08P01

At a glance

SQLSTATE 08P01 is protocol_violation in Class 08. 08P01 means that a frontend/backend protocol message violated the wire contract. The selected raw TCP case completes startup and observes ReadyForQuery (Z), sends an unknown frontend byte Y in a valid frame, receives C=08P01, S=FATAL, primary invalid frontend message type 89, and reads server EOF before the client closes the socket.

Meaning

The server protocol parser accepts the startup exchange, then rejects an unknown frontend message type before it can dispatch SQL. In the selected path this is a FATAL invalid frontend message type 89, followed by server EOF; the code is therefore a synchronization boundary for the affected socket, not a SQL parser error.

The important boundary is the wire state, not the SQL text. A client can reach ReadyForQuery and still fail on its next message type, as the selected case does; a malformed startup frame or a proxy that changes message framing can fail even earlier and may leave no usable session. The selected runtime exercises the unknown-message dispatch branch; the fixed source evidence below also covers distinct Bind and message-buffer parser branches, while other transport failures must be identified from their own ErrorResponse or log evidence.

08P01 does not imply one severity or one socket outcome. In the fixed extended-query path, a Bind message with a mismatched parameter-format count or parameter count reports ERROR; the top-level loop aborts the current command and waits for a protocol-valid Sync before sending the next ReadyForQuery. The fixed message-buffer readers likewise use ERROR for missing bytes, invalid strings, and trailing data. Those recoverable protocol errors are distinct from an unknown message type, which is a FATAL boundary because the server can no longer trust message synchronization.

Diagnosis

Inspect driver/proxy protocol version, message type, frame length, startup mode, and connection ownership. The collector recorded in the selected evidence is a raw protocol ErrorResponse collector (C/S/M plus server EOF), not csvlog/jsonlog. The FATAL socket is closed by the server and is never reused; a separate runner-owned connection returns SELECT 1 and IDLE. This is a wire-protocol boundary, not SQL syntax or a client-created SQLSTATE.

Use the phase to interpret recovery:

• Before startup completes, there is no session-level transaction and the driver may only have a connection exception. Preserve the raw server response if one was sent.
• After startup reaches Z, an unknown frontend message is rejected by the established backend, but the selected branch is FATAL; the server then closes that socket. There is no ROLLBACK to send on it, even if the client had begun work before the protocol desynchronization.
• On a pool or proxy path, compare the bytes sent by the owner with the protocol version and framing expected by the server. A fresh SELECT 1 on another connection proves reachability only; it does not prove that an in-flight request committed.

Use the primary text to identify the branch before choosing a recovery action. bind message has ... parameter formats and bind message supplies ... parameters point to extended-query cardinality; no data left in message, insufficient data left in message, invalid string in message, and invalid message format point to a malformed message body or boundary. These source-defined ERROR variants may be followed by Sync recovery when the driver preserves framing. invalid frontend message type ... with FATAL means the selected socket is already lost.

Response

For a FATAL response or server EOF, close and discard the affected socket, correct the protocol or proxy framing, and reconnect. For an extended-query ERROR, let the driver send protocol-valid Sync and wait for ReadyForQuery, then inspect the transaction status; Sync does not roll back a failed explicit transaction, so status E still requires ROLLBACK or an intentional savepoint recovery. If a non-idempotent request was in flight, reconcile its result before replaying it; the independent probe proves only that a fresh connection works.

Treat the selected case as a session-termination branch: after server EOF, establish a fresh connection and repeat only a reconciled, idempotent operation. If the violation happened before a session existed, fix the startup/proxy configuration first. A client-side parser exception or a socket close without the server's C field is insufficient to label the event 08P01.

Do not improvise a byte sequence or treat the transaction as successfully committed. If the driver cannot preserve the message boundary or does not implement the Sync contract, discard the connection and reconcile the request. This source-only flow does not change the selected unknown-byte runtime, whose FATAL socket must be discarded.

Messages

The fixed parser branch emits FATAL with primary invalid frontend message type %d; the numeric byte is dynamic. The selected byte Y is reported as 89. The raw ErrorResponse, not a client exception, is the SQLSTATE authority.

Other fixed source branches emit ERROR with these primary templates:

• bind message has %d parameter formats but %d parameters
• bind message supplies %d parameters, but prepared statement "%s" requires %d
• no data left in message
• insufficient data left in message
• invalid string in message
• invalid message format

These Bind and message-buffer variants are source-only in this page; they are not additional runtime observations and do not all terminate the socket.

The selected wire sequence is: startup exchange → Z ReadyForQuery → valid frame with type byte Y (decimal 89) → ErrorResponse C=08P01, S=FATAL, M=invalid frontend message type 89 → server EOF. The collector captures those protocol fields and EOF directly; it is neither a csvlog/jsonlog record nor the later independent probe.

