diff --git a/modules/nf-core/gridss/assemble/environment.yml b/modules/nf-core/gridss/assemble/environment.yml
new file mode 100644
index 000000000000..db37d675e605
--- /dev/null
+++ b/modules/nf-core/gridss/assemble/environment.yml
@@ -0,0 +1,5 @@
+channels:
+  - conda-forge
+  - bioconda
+dependencies:
+  - bioconda::gridss=2.13.2
diff --git a/modules/nf-core/gridss/assemble/main.nf b/modules/nf-core/gridss/assemble/main.nf
new file mode 100644
index 000000000000..88e8602781ca
--- /dev/null
+++ b/modules/nf-core/gridss/assemble/main.nf
@@ -0,0 +1,66 @@
+process GRIDSS_ASSEMBLE {
+    tag "$meta.id"
+    label 'process_medium'
+
+    conda "${moduleDir}/environment.yml"
+    container "${ workflow.containerEngine in ['singularity', 'apptainer'] && !task.ext.singularity_pull_docker_container ?
+        'https://depot.galaxyproject.org/singularity/gridss:2.13.2--h50ea8bc_3':
+        'quay.io/biocontainers/gridss:2.13.2--h50ea8bc_3' }"
+
+    input:
+    tuple val(meta), path(bam), path(bai), path(preprocess_dir)
+    tuple val(meta2), path(fasta), path(fasta_fai), path(bwa_index)
+    tuple val(meta3), path(gridss_config)
+
+    output:
+    tuple val(meta), path("*.gridss.working"), path("*.sv.assembly.bam"),  emit: assemble_dir
+    tuple val("${task.process}"), val('gridss'), eval("CallVariants --version 2>&1 | sed 's/-gridss//'")  , topic: versions, emit: versions_gridss
+
+    when:
+    task.ext.when == null || task.ext.when
+
+    script:
+    def args = task.ext.args ?: ''
+    def prefix = task.ext.prefix ?: "${meta.id}"
+    def arg_config = gridss_config ? "-c ${gridss_config}" : ""
+
+    def bam_list = bam instanceof List ? bam : [bam]
+	def index_files = bwa_index instanceof List ? bwa_index : [bwa_index]
+	// GRIDSS requires all BWA index files to have the exact same basename as the reference fasta
+	def link_cmds = index_files.collect { idx -> "ln -sf ${idx} ./${fasta}.${idx.extension}" }.join('\n')
+	"""
+	${link_cmds}
+
+    gridss ${args} \\
+        --jvmheap ${Math.round(task.memory.bytes * 0.95)} \\
+        --steps assemble \\
+        --reference ${fasta} \\
+        --workingdir "." \\
+        --assembly ${prefix}.sv.assembly.bam \\
+        --threads ${task.cpus} \\
+        ${arg_config} \\
+        ${bam_list.join(' ')}
+
+    """
+
+    stub:
+    def prefix = task.ext.prefix ?: "${meta.id}"
+
+    """
+    mkdir -p ${prefix}.sv.assembly.bam.gridss.working
+
+    touch ${prefix}.sv.assembly.bam
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.cigar_metrics
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.coverage.blacklist.bed
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.downsampled_0.bed
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.excluded_0.bed
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.idsv_metrics
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.mapq_metrics
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.quality_distribution_metrics
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.subsetCalled_0.bed
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.sv.bam
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.sv.bam.bai
+    touch ${prefix}.sv.assembly.bam.gridss.working/${prefix}.sv.assembly.bam.tag_metrics
+
+    """
+}
diff --git a/modules/nf-core/gridss/assemble/meta.yml b/modules/nf-core/gridss/assemble/meta.yml
new file mode 100644
index 000000000000..923ca80f52f5
--- /dev/null
+++ b/modules/nf-core/gridss/assemble/meta.yml
@@ -0,0 +1,115 @@
+name: "gridss_assemble"
+description: Assemble breakend contigs for GRIDSS structural variant calling
+keywords:
+  - bam
+  - assembly
+  - structural variants
+  - gridss
+  - breakend
+  - variant calling
+tools:
+  - gridss:
+      description: "GRIDSS: the Genomic Rearrangement IDentification Software Suite"
+      homepage: "https://github.com/PapenfussLab/gridss"
+      documentation: "https://github.com/PapenfussLab/gridss/wiki/GRIDSS-Documentation"
+      tool_dev_url: "https://github.com/PapenfussLab/gridss"
+      doi: "10.1186/s13059-021-02423-x"
+      licence:
+        - "GPL v3"
+      identifier: biotools:gridss
+input:
+  - - meta:
+        type: map
+        description: |
+          Groovy Map containing sample information
+          e.g. `[ id:'sample1' ]`
+    - bam:
+        type: file
+        description: Input BAM file(s)
+        pattern: "*.bam"
+        ontologies:
+          - edam: http://edamontology.org/format_2572
+    - bai:
+        type: file
+        description: BAM index file(s)
+        pattern: "*.bam.bai"
+        ontologies: []
+    - preprocess_dir:
+        type: directory
+        description: GRIDSS preprocessing working directories from the
+          GRIDSS_PREPROCESS step
+        pattern: "*.gridss.working/"
