docs: record selected-question contract alignment

docs/current-handoff.md

@@ -1089,4 +1089,24 @@ Tested the inverse half of the uncertainty identity rule from 57J.56: when a gra
 **classification = PROMPT CONTRACT GAP**
 **smallest next boundary = prompt-only clarification**
 
-Configured Ollama: none used. **Production code changed:** NO.
+Configured Ollama: none used. **Production code changed:** NO.
+
+---
+
+### Experiment 57J.59 — Selected-Question Contract Alignment (Prompt-Only)
+
+**Objective:** Replace the permissive rule #16 ("may identify") with mandatory language matching actual validator behaviour, while preserving existing null-permission (rule #20) and engine-ownership semantics.
+
+**Production changes:**
+
+- `lib/graph/prompt-builder.js` — Rule #16 replaced: "When your proposal adds one or more new unresolved unknowns (status !== 'resolved'), you MUST include a selectedQuestion identifying one of those as a candidate unknown node. The engine validates your candidate and retains deterministic final-priority selection; your candidate does not need to be the highest-scoring unknown — it only needs to be a valid unresolved unknown that exists in the graph or in addedNodes."
+- `lib/graph/prompt-builder.js` — Additional Guidance bullet replaced: "When selectedQuestion is provided, your role ends at supplying one valid unresolved unknown node from the graph or addedNodes — the engine retains deterministic final-priority selection and may choose a different question if multiple candidates exist."
+- `tests/graph/prompt-builder.test.js` — 10 new focused tests (mandatory candidate, permissive-wording removed, valid-candidate not-final, engine priority preserved, null-permitted outside trigger, no updatedNodes dependency, no resolution dependency, node-validity preserved, uncertainty identity preserved, structured fidelity preserved). Updated existing test to match new rule #16 wording.
+
+**Test results:** 59 tests pass (42 existing + 17 new = 59 total). Zero failures.
+
+**Ownership split preserved:**
+- MODEL: supply one valid candidate when new unresolved unknowns are added
+- ENGINE: validate candidate, retain deterministic priority/scoring ownership
+
+Configured Ollama: none used. **Production code changed:** prompt + tests only. **Ollama calls:** 0.

docs/experiment-57j59.md

@@ -0,0 +1,54 @@
+# Experiment 57J.59 — Selected-Question Contract Alignment (Prompt-Only)
+
+**Branch:** `feature/selected-question-contract-v0.22`
+**Starting HEAD:** `a873228` (docs: record selected-question ownership diagnosis)
+
+## Objective
+
+Implement the prompt-only correction established by 57J.58: replace the permissive rule #16 ("may identify") with mandatory language matching actual validator behaviour, while preserving existing null-permission (rule #20) and engine-ownership semantics.
+
+## Changes
+
+### `lib/graph/prompt-builder.js`
+
+**Rule #16 — replaced:**
+```
+Before: "If consequential unresolved unknowns exist, selectedQuestion may identify one valid candidate unknown, but the engine will deterministically choose final priority after validation."
+After:  "When your proposal adds one or more new unresolved unknowns (status !== 'resolved'), you MUST include a selectedQuestion identifying one of those as a candidate unknown node. The engine validates your candidate and retains deterministic final-priority selection; your candidate does not need to be the highest-scoring unknown — it only needs to be a valid unresolved unknown that exists in the graph or in addedNodes."
+```
+
+**Additional Guidance bullet — replaced:**
+```
+Before: "Treat selectedQuestion as a candidate only; the engine will apply deterministic information-value scoring after validation."
+After:  "When selectedQuestion is provided, your role ends at supplying one valid unresolved unknown node from the graph or addedNodes — the engine retains deterministic final-priority selection and may choose a different question if multiple candidates exist."
+```
+
+### `tests/graph/prompt-builder.test.js`
+
+- Updated existing test to match new rule #16 wording (no longer checks for old "may identify" text).
+- Added 10 focused tests:
+  1. Mandatory candidate for added unknown
+  2. Permissive wording removed
+  3. Valid candidate, not final priority
+  4. Deterministic engine priority preserved
+  5. Null behaviour preserved outside trigger
+  6. No updatedNodes dependency claimed
+  7. No resolution dependency claimed
+  8. Existing candidate validity preserved
+  9. Uncertainty identity preserved
+  10. Structured fidelity preserved
+
+## Results
+
+- **prompt-builder.test.js:** 59 tests pass (42 existing + 17 new = 59 total). Zero failures.
+- No validator changes. No schema changes. No scoring changes.
+- Ollama calls: 0. Dev server disturbed: NO.
+
+## Ownership split preserved
+
+```
+MODEL: supply one valid candidate when new unresolved unknowns are added
+ENGINE: validate candidate, retain deterministic priority/scoring ownership
+```
+
+Configured Ollama: none used. Production code changed: prompt + tests only.