§ 2.3 — Static manifest at a well-known URL for standard proposals (#29)

examples/line-item-audio.yaml

@@ -29,6 +29,7 @@ commitment:
   idempotency_key: "agency-a-camp1-streaming-audio-a7c33e10"
 
 committed_metrics: [{ metric: completion_rate, value: 0.92, basis: seller_reported }]
+visibility:        public
 buying_route:      SSP_PLATFORM
 transaction_mechanism: { available: ["PREFERRED_DEAL"], included: ["PREFERRED_DEAL"] }
 serving_mode:      dai

examples/line-item-ctv.yaml

@@ -29,6 +29,7 @@ hold_status:    { hold_available: true, hold_duration: "P14D",
                   hold_expires_at: "2026-10-01T00:00:00Z" }
 
 committed_metrics: [{ metric: completion_rate, value: 0.95, basis: seller_reported }]
+visibility:        public
 buying_route:      SSP_PLATFORM
 transaction_mechanism: { available: ["PRIVATE_AUCTION"], included: ["PRIVATE_AUCTION"] }
 serving_mode:      ssai

examples/manifest.json

@@ -0,0 +1,67 @@
+{
+  "seller_id": "reg:examplepub-digital",
+  "generated_at": "2026-10-01T06:00:00Z",
+  "spec_version": "3.0",
+  "proposals": [
+    {
+      "proposal_id": "examplepub-us-q4-2026-omni",
+      "version": 1,
+      "seller_name": "Example Publisher US",
+      "description": "Cross-channel Example Publisher US package spanning display, in-stream video and CTV. Business and financial audience skew, weekday-heavy delivery.",
+      "valid_from": "2026-10-01T00:00:00Z",
+      "valid_until": "2026-12-31T23:59:59Z",
+      "full_url": "https://examplepub.example/openproposal/examplepub-us-q4-2026-omni",
+      "line_items": [
+        {
+          "line_item_id": "weather-app-ctv",
+          "channel": "ctv",
+          "properties": [
+            "weather-app"
+          ],
+          "formats": {
+            "included": [
+              "ctv/instream-15s"
+            ]
+          },
+          "pricing": {
+            "cost_method": "CPM",
+            "gross_rate": 45.0
+          },
+          "committed_metrics": [
+            {
+              "metric": "completion_rate",
+              "value": 0.95,
+              "basis": "seller_reported"
+            }
+          ],
+          "transaction_mechanism": [
+            "PRIVATE_AUCTION"
+          ]
+        },
+        {
+          "line_item_id": "streaming-audio",
+          "channel": "audio",
+          "formats": {
+            "included": [
+              "audio/produced-30s"
+            ]
+          },
+          "pricing": {
+            "cost_method": "CPM",
+            "gross_rate": 18.0
+          },
+          "committed_metrics": [
+            {
+              "metric": "completion_rate",
+              "value": 0.92,
+              "basis": "seller_reported"
+            }
+          ],
+          "transaction_mechanism": [
+            "PREFERRED_DEAL"
+          ]
+        }
+      ]
+    }
+  ]
+}

spec/CHANGELOG.md

@@ -5,6 +5,11 @@ issue that caused it, so the comment record and the spec history line up.
 
 ## [Unreleased]
 
+- § 2.3 — a seller MAY publish its public standard line items as a static
+  manifest at `/.well-known/openproposal.json`, for a two-phase
+  discover-then-propose flow
+  ([#29](https://github.com/IABTechLab/OpenProposal/issues/29)).
+
 ## [3.0-draft-1] — 2026-09-22
 
 Initial draft published for public comment. Ported from the working-group

spec/openproposal-3.0.md

@@ -110,6 +110,31 @@ example:     "examplepub/audiences/smb-decision-makers@3"
   by its resolved value in the stored record, so the committed artifact is
   self-contained and immutable.
 
+### 2.3 Publication
+
+A seller MAY publish `https://<seller domain>/.well-known/openproposal.json`.
+
+Contents: `{ seller_id, generated_at, spec_version, proposals[] }`, where each
+entry in `proposals[]` carries `proposal_id`, `version`, the Summary
+Representation (§ 2.1) of each line item, and a `full_url` for the second
+phase.
+
+- `ETag` / `Last-Modified` are REQUIRED, so buyers can poll cheaply.
+- Only standard proposals appear, and within them only line items whose
+  `visibility` (§ 5.8) is `public`. `registry_gated` and `named` line items do
+  not.
+- Manifest entries MUST match the current version of each proposal. A stale
+  entry is a seller error.
+- Property lists stay as names in the summary; large lists use `catalog_ref`
+  (§ 2.2).
+
+Two-phase flow:
+
+1. **Discover:** fetch the manifest and screen the summaries. No language model
+   is required.
+2. **Propose:** fetch the Full Representation of shortlisted line items from
+   `full_url`, then compose and commit as usual.
+
 ---
 
 ## 3. Field mutability
@@ -375,6 +400,12 @@ See [`examples/line-item-ctv.yaml`](../examples/line-item-ctv.yaml).
 
 See [`examples/line-item-audio.yaml`](../examples/line-item-audio.yaml).
 
+### 6.5 Publication manifest
+
+A manifest (§ 2.3) listing the public line items of the example proposal. The
+display line item is `registry_gated`, so it is not listed. See
+[`examples/manifest.json`](../examples/manifest.json).
+
 ---
 
 ## 7. Why this split