astrid-runtime/astrid · error

delta has trailing bytes

Error message

delta has trailing bytes

What it means

`DeltaCursor::done` is called at the end of `apply_delta` to assert the cursor consumed exactly the whole input. Leftover bytes after the last operation mean the blob contains unrecognized trailing data — either it was corrupted/appended-to, or it is not a well-formed delta for this decoder.

Source

Thrown at crates/astrid-storage-chunker-evidence/src/sketch.rs:755

    fn take(&mut self, length: usize) -> Result<&'a [u8]> {
        let end = self
            .offset
            .checked_add(length)
            .ok_or_else(|| anyhow::anyhow!("delta cursor overflow"))?;
        let bytes = self
            .bytes
            .get(self.offset..end)
            .ok_or_else(|| anyhow::anyhow!("truncated delta"))?;
        self.offset = end;
        Ok(bytes)
    }

    fn done(self) -> Result<()> {
        if self.offset == self.bytes.len() {
            Ok(())
        } else {
            bail!("delta has trailing bytes")
        }
    }
}

fn unlimited_context() -> RefineryBatchContext {
    RefineryBatchContext::new(
        RefinerySnapshotId::new(ObjectId::new([0; 32])),
        PlacementEpoch::new(1),
        RefineryResourceBudget::new(u64::MAX, u128::MAX, u64::MAX, u64::MAX, u64::MAX, u64::MAX),
        None,
    )
}

fn deterministic_random_candidate(
    target: ObjectId,
    corpus_kind: CorpusKind,
    versions: &[Version],
    target_index: usize,

View on GitHub (pinned to affd8760f4)

Solutions

1. Re-encode the delta cleanly with encode_delta instead of concatenating or appending.
2. Strip any trailing metadata/footer the producer added before calling apply_delta.
3. Compare the blob length with the size recorded at encode time to detect appended data.
4. Investigate the writer that produced the blob for post-hoc writes.

fn delta_length_recorded(blob: &[u8], expected_len: usize) -> bool {
    blob.len() == expected_len
}

match apply_delta(&base_bytes, &encoded) {
    Err(e) if e.to_string().contains("trailing bytes") => {
        eprintln!("delta blob has appended data; re-encode cleanly");
    },
    r => r?,
}

When it happens

Trigger: Calling `apply_delta` on a delta blob with extra bytes appended after the final operation — e.g. concatenated deltas, padding added by a writer, or a blob from a format variant that includes a footer.

Common situations: Naive delta concatenation when merging stores; writers that add trailing metadata; partial-overwrite corruption leaving stale bytes.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• unknown delta operation
• delta output length differs from its header
• delta magic mismatch
• encoded evidence delta did not reconstruct its target
• cannot remove capsule authority while an install transaction

AI-assisted analysis of astrid-runtime/astrid@affd8760f4 (2026-09-09). Data as JSON: /api/errors/2c9fc9e5e049495d. Report an issue: GitHub.