System Requirements Document for multi-vendor-shopping

1. Introduction

Product intent. multi-vendor-shopping is a multi-vendor shopping website, similar in kind to Shopify: one marketplace that hosts multiple independent vendors rather than a single seller. Vendors sell through the marketplace; shoppers browse and purchase products from multiple vendors; the party running the marketplace oversees vendor participation and the overall catalog so the marketplace stays usable.

Audience. Three active human roles use the product: Shopper, Vendor, and Marketplace Operator. The marketplace is an information problem before it is a shopping problem — thousands of listings from independent sellers, each needing to be scannable, comparable, and trustworthy — so the product is designed as a well-signed system rather than a boutique or a toy.

Scope of this document. This SRD specifies the current delivery: the marketplace catalog, the shopper purchase path, the vendor listing workspace, and the operator oversight workspaces, together with the identity continuity those journeys require. It preserves the explicit multi-vendor constraint and the explicit likeness reference to Shopify as inspiration only.

2. System Overview

multi-vendor-shopping is a first-party web application with a custom UI and application-owned identity. It delivers:

• A public marketplace entry that explains the multi-vendor model and directs shoppers toward product discovery.
• Self-service enrollment for shoppers and vendors, and returning verification for shoppers, vendors, and marketplace operators.
• A cross-vendor catalog with browsing and search, and a focused product destination where a shopper reviews an item and its vendor offer before adding it to the cart.
• A revisitable cart, a focused checkout that submits an order from the cart, and a returning orders destination for reviewing completed purchases and order status.
• A vendor workspace for creating and managing the vendor's own product listings and offers.
• Operator workspaces for reviewing and managing vendor participation and for reviewing and managing listings across vendors.

Actors. Three accepted human personas (Shopper, Vendor, Marketplace Operator) and supporting system processes (catalog persistence, cart and order persistence, authorization enforcement).

Ownership. All eleven destinations are application-owned custom pages. Identity is application-owned: shoppers and vendors enroll themselves; marketplace operator access is provisioned rather than self-enrolled. Backend persistence and authorization cover products, vendor participation, listings, carts, and orders.

Narrow exclusions. This document does not add adjacent commerce capabilities that the source did not accept — no payment-provider integration surface, no shipping-carrier integration, no reviews or ratings module, no messaging between shoppers and vendors, no promotions or discount engine, no analytics dashboard, and no theme or storefront-design editor. The Shopify reference is a likeness for a multi-vendor shopping website only; it is not an authoritative specification and supplies no product names, copy, facts, or capabilities.

2a. Product Interpretation and Delivery Boundary

Delivery. The marketplace is delivered as a first-party web application with custom UI. Every destination in the current contract is owned by the application itself; there is no provider-owned or external-only surface in the current delivery, and no headless delivery boundary is established.

Access ownership. Identity is application-owned. Anonymous visitors can reach the Landing page, the Products catalog, and Product Details, and can enroll through Sign Up or verify through Login. Cart, Checkout, Orders, Vendor Products, Vendors, and Listing Management are protected destinations that require an established identity; the interaction that establishes access to them lives on the anonymous Sign Up and Login surfaces, never inside the protected destinations themselves. Sign Up serves shoppers and vendors, who enroll themselves. Marketplace operator access is not self-enrolled: it is provisioned, and the Login surface verifies returning operators and routes them to their operator workspaces.

Current versus future. Everything specified in sections 2c through 5 is current. No future-horizon requirements were accepted in the authoritative thread; section 11 records the boundaries that keep the current scope from expanding.

2b. Source Content Inventory

Not applicable. The only reference directive (Shopify) declares feature_reference and domain_context uses with inspiration_only authority and is not a content_source; it supplies no verified factual entities, collections, fields, values, dates, contacts, links, or media references to inventory.

2c. Page Content and Component Coverage

Landing

• Information and state. Anonymous public entry. States the multi-vendor premise — many independent vendors, one marketplace — and directs visitors toward product discovery. No personalized or account state is shown.
• Primary action. Browse the marketplace (into Products). Supporting actions. Sign Up (enroll as shopper or vendor); Login (returning verification).
• Domain entities. Vendor (as a named participant in the marketplace), Product (as a discoverable listing).
• Component responsibilities. Hero field carrying the marketplace premise and the browse entry; a product-crop grid that previews real listings from multiple vendors; a vendor ticker naming participating vendors; entry controls for Sign Up and Login.
• States. Loading: hero and preview grid render immediately; preview tiles show placeholder modules while listings load. Empty: if no listings are available, the preview grid is replaced by a plain statement that the catalog is being populated, and the browse entry remains available. Success: premise, preview grid, and vendor ticker render. Error: if preview listings fail to load, the hero and both entry controls remain fully usable and the preview area shows a non-blocking notice. Recovery: the preview area offers a retry; the visitor can proceed to Products regardless.

Sign Up

• Information and state. Anonymous enrollment surface for shoppers and vendors. Collects the information needed to establish an application identity and the choice of enrolling as a shopper or as a vendor. No protected marketplace state is shown.
• Primary action. Create the account. Supporting action. Switch to Login for returning users.
• Domain entities. Account (identity), Role selection (shopper or vendor), Vendor participation record (created when the vendor path is chosen).
• Component responsibilities. Enrollment form; role selection between shopper and vendor; inline validation messaging; submission control; link to Login.
• States. Loading: submission control shows an in-progress state and blocks duplicate submission. Empty: the form starts blank with role unselected. Success: identity is established and the new actor is taken to the destination appropriate to the chosen role — a shopper to the catalog, a vendor to the vendor product workspace. Error: invalid or incomplete input is reported inline against the offending field with the entered values preserved; a duplicate-identity conflict is reported against the identity field with a route to Login. Recovery: the form remains populated after any error so the actor can correct and resubmit.

