Dune 3.25.0

CHANGES:

Fixed

• Fix crashes when expanding module artifact pforms (%{cmi:...} etc.) with
  (include_subdirs qualified). Qualified modules can now be referenced by
  dotted logical paths such as %{cmi:Sub_a.Foo}.
  (#14498, #16214, fixes #14496, @Alizter, @anmonteiro)

• dune show targets now accepts build-only directories such as
  _build/default/.simple.objs. (#14664, fixes #13782, @Alizter)

• Reword the error raised when %{target} is used in a rule that omits the
  (target ...) (or (targets ...)) field, so it points at the missing
  field instead of mentioning "inferred rules". (#14668, fixes #12439,
  @Alizter)

• Fix watch mode on Windows by creating the file-watcher sync directory before
  using it, avoiding open(_build/.sync\0): No such file or directory when an
  RPC client requests a build. (#14678, fixes #14632, @rgrinberg)

• Add file watcher trace events for the Mac and Windows backends (#14722, @rgrinberg)

• Fix decoding coalesced MacOS file notification events. (#14725, @rgrinberg)

• Handle directory invalidations correctly in watch mode on MacOS (#14756, @rgrinberg)

• Update ctime when restoring from the shared cache in copy mode. This prevents
  the trimmer from deleting the file. (#14777, @rgrinberg)

• Allow the use of all the available variables in the (enabled_if) field in
  (executable ...) and (install ...) stanzas, similar to other stanzas like
  (library ...). (#14860, fixes #14789, @punchagan)

• Linux: dune will now wait for the process group to be dead after the group
  leader is dead. This tightens dune's policy for what constitutes
  a successful action. Actions for which dune cannot be clean up the process
  group will now fail. (@rgrinberg, #14868)

• Fix caching of package sources with symlinks by resolving symlinks after
  fetching the sources, similar to the directory symlinks resolution introduced
  in #13792 (#14871, fixes #14509, @punchagan)

• Fixed wrong suggestion for duplicate entries in conflicts field (#14956,
  fixes #14903, @Leonidas-from-XIV)

• Fix building Dune on Solaris/illumos by handling its wait4 semantics
  and retrying interrupted reads when spawning processes. (#14980, fixes #14182,
  @jperkin)

• Fix dune-rpc-lwt clients so disconnecting shuts down socket output
  without invalidating pending input reads, avoiding EBADF errors. (#14983,
  fixes #7624, @rgrinberg)

• Dune now restores dependency cutoffs concurrently when they were originally
  computed in parallel, instead of recomputing them one at a time. The
  cutoffs_that_reduce_concurrency_in_watch_mode setting, which existed to
  avoid this serialisation, is no longer needed and has been removed.
  (#15012, @snowleopard)

• Validate project module names before creating the project directory in
  dune init project, so aborted initializations no longer leave empty
  directories behind. (#15014, fixes #9963, @rgrinberg)

• Fix cram test output sanitization when the project path contains a space.
  Absolute paths are now rewritten to $TESTCASE_ROOT even when the path
  contains spaces, and lines with multiple paths have every path sanitized.
  (#15017, fixes #14943, @yussypu)

• Improve the error message for private libraries that cannot be dependencies of
  public libraries by mentioning the (package ...) field as an alternative to
  giving the private library a public name (#15070, fixes #10230, @rgrinberg).

• Clarify the module conflict error shown when a module is used in multiple
  stanzas. The message now explains implicit module ownership and lists all
  relevant stanza kinds (#15072, fixes #6598, @rgrinberg).

• Emit relative artifact references in installed dune-package files when using
  an absolute external DUNE_BUILD_DIR, avoiding build-directory-dependent
  archive and module paths (#15077, fixes #11774, @rgrinberg).

• Simplify away (when false _) expressions (encoded Nils) that previously
  survived inside concat and when forms, producing cleaner generated lock
  directories. (#15092, fixes #15090, @chizy7)

• Drop (when false _) arguments from run actions in generated lock
  directories instead of keeping them as no-op entries that were re-encoded as
  (when false ""). (#15128, fixes #15099, @chizy7)

• Make dune-configurator pass --personality to pkgconf only for
  version 1.7.0 and later. (#15142, fixes #11536, @dra27)

• dune utop now accepts an absolute path to a workspace directory instead of
  crashing with an internal error. (#15272, fixes #15108, @chizy7)

