feat(mojibake): new rule MD083 for mojibake detection

README.md

@@ -52,7 +52,7 @@ Python linting, rumdl brings similar speed and developer experience improvements
 It offers:
 
 - ⚡️ **Built for speed** with Rust - significantly faster than alternatives
-- 🔍 **<!-- RULE_COUNT -->76<!-- /RULE_COUNT --> lint rules** covering common Markdown issues
+- 🔍 **<!-- RULE_COUNT -->77<!-- /RULE_COUNT --> lint rules** covering common Markdown issues
 - 🛠️ **Automatic formatting** with `--fix` for files and stdin/stdout
 - 📦 **Zero dependencies** - single binary with no runtime requirements
 - 🔧 **Highly configurable** with TOML-based config files
@@ -526,7 +526,7 @@ The action ref (`rvben/rumdl@v0`) selects the GitHub Action version, while the o
 
 ## Rules
 
-rumdl implements <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> lint rules for Markdown files. Here are some key rule categories:
+rumdl implements <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> lint rules for Markdown files. Here are some key rule categories:
 
 | Category       | Description                              | Example Rules       |
 | -------------- | ---------------------------------------- | ------------------- |

docs/comparison.md

@@ -13,7 +13,7 @@ For detailed comparisons with specific tools, see:
 
 | Tool                  | Type          | Language | Rules                                     | Auto-fix | Flavors | Config format           | Plugins      | LSP |
 | --------------------- | ------------- | -------- | ----------------------------------------- | -------- | ------- | ----------------------- | ------------ | --- |
-| **rumdl**             | Lint + Format | Rust     | <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> | Yes      | 9       | TOML, JSON, YAML        | No           | Yes |
+| **rumdl**             | Lint + Format | Rust     | <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> | Yes      | 9       | TOML, JSON, YAML        | No           | Yes |
 | **markdownlint-cli**  | Lint          | Node.js  | 53                                        | Yes      | No      | JSON, JSONC, YAML, TOML | Yes (JS)     | No  |
 | **markdownlint-cli2** | Lint          | Node.js  | 53                                        | Yes      | No      | JSONC, YAML, JS         | Yes (JS)     | No  |
 | **remark-lint**       | Lint          | Node.js  | ~80 (via presets)                         | No       | No      | JS, JSON, YAML          | Yes (JS)     | No  |
@@ -33,7 +33,7 @@ cover common cases. No built-in auto-fix for lint violations (remark itself can
 
 **mado** is a Rust-based linter with 38 rules (33 stable, 5 unstable). It has no auto-fix and no plugin system.
 
-**rumdl** implements all 53 markdownlint rules plus <!-- RULE_COUNT_ADDITIONAL -->23<!-- /RULE_COUNT_ADDITIONAL --> additional rules (<!-- RULE_COUNT -->76<!-- /RULE_COUNT --> total). It supports
+**rumdl** implements all 53 markdownlint rules plus <!-- RULE_COUNT_ADDITIONAL -->24<!-- /RULE_COUNT_ADDITIONAL --> additional rules (<!-- RULE_COUNT -->77<!-- /RULE_COUNT --> total). It supports
 auto-fix for most rules and includes rules not found in other tools, such as relative link validation (MD057), footnote checks (MD066-MD068), nested code fence detection (MD070), and TOC validation
 (MD073).
 
@@ -136,7 +136,7 @@ Cold start benchmark on the Rust Book (478 Markdown files), measured with [hyper
 
 **Notes:**
 
-- **mado** is faster in cold-start benchmarks because it does less work per file: fewer rules (38 vs <!-- RULE_COUNT -->76<!-- /RULE_COUNT -->), no fix generation, and no flavor detection.
+- **mado** is faster in cold-start benchmarks because it does less work per file: fewer rules (38 vs <!-- RULE_COUNT -->77<!-- /RULE_COUNT -->), no fix generation, and no flavor detection.
   The gap reflects feature surface area, not implementation quality.
 - **rumdl** supports result caching (`rumdl check` without `--no-cache`), which skips unchanged files on subsequent runs — typically under 50 ms, faster than mado's cold start.
 - **pymarkdown** performs well for a Python tool due to its efficient scanner architecture.
@@ -147,5 +147,5 @@ Cold start benchmark on the Rust Book (478 Markdown files), measured with [hyper
 
