ipfs/kubo · error

dagStore: key was not a cid: had %d bytes leftover

Error message

dagStore: key was not a cid: had %d bytes leftover

What it means

The sibling validation in `cidFromBinString`: even when `cid.CidFromBytes` succeeds, it may consume fewer bytes than the key holds (`l != len(key)`). A dagStore key must be exactly one CID with no trailing bytes, so leftover bytes indicate a malformed key and this error reports how many bytes remain.

Source

Thrown at core/commands/dag/export.go:289

func (ds *dagStore) Has(ctx context.Context, key string) (bool, error) {
	_, err := ds.Get(ctx, key)
	if err != nil {
		if errors.Is(err, ipld.ErrNotFound{}) {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

func cidFromBinString(key string) (cid.Cid, error) {
	l, k, err := cid.CidFromBytes([]byte(key))
	if err != nil {
		return cid.Undef, fmt.Errorf("dagStore: key was not a cid: %w", err)
	}
	if l != len(key) {
		return cid.Undef, fmt.Errorf("dagStore: key was not a cid: had %d bytes leftover", len(key)-l)
	}
	return k, nil
}

View on GitHub (pinned to 329838acdf)

Solutions

1. Check the key format of the underlying blockstore/datastore; it must be the exact CID bytes with no extra bytes.
2. Fix or regenerate keys in the custom writer that produced suffixed keys.
3. Run `ipfs repo gc` / rebuild the local datastore if corruption shifted key boundaries.
4. Capture the full offending key from the error and open an issue if it came from stock kubo.

c, rest, err := cid.CidFromBytes([]byte(key))
if err != nil || len(rest) != 0 {
    return fmt.Errorf("key must be exactly one CID, got trailing bytes: %q", key)
}

When it happens

Trigger: dagStore `Get` receives a key string that starts with valid CID bytes but contains additional trailing data — e.g. a key encoding that embeds the CID as a prefix rather than the whole value.

Common situations: A datastore written by tooling that concatenated CID + suffix keys; data corruption shifting byte boundaries; using a dagStore view over a blockstore with a different key format.

Related errors

• dagStore: key was not a cid: %w
• CheckCIDSize: getting dag: %w
• checking if new root exists: %w
• new root %s does not exist locally; fetch it first with 'ipf
• pin check failed: %w

AI-assisted analysis of ipfs/kubo@329838acdf (2026-09-03). Data as JSON: /api/errors/418eed239d519597. Report an issue: GitHub.