diff --git a/conformance/descriptor_invariants_test.go b/conformance/descriptor_invariants_test.go
index 7c66642..ad6f602 100644
--- a/conformance/descriptor_invariants_test.go
+++ b/conformance/descriptor_invariants_test.go
@@ -297,25 +297,17 @@ func fieldEnum(t *testing.T, md protoreflect.MessageDescriptor, field string) pr
 }
 
 // TestRequesterBillingRefStaysRemoved pins the billing_ref removal at the
-// descriptor level: Requester carries no billing_ref field and no field 5,
-// and both stay reserved. protoc enforces the reservation only while the two
-// `reserved` statements exist in the source; `buf breaking` (which would flag
-// deleting them) is non-blocking pre-v1, and the remark-proto guard runs only
-// in the docs build. This is the blocking-CI pin: reusing the number under a
-// new name, or the name under a new number, fails here.
+// descriptor level: Requester carries no caller-written billing_ref field.
+// Billing identity is resolved from the verified request signature and the
+// account minted at Register, never from a request field — a reappearing
+// billing_ref would also collide by name with the authoritative account
+// handle (RegisterResponse.billing_ref). The freed field number is NOT
+// pinned: pre-v1, removed numbers return to the free pool (no `reserved`
+// statements until v1.0.0 is tagged).
 func TestRequesterBillingRefStaysRemoved(t *testing.T) {
 	md := (&rampv1.Requester{}).ProtoReflect().Descriptor()
 	if fd := md.Fields().ByName("billing_ref"); fd != nil {
-		t.Errorf("Requester regained a billing_ref field (number %d) — it was removed and its number reserved", fd.Number())
-	}
-	if fd := md.Fields().ByNumber(5); fd != nil {
-		t.Errorf("Requester field number 5 reused by %q — it must stay reserved", fd.Name())
-	}
-	if !md.ReservedRanges().Has(5) {
-		t.Error("Requester no longer reserves field number 5 — restore `reserved 5;`")
-	}
-	if !md.ReservedNames().Has("billing_ref") {
-		t.Error(`Requester no longer reserves the name billing_ref — restore 'reserved "billing_ref";'`)
+		t.Errorf("Requester regained a billing_ref field (number %d) — billing keys on the verified caller identity, never a request field", fd.Number())
 	}
 }
 
diff --git a/docs/design-history.md b/docs/design-history.md
index ac44036..37c0b98 100644
--- a/docs/design-history.md
+++ b/docs/design-history.md
@@ -145,7 +145,8 @@ records only the wire-shaping reasoning.
 > after the Broker cost guard moved to the authenticated agent identity,
 > nothing read `Requester.billing_ref`, and the caller-written
 > label collided by name with the authoritative account handle minted at
-> `Register`. Field 5 and the name are now `reserved`. The reasoning below
+> `Register`. The field was deleted outright — pre-v1, removed field numbers
+> return to the free pool rather than being `reserved`. The reasoning below
 > still stands — it is the same separation (identity = signature,
 > entitlement = scopes/delegation) taken one step further: billing needs no
 > request field at all.
diff --git a/gen/descriptor.binpb b/gen/descriptor.binpb
index 989a21d..e3c9ee6 100644
Binary files a/gen/descriptor.binpb and b/gen/descriptor.binpb differ
diff --git a/gen/go/ramp/v1/ramp.pb.go b/gen/go/ramp/v1/ramp.pb.go
index d921674..f5ad886 100644
--- a/gen/go/ramp/v1/ramp.pb.go
+++ b/gen/go/ramp/v1/ramp.pb.go
@@ -9007,7 +9007,7 @@ const file_ramp_v1_ramp_proto_rawDesc = "" +
 	"\x13_estimated_quantityB\x1a\n" +
 	"\x18_license_duration_monthsB\a\n" +
 	"\x05_unitB\v\n" +
-	"\t_metering\"\xd7\x02\n" +
+	"\t_metering\"\xc4\x02\n" +
 	"\tRequester\x12\x0e\n" +
 	"\x02id\x18\x01 \x01(\tR\x02id\x12\x16\n" +
 	"\x06domain\x18\x02 \x01(\tR\x06domain\x124\n" +
@@ -9020,7 +9020,7 @@ const file_ramp_v1_ramp_proto_rawDesc = "" +
 	"\x03ext\x18\x0f \x01(\v2\x17.google.protobuf.StructR\x03ext\x12!\n" +
 	"\fext_critical\x18Z \x03(\tR\vextCriticalB\a\n" +
 	"\x05_nameB\r\n" +
-	"\v_delegationJ\x04\b\x05\x10\x06R\vbilling_ref\"\xe9\x04\n" +
+	"\v_delegation\"\xe9\x04\n" +
 	"\n" +
 	"Delegation\x12)\n" +
 	"\x10principal_domain\x18\x01 \x01(\tR\x0fprincipalDomain\x12!\n" +
diff --git a/proto/CHANGELOG.md b/proto/CHANGELOG.md
index b8f9e12..31dd870 100644
--- a/proto/CHANGELOG.md
+++ b/proto/CHANGELOG.md
@@ -50,9 +50,10 @@ two flags (`SKIP_SSRF`, `ALLOW_INSECURE`). See `docs/sdk-parity-matrix.md` for t
 per-language surface.
 
