diff --git a/Cargo.toml b/Cargo.toml
index 35e9e474..b48e4e60 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -356,10 +356,10 @@ pkcs12 = { version = "=0.2.0-pre.0", default-features = false, features = ["kdf"
 pbkdf2 = { version = "0.13", default-features = false, features = ["hmac"], optional = true }
 
 # X.509 certificates
-structured-asn1 = { version = "0.18.0", default-features = false, features = ["alloc"], optional = true }
-structured-pkix = { version = "0.18.0", default-features = false, features = ["alloc"], optional = true }
+structured-asn1 = { version = "0.18.2", default-features = false, features = ["alloc"], optional = true }
+structured-pkix = { version = "0.18.2", default-features = false, features = ["alloc"], optional = true }
 # PKCS#12 container framing; this crate keeps the password, KDF and cipher work.
-structured-cms = { version = "0.18.0", default-features = false, features = ["alloc"], optional = true }
+structured-cms = { version = "0.18.2", default-features = false, features = ["alloc"], optional = true }
 tinyvec = { version = "1.13", optional = true }
 # `pem` is RFC 7468 decoding of caller key and certificate text.
 der = { version = "0.8", default-features = false, features = ["alloc", "pem"], optional = true }
diff --git a/benches/security.rs b/benches/security.rs
index de902beb..81edc531 100644
--- a/benches/security.rs
+++ b/benches/security.rs
@@ -86,13 +86,14 @@ fn large_reference_sign(bencher: divan::Bencher, units: usize) {
 #[divan::bench(args = specs().filter(|spec| spec.backend != xml_sec::XmlBackend::Differential))]
 fn projection(bencher: divan::Bencher, spec: Spec) {
     let fixture = Fixture::new(spec);
-    let projection = xml_sec::benchmark_support::Projection::new(&fixture.unsigned, spec.backend)
-        .expect("prepared backend");
     bencher
         .counter(divan::counter::BytesCount::new(fixture.unsigned.len()))
-        .bench_local(|| {
-            std::hint::black_box(projection.project().expect("project"));
-        });
+        // Projection consumes its backend DOM, so each sample prepares a new one.
+        .with_inputs(|| {
+            xml_sec::benchmark_support::Projection::new(&fixture.unsigned, spec.backend)
+                .expect("prepared backend")
+        })
+        .bench_local_values(|projection| projection.project().expect("project"));
 }
 
 /// Signed-document shape for node-set measurements: `elements` siblings with
diff --git a/benchmarks/competitors/Cargo.lock b/benchmarks/competitors/Cargo.lock
index 3e161fbf..8fd6c629 100644
--- a/benchmarks/competitors/Cargo.lock
+++ b/benchmarks/competitors/Cargo.lock
@@ -2453,9 +2453,9 @@ checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
 
 [[package]]
 name = "structured-asn1"
-version = "0.18.0"
+version = "0.18.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a4fd0f31722fb17bb889fde5cf9dd363b7b6d1724412a70b6fd8656c766cdea"
+checksum = "1929d0c152f8c4f46777f01757d38df8dc0a8fd05dcf8ca5c1bc33ffe102d609"
 dependencies = [
  "allocator-api2 0.2.21",
  "allocator-api2 0.4.0",
@@ -2465,9 +2465,9 @@ dependencies = [
 
 [[package]]
 name = "structured-cms"
-version = "0.18.0"
+version = "0.18.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2353777c8f6c27d916875e9a4f42a671d5316a97b40db1219883864a82cc8731"
+checksum = "3c74074e07917756c831081389c342c7176c0399be4cbe966c0d5f23092c1a96"
 dependencies = [
  "structured-asn1",
  "structured-pkix",
@@ -2487,9 +2487,9 @@ dependencies = [
 
 [[package]]
 name = "structured-pkix"
-version = "0.18.0"
+version = "0.18.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "858a254ee9d7e67f3d48c6f41f57511a53c3fb1d537865052df6a18b81bd7eeb"
+checksum = "d9e67176be19f5f1244c8c30021294c845a304b6189a8cf34b294a18b46a1b95"
 dependencies = [
  "structured-asn1",
  "structured-email-address",
diff --git a/docs/key-management.md b/docs/key-management.md
index 352addaa..2016a6d9 100644
--- a/docs/key-management.md
+++ b/docs/key-management.md
@@ -125,7 +125,8 @@ table from the host, network or a built-in default. Missing facts return
 `CrlTimeUncertain`, never non-revocation. Cached complete CRLs permit the exact
 `nextUpdate` boundary, but even one nanosecond later fails freshness. Revocation
 dates are checked against the same lossless operation time. Unsupported critical
-demands, entry conflicts and unpaired delta CRLs cannot authorize a key.
+demands, entry conflicts and delta CRLs without their complete CRL cannot
+authorize a key; a bound complete-plus-delta pair is evaluated as one source.
 Applicable partial lists must collectively cover all revocation reasons;
 otherwise `IncompleteCrlCoverage` is returned. This checks supplied evidence,
 not an implicit online revocation fetch or a requirement to supply a CRL for
diff --git a/docs/xmldsig.md b/docs/xmldsig.md
index 04a62eac..4f042e2b 100644
--- a/docs/xmldsig.md
+++ b/docs/xmldsig.md
@@ -624,11 +624,17 @@ CRL checking is meaningful only inside authenticated X.509 path validation. A po
 CRLs without enabling certificate-chain validation is rejected during context construction rather
 than silently accepting a control the resolver cannot enforce.
 CRL structure is validated before authority-key applicability is selected: duplicate CRL or
-CRL-entry extension OIDs fail closed, and `deltaCRLIndicator` is rejected regardless of criticality.
+CRL-entry extension OIDs fail closed.
 Applicable CRLs must include the RFC 5280 `nextUpdate` field and the verification time must remain
 inside the bounded `thisUpdate` through `nextUpdate` validity window.
-The `removeFromCRL` reason is rejected in complete CRLs because it is meaningful only in a delta
-CRL. URI subject alternative names
+A delta CRL is evaluated together with the complete CRL it binds to under RFC 5280 section 5.2.4:
+same issuer, key and scope, a critical `deltaCRLIndicator`, and a complete CRL number from
+`BaseCRLNumber` up to but excluding the delta's own. The newest bound delta decides, and its
+validity window governs the pair, so a current delta keeps an expired complete CRL usable while an
+expired delta is refused even over a current one. An applicable delta bound to no supplied complete
+CRL fails closed.
+The `removeFromCRL` reason lifts an entry only from a delta CRL and is rejected in complete CRLs.
+URI subject alternative names
 likewise require one RFC 3986 authority, including syntactically valid userinfo, before their host
 can participate in `NameConstraints` matching.
 Critical `NameConstraints` also retain their DER structure during validation: the extension must
diff --git a/examples/benchmark_latency.rs b/examples/benchmark_latency.rs
index d5a4080e..b57c055a 100644
--- a/examples/benchmark_latency.rs
+++ b/examples/benchmark_latency.rs
@@ -25,10 +25,15 @@ fn percentile(sorted: &[u128], percent: usize) -> u128 {
 fn measure(
     fixture: &Fixture,
     operation: &str,
-    projection: Option<&xml_sec::benchmark_support::Projection<'_>>,
+    backend: XmlBackend,
     policy: &xml_sec::policy::VerificationPolicy,
 ) -> (u128, usize) {
     // Per-sample preparation is excluded, just as Divan's with_inputs excludes it.
+    // Projection consumes its backend DOM, so each sample prepares a new one.
+    let projection = (operation == "projection").then(|| {
+        xml_sec::benchmark_support::Projection::new(&fixture.unsigned, backend)
+            .expect("prepared projection")
+    });
     let mut plan = match operation {
         "plan_compile" | "plan_execute" => Some(xml_sec::benchmark_support::Plan::new(
             fixture.spec.units.min(64),
@@ -332,14 +337,6 @@ fn main() -> Result<(), Box<dyn Error>> {
     } = parse_request(&args)?;
     let (units, backend) = (spec.units, spec.backend);
     let fixture = Fixture::new(spec);
-    let projection = if operation == "projection" {
-        Some(xml_sec::benchmark_support::Projection::new(
-            &fixture.unsigned,
-            backend,
-        )?)
-    } else {
-        None
-    };
     let policy = xml_sec::policy::VerificationPolicy {
         signature_algorithms: Some(
             [xml_sec::xmldsig::SignatureAlgorithm::RsaSha256]
@@ -349,12 +346,12 @@ fn main() -> Result<(), Box<dyn Error>> {
         ..Default::default()
     };
     for _ in 0..8 {
-        std::hint::black_box(measure(&fixture, operation, projection.as_ref(), &policy));
+        std::hint::black_box(measure(&fixture, operation, backend, &policy));
     }
     let mut timings = Vec::with_capacity(samples);
     let mut output_bytes = 0;
     for _ in 0..samples {
-        let (elapsed, bytes) = measure(&fixture, operation, projection.as_ref(), &policy);
+        let (elapsed, bytes) = measure(&fixture, operation, backend, &policy);
         output_bytes = bytes;
         timings.push(elapsed);
     }
diff --git a/scripts/generate-delta-crl-fixtures.sh b/scripts/generate-delta-crl-fixtures.sh
new file mode 100755
index 00000000..6ab75fd5
--- /dev/null
+++ b/scripts/generate-delta-crl-fixtures.sh
@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+# Regenerate the delta CRL fixtures of tests/delta_crl.rs.
+#
+# OpenSSL acts as an independent certificate authority: it issues one complete
+# CRL and two delta CRLs against it, one silent and one revoking the leaf. Its
+# own verifier checks both pairs here, so the fixtures carry its answer. It only
+# reads a delta for a certificate that has freshestCRL (RFC 5280 4.2.1.15).
+#
+# Usage: scripts/generate-delta-crl-fixtures.sh
+# DELTA_CRL_FIXTURE_OUTPUT optionally selects an absolute output directory.
+# Requires OpenSSL 3.4 or later for fixed certificate validity dates.
+set -euo pipefail
+
+repository="$(cd "$(dirname "$0")/.." && pwd)"
+output="${DELTA_CRL_FIXTURE_OUTPUT:-$repository/tests/fixtures/x509/delta-crl}"
+mkdir -p "$output"
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT
+cd "$work"
+
+NOT_BEFORE=20260101000000Z
+NOT_AFTER=20450101000000Z
+# 2040-01-01T00:00:00Z, after any revocation made while generating.
+VERIFICATION_TIME=2208988800
+
+cat >ca.cnf <<'EOF'
+[ca]
+default_ca = authority
+
+[authority]
+database = index.txt
+crlnumber = crlnumber
+default_md = sha256
+crl_extensions = complete
+
+[complete]
+authorityKeyIdentifier = keyid
+
+[delta]
+authorityKeyIdentifier = keyid
+2.5.29.27 = critical,ASN1:INTEGER:5
+EOF
+: >index.txt
+echo 05 >crlnumber
+
+openssl genpkey -algorithm EC -pkeyopt ec_paramgen_curve:P-256 -out ca.key 2>/dev/null
+openssl req -x509 -new -key ca.key -out ca.pem \
+  -not_before "$NOT_BEFORE" -not_after "$NOT_AFTER" \
+  -subj "/CN=xml-sec Test Delta CA" \
+  -addext "basicConstraints=critical,CA:TRUE" \
+  -addext "keyUsage=critical,keyCertSign,cRLSign" 2>/dev/null
+openssl genpkey -algorithm EC -pkeyopt ec_paramgen_curve:P-256 -out leaf.key 2>/dev/null
+openssl req -x509 -new -key leaf.key -CA ca.pem -CAkey ca.key -out leaf.pem \
+  -not_before "$NOT_BEFORE" -not_after "$NOT_AFTER" \
+  -subj "/CN=xml-sec Test Delta Leaf" \
+  -addext "basicConstraints=critical,CA:FALSE" \
+  -addext "keyUsage=critical,digitalSignature" \
+  -addext "freshestCRL=URI:https://example.test/delta.crl" 2>/dev/null
+
+# list <file> <extension section>: the next CRL of this authority.
+list() {
+  openssl ca -gencrl -config ca.cnf -keyfile ca.key -cert ca.pem \
+    -crlexts "$2" -crl_lastupdate "$NOT_BEFORE" -crl_nextupdate "$NOT_AFTER" \
+    -out "$1"
+}
+
+list complete.pem complete
+list silent.pem delta
+openssl ca -revoke leaf.pem -config ca.cnf -keyfile ca.key -cert ca.pem 2>/dev/null
+list revoking.pem delta
+
+# accepted <delta>: the verifier's answer for the leaf under that pair.
+accepted() {
+  openssl verify -CAfile ca.pem -CRLfile complete.pem -CRLfile "$1" \
+    -crl_check -use_deltas -attime "$VERIFICATION_TIME" leaf.pem >/dev/null 2>&1
+}
+
+accepted silent.pem
+if accepted revoking.pem; then
+  echo "OpenSSL accepted a leaf its delta CRL revokes" >&2
+  exit 1
+fi
+
+openssl x509 -in ca.pem -outform DER -out "$output/ca.der"
+openssl x509 -in leaf.pem -outform DER -out "$output/leaf.der"
+for name in complete silent revoking; do
+  openssl crl -in "$name.pem" -outform DER -out "$output/$name.crl"
+done
diff --git a/scripts/patches/xmloxide-0.5.0.patch b/scripts/patches/xmloxide-0.5.0.patch
index 92d51b4c..93c44949 100644
--- a/scripts/patches/xmloxide-0.5.0.patch
+++ b/scripts/patches/xmloxide-0.5.0.patch
@@ -201,7 +201,31 @@
  
  // -------------------------------------------------------------------------
  // Security defaults
-@@ -177,26 +266,6 @@
+@@ -93,9 +182,22 @@
+ ///
+ /// Covers the ASCII subset of XML 1.0 §2.3 `[4a]`: `[A-Za-z0-9_:.-]`.
+ fn is_ascii_name_char(b: u8) -> bool {
+-    b.is_ascii_alphanumeric() || b == b'_' || b == b':' || b == b'-' || b == b'.'
++    ASCII_NAME_CHARS[b as usize]
+ }
+ 
++/// The table behind [`is_ascii_name_char`]: names are the most scanned bytes in
++/// a document, and a lookup replaces a chain of range checks per byte.
++const ASCII_NAME_CHARS: [bool; 256] = {
++    let mut table = [false; 256];
++    let mut value = 0_u8;
++    while value < 0x80 {
++        table[value as usize] =
++            value.is_ascii_alphanumeric() || matches!(value, b'_' | b':' | b'-' | b'.');
++        value += 1;
++    }
++    table
++};
++
+ /// Matches one of the five XML builtin entity references at the byte level.
+ ///
+ /// Given bytes starting after `&`, returns `(replacement_char, bytes_to_skip)`
+@@ -177,26 +279,6 @@
      }
  }
  
@@ -228,7 +252,7 @@
  /// Validates that a name is a legal `QName` per Namespaces in XML 1.0 §4.
  ///
  /// A `QName` has at most one colon, and neither prefix nor local part may be
-@@ -228,22 +297,6 @@
+@@ -228,22 +310,6 @@
      )
  }
  
@@ -251,7 +275,7 @@
  // -------------------------------------------------------------------------
  // Position checkpointing (for backtracking)
  // -------------------------------------------------------------------------
-@@ -266,22 +319,19 @@
+@@ -266,22 +332,19 @@
  // ParserInput
  // -------------------------------------------------------------------------
  
@@ -281,7 +305,7 @@
      /// The input bytes (must be valid UTF-8).
      input: &'a [u8],
  
-@@ -313,16 +363,11 @@
+@@ -313,16 +376,11 @@
      recover: bool,
  
      /// Accumulated diagnostics (warnings and recoverable errors).
@@ -300,7 +324,7 @@
  
      /// Whether the DTD internal subset contained parameter entity references.
      /// Per XML 1.0 §4.1 WFC: Entity Declared, undeclared entity references
-@@ -336,10 +381,6 @@
+@@ -336,10 +394,6 @@
      /// external DTD subset that was not read.
      pub(crate) has_external_dtd: bool,
  
@@ -311,7 +335,7 @@
      /// Optional callback for resolving external entities.
      entity_resolver: Option<EntityResolver>,
  }
-@@ -347,7 +388,28 @@
+@@ -347,7 +401,28 @@
  impl<'a> ParserInput<'a> {
      /// Creates a new `ParserInput` from a UTF-8 string with default limits.
      pub fn new(input: &'a str) -> Self {
@@ -341,7 +365,7 @@
              input: input.as_bytes(),
              pos: 0,
              line: 1,
-@@ -358,19 +420,12 @@
+@@ -358,19 +433,12 @@
              entity_expansions: 0,
              max_entity_expansions: DEFAULT_MAX_ENTITY_EXPANSIONS,
              recover: false,
@@ -364,7 +388,7 @@
      }
  
      /// Sets the maximum nesting depth.
-@@ -398,13 +453,32 @@
+@@ -398,13 +466,32 @@
          self.recover
      }
  
@@ -399,7 +423,7 @@
                  "maximum nesting depth exceeded ({})",
                  self.max_depth
              )));
-@@ -458,7 +532,7 @@
+@@ -458,7 +545,7 @@
      /// Returns a slice of the raw input bytes from `start` to `end`.
      #[allow(dead_code)]
      #[inline]
@@ -408,7 +432,7 @@
          &self.input[start..end]
      }
  
-@@ -528,7 +602,7 @@
+@@ -528,7 +615,7 @@
          if remaining.len() < len {
              return None;
          }
@@ -417,7 +441,7 @@
              .ok()
              .and_then(|s| s.chars().next())
      }
-@@ -537,9 +611,10 @@
+@@ -537,9 +624,10 @@
  
      /// Advances the position by `count` bytes, updating line/column.
      #[inline]
@@ -429,7 +453,7 @@
              if self.pos < self.input.len() {
                  if self.input[self.pos] == b'\n' {
                      self.line += 1;
-@@ -549,15 +624,16 @@
+@@ -549,15 +637,16 @@
                  }
                  self.pos += 1;
              }
@@ -449,7 +473,7 @@
          if ch == '\n' {
              self.line += 1;
              self.column = 1;
-@@ -565,23 +641,25 @@
+@@ -565,23 +654,25 @@
              self.column += 1;
          }
          self.pos += len;
@@ -478,7 +502,7 @@
          if self.pos >= self.input.len() {
              return Err(self.fatal("unexpected end of input"));
          }
-@@ -608,11 +686,11 @@
+@@ -608,11 +699,11 @@
                      if self.recover {
                          self.push_diagnostic(
                              ErrorSeverity::Error,
@@ -493,7 +517,7 @@
                          );
                      }
                  }
-@@ -623,16 +701,16 @@
+@@ -623,16 +714,16 @@
          let ch = self
              .peek_char()
              .ok_or_else(|| self.fatal("unexpected end of input"))?;
@@ -514,7 +538,7 @@
              }
          }
          Ok(ch)
-@@ -640,31 +718,46 @@
+@@ -640,31 +731,46 @@
  
      // -- Bulk scanning --
  
@@ -575,7 +599,7 @@
      }
  
      /// Scans forward to find the next attribute value delimiter: the given
-@@ -672,22 +765,16 @@
+@@ -672,22 +778,16 @@
      /// Returns the number of safe bytes before the delimiter.
      /// Avoids the 256-byte lookup table of `scan_until_any`.
      #[inline]
@@ -603,7 +627,7 @@
      }
  
      /// Scans forward to find the next occurrence of any of the given marker
-@@ -696,63 +783,72 @@
+@@ -696,63 +796,72 @@
      /// Uses a 256-byte lookup table for O(1) per-byte matching instead of
      /// linear `contains()` on the marker slice.
      #[allow(dead_code)]
@@ -703,7 +727,7 @@
          let end = self.pos + count;
          let slice = &self.input[self.pos..end];
          // Fast path: if no newlines in the slice, just bump column
-@@ -766,22 +862,21 @@
+@@ -766,22 +875,21 @@
                  }
              }
          } else {
@@ -731,7 +755,7 @@
                  "expected '{}', found '{}'",
                  expected as char, b as char
              )));
-@@ -791,12 +886,13 @@
+@@ -791,12 +899,13 @@
  
      /// Consumes bytes and asserts they match the `expected` sequence.
      #[inline]
@@ -747,7 +771,7 @@
          } else {
              // Fall back to per-byte for precise error reporting
              for &b in expected {
-@@ -828,51 +924,30 @@
+@@ -828,51 +937,30 @@
  
      /// Skips whitespace characters. Returns `true` if any were consumed.
      #[inline]
@@ -812,7 +836,7 @@
              return Err(self.fatal("whitespace required"));
          }
          Ok(())
-@@ -880,23 +955,18 @@
+@@ -880,23 +968,18 @@
  
