diff --git a/crates/aisix-core/src/models/model.rs b/crates/aisix-core/src/models/model.rs
index 68b73635..be018e12 100644
--- a/crates/aisix-core/src/models/model.rs
+++ b/crates/aisix-core/src/models/model.rs
@@ -204,11 +204,10 @@ pub struct Model {
     ///    `dispatch::require_provider()` on every bridge-dispatching
     ///    endpoint (chat, completions, embeddings, images, audio,
     ///    rerank).
-    /// 4. The one-cycle compat shim in
-    ///    `crates/aisix-proxy/src/dispatch.rs::resolve_bridge` (called
-    ///    by every bridge-dispatching endpoint) that rescues pre-
-    ///    Phase-A on-disk PK rows (empty `provider` + `None` `adapter`)
-    ///    by falling back to `hub.get_specialized(Model.provider)`.
+    ///
+    /// Bridge dispatch itself is keyed on the ProviderKey's
+    /// `provider`/`adapter` (`Hub::dispatch_two_tier`), not on this
+    /// field.
     ///
     /// `None` for routing models.
     ///
diff --git a/crates/aisix-core/src/models/provider_key.rs b/crates/aisix-core/src/models/provider_key.rs
index a5ad8b2d..1530826f 100644
--- a/crates/aisix-core/src/models/provider_key.rs
+++ b/crates/aisix-core/src/models/provider_key.rs
@@ -56,26 +56,23 @@ pub struct ProviderKey {
     pub api_base: Option<String>,
 
     /// Vendor identity (e.g. `"deepseek"`, `"openai"`, any models.dev
-    /// catalog id). Post-#302 Phase A this is the primary specialized-
-    /// dispatch key consumed by `Hub::dispatch_two_tier` (specialized
-    /// lookup tier) and by both family bridges' `resolve_base` safety
-    /// guard (the guard rejects an empty `api_base` for any vendor
-    /// whose identity doesn't match the family's canonical vendor).
-    /// Empty for pre-Phase-A on-disk rows still in etcd — those route
-    /// via the compat shim in `aisix-proxy::dispatch::resolve_bridge`
-    /// that falls back to `Model.provider`. Old payloads that omit
-    /// `provider` continue to deserialize via `#[serde(default)]`.
+    /// catalog id). The primary specialized-dispatch key consumed by
+    /// `Hub::dispatch_two_tier` (specialized lookup tier) and by both
+    /// family bridges' `resolve_base` safety guard (the guard rejects an
+    /// empty `api_base` for any vendor whose identity doesn't match the
+    /// family's canonical vendor). cp-api always writes it; the
+    /// `#[serde(default)]` only covers in-memory test fixtures.
     #[serde(default)]
     pub provider: String,
 
     /// Wire-shape adapter (`openai` / `anthropic` / `bedrock` /
-    /// `vertex` / `azure-openai`). Post-#302 Phase A this is the
-    /// family-fallback dispatch key for `Hub::dispatch_two_tier` when
-    /// the specialized lookup misses; long-tail OpenAI-compat vendors
-    /// (xai, openrouter, groq, …) reach the right bridge through this
-    /// path without a DP code change. `None` for pre-Phase-A on-disk
-    /// rows — those dispatch via the compat shim. Old payloads that
-    /// omit `adapter` continue to deserialize via `#[serde(default)]`.
+    /// `vertex` / `azure-openai`). The family-fallback dispatch key for
+    /// `Hub::dispatch_two_tier` when the specialized lookup misses;
+    /// long-tail OpenAI-compat vendors (xai, openrouter, groq, …) reach
+    /// the right bridge through this path without a DP code change.
+    /// cp-api always writes it; a `ProviderKey` that resolves to neither
+    /// a specialized `provider` nor a registered `adapter` family is a
+    /// misconfiguration and surfaces as 503.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub adapter: Option<Adapter>,
 
diff --git a/crates/aisix-proxy/src/background.rs b/crates/aisix-proxy/src/background.rs
index eba45504..9762f828 100644
--- a/crates/aisix-proxy/src/background.rs
+++ b/crates/aisix-proxy/src/background.rs
@@ -106,8 +106,12 @@ async fn check_direct_model(
         dispatch::require_provider(model).map_err(|e| BridgeError::Config(e.to_string()))?;
     let pk_entry = dispatch::resolve_provider_key(snapshot, model)
         .map_err(|e| BridgeError::Config(e.to_string()))?;
-    let bridge = dispatch::resolve_bridge(hub, &pk_entry.value, model.provider.as_deref())
-        .ok_or_else(|| BridgeError::Config("no bridge registered for provider".into()))?;
+    let bridge = dispatch::resolve_bridge(hub, &pk_entry.value).ok_or_else(|| {
+        BridgeError::Config(format!(
+            "no bridge registered for provider_key provider={:?} adapter={:?}",
+            pk_entry.value.provider, pk_entry.value.adapter
+        ))
+    })?;
 
