V3 permits external event, source and content identities and additional
request-tool fields. Copying those values into V4 can give an old plugin
named tool a core source identity, turn old tool-addition content into a
registry instruction, or activate formerly ignored deferLoading and delivery
metadata. Rejecting such collisions would instead refuse valid source logs.
Keep historical extensions in the existing extensible JSON representation.
Prefix unknown content and ignorable event tags with plugin:, preserving
all other content fields and opaque event payloads. Prefix external source
identities with plugin:plugin: or plugin:source: so wrapper and direct kinds
cannot collide even when original names already contain a category prefix.
Known first-party mappings remain explicit and unchanged.
Prefix extra request-tool field names and block-start field names with
plugin:, retaining exact values and existing-prefix doubling. Core schema
parameters, arguments, replay state and nested plugin data are not traversed.
Keep future-generation delivery records inactive after header promotion.
Pin the V3 event vocabulary independently of the current writer and provide
an offline verifier against an explicitly selected historical source commit.
Attachment authorization and export inspect declared event content only.
Team checkpoints preserve all own keys of unknown JSON blocks while still
rejecting malformed known content and retired core tool-result blocks.
Exercise physical read/write/reopen, prefix injectivity, own __proto__ keys,
provider opacity and retained source-identity snapshots.
No generic extension block, metadata wrapper or new schema-tooling type is
introduced. V4 type declarations, persistence schema, checkpoint and frozen
V0-V3 codecs remain unchanged. Canonical tool-result lifting and incomplete
child-catalog policy remain separate concerns.
Adapted from the extension-preservation work in 7ba7e174dd1 by Tianyi Cui.
Co-authored-by: Tianyi Cui <53024+tianyicui@users.noreply.github.com>
The integrated V3-to-V4 records contain the header increase that authorizes
their breaking changes. Leaving those terminal records editable would let a
later change reuse that already accepted 3-to-4 increase, so version 4 would
not establish a stable compatibility baseline for persisted user data.
Capture the accepted root classifications and semantic record digests in a
separate finalization checkpoint. Validate that checkpoint before rendering
or writing acknowledgement artifacts, and preserve its accepted records even
after the current writer advances. Keep publication evidence independent:
the verified released version remains 3 until a release establishes otherwise.
Compare future writer-4 schemas with the accepted baseline using the existing
compatibility classifier. Compatible additions remain permitted through new
same-version acknowledgement records. Breaking changes require a higher
writer and their own header transition; comments, aliases and source-location
changes do not alter the accepted semantics. Later unaccepted compatible
records retain the existing update workflow.
Document the distinction between finalization, publication and compatible
evolution, with regression coverage for locked records, incomplete or
inconsistent checkpoints, additive changes and future-version transitions.
Yixiang Tu