Login

• Information and state. Anonymous returning-verification surface for shoppers, vendors, and marketplace operators. Verifies an existing application identity and routes the actor to the workspace their role owns. No protected marketplace state is shown before verification.
• Primary action. Verify and continue. Supporting action. Switch to Sign Up for new shoppers and vendors.
• Domain entities. Account (identity), Role (shopper, vendor, marketplace operator).
• Component responsibilities. Credential form; submission control; error region; link to Sign Up; role-aware routing after successful verification.
• States. Loading: submission control shows an in-progress state and blocks duplicate submission. Empty: the form starts blank. Success: the actor is verified and routed by role — shopper to the catalog or their cart, vendor to Vendor Products, marketplace operator to Vendors. Error: failed verification is reported without disclosing which credential element was wrong; the identity field is preserved. Recovery: the actor can retry immediately, or use Sign Up if they have no account. Marketplace operators who have not been provisioned cannot self-enroll here; the surface states that operator access is provisioned.

Products

• Information and state. Anonymous-reachable marketplace catalog. Shows listings from multiple independent vendors in one browsable field, with each listing attributable to its vendor. Search and filter state is visible as applied state.
• Primary action. Open a listing (into Product Details). Supporting actions. Search the catalog; apply and clear filters; add a listing to the cart.
• Domain entities. Product, Listing (a vendor's offer of a product), Vendor, Price, Category.
• Component responsibilities. Search input; filter rail with applied-state chips; product field rendering listing modules; per-listing vendor attribution and price; pagination or progressive loading of further results; empty and error regions.
• States. Loading: the product field shows placeholder modules while results load; search and filters stay interactive. Empty: no results for the current query or filter set — the applied filters are shown as removable chips with a clear-all action, and the field states that no listings match. Success: matching listings render with vendor attribution and price. Error: a failed catalog request shows a non-blocking notice with a retry, and the last successfully loaded results remain visible. Recovery: retry reloads the field; clearing filters restores the unfiltered catalog.

Product Details

• Information and state. Focused destination for one listing. Shows the product, its price, and the vendor offer behind it, so the shopper can judge the item and its seller before committing.
• Primary action. Add to cart. Supporting actions. Adjust quantity; return to the catalog; open the vendor's other listings.
• Domain entities. Product, Listing, Vendor, Price, Quantity, Cart.
• Component responsibilities. Product media region; product information region; vendor attribution block; quantity control; add-to-cart control; cart confirmation feedback; related-listings region from the same vendor.
• States. Loading: media and information regions show placeholders. Empty: if the listing is no longer available, the page states that it is unavailable and offers a route back to the catalog and to the vendor's other listings. Success: the listing renders and add-to-cart confirms the item is in the cart with an updated cart count. Error: a failed add-to-cart reports the failure inline, leaves the quantity selection intact, and offers retry. Recovery: retry re-attempts the add; the shopper can continue browsing without losing their place.

Cart

• Information and state. Protected, revisitable shopping context. Shows the products the shopper selected from the multi-vendor catalog, grouped so each item's vendor is clear, with per-item and total pricing. Persists across sessions for the signed-in shopper.
• Primary action. Proceed to checkout. Supporting actions. Change item quantity; remove an item; return to the catalog to continue shopping.
• Domain entities. Cart, Cart item, Product, Listing, Vendor, Price, Quantity, Total.
• Component responsibilities. Item list with vendor attribution; quantity controls; remove controls; totals region; checkout entry; empty-cart region.
• States. Loading: the item list shows placeholders while the cart loads. Empty: the cart states that no items have been selected and offers a direct route into the catalog. Success: items render with vendor attribution, quantities, and totals, and the checkout entry is available. Error: a failed quantity change or removal reports inline against the affected item and restores the previous value; a failed cart load shows a retry. Recovery: retry reloads the cart; the shopper can continue shopping and return later without losing the cart.

Checkout

• Information and state. Protected, focused purchase workflow for submitting an order from the shopper's cart. Shows the order being placed — items, their vendors, quantities, and totals — and collects the information required to submit it.
• Primary action. Submit the order. Supporting action. Return to the cart to adjust items before submitting.
• Domain entities. Order, Order line, Cart, Product, Listing, Vendor, Price, Quantity, Total, Shopper.
• Component responsibilities. Order summary with per-vendor grouping; required purchase-information form; submission control; confirmation region; failure region.
• States. Loading: the order summary shows placeholders while the cart is read. Empty: if the cart is empty, checkout states that there is nothing to submit and routes the shopper to the catalog. Success: the order is submitted, a confirmation with the order reference is shown, and the cart is cleared. Error: a failed submission reports the failure without clearing the cart, preserves the entered information, and offers retry; validation problems are reported inline against the offending field. Recovery: retry resubmits the same order; the shopper can return to the cart, adjust, and re-enter checkout.

Orders

• Information and state. Protected returning destination for reviewing completed purchases and order status. Lists the shopper's submitted orders with their items, vendors, totals, and current status.
• Primary action. Open an order to review its detail. Supporting action. Return to the catalog to shop again.
• Domain entities. Order, Order line, Product, Listing, Vendor, Price, Quantity, Order status, Shopper.
• Component responsibilities. Order list with status per order; order detail region with per-vendor line grouping; empty-orders region; error region.
• States. Loading: the order list shows placeholders. Empty: the shopper has no orders yet — the page states this and offers a direct route into the catalog. Success: orders render with status and detail. Error: a failed order load shows a retry and preserves any already-loaded orders. Recovery: retry reloads the list; the shopper can continue shopping at any time.

Vendor Products

• Information and state. Protected vendor workspace for creating and managing the vendor's own product listings and offers. Shows only the signed-in vendor's own listings and their current state.
• Primary action. Create a listing. Supporting actions. Edit an existing listing; change a listing's price or availability; remove a listing.
• Domain entities. Vendor, Product, Listing, Price, Availability, Listing state.
• Component responsibilities. Own-listing list with per-listing state; create/edit form for listing details, price, and availability; save and remove controls; validation messaging; empty-list region.
• States. Loading: the listing list shows placeholders. Empty: the vendor has no listings yet — the workspace states this and presents the create action as the next step. Success: created and edited listings appear in the list with their current state, and saved changes are reflected in the marketplace catalog. Error: validation problems are reported inline against the offending field with entered values preserved; a failed save or removal reports inline and leaves the listing's previous state intact. Recovery: the form remains populated after a validation error; a failed save can be retried without re-entering the listing.