• Fix watch-mode status lines after source changes interrupt a build. Dune now
  shows the restart status while cancelling the current build and resumes the
  normal progress counter when the next build starts. (#15289, fixes #11134,
  @rgrinberg)

• Short-circuit AND and OR expressions in blang. This makes their evaluation
  lazy by default.
  (#15291, @Sudha247)

• Fix the %{ppx:ppx1+..+ppxn} form. Previously, it was just broken
  and pointed at the wrong binary (#15361, @rgrinberg)

• Remove ppx runtime dependencies from the list of dependencies provided via
  the root_module field. If such a runtime dependency is needed, it should be
  written in the libraries field. (#15419, @rgrinberg)

• Avoid rebuilding js_of_ocaml library archives on every invocation for
  interface-only and empty libraries. (#15427, @anmonteiro)

• Do not crash when ~/.config/dune is a file instead of a directory. Just
  pretend it doesn't exist (#15475, fixes #15406, @rgrinberg)

• Dune will now terminate all launched sub-processes even if it received
  SIGKILL itself (#15483, @rgrinberg)

• Account for ctime in stat based digest cache (#15495, @rgrinberg)

• $ dune install --dry-run now checks for non empty directories as part of its
  validation (#15501, @rgrinberg)

• Fix a target-less rule attached to multiple aliases ((rule (aliases a b) ...)) leaking unrelated contributions between those aliases. Building one
  alias no longer pulls in actions or dependencies that were added only to
  another of the rule's aliases. (#15581, @NatKarmios)

• Make dune pkg enabled query a running Dune RPC server, so it observes
  transient server-side --pkg enabled and --pkg disabled settings without
  trying to acquire the build lock (#15589, fixes #15587, @Alizter)

• Make generated MDX executables inherit link_flags from env stanzas.
  (#15614, fixes #15613, @Alizter)

• Return Unix errors from Fs_io.read_file rather than raising them. (#15641,
  @rgrinberg)

• Correct filesystem trace metrics for file writes and directory scans.
  (#15686, @rgrinberg)

• Preserve runtime-event ring IDs in Dune traces so consumers can distinguish
  interleaved event streams. (#15687, @rgrinberg)

• BREAKING CHANGE: in dune-project, (warnings (duplicate_deps ..)) requires
  a dune lang version of 3.22, instead of 3.18 (#15696, @v-gb).

• Preserve spaces in unquoted filenames when applying Git patches instead of
  truncating paths at the first space (#15781, @rgrinberg)

• Respect enabled_if on install stanzas when adding their files and
  directories to the @all alias. (#15895, fixes #15825, @aryemans)

• Fix Melange emission with installed libraries whose .cmj and .cmi files
  are stored in the melange object directory (#15949, fixes #14820,
  @anmonteiro)

• Reject package dependencies in named dependency bindings while decoding
  dependency fields, including for disabled stanzas. (#15966, @rgrinberg)

• Fix Merlin definition lookup for libraries with private modules
  (#15977, fixes #4892, @anmonteiro)

• Fix a crash when generating install rules for a Melange-only implementation
  of an installed virtual library (#16033, @anmonteiro)

• Prevent build cancellation from crashing Dune when macOS reports EPERM
  while signaling a process group (#16059, fixes #16053, @rgrinberg)

• Fix dune pkg outdated so it fails early with a clear user message if it is
  run when package management is not enabled. (#16065, @shonfeder)

• Fix watch mode builds remaining stale after the file watcher event queue
  overflows (#16068, fixes #16052, @rgrinberg)

• Reject Windows path separators in validated filename components (#16076,
  @rgrinberg)

• Preserve output following malformed ANSI escape sequences and erase-line
  controls (#16116, @rgrinberg).

• Resolve relative paths passed to dune ocaml top-module from the directory
  where Dune was started, allowing use from workspace subdirectories. (#16135,
  @rgrinberg)

• Allow dune ocaml top to accept absolute directory paths inside the
  workspace. (#16142, @rgrinberg)

• Allow Dune promotion commands to accept absolute source paths inside the
  workspace. (#16143, @rgrinberg)

• Allow dune describe workspace to accept absolute directory filters inside
  the workspace. (#16144, @rgrinberg)

• Reject empty module_systems fields in melange.emit stanzas instead of
  silently producing no JavaScript files (#16162, @anmonteiro)

• Sandbox PPX lint actions starting with Dune language 3.25 so linters cannot
  observe undeclared build targets. (#16176, @rgrinberg)

