feat: support Claude Code alongside the Agent Plugins standard - #4
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Claude Code rejected the repository with "no manifest found at .claude-plugin/marketplace.json". It reads its own manifests, so supporting both clients means shipping both sets. Only skills/ is genuinely shared. concern Agent Plugins Claude Code plugin manifest plugin.json .claude-plugin/plugin.json marketplace .agents/plugins/marketplace.json .claude-plugin/marketplace.json mcp config mcp.json .mcp.json remote transport streamable-http http Schema taken from Claude Code's documentation and cross-checked against Slack's official plugin, which ships .claude-plugin/, .codex-plugin/, .cursor-plugin/ and .agents/ side by side — so this is the established multi-client pattern, not an invention. Verified on Claude Code 2.1.227: `claude plugin marketplace add ./` registers and `claude plugin install usable@usable` installs and enables at 0.1.0. Note a bare `.` is rejected; the ./ form is required. OAuth client id: .mcp.json declares oauth.clientId = mcp_oauth_client, which is where Claude Code reads it (same field Slack's plugin uses). A client_id is a public identifier, not a secret, so it is safe to package. mcp.json stays URL-only because the Agent Plugins schema defines no oauth field and inventing one risks rejection by a strict client. Duplication is a drift risk, so it is guarded rather than trusted: - the two MCP documents must declare the same servers at the same URLs - the two plugin manifests must agree on name and version - oauth blocks are validated fail-closed — only clientId, callbackPort and scopes are permitted, so a clientSecret cannot ship by being an unrecognised field Twelve new self-tests; suite is 27/27. Also added .claude-plugin/ and .mcp.json to the release allowlist, without which the published artifact would have shipped a package Claude Code could not install. Collision now confirmed, not hypothesised: a user-level MCP server named `usable` shadows the plugin's declaration. No plugin:usable:usable server appeared while other plugins' servers did show under that prefix. This was previously recorded as a suspicion for Codex; it is real, and it means the MCP step cannot be verified on a machine that already has such an entry. Documented in authentication.md with the remedy. Claude Code skills are NOT yet confirmed reaching the model. The plugin installs, but Claude Code exposes no CLI listing of available skills, so the matrix records skills as untested rather than assuming parity with Codex. Co-Authored-By: Oz <oz-agent@warp.dev>
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Fixes
This repository isn't a marketplace — no manifest found at .claude-plugin/marketplace.json.Answer to "should we support both?" — yes, and the cost is low because the two formats overlap where it matters.
What differs
plugin.json.claude-plugin/plugin.json.agents/plugins/marketplace.json(Codex).claude-plugin/marketplace.jsonmcp.json.mcp.jsonstreamable-httphttpskills/skills/skills/is shared, so the actual product isn't duplicated — only thin manifests are.Schema came from Claude Code's docs and was cross-checked against Slack's official plugin, which ships
.claude-plugin/,.codex-plugin/,.cursor-plugin/and.agents/side by side. This is the established multi-client pattern, not something I invented.Verified
Claude Code 2.1.227 on macOS:
claude plugin marketplace add ./— note a bare.is rejected withInvalid marketplace source format.OAuth client id
.mcp.jsondeclaresoauth.clientId: "mcp_oauth_client"— the field Claude Code reads, and the same one Slack's plugin uses. Aclient_idis a public identifier, not a secret, so it's safe to package.mcp.jsonstays URL-only: the Agent Plugins schema defines nooauthfield, and inventing one risks rejection by a strict client. Both clients'addcommands are documented inauthentication.md.Duplication is guarded, not trusted
Shipping two configs invites drift, so CI now fails on it:
oauthblocks validate fail-closed — onlyclientId,callbackPort,scopespermitted, so aclientSecretcan't ship by being unrecognisedTwelve new self-tests, each confirmed to actually fail when the defect is introduced. Suite is 27/27.
Also added
.claude-plugin/and.mcp.jsonto the release allowlist — without that the published artifact would have shipped a package Claude Code cannot install.Collision: now confirmed, was a hypothesis
A user-level MCP server named
usableshadows the plugin's declaration. Noplugin:usable:usableappeared, while other plugins' servers did show under that prefix.I'd previously recorded this as a suspicion for Codex. It's real, and it means the MCP acceptance step can't be verified on a machine that already has such an entry. Documented with the remedy.
Not verified
Claude Code skills reaching the model. The plugin installs, but Claude Code exposes no CLI listing of available skills. The matrix records skills as ⏳ rather than assuming parity with Codex. To check, ask in a session: "Which skills do you have available?" and look for
usable:usable-knowledge-workflow.