How to Fix BlueSky PDS Data Corruption and Sync Errors

A BlueSky PDS sync error is not the same thing as a failed social media post. It usually means a repository mirror, relay, indexer, or custom service believes the account repository state is inconsistent, incomplete, unavailable, or no longer aligned with the latest signed commit chain.

The AT Protocol repository model is content-addressed and verifiable. Each account repository is a Merkle Search Tree, each commit points at a root data CID, and commit signatures let receiving services verify that the repository state was produced by the account's current signing key.

Read the AT Protocol repository specification for the underlying Merkle tree, commit, CAR export, and security model.

What a PDS sync error usually means

The most common failure pattern is a broken view of state. A relay or service expected the next repository revision, but the event it received does not line up with the previous revision, previous tree root, operation list, or signed commit block it already had.

That can happen because of missed events, delayed identity refresh, PDS outage, invalid signatures after a key change, corrupted or incomplete CAR blocks, repository takedown state, or a service falling behind and needing to resynchronize.

Start with the official sync model

The AT Protocol sync spec says receiving services should track repository revision and tree root for each DID. If a commit or sync message breaks that chain, the service marks the repository out of sync and usually fetches the full repository CAR export again.

Review the AT Protocol sync specification for commit chain validation, resynchronization behavior, and message validation rules.

Check identity before blaming storage

Identity drift can look like data corruption. Before rebuilding a repository mirror, resolve the DID, confirm the current DID document, verify the signing key, confirm the account's current PDS service endpoint, and make sure the handle still resolves bidirectionally.

If the account uses a custom domain handle, run the BlueSky DNS TXT record validator before assuming the PDS repository itself is damaged.

Use getRepo and getBlocks carefully

The com.atproto.sync.getRepo endpoint downloads a repository export as a CAR file and can optionally request a diff since a previous revision. The com.atproto.sync.getBlocks endpoint returns data blocks from a repo by CID. Both are PDS-implemented sync tools and should be treated as diagnostic or synchronization operations, not marketing APIs.

Inspect the getRepo lexicon to confirm the DID, since, CAR output, and error shape.

A practical diagnostic sequence

Confirm the account DID and current handle resolution before checking repository data.

Resolve the DID document and verify the current PDS endpoint and signing key.

Check whether the repo is active, taken down, suspended, deactivated, or temporarily unavailable.

Fetch the current repo CAR export with getRepo and verify that the commit object, root data CID, and MST structure parse cleanly.

Compare the latest processed rev and data root against the incoming commit or sync event.

If the chain is broken, mark the mirror desynchronized and perform a full resync instead of patching unknown gaps.

What not to do

Do not blindly replay writes, regenerate sessions, or hammer the PDS with repeated full exports. The sync spec warns about thundering herd behavior during repository resynchronization. Back off, cache where appropriate, fetch from the direct upstream when possible, and avoid turning one broken mirror into a service-wide load problem.

Where ONYX fits

ONYX is not a PDS repair tool, a relay, or a repository rebuild service. It is the reviewed scheduling layer for approved BlueSky posts. That means ONYX should help teams prepare clean text, schedule responsibly, and avoid reckless retry behavior while platform or infrastructure issues are investigated.

If a PDS, relay, or identity issue is active, pause high-risk publishing, keep approved drafts in the ONYX calendar, and resume after the account's identity and repository state are stable. A clean queue is only useful when the underlying account path is healthy.

Keep approved BlueSky posts organized in ONYX while technical teams resolve repository, identity, or sync-layer issues.