Parallax House View Diff

---
name: parallax-house-view-diff
description: "Interface spec for verifying that a house view actually changes downstream portfolio output. Trigger: 'did the house view shift my portfolio output?' Describes the dual-leg paired-call protocol and output contract. NOT for loading or making a view (use /parallax-load-house-view or /parallax-make-house-view), not for comparing two saved views (use /parallax-make-house-view --compare). Calibration and reference runner are internal to Parallax."
---

# House View Diff — Interface Spec

## When not to use

- Just loading a view → use /parallax-load-house-view
- General portfolio building → use /parallax-portfolio-builder
- Comparing two saved house-view bundles side by side → use /parallax-make-house-view --compare

## Gotchas

- This skill is a SPEC, not an executable runner. Consumers implementing the protocol provide their own execution + calibration.
- JIT-load _parallax/house-view/tests/portfolio_diff_harness.md for the protocol definition.
- Output MUST follow the `<diff_output>` JSON contract defined in the protocol spec.

Defines the protocol shape for verifying that an active house view shifts the output of a downstream consumer skill.

## Purpose

A consuming agent running a portfolio workflow with an active house view should be able to demonstrate — in the same session — that the view actually changed the resulting portfolio vs. the baseline. This skill describes *how* that demonstration is structured. It does not ship the calibration thresholds or a reference runner.

## Protocol (summary)

1. **Leg A:** execute the downstream skill with `PARALLAX_HOUSE_VIEW_DIR` pointing at an empty directory.
2. **Leg B:** execute the same skill with `PARALLAX_HOUSE_VIEW_DIR` pointing at the active view bundle.
3. Both legs must use identical `build_stock_universe` query parameters (except for tilt-prepended context).
4. Emit a `<diff_output>` JSON block comparing ranks and weights.
5. Append mechanical "what changed why" lines for shifted positions.

Full protocol: [`_parallax/house-view/tests/portfolio_diff_harness.md`](../_parallax/house-view/tests/portfolio_diff_harness.md).

**Cost:** total cost is 2× the child skill's cost (Leg A + Leg B); see `_parallax/token-costs.md`.

## Exit semantics

Consumer runners should surface at least three outcomes — PASS, WEAK, KILL — corresponding to the shift magnitude falling within the pass band, outside the warning band, or below the economic-viability threshold respectively. Specific band values are maintained internally by the reference-implementation provider.

## Error Contracts

Consumers implementing the paired-call protocol must handle these failure modes:

| Scenario | Behavior |
|----------|----------|
| **Leg A succeeds, Leg B times out** | Diff output shows baseline only. Surface message: "View load timed out; baseline results shown. Diff unavailable." Include Leg A results but do not emit `PASS/WEAK/KILL` verdict. |
| **Leg A times out, Leg B succeeds** | Diff output incomplete. Surface message: "Universe build timed out; view results shown. Diff incomplete." Include Leg B results but do not emit verdict. |
| **Both Leg A and Leg B timeout simultaneously** | No diff output possible. **Fail loudly with explicit error:** "Both legs timed out (>30s each). Diff protocol requires both results; cannot proceed. Retry with simpler theme or larger time budget." Do not emit partial output; do not emit verdict. Exit with error status. |
| **Leg B fails (view validation error, not timeout)** | If Leg A succeeded, surface both: Leg A results (solid) and error message for Leg B. Do not emit diff; do not emit verdict. Flag as "View validation failed — comparison incomplete." |
| **Both legs fail (query error, bad theme)** | Fail loudly with the error from whichever leg ran first. "Query error: [theme interpretation failed / no candidates found]. Could not construct baseline; diff not applicable." Exit with error status. |

## Troubleshooting

- **"View did not load"** → Check `PARALLAX_HOUSE_VIEW_DIR` resolution per `_parallax/house-view/loader.md §1`.
- **"Paired-call protocol violated"** → Ensure `build_stock_universe` query is identical across legs.
- **"Markers absent"** → Ensure output is wrapped in `<diff_output>` tags.