     let req = ChatFormat {
         model: model.display_name.clone(),
diff --git a/crates/aisix-proxy/src/chat.rs b/crates/aisix-proxy/src/chat.rs
index e0628ec0..31029a2e 100644
--- a/crates/aisix-proxy/src/chat.rs
+++ b/crates/aisix-proxy/src/chat.rs
@@ -730,9 +730,7 @@ async fn dispatch(
         // we commit to a long upstream call.
         let pk_entry =
             crate::dispatch::resolve_provider_key(&snapshot, only).map_err(with_model)?;
-        if crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, only.provider.as_deref())
-            .is_none()
-        {
+        if crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value).is_none() {
             return Err(with_model(ProxyError::ProviderUnavailable));
         }
     }
@@ -756,9 +754,8 @@ async fn dispatch(
         let provider = crate::dispatch::require_provider(model).map_err(with_model)?;
         let pk_entry =
             crate::dispatch::resolve_provider_key(&snapshot, model).map_err(with_model)?;
-        let bridge =
-            crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, model.provider.as_deref())
-                .ok_or_else(|| with_model(ProxyError::ProviderUnavailable))?;
+        let bridge = crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value)
+            .ok_or_else(|| with_model(ProxyError::ProviderUnavailable))?;
         let model_arc = Arc::new(model.clone());
         let pk_arc = Arc::new(pk_entry.value.clone());
         let ctx = BridgeContext::new(request_id, model_arc, pk_arc);
@@ -1207,17 +1204,13 @@ async fn dispatch(
         // Two-tier dispatch via `Hub::dispatch_two_tier`: specialized
         // vendor (ProviderKey.provider) first, then adapter family
         // (ProviderKey.adapter). The legacy `Provider`-keyed registry
-        // is gone after #302 Phase A. `resolve_bridge` carries a
-        // one-cycle compat shim for pre-Phase-A PK rows that still
-        // have empty `provider` and `adapter: None` on disk — those
-        // resolve via `Model.provider` (passed below). Once cp-api
-        // has backfilled every PK, the shim becomes unreachable.
-        let Some(bridge) =
-            crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, model.provider.as_deref())
-        else {
-            last_err = Some(BridgeError::Config(
-                "no bridge registered for provider".into(),
-            ));
+        // is gone after #302 Phase A; a PK that matches neither tier is
+        // a misconfiguration and surfaces as 503.
+        let Some(bridge) = crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value) else {
+            last_err = Some(BridgeError::Config(format!(
+                "no bridge registered for provider_key provider={:?} adapter={:?}",
+                pk_entry.value.provider, pk_entry.value.adapter
+            )));
             continue;
         };
         let model_arc = Arc::new(model.clone());
diff --git a/crates/aisix-proxy/src/completions.rs b/crates/aisix-proxy/src/completions.rs
index bcaa1c78..b81532a0 100644
--- a/crates/aisix-proxy/src/completions.rs
+++ b/crates/aisix-proxy/src/completions.rs
@@ -170,9 +170,8 @@ async fn dispatch(
     let provider = crate::dispatch::require_provider(model)?;
     let pk_entry = crate::dispatch::resolve_provider_key(&snapshot, model)?;
 
-    let bridge =
-        crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, model.provider.as_deref())
-            .ok_or(ProxyError::ProviderUnavailable)?;
+    let bridge = crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value)
+        .ok_or(ProxyError::ProviderUnavailable)?;
 
     let model_arc = Arc::new(model.clone());
     let pk_arc = Arc::new(pk_entry.value.clone());
diff --git a/crates/aisix-proxy/src/dispatch.rs b/crates/aisix-proxy/src/dispatch.rs
index 1ea68a4a..81864426 100644
--- a/crates/aisix-proxy/src/dispatch.rs
+++ b/crates/aisix-proxy/src/dispatch.rs
@@ -27,55 +27,20 @@ use crate::error::ProxyError;
 
