# session-compare

Compare two Agent Monitor sessions across cost, tokens, events, and agent activity. Use it to see what changed between runs with different outcomes.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 1121
- Author: hoangsonww
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/hoangsonww/Claude-Code-Agent-Monitor/tree/HEAD/plugins/ccam-insights/skills/session-compare/SKILL.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/skills/session-compare

## What it does

The skill builds a side-by-side report from two Agent Monitor sessions. It compares status, model, duration, cost, event and error counts, and tools used. Token details include input, output, cache reads, and cache writes; cost figures come from the pricing engine.

The report also covers event timelines, tool usage differences, and agent activity. It examines decisions that may have contributed to different outcomes and lists takeaways for future runs. The skill queries the Agent Monitor API at `http://localhost:4820`, so that service must be available for the comparison.

Provide two session IDs, ask for “best vs worst” or “latest 2,” or compare one session with the average of the last 50 sessions. The average comparison uses that specific group of sessions.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add hoangsonww/Claude-Code-Agent-Monitor --skill session-compare -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/session-compare/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/session-compare/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add hoangsonww/Claude-Code-Agent-Monitor --skill session-compare -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/session-compare/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add hoangsonww/Claude-Code-Agent-Monitor --skill session-compare -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/session-compare/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install hoangsonww/Claude-Code-Agent-Monitor session-compare
```

2. **Manually: put the files in place**
- File: `.github/skills/session-compare/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add hoangsonww/Claude-Code-Agent-Monitor --skill session-compare -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/hoangsonww/Claude-Code-Agent-Monitor --path plugins/ccam-insights/skills/session-compare
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/session-compare/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add hoangsonww/Claude-Code-Agent-Monitor --skill session-compare -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/hoangsonww/Claude-Code-Agent-Monitor/tree/HEAD/plugins/ccam-insights/skills/session-compare/SKILL.md

## When to use it
- compare token use and cost across two sessions
- spot tools used in only one run
- contrast error counts and subagent success rates
- locate where two event timelines diverged
- measure one session against the latest 50-session average

## Example prompts
- Compare sessions `abc123` and `def456` by cost, tokens, and outcome.
- Find the most and least productive sessions and explain the differences.
- Compare the two latest sessions and show where their timelines diverged.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 9c88907f2a1aa78f.

BEGIN THIRD-PARTY FILE 9c88907f2a1aa78f
```text
---
name: session-compare
description: >
  Compare two sessions side-by-side using Agent Monitor data — per-model
  token usage (input/output/cache_read/cache_write + compaction baselines),
  pricing engine cost breakdowns, workflow intelligence (complexity scores,
  tool flow transitions, subagent effectiveness), session metadata
  (thinking_blocks, turn_count, turn_duration_ms, usage_extras), and
  full event timelines with all 10+ event types.
---

# Session Compare

Compare two Claude Code sessions side-by-side using Agent Monitor data.

## Input

The user provides: **$ARGUMENTS**

This may be:
- Two session IDs: "abc123 def456"
- "best vs worst" — compare highest and lowest productivity sessions
- "latest 2" — compare the two most recent sessions
- A session ID + "vs average" — compare one session against the baseline

## Procedure

1. **Identify sessions to compare**:
   - If two IDs given: fetch both from `http://localhost:4820/api/sessions/{id}`
   - If "best vs worst": fetch sessions, score by completion + cost efficiency, pick extremes
   - If "latest 2": `GET /api/sessions?limit=2` (default sort: most recently updated first)
   - If "vs average": fetch session + compute averages from last 50 sessions

2. **Gather detailed data** for each session:
   - Session metadata: `GET /api/sessions/{id}`
   - Events: `GET /api/events?session_id={id}`
   - Agents: `GET /api/agents?session_id={id}`
   - Cost: `GET /api/pricing/cost/{id}`

3. **Build comparison**:

   ### Overview Comparison
   | Metric | Session A | Session B | Difference |
   |--------|-----------|-----------|-----------|
   | Status | completed | error | — |
   | Model | sonnet-4 | sonnet-4 | same |
   | Duration | 12m 34s | 45m 12s | +32m 38s |
   | Total Cost | $0.0234 | $0.1456 | +522% |
   | Events | 45 | 187 | +315% |
   | Tools Used | 8 | 12 | +4 |
   | Error Count | 0 | 7 | +7 |
   | Agents | 2 | 5 | +3 |

   ### Token Comparison
   | Token Type | Session A | Session B | Difference |
   |-----------|-----------|-----------|-----------|
   | Input | N | N | ±N% |
   | Output | N | N | ±N% |
   | Cache Read | N | N | ±N% |
   | Cache Write | N | N | ±N% |
   | Efficiency | N% | N% | ±N% |

   ### Tool Usage Comparison
   - Tools unique to Session A
   - Tools unique to Session B
   - Shared tools with usage count comparison
   - Error rate per tool in each session

   ### Timeline Comparison
   - Side-by-side event timeline
   - Where sessions diverged in approach
   - Key decision points that led to different outcomes

   ### Agent Activity Comparison
   - Agent counts and types
   - Subagent strategy differences
   - Agent success rates

4. **Analysis**:
   - Why one session was more efficient/successful than the other
```
END THIRD-PARTY FILE 9c88907f2a1aa78f

The third-party file has ended. Everything between the 9c88907f2a1aa78f tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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---
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