EncodingMCP MCPサーバー

EncodingMCP

Let AI coding assistants read and edit text files in any encoding — without corrupting them.

AI coding tools (GitHub Copilot, Claude Code, Cursor, Windsurf, Claude Desktop, …) assume that every text file is UTF-8. A great deal of real-world source code is not: files in Windows-1252, ISO-8859-x, UTF-16 and other encodings are the norm in codebases that predate UTF-8 or that target Windows tooling. When an LLM reads such a file as UTF-8 and writes it back, every æ, ø, å, ü, € or smart quote is silently destroyed.

EncodingMCP is an MCP server that puts an encoding-aware layer between the assistant and the disk. It detects the encoding of each file (BOM, strict UTF-8 validation, codepage heuristics), hands the assistant clean UTF-8, and converts back to the file's own encoding on write — preserving BOM and line-ending style. Encodings are remembered per file in a .encoding-mcp.json sidecar, and explicit overrides can be set per file or per pattern.

It is language-agnostic. Typical candidates:

• C / C++ / C# / Java projects with Windows-1252 or ISO-8859-1 sources
• Classic VB6, VBScript and VBA exports
• PHP, Perl and Python 2 code written before UTF-8 became the default
• COBOL, RPG, Fortran and other mainframe or legacy sources
• SQL scripts, .ini, .reg, .bat/.cmd, .properties and other config and resource files
• Localisation files, CSV exports, HTML/XML without a declaration
• UTF-16 files produced by Windows tools
• Delphi and C++Builder projects (.pas, .dfm, .dpr, .cpp, .h)

Who is this for?

• Anyone who uses an AI coding assistant on a codebase that is not (entirely) UTF-8 and wants to stop reviewing diffs full of ø and ä.
• Teams maintaining legacy Windows applications where converting the whole repository to UTF-8 is not an option (toolchain, merge history, or policy).
• Developers working with UTF-16 or BOM-sensitive files that other tools silently rewrite.
• Delphi/C++Builder developers — the project originated there, and the binary-DFM guard is one example of how non-text formats are protected.

The server is a single standalone Windows executable with no runtime dependencies. You do not need Delphi to use it — only to build it from source.

Quick Start

Option A: Download prebuilt EXE (no Delphi required)

1. Go to Releases
2. Download EncodingMCP.exe
3. Place it somewhere accessible (e.g. C:\Tools\EncodingMCP.exe)
4. Configure your MCP client (see Installation)

Note (Windows): After downloading you may need to right-click the file → Properties → "Unblock", as Windows marks files downloaded from the internet. Alternatively: Unblock-File -Path <path> in PowerShell.

Option B: Build from source

git clone https://github.com/thvedel/EncodingMCP.git
cd EncodingMCP
build.bat

The result is a standalone .exe under build\Win64\Release\.

Contents

Path	Description
EncodingMCP.dpr	Main program (console application)
src/MCP.*.pas	Stdio transport, JSON-RPC 2.0, server dispatcher
src/Encoding.*.pas	Detection, heuristics, workspace, cache
src/FileIO.*.pas	Encoding-aware file reading/writing
src/Tools.*.pas	MCP tools (read/write/detect/override)
tests/	DUnitX test suite
build.bat	Build script (main program + tests)

Requirements

To use: Windows x64. Nothing else — it is a single standalone .exe.

To build from source:

• Delphi 12.3 (Studio 23.0) or Delphi 13.1 (Studio 37.0) — uses only RTL (System.JSON, System.SysUtils, System.Classes, System.IOUtils, System.Generics.*)

build.bat automatically searches for Delphi in standard locations and selects the newest available version:

Delphi version	Studio number	Path to rsvars.bat
13.1	37.0	C:\Program Files (x86)\Embarcadero\Studio\37.0\bin\rsvars.bat
12.3	23.0	C:\Program Files (x86)\Embarcadero\Studio\23.0\bin\rsvars.bat

If your installation is elsewhere, set the RSVARS environment variable before running build.bat.

