diff --git a/tasks/eva_2326/src/main/groovy/eva2326/nextflow.nf b/tasks/eva_2326/src/main/groovy/eva2326/nextflow.nf
new file mode 100644
index 0000000..5e44cf6
--- /dev/null
+++ b/tasks/eva_2326/src/main/groovy/eva2326/nextflow.nf
@@ -0,0 +1,85 @@
+nextflow.enable.dsl=2
+
+params.input_file             = null
+params.chunk_size             = 1_000_000
+params.working_dir            = null
+params.env_properties_file    = null
+params.db_name                = null
+params.max_parallel_chunks    = 5
+params.project_dir            = null
+params.groovy_script          = null
+
+// ── PROCESS 1: split into named chunks ───────────────────────────────────────
+process SPLIT_INPUT {
+    output:
+    path "chunk_*.txt", emit: chunks
+
+    script:
+    """
+    awk -v chunk_size=${params.chunk_size} '
+    {
+        line_num = NR
+        if ((line_num - 1) % chunk_size == 0) {
+            start = line_num
+            end   = start + chunk_size - 1
+            # zero-pad to 10 digits so filenames sort correctly
+            filename = sprintf("chunk_%010d-%010d.txt", start, end)
+        }
+        print > filename
+    }
+    ' ${params.input_file}
+    """
+}
+
+// ── PROCESS 2: remediate one chunk ───────────────────────────────────────────
+process REMEDIATE_CHUNK {
+    label 'long_time'
+    label 'med_mem'
+    maxForks params.max_parallel_chunks
+
+    tag { chunk_file.name }
+
+    input:
+    path chunk_file
+
+    output:
+    path "${chunk_file.baseName}.done", emit: done_flag
+
+    script:
+    """
+    CHUNK_NAME=\$(basename ${chunk_file} .txt)
+    NOT_REMEDIATED_FILE=${params.working_dir}/variants_not_remediated/${params.db_name}_\$CHUNK_NAME.txt
+    mkdir -p \$(dirname "\$NOT_REMEDIATED_FILE")
+
+    bash run_groovy_script.sh \
+        ${params.project_dir} \
+        ${params.groovy_script} \
+        -envPropertiesFile=${params.env_properties_file} \
+        -dbName=${params.db_name} \
+        -annotationRemediationInputFile=\$(realpath ${chunk_file}) \
+        -notRemediatedVariantsFilePath="\$NOT_REMEDIATED_FILE" \
+        > ${params.working_dir}/\$CHUNK_NAME.log 2>&1
+
+    echo "Done: ${chunk_file.name}" > ${chunk_file.baseName}.done
+    """
+}
+
+// ── WORKFLOW ──────────────────────────────────────────────────────────────────
+workflow {
+    if (!params.input_file)          error "Please provide --input_file"
+    if (!params.env_properties_file) error "Please provide --env_properties_file"
+    if (!params.db_name)             error "Please provide --db_name"
+    if (!params.working_dir)         error "Please provide --working_dir"
+    if (!params.project_dir)         error "Please provide --project_dir"
+    if (!params.groovy_script)       error "Please provide --groovy_script"
+
+    SPLIT_INPUT()
+
+    chunks_ch = SPLIT_INPUT.out.chunks.flatten()
+
+    REMEDIATE_CHUNK(chunks_ch)
+
+    REMEDIATE_CHUNK.out.done_flag
+        .collect()
+        .view { flags -> "All chunks complete: ${flags.size()} chunks processed" }
+}
\ No newline at end of file
diff --git a/tasks/eva_2326/src/main/groovy/eva2326/remediate_annotations.groovy b/tasks/eva_2326/src/main/groovy/eva2326/remediate_annotations.groovy
new file mode 100644
index 0000000..1f9eca6
--- /dev/null
+++ b/tasks/eva_2326/src/main/groovy/eva2326/remediate_annotations.groovy
@@ -0,0 +1,275 @@
+package eva2326
+
+import groovy.cli.picocli.CliBuilder
+import org.bson.Document
+import org.bson.BsonSerializationException
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.CommandLineRunner
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
+import org.springframework.boot.builder.SpringApplicationBuilder
+import org.springframework.data.mongodb.core.MongoTemplate
+import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper
+import org.springframework.data.mongodb.core.convert.MappingMongoConverter
+import org.springframework.data.mongodb.core.query.Criteria
+import org.springframework.data.mongodb.core.query.Query
+import uk.ac.ebi.eva.commons.models.mongo.entity.VariantDocument
+
+import java.util.regex.Pattern
+import java.util.stream.Collectors
+
+import static org.springframework.data.mongodb.core.query.Criteria.where
+
+def cli = new CliBuilder()
+cli.envPropertiesFile(args: 1, "Properties file with db details to use for update", required: true)
+cli.dbName(args: 1, "Database name that needs to be updated", required: true)
+cli.annotationRemediationInputFile(args: 1, "Path to CSV file with old_variant_id,new_variant_id,insdc_contig for annotation remediation", required: true)
