dchud · dchud · Apr 12, 2026 · Apr 10, 2026 · Apr 10, 2026 · Apr 12, 2026
diff --git a/.beads/issues.jsonl b/.beads/issues.jsonl
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,13 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-### Added
+### Fixed
 
-### Changed
+- **Repeated control fields silently dropped** ([#77](https://github.com/dchud/mrrc/issues/77), [#79](https://github.com/dchud/mrrc/pull/79)): Control fields (e.g., multiple 007s) were stored in `IndexMap<String, String>`, causing later values to overwrite earlier ones. Changed to `IndexMap<String, Vec<String>>` across all three record types (`Record`, `AuthorityRecord`, `HoldingsRecord`). Updated all 7 serialization formats (ISO 2709, JSON, MARCJSON, MARCXML, CSV, Dublin Core/MODS, BIBFRAME) to emit all values. The pymarc-compatible `get_fields()` API now correctly returns all repeated control fields, matching pymarc behavior.
 
-### Fixed
+### Changed
 
-### Documentation
+- **Simplified control field API**: Removed `get_control_field_values()` accessor from `Record` — redundant with direct access to the public `control_fields` map. `get_control_field()` remains as a convenience for non-repeatable tags (001, 003, 005, 008).
 
 ## [0.7.5] - 2026-04-05
 

diff --git a/mrrc/__init__.py b/mrrc/__init__.py
@@ -849,8 +849,7 @@ def get_fields(self, *tags: str) -> List['Field']:
         if not tags:
             # Return all control fields, then all data fields
             for tag in _CONTROL_TAGS:
-                value = self._inner.control_field(tag)
-                if value is not None:
+                for value in self._inner.control_field_values(tag):
                     result.append(Field(tag, data=value))
             for field in self._inner.fields():
                 wrapper = Field.__new__(Field)
@@ -861,8 +860,7 @@ def get_fields(self, *tags: str) -> List['Field']:
             # Return fields for specified tags
             for tag in tags:
                 if _is_control_tag(tag):
-                    value = self._inner.control_field(tag)
-                    if value is not None:
+                    for value in self._inner.control_field_values(tag):
                         result.append(Field(tag, data=value))
                 else:
                     for field in self._inner.get_fields(tag):
@@ -1453,11 +1451,10 @@ def __eq__(self, other: Any) -> bool:
                     return False
 
         # Compare control fields
-        for code, value in self._inner.control_fields():
-            if self._inner.control_field(code) != value:
-                return False
-            if other._inner.control_field(code) != value:
-                return False
+        self_cfs = self._inner.control_fields()
+        other_cfs = other._inner.control_fields()
+        if self_cfs != other_cfs:
+            return False
 
         return True
 

diff --git a/mrrc/_mrrc.pyi b/mrrc/_mrrc.pyi
@@ -202,7 +202,17 @@ class Record:
         """
         ...
     def control_fields(self) -> List[tuple[str, str]]:
-        """Get all control fields as (tag, value) tuples."""
+        """Get all control fields as (tag, value) tuples.
+
+        Repeated tags (e.g., multiple 007 fields) produce multiple entries.
+        """
+        ...
+    def control_field_values(self, tag: str) -> List[str]:
+        """Get all values for a control field tag.
+
+        Returns all values for tags that may be repeated (e.g., 006, 007).
+        Returns an empty list if the tag doesn't exist.
+        """
         ...
     def get_field(self, tag: str) -> Optional[Field]: ...
     def get_fields(self, tag: str) -> List[Field]: ...

diff --git a/src-python/src/wrappers.rs b/src-python/src/wrappers.rs
@@ -705,15 +705,28 @@ impl PyRecord {
         result
     }
 
-    /// Get all control fields as a dict-like structure
+    /// Get all control fields as a list of (tag, value) tuples
+    ///
+    /// Repeated tags (e.g., multiple 007 fields) produce multiple entries.
     pub fn control_fields(&self) -> Vec<(String, String)> {
         self.inner
             .control_fields
             .iter()
-            .map(|(tag, value)| (tag.clone(), value.clone()))
+            .flat_map(|(tag, values)| values.iter().map(move |value| (tag.clone(), value.clone())))
             .collect()
     }
 
