diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 000000000..292cb435d
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,16 @@
+version: 2
+updates:
+  # Keep third-party Actions SHA pins current. See CONTRIBUTING.md — when
+  # reviewing these bumps, verify the SHA corresponds to the claimed tag by
+  # running `gh api repos/<owner>/<action>/git/refs/tags/<tag>` before merge.
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: chore
+      include: scope
+    labels:
+      - dependencies
+      - ci
diff --git a/.github/release-drafter.yml b/.github/release-drafter.yml
new file mode 100644
index 000000000..378a60e2c
--- /dev/null
+++ b/.github/release-drafter.yml
@@ -0,0 +1,53 @@
+# release-drafter config — used only for PR autolabeling by
+# `.github/workflows/pr-labeler.yml` (the workflow passes `disable-releaser: true`,
+# so the draft-release side of release-drafter never runs).
+#
+# The labels applied here are the same ones `.github/release.yml` maps to
+# categorized release-notes sections.
+#
+# `sync-labels: true` removes managed autolabels that no longer match the PR —
+# critical for the breaking-change case: if a PR title drops the `!` or the body
+# drops `BREAKING CHANGE:`, the `breaking` label is pulled off automatically.
+
+# Required by release-drafter; not used because releaser is disabled.
+name-template: 'unused'
+tag-template: 'unused'
+template: |
+  $CHANGES
+
+sync-labels: true
+
+autolabeler:
+  - label: enhancement
+    title:
+      - '/^feat(\([^)]+\))?!?:/i'
+  - label: bug
+    title:
+      - '/^fix(\([^)]+\))?!?:/i'
+  - label: performance
+    title:
+      - '/^perf(\([^)]+\))?!?:/i'
+  - label: refactor
+    title:
+      - '/^refactor(\([^)]+\))?!?:/i'
+  - label: documentation
+    title:
+      - '/^docs(\([^)]+\))?!?:/i'
+  - label: test
+    title:
+      - '/^test(\([^)]+\))?!?:/i'
+  - label: ci
+    title:
+      - '/^ci(\([^)]+\))?!?:/i'
+  - label: dependencies
+    title:
+      - '/^(build|deps)(\([^)]+\))?!?:/i'
+  - label: chore
+    title:
+      - '/^(chore|revert)(\([^)]+\))?!?:/i'
+  # Breaking-change marker: either `!` in the type prefix or `BREAKING CHANGE:` in body.
+  - label: breaking
+    title:
+      - '/^[a-z]+(\([^)]+\))?!:/i'
+    body:
+      - '/BREAKING[ -]CHANGE:/i'
diff --git a/.github/scripts/check-workflow-concurrency.py b/.github/scripts/check-workflow-concurrency.py
new file mode 100644
index 000000000..300cc7f4b
--- /dev/null
+++ b/.github/scripts/check-workflow-concurrency.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+"""Enforce the GitHub Actions concurrency convention.
+
+See CONTRIBUTING.md -> "GitHub Actions — Concurrency Convention" for the rules.
+
+Invoked from .github/workflows/ci-quality.yml. Runs locally too:
+    python3 .github/scripts/check-workflow-concurrency.py .github/workflows
+
+Rules:
+  1. Every entry-point (non-reusable) workflow declares a top-level
+     `concurrency:` block.
+  2. Reusable workflows (on: workflow_call ONLY) do NOT declare one.
+  3. The `concurrency.group` expression MUST reference either
+     `${{ github.workflow }}` or a literal `CI-` prefix (the documented
+     ci.yml reusable-workflow-safe exception). This is checked by substring
+     containment rather than prefix match because ci.yml's group is a
+     conditional expression that resolves to a `CI-…` literal at runtime.
+
+We deliberately do not use a YAML library — keeps the script dependency-free
+on any vanilla runner. `on:` block parsing is line-based and handles both the
+flat (`on: workflow_call`) and mapping (`on:\n  workflow_call:`) forms.
+"""
+
+from __future__ import annotations
+
+import pathlib
+import re
+import sys
+
+
+REQUIRED_TOKENS = ("${{ github.workflow }}", "CI-")
+
+
+def is_reusable(lines: list[str]) -> bool:
+    """Return True iff the workflow's `on:` block names only `workflow_call`."""
+    in_on = False
+    on_indent: int | None = None
+    keys: list[str] = []
+
+    for raw in lines:
+        # Skip blank lines and comments
+        stripped = raw.strip()
+        if not stripped or stripped.startswith("#"):
+            continue
+
+        indent = len(raw) - len(raw.lstrip(" "))
+
+        if not in_on:
+            if raw.startswith("on:"):
+                remainder = raw[len("on:"):].strip()
+                if not remainder:
+                    # `on:` followed by indented mapping on next lines
+                    in_on = True
+                    on_indent = indent
+                    continue
+                if remainder.startswith("[") and remainder.endswith("]"):
+                    # Flow-style list: on: [workflow_call]
+                    items = [
+                        item.strip() for item in remainder.strip("[]").split(",")
+                    ]
+                    return items == ["workflow_call"]
+                # Scalar form: on: workflow_call  (or a single other event)
+                return remainder == "workflow_call"
+            continue
+
+        # Inside the `on:` block; stop when indentation returns to <= on_indent
+        if on_indent is not None and indent <= on_indent:
+            break
+
+        # Only consider keys at on_indent + indentation step (anything deeper
+        # is nested config like `types:`)
+        if ":" not in stripped:
+            continue
+        # Heuristic: first-level event keys are those with indent == on_indent + 2
+        # (the canonical step for a 2-space YAML doc). We collect all first-level
+        # keys by tracking the smallest indent seen inside the block.
+        keys.append((indent, stripped.split(":", 1)[0].strip()))
+
+    if not keys:
+        return False
+
+    # Take only the outermost-indented keys as the event list
+    min_indent = min(i for i, _ in keys)
+    events = [name for i, name in keys if i == min_indent]
+    return events == ["workflow_call"]
+
+
+CONCURRENCY_RE = re.compile(r"^concurrency:\s*$")
+GROUP_RE = re.compile(r"^\s+group:\s*(.+?)\s*$")
+
+
+def extract_group_key(lines: list[str]) -> str | None:
+    """Return the `group:` value of the top-level `concurrency:` block, or None."""
+    for idx, raw in enumerate(lines):
+        if CONCURRENCY_RE.match(raw):
+            # Scan forward until we leave the concurrency block (next top-level key
+            # is at column 0 and ends with `:`).
+            for follow in lines[idx + 1:]:
+                if follow and not follow.startswith(" ") and follow.rstrip().endswith(":"):
+                    break
+                m = GROUP_RE.match(follow)
+                if m:
+                    return m.group(1).strip().strip("'").strip('"')
+            break
+    return None
+
+
+def has_top_level_concurrency(lines: list[str]) -> bool:
+    return any(CONCURRENCY_RE.match(raw) for raw in lines)
+
+
+def check(workflows_dir: pathlib.Path) -> int:
+    fail = 0
+    files = sorted(
+        list(workflows_dir.glob("*.yml")) + list(workflows_dir.glob("*.yaml"))
+    )
+    for path in files:
+        lines = path.read_text(encoding="utf-8").splitlines()
+        reusable = is_reusable(lines)
+        has_conc = has_top_level_concurrency(lines)
+
+        if reusable:
+            if has_conc:
+                print(
+                    f"::error file={path}::Reusable workflow (on: workflow_call) "
+                    "must NOT declare its own concurrency block — it inherits "
+                    "from the caller. See CONTRIBUTING.md -> GitHub Actions — "
+                    "Concurrency Convention."
+                )
+                fail = 1
+            continue
+
+        if not has_conc:
+            print(
+                f"::error file={path}::Missing top-level concurrency block. "
+                "See CONTRIBUTING.md -> GitHub Actions — Concurrency Convention."
+            )
+            fail = 1
+            continue
+
+        group = extract_group_key(lines)
+        if group is None:
+            print(
+                f"::error file={path}::concurrency block is missing a "
+                "`group:` key."
+            )
+            fail = 1
+            continue
+
+        if not any(token in group for token in REQUIRED_TOKENS):
+            print(
+                f"::error file={path}::concurrency.group `{group}` must "
+                f"reference one of {REQUIRED_TOKENS}. See CONTRIBUTING.md -> "
+                "GitHub Actions — Concurrency Convention."
+            )
+            fail = 1
+
+    return fail
+
+
+def main(argv: list[str]) -> int:
+    if len(argv) != 2:
+        print(f"usage: {argv[0]} <workflows-dir>", file=sys.stderr)
+        return 2
+    workflows_dir = pathlib.Path(argv[1])
+    if not workflows_dir.is_dir():
+        print(f"not a directory: {workflows_dir}", file=sys.stderr)
+        return 2
+    return check(workflows_dir)
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/.github/workflows/ci-e2e.yml b/.github/workflows/ci-e2e.yml
index 675d9b382..a017af628 100644
--- a/.github/workflows/ci-e2e.yml
+++ b/.github/workflows/ci-e2e.yml
@@ -11,8 +11,8 @@ jobs:
     outputs:
       web_changed: ${{ steps.filter.outputs.web }}
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: dorny/paths-filter@fbd0ab8f3e69293af611ebaee6363fc25e6d187d # v3
         id: filter
         with:
           filters: |
@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 20
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - uses: ./.github/actions/setup-gitnexus-web
 