+cli.notRemediatedVariantsFilePath(args: 1, "Path to file where the variants which are not remediated will be stored", required: true)
+def options = cli.parse(args)
+if (!options) {
+    cli.usage()
+    System.exit(1)
+}
+
+new SpringApplicationBuilder(RemediateAnnotationsApplication.class).properties([
+        'spring.config.location'      : options.envPropertiesFile,
+        'spring.data.mongodb.database': options.dbName])
+        .run(options.annotationRemediationInputFile, options.notRemediatedVariantsFilePath)
+
+
+@SpringBootApplication(exclude = [DataSourceAutoConfiguration.class])
+class RemediateAnnotationsApplication implements CommandLineRunner {
+    static Logger logger = LoggerFactory.getLogger(RemediateAnnotationsApplication.class)
+    private static int BATCH_SIZE = 1000
+    public static final String VARIANTS_COLLECTION = "variants_2_0"
+    public static final String ANNOTATIONS_COLLECTION = "annotations_2_0"
+    @Autowired
+    MongoTemplate mongoTemplate
+    MappingMongoConverter converter
+    String notRemediatedVariantsFilePath
+    BufferedWriter notRemediatedWriter
+
+    @Override
+    void run(String... args) throws Exception {
+        String annotationRemediationInputFile = args[0]
+        this.notRemediatedVariantsFilePath = args[1]
+
+        // workaround to not save _class field in documents
+        converter = mongoTemplate.getConverter()
+        converter.setTypeMapper(new DefaultMongoTypeMapper(null))
+
+        File inputFile = new File(annotationRemediationInputFile)
+        if (!inputFile.exists()) {
+            logger.error("Annotation remediation input file does not exist: {}", annotationRemediationInputFile)
+            System.exit(1)
+        }
+
+        notRemediatedWriter = new BufferedWriter(new FileWriter(notRemediatedVariantsFilePath, true))
+        // Stream through the file line by line, accumulating into a batch.
+        // Once the batch reaches BATCH_SIZE, process and clear it before reading further.
+        try {
+            List<String[]> batch = new ArrayList<>()
+            int lineNumber = 0
+            int skippedLines = 0
+            int totalProcessed = 0
+
+            inputFile.withReader { reader ->
+                String line
+                while ((line = reader.readLine()) != null) {
+                    lineNumber++
+                    String trimmed = line.trim()
+                    if (!trimmed) {
+                        continue
+                    }
+
+                    String[] parts = trimmed.split(",", -1)
+                    if (parts.length < 3 || !parts[0].trim() || !parts[1].trim() || !parts[2].trim()) {
+                        logger.warn("Skipping malformed line {} in input file: '{}'", lineNumber, trimmed)
+                        skippedLines++
+                        continue
+                    }
+
+                    batch.add([parts[0].trim(), parts[1].trim(), parts[2].trim()] as String[])
+
+                    if (batch.size() >= RemediateAnnotationsApplication.BATCH_SIZE) {
+                        processBatch(batch)
+                        totalProcessed += batch.size()
+                        logger.info("Total entries processed so far: {}", totalProcessed)
+                        batch.clear()
+                    }
+                }
+            }
+
+            if (!batch.isEmpty()) {
+                processBatch(batch)
+                totalProcessed += batch.size()
+                batch.clear()
+            }
+
+            logger.info("Annotation remediation complete. Total entries processed: {}, malformed lines skipped: {}",
+                    totalProcessed, skippedLines)
+        } finally {
+            notRemediatedWriter.close()
+        }
+
+        System.exit(0)
+    }
+
+    void processBatch(List<String[]> batch) {
+        // keyed by old variant id
+        Map<String, String> orgIdNewIdMap = new LinkedHashMap<>()     // oldId -> newId
+        Map<String, String> orgIdInsdcChrMap = new LinkedHashMap<>()  // oldId -> insdcContig
+
+        for (String[] entry : batch) {
+            orgIdNewIdMap.put(entry[0], entry[1])
+            orgIdInsdcChrMap.put(entry[0], entry[2])
+        }
+
+        // Fetch all new variants from DB in one query for the whole batch
+        Map<String, VariantDocument> variantsInDBMap = getVariantsByIds(new ArrayList<>(orgIdNewIdMap.values()))
+
+        // Verify each entry: new variant must exist in DB with the expected INSDC contig.
