diff --git a/backends/generators/overlap_list/overlap_list_generator.py b/backends/generators/overlap_list/overlap_list_generator.py
new file mode 100644
index 0000000000..cc37281282
--- /dev/null
+++ b/backends/generators/overlap_list/overlap_list_generator.py
@@ -0,0 +1,291 @@
+#!/usr/bin/env python3
+"""
+Generator script for overlapping instruction declarations.
+"""
+import os
+import sys
+import logging
+import argparse
+import yaml
+from collections import defaultdict
+
+# Add parent directory to path to import generator.py
+parent_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+sys.path.append(parent_dir)
+
+logging.basicConfig(level=logging.INFO, format="%(levelname)s:: %(message)s")
+
+
+def get_extension_name(instruction_yaml_path):
+    """Extract the extension name from the instruction YAML file."""
+    try:
+        with open(instruction_yaml_path, encoding="utf-8") as f:
+            data = yaml.safe_load(f)
+
+        definedBy = data.get("definedBy")
+        if not definedBy:
+            return None
+
+        if isinstance(definedBy, str):
+            return definedBy
+
+        if isinstance(definedBy, dict):
+            # Try anyOf - prefer simple strings, take last alternative
+            if "anyOf" in definedBy:
+                alternatives = definedBy["anyOf"]
+                if isinstance(alternatives, list):
+                    for alt in reversed(alternatives):
+                        if isinstance(alt, str):
+                            return alt
+                        if isinstance(alt, dict):
+                            if "name" in alt:
+                                return alt["name"]
+                            if "allOf" in alt and isinstance(alt["allOf"], list):
+                                last = alt["allOf"][-1]
+                                if isinstance(last, str):
+                                    return last
+                                if isinstance(last, dict) and "name" in last:
+                                    return last["name"]
+
+            # Try allOf - take last extension
+            if "allOf" in definedBy and isinstance(definedBy["allOf"], list):
+                last_ext = definedBy["allOf"][-1]
+                if isinstance(last_ext, str):
+                    return last_ext
+                if isinstance(last_ext, dict) and "name" in last_ext:
+                    return last_ext["name"]
+
+            # Try oneOf - take first alternative
+            if "oneOf" in definedBy and isinstance(definedBy["oneOf"], list):
+                first_ext = definedBy["oneOf"][0]
+                if isinstance(first_ext, str):
+                    return first_ext
+                if isinstance(first_ext, dict) and "name" in first_ext:
+                    return first_ext["name"]
+
+            # Direct name field
+            if "name" in definedBy:
+                return definedBy["name"]
+
+        return None
+    except Exception as e:
+        logging.debug(f"Error extracting extension from {instruction_yaml_path}: {e}")
+        return None
+
+
+def load_all_instructions_with_metadata(root_dir):
+    """Load all instructions with their encoding metadata."""
+    instructions = {}
+
+    for dirpath, _, filenames in os.walk(root_dir):
+        for fname in filenames:
+            if not fname.endswith(".yaml"):
+                continue
+
+            path = os.path.join(dirpath, fname)
+            try:
+                with open(path, encoding="utf-8") as f:
+                    data = yaml.safe_load(f)
+            except Exception as e:
+                logging.debug(f"Error parsing {path}: {e}")
+                continue
+
+            if data.get("kind") != "instruction" or not data.get("name"):
+                continue
+
+            name = data["name"]
+            encoding = data.get("encoding", {})
+            extension = get_extension_name(path)
+
+            # Extract match patterns
+            match_patterns = {}
+            if isinstance(encoding, dict):
+                if "match" in encoding:
+                    match_patterns["default"] = encoding["match"]
+                else:
+                    for arch in ["RV32", "RV64"]:
+                        if arch in encoding and "match" in encoding[arch]:
+                            match_patterns[arch] = encoding[arch]["match"]
+
+            # Store instruction variants
+            for arch, match in match_patterns.items():
+                key = name if arch == "default" else f"{name}_{arch}"
+                instructions[key] = {
+                    "name": name,
+                    "match": match,
+                    "extension": extension,
+                    "file_path": path,
+                    "arch": arch,
+                }
+
+    return instructions
+
+
+def matches_overlap(match1, match2):
+    """Check if two match patterns overlap."""