@@ -74,7 +74,7 @@ jobs:
 
       - name: Upload test results
         if: always()
-        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           name: e2e-results
           path: |
diff --git a/.github/workflows/ci-global-upgrade.yml b/.github/workflows/ci-global-upgrade.yml
new file mode 100644
index 000000000..e181f46ad
--- /dev/null
+++ b/.github/workflows/ci-global-upgrade.yml
@@ -0,0 +1,113 @@
+name: Global Install Upgrade Smoke
+
+# Catches regressions where `npm install -g gitnexus@<new>` fails to upgrade
+# cleanly over a prior global install. Prior precedent: issue #836 and PR #843's
+# incomplete fix slipped past CI because no global-upgrade test existed.
+#
+# Reusable workflow — only callable from ci.yml. Concurrency is governed by the
+# caller (ci.yml), so no `concurrency:` block here.
+
+on:
+  workflow_call:
+
+jobs:
+  global-upgrade:
+    name: ${{ matrix.os }} / upgrade over ${{ matrix.prior }}
+    strategy:
+      fail-fast: false
+      matrix:
+        # macOS is the reporter's platform (issue #836) and the highest-risk
+        # surface for npm global-install rmdir behavior. Linux and Windows
+        # provide cross-platform regression coverage.
+        os: [macos-latest, ubuntu-latest, windows-latest]
+        # Prior version that must be upgraded OVER. Should be a published rc
+        # that preceded the fix. Bump when a known-bad version changes.
+        prior: ['1.6.2-rc.8']
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - uses: ./.github/actions/setup-gitnexus
+        with:
+          build: 'false'
+
+      - name: Install prior published version globally
+        run: npm install -g gitnexus@${{ matrix.prior }}
+
+      - name: Verify prior version installed
+        run: gitnexus --version
+
+      - name: Pack current branch
+        working-directory: gitnexus
+        run: npm pack
+        shell: bash
+
+      - name: Compute packed tarball path
+        id: tarball
+        working-directory: gitnexus
+        run: |
+          TARBALL=$(ls gitnexus-*.tgz | head -1)
+          echo "path=$(pwd)/$TARBALL" >> "$GITHUB_OUTPUT"
+        shell: bash
+
+      - name: Upgrade over prior version (the actual regression test)
+        run: npm install -g "${{ steps.tarball.outputs.path }}"
+        shell: bash
+
+      - name: Verify upgraded version runs
+        run: gitnexus --version
+
+      - name: Verify vendor/ has no nested node_modules after install
+        shell: bash
+        run: |
+          # The original #836 bug was about vendor/tree-sitter-proto/node_modules/
+          # blocking rmdir on upgrade. That is what the fix eliminates. A
+          # vendor/tree-sitter-proto/build/ directory can still appear because
+          # node-gyp-build compiles through the npm-created symlink; the
+          # contents are plain object files and .node binaries that rmdir
+          # handles fine, evidenced by this test getting past the upgrade step.
+          GLOBAL_PREFIX=$(npm root -g)
+          if [ -d "$GLOBAL_PREFIX/gitnexus/vendor/tree-sitter-proto" ]; then
+            echo "=== Contents of global vendor/tree-sitter-proto/ ==="
+            ls -la "$GLOBAL_PREFIX/gitnexus/vendor/tree-sitter-proto/"
+            if [ -d "$GLOBAL_PREFIX/gitnexus/vendor/tree-sitter-proto/node_modules" ]; then
+              echo "::error::vendor/tree-sitter-proto/node_modules/ was created — this is the #836 hazard"
+              exit 1
+            fi
+          fi
+
+  ignore-scripts:
+    name: ${{ matrix.os }} / --ignore-scripts degraded mode
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-latest, ubuntu-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - uses: ./.github/actions/setup-gitnexus
+        with:
+          build: 'false'
+
+      - name: Pack current branch
+        working-directory: gitnexus
+        run: npm pack
+        shell: bash
+
+      - name: Compute packed tarball path
+        id: tarball
+        working-directory: gitnexus
+        run: |
+          TARBALL=$(ls gitnexus-*.tgz | head -1)
+          echo "path=$(pwd)/$TARBALL" >> "$GITHUB_OUTPUT"
+        shell: bash
+
+      - name: Install globally with --ignore-scripts
+        run: npm install -g --ignore-scripts "${{ steps.tarball.outputs.path }}"
+        shell: bash
+
+      - name: Verify CLI boots without postinstall (proto parsing may be unavailable)
+        run: gitnexus --version
diff --git a/.github/workflows/ci-quality.yml b/.github/workflows/ci-quality.yml
index 9a5b9fedd..5a0da5fd1 100644
--- a/.github/workflows/ci-quality.yml
+++ b/.github/workflows/ci-quality.yml
@@ -8,8 +8,8 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 20
           cache: npm
@@ -21,8 +21,8 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 20
           cache: npm
@@ -34,7 +34,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: ./.github/actions/setup-gitnexus
       - run: npx tsc --noEmit
         working-directory: gitnexus
@@ -43,7 +43,30 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: ./.github/actions/setup-gitnexus-web
       - run: npx tsc -b --noEmit
         working-directory: gitnexus-web
+
+  # Enforces the convention documented in CONTRIBUTING.md → "GitHub Actions —
+  # Concurrency Convention":
+  #   1. Every entry-point (non-reusable) workflow declares a top-level
+  #      `concurrency:` block.
+  #   2. Reusable workflows (`on: workflow_call` only) do NOT declare one —
+  #      they inherit concurrency from the caller.
+  #   3. The concurrency group key starts with `${{ github.workflow }}` or
+  #      the literal `CI-` prefix (the documented ci.yml exception for
+  #      reusable-workflow-safe grouping).
+  # Reusability is detected by parsing each workflow's `on:` block, not an
+  # allowlist, so new reusable workflows never produce false positives.
+  workflow-convention:
+    name: Workflow concurrency convention
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Validate workflow concurrency convention
+        shell: bash
+        run: |
+          set -euo pipefail
+          python3 .github/scripts/check-workflow-concurrency.py .github/workflows
diff --git a/.github/workflows/ci-report.yml b/.github/workflows/ci-report.yml
index 2a6e5cea8..a1fa33219 100644
--- a/.github/workflows/ci-report.yml
+++ b/.github/workflows/ci-report.yml
@@ -14,6 +14,16 @@ permissions:
   contents: read # needed for sparse checkout of vitest.config.ts
   pull-requests: write # needed to post sticky PR comment
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Serialize sticky-comment writes per PR so two rapid CI completions don't race.
+# Internal PRs surface in `pull_requests[0].number`. Fork PRs leave that array empty,
+# so we fall back to `<head-repo-full-name>/<head-branch>`, which is stable across
+# reruns and subsequent pushes for the same fork PR (unlike `workflow_run.id` which
+# is unique per run and therefore does not serialize anything).
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.workflow_run.pull_requests[0].number || format('{0}/{1}', github.event.workflow_run.head_repository.full_name, github.event.workflow_run.head_branch) }}
+  cancel-in-progress: false
+
 jobs:
   pr-report:
     name: PR Report
@@ -113,7 +123,7 @@ jobs:
 