      // -- Take while --
  
@@ -845,7 +869,7 @@
      }
  
      // -- Name parsing (XML 1.0 §2.3) --
-@@ -910,7 +980,16 @@
+@@ -910,7 +993,16 @@
      /// Uses an ASCII fast path that scans name characters as bytes,
      /// avoiding per-character UTF-8 decoding for the common case.
      #[inline]
@@ -863,7 +887,7 @@
          let start = self.pos;
          if self.pos >= self.input.len() {
              return Err(self.fatal("expected name, found end of input"));
-@@ -919,26 +998,31 @@
+@@ -919,26 +1011,35 @@
          let first = self.input[self.pos];
  
          // ASCII fast path: most XML names are pure ASCII
@@ -882,7 +906,11 @@
 +            let count = self.scan_bytes(self.input.len() - self.pos, 1, |bytes, i| {
 +                !is_ascii_name_char(bytes[i])
 +            })?;
-+            self.advance_counting_lines(count)?;
++            // Name characters exclude newlines, so no second scan looks for one.
++            self.storage.charge(count * 2)?;
++            self.pos += count;
++            self.column +=
++                u32::try_from(count).expect("XML source windows fit the admitted byte ceiling");
              // Check if we stopped at a non-ASCII byte (need slow path)
              if self.pos >= self.input.len() || self.input[self.pos] < 0x80 {
                  let len = self.pos - start;
@@ -903,7 +931,7 @@
              }
              // Fall through: hit a non-ASCII continuation byte, continue
              // with the char-by-char path below.
-@@ -948,16 +1032,22 @@
+@@ -948,16 +1049,22 @@
              let ch = self
                  .peek_char()
                  .ok_or_else(|| self.fatal("expected name"))?;
@@ -931,7 +959,7 @@
              } else {
                  break;
              }
-@@ -965,90 +1055,32 @@
+@@ -965,90 +1072,32 @@
  
          let len = self.pos - start;
          if len > self.max_name_length {
@@ -1033,7 +1061,7 @@
      }
  
      /// Parses a name and checks whether it matches the given prefix + local
-@@ -1060,111 +1092,46 @@
+@@ -1060,111 +1109,46 @@
          &mut self,
          prefix: Option<&str>,
          local: &str,
@@ -1165,7 +1193,7 @@
      /// Parses an entity or character reference (`&...;`).
      ///
      /// Handles the five built-in XML entities (`amp`, `lt`, `gt`, `apos`,
-@@ -1175,8 +1142,8 @@
+@@ -1175,8 +1159,8 @@
      /// Increments the entity expansion counter and returns an error if the
      /// limit is exceeded.
      #[cfg(test)]
@@ -1176,7 +1204,7 @@
          self.parse_reference_into(&mut buf)?;
          Ok(buf)
      }
-@@ -1190,34 +1157,47 @@
+@@ -1190,34 +1174,47 @@
      ///
      /// Returns the resolved text as a `&str` slice of `buf` (the portion
      /// that was appended), which callers can use for validation.
@@ -1234,7 +1262,7 @@
                  if dec.is_empty() {
                      return Err(self.fatal("empty decimal character reference"));
                  }
-@@ -1226,68 +1206,191 @@
+@@ -1226,68 +1223,191 @@
              };
              self.expect_byte(b';')?;
  
@@ -1475,7 +1503,7 @@
          }
      }
  
-@@ -1295,196 +1398,128 @@
+@@ -1295,196 +1415,128 @@
      ///
      /// Per XML 1.0 §4.4, when an entity's replacement text is included,
      /// character references and entity references within it are resolved.
@@ -1620,11 +1648,23 @@
 -                        "amp" => {
 -                            result.push('&');
 -                            continue;
+-                        }
+-                        "lt" => {
+-                            result.push('<');
+-                            continue;
+-                        }
+-                        "gt" => {
+-                            result.push('>');
+-                            continue;
+-                        }
+-                        "apos" => {
+-                            result.push('\'');
+-                            continue;
 +                        if i >= bytes.len() {
 +                            return Err(self.fatal("incomplete entity reference in entity value"));
                          }
--                        "lt" => {
--                            result.push('<');
+-                        "quot" => {
+-                            result.push('"');
 +                        let name = core::str::from_utf8(&bytes[start..i])
 +                            .map_err(|_| self.fatal("invalid UTF-8 in entity name"))?;
 +                        i += 1; // skip ';'
@@ -1635,18 +1675,6 @@
 +                        if self.append_builtin_replacement(name, result)? {
                              continue;
                          }
--                        "gt" => {
--                            result.push('>');
--                            continue;
--                        }
--                        "apos" => {
--                            result.push('\'');
--                            continue;
--                        }
--                        "quot" => {
--                            result.push('"');
--                            continue;
--                        }
 -                        _ => {}
 -                    }
  
@@ -1774,7 +1802,7 @@
      // -- Attribute value parsing (XML 1.0 §3.3.3) --
  
      /// Parses a quoted attribute value with entity resolution and
-@@ -1493,19 +1528,23 @@
+@@ -1493,19 +1545,23 @@
      /// Uses bulk scanning to find the next `&`, `<`, or quote character,
      /// then extracts safe chunks with a single `push_str()` instead of
      /// processing character by character.
@@ -1802,7 +1830,7 @@
                      .map_err(|_| self.fatal("invalid UTF-8 in attribute value"))?;
                  // Fast byte-level pre-check: only validate when bytes suggest
                  // possible invalid chars (0x7F or U+FFFE/U+FFFF sequences).
-@@ -1516,30 +1555,18 @@
+@@ -1516,30 +1572,18 @@
                      if self.recover {
                          self.push_diagnostic(
                              ErrorSeverity::Error,
@@ -1840,7 +1868,7 @@
              }
  
              if self.at_end() {
-@@ -1548,57 +1575,45 @@
+@@ -1548,57 +1592,45 @@
  
              let b = self.input[self.pos];
              if b == quote {
@@ -1913,7 +1941,7 @@
          self.expect_byte(quote)?;
          Ok(value)
      }
-@@ -1606,21 +1621,44 @@
+@@ -1606,21 +1638,44 @@
      // -- Error helpers --
  
      /// Creates a fatal `ParseError` at the current location.
@@ -1966,7 +1994,7 @@
      }
  }
  
-@@ -1630,100 +1668,111 @@
+@@ -1630,100 +1685,111 @@
  
  /// Manages namespace scope for XML parsers.
  ///
@@ -2136,7 +2164,7 @@
      }
  }
  
-@@ -1736,54 +1785,56 @@
+@@ -1736,54 +1802,56 @@
  /// The opening `<!--` must not have been consumed yet.
  ///
  /// See XML 1.0 §2.5 production `[15]`.
@@ -2221,7 +2249,7 @@
                  } else {
                      return Err(input.fatal("'--' not allowed inside comments"));
                  }
-@@ -1793,8 +1844,6 @@
+@@ -1793,8 +1861,6 @@
              }
          }
      }
@@ -2230,7 +2258,7 @@
  }
  
  /// Parses a CDATA section (`<![CDATA[ ... ]]>`), returning the content text.
-@@ -1802,32 +1851,34 @@
+@@ -1802,32 +1868,34 @@
  /// The opening `<![CDATA[` must not have been consumed yet.
  ///
  /// See XML 1.0 §2.7 production `[18]`.
@@ -2283,7 +2311,7 @@
              Ok(content)
          }
          None => Err(input.fatal("unexpected end of input in CDATA section")),
-@@ -1840,9 +1891,9 @@
+@@ -1840,9 +1908,9 @@
  /// The opening `<?` must not have been consumed yet.
  ///
  /// See XML 1.0 §2.6 production `[16]`.
@@ -2296,7 +2324,7 @@
      input.expect_str(b"<?")?;
      let target = input.parse_name()?;
  
-@@ -1852,39 +1903,35 @@
+@@ -1852,39 +1920,35 @@
      }
  
      // Namespaces in XML 1.0 §3: PI targets must be NCNames (no colons).
@@ -2355,7 +2383,7 @@
              }
              None => {
                  return Err(input.fatal("unexpected end of input in processing instruction"));
-@@ -1900,11 +1947,11 @@
+@@ -1900,11 +1964,11 @@
  
  /// Parsed XML declaration data.
  #[derive(Debug, Clone)]
@@ -2370,7 +2398,7 @@
      /// Optional standalone declaration.
      pub standalone: Option<bool>,
  }
-@@ -1916,37 +1963,41 @@
+@@ -1916,37 +1980,41 @@
  /// verified by the caller via `looking_at`).
  ///
  /// See XML 1.0 §2.8 production `[23]`.
@@ -2422,7 +2450,7 @@
          }
  
          Some(enc)
-@@ -1958,17 +2009,17 @@
+@@ -1958,17 +2026,17 @@
      // If encoding was present, we need fresh whitespace before standalone.
      // If encoding was absent, the whitespace consumed when looking for
      // encoding already separates version from standalone.
@@ -2444,7 +2472,7 @@
              "yes" => Some(true),
              "no" => Some(false),
              _ => return Err(input.fatal("standalone must be 'yes' or 'no'")),
-@@ -1977,7 +2028,7 @@
+@@ -1977,7 +2045,7 @@
          None
      };
  
@@ -2453,7 +2481,7 @@
      input.expect_str(b"?>")?;
  
      Ok(XmlDeclaration {
-@@ -2024,9 +2075,9 @@
+@@ -2024,9 +2092,9 @@
          let mut input = ParserInput::new("abc");
          assert_eq!(input.peek(), Some(b'a'));
          assert_eq!(input.peek_at(1), Some(b'b'));
@@ -2465,7 +2493,7 @@
          assert!(input.at_end());
      }
  
-@@ -2035,9 +2086,9 @@
+@@ -2035,9 +2103,9 @@
          let mut input = ParserInput::new("ab\ncd");
          assert_eq!(input.location().line, 1);
          assert_eq!(input.location().column, 1);
@@ -2477,7 +2505,7 @@
          assert_eq!(input.location().line, 2);
          assert_eq!(input.location().column, 1);
      }
-@@ -2058,13 +2109,29 @@
+@@ -2058,13 +2126,29 @@
      }
  
      #[test]
@@ -2508,7 +2536,7 @@
      }
  
      #[test]
-@@ -2112,9 +2179,25 @@
+@@ -2112,9 +2196,25 @@
          assert_eq!(input.diagnostics.len(), 1);
      }
  
@@ -2535,7 +2563,7 @@
          input.set_max_entity_expansions(2);
          assert!(input.parse_reference().is_ok());
          assert!(input.parse_reference().is_ok());
-@@ -2145,6 +2228,14 @@
+@@ -2145,6 +2245,14 @@
      }
  
      #[test]
@@ -2550,7 +2578,7 @@
      fn test_parse_quoted_value() {
          let mut input = ParserInput::new("'hello'");
          let value = input.parse_quoted_value().unwrap();
-@@ -2154,7 +2245,7 @@
+@@ -2154,7 +2262,7 @@
      #[test]
      fn test_skip_whitespace() {
          let mut input = ParserInput::new("  \t\n  abc");
@@ -2559,7 +2587,7 @@
          assert_eq!(input.peek(), Some(b'a'));
      }
  
-@@ -2168,12 +2259,211 @@
+@@ -2168,12 +2276,211 @@
      #[test]
      fn test_take_while() {
          let mut input = ParserInput::new("12345abc");
@@ -2772,7 +2800,7 @@
      fn test_split_name() {
          assert_eq!(split_name("foo:bar"), (Some("foo"), "bar"));
          assert_eq!(split_name("bar"), (None, "bar"));
-@@ -2182,37 +2472,94 @@
+@@ -2182,37 +2489,94 @@
  
      #[test]
      fn test_namespace_resolver() {
@@ -2890,7 +2918,7 @@
      }
  
      #[test]
-@@ -2234,7 +2581,7 @@
+@@ -2234,7 +2598,7 @@
          let mut input = ParserInput::new("<?target data?>");
          let (target, data) = parse_pi_content(&mut input).unwrap();
          assert_eq!(target, "target");
@@ -2899,7 +2927,7 @@
      }
  
      #[test]
-@@ -2250,7 +2597,7 @@
+@@ -2250,7 +2614,7 @@
          let mut input = ParserInput::new("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
          let decl = parse_xml_decl(&mut input).unwrap();
          assert_eq!(decl.version, "1.0");
@@ -2908,7 +2936,7 @@
          assert_eq!(decl.standalone, None);
      }
  
-@@ -2301,7 +2648,10 @@
+@@ -2301,7 +2665,10 @@
          input.set_max_depth(1);
          assert!(input.increment_depth().is_ok()); // depth = 1
          let err = input.increment_depth().unwrap_err();
@@ -2920,7 +2948,7 @@
      }
  
      #[test]
-@@ -2310,7 +2660,10 @@
+@@ -2310,7 +2677,10 @@
          let mut input = ParserInput::new("");
          input.set_max_depth(0);
          let err = input.increment_depth().unwrap_err();
@@ -2932,7 +2960,7 @@
      }
  
      #[test]
-@@ -2345,64 +2698,75 @@
+@@ -2345,64 +2715,75 @@
      #[test]
      fn test_entity_expansion_limit_exact_boundary() {
          // max_entity_expansions = 3 means exactly 3 are allowed
@@ -3031,7 +3059,7 @@
          let xml = r#"<!DOCTYPE r [
  <!ENTITY greet "Hello">
  ]>
-@@ -2414,7 +2778,7 @@
+@@ -2414,7 +2795,7 @@
  
      #[test]
      fn test_entity_expansion_nested_dtd_entities() {
@@ -3040,7 +3068,7 @@
          // Entity "b" references entity "a". The nested reference is parsed
          // as content (XML 1.0 §4.4), so the entity expansion is visible
          // through text_content.
-@@ -2430,7 +2794,7 @@
+@@ -2430,7 +2811,7 @@
  
      #[test]
      fn test_entity_expansion_limit_nested_dtd_entities_in_attributes() {
@@ -3049,7 +3077,7 @@
          // In attribute values, entity references ARE fully expanded through
          // parse_reference_into + expand_entity_text. Each expansion counts
          // against the limit. Chain: c -> 3*b -> 9*a = 13 total expansions.
-@@ -2443,17 +2807,19 @@
+@@ -2443,17 +2824,19 @@
          let opts = ParseOptions::default().max_entity_expansions(5);
          let result = parse_str_with_options(xml, &opts);
          assert!(result.is_err());
@@ -3074,7 +3102,7 @@
          // Classic billion laughs pattern in an attribute value where
          // entities ARE fully expanded. Each entity references the
          // previous one multiple times, causing exponential expansion.
-@@ -2470,15 +2836,15 @@
+@@ -2470,15 +2853,15 @@
          assert!(result.is_err());
          let err = result.unwrap_err();
          assert!(
@@ -3093,7 +3121,7 @@
          // When entity replacement text contains '<', the parser must expand
          // it (to validate the markup), which triggers entity expansion
          // counting. This tests the billion laughs pattern for text content
-@@ -2494,9 +2860,9 @@
+@@ -2494,9 +2877,9 @@
          assert!(result.is_err());
          let err = result.unwrap_err();
          assert!(
@@ -3105,7 +3133,7 @@
          );
      }
  
-@@ -2504,7 +2870,7 @@
+@@ -2504,7 +2887,7 @@
  
      #[test]
      fn test_xxe_external_entity_rejected_by_default() {
@@ -3114,7 +3142,7 @@
          let xml = r#"<!DOCTYPE r [
  <!ENTITY xxe SYSTEM "file:///etc/passwd">
  ]>
-@@ -2513,15 +2879,15 @@
+@@ -2513,15 +2896,15 @@
          assert!(result.is_err());
          let err = result.unwrap_err();
          assert!(
@@ -3133,7 +3161,7 @@
          let xml = r#"<!DOCTYPE r [
  <!ENTITY xxe PUBLIC "-//Evil//EN" "http://evil.com/payload">
  ]>
-@@ -2530,15 +2896,15 @@
+@@ -2530,15 +2913,15 @@
          assert!(result.is_err());
          let err = result.unwrap_err();
          assert!(
@@ -3152,7 +3180,7 @@
          let xml = r#"<!DOCTYPE r [
  <!ENTITY xxe SYSTEM "file:///etc/shadow">
  ]>
-@@ -2549,7 +2915,7 @@
+@@ -2549,7 +2932,7 @@
  
      #[test]
      fn test_xxe_multiple_external_entities_all_rejected() {
@@ -3161,7 +3189,7 @@
          // Even if one entity is internal, the external one should fail
          let xml = r#"<!DOCTYPE r [
  <!ENTITY safe "ok">
-@@ -2568,9 +2934,9 @@
+@@ -2568,9 +2951,9 @@
          let mut input = ParserInput::new("&#0;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3173,7 +3201,7 @@
          );
      }
  
-@@ -2579,9 +2945,9 @@
+@@ -2579,9 +2962,9 @@
          let mut input = ParserInput::new("&#x0;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3185,7 +3213,7 @@
          );
      }
  
-@@ -2619,17 +2985,17 @@
+@@ -2619,17 +3002,17 @@
          let mut input = ParserInput::new("&#xD800;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3207,7 +3235,7 @@
          );
      }
  
-@@ -2639,17 +3005,17 @@
+@@ -2639,17 +3022,17 @@
          let mut input = ParserInput::new("&#xFFFE;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3229,7 +3257,7 @@
          );
      }
  
-@@ -2668,9 +3034,9 @@
+@@ -2668,9 +3051,9 @@
          let mut input = ParserInput::new("&#x110000;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3241,7 +3269,7 @@
          );
      }
  
-@@ -2680,9 +3046,10 @@
+@@ -2680,9 +3063,10 @@
          let mut input = ParserInput::new("&#99999999999;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3254,7 +3282,7 @@
          );
      }
  
-@@ -2692,9 +3059,10 @@
+@@ -2692,9 +3076,10 @@
          let mut input = ParserInput::new("&#xFFFFFFFFFF;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3267,7 +3295,7 @@
          );
      }
  
-@@ -2703,9 +3071,10 @@
+@@ -2703,9 +3088,10 @@
          let mut input = ParserInput::new("&#;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3280,7 +3308,7 @@
          );
      }
  
-@@ -2714,9 +3083,10 @@
+@@ -2714,9 +3100,10 @@
          let mut input = ParserInput::new("&#x;");
          let err = input.parse_reference().unwrap_err();
          assert!(
@@ -3293,7 +3321,7 @@
          );
      }
  
-@@ -2760,7 +3130,7 @@
+@@ -2760,7 +3147,7 @@
          input.set_max_name_length(50);
          let result = input.parse_name();
          assert!(result.is_err());
@@ -3302,7 +3330,7 @@
      }
  
      #[test]
-@@ -2806,7 +3176,7 @@
+@@ -2806,7 +3193,7 @@
          input.set_max_name_length(50);
          let result = input.parse_name_eq("something");
          assert!(result.is_err());
@@ -3311,7 +3339,7 @@
      }
  
      #[test]
-@@ -2817,7 +3187,59 @@
+@@ -2817,7 +3204,59 @@
          input.set_max_name_length(50);
          let result = input.parse_name_eq_parts(None, "something");
          assert!(result.is_err());
@@ -3372,7 +3400,7 @@
      }
  
      // -- Comment boundary edge cases --
-@@ -2829,7 +3251,10 @@
+@@ -2829,7 +3268,10 @@
          let result = parse_comment_content(&mut input);
          assert!(result.is_err());
          assert!(
@@ -3384,7 +3412,7 @@
              "double dash inside comment should be rejected"
          );
      }
-@@ -2848,10 +3273,12 @@
+@@ -2848,10 +3290,12 @@
          let mut input = ParserInput::new("<!-- no end");
          let result = parse_comment_content(&mut input);
          assert!(result.is_err());
@@ -3401,7 +3429,7 @@
      }
  
      #[test]
-@@ -2893,10 +3320,12 @@
+@@ -2893,10 +3337,12 @@
          let mut input = ParserInput::new("<![CDATA[no end");
          let result = parse_cdata_content(&mut input);
          assert!(result.is_err());
@@ -3418,7 +3446,7 @@
      }
  
      #[test]
-@@ -2937,10 +3366,12 @@
+@@ -2937,10 +3383,12 @@
          let mut input = ParserInput::new("<?xml data?>");
          let result = parse_pi_content(&mut input);
          assert!(result.is_err());
@@ -3435,7 +3463,7 @@
      }
  
      #[test]
-@@ -2959,10 +3390,12 @@
+@@ -2959,10 +3407,12 @@
          let mut input = ParserInput::new("<?ns:target data?>");
          let result = parse_pi_content(&mut input);
          assert!(result.is_err());
@@ -3452,7 +3480,7 @@
      }
  
      #[test]
-@@ -2988,10 +3421,12 @@
+@@ -2988,10 +3438,12 @@
          let mut input = ParserInput::new("\"abc<def\"");
          let result = input.parse_attribute_value();
          assert!(result.is_err());
@@ -3469,7 +3497,7 @@
      }
  
      #[test]
-@@ -2999,10 +3434,12 @@
+@@ -2999,10 +3451,12 @@
          let mut input = ParserInput::new("\"no closing quote");
          let result = input.parse_attribute_value();
          assert!(result.is_err());
@@ -3486,7 +3514,7 @@
      }
  
