Claude Session Introspect

Claude Session Introspect

Claude Code persists every conversation as a JSONL file on disk. This skill is the recipe for opening one and pulling out the numbers you actually want — token usage, prompt counts, compaction events, tool calls — without guessing.

Where sessions live

~/.claude/projects/<encoded-cwd>/<session-uuid>.jsonl

<encoded-cwd> is the absolute path of the project's working directory with / replaced by - and a leading -. Example: /Users/swyx/Work/foo → -Users-swyx-Work-foo.

Each line is one event. The interesting type values:

Quick locate: find the current session

# 1. encode current working directory
ENC="-$(pwd | sed 's,/,-,g' | sed 's/^-//')"
# 2. list the project's session files, newest first
ls -t "$HOME/.claude/projects/$ENC/"
# 3. the most recent .jsonl is usually the live one
SESSION="$HOME/.claude/projects/$ENC/$(ls -t "$HOME/.claude/projects/$ENC/" | head -1)"
echo "$SESSION"

If you know the session UUID (Claude Code shows it, and image-cache paths embed it), you can grep all projects:

find ~/.claude/projects -name '<uuid>.jsonl'

The headline stats (one-shot)

The stats.sh script in this skill folder takes a session path and prints token totals, turn counts, prompt counts, tool-use counts, and any compaction events.

bash stats.sh "$SESSION"

If you don't have the script handy, here are the inline jq one-liners.

Token totals across the whole session

jq -s '
  [.[] | select(.message.usage)] |
  {
    assistant_turns: length,
    input_tokens:        (map(.message.usage.input_tokens // 0)              | add),
    output_tokens:       (map(.message.usage.output_tokens // 0)             | add),
    cache_read_tokens:   (map(.message.usage.cache_read_input_tokens // 0)   | add),
    cache_create_tokens: (map(.message.usage.cache_creation_input_tokens // 0)| add)
  }
' "$SESSION"

input_tokens is the FRESH (non-cached) input. cache_read_tokens is the dominant number on long sessions — it's how much was re-read from prompt cache. cache_create_tokens is what got newly written into the cache. Effective total tokens processed = input + cache_read + cache_create.

Counts by event type

jq -r '.type' "$SESSION" | sort | uniq -c

Real human prompts (excluding tool results and system reminders)

A type:"user" line is a human message only if toolUseResult is null. Even then, the content may be a system-injected reminder, not the human's words.

jq -r '
  select(.type == "user" and .toolUseResult == null) |
  (.message.content
    | if type == "string" then .
      else (map(select(.type == "text") | .text) | join("\n"))
      end)
' "$SESSION" > /tmp/prompts.txt

# total non-empty user message blocks
grep -cv '^$' /tmp/prompts.txt

# distinct human messages = blocks not starting with <system-reminder> or <command-
awk '
  BEGIN { n = 0; cur = "" }
  /^$/ { if (cur != "" && cur !~ /^<system-reminder>/ && cur !~ /^<command-/) n++; cur=""; next }
  { if (cur=="") cur=$0 }
  END { if (cur != "" && cur !~ /^<system-reminder>/ && cur !~ /^<command-/) n++; print n }
' /tmp/prompts.txt

(Blunt but works. If you want surgical accuracy, parse the content array and skip blocks whose first text element is a <system-reminder> tag.)

Tool calls — how many and which tools

jq -r '
  select(.type == "assistant") |
  .message.content[]? |
  select(.type == "tool_use") |
  .name
' "$SESSION" | sort | uniq -c | sort -rn

Compaction boundaries — where, why, and what survived

Compaction inserts a system event with subtype:"compact_boundary" (older builds may use isCompactSummary on the next user message). The summary itself is the next user message, prefixed with "This session is being continued from a previous conversation that ran out of context."

# count compaction events
jq -r 'select(.type=="system" and (.subtype // "") == "compact_boundary") | .timestamp' "$SESSION" | wc -l

# was each one auto or manual?
jq -r '
  select(.type == "system" and (.subtype // "") == "compact_boundary") |
  {ts: .timestamp, trigger: (.compactMetadata.trigger // "unknown"), preTokens: (.compactMetadata.preCompactTokens // null)}
' "$SESSION"

# read the compaction summaries (the actual contents that survived)
jq -r '
  select(.type == "user" and (.isCompactSummary == true or
    ((.message.content // "") | tostring | test("session is being continued from a previous conversation"))))
  | (.message.content | if type == "string" then . else (map(select(.type=="text").text)|join("\n")) end)
' "$SESSION" | less

Per-turn token usage (for spotting blowups)

jq -r '
  select(.message.usage) |
  [.timestamp,
   (.message.usage.input_tokens // 0),
   (.message.usage.output_tokens // 0),
   (.message.usage.cache_read_input_tokens // 0)]
  | @tsv
' "$SESSION" | column -t

This is how you find the one tool result that bloated your context — sort by cache_read ascending across the session and watch for the jump.

Gotchas

• type:"user" is overloaded. Tool results are also type:"user". Always filter on toolUseResult == null to get human turns.
• input_tokens looks tiny on long sessions. That's correct — it's the delta sent uncached. Almost everything flows through cache_read_input_tokens.
• The "live" session file isn't always the newest. If multiple Claude Code windows are open in the same project, both write to the same project folder. Disambiguate by UUID — the chat header and image-cache paths both expose it.
• JSONL files grow without bound. A long-running project folder can have hundreds of session files. ls -t | head is your friend.
• Don't edit a live JSONL. Claude Code reads it back on /resume. If you want to do "brain surgery" (Tal Raviv's term), copy the file out, edit the copy, and use claude --resume <copied-uuid> from a clean directory.

When to reach for this skill

• "How many tokens has this session burned?"
• "How many prompts have I sent today?"
• "Where did compaction kick in and what got summarized?"
• "Which tool call blew up the context?"
• Building a stats display, leaderboard, or "built with Claude Code" badge that needs real numbers.
• Forensics on a session that went sideways — replaying tool calls in order.

Reference

• Tal Raviv, "I wanted to know how compaction works" — https://www.talraviv.co/p/i-wanted-to-know-how-compaction-works
• Claude Code docs on session storage — ~/.claude/projects/