# Session Report

> Use when the user asks what they are spending on Claude, how many tokens something cost, why a session got expensive, or how well caching is working. Triggers: 'session report', 'token usage', 'how many tokens', 'what did that cost', 'am I burning tokens', 'cache hit rate', 'why is this session so expensive', 'which project costs most', 'show my usage', 'usage this week', 'last 7 days', 'claude stats', 'token breakdown', 'subagent cost'. Also use proactively after a long or context-heavy session when the user wonders where the budget went. Reads Claude Code's own JSONL transcripts under ~/.claude/projects; on other harnesses it reports that no compatible transcripts exist rather than inventing numbers.

- Skill: `tamircohen28/session-report` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add tamircohen28/session-report`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tamircohen28/session-report/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Docs & Writing
- Author: Tamircohen28 (https://skillmd.com/u/tamircohen28)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tamircohen28/session-report

---


# Session Report

## Compatibility — this skill is Claude Code specific

**It is not portable, and it does not pretend to be.** `analyze-sessions.mjs` parses Claude
Code's own JSONL transcript format, and it depends on details of that format that no other
harness produces:

- one API response split across multiple `type:"assistant"` entries sharing a `requestId`,
  where only the last carries the final `output_tokens` (dedupe by `requestId`, keep the max
  — without this the totals are 3–10× too high);
- `isSidechain` / `isMeta` / `isCompactSummary` flags to tell a human turn from a tool
  result, an interrupt marker, or a compaction summary;
- subagent transcripts at `<project>/<sessionId>/subagents/*.jsonl` with a sibling
  `*.meta.json` carrying `agentType`;
- `usage.cache_read_input_tokens` / `cache_creation_input_tokens` for the cache-hit rate;
- global dedupe by entry `uuid`, because a resumed session re-serializes prior entries.

These were established empirically against Claude Code transcripts. They are Claude Code
internals, not a standard.

| Target | Status | Basis |
|---|---|---|
| Claude Code | supported | Writes the format this parser reads |
| Claude Desktop | partial | Same plugin artifact, but its transcripts are only readable here if they land in `~/.claude/projects` in the same JSONL shape. The skill **checks this at run time** (step 0a) rather than assuming it. |
| Codex CLI, Cursor, Gemini CLI, OpenCode | unsupported | None of them writes this format. There is no adapter parser, and none is faked. |

Note the registry marks `session_transcripts` as `unknown` for those four — meaning it is
unverified whether they persist transcripts at all. This skill's `unsupported` is a stronger
and separately-founded claim: even where transcripts exist, they are not in the format this
parser reads, so the answer is the same either way.

### Why there are no adapter parsers yet

Writing a parser for another harness's transcripts requires reading that harness's real
output and verifying the token accounting against it. Nothing here has been verified against
Codex, Cursor, Gemini CLI or OpenCode transcripts, so shipping a parser for them would be a
guess presented as support — precisely the failure this framework calls out. The honest
statement is "unsupported", and it stays that way until someone produces evidence.

**The extension point exists** for when that evidence arrives: `analyze-sessions.mjs` already
takes `--dir <transcripts-dir>`, so an adapter's job is to normalise another harness's logs
into this JSONL shape and point `--dir` at the result. Adding an adapter means adding a
parser, a fixture, and a test that proves the token accounting — then, and only then,
changing that row from `unsupported`.

**Never** run this skill on another platform and present a partial or empty result as a usage
report. Report the incompatibility.

---

Generate a self-contained interactive HTML report of Claude Code session usage — tokens consumed, cache performance, subagent costs, skill invocations, and the single most expensive prompts — from the local `~/.claude/projects` transcripts.

## Why this skill exists

Claude Code stores full JSONL transcripts per project under `~/.claude/projects/`. Without tooling, finding where tokens are going requires manually parsing thousands of JSON lines. The bundled `analyze-sessions.mjs` script reads all transcripts in a configurable time window, aggregates by project/skill/subagent type, computes cache-hit rates, and surfaces the top prompts by raw token cost. The companion `template.html` renders this data as sortable tables with inline bar charts — no external CDN, no server, just a single HTML file. The model's job is to run the analysis, inject the JSON data blob, and write 3–5 human-readable findings into the anomalies and optimizations blocks.

