[3metaJun]

Problem

mstack's Claude Code plugin ships skills and agents but nothing tells a fresh session to route multi-file changes or bugs with an unknown cause through /meta-mode. pstack-claude closes that gap with a SessionStart hook, but with Bash and PowerShell copies and a Cursor-style sheet. mstack needs a portable version that follows its own config layout.

Solution

• hooks/hooks.json registers a SessionStart hook (matcher startup|resume|clear|compact) running node "${CLAUDE_PLUGIN_ROOT}/scripts/session-hook.mjs". Claude Code loads hooks/hooks.json by default, so plugin.json does not reference it. validatePluginHooks rejects a duplicate manifest reference.
• scripts/session-hook.mjs is one Node script for Windows, macOS, and Linux. It prints hookSpecificOutput.additionalContext JSON from hooks/session-start-context.md (routing to mstack:meta-mode, reversible work proceeds, irreversible asks, user CLAUDE.md wins). It always exits 0 and prints nothing on any failure.
• Off switch: "sessionHook": false in ~/.config/mstack/models.json. Only boolean false disables it. A missing, unreadable, or malformed config leaves the hook on. A UTF-8 or UTF-16 LE byte-order mark and CRLF are accepted. validateModelConfig rejects a non-boolean value (small additive edit to model-config-lib.mjs).
• Validation: validate.mjs now checks the hook file, its script reference, the context file, and agents/*.md (frontmatter name equals file name, manifest agent paths exist). check-package requires the new files in the npm tarball. package.json files gains hooks.
• Docs: new guide page 12 (layers: agent coordination, principles, playbooks, user-invocable skills; the hook; autonomy stance; how to turn it off), plus README and docs/harness-adapters.md.
• The hook ships with the plugin only. The installer would have to merge into the user's settings.json, which mstack leaves to the user, so installer-only setups get no hook and the two routes cannot double-load it.
• No meta-agent-<effort> variants. Nothing in the skills dispatches by effort, agents/ is shared with Codex TOML conversion (which rejects an effort field) and OpenCode, and a Claude-only generated copy would be dead code. The guide explains claude --effort and user-owned agent files instead.

Verification

• npm test: 258 tests pass, including 8 new ones in scripts/session-hook.test.mjs (output shape through the real script, off switch with BOM, UTF-16, CRLF, missing, directory-in-place-of-file, malformed, non-boolean values, context skill names exist, manifest and hook reference checks).
• npm run check-package passes.
• claude plugin validate . --strict passes (Claude Code 2.1.289).
• Loaded the repo with claude --plugin-dir . in stream-json mode: the SessionStart:startup hook ran, exit 0, and returned the expected additionalContext.

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Model: Claude Sonnet 5.5 | Harness: Claude Code

🤖 Generated with Claude Code