       - name: Checkout (for vitest config)
         if: steps.meta.outputs.skip != 'true'
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           sparse-checkout: gitnexus/vitest.config.ts
           sparse-checkout-cone-mode: false
diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 6a20032c6..27eb75383 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 25
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: ./.github/actions/setup-gitnexus
         with:
           build: 'true'
@@ -43,7 +43,7 @@ jobs:
 
       - name: Upload test reports
         if: always()
-        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           name: test-reports
           path: |
@@ -63,7 +63,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 25
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: ./.github/actions/setup-gitnexus
         with:
           build: 'true'
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ba7184ace..e2eeeaab2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,9 +9,20 @@ on:
     paths-ignore: ['**.md', 'docs/**', 'LICENSE']
   workflow_call:
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Hardcoded `CI-` prefix (not `${{ github.workflow }}`) because this workflow is
+# invoked as a reusable workflow from publish.yml and release-candidate.yml. In
+# called-workflow context `github.workflow` evaluation is ambiguous across GitHub
+# Actions versions, and a prefix that could resolve to the caller's name would
+# share a concurrency group with the caller → deadlock. A literal prefix is
+# immune. Direct `push`/`pull_request` invocations use `CI-<ref>`; invocations
+# from a reusable-workflow caller fall into a per-run-unique group that never
+# serializes with the caller.
+# cancel-in-progress is event-aware: cancel superseded PR runs, queue every other
+# event (push to main, workflow_call from publish.yml, etc.).
 concurrency:
-  group: ci-${{ github.ref }}
-  cancel-in-progress: true
+  group: ${{ (github.event_name == 'pull_request' || github.event_name == 'push') && format('CI-{0}', github.ref) || format('CI-nested-{0}', github.run_id) }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 # ── Reusable workflow orchestration ─────────────────────────────────
 # Each concern lives in its own workflow file for maintainability:
@@ -37,6 +48,11 @@ jobs:
     permissions:
       contents: read
 
+  global-upgrade:
+    uses: ./.github/workflows/ci-global-upgrade.yml
+    permissions:
+      contents: read
+
   # ── Save PR metadata for the reporting workflow ─────────────────
   # The ci-report.yml workflow (triggered by workflow_run) needs the
   # PR number and job results to post a comment.  We save them as an
@@ -45,7 +61,7 @@ jobs:
   save-pr-meta:
     name: Save PR Metadata
     if: always() && github.event_name == 'pull_request'
-    needs: [quality, tests, e2e]
+    needs: [quality, tests, e2e, global-upgrade]
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
@@ -56,6 +72,7 @@ jobs:
           QUALITY: ${{ needs.quality.result }}
           TESTS: ${{ needs.tests.result }}
           E2E: ${{ needs.e2e.result }}
+          GLOBAL_UPGRADE: ${{ needs.global-upgrade.result }}
         run: |
           mkdir -p pr-meta
           echo "$PR_NUMBER"  > pr-meta/pr_number
@@ -74,7 +91,7 @@ jobs:
           cp pr-meta/e2e_result      pr-meta/e2e-result
 