      #[test]
-@@ -3010,10 +3447,12 @@
+@@ -3010,10 +3464,12 @@
          let mut input = ParserInput::new("unquoted");
          let result = input.parse_attribute_value();
          assert!(result.is_err());
@@ -3503,7 +3531,7 @@
      }
  
      #[test]
-@@ -3024,22 +3463,19 @@
+@@ -3024,22 +3480,19 @@
      }
  
      #[test]
@@ -3535,7 +3563,7 @@
      }
  
      // -- Invalid XML character detection --
-@@ -3076,10 +3512,12 @@
+@@ -3076,10 +3529,12 @@
          let mut input = ParserInput::new(input_bytes);
          let result = input.next_char();
          assert!(result.is_err());
@@ -3552,7 +3580,7 @@
      }
  
      #[test]
-@@ -3101,138 +3539,150 @@
+@@ -3101,138 +3556,150 @@
      fn test_scan_char_data_cdata_end_marker() {
          // `]]>` in character data is not allowed — the scanner should stop before it
          let input = ParserInput::new("text]]>more");
@@ -3759,7 +3787,7 @@
      }
  
      // -- QName validation edge cases --
-@@ -3265,34 +3715,46 @@
+@@ -3265,34 +3732,46 @@
          assert!(result.unwrap().contains("empty prefix or local part"));
      }
  
@@ -3816,7 +3844,7 @@
      }
  
      // -- XML declaration edge cases --
-@@ -3302,10 +3764,12 @@
+@@ -3302,10 +3781,12 @@
          let mut input = ParserInput::new("<?xml version=\"2.0\"?>");
          let result = parse_xml_decl(&mut input);
          assert!(result.is_err());
@@ -3833,7 +3861,7 @@
      }
  
      #[test]
-@@ -3313,10 +3777,12 @@
+@@ -3313,10 +3794,12 @@
          let mut input = ParserInput::new("<?xml version=\"1.0\" encoding=\"123bad\"?>");
          let result = parse_xml_decl(&mut input);
          assert!(result.is_err());
@@ -3850,7 +3878,7 @@
      }
  
      #[test]
-@@ -3324,10 +3790,12 @@
+@@ -3324,10 +3807,12 @@
          let mut input = ParserInput::new("<?xml version=\"1.0\" standalone=\"maybe\"?>");
          let result = parse_xml_decl(&mut input);
          assert!(result.is_err());
@@ -3867,7 +3895,7 @@
      }
  
      #[test]
-@@ -3342,10 +3810,10 @@
+@@ -3342,10 +3827,10 @@
      #[test]
      fn test_save_restore_position() {
          let mut input = ParserInput::new("abcdef");
@@ -3880,7 +3908,7 @@
          assert_eq!(input.peek(), Some(b'f'));
          input.restore_position(saved);
          assert_eq!(input.peek(), Some(b'd'));
-@@ -3357,7 +3825,7 @@
+@@ -3357,7 +3842,7 @@
  
      #[test]
      fn test_depth_limit_via_parse_str_with_options() {
@@ -3889,7 +3917,7 @@
          // 3 levels with limit 3 should succeed
          let xml = "<a><b><c/></b></a>";
          let opts = ParseOptions::default().max_depth(3);
-@@ -3367,7 +3835,7 @@
+@@ -3367,7 +3852,7 @@
          let xml = "<a><b><c><d/></c></b></a>";
          let result = parse_str_with_options(xml, &opts);
          assert!(result.is_err());
@@ -3898,7 +3926,7 @@
      }
  
      // -- Builtin entity matching edge cases --
-@@ -3403,12 +3871,24 @@
+@@ -3403,12 +3888,24 @@
      fn test_expand_entity_text_counts_against_limit() {
          // Set up a ParserInput with entity_map containing nested references
          let mut input = ParserInput::new("");
@@ -3929,7 +3957,7 @@
          input.set_max_entity_expansions(2);
  
          // Expanding "b" should expand &a; twice, hitting the limit
-@@ -3465,6 +3945,54 @@
+@@ -3465,6 +3962,54 @@
          assert_eq!(result, "<![CDATA[&amp; not expanded]]>");
      }
  
diff --git a/src/benchmark_support.rs b/src/benchmark_support.rs
index 2c91da21..c867e00c 100644
--- a/src/benchmark_support.rs
+++ b/src/benchmark_support.rs
@@ -21,8 +21,9 @@ impl<'a> Projection<'a> {
         )?))
     }
 
-    /// Build the real normalized arena, retaining it until the caller drops it.
-    pub fn project(&self) -> Result<crate::xml::dom::Document<'a>, crate::xml::dom::ParseError> {
+    /// Build the real normalized arena from the prepared tree, which it
+    /// consumes, retaining the arena until the caller drops it.
+    pub fn project(self) -> Result<crate::xml::dom::Document<'a>, crate::xml::dom::ParseError> {
         self.0.project()
     }
 }
diff --git a/src/c14n/mod.rs b/src/c14n/mod.rs
index 0e32adfb..bdf66b44 100644
--- a/src/c14n/mod.rs
+++ b/src/c14n/mod.rs
@@ -230,6 +230,11 @@ pub(crate) fn is_output_limit_error(error: &C14nError) -> bool {
 pub(crate) trait NodeVisibility<D: DomStorage = NativeDom> {
     fn contains_node(&self, node: Node<'_, '_, D>) -> Result<bool, C14nError>;
 
+    /// The element whose whole subtree, and nothing else, this set selects.
+    fn apex(&self) -> Option<NodeId> {
+        None
+    }
+
     fn contains_attribute(
         &self,
         owner: Node<'_, '_, D>,
@@ -290,6 +295,41 @@ impl NodeVisibility for ClosureVisibility<'_> {
     }
 }
 
+/// One element's whole subtree, with every attribute and namespace node on it.
+#[cfg(feature = "xmldsig")]
+pub(crate) struct SubtreeVisibility<'a, 'input> {
+    pub(crate) apex: Node<'a, 'input>,
+}
+
+#[cfg(feature = "xmldsig")]
+impl NodeVisibility for SubtreeVisibility<'_, '_> {
+    fn contains_node(&self, node: Node<'_, '_>) -> Result<bool, C14nError> {
+        Ok(self.apex.subtree_contains_id(node.id()))
+    }
+
+    fn apex(&self) -> Option<NodeId> {
+        Some(self.apex.id())
+    }
+
+    fn contains_attribute(
+        &self,
+        owner: Node<'_, '_>,
+        _namespace: Option<&str>,
+        _local_name: &str,
+    ) -> Result<bool, C14nError> {
+        self.contains_node(owner)
+    }
+
+    fn contains_namespace(
+        &self,
+        owner: Node<'_, '_>,
+        _prefix: &str,
+        _uri: &str,
+    ) -> Result<bool, C14nError> {
+        self.contains_node(owner)
+    }
+}
+
 /// Canonicalize an XML document or document subset.
 ///
 /// - `doc`: parsed backend-neutral semantic document (read-only DOM).
@@ -318,51 +358,21 @@ pub fn canonicalize(
     )
 }
 
-/// Canonicalize through the closure visibility API while enforcing both the
-/// output ceiling and the caller's operation-wide XML Base work budget.
-#[cfg(feature = "xmldsig")]
-pub(crate) fn canonicalize_bounded_with_xml_base_budget(
-    doc: &Document,
-    node_set: Option<&dyn Fn(Node) -> bool>,
-    algo: &C14nAlgorithm,
-    max_output_bytes: usize,
-    xml_base_resolution: &xml_base::XmlBaseResolutionBudget,
-    output: &mut Vec<u8>,
-) -> Result<(), C14nError> {
-    let visibility = node_set.map(|predicate| ClosureVisibility { predicate });
-    let initial_offset = output.len();
-    canonicalize_visible_to_writer_bounded(
-        doc,
-        visibility
-            .as_ref()
-            .map(|visibility| visibility as &dyn NodeVisibility),
-        algo,
-        max_output_bytes,
-        xml_base_resolution,
-        output,
-        initial_offset,
-    )?;
-    Ok(())
-}
-
-/// [`canonicalize_bounded_with_xml_base_budget`] that also reports where each
-/// tracked element's start tag begins in `output`.
+/// Bounded canonicalization that also reports where each tracked element's
+/// start tag begins in `output`.
 #[cfg(feature = "xmldsig-sign")]
 pub(crate) fn canonicalize_bounded_with_xml_base_budget_and_positions(
     doc: &Document,
-    node_set: &dyn Fn(Node) -> bool,
+    visibility: &dyn NodeVisibility,
     algo: &C14nAlgorithm,
     tracked_elements: &[NodeId],
     max_output_bytes: usize,
     xml_base_resolution: &xml_base::XmlBaseResolutionBudget,
     output: &mut Vec<u8>,
 ) -> Result<Vec<(NodeId, usize)>, C14nError> {
-    let visibility = ClosureVisibility {
-        predicate: node_set,
-    };
     canonicalize_with_visibility_and_positions_bounded_with_xml_base_budget(
         doc,
-        Some(&visibility),
+        Some(visibility),
         algo,
         tracked_elements,
         max_output_bytes,
@@ -778,6 +788,76 @@ pub fn canonicalize_document(
 mod tests {
     use super::*;
 
+    #[cfg(feature = "xmldsig")]
+    fn subtree_bytes(
+        document: &Document,
+        apex: Node<'_, '_>,
+        algorithm: &C14nAlgorithm,
+    ) -> Vec<u8> {
+        let mut output = Vec::new();
+        canonicalize_visible_to_writer_bounded(
+            document,
+            Some(&SubtreeVisibility { apex }),
+            algorithm,
+            usize::MAX,
+            &xml_base::XmlBaseResolutionBudget::default(),
+            &mut output,
+            0,
+        )
+        .expect("subtree canonicalization");
+        output
+    }
+
+    #[cfg(feature = "xmldsig")]
+    #[test]
+    fn walking_from_the_apex_matches_filtering_the_whole_document() {
+        // SignedInfo starts at its own element. Ancestors still supply in-scope
+        // namespaces and inherited xml:* attributes, in every mode.
+        let xml = r#"<r xmlns="urn:d" xmlns:p="urn:p" xmlns:q="urn:q" xml:lang="en" xml:base="http://a/b/"><!--c-->text<p:s xml:space="preserve" q:a="1" b="2"><p:i xml:base="c/">t</p:i><!--in--><?pi x?></p:s><p:after/></r>"#;
+        let document = Document::parse(xml).expect("parse");
+        let apex = document.root_element().first_element_child().expect("apex");
+        let subtree: Vec<_> = apex.descendants().map(Node::id).collect();
+        for mode in [
+            C14nMode::Inclusive1_0,
+            C14nMode::Inclusive1_1,
+            C14nMode::Exclusive1_0,
+        ] {
+            for comments in [false, true] {
+                let algorithm = C14nAlgorithm::new(mode, comments);
+                let mut filtered = Vec::new();
+                canonicalize(
+                    &document,
+                    Some(&|node| subtree.contains(&node.id())),
+                    &algorithm,
+                    &mut filtered,
+                )
+                .expect("filtered canonicalization");
+                assert_eq!(subtree_bytes(&document, apex, &algorithm), filtered);
+            }
+        }
+    }
+
+    #[cfg(feature = "xmldsig")]
+    #[test]
+    fn relative_namespace_outside_the_apex_still_fails() {
+        // Canonical XML 1.0 §2.3 refuses the document, not just the subset, so
+        // starting at the apex must not skip a binding declared elsewhere.
+        let document = Document::parse("<r><a/><b xmlns:p='relative'><c/></b></r>").expect("parse");
+        let apex = document.root_element().first_element_child().expect("apex");
+        let algorithm = C14nAlgorithm::new(C14nMode::Exclusive1_0, false);
+        let mut output = Vec::new();
+        let result = canonicalize_visible_to_writer_bounded(
+            &document,
+            Some(&SubtreeVisibility { apex }),
+            &algorithm,
+            usize::MAX,
+            &xml_base::XmlBaseResolutionBudget::default(),
+            &mut output,
+            0,
+        );
+        assert!(matches!(result, Err(C14nError::RelativeNamespace)));
+    }
+
     #[test]
     fn from_uri_roundtrip() {
         let uris = [
diff --git a/src/c14n/scratch.rs b/src/c14n/scratch.rs
index 4eb509b2..03bb190d 100644
--- a/src/c14n/scratch.rs
+++ b/src/c14n/scratch.rs
@@ -209,29 +209,73 @@ impl<T> List<T> for Vec<T> {
     }
 }
 
-#[derive(Clone, Default)]
-pub(crate) struct NativeNamespaces<'a>(Map<NamespaceKey<'a>, Option<&'a str>>);
+/// Bindings held without a heap table. Elements rarely see more prefixes, and
+/// each element builds and copies these maps.
+const INLINE_NAMESPACES: usize = 6;
+
+type NamespaceEntry<'a> = (NamespaceKey<'a>, Option<&'a str>);
+
+const EMPTY_NAMESPACE: NamespaceEntry<'static> = (
+    NamespaceKey {
+        prefix: "",
+        utilizer: false,
+    },
+    None,
+);
+
+/// Prefix bindings: a short inline list, then the keyed table, so a document
+/// declaring many prefixes keeps constant-time lookups.
+#[derive(Clone)]
+pub(crate) struct NativeNamespaces<'a> {
+    inline: [NamespaceEntry<'a>; INLINE_NAMESPACES],
+    used: usize,
+    table: Option<Map<NamespaceKey<'a>, Option<&'a str>>>,
+}
+
+impl Default for NativeNamespaces<'_> {
+    fn default() -> Self {
+        Self {
+            inline: [EMPTY_NAMESPACE; INLINE_NAMESPACES],
+            used: 0,
+            table: None,
+        }
+    }
+}
+
+impl NativeNamespaces<'_> {
+    fn position(&self, prefix: &str, utilizer: bool) -> Option<usize> {
+        self.inline[..self.used]
+            .iter()
+            .position(|(key, _)| key.utilizer == utilizer && key.prefix == prefix)
+    }
+}
 
 #[cfg(test)]
 impl<'a> NativeNamespaces<'a> {
     pub(super) fn into_pairs(self) -> impl Iterator<Item = (&'a str, &'a str)> {
-        self.0.into_iter().filter_map(|(key, value)| {
-            if key.utilizer {
-                None
-            } else {
-                value.map(|uri| (key.prefix, uri))
-            }
-        })
+        let inline = self.inline[..self.used].to_vec();
+        inline
+            .into_iter()
+            .chain(self.table.into_iter().flatten())
+            .filter_map(|(key, value)| {
+                if key.utilizer {
+                    None
+                } else {
+                    value.map(|uri| (key.prefix, uri))
+                }
+            })
     }
 }
 
 impl<'a> NamespaceMap<'a> for NativeNamespaces<'a> {
     fn get(&self, prefix: &str, utilizer: bool) -> Result<NamespaceState<'a>, C14nError> {
-        Ok(self
-            .0
-            .get(&NamespaceKey { prefix, utilizer })
-            .copied()
-            .map_or(NamespaceState::Absent, NamespaceState::binding))
+        let entry = match &self.table {
+            Some(table) => table.get(&NamespaceKey { prefix, utilizer }).copied(),
+            None => self
+                .position(prefix, utilizer)
+                .map(|index| self.inline[index].1),
+        };
+        Ok(entry.map_or(NamespaceState::Absent, NamespaceState::binding))
     }
     fn insert(
         &mut self,
@@ -239,14 +283,32 @@ impl<'a> NamespaceMap<'a> for NativeNamespaces<'a> {
         utilizer: bool,
         value: Option<&'a str>,
     ) -> Result<(), C14nError> {
-        self.0.insert(NamespaceKey { prefix, utilizer }, value);
+        let key = NamespaceKey { prefix, utilizer };
+        if let Some(table) = &mut self.table {
+            table.insert(key, value);
+        } else if let Some(index) = self.position(prefix, utilizer) {
+            self.inline[index].1 = value;
+        } else if self.used < INLINE_NAMESPACES {
+            self.inline[self.used] = (key, value);
+            self.used += 1;
+        } else {
+            let mut table: Map<_, _> = self.inline.iter().copied().collect();
+            table.insert(key, value);
+            self.table = Some(table);
+            self.used = 0;
+        }
         Ok(())
     }
     fn remove(&mut self, prefix: &'a str) -> Result<(), C14nError> {
-        self.0.remove(&NamespaceKey {
-            prefix,
-            utilizer: false,
-        });
+        if let Some(table) = &mut self.table {
+            table.remove(&NamespaceKey {
+                prefix,
+                utilizer: false,
+            });
+        } else if let Some(index) = self.position(prefix, false) {
+            self.used -= 1;
+            self.inline[index] = self.inline[self.used];
+        }
         Ok(())
     }
     fn copy(&self) -> Result<Self, C14nError> {
diff --git a/src/c14n/scratch/namespace_tests.rs b/src/c14n/scratch/namespace_tests.rs
index dc4f4e96..d11693ed 100644
--- a/src/c14n/scratch/namespace_tests.rs
+++ b/src/c14n/scratch/namespace_tests.rs
@@ -65,6 +65,48 @@ fn native_namespaces_keep_absent_excluded_and_empty_uri_distinct() {
     check_namespace_states(Native.namespaces());
 }
 
+#[test]
+fn native_namespaces_keep_every_state_across_the_inline_boundary() {
+    // The same contract holds with free inline slots, exactly full and spilled,
+    // and no earlier binding is lost when the bindings move to the table.
+    const PREFIXES: [&str; 8] = ["a", "b", "c", "d", "e", "f", "g", "h"];
+    for filled in 0..=PREFIXES.len() {
+        let mut namespaces = Native.namespaces();
+        for prefix in &PREFIXES[..filled] {
+            namespaces
+                .insert(prefix, false, Some(prefix))
+                .expect("fill binding");
+        }
+        for prefix in &PREFIXES[..filled] {
+            assert_eq!(
+                namespaces.get(prefix, false).expect("filled binding"),
+                NamespaceState::Bound(prefix),
+                "{filled} bindings"
+            );
+        }
+        check_namespace_states(namespaces.clone());
+        // A repeated insert replaces, so it must not consume another slot.
+        for _ in 0..PREFIXES.len() {
+            namespaces
+                .insert("repeat", false, Some("urn:repeat"))
+                .expect("repeat binding");
+        }
+        if let Some(first) = PREFIXES[..filled].first() {
+            namespaces.remove(first).expect("remove first binding");
+            assert_eq!(
+                namespaces.get(first, false).expect("removed binding"),
+                NamespaceState::Absent
+            );
+        }
+        if let Some(last) = PREFIXES[..filled].last().filter(|_| filled > 1) {
+            assert_eq!(
+                namespaces.get(last, false).expect("last binding survives"),
+                NamespaceState::Bound(last)
+            );
+        }
+    }
+}
+
 #[cfg(feature = "xmldsig")]
 #[test]
 fn accounted_namespaces_share_states_and_release_retained_capacity() {
diff --git a/src/c14n/serialize.rs b/src/c14n/serialize.rs
index 89d11f4a..1db00b8d 100644
--- a/src/c14n/serialize.rs
+++ b/src/c14n/serialize.rs
@@ -361,6 +361,16 @@ pub(super) fn serialize_with_scratch<W: ByteSink + ?Sized, S: Scratch, D: DomSto
     initial_offset: usize,
     scratch: &S,
 ) -> Result<(Option<usize>, TrackedPositions), C14nError> {
+    // Canonical XML 1.0 §2.3 requires operation failure on documents containing
+    // relative namespace URIs, including outside the selected subset. Elements
+    // share binding lists, so each list is checked once for the whole document.
+    // https://www.w3.org/TR/2001/REC-xml-c14n-20010315#DataModel
+    for uri in doc.namespace_uris() {
+        scratch.charge(uri.len().saturating_mul(2).saturating_add(1))?;
+        if !uri.is_empty() && !super::xml_base::has_scheme(uri) {
+            return Err(C14nError::RelativeNamespace);
+        }
+    }
     let root = doc.root();
     let max_len = match options.max_output_bytes {
         Some(limit) => initial_offset
@@ -380,15 +390,32 @@ pub(super) fn serialize_with_scratch<W: ByteSink + ?Sized, S: Scratch, D: DomSto
         xml_base_resolution: options.xml_base_resolution,
         scratch,
     };
-    serialize_children(
-        root,
-        visibility,
-        with_comments,
-        ns_renderer,
-        config,
-        &scratch.namespaces(),
-        &mut output,
-    )?;
+    let top = scratch.namespaces();
+    // No node outside a whole subtree can contribute, so the walk starts there.
+    if let Some(apex) = visibility
+        .and_then(NodeVisibility::apex)
+        .and_then(|apex| doc.get_node(apex))
+    {
+        serialize_element(
+            apex,
+            visibility,
+            with_comments,
+            ns_renderer,
+            config,
+            &top,
+            &mut output,
+        )?;
+    } else {
+        serialize_children(
+            root,
+            visibility,
+            with_comments,
+            ns_renderer,
+            config,
+            &top,
+            &mut output,
+        )?;
+    }
     Ok((output.tracked_position, output.tracked_positions))
 }
 
