docs(protocol): the pre-1.0 disclaimer's substance survived — restate it as the launch-window rule instead of deleting it

.changeset/docs-backward-compat-launch-window.md

@@ -0,0 +1,51 @@
+---
+"@objectstack/docs": patch
+---
+
+fix(docs): the Backward Compatibility page said MINOR may break "during 0.x" — restate it as the launch-window rule it actually is (#13779)
+
+`content/docs/protocol/backward-compatibility.mdx` closed with a `Pre-1.0
+Disclaimer` reading:
+
+> During the **0.x** development phase, MINOR versions may contain breaking
+> changes. The full backward compatibility policy takes effect starting with
+> version **1.0.0**.
+
+The published stack is at **17.2.0**, so a reader dismisses that paragraph as
+obviously stale and is left with the page's opening SemVer table, which says a
+MINOR keeps existing code working. **That is the wrong way round.** The
+disclaimer's *substance* is the part that survived; only its `0.x` / `1.0.0`
+framing died.
+
+Deleting the paragraph would therefore have silently **strengthened** a
+customer-facing compatibility promise into one the repo contradicts on every
+release. Four independent sources say breaking changes ship as MINOR today:
+
+- **`.changeset/config.json`** — all **69** published packages sit in one
+  Changesets `fixed` group (`check:changeset-fixed`: *"fixed group is in sync
+  with 69 public workspace packages"*), so no published surface is exempt and a
+  single `major` would promote the whole stack.
+- **`scripts/check-changeset-no-major.mjs`** — a wired, currently-enforcing CI
+  guard (`.changeset/pre.json` is absent, so the RC exemption is not in play)
+  whose header states the convention outright: *"During the launch window we ship
+  breaking changes as `minor`."* `--list` reports **559 pending changesets, 0
+  declaring a major**.
+- **`packages/spec/CHANGELOG.md`** — the `17.2.0` **Minor Changes** section
+  carries an entry marked `**BREAKING**` (the `http_request_errors_total`
+  retirement under ADR-0049).
+- **`content/docs/releases/`** — v13, v14, v15 and v17 already tell customers
+  this. v15.1.0: *"Strict-semver breaking, shipped in a minor under the
+  launch-window policy."* v17: *"17.1.0 and 17.2.0 are minors by version number,
+  not by blast radius."*
+
+The section is retitled `Launch Window: MINOR Releases Can Contain Breaking
+Changes` and now states the rule definitely rather than hedging it: which
+surfaces it covers (all 69), that it is gate-enforced, what an upgrader should do
+instead of trusting the version number, that MAJORs still happen when breaking
+density demands one, and that it overrides the tables above wherever they
+disagree.
+
+Nothing links to the old `#pre-10-disclaimer` anchor (grepped repo-wide), so the
+retitle breaks no inbound reference.
+
+<!-- adr-0087: not-required (unpublished) The only bumped package is @objectstack/docs, which is `private: true` and absent from the Changesets `fixed` group, so nothing here reaches a published surface. This changeset removes, renames and narrows nothing; the BREAKING wording in the body quotes changelog entries that already shipped, and is not a breaking change declared by this diff. -->

content/docs/protocol/backward-compatibility.mdx

@@ -174,12 +174,30 @@ The `@objectstack/spec` package provides additional stability guarantees:
 
 ---
 
-## Pre-1.0 Disclaimer
+## Launch Window: MINOR Releases Can Contain Breaking Changes
 
 <Callout type="warn">
-During the **0.x** development phase, MINOR versions may contain breaking changes. The full backward compatibility policy takes effect starting with version **1.0.0**.
+**This exception overrides the MAJOR/MINOR mapping above — read it before you plan an upgrade.** Every published `@objectstack/*` package versions in **lockstep**, and while the launch window is open a breaking change ships as a **MINOR** release rather than burning a MAJOR. The current release, **17.2.0**, is a MINOR and it contains a documented breaking change.
 </Callout>
 
+### Which surfaces this covers
+
+**All of them.** This is not scoped to an experimental corner or a pre-release channel: all **69** packages published from this repository belong to a single Changesets `fixed` group, so they share one version number and one policy. No published surface is exempt.
+
+The convention is enforced rather than informal — `scripts/check-changeset-no-major.mjs` fails any pull request that introduces a `major` bump, because under lockstep a single `major` on one package would promote the entire stack.
+
+### What this means for an upgrade
+
+- **Do not read a MINOR bump as safe to take unattended.** Read the [release notes](/docs/releases) for the version you are moving to: they lead with breaking changes and carry the migration steps.
+- **Pin exact versions** instead of caret ranges if you cannot review each MINOR before it lands.
+- **Diff your own metadata** across the upgrade with `os diff <before> <after> --breaking-only`.
+
+MAJOR releases do still happen — 17.0.0 was cut precisely because its breaking density was too high to carry `^16.x` consumers across on a caret range — but an individual breaking change does not, on its own, force one.
+
+### When it stops applying
+
+The versioning tables and deprecation timeline above describe the policy in its settled form; they take full effect when the launch window closes and a breaking change once again requires a MAJOR. Until then, **this section is the operative rule wherever the two disagree.**
+
 ---
 
 ## Reporting Compatibility Issues