Representative case

The SQL probe is the independent connection check. The actual trigger is a runner-owned TCP handshake followed by an unknown frontend message byte; it cannot be represented by SQL alone.

SELECT 1;

The selected 18.6 server record is C=08P01, S=FATAL, primary invalid frontend message type 89; startup reached Z, the server EOF assertion was True, and the separate probe returned 1 and IDLE. The raw trigger connection is therefore closed and never reused.

The downloadable case and evidence projections are 08P01 case JSON and authored evidence. The runner manifest is verify/cases/08P01/cases.json; the page SQL is checked against its shared registry before publication.

Versions

The generated facts table records the locked catalogue snapshots and earliest observed definition. The selected natural runtime scope is PostgreSQL 18.6 and 10.21; this does not infer behavior for every intermediate release.

Related

• 08001 — sqlclient_unable_to_establish_sqlconnection
• 28000 — invalid_authorization_specification

Sources

• src.protocol-invalid-frontend.18.6 — src/backend/tcop/postgres.c at REL_18_6 commit 724edf9bde9d356724ad384a2e196edc3c9f80f7; fixed blob SHA-256 9fb62275b1badf94d01ab351337b60410cd9b3ab1fe63fa9f23d6d2185a21061 (source).
• src.protocol-invalid-frontend.10.23 — src/backend/tcop/postgres.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 badfe30749794afa80a799dcdbd142fd4e4732ac1c913002d365549ae5313497 (source).
• src.postgres-bind.10.23 — src/backend/tcop/postgres.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 badfe30749794afa80a799dcdbd142fd4e4732ac1c913002d365549ae5313497 (source).
• src.pqformat.10.23 — src/backend/libpq/pqformat.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 637923dbf2b9d9a0610350784f3b1d7d36a545cd8a6bd2cbe6272d9549873a91 (source).
• src.postgres-sync.10.23 — src/backend/tcop/postgres.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 badfe30749794afa80a799dcdbd142fd4e4732ac1c913002d365549ae5313497 (source).
• src.calls.REL_18_6 / src.calls.REL_10_23 — fixed local call scans, SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf / 00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c; these scans preserve the resolved call context used by the claims.

Source evidence

Evidence belongs to the frozen source and runtime versions listed here. It is not a runtime verification of the selected manual version.

• src/backend/utils/errcodes.txt · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• raw/calls/REL_18_6.jsonl · REL_18_6 ·
• raw/calls/REL_10_23.jsonl · REL_10_23 ·
• src/backend/tcop/postgres.c · REL_18_6 ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/tcop/postgres.c · REL_10_23 ·
  02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4
• src/backend/tcop/postgres.c · REL_10_23 ·
  02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4
• src/backend/libpq/pqformat.c · REL_10_23 ·
  02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4
• src/backend/tcop/postgres.c · REL_10_23 ·
  02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4
• doc/src/sgml/protocol.sgml · PG18-docs ·
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• verify/cases/08P01/cases.json · workspace ·
• verify/cases/08P01/snippets.json · workspace ·

Message templates

invalid frontend message type %d

bind message has %d parameter formats but %d parameters

bind message supplies %d parameters, but prepared statement "%s" requires %d

no data left in message

insufficient data left in message

invalid string in message

invalid message format

Reproduction & repair cases

Recorded runtime evidence

{
  "probe": 1,
  "collector": {
    "primary": "invalid frontend message type 89",
    "severity": "FATAL",
    "sqlstate": "08P01"
  },
  "probe_status": "IDLE",
  "server_error": {
    "C": "08P01",
    "F": "postgres.c",
    "L": "456",
    "M": "invalid frontend message type 89",
    "R": "SocketBackend",
    "S": "FATAL",
    "V": "FATAL"
  },
  "eof_probe_error": null,
  "connection_scope": "runner-owned TCP endpoint",
  "startup_messages": [
    "R",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "K",
    "Z"
  ],
  "server_eof_after_fatal": true,
  "invalid_frontend_message_type": "Y"
}

{
  "probe": 1,
  "collector": {
    "primary": "invalid frontend message type 89",
    "severity": "FATAL",
    "sqlstate": "08P01"
  },
  "probe_status": "IDLE",
  "server_error": {
    "C": "08P01",
    "F": "postgres.c",
    "L": "467",
    "M": "invalid frontend message type 89",
    "R": "SocketBackend",
    "S": "FATAL",
    "V": "FATAL"
  },
  "eof_probe_error": null,
  "connection_scope": "runner-owned TCP endpoint",
  "startup_messages": [
    "R",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "S",
    "K",
    "Z"
  ],
  "server_eof_after_fatal": true,
  "invalid_frontend_message_type": "Y"
}