Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed thresholds. Discovers available MCPs and queries each evidence category (source control, issue tracker, long-form docs, real-time chat, infrastructure observability, error tracking, product analytics warehouse) in parallel, then returns a cited read on decisions and tradeoffs. Use how for runtime behavior.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Why
In Claude Code, read [the Claude Code adapter](../../docs/harness/claude-code.md) once per session before you follow this skill. It maps the Cursor names in pstack skills to Claude Code.
Investigate the motivation and intent behind code. The companion `how` skill answers what the code does and how it works. `why` answers what forces led to its shape.
Each spawn below names a role line in the `pstack-models.mdc` rule and a default. Set `model` to that line's value, or to the default if the rule or the line is missing. Leave `model` unset when the value is `auto` or `inherit-parent`. If the Task tool rejects a slug, use the default and say so. If it rejects the default, use the closest valid slug of the same family from its error message. Pick each subagent's reasoning level and fast or standard speed for the job, per the Subagents section of the **poteto-mode** skill.
Every spawn is `generalPurpose` with `readonly: false` (agent mode). **Do not use readonly/Ask mode.** It strips MCP access, which disables the MCP-backed investigators and the synthesizer's citation spot-checks. Investigators still shouldn't write anything.
## Operating Posture
…
The line at the top of this page pins the label git:20261016.182f2ce, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_3bxzamv6wzdlbza7
GET https://markdownregistry.com/api/v1/resolve?ref=cursor/plugins/why
GET https://markdownregistry.com/api/v1/blob/09405adc5afda90841f16318e471f25329d17da908956d79973edb34cdccb188
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
cursor/plugins · advisor/skills/advisor/SKILL.md · Advisor mode. Consult a stronger (or different) model at key checkpoints: before major decisions, when stuck on an…
cursor/plugins · agent-compatibility/skills/check-agent-compatibility/SKILL.md · Run the full repository compatibility pass: scanner score, startup path, validation loop, and docs reliability.
cursor/plugins · cli-for-agent/skills/cli-for-agents/SKILL.md · Designs or reviews CLIs so coding agents can run them reliably: non-interactive flags, layered --help with examples…
cursor/plugins · create-plugin/skills/create-plugin-scaffold/SKILL.md · Create a new Cursor plugin scaffold with a valid manifest, component directories, and marketplace wiring. Use when…
cursor/plugins · create-plugin/skills/review-plugin-submission/SKILL.md · Audit a Cursor plugin for marketplace readiness. Use when validating manifests, component metadata, discovery paths…
cursor/plugins · cursor-sdk/skills/cursor-sdk/SKILL.md · Guide users building apps, scripts, CI pipelines, or automations on top of the Cursor TypeScript SDK (`@cursor/sdk`)…
cursor/plugins · cursor-team-kit/skills/control-cli/SKILL.md · Build or adapt a local harness to drive, inspect, and profile an interactive CLI or TUI without external services. Use…
cursor/plugins · cursor-team-kit/skills/control-ui/SKILL.md · Build or adapt a local browser/CDP harness to drive and inspect a web, IDE, or Electron UI. Use for local UI…
cursor/plugins · pstack/skills/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
michael-denyer/pstack-claude · plugins/pstack/skills/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
backnotprop/pstack · skills/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
bastani-inc/atomic · packages/workflows/skills/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
millw14/merrymen · plugins/merrymen/skills/why/SKILL.md · Explain why the user's Merrymen trading agent has or hasn't traded, from its recorded state, blockers and recent…
j-star-films-studios/vibecode-protocol-suite · assets/.agent/skills/code-intelligence/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
creedants/pstack-t3 · t3/overrides/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
creedants/pstack-t3 · skills/why/SKILL.md · Use for 'why does X work this way', 'why we picked Y', design rationale, regressions, postmortems, or data-backed…