• Prevent diagnostic source locations at compact-position field boundaries from
  being truncated (#16180, @rgrinberg)

• Sandbox ocaml-mdx deps when using MDX extension 0.6 so dependency
  discovery cannot observe undeclared workspace inputs. (#16183, @rgrinberg)

• Fix missing Odoc generation of OxCaml parameter implementations (#16200, @art-w)

• Make Dune_rpc_lwt.V1.Action_plugin.read_directory_with_glob return an empty listing
  for absent directories (#16207, fixes #4445, @rgrinberg)

• Fix compiling Melange implementations of installed virtual libraries, both
  with and without binary annotations, including transitive private module
  dependencies (#16211, #16212, #16272, @anmonteiro)

• Run Ctypes stub generation in a sandbox and honor its declared dependencies.
  (#16223, @rgrinberg)

• Fix @opam failing to promote a generated opam file after it is deleted
  (#16234, fixes #16233, @Alizter)

• Rebuild generated Ctypes helpers when headers from Ctypes' implicit include
  directories change (#16243, @rgrinberg)

• Collect action-provided trace events when an action fails instead of dropping
  them during result validation. (#16250, @rgrinberg)

• Report the usual program-not-found error when a dynamic-run executable is
  missing instead of failing with an assertion. (#16251, @rgrinberg)

• Prevent rules with duplicate lock declarations from deadlocking by acquiring
  each lock only once. (#16252, @rgrinberg)

• Prevent concurrent action children from closing shared redirections before
  their siblings use them (#16257, @rgrinberg)

• Resolve relative paths in forwarded build, runtest, and exec commands from
  the client's directory instead of the RPC server's directory (#16267,
  @rgrinberg)

• (env (env-vars ...)) in a (context ...) stanza of dune-workspace now
  takes precedence over the root env stanza, as documented. This affects
  commands such as dune exec; rules already used the documented order.
  (#16290, @punchagan)

• Fix a crash when an opam filter is not a boolean (#16313, @art-w)

• Correct module paths for generated interfaces of nested qualified module
  groups. (#16322, @anmonteiro)

• Resolve %{cmi:...}, %{cmt:...}, and %{cmti:...} against Melange
  module sets when no OCaml module is selected, while preferring OCaml for
  modules selected in both modes. (#16339, @anmonteiro)

• Reject . and .. as melange.emit targets instead of raising an internal
  error (#16371, @anmonteiro)

• Validate custom toplevel names as filenames, reporting an error for empty
  names and avoiding crashes for names containing paths (#16373, @anmonteiro)

• Fix Menhir type inference with package-managed relocatable compilers on macOS
  by making the compiler standard library available in the sandbox (#16374,
  fixes #15642, @Alizter, @shonfeder)

• Reject invalid Menhir merge_into names during parsing to prevent internal
  errors (#16387, @anmonteiro)

• Reject conflicting module sources in unqualified directory groups,
  including generated sources, instead of silently discarding one
  (#16414, @anmonteiro)

• fix copying of directory targets on windows (#16434, @kentookura)

• Track local module dependencies used by Menhir's type inference so generated
  parsers and dependent modules build and rebuild correctly
  (#16447, fixes #14450, @anmonteiro)

• Fix Menhir type inference for qualified module group interfaces while keeping
  dependency lookup in terms of logical module names (#16464, #16489, #16497,
  fixes #8989, @anmonteiro)

• Fix intermittent crashes on Windows caused by unstable file descriptor
  hashing (#16476, fixes #16459, @Alizter)

• Explain that forwarded build requests require a watch-mode Dune server instead
  of reporting an internal RPC error. (#16486, fixes #16219, @Alizter)

• (deps (package ...)) now tracks installed files of lock-built packages
  and their package dependencies, rebuilding actions when they change.
  (#16507, @Alizter)

• Share Rocq plugin layout dependencies between discovery and compilation
  rules, reducing repeated dependency processing in unchanged builds.
  (#16622, @Alizter)

• Support directory dependencies in hardlink sandboxes by linking their files
  rather than the directories themselves (#16675, @Alizter).

• Fix recursive copy actions rejecting symbolic links, including file links
  created by symlink sandboxes (#16686, @rgrinberg).

