fix(parser): preserve link destinations during streaming

.changeset/bright-links-preserve.md

@@ -0,0 +1,5 @@
+---
+"markdown-to-jsx": patch
+---
+
+Link destinations now preserve punctuation such as underscores while markdown is streamed, preventing generated links from being changed or broken.

lib/src/parse.streaming.spec.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'bun:test'
 import { compiler as htmlCompiler } from './html.ts'
 import { parser } from './parse.ts'
+import type { MarkdownToJSX } from './types.ts'
 
 describe('Streaming optimization - inline code', () => {
   it('should remove incomplete inline code backtick and content', () => {
@@ -36,6 +37,28 @@ describe('Streaming optimization - inline code', () => {
   })
 })
 
+describe('Streaming optimization - link destinations', () => {
+  it('should preserve underscores in complete link destinations', () => {
+    const url = 'https://example.com/search?geoShape=KLUv_WCPBdUbAFa'
+    const ast = parser(`[View results](${url})`, {
+      optimizeForStreaming: true,
+    })
+    const paragraph = ast[0] as MarkdownToJSX.ParagraphNode
+    const link = paragraph.children[0] as MarkdownToJSX.LinkNode
+
+    expect(link.target).toBe(url)
+  })
+
+  it('should still suppress delimiters in incomplete links', () => {
+    const html = htmlCompiler('[View_results](https://example.com/search?x=1', {
+      optimizeForStreaming: true,
+    })
+
+    expect(html).not.toContain('_')
+    expect(html).toContain('Viewresults')
+  })
+})
+
 describe('Streaming optimization - code blocks', () => {
   it('should show incomplete code block content', () => {
     const html = htmlCompiler('```js\nconst x = 1', {

lib/src/parse.ts

@@ -5306,7 +5306,7 @@ function _skipLinkOrImage(s: string, i: number, e: number): number {
 
   // j is now past the ]
   if (j >= e) {
-    return j // just [text]
+    return i // shortcut links may not resolve, so keep their text parseable
   }
 
   const nextChar = s.charCodeAt(j)
@@ -5329,7 +5329,7 @@ function _skipLinkOrImage(s: string, i: number, e: number): number {
       }
       j++
     }
-    return j
+    return parenDepth === 0 ? j : i
   }
 
   // Reference link: [text][ref]
@@ -5346,10 +5346,10 @@ function _skipLinkOrImage(s: string, i: number, e: number): number {
       }
       j++
     }
-    return j
+    return depth2 === 0 ? j : i
   }
 
-  return j // shortcut link [text]
+  return i // shortcut links may not resolve, so keep their text parseable
 }
 
 /** Scan strikethrough ~~text~~ */
@@ -7224,6 +7224,17 @@ function parseInline(
     var lastTilDbl = -1
     for (var ei = 0; ei < content.length; ei++) {
       var ec = content.charCodeAt(ei)
+      // Link destinations are opaque to emphasis parsing. Skip complete links
+      // and images so punctuation such as `_` in a URL is not treated as a
+      // streaming delimiter. Incomplete links return their start position from
+      // _skipLinkOrImage and continue through the normal suppression logic.
+      if (ec === $.CHAR_BRACKET_OPEN) {
+        var linkEnd = _skipLinkOrImage(content, ei, content.length)
+        if (linkEnd > ei) {
+          ei = linkEnd - 1
+          continue
+        }
+      }
       if (ec === $.CHAR_ASTERISK) {
         if (
           ei + 1 < content.length &&