       - name: Upload PR metadata
-        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           name: pr-meta
           path: pr-meta/
@@ -84,7 +101,7 @@ jobs:
   # Single required check for branch protection.
   ci-status:
     name: CI Gate
-    needs: [quality, tests, e2e]
+    needs: [quality, tests, e2e, global-upgrade]
     if: always()
     runs-on: ubuntu-latest
     timeout-minutes: 5
@@ -95,10 +112,12 @@ jobs:
           QUALITY: ${{ needs.quality.result }}
           TESTS: ${{ needs.tests.result }}
           E2E: ${{ needs.e2e.result }}
+          GLOBAL_UPGRADE: ${{ needs.global-upgrade.result }}
         run: |
-          echo "Quality:     $QUALITY"
-          echo "Tests:       $TESTS"
-          echo "E2E:         $E2E"
+          echo "Quality:        $QUALITY"
+          echo "Tests:          $TESTS"
+          echo "E2E:            $E2E"
+          echo "Global upgrade: $GLOBAL_UPGRADE"
           if [[ "$QUALITY" != "success" ]] ||
              [[ "$TESTS" != "success" ]]; then
             echo "::error::Quality or test jobs failed"
@@ -108,3 +127,7 @@ jobs:
             echo "::error::E2E job failed"
             exit 1
           fi
+          if [[ "$GLOBAL_UPGRADE" != "success" && "$GLOBAL_UPGRADE" != "skipped" ]]; then
+            echo "::error::Global upgrade smoke failed"
+            exit 1
+          fi
diff --git a/.github/workflows/claude-code-review.yml b/.github/workflows/claude-code-review.yml
index 82a65f844..d9d9decf6 100644
--- a/.github/workflows/claude-code-review.yml
+++ b/.github/workflows/claude-code-review.yml
@@ -16,9 +16,10 @@ on:
   issue_comment:
     types: [created]
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
 # Serialize per-PR to avoid racing review comments.
 concurrency:
-  group: claude-review-${{ github.event.issue.number || github.event.pull_request.number }}
+  group: ${{ github.workflow }}-${{ github.event.issue.number || github.event.pull_request.number }}
   cancel-in-progress: false
 
 jobs:
@@ -76,7 +77,7 @@ jobs:
             core.setOutput('branch', pr.head.ref);
 
       - name: Checkout PR head
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           repository: ${{ steps.pr.outputs.repo }}
           ref: ${{ steps.pr.outputs.sha }}
diff --git a/.github/workflows/claude.yml b/.github/workflows/claude.yml
index 407b2fcf8..c4a2e9450 100644
--- a/.github/workflows/claude.yml
+++ b/.github/workflows/claude.yml
@@ -10,9 +10,10 @@ on:
   pull_request_review:
     types: [submitted]
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
 # Serialize per-PR/issue to avoid racing comments.
 concurrency:
-  group: claude-code-${{ github.event.issue.number || github.event.pull_request.number || github.event.issue.id }}
+  group: ${{ github.workflow }}-${{ github.event.issue.number || github.event.pull_request.number || github.event.issue.id }}
   cancel-in-progress: false
 
 jobs:
@@ -90,7 +91,7 @@ jobs:
             core.setOutput('branch', pr.head.ref);
 
       - name: Checkout repository
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           repository: ${{ steps.pr.outputs.is_pr == 'true' && steps.pr.outputs.repo || github.repository }}
           ref: ${{ steps.pr.outputs.is_pr == 'true' && steps.pr.outputs.sha || '' }}
diff --git a/.github/workflows/pr-description-check.yml b/.github/workflows/pr-description-check.yml
index d722dfff3..de562fd35 100644
--- a/.github/workflows/pr-description-check.yml
+++ b/.github/workflows/pr-description-check.yml
@@ -8,8 +8,9 @@ on:
 permissions:
   pull-requests: write
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
 concurrency:
-  group: pr-desc-${{ github.event.pull_request.number }}
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
   cancel-in-progress: true
 
 jobs:
diff --git a/.github/workflows/pr-labeler.yml b/.github/workflows/pr-labeler.yml
new file mode 100644
index 000000000..aab2fcaef
--- /dev/null
+++ b/.github/workflows/pr-labeler.yml
@@ -0,0 +1,113 @@
+name: PR Conventional Labeler
+
+# Two workflows in one file with different triggers, matched to the minimum
+# privilege each needs:
+#
+#   validate-title (on: pull_request)
+#     Fork-safe. Runs with the PR-head's read-only GITHUB_TOKEN. Uses
+#     `amannn/action-semantic-pull-request` to fail the check when the PR
+#     title doesn't follow the conventional-commit format. Because the
+#     action only reads the event payload, no fork-controlled code runs.
+#
+#   autolabel (on: pull_request_target)
+#     Needs `pull-requests: write` to apply labels, so must be
+#     pull_request_target. Uses `release-drafter/release-drafter` with
+#     `disable-releaser: true` to only run the autolabeler against the
+#     `.github/release-drafter.yml` config from the BASE ref (release-
+#     drafter reads the config from the repository's default branch, NOT
+#     the PR head — verify with `gh api repos/release-drafter/release-drafter/contents/...`
+#     or a fork-test PR before merging if the repo is high-value).
+#     `sync-labels: true` in the config removes managed autolabels that no
+#     longer match (e.g. when `!` or `BREAKING CHANGE:` is dropped).
+#
+# Title format: <type>[(scope)][!]: <subject>
+#   Allowed types: feat, fix, perf, refactor, docs, test, ci, build, chore, revert, deps
+#   Trailing `!` on the type marks a breaking change.
+# See CONTRIBUTING.md → "Pull request titles".
+
+on:
+  pull_request:
+    # Title-only changes fire `edited`. `opened` and `reopened` cover creation.
+    # `synchronize` (push to the PR branch) is intentionally excluded — titles
+    # don't change on push, so it only wastes CI minutes and broadens the
+    # privileged-token exposure window on the autolabel job.
+    types: [opened, edited, reopened]
+  pull_request_target:
+    types: [opened, edited, reopened]
+
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Include `github.event_name` so `pull_request` (validate-title) and
+# `pull_request_target` (autolabel) runs for the same PR do NOT share a slot
+# and therefore cannot cancel each other — a cancelled required-check would
+# permanently block merge until the next title edit.
+# Within each trigger the latest title edit still supersedes the prior run.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  validate-title:
+    # Fork-safe job — only runs on `pull_request` (not `pull_request_target`).
+    # Token is read-only; writes a commit status that branch protection can
+    # require before merge.
+    name: Validate PR title
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      pull-requests: read
+    steps:
+      # Pinned to v5.5.3. Verify SHA via:
+      #   gh api repos/amannn/action-semantic-pull-request/git/refs/tags/v5.5.3
+      - uses: amannn/action-semantic-pull-request@0723387faaf9b38adef4775cd42cfd5155ed6017 # v5.5.3
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          types: |
+            feat
+            fix
+            perf
+            refactor
+            docs
+            test
+            ci
+            build
+            chore
+            revert
+            deps
+          requireScope: false
+          # Subject must be non-empty. We DO allow capitalized proper nouns
+          # (MCP, GitHub, API, etc.) — the old `^(?![A-Z]).+$` pattern
+          # rejected legitimate titles like `fix: MCP tool schema`.
+          subjectPattern: ^\S.{2,}$
+          subjectPatternError: |
+            The subject "{subject}" in PR title "{title}" is invalid.
+            Subjects must be at least 3 characters and must not start with whitespace.
+          wip: false
+
+  autolabel:
+    # Privileged job — runs only on `pull_request_target` so it can write labels.
+    # Never checks out fork code, never executes fork-controlled input; only
+    # reads the PR metadata (title, body, labels) and calls the GitHub API.
+    name: Apply conventional label
+    if: github.event_name == 'pull_request_target'
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      # `contents: read` is required — release-drafter's context.config() reads
+      # `.github/release-drafter.yml` from the repo's default branch via the
+      # repo-contents API. Without it the job silently 403s and no labels are
+      # applied. Job-level permissions nullify all unlisted scopes, so an
+      # explicit grant is necessary here.
+      contents: read
+      pull-requests: write
+    steps:
+      # Pinned to v6.0.0. Verify SHA via:
+      #   gh api repos/release-drafter/release-drafter/git/refs/tags/v6.0.0
+      # Note: dependabot will likely propose a bump to v6.x on first run.
+      - uses: release-drafter/release-drafter@3f0f87098bd6b5c5b9a36d49c41d998ea58f9348 # v6.0.0
+        with:
+          config-name: release-drafter.yml
+          disable-releaser: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 8a0ee6ebc..03898a267 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -7,13 +7,22 @@ on:
 
