apache/beam · error · CoderException

Invalid pane encoding

Error message

Invalid pane encoding 

What it means

PaneInfo.Encoding.fromTag decodes the high nibble of the pane's tag byte into an Encoding enum. If the nibble does not map to a known encoding, the encoded element is corrupt or was produced by an incompatible Beam version, and a CoderException is thrown.

Solutions

1. Verify the data was serialized and deserialized with the same Apache Beam version on both ends.
2. Re-generate or re-ingest the corrupted data; check storage/transport for truncation or bit corruption.
3. Inspect the offending first byte to confirm whether it is truncated/garbage vs a legitimately newer encoding.
4. If bridging versions is required, upgrade both producer and consumer to a common Beam release before exchanging encoded data.

Example fix

// before
Encoding e = Encoding.fromTag(rawByte); // throws CoderException on garbage byte
// after
int index = rawByte >> 4;
if (index < 0 || index >= Encoding.values().length) {
  LOG.warn("Corrupt pane tag byte 0x{}; defaulting to NO_FIRING", Integer.toHexString(rawByte & 0xFF));
  return PaneInfo.NO_FIRING;
}
Encoding e = Encoding.fromTag(rawByte);

boolean validPaneTag(byte b) {
  int index = b >> 4;
  return index >= 0 && index < PaneInfo.Encoding.values().length;
}
// validate before decoding raw bytes from external storage

try {
  PaneInfo info = paneInfoCoder.decode(stream);
} catch (CoderException e) {
  LOG.error("Corrupt PaneInfo tag byte; data may be truncated or written by another Beam version", e);
  // skip element / re-ingest / dead-letter
}

When it happens

Trigger: Decoding a PaneInfo from a byte stream whose tag byte's high nibble (b >> 4) is negative or >= Encoding.values().length — i.e. a corrupted serialized element, a hand-crafted/truncated stream, or data written by a newer Beam version with extra encodings.

Common situations: Reading already-serialized runner state or test data written by a different Beam version; corrupted transport/storage of encoded bundles; custom runners mangling the first byte of PaneInfo encodings.

Understand the failure class

Background: "cannot parse invalid wire-format data", "cannot unmarshal", "failed unmarshalling": protobuf unmarshal errors explained — this error's family across 10 libraries.

Related errors

• Error deserializing via Coder
• Failed to read PipelineOptions from Protocol
• Field ' ' has a null value in the JSON object.
• Field ' ' is not present in the JSON object.
• Unable to parse representation

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/aa9691e5931066cd. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/windowing/PaneInfo.java:347

    private enum Encoding {
      FIRST,
      ONE_INDEX,
      TWO_INDICES;

      // NOTE: Do not reorder fields. The ordinal is used as part of
      // the encoding.

      public final byte tag;

      Encoding() {
        assert ordinal() < 16;
        tag = (byte) (ordinal() << 4);
      }

      public static Encoding fromTag(byte b) throws CoderException {
        int index = b >> 4;
        if (index < 0 || index >= values().length) {
          throw new CoderException("Invalid pane encoding " + index);
        }
        return Encoding.values()[b >> 4];
      }
    }

    private Encoding chooseEncoding(PaneInfo value) {
      if ((value.index == 0 && value.nonSpeculativeIndex == 0) || value.timing == Timing.UNKNOWN) {
        return Encoding.FIRST;
      } else if (value.index == value.nonSpeculativeIndex || value.timing == Timing.EARLY) {
        return Encoding.ONE_INDEX;
      } else {
        return Encoding.TWO_INDICES;
      }
    }

    public static final PaneInfoCoder INSTANCE = new PaneInfoCoder();

    public static PaneInfoCoder of() {

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