diff --git a/docs/current-handoff.md b/docs/current-handoff.md
index 587dafd..0da581d 100644
--- a/docs/current-handoff.md
+++ b/docs/current-handoff.md
@@ -1066,4 +1066,27 @@ Tested the inverse half of the uncertainty identity rule from 57J.56: when a gra
 
 **Key finding:** Semantic interpretation works correctly (distinct savings-realism uncertainty identified), but structural linkage failed silently — no existing node was updated to reflect the uncertainty, so the proposal lacked the graph state needed for downstream question selection. This is a different failure mode from 57J.56 which DID update nx54wwa successfully.
 
-**What remains unproven:** Whether Answer 2 would reuse or duplicate; downstream investigation viability; cross-domain generalisation. Configured Ollama: qwen-claude:latest at http://192.168.1.111:11434. **Production code changed:** NO. **Ollama calls:** 0 live calls (update rejected before mutation). APPEND_EOF
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+**What remains unproven:** Whether Answer 2 would reuse or duplicate; downstream investigation viability; cross-domain generalisation. Configured Ollama: qwen-claude:latest at http://192.168.1.111:11434. **Production code changed:** NO. **Ollama calls:** 0 live calls (update rejected before mutation).
+
+---
+
+### Experiment 57J.58 — Selected-Question Ownership Diagnosis Confirmation
+
+**Objective:** Record durable handoff facts from `docs/experiment-57j58.md` which diagnosed why a proposal adding a new unresolved unknown was rejected due to missing `selectedQuestion`, and classified the root cause.
+
+**validateQuestionSelectionRequirement() rejects when:**
+- `selectedQuestion == null`
+- AND
+- proposal adds at least one non-resolved unknown
+
+**requirement does NOT depend on:**
+- `updatedNodes`
+- actual `resolvedUnknownNodeIds`
+- total existing unresolved-node count
+
+**prompt rule #16 says selectedQuestion "may" identify a candidate**
+**validator treats it as mandatory for added unresolved unknowns**
+**classification = PROMPT CONTRACT GAP**
+**smallest next boundary = prompt-only clarification**
+
+Configured Ollama: none used. **Production code changed:** NO.
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