Vendors

• Information and state. Protected marketplace operator workspace for reviewing and managing vendor participation. Shows the vendors participating in the marketplace and the state of each participation.
• Primary action. Change a vendor's participation state. Supporting action. Open a vendor to review its participation detail and its listings.
• Domain entities. Vendor, Vendor participation, Participation state, Listing (as the vendor's catalog footprint).
• Component responsibilities. Vendor list with participation state; vendor detail region; participation-state control; empty-list region; error region.
• States. Loading: the vendor list shows placeholders. Empty: no vendors are participating — the workspace states this and notes that vendors enroll through Sign Up. Success: vendors render with their participation state, and a state change is reflected immediately in the list. Error: a failed state change reports inline and restores the previous state; a failed list load shows a retry. Recovery: retry reloads the list; the operator can re-attempt the state change.

Listing Management

• Information and state. Protected marketplace operator workspace for reviewing and managing listings across vendors. Shows listings from all vendors together, each attributable to its vendor, with the listing's current state.
• Primary action. Change a listing's marketplace state. Supporting actions. Filter listings by vendor or state; open a listing to review its detail.
• Domain entities. Listing, Product, Vendor, Price, Availability, Listing state.
• Component responsibilities. Cross-vendor listing list with vendor attribution and state; filter controls with applied-state chips; listing detail region; state control; empty-list region; error region.
• States. Loading: the listing list shows placeholders. Empty: no listings match the current filter — the applied filters are shown as removable chips with a clear-all action, and the list states that nothing matches. Success: listings render with vendor attribution and state, and a state change is reflected immediately. Error: a failed state change reports inline and restores the previous state; a failed list load shows a retry. Recovery: retry reloads the list; clearing filters restores the unfiltered cross-vendor view.

3. Functional Requirements

Each requirement is a distinct story point with provenance, lifecycle facts, and observable acceptance. Provenance is explicit (stated in the authoritative thread), basic_default (accepted default), or required_inference (indispensable mechanics for an accepted outcome).

FR-1 — Multi-vendor marketplace. As a Marketplace Operator, I should run one marketplace that hosts multiple independent vendors rather than a single seller, so that many sellers can trade through a single system. Provenance: explicit. Lifecycle: triggered by the marketplace existing; the observable result is that listings from more than one vendor appear together in the catalog and each listing is attributable to its vendor. Access: public catalog. Failure/recovery: if a vendor's listings cannot be read, the rest of the catalog still renders and the affected listings are omitted rather than blocking the field. Continuation: the operator manages participation in Vendors.

FR-2 — Shopper browses the cross-vendor catalog. As a Shopper, I should browse products from multiple vendors in one catalog, so that I can see what the marketplace offers without visiting vendors separately. Provenance: explicit. Lifecycle: initiated by the shopper opening Products; input is the catalog request; the observable result is a listing field with vendor attribution and price. Access: anonymous or signed in. Failure/recovery: a failed catalog request shows a non-blocking notice with retry and keeps the last loaded results. Continuation: the shopper opens a listing or adds it to the cart.

FR-3 — Shopper searches and filters the catalog. As a Shopper, I should search and filter the catalog, so that I can narrow a large multi-vendor field to what I want. Provenance: required_inference. Lifecycle: initiated by the shopper entering a query or applying a filter; the observable result is a narrowed listing field with the applied state visible as removable chips. Access: anonymous or signed in. Failure/recovery: a failed filtered request keeps the previous results and offers retry; clearing filters restores the unfiltered catalog. Continuation: the shopper opens a matching listing.

FR-4 — Shopper reviews a product and its vendor offer. As a Shopper, I should open a listing and review the product together with the vendor offer behind it, so that I can judge the item and its seller before committing. Provenance: required_inference. Lifecycle: initiated by the shopper selecting a listing; the observable result is the product, its price, and its vendor attribution on one focused destination. Access: anonymous or signed in. Failure/recovery: if the listing is unavailable, the page says so and routes back to the catalog and to the vendor's other listings. Continuation: the shopper adds the item to the cart or returns to the catalog.

FR-5 — Shopper adds a product to the cart. As a Shopper, I should add a product to my cart from its listing, so that I can assemble a purchase across vendors. Provenance: required_inference. Lifecycle: initiated by the shopper's add-to-cart action with a chosen quantity; the observable result is the item in the cart and an updated cart count. Access: the cart itself is protected; the add action is available from the catalog. Failure/recovery: a failed add reports inline, leaves the quantity selection intact, and offers retry. Continuation: the shopper continues browsing or opens the cart.

FR-6 — Shopper reviews and adjusts the cart. As a Shopper, I should review my cart, change quantities, and remove items, so that the order I submit is the one I intend. Provenance: required_inference. Lifecycle: initiated by the shopper opening Cart; the observable result is the item list with vendor attribution, quantities, and totals. Access: protected — requires an established identity. Failure/recovery: a failed quantity change or removal reports inline and restores the previous value; a failed cart load offers retry. Continuation: the shopper proceeds to checkout or returns to the catalog.

FR-7 — Cart continuity across sessions. As a Shopper, I should find my cart as I left it when I return, so that I do not lose a selection I built across vendors. Provenance: required_inference. Lifecycle: initiated by the shopper returning and verifying; the observable result is the previously selected items restored with their quantities. Access: protected. Failure/recovery: if the cart cannot be read, the shopper is told and can retry or rebuild the cart from the catalog. Continuation: the shopper proceeds to checkout.

FR-8 — Shopper submits an order from the cart. As a Shopper, I should submit an order from my cart through a focused checkout, so that my purchase is placed. Provenance: explicit. Lifecycle: initiated by the shopper's submit action at Checkout; input is the cart plus the required purchase information; the observable result is a submitted order with a confirmation and reference, and a cleared cart. Access: protected. Failure/recovery: a failed submission reports the failure, preserves the entered information, does not clear the cart, and offers retry; validation problems are reported inline. Continuation: the shopper reviews the order in Orders.