@@ -414,19 +441,6 @@ fn serialize_children<'n, W: ByteSink + ?Sized, S: Scratch, D: DomStorage>(
 
         match child.node_type() {
             NodeType::Element => {
-                // Canonical XML 1.0 §2.3 requires operation failure on
-                // documents containing relative namespace URIs. Apply before
-                // visibility filtering, including Exclusive C14N subsets.
-                // https://www.w3.org/TR/2001/REC-xml-c14n-20010315#DataModel
-                for namespace in child.namespaces() {
-                    let uri = namespace.uri();
-                    output
-                        .scratch
-                        .charge(uri.len().saturating_mul(2).saturating_add(1))?;
-                    if !uri.is_empty() && !super::xml_base::has_scheme(uri) {
-                        return Err(C14nError::RelativeNamespace);
-                    }
-                }
                 if in_set {
                     serialize_element(
                         child,
diff --git a/src/collections.rs b/src/collections.rs
index 8eaf6280..98e22ef4 100644
--- a/src/collections.rs
+++ b/src/collections.rs
@@ -5,12 +5,16 @@
 //! so ordered trees take their place.
 
 use alloc::collections::TryReserveError;
+#[cfg(all(not(feature = "std"), any(feature = "xmldsig", test)))]
+pub(crate) use alloc::collections::btree_map::Entry;
 #[cfg(not(feature = "std"))]
-pub(crate) use alloc::collections::{BTreeMap as Map, BTreeSet as Set, btree_map::Entry};
+pub(crate) use alloc::collections::{BTreeMap as Map, BTreeSet as Set};
 #[cfg(all(not(feature = "std"), feature = "xmldsig"))]
 pub(crate) use alloc::collections::{btree_map as map, btree_set as set};
+#[cfg(all(feature = "std", any(feature = "xmldsig", test)))]
+pub(crate) use std::collections::hash_map::Entry;
 #[cfg(feature = "std")]
-pub(crate) use std::collections::{HashMap as Map, HashSet as Set, hash_map::Entry};
+pub(crate) use std::collections::{HashMap as Map, HashSet as Set};
 #[cfg(all(feature = "std", feature = "xmldsig"))]
 pub(crate) use std::collections::{hash_map as map, hash_set as set};
 
diff --git a/src/document.rs b/src/document.rs
index 3dd000f5..103d9e45 100644
--- a/src/document.rs
+++ b/src/document.rs
@@ -21,7 +21,9 @@ use core::sync::atomic::Ordering;
 #[cfg(not(target_has_atomic = "64"))]
 use portable_atomic::AtomicU64;
 
-use crate::collections::{Entry, Map, Set, Table};
+#[cfg(feature = "xmldsig")]
+use crate::collections::Map;
+use crate::collections::{Set, Table};
 use crate::xml::dom::storage::names::{NameStorage, Names};
 use crate::xml::dom::storage::{
     Native as NativeXmlStorage, Storage as XmlStorage, Values as XmlValues,
@@ -447,13 +449,6 @@ impl ContentReplacementEdit<'_> {
     }
 }
 
-#[derive(Debug)]
-struct DocumentIndexes {
-    order: Map<NodeId, usize>,
-    default_ids: Map<String, Option<NodeId>>,
-    attributes_by_value: Map<(String, String), Vec<NodeId>>,
-}
-
 #[cfg(any(feature = "xmldsig", feature = "xmlenc"))]
 mod policy_sealed {
     pub trait Sealed {}
@@ -502,7 +497,6 @@ impl_document_policy!(crate::policy::DecryptionPolicy);
 
 struct ParsedDocument<'input> {
     document: Document<'input>,
-    indexes: DocumentIndexes,
     node_count: usize,
     #[cfg(any(feature = "xmldsig", feature = "xmlenc"))]
     max_depth: usize,
@@ -2077,31 +2071,23 @@ impl<'a> DocumentView<'a> {
         value: &str,
         registrations: &[IdAttributeRegistration],
     ) -> Option<NodeIdentity> {
-        let mut matched = match self.parsed.indexes.default_ids.get(value) {
-            Some(Some(node)) => Some(*node),
-            Some(None) => return None,
-            None => None,
-        };
-        for registration in registrations {
-            let key = (
-                registration.attribute_local_name().to_owned(),
-                value.to_owned(),
-            );
-            if let Some(nodes) = self.parsed.indexes.attributes_by_value.get(&key) {
-                for node_id in nodes {
-                    let recognized = self.parsed.document.get_node(*node_id).is_some_and(|node| {
-                        node.attributes().any(|attribute| {
-                            attribute.value() == value && registration.matches(node, attribute)
-                        })
-                    });
-                    if !recognized {
-                        continue;
-                    }
-                    if matched.is_some_and(|previous| previous != *node_id) {
-                        return None;
-                    }
-                    matched = Some(*node_id);
+        // One walk per query: operations resolve through their own ID index, so
+        // parsing does not pay to copy every attribute for this rare lookup.
+        let mut matched = None;
+        for node in self.parsed.document.descendants() {
+            if !node.is_element() {
+                continue;
+            }
+            for attribute in node.attributes() {
+                if attribute.value() != value
+                    || !crate::xml::is_id_attribute(node, attribute, registrations)
+                {
+                    continue;
                 }
+                if matched.is_some_and(|previous| previous != node.id()) {
+                    return None;
+                }
+                matched = Some(node.id());
             }
         }
         matched.map(|node| self.node_identity_by_id(node))
@@ -2120,12 +2106,9 @@ impl<'a> DocumentView<'a> {
     /// Rejects foreign/stale identities or nodes absent from this generation.
     pub fn document_order(self, identity: NodeIdentity) -> Result<usize, XmlDocumentError> {
         self.validate_identity(identity)?;
-        self.parsed
-            .indexes
-            .order
-            .get(&self.resolve_node(identity)?.id())
-            .copied()
-            .ok_or(XmlDocumentError::MissingNode)
+        // The arena stores every subtree contiguously in preorder, so a node's
+        // arena index is its document position.
+        Ok(self.resolve_node(identity)?.id().get_usize())
     }
 
     /// Return a total order key for a current tree node.
@@ -2381,10 +2364,15 @@ fn build_semantic_cell(
     let _ = parse_work;
     DocumentCell::try_new(xml, |source| {
         let (document, metrics) = parse_semantic_document(source, settings)?;
-        let indexes = DocumentIndexes::build(&document);
+        debug_assert!(
+            document
+                .descendants()
+                .enumerate()
+                .all(|(position, node)| node.id().get_usize() == position),
+            "document order must equal the preorder arena index"
+        );
         Ok::<_, XmlDocumentError>(ParsedDocument {
             document,
-            indexes,
             node_count: metrics.node_count,
             #[cfg(any(feature = "xmldsig", feature = "xmlenc"))]
             max_depth: metrics.max_depth,
@@ -4171,48 +4159,6 @@ fn validate_wrappers(
     }
 }
 
-impl DocumentIndexes {
-    fn build(document: &Document<'_>) -> Self {
-        let mut order = Map::new();
-        let mut default_ids = Map::new();
-        let mut duplicate_ids = Set::new();
-        let mut attributes_by_value: Map<(String, String), Vec<NodeId>> = Map::new();
-
-        for (position, node) in document.descendants().enumerate() {
-            order.insert(node.id(), position);
-            if !node.is_element() {
-                continue;
-            }
-            for attribute in node.attributes() {
-                attributes_by_value
-                    .entry((attribute.name().to_owned(), attribute.value().to_owned()))
-                    .or_default()
-                    .push(node.id());
-                if !crate::xml::is_id_attribute(node, attribute, &[])
-                    || duplicate_ids.contains(attribute.value())
-                {
-                    continue;
-                }
-                match default_ids.entry(attribute.value().to_owned()) {
-                    Entry::Vacant(entry) => {
-                        entry.insert(Some(node.id()));
-                    }
-                    Entry::Occupied(mut entry) if entry.get() != &Some(node.id()) => {
-                        entry.insert(None);
-                        duplicate_ids.insert(attribute.value().to_owned());
-                    }
-                    Entry::Occupied(_) => {}
-                }
-            }
-        }
-        Self {
-            order,
-            default_ids,
-            attributes_by_value,
-        }
-    }
-}
-
 fn element_content_range(element: &str) -> Result<(Range<usize>, String, bool), XmlDocumentError> {
     let start_end = element_opening_end(element)?;
     let start_tag = &element[..=start_end];
@@ -4686,16 +4632,13 @@ mod tests {
         let retained = build_semantic_cell(xml.to_owned(), settings, 1, 0)
             .expect("selected backend semantic projection must parse");
         retained.with_dependent(|_, parsed| {
-            assert!(parsed.indexes.default_ids.contains_key("target"));
-            assert_eq!(
-                parsed
-                    .document
-                    .root_element()
-                    .first_element_child()
-                    .expect("fixture must contain the indexed child element")
-                    .text(),
-                Some("value")
-            );
+            let item = parsed
+                .document
+                .root_element()
+                .first_element_child()
+                .expect("fixture must contain the identified child element");
+            assert_eq!(item.attribute("ID"), Some("target"));
+            assert_eq!(item.text(), Some("value"));
         });
     }
 
diff --git a/src/parser_xmloxide/parser/input.rs b/src/parser_xmloxide/parser/input.rs
index e5284987..87727965 100644
--- a/src/parser_xmloxide/parser/input.rs
+++ b/src/parser_xmloxide/parser/input.rs
@@ -182,9 +182,22 @@ fn is_ascii_name_start(b: u8) -> bool {
 ///
 /// Covers the ASCII subset of XML 1.0 §2.3 `[4a]`: `[A-Za-z0-9_:.-]`.
 fn is_ascii_name_char(b: u8) -> bool {
-    b.is_ascii_alphanumeric() || b == b'_' || b == b':' || b == b'-' || b == b'.'
+    ASCII_NAME_CHARS[b as usize]
 }
 
+/// The table behind [`is_ascii_name_char`]: names are the most scanned bytes in
+/// a document, and a lookup replaces a chain of range checks per byte.
+const ASCII_NAME_CHARS: [bool; 256] = {
+    let mut table = [false; 256];
+    let mut value = 0_u8;
+    while value < 0x80 {
+        table[value as usize] =
+            value.is_ascii_alphanumeric() || matches!(value, b'_' | b':' | b'-' | b'.');
+        value += 1;
+    }
+    table
+};
+
 /// Matches one of the five XML builtin entity references at the byte level.
 ///
 /// Given bytes starting after `&`, returns `(replacement_char, bytes_to_skip)`
@@ -1008,7 +1021,11 @@ impl<'a, S: NameStorage> ParserInput<'a, S> {
             let count = self.scan_bytes(self.input.len() - self.pos, 1, |bytes, i| {
                 !is_ascii_name_char(bytes[i])
             })?;
-            self.advance_counting_lines(count)?;
+            // Name characters exclude newlines, so no second scan looks for one.
+            self.storage.charge(count * 2)?;
+            self.pos += count;
+            self.column +=
+                u32::try_from(count).expect("XML source windows fit the admitted byte ceiling");
             // Check if we stopped at a non-ASCII byte (need slow path)
             if self.pos >= self.input.len() || self.input[self.pos] < 0x80 {
                 let len = self.pos - start;
diff --git a/src/xml.rs b/src/xml.rs
index 17127897..c17d5375 100644
--- a/src/xml.rs
+++ b/src/xml.rs
@@ -121,10 +121,6 @@ impl IdAttributeRegistration {
             && self.matches_node(node)
     }
 
-    pub(crate) fn attribute_local_name(&self) -> &str {
-        &self.attribute_local_name
-    }
-
     pub(crate) fn matches_node<S: dom::storage::Storage>(&self, node: Node<'_, '_, S>) -> bool {
         match &self.element_scope {
             IdAttributeElementScope::AnyElement => true,
diff --git a/src/xml/dom/benchmark.rs b/src/xml/dom/benchmark.rs
index a98ce1d7..a496e8e7 100644
--- a/src/xml/dom/benchmark.rs
+++ b/src/xml/dom/benchmark.rs
@@ -45,10 +45,10 @@ impl<'a> Projection<'a> {
         })
     }
 
-    pub(crate) fn project(&self) -> Result<Document<'a>, ParseError> {
-        match &self.parsed {
+    pub(crate) fn project(self) -> Result<Document<'a>, ParseError> {
+        match self.parsed {
             Parsed::Roxmltree(parsed) => {
-                super::roxmltree::project(self.input, parsed, &self.preflight)
+                super::roxmltree::project(self.input, &parsed, &self.preflight)
             }
             Parsed::Xmloxide(parsed) => super::xmloxide::project(
                 self.input,
diff --git a/src/xml/dom/preflight.rs b/src/xml/dom/preflight.rs
index b4454c4b..324ec18c 100644
--- a/src/xml/dom/preflight.rs
+++ b/src/xml/dom/preflight.rs
@@ -161,10 +161,11 @@ impl<'input, S: Storage> LexicalPreflight<'input, S> {
                         &mut nodes,
                         SourceNode {
                             kind: SourceKind::Element,
-                            range: element.range.clone(),
+                            range: element.range,
                         },
                     )?;
                     elements.push(index)?;
+                    reader.recycle(element.attributes);
                 }
                 Event::Empty(element) => {
                     enforce_depth(elements.len() + 1)?;
@@ -175,6 +176,7 @@ impl<'input, S: Storage> LexicalPreflight<'input, S> {
                             range: element.range,
                         },
                     )?;
+                    reader.recycle(element.attributes);
                 }
                 Event::End { range, .. } => {
                     if let Some(index) = elements.pop() {
@@ -513,6 +515,26 @@ mod accounted_tests {
         assert_eq!(memory.used(), 0);
     }
 
+    #[test]
+    fn recycling_a_tag_releases_its_accounted_capacity() {
+        use std::fmt::Write as _;
+        // A finished wide tag must not stay charged while later source
+        // positions allocate: a document at its limit would be refused.
+        let mut source = String::from("<r");
+        for index in 0..64 {
+            write!(source, " a{index}='v'").expect("scanner attribute");
+        }
+        source.push_str("/>");
+        let memory = Memory::new(std::sync::Arc::new(MemoryAccount::new(1 << 20, 1 << 24)));
+        let mut scanner = Scanner::with_storage(&source, Accounted(&memory));
+        let Some(Event::Empty(tag)) = scanner.next_event().expect("funded empty tag") else {
+            panic!("one empty tag");
+        };
+        assert!(memory.used() > 0);
+        scanner.recycle(tag.attributes);
+        assert_eq!(memory.used(), 0);
+    }
+
     #[test]
     fn scanner_refusal_precedes_lexing_and_releases_partial_attribute_buffers() {
         // A current query's work ceiling is not replaced by its account;
diff --git a/src/xml/dom/roxmltree.rs b/src/xml/dom/roxmltree.rs
index e0827cd0..850a5ae8 100644
--- a/src/xml/dom/roxmltree.rs
+++ b/src/xml/dom/roxmltree.rs
@@ -6,7 +6,9 @@ use alloc::string::ToString;
 
 use super::{
     Document, LexicalPreflight, ParseError, ParsingOptions, XmlBackendImplementation,
-    tree::{AttributeData, NamespaceData, NodeId, NodeKind, TreeBuilder, range_contains},
+    tree::{
+        AttributeData, NamespaceData, NamespaceSet, NodeId, NodeKind, TreeBuilder, range_contains,
+    },
 };
 
 pub(super) struct RoxmltreeBackend;
@@ -159,14 +161,7 @@ fn project_document<R: Storage, S: Storage, P: Storage>(
                                 xml_id_error: None,
                             })?;
                         }
-                        let mut namespaces = storage.values(source.namespaces().len())?;
-                        for namespace in source.namespaces() {
-                            storage.charge(1)?;
-                            namespaces.push(NamespaceData {
-                                prefix: storage.optional_text(namespace.name())?,
-                                uri: storage.text(namespace.uri())?,
-                            })?;
-                        }
+                        let namespaces = project_namespaces(target, source, parent)?;
                         NodeKind::Element {
                             name: storage.text(source.tag_name().name())?,
                             namespace: storage.optional_text(
@@ -213,6 +208,39 @@ fn project_document<R: Storage, S: Storage, P: Storage>(
     Ok(())
 }
 
+/// The element's in-scope set, sharing its parent's when the bindings agree.
+fn project_namespaces<R: Storage, S: Storage>(
+    target: &mut TreeBuilder<'_, S>,
+    source: backend::Node<'_, '_, R>,
+    parent: Option<NodeId>,
+) -> Result<NamespaceSet, ParseError> {
+    let storage = target.storage();
+    let inherited = target.namespace_set_of(parent);
+    let bindings = target.namespace_bindings(inherited);
+    let mut same = bindings.len() == source.namespaces().len();
+    if same {
+        for (binding, namespace) in bindings.iter().zip(source.namespaces()) {
+            storage.charge(binding.uri.len().saturating_add(1))?;
+            if binding.prefix.as_deref() != namespace.name() || &*binding.uri != namespace.uri() {
+                same = false;
+                break;
+            }
+        }
+    }
+    if same {
+        return Ok(inherited);
+    }
+    let mut namespaces = storage.values(source.namespaces().len())?;
+    for namespace in source.namespaces() {
+        storage.charge(1)?;
+        namespaces.push(NamespaceData {
+            prefix: storage.optional_text(namespace.name())?,
+            uri: storage.text(namespace.uri())?,
+        })?;
+    }
+    target.add_namespace_set(namespaces)
+}
+
 fn element_prefix<'input, R: Storage, S: Storage>(
     node: backend::Node<'_, 'input, R>,
     storage: S,
diff --git a/src/xml/dom/storage/lexical.rs b/src/xml/dom/storage/lexical.rs
index bf857837..46f93bdc 100644
--- a/src/xml/dom/storage/lexical.rs
+++ b/src/xml/dom/storage/lexical.rs
@@ -47,6 +47,9 @@ impl<'a, W: Work> AttributeBuffer<'a, Accounted<'_, W>> for OwnedVec<Attribute<'
     fn push(&mut self, attribute: Attribute<'a>) -> Result<(), MemoryError> {
         self.try_push(attribute)
     }
+    fn into_reusable(self) -> Option<Self> {
+        None
+    }
     fn sort(
         &mut self,
         compare: impl FnMut(&Attribute<'a>, &Attribute<'a>) -> Result<Ordering, MemoryError>,
diff --git a/src/xml/dom/tree.rs b/src/xml/dom/tree.rs
index 3bc90ed3..83efab23 100644
--- a/src/xml/dom/tree.rs
+++ b/src/xml/dom/tree.rs
@@ -52,7 +52,9 @@ pub enum NodeType {
 
 pub(super) struct NodeData<S: Storage = Native> {
     pub(super) parent: Option<NodeId>,
-    pub(super) children: S::Values<NodeId>,
+    // Subtrees are contiguous in preorder, so children are reached through
+    // `subtree_end` and need no list of their own.
+    pub(super) child_count: u32,
     pub(super) kind: NodeKind<S>,
     pub(super) range: Range<usize>,
     pub(super) range_actionable: bool,
@@ -63,6 +65,20 @@ pub(super) struct NodeData<S: Storage = Native> {
     pub(super) xpath_start: u32,
 }
 
