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type: adr id: adr-0098 status: accepted created: 2026-06-23 updated: 2026-06-23

ADR-0098 — Portability: ship a Codex emitter + the universal AGENTS.md discipline; drop Antigravity

Context

ADR-0092 founded corpus-agents as a Claude-Code-first agent-definition catalog and held a portable layer behind a "do-not-found" gate (needs ≥2 runners demonstrating value). The prior deep-research survey (corpus-works) found the gate's second-runner question is now answerable: OpenAI Codex reads file-based agent definitions (.codex/agents/*.toml, developer_instructions + optional model), and AGENTS.md is an open cross-tool format read by Codex, Cursor, Copilot, Gemini CLI, and Aider. The owner directed building the portable layer now — Codex + the universal layer, drop Antigravity, reuse as much as possible and duplicate as little.

Decision

Ship a Codex emitter as a generator over the single-source definitions, formalize the AGENTS.md universal-discipline layer, and drop Antigravity. Enforcement does not travel — only the prose discipline.

1. Codex TOML emitter — corpus agents emit --codex (corpus-cli). Reads the corpus-agents agents/*.md definitions and generates .codex/agents/<name>.toml (developer_instructions = the markdown body). It is reuse, not duplication: the agents/*.md files stay the single source; the TOML is generated, so the two never drift by hand (re-run to regenerate; the files say "do not hand-edit"). No agent is launched and no network is touched — it emits a definition, never runs one, so the reconcile-only posture holds (ADR-0077). It is a runner adapter (like corpus run's launcher), so it lives in corpus-cli's Workspace leaf, NOT the agent-agnostic Core — naming a runner is exactly what Core's boundary forbids.

2. The universal AGENTS.md discipline layer (corpus-agents). The shared discipline — evidence over assertion (ADR-0056), reconcile-only / no self-issued verdict (ADR-0077 D8), the delegation trace as reviewability not a guarantee (ADR-0088), honesty levels (ADR-0063) — is single-sourced in corpus-agents' AGENTS.md, which is the open format that ports to every AGENTS.md-reading runner. The per-worker agents/*.md files are the Claude-Code specialization of that universal contract. No hand-duplicated per-worker SKILL.md is added (it would duplicate the bodies, against the reuse-don't-duplicate directive); the universal layer is the AGENTS.md prose + the emitter.

3. Enforcement does not travel — honest scope (ADR-0063). The tools allowlist and the hooks/ (read-only guard, delegation trace) are Claude-Code structural mechanisms — they do not port. Every emitted Codex file carries a header saying so; a Codex adopter gets the prose discipline and scopes tools in their own config. Level for the emitter and the universal layer: toolable (the tool is corpus agents emit). The portability claim is "the discipline is portable," never "the enforcement is portable."

4. Drop Antigravity. Google Antigravity's managed agents are configured programmatically, not via a portable definition file, so there is no honest file-emitter target. The universal AGENTS.md discipline reaches it without an adapter; building an Antigravity emitter would be inventing a file format Antigravity does not consume. No Antigravity emitter ships.

5. The measurement wave stays the honest exception (ADR-0092's gate). Demonstrating value across ≥2 real external runner teams is un-fabricatable; it remains a standing owner-run activity, recorded as the named exception — not a build item.

Consequences

• corpus-cli gains the agents command (emit --codex), a codexToml renderer + emit_agents engine in the Workspace leaf, the catalog entry, and the dispatch parity (AC-004). Hand-rolled TOML (no dependency); the """-escaping is tested (a body with \, ", and """ round-trips).
• corpus-agents' AGENTS.md gains a Portability section (the universal layer + what does/doesn't travel); docs/runners.md is refreshed to "Codex emitter shipped."
• The Claude-Code-first founding stance is preserved: Claude Code reads the agents/*.md natively; the emitter is an addition for a second runner, not a re-platforming.
• This is a conscious owner override of ADR-0092's hold-until-2-runners gate, narrowed: the emitter + universal layer ship now (the second runner, Codex, is real and the cost is a generator); the value-measurement wave — the part the gate actually protected — stays the honest exception.