+    /// Get all values for a control field tag
+    ///
+    /// Returns all values for tags that may be repeated (e.g., 006, 007).
+    pub fn control_field_values(&self, tag: &str) -> Vec<String> {
+        self.inner
+            .control_fields
+            .get(tag)
+            .map(|values| values.iter().map(String::clone).collect())
+            .unwrap_or_default()
+    }
+
     /// Remove all fields with a given tag
     ///
     /// Returns the removed fields.

diff --git a/src/authority_record.rs b/src/authority_record.rs
@@ -19,7 +19,8 @@ pub struct AuthorityRecord {
     /// Record leader (24 bytes)
     pub leader: Leader,
     /// Control fields (000-009) - preserves insertion order
-    pub control_fields: IndexMap<String, String>,
+    /// Multiple values per tag are supported (e.g., repeated 006/007 fields)
+    pub control_fields: IndexMap<String, Vec<String>>,
     /// Variable fields (010+) - unified storage, preserves insertion order
     pub fields: IndexMap<String, Vec<Field>>,
 }
@@ -100,13 +101,16 @@ impl AuthorityRecord {
 
     /// Add a control field
     pub fn add_control_field(&mut self, tag: String, value: String) {
-        self.control_fields.insert(tag, value);
+        self.control_fields.entry(tag).or_default().push(value);
     }
 
-    /// Get a control field value
+    /// Get the first control field value for a tag
     #[must_use]
     pub fn get_control_field(&self, tag: &str) -> Option<&str> {
-        self.control_fields.get(tag).map(String::as_str)
+        self.control_fields
+            .get(tag)
+            .and_then(|v| v.first())
+            .map(String::as_str)
     }
 
     /// Set the heading (1XX field)
@@ -327,19 +331,25 @@ impl MarcRecord for AuthorityRecord {
     }
 
     fn add_control_field(&mut self, tag: impl Into<String>, value: impl Into<String>) {
-        self.control_fields.insert(tag.into(), value.into());
+        self.control_fields
+            .entry(tag.into())
+            .or_default()
+            .push(value.into());
     }
 
     fn get_control_field(&self, tag: &str) -> Option<&str> {
-        self.control_fields.get(tag).map(String::as_str)
+        self.control_fields
+            .get(tag)
+            .and_then(|v| v.first())
+            .map(String::as_str)
     }
 
     fn control_fields_iter(&self) -> Box<dyn Iterator<Item = (&str, &str)> + '_> {
-        Box::new(
-            self.control_fields
+        Box::new(self.control_fields.iter().flat_map(|(tag, values)| {
+            values
                 .iter()
-                .map(|(tag, value)| (tag.as_str(), value.as_str())),
-        )
+                .map(move |value| (tag.as_str(), value.as_str()))
+        }))
     }
 
     fn get_fields(&self, tag: &str) -> Option<&[Field]> {

diff --git a/src/authority_writer.rs b/src/authority_writer.rs
@@ -87,8 +87,10 @@ impl<W: Write> AuthorityMarcWriter<W> {
         };
 
         // Write control fields
-        for (tag, value) in &record.control_fields {
-            add_field(tag, None, Some(value), None, &mut directory, &mut data)?;
+        for (tag, values) in &record.control_fields {
+            for value in values {
+                add_field(tag, None, Some(value), None, &mut directory, &mut data)?;
+            }
         }
 
         // Write all variable fields (010+) in tag order

diff --git a/src/bibframe/converter.rs b/src/bibframe/converter.rs
@@ -220,6 +220,7 @@ impl<'a> MarcToBibframeConverter<'a> {
                 self.record
                     .control_fields
                     .get("001")
+                    .and_then(|v| v.first())
                     .map_or("unknown", String::as_str)
             } else {
                 "unknown"
@@ -1637,6 +1638,7 @@ impl<'a> MarcToBibframeConverter<'a> {
                 self.record
                     .control_fields
                     .get("001")
+                    .and_then(|v| v.first())
                     .map_or("unknown", String::as_str)
             } else {
                 "unknown"
@@ -1674,7 +1676,12 @@ impl<'a> MarcToBibframeConverter<'a> {
         }
 