 # No workflow-level permissions — scoped per job below.
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Tag refs are unique per release, so distinct tags run in parallel. Re-pushes of the
+# same tag serialize. cancel-in-progress: false — never cancel a publish mid-flight.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: false
+
 jobs:
   ci:
     uses: ./.github/workflows/ci.yml
     permissions:
       contents: read
       actions: read
-      pull-requests: write
+      # No pull-requests:write — `ci.yml`'s save-pr-meta job is gated on
+      # `github.event_name == 'pull_request'`, so it never runs during a
+      # tag-triggered publish. Least-privilege for release-critical paths.
 
   publish:
     needs: ci
@@ -23,8 +32,8 @@ jobs:
       contents: write
       id-token: write
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 20
           registry-url: https://registry.npmjs.org
diff --git a/.github/workflows/release-candidate.yml b/.github/workflows/release-candidate.yml
index ed9bb1780..cc22f4749 100644
--- a/.github/workflows/release-candidate.yml
+++ b/.github/workflows/release-candidate.yml
@@ -38,11 +38,11 @@ on:
 # No workflow-level permissions — scoped per job below.
 permissions: {}
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Serialize all runs on the same ref (push + workflow_dispatch) to prevent two publishes
+# racing on the rc counter. cancel-in-progress: false — the earlier merge publishes first.
 concurrency:
-  # Serialize all runs on the same ref (push + workflow_dispatch) to prevent
-  # two publishes racing on the rc counter. Do not cancel an in-progress run
-  # when a newer one is queued — we want the earlier merge to publish first.
-  group: release-candidate-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: false
 
 jobs:
@@ -62,7 +62,7 @@ jobs:
       should_run: ${{ steps.decide.outputs.should_run }}
       head_sha: ${{ steps.decide.outputs.head_sha }}
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           fetch-depth: 0
           fetch-tags: true
@@ -126,12 +126,12 @@ jobs:
       contents: write # push rc tag + marker
       id-token: write # npm provenance
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           fetch-depth: 0
           fetch-tags: true
 
-      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
+      - uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: 20
           registry-url: https://registry.npmjs.org
diff --git a/.github/workflows/triage-sweep.yml b/.github/workflows/triage-sweep.yml
index ba5514dbf..43d67828d 100644
--- a/.github/workflows/triage-sweep.yml
+++ b/.github/workflows/triage-sweep.yml
@@ -47,8 +47,10 @@ permissions:
   issues: write
   pull-requests: write
 
+# Concurrency convention: see CONTRIBUTING.md → "GitHub Actions — Concurrency Convention".
+# Single global slot — newest manual dispatch supersedes any in-flight run.
 concurrency:
-  group: triage-sweep
+  group: ${{ github.workflow }}
   cancel-in-progress: true
 
 jobs:
@@ -74,7 +76,7 @@ jobs:
         run: pip install -r .github/scripts/triage/requirements.txt
 
       - name: Cache FastEmbed model weights
-        uses: actions/cache@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: ${{ github.workspace }}/.fastembed_cache
           key: fastembed-bge-small-en-v1.5
diff --git a/.gitignore b/.gitignore
index a19a6a556..c775f0ba5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -82,6 +82,11 @@ GitNexus.sln
 # Git worktrees
 .worktrees/
 
+# Vendored tree-sitter grammar build artifacts (created at install time,
+# never committed). See docs/plans/2026-04-15-002-fix-tree-sitter-proto-vendor-deps-plan.md
+gitnexus/vendor/**/build/
+gitnexus/vendor/**/node_modules/
+
 /github/scripts/triage/__pycache__/
 
 .claude-flow/
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 7247750f5..d2d48f017 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -21,18 +21,41 @@ This project uses the [PolyForm Noncommercial License 1.0.0](https://polyformpro
 ## Branch and pull requests
 
 - Use short-lived branches off the default branch of the repo you are targeting.
-- Prefer **conventional commits** (short prefix + description), for example:
-
-  ```text
-  feat: add graph export option
-  fix: correct MCP tool schema for query
-  test: cover cluster merge edge case
-  docs: clarify analyze flags
-  ```
-
-- **PR title:** `[area] Short description` (e.g. `[cli] Fix index refresh race`).
+- **PR titles MUST follow the conventional-commit format** — `pr-labeler.yml` enforces this on every PR and auto-applies the matching label so release notes group the change correctly.
 - **PR description:** what changed, why, how to verify (commands), and any risk or rollback notes.
 