+        // Failures are logged and written to the not-remediated file; only verified entries proceed.
+        Map<String, String> verifiedOrgIdNewIdMap = new LinkedHashMap<>()
+
+        for (Map.Entry<String, String> entry : orgIdNewIdMap.entrySet()) {
+            String oldVariantId = entry.getKey()
+            String newVariantId = entry.getValue()
+
+            VariantDocument variantInDB = variantsInDBMap.get(newVariantId)
+
+            if (variantInDB == null) {
+                logger.error("Variant check failed: new variant id {} not found in DB (old id: {}). " +
+                        "Skipping annotation remediation for this variant.", newVariantId, oldVariantId)
+                storeNotRemediatedVariant(oldVariantId, newVariantId, "New variant id not found in DB")
+                continue
+            }
+
+            verifiedOrgIdNewIdMap.put(oldVariantId, newVariantId)
+        }
+
+        logger.info("Batch: {} entries passed variant check, {} skipped",
+                verifiedOrgIdNewIdMap.size(), orgIdNewIdMap.size() - verifiedOrgIdNewIdMap.size())
+
+        if (!verifiedOrgIdNewIdMap.isEmpty()) {
+            logger.info("Remediate Annotations for Ids: " + verifiedOrgIdNewIdMap.keySet())
+            remediateAnnotations(verifiedOrgIdNewIdMap, orgIdInsdcChrMap)
+        }
+    }
+
+    Map<String, VariantDocument> getVariantsByIds(List<String> ids) {
+        Query idQuery = new Query(where("_id").in(ids))
+        List<VariantDocument> variants = mongoTemplate.find(idQuery, VariantDocument.class, VARIANTS_COLLECTION)
+        return variants.stream().collect(Collectors.toMap(v -> v.getId(), v -> v))
+    }
+
+    void storeNotRemediatedVariant(String oldVariantId, String newVariantId, String reason) {
+        try {
+            notRemediatedWriter.write("${oldVariantId},${newVariantId},${reason}\n")
+            notRemediatedWriter.flush()
+        } catch (IOException e) {
+            logger.error("Error writing to not-remediated variants file for old id {}: {}", oldVariantId, e.getMessage())
+        }
+    }
+
+    void remediateAnnotations(Map<String, String> orgIdNewIdMap, Map<String, String> orgIdInsdcChrMap) {
+        Set<String> idProcessed = new HashSet<>()
+
+        // fetch annotations for all old variant ids
+        List<Criteria> oldIdCriteria = new ArrayList<>()
+        for (String oldId : orgIdNewIdMap.keySet()) {
+            oldIdCriteria.add(Criteria.where("_id").regex("^" + Pattern.quote(oldId) + "_\\d"))
+        }
+
+        // fetch annotations for all new variant ids
+        List<Criteria> newIdCriteria = new ArrayList<>()
+        for (String newId : orgIdNewIdMap.values()) {
+            newIdCriteria.add(Criteria.where("_id").regex("^" + Pattern.quote(newId) + "_\\d"))
+        }
+
+        try {
+            List<Document> oldAnnotationsList = mongoTemplate.getCollection(ANNOTATIONS_COLLECTION)
+                    .find(new Query(new Criteria().orOperator(oldIdCriteria.toArray(new Criteria[0]))).getQueryObject())
+                    .into(new ArrayList<>())
+            Map<String, Set<Document>> oldVariantIdToDocuments = new HashMap<>()
+            for (Document doc : oldAnnotationsList) {
+                String variantId = extractVariantIdFromAnnotationId(doc.getString("_id"))
+                if (variantId != null) {
+                    oldVariantIdToDocuments.computeIfAbsent(variantId, k -> new HashSet<>()).add(doc)
+                }else{
+                    logger.error("Could not get variantId from the annotation: " + doc)
+                }
+            }
+
+            List<Document> newAnnotationsList = mongoTemplate.getCollection(ANNOTATIONS_COLLECTION)
+                    .find(new Query(new Criteria().orOperator(newIdCriteria.toArray(new Criteria[0]))).getQueryObject())
+                    .into(new ArrayList<>())
+            Map<String, Set<String>> newVariantIdToAnnotationIds = new HashMap<>()
+            for (Document doc : newAnnotationsList) {