         // Add creation date from 008/00-05 if available
-        if let Some(field_008) = self.record.control_fields.get("008") {
+        if let Some(field_008) = self
+            .record
+            .control_fields
+            .get("008")
+            .and_then(|v| v.first())
+        {
             if field_008.len() >= 6 {
                 let date_entered = &field_008[0..6];
                 self.graph.add(

diff --git a/src/csv.rs b/src/csv.rs
@@ -118,10 +118,12 @@ pub fn records_to_csv(records: &[Record]) -> Result<String> {
 
     for record in records {
         // Write control fields
-        for (tag, value) in &record.control_fields {
-            // Escape value if needed
-            let escaped_value = escape_csv_value(value);
-            writeln!(output, "{tag},,,{escaped_value}").ok();
+        for (tag, values) in &record.control_fields {
+            for value in values {
+                // Escape value if needed
+                let escaped_value = escape_csv_value(value);
+                writeln!(output, "{tag},,,{escaped_value}").ok();
+            }
         }
 
         // Write data fields with subfields
@@ -188,10 +190,12 @@ where
 
     for record in records {
         // Write control fields
-        for (tag, value) in &record.control_fields {
+        for (tag, values) in &record.control_fields {
             if filter(tag) {
-                let escaped_value = escape_csv_value(value);
-                writeln!(output, "{tag},,,{escaped_value}").ok();
+                for value in values {
+                    let escaped_value = escape_csv_value(value);
+                    writeln!(output, "{tag},,,{escaped_value}").ok();
+                }
             }
         }
 

diff --git a/src/dublin_core.rs b/src/dublin_core.rs
@@ -309,7 +309,7 @@ fn extract_identifiers(record: &Record, dc: &mut DublinCoreRecord) {
     }
 
     // Control number (001)
-    if let Some(control_001) = record.control_fields.get("001") {
+    if let Some(control_001) = record.control_fields.get("001").and_then(|v| v.first()) {
         dc.identifier.push(format!("Control#: {control_001}"));
     }
 }

diff --git a/src/encoding_validation.rs b/src/encoding_validation.rs
@@ -46,13 +46,15 @@ impl EncodingValidator {
         let mut inconsistent_field_count = 0usize;
 
         // Check control fields
-        for value in record.control_fields.values() {
-            if Self::is_likely_different_encoding(value, primary_encoding) {
-                inconsistent_field_count += 1;
-                let detected = Self::detect_encoding_from_string(value);
-                if let Some(enc) = detected {
-                    if enc != primary_encoding && !mixed_encodings.contains(&enc) {
-                        mixed_encodings.push(enc);
+        for values in record.control_fields.values() {
+            for value in values {
+                if Self::is_likely_different_encoding(value, primary_encoding) {
+                    inconsistent_field_count += 1;
+                    let detected = Self::detect_encoding_from_string(value);
+                    if let Some(enc) = detected {
+                        if enc != primary_encoding && !mixed_encodings.contains(&enc) {
+                            mixed_encodings.push(enc);
+                        }
                     }
                 }
             }

diff --git a/src/holdings_reader.rs b/src/holdings_reader.rs
@@ -143,7 +143,7 @@ impl<R: Read> HoldingsMarcReader<R> {
 
         // Parse directory (entries are 12 bytes each: 3 bytes tag + 4 bytes length + 5 bytes start position)
         let mut fields: indexmap::IndexMap<String, Vec<Field>> = indexmap::IndexMap::new();
-        let mut control_fields: indexmap::IndexMap<String, String> = indexmap::IndexMap::new();
+        let mut control_fields: indexmap::IndexMap<String, Vec<String>> = indexmap::IndexMap::new();
 
         let mut i = 0;
         while i + 12 <= directory_bytes.len() {
@@ -180,7 +180,7 @@ impl<R: Read> HoldingsMarcReader<R> {
                         MarcError::InvalidRecord("Invalid control field encoding".to_string())
                     })?
                     .to_string();
-                control_fields.insert(tag, value);
+                control_fields.entry(tag).or_default().push(value);
             } else {
                 // Data field
                 if field_data.len() < 3 {
@@ -238,8 +238,10 @@ impl<R: Read> HoldingsMarcReader<R> {
         let mut record = HoldingsRecord::new(leader);
 
