diff --git a/make_post_sell/templates/product.j2 b/make_post_sell/templates/product.j2
index 7d9dff1..58eba17 100644
--- a/make_post_sell/templates/product.j2
+++ b/make_post_sell/templates/product.j2
@@ -217,11 +217,42 @@
         {% endif %}
       {% endif %}
     {% else %}
+{% if product.is_buy_now_allowed %}
 <form method="POST" action="{{ request.route_url('cart_add_product') }}">
   {% include "snippets/csrf.j2" %}
   <input type="hidden" name="product_id" value="{{ product.id }}">
   <button type="submit" class="product-download-button mps-button">Add To Cart</button>
 </form>
+{% endif %}
+    {% endif %}
+
+    {# MPS-20: View Auction link when product is in auction mode. #}
+    {% if product.is_auction and product.auction %}
+    <p style="margin-top: var(--space-3)">
+      <a href="/a/{{ product.auction.uuid_str }}" class="mps-button mps-button-blue">
+        View live auction &rarr;
+      </a>
+    </p>
+    {% endif %}
+
+    {# MPS-21: Make Offer button when offers are allowed for this product. #}
+    {% if product.offers_allowed and request.user and request.user.authenticated and request.user not in product.shop.owners %}
+    <details style="margin-top: var(--space-3)">
+      <summary class="mps-button">Make an offer</summary>
+      <form method="POST" action="/p/{{ product.id }}/offer" style="margin-top: var(--space-2)">
+        {% include "snippets/csrf.j2" %}
+        <label for="offer_amount">Your offer (USD)</label>
+        <input type="number" step="0.01" min="0.01" name="amount" id="offer_amount" required />
+        <input type="text" name="message" placeholder="Optional message" />
+        <input type="submit" class="mps-submit" value="Submit Offer" />
+      </form>
+    </details>
+    {% elif product.offers_allowed and (not request.user or not request.user.authenticated) %}
+    <p style="margin-top: var(--space-3)">
+      <a href="/join-or-log-in?next={{ request.path | urlencode }}" class="mps-button">
+        Log in to make an offer
+      </a>
+    </p>
     {% endif %}
 
     <br/>
diff --git a/make_post_sell/templates/product_edit.j2 b/make_post_sell/templates/product_edit.j2
index 7e71238..5752f1e 100644
--- a/make_post_sell/templates/product_edit.j2
+++ b/make_post_sell/templates/product_edit.j2
@@ -262,6 +262,74 @@ Your cover (<code>thumbnail1</code>) will show up on search pages.
 
     <br />
     <br />
+
+    {# MPS-20 + MPS-21: pricing mode #}
+    <fieldset>
+      <legend>Pricing mode</legend>
+      <label style="display:block">
+        <input type="radio" name="pricing_mode" value="0"
+               {% if product.pricing_mode == 0 %}checked{% endif %} />
+        Fixed price (today's behavior)
+      </label>
+      <label style="display:block">
+        <input type="radio" name="pricing_mode" value="1"
+               {% if product.pricing_mode == 1 %}checked{% endif %} />
+        Auction
+      </label>
+      <label style="display:block">
+        <input type="radio" name="pricing_mode" value="2"
+               {% if product.pricing_mode == 2 %}checked{% endif %} />
+        Auction with buy-now
+      </label>
+      <label style="display:block">
+        <input type="radio" name="pricing_mode" value="3"
+               {% if product.pricing_mode == 3 %}checked{% endif %} />
+        Make an offer (negotiation)
+      </label>
+      <label style="display:block">
+        <input type="radio" name="pricing_mode" value="4"
+               {% if product.pricing_mode == 4 %}checked{% endif %} />
+        Make an offer with buy-now
+      </label>
+    </fieldset>
+
+    <br />
+
+    {# MPS-21: per-product offer override #}
+    {% if product.is_offer_mode %}
+    <fieldset>
+      <legend>Allow offers (override shop default)</legend>
+      <label style="display:block">
+        <input type="radio" name="allow_offers" value="inherit"
+               {% if product.allow_offers is none %}checked{% endif %} />
+        Use shop default
+        ({% if request.shop.offer_enabled %}enabled{% else %}disabled{% endif %})
+      </label>
+      <label style="display:block">
+        <input type="radio" name="allow_offers" value="yes"
+               {% if product.allow_offers == True %}checked{% endif %} />
+        Yes — accept offers on this product
+      </label>
+      <label style="display:block">
+        <input type="radio" name="allow_offers" value="no"
+               {% if product.allow_offers == False %}checked{% endif %} />
+        No — block offers on this product
+      </label>
+    </fieldset>
+
+    <br />
+    {% endif %}
+
+    {% if product.auction %}
+    <p>
+      <a href="/a/{{ product.auction.uuid_str }}" class="mps-button">
+        View live auction page
+      </a>
+      <small>(state: {{ product.auction.state_human }})</small>
+    </p>
+
+    <br />
+    {% endif %}
   {% endif %}
 
     <style>
diff --git a/make_post_sell/templates/shop_settings.j2 b/make_post_sell/templates/shop_settings.j2
index dbf2dd9..941673c 100644
--- a/make_post_sell/templates/shop_settings.j2
+++ b/make_post_sell/templates/shop_settings.j2
@@ -1170,6 +1170,77 @@ Existing sales honored for download buy purchasers.