 **`Requester.billing_ref` removed (breaking, pre-1.0).** The caller-written
-billing label on `Requester` is gone; field number 5 and the name are
-`reserved` so they can never be reused with a different meaning. Nothing read
-it: billing and cost attribution key on the verified caller identity and the
+billing label on `Requester` is gone; the field is deleted outright with no
+`reserved` statement — pre-v1 the number returns to the free pool, and
+`reserved` becomes the tool for field removals only once v1.0.0 is tagged.
+Nothing read it: billing and cost attribution key on the verified caller identity and the
 account handle minted at `Register` (`RegisterResponse.billing_ref`), which the
 Exchange resolves from the request signature — never from anything the caller
 sends. Dropping the field also removes the name collision between the
diff --git a/proto/ramp/v1/ramp.proto b/proto/ramp/v1/ramp.proto
index 266a938..43f6362 100644
--- a/proto/ramp/v1/ramp.proto
+++ b/proto/ramp/v1/ramp.proto
@@ -1435,13 +1435,6 @@ message Requester {
   // Human-readable name (e.g., "Acme Research Assistant").
   optional string name = 4;
 
-  // Field 5 was a caller-written billing label. Removed: billing and cost
-  // attribution key on the verified caller identity and the account minted at
-  // Register, never on anything the caller writes into the request. Reserved
-  // so the number and name can never be reused with a different meaning.
-  reserved 5;
-  reserved "billing_ref";
-
   // Entitlement scopes. Declare what the requester can access.
   //
   // The Exchange filters its catalog to resources matching these scopes.
diff --git a/website/src/content/docs/reference/changelog.mdx b/website/src/content/docs/reference/changelog.mdx
index ca2e180..457d64e 100644
--- a/website/src/content/docs/reference/changelog.mdx
+++ b/website/src/content/docs/reference/changelog.mdx
@@ -33,9 +33,10 @@ in Python; `parseErrorDetail` / `errorDetailFrom` in TS). The SSRF-guarded trans
 is a single env-driven client governed by two flags (`SKIP_SSRF`, `ALLOW_INSECURE`).
 
 **`Requester.billing_ref` removed (breaking, pre-1.0).** The caller-written
-billing label on `Requester` is gone; field number 5 and the name are
-`reserved` so they can never be reused with a different meaning. Nothing read
-it: billing and cost attribution key on the verified caller identity and the
+billing label on `Requester` is gone; the field is deleted outright with no
+`reserved` statement — pre-v1 the number returns to the free pool, and
+`reserved` becomes the tool for field removals only once v1.0.0 is tagged.
+Nothing read it: billing and cost attribution key on the verified caller identity and the
 account handle minted at `Register` (`RegisterResponse.billing_ref`), which the
 Exchange resolves from the request signature — never from anything the caller
 sends. Dropping the field also removes the name collision between the