thinkback

thinkback is a skill for Claude Code from irfad7/claude-power-skills. It costs 99 tokens per session (1,803 once invoked), scanned A, original, MIT.

A decision-review skill that examines the evidence and reasoning behind choices already made in a codebase. It uses records such as Git history, pull requests, comments, and architecture notes.

In plain words
What is it for?
Use it to investigate past technical decisions, judge whether they still make sense, and record lessons for future choices.
Why use it?
It helps you understand why a change was made before keeping or undoing it, even when the original context is gone.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the claude-power-skills plugin — 20 skills shipped together

Good fit Use it to investigate past technical decisions, judge whether they still make sense, and record lessons for future choices.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/irfad7/claude-power-skills/thinkback
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add irfad7/claude-power-skills --skill thinkback
Clone the repo
git clone --depth 1 https://github.com/irfad7/claude-power-skills

Made for: Claude Code.

Or install claude-power-skills, the plugin that ships this one along with the rest of its 20 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for thinkback

README.md
[![agentmods](https://agentmods.dev/badge/skills/irfad7/claude-power-skills/thinkback/github.svg)](https://agentmods.dev/skills/irfad7/claude-power-skills/thinkback)
Your own site
<a href="https://agentmods.dev/skills/irfad7/claude-power-skills/thinkback"><img src="https://agentmods.dev/badge/skills/irfad7/claude-power-skills/thinkback/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for thinkback

Your own site · 80×15
<a href="https://agentmods.dev/skills/irfad7/claude-power-skills/thinkback"><img src="https://agentmods.dev/badge/skills/irfad7/claude-power-skills/thinkback.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,803 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00099 $0.01803
Opus 5 $0.00049 $0.00901
Sonnet 5 $0.00020 $0.00361
Haiku 4.5 $0.00010 $0.00180

Measured 10d ago against content hash b670cf0f0fdd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

thinkback scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/thinkback/SKILL.md · 241 lines

How it starts

The opening of the file, as written. The whole thing — 241 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Thinkback — Decision Archaeology & Reasoning Replay

You are a decision archaeologist. You dig up past decisions, reconstruct the reasoning that led to them, evaluate whether those reasons still hold, and extract lessons for future decision-making.

Why Thinkback Exists

Every codebase is a fossil record of decisions. Most of those decisions made sense when they were made — but the context that justified them is lost. Developers inherit code and either: (a) blindly preserve decisions they don't understand, or (b) blindly undo decisions that were actually good. Thinkback prevents both.

Three Modes

Mode 1: Decision Archaeology (/thinkback dig [topic])

Reconstruct the full reasoning chain behind a past decision.

The Dig Process:

Step 1: Evidence Collection Gather every trace of the decision:

Evidence Sources:
1. Git blame — who wrote this code, when, what commit message?
2. Git log — what changed around the same time?
3. PR history — was there a PR? What was discussed?
4. Comments in code — any TODO, HACK, FIXME, NOTE annotations?
5. Decision files — LINEAGE.md, ADRs, design docs?
6. Memory files — MEMORY.md, SCARS.md references?
7. The code itself — what does the implementation reveal about intent?
8. Dependencies added — what was introduced around the same time?
9. Config changes — did environment or settings change?
10. Test files — what was tested (and what wasn't)?

Step 2: Context Reconstruction Build a picture of the world when the decision was made:

DECISION CONTEXT:
═══════════════════
When: [date from git blame/log]
Who: [author]
What existed then:
- [tech stack at the time]
- [scale/usage at the time]
- [team size/skills at the time]
- [constraints that may no longer exist]

What didn't exist yet:
- [features built after this decision]
- [tools/libraries that now exist]
- [requirements that came later]

Step 3: Reasoning Reconstruction Based on the evidence, reconstruct the likely reasoning:

RECONSTRUCTED REASONING:
═══════════════════════
The decision was: [what was decided]

Likely because:
1. [First reason — evidence: commit message / code pattern / timing]
2. [Second reason — evidence: dependency added / test written]
3. [Third reason — evidence: config change / comment in code]

Alternatives they likely considered:
- [Alternative A] — probably rejected because [reason]
- [Alternative B] — probably rejected because [reason]

Confidence in this reconstruction: [HIGH / MEDIUM / LOW]
- [Why this confidence level — what evidence is strong/weak]

Read the full file on GitHub · 241 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 241 lines · 99 tokens per session scan A b670cf0f0fdd

Subscribe to this mod's changes

thinkback is a skill published in the GitHub repository irfad7/claude-power-skills (4 stars, last pushed 1mo ago), licensed MIT. It adds 99 tokens to every session and 1,803 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.