FR-9 — Shopper reviews completed purchases and order status. As a Shopper, I should review my completed purchases and their status, so that I can track what I ordered. Provenance: required_inference. Lifecycle: initiated by the shopper opening Orders; the observable result is the order list with items, vendors, totals, and current status, and per-order detail. Access: protected. Failure/recovery: a failed load offers retry and preserves already-loaded orders. Continuation: the shopper returns to the catalog to shop again.

FR-10 — Vendor enrolls on the marketplace. As a Vendor, I should enroll myself on the marketplace, so that I can begin selling without an external provisioning step. Provenance: required_inference. Lifecycle: initiated by the vendor choosing the vendor path at Sign Up; input is the enrollment information; the observable result is an established identity with vendor participation and access to the vendor workspace. Access: anonymous entry at Sign Up. Failure/recovery: invalid input is reported inline with values preserved; a duplicate identity is reported with a route to Login. Continuation: the vendor creates their first listing.

FR-11 — Vendor creates a listing. As a Vendor, I should create a product listing with its price and availability, so that my product becomes purchasable on the marketplace. Provenance: required_inference. Lifecycle: initiated by the vendor's create action in Vendor Products; input is the listing details, price, and availability; the observable result is the listing saved, visible in the vendor's own list, and available in the marketplace catalog. Access: protected, vendor role. Failure/recovery: validation problems are reported inline with entered values preserved; a failed save reports inline and leaves the listing unsaved rather than partially applied. Continuation: the vendor edits or removes the listing, or creates another.

FR-12 — Vendor manages their own listings. As a Vendor, I should edit and remove my own listings and change their price or availability, so that my catalog stays accurate. Provenance: required_inference. Lifecycle: initiated by the vendor selecting one of their own listings; the observable result is the updated listing reflected in the vendor's list and in the marketplace catalog. Access: protected, vendor role, scoped to the vendor's own listings. Failure/recovery: a failed save or removal reports inline and leaves the listing's previous state intact. Continuation: the vendor continues managing their catalog.

FR-13 — Vendor sees only their own listings in their workspace. As a Vendor, I should see only my own listings in my workspace, so that my catalog work is not mixed with other vendors'. Provenance: required_inference. Lifecycle: initiated by the vendor opening Vendor Products; the observable result is a list containing only that vendor's listings. Access: protected, vendor role. Failure/recovery: a failed load offers retry. Continuation: the vendor creates or edits a listing.

FR-14 — Marketplace Operator reviews vendor participation. As a Marketplace Operator, I should review the vendors participating in the marketplace and the state of each participation, so that I can see who is trading. Provenance: required_inference. Lifecycle: initiated by the operator opening Vendors; the observable result is the vendor list with participation state and per-vendor detail. Access: protected, operator role. Failure/recovery: a failed list load offers retry. Continuation: the operator changes a participation state or opens a vendor's listings.

FR-15 — Marketplace Operator manages vendor participation. As a Marketplace Operator, I should change a vendor's participation state, so that the marketplace stays usable. Provenance: required_inference. Lifecycle: initiated by the operator's state change; the observable result is the new state reflected immediately in the vendor list and in what the marketplace offers. Access: protected, operator role. Failure/recovery: a failed change reports inline and restores the previous state. Continuation: the operator continues reviewing vendors or moves to Listing Management.

FR-16 — Marketplace Operator reviews listings across vendors. As a Marketplace Operator, I should review listings from all vendors together, each attributable to its vendor, so that I can police the whole board. Provenance: required_inference. Lifecycle: initiated by the operator opening Listing Management; the observable result is a cross-vendor listing list with vendor attribution and state, filterable by vendor or state. Access: protected, operator role. Failure/recovery: a failed load offers retry; an empty filter result shows the applied filters as removable chips. Continuation: the operator changes a listing's state or opens a listing's detail.

FR-17 — Marketplace Operator manages listings across vendors. As a Marketplace Operator, I should change a listing's marketplace state, so that unsuitable or unavailable listings do not remain purchasable. Provenance: required_inference. Lifecycle: initiated by the operator's state change; the observable result is the new state reflected immediately in the listing list and in the marketplace catalog. Access: protected, operator role. Failure/recovery: a failed change reports inline and restores the previous state. Continuation: the operator continues reviewing listings.

FR-18 — Self-service enrollment for shoppers and vendors. As a Shopper or Vendor, I should enroll myself on the marketplace, so that I can start using it without an external provisioning step. Provenance: required_inference. Lifecycle: initiated at Sign Up; input is the enrollment information and the shopper-or-vendor choice; the observable result is an established application identity routed to the destination appropriate to the chosen role. Access: anonymous entry. Failure/recovery: invalid input is reported inline with values preserved; a duplicate identity is reported with a route to Login. Continuation: the shopper browses the catalog; the vendor creates a listing.

FR-19 — Returning verification for all application actors. As a Shopper, Vendor, or Marketplace Operator, I should verify my identity when I return, so that I reach the workspace my role owns. Provenance: required_inference. Lifecycle: initiated at Login; input is the actor's credentials; the observable result is verification and role-aware routing — shopper to the catalog or cart, vendor to Vendor Products, operator to Vendors. Access: anonymous entry at Login; protected destinations remain unavailable until verification succeeds. Failure/recovery: failed verification is reported without disclosing which credential element was wrong, the identity field is preserved, and the actor can retry or go to Sign Up. Continuation: the actor proceeds into their workspace.

FR-20 — Marketplace operator access is provisioned. As a Marketplace Operator, I should receive my operator access through provisioning rather than self-enrollment, so that operator control over vendors and listings is not self-granted. Provenance: required_inference. Lifecycle: initiated outside self-service enrollment; the observable result is an operator identity that Login verifies and routes to the operator workspaces. Access: operator role; Sign Up does not offer the operator path. Failure/recovery: an unprovisioned actor attempting operator access is told that operator access is provisioned and is not granted operator workspaces. Continuation: the provisioned operator signs in and reviews vendors.

