diff --git a/CHANGELOG.md b/CHANGELOG.md
index dcc2f40..dffd84e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,11 @@
 # Changelog
 
-Each entry records a versioned change to a specification in this repository.
-Each specification is versioned independently, starting at version 1. Every
-pull request that alters normative content bumps the affected spec's `Version`
-field and adds an entry here.
+Each entry records a change to a specification in this repository. Each
+specification carries a `Version` field equal to its V0/V1/V2 compatibility
+class (VERSIONING.md): `1` for a formalization compatible with the pre-spec
+status quo, `2` once it is not backwards compatible. Entries are grouped under
+the spec's current class. Every pull request that alters normative content adds
+an entry here.
 
 ## OVOS-INTENT-1 — Sentence Template Grammar
 
diff --git a/GLOSSARY.md b/GLOSSARY.md
index 00a07fc..6eebc3d 100644
--- a/GLOSSARY.md
+++ b/GLOSSARY.md
@@ -16,23 +16,23 @@ open a PR adding it.
 
 | Term | Meaning |
 |------|---------|
-| **Template** | A string in the OVOS-INTENT-1 grammar describing a set of sentences ([INTENT-1 §3](ovos-intent-1.md)). |
-| **Expansion** | Resolving `(a\|b)` / `[x]` into a finite set of concrete sentences ([INTENT-1 §4](ovos-intent-1.md)). |
-| **Sample / sample set** | A concrete sentence produced by expansion; the set of all of them for a template ([INTENT-1 §4](ovos-intent-1.md)). |
-| **Slot** | A named placeholder `{name}` filled with a value rather than written out ([INTENT-1 §3.4, §5](ovos-intent-1.md)). |
-| **Capture map** | The names→values mapping a match produces — slot names or vocabulary names as keys ([INTENT-3 §7](ovos-intent-3.md)). |
-| **Resource file / role** | A skill's plain-text files: `.intent`, `.dialog`, `.entity`, `.voc`, `.blacklist` ([INTENT-2 §1](ovos-intent-2.md)). |
-| **Vocabulary** | A named slot-free phrase set; the unit a keyword intent constrains over ([INTENT-3 §4.1](ovos-intent-3.md)). |
-| **Occurrence** | A phrase appearing in an utterance as a contiguous whole-word subsequence ([INTENT-2 §4.3](ovos-intent-2.md), [INTENT-3 §4.1](ovos-intent-3.md)). |
-| **Skill** | An app — a self-contained unit of assistant functionality ([INTENT-3 §1, §3](ovos-intent-3.md)). |
-| **Skill id** | A skill's identifier, unique across the assistant ([INTENT-3 §3](ovos-intent-3.md)). |
-| **Intent** | A developer-defined binding from a natural-language command to one handler ([INTENT-3 §1](ovos-intent-3.md)). |
-| **Intent name / qualified name** | The intent's name, unique within its skill / the `skill_id:intent_name` pair ([INTENT-3 §3](ovos-intent-3.md)). |
-| **Keyword intent / template intent** | The two definition methods — keyword constraints, or sentence templates ([INTENT-3 §2](ovos-intent-3.md)). |
-| **Handler** | The code an intent triggers when its command is recognized ([INTENT-3 §1, §6](ovos-intent-3.md)). |
-| **Intent engine** | A classifier + slot extractor: consumes definitions, identifies the triggered intent ([INTENT-3 §6.2](ovos-intent-3.md)). |
-| **Orchestrator** | The component that coordinates intent matching and dispatch — owns the engines / pipeline plugins and routes match results to handlers ([INTENT-3 §6.1](ovos-intent-3.md)). Distinct from the messagebus (transport) and from individual engines / plugins. |
-| **Registration** | Submitting an intent's definition and handler together, as one unit ([INTENT-3 §6.1](ovos-intent-3.md)). |
-| **Message** | The unit of communication on the bus: a JSON object with `type`, `data`, `context` ([MSG-1 §2](ovos-msg-1.md)). |
