Primitive catalog — the decision layer for plugin composition

Use this catalog while drafting a Primitive Decision Record (PDR) in design/CONTRACT.md. Each card in references/cards/ is a decision-oriented distillation: exact syntax, version floors, context costs, and failure modes. For exhaustive syntax the cards point to the official Claude Code docs (https://code.claude.com/docs — fetch llms.txt for the page index) — never duplicate that encyclopedia here.

Rules of use:

• Answer every loaded card's Consequence prompts in the PDR chain columns C1–C6 before committing to that primitive.
• When a card's Reject when criteria match, record the rejection as that capability's rejected alternative, naming the chain step that killed it.
• When a card's Eval hooks section cannot name a grader that observes the primitive in the target design, the choice is unverifiable → unbuildable (the C5 hard gate).

Master rubric 1 — who holds the plan

Escalate only as far as the capability demands; every step up costs tokens, latency, or interactivity.

Master rubric 2 — loop primitives

A plugin cannot ship /goal itself. The distributable equivalent is a prompt- or agent-type Stop hook in hooks/hooks.json (honoring stop_hook_active and the 8-block cap, CLAUDE_CODE_STOP_HOOK_BLOCK_CAP), plus documented "goal recipes" — pre-written ≤4,000-char conditions users paste into /goal. Note: scheduled tasks cannot invoke disable-model-invocation: true skills (v2.1.196+). Full loop mechanics: references/cards/loops-card.md.

Master rubric 3 — MCP server vs bundled script

Does the capability need persistent connection state, OAuth to a remote API,
server push (channels), elicitation dialogs, MCP resources/prompts, or a large
tool surface (tool search scales)?
├─ YES → bundle an MCP server (.mcp.json at plugin root)      → mcp-card.md
└─ NO
   ├─ One-shot computation or CLI call, no connection state
   │    → bundled stdlib script + skill with
   │      allowed-tools: Bash(${CLAUDE_SKILL_DIR}/scripts/x.sh *)
   │      (zero prompts, no server lifecycle, no approval dialog,
   │       no timeout design, headless-safe)                   → skills-card.md
   ├─ Long-running local watch (tail a log, poll a queue)      → monitors-bin-card.md
   └─ CLI users should call directly by name                   → bin/ on PATH, monitors-bin-card.md

Default to the script. MCP must earn its lifecycle cost: approval prompts, trust dialogs, timeout/idle design, headless auth preflight, and stdio's never-reconnects failure mode.

Card index

Load only the cards relevant to the candidate compositions under discussion.

• references/cards/skills-card.md — load when any capability could be a skill or command: invocation-control matrix (disable-model-invocation vs user-invocable), 1,536-char description cap and 1% listing budget, arguments, the !-backtick dynamic injection and its policy fallback, context: fork narrowing, 5k/25k compaction budgets, paths scoping, model/effort routing, stacking stop rule.
• references/cards/hooks-card.md — load when behavior must be enforced rather than suggested, or automated at a lifecycle point: 30-event catalog with per-event matcher vocabulary, five executor types and their selection rule, exit-code discipline, per-event output schemas, Stop-loop mechanics, headless gaps.
• references/cards/agents-teams-card.md — load when delegating to subagents or coordinating an agent team: plugin frontmatter stripping and its two workarounds, background 19-tool filter, memory: project, isolation: worktree base-branch gotcha, dual-mode bodies, resume-via-SendMessage, team task DAGs, plan approval, TaskCompleted gates.
• references/cards/mcp-card.md — load when integrating external systems: transport selection, plugin-scoped tool naming, tool search and 2KB instruction discovery, timeouts and backgrounding, tools vs resources vs prompts vs elicitation vs channels, headless auth preflight, and the honest MCP-apps status note.
• references/cards/lsp-card.md — load when the target plugin serves a programming language and post-edit diagnostics or code navigation would help: configure-never-bundle rule, official-plugin dependency route, first-server-wins, diagnostics toggle.
• references/cards/workflows-card.md — load when a capability fans out over many homogeneous items: agent()/pipeline() with schema and label, 16/1000 caps, resume replay order, the ultracode-never-fires-headless trap, always-pair-with-a-script rule.
• references/cards/loops-card.md — load when a capability is "keep working until done": /goal condition authoring, evaluator mechanics, shipped Stop-hook productization, /loop, ralph/karpathy outer-loop patterns.
• references/cards/headless-card.md — load when anything must run under claude -p (CI, evals, routines): --bare hermeticity, output formats, --json-schema, system/init gating, permission rule syntax, session chaining.
• references/cards/worktrees-card.md — load when work needs filesystem isolation: --worktree lifecycle, -p never cleans up, worktree.baseRef, .worktreeinclude, sharing semantics.
• references/cards/monitors-bin-card.md — load for long-running background watchers (monitors/monitors.json, when: on-skill-invoke) and bin/ executables added to the Bash PATH.
• references/cards/output-styles-settings-card.md — load when the plugin needs a persona shift or fleet display: output styles vs CLAUDE.md vs agents, force-for-plugin, plugin settings.json (agent, subagentStatusLine only).
• references/cards/distribution-card.md — load when deciding install level and lifecycle: marketplaces, version strategy (SHA vs pinned semver), dependencies, renames, seed dirs for CI, cloud-session declaration.