query

name	query
description	Answer ad-hoc questions about the user's Claude Code usage with read-only SQL over the cclens store (cclens sql) — which files keep failing to edit, which tool errors most, usage per month, any slice the fixed views don't cover. Use when the user asks a specific question about their Claude Code sessions, tool errors, or skill usage.

cclens query — ad-hoc SQL over the usage store

cclens extracts every Claude Code session into a local SQLite store; any slice its fixed views don't cover is one read-only query away. Answer the user's question by querying the store — never by re-parsing the raw ~/.claude/projects transcripts yourself.

1. Resolve the binary and the store

• Binary: use cclens if command -v cclens finds it. Otherwise run every command below through Nix instead: nix run github:lambdalisue/cclens -- <subcommand …>. If neither cclens nor nix is available, stop and tell the user how to install it (nix profile install github:lambdalisue/cclens, or cargo install --git https://github.com/lambdalisue/cclens).

• Store: if ./cclens.db exists, use it and omit --db. Otherwise use the per-user store so no file is dropped into the current project:

  DB="${XDG_CACHE_HOME:-$HOME/.cache}/cclens/cclens.db"
  mkdir -p "$(dirname "$DB")"
  

  and pass --db "$DB" to every command below. cclens sql errors on an absent store — run cclens analyze --db "$DB" first in that case (also run it when the user wants current data; it is incremental and fast).

2. Query

The query is an argument, or stdin (which sidesteps shell quoting):

cclens sql --db "$DB" "SELECT category, tool, COUNT(*) n FROM tool_errors GROUP BY 1,2 ORDER BY n DESC"
echo "SELECT excerpt FROM tool_errors WHERE category='path-not-found'" | cclens sql --db "$DB"

The store is opened read-only, so a query can never mutate it.

Schema crib — confirm with cclens sql "SELECT sql FROM sqlite_master" and sample the data before relying on an encoding:

• tool_errors (view): one row per failed tool call — session_id, project, category, excerpt, tool, target, started_epoch. category is the failure class (edit-precondition, path-not-found, blocked-by-hook, …), excerpt the actual error text (carries the failing path), target the file/command when the text omits it, project the session's cwd slug.
• sessions and events hold everything else (skill spans, tokens, models, timestamps); surfaces is the config catalog with static token costs.

3. Present

Answer the user's actual question, with the query you ran shown so it can be tweaked. Timestamps in the store are UTC epoch — convert before presenting. For "how is my setup doing overall", point at /cclens:doctor instead of assembling it by hand.