Codex vs Claude Code Skills: Native and Portable Compatibility

Native support answers whether the Skill or platform explicitly targets a particular Agent. Portable support answers whether its instructions can plausibly be adapted through a compatible SKILL.md workflow. Both can be useful, but they provide different confidence.

SkillSignal keeps these labels separate. A known installation path never upgrades a portable pairing into a native claim, and a source pin never proves runtime compatibility.

First compare discovery and install paths. Then inspect referenced commands and tool names. Next map filesystem, shell, browser, and network permissions. Check whether examples assume Agent-specific context, subagents, hooks, or UI behavior. Finally, run one acceptance task and preserve the exact source revision and result.

• Installation: project and personal paths are known for the target Agent.
• Tools: every referenced command or tool has a target equivalent.
• Permissions: approval points and writable scope remain at least as strict.
• Assets: scripts, templates, and linked references resolve after the move.
• Evidence: the same acceptance task produces reviewable output.

For Codex, inspect whether the workflow fits the available project context, command environment, approval boundary, and repeatable validation. A portable Skill may work well when it uses clear file paths, ordinary commands, explicit outputs, and no hidden Agent-specific hooks.

Do not treat a successful copy as complete validation. Run the smallest representative task, verify changed files and external calls, and compare the outcome with the Skill's stated limitation.

For Claude Code, check whether the upstream Skill explicitly uses Claude-oriented paths, tools, subagent patterns, or permission prompts. Explicit targeting is useful evidence, but referenced scripts and external services still need their own review.

When moving a Claude-targeted Skill elsewhere, translate each tool call and approval point instead of preserving only the prose. If a behavior has no target equivalent, narrow the workflow or keep it on the original Agent.

Choose one small, reversible task with an observable result. Run it on the original environment and record source revision, inputs, commands, permissions, outputs, and stop conditions. Move the Skill, translate only the necessary Agent-specific pieces, and repeat the task. Compare evidence, not tone or response style.

Mark the result as locally verified for that task and environment only. One successful test does not establish universal compatibility across repositories, operating systems, credentials, or future source revisions.

• No additional credential or writable scope was required.
• The target Agent used equivalent tools or documented substitutions.
• The final artifact passes the same acceptance check.
• Failure and rollback behavior remain understandable.
• The compatibility note names the tested source revision and environment.