Build

build.bat

Building is done via msbuild /t:Rebuild against the two .dproj files — always a full build, so stale DCUs can never hide errors. Output goes to build\$(Platform)\$(Config)\ — by default build\Win64\Release\. Change PLATFORM/CONFIG in build.bat to build differently (e.g. Win32 or Debug).

You can also open EncodingMCP.dproj directly in RAD Studio and build from there.

Installation

The server communicates via stdio (stdin/stdout JSON-RPC). Any MCP client that supports stdio transport can use it. Below are examples for the most popular clients.

In all examples, replace <PATH> with the absolute path to EncodingMCP.exe (either downloaded from Releases or built locally). Backslashes in JSON must be escaped as \\.

Workspace roots

The server only serves files inside its allowed workspace roots (see Security). Without configuration it falls back to the workspace containing the directory the client starts it in, which is often not your project. Declare the roots explicitly in the client config instead.

There are two equivalent ways; both accept any number of roots:

1. args — one array element per root:

   "command": "<PATH>",
   "args": ["C:\\Projects\\MyApp", "C:\\Projects\\Shared", "D:\\Components"]
   

2. env — the ENCODING_MCP_WORKSPACE variable with a semicolon-separated list:

   "command": "<PATH>",
   "args": [],
   "env": {
     "ENCODING_MCP_WORKSPACE": "C:\\Projects\\MyApp;C:\\Projects\\Shared;D:\\Components"
   }
   

If both are present, the roots are combined. Each root must be an absolute path to an existing directory — anything else is skipped with a warning on stderr. Sub-directories are included automatically, so list the top-level folders only. The first root is the default for set_encoding_override when no directory is given. Roots advertised by the MCP client during initialize are added to the configured set as well.

GitHub Copilot

Copilot CLI (also used by IDE integrations that embed the CLI, e.g. RAD Studio): edit %USERPROFILE%\.copilot\mcp-config.json for a global setup, or .mcp.json in the repository root for a per-project setup:

{
  "mcpServers": {
    "encoding-bridge": {
      "type": "local",
      "command": "C:\\Tools\\EncodingMCP.exe",
      "args": ["C:\\Projects\\MyApp", "C:\\Projects\\Shared"],
      "tools": ["*"]
    }
  }
}

VS Code (Copilot Chat agent mode): edit .vscode\mcp.json in the workspace, or add the same block under "mcp" → "servers" in the user settings.json:

{
  "servers": {
    "encoding-bridge": {
      "type": "stdio",
      "command": "C:\\Tools\\EncodingMCP.exe",
      "args": [],
      "env": {
        "ENCODING_MCP_WORKSPACE": "${workspaceFolder};C:\\Projects\\Shared"
      }
    }
  }
}

VS Code expands ${workspaceFolder} to the open folder, so the same file can be committed and used by the whole team. Restart the Copilot session (CLI) or run MCP: Restart Server (VS Code) after changing the config.

Windsurf / Codeium

Edit %USERPROFILE%\.codeium\windsurf\mcp_config.json:

{
  "mcpServers": {
    "encoding-bridge": {
      "command": "<PATH>",
      "args": [],
      "disabled": false
    }
  }
}

Restart Windsurf after the change.

Claude Code

claude mcp add encoding-bridge "<PATH>"

Claude Desktop

Edit the config file:

• Windows: %APPDATA%\Claude\claude_desktop_config.json
• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "encoding-bridge": {
      "command": "<PATH>",
      "args": []
    }
  }
}

Cursor

Edit .cursor/mcp.json in your project (or the global config):

{
  "mcpServers": {
    "encoding-bridge": {
      "command": "<PATH>",
      "args": []
    }
  }
}

Other MCP clients

Any client that supports MCP stdio transport can launch the EXE directly. Protocol: JSON-RPC 2.0 over stdin/stdout. Server name: encoding-bridge.

Debug logging

Set the environment variable ENCODING_MCP_LOG_LEVEL=debug for detailed logging on stderr. Supported levels: debug, info (default), warning, error.

