Compatibility

codeArbiter’s requirements are deliberately narrow: Claude Code, Codex, or Pi, plus Python 3 on PATH. All three hosts share .codearbiter/; see the Claude Code + Codex evidence for the verified boundary and the Pi install page for the ca-pi install flow.

Requirements Matrix

Requirement	What’s needed	Notes
Claude Code	Any version with plugin support	plugin.json states no explicit minimum version; the plugin uses standard hook events (SessionStart, PreToolUse, PostToolUse) and the plugin/marketplace install commands documented in Install.
Codex	Minimum 0.143.0; live-verified on 0.144.1	ca-codex uses one OS-specific handler per event and a Codex adapter that converts the shared guard verdict to structured deny output. Trust the hook set through /hooks.
Pi	0.80.5 or 0.80.10 (this release line)	ca-pi is a Feature Forge preview, available and welcomed for real use while broader testing continues before stable status or a claim of 100% validation. Install it Git-only: pi install git:github.com/arbiterForge/codeArbiter@ca-pi-v<version>. Also requires Node.js 22.19+. Requires an affirmative project-trust decision before repository-aware startup. Its human-readable generated catalog is plugins/ca-pi/SKILLS.md. See Install for Pi.
Python	Python 3, stdlib only, available under the interpreter name your adapter registers	Claude Code carries its documented python3/python fallback shape. Codex uses OS-specific command and commandWindows handlers and fails loud if its selected interpreter is absent. Pi installs final TypeScript wrappers first, then blocks mutating calls with an interpreter breadcrumb until the Python bridge is healthy. No adapter treats that state as active enforcement. No third-party Python packages are installed or imported (ADR-0004).
Operating system	Windows, macOS, or Linux	Hooks are pure Python stdlib and carry no OS-specific code path beyond the interpreter-name fallback above. The .git/hooks backstop shim is a POSIX sh script; on Windows this runs under Git for Windows’ bundled sh.exe, which ships with every standard Git install. Windows is also a promoted, tested platform for ca-pi; see Windows notes.
git	Any reasonably current git	Required regardless of codeArbiter: the plugin reads repo state (git config user.email, branch, diff) via subprocess calls to your existing git binary, and installs the .git/hooks backstop through it.
Node.js	Not required for Claude Code or Codex	Node is required for ca-pi (22.19+) and is only otherwise needed to build or develop this documentation site (site/) and the optional pluggable-execution-farm TypeScript dispatcher (plugins/ca/tools/) if you use /ca:sprint --farm. Node is not a runtime dependency of the Claude Code/Codex enforcement hooks themselves.
Network access	Not required for enforcement	See Network Calls below. The gate-enforcement hook chain makes zero network calls; two clearly-scoped, opt-in-by-default exceptions exist outside that chain.

Host Differences

Surface	Claude Code	Codex	Pi
Entry commands	/ca:<name>	$ca-<name>	/ca-<name> (generated alias); /skill:ca-<name> fallback
Plugin	ca	ca-codex	ca-pi (Feature Forge preview)
Distribution	Marketplace + npm-backed release	Marketplace + npm-backed release	Git tags only (ca-pi-v<version>); no npm release
Trust/approval	Claude Code plugin trust flow	Review through /hooks; start a fresh thread	Affirmative project-trust decision, then a fresh session
Statusline / footer	Available	No statusline surface	Rich footer in every interactive parent repository; governance row only when enabled and affirmatively trusted; rate-window telemetry is omitted
Mutation permission	Host permission flow plus gates	Codex approval plus gates	Execute mode asks before governed mutations or external side effects; hard blocks deny first
Plan mode	Host plan workflow	Read-only collaboration mode	Plan mode is read-only except for the current canonical spec, plan, and plan ledger
Background jobs	Host managed	Host managed	Bounded session-only jobs, never restored from Pi session entries; unverified cleanup blocks later launches with /ca-doctor direction
/ca:sprint --farm	preview, shared farm.js backend	preview, shared farm.js backend	preview, same shared farm.js backend through the trusted parent extension; no Pi-native farm engine
Subagent/child dispatch	Plugin agents dispatched directly	Current hosts provide agent threads: codeArbiter loads the role charter and retains the thread receipt; older hosts may fall back inline, but context creation blocks without isolated scouts	Fresh child Pi processes via the parent-only codearbiter_dispatch EXEC tool; single/chain/parallel modes share bounded depth, concurrency, timeout, cancellation, and process-tree cleanup
Transcript pruning / compaction	Claude transcript-pruning engine	No transcript pruning; host-neutral staleness warning	Native Pi compaction event; codeArbiter does not rewrite Pi session JSONL
Project state	Shared .codearbiter/ store	Shared .codearbiter/ store	Shared .codearbiter/ store

