ACH Language Support

Language server and editing support for NACHA ACH files in VS Code.

ACH (Automated Clearing House) files are the fixed-width, 94-character-per-line format used for electronic banking transactions across the US financial system. This extension provides full Language Server Protocol support — diagnostics, hover, completions, formatting, navigation, and more — so you can inspect, edit, and validate ACH files directly in your editor.

Features

Diagnostics — Real-time parse and validation errors with 20+ configurable rules covering check digits, routing numbers, batch totals, addenda counts, and more
Hover — Field descriptions, format, column range, and current value; contextual info for amounts (cents → dollars), routing numbers (valid/invalid), dates, SEC codes, and transaction codes
Completions — Record type templates (1/5/6/7/8/9), SEC codes (PPD, CCD, IAT, WEB, …), transaction codes, service class codes, addenda types, and file ID modifiers
Code Actions — Quick fixes to recalculate check digits, pad short lines, set record size, fix batch/file control totals, fix service class codes, fix dates/times; "Recalculate All" source action
Formatting — Document and range formatting via the ach-ts library; pads short lines in range selections
Go to Definition — Jump between batch headers and controls, entries and their batch headers, addenda and their entries
Find References — Find all entries/addenda in a batch, sibling entries, or linked header/control records
CodeLens — Inline stats above file header (batch/entry counts, DR/CR totals), batch headers (entry counts, totals), and entries with addenda (addenda count)
Document Links — Clickable routing numbers linking to FedACH lookup
Selection Range — Smart expand selection: field → record → batch → file
Workspace Symbols — Search company names, entry names, and batch descriptions across all open ACH files
Document Symbols — Outline view showing file header → batches → entries → addenda hierarchy with amounts and names
Semantic Tokens — Per-field syntax highlighting using 8 token types (keyword, number, string, type, variable, comment, parameter, enum) with adjacency-aware coloring
Folding — Collapse batches (header through control) and entries with their addenda records
Inlay Hints — Cursor-aware field labels displayed inline; toggle with Ctrl+Alt+H
ACH Explorer — Tree view in the sidebar showing file structure; click a node to jump to its line
Preview Panel — Structured viewer with view, edit, search, and diff modes; auto-opens when you open an ACH file
Field Decorations — Zebra-striped alternating backgrounds to visually separate fields on each line
Field Navigation — Ctrl+Arrow moves the cursor between fields instead of words; Ctrl+Up/Down moves between sections (batches, file header/control)
Status Bar — Batch/entry counts, debit/credit totals, and error/warning counts at a glance
Context Menu — Select Field and Copy Field Value from the right-click menu
Snippets — 10 templates for record types, complete batches, and full ACH files
Merge Files — Merge multiple ACH files into as few files as possible using NACHA rules
Export/Import JSON — Round-trip ACH files through JSON using ach-ts serialization
Create New File — Scaffold a new ACH file with today's date
Validate All — Batch-validate every .ach file in the workspace with a progress report

Installation

Search for ACH Language Support in the VS Code Extensions view, or install from the command line:

code --install-extension christopherdavenport.ach-lsp

To install from a .vsix file:

code --install-extension ach-lsp-0.1.0.vsix

Keyboard Shortcuts

Command	Windows / Linux	macOS
Open Preview	`Ctrl+Shift+V`	`Cmd+Shift+V`
Move to Next Field	`Ctrl+Right`	`Alt+Right`
Move to Previous Field	`Ctrl+Left`	`Alt+Left`
Select to Next Field	`Ctrl+Shift+Right`	`Alt+Shift+Right`
Select to Previous Field	`Ctrl+Shift+Left`	`Alt+Shift+Left`
Move to Next Section	`Ctrl+Down`	`Alt+Down`
Move to Previous Section	`Ctrl+Up`	`Alt+Up`
Select to Next Section	`Ctrl+Shift+Down`	`Alt+Shift+Down`
Select to Previous Section	`Ctrl+Shift+Up`	`Alt+Shift+Up`
Toggle Inlay Hints	`Ctrl+Alt+H`	`Cmd+Alt+H`

Commands

All commands are available via the Command Palette (Ctrl+Shift+P):

ACH: Open Preview — Open the structured preview panel
ACH: Toggle Inlay Hints — Show or hide inline field labels
ACH: Toggle Field Separators — Show or hide zebra-striped field backgrounds
ACH: Select Field — Select the field at the cursor position
ACH: Copy Field Value — Copy the trimmed value of the field at cursor
ACH: Validate All ACH Files — Validate every .ach file in the workspace
ACH: Export to JSON — Export the active ACH file to JSON format
ACH: Import from JSON — Import a JSON file and convert to ACH
ACH: Merge ACH Files — Merge multiple workspace ACH files into one
ACH: Create New ACH File — Scaffold a new ACH file with today's date
ACH: Move Cursor to Next Field / Previous Field
ACH: Select to Next Field / Previous Field
ACH: Move to Next Section / Previous Section
ACH: Select to Next Section / Previous Section

Configuration

General

Setting	Type	Default	Description
`ach.maxNumberOfProblems`	number	`1000`	Maximum number of problems reported by the server
`ach.trace.server`	string	`"off"`	Traces communication between VS Code and the language server (`off`, `messages`, `verbose`)
`ach.fieldSeparators`	boolean	`true`	Show visual separators between fields in the editor
`ach.autoOpenPreview`	boolean	`true`	Automatically open the preview panel when opening an ACH file

Validation

All validation settings are booleans defaulting to false. Set to true to relax the corresponding rule.

Setting	Description
`ach.validation.skipAll`	Disable all validation
`ach.validation.allowZeroBatches`	Allow files with no batches
`ach.validation.customTraceNumbers`	Allow trace numbers that don't match ODFI
`ach.validation.requireABAOrigin`	Require valid ABA routing number as origin
`ach.validation.bypassOriginValidation`	Skip origin field validation
`ach.validation.bypassDestinationValidation`	Skip destination field validation
`ach.validation.allowMissingFileHeader`	Allow files without a File Header record
`ach.validation.allowMissingFileControl`	Allow files without a File Control record
`ach.validation.bypassCompanyIdentificationMatch`	Skip batch header/control company ID match
`ach.validation.customReturnCodes`	Allow non-standard return codes in Addenda 99
`ach.validation.unequalServiceClassCode`	Allow mismatched service class codes
`ach.validation.allowUnorderedBatchNumbers`	Allow non-ascending batch numbers
`ach.validation.allowInvalidCheckDigit`	Skip routing number check digit validation
`ach.validation.unequalAddendaCounts`	Allow addenda count mismatches
`ach.validation.preserveSpaces`	Retain trailing whitespace during parsing
`ach.validation.allowInvalidAmounts`	Allow malformed amount fields
`ach.validation.allowZeroEntryAmount`	Allow entries with zero dollar amounts
`ach.validation.allowSpecialCharacters`	Allow non-alphanumeric characters in fields
`ach.validation.allowEmptyIndividualName`	Allow blank individual name fields
`ach.validation.bypassBatchValidation`	Skip all batch-level validation
`ach.validation.skipFileCreationValidation`	Skip file creation date validation
`ach.validation.skipBatchHeaderCompanyValidation`	Skip company name/ID validation in batch headers

Development

Prerequisites: Node.js 20+

git clone https://github.com/christopherdavenport/ach-lsp.git
cd ach-lsp
npm install
npm run compile

Press F5 in VS Code to launch the Extension Development Host with the extension loaded.

npm test          # Run server tests (vitest)
npm run lint      # Lint client and server
npm run package   # Build .vsix for distribution

License

MIT

ACH

Christopher Davenport