-spacing) 0;
+}
+
+/* The markdown renderer wraps each block in a display:contents [data-md-block]
+   element, so the message-level [&_.markdown-content>*:last-child]:mb-0
+   nullifiers target the wrapper (where margin is ignored), not the paragraph.
+   Drop the trailing margin on the last paragraph of the last block directly so
+   messages don't gain extra space at the bottom. */
+.markdown-content > [data-md-block]:last-child p:last-child {
+  margin-bottom: 0;
+}
+
+/* Tool cards (code size) and reasoning (meta size, dimmed) are intentionally
+   compact — keep their paragraphs tight, matching prior behavior. */
+.markdown-content.markdown-tool p,
+.markdown-content.markdown-reasoning p {
+  margin-bottom: 0;
+}
+
 /* Tool markdown should render at code size to match tool card typography. */
 .markdown-content.markdown-tool {
   font-size: var(--text-code) !important;

packages/ui/src/styles/design-system.css

@@ -328,7 +328,7 @@
   --markdown-blockquote-border: var(--markdown-blockquote-border);
 
   /* Markdown spacing defaults */
-  --markdown-paragraph-spacing: 0.35rem;
+  --markdown-paragraph-spacing: 0.75rem;
   --markdown-heading-primary-top: 0.75rem;
   --markdown-heading-primary-bottom: 0.35rem;
   --markdown-heading-secondary-top: 0.6rem;