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.
npx agentmods add skills/tellahq/opensession/pstacknpx skills add tellahq/opensession --skill pstackgit clone --depth 1 https://github.com/tellahq/opensessionWhat 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 | $0.00037 | $0.01002 |
| Opus 5 | $0.00018 | $0.00501 |
| Sonnet 5 | $0.00007 | $0.00200 |
| Haiku 4.5 | $0.00004 | $0.00100 |
Grade A, and why
pstack 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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 78 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Pstack mode
Treat the text after /pstack as the task. Pstack mode remains enabled for later turns in this Open Session session. /pstack off disables it. /poteto-mode is the longer name for the same mode.
This is the Open Session adaptation of pstack's Poteto Mode. It keeps the methodology, but uses Open Session's policy-gated tools and isolated child sessions instead of Pi extension tools. Higher-priority Open Session, repository, and user instructions always win. This mode never grants tools, credentials, or permission for external actions.
Start
For every nontrivial task:
- Inspect the current checkout and any partial work before proposing changes.
- Name the task shape and choose one playbook below.
- Keep a short checklist. Include skipped playbook steps with the reason when a step does not apply.
- State the data shape or invariant before changing code.
- Finish the promised work and verify the real artifact before reporting completion.
Do not turn a small task into ceremony. The smallest coherent process that produces trustworthy evidence is the goal.
Principles
Apply only principles that affect a real decision. Do not list principles decoratively in the final reply.
- Subtract first. Delete or reuse before adding a layer, abstraction, compatibility path, or dependency.
- Model the domain. Prefer a table, state machine, typed model, reducer, registry, or clear ownership boundary over scattered conditionals and coupled booleans.
- Design from the requirement. Integrate the requirement as if it had existed from the start instead of bolting on a side path.
- Keep boundaries strict. Validate external data at the edge. Keep internal logic typed and direct.
- Separate writers. Give concurrent workers isolated files, branches, or worktrees before adding locks or coordination.
- Fix root causes. Reproduce the symptom, trace the mechanism, and change the owning layer. Do not silence it with a guard unless the guard is the domain rule.
- Sequence verifiable units. Break large work into slices that each end in a meaningful check.
- Prove behavior. Compilation is supporting evidence. Exercise the user-facing behavior, protocol, output, or measured hot path that changed.
- Reduce reader load. Prefer fewer layers, less hidden state, and a shorter path from question to answer.
- Encode repeated lessons. If an instruction is needed twice, consider a test, type, lint, script, or metadata rule instead of more prose.
What ships with it
10 files 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.
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.
- 2d ago First seen · 78 lines · 37 tokens per session scan A 032357c67e1f
pstack is a skill published in the GitHub repository tellahq/opensession (327 stars, last pushed 2d ago), licensed MIT. It adds 37 tokens to every session and 1,002 once invoked, about $0.0002 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 2026-08-30.
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