## Workflow

### 0. Resolve the skill directory

Before running any script, locate the skill directory. Try in order:

1. Use `$CLAUDE_SKILL_DIR` if set
2. Use `$CLAUDE_PLUGIN_ROOT/skills/toolkit/session-report` if `$CLAUDE_PLUGIN_ROOT` is set
3. Resolve via: `find ~/.claude/plugins -path "*/toolkit/session-report/analyze-sessions.mjs" -print -quit | xargs dirname`

Assign the resolved path to `SKILL_DIR`. If none of the above produces a valid path with `analyze-sessions.mjs` present, stop and tell the user the plugin root could not be found.

### 0a. Verify transcript compatibility before analysing anything

```bash
TRANSCRIPT_DIR="${CLAUDE_PROJECTS_DIR:-$HOME/.claude/projects}"
if [ ! -d "$TRANSCRIPT_DIR" ]; then
  echo "no-transcript-dir"
elif [ -z "$(find "$TRANSCRIPT_DIR" -name '*.jsonl' -print -quit 2>/dev/null)" ]; then
  echo "no-transcripts"
else
  echo "ok"
fi
```

| Result | What to do |
|---|---|
| `ok` | Proceed to step 1. |
| `no-transcripts` | Directory exists but holds no JSONL. Normal on a fresh install — say so and stop. |
| `no-transcript-dir` | **Stop.** Report the incompatibility, do not analyse anything. |

For `no-transcript-dir`, say exactly what is true:

```
session-report reads Claude Code's JSONL transcripts from ~/.claude/projects. That directory
does not exist here, so there is nothing to analyse.

This skill is Claude Code specific — it parses Claude Code's own transcript format and has no
adapter for <platform>. It is not that your usage is zero; it is that this skill cannot see
it. For usage figures on <platform>, use that platform's own reporting.
```

Never soften this into "no usage found" — an empty report and an incompatible platform look
identical to the user and mean completely different things.

### 1. Parse the time window from user input

If the user provided a time window (e.g. "7 days", "last week", "since Monday", "30d", "24h"), map it to the `--since` flag:

| User says | Flag |
|-----------|------|
| "last 7 days" / "this week" / "7d" | `--since 7d` |
| "last 24 hours" / "today" / "24h" | `--since 24h` |
| "last 30 days" / "this month" / "30d" | `--since 30d` |
| "since Monday" | `--since <ISO date of most recent Monday>` |
| nothing / "all time" | (no `--since` flag) |

Default to `--since 7d` if the user didn't specify.

### 2. Run the analyzer

```bash
node "$SKILL_DIR/analyze-sessions.mjs" --json --since 7d > /tmp/session-report.json
```

Capture stderr separately if debugging. Check that the exit code is 0 before proceeding.

**If node is not installed:** Tell the user to install Node.js (>= 18) and re-run.

**If `~/.claude/projects` doesn't exist or is empty:** Tell the user no transcripts were found. This is normal on a fresh install. The report cannot be generated without transcript data.

**If the JSON output is `{}` or has `overall.api_calls == 0`:** The time window produced no data. Ask the user if they want to widen the window (e.g. remove `--since` for all-time).

### 3. Read and internalize the JSON

Read `/tmp/session-report.json`. Key fields to review before writing findings:

| Field | What to look for |
|-------|-----------------|
| `overall.input_tokens.total` + `overall.output_tokens` | Baseline — denominates all percentages |
| `overall.input_tokens.pct_cached` | Flag if below 85% |
| `by_project` | Any single project >40% of total |
| `by_subagent_type` | Any type averaging >1M tokens/call |
| `by_skill` | Skills with high call counts and high per-call token cost |
| `top_prompts[0].total_tokens` | Any single prompt >2% of total tokens |
| `cache_breaks` | Clustering (same project, same time window) |
| `overall.subagent.calls` | 0 = no subagents used (normal for some workflows) |

If `overall.api_calls` is 0 or the JSON is empty, stop and report that no data was found for the requested window.

### 4. Copy the template to the output path

```bash
cp "$SKILL_DIR/template.html" "./session-report-$(date +%Y%m%d-%H%M).html"
```

Capture the exact output path — you will report it to the user at the end. Do NOT write to `/tmp/` — the user expects the file in the current working directory.

### 5. Inject data and write findings

Use `Edit` (not `Write`) to preserve the template's CSS and JS.

**a) Inject the raw JSON data blob**

Replace the contents of:
```html
<script id="report-data" type="application/json">
```
...with the full contents of `/tmp/session-report.json`. The page JS renders everything (tables, bars, drill-downs) from this blob automatically.

If the JSON exceeds 2 MB, trim `top_prompts` and `cache_breaks` to 100 entries each before embedding. Parse the JSON in Bash, trim, re-serialize, then inject.