+### Pull request titles
+
+Format: `<type>[(scope)][!]: <subject>`
+
+Allowed types and the release-notes section each one lands in (defined in `.github/release.yml`):
+
+| Type | Label applied | Release-notes section |
+|------|---------------|-----------------------|
+| `feat` | `enhancement` | 🚀 Features |
+| `fix` | `bug` | 🐛 Bug Fixes |
+| `perf` | `performance` | 🏎️ Performance |
+| `refactor` | `refactor` | 🔄 Refactoring |
+| `test` | `test` | 🧪 Tests |
+| `ci` | `ci` | 👷 CI/CD |
+| `build` / `deps` | `dependencies` | 📦 Dependencies |
+| `docs` | `documentation` | (grouped under Other Changes unless a Docs section is added) |
+| `chore` / `revert` | `chore` | (excluded from release notes) |
+
+Append `!` to the type (e.g. `feat(api)!: drop /v1 endpoint`) or include `BREAKING CHANGE:` in the PR body to flag a breaking change — the labeler then adds the `breaking` label and the 💥 Breaking Changes section is rendered first.
+
+Examples:
+
+```text
+feat(web): add smart chat scroll
+fix(extractors): resolve silent contract mis-resolution
+perf: avoid O(n²) traversal in heritage walker
+chore(deps): bump vitest to 3.0.0
+ci: standardize workflow concurrency
+```
+
+Commits within a PR may use any style — only the **merged PR title** shows up in release notes, so that's the one the convention applies to.
+
 ## Before you open a PR
 
 - [ ] Tests pass for the packages you touched (`gitnexus` and/or `gitnexus-web`).
@@ -45,6 +68,41 @@ This project uses the [PolyForm Noncommercial License 1.0.0](https://polyformpro
 
 Maintainers may request changes for correctness, tests, performance, or consistency with existing patterns. Keeping diffs focused makes review faster.
 