 /// Resolve the Bridge to dispatch this request through.
 ///
-/// Primary path: `Hub::dispatch_two_tier` — specialized vendor first
-/// (keyed on `ProviderKey.provider`), then adapter family (keyed on
-/// `ProviderKey.adapter`). Vendor identity is an open string;
-/// adapter is the closed 5-value enum. Any catalog vendor cp-api
-/// admits (xai, openrouter, future long-tail) resolves through the
-/// family fallthrough without a DP code change.
+/// `Hub::dispatch_two_tier` — specialized vendor first (keyed on
+/// `ProviderKey.provider`), then adapter family (keyed on
+/// `ProviderKey.adapter`). Vendor identity is an open string; adapter
+/// is the closed 5-value enum. Any catalog vendor cp-api admits (xai,
+/// openrouter, future long-tail) resolves through the family
+/// fallthrough without a DP code change.
 ///
-/// Compat shim: pre-Phase-A `ProviderKey` rows still on disk have
-/// empty `provider` AND `adapter: None`. For those, fall back to
-/// the specialized registry keyed on `Model.provider`. This keeps
-/// existing on-disk data routable through the upgrade cycle. Once
-/// cp-api has backfilled every PK with `provider` + `adapter`,
-/// the fallback path becomes unreachable and can be removed.
-///
-/// Returns `None` when the two-tier path AND the compat fallback
-/// both miss — caller surfaces this as 503 "no dispatch path".
-pub(crate) fn resolve_bridge(
-    hub: &Hub,
-    provider_key: &ProviderKey,
-    model_provider: Option<&str>,
-) -> Option<Arc<dyn Bridge>> {
-    if let Some(b) = hub.dispatch_two_tier(provider_key) {
-        return Some(b);
-    }
-    // One-cycle compat for pre-Phase-A PK rows. cp-api now writes
-    // `provider` + `adapter` for every PK row; once any pre-cutover
-    // rows have been re-saved (or the operator's etcd has been wiped
-    // and reseeded), this `if` body becomes unreachable.
-    if provider_key.provider.is_empty() && provider_key.adapter.is_none() {
-        if let Some(mp) = model_provider {
-            if !mp.is_empty() {
-                // Emit a tracing::warn! so an operator (or SREs reading
-                // logs) can detect un-migrated PK rows still in the
-                // wild. The "one-cycle" deprecation promise is only
-                // enforceable if dispatching through the shim is
-                // observable.
-                tracing::warn!(
-                    target: "aisix_proxy::dispatch",
-                    pk_display_name = %provider_key.display_name,
-                    model_provider = %mp,
-                    "compat shim: pre-Phase-A PK row (empty `provider` + `adapter: None`) \
-                     dispatched via Model.provider fallback — re-save this PK to remove the \
-                     legacy code path"
-                );
-                return hub.get_specialized(mp);
-            }
-        }
-    }
-    None
+/// Returns `None` when both tiers miss (the PK carries neither a
+/// registered `provider` nor a registered `adapter`) — caller surfaces
+/// this as 503 "no dispatch path". cp-api writes `provider` + `adapter`
+/// on every PK, so a miss means a genuine misconfiguration, not a
+/// migration gap.
+pub(crate) fn resolve_bridge(hub: &Hub, provider_key: &ProviderKey) -> Option<Arc<dyn Bridge>> {
+    hub.dispatch_two_tier(provider_key)
 }
 
 /// Look up the `ProviderKey` a given `Model` references. Returns a
@@ -545,13 +510,11 @@ mod tests {
 
     // --- resolve_bridge tests -------------------------------------
     //
-    // Cover the three reachable outcomes of resolve_bridge:
+    // Cover the reachable outcomes of resolve_bridge:
     //   1. specialized hit — pk.provider matches a specialized entry
     //   2. family hit       — pk.adapter matches a family entry,
     //                          specialized misses
-    //   3. legacy fallback  — both new-tier maps miss, legacy hub.get
-    //                          serves the bridge
-    //   4. none miss        — nothing registered at all
+    //   3. none miss        — neither tier matches (misconfigured PK)
     //
     // A minimal Bridge stub is used so the test doesn't need reqwest
     // or a real upstream.
@@ -626,7 +589,7 @@ mod tests {
         }
 
         #[test]
-        fn specialized_hit_wins_over_family_and_legacy() {
+        fn specialized_hit_wins_over_family() {
             let hub = Hub::new();
             hub.register_specialized(
                 "deepseek",
@@ -635,10 +598,9 @@ mod tests {
                 }),
             );
             hub.register_family(Adapter::Openai, Arc::new(StubBridge { name: "family" }));
-            hub.register_specialized("openai", Arc::new(StubBridge { name: "legacy" }));
 
             let pk = pk_with_provider_and_adapter("deepseek", Some("openai"));
-            let bridge = resolve_bridge(&hub, &pk, None).unwrap();
+            let bridge = resolve_bridge(&hub, &pk).unwrap();
             assert_eq!(bridge.name(), "specialized");
         }
 
@@ -646,69 +608,51 @@ mod tests {
         fn family_hit_when_specialized_misses() {
             let hub = Hub::new();
             hub.register_family(Adapter::Openai, Arc::new(StubBridge { name: "family" }));
-            hub.register_specialized("openai", Arc::new(StubBridge { name: "legacy" }));
 
             // pk.provider = "unknown-vendor" → no specialized; pk.adapter
             // = Openai → family hit.
             let pk = pk_with_provider_and_adapter("unknown-vendor", Some("openai"));
-            let bridge = resolve_bridge(&hub, &pk, None).unwrap();
+            let bridge = resolve_bridge(&hub, &pk).unwrap();
             assert_eq!(bridge.name(), "family");
         }
 