+  - - meta2:
+        type: map
+        description: |
+          Groovy Map containing reference genome information
+          e.g. `[ id:'genome' ]`
+    - fasta:
+        type: file
+        description: Reference genome FASTA file
+        pattern: "*.{fasta,fa,fna}"
+        ontologies:
+          - edam: http://edamontology.org/format_1929
+    - fasta_fai:
+        type: file
+        description: Reference genome FASTA index file
+        pattern: "*.fai"
+        ontologies: []
+    - bwa_index:
+        type: directory
+        description: Directory containing the GRIDSS/BWA index files for the
+          reference genome
+        pattern: "*"
+  - - meta3:
+        type: map
+        description: |
+          Groovy Map containing GRIDSS configuration information
+          e.g. `[ id:'gridss_config' ]`
+    - gridss_config:
+        type: file
+        description: Optional GRIDSS configuration file
+        pattern: "*.{properties,config}"
+        ontologies: []
+output:
+  assemble_dir:
+    - - meta:
+          type: map
+          description: |
+            Groovy Map containing sample information
+            e.g. `[ id:'sample1' ]`
+      - "*.gridss.working":
+          type: directory
+          description: GRIDSS assembly working directory containing assembled
+            breakend contigs
+          pattern: "*.gridss.working"
+      - "*.sv.assembly.bam":
+          type: file
+          description: BAM file containing the assembled breakend contigs
+          pattern: "*.sv.assembly.bam"
+          ontologies:
+            - edam: http://edamontology.org/format_2572
+  versions_gridss:
+    - - ${task.process}:
+          type: string
+          description: The process
+      - gridss:
+          type: string
+          description: The tool name
+      - CallVariants --version 2>&1 | sed 's/-gridss//':
+          type: eval
+          description: The expression to obtain the version of the tool
+topics:
+  versions:
+    - - ${task.process}:
+          type: string
+          description: The process
+      - gridss:
+          type: string
+          description: The tool name
+      - CallVariants --version 2>&1 | sed 's/-gridss//':
+          type: eval
+          description: The expression to obtain the version of the tool
+authors:
+  - "@imsarath"
+maintainers:
+  - "@imsarath"
diff --git a/modules/nf-core/gridss/assemble/tests/main.nf.test b/modules/nf-core/gridss/assemble/tests/main.nf.test
new file mode 100644
index 000000000000..c11aa76b978f
--- /dev/null
+++ b/modules/nf-core/gridss/assemble/tests/main.nf.test
@@ -0,0 +1,115 @@
+nextflow_process {
+
+    name "Test Process GRIDSS_ASSEMBLE"
+    script "../main.nf"
+    process "GRIDSS_ASSEMBLE"
+
+    tag "modules"
+    tag "modules_nfcore"
+    tag "bwa/index"
+    tag "gridss"
+    tag "gridss/preprocess"
+    tag "gridss/assemble"
+
+    setup {
+        run("BWA_INDEX") {
+            script "../../../bwa/index/main.nf"
+            process {
+                """
+                input[0] = [
+                    [ id: 'fasta' ],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta', checkIfExists: true)
+                ]
+                """
+            }
+        }
+
+        run("GRIDSS_PREPROCESS") {
+            script "../../preprocess/main.nf"
+            process {
+                """
+                input[0] = [
+                    [ id:'test' ],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam.bai', checkIfExists: true)
+                ]
+                input[1] = channel.of([
+                    [id:'fasta'],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta.fai', checkIfExists: true)
+                ]).join(BWA_INDEX.out.index)
+                """
+            }
+        }
+    }
+
+    test("human - bam") {
+
+        when {
+            process {
+                """
+                input[0] = channel.of([
+                    [ id:'test' ],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam.bai', checkIfExists: true)
+                ]).join(GRIDSS_PREPROCESS.out.preprocess_dir)
+                input[1] = channel.of([
+                    [id:'fasta'],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta.fai', checkIfExists: true)
+                ]).join(BWA_INDEX.out.index)
+                input[2] = channel.of([
+                    [id:'gridss_config'],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/gridss/gridss.properties', checkIfExists: true)
+                ])
+                """
+            }
+        }
+
+        then {
+            assertAll(
+                { assert process.success },
+                { assert snapshot(
+                    process.out.assemble_dir.collect { meta, working, assembly ->
