beam

BEAM (Erlang / Elixir)

disrobe parses BEAM IFF files, recovers Erlang or Elixir source when debug chunks survive, lifts to Core Erlang otherwise, and disassembles the Code chunk per instruction. A flat text disassembly listing lands beside the JSON automatically.

At a glance

Layer	Coverage
Chunks	AtU8 (short and long form), Code, StrT, Attr, CInf, Dbgi, Docs, ExpT, ImpT, LocT, FunT, Line, LitT (zlib-deflated on OTP 26 and earlier, raw on OTP 27+); unknown chunks are preserved verbatim
Source recovery	Erlang abstract code when present, Elixir source from a Dbgi form, best-effort Core Erlang lift as the floor; provenance is recorded in recovered_from
Disassembly	Per-instruction Code-chunk trace including the bs_match (opcode 182) command list; a flat .txt listing lands beside the JSON
Containers	.ez archives extract through the container layer

Parsing

disrobe beam parse module.beam --out ./out/module-beam.json

Reports the module name, atom / export / import / fun counts, which optional chunks are present, and any unrecognized chunk names.

Output shape (illustrative):

beam parse: OK
  module:       my_module
  atoms:        42
  exports:      8
  imports:      15
  funs:         3
  wrote:        ./out/module-beam.json

Lifting to source

disrobe beam lift module.beam --out out/module-beam-lift/

Writes three files: <stem>.<ext> (recovered Erlang or Elixir source, extension derived from recovered_from), <stem>.surface.json (the surface record with provenance), and <stem>.core.json (lifted Core Erlang functions), plus a manifest.json linking them.

When a Dbgi chunk is present the original forms are recovered directly and labelled AbstractCode (Erlang) or ElixirDbgiForm (Elixir). Without it the output is a best-effort Core Erlang lift labelled CoreLifted.

Output shape (illustrative):

beam lift: OK
  module:       my_module
  core fns:     8
  recovered:    AbstractCode
  source:       ./out/module-beam-lift/module.erl
  surface:      ./out/module-beam-lift/module.surface.json
  core erlang:  ./out/module-beam-lift/module.core.json
  manifest:     ./out/module-beam-lift/manifest.json

Disassembling

disrobe beam disasm module.beam --out ./out/module-beam.disasm.json

Emits the per-instruction Code-chunk trace as JSON and a flat .txt listing beside it. Opcodes beyond the known table fail with an explicit DR-BEAM-0012 error naming the offending opcode rather than silently skipping bytes.

Output shape (illustrative):

beam disasm: OK
  input:        module.beam
  instructions: 214
  wrote:        ./out/module-beam.disasm.json
  listing:      ./out/module-beam.disasm.txt