Naja Scope

naja-scope

Let your AI assistant explore SystemVerilog designs — without pasting source code into the chat.

naja-scope is an MCP server that gives AI agents (Claude, and any MCP-compatible assistant) a precise, structured view of your elaborated SystemVerilog design. Instead of dumping thousands of lines of RTL into the model's context, the agent asks targeted questions — what drives this signal? what's inside this module? where does this net come from? — and gets back small, exact answers with file-and-line references.

Built on the najaeda netlist engine.

On a 17-question CVA6 benchmark, the same Claude Code agent scored 17/17 with naja-scope versus 10/17 with grep/read source tools — in 77 turns instead of 123, processing about 5× less input. How it was measured ↓

pip install naja-scope
claude mcp add naja-scope -- naja-scope-mcp

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Why

Large designs don't fit in a chat window. Pasting RTL is slow, expensive, and the model still can't reliably trace connectivity across hierarchy. naja-scope turns your design into something an agent can navigate:

• 🔎 Trace connectivity — find what drives or loads any signal, across module boundaries.
• 🌲 Walk the hierarchy — explore modules, instances, and ports on demand.
• 🎯 Jump to source — every answer comes with file:line ranges, so the agent can quote the exact RTL that matters.
• 🧩 Logic cones — trace fan-in / fan-out combinational cones up to the register boundary.
• 💡 Recover design intent — enum state names, struct/union fields, and parameter formulas that normally vanish when a design is elaborated.

Works on RTL and gate-level netlists alike: load elaborated SystemVerilog, or load a post-synthesis structural Verilog netlist together with its Liberty standard-cell library and navigate the gates the same way (see Gate-level designs). VHDL loading is in beta.

All responses are token-bounded: lists paginate, large results truncate with clear markers. Your context stays small; your answers stay accurate.

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Does it actually help?

naja-scope helps most when the answer exists in the elaborated design rather than in any single source file. In an initial 17-question run on the cv32a6_imac_sv32 configuration of CVA6, the same Claude Code agent was tested with naja-scope and with source-search tools alone.

The difference is clearest on structural questions that source search cannot answer directly:

Source search remains the right tool for local textual questions. naja-scope adds the elaborated hierarchy, connectivity, lowered primitives, and generated or uniquified structures that are otherwise difficult to reconstruct.

See the benchmark methodology and multi-model runner and historical result record for configuration, scoring, token accounting, and reproducibility details.

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Install

pip install naja-scope        # pulls najaeda and the MCP runtime from PyPI
naja-scope-mcp                # stdio MCP server

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Connect it to Claude Code

claude mcp add naja-scope -- naja-scope-mcp

Or add it to any MCP client's config:

{
  "mcpServers": {
    "naja-scope": {
      "command": "naja-scope-mcp"
    }
  }
}

Then just ask your assistant to load a design and start exploring:

"Load my UART design from rtl/uart.sv with top uart_top, then show me everything that drives tx_o."

The agent loads the design once and answers follow-up questions instantly — no re-reading source, no giant pastes.

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Connect it to ChatGPT

ChatGPT connects to MCP servers over an HTTP endpoint (custom connectors / Developer mode), so run naja-scope as an HTTP server instead of stdio:

naja-scope-mcp --transport streamable-http --host 127.0.0.1 --port 8000

This serves MCP at http://<host>:8000/mcp. Because ChatGPT reaches the server over the network, expose that URL where ChatGPT can see it — e.g. a public tunnel for a local run:

# example: a tunnel to your local server (ngrok, cloudflared, …)
ngrok http 8000        # -> https://<something>.ngrok.app  →  add /mcp

Then in ChatGPT, open Settings → Connectors (enable Developer mode if needed), add a custom connector, and paste the server URL (https://<your-host>/mcp). Once connected, ask it to load a design and explore exactly as above. (ChatGPT's connector UI evolves; the constant is: it needs an HTTPS MCP URL, which --transport streamable-http provides.)

⚠️ The HTTP server has no built-in auth — only expose it over a trusted tunnel, and prefer short-lived tunnels for local experiments.

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Gate-level designs

Already synthesized? Load the structural Verilog netlist together with the Liberty library that defines its standard cells, and navigate the gates the same way as RTL:

"Load the Liberty library pdk/stdcells.lib, then the gate netlist build/top.v, and tell me what cells top is built from and what drives data_out."

Hierarchy, per-cell counts (get_module_card), drivers/loads, and logic cones all work on the netlist; cones stop at the sequential cells. get_source shows a cell's or net's line in the netlist. For Yosys output, load with yosys_source_attributes=True: the (* src = ... *) attributes become origins that get_source(path, origin=0) reads back in the RTL. A runnable example lives in examples/ (stdcells.lib + counter2.v + gate_level.py).

