v4.0.11

ProxySQL 4.0.11 Release Notes

Release date: 2026-08-27

ProxySQL 4.0.11 is the Plugin Chassis / AI-tier release. It contains every
Stable 3.0.11 and Innovative 3.1.11 change, and adds a concentrated reliability
update for the GenAI plugin, MCP endpoints, RAG and vector tooling, runtime
configuration reloads, and the shared TSDB metrics store.

This release is primarily about making the plugin ecosystem predictable under
real operational pressure. Fresh installations receive a complete set of MCP
and GenAI defaults, existing installations keep their configured values, live
reloads coordinate with active tool calls, and shutdown waits for plugin client
threads before unloading shared state. Authentication and readiness checks now
follow the same MCP endpoint contract, while statistics and metric discovery no
longer race with configuration or TSDB activity.

Why upgrade

• A fresh plugin database receives every missing mcp-* and genai-* default,
  so valid settings such as mcp-enabled can be changed immediately.
• Existing operator values are preserved during startup seeding and runtime
  reload; defaults fill gaps rather than resetting the configuration.
• MCP endpoints consistently require their configured bearer token, including
  health/readiness probes used by automation.
• LOAD MCP VARIABLES TO RUNTIME and LOAD GENAI VARIABLES TO RUNTIME replace
  shared dependencies safely while Admin, status, query-hook, MCP AI, and RAG
  work may be active.
• Plugin teardown drains client threads before destroying their modules,
  reducing shutdown and unload races.
• TSDB metric discovery, ingestion, and downsampling use synchronized access to
  the shared SQLite connection and tolerate transient locks.

Before upgrading

• mcp-enabled remains disabled by default. Startup creates missing rows but
  does not silently enable the listener or overwrite an existing value.
• Review all endpoint authentication variables before enabling MCP. An endpoint
  whose corresponding mcp-*_endpoint_auth value is empty refuses requests;
  this is a fail-closed security policy, not an anonymous mode.
• Readiness clients must send the same bearer authentication required by the
  endpoint they probe. Update external health checks that previously assumed an
  unauthenticated request.
• Runtime reloads are safer, but they are still configuration changes. Validate
  the values in global_variables, load the intended variable family, and
  verify the runtime view before persisting to disk.
• ProxySQL 4.0.11 inherits the 3.1 authentication changes. In particular, an
  existing mysql_users.attributes value of "require_x509": true is enforced
  in this tier even though Stable 3.0.x ignores it.

Complete defaults without destroying operator configuration

The GenAI plugin reads its settings from main.global_variables. On a fresh or
partially upgraded database, missing canonical rows could leave the plugin only
partly initialized: a valid SET mcp-enabled=true might be rejected because the
runtime did not know the variable, or the runtime projection could contain an
incomplete configuration.

ProxySQL 4.0.11 collects the canonical defaults from the MCP and GenAI runtime
handlers and transactionally inserts only the rows that are missing. Existing
values win. If seeding fails, the transaction rolls back rather than leaving a
half-populated configuration. The complete MCP set is then validated and
published as one runtime snapshot, so readers do not observe a mixture of old
and new values.

Operators can inspect the stored configuration before and after an upgrade with:

SELECT variable_name, variable_value
FROM global_variables
WHERE variable_name LIKE 'mcp-%'
   OR variable_name LIKE 'genai-%'
ORDER BY variable_name;

The same preservation rule applies to the LLM cache setting and other GenAI
runtime values: reloads use the operator's current configuration rather than
reverting a working value to an internal default. (#6107)

Runtime reloads coordinate with active consumers

MCP, RAG, AI tools, query hooks, status collection, and Admin commands share
runtime objects. Replacing those objects while another thread was still using
them could expose stale pointers, mismatched variables, or an inconsistent
combination of old and new dependencies.