 <br />
 <br />
 
+{# MPS-21: Make-an-Offer settings #}
+<section class="one-column">
+  <section class="shop-settings well">
+    <h3>Make an Offer</h3>
+    <p>Allow buyers to negotiate a price for products in offer mode. Offers ≥ auto-accept threshold are accepted instantly. Offers below auto-decline threshold are silently rejected.</p>
+
+    <form method="post" action="/s/{{ request.shop.uuid_str }}/settings" onsubmit="submit.disabled = true; return true;">
+      {% include "snippets/csrf.j2" %}
+      <input type="hidden" name="form_section" value="offer-settings" />
+
+      <label>
+        <input type="checkbox" name="offer_enabled_checkbox"
+               {% if request.shop.offer_enabled %}checked{% endif %} />
+        Enable make-an-offer (shop-wide default)
+      </label>
+
+      <br /><br />
+
+      <label for="offer_auto_accept">Auto-accept threshold (% of list price)</label>
+      <input type="number" name="offer_auto_accept_threshold_pct" id="offer_auto_accept"
+             value="{{ request.shop.offer_auto_accept_threshold_pct }}"
+             min="0" max="100" step="1" class="mps-text-input" />
+
+      <br /><br />
+
+      <label for="offer_auto_decline">Auto-decline threshold (% of list price)</label>
+      <input type="number" name="offer_auto_decline_threshold_pct" id="offer_auto_decline"
+             value="{{ request.shop.offer_auto_decline_threshold_pct }}"
+             min="0" max="100" step="1" class="mps-text-input" />
+      <small>Must be strictly below auto-accept; otherwise auto-clamped.</small>
+
+      <br /><br />
+
+      <label for="offer_min">Minimum offer amount ($)</label>
+      <input type="number" name="offer_min" id="offer_min"
+             value="{% if request.shop.offer_min_in_cents %}{{ '%.2f'|format(request.shop.offer_min_in_cents / 100.0) }}{% endif %}"
+             min="0" step="0.01" class="mps-text-input"
+             placeholder="No floor" />
+
+      <br /><br />
+
+      <label for="offer_expiration">Offer expiration (hours)</label>
+      <input type="number" name="offer_expiration_hours" id="offer_expiration"
+             value="{{ request.shop.offer_expiration_hours }}"
+             min="1" max="8760" step="1" class="mps-text-input" />
+
+      <br /><br />
+
+      <label for="offer_max_rounds">Max counter rounds</label>
+      <input type="number" name="offer_max_rounds" id="offer_max_rounds"
+             value="{{ request.shop.offer_max_rounds }}"
+             min="1" max="100" step="1" class="mps-text-input" />
+
+      <br /><br />
+
+      <label for="offer_min_age">Minimum buyer account age (hours)</label>
+      <input type="number" name="offer_min_buyer_account_age_hours" id="offer_min_age"
+             value="{{ request.shop.offer_min_buyer_account_age_hours }}"
+             min="0" max="8760" step="1" class="mps-text-input"
+             placeholder="0 = open" />
+
+      <br /><br />
+
+      <input type="submit" name="submit" class="mps-submit" value="Save Settings" />
+    </form>
+  </section>
+</section>
+
+<br />
+<br />
+
 <section class="one-column">
   <section class="shop-settings well">
 
diff --git a/make_post_sell/tests/test_functional.py b/make_post_sell/tests/test_functional.py
index 5e8e458..41ae3a2 100644
--- a/make_post_sell/tests/test_functional.py
+++ b/make_post_sell/tests/test_functional.py
@@ -5942,3 +5942,215 @@ class TestOfferRoutes(_AuthenticatedBase):
             expect_errors=True,
         )
         self.assertEqual(res.status_int, 403)
+
+
+class TestOfferSettingsForm(_AuthenticatedBase):
+    """MPS-21: shop-settings offer-settings form section."""
