Add /this-session plugin — live session token & cost monitor

[afmuhaidib]

What this adds

A new plugin and /this-session slash command that prints a live dashboard of the current Claude Code session directly in chat.

Why

When working on a long session it's hard to know how many tokens you've burned, what the actual cost looks like, or whether the prompt cache is doing its job. This command gives you that at a glance without leaving the chat.

Dashboard

╔════════════════════════════════════════════════════════════╗
║  SESSION MONITOR                                           ║
╚════════════════════════════════════════════════════════════╝

  SESSION ID   7003719e-9333-448c-b8a5-dae15f4f5823
  STARTED      6/10/2026, 2:41:25 PM
  DURATION     18m 42s
  USER TURNS   12
  API CALLS    31

  ┌────────────────────────────────────────────────────────────┐
  │ TOKENS                                                     │
  ├────────────────────────────────────────────────────────────┤
  │  Input (direct)               34  ░░░░░░░░░░░░░░░░░░░░    │
  │  Output                   10,006  ░░░░░░░░░░░░░░░░░░░░    │
  │  Cache write              37,182  █░░░░░░░░░░░░░░░░░░░    │
  │  Cache read            1,119,335  ███████████████████░    │
  │  TOTAL                 1,166,557                          │
  │  Cache hit rate             96.8%                         │
  └────────────────────────────────────────────────────────────┘

  ┌────────────────────────────────────────────────────────────┐
  │ COST                                                       │
  ├────────────────────────────────────────────────────────────┤
  │  Actual cost               $0.6254                        │
  │  Without cache             $3.6197                        │
  │  Cache savings             $2.9943                        │
  └────────────────────────────────────────────────────────────┘

  ┌────────────────────────────────────────────────────────────┐
  │ MODELS                                                     │
  ├────────────────────────────────────────────────────────────┤
  │  claude-sonnet-4-6         32 calls    $0.6254            │
  │    in 34                  out  10,006  ████████████       │
  └────────────────────────────────────────────────────────────┘

  ┌────────────────────────────────────────────────────────────┐
  │ TOOLS (top 3)                                              │
  ├────────────────────────────────────────────────────────────┤
  │  Bash                          18×  ██████████████████    │
  │  Edit                           2×  ██░░░░░░░░░░░░░░░░    │
  │  Write                          1×  █░░░░░░░░░░░░░░░░░    │
  └────────────────────────────────────────────────────────────┘

How it works

• Reads ~/.claude/projects/<cwd-slug>/*.jsonl (the live session transcript written by Claude Code)
• De-duplicates repeated assistant message entries
• Aggregates per-model token counts: input, output, cache-write, cache-read
• Applies current Anthropic pricing for Opus 4.x, Sonnet 4.6, Haiku 4.5 to compute actual cost and what it would cost without caching
• Handles case-insensitive path matching (macOS symlink/case edge cases)

Files

plugins/this-session/
├── README.md                      # Plugin docs
├── this-session.mjs               # Zero-dependency Node.js analyzer
└── commands/
    └── this-session.md            # Slash command definition

Installation

cp plugins/this-session/commands/this-session.md ~/.claude/commands/
cp plugins/this-session/this-session.mjs ~/.claude/commands/

Type /this-session in any session.

Notes

• Zero npm dependencies — plain Node.js ≥ 18
• Works with mixed-model sessions (e.g. Sonnet main + Opus subagents)
• Pricing table is easy to update in the script as Anthropic adjusts rates

[stevei101]

Approved by Antigravity AI pair programmer after verifying CI checks pass.