docs: document selective upstream synchronization

README.md

@@ -11,6 +11,25 @@ for source reference, but `gif-download` and `userbot` still depend on
 before they can be built against this renamed module and are not part of this
 fork's release gate.
 
+## Fork maintenance
+
+Upstream synchronization is selective by design. Do not merge or rebase the
+whole `gotd/td` branch into this fork's release line. For every fetched upstream
+range, record the old and candidate base commits, review each commit or cohesive
+feature group, and replay only the selected source, runtime, diagnostic,
+performance, security, and required dependency changes. Record skipped changes
+and the reason they do not belong in the fork.
+
+Upstream-generated `tg/*_gen.go` files are never copied or conflict-merged.
+Schema changes enter through the versioned manifest, semantic policy audit, and
+sparse AOT generation workflow documented in
+[`_schema/layers/README.md`](_schema/layers/README.md). If the upstream schema
+has the same Layer, normalized SHA-256, and body as the fork's canonical schema,
+provenance-only differences do not trigger canonical regeneration. A candidate
+upstream base becomes the documented baseline only after deterministic
+generation, fork tests, downstream `telesrv` validation, and publication of a
+new immutable tag.
+
 Telegram MTProto API client in Go for users and bots.
 
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_schema/layers/README.md

@@ -18,6 +18,34 @@ active updates and difference responses all use `Call.EncodeResult`,
 `EncodeObject` or `FrozenObject.Encode`; there is no push-specific codec and no
 fallback to canonical bytes when a projection fails.
 
+## Synchronizing `gotd/td` upstream
+
+Upstream is an evidence and patch source, not a branch that is merged wholesale
+into the fork. Every synchronization uses this sequence:
+
+1. Fetch upstream and record the current base, candidate new base, and exact
+   commit range. Classify each non-merge commit or cohesive feature group as
+   `selected` or `skipped`, with a short reason.
+2. Replay selected source/runtime changes on a dedicated fork branch. Preserve
+   the `github.com/iamxvbaba/td` module boundary and resolve upstream import-path
+   differences in source. Keep required dependency changes in the same reviewed
+   patch set as the feature that needs them.
+3. Never copy, cherry-pick, or conflict-merge upstream-generated `tg/*_gen.go`
+   files. They are an oracle for schema/codegen comparison only. Fork-generated
+   outputs must come exclusively from the fork's manifest, semantic IR, policy,
+   templates, and sparse AOT emitter.
+4. Compare schema Layer, normalized SHA-256, and body before importing it. An
+   identical schema with different generator/source header provenance is a
+   no-op for canonical generation. A genuinely new or changed schema must use
+   the import and policy-audit workflow below.
+5. Run deterministic generation, targeted and full fork tests, `go vet`, source
+   budgets, cross-Layer wire oracles, and downstream `telesrv` validation. Only
+   after all gates pass may documentation adopt the candidate upstream base and
+   a new immutable fork tag be published.
+
+This policy applies to every future upstream update. A full upstream
+merge/rebase into the release line is not a shortcut for this review.
+
 ## Adding a Layer
 
 1. Import the exact source from a local upstream checkout. `gotdgen` discovers