The reload path now quiesces shared consumers before replacing their runtime
dependencies. It republishes a complete variable snapshot, refreshes the RAG
and AI tool dependencies, and only then resumes normal work. This applies to
the standard Admin commands:

LOAD MCP VARIABLES TO RUNTIME;
LOAD GENAI VARIABLES TO RUNTIME;

The corresponding FROM DISK, FROM CONFIG, and save-to-memory flows use the
same ownership boundaries, so configuration round-tripping no longer leaves the
running plugin with stale values. The listener is recreated only when relevant
settings such as enablement, port, or TLS mode require it; otherwise the active
server is retained. (#6107)

Safer MCP authentication and health checks

Each MCP endpoint has a corresponding bearer-authentication variable. ProxySQL
now applies that contract consistently to real tool calls, test clients, and
readiness checks. If a token is empty, the endpoint refuses the request and logs
which mcp-<endpoint>_endpoint_auth setting must be configured. This avoids the
ambiguous state where an enabled endpoint appears healthy but is unintentionally
unauthenticated.

For operators, the practical change is that monitoring must behave like a real
client: use HTTPS verification as configured, supply the correct bearer token,
and honor bounded request timeouts. A readiness failure can now indicate missing
authentication rather than a dead listener, so health-check diagnostics should
retain the HTTP response and ProxySQL log message. (#6107)

Predictable plugin shutdown and live operation

Plugin unload and process shutdown now drain client threads before module
destruction. Shared AI/RAG bridges are detached in an ordered sequence, and MCP
workers stop using a dependency before it is replaced or freed. This prevents a
late client, status query, or query hook from observing a partially destroyed
runtime.

The PostgreSQL processlist snapshot exposed to MCP is now bounded, avoiding an
unlimited copy when a busy proxy has many frontend sessions. Discovery-schema
resources are released on all relevant paths, closing leaks that became visible
during long-running sanitizer tests. Statistics tests and runtime counters no
longer depend on execution order or mutable state left by a previous operation.
(#6107)

TSDB and metric discovery no longer race

Metric ingestion, MCP/GenAI discovery, statistics queries, and hourly
downsampling all touch the TSDB SQLite database. Previously, these callers could
use the shared connection concurrently. A transient SQLITE_BUSY, discovery
request, or hour rollover could therefore interfere with another operation and,
in the worst case, terminate ProxySQL.

Access is now serialized with the same pthread-backed lock across every shared
caller, including REST metric discovery. Hour rollover and downsampling happen
inside that coordinated lifecycle, and a temporary SQLite lock is handled
without aborting the daemon. The result is especially important for deployments
where monitoring systems query discovery endpoints while metrics are being
written continuously. (#6004, #6107)

Innovative-tier capabilities included in 4.0.11

Because the 4.0 tier includes the 3.1 feature set, it also receives the complete
Innovative 3.1.11 authentication and observability update:

• non-TLS caching_sha2_password full authentication for clients that request
  ProxySQL's RSA public key or pin it locally, with validated key generation and
  rotation-safe snapshots (#6017, #6032);
• frontend MariaDB client_ed25519 authentication, including
  COM_CHANGE_USER, plus backend ed25519 support when a cleartext upstream
  credential is available (#6033);
• per-user {"require_x509": true} frontend certificate policy, enforced before
  password or row-backed pass-through authentication (#6028);
• independent Admin/Stats and frontend credential scopes, allowing the same
  username to carry different credentials on different interfaces (#5993);
• accurate MySQL and PostgreSQL FFTO accounting for deprecated EOF, multi-result
  responses, prepared-statement fetches, and pipelined extended queries (#6047,
  #6021).

Stable improvements included in 4.0.11

ProxySQL 4.0.11 also carries every Stable 3.0.11 improvement, including:

• opt-in literal MySQL user-variable tracking and replay across multiplexed
  backends (#6043);
• opt-in endpoint-wide GTID learning from successful OK packets (#6035);
• hardened authentication response bounds and OpenSSL handshake randomness
  (#5998, #6104);
• safe --idle-threads shutdown and single-flight soft-TTL cache refreshes
  (#6087, #6015);
• MySQL/Admin/SQLite3 compatibility fixes and visible client connection
  attributes (#5994, #6079, #6076, #5978, #6077);
• cleanup of the temporary PostgreSQL termination connection and the PostgreSQL
  user-synchronization Scheduler sample (#6130, #6045);
• portable Linux tarballs with bundled OpenSSL and FreeBSD portability work
  (#6105, #6030).

Release commit: 7c91137a465454dfc1a62b56f8c188c1ce59c130

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