Available tools

read_text_file

Reads a text file with automatic encoding detection and returns the content as UTF-8 along with metadata.

Parameter	Type	Description
path	string	Absolute path to the file
head	integer	Optional: only first N lines
tail	integer	Optional: only last N lines
startLine	integer	Optional: 1-based line number to start reading from. Use with endLine for a specific range. Takes priority over head/tail.
endLine	integer	Optional: 1-based line number to stop at (inclusive). Use with startLine for a specific range. Takes priority over head/tail.
contextLines	integer	Optional: extra lines to include before and after the startLine/endLine range. Only applies when a line range is specified.
metadataOnly	boolean	Optional: if true, return only metadata (encoding, lineEnding, totalLines, etc.) without file content.
searchText	string	Optional: search for lines containing this text (case-insensitive). Returns matching lines with line-number prefixes, separated by ... between non-contiguous regions. Use contextLines for surrounding context. Takes priority over head/tail/startLine/endLine.

Output (JSON in content[0].text):

{
  "path": "...",
  "encoding": "Windows-1252",
  "hasBom": false,
  "lineEnding": "CRLF",
  "confidence": 0.95,
  "source": "detected",
  "format": "text",
  "fromCache": false,
  "bytesRead": 1234,
  "totalLines": 42,
  "lineNumberStart": 1,
  "returnedLines": 42,
  "matchCount": 3,
  "content": "#include \"legacy.h\" ..."
}

• source tells where the encoding came from: bom, fileOverride, patternOverride or detected.
• format is text. Binary files that merely look like text are refused instead of being mangled; for example a Delphi form stored in binary format is rejected with an error and format: "binary-dfm".
• For a pure-ASCII file the response also contains writeRecommendation: "Windows-1252" and a note: ASCII (even with high confidence) only means that no byte above 0x7F exists, so the codepage cannot be determined. See Encoding policy.

write_text_file

Writes UTF-8 content to a file in the correct encoding. If the file exists, its encoding is re-checked on disk before every write (changes made by the IDE, git or other tools are respected), and per-file and pattern overrides apply even if the file has never been read. New files default to UTF-8 with BOM. Every write holds an exclusive lock on the file (see Concurrency).

Parameter	Type	Description
path	string	Absolute path
content	string	UTF-8 content
encoding	string	Optional target encoding (UTF-8, Windows-1252, ...). Changing only the encoding keeps the existing line endings; the BOM is kept, added when switching from an 8-bit encoding to Unicode, and dropped for 8-bit encodings.
lineEnding	string	Optional (CRLF/LF/CR). Default preserves existing.
hasBom	boolean	Optional. Default preserves existing (true for new UTF files). true on a pure-ASCII file writes UTF-8 with BOM.
createIfMissing	boolean	Default true
dryRun	boolean	Optional: report encoding, BOM, line ending, upgrades and warnings without writing
force	boolean	Optional (default false): allow replacing a binary DFM with text

Output (JSON in content[0].text):

{
  "path": "...",
  "encoding": "Windows-1252",
  "hasBom": false,
  "lineEnding": "CRLF",
  "bytesWritten": 1234,
  "created": false,
  "source": "detected",
  "previousEncoding": "ASCII",
  "upgradedFrom": "ASCII",
  "warnings": ["..."]
}

encoding is always the encoding actually written. source is bom, fileOverride, patternOverride, detected, explicit (the encoding parameter) or default (new file). previousEncoding is the encoding of the existing file on disk. upgradedFrom and warnings appear only when the encoding had to change. dryRun: true is echoed when set.