+/// One in-scope binding list in the document's table. An element without its
+/// own declarations shares its parent's list.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) struct NamespaceSet(u32);
+
+impl NamespaceSet {
+    /// No bindings; every document's first table entry.
+    pub(super) const EMPTY: Self = Self(0);
+
+    fn index(self) -> usize {
+        self.0 as usize
+    }
+}
+
 pub(super) enum NodeKind<S: Storage = Native> {
     Root,
     Element {
@@ -70,7 +86,7 @@ pub(super) enum NodeKind<S: Storage = Native> {
         namespace: Option<S::Text>,
         prefix: Option<S::Text>,
         attributes: S::Values<AttributeData<S>>,
-        namespaces: S::Values<NamespaceData<S>>,
+        namespaces: NamespaceSet,
     },
     Text(S::Text),
     Comment(S::Text),
@@ -182,60 +198,16 @@ impl<S: Storage> core::fmt::Debug for NodeKind<S> {
                 .field("namespace", namespace)
                 .field("prefix", prefix)
                 .field("attributes", &&attributes[..])
-                .field("namespaces", &&namespaces[..])
+                .field("namespaces", namespaces)
                 .finish(),
         }
     }
 }
-impl<S: Storage> PartialEq for NodeKind<S> {
-    fn eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (Self::Root, Self::Root) => true,
-            (Self::Text(a), Self::Text(b)) | (Self::Comment(a), Self::Comment(b)) => {
-                a.as_ref() == b.as_ref()
-            }
-            (
-                Self::PI {
-                    target: a,
-                    value: av,
-                },
-                Self::PI {
-                    target: b,
-                    value: bv,
-                },
-            ) => a.as_ref() == b.as_ref() && av.as_deref() == bv.as_deref(),
-            (
-                Self::Element {
-                    name: a,
-                    namespace: an,
-                    prefix: ap,
-                    attributes: aa,
-                    namespaces: ans,
-                },
-                Self::Element {
-                    name: b,
-                    namespace: bn,
-                    prefix: bp,
-                    attributes: ba,
-                    namespaces: bns,
-                },
-            ) => {
-                a.as_ref() == b.as_ref()
-                    && an.as_deref() == bn.as_deref()
-                    && ap.as_deref() == bp.as_deref()
-                    && aa[..] == ba[..]
-                    && ans[..] == bns[..]
-            }
-            _ => false,
-        }
-    }
-}
-impl<S: Storage> Eq for NodeKind<S> {}
 impl<S: Storage> core::fmt::Debug for NodeData<S> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         f.debug_struct("NodeData")
             .field("parent", &self.parent)
-            .field("children", &&self.children[..])
+            .field("child_count", &self.child_count)
             .field("kind", &self.kind)
             .field("range", &self.range)
             .field("range_actionable", &self.range_actionable)
@@ -248,6 +220,7 @@ impl<S: Storage> core::fmt::Debug for NodeData<S> {
 pub(super) struct TreeBuilder<'input, S: Storage = Native> {
     input: &'input str,
     nodes: S::Values<NodeData<S>>,
+    namespace_sets: S::Values<S::Values<NamespaceData<S>>>,
     storage: S,
 }
 
@@ -256,13 +229,40 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
         self.storage
     }
     pub(super) fn new(input: &'input str, capacity: usize, storage: S) -> Result<Self, ParseError> {
+        let mut namespace_sets = storage.values(1)?;
+        namespace_sets.push(storage.values(0)?)?;
         Ok(Self {
             input,
             nodes: storage.values(capacity)?,
+            namespace_sets,
             storage,
         })
     }
 
+    /// The set of `node`, or the empty one when it is not an element.
+    pub(super) fn namespace_set_of(&self, node: Option<NodeId>) -> NamespaceSet {
+        match node.map(|node| &self.nodes[node.index()].kind) {
+            Some(NodeKind::Element { namespaces, .. }) => *namespaces,
+            _ => NamespaceSet::EMPTY,
+        }
+    }
+
+    pub(super) fn namespace_bindings(&self, set: NamespaceSet) -> &[NamespaceData<S>] {
+        &self.namespace_sets[set.index()]
+    }
+
+    pub(super) fn add_namespace_set(
+        &mut self,
+        bindings: S::Values<NamespaceData<S>>,
+    ) -> Result<NamespaceSet, ParseError> {
+        let set = NamespaceSet(
+            u32::try_from(self.namespace_sets.len())
+                .expect("bounded XML node count must fit into u32"),
+        );
+        self.namespace_sets.push(bindings)?;
+        Ok(set)
+    }
+
     #[cfg(feature = "xml-backend-xmloxide")]
     pub(super) fn push(
         &mut self,
@@ -285,7 +285,7 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
         );
         self.nodes.push(NodeData {
             parent,
-            children: self.storage.values(0)?,
+            child_count: 0,
             kind,
             range,
             range_actionable,
@@ -294,7 +294,7 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
             xpath_start: 0,
         })?;
         if let Some(parent) = parent {
-            self.nodes[parent.index()].children.push(id)?;
+            self.nodes[parent.index()].child_count += 1;
         }
         Ok(id)
     }
@@ -306,25 +306,26 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
 
     #[cfg(feature = "xml-backend-xmloxide")]
     pub(super) fn has_text_tail(&self, parent: NodeId) -> bool {
-        self.nodes[parent.index()]
-            .children
-            .last()
-            .is_some_and(|last| matches!(self.nodes[last.index()].kind, NodeKind::Text(_)))
+        // In preorder a parent's text tail is the last node pushed: an element
+        // child, or anything below it, would have been pushed after it.
+        self.nodes.last().is_some_and(|last| {
+            last.parent == Some(parent) && matches!(last.kind, NodeKind::Text(_))
+        })
     }
 
     #[cfg(feature = "xml-backend-xmloxide")]
     pub(super) fn append_text(
         &mut self,
         parent: NodeId,
-        value: &str,
+        value: S::Text,
         range: Range<usize>,
         range_actionable: bool,
     ) -> Result<(), ParseError> {
-        if let Some(last) = self.nodes[parent.index()].children.last().copied()
-            && let node = &mut self.nodes[last.index()]
+        if let Some(node) = self.nodes.last_mut()
+            && node.parent == Some(parent)
             && let NodeKind::Text(existing) = &mut node.kind
         {
-            self.storage.append(existing, value)?;
+            self.storage.append(existing, &value)?;
             // One semantic text node can fold several adjacent lexical tokens
             // (plain text, CDATA, and references). Its source range must cover
             // every token so mutation never splices only a semantic prefix.
@@ -333,12 +334,7 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
             node.range_actionable &= range_actionable;
             return Ok(());
         }
-        self.push_with_actionability(
-            Some(parent),
-            NodeKind::Text(self.storage.text(value)?),
-            range,
-            range_actionable,
-        )?;
+        self.push_with_actionability(Some(parent), NodeKind::Text(value), range, range_actionable)?;
         Ok(())
     }
 
@@ -347,14 +343,6 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
         self.nodes.len()
     }
 
-    #[cfg(feature = "xml-backend-xmloxide")]
-    pub(super) fn namespaces(&self, node: NodeId) -> Option<&[NamespaceData<S>]> {
-        match &self.nodes[node.index()].kind {
-            NodeKind::Element { namespaces, .. } => Some(namespaces),
-            _ => None,
-        }
-    }
-
     pub(super) fn finish<P: Storage>(
         mut self,
         preflight: &super::LexicalPreflight<'_, P>,
@@ -371,7 +359,9 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
                         attributes,
                         namespaces,
                         ..
-                    } => attributes.len().checked_add(namespaces.len()),
+                    } => attributes
+                        .len()
+                        .checked_add(self.namespace_sets[namespaces.index()].len()),
                     _ => Some(0),
                 };
                 xpath_nodes = axes
@@ -429,6 +419,7 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
         Ok(Document {
             input: self.input,
             nodes: self.nodes,
+            namespace_sets: self.namespace_sets,
             #[cfg(feature = "xmldsig")]
             xpath_nodes,
         })
@@ -447,6 +438,7 @@ impl<'input, S: Storage> TreeBuilder<'input, S> {
 pub struct Document<'input, S: Storage = Native> {
     input: &'input str,
     nodes: S::Values<NodeData<S>>,
+    namespace_sets: S::Values<S::Values<NamespaceData<S>>>,
     #[cfg(feature = "xmldsig")]
     xpath_nodes: u32,
 }
@@ -566,6 +558,31 @@ impl<'input, S: Storage> Document<'input, S> {
             .map(|_| Node { document: self, id })
     }
 
+    pub(super) fn namespace_bindings(&self, set: NamespaceSet) -> &[NamespaceData<S>] {
+        &self.namespace_sets[set.index()]
+    }
+
+    /// Every namespace URI any element has in scope, repeats included.
+    pub(crate) fn namespace_uris(&self) -> impl Iterator<Item = &str> {
+        self.namespace_sets
+            .iter()
+            .flat_map(|set| set.iter().map(|namespace| namespace.uri.as_ref()))
+    }
+
+    /// The child of `parent` whose subtree ends at `end`. That subtree's last
+    /// node is `end - 1`, so its ancestor chain reaches the child within the
+    /// document's depth.
+    fn last_child_before(&self, parent: NodeId, end: u32) -> Option<NodeId> {
+        let mut id = NodeId(end.checked_sub(1)?);
+        loop {
+            let up = self.nodes.get(id.index())?.parent?;
+            if up == parent {
+                return Some(id);
+            }
+            id = up;
+        }
+    }
+
     /// Number of `XPath` nodes: tree nodes with their attribute and namespace nodes.
     #[cfg(feature = "xmldsig")]
     pub(crate) fn xpath_node_count(&self) -> u32 {
@@ -726,7 +743,10 @@ impl<'a, 'input, S: Storage> Node<'a, 'input, S> {
     pub fn children(self) -> Children<'a, 'input, S> {
         Children {
             document: self.document,
-            ids: self.data().children.iter(),
+            parent: self.id,
+            front: self.id.0 + 1,
+            back: self.data().subtree_end,
+            remaining: self.data().child_count,
         }
     }
     /// Returns the first direct child node.
@@ -752,6 +772,11 @@ impl<'a, 'input, S: Storage> Node<'a, 'input, S> {
             ids: self.id.0..self.data().subtree_end,
         }
     }
+    /// Whether `other` is this node or one of its descendants.
+    #[cfg(feature = "xmldsig")]
+    pub(crate) fn subtree_contains_id(self, other: NodeId) -> bool {
+        (self.id.0..self.data().subtree_end).contains(&other.0)
+    }
     /// Document-order `XPath` index of this tree node.
     #[cfg(feature = "xmldsig")]
     pub(crate) fn xpath_index(self) -> u32 {
@@ -773,36 +798,20 @@ impl<'a, 'input, S: Storage> Node<'a, 'input, S> {
     /// Returns the preceding sibling.
     #[must_use]
     pub fn prev_sibling(self) -> Option<Self> {
-        let parent = self.parent()?;
-        let position = parent
-            .data()
-            .children
-            .iter()
-            .position(|id| *id == self.id)?;
-        position
-            .checked_sub(1)
-            .and_then(|index| self.document.get_node(parent.data().children[index]))
+        let parent = self.data().parent?;
+        if self.id.0 == parent.0 + 1 {
+            return None;
+        }
+        // The node before this one ends the previous sibling's subtree.
+        self.document
+            .last_child_before(parent, self.id.0)
+            .and_then(|id| self.document.get_node(id))
     }
-    /// Returns the following sibling.
+    /// Returns the following sibling. The arena stores each subtree
+    /// contiguously in preorder, so the node after this subtree is the next
+    /// sibling exactly when it has the same parent.
     #[must_use]
     pub fn next_sibling(self) -> Option<Self> {
-        let parent = self.parent()?;
-        let position = parent
-            .data()
-            .children
-            .iter()
-            .position(|id| *id == self.id)?;
-        parent
-            .data()
-            .children
-            .get(position + 1)
-            .and_then(|id| self.document.get_node(*id))
-    }
-    /// Returns the following sibling in constant time. The arena stores each
-    /// subtree contiguously in preorder, so the node after this subtree is the
-    /// next sibling exactly when it has the same parent.
-    #[cfg(feature = "xmldsig")]
-    pub(crate) fn following_sibling(self) -> Option<Self> {
         let parent = self.data().parent?;
         let next = NodeId(self.data().subtree_end);
         let data = self.document.nodes.get(next.index())?;
@@ -892,7 +901,7 @@ impl<'a, 'input, S: Storage> Node<'a, 'input, S> {
     #[must_use]
     pub fn namespaces(self) -> Namespaces<'a, S> {
         let values: &[NamespaceData<S>] = match &self.data().kind {
-            NodeKind::Element { namespaces, .. } => &namespaces[..],
+            NodeKind::Element { namespaces, .. } => self.document.namespace_bindings(*namespaces),
             _ => &[],
         };
         Namespaces {
@@ -1110,23 +1119,37 @@ pub struct PI<'a> {
 /// Iterator over direct child nodes.
 pub struct Children<'a, 'input, S: Storage = Native> {
     document: &'a Document<'input, S>,
-    ids: core::slice::Iter<'a, NodeId>,
+    parent: NodeId,
+    front: u32,
+    back: u32,
+    remaining: u32,
 }
 impl<'a, 'input, S: Storage> Iterator for Children<'a, 'input, S> {
     type Item = Node<'a, 'input, S>;
     fn next(&mut self) -> Option<Self::Item> {
-        self.ids.next().and_then(|id| self.document.get_node(*id))
+        if self.remaining == 0 {
+            return None;
+        }
+        self.remaining -= 1;
+        let node = self.document.get_node(NodeId(self.front))?;
+        self.front = node.data().subtree_end;
+        Some(node)
     }
     fn size_hint(&self) -> (usize, Option<usize>) {
-        self.ids.size_hint()
+        let remaining = self.remaining as usize;
+        (remaining, Some(remaining))
     }
 }
 impl<S: Storage> ExactSizeIterator for Children<'_, '_, S> {}
 impl<S: Storage> DoubleEndedIterator for Children<'_, '_, S> {
     fn next_back(&mut self) -> Option<Self::Item> {
-        self.ids
-            .next_back()
-            .and_then(|id| self.document.get_node(*id))
+        if self.remaining == 0 {
+            return None;
+        }
+        self.remaining -= 1;
+        let id = self.document.last_child_before(self.parent, self.back)?;
+        self.back = id.0;
+        self.document.get_node(id)
     }
 }
 
@@ -1295,15 +1318,17 @@ mod tests {
         let xml = "<r xmlns:p='urn:p' xml:id=' a  b ' p:x='value'>left<![CDATA[middle]]>right</r>";
         let preflight =
             super::super::LexicalPreflight::scan(xml, false).expect("fixed XML preflight");
-        let raw = crate::parser_xmloxide::parser::parse_str_with_options(
-            xml,
-            &super::super::xmloxide::backend_options(),
-        )
-        .expect("fixed backend XML");
+        let raw = || {
+            crate::parser_xmloxide::parser::parse_str_with_options(
+                xml,
+                &super::super::xmloxide::backend_options(),
+            )
+            .expect("fixed backend XML")
+        };
         let memory = Memory::new(std::sync::Arc::new(MemoryAccount::new(1 << 20, 1 << 20)));
         let document = super::super::xmloxide::project_in(
             xml,
-            &raw,
+            raw(),
             super::ParsingOptions::default(),
             &preflight,
             super::super::storage::Accounted(&memory),
@@ -1317,7 +1342,7 @@ mod tests {
         assert!(matches!(
             super::super::xmloxide::project_in(
                 xml,
-                &raw,
+                raw(),
                 super::ParsingOptions::default(),
                 &preflight,
                 super::super::storage::Accounted(&denied)
@@ -1339,16 +1364,16 @@ mod tests {
         let source = format!("<r a='{}'/>", "x".repeat(65536));
         let preflight =
             super::super::LexicalPreflight::scan(&source, false).expect("native lexical baseline");
-        let raw = crate::parser_xmloxide::parser::parse_str_with_options(
-            &source,
-            &super::super::xmloxide::backend_options(),
-        )
-        .expect("native raw XML baseline");
         for (limit, capacity) in [(0, 0), (1, 4096)] {
+            let raw = crate::parser_xmloxide::parser::parse_str_with_options(
+                &source,
+                &super::super::xmloxide::backend_options(),
+            )
+            .expect("native raw XML baseline");
             let memory = Memory::new(std::sync::Arc::new(MemoryAccount::new(capacity, 1 << 24)));
             let result = super::super::xmloxide::project_in(
                 &source,
-                &raw,
+                raw,
                 super::ParsingOptions {
                     nodes_limit: limit,
                     allow_dtd: false,
diff --git a/src/xml/dom/tree/comparison.rs b/src/xml/dom/tree/comparison.rs
index e123620b..bbebe3e6 100644
--- a/src/xml/dom/tree/comparison.rs
+++ b/src/xml/dom/tree/comparison.rs
@@ -141,7 +141,7 @@ impl<L: Storage> Document<'_, L> {
             ))?));
         }
         for (index, (left, right)) in self.nodes.iter().zip(other.nodes.iter()).enumerate() {
-            if let Some(field) = difference(left, right, doctype, storage)? {
+            if let Some(field) = difference(self, other, left, right, doctype, storage)? {
                 let reason = if field == "source range" {
                     storage.formatted(format_args!(
                         "retained semantic node {index} differs in source range ({}..{} versus {}..{})",
@@ -180,6 +180,8 @@ fn optional_equal<S: Storage>(
 }
 
 fn difference<L: Storage, R: Storage, S: ComparisonStorage>(
+    left_document: &Document<'_, L>,
+    right_document: &Document<'_, R>,
     left: &NodeData<L>,
     right: &NodeData<R>,
     doctype: Option<&Range<usize>>,
@@ -189,14 +191,16 @@ fn difference<L: Storage, R: Storage, S: ComparisonStorage>(
     if left.parent != right.parent {
         return Ok(Some("parent identity"));
     }
-    if left.children.len() != right.children.len() {
+    // With every node's parent compared, the child count catches a difference
+    // in child identities here and keeps its diagnostic.
+    if left.child_count != right.child_count {
         return Ok(Some("child identities"));
     }
-    storage.charge(left.children.len())?;
-    if left.children[..] != right.children[..] {
-        return Ok(Some("child identities"));
-    }
-    if let Some(field) = kind_difference(&left.kind, &right.kind, storage)? {
+    if let Some(field) = kind_difference(
+        (left_document, &left.kind),
+        (right_document, &right.kind),
+        storage,
+    )? {
         return Ok(Some(field));
     }
     if !source_ranges_equivalent(&left.range, &right.range, doctype) {
@@ -214,8 +218,8 @@ fn difference<L: Storage, R: Storage, S: ComparisonStorage>(
 }
 
 fn kind_difference<L: Storage, R: Storage, S: ComparisonStorage>(
-    left: &NodeKind<L>,
-    right: &NodeKind<R>,
+    (left_document, left): (&Document<'_, L>, &NodeKind<L>),
+    (right_document, right): (&Document<'_, R>, &NodeKind<R>),
     storage: S,
 ) -> Result<Option<&'static str>, ParseError> {
     match (left, right) {
@@ -284,7 +288,11 @@ fn kind_difference<L: Storage, R: Storage, S: ComparisonStorage>(
             if !attributes_equal(la, ra, storage)? {
                 return Ok(Some("attribute axis"));
             }
-            if !namespaces_equal(lx, rx, storage)? {
+            if !namespaces_equal(
+                left_document.namespace_bindings(*lx),
+                right_document.namespace_bindings(*rx),
+                storage,
+            )? {
                 return Ok(Some("namespace axis"));
             }
             Ok(None)
diff --git a/src/xml/dom/xmloxide.rs b/src/xml/dom/xmloxide.rs
index 17d87d56..e3713271 100644
--- a/src/xml/dom/xmloxide.rs
+++ b/src/xml/dom/xmloxide.rs
@@ -1,6 +1,6 @@
 //! `xmloxide` parser adapter for the shared semantic arena.
 