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Storage summaries

get_module_card reports direct-child register bits and inferred RAM/ROM summaries: width, depth, capacity in bits, read/write port counts, and initialization status. It lists up to 12 memories, with memories_truncated when more exist; initialized memories include a 64-character init_preview and init_truncated. Address zero occupies the least-significant word.

get_stats aggregates these counts below the selected instance using flat_register_bits, flat_memory_instances, flat_rom_instances, flat_ram_instances, and flat_memory_bits. Register bits count modeled flip-flop/latch states, including multibit Liberty banks; RAM capacity is separate. Sequential cells without a state model are counted in register_bits_unknown_instances (flat_ in statistics), so known bit counts remain explicit lower bounds when that count is nonzero. Memories are recognized from native naja primitives; opaque memory macros are not assigned an inferred capacity.

VHDL (beta)

VHDL loading is available in beta. Call load_vhdl(file=["pkg.vhd", "child.vhd", "top.vhd"], top="my_entity") to explore its elaborated hierarchy and connectivity; the files may be listed in any order. A single path per call also works (load packages first); package-only files may return top: null until the top file is loaded. The frontend supports a restricted two-state RTL subset, and supported constructs may change. get_intent/load_intent remain SystemVerilog-only; VHDL source ranges are not guaranteed.

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What you can ask

Once a design is loaded, your assistant can:

• Resolve any signal or instance by hierarchical path (with glob and did-you-mean suggestions).
• Find objects design-wide by pattern.
• Show the hierarchy of any module.
• Get drivers / loads of a net — the real endpoints, across hierarchy; literal drivers preserve four-state 0 / 1 / X / Z values.
• Trace logic cones (fan-in / fan-out) and see the register frontier.
• Get source — the exact SystemVerilog lines behind any object.
• Get a module card — ports, counts, clock/reset at a glance.
• Recover design intent — state-machine names, struct fields, parameter expressions lost during elaboration.

A runnable end-to-end walkthrough lives in examples/, including versions that run against CVA6 (a production RISC-V core, cloned on demand — see examples/cva6_demo.sh) and CORE-V-MCU (a full multi-vendor RISC-V SoC — see examples/core_v_mcu_demo.sh).

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The Python escape hatch (off by default)

naja-scope also has a query_python tool that runs Python directly against the loaded design, for queries the typed tools above cannot express. It is not registered unless you opt in:

NAJA_SCOPE_ENABLE_PYTHON=1 naja-scope-mcp

It is unsandboxed eval/exec inside the server process — read-only by convention, not enforced — so anything that can reach the server can run arbitrary Python as the server's user. That matters most under --transport streamable-http, where the server listens on a socket. Leave it off unless you need it and trust every client that can reach the endpoint.

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Requirements

• Python 3.10+
• Works anywhere najaeda runs (Linux, macOS, Windows)

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Development

# from a checkout
python3 -m venv .venv
.venv/bin/pip install -e .
.venv/bin/python -m pytest -q

The full test suite runs against a plain pip install of najaeda — no native build required. The CVA6 cross-hierarchy cone regression (tests/test_zzz_cone_cva6.py) is slow and skips automatically unless a CVA6 snapshot is present.

CI tests every supported Python version on Linux x86_64, plus native platform lanes for Linux x86_64/aarch64, macOS x86_64/arm64, and Windows x86_64. The macOS x86_64 lane builds najaeda from its source distribution because PyPI does not currently provide an Intel macOS wheel.

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Support & contact

• 🐛 Found a bug or have a feature request? Open an issue on GitHub →
• 📫 Get in touch: contact@keplertech.io

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License

Apache-2.0. See LICENSE. </content> </invoke>

Optional browser schematic

Requires naja-schematic 0.2.0 or later (the release containing the embeddable viewer API):

pip install "naja-scope[schematic]"

Restart the MCP server after installation. Load a design as usual, then use:

• open_schematic(path="top.u_cpu"): returns a local browser URL and focuses the instance. Omit path for the top. Anonymous #id instances are supported.
• annotate_schematic(items=[{"path": "top.u_cpu", "message": "Check reset", "severity": "warning"}]): replaces the overlay. Use kind="term" with a pin/port path to annotate that terminal; annotations apply to the whole port, not individual bus bits. Pass items=[] to clear. At most 200 annotations, each with at most 2000 message characters.
• get_schematic_selection(): returns the last clicked instance as a regular naja-scope path, usable with source, hierarchy and module-card queries.

The viewer shares the existing raw naja universe; it does not elaborate again. The server binds to loopback and returns a token-bearing URL. Open that URL on the machine running the MCP server; it is not a remote or embedded MCP UI. Treat the URL as access to the loaded design. Design loads/resets refresh open viewers and clear selection, focus and annotations. The browser server stops with naja-scope. Existing tools remain usable without the schematic extra.