fix(plugin): provision externalised MCP runtime deps on first launch

.mcp.json

@@ -1,8 +1,11 @@
 {
   "mcpServers": {
     "prd-gen": {
-      "command": "node",
-      "args": ["${CLAUDE_PLUGIN_ROOT}/mcp-server/index.js"],
+      "command": "bash",
+      "args": [
+        "${CLAUDE_PLUGIN_ROOT}/bin/ensure-deps.sh",
+        "${CLAUDE_PLUGIN_ROOT}"
+      ],
       "env": {
         "PRD_GEN_SKILL_CONFIG": "${CLAUDE_PLUGIN_ROOT}/packages/skill/skill-config.json",
         "PRD_GEN_EVIDENCE_DB": "${CLAUDE_PLUGIN_ROOT}/.prd-gen/evidence.db"

bin/ensure-deps.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+#
+# ensure-deps.sh — provision the MCP server bundle's externalised runtime
+# dependencies on first launch, then exec the server.
+#
+# The committed bundle (mcp-server/index.js) is produced by `pnpm bundle`
+# (esbuild). Three runtime dependencies are intentionally *external* to that
+# bundle and must resolve from node_modules at launch:
+#
+#   - ajv, ajv-formats — ajv's runtime-compiled validators `require()` their
+#     helpers (ajv/dist/runtime/*) via specifiers esbuild cannot statically
+#     inline, so ajv must exist on disk. Static require => needed at load.
+#   - better-sqlite3   — native addon; the platform-specific binary cannot be
+#     bundled or committed cross-platform. Loaded via dynamic import() and
+#     guarded by tryCreateEvidenceRepository => OPTIONAL: its absence only
+#     disables the evidence-DB cache, it does not block startup. Declared as
+#     an optionalDependency so a failed native build is non-fatal.
+#
+# `claude plugin install` clones repository files but runs no install step, so
+# this launcher provisions `mcp-server/node_modules` next to the bundle on the
+# first run, then hands off to node. Idempotent: it no-ops once the deps are
+# present, so steady-state launch cost is a single directory check.
+#
+# Mirrors automatised-pipeline's bin/ensure-binary.sh ensure-then-exec launcher.
+# source: coding-standards.md §2.2 (composition-root provisioning); follow-up to
+# the MCP-startup-deadlock fix (PR #2).
+#
+set -euo pipefail
+
+ROOT="${1:?usage: ensure-deps.sh <plugin-root>}"
+SERVER_DIR="${ROOT}/mcp-server"
+
+# ajv is a hard (static) dependency of the bundle; its presence is the
+# provisioning sentinel. better-sqlite3 (optional) is installed in the same
+# pass and, being an optionalDependency, will not fail the install if its
+# native build is unavailable on the host.
+if [[ ! -d "${SERVER_DIR}/node_modules/ajv" ]]; then
+  echo "prd-gen: first launch — installing MCP server runtime deps…" >&2
+  # --no-package-lock: the workspace pins versions via pnpm-lock.yaml; this is a
+  # runtime provisioning step into an ephemeral install dir, so we don't litter
+  # it with a second (npm) lockfile.
+  npm install \
+    --prefix "${SERVER_DIR}" \
+    --omit=dev --no-audit --no-fund --no-package-lock --loglevel=error >&2
+fi
+
+exec node "${SERVER_DIR}/index.js"

mcp-server/package.json

@@ -1,8 +1,15 @@
 {
   "name": "@prd-gen/mcp-server-bundle",
   "version": "0.2.0",
-  "description": "Self-contained ESM bundle of the prd-spec-generator MCP server. Built by `pnpm bundle` from the workspace TypeScript source. The marketplace .mcp.json runs index.js directly via `node`.",
+  "description": "Self-contained ESM bundle of the prd-spec-generator MCP server. Built by `pnpm bundle` from the workspace TypeScript source. `bin/ensure-deps.sh` provisions the externalised runtime deps below on first launch, then runs index.js via `node`.",
   "type": "module",
   "main": "./index.js",
-  "private": true
+  "private": true,
+  "dependencies": {
+    "ajv": "^8.17.1",
+    "ajv-formats": "^3.0.1"
+  },
+  "optionalDependencies": {
+    "better-sqlite3": "^11.7.0"
+  }
 }