• Fix copy sandbox failures caused by overlapping directory and file
  dependencies (#16806, fixes #16547, @Alizter)

• Fix Menhir inference producing invalid module paths for types imported from
  other modules (#16952, @anmonteiro)

Added

• Add (dirs ...) to (include_subdirs (mode qualified) ...), allowing
  qualified source directories to be renamed in the module path, including
  when bootstrapping. Mappings can use variables, including reads from generated
  files outside the qualified group (#13691, #16418, #16420, fixes #7605,
  @anmonteiro).

• Add opt-in action runners via --action-runner, and add
  --sandbox-actions to run eligible process-spawning actions in a
  bubblewrap-wrapped worker. (#14240, @rgrinberg)

• Add platform support for DragonFly BSD (#14774, fixes same issue with lev
  as seen on NetBSD in #14484, @mneumann).

• Added command, subcommand, and flag completion in the command line.
  Supported shells are bash, zsh, and pwsh.
  See dune completion [shell] --help.
  (#14779, @ElectreAAS)

• Add %{git-sha} variable that expands to the short git SHA of the current
  HEAD commit, or the empty string when git is unavailable or the workspace is
  not inside a git repository (#14810, @toots).

• Add a ?static optional argumentin Configurator.V1.Pkg_config.get to instruct pkg-config to get static linking options. (#14947, @raphael-proust)

• Only generate Melange rule for multi-mode libraries if melc is installed
  (#15021, @anmonteiro)

• Add Configurator.V1.Pkg_config.query_variable to query package variables
  through pkg-config --variable (#15078, fixes #3332, @rgrinberg).

• Add env_vars as an alias for the env-vars field in env stanzas
  (#15187, fixes #11424, @rgrinberg).

• Add @rocqproject alias to generate all `_RocqProject files
  (#15221, @rlepigre-skylabs-ai).

• Tab completion for dune promote now lists pending promotion files.
  (#15338, fixes #7254, @Alizter).

• Add build time information to watch mode (#15384, @rgrinberg)

• Added the missing dune tools exec utop and dune tools exec odoc options.
  (#15388, @Leonidas-from-XIV)

• Display build parallelism in watch mode. (#15390, @rgrinberg)

• Add process counts, system cpu, user cpu, and wall clock cpu times to trace
  events (#15401, @rgrinberg)

• Support --sandbox-actions on macOS using sandbox-exec. (#15500,
  @rgrinberg)

• Add fish to the shells supported by dune completion, enabling
  command, subcommand, and flag completion in the fish shell (#15515,
  fixes #15334, @chizy7)

• Display build duration and average process parallelism in the status line for
  batch builds. (#15564, @rgrinberg)

• Add a --split-public-names flag to dune describe workspace and dune describe external-lib-deps. When enabled, the name/names fields report
  only private names and a new public_name/public_names field reports the
  public names. (#15582, @NatKarmios)

• Add a --include-empty flag to dune describe external-lib-deps to also
  print libraries that have no internal or external dependencies (#15585,
  @NatKarmios)

• Support qualified module references in fields such as per_module when using
  (include_subdirs qualified) (#15633, fixes #15578, @anmonteiro)

• Display the current build run at the end of watch-mode status lines.
  (#15673, @rgrinberg)

• Record per-build Memo compute, restore, and cycle-detection metrics in Dune
  traces. (#15698, @rgrinberg)

• Record discovered, validated, and failed rule counts in Dune traces.
  (#15701, @rgrinberg)

• Add %{melange.emit:...} to reference a Melange output directory and
  depend on its emitted files (#15751, @anmonteiro)

• Add (flags ...) to the ocamllex and ocamlyacc stanzas to pass custom
  options to parser generators. (#15907, @rgrinberg)

• Added an opt-in sat trace category emitting a sat/solve event with
  the SAT solver's stats (variables, clauses, decisions, conflicts) and
  duration. Enable with DUNE_TRACE=+sat. (#15923, @Alizter)

• Add dune ocaml inferred-mli to infer an interface with a module's build
  configuration and register it for promotion. (#16111, fixes #12727,
  @rgrinberg)

• Add --no-actions and --only-actions to dune trace cat to filter
  events collected from actions. (#16245, @rgrinberg)

Changed

• BREAKING CHANGE: Actions no longer see the shared install staging area
  (_build/install/<context>/{bin,lib,lib/stublibs}) on PATH, OCAMLPATH and
  CAML_LD_LIBRARY_PATH. An action's environment only contains the packages it
  declares with (deps (package <pkg>)) (and their library closure, see below).
  Actions that rely on packages being visible (such as tests that #require the
  package under test from an mdx block, steps that run ocamlfind, a nested dune
  build, or load a bytecode stub library) must now declare the package
  dependency explicitly.
  (#14373, #16617, @Alizter)

