Frontend Perception Engine (CRG as Optional Library)

This project implements a frontend navigation layer where:

• Browser Use stays the browser automation engine.

• Code Review Graph (CRG) is used only as an optional knowledge source.

• Browser execution continues even when CRG is unavailable.

Architecture

Cursor / Claude
   ↓
Our MCP
   ↓
Frontend Navigation Layer
   ↓
Browser Use
   ↓
Browser

CRG is integrated behind ICodeGraph, so it can be replaced later by another backend such as FrontendInteractionGraph without changing Browser Use orchestration.

Related MCP server: Playwright MCP Server

Dependency Integration

CRG is integrated as a dependency (not forked, not modified):

• code-review-graph>=2.3.6

• browser-use>=0.13.3

Install:

pip install -e .

Frontend Perception MCP (No LLM in Server)

The MCP server is deterministic runtime only (browser observation + actions + verify).
Your coding agent (Cursor/Claude/Codex) remains the brain.

Install

Both PyPI names install the same MCP server:

Use --upgrade when a version is already installed — plain pip install may leave an older release in place.

Do not mix PyPI installs with pip install -e . in this repo; editable installs can leave broken metadata that blocks upgrades. Use one or the other.

Recommended (quiet output + next steps):

uvx --from frontend-perception-engine frontend-perception-install

Or the shorter alias name:

uvx --from frontend-mcp frontend-mcp-install

With Chromium for Browser Use:

uvx --from frontend-perception-engine frontend-perception-install --with-browser

Development install from this repo:

python -m navigation.cli.install --editable .

Or classic pip:

pip install frontend-perception-engine

Run MCP server

Using module entrypoint:

python -m navigation.mcp

Using script entrypoint:

frontend-perception-mcp

Using uvx (no local install in current environment):

uvx --from frontend-perception-engine frontend-perception-mcp
# or
uvx --from frontend-mcp frontend-mcp

Cursor MCP config

{
  "mcpServers": {
    "frontend-perception": {
      "command": "python",
      "args": ["-m", "navigation.mcp"],
      "env": {
        "PYTHONPATH": "C:/Users/usman/Projects/frontend-perception-engine/src"
      }
    }
  }
}

Runtime prerequisites

• Start the sandbox app: cd sandbox && npm run dev

• Default URL used by tests/tools: http://localhost:5173

• No API keys are required to run the MCP path itself

Platform documentation

Architecture, roadmap, tool reference, and feature subsystem docs: docs/README.md.

CRG Documentation and Public API Notes

The integration uses CRG public tool functions from:

• code_review_graph.tools.build.build_or_update_graph

• code_review_graph.tools.query.query_graph

• code_review_graph.tools.query.semantic_search_nodes

• code_review_graph.tools.query.get_impact_radius

• code_review_graph.tools.query.list_graph_stats

• code_review_graph.tools.query.traverse_graph_func

Graph lifecycle

• Initialize graph (incremental/minimal): build_or_update_graph(full_rebuild=False, postprocess="minimal")

• Refresh graph (incremental): build_or_update_graph(full_rebuild=False)

• Rebuild graph (full): build_or_update_graph(full_rebuild=True)

Incremental indexing

CRG incremental path is handled by incremental_update under the hood and can detect changed files from VCS (base=HEAD~1 by default).

Watch mode

CRG supports continuous updates via:

• CLI: code-review-graph watch

• API internals: code_review_graph.incremental.watch and start_watch_thread

This wrapper does not require watch mode, but is compatible with repositories kept fresh by CRG watch/daemon.

Querying

• Pattern queries (neighbors/file relationships): query_graph

• Search (hybrid semantic + keyword): semantic_search_nodes

• Blast radius / route impact: get_impact_radius

• Traversal/path-like exploration: traverse_graph_func

• Stats/health: list_graph_stats

Wrapper Layer

All CRG coupling is isolated in:

src/navigation/codeGraph/

Public contract:

• initialize()

• refresh()

• rebuild()

• search()

• shortest_path()

• get_neighbors()

• get_component()

• get_file()

• get_route()

• query()

Future-oriented methods are already represented on ICodeGraph:

• findNavigationHint(...) style equivalent via find_navigation_hint(...)

• find_relevant_components(...)

• find_likely_route(...)

• find_related_files(...)

• find_button_candidates(...)

• find_component_hierarchy(...)

• find_entry_point(...)

Browser Use Integration

BrowserUseNavigator provides a lightweight dry-run timeline for tests.

PerceptionAgentRunner runs a real Browser Use agent with optional graph hints injected via extend_system_message. Graph output is never a mandatory stage — if CRG or AWS credentials are missing, the agent either skips hints or reports a clear error.

Live agent (Bedrock Nova)

1. Start the sandbox:

cd sandbox && npm run dev

2. Configure AWS (copy .env.example → .env):

AWS_ACCESS_KEY_ID=...
AWS_SECRET_ACCESS_KEY=...
AWS_REGION=us-east-1
BEDROCK_MODEL=amazon.nova-pro-v1:0
SANDBOX_URL=http://localhost:5173

3. Install AWS extra and run:

pip install -e ".[aws]"
python src/run_agent.py --task "Add Pulse Watch to cart and complete checkout"

Dry-run (graph hints only, no browser):

python src/run_agent.py --dry-run --task "Log in as admin and open admin report"

Flags:

• --no-graph — disable CRG hints

• --headless — headless browser

• --max-steps 25 — step limit

• --url http://localhost:5174 — custom sandbox URL

Demo

Run:

python src/demo.py

Expected behavior:

1. Browser Use execution starts.

2. Optional code graph query is attempted.

3. Browser Use continues regardless of query success.