-        /// A PK with empty `provider` AND `adapter: None` plus no
-        /// `Model.provider` to fall back on has nothing to dispatch
-        /// on — caller surfaces 503.
+        /// A PK whose `provider` matches no specialized entry and whose
+        /// `adapter` matches no family entry has nothing to dispatch on
+        /// — caller surfaces 503. cp-api always writes both fields, so
+        /// this is a genuine misconfiguration, not a migration gap.
         #[test]
-        fn none_when_neither_tier_matches_and_no_model_compat() {
+        fn none_when_neither_tier_matches() {
             let hub = Hub::new();
             hub.register_specialized("openai", Arc::new(StubBridge { name: "vendor" }));
-            let pk = pk_with_provider_and_adapter("", None);
-            assert!(resolve_bridge(&hub, &pk, None).is_none());
+            let pk = pk_with_provider_and_adapter("unknown-vendor", Some("anthropic"));
+            assert!(resolve_bridge(&hub, &pk).is_none());
         }
 
+        /// A PK with empty `provider` AND no `adapter` (the malformed
+        /// shape the removed compat shim used to rescue) now resolves to
+        /// nothing — 503.
         #[test]
-        fn none_when_nothing_registered() {
+        fn none_when_provider_and_adapter_both_empty() {
             let hub = Hub::new();
+            hub.register_specialized("openai", Arc::new(StubBridge { name: "vendor" }));
             let pk = pk_with_provider_and_adapter("", None);
-            assert!(resolve_bridge(&hub, &pk, None).is_none());
+            assert!(resolve_bridge(&hub, &pk).is_none());
         }
 
-        /// One-cycle compat for pre-Phase-A PK rows. A PK with empty
-        /// `provider` AND `adapter: None` (on-disk shape pre-cutover)
-        /// resolves through the specialized registry keyed on the
-        /// Model's vendor string, so existing data stays routable
-        /// across the upgrade without forcing operators to re-save
-        /// every PK first.
         #[test]
-        fn legacy_pk_with_empty_fields_falls_back_to_model_provider() {
+        fn none_when_nothing_registered() {
             let hub = Hub::new();
-            hub.register_specialized(
-                "openai",
-                Arc::new(StubBridge {
-                    name: "specialized-openai",
-                }),
-            );
-            // Pre-Phase-A PK shape: no `provider`, no `adapter`.
-            let pk = pk_with_provider_and_adapter("", None);
-            let bridge = resolve_bridge(&hub, &pk, Some("openai")).unwrap();
-            assert_eq!(bridge.name(), "specialized-openai");
+            let pk = pk_with_provider_and_adapter("openai", Some("openai"));
+            assert!(resolve_bridge(&hub, &pk).is_none());
         }
 
-        /// Compat shim must NOT fire when the PK carries either
-        /// `provider` or `adapter` — those rows go through the
-        /// two-tier path and miss authoritatively if nothing matches.
-        /// A future PR that drops `Adapter::Openai` family must FAIL
-        /// the test below, not get rescued by the compat shim.
-        ///
-        /// This test pins the regression vector exactly: PK has
-        /// `provider:"vendor-without-specialized"` + `adapter:Some(Openai)`,
-        /// hub has NO `Adapter::Openai` family registered. The
-        /// two-tier path returns None on both layers. The compat
-        /// shim must NOT rescue this because `provider` is non-empty.
-        /// If a future PR drops `Adapter::Openai` family registration
-        /// in `build_hub()`, this test fires.
+        /// A PK with a non-empty `provider` and an `adapter` whose
+        /// family isn't registered misses both tiers authoritatively —
+        /// it is NOT rescued by any fallback. If a future PR drops the
+        /// `Adapter::Openai` family registration in `build_hub()`, this
+        /// fires instead of silently routing elsewhere.
         #[test]
-        fn compat_shim_does_not_rescue_missing_family_for_post_phase_a_pk() {
+        fn none_when_adapter_family_not_registered() {
             let hub = Hub::new();
             hub.register_specialized(
                 "openai",
@@ -716,16 +660,10 @@ mod tests {
                     name: "specialized-openai",
                 }),
             );
-            // `vendor-without-specialized` is not registered as
-            // specialized; `Adapter::Openai` is not registered as
-            // family. Compat shim must not fire because `provider`
-            // is non-empty.
+            // `vendor-without-specialized` has no specialized entry;
+            // `Adapter::Openai` has no family entry → None.
             let pk = pk_with_provider_and_adapter("vendor-without-specialized", Some("openai"));
-            assert!(
-                resolve_bridge(&hub, &pk, Some("openai")).is_none(),
-                "compat shim MUST NOT rescue a missing Adapter::Openai family — \
-                 provider is non-empty, so post-Phase-A path is authoritative",
-            );
+            assert!(resolve_bridge(&hub, &pk).is_none());
         }
     }
 }
diff --git a/crates/aisix-proxy/src/embeddings.rs b/crates/aisix-proxy/src/embeddings.rs
index 05921432..b2d7c1c7 100644
--- a/crates/aisix-proxy/src/embeddings.rs
+++ b/crates/aisix-proxy/src/embeddings.rs
@@ -219,9 +219,8 @@ async fn dispatch(
     let provider = crate::dispatch::require_provider(model)?;
     let pk_entry = crate::dispatch::resolve_provider_key(&snapshot, model)?;
 
