implementation-notes

A decision log for coding work that spans several steps or files. It records the plan, important choices, departures from the plan, and unresolved questions.

In plain words
What is it for?
Use it to document architecture, library, data-handling, and error-handling decisions during a longer coding session.
Why use it?
It makes hidden assumptions visible and preserves why implementation choices were made.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/orenluxy/fable-method/implementation-notes
Any agent
npx skills add orenluxy/fable-method --skill implementation-notes
Clone the repo
git clone --depth 1 https://github.com/orenluxy/fable-method

Made for: Claude Code, Codex.

Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 552 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00066 $0.00552
Opus 5 $0.00033 $0.00276
Sonnet 5 $0.00013 $0.00110
Haiku 4.5 $0.00007 $0.00055

Measured yesterday against content hash 4392e38b7af9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implementation-notes 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 yesterday.

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/implementation-notes/SKILL.md · 49 lines

How it starts

The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Implementation Notes

Purpose: during long implementation runs, unknowns are discovered continuously. Without a log, they get resolved by silent guesses that the user never sees. This skill makes every guess visible and auditable.

Setup

At the start of implementation, create (or append to) IMPLEMENTATION_NOTES.md in the project root or the current working directory:

# Implementation Notes — <task name>
Session started: <date>

## Plan summary
<2–5 lines: what we agreed to build>

## Decisions
<!-- Choices made where alternatives existed. Format: what / why / alternative rejected -->

## Deviations
<!-- Any point where reality forced a departure from the plan. Format: what the plan said / what was found / conservative option taken -->

## Open questions
<!-- Unknowns deferred to the user. Must be empty or acknowledged before merge. -->

Rules during implementation

  1. Every non-obvious choice gets a Decisions entry. One line each. If you chose a library, a data structure, an error-handling strategy — log it.

  2. Deviation protocol. When an edge case or discovered constraint forces departure from the plan:

    • Take the most conservative option (least code changed, most reversible).
    • Log it under Deviations with: plan said → territory showed → what I did.
    • Continue. Do NOT stop the run for deviations resolvable conservatively.
    • Exception: if the deviation invalidates the plan's architecture, STOP and ask the user. Logging is not a license to rebuild the design silently.
  3. Deviations are a convergence signal. If the Deviations section is growing while tests are not converging, the plan is wrong — stop, summarize the deviations, and propose replanning instead of continuing to patch. Three or more deviations touching the same subsystem = automatic stop-and-replan.

  4. End of session. Read back the file. Anything under Open questions must be either answered by the user or explicitly accepted. Summarize the log in your final message — do not assume the user will open the file.

Read the full file on GitHub · 49 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. yesterday First seen · 49 lines · 66 tokens per session scan A 4392e38b7af9

Subscribe to this mod's changes

implementation-notes is a skill published in the GitHub repository orenluxy/fable-method (1 stars, last pushed 25d ago), licensed MIT. It adds 66 tokens to every session and 552 once invoked, about $0.0003 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.