+
+    def test_enable_and_set_thresholds(self):
+        shop = self._create_shop_helper()
+        # Defaults pre-form:
+        self.assertFalse(bool(shop.offer_enabled))
+        self.assertEqual(shop.offer_auto_accept_threshold_pct, 95)
+
+        res = self.testapp.post(
+            f"/s/{shop.id}/settings",
+            {
+                "form_section": "offer-settings",
+                "offer_enabled_checkbox": "on",
+                "offer_auto_accept_threshold_pct": "90",
+                "offer_auto_decline_threshold_pct": "40",
+                "offer_min": "5.00",
+                "offer_expiration_hours": "72",
+                "offer_max_rounds": "5",
+                "offer_min_buyer_account_age_hours": "24",
+                "submit": "Save Settings",
+            },
+            status=302,
+        )
+        res.follow()
+        self.dbsession.refresh(shop)
+        self.assertTrue(shop.offer_enabled)
+        self.assertEqual(shop.offer_auto_accept_threshold_pct, 90)
+        self.assertEqual(shop.offer_auto_decline_threshold_pct, 40)
+        self.assertEqual(shop.offer_min_in_cents, 500)
+        self.assertEqual(shop.offer_expiration_hours, 72)
+        self.assertEqual(shop.offer_max_rounds, 5)
+        self.assertEqual(shop.offer_min_buyer_account_age_hours, 24)
+
+    def test_decline_clamped_below_accept(self):
+        # Setting decline >= accept should clamp decline to accept-1.
+        shop = self._create_shop_helper()
+        res = self.testapp.post(
+            f"/s/{shop.id}/settings",
+            {
+                "form_section": "offer-settings",
+                "offer_auto_accept_threshold_pct": "60",
+                "offer_auto_decline_threshold_pct": "60",  # tied — should clamp
+                "submit": "Save Settings",
+            },
+            status=302,
+        )
+        res.follow()
+        self.dbsession.refresh(shop)
+        self.assertEqual(shop.offer_auto_accept_threshold_pct, 60)
+        self.assertEqual(shop.offer_auto_decline_threshold_pct, 59)
+
+    def test_offer_min_blank_clears_floor(self):
+        shop = self._create_shop_helper()
+        # First set a floor.
+        self.testapp.post(
+            f"/s/{shop.id}/settings",
+            {
+                "form_section": "offer-settings",
+                "offer_min": "10.00",
+                "submit": "Save Settings",
+            },
+            status=302,
+        )
+        self.dbsession.refresh(shop)
+        self.assertEqual(shop.offer_min_in_cents, 1000)
+
+        # Then clear it (blank input).
+        self.testapp.post(
+            f"/s/{shop.id}/settings",
+            {
+                "form_section": "offer-settings",
+                "offer_min": "",
+                "submit": "Save Settings",
+            },
+            status=302,
+        )
+        self.dbsession.refresh(shop)
+        self.assertIsNone(shop.offer_min_in_cents)
+
+
+class TestPricingModeFormSection(_AuthenticatedBase):
+    """MPS-20 + MPS-21: pricing_mode + allow_offers on product edit."""
+
+    def _make_product(self, owner_creds=None):
+        if owner_creds is None:
+            owner_creds = self.user1_creds
+        shop = self._create_shop_helper(user_creds=owner_creds)
+        from ..models.product import Product
+        product = Product(title="P1", description="...")
+        product.shop = shop
+        product.price_in_cents = 5000
+        product.is_physical = False
+        product.is_sellable = True
+        self.dbsession.add(product)
+        self.dbsession.flush()
+        product_id = product.uuid_str
+        transaction.commit()
+        return shop, product_id
+
+    def _post_edit(self, product_id, **kw):
+        # The product edit form_url is /p/{id}/edit; minimal fields required.
+        params = {
+            "title": "P1",
+            "description": "...",
+            "price": "50.00",
+            "visibility": "1",
+            "submit": "true",
+        }
+        params.update(kw)
+        return self.testapp.post(f"/p/{product_id}/edit", params)
+
+    def test_flip_to_auction_creates_draft_auction(self):
+        from ..models.auction import (
+            MpsAuction, AUCTION_STATE_DRAFT,
+        )
+        shop, product_id = self._make_product()
+        self._post_edit(product_id, pricing_mode="1")
+
+        from ..models.product import get_product_by_id
+        product = get_product_by_id(self.dbsession, product_id)
+        self.assertEqual(product.pricing_mode, 1)
+        self.assertIsNotNone(product.auction)
+        self.assertEqual(product.auction.state, AUCTION_STATE_DRAFT)
+        # Auction inherits product price as default start.