-    let bridge =
-        crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, model.provider.as_deref())
-            .ok_or(ProxyError::ProviderUnavailable)?;
+    let bridge = crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value)
+        .ok_or(ProxyError::ProviderUnavailable)?;
 
     let model_rl =
         crate::quota::ModelRateLimit::from_model(&body.model, &model_entry.id, &model_entry.value);
diff --git a/crates/aisix-proxy/src/images.rs b/crates/aisix-proxy/src/images.rs
index eb4a667d..a8225453 100644
--- a/crates/aisix-proxy/src/images.rs
+++ b/crates/aisix-proxy/src/images.rs
@@ -173,9 +173,8 @@ async fn dispatch(
     let provider = crate::dispatch::require_provider(model)?.to_string();
     let pk_entry = crate::dispatch::resolve_provider_key(&snapshot, model)?;
 
-    let bridge =
-        crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value, model.provider.as_deref())
-            .ok_or(ProxyError::ProviderUnavailable)?;
+    let bridge = crate::dispatch::resolve_bridge(&state.hub, &pk_entry.value)
+        .ok_or(ProxyError::ProviderUnavailable)?;
 
     let model_arc = Arc::new(model.clone());
     let pk_arc = Arc::new(pk_entry.value.clone());
diff --git a/crates/aisix-proxy/src/messages.rs b/crates/aisix-proxy/src/messages.rs
index edea18e3..e6fc8c1a 100644
--- a/crates/aisix-proxy/src/messages.rs
+++ b/crates/aisix-proxy/src/messages.rs
@@ -844,9 +844,8 @@ async fn cross_provider_dispatch(
             ProxyError::InvalidRequest(format!("model `{model_name}` has no provider prefix"))
         })?
         .to_string();
-    let bridge: Arc<dyn Bridge> =
-        crate::dispatch::resolve_bridge(&state.hub, provider_key, model.provider.as_deref())
-            .ok_or(ProxyError::ProviderUnavailable)?;
+    let bridge: Arc<dyn Bridge> = crate::dispatch::resolve_bridge(&state.hub, provider_key)
+        .ok_or(ProxyError::ProviderUnavailable)?;
 
     // Parse the Anthropic-shape body into the gateway's normalised
     // ChatFormat. Errors here are 400 — the request is malformed
diff --git a/crates/aisix-server/src/main.rs b/crates/aisix-server/src/main.rs
index be078444..8f34f1e8 100644
--- a/crates/aisix-server/src/main.rs
+++ b/crates/aisix-server/src/main.rs
@@ -836,20 +836,14 @@ fn build_hub() -> Hub {
     hub.register_family(Adapter::AzureOpenai, Arc::new(AzureOpenAiBridge::new()));
     hub.register_family(Adapter::Bedrock, Arc::new(BedrockBridge::new()));
 
-    // ─── Specialized vendor bridges (one-cycle compat shim) ──────────
+    // ─── Specialized vendor bridges ─────────────────────────────────
     //
-    // Pre-Phase-A ProviderKeys on disk may carry `provider` but no
-    // `adapter` field (cp-api started writing `adapter` at the same
-    // commit as Phase A — older rows haven't been resaved). Without
-    // these explicit specialized registrations, `dispatch_two_tier`
-    // would fall through to the None branch and 503 those PKs.
-    //
-    // Only `openai` and `anthropic` are registered — every other
-    // vendor only existed in the catalog post-Phase-A (Phase A added
-    // them as long-tail OpenAI-compat) and is guaranteed to have
-    // `adapter` populated, so the family bridge above already covers
-    // them. Once cp-api has resaved all pre-Phase-A rows these two
-    // entries become safe to delete.
+    // `openai` and `anthropic` are the two canonical vendors with a
+    // dedicated specialized bridge, so a ProviderKey whose `provider`
+    // is exactly `"openai"`/`"anthropic"` resolves through the
+    // specialized tier of `dispatch_two_tier`. Long-tail OpenAI-compat
+    // vendors (xai, openrouter, groq, deepseek, …) carry `adapter:
+    // openai` and resolve through the family tier above instead.
     hub.register_specialized("openai", Arc::new(OpenAiBridge::new()));
     hub.register_specialized("anthropic", Arc::new(AnthropicBridge::new()));
 
