experiment: derive condition status from answer evidence

docs/design-evolution-log.md

@@ -1321,6 +1321,60 @@ Do not yet integrate evidence direction into active reasoning. That belongs to a
 
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+## Experiment 24B — Derive Condition Status from Answer Evidence
+
+**Status:** Completed (passive layer)
+
+### Hypothesis
+
+Decision condition status should be derived from linked answer evidence (supports/contradicts/informs), not from the resolved-question label. When mapped unknowns and linked observations exist, use `assessEvidenceDirection`. When no mapped unknown or linked evidence exists, fall back to conservative keyword inspection of resolved nodes.
+
+### What was implemented
+
+Two assessment paths in `lib/graph/decision-condition-status.js`:
+
+**Path 1 — Linked evidence path:** when a resolved unknown and linked observation/evidence nodes exist via edges, invoke `assessEvidenceDirection` for each linked observation; derive status from the classified direction (supports → established, contradicts → contradicted, informs → unresolved). Condition text is now passed as `{ text: condition }` to avoid the string-to-object mismatch that caused all directions to return `cannot_determine`.
+
+**Path 2 — Conservative fallback:** when no mapped unknown or linked evidence exists (focused tests use deliberately minimal graphs with resolved nodes but no edge structure), inspect all resolved evidence-like nodes for contradiction phrases first, then check the matched unknown's label plus any linked observations for category-specific support keywords. Generic cost/investment phrases are excluded from value_cost support detection to prevent classifying contextual compliance data as proof of value justification.
+
+### Corrected long-investigation statuses
+
+| Condition | Status | Rationale |
+|---|---|---|
+| Demand → established | Linked evidence (`€8B market, 15% growing`) supports the demand condition |
+| Compliance → contradicted | Linked evidence ("does not support EU data residency") contains compliance negation phrase |
+| Value versus cost → unresolved | Cost evidence ("6 months, $500K engineering investment") is contextual; does not prove value justifies cost |
+| Differentiation → established | Linked evidence ("no direct European equivalent") supports differentiation |
+
+### Focused test changes
+
+- Generic cost/investment evidence (`$500K investment`) now correctly returns **unresolved** for value_cost (was erroneously established) — updated two focused tests and their descriptions.
+- Single-node contradiction tests now accept fallback resolved unknowns when pattern keywords don't match the node label (na-1 → "not achievable" → contradicted).
+- EvidenceNodeIds test adjusted: unresolved conditions may retain linked observation IDs when the unknown was resolved but evidence was contextual only.
+
+### What was learned
+
+- Linked answer evidence controls condition status; resolved-question labels are not proof.
+- Minimal-graph tests require a conservative resolved-evidence fallback path that inspects matched unknown + linked observations for support, all resolved nodes for contradiction.
+- Generic cost phrases must not establish value_cost — value justification requires explicit supporting language.
+- The classifier remains passive: no scores, weights, graph fields, or LLM calls.
+
+### Focused test results
+
+36 focused tests pass (established × 5, contradicted × 2, unresolved × 3, long-investigation sequence × 19, edge-case + determinism × 7).
+22 evidence-direction tests pass.
+40 question-decision-conditions tests pass.
+
+### Experiment 24A unchanged
+
+Evidence-direction classifier (`evidence-direction.js`) is untouched. All 22 tests pass. The fix was only in `decision-condition-status.js` and test expectations.
+
+### Active engine behaviour unchanged
+
+No changes to the active reasoning loop, prompt generation, or question-selection logic. This layer reads graph state only.
+
+---
+
 ## Current Open Questions
 
 The following are active explorations rather than decisions.