         // Add control fields
-        for (tag, value) in control_fields {
-            record.add_control_field(tag, value);
+        for (tag, values) in control_fields {
+            for value in values {
+                record.add_control_field(tag.clone(), value);
+            }
         }
 
         // Organize data fields by their functional role

diff --git a/src/holdings_record.rs b/src/holdings_record.rs
@@ -19,7 +19,8 @@ pub struct HoldingsRecord {
     /// Record leader (24 bytes)
     pub leader: Leader,
     /// Control fields (000-009) - preserves insertion order
-    pub control_fields: IndexMap<String, String>,
+    /// Multiple values per tag are supported (e.g., repeated 006/007 fields)
+    pub control_fields: IndexMap<String, Vec<String>>,
     /// Variable fields (010+) - unified storage, preserves insertion order
     pub fields: IndexMap<String, Vec<Field>>,
 }
@@ -103,13 +104,16 @@ impl HoldingsRecord {
 
     /// Add a control field
     pub fn add_control_field(&mut self, tag: String, value: String) {
-        self.control_fields.insert(tag, value);
+        self.control_fields.entry(tag).or_default().push(value);
     }
 
-    /// Get a control field value
+    /// Get the first control field value for a tag
     #[must_use]
     pub fn get_control_field(&self, tag: &str) -> Option<&str> {
-        self.control_fields.get(tag).map(String::as_str)
+        self.control_fields
+            .get(tag)
+            .and_then(|v| v.first())
+            .map(String::as_str)
     }
 
     /// Add a location field (852)
@@ -371,19 +375,25 @@ impl MarcRecord for HoldingsRecord {
     }
 
     fn add_control_field(&mut self, tag: impl Into<String>, value: impl Into<String>) {
-        self.control_fields.insert(tag.into(), value.into());
+        self.control_fields
+            .entry(tag.into())
+            .or_default()
+            .push(value.into());
     }
 
     fn get_control_field(&self, tag: &str) -> Option<&str> {
-        self.control_fields.get(tag).map(String::as_str)
+        self.control_fields
+            .get(tag)
+            .and_then(|v| v.first())
+            .map(String::as_str)
     }
 
     fn control_fields_iter(&self) -> Box<dyn Iterator<Item = (&str, &str)> + '_> {
-        Box::new(
-            self.control_fields
+        Box::new(self.control_fields.iter().flat_map(|(tag, values)| {
+            values
                 .iter()
-                .map(|(tag, value)| (tag.as_str(), value.as_str())),
-        )
+                .map(move |value| (tag.as_str(), value.as_str()))
+        }))
     }
 
     fn get_fields(&self, tag: &str) -> Option<&[Field]> {

diff --git a/src/holdings_writer.rs b/src/holdings_writer.rs
@@ -87,8 +87,10 @@ impl<W: Write> HoldingsMarcWriter<W> {
         };
 
         // Write control fields
-        for (tag, value) in &record.control_fields {
-            add_field(tag, None, Some(value), None, &mut directory, &mut data)?;
+        for (tag, values) in &record.control_fields {
+            for value in values {
+                add_field(tag, None, Some(value), None, &mut directory, &mut data)?;
+            }
         }
 
         // Write data fields (all organized in fields map)

diff --git a/src/json.rs b/src/json.rs
@@ -58,10 +58,12 @@ pub fn record_to_json(record: &Record) -> Result<Value> {
     }));
 
     // Add control fields
-    for (tag, value) in &record.control_fields {
-        fields.push(json!({
-            tag: value
-        }));
+    for (tag, values) in &record.control_fields {
+        for value in values {
+            fields.push(json!({
+                tag: value
+            }));
+        }
     }
 
     // Add data fields