@@ -1290,46 +1284,36 @@ mod tests {
         );
     }
 
-    /// `build_hub()` MUST keep `register_specialized("openai", …)` so
-    /// `crates/aisix-proxy/src/dispatch.rs::resolve_bridge`'s
-    /// compat-shim fallback (`hub.get_specialized(Model.provider)`)
-    /// resolves a pre-Phase-A PK row (empty `provider`, no `adapter`).
-    /// A future PR that drops this registration prematurely — before
-    /// cp-api has re-saved every legacy PK — would silently 503 those
-    /// rows. This test pins the shim contract end-to-end against the
+    /// `build_hub()` MUST register the specialized `openai` vendor so a
+    /// ProviderKey with `provider: "openai"` dispatches to the dedicated
+    /// `OpenAiBridge`. This pins the registration end-to-end against the
     /// real `build_hub()` registry (not a stub Hub), so it fails the
     /// moment the registration disappears.
     #[test]
-    fn build_hub_compat_shim_resolves_pre_phase_a_openai_pk() {
+    fn build_hub_registers_specialized_openai_vendor() {
         let hub = build_hub();
         let bridge = hub
             .get_specialized("openai")
-            .expect("openai compat shim must dispatch pre-Phase-A PK rows");
+            .expect("openai vendor must be registered as specialized");
         assert_eq!(
             bridge.name(),
             "openai",
-            "specialized 'openai' compat shim MUST be `OpenAiBridge::new()` \
-             (returning bridge name 'openai') so pre-Phase-A PK rows with \
-             empty `provider` + no `adapter` resolve via \
-             `dispatch::resolve_bridge`'s `hub.get_specialized(Model.provider)` \
-             fallback",
+            "specialized 'openai' MUST be `OpenAiBridge::new()` (bridge name 'openai')",
         );
     }
 
