diff --git a/.changeset/capability-flag-scenario-cross-reference.md b/.changeset/capability-flag-scenario-cross-reference.md
new file mode 100644
index 0000000000..e14755e09d
--- /dev/null
+++ b/.changeset/capability-flag-scenario-cross-reference.md
@@ -0,0 +1,14 @@
+---
+---
+
+docs: add capability-flag → scenario cross-reference section to compliance-catalog.mdx
+
+Adds a "Capability-gated scenarios" section to the compliance catalog that maps each
+`get_adcp_capabilities` flag to the scenarios it controls, so adopters can understand
+how a flag toggle changes their grading surface without grepping scenario YAMLs.
+
+Also updates `sales-proposal-mode` specialism status from `stable` to `deprecated` in
+the catalog table and adds a migration note, matching the enum's `x-deprecated-enum-values`
+declaration.
+
+Closes #4039.
diff --git a/docs/building/verification/compliance-catalog.mdx b/docs/building/verification/compliance-catalog.mdx
index 48d851dfb9..06682d663d 100644
--- a/docs/building/verification/compliance-catalog.mdx
+++ b/docs/building/verification/compliance-catalog.mdx
@@ -91,7 +91,7 @@ Specialisms are grouped below by parent protocol.
|-----------|--------|---------|
| `sales-guaranteed` | stable | Guaranteed media buys with human IO approval |
| `sales-non-guaranteed` | stable | Non-guaranteed auction-based media buys |
-| `sales-proposal-mode` | stable | Media buys negotiated via proposal acceptance |
+| `sales-proposal-mode` | deprecated | Proposal-mode selling — absorbed into `sales-guaranteed` + `media_buy.supports_proposals: true`. Do not claim for new agents. |
| `sales-catalog-driven` | stable | Catalog-driven commerce with conversion tracking |
| `sales-broadcast-tv` | stable | Broadcast linear TV with guaranteed inventory and FCC cancellation rules |
| `sales-social` | stable | Social media advertising platform with self-service flows |
@@ -102,6 +102,10 @@ Specialisms are grouped below by parent protocol.
**Coming in 3.1.** `sales-streaming-tv` (CTV / streaming), `sales-exchange` (programmatic SSP / exchange), and `sales-retail-media` (retail media network) are scheduled for 3.1. Sellers in those categories should claim `sales-guaranteed` or `sales-non-guaranteed` at 3.0 GA.
+
+**`sales-proposal-mode` deprecated.** Proposal-driven selling is now handled by `sales-guaranteed` with `media_buy.supports_proposals: true`. New agents should claim `sales-guaranteed`; the runner grades the proposal lifecycle (`media_buy_seller/proposal_finalize`) when `supports_proposals: true` and skips it when `false`. The `sales-proposal-mode` ID remains valid for existing implementations and will be removed in a future major version.
+
+
`audience-sync` moved from the `governance` protocol to `media-buy` to match its tool family. If your agent claims `audience-sync` but only declares `governance` in `supported_protocols`, add `media_buy` to `supported_protocols` — the runner now expects the media-buy baseline to run alongside the audience-sync storyboard.
@@ -165,6 +169,22 @@ The storyboard runner:
If any `stable` storyboard fails, your agent is not compliant for that claim. See [Validate Your Agent](/docs/building/verification/validate-your-agent) for how to run the suite locally.
+## Capability-gated scenarios
+
+Some compliance scenarios only execute when the seller explicitly declares a matching capability flag in `get_adcp_capabilities`. Setting a flag to `false` opts out of the scenario — the runner grades it `capability_unsupported` (a skip, not a fail) rather than executing the steps. This lets sellers scope their compliance surface to the features they actually support.
+
+{/* Lint: NO automated enforcement — this table is maintained by hand against
+ requires_capability: blocks in static/compliance/source/protocols/**\/scenarios\/**\.yaml.
+ Verify this table when adding or removing a capability-gated scenario YAML. */}
+
+| Capability flag | Default (when absent) | When `true` | When `false` |
+|---|---|---|---|
+| `media_buy.supports_proposals` | treated as `true` — runs (graded) | `media_buy_seller/proposal_finalize` runs — graded as part of the `sales-guaranteed` storyboard | `capability_unsupported` — scenario skips, not a compliance fail |
+
+
+When `media_buy.supports_proposals` is omitted, the compliance runner treats it the same as `true` — the `proposal_finalize` scenario runs and is graded. To opt out, declare `false` explicitly. Direct-buy guaranteed sellers (auction PG, retail SKU, quoted-rate) declare `false`; full-service guaranteed sellers that generate curated proposals declare `true`.
+
+
## Naming conventions
Four casings coexist in the taxonomy. Which one applies depends on where the identifier is read:
diff --git a/static/schemas/source/protocol/get-adcp-capabilities-response.json b/static/schemas/source/protocol/get-adcp-capabilities-response.json
index 0be0a1b2fb..b7e34d2e02 100644
--- a/static/schemas/source/protocol/get-adcp-capabilities-response.json
+++ b/static/schemas/source/protocol/get-adcp-capabilities-response.json
@@ -208,7 +208,7 @@
},
"supports_proposals": {
"type": "boolean",
- "description": "Whether this seller commits to the proposal lifecycle on get_products: when called with buying_mode: 'brief' the seller will return at least one entry in proposals[]; when called with buying_mode: 'refine' + action: 'finalize' the seller will transition a proposal from draft to committed. A declaration of true is a commitment the seller will be graded against, not just a feature flag — sellers that decline a brief on policy grounds still owe a structured proposal-shaped rejection rather than an empty proposals[]. Most guaranteed-deal sellers (premium pubs, broadcast, CTV) declare true; auction-based PG, retail SKU, and quoted-rate direct-buy flows declare false. When false or absent, the seller serves products directly without proposal abstraction; conformance runners skip proposal-lifecycle storyboards.",
+ "description": "Whether this seller commits to the proposal lifecycle on get_products: when called with buying_mode: 'brief' the seller will return at least one entry in proposals[]; when called with buying_mode: 'refine' + action: 'finalize' the seller will transition a proposal from draft to committed. A declaration of true is a commitment the seller will be graded against, not just a feature flag — sellers that decline a brief on policy grounds still owe a structured proposal-shaped rejection rather than an empty proposals[]. Most guaranteed-deal sellers (premium pubs, broadcast, CTV) declare true; auction-based PG, retail SKU, and quoted-rate direct-buy flows declare false. When false, the seller serves products directly without proposal abstraction; conformance runners skip proposal-lifecycle storyboards. When absent, the compliance runner treats the flag as true — the proposal lifecycle runs and is graded; declare false explicitly to opt out.",
"default": false
},
"features": {