-use alloc::string::ToString;
+use alloc::string::{String, ToString};
 use core::ops::Range;
 
 use super::storage::names::NameStorage;
@@ -11,7 +11,7 @@ use xmloxide::tree::{NodeId as XmloxNodeId, NodeKind as XmloxNodeKind};
 use super::{
     Document, LexicalPreflight, ParseError, ParsingOptions, XmlBackendImplementation,
     preflight::{PositionCursor, SourceKind},
-    tree::{AttributeData, NamespaceData, NodeId, NodeKind, TreeBuilder},
+    tree::{AttributeData, NamespaceData, NamespaceSet, NodeId, NodeKind, TreeBuilder},
 };
 
 pub(super) struct XmloxideBackend;
@@ -41,10 +41,46 @@ impl XmloxideBackend {
                     diagnostics: diagnostics.into_owned(),
                 }),
             })?;
-        Ok(project_in(input, &parsed, options, preflight, storage)?)
+        Ok(project_in(input, parsed, options, preflight, storage)?)
     }
 }
 
+/// Takes a backend text into the semantic tree. The two trees share one storage
+/// in a parse, so the text moves with its allocation and its charge.
+pub(super) trait AdoptText<R: Storage>: Storage {
+    fn adopt(&self, text: R::Text) -> Result<Self::Text, ParseError>;
+}
+
+impl AdoptText<Native> for Native {
+    fn adopt(&self, text: String) -> Result<String, ParseError> {
+        Ok(text)
+    }
+}
+
+#[cfg(feature = "xmldsig")]
+impl<'w, W: structured_asn1::memory::Work> AdoptText<super::storage::Accounted<'w, W>>
+    for super::storage::Accounted<'w, W>
+{
+    fn adopt(&self, text: Self::Text) -> Result<Self::Text, ParseError> {
+        Ok(text)
+    }
+}
+
+// Tests project a natively parsed tree into a limited account.
+#[cfg(all(test, feature = "xmldsig"))]
+impl<W: structured_asn1::memory::Work> AdoptText<Native> for super::storage::Accounted<'_, W> {
+    fn adopt(&self, text: String) -> Result<Self::Text, ParseError> {
+        self.text(&text)
+    }
+}
+
+fn adopt_optional<S: AdoptText<R>, R: Storage>(
+    storage: S,
+    text: Option<R::Text>,
+) -> Result<Option<S::Text>, ParseError> {
+    text.map(|text| storage.adopt(text)).transpose()
+}
+
 impl XmlBackendImplementation for XmloxideBackend {
     fn parse<'input>(
         input: &'input str,
@@ -60,22 +96,22 @@ impl XmlBackendImplementation for XmloxideBackend {
                 },
             },
         )?;
-        project(input, &parsed, options, preflight)
+        project(input, parsed, options, preflight)
     }
 }
 
 pub(super) fn project<'input>(
     input: &'input str,
-    parsed: &xmloxide::Document,
+    parsed: xmloxide::Document,
     options: ParsingOptions,
     preflight: &LexicalPreflight,
 ) -> Result<Document<'input>, ParseError> {
     project_in(input, parsed, options, preflight, Native)
 }
 
-pub(super) fn project_in<'input, S: Storage, P: Storage, R: NameStorage>(
+pub(super) fn project_in<'input, S: AdoptText<R>, P: Storage, R: NameStorage>(
     input: &'input str,
-    parsed: &xmloxide::Document<R>,
+    parsed: xmloxide::Document<R>,
     options: ParsingOptions,
     preflight: &LexicalPreflight<'_, P>,
     storage: S,
@@ -83,20 +119,21 @@ pub(super) fn project_in<'input, S: Storage, P: Storage, R: NameStorage>(
     if options.nodes_limit == 0 {
         return Err(ParseError::NodesLimitReached);
     }
+    let parsed_root = parsed.root();
     let mut projector = Projector {
-        source: parsed,
         target: TreeBuilder::new(
             input,
             parsed.node_count().min(options.nodes_limit as usize),
             storage,
         )?,
+        source: parsed,
         positions: preflight.positions(),
         nodes_limit: options.nodes_limit,
     };
     let root = projector
         .target
         .push(None, NodeKind::Root, 0..input.len())?;
-    projector.project_children(parsed.root(), root)?;
+    projector.project_children(parsed_root, root)?;
     projector.positions.finish()?;
     projector.target.finish_subtree(root);
     projector.target.finish(preflight)
@@ -118,8 +155,8 @@ pub(super) fn backend_options() -> xmloxide::parser::ParseOptions {
         .max_entity_expansions(crate::hard_limits::XML_ENTITY_EXPANSION_CEILING)
 }
 
-struct Projector<'source, 'input, 'positions, S: Storage = Native, R: NameStorage = Native> {
-    source: &'source xmloxide::Document<R>,
+struct Projector<'input, 'positions, S: Storage = Native, R: NameStorage = Native> {
+    source: xmloxide::Document<R>,
     target: TreeBuilder<'input, S>,
     positions: PositionCursor<'positions>,
     nodes_limit: u32,
@@ -136,7 +173,7 @@ enum ProjectionFrame {
     Exit(NodeId),
 }
 
-impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
+impl<S: AdoptText<R>, R: NameStorage> Projector<'_, '_, S, R> {
     fn project_children(&mut self, source: XmloxNodeId, parent: NodeId) -> Result<(), ParseError> {
         let storage = self.target.storage();
         let mut stack = storage.values(0)?;
@@ -152,8 +189,12 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                     inherited_range,
                     range_actionable,
                 } => {
-                    let source_node = self.source.node(source);
-                    match &source_node.kind {
+                    // Each node is entered once, so its payload moves out.
+                    let kind = core::mem::replace(
+                        &mut self.source.node_mut(source).kind,
+                        XmloxNodeKind::Document,
+                    );
+                    match kind {
                         XmloxNodeKind::Document | XmloxNodeKind::DocumentType { .. } => {
                             self.push_children(
                                 &mut stack,
@@ -210,6 +251,7 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                                 )?;
                             } else if let Some(value) = value {
                                 self.admit_text(parent)?;
+                                let value = self.target.storage().adopt(value)?;
                                 self.target.append_text(parent, value, range, false)?;
                             }
                         }
@@ -222,7 +264,7 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
 
     fn project_element(
         &mut self,
-        kind: &XmloxNodeKind<R>,
+        kind: XmloxNodeKind<R>,
         parent: NodeId,
         namespace_owner: Option<NodeId>,
         inherited_range: Option<&Range<usize>>,
@@ -243,35 +285,16 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
             Some(range) => range.clone(),
             None => self.positions.take(SourceKind::Element)?,
         };
-        let inherited = namespace_owner
-            .and_then(|owner| self.target.namespaces(owner))
-            .unwrap_or_default();
-        let mut namespaces = storage.values(inherited.len())?;
-        for namespace in inherited {
-            storage.charge(1)?;
-            namespaces.push(NamespaceData {
-                prefix: storage.optional_text(namespace.prefix.as_deref())?,
-                uri: storage.text(namespace.uri.as_ref())?,
-            })?;
-        }
+        let namespaces = self.project_namespaces(&attributes, namespace_owner)?;
         let mut semantic_attributes = storage.values(attributes.len())?;
-        for attribute in &**attributes {
+        for attribute in attributes {
             storage.charge(1)?;
-            if attribute.prefix.as_deref() == Some("xmlns") {
-                set_namespace(
-                    &mut namespaces,
-                    Some(&attribute.name),
-                    &attribute.value,
-                    storage,
-                )?;
-            } else if attribute.prefix.is_none() && attribute.name.as_ref() == "xmlns" {
-                set_namespace(&mut namespaces, None, &attribute.value, storage)?;
-            } else {
+            if namespace_declaration(&attribute).is_none() {
                 semantic_attributes.push(AttributeData {
-                    name: storage.text(&attribute.name)?,
-                    namespace: storage.optional_text(attribute.namespace.as_deref())?,
-                    prefix: storage.optional_text(attribute.prefix.as_deref())?,
-                    value: storage.text(&attribute.value)?,
+                    name: storage.adopt(attribute.name)?,
+                    namespace: adopt_optional(storage, attribute.namespace)?,
+                    prefix: adopt_optional(storage, attribute.prefix)?,
+                    value: storage.adopt(attribute.value)?,
                     is_id: false,
                     xml_id_error: None,
                 })?;
@@ -280,10 +303,9 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
         self.target.push_with_actionability(
             Some(parent),
             NodeKind::Element {
-                name: storage.text(name)?,
-                namespace: storage
-                    .optional_text(namespace.as_deref().filter(|uri| !uri.is_empty()))?,
-                prefix: storage.optional_text(prefix.as_deref())?,
+                name: storage.adopt(name)?,
+                namespace: adopt_optional(storage, namespace.filter(|uri| !uri.is_empty()))?,
+                prefix: adopt_optional(storage, prefix)?,
                 attributes: semantic_attributes,
                 namespaces,
             },
@@ -292,11 +314,48 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
         )
     }
 
+    /// The element's in-scope set: its parent's, unless it declares bindings.
+    fn project_namespaces(
+        &mut self,
+        attributes: &[xmloxide::tree::Attribute<R>],
+        namespace_owner: Option<NodeId>,
+    ) -> Result<NamespaceSet, ParseError> {
+        let storage = self.target.storage();
+        let inherited = self.target.namespace_set_of(namespace_owner);
+        storage.charge(attributes.len())?;
+        if attributes
+            .iter()
+            .all(|attribute| namespace_declaration(attribute).is_none())
+        {
+            return Ok(inherited);
+        }
+        let inherited = self.target.namespace_bindings(inherited);
+        let mut namespaces = storage.values(inherited.len())?;
+        for namespace in inherited {
+            storage.charge(1)?;
+            namespaces.push(NamespaceData {
+                prefix: storage.optional_text(namespace.prefix.as_deref())?,
+                uri: storage.text(namespace.uri.as_ref())?,
+            })?;
+        }
+        for attribute in attributes {
+            if let Some(declared) = namespace_declaration(attribute) {
+                set_namespace(
+                    &mut namespaces,
+                    declared.prefix(),
+                    &attribute.value,
+                    storage,
+                )?;
+            }
+        }
+        self.target.add_namespace_set(namespaces)
+    }
+
     fn project_leaf(
         &mut self,
         source: XmloxNodeId,
         parent: NodeId,
-        kind: &XmloxNodeKind<R>,
+        kind: XmloxNodeKind<R>,
         inherited_range: Option<Range<usize>>,
         range_actionable: bool,
     ) -> Result<(), ParseError> {
@@ -314,8 +373,12 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                     Some(range) => range,
                     None => self.positions.take(SourceKind::Text)?,
                 };
-                self.target
-                    .append_text(parent, content, range, range_actionable)?;
+                self.target.append_text(
+                    parent,
+                    storage.adopt(content)?,
+                    range,
+                    range_actionable,
+                )?;
             }
             XmloxNodeKind::CData { content } => {
                 self.admit_text(parent)?;
@@ -323,8 +386,12 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                     Some(range) => range,
                     None => self.positions.take(SourceKind::CData)?,
                 };
-                self.target
-                    .append_text(parent, content, range, range_actionable)?;
+                self.target.append_text(
+                    parent,
+                    storage.adopt(content)?,
+                    range,
+                    range_actionable,
+                )?;
             }
             XmloxNodeKind::Comment { content } => {
                 self.admit_node()?;
@@ -334,7 +401,7 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                 };
                 self.target.push_with_actionability(
                     Some(parent),
-                    NodeKind::Comment(storage.text(content)?),
+                    NodeKind::Comment(storage.adopt(content)?),
                     range,
                     range_actionable,
                 )?;
@@ -351,8 +418,8 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
                 self.target.push_with_actionability(
                     Some(parent),
                     NodeKind::PI {
-                        target: storage.text(pi_target)?,
-                        value: storage.optional_text(data.as_deref())?,
+                        target: storage.adopt(pi_target)?,
+                        value: adopt_optional(storage, data)?,
                     },
                     range,
                     range_actionable,
@@ -404,6 +471,34 @@ impl<S: Storage, R: NameStorage> Projector<'_, '_, '_, S, R> {
     }
 }
 
+/// What a namespace declaration attribute binds.
+#[derive(Clone, Copy)]
+enum Declared<'a> {
+    Default,
+    Prefix(&'a str),
+}
+
+impl<'a> Declared<'a> {
+    fn prefix(self) -> Option<&'a str> {
+        match self {
+            Self::Default => None,
+            Self::Prefix(prefix) => Some(prefix),
+        }
+    }
+}
+
+fn namespace_declaration<R: NameStorage>(
+    attribute: &xmloxide::tree::Attribute<R>,
+) -> Option<Declared<'_>> {
+    if attribute.prefix.as_deref() == Some("xmlns") {
+        Some(Declared::Prefix(&attribute.name))
+    } else if attribute.prefix.is_none() && attribute.name.as_ref() == "xmlns" {
+        Some(Declared::Default)
+    } else {
+        None
+    }
+}
+
 fn set_namespace<S: Storage>(
     namespaces: &mut S::Values<NamespaceData<S>>,
     prefix: Option<&str>,
diff --git a/src/xml_input/lexical.rs b/src/xml_input/lexical.rs
index d7e512dd..a6551705 100644
--- a/src/xml_input/lexical.rs
+++ b/src/xml_input/lexical.rs
@@ -216,6 +216,7 @@ pub struct Scanner<'a, S: Storage = Native> {
     pending_text: Option<PendingText<'a>>,
     pending_start: Option<PendingStart<'a, S>>,
     dtd_start: Option<(usize, &'a str)>,
+    spare_attributes: Option<S::Attributes<'a>>,
     storage: S,
     admitted: bool,
 }
@@ -309,11 +310,17 @@ impl<'a, S: Storage> Scanner<'a, S> {
             pending_text: None,
             pending_start: None,
             dtd_start: None,
+            spare_attributes: None,
             storage,
             admitted: false,
         }
     }
 
+    /// Return a finished tag's attribute buffer for the next start tag.
+    pub fn recycle(&mut self, attributes: S::Attributes<'a>) {
+        self.spare_attributes = attributes.into_reusable();
+    }
+
     /// Return the next event, or `None` at end of input.
     ///
     /// # Errors
@@ -461,7 +468,10 @@ impl<'a, S: Storage> Scanner<'a, S> {
                         prefix: prefix.as_str(),
                         local: local.as_str(),
                     },
-                    attributes: self.storage.attributes(),
+                    attributes: self
+                        .spare_attributes
+                        .take()
+                        .unwrap_or_else(|| self.storage.attributes()),
                     start: span.range().start,
                 });
                 Ok(None)
@@ -576,16 +586,28 @@ fn validate_qualified_lexeme<L, R>(source: &str) -> Result<(), Error<L, R>> {
         .strip_prefix("</")
         .or_else(|| source.strip_prefix('<'))
         .unwrap_or(source);
-    let name = source
-        .split(|character: char| {
-            character.is_ascii_whitespace() || matches!(character, '=' | '/' | '>')
-        })
-        .next()
-        .unwrap_or_default();
-    let mut parts = name.split(':');
-    let first = parts.next().unwrap_or_default();
-    let second = parts.next();
-    if first.is_empty() || second.is_some_and(str::is_empty) || parts.next().is_some() {
+    // Every delimiter is ASCII and UTF-8 continuation bytes never are, so bytes
+    // decide this without decoding characters.
+    let mut colon = None;
+    let mut length = source.len();
+    for (index, &byte) in source.as_bytes().iter().enumerate() {
+        match byte {
+            b':' if colon.is_some() => {
+                return Err(Error::Static("invalid qualified XML name"));
+            }
+            b':' => colon = Some(index),
+            b'=' | b'/' | b'>' => {
+                length = index;
+                break;
+            }
+            byte if byte.is_ascii_whitespace() => {
+                length = index;
+                break;
+            }
+            _ => {}
+        }
+    }
+    if length == 0 || colon.is_some_and(|colon| colon == 0 || colon + 1 == length) {
         return Err(Error::Static("invalid qualified XML name"));
     }
     Ok(())
diff --git a/src/xml_input/lexical/storage.rs b/src/xml_input/lexical/storage.rs
index 4c9b5e15..a75558d1 100644
--- a/src/xml_input/lexical/storage.rs
+++ b/src/xml_input/lexical/storage.rs
@@ -29,6 +29,11 @@ pub trait Storage: Copy {
 pub trait AttributeBuffer<'a, S: Storage>: Deref<Target = [Attribute<'a>]> + DerefMut {
     /// Append one borrowed attribute, admitting actual growth first.
     fn push(&mut self, attribute: Attribute<'a>) -> Result<(), S::Refusal>;
+    /// Empty the buffer for the next tag, or release it when its capacity
+    /// would stay charged against an operation's memory budget.
+    fn into_reusable(self) -> Option<Self>
+    where
+        Self: Sized;
     /// In-place ordering without a second allocation.
     fn sort(
         &mut self,
@@ -72,6 +77,11 @@ impl<'a, S: Storage<Refusal = TryReserveError>> AttributeBuffer<'a, S> for Vec<A
         Vec::push(self, attribute);
         Ok(())
     }
+    fn into_reusable(mut self) -> Option<Self> {
+        // No budget can refuse later work here, and capacity is bounded by the input.
+        Vec::clear(&mut self);
+        Some(self)
+    }
     fn sort(
         &mut self,
         mut compare: impl FnMut(&Attribute<'a>, &Attribute<'a>) -> Result<Ordering, TryReserveError>,
diff --git a/src/xmldsig/builder.rs b/src/xmldsig/builder.rs
index 5c09fcdc..4ee8d15e 100644
--- a/src/xmldsig/builder.rs
+++ b/src/xmldsig/builder.rs
@@ -1,12 +1,14 @@
 //! Builders for deterministic `XMLDSig` signature templates.
 
 use crate::xml_input as xml_sec_xml_input;
-use std::{collections::HashSet, io::Write};
+use std::io::Write;
 
 use base64::Engine;
 use xml_sec_xml_input::lexical::Writer;
 
-use crate::c14n::{C14nAlgorithm, C14nMode, canonicalize_bounded_with_xml_base_budget};
+use crate::c14n::{
+    C14nAlgorithm, C14nMode, SubtreeVisibility, canonicalize_visible_to_writer_bounded,
+};
 use crate::policy::{PolicyViolation, SigningPolicy};
 use crate::xml::{is_xml_1_0_character, is_xml_ncname};
 
@@ -459,18 +461,15 @@ impl SignatureBuilder {
             .children()
             .find(|node| node.has_tag_name((XMLDSIG_NS, "SignedInfo")))
             .ok_or(SignatureBuilderError::MissingGeneratedSignedInfo)?;
-        let signed_info_subtree: HashSet<_> = signed_info
-            .descendants()
-            .map(crate::xml::dom::Node::id)
-            .collect();
         let mut canonical_signed_info = Vec::new();
-        canonicalize_bounded_with_xml_base_budget(
+        canonicalize_visible_to_writer_bounded(
             &document,
-            Some(&|node| signed_info_subtree.contains(&node.id())),
+            Some(&SubtreeVisibility { apex: signed_info }),
             &self.c14n_method,
             budget.remaining_c14n_output(),
             budget.xml_base_resolution(),
             &mut canonical_signed_info,
+            0,
         )
         .map_err(|error| {
             map_c14n_resource_policy_violation(
diff --git a/src/xmldsig/extension/tree.rs b/src/xmldsig/extension/tree.rs
index 9ca1ca16..dff07a43 100644
--- a/src/xmldsig/extension/tree.rs
+++ b/src/xmldsig/extension/tree.rs
@@ -112,7 +112,7 @@ pub fn next_sibling<W: Work>(
         return Err(TreeError::NotChild);
     }
     Ok(node
-        .following_sibling()
+        .next_sibling()
         .map(|sibling| view.node_identity(sibling)))
 }
 
diff --git a/src/xmldsig/pkix.rs b/src/xmldsig/pkix.rs
index e46d9b9b..c5d7d557 100644
--- a/src/xmldsig/pkix.rs
+++ b/src/xmldsig/pkix.rs
@@ -1,6 +1,7 @@
 //! Adapter-owned execution domain for the published ASN.1 and PKIX mechanisms.
 
 use alloc::{borrow::ToOwned, string::String, sync::Arc, vec::Vec};
+use core::cell::Cell;
 
 use structured_asn1::memory::{Memory, MemoryAccount, MemoryError, OwnedVec, Work};
 use structured_asn1::{Encoding, Limits, Parser};
@@ -280,8 +281,6 @@ pub(crate) fn verify_crls<'a>(
     provider: &dyn crate::provider::CryptoProvider,
     session: &'a CertificateSession,
 ) -> Result<(), X509ChainError> {
-    use structured_pkix::crl::{Authentication, AuthenticationFailure};
-    use structured_pkix::error::CallbackError;
     use structured_pkix::path::WorkingKey;
 
     if embedded.is_empty() && additional.is_empty() {
@@ -305,54 +304,19 @@ pub(crate) fn verify_crls<'a>(
         let issuer = &path[position + 1];
         let target = &path[position];
         let mut reasons = structured_pkix::crl::Reasons::NONE;
-        for (index, crl) in crls.iter().enumerate() {
-            if !crl
-                .tbs()
-                .issuer()
-                .matches(issuer.tbs().subject(), execution)
-                .map_err(|error| session.error(error))?
-            {
-                continue;
-            }
-            let identified = match crl_key_identifier_match(crl, issuer, session)? {
-                KeyIdentifierMatch::Mismatch => continue,
-                KeyIdentifierMatch::Identified => true,
-                KeyIdentifierMatch::Unidentified => false,
+        let lists = authenticated_crls(&crls, issuer, issuer_key, position, &verifier, session)?;
+        for list in lists.iter().filter(|list| !list.delta) {
+            let evaluation = CrlEvaluation {
+                utc: options.utc_facts.as_ref(),
+                now,
+                index: list.index,
+                position,
             };
-            let proof = crl
-                .authenticate(issuer, issuer_key, &verifier, execution)
-                .map_err(|error| match error {
-                    CallbackError::Processing(error) => session.error(error),
-                    CallbackError::Callback(error) => error,
-                })?;
-            let proof = match proof {
-                Authentication::Authenticated(proof) => proof,
-                Authentication::Rejected(AuthenticationFailure::KeyUsage) => {
-                    return Err(X509ChainError::InvalidKeyUsage {
-                        position: position + 1,
-                        required: "cRLSign",
-                    });
-                }
-                Authentication::Rejected(AuthenticationFailure::Signature) if !identified => {
-                    continue;
-                }
-                Authentication::Rejected(_) | Authentication::Unsupported => {
-                    return Err(X509ChainError::InvalidCrl(index));
-                }
+            let covered = match newest_delta(list, &lists, session)? {
+                Some((delta, pair)) => delta_reasons(pair, target, delta, evaluation, session)?,
+                None => crl_reasons(&list.proof, target, evaluation, session)?,
             };
-            let Some(covered) = crl_reasons(
-                &proof,
-                crl,
-                target,
-                CrlEvaluation {
-                    utc: options.utc_facts.as_ref(),
-                    now,
-                    index,
-                    position,
-                },
-                session,
-            )?
-            else {
+            let Some(covered) = covered else {
                 continue;
             };
             // RFC 5280 §6.3.3(d),(l): partial-list absence cannot establish
@@ -361,6 +325,17 @@ pub(crate) fn verify_crls<'a>(
             // https://www.rfc-editor.org/rfc/rfc5280#section-6.3.3
             reasons = reasons.union(covered);
         }
+        for list in lists.iter().filter(|list| list.delta && !list.bound.get()) {
+            // A delta alone lists changes, not status (RFC 5280 §5.2.4), and it
+            // may carry a revocation, so an applicable unbound one fails closed.
+            let scope = list
+                .proof
+                .scope(target, execution)
+                .map_err(|error| session.error(error))?;
+            if matches!(scope, structured_pkix::crl::ScopeOutcome::Applicable(_)) {
+                return Err(X509ChainError::InvalidCrl(list.index));
+            }
+        }
         // The existing policy validates supplied applicable lists, rather than
         // requiring callers to provide a list for every path certificate.
         if !reasons.is_empty() && !reasons.is_complete() {
@@ -373,6 +348,126 @@ pub(crate) fn verify_crls<'a>(
     Ok(())
 }
 