-| **Context** | The assistant-metadata object on a Message; an extensible JSON object whose keys are defined by companion specs ([MSG-1 §2.3](ovos-msg-1.md)). |
-| **Session** | The per-conversation carrier in `context.session`; carries `session_id` (with `"default"` reserved for "originates from the device itself") and `lang` (the user's preferred language, distinct from any `data.lang` describing the payload's own language) ([MSG-1 §4](ovos-msg-1.md)). |
+| **Template** | A string in the OVOS-INTENT-1 grammar describing a set of sentences ([INTENT-1 §3](intent-1.md)). |
+| **Expansion** | Resolving `(a\|b)` / `[x]` into a finite set of concrete sentences ([INTENT-1 §4](intent-1.md)). |
+| **Sample / sample set** | A concrete sentence produced by expansion; the set of all of them for a template ([INTENT-1 §4](intent-1.md)). |
+| **Slot** | A named placeholder `{name}` filled with a value rather than written out ([INTENT-1 §3.4, §5](intent-1.md)). |
+| **Capture map** | The names→values mapping a match produces — slot names or vocabulary names as keys ([INTENT-3 §7](intent-3.md)). |
+| **Resource file / role** | A skill's plain-text files: `.intent`, `.dialog`, `.entity`, `.voc`, `.blacklist` ([INTENT-2 §1](intent-2.md)). |
+| **Vocabulary** | A named slot-free phrase set; the unit a keyword intent constrains over ([INTENT-3 §4.1](intent-3.md)). |
+| **Occurrence** | A phrase appearing in an utterance as a contiguous whole-word subsequence ([INTENT-2 §4.3](intent-2.md), [INTENT-3 §4.1](intent-3.md)). |
+| **Skill** | An app — a self-contained unit of assistant functionality ([INTENT-3 §1, §3](intent-3.md)). |
+| **Skill id** | A skill's identifier, unique across the assistant ([INTENT-3 §3](intent-3.md)). |
+| **Intent** | A developer-defined binding from a natural-language command to one handler ([INTENT-3 §1](intent-3.md)). |
+| **Intent name / qualified name** | The intent's name, unique within its skill / the `skill_id:intent_name` pair ([INTENT-3 §3](intent-3.md)). |
+| **Keyword intent / template intent** | The two definition methods — keyword constraints, or sentence templates ([INTENT-3 §2](intent-3.md)). |
+| **Handler** | The code an intent triggers when its command is recognized ([INTENT-3 §1, §6](intent-3.md)). |
+| **Intent engine** | A classifier + slot extractor: consumes definitions, identifies the triggered intent ([INTENT-3 §6.2](intent-3.md)). |
+| **Orchestrator** | The component that coordinates intent matching and dispatch — owns the engines / pipeline plugins and routes match results to handlers ([INTENT-3 §6.1](intent-3.md)). Distinct from the messagebus (transport) and from individual engines / plugins. |
+| **Registration** | Submitting an intent's definition and handler together, as one unit ([INTENT-3 §6.1](intent-3.md)). |
+| **Message** | The unit of communication on the bus: a JSON object with `type`, `data`, `context` ([MSG-1 §2](msg-1.md)). |
+| **Context** | The assistant-metadata object on a Message; an extensible JSON object whose keys are defined by companion specs ([MSG-1 §2.3](msg-1.md)). |
+| **Session** | The per-conversation carrier in `context.session`; carries `session_id` (with `"default"` reserved for "originates from the device itself") and `lang` (the user's preferred language, distinct from any `data.lang` describing the payload's own language) ([MSG-1 §4](msg-1.md)). |
diff --git a/README.md b/README.md
index 3898b64..b8eeaa5 100644
--- a/README.md
+++ b/README.md
@@ -87,33 +87,48 @@ below). Adoption is voluntary; conformance, once adopted, is not.
 