• (package <pkg>) now also includes the packages owning the library closures
  of libraries in workspace and installed packages. Installed packages reached
  through those closures also work with Dune language versions older than 2.9.
  (#14373, #16362, #16529, @Alizter, @anmonteiro)

• Extract the structural-hash accumulator into a new Stdune.Hash
  module and route Stdune.Tuple.T2.hash, Stdune.Tuple.T3.hash,
  Stdune.List.hash, Stdune.Result.hash, and Resolve.error_hash
  through it. Hashing these structural shapes no longer allocates per
  call.
  (#14542, @robinbb)

• Remove (using melange 0.1) in Dune 3.25 in favor of version 1.0 of the
  extension. (#14574, @anmonteiro)

• $ dune rpc build invocations no longer queue. All build requests are built
  in parallel. Watch servers started by $ dune exec --watch can now also
  handle forwarded build and runtest requests (#14954, @rgrinberg)

• Report rule build progress as the number of rules built against the total
  number of live rules, rather than rules executed against rules discovered
  during the current run. This affects both the status line and the progress
  reported over RPC. (#14985, @snowleopard, @pWhite)

• With --error-reporting=twice, print an ==== Error Summary ==== separator
  before the deterministic list of errors reported at the end of the build. The
  separator is omitted when there are no errors to report.
  (#15016, fixes #14757, @yussypu)

• Enable fuzzy patch application by default for Dune. This is similar to OPAM's
  behaviour, and this makes it easier for packages like OxCaml to build.
  (#15146, fixes #15145, @Sudha247)

• Odoc rules are now sandboxed (#15190, @rgrinberg)

• In watch mode, $ dune rpc build requests now complete as soon as their
  requested build finishes, instead of waiting for unrelated concurrent RPC build
  requests in the same build iteration. (#15191, fixes #13788, @rgrinberg)

• Cleanup all build processes spawned by dune before starting a fresh build on
  Linux. (#15239, #15274, @rgrinberg)

• Show partial output timed out cram tests (#15269, @rgrinberg)

• In watch mode, $ dune rpc build now exits with status 1 when the
  requested build fails. (#15341, @rgrinberg)

• Debounce file change events in watch mode (#15344, @rgrinberg)

• Align dune's C compiler vendor detection with the OCaml compiler's own
  identifiers (msvc, icc, mingw, clang, gcc, xlc, sunc), so more C
  compilers are recognized without emitting a spurious warning. (#15423,
  fixes #14870, @chizy7)

• Never use $ lsof for counting file descriptors, as it is not allowed
  to reap processes outside of the scheduler. We have better mechanisms
  on MacOS and Linux for counting file descriptors. So this is only an
  issue on other Unices. (#15477, @rgrinberg)

• dune describe workspace now reports an origin field for every module,
  indicating whether its source was written by hand (source), generated by a
  rule stanza (dune, with the generating dune file), produced by ocamllex,
  ocamlyacc, or menhir, or synthesised by dune itself for wrapping
  (wrapper). Generated modules point at the responsible file. The
  --with-origin-deps and --with-origin-deps-expanded flags additionally
  report the dependencies of a rule-generated module, as declared and expanded
  to concrete files respectively.
  (#15478, @nat-karmios)

• Numbers with unit now allow dropping the unit if the number is zero ("0").
  For example, dune cache trim --trimmed-size 0 and dune cache trim --trimmed-size 0TiB are now both accepted and equivalent. (#15498, @reynir)

• Run artifact substitution in background workers. (#15559, @anmonteiro)

• dune describe now reports the public name of an executable (from
  public_name/public_names) instead of its private name when one is
  available, falling back to the private name otherwise. (#15582, @NatKarmios)

• Calculate status-line build parallelism from process CPU time rather than
  wall-clock action time; Windows continues to use wall-clock time.
  (#15685, @rgrinberg)

• Use sha256 instead of md5 for source archives that lack a checksum
  (#15824, @shunueda)

• Starting with Dune language 3.25, restrict sandboxed actions on Linux
  systems with Landlock ABI 3 or newer from writing outside their sandbox,
  temporary directory, action-trace directory, and /dev. Set
  DUNE_CONFIG__LANDLOCK=disabled to opt out. (#15858, @rgrinberg)