 - [Comparison with markdownlint](markdownlint-comparison.md) — detailed rule-by-rule comparison and migration guide
 - [Comparison with mdformat](mdformat-comparison.md) — formatting feature comparison and migration guide
-- [Rules Reference](rules.md) — complete list of rumdl's <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules
+- [Rules Reference](rules.md) — complete list of rumdl's <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules
 - [Markdown Flavors](flavors.md) — flavor configuration and per-rule adjustments

docs/getting-started/quickstart.md

@@ -145,5 +145,5 @@ Each line shows:
 ## Next Steps
 
 - [CLI Commands](../usage/cli.md) - Full command reference
-- [Rules Reference](../rules.md) - Explore all <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules
+- [Rules Reference](../rules.md) - Explore all <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules
 - [Configuration](../global-settings.md) - Advanced configuration options

docs/index.md

@@ -16,7 +16,7 @@ icon: lucide/file-check
 
     [:octicons-arrow-right-24: Benchmarks](#performance)
 
--   :mag:{ .lg .middle } **<!-- RULE_COUNT -->76<!-- /RULE_COUNT --> lint rules**
+-   :mag:{ .lg .middle } **<!-- RULE_COUNT -->77<!-- /RULE_COUNT --> lint rules**
 
     ---
 
@@ -76,7 +76,7 @@ With intelligent caching, subsequent runs are even faster - rumdl only re-lints
 ## Features
 
 - :zap: **Built for speed** with Rust - significantly faster than alternatives
-- :mag: **<!-- RULE_COUNT -->76<!-- /RULE_COUNT --> lint rules** covering common Markdown issues
+- :mag: **<!-- RULE_COUNT -->77<!-- /RULE_COUNT --> lint rules** covering common Markdown issues
 - :wrench: **Automatic formatting** with `--fix` for files and stdin/stdout
 - :package: **Zero dependencies** - single binary with no runtime requirements
 - :gear: **Highly configurable** with TOML-based config files
@@ -100,7 +100,7 @@ With intelligent caching, subsequent runs are even faster - rumdl only re-lints
 
 -   [:octicons-book-24: **Rules Reference**](rules.md)
 
-    Explore all <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> linting rules with examples.
+    Explore all <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> linting rules with examples.
 
 -   [:octicons-gear-24: **Configuration**](global-settings.md)
 

docs/markdownlint-comparison.md

@@ -10,22 +10,22 @@ rumdl offers **high markdownlint compatibility with intentional differences** wh
 
 - **Performance**: rumdl is significantly faster (30-100x in many cases) thanks to Rust and intelligent caching
 - **Rule Coverage**: All 53 markdownlint rules are implemented, with a small number of intentional behavioral differences documented below
-- **Unique Features**: <!-- RULE_COUNT_ADDITIONAL -->23<!-- /RULE_COUNT_ADDITIONAL --> additional rules (MD057, MD061-<!-- RULE_MAX -->MD082<!-- /RULE_MAX -->), built-in LSP server, VS Code extension, 6 Markdown flavors
+- **Unique Features**: <!-- RULE_COUNT_ADDITIONAL -->24<!-- /RULE_COUNT_ADDITIONAL --> additional rules (MD057, MD061-<!-- RULE_MAX -->MD083<!-- /RULE_MAX -->), built-in LSP server, VS Code extension, 6 Markdown flavors
 - **Configuration**: Automatic markdownlint config discovery and conversion
 
 ## Rule Coverage
 
 ### Implemented Rules
 
-rumdl implements **<!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules total**: all 53 markdownlint rules plus <!-- RULE_COUNT_ADDITIONAL -->23<!-- /RULE_COUNT_ADDITIONAL --> unique rules.
+rumdl implements **<!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules total**: all 53 markdownlint rules plus <!-- RULE_COUNT_ADDITIONAL -->24<!-- /RULE_COUNT_ADDITIONAL --> unique rules.
 