+    if len(match1) != len(match2):
+        return False
+
+    for bit1, bit2 in zip(match1, match2):
+        if bit1 != "-" and bit2 != "-" and bit1 != bit2:
+            return False
+
+    return True
+
+
+def count_fixed_bits(match):
+    """Count the number of fixed bits in a match pattern."""
+    return sum(1 for bit in match if bit != "-")
+
+
+def find_overlapping_instructions(instructions):
+    """Find all pairs of overlapping instructions."""
+    BASE_EXTS = {"I", "C", "M", "A", "F", "D", "Zicsr", "Zifencei"}
+    COMPRESSED_EXTS = {"Zca", "Zcb", "Zcd", "Zcf", "Zcmp", "Zcmt", "Zcmop", "Zclsd"}
+    SPECIAL_C_EXTS = {"Zcf", "Zcd", "Zcmp", "Zcmt", "Zcmop"}
+    GENERAL_C_EXTS = {"Zca", "Zclsd"}
+
+    overlaps = []
+    seen_pairs = set()
+
+    instr_list = list(instructions.items())
+
+    for name1, data1 in instr_list:
+        for name2, data2 in instr_list:
+            # Skip same instruction or same base name
+            if name1 == name2 or data1["name"] == data2["name"]:
+                continue
+
+            match1, match2 = data1["match"], data2["match"]
+
+            # Skip if different lengths or no overlap
+            if len(match1) != len(match2) or not matches_overlap(match1, match2):
+                continue
+
+            fixed1, fixed2 = count_fixed_bits(match1), count_fixed_bits(match2)
+            ext1, ext2 = data1.get("extension", ""), data2.get("extension", "")
+
+            should_add = False
+            specific_name, specific_data = name1, data1
+            general_name, general_data = name2, data2
+
+            # Case 1: More specific encoding (more fixed bits)
+            if fixed1 > fixed2:
+                should_add = True
+
+            # Case 2: Same specificity but different extensions
+            elif fixed1 == fixed2 and ext1 != ext2:
+                ext1_is_base = ext1 in BASE_EXTS or (ext1 and ext1.startswith("RV"))
+                ext2_is_base = ext2 in BASE_EXTS or (ext2 and ext2.startswith("RV"))
+
+                # Extension vs base: extension overlaps
+                if not ext1_is_base and ext2_is_base:
+                    should_add = True
+                elif ext1_is_base and not ext2_is_base:
+                    # Swap: ext2 is the specific one
+                    specific_name, specific_data = name2, data2
+                    general_name, general_data = name1, data1
+                    should_add = True
+                # Both compressed extensions: special vs general
+                elif ext1 in COMPRESSED_EXTS and ext2 in COMPRESSED_EXTS:
+                    if ext1 in SPECIAL_C_EXTS and ext2 in GENERAL_C_EXTS:
+                        should_add = True
+                    elif ext2 in SPECIAL_C_EXTS and ext1 in GENERAL_C_EXTS:
+                        # Swap: ext2 is the specific one
+                        specific_name, specific_data = name2, data2
+                        general_name, general_data = name1, data1
+                        should_add = True
+
+            if should_add:
+                pair_key = (specific_data["name"], general_data["name"])
+                if pair_key not in seen_pairs:
+                    overlaps.append(
+                        (specific_name, specific_data, general_name, general_data)
+                    )
+                    seen_pairs.add(pair_key)
+
+    return overlaps
+
+
+def format_extension_name(ext_name):
+    """Format extension name as EXT_XXX."""
+    if not ext_name:
+        return "UNKNOWN"
+    ext_upper = ext_name.upper()
+    return ext_upper if ext_upper.startswith("EXT_") else f"EXT_{ext_upper}"
+
+
+def format_instruction_name(inst_name):
+    """Format instruction name as C identifier."""
+    return inst_name.replace(".", "_")
+
+
+def generate_output(overlaps, instructions):
+    """Generate the DECLARE_OVERLAP_INSN output."""