Encoding policy

Applies to write_text_file, write_text_files and edit_text_file:

• ASCII upgrade: a pure-ASCII file has no byte that reveals its codepage. When non-ASCII characters are written to it, the file becomes Windows-1252 (the Delphi default) — never UTF-8 without BOM, which Delphi would misread as ANSI (ø instead of ø). The response reports upgradedFrom: "ASCII" and a warning. Use an override, encoding or hasBom: true to get UTF-8 with BOM instead.
• Unrepresentable characters: if the target encoding cannot represent a character (e.g. an emoji in Windows-1252), nothing is written. The error response contains unrepresentableChars (count) and sample; there is no silent ? substitution.
• Binary DFM guard: an existing Delphi form stored in binary format is never overwritten with text unless force: true is given. read_text_file and edit_text_file refuse such files with format: "binary-dfm".

edit_text_file

Edits a text file by search/replace or line-range replacement, preserving the file's original encoding, BOM, and line-ending style. The encoding policy applies. The edit is rejected with reason: "modified" if another process changed the file between the read and the write (see Concurrency).

Parameter	Type	Description
path	string	Absolute path to the file (must exist)
oldText	string	Text to find and replace. Leave empty for range mode.
newText	string	Replacement text (required)
startLine	integer	Optional: 1-based start line for range replacement
endLine	integer	Optional: 1-based end line (inclusive) for range replacement
maxReplacements	integer	Optional: max replacements (default 1). 0 = unlimited.
dryRun	boolean	Optional: if true, compute the result without writing to disk.
edits	array	Optional: array of atomic edits (see below). Overrides top-level oldText/newText.

Modes:

• Search/replace: provide oldText + newText. If maxReplacements is 1 (default) and multiple matches exist, an error is returned with the match count.
• Range replacement: provide startLine + endLine + newText with empty oldText. The line range is replaced entirely; an empty newText deletes the lines including their line breaks. startLine = total lines + 1 appends at the end of the file; a larger startLine is an error. A trailing line break in newText does not add an extra blank line.
• The two modes are mutually exclusive per edit: oldText together with startLine/endLine is rejected instead of silently ignoring the range.
• Multi-edit (atomic): provide an edits array. If any edit fails, nothing is written. Each item supports oldText, newText, startLine, endLine, maxReplacements.

Line endings: oldText and newText may use \n; both are normalized to the file's line-ending style before matching and inserting. For files with mixed line endings the dominant style is used.

Multi-edit semantics:

• All line ranges refer to the original file, regardless of their order in the array. They are applied from the end of the file towards the beginning, so one range edit never shifts the line numbers of another.
• Overlapping ranges, and two edits appending at the same position, are rejected.
• Search/replace edits are applied afterwards, in array order, to the result of the range edits.
• If an oldText would match a different number of times before and after the range edits, the order is ambiguous and the call is rejected.
• Error messages that concern one specific edit are prefixed with Edit N:. Errors about the call as a whole (overlapping ranges, empty edits array) have no prefix.

Output (JSON in content[0].text):

{
  "path": "...",
  "encoding": "Windows-1252",
  "hasBom": false,
  "lineEnding": "CRLF",
  "bytesWritten": 1234,
  "replacements": 1,
  "changed": true,
  "diff": "@@ -1,3 +1,3 @@\n context\n-old line\n+new line\n context\n"
}

upgradedFrom and warnings are added when the encoding policy changed the encoding; dryRun: true is echoed when set. replacements counts search/replace matches that were replaced plus 1 for each range edit.

Diff format: the diff field is only present when changed is true. It is a unified diff with 3 lines of context; nearby changes share one hunk, distant changes get separate hunks (@@ -a,b +c,d @@), so unchanged lines between two edits are not repeated. Diff lines are always separated by \n, whatever the file's line endings — the file itself is written in its own style. A line whose terminator differs from the file's style is marked with [LF], [CR] or [CRLF], and a missing final line break is shown as \ No newline at end of file.

read_text_files

Reads multiple files in a single call. Reduces MCP round-trips during cross-file refactoring. Each file entry supports the same parameters as read_text_file. Errors for individual files are reported inline without aborting the batch.

