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. Separating them works because a decision row that must cite a registry entry can be re-checked by anyone, while a decision made from impressions cannot be re-checked by its own author. 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".

Prompt

Reverse-engineer the beads CLI (github.com/steveyegge/beads, tag v2.1.0)
in repo mode, then author steal-map.md comparing its dependency-graph
reconciler against our cli/internal/gates/ package. I own this analysis
and have authorization for the clone.

It's working if

Observable in the trace, without reading the prose:

• feature-registry.yaml and clone-metadata.json land under .agents/scratch/reverse-engineer/<product>/ with the resolved upstream commit recorded.
• Every steal-map.md row cites a teardown registry entry and our matching surface, using the full have/gap/steal/park/reject set.
• bash skills/reverse-engineer/scripts/validate-output.sh --output-dir "$output_dir" --phase complete exits 0 before handoff.
• A one-way-door adoption row is routed to Plan instead of decided inside steal-map.md.

⚠️ 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/scratch/reverse-engineer/<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/scratch/reverse-engineer/<product>/steal-map.md with a table; every row cites the teardown evidence and the matching surface in our repo.

The mechanical script intentionally stops after validating Phase 1. It cannot truthfully decide whether our live tree has, lacks, or should adopt a capability. The caller authors steal-map.md from the generated registry plus a fresh read of our repository, then runs the complete-output validator below. A missing or malformed map is therefore an incomplete skill result, not a script success silently relabelled as a decision.

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:

• Independently checked, not self-report. Get facts on how they implement each capability from code, cross-checked by a fresh reader — never from a README or one context's summary. Model family is optional metadata, not a trust requirement.
• 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 planning

If adopting a steal is a one-way door (an architecture fork, a new bounded context, or a migration), do not decide it here. Hand the steal-map to Plan. Dueling Idea Genies or Premortem may challenge the choice as advisory evidence. Plan alone shapes the selected option in the existing intent source; neither strategy grants readiness or continuation authority.

Invocation Contract

Required: product_name. Common flags: --mode=repo|binary|both, --upstream-repo, --upstream-ref (requires the selected checkout to be at that exact commit and records its resolved SHA in clone-metadata.json), --local-clone-dir (selects that exact tree, including a non-Git tree; it never falls back to the caller's checkout), --output-dir (default .agents/scratch/reverse-engineer/<product>/), --security-audit, --materialize-archives (authorized-only opt-in; embedded-archive extraction is off/index-only by default), --authorized (mandatory for binary mode — refuses without it). Full list: python3 skills/reverse-engineer/scripts/reverse_engineer.py --help.

Output Specification

Phase-1 teardown under output_dir/: feature-inventory.md, feature-registry.yaml, feature-catalog.md, spec-architecture.md, spec-code-map.md, spec-clone-vs-use.md, spec-clone-mvp.md, plus spec-cli-surface.md only when a CLI is detected. clone-metadata.json is written whenever an upstream repo/ref is selected and binds the exact analyzed commit, including an already-present checkout. 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 adds the caller-authored steal-map.md.

• Artifact directory: the exact --output-dir, defaulting to $REPO/.agents/scratch/reverse-engineer/<product>/.

• Filename convention: the fixed phase-1 and phase-2 names above; security files live only in the security/ child directory.

• Serialization/schema format: registry is YAML, clone metadata is one JSON object, and inventories/specs/steal-map are nonempty Markdown files.

• Validator command: Phase 1 runs this automatically with --phase teardown. After authoring steal-map.md, validate the complete skill output with $output_dir, $security_audit, $sbom, and $upstream_ref_set (each numeric flag 0|1):

  bash skills/reverse-engineer/scripts/validate-output.sh \
    --output-dir "$output_dir" --phase complete \
    --security-audit "$security_audit" --sbom "$sbom" \
    --upstream-ref-set "$upstream_ref_set"
  

• Downstream handoff: give the validated steal-map.md to Plan for one-way-door candidates; ordinary have, park, and reject decisions remain evidence-backed terminal rows.

Earlier default compatibility

Existing teardowns under .agents/research/<product>/ remain in place and usable. The script accepts that directory when it is passed explicitly with --output-dir; that flag is caller authorization to write the teardown at the exact selected path. It does not relocate or duplicate existing artifacts. An invocation that omits the flag writes only to the current scratch default and never creates output under the earlier root. Consumers must retain the exact selected output_dir with their evidence references instead of rediscovering outputs by globbing one root. This owning skill contract is the compatibility authority; no separate migration receipt is required.

Reproducibility + fixtures

--upstream-ref binds the selected checkout to one full commit: a new clone is checked out detached at the fetched ref, while an existing checkout must already match or the run refuses before analysis. clone-metadata.json records that resolved commit. 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 and registry generated; the exact Phase-1 validator passes; the complete validator rejects a missing and malformed steal-map and accepts a valid caller-authored fixture; existing-checkout ref mismatch and output symlinks fail closed; in security mode validate-security-audit.sh exits 0 only after the scaffold is completed and the secret scan passes.

Examples

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

Run Phase 1 for cc-sdd with --mode=repo --upstream-repo="https://github.com/gotalab/cc-sdd.git" --upstream-ref=v1.0.0. It clones the pinned source, scans the surface, writes inventory/registry/specs, and validates the teardown. Then inspect our live surfaces, author each have/gap/steal/park/reject row in steal-map.md, and run the complete-output validator. Supply selected steals to Plan.

Binary analysis with security audit

Run the skill for ao with --authorized --mode=binary --binary-path="$(command -v ao)" --security-audit. It performs authorized static analysis plus the security suite under output_dir/security/; the secret-scan check must pass.

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 code and a fresh independent check — not a README.
• One-way-door adoptions are supplied to Plan, not decided here.
• Secret-scan gate passed over all outputs; no proprietary source/prompts reproduced.

See Also

• plan — shape selected steals in the existing intent source
• idea-genie — optional advisory challenge (duel mode)
• premortem — optional advisory challenge of the exact plan
• 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