+## GitHub Actions — Concurrency Convention
+
+Every workflow under `.github/workflows/` MUST declare a top-level `concurrency:` block using this convention:
+
+- **Group key** starts with `${{ github.workflow }}` so no two workflows can collide on the same group name. The discriminator that follows is chosen per event shape:
+  - Branch/tag scope: `${{ github.workflow }}-${{ github.ref }}`
+  - Per-PR scope (for `issue_comment`, `pull_request_review*`, `pull_request` meta events): `${{ github.workflow }}-${{ github.event.pull_request.number || github.event.issue.number }}`
+  - `workflow_run` scope (e.g. `ci-report.yml`): `${{ github.workflow }}-${{ github.event.workflow_run.pull_requests[0].number || format('{0}/{1}', github.event.workflow_run.head_repository.full_name, github.event.workflow_run.head_branch) }}` — the fork fallback must be stable across reruns (never `workflow_run.id`, which is per-run-unique and defeats serialization).
+  - Global single-slot (manual dispatch utilities): `${{ github.workflow }}`
+  - **Reusable workflows invoked via `workflow_call`:** do NOT use `${{ github.workflow }}` in the group key — in called-workflow context its evaluation is ambiguous and can resolve to the caller's name, which would deadlock against the caller's own group. Use a hardcoded literal prefix and a `github.event_name`-aware expression that falls through to `github.run_id` for reusable invocations (see `ci.yml` for the canonical form).
+  - **Merge queue (`merge_group`)**: when this event is added, use `${{ github.workflow }}-${{ github.event.merge_group.head_ref }}` with `cancel-in-progress: false` (every queue entry is a distinct ref; never cancel).
+- **`cancel-in-progress` policy:**
+
+  | Event | `cancel-in-progress` | Why |
+  |-------|----------------------|-----|
+  | `pull_request` CI run | `true` | New push supersedes old run |
+  | `push` to `main` | `false` | Every main commit gets validated |
+  | Tag push (`v*` publish) | `false` | Never cancel mid-publish |
+  | `push` to `main` for release-candidate | `false` | Never cancel mid-RC publish |
+  | `workflow_dispatch` (release/publish) | `false` | Manual runs are intentional |
+  | `workflow_run` (sticky-comment reports) | `false` | Serialize, don't race |
+  | Per-PR bot workflows (`@claude`, review) | `false` | Serialize comments per PR |
+  | PR-meta re-checks (pr-description-check) | `true` | Cheap, latest wins |
+  | Single-slot utilities (triage sweep) | `true` | Latest dispatch supersedes |
+
+- For workflows that serve multiple events at once (e.g. `ci.yml` handles `pull_request`, `push`, and `workflow_call`), make `cancel-in-progress` event-aware:
+
+  ```yaml
+  concurrency:
+    group: ${{ github.workflow }}-${{ github.ref }}
+    cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+  ```
+
+- When adding a new workflow, copy the concurrency block from an existing workflow of the same event shape.
+
 ## AI-assisted contributions
 
 If you use coding agents, follow project context files (e.g. `AGENTS.md`, `CLAUDE.md`) and avoid drive-by refactors unrelated to the issue. Prefer incremental, test-backed changes.
diff --git a/gitnexus/.npmignore b/gitnexus/.npmignore
index 6a4cfb118..cf403314a 100644
--- a/gitnexus/.npmignore
+++ b/gitnexus/.npmignore
@@ -9,6 +9,10 @@ tsconfig.json
 .gitignore
 node_modules/
 
+# Vendor build artifacts (created during install, not shipped)
+vendor/**/node_modules
+vendor/**/build
+
 # Package lock (consumers use their own)
 package-lock.json
 
diff --git a/gitnexus/package-lock.json b/gitnexus/package-lock.json
index bf8b5bb35..def88c93c 100644
--- a/gitnexus/package-lock.json
+++ b/gitnexus/package-lock.json
@@ -62,6 +62,8 @@
         "node": ">=20.0.0"
       },
       "optionalDependencies": {
+        "node-addon-api": "^8.0.0",
+        "node-gyp-build": "^4.8.0",
         "tree-sitter-dart": "git+https://github.com/UserNobody14/tree-sitter-dart.git#80e23c07b64494f7e21090bb3450223ef0b192f4",
         "tree-sitter-kotlin": "^0.3.8",
         "tree-sitter-proto": "file:./vendor/tree-sitter-proto",
@@ -1226,6 +1228,12 @@
         "win32"
       ]
     },
+    "node_modules/@ladybugdb/core/node_modules/node-addon-api": {
+      "version": "6.1.0",
+      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-6.1.0.tgz",
+      "integrity": "sha512-+eawOlIgy680F0kBzPUNFhMZGtJ1YmqM6l4+Crf4IkImjYrO/mqPwRMh352g23uIaQKFItcQ64I7KMaJxHgAVA==",
+      "license": "MIT"
+    },
     "node_modules/@modelcontextprotocol/sdk": {
       "version": "1.28.0",
       "resolved": "https://registry.npmjs.org/@modelcontextprotocol/sdk/-/sdk-1.28.0.tgz",
@@ -4118,10 +4126,13 @@
       }
     },
     "node_modules/node-addon-api": {
-      "version": "6.1.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-6.1.0.tgz",
-      "integrity": "sha512-+eawOlIgy680F0kBzPUNFhMZGtJ1YmqM6l4+Crf4IkImjYrO/mqPwRMh352g23uIaQKFItcQ64I7KMaJxHgAVA==",
-      "license": "MIT"
+      "version": "8.7.0",
+      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
+      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
+      "license": "MIT",
+      "engines": {
+        "node": "^18 || ^20 || >= 21"
+      }
     },
     "node_modules/node-api-headers": {
       "version": "1.8.0",
@@ -5069,24 +5080,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-c-sharp/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
-    "node_modules/tree-sitter-c/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-cli": {
       "version": "0.23.2",
       "resolved": "https://registry.npmjs.org/tree-sitter-cli/-/tree-sitter-cli-0.23.2.tgz",
@@ -5121,18 +5114,9 @@
         }
       }
     },
-    "node_modules/tree-sitter-cpp/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-dart": {
       "version": "1.0.0",
-      "resolved": "git+https://github.com/UserNobody14/tree-sitter-dart.git#80e23c07b64494f7e21090bb3450223ef0b192f4",
+      "resolved": "git+ssh://git@github.com/UserNobody14/tree-sitter-dart.git#80e23c07b64494f7e21090bb3450223ef0b192f4",
       "integrity": "sha512-Bs/1wAOIJ2akPEXlE/XVpuES19Oo3NqoSJRJ/0N2r38qAd9nTXdqmaGHQ44/JXnA6QHcbgD2YzCCc4wUc98cyQ==",
       "hasInstallScript": true,
       "license": "ISC",
@@ -5176,15 +5160,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-go/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-java": {
       "version": "0.23.5",
       "resolved": "https://registry.npmjs.org/tree-sitter-java/-/tree-sitter-java-0.23.5.tgz",
@@ -5204,15 +5179,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-java/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-javascript": {
       "version": "0.23.1",
       "resolved": "https://registry.npmjs.org/tree-sitter-javascript/-/tree-sitter-javascript-0.23.1.tgz",
@@ -5232,15 +5198,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-javascript/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-kotlin": {
       "version": "0.3.8",
       "resolved": "https://registry.npmjs.org/tree-sitter-kotlin/-/tree-sitter-kotlin-0.3.8.tgz",
@@ -5287,15 +5244,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-php/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-proto": {
       "resolved": "vendor/tree-sitter-proto",
       "link": true
@@ -5319,15 +5267,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-python/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-ruby": {
       "version": "0.23.1",
       "resolved": "https://registry.npmjs.org/tree-sitter-ruby/-/tree-sitter-ruby-0.23.1.tgz",
@@ -5347,15 +5286,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-ruby/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-rust": {
       "version": "0.23.1",
       "resolved": "https://registry.npmjs.org/tree-sitter-rust/-/tree-sitter-rust-0.23.1.tgz",
@@ -5375,15 +5305,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-rust/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-swift": {
       "version": "0.6.0",
       "resolved": "https://registry.npmjs.org/tree-sitter-swift/-/tree-sitter-swift-0.6.0.tgz",
@@ -5413,16 +5334,6 @@
       "license": "ISC",
       "optional": true
     },
-    "node_modules/tree-sitter-swift/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "optional": true,
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tree-sitter-swift/node_modules/which": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
