# Experiment 60B.11 — Prerequisite-aware preferred question targeting

**Branch:** `feature/question-target-alignment-v0.27`  
**Starting HEAD:** `854c3aa`  
**Date:** 2026-08-13  
**Status:** Complete

---

## Why 60B.9's broad honour-rule was too wide

The partial implementation inherited from 60B.9/60B.11 was already trying to preserve a model-selected node, but the broad idea behind the earlier change was still too permissive:

```text
if model-selected node is valid and unresolved,
preserve it
```

That rule is too broad because it treats these two cases as equivalent when they are not:

1. a same-proposal-added material unknown that is ready to investigate now
2. a same-proposal-added downstream unknown that still depends on another unresolved same-turn unknown

The pricing regression proves the difference matters:

```text
n_pricing depends_on n_commercial_value
```

Preserving `n_pricing` there would invert prerequisite-first investigation order.

---

## Winning rule implemented in production

The production boundary remains narrow and unchanged outside final target selection:

```text
Prefer the model-selected target only when ALL are true:

1. proposal.selectedQuestion.nodeId exists
2. that node was added in this proposal
3. it is still a selectable unresolved unknown after mutation
4. it has NO unresolved same-proposal-added unknown prerequisite via depends_on
```

If any condition fails, the engine falls back to the existing deterministic selector unchanged.

Final wording still comes from the existing deterministic question formulator.

---

## Exact production boundary

Implemented only in the existing final-question selection path inside:

```text
lib/graph/apply-proposal.js
```

No changes were made to:

- schema
- validator contract
- selection scoring weights
- question templates
- provider integration
- harness
- materiality rule semantics

No new dependencies were added.

---

## Prerequisite definition used

Only this direct same-proposal relationship blocks preference:

```text
target --depends_on--> unresolved same-proposal-added unknown
```

The implementation checks direct `dependsOn` references and direct `depends_on` edges only.

These do **not** block preference:

- `may_cause`
- `affects`
- `causes`
- `supports`
- `measures`
- `contained_in`
- any other non-`depends_on` relationship

No transitive prerequisite planning was added.

---

## Pricing regression preservation

The established regression remains intact:

```text
model-selected: n_pricing
prerequisite:  n_commercial_value
final selected node: n_commercial_value
```

This remains protected because `n_pricing` has an unresolved same-proposal-added `depends_on` prerequisite, so the preferred-target path is rejected and deterministic selection proceeds unchanged.

---

## Focused test results

### 60B.11 block

Command:

```bash
npx vitest run tests/graph/apply-proposal.test.js -t "60B.11"
```

Result:

```text
PASS — 10/10 tests
```

Covered:

- same-proposal selected target with no prerequisite is preferred
- same-proposal selected target with same-turn `depends_on` prerequisite is blocked
- pricing regression preserved
- pre-existing model target not auto-preferred
- invalid / contradicted / missing-target fallback behaviour
- deterministic wording remains authoritative
- non-prerequisite edge types do not block preference

### Focused suites

Command:

```bash
npx vitest run tests/graph/apply-proposal.test.js tests/graph/prompt-builder.test.js
```

Result:

```text
PASS — 174/174 tests
```

---

## Prompt boundary

Only the selectedQuestion guidance was clarified in the existing prompt text. The prompt now states, in bounded terms, that the engine:

- validates the model's candidate
- retains deterministic prerequisite ordering
- favours a selected same-proposal node only when no unresolved same-proposal `depends_on` prerequisite blocks it
- preserves deterministic fallback selection and deterministic formulation authority

It does **not** claim unconditional model authority.

---

## What remains unproven until live regression

The bounded implementation is covered by deterministic tests, but one thing remains unproven in live behaviour:

```text
the exact 60B.6 live continuation case,
where the model selects the newly exposed client-retention factor
and the final selected target preserves that same ready material unknown
```

That requires a live regression run against the exact live fixture path, which was intentionally out of scope here.