diff --git a/docs/adr/0116-rich-raw-transition-and-serialization-ownership.md b/docs/adr/0116-rich-raw-transition-and-serialization-ownership.md
new file mode 100644
index 00000000..081aa6e8
--- /dev/null
+++ b/docs/adr/0116-rich-raw-transition-and-serialization-ownership.md
@@ -0,0 +1,44 @@
+---
+type: ADR
+id: "0116"
+title: "Rich/raw transition and serialization ownership"
+status: active
+date: 2026-05-13
+---
+
+## Context
+
+Tolaria already relies on BlockNote as the rich editor and on a Markdown-first save path, but the rich/raw boundary had started to split that contract across multiple local helpers. Autosave and tab-swap logic serialized rich-editor content in one place, raw-mode entry rebuilt Markdown in another, and raw-mode toggles carried pending content and pending cursor/scroll restore state through separate refs.
+
+That fragmentation created two drift risks in one of the most correctness-sensitive parts of the app:
+
+- rich-editor Markdown output could diverge across autosave, tab switches, and raw-mode entry, especially around wikilink restoration, durable schema-node serialization, frontmatter preservation, and portable attachment paths
+- raw/rich mode switches could desynchronize pending content from pending position restoration, making stale transition state harder to reason about and harder to harden
+
+Tolaria's editor contract already prioritizes no crashes, no stale overwrites, and minimal per-keystroke work. The rich/raw boundary needs the same single-owner discipline.
+
+## Decision
+
+**Tolaria centralizes BlockNote-to-Markdown serialization for editor flows in one shared owner and treats raw/rich mode handoff as explicit transition state with a single owner per concern.**
+
+Specifically:
+
+1. `src/utils/richEditorMarkdown.ts` is the canonical owner for rich-editor body/document serialization used by autosave, tab-swap, and raw-mode entry.
+2. Raw-mode content handoff is modeled as one content transition object, so pending raw-exit content and raw-mode overrides move together.
+3. Cursor/scroll restoration across rich/raw toggles is modeled as one restore-transition ref consumed by the editor-mode position sync path.
+4. Editor surfaces should not keep independent ad hoc pending-content or pending-position refs outside those shared owners.
+
+## Options considered
+
+- **Shared serialization owner plus explicit transition owners** (chosen): keeps the Markdown contract and mode-switch lifecycle consistent across editor flows, while still allowing debounced work and focused testing.
+- **Per-flow local serializers and pending refs**: simpler inside each hook, but lets autosave, tab-swap, and raw-mode entry drift apart over time.
+- **Separate raw-mode-specific serialization and restore logic**: would preserve local autonomy, but duplicates correctness-sensitive rules at the exact boundary where stale state bugs are hardest to diagnose.
+- **Always rebuild all content/position state synchronously on every toggle**: reduces retained transition state, but increases work at toggle time and does not solve ownership drift in shared serialization logic.
+
+## Consequences
+
+- Autosave, tab-switch flushing, and raw-mode entry now share one Markdown serialization contract.
+- Wikilink restoration, durable editor-node serialization, frontmatter preservation, and portable attachment-path rewriting have one place to evolve.
+- Rich/raw mode toggles become easier to reason about because content transition state and restore transition state each have a single owner.
+- Future editor features that need rich-editor Markdown output or mode-transition bookkeeping should extend these shared owners rather than introducing local one-off refs or serializers.
+- Re-evaluation is warranted if Tolaria adopts a different editor runtime or if rich/raw mode stops being a first-class bidirectional workflow.
diff --git a/docs/adr/README.md b/docs/adr/README.md
index 1310b3fa..2b3122e7 100644
--- a/docs/adr/README.md
+++ b/docs/adr/README.md
@@ -168,3 +168,4 @@ proposed → active → superseded
 | [0112](0112-system-theme-mode.md) | System theme mode | active |
 | [0113](0113-shared-renderer-attachment-path-normalization.md) | Shared renderer attachment path normalization | active |
 | [0114](0114-mounted-workspaces-unified-graph.md) | Mounted workspaces unified graph | active |
+| [0116](0116-rich-raw-transition-and-serialization-ownership.md) | Rich/raw transition and serialization ownership | active |