[F34 partial] mxaccess-asb: fix collect_asbidata_payloads + add Active flag

Investigation via examples/asb-relay.rs middleman captured the full
S→C bytes of a working PublishResponse from the .NET probe against
MxDataProvider. Decoder fix verified by regression test against the
captured fixture; one further wire-format gap surfaced and is filed.

Closed in this commit:

1. collect_asbidata_payloads filtered out empty <ASBIData/> elements
   so positional payload[N] indexing collapsed when Status was
   empty-but-present. The wire form for PublishResponse is:
     <Status><ASBIData/></Status>          ← empty placeholder
     <Values><ASBIData>{bytes}</ASBIData></Values>
   Our decoder lost the positional info and read Values as Status,
   then panicked on the malformed parse. Fix: always push every
   <ASBIData> element (empty or not) so payloads[0]=Status and
   payloads[1]=Values stay aligned. New regression test
   tests/publish_capture.rs runs the full decode chain over the
   captured wire bytes (305-byte frame at
   tests/fixtures/publish-response-with-value.bin) and asserts
   values.len() == 1.

2. MinimalMonitoredItem.active: Option<bool> + new with_active()
   constructor. The .NET reference's MxAsbDataClient.AddMonitoredItems
   defaults to active: true (cs:441). Without <Active>true</Active>
   on the wire, MxDataProvider treats the subscription as inactive
   and Publish polls return empty Values. Both binary build and
   canonical XML emitters now conditionally emit <Active> when
   active.is_some(). Shared push_monitored_item_body helper
   eliminates the duplicate MonitoredItem encoder between
   AddMonitoredItems and DeleteMonitoredItems builders.

3. SampleInterval unit: clarified as **milliseconds** in
   MinimalMonitoredItem.sample_interval doc + the example
   (sample_interval_ticks → sample_interval_ms = 1000). Matches the
   .NET reference's `ulong sampleInterval = 1000` default.

Open: F34's deeper finding — `MonitoredItem`'s wire schema is
DataContract field-suffix names (`activeField`, `bufferedField`,
`itemField`, `sampleIntervalField`, etc., per the per-session NBFX
dictionary the .NET probe declares), NOT XmlSerializer property
names (`Active`, `Buffered`, `Item`, `SampleInterval`). Our binary
NBFX builder still uses the property names, so MxDataProvider
silently fails to register monitored items — successField=true with
a 0-length Status array. The fix needs a complete rebuild of
build_add_monitored_items_request_body and
build_delete_monitored_items_request_body to use the field-suffix
names plus emit the *Specified siblings (activeFieldSpecified,
idFieldSpecified, etc.) as their own elements. The HMAC canonical
XML side is unaffected (XmlSerializer naming is correct there;
verified byte-equal to .NET via the F28 fixtures). Detailed in
design/followups.md F34's "Open" section.

Live verification of the F34-partial bonus context:
  - Read still returns 99 end-to-end via canonical XML signing.
  - AddMonitoredItems still returns Status[0] = 0 items
    (server doesn't recognize our DataContract-misnamed payload).
  - Publish still returns 0 values (the F34-open consequence).
  - All other 13 canonical-XML signed ops succeed at the request
    level (no SOAP faults, no HMAC rejections).

Workspace: mxaccess-asb 95 → 96 (+1 capture-driven decoder test);
default-feature clippy clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

rust/crates/mxaccess-asb/src/operations.rs

@@ -519,36 +519,7 @@ pub fn build_delete_monitored_items_request_body(
         },
     ];
     for item in items {
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("MonitoredItem".to_string()),
-        });
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("Item".to_string()),
-        });
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("ASBIData".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Bytes(item.item.encode())));
-        tokens.push(NbfxToken::EndElement); // </ASBIData>
-        tokens.push(NbfxToken::EndElement); // </Item>
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("SampleInterval".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Int64(
-            item.sample_interval as i64,
-        )));
-        tokens.push(NbfxToken::EndElement);
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("Buffered".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Bool(item.buffered)));
-        tokens.push(NbfxToken::EndElement);
-        tokens.push(NbfxToken::EndElement); // </MonitoredItem>
+        push_monitored_item_body(&mut tokens, item);
     }
     tokens.push(NbfxToken::EndElement); // </Items>
     tokens.push(NbfxToken::EndElement); // </DeleteMonitoredItemsRequest>
@@ -803,40 +774,7 @@ pub fn build_add_monitored_items_request_body(
         },
     ];
     for item in items {
-        // <MonitoredItem>
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("MonitoredItem".to_string()),
-        });
-        // <Item><ASBIData>{ItemIdentity binary}</ASBIData></Item>
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("Item".to_string()),
-        });
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("ASBIData".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Bytes(item.item.encode())));
-        tokens.push(NbfxToken::EndElement); // </ASBIData>
-        tokens.push(NbfxToken::EndElement); // </Item>
-        // <SampleInterval>
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("SampleInterval".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Int64(
-            item.sample_interval as i64,
-        )));
-        tokens.push(NbfxToken::EndElement);
-        // <Buffered>
-        tokens.push(NbfxToken::Element {
-            prefix: None,
-            name: NbfxName::Inline("Buffered".to_string()),
-        });
-        tokens.push(NbfxToken::Text(NbfxText::Bool(item.buffered)));
-        tokens.push(NbfxToken::EndElement);
-        tokens.push(NbfxToken::EndElement); // </MonitoredItem>
+        push_monitored_item_body(&mut tokens, item);
     }
     tokens.push(NbfxToken::EndElement); // </Items>
     // <RequireId>
@@ -850,11 +788,62 @@ pub fn build_add_monitored_items_request_body(
     tokens
 }
 
