diff --git a/.gitignore b/.gitignore
index 96034e514a..dc1a4b17c7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@ book
 book.toml
 
 ci/date-check/target/
+ci/semantic-line-breaks/target/
 
 # Generated by check-in.sh
 pulls.json
diff --git a/ci/semantic-line-breaks/Cargo.lock b/ci/semantic-line-breaks/Cargo.lock
new file mode 100644
index 0000000000..b84ce4a23c
--- /dev/null
+++ b/ci/semantic-line-breaks/Cargo.lock
@@ -0,0 +1,193 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aho-corasick"
+version = "0.7.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e37cfd5e7657ada45f742d6e99ca5788580b5c529dc78faf11ece6dc702656f"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "anyhow"
+version = "1.0.62"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1485d4d2cc45e7b201ee3767015c96faa5904387c9d87c6efdd0fb511f12d305"
+
+[[package]]
+name = "bstr"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba3569f383e8f1598449f1a423e72e99569137b47740b1da11ef19af3d5c3223"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "51887d4adc7b564537b15adcfb307936f8075dfcd5f00dde9a9f1d29383682bc"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+]
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0a1e17342619edbc21a964c2afbeb6c820c6a2560032872f397bb97ea127bd0a"
+dependencies = [
+ "aho-corasick",
+ "bstr",
+ "fnv",
+ "log",
+ "regex",
+]
+
+[[package]]
+name = "ignore"
+version = "0.4.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "713f1b139373f96a2e0ce3ac931cd01ee973c3c5dd7c40c0c2efe96ad2b6751d"
+dependencies = [
+ "crossbeam-utils",
+ "globset",
+ "lazy_static",
+ "log",
+ "memchr",
+ "regex",
+ "same-file",
+ "thread_local",
+ "walkdir",
+ "winapi-util",
+]
+
+[[package]]
+name = "lazy_static"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "abb12e687cfb44aa40f41fc3978ef76448f9b6038cad6aef4259d3c095a2382e"
+dependencies = [
+ "cfg-if",
+]
+
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "074864da206b4973b84eb91683020dbefd6a8c3f0f38e054d93954e891935e4e"
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c4eb3267174b8c6c2f654116623910a0fef09c4753f8dd83db29c48a0df988b"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3f87b73ce11b1619a3c6332f45341e0047173771e8b8b73f87bfeefb7b56244"
+
+[[package]]
+name = "same-file"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
+[[package]]
+name = "semantic-line-breaks"
+version = "0.0.0"
+dependencies = [
+ "anyhow",
+ "ignore",
+ "regex",
+]
+
+[[package]]
+name = "thread_local"
+version = "1.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5516c27b78311c50bf42c071425c560ac799b11c30b31f87e3081965fe5e0180"
+dependencies = [
+ "once_cell",
+]
+
+[[package]]
+name = "walkdir"
+version = "2.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "808cf2735cd4b6866113f648b791c6adc5714537bc222d9347bb203386ffda56"
+dependencies = [
+ "same-file",
+ "winapi",
+ "winapi-util",
+]
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/ci/semantic-line-breaks/Cargo.toml b/ci/semantic-line-breaks/Cargo.toml
new file mode 100644
index 0000000000..656b4a2153
--- /dev/null
+++ b/ci/semantic-line-breaks/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "semantic-line-breaks"
+version = "0.0.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1"
+ignore = "0.4"
+
+[dependencies.regex]
+version = "1"
+features = ["pattern"]
diff --git a/ci/semantic-line-breaks/src/main.rs b/ci/semantic-line-breaks/src/main.rs
new file mode 100644
index 0000000000..b8504e7fe1
--- /dev/null
+++ b/ci/semantic-line-breaks/src/main.rs
@@ -0,0 +1,121 @@
+use std::{env, fs, process};
+
+use anyhow::Result;
+use ignore::Walk;
+use regex::Regex;
+
+fn main() -> Result<()> {
+    let mut args = env::args();
+    if args.len() == 1 {
+        eprintln!("error: expected root Markdown directory as CLI argument");
+        process::exit(1);
+    }
+    let root_dir = args.nth(1).unwrap();
+    for result in Walk::new(root_dir) {
+        let entry = result?;
+        if entry.file_type().expect("no stdin").is_dir() {
+            continue;
+        }
+        let path = entry.path();
+        if let Some(extension) = path.extension() {
+            if extension != "md" {
+                continue;
+            }
+        } else {
+            continue;
+        }
+        let old = fs::read_to_string(path)?;
+        let new = comply(&old)?;
+        if new != old {
+            fs::write(path, new)?;
+        }
+    }
+    Ok(())
+}
+
+fn comply(content: &str) -> Result<String> {
+    let content: Vec<_> = content.lines().map(|line| line.to_owned()).collect();
+    let mut new_content = content.clone();
+    let mut new_n = 0;
+    let mut in_code_block = false;
+    let split_re = Regex::new(r"(\.|\?|;|!)\s+")?;
+    let ignore_re = Regex::new(r"(\d\.|\-|\*|r\?)\s+")?;
+    for (n, line) in content.iter().enumerate() {
+        if n != 0 {
+            new_n += 1;
+        }
+        if ignore_re.is_match(line) {
+            continue;
+        }
+        let line = line.trim_end();
+        if line.is_empty() {
+            continue;
+        }
+        // not eol
+        if line.contains("e.g.") {
+            continue;
+        }
+        // not eol
+        if line.contains("i.e.") {
+            continue;
+        }
+        // tables
+        if line.contains(" | ") {
+            continue;
+        }
+        // code blocks
+        if line.starts_with("```") {
+            if in_code_block {
+                in_code_block = false;
+            } else {
+                in_code_block = true;
+                continue;
+            }
+        }
+        if in_code_block {
+            continue;
+        }
+        if split_re.is_match(line) {
+            let indent = line.find(|ch: char| !ch.is_whitespace()).unwrap();
+            let new_lines: Vec<_> = line
+                .split_inclusive(&split_re)
+                .map(|portion| format!("{:indent$}{}", "", portion.trim()))
+                .collect();
+            new_content.splice(new_n..new_n + 1, new_lines.clone());
+            new_n += new_lines.len() - 1;
+        }
+    }
+    Ok(new_content.join("\n") + "\n")
+}
+
+#[test]
+fn test() {
+    let original = "\
+# some heading
+
+must! be; split? now.
+1. ignore numbered
+ignore | tables
+ignore e.g. and i.e. for realsies
+```
+some code. block
+```
+some more text.
+";
+    let reformatted = "\
+# some heading
+
+must!
+be;
+split?
+now.
+1. ignore numbered
+ignore | tables
+ignore e.g. and i.e. for realsies
+```
+some code. block
+```
+some more text.
+";
+    assert_eq!(comply(original).unwrap(), reformatted);
+}