Context checkup

Find what loads automatically into the session's context at startup, quantify it, and propose reversible trims ranked by payoff — shrink the startup context window by cutting what isn't worth its tokens. Read-only — measure and recommend; change settings only on explicit approval.

Mental model (spend attention top-down)

Cost hierarchy, biggest first:

1. MCP tool schemas — large, but deferred by tool search. Only a problem if tool search is OFF.
2. Always-on text — every always-on instruction file (entry-file chain, @imports, unscoped rules files) and skill/agent/command descriptions: every available one's description loads every session, except skills flagged non-model-invocable (their description never loads; a manual-only skill costs nothing until invoked).
3. MCP server instructions — load per enabled server at startup; a chatty preamble can dwarf its tool names.
4. MCP tool names — ~10 tokens each. Cheap; 30 names ≈ 300 tokens isn't worth a recommendation.

Rules: measure, never guess — wc/count each source, convert with tokens ≈ words × 1.3 for prose and characters / 4 otherwise, and state that rule once in the table header. When the agent has a built-in context breakdown command, ask the user to paste its output and use its numbers as the baseline; estimate only what it does not break down. Rank by tokens-saved × reversibility. Distinguish auto-loaded from lazy-linked (nested AGENTS.md referenced from a parent are not loaded — don't flag them).

Tool-name counts, the skills/agents/commands lists, and tool-search status come from the session's system-reminders, not disk — read them from your own context.

Checklist

Mechanics below are one agent's (settings keys, ~/.claude paths, which CLAUDE_CONFIG_DIR relocates); on another agent, map each item to its equivalent or ask. p, s and r are the anchors defined under Useful probes.

0. Verify tool search is on first. Evidence is the session itself: MCP tools listed as deferred (names only, searched on demand) means on, even once a search has pulled some schemas in; full schemas loaded from the start means off, and every "names are cheap" conclusion flips. Only then read the env var or setting (ENABLE_TOOL_SEARCH, incl. auto:N threshold modes) to explain why.

1. Always-on instruction files. Measure the entry-file chain (CLAUDE.md, .claude/CLAUDE.md, CLAUDE.local.md, or AGENTS.md and .claude/AGENTS.md when read natively) in p and every parent dir up to root, the user-level entry file (~/.claude/CLAUDE.md), the managed-policy one (a file such as /Library/Application Support/ClaudeCode/CLAUDE.md or /etc/claude-code/CLAUDE.md, or the managed claudeMd setting), and every rules file, subdirectories and symlinks included, in the project and user rules dirs ($p/.claude/rules/, ~/.claude/rules/) that is not path-scoped (a paths: key in its --- frontmatter; a body paths: line scopes nothing) — a project-rules symlink leading outside the project only once external imports are approved. Expand @import lines (recursive). wc -w each; an AGENTS.md or the user-level file counts once, whether read natively, imported or met on the parent walk.

2. Descriptions (often the largest unexamined chunk). Skim the in-session lists of skills, subagent types, and slash commands — their descriptions are always loaded, except non-model-invocable skills (see Mental model). Many rarely-used entries = standing cost. When the agent offers a skills list with token sizes or a visibility override, take the sizes from it; the override (e.g. Claude Code's skillOverrides) hides a description without editing the skill.

3. MCP servers. From $s/.mcp.json (a /cd does not move it) + settings, list enabled servers. Count tool names per server; note any server with long instructions. Flag servers irrelevant to the user's work.

4. Enablement levers and hooks. Read ~/.claude/settings.json, $p/.claude/settings.json, $r/.claude/settings.local.json and, when s differs from r, the legacy $s/.claude/settings.local.json. Check enableAllProjectMcpServers, enabledMcpjsonServers, enabledPlugins. Precedence: managed > local > project > user. Each plugin can pull in MCP servers, skills, agents, hooks. Measure SessionStart hook output (from its script, or a run the user approves) as a startup cost, and per-prompt UserPromptSubmit output as a cost per turn. Tool hooks' plain stdout stays out of the context, but their additionalContext enters it, a cost per matching tool call.

5. Memory. Lines of the memory index up to the agent's load cap (e.g. the first 200 lines or 25KB of MEMORY.md, whichever comes first); topic files load on demand and are not a startup cost.

Output

A short sizes table (source → ≈ tokens → auto-loaded? → relevant to user's work?), then a prioritized action list. For each action give the exact setting/file edit, the rough savings, and how to reverse it (prefer per-session toggles). Skip anything under ~a few hundred tokens unless asked to be exhaustive. Each action names the skill that performs it when available (look in the agent's skills and plugin dirs, as manual-only skills are missing from the in-session list), with this skill's own namespace prefix if any: a fat entry file → /agentify-project (slimming into docs); a fat memory index → /memory-doctor. Then ask before editing.

Useful probes

# anchors — p: the session's primary working directory after any /cd ($PWD when the shell sits there)
# s: the project root the session started in — p resolved below, right without a /cd; after one, or in a desktop-app worktree session (the main checkout root, which also serves its settings and hooks), set it by hand from the session's start context
# r: where settings.local.json lives — the repo root, or the main checkout's root in a linked worktree; outside git, when that root is $HOME, on Windows, or when its .git/.claude is not the user's: p
c=${CLAUDE_CONFIG_DIR:-$HOME/.claude}; p=$PWD; s=$(cd "$p" && pwd -P); g=$(git -C "$s" rev-parse --path-format=absolute --git-common-dir 2>/dev/null); r=${g:+$(dirname "$g")}; { [ -n "$r" ] && [ "$r" != "$HOME" ]; } || r=$p
# always-on instruction files: entry-file chain up to /, user-level and managed entry files, unscoped rules
d=$p; while :; do for f in AGENTS.md .claude/AGENTS.md CLAUDE.md .claude/CLAUDE.md CLAUDE.local.md; do [ "$d/$f" = "$c/CLAUDE.md" ] || { [ -f "$d/$f" ] && wc -w "$d/$f"; }; done; [ "$d" = / ] && break; d=$(dirname "$d"); done
wc -w "$c/CLAUDE.md" "/Library/Application Support/ClaudeCode/CLAUDE.md" /etc/claude-code/CLAUDE.md 2>/dev/null
find -L "$p/.claude/rules" "$c/rules" -name '*.md' -exec sh -c 'for f; do awk '"'"'NR==1&&$0!="---"{exit 1} NR>1&&$0=="---"{exit 1} NR>1&&/^paths:/{f=1;exit} END{exit !f}'"'"' "$f" || printf "%s\0" "$f"; done' _ {} + 2>/dev/null | xargs -0 -r wc -w
# enabled MCP + settings
{ [ -f "$s/.mcp.json" ] && cat "$s/.mcp.json"; } || echo "no .mcp.json at $s"; cat "$p/.claude/settings.json" "$r/.claude/settings.local.json" 2>/dev/null; [ "$s" = "$r" ] || cat "$s/.claude/settings.local.json" 2>/dev/null; cat "$c/settings.json" 2>/dev/null