lens-view

A viewer for lens traces: what a Jacobian lens, logit lens or tuned lens reads out at every layer and token position. It runs beside a coding agent, so you can look at a trace while you work on the code that produced it.

The trace format is described in FORMAT.md. It is a draft and will change.

Front ends

| Where | What you get | Install | | --- | --- | --- | | Claude Code (default) | A mod: a /lens-view <path> command and a tool the model calls, both opening a pane inside Claude Code | Plugin, below | | Codex, or any agent with MCP | An MCP tool, lens_view, that opens the terminal viewer in a tmux pane beside the agent | MCP, below | | A terminal | The terminal viewer on its own: lens-view trace.json | uv tool install git+https://github.com/johntrob14/lens-view |

All three read traces through the Python package (src/lens_view/trace.py). The mod calls lens-view-json, which prints a trace as normalized JSON, so there is one parser.

All three need uv. The tmux front end needs the agent to run inside tmux.

Claude Code plugin

/plugin marketplace add johntrob14/lens-view
/plugin install lens-view@lens-view

Codex and other MCP clients

# ~/.codex/config.toml
[mcp_servers.lens-view]
command = "uv"
args = ["run", "--quiet", "--frozen", "--no-dev", "--project", "/path/to/lens-view", "lens-view-mcp"]
env_vars = ["TMUX", "TMUX_PANE"]

The repository also carries a Codex plugin manifest (.codex-plugin/plugin.json, mcp.json).

Layout

| Path | What | | --- | --- | | src/lens_view/trace.py | Trace format: parsing, loading, lens-view-json | | src/lens_view/app.py | Terminal viewer (Textual), lens-view | | src/lens_view/pane.py, mcp_server.py | tmux pane launcher and MCP server, lens-view-mcp | | .claude-plugin/, hooks/, types/ | Claude Code plugin: the mod | | .codex-plugin/, mcp.json | Codex plugin |

Development

uv run --group dev pytest           # Python
claude plugin validate . && claude plugin test .   # the mod