 **Markdownlint-compatible rules (53):** All markdownlint rules are implemented with full compatibility. See the [Rules Reference](rules.md) for the complete list.
 
 **Note:** Rule numbers MD001-MD060 have gaps (MD002, MD006, MD008, MD015-MD017 were never implemented in markdownlint). rumdl maintains these gaps for compatibility.
 
 ### Rules Unique to rumdl
 
-rumdl implements <!-- RULE_COUNT_ADDITIONAL -->23<!-- /RULE_COUNT_ADDITIONAL --> additional rules not found in markdownlint:
+rumdl implements <!-- RULE_COUNT_ADDITIONAL -->24<!-- /RULE_COUNT_ADDITIONAL --> additional rules not found in markdownlint:
 
 | Rule   | Name                           | Description                                                |
 | ------ | ------------------------------ | ---------------------------------------------------------- |

docs/md083.md

@@ -0,0 +1,70 @@
+# MD083 - Detect mojibake due to encoding issues
+
+Aliases: `mojibake`
+
+**Disabled by default.** This rule is opt-in: enable it explicitly with
+`extend-enable`. There is no markdownlint equivalent; this is a rumdl-specific
+structure rule.
+
+## What this rule does
+
+Mojibake is text that appears corrupted because it was decoded using a wrong character encoding.
+
+This rule detects common Mojibake patterns, such as UTF-8 text that has been misread as Windows-1252 or ISO-8859-1.
+
+Examples of Mojibake include:
+
+- `Café` instead of `Café`
+- `–` instead of `–`
+- `’` instead of `’`
+
+## Why this matters
+
+Encoding problems may replace valid Unicode characters such as ✓, ©, §, or ✅ by weird uncommonly used characters such as ✓, ©, §, or ✅
+
+Such issues typically happen when several people work collaboratively using different editors, IDEs, OS and configurations.
+Detecting encoding problems early allows the team to identify the causes of the issues and to fix them before they spread.
+
+This rule uses regex-based detection for suspicious character sequences commonly associated with encoding issues.
+
+To fix existing issues in a documentation base, you can use tools such as [`ftfy`](https://github.com/rspeer/python-ftfy/) (in Python)
+or [`plsfix`](https://github.com/kevinhu/plsfix) (a reimplementation in Rust).
+
+## Examples
+
+### Incorrect
+
+```text
+# Café menu
+
+This line contains a broken dash – and a broken apostrophe ’.
+```
+
+### Correct
+
+```text
+# Café menu
+
+This line contains an en dash – and a typographic apostrophe ’.
+```
+
+## Configuration
+
+```toml
+[MD083]
+ignore = []
+ignore-code-blocks = true
+```
+
+- `ignore`: A list of exact mojibake sequences to ignore, such as `"–"` or `"’"`. Default: `[]`.
+- `ignore-code-blocks`: Whether to ignore findings inside code, meaning fenced and indented code blocks as well as inline code spans. Default: `true`.
+
+Example:
+
+```toml
+[MD083]
+ignore = ["–", "’"]
+ignore-code-blocks = false
+```
+
+With this configuration, MD083 skips findings for those exact mojibake sequences and also reports mojibake inside code blocks and inline code spans.

docs/mdformat-comparison.md

@@ -7,7 +7,7 @@ This document compares rumdl and mdformat, focusing on their formatting capabili
 Both tools format Markdown files, but serve different purposes:
 
 - **mdformat**: Pure formatter focused on consistent Markdown output
-- **rumdl**: Combined linter and formatter with <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules plus formatting
+- **rumdl**: Combined linter and formatter with <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules plus formatting
 