+        self.assertEqual(product.auction.start_price_in_cents, 5000)
+
+    def test_flip_to_offer_does_not_create_auction(self):
+        shop, product_id = self._make_product()
+        self._post_edit(product_id, pricing_mode="3")
+
+        from ..models.product import get_product_by_id
+        product = get_product_by_id(self.dbsession, product_id)
+        self.assertEqual(product.pricing_mode, 3)
+        self.assertIsNone(product.auction)
+        self.assertTrue(product.is_offer_mode)
+
+    def test_allow_offers_override(self):
+        shop, product_id = self._make_product()
+        # First flip to offer mode.
+        self._post_edit(product_id, pricing_mode="3", allow_offers="yes")
+
+        from ..models.product import get_product_by_id
+        product = get_product_by_id(self.dbsession, product_id)
+        self.dbsession.refresh(product)
+        self.assertTrue(product.allow_offers)
+
+        # Flip override to "no" (block on this product).
+        self._post_edit(product_id, pricing_mode="3", allow_offers="no")
+        self.dbsession.expire_all()
+        product = get_product_by_id(self.dbsession, product_id)
+        self.assertEqual(product.allow_offers, False)
+
+        # Flip back to "inherit" (None).
+        self._post_edit(product_id, pricing_mode="3", allow_offers="inherit")
+        self.dbsession.expire_all()
+        product = get_product_by_id(self.dbsession, product_id)
+        self.assertIsNone(product.allow_offers)
+
+    def test_invalid_pricing_mode_ignored(self):
+        shop, product_id = self._make_product()
+        self._post_edit(product_id, pricing_mode="99")
+
+        from ..models.product import get_product_by_id
+        product = get_product_by_id(self.dbsession, product_id)
+        self.assertEqual(product.pricing_mode, 0)  # unchanged
+
+    def _make_ready_offer_product(self):
+        """Create a product that's is_ready=True (has product file) and
+        opted into offer mode. Returns (shop, product_id, product_slug)."""
+        from ..models.product import Product, get_product_by_id
+        shop = self._create_shop_helper()
+        shop.offer_enabled = True
+
+        product = Product(title="Ready P1", description="...")
+        product.shop = shop
+        product.price_in_cents = 5000
+        product.is_physical = False
+        product.is_sellable = True
+        product.pricing_mode = 3  # offer mode
+        # Fake a product file so is_ready=True (file_metadata.extensions.product).
+        import json
+        product.json_file_metadata = json.dumps({
+            "originals": {},
+            "extensions": {"product": "pdf"},
+        })
+        self.dbsession.add(product)
+        self.dbsession.flush()
+        product_id = product.uuid_str
+        product_slug = product.slug
+        transaction.commit()
+        return shop, product_id, product_slug
+
+    def test_make_offer_button_renders_when_eligible(self):
+        shop, product_id, product_slug = self._make_ready_offer_product()
+        self.testapp.get("/log-out")
+        self.log_in_user(self.user2_creds)
+
+        res = self.testapp.get(
+            f"/p/{product_id}/{product_slug}", status=200,
+        )
+        self.assertIn(b"Make an offer", res.body)
+
+    def test_make_offer_hidden_for_seller(self):
+        shop, product_id, product_slug = self._make_ready_offer_product()
+        # user1 (shop owner) is logged in.
+        res = self.testapp.get(
+            f"/p/{product_id}/{product_slug}", status=200,
+        )
+        self.assertNotIn(b"Make an offer", res.body)
diff --git a/make_post_sell/views/product.py b/make_post_sell/views/product.py
index 6b059d8..0c3da61 100644
--- a/make_post_sell/views/product.py
+++ b/make_post_sell/views/product.py
@@ -311,6 +311,52 @@ def product_edit(request):
         request.dbsession.add(product.set_price(price))
         request.session.flash(("You updated the product's price.", "success"))
 
+    # MPS-20 + MPS-21: pricing_mode + allow_offers (per-product overrides).
+    if "submit" in request.params:
+        try:
+            new_mode = int(request.params.get("pricing_mode", product.pricing_mode))
+        except (TypeError, ValueError):
+            new_mode = product.pricing_mode
+        if new_mode in (0, 1, 2, 3, 4) and new_mode != product.pricing_mode:
+            product_modified = True
+            product.pricing_mode = new_mode
+            mode_label = {
+                0: "fixed price", 1: "auction", 2: "auction + buy now",
+                3: "make an offer", 4: "make an offer + buy now",
+            }[new_mode]
+            request.session.flash(
+                (f"Pricing mode set to {mode_label}.", "success")
+            )
+            # If switching INTO auction mode and no auction exists, create one
+            # in DRAFT state with sane defaults from the product price.