+/// One supplied list authenticated by the selected issuer key.
+struct AuthenticatedCrl<'r, 'a> {
+    /// Original embedded/inventory source index.
+    index: usize,
+    proof: structured_pkix::crl::Authenticated<'r, 'a>,
+    delta: bool,
+    /// A delta bound to some complete list of this issuer.
+    bound: Cell<bool>,
+}
+
+/// The supplied lists of `issuer` that its key authenticates. A same-name list
+/// of another key is skipped; a list naming this key must verify.
+fn authenticated_crls<'r, 'a>(
+    crls: &'r [structured_pkix::crl::CertificateList<'a>],
+    issuer: &'r Certificate<'a>,
+    issuer_key: structured_pkix::path::WorkingKey<'a>,
+    position: usize,
+    verifier: &ProviderVerifier<'_>,
+    session: &'r CertificateSession,
+) -> Result<OwnedVec<AuthenticatedCrl<'r, 'a>>, X509ChainError> {
+    use structured_pkix::crl::{Authentication, AuthenticationFailure};
+    use structured_pkix::error::CallbackError;
+    let execution = session.memory();
+    let mut lists = execution.vector();
+    for (index, crl) in crls.iter().enumerate() {
+        if !crl
+            .tbs()
+            .issuer()
+            .matches(issuer.tbs().subject(), execution)
+            .map_err(|error| session.error(error))?
+        {
+            continue;
+        }
+        let identified = match crl_key_identifier_match(crl, issuer, session)? {
+            KeyIdentifierMatch::Mismatch => continue,
+            KeyIdentifierMatch::Identified => true,
+            KeyIdentifierMatch::Unidentified => false,
+        };
+        let proof = crl
+            .authenticate(issuer, issuer_key, verifier, execution)
+            .map_err(|error| match error {
+                CallbackError::Processing(error) => session.error(error),
+                CallbackError::Callback(error) => error,
+            })?;
+        let proof = match proof {
+            Authentication::Authenticated(proof) => proof,
+            Authentication::Rejected(AuthenticationFailure::KeyUsage) => {
+                return Err(X509ChainError::InvalidKeyUsage {
+                    position: position + 1,
+                    required: "cRLSign",
+                });
+            }
+            Authentication::Rejected(AuthenticationFailure::Signature) if !identified => {
+                continue;
+            }
+            Authentication::Rejected(_) | Authentication::Unsupported => {
+                return Err(X509ChainError::InvalidCrl(index));
+            }
+        };
+        validate_crl_serials(crl, session)?;
+        let delta = crl
+            .tbs()
+            .extensions()
+            .get(structured_pkix::oid::DELTA_CRL_INDICATOR, execution)
+            .map_err(|error| session.error(error))?
+            .is_some();
+        lists
+            .try_push(AuthenticatedCrl {
+                index,
+                proof,
+                delta,
+                bound: Cell::new(false),
+            })
+            .map_err(|reason| {
+                session.error(structured_pkix::Error::resource(
+                    reason,
+                    "certificateList.pool",
+                    crl.span().start,
+                ))
+            })?;
+    }
+    Ok(lists.into_owned())
+}
+
+/// The newest delta bound to `base`, with its source index. Deltas accumulate
+/// from their base, so an older one is superseded and takes no part.
+fn newest_delta<'b, 'r, 'a>(
+    base: &'b AuthenticatedCrl<'r, 'a>,
+    lists: &'b [AuthenticatedCrl<'r, 'a>],
+    session: &CertificateSession,
+) -> Result<Option<(usize, structured_pkix::crl::BoundDelta<'b, 'r, 'a>)>, X509ChainError> {
+    use structured_pkix::crl::DeltaBinding;
+    let mut newest: Option<(usize, structured_pkix::crl::BoundDelta<'b, 'r, 'a>)> = None;
+    for candidate in lists.iter().filter(|list| list.delta) {
+        let binding = base
+            .proof
+            .bind_delta(&candidate.proof, session.memory())
+            .map_err(|error| session.error(error))?;
+        let DeltaBinding::Bound(pair) = binding else {
+            continue;
+        };
+        candidate.bound.set(true);
+        // Numbers are compared only when a second bound delta exists.
+        // RFC 5280 §5.2.3: the larger CRL number is the newer list. Equal numbers
+        // keep the delta already selected.
+        // <https://www.rfc-editor.org/rfc/rfc5280#section-5.2.3>
+        let newer = match newest {
+            None => true,
+            Some((_, current)) => pair
+                .compare_delta_number(current, session.memory())
+                .map_err(|error| session.error(error))?
+                .is_gt(),
+        };
+        if newer {
+            newest = Some((candidate.index, pair));
+        }
+    }
+    Ok(newest)
+}
+
 /// How a CRL's authority key identifier relates to a candidate issuer.
 enum KeyIdentifierMatch {
     /// Both carry key identifiers and they are equal.
@@ -431,29 +526,39 @@ struct CrlEvaluation<'u> {
     position: usize,
 }
 
-/// Reason coverage an authenticated CRL contributes for `target`, or `None`
-/// when it does not apply. Revocation and unusable lists are errors.
+/// The caller's UTC history, a fact and no implicit clock/table default: `None`
+/// when the list does not apply anyway, so that absence costs nothing.
+fn required_utc<'u, 'a>(
+    proof: &structured_pkix::crl::Authenticated<'_, 'a>,
+    target: &'a Certificate<'a>,
+    evaluation: CrlEvaluation<'u>,
+    session: &CertificateSession,
+) -> Result<Option<&'u structured_pkix::temporal::LeapTable<'u>>, X509ChainError> {
+    use structured_pkix::crl::ScopeOutcome;
+    if evaluation.utc.is_some() {
+        return Ok(evaluation.utc);
+    }
+    match proof
+        .scope(target, session.memory())
+        .map_err(|error| session.error(error))?
+    {
+        ScopeOutcome::NotApplicable(_) => Ok(None),
+        ScopeOutcome::Applicable(_) => Err(X509ChainError::MissingUtcFacts),
+    }
+}
+
+/// Reason coverage an authenticated complete CRL contributes for `target`, or
+/// `None` when it does not apply. Revocation and unusable lists are errors.
 fn crl_reasons<'a>(
     proof: &structured_pkix::crl::Authenticated<'_, 'a>,
-    crl: &structured_pkix::crl::CertificateList<'_>,
     target: &'a Certificate<'a>,
     evaluation: CrlEvaluation<'_>,
     session: &CertificateSession,
 ) -> Result<Option<structured_pkix::crl::Reasons>, X509ChainError> {
-    use structured_pkix::crl::{CompleteEvidence, Evaluation, ScopeOutcome, SourceOrigin};
+    use structured_pkix::crl::{CompleteEvidence, Evaluation, SourceOrigin};
     let execution = session.memory();
-    validate_crl_serials(crl, session)?;
-    // UTC history is a caller fact, not an implicit clock/table default.
-    let Some(utc) = evaluation.utc else {
-        if matches!(
-            proof
-                .scope(target, execution)
-                .map_err(|error| session.error(error))?,
-            ScopeOutcome::NotApplicable(_)
-        ) {
-            return Ok(None);
-        }
-        return Err(X509ChainError::MissingUtcFacts);
+    let Some(utc) = required_utc(proof, target, evaluation, session)? else {
+        return Ok(None);
     };
     let evidence = proof
         .evaluate(
@@ -485,12 +590,146 @@ fn crl_reasons<'a>(
         session.error(structured_pkix::Error::resource(
             reason,
             "certificateList.reasons",
-            crl.span().start,
+            proof.crl().span().start,
         ))
     })?;
     Ok(Some(facts.reasons()))
 }
 
+/// Reason coverage a bound complete-plus-delta pair contributes for `target`,
+/// or `None` when it does not apply. `evaluation.index` names the complete list
+/// and `delta` the updating one.
+fn delta_reasons<'a>(
+    pair: structured_pkix::crl::BoundDelta<'_, '_, 'a>,
+    target: &'a Certificate<'a>,
+    delta: usize,
+    evaluation: CrlEvaluation<'_>,
+    session: &CertificateSession,
+) -> Result<Option<structured_pkix::crl::Reasons>, X509ChainError> {
+    use structured_pkix::crl::{DeltaEvidence, Evaluation, ScopeOutcome, SourceOrigin};
+    let execution = session.memory();
+    let Some(utc) = required_utc(pair.base(), target, evaluation, session)? else {
+        return Ok(None);
+    };
+    let evidence = pair
+        .evaluate(
+            target,
+            &Evaluation {
+                now: evaluation.now,
+                utc,
+                execution,
+                origin: SourceOrigin::Cached,
+            },
+        )
+        .map_err(|error| session.error(error))?;
+    let facts = match evidence {
+        DeltaEvidence::Facts(facts) => facts,
+        DeltaEvidence::NotApplicable(_) => return Ok(None),
+    };
+    validate_delta_window(&facts, delta, evaluation.index)?;
+    validate_delta_entry(&facts, delta, utc, evaluation, session)?;
+    if let Some(absence) = facts.absence() {
+        return Ok(Some(absence.reasons()));
+    }
+    // The facts expose reasons only through absence, which a not yet effective
+    // entry does not establish; the pair shares the base's scope.
+    match pair
+        .base()
+        .scope(target, execution)
+        .map_err(|error| session.error(error))?
+    {
+        ScopeOutcome::Applicable(reasons) => Ok(Some(reasons)),
+        ScopeOutcome::NotApplicable(_) => Ok(None),
+    }
+}
+
+/// RFC 5280 §5.2.4: the delta's window governs the combined list. An expired
+/// complete list stays usable under it, one not yet valid does not.
+/// <https://www.rfc-editor.org/rfc/rfc5280#section-5.2.4>
+fn validate_delta_window(
+    facts: &structured_pkix::crl::DeltaFacts<'_, '_, '_>,
+    delta: usize,
+    base: usize,
+) -> Result<(), X509ChainError> {
+    use structured_pkix::crl::Freshness;
+    match facts.delta_freshness() {
+        Freshness::Current | Freshness::AtNextUpdate => (),
+        Freshness::Uncertain(reason) => {
+            return Err(X509ChainError::CrlTimeUncertain {
+                index: delta,
+                reason,
+            });
+        }
+        _ => return Err(X509ChainError::InvalidCrl(delta)),
+    }
+    match facts.base_freshness() {
+        Freshness::Uncertain(reason) => Err(X509ChainError::CrlTimeUncertain {
+            index: base,
+            reason,
+        }),
+        Freshness::NotYetCurrent | Freshness::InvalidUpdateOrder => {
+            Err(X509ChainError::InvalidCrl(base))
+        }
+        _ => Ok(()),
+    }
+}
+
+fn validate_delta_entry(
+    facts: &structured_pkix::crl::DeltaFacts<'_, '_, '_>,
+    delta: usize,
+    utc: &structured_pkix::temporal::LeapTable<'_>,
+    evaluation: CrlEvaluation<'_>,
+    session: &CertificateSession,
+) -> Result<(), X509ChainError> {
+    use structured_pkix::crl::{CombinedEntry, EntryOrigin};
+    let source = |origin| match origin {
+        EntryOrigin::Complete => evaluation.index,
+        EntryOrigin::Delta => delta,
+    };
+    match *facts.entry() {
+        CombinedEntry::Absent | CombinedEntry::Removed { .. } => Ok(()),
+        CombinedEntry::Revoked { origin, entry, .. } => revocation_in_effect(
+            entry,
+            source(origin),
+            RevocationCheck {
+                now: evaluation.now,
+                utc,
+                position: evaluation.position,
+            },
+            session,
+        ),
+        CombinedEntry::Conflict { origin, .. } | CombinedEntry::Unsupported { origin, .. } => {
+            Err(X509ChainError::InvalidCrl(source(origin)))
+        }
+    }
+}
+
+/// The instant and path member a found revocation entry is checked against.
+#[derive(Clone, Copy)]
+struct RevocationCheck<'u> {
+    now: structured_pkix::temporal::Reading,
+    utc: &'u structured_pkix::temporal::LeapTable<'u>,
+    position: usize,
+}
+
+/// An entry revokes from its date on; a later date is not yet in effect.
+fn revocation_in_effect(
+    entry: &structured_pkix::crl::RevokedCertificate<'_>,
+    index: usize,
+    check: RevocationCheck<'_>,
+    session: &CertificateSession,
+) -> Result<(), X509ChainError> {
+    use structured_pkix::time::Relation;
+    match entry
+        .time_relation(check.now, check.utc, session.memory())
+        .map_err(|error| session.error(error))?
+    {
+        Relation::Before | Relation::At => Err(X509ChainError::Revoked(check.position)),
+        Relation::After => Ok(()),
+        Relation::Uncertain(reason) => Err(X509ChainError::CrlTimeUncertain { index, reason }),
+    }
+}
+
 fn read_crl_pool<'a>(
     embedded: &'a [Vec<u8>],
     additional: &'a [Vec<u8>],
@@ -525,7 +764,6 @@ fn validate_complete_crl(
     position: usize,
 ) -> Result<(), X509ChainError> {
     use structured_pkix::crl::{EntryLookup, Freshness};
-    use structured_pkix::time::Relation;
     match facts.freshness() {
         Freshness::Current | Freshness::AtNextUpdate => (),
         Freshness::Uncertain(reason) => {
@@ -536,16 +774,12 @@ fn validate_complete_crl(
     match facts.entry() {
         EntryLookup::Absent => (),
         EntryLookup::Found(entry) => {
-            match entry
-                .time_relation(now, utc, session.memory())
-                .map_err(|error| session.error(error))?
-            {
-                Relation::Before | Relation::At => return Err(X509ChainError::Revoked(position)),
-                Relation::After => (),
-                Relation::Uncertain(reason) => {
-                    return Err(X509ChainError::CrlTimeUncertain { index, reason });
-                }
-            }
+            revocation_in_effect(
+                entry,
+                index,
+                RevocationCheck { now, utc, position },
+                session,
+            )?;
         }
         EntryLookup::Conflict { .. } | EntryLookup::Unsupported { .. } => {
             return Err(X509ChainError::InvalidCrl(index));
diff --git a/src/xmldsig/sign.rs b/src/xmldsig/sign.rs
index 81101de8..b8362ba9 100644
--- a/src/xmldsig/sign.rs
+++ b/src/xmldsig/sign.rs
@@ -34,7 +34,6 @@ use std::{
 };
 use zeroize::Zeroizing;
 
-use crate::c14n::canonicalize_bounded_with_xml_base_budget;
 use crate::operation::{
     OperationExecutionContext, OperationNodeId, OperationNodeKind, OperationPlanError,
     OperationStage,
@@ -3890,24 +3889,23 @@ fn canonicalize_signed_info(
             }
             .into());
         }
-        let signed_info_subtree: HashSet<_> = signed_info_node
-            .descendants()
-            .map(|node: Node<'_, '_>| node.id())
-            .collect();
         let mut canonical_signed_info = Vec::new();
         let canonicalized = if pending_digests.is_empty() {
-            canonicalize_bounded_with_xml_base_budget(
+            crate::c14n::canonicalize_visible_to_writer_bounded(
                 doc,
-                Some(&|node| signed_info_subtree.contains(&node.id())),
+                Some(&crate::c14n::SubtreeVisibility {
+                    apex: signed_info_node,
+                }),
                 &signed_info.c14n_method,
                 budgets.transforms.remaining_c14n_output(),
                 budgets.transforms.xml_base_resolution(),
                 &mut canonical_signed_info,
+                0,
             )
         } else {
             canonicalize_with_pending_digests(
                 doc,
-                &signed_info_subtree,
+                signed_info_node,
                 &signed_info.c14n_method,
                 budgets,
                 &pending_digests,
@@ -3945,7 +3943,7 @@ const SECOND_EDITION_GENERATION_C14N_URI: &str = "http://www.w3.org/2006/12/xml-
 /// <https://www.w3.org/TR/2001/REC-xml-c14n-20010315#ProcessingModel>
 fn canonicalize_with_pending_digests(
     document: &Document<'_>,
-    signed_info_subtree: &HashSet<NodeId>,
+    signed_info: Node<'_, '_>,
     algorithm: &crate::c14n::C14nAlgorithm,
     budgets: &SigningOperationBudgets,
     pending_digests: &[(NodeId, &str)],
@@ -3954,7 +3952,7 @@ fn canonicalize_with_pending_digests(
     let digests = pending_digests
         .iter()
         .copied()
-        .filter(|(node, _)| signed_info_subtree.contains(node))
+        .filter(|(node, _)| signed_info.subtree_contains_id(*node))
         .collect::<HashMap<_, _>>();
     let tracked = digests.keys().copied().collect::<Vec<_>>();
     let inserted = digests.values().map(|digest| digest.len()).sum::<usize>();
@@ -3968,7 +3966,7 @@ fn canonicalize_with_pending_digests(
     let mut unfilled = Vec::new();
     let mut positions = crate::c14n::canonicalize_bounded_with_xml_base_budget_and_positions(
         document,
-        &|node| signed_info_subtree.contains(&node.id()),
+        &crate::c14n::SubtreeVisibility { apex: signed_info },
         algorithm,
         &tracked,
         allowance,
diff --git a/src/xmldsig/verify.rs b/src/xmldsig/verify.rs
index cb6cac12..4154b7f0 100644
--- a/src/xmldsig/verify.rs
+++ b/src/xmldsig/verify.rs
@@ -25,7 +25,6 @@ use alloc::{
 use base64::Engine;
 use core::cell::{Cell, RefCell};
 