FR-21 — Authenticated continuity for carts, checkout, and order review. As a Shopper, I should have my cart, checkout, and order review bound to my identity, so that my purchase state stays mine across sessions. Provenance: required_inference. Lifecycle: initiated by the shopper verifying; the observable result is that cart, checkout, and orders resolve to that shopper's own state. Access: protected destinations. Failure/recovery: if continuity cannot be established, the shopper is returned to Login rather than shown another shopper's state. Continuation: the shopper resumes the cart or reviews orders.

FR-22 — Backend persistence and authorization for marketplace state. As the marketplace system, I should persist and authorize products, vendor participation, listings, carts, and orders, so that every accepted journey has durable, correctly-scoped state. Provenance: required_inference. Lifecycle: triggered by any accepted write or read; the observable result is durable state that survives sessions and is returned only to the actor entitled to it. Access: enforced per destination — vendor workspace scoped to the vendor's own listings, operator workspaces scoped to the operator role, cart/checkout/orders scoped to the owning shopper. Failure/recovery: a failed persistence operation surfaces as the inline failure and retry described in the affected requirement rather than as silent data loss. Continuation: the affected journey resumes from its last confirmed state.

4. User Personas

Shopper

Product context. The Shopper is a customer browsing the multi-vendor marketplace. They arrive without knowing which vendor sells what, and their work happens across vendors rather than inside one store.

Primary goal. Discover products across vendors and complete a purchase, and receive the items they ordered.

Distinct accepted responsibilities. Browsing and searching listings across independent vendors; comparing items from different vendors; reviewing a listing together with the vendor offer behind it; assembling a cart from more than one vendor; reviewing and adjusting that cart; submitting an order through checkout; and returning to review completed purchases and order status.

Relevant inputs and decisions. Search terms and filters; which listing to open; quantity; whether to add an item or keep browsing; whether the cart is correct before submitting; whether to adjust the cart and re-enter checkout after a failure.

Interactions with other accepted participants. The Shopper's purchase is fulfilled by the Vendor whose listing they bought, so the Shopper's order is grouped by vendor and the vendor attribution is visible at every step from catalog to order. The Shopper's experience of the marketplace depends on the Marketplace Operator keeping vendors participating and listings purchasable.

Observable success. The Shopper finds matching listings, sees each item's vendor, submits an order that confirms with a reference, and later finds that order with its status in Orders.

What makes this role different. The Shopper is the only persona whose work is read-mostly across the whole catalog and whose durable state is a cart and an order history. They never create or govern listings, and their access is scoped to their own cart, checkout, and orders.

Vendor

Product context. The Vendor is a seller on the multi-vendor marketplace. They are one of several independent sellers sharing one catalog, so their work is maintaining their own offers inside a system they do not control.

Primary goal. Have their products available to shoppers on the marketplace.

Distinct accepted responsibilities. Enrolling themselves on the marketplace; creating product listings with price and availability; editing and removing their own listings; and keeping their catalog accurate so it stays purchasable.

Relevant inputs and decisions. Listing details, price, and availability; which of their own listings to edit or remove; whether a listing is ready to be purchasable.

Interactions with other accepted participants. The Vendor's listings are what the Shopper browses and buys, so listing accuracy directly determines the Shopper's experience. The Vendor's participation and listings are reviewed and managed by the Marketplace Operator, whose state changes affect whether the Vendor's offers remain purchasable.

Observable success. The Vendor's listings appear in the marketplace catalog with correct price and availability, and shoppers can purchase them.

What makes this role different. The Vendor is the only persona who authors catalog content, and their workspace is scoped strictly to their own listings — they see and change nothing belonging to another vendor. Their recurring work is maintenance of a small owned catalog rather than discovery across a large one.

Marketplace Operator

Product context. The Marketplace Operator is the party running the multi-vendor marketplace. Their work is oversight of the whole board — vendors and listings together — rather than any single seller's catalog.

Primary goal. A functioning marketplace with active vendors and purchasable products.

Distinct accepted responsibilities. Reviewing the vendors participating in the marketplace and the state of each participation; changing a vendor's participation state; reviewing listings from all vendors together with vendor attribution; and changing a listing's marketplace state.

Relevant inputs and decisions. Which vendor's participation to change and to what state; which listings to filter by vendor or state; which listing's marketplace state to change.

Interactions with other accepted participants. The Operator's decisions determine which Vendors are participating and which listings remain purchasable, which in turn shapes what the Shopper can find and buy. Operator access is provisioned rather than self-enrolled, so the Operator does not appear in the self-service enrollment path that serves shoppers and vendors.

Observable success. The vendor list reflects current participation, the cross-vendor listing view reflects current listing state, and the marketplace catalog matches those decisions.

What makes this role different. The Operator is the only persona with cross-vendor visibility and the only one whose access is provisioned rather than self-enrolled. Their work is governance of shared marketplace state, not authorship of listings and not purchasing.

5. Core User Flows

Flow 1 — Shopper discovers products across vendors

1. The Shopper arrives at Landing as an anonymous visitor and reads the multi-vendor premise: many independent vendors, one marketplace.
2. The Shopper selects the browse entry and lands on Products, where listings from multiple vendors appear in one field, each with its vendor attribution and price.
3. The Shopper searches or applies filters; the applied state appears as removable chips and the field narrows to matching listings.
4. If nothing matches, the Shopper sees the applied filters as removable chips with a clear-all action, clears them, and the unfiltered catalog returns.
5. The Shopper selects a listing and lands on Product Details, where the product, its price, and the vendor offer behind it are shown together.
6. Next step: the Shopper adds the item to the cart (Flow 2) or returns to Products to keep browsing.

Flow 2 — Shopper assembles a cart across vendors

1. On Product Details, the Shopper sets a quantity and selects add to cart.
2. The item is added and the cart count updates; the Shopper sees the confirmation on the page.
3. The Shopper returns to Products and adds a listing from a different vendor the same way, so the cart now spans more than one vendor.
4. If an add fails, the failure is reported inline, the quantity selection stays intact, and the Shopper retries without losing their place.
5. The Shopper opens Cart. Because the cart is a protected destination, an anonymous Shopper is first taken to Login or Sign Up to establish identity, and returns to the cart once verified.
6. In Cart, the Shopper reviews items grouped with their vendor attribution, changes quantities, and removes anything unwanted; totals update accordingly.
7. If a quantity change or removal fails, the failure is reported against that item and the previous value is restored.
8. Next step: the Shopper proceeds to checkout (Flow 3), or returns to Products to continue shopping — the cart persists for the next visit.