• dune pkg lock now fails without writing a lock directory when any platform
  requested by solve_for_platforms cannot be solved, instead of producing a
  partial lock directory containing only the successful platforms. (#15981,
  @Alizter)

• Portable lock directories now select one package version across all requested
  platforms, and fail when no common version exists. (#15982, fixes #13645,
  fixes #13647, @Alizter)

• BREAKING CHANGE: Reject : in context names so they remain portable path
  components (#16085, @rgrinberg)

• Keep .t suffixes in cram test names, including aliases and applies_to,
  starting with Dune language 3.25 (#16146, @rgrinberg)

• Sandbox ocaml-mdx dune-gen when using MDX extension 0.6, available from
  Dune 3.25. (#16177, @rgrinberg)

• Sandbox pkg-config queries starting with Dune language 3.25 so they cannot
  observe undeclared workspace inputs. (#16178, @rgrinberg)

• Remove the experimental OCamlFDO integration, including the (fdo ...)
  workspace field (#16198, @rgrinberg)

• BREAKING CHANGE: Generated files are now read-only even with Dune language
  versions before 2.4, regardless of whether the shared cache is enabled.
  Executable permissions are preserved. (#16388, @rgrinberg)

• Make newly written shared-cache metadata files read-only to guard against
  accidental modification. (#16393, @rgrinberg)

Utop 2.18.0

CHANGES:

• Add OCaml 5.6 support (#519 @kit-ty-kate @anmonteiro)
• Allow running the tests with dune >= 3.25 (#520 @anmonteiro)
• Add ability to toggle off welcome message using new {set,get,}show_welcome functions (#514 @jg791)

OCaml-LSP 1.26.1

CHANGES:

Features

• Add custom
  ocamllsp/completePrefixAtPos
  request, which completes a given prefix at a given position and returns
  function argument labels separately from the completions.
  This will be used by Emacs via the
  ocaml-eglot package. (#2230, @spwhitton)

OCaml OCaml 4.14.5

Bug fixes release with 6 security fixes, and 2 ordinary bug fixes:

• Security fix OSEC-2026-18: Marshal.from_{string,bytes}
• Security fix OSEC-2026-21: Str.string_partial_match
• Security fix OSEC-2026-22: Unix.map_file
• Security fix OSEC-2026-23: multiple issues in demarshaling
• Security fix OSEC 2026-24: multiple issues in command quoting on Windows
• Security fix OSEC-2026-30: ephemeron runtime fix
• Bug fix for pattern compilation
• Bug fix for new version of macOS.

See detailed list of changes

Dune-release 2.3.0

CHANGES:

Added

• Support .gitattributes export-ignore attribute to exclude files from
  distribution archives. (#515, @jberdine, reviewed by @Leonidas-from-XIV)

Changed

• Require dune 3.14 to build. (#532, @samoht)
• Declare the maintenance intent of the opam package, so that opam-repository
  can archive its older releases. (#507, #533, @samoht, reported by @hannesm)
• The pull request to opam-repository no longer links to the doc field of
  the opam file: dune-release stopped publishing the documentation in
  2.1.0, so the link was often broken. (#511, #534, @samoht, reported by
  @talex5)

Fixed

• dune-release publish now respects the --dev-repo or
  DUNE_RELEASE_DEV_REPO CLI inputs. (#521, #522, @shonfeder, reviewed by
  @Leonidas-from-XIV)
• Fix distrib and check on Windows: the temporary clone copies the git
  objects instead of hardlinking them, which git refuses there, and their
  read-only attribute is cleared before the clone is deleted. Warnings and
  errors show the executable name without its .exe suffix.
  (#378, #529, @emillon, @samoht)
• A yes or no question with no input left to read takes its default answer
  instead of failing with an uncaught End_of_file. (#525, @samoht)
• On a terminal, answers are typed on the line of their question, instead of
  on the next line. (#526, @samoht, reported and reviewed by @xvw)
• dune-release opam submit always prints the URL of the pull request it
  opened, and no longer shows the errors of xdg-open when there is no
  browser to open it with. (#306, #535, @samoht, reported by @mato)
• Build with the opam 2.6 libraries. (#524, #527, @vbgl, @samoht)
• The README no longer lists opam and ocamlfind as runtime dependencies,
  which dune-release lint stopped calling in 2.2.0. (#430, #509, #528,
  @samoht, reviewed by @Leonidas-from-XIV)
• The README explains how to publish through an ssh alias. (#440, @pbaudin)
• When the change log cannot be parsed, dune-release says what it expects
  of its first heading, and no longer prints a raw debug line. (#207, #537,
  @samoht, reported by @Drup)
• dune-release distrib skips dune subst when dune-project disables it
  with (subst disabled), instead of failing. (#496, #538, @samoht, reported
  by @talex5)
• dune-release publish no longer aborts when the release asset was already
  uploaded, or when its upload is declined: the asset on the release is used
  instead. (#513, #539, @samoht, reported by @davesnx)
• dune-release publish accepts a dev-repo that names a branch with
  #branch: the fragment is dropped from the URL used to push the tag and to
  find the GitHub repository. (#203, #540, @samoht, reported by @hannesm)
• dune-release opam pkg run without publish now infers the right archive
  URL for an https GitHub dev-repo. (#541, @samoht)
• The lint man page describes the checks lint performs today. (#542,
  @samoht)

