diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7e0abc18..a2819429 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@
 - Syntax highlighting for Python files using uv as script runner in shebang #3689 (@janlarres)
 
 ## Bugfixes
+- Avoid repeated scans of long lines in Log syntax highlighting, see #3876 (@Matei02355)
 - Fix `--list-languages` respecting `--paging=never`, see #3828 (@cyphercodes)
 - Fix `--sanitize` passing through the bidi control characters U+200E, U+200F and U+061C, see #3862 (@lenamonj)
 - `--strip-ansi`: also strip 8-bit C1 introducers (U+0090, U+0098, U+009B, U+009D, U+009E, U+009F) and DCS/SOS/PM/APC sequence bodies, which previously passed through. See #3729 (@curious-rabbit)
diff --git a/assets/syntaxes/02_Extra/log.sublime-syntax b/assets/syntaxes/02_Extra/log.sublime-syntax
index 0ce01f10..329da39d 100644
--- a/assets/syntaxes/02_Extra/log.sublime-syntax
+++ b/assets/syntaxes/02_Extra/log.sublime-syntax
@@ -38,22 +38,41 @@ contexts:
       scope: markup.underline.link.scheme.log
       push: url-host
   log_level_lines:
-    - match: (?=.*{{error}})
+    # Prevent retrying each lookahead at every position.
+    - match: ^(?=.*{{error}})
       push:
         - error_line_meta
         - main_pop_at_eol
-    - match: (?=.*{{warning}})
+    - match: ^(?=.*{{warning}})
       push:
         - warning_line_meta
         - main_pop_at_eol
-    - match: (?=.*{{info}})
+    - match: ^(?=.*{{info}})
       push:
         - info_line_meta
         - main_pop_at_eol
-    - match: (?=.*{{debug}})
+    - match: ^(?=.*{{debug}})
       push:
         - debug_line_meta
         - main_pop_at_eol
+  # For syntaxes that embed Log after consuming a prefix. Call this context once.
+  log_level_lines_at_current_position:
+    - match: (?=.*{{error}})
+      set:
+        - error_line_meta
+        - main_pop_at_eol
+    - match: (?=.*{{warning}})
+      set:
+        - warning_line_meta
+        - main_pop_at_eol
+    - match: (?=.*{{info}})
+      set:
+        - info_line_meta
+        - main_pop_at_eol
+    - match: (?=.*{{debug}})
+      set:
+        - debug_line_meta
+        - main_pop_at_eol
   log_levels:
     - match: '{{error}}'
       scope: markup.error.log
diff --git a/assets/syntaxes/02_Extra/syslog.sublime-syntax b/assets/syntaxes/02_Extra/syslog.sublime-syntax
index 01ed58db..7cc9580b 100644
--- a/assets/syntaxes/02_Extra/syslog.sublime-syntax
+++ b/assets/syntaxes/02_Extra/syslog.sublime-syntax
@@ -50,6 +50,17 @@ contexts:
     - match: (?=\])
       pop: true
   text:
+    - include: text_special
+    - match: ''
+      set: classify_log_text
+  classify_log_text:
+    - include: scope:text.log#log_level_lines_at_current_position
+    - match: ''
+      set: text_body
+  text_body:
+    - include: text_special
+    - include: scope:text.log
+  text_special:
     - match: $
       pop: true
     - match: '<\w+>'
@@ -62,4 +73,3 @@ contexts:
       escape: \)$
       escape_captures:
         0: punctuation.section.block.end.syslog
-    - include: scope:text.log