+                        [meta, file(working).list().sort(), file(assembly).name]
+                    },
+                    process.out.findAll { key, val -> key.startsWith("versions") }
+                ).match() }
+            )
+        }
+    }
+
+    test("human - bam - stub") {
+
+        options "-stub"
+
+        when {
+            process {
+                """
+                input[0] = channel.of([
+                    [ id:'test' ],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/bam/test.paired_end.sorted.bam.bai', checkIfExists: true)
+                ]).join(GRIDSS_PREPROCESS.out.preprocess_dir)
+                input[1] = channel.of([
+                    [id:'fasta'],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta', checkIfExists: true),
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/genome/genome.fasta.fai', checkIfExists: true)
+                ]).join(BWA_INDEX.out.index)
+                input[2] = channel.of([
+                    [id:'gridss_config'],
+                    file(params.modules_testdata_base_path + 'genomics/homo_sapiens/illumina/gridss/gridss.properties', checkIfExists: true)
+                ])
+                """
+            }
+        }
+
+        then {
+            assertAll(
+                { assert process.success },
+                { assert snapshot(sanitizeOutput(process.out)).match() }
+            )
+        }
+    }
+
+}
diff --git a/modules/nf-core/gridss/assemble/tests/main.nf.test.snap b/modules/nf-core/gridss/assemble/tests/main.nf.test.snap
new file mode 100644
index 000000000000..07ca355bb3e9
--- /dev/null
+++ b/modules/nf-core/gridss/assemble/tests/main.nf.test.snap
@@ -0,0 +1,80 @@
+{
+    "human - bam - stub": {
+        "content": [
+            {
+                "assemble_dir": [
+                    [
+                        {
+                            "id": "test"
+                        },
+                        [
+                            "test.sv.assembly.bam.cigar_metrics:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.coverage.blacklist.bed:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.downsampled_0.bed:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.excluded_0.bed:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.idsv_metrics:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.mapq_metrics:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.quality_distribution_metrics:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.subsetCalled_0.bed:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.sv.bam:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.sv.bam.bai:md5,d41d8cd98f00b204e9800998ecf8427e",
+                            "test.sv.assembly.bam.tag_metrics:md5,d41d8cd98f00b204e9800998ecf8427e"
+                        ],
+                        "test.sv.assembly.bam:md5,d41d8cd98f00b204e9800998ecf8427e"
+                    ]
+                ],
+                "versions_gridss": [
+                    [
+                        "GRIDSS_ASSEMBLE",
+                        "gridss",
+                        "2.13.2"
+                    ]
+                ]
+            }
+        ],
+        "timestamp": "2026-07-24T10:34:32.103764795",
+        "meta": {
+            "nf-test": "0.9.4",
+            "nextflow": "26.04.3"
+        }
+    },
+    "human - bam": {
+        "content": [
+            [
+                [
+                    {
+                        "id": "test"
+                    },
+                    [
+                        "test.sv.assembly.bam.cigar_metrics",
+                        "test.sv.assembly.bam.coverage.blacklist.bed",
+                        "test.sv.assembly.bam.downsampled_0.bed",
+                        "test.sv.assembly.bam.excluded_0.bed",
+                        "test.sv.assembly.bam.idsv_metrics",
+                        "test.sv.assembly.bam.mapq_metrics",
+                        "test.sv.assembly.bam.quality_distribution_metrics",
+                        "test.sv.assembly.bam.subsetCalled_0.bed",
+                        "test.sv.assembly.bam.sv.bam",
+                        "test.sv.assembly.bam.sv.bam.bai",
+                        "test.sv.assembly.bam.tag_metrics"
+                    ],
+                    "test.sv.assembly.bam"
+                ]
+            ],
+            {
+                "versions_gridss": [
+                    [
+                        "GRIDSS_ASSEMBLE",
+                        "gridss",
+                        "2.13.2"
+                    ]
+                ]
+            }
+        ],
+        "timestamp": "2026-07-24T10:34:17.884396972",
+        "meta": {
+            "nf-test": "0.9.4",
+            "nextflow": "26.04.3"
+        }
+    }
+}
\ No newline at end of file