What is agent-session-format-check?

A compatibility-checking procedure for agent session data, including stored session details, usage limits, and discovery paths. It compares current session formats with the latest available agent builds.

Use it for recurring compatibility checks, investigating agent CLI updates, checking monitoring flags, reviewing sample session files, and deciding whether supported-version records need attention.

It helps reveal when an agent update may have changed the data format or storage behaviour that monitoring tools depend on. It provides evidence before parsers, test fixtures, or documentation are changed.

agent-session-format-check — Skill by jazzyalex/agent-sessions

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/jazzyalex/agent-sessions

agentmods

npx agentmods add skills/jazzyalex/agent-sessions/agent-session-format-check

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/jazzyalex/agent-sessions/agent-session-format-check/github.svg)](https://agentmods.dev/skills/jazzyalex/agent-sessions/agent-session-format-check)

Your own site

<a href="https://agentmods.dev/skills/jazzyalex/agent-sessions/agent-session-format-check"><img src="https://agentmods.dev/badge/skills/jazzyalex/agent-sessions/agent-session-format-check/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jazzyalex/agent-sessions/agent-session-format-check"><img src="https://agentmods.dev/badge/skills/jazzyalex/agent-sessions/agent-session-format-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 15,480 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 4 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high Rogue Agent · line 217
Skill modifies its own code, configuration, or behavior at runtime. Self-modification enables an agent to escalate privileges, disable safety constraints, or install persistent backdoors.

Fix: Prevent the skill from modifying its own code, SKILL.md, or configuration files. Treat skill files as read-only at runtime.
high Agent Snooping · line 495
Skill reads from agent configuration directories (.claude/, .codex/, .gemini/). These directories may contain API keys, personal settings, and other credentials that the skill has no legitimate need to access.

Fix: Remove all code or instructions that access agent configuration directories (.claude/, .codex/, .gemini/). If configuration values are needed, pass them explicitly as parameters or environment variabl
high Agent Snooping · line 497
Skill reads from agent configuration directories (.claude/, .codex/, .gemini/). These directories may contain API keys, personal settings, and other credentials that the skill has no legitimate need to access.

Fix: Remove all code or instructions that access agent configuration directories (.claude/, .codex/, .gemini/). If configuration values are needed, pass them explicitly as parameters or environment variabl
medium Rogue Agent · line 353
Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.

Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00062	$0.15480
Opus 5.5	$0.00025	$0.06192
Sonnet 5.5	$0.00012	$0.03096
Haiku 4.5	$0.00006	$0.01548

Measured today against content hash f588e4a302d9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

agent-session-format-check scanned grade B with 1 finding 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 today.

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.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

grep -ho '"model":"[^"]*"' ~/.codex/sessions/$(date +%Y/%m)/*/*.jsonl | sort -u

skills/agent-session-format-check/SKILL.md · 1,024 lines

How it starts

The opening of the file, as written. The whole thing — 1,024 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Session Format Check

Answer one precise question for every supported agent:

Can current Agent Sessions code support the latest available session/storage/usage format from the latest available agent build?

The answer must be layered. Do not collapse version checks, stale samples, schema fingerprints, discovery contracts, and usage probes into a vague severity label.

Evidence-first:

Gather a report + sample paths first.
Do not change parsers/fixtures/docs without explicit user approval.

Related skill: agent-support-matrix — maintains the matrix YAML, ledger, and update-checklist workflow. This skill focuses on detection and evidence collection; agent-support-matrix focuses on recording and gating version bumps.

Process doc: docs/agent-support/monitoring.md — defines the compatibility verdicts, legacy severity model, cadence, and escalation workflow that feed into this skill.

1 Quick Start (all agents)

Run weekly monitoring:
```
./scripts/agent_watch.py --mode weekly
```
Report path prints to stdout and is written under scripts/probe_scan_output/agent_watch/*/report.json.
In report.json, check each agent under results.<agent>:
- compatibility.verdict, compatibility.scope, compatibility.blockers, and compatibility.next_action
- verified_version, installed.parsed_version, upstream.parsed_version
- compatibility.latest_status to distinguish current_fetch_known, cached_latest, and unknown latest-source states
- weekly.local_schema (newest local session used for fingerprinting)
- weekly.schema_diff and evidence.schema_matches_baseline
- evidence.sample_freshness and evidence.fresh_evidence_source
- compatibility.latest_real_session_failure when a prebump attempt failed
- severity and recommendation only as legacy escalation fields
Sanity-check version identity before acting on it. If a monotonic CLI reports an installed version newer than upstream.parsed_version, or the fetched tag belongs to a different release family (for example an SDK release instead of the CLI), treat the latest source as broken/unknown. Do not follow a generated prebump recommendation for an agent with no driver, and do not lower a verified ceiling to match a bad source.

Read the full file on GitHub · 1,024 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.

today Changed · +61 lines f588e4a302d9
yesterday Changed · +44 lines fb1442fdb088
7d ago Changed · +25 lines 97c8f62d92d4
1mo ago Changed · +34 lines c8e70eaff4d4
1mo ago Changed · +65 lines 5e0db1dd7023
1mo ago First seen · 795 lines · 62 tokens per session scan B ec6fb17eb515

Subscribe to this mod's changes

agent-session-format-check is a skill published in the GitHub repository jazzyalex/agent-sessions (907 stars, last pushed today), licensed MIT. It adds 62 tokens to every session and 15,480 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Claude Code Testing agentic-workflow ai codex codex-cli developer-tools

do-it-verify

Use when selecting evidence for a delivery claim, regression fix, installation, or branch closeout.

tdwhere123/do-it · 24 tokens

build-and-runtime-verification

Use when running build, compile, test, launch, or runtime checks and producing a verdict tied to exact commands, exit codes, artifact paths, limitations, and fresh evidence.

hoatv2211/GameStudio-CodexKIT · 41 tokens

evidence-first-debugging

Use when debugging a crash, lỗi, failing game, tool, build, service, script, or reproducible local code failure requires repro or reproduction, giả thuyết or ranked hypotheses, instrumentation, root-cause isolation, a minimal fix, regression proof, and a regression test.

hoatv2211/GameStudio-CodexKIT · 63 tokens

agent-session-format-check