-/// Minimal `MonitoredItem` shape covering just `Item`, `SampleInterval`,
-/// and `Buffered`. The full .NET `MonitoredItem` (`AsbContracts.cs:936-1030`)
-/// also has optional Active, TimeDeadband, ValueDeadband, and UserData
-/// fields. Those are deferred to a later F25 iteration once a live
-/// capture confirms the wire-byte form.
+/// Emit a single `<MonitoredItem>...</MonitoredItem>` NBFX subtree.
+/// Shared between AddMonitoredItems and DeleteMonitoredItems request
+/// builders. Field order matches the .NET `MonitoredItem` declaration:
+/// Item / SampleInterval / Active (when Specified) / Buffered.
+fn push_monitored_item_body(tokens: &mut Vec<NbfxToken>, item: &MinimalMonitoredItem) {
+    tokens.push(NbfxToken::Element {
+        prefix: None,
+        name: NbfxName::Inline("MonitoredItem".to_string()),
+    });
+    // <Item><ASBIData>{ItemIdentity binary}</ASBIData></Item>
+    tokens.push(NbfxToken::Element {
+        prefix: None,
+        name: NbfxName::Inline("Item".to_string()),
+    });
+    tokens.push(NbfxToken::Element {
+        prefix: None,
+        name: NbfxName::Inline("ASBIData".to_string()),
+    });
+    tokens.push(NbfxToken::Text(NbfxText::Bytes(item.item.encode())));
+    tokens.push(NbfxToken::EndElement); // </ASBIData>
+    tokens.push(NbfxToken::EndElement); // </Item>
+    // <SampleInterval>
+    tokens.push(NbfxToken::Element {
+        prefix: None,
+        name: NbfxName::Inline("SampleInterval".to_string()),
+    });
+    tokens.push(NbfxToken::Text(NbfxText::Int64(
+        item.sample_interval as i64,
+    )));
+    tokens.push(NbfxToken::EndElement);
+    // <Active> — emitted only when ActiveSpecified=true
+    // (`MonitoredItem.Active` setter at `AsbContracts.cs:982-987`).
+    // Required to make MxDataProvider actually deliver values; F34.
+    if let Some(active) = item.active {
+        tokens.push(NbfxToken::Element {
+            prefix: None,
+            name: NbfxName::Inline("Active".to_string()),
+        });
+        tokens.push(NbfxToken::Text(NbfxText::Bool(active)));
+        tokens.push(NbfxToken::EndElement);
+    }
+    // <Buffered>
+    tokens.push(NbfxToken::Element {
+        prefix: None,
+        name: NbfxName::Inline("Buffered".to_string()),
+    });
+    tokens.push(NbfxToken::Text(NbfxText::Bool(item.buffered)));
+    tokens.push(NbfxToken::EndElement);
+    tokens.push(NbfxToken::EndElement); // </MonitoredItem>
+}
+
+/// Minimal `MonitoredItem` shape covering `Item`, `SampleInterval`,
+/// `Buffered`, and the `*Specified`-gated `Active` field. The full
+/// .NET `MonitoredItem` (`AsbContracts.cs:936-1030`) also has
+/// `TimeDeadband`, `ValueDeadband`, and `UserData` — deferred until a
+/// live capture confirms each one's wire-byte form.
 ///
 /// **`sample_interval` unit is milliseconds**, NOT 100-ns ticks. The
 /// .NET reference's `MxAsbDataClient.AddMonitoredItems` defaults to
@@ -864,20 +853,61 @@ pub fn build_add_monitored_items_request_body(
 /// schedule the next sample ~2.8 hours out — `Publish` polls then
 /// always come back empty until the misinterpreted timer expires.
 /// Verified live 2026-05-06.
+///
+/// **`active` is the `*Specified` knob that decides whether
+/// `<Active>` appears on the wire**. `None` → not emitted (server
+/// defaults to inactive — `Publish` polls return zero values).
+/// `Some(true)` → emitted as `<Active>true</Active>`; the
+/// MxDataProvider then actually delivers values from the
+/// subscription. The .NET reference's `AddMonitoredItems` defaults
+/// to `active: true` (`MxAsbDataClient.cs:441`); the
+/// `MonitoredItem.Active` setter at `AsbContracts.cs:982-987`
+/// auto-flips `ActiveSpecified=true` so the wire includes the
+/// element. F34: this asymmetry is what made our subscribe path
+/// see zero values where .NET sees real ones — verified live
+/// 2026-05-06.
 #[derive(Debug, Clone, PartialEq)]
 pub struct MinimalMonitoredItem {
     pub item: ItemIdentity,
     /// Sample interval in **milliseconds** (matches the .NET wire form).
     pub sample_interval: u64,
     pub buffered: bool,
+    /// `Some(b)` emits `<Active>{b}</Active>` on the wire (the
+    /// `*Specified` pattern). `None` omits the element entirely —
+    /// MxDataProvider then treats the item as inactive and delivers
+    /// no values. Use `Some(true)` to actually receive samples.
+    pub active: Option<bool>,
 }
 