-    /// Parallel of the openai compat-shim test, for the Anthropic side.
+    /// Parallel of the openai specialized-registration test, for the
+    /// Anthropic side.
     #[test]
-    fn build_hub_compat_shim_resolves_pre_phase_a_anthropic_pk() {
+    fn build_hub_registers_specialized_anthropic_vendor() {
         let hub = build_hub();
         let bridge = hub
             .get_specialized("anthropic")
-            .expect("anthropic compat shim must dispatch pre-Phase-A PK rows");
+            .expect("anthropic vendor must be registered as specialized");
         assert_eq!(
             bridge.name(),
             "anthropic",
-            "specialized 'anthropic' compat shim MUST be `AnthropicBridge::new()` \
-             so pre-Phase-A PK rows with empty `provider` + no `adapter` resolve \
-             via `dispatch::resolve_bridge`'s `hub.get_specialized(Model.provider)` \
-             fallback",
+            "specialized 'anthropic' MUST be `AnthropicBridge::new()` (bridge name 'anthropic')",
         );
     }
 }
diff --git a/schemas/resources/model.schema.json b/schemas/resources/model.schema.json
index 5529687c..ec4016d3 100644
--- a/schemas/resources/model.schema.json
+++ b/schemas/resources/model.schema.json
@@ -51,7 +51,7 @@
       ]
     },
     "provider": {
-      "description": "Upstream vendor identity, free-form string (e.g. `\"openai\"`, `\"xai\"`, `\"openrouter\"`, any models.dev catalog id). Primary dispatch reads `ProviderKey.adapter` + `ProviderKey.provider` via `Hub::dispatch_two_tier`, so a new long-tail vendor admitted by cp-api works without a DP code change. `Model.provider` is additionally consumed by:\n\n1. Anti-misdispatch gates that reject cross-provider routing for endpoints whose wire shape is vendor-specific: - `/v1/messages` (`crates/aisix-proxy/src/messages.rs:290`) — non-anthropic Models go through `cross_provider_dispatch`. - `/v1/responses` (`crates/aisix-proxy/src/responses.rs:117`) — non-openai Models rejected with 400. - `/v1/images/generations` (`crates/aisix-proxy/src/images.rs:124`) — non-openai Models rejected with 400. 2. `/v1/rerank` vendor gate + access-log label (`crates/aisix-proxy/src/rerank.rs:125,145`); Cohere/Jina each have a native rerank surface that bypasses the Bridge trait, so this path stays keyed on `Model.provider`. 3. Telemetry / access-log labels via `dispatch::require_provider()` on every bridge-dispatching endpoint (chat, completions, embeddings, images, audio, rerank). 4. The one-cycle compat shim in `crates/aisix-proxy/src/dispatch.rs::resolve_bridge` (called by every bridge-dispatching endpoint) that rescues pre- Phase-A on-disk PK rows (empty `provider` + `None` `adapter`) by falling back to `hub.get_specialized(Model.provider)`.\n\n`None` for routing models.\n\nCloses the schema-validation half of api7/AISIX-Cloud#417 and the dispatch half of api7/AISIX-Cloud#302 Phase A.",
+      "description": "Upstream vendor identity, free-form string (e.g. `\"openai\"`, `\"xai\"`, `\"openrouter\"`, any models.dev catalog id). Primary dispatch reads `ProviderKey.adapter` + `ProviderKey.provider` via `Hub::dispatch_two_tier`, so a new long-tail vendor admitted by cp-api works without a DP code change. `Model.provider` is additionally consumed by:\n\n1. Anti-misdispatch gates that reject cross-provider routing for endpoints whose wire shape is vendor-specific: - `/v1/messages` (`crates/aisix-proxy/src/messages.rs:290`) — non-anthropic Models go through `cross_provider_dispatch`. - `/v1/responses` (`crates/aisix-proxy/src/responses.rs:117`) — non-openai Models rejected with 400. - `/v1/images/generations` (`crates/aisix-proxy/src/images.rs:124`) — non-openai Models rejected with 400. 2. `/v1/rerank` vendor gate + access-log label (`crates/aisix-proxy/src/rerank.rs:125,145`); Cohere/Jina each have a native rerank surface that bypasses the Bridge trait, so this path stays keyed on `Model.provider`. 3. Telemetry / access-log labels via `dispatch::require_provider()` on every bridge-dispatching endpoint (chat, completions, embeddings, images, audio, rerank).\n\nBridge dispatch itself is keyed on the ProviderKey's `provider`/`adapter` (`Hub::dispatch_two_tier`), not on this field.\n\n`None` for routing models.\n\nCloses the schema-validation half of api7/AISIX-Cloud#417 and the dispatch half of api7/AISIX-Cloud#302 Phase A.",
       "type": [
         "string",
         "null"
diff --git a/schemas/resources/provider_key.schema.json b/schemas/resources/provider_key.schema.json
index 43f4f2d8..0f2e99f9 100644
--- a/schemas/resources/provider_key.schema.json
+++ b/schemas/resources/provider_key.schema.json
@@ -8,7 +8,7 @@
   ],
   "properties": {
     "adapter": {
-      "description": "Wire-shape adapter (`openai` / `anthropic` / `bedrock` / `vertex` / `azure-openai`). Post-#302 Phase A this is the family-fallback dispatch key for `Hub::dispatch_two_tier` when the specialized lookup misses; long-tail OpenAI-compat vendors (xai, openrouter, groq, …) reach the right bridge through this path without a DP code change. `None` for pre-Phase-A on-disk rows — those dispatch via the compat shim. Old payloads that omit `adapter` continue to deserialize via `#[serde(default)]`.",
+      "description": "Wire-shape adapter (`openai` / `anthropic` / `bedrock` / `vertex` / `azure-openai`). The family-fallback dispatch key for `Hub::dispatch_two_tier` when the specialized lookup misses; long-tail OpenAI-compat vendors (xai, openrouter, groq, …) reach the right bridge through this path without a DP code change. cp-api always writes it; a `ProviderKey` that resolves to neither a specialized `provider` nor a registered `adapter` family is a misconfiguration and surfaces as 503.",
       "anyOf": [
         {
