diff --git a/docs/oddkit/proactive/dolche-vocabulary.md b/docs/oddkit/proactive/dolche-vocabulary.md
index 502334a2..6c4d105d 100644
--- a/docs/oddkit/proactive/dolche-vocabulary.md
+++ b/docs/oddkit/proactive/dolche-vocabulary.md
@@ -13,11 +13,16 @@ supersedes: "docs/oddkit/proactive/oldc-h-vocabulary.md"
 derives_from: "canon/values/axioms.md, docs/oddkit/proactive/continuous-encoding.md, docs/oddkit/proactive/encode-does-not-persist.md"
 complements: "docs/oddkit/proactive/posture-lapse.md, docs/oddkit/proactive/proactive-session-close.md, odd/ledger/project-journal-best-practices.md"
 governs: "All session capture, project journal entries, and encode invocations"
-status: active
+status: superseded
+superseded_by: "canon/definitions/dolcheo-vocabulary.md"
 ---
 
 # DOLCHE — Six Dimensions of Session Capture
 
+> **Superseded by [DOLCHEO](klappy://canon/definitions/dolcheo-vocabulary)** (2026-04-19). DOLCHEO extends DOLCHE with a seventh artifact type — Open, the forward-pointing thread that stays with the current owner — and promotes the vocabulary to canon at tier 2. This document remains for historical reference and as the canonical description of the six-dimension pattern. New work should reference the DOLCHEO umbrella.
+
+---
+
 > Decisions, Observations, Learnings, Constraints, Handoffs, Encodes. Five artifact types and one meta-level action that tracks the crystallization of all the others. DOLCHE supersedes OLDC+H by adding Encode — not as a sixth category of content, but as the act of encoding itself made visible. The E closes the loop: when you encode a Decision, the Encode tracks *that you did it*, when you did it, what quality it achieved, and whether it was persisted. Without the E, you can't distinguish between "this was discussed" and "this was captured."
 
 ---
diff --git a/odd/encoding-types/how-to-write-encoding-types.md b/odd/encoding-types/how-to-write-encoding-types.md
index 6f8bfef1..4010a5bb 100644
--- a/odd/encoding-types/how-to-write-encoding-types.md
+++ b/odd/encoding-types/how-to-write-encoding-types.md
@@ -247,7 +247,7 @@ With frontmatter tag `encoding-type`, a Type Identity table with `Letter: P`, a
 
 **Conventions for custom types:**
 
-- Letter should not collide with existing types (D, O, L, C, H, E)
+- Letter should not collide with existing types (D, O, L, C, H, E). One intentional exception exists in the default set: Observation and Open both register letter `O` and disambiguate by facet (`facet: open` on the Open doc) plus section placement in ledgers (`## Open items` sections). See `odd/encoding-types/open.md` and the DOLCHEO umbrella (`canon/definitions/dolcheo-vocabulary.md`) for how the collision is resolved. Custom types should not introduce new collisions unless they follow the same facet-based disambiguation pattern.
 - Letter should be a single uppercase character
 - Including all recommended sections produces the best results
 - Custom types are scoped to the knowledge base that defines them — they don't affect other KBs