fix(web): stage owned builtin extensions under /vscode/extensions

Owned esbuild workbench loads system extension resources from
/vscode/extensions (relative to FILE_ROOT). Stage
vendor/vscode/.build/web/extensions when keeping or packaging the owned
tree so TS/JSON/language features stop 404ing.

Author: aaqaishtyaq

docs/vscode-web.md

@@ -26,6 +26,27 @@ Dual mode (workbench):
 
 ### Dogfood (fast)
 
+### Owned web + system extensions
+
+Owned `dist/vscode-web` (esbuild) sets `_VSCODE_FILE_ROOT` to `/vscode/out/`. VS Code loads
+**system** extension files from `/vscode/extensions/*` (path `vs/../../extensions`).
+
+`scripts/fetch-vscode-web.sh` and `build-web.sh --package` stage
+`vendor/vscode/.build/web/extensions` → `dist/vscode-web/extensions`.
+
+Without that folder you get console errors like:
+
+- `ExtensionResourceLoaderService.readExtensionResource … Not Found`
+- `Activating extension 'vscode.typescript-language-features' failed: Not Found`
+- 404 on `/vscode/node_modules/...` (dogfood AMD only; owned ESM usually ignores these)
+
+**Harmless noise in pure browser mode:** `file:///.copilot`, `file:///.claude`, `file:///.agents`
+— VS Code agent/prompt discovery using the HTML File System API. No local disk handle is
+registered; safe to ignore.
+
+Product (ZCode) extensions stay at **`/extensions/zcode-*`** (separate from system
+`/vscode/extensions`).
+
 Third-party npm package packaging Microsoft’s web compile (not our pin; labeled dogfood):
 
 ```bash
@@ -91,7 +112,7 @@ Bootstrap injects `location.host` so extension URIs are absolute same-origin.
 | Load VS Code Web workbench | ✅ `/vscode` + `/` |
 | ZCode product.json | ✅ |
 | Dual-mode product payload | ✅ |
-| Built-in extensions served | ✅ `/extensions/*` |
+| Built-in extensions served | ✅ `/vscode/extensions/*` (owned web) + `/extensions/zcode-*` (product) |
 | `zcode-opfs` FileSystemProvider | ✅ seeded sample workspace |
 | Owned 1.129 web compile in CI | ⏳ scripts ready (`build-web.sh --package`); dogfood until staged |
 | Browser SCM (`zcode-git`) | ✅ status / commit / push over IDB |

scripts/build-web.sh

@@ -245,6 +245,27 @@ package_web() {
   fi
   [[ "${entry}" != "unknown" ]] || die "staged tree missing workbench entry under ${OUT_DIR}/out/vs"
 
+  # Workbench loads system extension files from /vscode/extensions (not only packageJSON embeds).
+  local web_ext_src=""
+  for c in "${VSCODE}/.build/web/extensions" "${VSCODE}/.build/extensions"; do
+    if [[ -d "${c}/typescript-language-features" ]] || [[ -d "${c}/json-language-features" ]]; then
+      web_ext_src="${c}"
+      break
+    fi
+  done
+  if [[ -n "${web_ext_src}" ]]; then
+    log "Staging builtin web extensions from ${web_ext_src}"
+    rm -rf "${OUT_DIR}/extensions"
+    mkdir -p "${OUT_DIR}/extensions"
+    if command -v rsync >/dev/null 2>&1; then
+      rsync -a "${web_ext_src}/" "${OUT_DIR}/extensions/"
+    else
+      cp -R "${web_ext_src}/." "${OUT_DIR}/extensions/"
+    fi
+  else
+    log "WARN: missing ${VSCODE}/.build/web/extensions — language features will 404 at runtime"
+  fi
+
   cat > "${OUT_DIR}/.zcode-vscode-web.json" <<EOF
 {
   "source": "owned",
@@ -254,7 +275,8 @@ package_web() {
   "vscodeCommit": "$(cd "${VSCODE}" && git rev-parse HEAD)",
   "vscodeTag": "$(cd "${VSCODE}" && git describe --tags --always 2>/dev/null || echo unknown)",
   "builtAt": "$(date -u +%Y-%m-%dT%H:%M:%SZ)",
-  "node": "$(node -v)"
+  "node": "$(node -v)",
+  "webExtensions": "$( [[ -d "${OUT_DIR}/extensions/typescript-language-features" ]] && echo yes || echo no )"
 }
 EOF
   mkdir -p "${ROOT}/dist/web"

scripts/fetch-vscode-web.sh

@@ -14,12 +14,51 @@ TARBALL_URL="${VSCODE_WEB_TARBALL_URL:-https://registry.npmjs.org/vscode-web/-/v
 log() { printf '==> %s\n' "$*"; }
 die() { echo "error: $*" >&2; exit 1; }
 
+# Owned esbuild/gulp workbench embeds builtin extension *metadata* in the bundle, but
+# loads language configs / extension files from /vscode/extensions/* (see
+# builtinExtensionsPath = vs/../../extensions relative to _VSCODE_FILE_ROOT=/vscode/out/).
+# Stage web-built extensions next to out/ so TS/JSON/language features activate.
+stage_owned_web_extensions() {
+  local dest="${OUT}/extensions"
+  local candidates=(
+    "${ROOT}/vendor/vscode/.build/web/extensions"
+    "${ROOT}/vendor/vscode/.build/extensions"
+  )
+  local src=""
+  for c in "${candidates[@]}"; do
+    if [[ -d "${c}/typescript-language-features" ]] || [[ -d "${c}/json-language-features" ]]; then
+      src="${c}"
+      break
+    fi
+  done
+  if [[ -z "${src}" ]]; then
+    log "WARN: no vendor/vscode/.build/web/extensions — TS/JSON language features will 404"
+    log "      rebuild with: cd vendor/vscode && npm run gulp compile-web-extensions-build"
+    return 0
+  fi
+  if [[ -d "${dest}/typescript-language-features" ]] && [[ -d "${dest}/json-language-features" ]]; then
+    log "Builtin web extensions already present at dist/vscode-web/extensions"
+    return 0
+  fi
+  log "Staging builtin web extensions from ${src}"
+  rm -rf "${dest}"
+  mkdir -p "${OUT}"
+  if command -v rsync >/dev/null 2>&1; then
+    rsync -a "${src}/" "${dest}/"
+  else
+    mkdir -p "${dest}"
+    cp -R "${src}/." "${dest}/"
+  fi
+  log "Staged $(ls -1 "${dest}" 2>/dev/null | wc -l | tr -d ' ') builtin web extensions → dist/vscode-web/extensions"
+}
+
 # Keep already-staged owned tree (do not clobber with dogfood npm)
 if [[ -f "${OUT}/.zcode-vscode-web.json" ]] \
   && grep -q '"source": "owned"' "${OUT}/.zcode-vscode-web.json" 2>/dev/null \
   && { [[ -f "${OUT}/out/vs/workbench/workbench.web.main.internal.js" ]] \
     || [[ -f "${OUT}/out/vs/loader.js" ]]; }; then
   log "Keeping existing owned dist/vscode-web"
+  stage_owned_web_extensions
   exit 0
 fi
 
@@ -48,6 +87,7 @@ for c in "${OWNED_CANDIDATES[@]}"; do
   "stagedAt": "$(date -u +%Y-%m-%dT%H:%M:%SZ)"
 }
 EOF
+    stage_owned_web_extensions
     log "Staged owned build → dist/vscode-web"
     exit 0
   fi