pi-lens

pi-lens gives AI coding agents fast, language-aware feedback while they write/edit.

Working in this project as an AI agent? Read the agent guide for how pi-lens surfaces diagnostics (honesty labels, blockers, read-before-edit) and how to respond.

What It Does

• LSP diagnostics and navigation across supported languages
• Impact cascade diagnostics that show which related files were affected and run LSP diagnostics on them
• Language-specific linters, type-checkers, and scanners on every write/edit
• Safe formatting/autofix where tools are configured or confidently detected
• ast-grep and tree-sitter structural rules for correctness/security smells
• Agent-facing tools for LSP navigation/diagnostics, AST search/replace, diagnostics state, and project intelligence
• Review-graph intelligence for supported languages via bundled tree-sitter WASMs
• Ranked identifier search (symbol_search) over an always-warm word index, feeding the discovery funnel (symbol_search → module_report → read_symbol)
• Diagnostic triage (lens_diagnostic_mark): findings can be marked false-positive, suppressed in source, deferred, or flagged-to-fix — honored across all surfaces
• /lens-map — interactive HTML dependency map of the project
• Read-guard and edit-autopatch support to reduce bad edits
• Background security/dependency scans for opted-in projects
• Runtime health telemetry (/lens-health) including a bounded degradation ledger for silently-degraded behavior (LSP breakers, formatter skips/failures, idle evictions, timeouts)
• MCP server (experimental) so Claude Code or any MCP client can drive the same diagnostics/read-substitute tools pi-lens exposes to pi

Architecture

Most lifecycle events enter through one wrapper, which drops and counts events that arrive on a replaced session. tool_call registers raw: it delegates straight to a handler that owns its own total guard. Events fan out into the edit-time lane and the LSP lane. Both lanes write into the findings stores. Nothing reaches the agent from those stores until a freshness gate or an explicit age label clears it.

flowchart TD
    subgraph host["pi host"]
        HOST["Host events<br/>tool_call, tool_result, turn_start/end,<br/>session_start/shutdown, agent_end, context"]
        WRAP["Stale-ctx wrapper<br/>skips and counts events on a replaced session<br/>tool_result, turn_start, turn_end, agent_end,<br/>agent_settled, session_start, context"]
    end

    subgraph guards["Guards"]
        RG["Read-guard<br/>blocks edits that lack prior reading"]
        GG["Git-guard<br/>holds commit/push while findings stay unresolved"]
    end

    subgraph edit["Edit-time lane"]
        PIPE["Post-write pipeline<br/>secrets, format, autofix, sync, lint, tests"]
        PLAN["Dispatch plan<br/>per file kind, per capability group"]
        RUN["Runners<br/>format, lint, types, security, smells, docs"]
        STRUCT["Structural rules<br/>tree-sitter queries and ast-grep"]
        BUS["files-touched bus<br/>tells extensions which paths moved"]
    end

    subgraph lsp["LSP lane"]
        POOL["Client pool<br/>warm reuse, idle eviction"]
        DIAGS["File and workspace diagnostics"]
        CASC["Impact cascade<br/>tiered wait policy"]
    end

    STORES["Findings stores<br/>widget state, warning caches, project snapshot"]

    subgraph gate["Freshness gating"]
        FRESH["Path freshness<br/>mtime vs scan time, past-EOF, dependency drift"]
        DISPO["Dispositions<br/>false-positive, suppress, defer, flagged"]
        LABEL["Explicit age label<br/>for findings no path gate can check"]
    end

    subgraph deliver["Delivery surfaces"]
        TURN["Turn-end findings injection"]
        WIDGET["Widget and footer tally"]
        TOOLS["lens_diagnostics tool"]
        NUDGE["Agent nudges"]
    end

    SESSION["Session lifecycle<br/>primary, sequential replacement, concurrent secondary"]
    SINKS["Observability sinks<br/>latency.log, degradation ledger, bounded telemetry,<br/>cache observability, cascade and tree-sitter logs"]

    HOST --> WRAP
    HOST -->|tool_call, raw| RG
    HOST -->|tool_call, raw| GG
    WRAP -->|session_start| SESSION
    WRAP -->|tool_result| PIPE
    WRAP -->|tool_result, records reads and writes| RG
    SESSION --> POOL
    SESSION --> STORES
    PIPE --> PLAN
    PLAN --> RUN
    PLAN --> STRUCT
    PIPE --> POOL
    PIPE --> BUS
    POOL --> DIAGS
    DIAGS --> CASC
    RUN --> STORES
    STRUCT --> STORES
    DIAGS --> STORES
    CASC --> STORES
    BUS --> NUDGE
    RG -->|read and edit history filter| NUDGE
    STORES --> FRESH
    STORES --> LABEL
    FRESH --> DISPO
    DISPO --> TURN
    DISPO --> WIDGET
    DISPO --> TOOLS
    LABEL --> TURN
    TURN --> GG
    WRAP --> SINKS
    PIPE --> SINKS
    RUN --> SINKS
    STRUCT --> SINKS
    POOL --> SINKS
    CASC --> SINKS
    RG --> SINKS
    GG --> SINKS
    FRESH --> SINKS

Architecture-level view, updated when a lane changes. Per-tool inventories live in features and language coverage. Today the edit-time lane carries 45+ runner modules over 35+ file kinds, and the LSP lane speaks to a dozen-plus language servers.

The gating box is an abstraction, not a call order. Freshness covers several independent mechanisms: path freshness against scan time, past-EOF line checks, and forward-import dependency drift. Dispositions are one more filter alongside them, not a second stage every finding walks through. Read the box as "a finding passes the gates that apply to it", and see clients/finding-delivery-gate.ts for the per-surface contract.

Install

pi install npm:pi-lens

Or from git:

pi install git:github.com/apmantza/pi-lens

Requires Node.js >=22.19.0 (matches the pi host's own floor — see engines in package.json).

Letting a coding agent do it: paste this into its prompt.

Install pi-lens (npm:pi-lens) into pi, then read AGENTS.md in
https://github.com/apmantza/pi-lens for how the extension works and how it
expects to be operated.

npm v12 users: dependency lifecycle scripts (e.g. @ast-grep/cli's postinstall) now require explicit approval — if npm install warns about unreviewed install scripts, review and allow them with npm approve-scripts, or trust the allowScripts entries already declared in this package's package.json. Installing from a git source (pi install git:... / pi update --extension git:...) may similarly prompt for git-dependency approval; accept it to let the prepare build step run.

Documentation

• Agent guide — how an AI agent should consume and respond to pi-lens
• Agent tools — pi tool names, scopes, and arguments
• Usage guide — lifecycle, tool behavior, MCP notes, and troubleshooting
• Features — detailed feature reference
• Word index — identifier search (symbol_search) and the discovery funnel
• Tools and commands — runtime flags and slash commands
• Diagnostic dispositions — triage: false-positive, suppress, defer, flagged-to-fix
• Settings — the configuration hub: defaults, env vars, CLI flags, and global vs project config at a glance
• Configuration — global and project config files
• Environment variables — common env vars and full reference
• Language coverage — supported languages, runners, and formatters
• Dependencies — auto-install policy and external tools
• Custom rules — project ast-grep and tree-sitter rules
• MCP server — experimental MCP server for Claude Code and other MCP clients

Contributing

See CONTRIBUTING.md for the development workflow, runner, LSP, formatter, and rule checklists, and issue/PR conventions.

Security issues should be reported privately; see SECURITY.md. pi-lens is released under the MIT License.

Contributors

Thanks goes to these wonderful people: