docs: add harness adapter compliance matrix (#1784)

docs/architecture/harness-adapter-compliance.md

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+# Harness Adapter Compliance Matrix
+
+This matrix is the public onramp for teams that want to use ECC across more
+than one coding harness. It turns the cross-harness architecture into a
+practical scorecard: what works today, what is instruction-only, what needs an
+adapter, and what evidence an operator should collect before trusting a setup.
+
+ECC's durable units stay in shared sources:
+
+- `skills/*/SKILL.md`
+- `rules/`
+- `commands/`
+- `hooks/hooks.json`
+- `scripts/hooks/`
+- MCP reference configs
+- session and observability contracts
+
+Harness-specific files should only adapt loading, event shape, command names,
+or platform limits.
+
+## Compliance States
+
+| State | Meaning |
+| --- | --- |
+| Native | ECC can install or verify the surface directly for this harness. |
+| Adapter-backed | ECC has a thin adapter, plugin, or package surface, but parity differs by harness. |
+| Instruction-backed | ECC can provide the guidance and files, but the harness does not expose the runtime hook/session surface ECC needs for enforcement. |
+| Reference-only | The tool is useful as a design pressure or external runtime, but ECC does not yet ship a direct installer or adapter for it. |
+
+## Matrix
+
+| Harness or runtime | State | Supported assets | Unsupported or different surfaces | Install or onramp | Verification command | Risk notes |
+| --- | --- | --- | --- | --- | --- | --- |
+| Claude Code | Native | Claude plugin assets, skills, commands, hooks, MCP config, local rules, statusline-oriented workflows | Claude-native hooks do not imply parity in other harnesses | `./install.sh --profile minimal --target claude` or Claude plugin install | `npm run harness:audit -- --format json` and `node scripts/session-inspect.js --list-adapters` | Avoid loading every skill by default; keep hooks opt-in and inspectable. |
+| Codex | Instruction-backed | `AGENTS.md`, Codex plugin metadata, skills, MCP reference config, command patterns | Native hook enforcement and Claude slash-command semantics are not equivalent | `./install.sh --profile minimal --target codex` plus repo-local `AGENTS.md` review | `npm run harness:audit -- --format json` | Treat hooks as policy text unless a native Codex hook surface exists. |
+| OpenCode | Adapter-backed | OpenCode package/plugin metadata, shared skills, MCP config, event adapter patterns | Event names, plugin packaging, and command dispatch differ from Claude Code | OpenCode package or plugin surface from this repo | `node tests/scripts/build-opencode.test.js` and `npm run harness:audit -- --format json` | Keep hook logic in shared scripts and adapt only event shape at the edge. |
+| Cursor | Adapter-backed | Cursor rules, project-local skills, hook adapter, shared scripts | Cursor hook events and rule loading differ from Claude Code | `./install.sh --profile minimal --target cursor` | `node tests/lib/install-targets.test.js` and `npm run harness:audit -- --format json` | Cursor adapters must preserve existing project rules and avoid silent overwrite. |
+| Gemini | Instruction-backed | Gemini project-local instructions, shared skills, rules, compatibility docs | No full ECC hook parity; ecosystem ports must document drift from upstream ECC | `./install.sh --profile minimal --target gemini` | `node tests/lib/install-targets.test.js` | Treat Gemini ports as ecosystem adapters until validated end to end inside Gemini CLI. |
+| Zed-adjacent workflows | Instruction-backed | Shared skills, `AGENTS.md` style project instructions, verification loops | Zed agent surfaces vary; no first-party ECC installer is shipped today | Manual copy from shared ECC sources until adapter requirements settle | `npm run harness:audit -- --format json` | Do not claim native Zed support before a real adapter and verification path exist. |
+| dmux | Adapter-backed | Session snapshots, tmux/worktree orchestration status, handoff exports | dmux is an orchestration runtime, not an install target for skills/rules | `node scripts/session-inspect.js --list-adapters` and dmux session target inspection | `node tests/lib/session-adapters.test.js` | Treat dmux events as session/runtime signals, not as a replacement for repo validation. |
+| Orca | Reference-only | Worktree lifecycle, review state, notification, and provider-identity design pressure | No ECC installer or direct adapter today | Use as a comparison target for worktree/session state requirements | `npm run observability:ready` | Do not import product-specific assumptions; convert lessons into ECC event fields. |
+| Superset | Reference-only | Workspace presets, parallel-agent review loops, worktree isolation design pressure | No ECC installer or direct adapter today | Use as a comparison target for workspace preset taxonomy | `npm run observability:ready` | Keep ECC portable; do not require a desktop workspace to get basic value. |
+| Ghast | Reference-only | Terminal-native pane grouping, cwd grouping, search, notifications | No ECC installer or direct adapter today | Use as a comparison target for terminal-first session grouping | `node scripts/session-inspect.js --list-adapters` | Preserve terminal ergonomics before adding visual UI assumptions. |
+| Terminal-only | Native | Skills, rules, commands, scripts, harness audit, observability readiness, handoffs | No external UI, no automatic session control unless scripts are run explicitly | Clone repo, run commands directly, use minimal profile for project installs | `npm run harness:audit -- --format json` and `npm run observability:ready` | This is the fallback contract; every higher-level adapter should degrade to it. |
+
+## Scorecard Onramp
+
+Use this sequence before asking ECC to make a team or repo setup more
+autonomous:
+
+```bash
+npm run harness:audit -- --format json
+npm run observability:ready
+node scripts/session-inspect.js --list-adapters
+node scripts/loop-status.js --json --write-dir .ecc/loop-status
+```
+
+Read the result as a setup scorecard, not a product badge:
+
+- `harness:audit` scores tool coverage, context efficiency, quality gates,
+  memory persistence, eval coverage, security guardrails, and cost efficiency.
+- `observability:ready` proves the repo still exposes the local status,
+  session, tool-activity, risk-ledger, and release-onramp signals.
+- `session-inspect --list-adapters` shows which session surfaces are actually
+  inspectable in the current environment.
+- `loop-status --json` creates a machine-readable handoff/status payload for
+  longer autonomous runs.
+
+## Evidence Fields For Future Data Matrix
+
+When this matrix moves from Markdown to a data-backed validator, each adapter
+record should expose:
+
+- `id`
+- `state`
+- `supported_assets`
+- `unsupported_surfaces`
+- `install_or_onramp`
+- `verification_commands`
+- `risk_notes`
+- `last_verified_at`
+- `owner`
+- `source_docs`
+
+The validator should fail if a public adapter claim has no install path,
+verification command, or risk note.
+
+## Operating Rules
+
+- Prefer small, additive adapters over harness-specific forks of the same
+  workflow.
+- Do not call a harness native until the adapter has an install path and a
+  verification command.
+- Keep Codex, Gemini, and Zed surfaces honest when enforcement is
+  instruction-backed rather than runtime-backed.
+- Treat reference-only tools as design pressure until ECC has a direct adapter.
+- Keep the terminal-only path healthy; it is the portability floor.