append-run-log

append-run-log is a skill for Claude Code, Codex from OutlineDriven/outline-driven-development. It costs 63 tokens per session (1,089 once invoked), scanned A, original, Apache-2.0.

A record-keeping tool that appends completed agent runs to a JSONL log, a text file with one JSON object per line. It also removes expired entries and updates a pointer to the latest run.

In plain words
What is it for?
Use it to record run identifiers, timestamps, measurements, models, outcomes, and other metrics for later reporting or auditing.
Why use it?
It provides durable, searchable evidence of what ran and when without rewriting earlier records.

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/outlinedriven/outline-driven-development/append-run-log
Any agent
npx skills add OutlineDriven/outline-driven-development --skill append-run-log
Clone the repo
git clone --depth 1 https://github.com/OutlineDriven/outline-driven-development

Made for: Claude Code, Codex.

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 append-run-log

README.md
[![agentmods](https://agentmods.dev/badge/skills/outlinedriven/outline-driven-development/append-run-log.svg)](https://agentmods.dev/skills/outlinedriven/outline-driven-development/append-run-log)
Your own site
<a href="https://agentmods.dev/skills/outlinedriven/outline-driven-development/append-run-log"><img src="https://agentmods.dev/badge/skills/outlinedriven/outline-driven-development/append-run-log.svg" alt="Measured on agentmods" height="20"></a>
Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,089 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 5.1 $0.00063 $0.01089
Opus 5 $0.00032 $0.00544
Sonnet 5 $0.00013 $0.00218
Haiku 4.5 $0.00006 $0.00109

Measured yesterday against content hash 601eefc8a138, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

append-run-log 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.

.devin/skills/append-run-log/SKILL.md · 45 lines

How it starts

The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Append run log

Contract

Field Bound contract
Trigger A completed agent run must be recorded as durable, queryable evidence.
Authority Reversible local write to the run log only; prior entries are never rewritten.
Side effect Appends one entry to the append-only JSONL run log under an ISO-only date guard, prunes entries older than the declared retention window, and updates the last-run pointer.
Done Exactly one entry exists per run with a unique run id, malformed lines are ignored rather than corrupting the log, and aggregate metrics are derivable from the log alone.

Inputs

  • run_id: must be supplied, non-empty, and unique within the log.
  • started_at and ended_at: must be supplied as ISO 8601 UTC timestamps (YYYY-MM-DDTHH:mm:ssZ). The entry date guard is derived from ended_at.
  • metrics: must be supplied as a JSON object of run measurements (for example, duration, token count, model, outcome). Aggregates are computed from these fields alone.
  • log_path: must be supplied; path to the append-only JSONL run log.
  • last_run_pointer_path: must be supplied; path to the last-run pointer file.
  • retention_window: optional; an ISO 8601 duration or day count. When omitted, no pruning is performed.

Procedure

  1. Validate inputs at the trust boundary before any mutation: run_id is non-empty; started_at and ended_at parse as ISO 8601 UTC and ended_at is not before started_at; metrics is a JSON object. Reject any timestamp that is not ISO-only. Scan the log for an existing line whose parsed run_id equals the supplied one; if found, stop with rejected-duplicate and do not mutate. Done when: inputs parse and no duplicate run_id exists.
  2. Bound scope: open log_path in append-only mode. Do not read-modify-write or rewrite any prior line. Done when: log_path is open in append-only mode.
  3. Compose one JSONL entry as a single line: run_id, started_at, ended_at, metrics, and date set to the ISO date portion of ended_at as the date guard. Done when: the entry is a single line with all fields and metrics sufficient to derive aggregates.
  4. Append the entry as exactly one line terminated by a newline, then flush. No other line is altered. Done when: exactly one line with this run_id exists in the log.
  5. If retention_window is supplied, compute the cutoff from the current UTC date minus the window. Delete whole lines whose date precedes the cutoff. Never alter the content of a surviving line; deletion is the only mutation permitted on prior entries. Done when: expired lines are deleted and surviving lines are unaltered.
  6. Update the last-run pointer at last_run_pointer_path to an object containing the new run_id and ended_at. Done when: the pointer contains the new run_id and ended_at.

Read the full file on GitHub · 45 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 45 lines · 63 tokens per session scan A 601eefc8a138

Subscribe to this mod's changes

append-run-log is a skill published in the GitHub repository OutlineDriven/outline-driven-development (52 stars, last pushed yesterday), licensed Apache-2.0. It adds 63 tokens to every session and 1,089 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 2026-09-03.

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