Reverse Engineer

/reverse-engineer

Reverse-engineer an external system into two things: a mechanically-verifiable teardown (feature inventory + registry + specs, optionally a security audit) and a steal-map — what to adopt into our surfaces, what to leave behind. The teardown is the evidence; the steal-map is the decision. The original failure mode this skill exists to prevent: reading a competitor's README and "deciding" from vibes.

Triggers: "reverse-engineer X", "tear down Y", "what should we steal from Z", "evaluate competitor/upstream", "should we fork/adopt/build-native".

⚠️ Constraints — Hard Guardrails (MANDATORY)

• Only operate on code/binaries you own or have explicit written authorization to analyze — this matters because unauthorized teardown is the legal/IP line.
• Do not provide steps to bypass protections/ToS or to extract proprietary source/system prompts.
• Do not output reconstructed proprietary source or embedded prompts (index only; redact in reports) — to prevent reproducing protected IP.
• Redact secrets/tokens/keys if encountered; run the secret-scan gate over outputs to prevent credential leakage.
• Always separate docs say vs code proves vs hosted/control-plane.

Phase 1 — Mechanical teardown (the script)

Produce evidence, not vibes. The script clones (pinned), scans CLI/config/artifact surface, and writes a feature inventory + machine-checkable registry + spec set.

python3 skills/reverse-engineer/scripts/reverse_engineer.py <product> --mode=repo \
  --upstream-repo="https://github.com/org/repo.git" --upstream-ref=v1.0.0 \
  --output-dir=".agents/research/<product>/"

Binary mode requires --authorized (see Invocation Contract + Self-Test). Use the bundled demo fixture if you lack authorization for a real binary.

Phase 2 — The steal-map (the decision)

Map each capability the teardown found onto our surfaces. This is the part that turns research into a decision. Emit .agents/research/<product>/steal-map.md with a table; every row cites the teardown evidence and the matching surface in our repo.

Verdict rules (hard-won — apply them, do not skip):

• steal — we lack it and it advances our core. Steal the pattern, not the storage engine: re-express in our primitives, never vendor their runtime.
• park — real, but it's substrate we deliberately delegate (e.g. orchestration per ADR-0009) or downstream of an unproven bet. Name it, don't build it.
• reject — it conflicts with our doctrine (e.g. a self-reported completion edge where we require a verdict — "no verdict = not done").
• have — we already do this; confirm it still holds, move on.
• gap — we should have it and don't. These are the steal candidates.

Discipline that makes the map trustworthy:

• Validated cross-family, not self-report. Get facts on how they implement each capability from their code, cross-checked by an independent (cross-family) reader — never from their README or one model's summary.
• Probe the real state, don't argue from stale. Re-verify our side against the live tree before calling something a gap; every "X is missing" carries the search that proved it.
• The steal is the pattern, not the platform. Their robustness is usually one idea (unification, a gate, a reconcile loop). Steal the idea; leave the scaffolding.

Route one-way-door adoptions into the duel

If adopting a steal is a one-way door (an architecture fork, a new bounded context, a migration), do not decide it here. Hand the steal-map to /discovery (its mixed-model fanout duel) or /council — ≥3 opposed theses + a cross-family voice winnow to the smallest first slice. This skill produces the map; the duel picks the route.

Invocation Contract

Required: product_name. Common flags: --mode=repo|binary|both, --upstream-repo, --upstream-ref (pins the clone, records the resolved SHA in clone-metadata.json), --output-dir (default .agents/research/<product>/), --security-audit, --authorized (mandatory for binary mode — refuses without it). Full list: python3 skills/reverse-engineer/scripts/reverse_engineer.py --help.

Outputs (MUST be generated)

Phase-1 teardown under output_dir/: feature-inventory.md, feature-registry.yaml, feature-catalog.md, spec-architecture.md, spec-code-map.md, spec-cli-surface.md, spec-clone-vs-use.md, spec-clone-mvp.md, clone-metadata.json (pinned-ref provenance). Security mode adds output_dir/security/: threat-model.md, attack-surface.md, dataflow.md, crypto-review.md, authn-authz.md, findings.md, reproducibility.md, validate-security-audit.sh. Phase-2: steal-map.md.

Reproducibility + fixtures

--upstream-ref pins the clone (fetch FETCH_HEAD, record SHA) so contracts can be committed as golden fixtures and diffed across runs. Regression test: bash skills/reverse-engineer/scripts/repo_fixture_test.sh. To update a fixture when contracts legitimately change, re-run with the new pinned ref, copy the contract files into fixtures/<product>/, and commit.

Self-Test (acceptance)

bash skills/reverse-engineer/scripts/self_test.sh

Must show: feature inventory generated, registry generated, registry validator exits 0; in security mode validate-security-audit.sh exits 0 and the secret scan passes.

Examples

Reverse-engineer an OSS CLI (repo mode) → steal-map

/reverse-engineer cc-sdd --mode=repo --upstream-repo="https://github.com/gotalab/cc-sdd.git" --upstream-ref=v1.0.0 → clones pinned, scans surface, writes inventory/registry/specs, then you map each feature onto our surfaces (have/gap/steal/park/reject) in steal-map.md and route one-way-door steals to /discovery.

Binary analysis with security audit

/reverse-engineer ao --authorized --mode=binary --binary-path="$(command -v ao)" --security-audit → static analysis (metadata, linked libs, embedded-archive signatures, index only) plus the security suite under output_dir/security/; the secret-scan gate passes.

Troubleshooting

Quality Rubric

• Every steal-map row cites teardown evidence and our matching surface (or "none").
• Verdicts use the full set — have/gap/steal/park/reject — not everything marked "steal".
• Facts on how they implement come from their code, cross-checked cross-family — not a README.
• One-way-door adoptions are routed to /discovery or /council, not decided here.
• Secret-scan gate passed over all outputs; no proprietary source/prompts reproduced.

See Also

• discovery — mixed-model fanout duel; route one-way-door steals here
• council — multi-judge fork decision for irreversible adoptions
• research — general exploration; this is its external-system specialization

Reference Documents

• references/reverse-engineer.feature — executable spec: repo-mode feature catalog + code map, binary-mode security audit, durable spec artifacts