OCaml-LSP 1.28.1

CHANGES:

Features

• Offer parenthesized application snippets for constructors with payloads, with
  independent argument slots, while retaining name-only completions. (#2212, @rgrinberg)
• Make generated destruct branch bodies interactive for clients with snippet edit
  support. (#2204, @rgrinberg)
• Offer whole-call completions for OCaml functions with multiple labelled or
  optional arguments, with editable slots for all arguments. (#2199, @rgrinberg)
• Make generated construct completions interactive for clients with snippet support.
  (#2198, @rgrinberg)
• Support ocp-indent as an alternative for document and range formatting.
  (#2148, @rgrinberg)
• Support textDocument/onTypeFormatting through the optional, persistent
  ocp-indent-rpc helper. (#1986, @rgrinberg)
• Report Dune RPC, build progress, and Merlin configuration process activity
  through LSP trace notifications. (#1899, @rgrinberg)
• Add a code action to open the closest Dune file for the current document.
  (#1817, fixes #1491, @rgrinberg)
• Distinguish operators from functions in semantic highlighting. (#1831, @rgrinberg)
• Support textDocument/implementation for type declarations in interface files,
  including nested modules, functor results, includes, and aliases.
  (#2074, fixes #1163, @rgrinberg)
• Classify function parameters and labels in semantic highlighting.
  (#1857, @rgrinberg)
• Distinguish built-in from user-defined types in semantic highlighting.
  (#1858, fixes #1139, @rgrinberg)
• Topiary formatter added (#2226, toastal)
• Add custom
  ocamllsp/completePrefixAtPos
  request, which completes a given prefix at a given position and returns
  function argument labels separately from the completions.
  This will be used by Emacs via the
  ocaml-eglot package. (#2230, @spwhitton)

