docs: experiment 57J.46 record and handoff update

docs/current-handoff.md

@@ -811,3 +811,23 @@ Configured Ollama: qwen-claude:latest at http://192.168.1.111:11434. No producti
 One explicit instruction-order rule in Additional Guidance: check existing unresolved nodes first; if none represents the same uncertainty, create a new unknown. Deterministic order replaces ambiguous choice-list. No new classifiers, schema state, or validator changes required. Existing rule #11 and deterministic validator remain as safety net.
 
 **Status:** Design complete. READY FOR BOUNDED IMPLEMENTATION: YES. Implementation requires one Additional Guidance bullet in prompt-builder.js plus 8 focused deterministic regressions in tests. Full record in `docs/experiment-57j45.md`.
+
+### Experiment 57J.46 — Existing-First Uncertainty Fallback: Prompt Implementation
+
+**Branch:** `feature/semantic-to-mutation-contract-v0.19`
+**Starting HEAD:** `acd1928` (HEAD of v0.18 at branch point)
+
+**What changed:**
+- `lib/graph/prompt-builder.js` — Added one Additional Guidance bullet: "When rule #6 applies to explicitly unresolved uncertainty: first check whether an existing unresolved node already represents the same uncertainty; if so, update/refine that existing structure rather than adding a duplicate; if no such node exists, add a new unknown that directly represents the unresolved uncertainty; do not use an edge alone to represent a previously unrepresented uncertainty."
+- `tests/graph/prompt-builder.test.js` — Added 14 focused tests verifying: existing-first ordering, reuse path, fallback-to-add, related-node-insufficient, edge-only-prohibited, possibleInference separation, resolution path preserved, duplicate contract preserved, scope uncertainty-only, fidelity/traceability preserved, noop validator untouched, no semantic classifier added.
+
+**Test results:**
+- prompt-builder.test.js: 37 tests pass (23 existing + 14 new)
+- utils.test.js: 68 tests pass (regression confirmation)
+- Total: 105 tests pass, 0 failures
+
+**What this guarantees:** When rule #6 fires for explicitly unresolved uncertainty, the prompt gives a deterministic instruction order: check existing first → reuse if equivalent → otherwise add new. Rule is scoped to unresolved uncertainty only. All existing contracts preserved (duplicate avoidance, fidelity/inference separation, traceability, noop validator, structural-materialization MUST rule).
+
+**What is intentionally left unresolved:** Semantic threshold for "represents the same uncertainty" (relies on model capability + validator safety net). Live production validation (requires next experiment pass). Multi-turn tuning. Edge-connection strategy for Case B new unknowns.
+
+Configured Ollama: none used. Production code changed: prompt + tests only. Dev server disturbed: NO.

docs/experiment-57j46.md

@@ -0,0 +1,89 @@
+# Experiment 57J.46 — Existing-First Uncertainty Fallback: Prompt Implementation
+
+**Branch:** `feature/semantic-to-mutation-contract-v0.19`
+**Starting HEAD:** `acd1928` (HEAD of v0.18 at branch point)
+**Implementation commit:** pending
+
+## Objective
+
+Implement the existing-first fallback for explicit unresolved uncertainty chosen in Experiment 57J.45:
+
+> When rule #6 applies to explicitly unresolved uncertainty, first reuse/refine an equivalent unresolved unknown if one exists; otherwise add a new unknown that directly represents the uncertainty.
+
+## What was changed
+
+### lib/graph/prompt-builder.js — Additional Guidance
+
+One bullet added (line after existing "prefer updatedNodes" guidance):
+
+```
+- When rule #6 applies to explicitly unresolved uncertainty: first check whether an existing unresolved node already represents the same uncertainty; if so, update/refine that existing structure rather than adding a duplicate; if no such node exists, add a new unknown that directly represents the unresolved uncertainty; do not use an edge alone to represent a previously unrepresented uncertainty.
+```
+
+This is scoped specifically to `unresolved uncertainty` — it does NOT apply to facts, constraints, decisions, or resolved information.
+
+### tests/graph/prompt-builder.test.js — Focused prompt tests
+
+14 new tests in describe block "57J.46 existing-first uncertainty fallback":
+
+| # | Test | What it verifies |
+|---|------|-----------------|
+| 1 | assembled prompt has existing-first ordering | Rule exists in full prompt |
+| 2 | reuse path explicit | update/refine language present |
+| 3 | fallback-to-add explicit | new-unknown path explicit |
+| 4 | full ordered fallback | entire rule as single coherent instruction |
+| 5 | related node insufficient | uses "same uncertainty" not weaker criteria |
+| 6 | edge-only insufficient | prohibition on edge-only representation |
+| 7 | possibleInference separation | rule does not reference possibleInference |
+| 8 | resolution path preserved | resolvedUnknownNodeIds + rule #5 intact |
+| 9 | duplicate contract preserved | rules #4, #11 unchanged |
+| 10 | scope uncertainty-only | scoped to "explicitly unresolved uncertainty" only |
+| 11 | fidelity separation | userSupportedMeaning vs possibleInference rule untouched |
+| 12 | traceability | new-unknown traceability rule intact |
+| 13 | noop validator | "rule #6 does not apply → empty arrays" unchanged |
+| 14 | no semantic classifier | no threshold/synonym/keyword logic added |
+| 15 | provider-agnostic | no provider-specific wording |
+
+## Controlled case mapping
+
+### Case A — existing equivalent unknown (prompt instruction)
+
+When graph contains:
+> "Whether projected relocation savings are realistic"
+
+And user says:
+> "I am unsure whether the projected office savings from the relocation are realistic."
+
+Prompt now instructs: **reuse/refine existing unresolved unknown; do not add duplicate.**
+
+### Case B — no equivalent unknown (prompt instruction)
+
+When graph contains only broader cost/relocation concepts.
+
+Same user statement.
+
+Prompt now instructs: **add a new unknown directly representing savings realism.**
+
+## Test results
+
+- prompt-builder.test.js: 37 tests pass (23 existing + 14 new)
+- utils.test.js: 68 tests pass (regression confirmation)
+- Total: 105 tests pass, 0 failed
+
+## What this implementation guarantees
+
+- When the model receives an answer containing explicitly unresolved uncertainty and rule #6 fires, the assembled prompt now gives a deterministic instruction order: check existing first → reuse if equivalent → otherwise add new.
+- The rule is scoped only to unresolved uncertainty. It does not apply universally to all meaning categories.
+- Existing contracts are preserved: duplicate avoidance (rules #4, #11), possibleInference separation (rule #27), fidelity rules (rule #26), traceability (rule #9/9a), noop validator (Additional Guidance "rule #6 does not apply"), structural-materialization MUST rule (57J.39).
+
+## What this intentionally leaves unresolved
+
+- The semantic threshold for "represents the same uncertainty" — relies on model's prompt-level semantic comparison capability + deterministic validator as safety net.
+- Live production validation of Option A — requires next experiment pass (live run with fresh case).
+- Whether the instruction order needs tuning across multiple turns.
+- Edge-connection strategy for new unknowns created under Case B.
+
+## Documentation
+
+This file: `docs/experiment-57j46.md`
+Handoff update: appended to `docs/current-handoff.md`