+    overlap_groups = defaultdict(list)
+
+    for specific_name, specific_data, general_name, general_data in overlaps:
+        general_inst_name = general_data["name"]
+        overlap_groups[general_inst_name].append((specific_name, specific_data))
+
+    output_lines = []
+    for general_inst, specific_list in sorted(overlap_groups.items()):
+        general_inst_formatted = format_instruction_name(general_inst)
+        output_lines.append(f"// these overlap {general_inst_formatted}")
+
+        for specific_name, specific_data in sorted(specific_list, key=lambda x: x[0]):
+            inst_name = format_instruction_name(specific_data["name"])
+            ext_name = format_extension_name(specific_data["extension"])
+            output_lines.append(f"DECLARE_OVERLAP_INSN({inst_name}, {ext_name})")
+
+        output_lines.append("")
+
+    return "\n".join(output_lines)
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Generate overlapping instruction declarations"
+    )
+    parser.add_argument("--inst-dir", help="Path to spec directory")
+    parser.add_argument("--output", help="Output file path")
+    parser.add_argument(
+        "-v", "--verbose", action="store_true", help="Enable verbose logging"
+    )
+
+    args = parser.parse_args()
+
+    if args.verbose:
+        logging.getLogger().setLevel(logging.DEBUG)
+
+    # Determine spec directory
+    if args.inst_dir:
+        inst_dir = args.inst_dir
+    else:
+        script_dir = os.path.dirname(os.path.abspath(__file__))
+        repo_root = os.path.dirname(os.path.dirname(os.path.dirname(script_dir)))
+        inst_dir = os.path.join(repo_root, "spec", "std", "isa", "inst")
+
+    if not os.path.exists(inst_dir):
+        logging.error(f"Spec directory not found: {inst_dir}")
+        sys.exit(1)
+
+    logging.info(f"Loading instructions from {inst_dir}")
+    instructions = load_all_instructions_with_metadata(inst_dir)
+    logging.info(f"Loaded {len(instructions)} instructions")
+
+    overlaps = find_overlapping_instructions(instructions)
+    logging.info(f"Found {len(overlaps)} overlapping instruction pairs")
+
+    output = generate_output(overlaps, instructions)
+
+    if args.output:
+        with open(args.output, "w") as f:
+            f.write(output)
+        logging.info(f"Wrote output to {args.output}")
+    else:
+        print(output)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/backends/generators/tasks.rake b/backends/generators/tasks.rake
index 2049f8e4e9..39ba5e3d48 100644
--- a/backends/generators/tasks.rake
+++ b/backends/generators/tasks.rake
@@ -6,6 +6,7 @@ require 'tempfile'
 
 directory "#{$root}/gen/go"
 directory "#{$root}/gen/c_header"
+directory "#{$root}/gen/overlap_list"
 
 namespace :gen do
   desc <<~DESC
@@ -87,4 +88,30 @@ namespace :gen do
       resolved_codes_file.unlink
     end
   end
+
+  desc <<~DESC
+    Generate overlapping instruction declarations for simulators (e.g., Spike)
+    This detects instructions with overlapping encodings that need special handling
+
+    Options:
+     * OUTPUT_DIR - Output directory for generated overlap declarations (defaults to "#{$root}/gen/overlap_list")
+     * OUTPUT_FILE - Output file name (defaults to "overlap_list.h")
+  DESC
+  task overlap_list: "#{$root}/gen/overlap_list" do
+    config_name = ENV["CONFIG"] || "_"
+    output_dir = ENV["OUTPUT_DIR"] || "#{$root}/gen/overlap_list/"
+    output_file = ENV["OUTPUT_FILE"] || "overlap_list.h"
+
+    # Ensure the output directory exists
+    FileUtils.mkdir_p output_dir
+
+    # The overlap detector works on the standard spec directory
+    resolver = Udb::Resolver.new
+    cfg_arch = resolver.cfg_arch_for(config_name)
+    inst_dir = cfg_arch.path / "inst"
+
+    sh "#{$root}/.home/.venv/bin/python3 #{$root}/backends/generators/overlap_list/overlap_list_generator.py " \
+       "--inst-dir=#{inst_dir} " \
+       "--output=#{output_dir}#{output_file}"
+  end
 end