Auto parts distribution breaks the assumptions ERPNext core makes about an Item. A brake pad is not one part number — it is an OE number, three aftermarket equivalents, two private-label SKUs, a supersession chain that has moved through four revisions, and a fitment list covering nine make/model/year/engine combinations. When a counter customer arrives with a plate number or a worn part in their hand, the parts advisor has seconds to find what actually fits, see what it supersedes to, check whether the shelf holds the superseded or the current revision, and quote a price that includes a refundable core charge. ERPNext gives you Item, Item Variant, Customer Item Code and Item Price — all useful, all one-to-one. It has no concept of an equivalence graph, no supersession direction, no vehicle-fitment dimension, and no core-charge liability tracked from the outbound invoice through to the returned casing. Distributors end up running the real catalog in a spreadsheet beside ERPNext, and the ERP becomes the place where stock is recorded after the fact rather than where the sale is made.

ECOSIRE builds this as a proper Frappe app — its own repository, its own module, installed with bench get-app and bench --site <site> install-app, versioned in git and upgradable independently of your ERPNext version. At its centre is a Part Cross Reference DocType that models equivalence as an explicit graph rather than a text field: each row links a source Item to a target Item or an external number and carries a reference type (OE, Aftermarket, Private Label, Competitor) plus confidence and source fields, so a match taken from a manufacturer catalog is distinguishable from one a counter clerk added. Part Supersession is deliberately a separate, directed DocType — superseded_by, effective date, and a bi-directional flag for parts that interchange both ways — because supersession is a chain, not an equivalence. A frappe.whitelist() method walks that chain to the current live revision while returning every intermediate node, so the counter can still sell what is physically on the shelf. Fitment lives in Vehicle Fitment (make, model, year range, engine, trim, position) with a composite index tuned for the lookup your counter actually performs.

The counter workflow is where the app earns its keep. A Counter Sale DocType wraps a fast, keyboard-first screen built as a Frappe page with client scripts over Sales Invoice, backed by whitelisted search methods that resolve a plate, VIN fragment, OE number or partial description into a ranked candidate list in one round trip — no per-keystroke DocType queries. Selecting a superseded part surfaces the chain inline with on-hand quantity per warehouse pulled from Bin, so substitution is a conscious decision rather than a surprise at picking. Core charges are modelled as a linked non-stock Item plus a Core Charge Ledger entry created in a Sales Invoice on_submit doc event registered in hooks.py; the returned casing is reconciled through a Credit Note flow that closes the ledger row, so outstanding core liability is a queryable number instead of a month-end reconstruction. Replenishment runs off a scheduler event that recomputes velocity classes (A/B/C by movement, not value alone) from Stock Ledger Entry over a rolling window, writes suggested levels back to Item Reorder, and produces a draft Material Request for human review rather than silently ordering stock.

Everything is built the way Frappe expects. Business logic sits in server scripts and controller hooks, not patched core files, so bench update stays safe. Permissions ship as role profiles — Parts Counter, Parts Manager, Warehouse — with field-level permissions, so a counter clerk can apply a supersession but not edit a cross-reference source. Every DocType is exposed over the Frappe REST API, and the performance-sensitive catalog lookups additionally have whitelisted methods with documented response shapes, so a workshop tablet, your website, or a trading partner's system can integrate without scraping the desk UI. Bulk catalog ingest runs through Frappe Data Import with a validation pass that reports unresolvable references instead of creating orphan records. We target Frappe/ERPNext v15 and v16, and confirm your exact version at scoping.

This is built to order, not downloaded. After you request a quotation we run a scoping call, agree the catalog shape, fitment data source, core-charge policy and counter workflow in writing, then build against your version. Typical delivery is one working week from confirmed scope, depending on catalog complexity and how much cross-reference data needs importing. You get the full source in a git repository you own, installation on staging first, a UAT window with your parts team, then production cutover with a documented rollback plan. Fixes and support are covered for an agreed window after go-live.