Flow 3 — Shopper submits an order

1. From Cart, the Shopper proceeds to Checkout, a protected destination.
2. Checkout shows the order being placed — items grouped by vendor, quantities, and totals — and collects the information required to submit it.
3. If the cart is empty, checkout states there is nothing to submit and routes the Shopper to Products.
4. The Shopper reviews the summary, corrects anything by returning to Cart if needed, and selects submit.
5. The order is submitted: a confirmation with the order reference is shown and the cart is cleared.
6. If submission fails, the failure is reported, the entered information is preserved, the cart is not cleared, and the Shopper retries; if a field is invalid, the problem is reported inline against that field.
7. Next step: the Shopper reviews the purchase in Orders (Flow 4).

Flow 4 — Shopper reviews completed purchases and order status

1. The Shopper signs in at Login and is routed by role to their shopper destinations.
2. The Shopper opens Orders, a protected destination, and sees their submitted orders with items, vendors, totals, and current status.
3. The Shopper opens an order to review its detail, with lines grouped by vendor.
4. If the Shopper has no orders yet, the page states this and offers a direct route into Products.
5. If the order list fails to load, a retry is offered and any already-loaded orders remain visible.
6. Next step: the Shopper returns to Products to shop again, or returns to Cart to resume an unfinished selection.

Flow 5 — Vendor enrolls and creates a listing

1. The Vendor arrives at Landing and selects Sign Up.
2. On Sign Up, the Vendor chooses the vendor path and submits the enrollment information.
3. If input is invalid, the problem is reported inline with the entered values preserved; if the identity already exists, the conflict is reported with a route to Login.
4. On success, the Vendor's identity is established with vendor participation and they are taken to Vendor Products.
5. Vendor Products is empty for a new vendor and states this, presenting the create action as the next step.
6. The Vendor creates a listing with its details, price, and availability and saves it.
7. If validation fails, the problem is reported inline with the entered values preserved; if the save fails, the failure is reported and the listing is not partially applied.
8. On success, the listing appears in the Vendor's own list and becomes available in the marketplace catalog.
9. Next step: the Vendor edits or removes the listing, or creates another (Flow 6).

Flow 6 — Vendor manages their own listings

1. The Vendor signs in at Login and is routed to Vendor Products.
2. The workspace shows only the Vendor's own listings with their current state.
3. The Vendor selects a listing and changes its details, price, or availability, then saves.
4. The change is reflected in the Vendor's list and in the marketplace catalog, so the Shopper sees the updated offer.
5. If the save fails, the failure is reported inline and the listing's previous state is left intact; the Vendor retries without re-entering the listing.
6. The Vendor removes a listing that should no longer be sold; it disappears from their list and from the marketplace catalog.
7. Next step: the Vendor continues managing their catalog, or returns to Products to see their offers as a shopper would.

Flow 7 — Marketplace Operator reviews and manages vendor participation

1. The Marketplace Operator signs in at Login with provisioned operator access and is routed to Vendors.
2. Vendors shows the vendors participating in the marketplace and the state of each participation.
3. The Operator opens a vendor to review its participation detail and its listings.
4. The Operator changes a vendor's participation state; the new state is reflected immediately in the vendor list and in what the marketplace offers.
5. If the change fails, the failure is reported inline and the previous state is restored; the Operator retries.
6. If no vendors are participating, the workspace states this and notes that vendors enroll through Sign Up.
7. Next step: the Operator moves to Listing Management (Flow 8).

Flow 8 — Marketplace Operator reviews and manages listings across vendors

1. From Vendors, the Operator opens Listing Management.
2. The workspace shows listings from all vendors together, each attributable to its vendor, with its current state.
3. The Operator filters by vendor or state; the applied filters appear as removable chips.
4. If nothing matches, the applied filters are shown as removable chips with a clear-all action, and clearing them restores the unfiltered cross-vendor view.
5. The Operator opens a listing to review its detail and changes its marketplace state; the new state is reflected immediately in the listing list and in the marketplace catalog.
6. If the change fails, the failure is reported inline and the previous state is restored; the Operator retries.
7. Next step: the Operator continues reviewing listings, or returns to Vendors to review participation.

Flow 9 — Returning actor verifies and resumes

1. A returning Shopper, Vendor, or Marketplace Operator opens Login.
2. The actor submits their credentials. Protected destinations remain unavailable until verification succeeds.
3. If verification fails, the failure is reported without disclosing which credential element was wrong, the identity field is preserved, and the actor retries or goes to Sign Up if they have no account.
4. On success, the actor is routed by role: a Shopper to the catalog or their cart, a Vendor to Vendor Products, a Marketplace Operator to Vendors.
5. A Shopper's cart, checkout, and orders resolve to their own state, so a selection built earlier is still there.
6. An actor seeking operator access who has not been provisioned is told that operator access is provisioned and is not granted operator workspaces.
7. Next step: the actor resumes their role's work — shopping, managing listings, or governing the marketplace.

6. Visuals Colors and Theme

Muse and headline. Swiss geometric rigour after Josef Müller-Brockmann. A multi-vendor marketplace is an information problem before it is a shopping problem: thousands of listings from independent sellers, each needing to be scannable, comparable, and trustworthy. The register is confidence and order — a marketplace that feels like a well-signed system, not a boutique or a toy. Vendor identity becomes a colour code, listings become grid modules, and trust comes from visible order rather than decoration.

Colour tokens — light mode.

Colour proportion and use. 80% off-white and black, 12% white cards, 8% coded colour. Warm off-white #F4F2ED carries the whole page; black #111111 is the primary ink for type, rules, and the header band. One pure red #E63329 is the signal colour: CTAs, sale flags, active filter state, and the cart count. Vendor identity uses the secondary alphabet — #1D4ED8, #F2B705, #0E7C4A — only as thin 4px vendor stripes and tag chips, never as large fills. No more than four colours carry meaning at once.