+                String variantId = extractVariantIdFromAnnotationId(doc.getString("_id"))
+                if (variantId != null) {
+                    newVariantIdToAnnotationIds.computeIfAbsent(variantId, k -> new HashSet<>()).add(doc.getString("_id"))
+                }else{
+                    logger.error("Could not get variantId from the annotation: " + doc)
+                }
+            }
+
+            // Process each old->new id pair
+            for (Map.Entry<String, String> entry : orgIdNewIdMap.entrySet()) {
+                String orgVariantId = entry.getKey()
+                String newVariantId = entry.getValue()
+
+                Set<Document> orgAnnotationsSet = oldVariantIdToDocuments.getOrDefault(orgVariantId, Collections.emptySet())
+                Set<String> existingNewAnnotationIds = newVariantIdToAnnotationIds.getOrDefault(newVariantId, Collections.emptySet())
+
+                if (orgAnnotationsSet.isEmpty()) {
+                    logger.info("No annotations found for old variant id {}, nothing to remediate", orgVariantId)
+                    continue
+                }
+
+                List<Document> toInsert = new ArrayList<>()
+                List<String> toDelete = new ArrayList<>()
+
+                for (Document annotation : orgAnnotationsSet) {
+                    try {
+                        String orgAnnotationId = annotation.getString("_id")
+                        String updatedAnnotationId = orgAnnotationId.replace(orgVariantId, newVariantId)
+
+                        if (!existingNewAnnotationIds.contains(updatedAnnotationId)) {
+                            if (!idProcessed.contains(updatedAnnotationId)) {
+                                Document updated = new Document(annotation)
+                                updated.put("_id", updatedAnnotationId)
+                                updated.put("chr", orgIdInsdcChrMap.get(orgVariantId))
+                                toInsert.add(updated)
+                                idProcessed.add(updatedAnnotationId)
+                            }
+                        }
+
+                        toDelete.add(orgAnnotationId)
+                    } catch (Exception e) {
+                        logger.error("Error processing annotation for original variant id {}: {}",
+                                orgVariantId, e.getMessage(), e)
+                    }
+                }
+
+                if (!toDelete.isEmpty()) {
+                    mongoTemplate.remove(Query.query(Criteria.where("_id").in(toDelete)), ANNOTATIONS_COLLECTION)
+                }
+                if (!toInsert.isEmpty()) {
+                    mongoTemplate.getCollection(ANNOTATIONS_COLLECTION).insertMany(toInsert)
+                }
+
+                logger.info("Annotation remediation for old variant id {}: {} inserted, {} deleted",
+                        orgVariantId, toInsert.size(), toDelete.size())
+            }
+        } catch (BsonSerializationException ex) {
+            logger.error("Exception occurred while trying to update annotations: {}", ex.getMessage(), ex)
+        }
+    }
+
+    static String extractVariantIdFromAnnotationId(String annotationId) {
+        return annotationId.replaceFirst(/_\w+_\w+$/, "")
+    }
+}
\ No newline at end of file
diff --git a/tasks/eva_2326/src/test/resources/application-test.properties b/tasks/eva_2326/src/test/resources/application-test.properties
index f5eba04..c15915c 100644
--- a/tasks/eva_2326/src/test/resources/application-test.properties
+++ b/tasks/eva_2326/src/test/resources/application-test.properties
@@ -1,7 +1,7 @@
 spring.data.mongodb.host=localhost
 spring.data.mongodb.port=27017
-spring.data.mongodb.username=eva_pipeline_mongo_user
-spring.data.mongodb.password=eva_pipeline_mongo_pass
+spring.data.mongodb.username=mongo_user
+spring.data.mongodb.password=mongo_pass
 spring.data.mongodb.authentication-database=admin
 mongodb.read-preference=secondaryPreferred
 spring.data.mongodb.authentication-mechanism=SCRAM-SHA-1