@@ -5459,24 +5370,6 @@
         }
       }
     },
-    "node_modules/tree-sitter-typescript/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
-    "node_modules/tree-sitter/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
-    },
     "node_modules/tslib": {
       "version": "2.8.1",
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
@@ -5884,26 +5777,11 @@
     },
     "vendor/tree-sitter-proto": {
       "version": "0.4.1",
-      "hasInstallScript": true,
       "license": "MIT",
       "optional": true,
-      "dependencies": {
-        "node-addon-api": "^8.0.0",
-        "node-gyp-build": "^4.8.0"
-      },
       "peerDependencies": {
         "tree-sitter": ">=0.21.0"
       }
-    },
-    "vendor/tree-sitter-proto/node_modules/node-addon-api": {
-      "version": "8.7.0",
-      "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-8.7.0.tgz",
-      "integrity": "sha512-9MdFxmkKaOYVTV+XVRG8ArDwwQ77XIgIPyKASB1k3JPq3M8fGQQQE3YpMOrKm6g//Ktx8ivZr8xo1Qmtqub+GA==",
-      "license": "MIT",
-      "optional": true,
-      "engines": {
-        "node": "^18 || ^20 || >= 21"
-      }
     }
   }
 }
diff --git a/gitnexus/package.json b/gitnexus/package.json
index 6448e716a..ad075041d 100644
--- a/gitnexus/package.json
+++ b/gitnexus/package.json
@@ -46,7 +46,7 @@
     "test:integration": "vitest run test/integration",
     "test:watch": "vitest",
     "test:coverage": "vitest run --coverage",
-    "postinstall": "node scripts/patch-tree-sitter-swift.cjs",
+    "postinstall": "node scripts/patch-tree-sitter-swift.cjs && node scripts/build-tree-sitter-proto.cjs",
     "prepare": "node scripts/build.js",
     "prepack": "node scripts/build.js"
   },
@@ -84,6 +84,8 @@
     "uuid": "^13.0.0"
   },
   "optionalDependencies": {
+    "node-addon-api": "^8.0.0",
+    "node-gyp-build": "^4.8.0",
     "tree-sitter-dart": "git+https://github.com/UserNobody14/tree-sitter-dart.git#80e23c07b64494f7e21090bb3450223ef0b192f4",
     "tree-sitter-kotlin": "^0.3.8",
     "tree-sitter-proto": "file:./vendor/tree-sitter-proto",
diff --git a/gitnexus/scripts/build-tree-sitter-proto.cjs b/gitnexus/scripts/build-tree-sitter-proto.cjs
new file mode 100644
index 000000000..d2828d5ba
--- /dev/null
+++ b/gitnexus/scripts/build-tree-sitter-proto.cjs
@@ -0,0 +1,82 @@
+#!/usr/bin/env node
+/**
+ * Build tree-sitter-proto native binding.
+ *
+ * Why this script exists:
+ *   tree-sitter-proto is vendored under gitnexus/vendor/tree-sitter-proto/
+ *   and declared as a `file:` optionalDependency. Previously, the vendored
+ *   package had its own `dependencies` and `install` script, which caused
+ *   npm to create `vendor/tree-sitter-proto/node_modules/` and
+ *   `vendor/tree-sitter-proto/build/` during install. Those directories
+ *   blocked `rmdir` on global-install upgrade, producing:
+ *
+ *     ENOTEMPTY: directory not empty, rmdir
+ *       '.../gitnexus/vendor/tree-sitter-proto/node_modules/node-addon-api'
+ *
+ *   (See https://github.com/abhigyanpatwari/GitNexus/issues/836.)
+ *
+ *   We stripped `dependencies` and the `install` script from the vendored
+ *   package.json, hoisted `node-addon-api` and `node-gyp-build` into
+ *   gitnexus's own optionalDependencies, and moved native compilation here.
+ *
+ * What this does:
+ *   Runs `npx node-gyp rebuild` inside `node_modules/tree-sitter-proto/`
+ *   (which npm creates as a copy of vendor/tree-sitter-proto/ when
+ *   resolving the file: dep). Build output lands in
+ *   `node_modules/tree-sitter-proto/build/Release/tree_sitter_proto_binding.node`
+ *   — under npm-managed territory, safe on upgrade.
+ *
+ *   Mirrors scripts/patch-tree-sitter-swift.cjs. Best-effort: if any
+ *   precondition fails (optional dep absent, no toolchain, --ignore-scripts),
+ *   warn and exit 0 so gitnexus install still succeeds.
+ */
+const fs = require('fs');
+const path = require('path');
+const { execSync } = require('child_process');
+
+const protoDir = path.join(__dirname, '..', 'node_modules', 'tree-sitter-proto');
+const bindingGyp = path.join(protoDir, 'binding.gyp');
+const bindingNode = path.join(protoDir, 'build', 'Release', 'tree_sitter_proto_binding.node');
+
+try {
+  if (!fs.existsSync(bindingGyp)) {
+    // tree-sitter-proto is an optionalDependency; absent when install
+    // skipped optional deps or the file: dep was not resolved.
+    process.exit(0);
+  }
+
+  // Skip if the native binding already exists (idempotent re-run).
+  if (fs.existsSync(bindingNode)) {
+    process.exit(0);
+  }
+
+  // Pre-flight: the hoisted build deps must be resolvable.
+  try {
+    require.resolve('node-addon-api');
+    require.resolve('node-gyp-build');
+  } catch (resolveErr) {
+    console.warn(
+      '[tree-sitter-proto] Skipping build: hoisted build deps not resolvable (%s).',
+      resolveErr.message,
+    );
+    console.warn(
+      '[tree-sitter-proto] Proto parsing will be unavailable. Install without --no-optional and with scripts enabled to build.',
+    );
+    process.exit(0);
+  }
+
+  console.log('[tree-sitter-proto] Building native binding...');
+  execSync('npx node-gyp rebuild', {
+    cwd: protoDir,
+    stdio: 'pipe',
+    timeout: 180000,
+  });
+  console.log('[tree-sitter-proto] Native binding built successfully');
+} catch (err) {
+  console.warn('[tree-sitter-proto] Could not build native binding:', err.message);
+  console.warn(
+    '[tree-sitter-proto] Proto (.proto) parsing will be unavailable. Non-proto gitnexus functionality is unaffected.',
+  );
+  // Exit 0: optionalDependency failures must not fail the gitnexus install.
+  process.exit(0);
+}
diff --git a/gitnexus/src/core/embeddings/embedder.ts b/gitnexus/src/core/embeddings/embedder.ts
index e2d26c9e7..d27718ce5 100644
--- a/gitnexus/src/core/embeddings/embedder.ts
+++ b/gitnexus/src/core/embeddings/embedder.ts
@@ -157,6 +157,11 @@ export const initEmbedder = async (
     try {
       // Configure transformers.js environment
       env.allowLocalModels = false;
+      // Default cache to user-writable location. transformers.js defaults to
+      // ./node_modules/.cache inside its own install dir, which is unwritable
+      // when gitnexus is installed globally (e.g. /usr/lib/node_modules/).
+      // Respect HF_HOME if set, otherwise fall back to ~/.cache/huggingface.
+      env.cacheDir = process.env.HF_HOME ?? `${process.env.HOME}/.cache/huggingface`;
 
       const isDev = process.env.NODE_ENV === 'development';
       if (isDev) {
diff --git a/gitnexus/src/mcp/core/embedder.ts b/gitnexus/src/mcp/core/embedder.ts
index e53a46542..592c2bba9 100644
--- a/gitnexus/src/mcp/core/embedder.ts
+++ b/gitnexus/src/mcp/core/embedder.ts
@@ -42,6 +42,11 @@ export const initEmbedder = async (): Promise<FeatureExtractionPipeline> => {
   initPromise = (async () => {
     try {
       env.allowLocalModels = false;
+      // Default cache to user-writable location. transformers.js defaults to
+      // ./node_modules/.cache inside its own install dir, which is unwritable
+      // when gitnexus is installed globally (e.g. /usr/lib/node_modules/).
+      // Respect HF_HOME if set, otherwise fall back to ~/.cache/huggingface.
+      env.cacheDir = process.env.HF_HOME ?? `${process.env.HOME}/.cache/huggingface`;
 
       console.error('GitNexus: Loading embedding model (first search may take a moment)...');
 
diff --git a/gitnexus/vendor/tree-sitter-proto/package.json b/gitnexus/vendor/tree-sitter-proto/package.json
index 387f3d9bb..aea236ea3 100644
--- a/gitnexus/vendor/tree-sitter-proto/package.json
+++ b/gitnexus/vendor/tree-sitter-proto/package.json
@@ -5,14 +5,8 @@
   "repository": "https://github.com/coder3101/tree-sitter-proto",
   "license": "MIT",
   "main": "bindings/node",
-  "scripts": {
-    "install": "node-gyp-build"
-  },
+  "_vendoredBy": "gitnexus — build deps (node-addon-api, node-gyp-build) are hoisted into gitnexus/package.json optionalDependencies, and native compilation is performed by gitnexus/scripts/build-tree-sitter-proto.cjs at gitnexus postinstall. Do NOT re-add a dependencies block or an install script here — doing so reintroduces https://github.com/abhigyanpatwari/GitNexus/issues/836 (ENOTEMPTY on global upgrade).",
   "peerDependencies": {
     "tree-sitter": ">=0.21.0"
-  },
-  "dependencies": {
-    "node-addon-api": "^8.0.0",
-    "node-gyp-build": "^4.8.0"
   }
 }