Typography. Headings and body both Archivo. Headings are grotesque, flush-left ragged-right, tight tracking (-0.02em), weight 700/800 for section heads and 500 for listing titles. Uppercase is reserved for micro-labels and vendor tags at 11px with 0.14em tracking. No centred headings anywhere.

Type scale (1.414 modular ratio, mobile → desktop).

Line-height 0.92 on display, 1.1 on H1/H2.

Shape language. Hard edges everywhere: 0px radius on cards, buttons, inputs, and images. Structure is carried by 1px and 4px black rules and by solid colour blocks — never by shadows or rounding. Circles appear only as data marks: vendor avatars, quantity steppers, colour swatches. Diagonal rules at 45° are permitted as section dividers where a transition needs force.

Layout. A 12-column modular grid with 24px gutters, max-width 1440px, and a persistent 1px vertical rule between the filter rail and the product field. The header is a black band with a red cart block pinned hard right. Product listings sit in a strict 4-up / 2-up / 1-up responsive grid; each card is a white module with a 4px vendor colour stripe along its top edge, image cropped flush, and price set in tabular numerals aligned to the card's baseline rule. Filter state is expressed as a row of hard-edged chips, not a dropdown.

Imagery. Product photography only, cropped hard to the grid with the subject centred on a plain ground and no lifestyle staging. Vendor identity leans on geometric marks — a solid circle, square, or triangle in the vendor's coded colour rather than a logo lockup. Diagrams and pictograms (size charts, shipping maps, category glyphs) are drawn as pure geometry in black on off-white.

Avoid. Rounded-corner cards, pill buttons, and soft drop shadows; centred hero headline with subtext and a blue button; blue or indigo as the primary accent on white; gradient blobs, glassmorphism, and frosted panels; lifestyle photography with models or staged rooms; playful illustration, stickers, and blob shapes; more than four colours carrying meaning at once; decorative animation, bounce, or easing theatrics. The generic indigo/blue-on-white SaaS template is forbidden for this project.

7. Signature Design Concept

The public entry is a signed system, not a storefront banner.

The Landing page is a full-bleed off-white field (#F4F2ED) split by one 4px vertical black rule at 62% width.

• Left 62%. A stacked flush-left headline at clamp(56px, 11vw, 148px), line-height 0.92, reading "EVERY VENDOR. ONE GRID." with the final word set in signal red #E63329. Beneath it, a single black rectangular CTA — BROWSE THE MARKETPLACE — sits flush to the headline's left edge with no centring, carrying the visitor into Products.
• Right 38%. A tight 3×3 grid of product crops, each separated by 1px black rules, each tile carrying a thin 4px vendor colour stripe on its top edge drawn from the coded alphabet (#1D4ED8, #F2B705, #0E7C4A, #E63329). The grid itself is the hero image — the marketplace's defining state, many vendors in one frame, shown rather than described.
• Bottom band. A black band runs along the very bottom of the viewport carrying a horizontal ticker of vendor names in white uppercase 11px with 0.14em tracking.
• Entry controls. Sign Up and Login sit as hard-edged, unrounded controls in the header band, so the anonymous visitor can enroll or verify without leaving the entry.

No gradient, no blob, no centred stack. The composition recomposes only accepted content — the marketplace premise, real listings from multiple vendors, the browse entry, and the enrollment and verification entries — and introduces no new behaviour, page, or destination.

8. Interaction Model & Motion Direction

Interaction Model: Animated Motion Tempo: restrained Hero Dimensionality: flat

Landing Hero Motion Brief.

• Focal subject. The 3×3 product-crop grid on the right 38% of the hero, divided by 1px black rules and topped by 4px vendor colour stripes — the grid itself is the hero image.
• Input → transformation → outcome thesis. As the visitor scrolls into the hero, the nine grid modules fade and rise 12px in staggered 40ms steps, resolving into a complete, rule-divided board; the outcome is that the marketplace's defining state — many vendors, one grid — is assembled in front of the visitor rather than merely asserted.
• Motion vocabulary. Restrained and rhythmic: fade-and-rise 12px in staggered 40ms steps on scroll entry; filter chips snap state in 100ms with no easing flourish; the header cart block does a single 120ms colour inversion when an item is added; the vendor ticker runs continuously.
• Composed first frame. Off-white field, the 4px vertical black rule at 62%, the flush-left headline fully set with the final word in red, the black CTA flush to the headline's left edge, and the 3×3 grid present but not yet resolved — its modules at their pre-rise offset, the black bottom band already carrying the vendor ticker.
• Reduced-motion state. Under prefers-reduced-motion, the staggered rise is removed and the grid renders complete in its first frame; the vendor ticker stops and wraps into rows so every vendor name is fully readable; the cart-block inversion becomes an instant state change with no transition.

9. Non-Functional Requirements

NFR-1 — Multi-vendor constraint. The marketplace hosts multiple independent vendors rather than a single seller. Provenance: explicit. Rationale: this is the explicit hard constraint in the authoritative source; the catalog, vendor workspace, and operator workspaces are all shaped by it.

NFR-2 — Vendor attribution is always visible. Every listing shown to a shopper carries its vendor attribution, from the catalog through product details, cart, checkout, and order review. Provenance: required_inference. Rationale: in a multi-vendor marketplace the shopper's purchase is fulfilled by a specific vendor, so the vendor must remain identifiable at every step where the shopper commits or reviews.

NFR-3 — Vendor workspace scoping. A vendor's workspace shows and changes only that vendor's own listings. Provenance: required_inference. Rationale: independent vendors share one marketplace; without scoping, one vendor's catalog work would affect another's.

NFR-4 — Operator access is provisioned, not self-enrolled. Operator workspaces are reachable only by a provisioned operator identity; Sign Up does not offer the operator path. Provenance: required_inference. Rationale: operator control over vendor participation and cross-vendor listing state must not be self-granted.

NFR-5 — Protected destinations require an established identity. Cart, Checkout, Orders, Vendor Products, Vendors, and Listing Management are unavailable until identity is established, and the interaction that establishes access lives on the anonymous Sign Up and Login surfaces. Provenance: required_inference. Rationale: cart, checkout, and order state must remain bound to the correct shopper, and vendor and operator workspaces must remain bound to the correct role.