+            if new_mode in (1, 2) and product.auction is None:
+                from ..models.auction import (
+                    MpsAuction, DEFAULT_BID_INCREMENT_IN_CENTS,
+                    DEFAULT_SOFT_CLOSE_SECONDS,
+                )
+                auction = MpsAuction(
+                    product=product,
+                    shop=product.shop,
+                    start_price_in_cents=product.price_in_cents or 100,
+                    bid_increment_in_cents=DEFAULT_BID_INCREMENT_IN_CENTS,
+                    soft_close_seconds=DEFAULT_SOFT_CLOSE_SECONDS,
+                )
+                request.dbsession.add(auction)
+                request.session.flash((
+                    "Auction created in draft state. Configure start/end "
+                    "times and reserve price below before scheduling.",
+                    "success",
+                ))
+
+        # allow_offers — three-state radio: inherit / yes / no.
+        allow_raw = request.params.get("allow_offers", "inherit")
+        new_allow = {
+            "inherit": None, "yes": True, "no": False,
+        }.get(allow_raw, None)
+        if new_allow != product.allow_offers:
+            product_modified = True
+            product.allow_offers = new_allow
+
     # torrent_opt_in — explicit per-product seeding consent.
     # MPS-22: gated by global torrent kill switch.
     if request.torrent_enabled and product.shop.torrent_enabled and "submit" in request.params:
diff --git a/make_post_sell/views/shop.py b/make_post_sell/views/shop.py
index e5e4274..9cefd40 100644
--- a/make_post_sell/views/shop.py
+++ b/make_post_sell/views/shop.py
@@ -1359,6 +1359,65 @@ def shop_settings(request):
                     # have a product file but no magnet link yet.
                     _torrent_backfill_async(request, shop)
 
+        # MPS-21: make-an-offer settings
+        if form_section == "offer-settings":
+            offer_enabled = checkbox_to_bool(
+                request.params.get("offer_enabled_checkbox", "off")
+            )
+            if shop.offer_enabled != offer_enabled:
+                shop.offer_enabled = offer_enabled
+                status = "enabled" if offer_enabled else "disabled"
+                request.session.flash((f"Make-an-offer {status}.", "success"))
+
+            # Numeric thresholds — silently clamp invalid input rather than
+            # rejecting the whole form.
+            def _int_param(name, default, lo=0, hi=10**9):
+                raw = (request.params.get(name) or "").strip()
+                if not raw:
+                    return default
+                try:
+                    val = int(float(raw))
+                except (TypeError, ValueError):
+                    return default
+                return max(lo, min(hi, val))
+
+            new_accept = _int_param(
+                "offer_auto_accept_threshold_pct",
+                shop.offer_auto_accept_threshold_pct, 0, 100,
+            )
+            new_decline = _int_param(
+                "offer_auto_decline_threshold_pct",
+                shop.offer_auto_decline_threshold_pct, 0, 100,
+            )
+            # Auto-decline must be strictly below auto-accept, else thresholds
+            # collide and the queue range disappears. Clamp.
+            if new_decline >= new_accept:
+                new_decline = max(0, new_accept - 1)
+
+            shop.offer_auto_accept_threshold_pct = new_accept
+            shop.offer_auto_decline_threshold_pct = new_decline
+            shop.offer_expiration_hours = _int_param(
+                "offer_expiration_hours", shop.offer_expiration_hours,
+                1, 24 * 365,
+            )
+            shop.offer_max_rounds = _int_param(
+                "offer_max_rounds", shop.offer_max_rounds, 1, 100,
+            )
+            shop.offer_min_buyer_account_age_hours = _int_param(
+                "offer_min_buyer_account_age_hours",
+                shop.offer_min_buyer_account_age_hours, 0, 24 * 365,
+            )
+
+            # offer_min_in_cents — dollar input, optional.
+            offer_min_dollars = (request.params.get("offer_min") or "").strip()
+            if offer_min_dollars:
+                try:
+                    shop.offer_min_in_cents = int(round(float(offer_min_dollars) * 100))
+                except (TypeError, ValueError):
+                    request.session.flash(("Invalid offer minimum.", "error"))
+            else:
+                shop.offer_min_in_cents = None
+
     # If we processed any form submission, respond accordingly
     if form_section:
         if request.headers.get("X-Requested-With") == "XMLHttpRequest":