 impl MinimalMonitoredItem {
+    /// Build a default `MinimalMonitoredItem`: item + interval, no
+    /// Active flag, no Buffered. Matches the .NET `new MonitoredItem
+    /// { Item = ..., SampleInterval = ... }` shape used by the
+    /// canonical-XML fixtures.
+    ///
+    /// **For live subscriptions that should actually deliver values,
+    /// prefer [`Self::with_active`].** Without `Active=true` on the
+    /// wire, the server defaults to inactive and `Publish` returns
+    /// empty payloads.
     pub fn new(item: ItemIdentity, sample_interval: u64) -> Self {
         Self {
             item,
             sample_interval,
             buffered: false,
+            active: None,
+        }
+    }
+
+    /// Build a `MinimalMonitoredItem` with `Active=true`. This is
+    /// what the .NET reference's `AddMonitoredItems` emits by default
+    /// (`MxAsbDataClient.cs:441`) and what makes MxDataProvider
+    /// actually deliver values from the subscription.
+    pub fn with_active(item: ItemIdentity, sample_interval: u64, active: bool) -> Self {
+        Self {
+            item,
+            sample_interval,
+            buffered: false,
+            active: Some(active),
         }
     }
 }
@@ -1368,18 +1398,24 @@ pub fn collect_asbidata_payloads(tokens: &[NbfxToken]) -> Vec<Vec<u8>> {
                 // token, but a `Bytes`-then-`EndElement` (from the
                 // `WithEndElement` variant) leaves a sequence of
                 // `Bytes` tokens we walk here.
-                let mut combined: Option<Vec<u8>> = None;
+                let mut buf = Vec::new();
                 while let Some(NbfxToken::Text(NbfxText::Bytes(payload))) = tokens.get(inner)
                 {
-                    match combined.as_mut() {
-                        Some(buf) => buf.extend_from_slice(payload),
-                        None => combined = Some(payload.clone()),
-                    }
+                    buf.extend_from_slice(payload);
                     inner += 1;
                 }
-                if let Some(buf) = combined {
-                    out.push(buf);
-                }
+                // F34: ALWAYS push, even when buf is empty. The wire
+                // uses `<ASBIData></ASBIData>` (empty) as positional
+                // placeholders — e.g. `PublishResponse` emits an
+                // empty `<ASBIData/>` for `Status` when the per-item
+                // status array is empty, followed by a populated
+                // `<ASBIData>{values}</ASBIData>` for `Values`. If we
+                // skip the empty one, the Values payload shifts down
+                // to index 0 where the decoder reads it as Status
+                // and corrupts the parse. Captured live 2026-05-06
+                // via `examples/asb-relay.rs` middleman; fixture at
+                // `tests/fixtures/publish-response-with-value.bin`.
+                out.push(buf);
             }
         }
         idx += 1;

rust/crates/mxaccess-asb/src/xml_canonical.rs

@@ -507,6 +507,13 @@ fn emit_monitored_item(s: &mut String, item: &MinimalMonitoredItem) {
     // xmlns redeclaration since they're already in iom:2.
     emit_inline_item_identity(s, "    ", "Item", &item.item);
     emit_iom_text(s, "    ", "SampleInterval", &item.sample_interval.to_string());
+    // <Active> is *Specified-gated; emit only when the consumer
+    // opted in (None → not on the wire). MxDataProvider's
+    // Publish path requires Active=true to actually deliver values
+    // — F34, verified live 2026-05-06.
+    if let Some(active) = item.active {
+        emit_iom_text(s, "    ", "Active", if active { "true" } else { "false" });
+    }
     // ValueDeadband + UserData: default-Variant shape (type=0,
     // length=0, payload nil).
     emit_iom_default_variant(s, "    ", "ValueDeadband");