 **Key Differences:**
 
@@ -16,7 +16,7 @@ Both tools format Markdown files, but serve different purposes:
 | Primary purpose | Formatting only           | Linting + formatting            |
 | Language        | Python                    | Rust                            |
 | Performance     | Good                      | Faster (native + caching)       |
-| Linting rules   | ❌                        | ✅ <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules                     |
+| Linting rules   | ❌                        | ✅ <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules                     |
 | Extensibility   | Plugin ecosystem          | Built-in flavors                |
 | CommonMark      | Strict compliance         | Strict compliance               |
 
@@ -47,7 +47,7 @@ Both tools format Markdown to a consistent style:
 
 ### Linting (rumdl only)
 
-rumdl provides <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> linting rules that mdformat does not have:
+rumdl provides <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> linting rules that mdformat does not have:
 
 - **Broken link detection** (MD051, MD052, MD057)
 - **Accessibility checks** (MD045 - image alt text)
@@ -299,7 +299,7 @@ style = "atx"
 | Capability              | mdformat           | rumdl                  |
 | ----------------------- | ------------------ | ---------------------- |
 | Markdown formatting     | ✅ Primary focus   | ✅ Via `rumdl fmt`     |
-| Markdown linting        | ❌                 | ✅ <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules            |
+| Markdown linting        | ❌                 | ✅ <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules            |
 | Performance             | Good               | Faster (native binary) |
 | Extended syntax         | Plugins            | Built-in flavors       |
 | Editor integration      | Basic              | LSP + VS Code          |

docs/rules.md

@@ -4,7 +4,7 @@
 
 ## Introduction
 
-rumdl implements <!-- RULE_COUNT -->76<!-- /RULE_COUNT --> rules for checking Markdown files. This document provides a comprehensive reference of all available rules, organized by category.
+rumdl implements <!-- RULE_COUNT -->77<!-- /RULE_COUNT --> rules for checking Markdown files. This document provides a comprehensive reference of all available rules, organized by category.
 Each rule has a brief description and a link to its detailed documentation.
 
 For information on global configuration settings (file selection, rule enablement, etc.), see the [Global Settings Reference](global-settings.md).
@@ -40,6 +40,7 @@ The following rules are **disabled by default** because they enforce opinionated
 | [MD074](md074.md) | MkDocs nav validation    | Requires `flavor = "mkdocs"` to activate                      |
 | [MD080](md080.md) | Heading anchor collision | Collisions are functional under platform auto-suffixing       |
 | [MD082](md082.md) | No empty sections        | Empty sections are sometimes intentional stubs                |
+| [MD083](md083.md) | Detect Mojibake          | Turn it on once you encounter encoding issues                 |
 
 ### Enabling Opt-in Rules
 

rules.json

@@ -764,5 +764,15 @@
     "fix": "Fix is not available.",
     "fix_availability": "None",
     "url": "https://rumdl.dev/md082/"
+  },
+  {
+    "code": "MD083",
+    "name": "mojibake",
+    "aliases": [],
+    "summary": "Detects common encoding issues (aka mojibake).",
+    "category": "other",
+    "fix": "Fix is not available.",
+    "fix_availability": "None",
+    "url": "https://rumdl.dev/md083/"
   }
 ]

src/config/registry.rs

@@ -261,6 +261,7 @@ pub static RULE_ALIAS_MAP: phf::Map<&'static str, &'static str> = phf::phf_map!
     "MD080" => "MD080",
     "MD081" => "MD081",
     "MD082" => "MD082",
+    "MD083" => "MD083",
 
     // Aliases (hyphen format)
     "HEADING-INCREMENT" => "MD001",
@@ -342,6 +343,7 @@ pub static RULE_ALIAS_MAP: phf::Map<&'static str, &'static str> = phf::phf_map!
     "HEADING-ANCHOR-COLLISION" => "MD080",
     "NO-EXCESSIVE-EMPHASIS" => "MD081",
     "NO-EMPTY-SECTIONS" => "MD082",
+    "MOJIBAKE" => "MD083",
 };
 
 /// Resolve a rule name alias to its canonical form with O(1) perfect hash lookup