 ## Specifications
 
+The **Version** column carries the V0/V1/V2 compatibility class
+([VERSIONING.md](VERSIONING.md)): `1` for a formalization compatible with the
+pre-spec status quo, `2` for one that is not backwards compatible.
+
 ### Intent stack — what a skill defines
 
 | ID | Document | Version | Status |
 |----|----------|---------|--------|
-| OVOS-INTENT-1 | [Sentence Template Grammar](ovos-intent-1.md) | 2 | Draft |
-| OVOS-INTENT-2 | [Locale Resource Formats](ovos-intent-2.md) | 2 | Draft · [v3 in review (PR #4)](https://github.com/OpenVoiceOS/architecture/pull/4) |
-| OVOS-INTENT-3 | [Intent Definition](ovos-intent-3.md) | 1 | Draft |
-| OVOS-INTENT-4 | [Intent and Entity Registration](ovos-intent-4.md) | 2 | [Draft — in review (PR #9)](https://github.com/OpenVoiceOS/architecture/pull/9) |
+| OVOS-INTENT-1 | [Sentence Template Grammar](intent-1.md) | 1 | Draft |
+| OVOS-INTENT-2 | [Locale Resource Formats](intent-2.md) | 1 | Draft |
+| OVOS-INTENT-3 | [Intent Definition](intent-3.md) | 1 | Draft |
+| OVOS-INTENT-4 | [Intent and Entity Registration](intent-4.md) | 2 | Draft |
 
 ### Bus stack — how components talk
 
 | ID | Document | Version | Status |
 |----|----------|---------|--------|
-| OVOS-MSG-1 | [Bus Message](ovos-msg-1.md) | 2 | Draft |
-| OVOS-SESSION-1 | [Session Carrier Wire Shape](ovos-session-1.md) | 1 | Draft |
-| OVOS-SESSION-2 | [Session Lifecycle and State Ownership](ovos-session-2.md) | 1 | Draft |
+| OVOS-MSG-1 | [Bus Message](msg-1.md) | 1 | Draft |
+| OVOS-SESSION-1 | [Session Carrier Wire Shape](session-1.md) | 1 | Draft |
+| OVOS-SESSION-2 | [Session Lifecycle and State Ownership](session-2.md) | 1 | Draft |
+| OVOS-BRIDGE-1 | [Bus Bridge and Opaque Relay](bridge-1.md) | 2 | Draft |
 
 ### Orchestrator stack — what processes utterances
 
 | ID | Document | Version | Status |
 |----|----------|---------|--------|
-| OVOS-PIPELINE-1 | [Utterance Lifecycle and Pipeline](ovos-pipeline-1.md) | 2 | Draft |
-| OVOS-TRANSFORM-1 | [Transformer Plugins](transformer.md) | 1 | [Draft — in review (PR #20)](https://github.com/OpenVoiceOS/architecture/pull/20) |
-| OVOS-CONTEXT-1 | [Intent Context](intent-context.md) | 1 | [Draft — in review (PR #18)](https://github.com/OpenVoiceOS/architecture/pull/18) |
-| OVOS-CONVERSE-1 | [Active Handlers and Interactive Response](converse.md) | 1 | [Draft — in review (PR #25)](https://github.com/OpenVoiceOS/architecture/pull/25) |
-| OVOS-STOP-1 | [Stop Pipeline Plugin](ovos-stop-1.md) | 1 | [Draft — in review (PR #33)](https://github.com/OpenVoiceOS/architecture/pull/33) |
-| OVOS-AUDIO-IN-1 | [Audio Input Service](ovos-audio-in-1.md) | 1 | Draft |
+| OVOS-PIPELINE-1 | [Utterance Lifecycle and Pipeline](pipeline-1.md) | 2 | Draft |
+| OVOS-TRANSFORM-1 | [Transformer Plugins](transformer.md) | 1 | Draft |
+| OVOS-CONTEXT-1 | [Intent Context](intent-context.md) | 2 | Draft |
+| OVOS-CONVERSE-1 | [Active Handlers and Interactive Response](converse.md) | 2 | Draft |
+| OVOS-STOP-1 | [Stop Pipeline Plugin](stop-1.md) | 2 | Draft |
+| OVOS-PERSONA-1 | [Persona Pipeline Plugin](persona.md) | 2 | Draft |
+| OVOS-FALLBACK-1 | [Fallback Pipeline Plugin](fallback.md) | 2 | Draft |
+| OVOS-COMMON-QUERY-1 | [Common Query Pipeline Plugin](common-query.md) | 2 | Draft |
+
+### I/O stack — input and output surfaces
+
+| ID | Document | Version | Status |
+|----|----------|---------|--------|
+| OVOS-AUDIO-IN-1 | [Audio Input Service](audio-in.md) | 2 | Draft |
+| OVOS-AUDIO-1 | [Audio Output Service](audio-out.md) | 2 | Draft |
+| OVOS-GUI-1 | [GUI Display Subsystem](gui-1.md) | 1 | Draft |
 
 Each spec carries its own scope statement, design rationale, and
 conformance section in its header. Open the document for the full
@@ -157,12 +172,11 @@ request, never committed directly.
 