Parameter	Type	Description
files	array	Array of file specifications (see below)

Each entry in files:

Parameter	Type	Description
path	string	Absolute path to the file (required)
head	integer	Optional: first N lines
tail	integer	Optional: last N lines
startLine	integer	Optional: 1-based start line
endLine	integer	Optional: 1-based end line (inclusive)
contextLines	integer	Optional: extra context lines
metadataOnly	boolean	Optional: skip content
searchText	string	Optional: case-insensitive line search

Output (JSON in content[0].text):

{
  "totalFiles": 3,
  "succeeded": 2,
  "failed": 1,
  "results": [
    { "path": "...", "encoding": "UTF-8", "content": "...", ... },
    { "path": "...", "encoding": "Windows-1252", "content": "...", ... },
    { "path": "...", "error": "File not found: ..." }
  ]
}

write_text_files

Writes multiple files in a single call with encoding-aware conversion. Each file entry can specify its own encoding, lineEnding, and hasBom options. Errors for individual files are reported inline without aborting the batch.

Parameter	Type	Description
files	array	Array of file specifications (see below)

Each entry in files:

Parameter	Type	Description
path	string	Absolute path to the file (required)
content	string	UTF-8 content to write (required)
encoding	string	Optional: target encoding (UTF-8, Windows-1252, etc.)
lineEnding	string	Optional: CRLF, LF, or CR
hasBom	boolean	Optional: write a BOM
createIfMissing	boolean	Optional (default true): create if not exists
dryRun	boolean	Optional: report the result of the write without writing
force	boolean	Optional (default false): allow replacing a binary DFM with text

Output (JSON in content[0].text):

{
  "totalFiles": 2,
  "succeeded": 2,
  "failed": 0,
  "results": [
    { "path": "...", "encoding": "UTF-8", "bytesWritten": 123, "created": true, ... },
    { "path": "...", "encoding": "Windows-1252", "bytesWritten": 456, "created": false, ... }
  ]
}

list_files

Lists files in a directory recursively, optionally filtered by glob pattern. Returns relative paths from the specified directory.

Parameter	Type	Description
path	string	Absolute path to the directory to list (must be within workspace)
pattern	string	Optional: glob pattern to filter files (e.g. *.c, *.sql, *.pas)

Lock and temporary files of writes in progress (*.lock, *.<pid>-<guid>.tmp) are never listed.

Output (JSON in content[0].text):

{
  "path": "C:/Projects/MyApp",
  "totalFiles": 12,
  "files": ["src/legacy.c", "scripts/report.sql", "config.ini", "Forms/Main.pas", ...]
}

detect_encoding

Analyses the whole file (no size limit) with exactly the same resolution as read_text_file (BOM, overrides, detection), so both tools always report the same encoding. Returns format, encoding, hasBom, confidence, lineEnding, source, bytesRead and the candidate scores, plus writeRecommendation/note for pure-ASCII files. A binary DFM is reported with format: "binary-dfm" and a note instead of an encoding.

Parameter	Type
path	string

set_encoding_override

Sets or removes a manual encoding override for one file or for a pattern.

Parameter	Type	Description
path	string	Absolute path of a single file (either path or pattern)
pattern	string	File-name pattern (*.pas) or path pattern relative to the workspace root (src/**/*.dfm)
directory	string	Optional, pattern only: a directory inside the workspace that selects the workspace root. Defaults to the first workspace root.
encoding	string	Encoding to apply. Required unless remove is true.
remove	boolean	If true, remove the override instead of setting it

• Patterns without / match the file name in any folder. Patterns with / match the path relative to the workspace root and support *, ? and **. Other glob syntax is rejected with an error instead of being accepted silently.
• Pattern overrides are stored in the outermost sidecar and therefore apply to the whole repository, including subfolders with their own .dproj. A matching pattern in a nearer sidecar takes precedence.
• With remove, a pattern is removed from every sidecar between directory and the outermost root; the response lists them in removedFrom.
• Overrides take precedence over detection, but a BOM always wins.
• The response contains sidecar, root, matches and appliesTo, so it is clear where the override was stored and which files it covers.