           "$ref": "#/definitions/Adapter"
@@ -30,7 +30,7 @@
       "type": "string"
     },
     "provider": {
-      "description": "Vendor identity (e.g. `\"deepseek\"`, `\"openai\"`, any models.dev catalog id). Post-#302 Phase A this is the primary specialized- dispatch key consumed by `Hub::dispatch_two_tier` (specialized lookup tier) and by both family bridges' `resolve_base` safety guard (the guard rejects an empty `api_base` for any vendor whose identity doesn't match the family's canonical vendor). Empty for pre-Phase-A on-disk rows still in etcd — those route via the compat shim in `aisix-proxy::dispatch::resolve_bridge` that falls back to `Model.provider`. Old payloads that omit `provider` continue to deserialize via `#[serde(default)]`.",
+      "description": "Vendor identity (e.g. `\"deepseek\"`, `\"openai\"`, any models.dev catalog id). The primary specialized-dispatch key consumed by `Hub::dispatch_two_tier` (specialized lookup tier) and by both family bridges' `resolve_base` safety guard (the guard rejects an empty `api_base` for any vendor whose identity doesn't match the family's canonical vendor). cp-api always writes it; the `#[serde(default)]` only covers in-memory test fixtures.",
       "default": "",
       "type": "string"
     },
diff --git a/tests/e2e/src/cases/anthropic-upstream-e2e.test.ts b/tests/e2e/src/cases/anthropic-upstream-e2e.test.ts
index 0f0aafc5..f0cac6f0 100644
--- a/tests/e2e/src/cases/anthropic-upstream-e2e.test.ts
+++ b/tests/e2e/src/cases/anthropic-upstream-e2e.test.ts
@@ -67,6 +67,8 @@ describe("anthropic upstream e2e: OpenAI in, Anthropic out, OpenAI back to calle
     // these mixed up was the lesson from the unit-level matrix tests.
     const pk = await admin.createProviderKey({
       display_name: "an-e2e-pk",
+      provider: "anthropic",
+      adapter: "anthropic",
       secret: "sk-ant-mock",
       api_base: upstream.baseUrl,
     });
diff --git a/tests/e2e/src/cases/api-base-tolerance-e2e.test.ts b/tests/e2e/src/cases/api-base-tolerance-e2e.test.ts
index 68f5e6a9..e7e6521b 100644
--- a/tests/e2e/src/cases/api-base-tolerance-e2e.test.ts
+++ b/tests/e2e/src/cases/api-base-tolerance-e2e.test.ts
@@ -182,6 +182,8 @@ describe("api_base tolerance e2e: endpoint suffix is stripped before dispatch",
     //   `${baseUrl}/v1/messages/v1/messages`.
     const pk = await admin.createProviderKey({
       display_name: "anthropic-suffix-tolerance-pk",
+      provider: "anthropic",
+      adapter: "anthropic",
       secret: "sk-ant-mock",
       api_base: `${upstream.baseUrl}/v1/messages`,
     });
diff --git a/tests/e2e/src/cases/chat-anthropic-stream-input-tokens-e2e.test.ts b/tests/e2e/src/cases/chat-anthropic-stream-input-tokens-e2e.test.ts
index 3324a7cc..a132be4e 100644
--- a/tests/e2e/src/cases/chat-anthropic-stream-input-tokens-e2e.test.ts
+++ b/tests/e2e/src/cases/chat-anthropic-stream-input-tokens-e2e.test.ts
@@ -60,6 +60,8 @@ describe("/v1/chat/completions anthropic streaming input tokens (#450)", () => {
     const admin = new AdminClient(app.adminUrl, app.adminKey);
     const pk = await admin.createProviderKey({
       display_name: "chat-anth-stream-pk",
+      provider: "anthropic",
+      adapter: "anthropic",
       secret: "sk-anth-mock",
       api_base: upstream.baseUrl,
     });
diff --git a/tests/e2e/src/cases/messages-model-group-e2e.test.ts b/tests/e2e/src/cases/messages-model-group-e2e.test.ts
index 1876167e..6dba6397 100644
--- a/tests/e2e/src/cases/messages-model-group-e2e.test.ts
+++ b/tests/e2e/src/cases/messages-model-group-e2e.test.ts
@@ -120,6 +120,8 @@ describe("model group via passthrough endpoints e2e (#471)", () => {
     if (!admin) throw new Error("admin client not initialized");
     const pk = await admin.createProviderKey({
       display_name: `${displayName}-pk`,
+      provider: "anthropic",
+      adapter: "anthropic",
       secret: "sk-ant-mock",
       // Anthropic bridge appends /v1/messages, so point at the bare host.
       api_base: upstream.baseUrl,
diff --git a/tests/e2e/src/cases/tools-cross-provider-e2e.test.ts b/tests/e2e/src/cases/tools-cross-provider-e2e.test.ts
index 11e96e7d..97423b5f 100644
--- a/tests/e2e/src/cases/tools-cross-provider-e2e.test.ts
+++ b/tests/e2e/src/cases/tools-cross-provider-e2e.test.ts
@@ -93,6 +93,8 @@ describe("tools cross-provider e2e: OpenAI tools → Anthropic upstream tool_use
     // (mirrors anthropic-upstream-e2e convention).
     const pk = await admin.createProviderKey({
       display_name: "tools-xprov-pk",
+      provider: "anthropic",
+      adapter: "anthropic",
       secret: "sk-ant-mock",
       api_base: upstream.baseUrl,
     });
diff --git a/tests/e2e/src/harness/admin.ts b/tests/e2e/src/harness/admin.ts
index 0de44c78..4cff8baa 100644
--- a/tests/e2e/src/harness/admin.ts
+++ b/tests/e2e/src/harness/admin.ts
@@ -25,7 +25,18 @@ export class AdminClient {
   async createProviderKey(
     pk: Record<string, unknown>,
   ): Promise<{ id: string; value: Record<string, unknown> }> {
-    return this.json("POST", "/admin/v1/provider_keys", pk);
+    // The DP dispatches a ProviderKey via its `provider` (specialized
+    // vendor) + `adapter` (protocol family) — cp-api always writes both
+    // in production, and the DP no longer carries a Model.provider
+    // fallback. So the harness mirrors cp-api and always sends them,
+    // defaulting to the OpenAI-compatible vendor/family that the bulk of
+    // the mock-upstream tests use. Tests against a non-OpenAI upstream
+    // (anthropic, etc.) pass `provider`/`adapter` explicitly.
+    return this.json("POST", "/admin/v1/provider_keys", {
+      provider: "openai",
+      adapter: "openai",
+      ...pk,
+    });
   }
 
   async listModels(): Promise<Array<Record<string, unknown>>> {