Setup Pstack

Setup pstack

Follow the portable runtime contract throughout this setup.

Write the optional pstack configuration at $PSTACK_CONFIG when that variable is set; otherwise use .pstack/config.md in the current project. This is an override layer, not a requirement. Never write to a vendor-specific home directory.

Steps

Model discovery and model assignment are different capabilities. A model listed by pi --list-models is available to the current Pi process, but that does not mean a workflow can send work to it. Per-role assignment also requires a host task or subagent facility that accepts a model choice. Native Pi intentionally does not include subagents. Do not claim that a role was assigned when that facility is absent.

Pi delegation prerequisite

For native Pi, recommend the maintained pi-subagents package when the user wants parallel workers or per-role models:

pi install npm:pi-subagents

Tell the user to restart Pi after installation, then run /subagents-doctor. Continue setup only when the subagent tool and the expected agents are visible. The package supplies the delegation facility; it does not choose pstack's model policy by itself.

OpenCode delegation prerequisite

OpenCode has its own native primary and subagent agents. Do not install pi-subagents or write Pi-specific settings when the current host is OpenCode. Use the agents and concrete provider/model-id choices reported by OpenCode, and keep their model configuration in the host's opencode.json or opencode.jsonc. If OpenCode does not expose a usable subagent, report that limitation instead of substituting a Pi-specific mechanism.

1. Detect available choices

Detect both of these independently:

1. The model IDs the current host actually exposes.
2. Whether the current host exposes a task or subagent facility that can select a model for each child.

For Pi, pi --list-models is the model inventory and the provider/model-id form is the concrete value to record. With pi-subagents installed, the subagent tool and /subagents-doctor establish the delegation inventory. The live host inventory is authoritative. Never copy a vendor slug from prose or guess that a model is available.

If the host has a task facility but cannot enumerate models, use only a host role mapping that the facility documents. Do not ask the user to invent a raw slug. inherit-parent is valid only when the host can pass the current model to a child.

2. Load current state

Read the selected configuration path when it exists and treat its concrete values as current choices. If it contains only portable role aliases from a host without per-child delegation, treat those aliases as stale inactive state and start from the detected models instead of carrying them into Pi's agent overrides.

3. Map and confirm

If both model inventory and per-child model selection are available, show every workflow role with its current concrete provider/model-id choice. Mark an explicit model absent from the live inventory as needing a replacement. Ask the user to accept or change the choices, offering only detected model IDs and inherit-parent when supported. Use the host's structured interaction tool when available; otherwise ask one focused question in normal conversation.

If the host exposes models but no task or subagent facility, stop model mapping with an explicit capability report. For native Pi, recommend pi install npm:pi-subagents, a restart, and /subagents-doctor. For OpenCode, explain that its native agents are not visible or configured and point the user to the host's agent configuration. For any other host, name the missing capability without proposing a vendor-specific substitute. Say that no pstack role can receive a different model in this session and do not present the portable defaults as an assignment or overwrite an existing role configuration with inactive aliases.

For panel roles (how critics, arena runners, arena cross-judge pool, architect runners, and interrogate reviewers), one child runs per entry, so list length controls fan-out. Prefer diversity for judgment-sensitive panels. swarm workers is the default choice for every worker unless a race assigns a different choice per arm.

4. Validate

Every explicit model written must be present in the detected host inventory. Role aliases pass only when the host task facility documents those aliases. inherit-parent passes only when the host can pass the current model to a child. If a selected explicit model is unavailable, stop and ask for a replacement. Never write a configuration that requires another host.

5. Write the configuration

When the host supports per-child selection, create the parent directory when needed and overwrite the selected file so re-runs remain idempotent. Use concrete detected model IDs in this shape. Replace every placeholder with a model the current host reported, and use inherit-parent only when the host supports it:

# pstack role and model configuration
# Values are concrete provider/model-id choices confirmed by the host.
feature, refactoring: <implementer-model>
bug-fix: <reviewer-model>
perf-issue: <reviewer-model>
hillclimb: <implementer-model>
judgment and prose: <reviewer-model>
hardest tasks: inherit-parent
how explorer: <explorer-model>
how explainer: <synthesizer-model>
how critics: <reviewer-model>, <planner-model>, <designer-model>, inherit-parent
why investigators: <researcher-model>
why synthesizer: <synthesizer-model>
reflect tooling: <researcher-model>
reflect judgment: <reviewer-model>
reflect divergent: <designer-model>
reflect synthesizer: <synthesizer-model>
arena runners: <designer-model>, <planner-model>, <implementer-model>, inherit-parent
arena cross-judge pool: <reviewer-model>, <planner-model>, <designer-model>, inherit-parent
swarm workers: <implementer-model>
architect runners: <designer-model>, <planner-model>, <reviewer-model>, inherit-parent
interrogate reviewers: <reviewer-model>, <planner-model>, <designer-model>, inherit-parent

For Pi with pi-subagents, also preserve unrelated keys and update the project's .pi/settings.json with the concrete model assignments for the discovered subagent names. Use this mapping unless the user chooses different agents:

Write the selected IDs under subagents.agentOverrides.<agent>.model:

{
  "subagents": {
    "agentOverrides": {
      "scout": { "model": "<explorer-model>" },
      "researcher": { "model": "<researcher-model>" },
      "worker": { "model": "<implementer-model>" },
      "reviewer": { "model": "<reviewer-model>" },
      "oracle": { "model": "<planner-model>" },
      "delegate": { "model": "<owner-model>" }
    }
  }
}

For OpenCode, do not write .pi/settings.json. Keep the concrete model choices in the user's existing opencode.json or opencode.jsonc, and use the live OpenCode agent names in the pstack role map. Preserve unrelated configuration.

6. Confirm

If a concrete configuration was written, tell the user the exact path and list the model IDs assigned to each role family. For Pi, name both .pstack/config.md and .pi/settings.json, and tell the user to run /subagents-models to inspect the live mapping. For OpenCode, name the opencode.json or opencode.jsonc path used. State that configuration does not create models, child agents, permissions, or delegation facilities.

If the host lacks per-child model selection, report that no role configuration was written or activated. Tell the user which model is active and how to switch the single Pi session model.

7. Offer a verification skill (optional)

Check whether the project has a way to drive the real app for proof, such as a verify-* skill or an existing harness. If not, offer once to invoke the sibling create-verification-skill skill. On no, move on without pushing.