NFR-6 — Durable marketplace state. Products, vendor participation, listings, carts, and orders persist across sessions and are returned only to the actor entitled to them. Provenance: required_inference. Rationale: accepted journeys include returning to a cart, reviewing past orders, and maintaining a catalog over time.

NFR-7 — Readable text and controls stay whole. Headlines, wordmarks, labels, numbers, card text, and controls stay entirely inside the viewport and their container at 375px, 768px, and 1280px, wrapping or scaling (for example font-size: clamp(...) with its mobile size) to fit, and no other element covers any part of them. Imagery, decoration, and motion may be cropped, bled off an edge, rotated, overlapped, or cut as the creative direction asks, provided they cover no readable text or control. Moving and scrollable content — the vendor ticker, any horizontally scrollable row — may cross the viewport or container edge by design and is judged by whether it actually moves and whether every item becomes fully readable as it passes. Under prefers-reduced-motion it stops and shows whole items, wrapping into rows or sitting in a horizontally scrollable row (overflow-x: auto). Provenance: explicit (creative direction).

NFR-8 — No shadows, no rounding. Cards, buttons, inputs, and images use 0px radius; structure is carried by 1px and 4px black rules and solid colour blocks, never by shadows or rounding. Provenance: explicit (creative direction).

NFR-9 — Colour discipline. No more than four colours carry meaning at once; vendor identity colour is used only as thin 4px stripes and tag chips, never as large fills. Provenance: explicit (creative direction).

NFR-10 — Reduced-motion compliance. All motion — the staggered grid rise, the cart-block inversion, the vendor ticker — has a defined reduced-motion state. Provenance: explicit (creative direction).

10. Tech Stack

No technology choices were specified in the authoritative user thread, so the following are coherent defaults for the accepted delivery shape (first-party web application, custom UI, application-owned identity, backend persistence and authorization).

• Frontend. React (web), built as a single-page application with client-side routing across the eleven destinations. [Default — not specified by user]
• Backend. Python with FastAPI, exposing the marketplace API for catalog, listings, carts, orders, vendor participation, and identity. [Default — not specified by user]
• Storage. A relational database for products, listings, vendors, vendor participation, carts, cart items, orders, and order lines, with identity records for shoppers, vendors, and provisioned operators. [Default — not specified by user]
• Packaging and local run. Docker with docker-compose for the application and its database. [Default — not specified by user]
• Deployment. Container deployment of the application and database. Kubernetes is not required by any accepted requirement and is therefore not included. [Default — not specified by user]

11. Assumptions and Constraints

Constraints (binding).

• C-1. The marketplace hosts multiple independent vendors rather than a single seller. (explicit)
• C-2. The Shopify reference is a likeness for a multi-vendor shopping website only, with inspiration_only authority; it is not an authoritative specification and supplies no product names, copy, facts, or capabilities. (explicit)
• C-3. Operator access is provisioned; it is not available through self-service enrollment. (required_inference)
• C-4. Cart, Checkout, Orders, Vendor Products, Vendors, and Listing Management are protected destinations; Landing, Sign Up, Login, Products, and Product Details are anonymously reachable. (required_inference)
• C-5. The creative direction is authoritative for visuals, theme, motion, and the signature entry concept; the generic indigo/blue-on-white SaaS template is forbidden. (explicit)

Assumptions (narrow, labeled).

• A-1. Shoppers and vendors enroll themselves because no external provisioning boundary is established for them; operator access is the exception and is provisioned. (required_inference)
• A-2. A vendor's participation record is created when the vendor enrolls through the vendor path at Sign Up, so the vendor can reach Vendor Products immediately after enrollment. (required_inference)
• A-3. Order status is a value the shopper can observe in Orders; no status-transition workflow beyond what the accepted journeys require is assumed. (required_inference)
• A-4. A listing's marketplace state is a value the operator can change in Listing Management, and a vendor's participation state is a value the operator can change in Vendors; the specific state vocabularies are not specified by the source and are left to implementation. (required_inference)
• A-5. Search and filtering on Products are assumed because a multi-vendor catalog of independent sellers is not usable without narrowing; no ranking, recommendation, or personalization behaviour is assumed. (required_inference)
• A-6. Payment and shipping are not specified by the source; checkout collects the information required to submit an order and produces an order record, without assuming a payment-provider or carrier integration surface. (required_inference)

Explicitly out of current scope. No payment-provider integration surface, no shipping-carrier integration, no reviews or ratings module, no shopper–vendor messaging, no promotions or discount engine, no analytics dashboard, and no theme or storefront-design editor. No future-horizon requirements were accepted in the authoritative thread.

12. Glossary

• Marketplace. The single multi-vendor shopping website that hosts multiple independent vendors.
• Vendor. An independent seller participating in the marketplace; one of the three accepted human personas.
• Shopper. A customer browsing and purchasing across the marketplace's vendors; one of the three accepted human personas.
• Marketplace Operator. The party running the marketplace, with oversight of vendor participation and listings across vendors; one of the three accepted human personas, and the only one whose access is provisioned.
• Listing. A vendor's offer of a product on the marketplace, carrying its price, availability, and marketplace state.
• Product. The item a listing offers; a product becomes purchasable on the marketplace through a vendor's listing.
• Vendor participation. A vendor's membership in the marketplace and the state of that membership, reviewed and managed by the Marketplace Operator.
• Cart. The shopper's protected, revisitable selection of listings from one or more vendors.
• Checkout. The protected, focused workflow in which a shopper submits an order from their cart.
• Order. The record produced when a shopper submits a cart at checkout, with lines grouped by vendor and an observable status.
• Vendor attribution. The visible identification of which vendor stands behind a listing or order line, carried from catalog through order review.
• Vendor colour code. The 4px stripe and tag-chip colour drawn from the coded alphabet (#1D4ED8, #F2B705, #0E7C4A, #E63329) that marks vendor identity throughout the interface.
• Provisioned access. Operator access established outside self-service enrollment, verified at Login and routed to the operator workspaces.