The full exception ledger with status and evidence for every host delta lives in docs/parity.md.

Maintainer verification only

When running Pi’s repository-level platform aggregate, a tools workspace without its resolved Vitest binary returns missing_prerequisite before fixtures start. Maintainers can prepare that workspace with npm --prefix plugins/ca-pi/tools ci --ignore-scripts; the verification path never installs dependencies itself. This setup is not required to install or use codeArbiter.

Footer, permission UI, plan UI, and background jobs are parent-interactive only and absent from JSON, RPC, print, and hardened children.

Prerequisites Checklist

Confirm both before installing, per Install:

• Python 3 on PATH. Without it, Claude Code can be inactive, Codex’s hook handler fails loud, and Pi blocks mutation. Run the host-native doctor command and require a healthy interpreter and live-fire row before treating the adapter as active.
• git config user.email set. Overrides and ADRs are attributed to this identity; an unset email is asked for once, interactively, rather than silently defaulting.

Network Calls

Grepping every file under plugins/ca/hooks/ for network-capable stdlib usage (urllib, http.client, socket) turns up exactly one file that actually opens a connection: _updatelib.py. (_ledgerlib.py matches a naive text search only because it uses the English word “requests” to mean tool-call records. It imports nothing network-capable.)

• The gate-enforcement hooks (pre-bash.py, pre-write.py, pre-edit.py, pre-read.py, post-write-edit.py, and session-start.py’s activation/briefing logic) make zero network calls. Every check is a local file read, a local git subprocess call against your own repo, or an in-process regex/parse. This is the enforcement chain compatibility and security actually depend on.
• The update-available notifier (_updatelib.py) is a separate, non-blocking mechanism: a best-effort, once-a-day, fail-silent, unauthenticated HTTPS GET against GitHub’s public Releases API (api.github.com), run as a detached background process off the SessionStart hot path so a slow or unreachable network never delays a session. It only ever displays a one-line notice; it never applies an update. This ships on by default but is easy to make fully offline: see Staying up to date in the project README for the opt-out.
• The pluggable execution farm (/ca:sprint --farm, opt-in, requires FARM_API_KEY) sends byte-capped, secret-redacted task context to an OpenAI-compatible HTTP provider you configure. This is a separate, explicitly opt-in feature, not part of the gate chain, and inert unless you pass --farm.

No hook writes anything off your machine as a side effect of enforcement. docs/hooks.md documents the same invariant per-hook, plus the one local, read-only git fetch session-start.py runs in the background against your own configured remote (the repo-hygiene briefing).

Third-Party Dependencies

Zero, for the plugin itself. plugins/ca/hooks/*.py import only the Python standard library: no pip install, no requirements.txt, no compiled binaries (ADR-0004). The one TypeScript toolchain in the repo, plugins/ca/tools/ (the farm dispatcher), carries its own devDependencies for its own build and test. Those are irrelevant to whether the enforcement hooks run, since the hooks never import from that package.

The docs site (site/) has its own, larger package.json (Astro, Starlight, vitest). That’s a dependency surface for building this website, never for using the plugin.