**b) Write the anomalies block**

Fill `<!-- AGENT: anomalies -->` with 3–5 findings. Exact markup per finding:
```html
<div class="take bad"><div class="fig">41.2%</div><div class="txt"><b>cc-monitor</b> consumed 41.2% of the week across just 3 sessions</div></div>
<div class="take good"><div class="fig">92.4%</div><div class="txt"><b>Cache hit rate</b> healthy at 92.4% — no action needed</div></div>
<div class="take info"><div class="fig">7</div><div class="txt"><b>repo-polish</b> was the most-invoked skill (7 calls, 3.2% of total)</div></div>
```

CSS class reference:

| Class | Color | Use for |
|-------|-------|---------|
| `.take.bad` | Red | Waste, anomalies, disproportionate cost |
| `.take.good` | Green | Healthy signals, goals met |
| `.take.info` | Blue | Neutral facts, context |

The `.fig` is one short value: a `%`, a count, or a multiplier like `12×`. Express token figures as a **% of total tokens** wherever possible — use the actual decimal from the JSON (`41.2%`, not `41%`). Name the subject (project/skill/prompt) in `<b>` inside `.txt`.

Look for these patterns:
- A single project or skill consuming >35% of total tokens → `.take.bad`
- Cache hit rate below 85% → `.take.bad`
- A single prompt exceeding 2% of all tokens → `.take.bad`
- Subagent types averaging >1M tokens/call → `.take.bad`
- Cache breaks clustering in the same project within a short window → `.take.info` or `.take.bad`
- Cache hit rate > 92% → `.take.good`
- Well-distributed projects (no outlier) → `.take.good`

If you find fewer than 3 anomalies, add `.take.info` neutral facts (total sessions, active hours, most-used skill) to reach 3 minimum.

**c) Write the optimizations block**

Fill `<!-- AGENT: optimizations -->` (near the bottom) with 1–4 suggestions tied to specific data rows:
```html
<div class="callout">/weekly-status spawned 7 subagents for 8.1% of total — consider scoping to fewer parallel agents or reducing the transcript window.</div>
```

Each suggestion must reference a specific project, skill, or prompt by name from the JSON. Do not write generic optimization advice.

### 6. Report the saved path

Tell the user the exact path to the saved HTML file. Do not open or render it inline.

```
Saved: ./session-report-20260616-1430.html
```

Optionally, summarize the top 2–3 findings in plain text so the user gets immediate value without opening the file.

## Hard rules

- **Never rewrite the template from scratch.** Use `Edit` to patch the two agent blocks and the data script tag only. All other markup, CSS, and JS must remain untouched.
- **Never omit the JSON injection.** An empty `<script id="report-data">` will render a blank page.
- **Express token figures as % of total** in the anomaly narrative. Raw counts are already in the table.
- **Do not invent findings.** Every anomaly sentence must reference an actual field value from the JSON (a project name, a number, a rate).
- **Use the correct output filename pattern** `session-report-$(date +%Y%m%d-%H%M).html` — never overwrite a previous report.
- **Do not hardcode absolute user paths** in commands. Always use `$SKILL_DIR` resolved in step 0.
- **Do not round figures to round numbers** — that signals hallucination. Use the actual decimal from the JSON.
- **Always check for zero-data before proceeding.** Do not inject an empty JSON blob and silently produce a blank report.

## What NOT to do

- **Do not skip the analyzer step and hallucinate numbers.** Always run `analyze-sessions.mjs --json` first.
- **Do not write the report to a temp path.** The user expects the file in the current working directory.
- **Do not add new HTML sections.** The template layout is fixed; only the two agent comment blocks and the data tag are yours to fill.
- **Do not use `Write` to save the report.** `Write` would discard the template's CSS/JS. Always `cp` first, then `Edit`.
- **Do not proceed if node is missing.** Give the user actionable install instructions instead.
- **Do not silently produce an empty report.** If data is zero or the window produces nothing, ask the user to widen the window.

## Quick-reference: anomaly detection checklist

```
[ ] cache_hit_rate < 85%             → .take.bad finding
[ ] any project  > 35% of total      → .take.bad finding
[ ] any prompt   > 2% of total       → .take.bad finding
[ ] any subagent type avg > 1M tok/call → .take.bad finding
[ ] cache_breaks clustering (same proj) → .take.info or .take.bad
[ ] cache_hit_rate > 92%             → .take.good finding
[ ] well-distributed projects        → .take.good finding
[ ] zero api_calls in window         → ask user to widen window, stop
[ ] node not found                   → give install instructions, stop
[ ] ~/.claude/projects missing       → explain fresh-install state, stop
```