-use crate::c14n::canonicalize_bounded_with_xml_base_budget;
 use crate::document::{
     DocumentParseSettings, DocumentView, NodeIdentity, XmlDocument, XmlDocumentError,
 };
@@ -2688,20 +2687,22 @@ fn canonicalize_verification_signed_info(
     >,
 ) -> Result<Vec<u8>, DsigError> {
     let doc = signed_info_node.document();
-    let signed_info_subtree: Set<_> = signed_info_node.descendants().map(Node::id).collect();
     let mut canonical_signed_info = Vec::new();
     let signed_info_limit = operation
         .budgets()
         .canonicalized
         .remaining()
         .min(operation.budgets().transforms.remaining_c14n_output());
-    canonicalize_bounded_with_xml_base_budget(
+    crate::c14n::canonicalize_visible_to_writer_bounded(
         doc,
-        Some(&|node| signed_info_subtree.contains(&node.id())),
+        Some(&crate::c14n::SubtreeVisibility {
+            apex: signed_info_node,
+        }),
         method,
         signed_info_limit,
         operation.budgets().transforms.xml_base_resolution(),
         &mut canonical_signed_info,
+        0,
     )
     .map_err(|error| {
         if let Some(violation) = map_c14n_resource_policy_violation(
diff --git a/src/xslt/model/lexical_storage.rs b/src/xslt/model/lexical_storage.rs
index a5766640..e6b311b7 100644
--- a/src/xslt/model/lexical_storage.rs
+++ b/src/xslt/model/lexical_storage.rs
@@ -100,6 +100,9 @@ impl Drop for Attributes<'_, '_> {
 }
 
 impl<'a, 's> AttributeBuffer<'a, Storage<'s>> for Attributes<'a, 's> {
+    fn into_reusable(self) -> Option<Self> {
+        None
+    }
     fn push(&mut self, attribute: Attribute<'a>) -> Result<()> {
         if self.values.len() == self.values.capacity() {
             let capacity = self
diff --git a/tests/delta_crl.rs b/tests/delta_crl.rs
new file mode 100644
index 00000000..043f5098
--- /dev/null
+++ b/tests/delta_crl.rs
@@ -0,0 +1,579 @@
+#![cfg(feature = "xmldsig")]
+//! RFC 5280 5.2.4 and 6.3.3 complete-plus-delta evaluation through the public
+//! chain API. Every list is really signed by the path's issuing key.
+
+use der::{Decode as _, Encode as _, asn1::BitString};
+use rcgen::SigningKey as _;
+use rcgen::{
+    BasicConstraints, CertificateParams, CertificateRevocationListParams, CertifiedIssuer, IsCa,
+    KeyIdMethod, KeyPair, KeyUsagePurpose, RevocationReason, RevokedCertParams, SerialNumber,
+    date_time_ymd,
+};
+use time::OffsetDateTime;
+use x509_cert::ext::pkix::crl::dp::{IssuingDistributionPoint, Reasons};
+use xml_sec::policy::Instant;
+use xml_sec::xmldsig::{
+    X509ChainError, X509ChainOptions, X509DataInfo, verify_x509_certificate_chain,
+};
+
+const VERIFICATION_TIME: i64 = 1_773_964_800; // 2026-03-20T00:00:00Z
+const LEAF_SERIAL: u64 = 0x51;
+const INTERMEDIATE_SERIAL: u64 = 0x52;
+const DELTA_CRL_INDICATOR: &str = "2.5.29.27";
+const ISSUING_DISTRIBUTION_POINT: &str = "2.5.29.28";
+
+type Issuer = CertifiedIssuer<'static, KeyPair>;
+
+fn current() -> (OffsetDateTime, OffsetDateTime) {
+    (date_time_ymd(2026, 3, 15), date_time_ymd(2026, 4, 15))
+}
+
+fn expired() -> (OffsetDateTime, OffsetDateTime) {
+    (date_time_ymd(2026, 2, 1), date_time_ymd(2026, 3, 1))
+}
+
+fn root_named(name: &str) -> Issuer {
+    let mut params = CertificateParams::new(Vec::new()).unwrap();
+    params
+        .distinguished_name
+        .push(rcgen::DnType::CommonName, name);
+    params.is_ca = IsCa::Ca(BasicConstraints::Unconstrained);
+    params.key_usages = vec![KeyUsagePurpose::KeyCertSign, KeyUsagePurpose::CrlSign];
+    params.use_authority_key_identifier_extension = true;
+    CertifiedIssuer::self_signed(params, KeyPair::generate().unwrap()).unwrap()
+}
+
+/// Leaf directly under `issuer`, with a serial the lists below can name.
+fn leaf_of(issuer: &Issuer) -> Vec<u8> {
+    let mut params = CertificateParams::new(Vec::new()).unwrap();
+    params.serial_number = Some(SerialNumber::from(LEAF_SERIAL));
+    params.use_authority_key_identifier_extension = true;
+    params
+        .signed_by(&KeyPair::generate().unwrap(), issuer)
+        .unwrap()
+        .der()
+        .to_vec()
+}
+
+fn entry(serial: u64, reason: Option<RevocationReason>) -> RevokedCertParams {
+    RevokedCertParams {
+        serial_number: SerialNumber::from(serial),
+        revocation_time: date_time_ymd(2026, 3, 10),
+        reason_code: reason,
+        invalidity_date: None,
+    }
+}
+
+/// One list as rcgen writes it: crlNumber and authorityKeyIdentifier included.
+fn list(
+    issuer: &Issuer,
+    number: u64,
+    (this_update, next_update): (OffsetDateTime, OffsetDateTime),
+    revoked_certs: Vec<RevokedCertParams>,
+) -> Vec<u8> {
+    CertificateRevocationListParams {
+        this_update,
+        next_update,
+        crl_number: SerialNumber::from(number),
+        issuing_distribution_point: None,
+        revoked_certs,
+        key_identifier_method: KeyIdMethod::Sha256,
+    }
+    .signed_by(issuer)
+    .unwrap()
+    .der()
+    .to_vec()
+}
+
+/// Add extensions to a signed list and sign the result again.
+fn extended(
+    issuer: &Issuer,
+    list: &[u8],
+    extensions: impl IntoIterator<Item = x509_cert::ext::Extension>,
+) -> Vec<u8> {
+    let mut encoded: x509_cert::crl::CertificateList =
+        x509_cert::crl::CertificateList::from_der(list).unwrap();
+    encoded
+        .tbs_cert_list
+        .crl_extensions
+        .as_mut()
+        .unwrap()
+        .extend(extensions);
+    let signature = issuer
+        .key()
+        .sign(&encoded.tbs_cert_list.to_der().unwrap())
+        .unwrap();
+    encoded.signature = BitString::from_bytes(&signature).unwrap();
+    encoded.to_der().unwrap()
+}
+
+fn extension(oid: &str, critical: bool, value: Vec<u8>) -> x509_cert::ext::Extension {
+    x509_cert::ext::Extension {
+        extn_id: der::asn1::ObjectIdentifier::new_unwrap(oid),
+        critical,
+        extn_value: der::asn1::OctetString::new(value).unwrap(),
+    }
+}
+
+/// The `BaseCRLNumber` value of `deltaCRLIndicator`, as a DER INTEGER.
+fn base_number(base: u8) -> Vec<u8> {
+    assert!(base < 0x80, "one positive content octet");
+    vec![0x02, 0x01, base]
+}
+
+fn indicator(base: u8) -> x509_cert::ext::Extension {
+    extension(DELTA_CRL_INDICATOR, true, base_number(base))
+}
+
+fn delta(
+    issuer: &Issuer,
+    number: u64,
+    base: u8,
+    window: (OffsetDateTime, OffsetDateTime),
+    revoked: Vec<RevokedCertParams>,
+) -> Vec<u8> {
+    extended(
+        issuer,
+        &list(issuer, number, window, revoked),
+        [indicator(base)],
+    )
+}
+
+fn scope(point: &IssuingDistributionPoint) -> x509_cert::ext::Extension {
+    extension(
+        ISSUING_DISTRIBUTION_POINT,
+        true,
+        point.to_der().unwrap().clone(),
+    )
+}
+
+fn reasons_scope(reason: Reasons) -> x509_cert::ext::Extension {
+    scope(&IssuingDistributionPoint {
+        distribution_point: None,
+        only_contains_user_certs: false,
+        only_contains_ca_certs: false,
+        only_some_reasons: Some(reason.into()),
+        indirect_crl: false,
+        only_contains_attribute_certs: false,
+    })
+}
+
+fn user_scope(ca_only: bool) -> x509_cert::ext::Extension {
+    scope(&IssuingDistributionPoint {
+        distribution_point: None,
+        only_contains_user_certs: !ca_only,
+        only_contains_ca_certs: ca_only,
+        only_some_reasons: None,
+        indirect_crl: false,
+        only_contains_attribute_certs: false,
+    })
+}
+
+fn chain(certificates: Vec<Vec<u8>>, crls: Vec<Vec<u8>>) -> X509DataInfo {
+    let mut info = X509DataInfo::default();
+    info.certificate_chain = (0..certificates.len()).collect();
+    info.certificates = certificates;
+    info.crls = crls;
+    info
+}
+
+fn verify(info: &X509DataInfo, root: &Issuer) -> Result<(), X509ChainError> {
+    verify_with_utc(info, root, true)
+}
+
+fn verify_with_utc(info: &X509DataInfo, root: &Issuer, utc: bool) -> Result<(), X509ChainError> {
+    let anchors = [root.der().to_vec()];
+    verify_x509_certificate_chain(
+        info,
+        &X509ChainOptions {
+            // Explicit synthetic UTC coverage belongs to this test request.
+            utc_facts: utc.then(|| {
+                structured_pkix::temporal::LeapTable::new(-2_208_988_800, 4_102_444_800, &[])
+                    .expect("test UTC facts")
+            }),
+            trusted_certs: &anchors,
+            verification_time: Instant::new(VERIFICATION_TIME, 0).unwrap(),
+            max_chain_depth: 3,
+            check_crls: true,
+            allowed_extended_key_usages: None,
+            rsa_keys: xml_sec::policy::RsaKeyPolicy::default(),
+            dsa_keys: xml_sec::policy::DsaKeyPolicy::default(),
+            certificate_signature_algorithms: None,
+        },
+    )
+}
+
+fn leaf_chain(root: &Issuer, crls: Vec<Vec<u8>>) -> X509DataInfo {
+    chain(vec![leaf_of(root), root.der().to_vec()], crls)
+}
+
+#[test]
+fn delta_with_its_complete_list_accepts_an_unlisted_certificate() {
+    // The pair must establish absence, not fail as an unpaired delta.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = delta(&root, 4, 3, current(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn revocation_listed_only_in_the_delta_rejects_the_certificate() {
+    // The update, not the older complete list, carries this revocation.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = delta(&root, 4, 3, current(), vec![entry(LEAF_SERIAL, None)]);
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::Revoked(0))
+    );
+}
+
+#[test]
+fn revocation_in_the_complete_list_survives_a_delta_that_omits_it() {
+    // A delta lists changes only; silence does not lift the base entry.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), vec![entry(LEAF_SERIAL, None)]);
+    let update = delta(&root, 4, 3, current(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::Revoked(0))
+    );
+}
+
+#[test]
+fn remove_from_crl_in_the_delta_lifts_a_hold_in_the_complete_list() {
+    // RFC 5280 5.3.1: removeFromCRL appears only in delta CRLs.
+    let root = root_named("delta root");
+    let hold = Some(RevocationReason::CertificateHold);
+    let base = list(&root, 3, current(), vec![entry(LEAF_SERIAL, hold)]);
+    let removal = Some(RevocationReason::RemoveFromCrl);
+    let update = delta(&root, 4, 3, current(), vec![entry(LEAF_SERIAL, removal)]);
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn current_delta_keeps_an_expired_complete_list_usable() {
+    // RFC 5280 5.2.4: the delta's update window governs the combined list.
+    let root = root_named("delta root");
+    let base = list(&root, 3, expired(), Vec::new());
+    let update = delta(&root, 4, 3, current(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn expired_delta_is_refused_even_over_a_current_complete_list() {
+    // The delta may carry a revocation the base lacks, so it cannot be skipped.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = delta(&root, 4, 3, expired(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::InvalidCrl(1))
+    );
+}
+
+#[test]
+fn delta_without_a_complete_list_is_refused() {
+    let root = root_named("delta root");
+    let update = delta(&root, 4, 3, current(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![update]), &root),
+        Err(X509ChainError::InvalidCrl(0))
+    );
+}
+
+#[test]
+fn delta_that_cannot_bind_its_complete_list_is_refused() {
+    // RFC 5280 5.2.4: baseCRLNumber <= complete number < delta number.
+    let root = root_named("delta root");
+    let cases = [
+        ("complete list older than the delta's base", 3, 5, 6),
+        ("delta not newer than the complete list", 4, 3, 4),
+    ];
+    for (case, complete, base, number) in cases {
+        let info = leaf_chain(
+            &root,
+            vec![
+                list(&root, complete, current(), Vec::new()),
+                delta(&root, number, base, current(), Vec::new()),
+            ],
+        );
+        assert_eq!(
+            verify(&info, &root),
+            Err(X509ChainError::InvalidCrl(1)),
+            "{case}"
+        );
+    }
+}
+
+#[test]
+fn delta_indicator_must_be_critical_to_bind() {
+    // RFC 5280 5.2.4 requires criticality; a noncritical marker binds nothing.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = extended(
+        &root,
+        &list(&root, 4, current(), Vec::new()),
+        [extension(DELTA_CRL_INDICATOR, false, base_number(3))],
+    );
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::InvalidCrl(1))
+    );
+}
+
+#[test]
+fn delta_of_another_scope_does_not_update_the_complete_list() {
+    // RFC 5280 6.3.3(c): the pair needs the same distribution scope.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = extended(
+        &root,
+        &list(&root, 4, current(), Vec::new()),
+        [indicator(3), user_scope(false)],
+    );
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::InvalidCrl(1))
+    );
+}
+
+#[test]
+fn unbound_delta_outside_the_target_scope_is_ignored() {
+    // A list covering only CA certificates says nothing about this leaf.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = extended(
+        &root,
+        &list(&root, 4, current(), Vec::new()),
+        [indicator(3), user_scope(true)],
+    );
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn delta_signed_by_a_rolled_over_key_is_ignored_for_the_selected_issuer() {
+    // Equal names are not key identities: its authority key identifier selects
+    // another issuer, so this list is no evidence about the selected path.
+    let root = root_named("delta root");
+    let previous = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = delta(&previous, 4, 3, current(), vec![entry(LEAF_SERIAL, None)]);
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn newest_delta_supersedes_an_older_one_in_either_order() {
+    // Deltas accumulate from their base, so the older hold is already resolved
+    // by the newer removal. Supply order must not change the answer.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let hold = Some(RevocationReason::CertificateHold);
+    let removal = Some(RevocationReason::RemoveFromCrl);
+    let older = delta(&root, 4, 3, expired(), vec![entry(LEAF_SERIAL, hold)]);
+    let newer = delta(&root, 5, 3, current(), vec![entry(LEAF_SERIAL, removal)]);
+    for crls in [
+        vec![base.clone(), older.clone(), newer.clone()],
+        vec![newer, older, base],
+    ] {
+        assert_eq!(verify(&leaf_chain(&root, crls), &root), Ok(()));
+    }
+}
+
+#[test]
+fn newest_delta_decides_by_number_beyond_one_octet() {
+    // CRL numbers are integers: 0x0100 is newer than 0xFF though its first
+    // content octet is smaller.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let older = delta(&root, 0xFF, 3, current(), vec![entry(LEAF_SERIAL, None)]);
+    let newer = delta(&root, 0x0100, 3, current(), Vec::new());
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, newer, older]), &root),
+        Ok(())
+    );
+}
+
+#[test]
+fn pair_coverage_is_limited_to_the_reasons_of_its_scope() {
+    // RFC 5280 6.3.3(d): a bound pair qualifies only the base's reasons.
+    let root = root_named("delta root");
+    let reason = reasons_scope(Reasons::KeyCompromise);
+    let base = extended(
+        &root,
+        &list(&root, 3, current(), Vec::new()),
+        [reason.clone()],
+    );
+    let update = extended(
+        &root,
+        &list(&root, 4, current(), Vec::new()),
+        [indicator(3), reason],
+    );
+    assert_eq!(
+        verify(&leaf_chain(&root, vec![base, update]), &root),
+        Err(X509ChainError::IncompleteCrlCoverage(0))
+    );
+}
+
+#[test]
+fn delta_evaluation_requires_caller_utc_facts() {
+    // Without UTC history no absence can be established for an applicable pair.
+    let root = root_named("delta root");
+    let base = list(&root, 3, current(), Vec::new());
+    let update = delta(&root, 4, 3, current(), Vec::new());
+    assert_eq!(
+        verify_with_utc(&leaf_chain(&root, vec![base, update]), &root, false),
+        Err(X509ChainError::MissingUtcFacts)
+    );
+}
+
+#[test]
+fn exhausted_work_during_delta_evaluation_stays_a_resource_refusal() {
+    // Spent budget must not read as a bad list or as an established status.
+    let root = root_named("delta root");
+    let info = leaf_chain(
+        &root,
+        vec![
+            list(&root, 3, current(), Vec::new()),
+            delta(&root, 4, 3, current(), Vec::new()),
+            delta(&root, 5, 3, current(), Vec::new()),
+        ],
+    );
+    let anchors = [root.der().to_vec()];
+    let options = X509ChainOptions {
+        utc_facts: Some(
+            structured_pkix::temporal::LeapTable::new(-2_208_988_800, 4_102_444_800, &[])
+                .expect("test UTC facts"),
+        ),
+        trusted_certs: &anchors,
+        verification_time: Instant::new(VERIFICATION_TIME, 0).unwrap(),
+        max_chain_depth: 3,
+        check_crls: true,
+        allowed_extended_key_usages: None,
+        rsa_keys: xml_sec::policy::RsaKeyPolicy::default(),
+        dsa_keys: xml_sec::policy::DsaKeyPolicy::default(),
+        certificate_signature_algorithms: None,
+    };
+    let mut completed = false;
+    for max_x509_work in (1..200_000).step_by(64) {
+        let resources = xml_sec::policy::ResourcePolicy {
+            max_x509_work,
+            ..Default::default()
+        };
+        match xml_sec::xmldsig::verify_x509_certificate_chain_with_resources(
+            &info,
+            &options,
+            &resources,
+            xml_sec::provider::default_provider(),
+        ) {
+            Ok(()) => {
+                completed = true;
+                break;
+            }
+            Err(X509ChainError::Policy(_)) => (),
+            Err(X509ChainError::Processing(error)) if error.is_resource() => (),
+            Err(other) => panic!("work {max_x509_work}: {other:?}"),
+        }
+    }
+    assert!(completed, "the sweep must reach a sufficient budget");
+}
+
+/// Independent issuer: `scripts/generate-delta-crl-fixtures.sh`, whose OpenSSL
+/// verifier accepted the silent pair and refused the revoking one.
+fn openssl_pair(delta: &[u8]) -> Result<(), X509ChainError> {
+    let root = include_bytes!("fixtures/x509/delta-crl/ca.der").to_vec();
+    let info = chain(
+        vec![
+            include_bytes!("fixtures/x509/delta-crl/leaf.der").to_vec(),
+            root.clone(),
+        ],
+        vec![
+            include_bytes!("fixtures/x509/delta-crl/complete.crl").to_vec(),
+            delta.to_vec(),
+        ],
+    );
+    let anchors = [root];
+    verify_x509_certificate_chain(
+        &info,
+        &X509ChainOptions {
+            utc_facts: Some(
+                structured_pkix::temporal::LeapTable::new(-2_208_988_800, 4_102_444_800, &[])
+                    .expect("test UTC facts"),
+            ),
+            trusted_certs: &anchors,
+            // 2040-01-01T00:00:00Z, after the fixtures' revocation date.
+            verification_time: Instant::new(2_208_988_800, 0).unwrap(),
+            max_chain_depth: 3,
+            check_crls: true,
+            allowed_extended_key_usages: None,
+            rsa_keys: xml_sec::policy::RsaKeyPolicy::default(),
+            dsa_keys: xml_sec::policy::DsaKeyPolicy::default(),
+            certificate_signature_algorithms: None,
+        },
+    )
+}
+
+#[test]
+fn openssl_issued_silent_delta_is_accepted_as_openssl_accepts_it() {
+    assert_eq!(
+        openssl_pair(include_bytes!("fixtures/x509/delta-crl/silent.crl")),
+        Ok(())
+    );
+}
+
+#[test]
+fn openssl_issued_revoking_delta_is_refused_as_openssl_refuses_it() {
+    assert_eq!(
+        openssl_pair(include_bytes!("fixtures/x509/delta-crl/revoking.crl")),
+        Err(X509ChainError::Revoked(0))
+    );
+}
+
+#[test]
+fn delta_applies_at_its_own_path_position() {
+    // The root's delta revokes the intermediate, not the leaf below it.
+    let root = root_named("delta root");
+    let mut params = CertificateParams::new(Vec::new()).unwrap();
+    params
+        .distinguished_name
+        .push(rcgen::DnType::CommonName, "delta intermediate");
+    params.serial_number = Some(SerialNumber::from(INTERMEDIATE_SERIAL));
+    params.is_ca = IsCa::Ca(BasicConstraints::Unconstrained);
+    params.key_usages = vec![KeyUsagePurpose::KeyCertSign, KeyUsagePurpose::CrlSign];
+    params.use_authority_key_identifier_extension = true;
+    let intermediate: Issuer =
+        CertifiedIssuer::signed_by(params, KeyPair::generate().unwrap(), &root).unwrap();
+    let info = chain(
+        vec![
+            leaf_of(&intermediate),
+            intermediate.der().to_vec(),
+            root.der().to_vec(),
+        ],
+        vec![
+            list(&root, 3, current(), Vec::new()),
+            delta(
+                &root,
+                4,
+                3,
+                current(),
+                vec![entry(INTERMEDIATE_SERIAL, None)],
+            ),
+        ],
+    );
+    assert_eq!(verify(&info, &root), Err(X509ChainError::Revoked(1)));
+}
diff --git a/tests/fixtures/x509/delta-crl/ca.der b/tests/fixtures/x509/delta-crl/ca.der
new file mode 100644
index 00000000..71178d6b
Binary files /dev/null and b/tests/fixtures/x509/delta-crl/ca.der differ
diff --git a/tests/fixtures/x509/delta-crl/complete.crl b/tests/fixtures/x509/delta-crl/complete.crl
new file mode 100644
index 00000000..177832d9
Binary files /dev/null and b/tests/fixtures/x509/delta-crl/complete.crl differ
diff --git a/tests/fixtures/x509/delta-crl/leaf.der b/tests/fixtures/x509/delta-crl/leaf.der
new file mode 100644
index 00000000..1ca79b7b
Binary files /dev/null and b/tests/fixtures/x509/delta-crl/leaf.der differ
diff --git a/tests/fixtures/x509/delta-crl/revoking.crl b/tests/fixtures/x509/delta-crl/revoking.crl
new file mode 100644
index 00000000..489ee620
Binary files /dev/null and b/tests/fixtures/x509/delta-crl/revoking.crl differ
diff --git a/tests/fixtures/x509/delta-crl/silent.crl b/tests/fixtures/x509/delta-crl/silent.crl
new file mode 100644
index 00000000..408a7fa7
Binary files /dev/null and b/tests/fixtures/x509/delta-crl/silent.crl differ