 Each PR that alters normative content **MUST**:
 
-- bump the spec's `Version` field in its header;
-- add a corresponding entry to [CHANGELOG.md](CHANGELOG.md).
-
-A version identifies an exact, citable state of a document, so
-implementations and conformance results can name the version they
-target.
+- add a corresponding entry to [CHANGELOG.md](CHANGELOG.md);
+- set the spec's `Version` field to its V0/V1/V2 compatibility class
+  (`1` for a backwards-compatible formalization, `2` once any change makes
+  the spec incompatible with the pre-spec status quo). The field is the
+  compatibility class, not a per-revision counter (VERSIONING.md).
 
 PRs that touch only the non-normative material —
 [APPENDIX.md](APPENDIX.md) and [appendix/](appendix/) files,
diff --git a/VERSIONING.md b/VERSIONING.md
new file mode 100644
index 0000000..8906efe
--- /dev/null
+++ b/VERSIONING.md
@@ -0,0 +1,33 @@
+# Spec versioning policy
+
+Version numbers in this repository carry compatibility semantics anchored to
+the pre-specification behavior of the OVOS stack:
+
+| Version | Meaning |
+| --- | --- |
+| **V0** | The de facto, undocumented status quo — the behavior the stack ships before a subsystem is formalized. V0 is never written down as a spec; it is the reference point. |
+| **V1** | A formalization of behavior that is **compatible with V0**. A V0 component keeps working against a V1 implementation, even if degraded (missing optional fields, reduced guarantees, legacy namespaces honored). |
+| **V2** | Behavior that is **not backwards compatible** with V0. Adopting it requires coordinated migration (e.g. the `legacy_namespace` configuration gate). |
+
+Until launch day, every spec in this repository MUST be classified as V1 or
+V2. The classification is part of the spec header. Rules of thumb:
+
+- A spec that documents existing message flows, adds optional fields, or
+  introduces parallel namespaces while the legacy ones keep working → **V1**.
+- A spec that renames or removes message types, changes payload semantics, or
+  requires consumers to change before producers (or vice versa) → **V2**.
+- A single spec MAY contain V1 sections and V2 sections only if the V2 parts
+  are explicitly gated (configuration flag) and the ungated behavior is V1.
+
+Within a class, editorial revisions bump the spec's own revision number in
+its header; compatibility class changes (V1 → V2) are a new spec version, not
+a revision.
+
+## The 1.0 definition
+
+The compatibility classes define the project roadmap. The stack starts at V0
+(the undocumented status quo — beta). Each subsystem is formalized as V1, then
+migrated to V2 where the spec demands incompatible change. **OVOS is fully
+spec compliant when every subsystem operates on V2 — that state is the
+"breakthrough" in "from beta to breakthrough", and it is the 1.0 release
+criterion.**
diff --git a/ovos-audio-in-1.md b/audio-in.md
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+++ b/audio-in.md
@@ -1,6 +1,6 @@
 # Audio Input Service Specification
 
-**Spec ID:** OVOS-AUDIO-IN-1 · **Version:** 1 · **Status:** Draft
+**Spec ID:** OVOS-AUDIO-IN-1 · **Version:** 2 · **Status:** Draft
 
 This specification defines the **audio input service** — the component
 that acquires audio, runs the pre-STT transformer chain, transcribes
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diff --git a/ovos-stop-1.md b/stop-1.md
similarity index 99%
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rename to stop-1.md
index e519890..0051fd4 100644
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+++ b/stop-1.md
@@ -1,6 +1,6 @@
 # Stop Pipeline Plugin Specification
 
-**Spec ID:** OVOS-STOP-1 · **Version:** 1 · **Status:** Draft
+**Spec ID:** OVOS-STOP-1 · **Version:** 2 · **Status:** Draft
 
 This specification defines the **stop pipeline plugin** — a pipeline
 plugin that matches utterances expressing the user's intention to