Fixes

• Avoid overlapping semantic tokens in with type constraints and destructive
  substitutions. (#2206, @rgrinberg)
• Preserve nested or-patterns when formatting destruct-line case-analysis
  replies. (#2194, @rgrinberg)
• Clear stale Dune diagnostics and promotion actions when an RPC instance exits,
  without removing a replacement instance for the same root. (#2189, @rgrinberg)
• Ensure recovered selection ranges contain the requested position. (#2170,
  @rgrinberg)
• Suppress function extraction when a constructor would move out of scope or
  resolve to a shadowing declaration. (#2169, @rgrinberg)
• Clamp recovered selection ranges to the document bounds. (#2061, @rgrinberg)
• Exclude symbol declarations from reference results when requested by the
  client. (#2164, @rgrinberg)
• Convert related locations parsed from Merlin diagnostic messages to zero-based
  LSP line numbers. (#2163, fixes #2145, @rgrinberg)
• Preserve trailing newlines when computing post-edit ranges. (#2159,
  @rgrinberg)
• Return only inlay hints within the range requested by the client. (#2155,
  @rgrinberg)
• Return document symbol kinds the client supports, falling back to
  Constructor and Class when it does not advertise the newer kinds.
  (#2122, fixes #2121, @dayangac)
• Offer the unused-code quick fixes again: they matched diagnostic messages the
  server does not emit, and marking an unused open! produced open!!.
  (#2117, fixes #2116, @dayangac)
• Offer to create a missing implementation or interface counterpart only when
  the client supports the create resource operation. (#2115, fixes #2114,
  @dayangac)
• Tag unused and deprecated values in diagnostics, so clients can grey them out
  or strike them through. (#2110, fixes #2109, @dayangac)
• Honor client support for deprecation tags in workspace-symbol results.
  (#2113, @rgrinberg)
• Respect the client's folding range capabilities: omit character positions for
  lineFoldingOnly clients, omit unsupported folding range kinds, and honor
  rangeLimit. (#2099, fixes #911, @dayangac)
• Classify module names in with constraints and in signature opens in
  semantic highlighting. (#2098, fixes #808, @dayangac)
• Report a type when hovering a variant constructor or an exception where it is
  declared. (#2102, fixes #1300, @dayangac)
• Return no location instead of failing the request when a definition,
  declaration or type definition cannot be found, so clients that request them
  eagerly no longer surface spurious errors. (#2100, fixes #1161, @dayangac)
• Prefer a same-document related location when a Dune diagnostic has an empty
  primary range, such as ml/mli mismatches. (#2093, @rgrinberg)
• Stop offering the inferred-interface code action when the interface already
  declares everything the implementation exports. (#2096, fixes #347, @dayangac)
• Unregister Dune promotion code actions when an RPC instance finishes.
  (#2076, @rgrinberg)
• Avoid unregistering promotion code actions when clearing the last promotion
  for an already open document. (#2075, @rgrinberg)
• Find destruct-line cases after module-type constraints in match scrutinees.
  (#2072, @rgrinberg)
• Keep Dune RPC registry polling responsive while connected instances are
  running. (#1919, @rgrinberg)
• Fix the build on FreeBSD, where statfs(2) is declared in <sys/mount.h>
  rather than <sys/statfs.h>. (#2070, fixes #1069, @dayangac)
• Deduplicate identical rename text edits returned by Merlin recovery.
  (#2064, @rgrinberg)
• Reject cross-line destruct recovery locations before applying line-local
  source offsets. (#2063, @rgrinberg)
• Use consistent document snapshots and versions when converting rename
  occurrences into workspace edits. (#2062, @rgrinberg)
• Reject malformed destruct-line recovery replies and find match separators
  lexically instead of treating identifier substrings as with. (#2043, @rgrinberg)
• Skip inline edit construction for bindings without applicable uses, avoiding
  stack exhaustion when printing deeply recovered expressions. (#2041, @rgrinberg)
• Keep construct-completion text edits on the request line when Merlin recovery
  returns a multiline location. (#2034, @rgrinberg)
• Advertise Dune promotion code actions using their returned quickfix kind.
  (#2055, @rgrinberg)
• Reject interface documents passed to the ocamllsp/inferIntf custom request
  with InvalidParams. (#2051, @rgrinberg)
• Report malformed type-enclosing custom-request parameters as InvalidParams
  instead of an internal error. (#2050, @rgrinberg)
• Return null from the refactor-extract custom request for empty ranges.
  (#2049, @rgrinberg)
• Return null from the destruct custom request for inapplicable ranges.
  (#2048, @rgrinberg)
• Return null from the construct custom request when the cursor is not at a
  typed hole. (#2047, @rgrinberg)
• Preserve deprecation status in workspace-symbol results. (#2044, @rgrinberg)
• Render empty odoc tables in hover documentation without raising an internal
  error. (#2038, @rgrinberg)
• Enable function parameter inlay hints when the client sends no configuration.
  (#2097, fixes #1371, @dayangac)
• Respect client support for signature-help parameter-label offsets. (#2009,
  @rgrinberg)
• Keep Merlin diagnostic ranges within document bounds. (#2008, @rgrinberg)
• Suppress triggered completion and signature help inside comments after Unicode.
  (#1994, @rgrinberg)
• Emit semantic tokens in source order so their relative positions remain valid.
  (#1992, @rgrinberg)
• Stop stale signature help at expression boundaries. (#1987, fixes #1162,
  @rgrinberg)
• Suppress signature help for completed applications. (#1982, #1162, @rgrinberg)
• Encode remove-unused code-action edits using the client's negotiated position
  encoding. (#1969, @rgrinberg)
• Exclude surrounding parentheses from infix operator rename placeholders and
  edits. (#1966, fixes #1190, @rgrinberg)
• Suppress signature help for applications after the cursor. (#1965, #1162,
  @rgrinberg)
• Use each document's current version in multi-file rename edits. (#1958, @rgrinberg)
• Handle zero-work Dune build progress updates. (#1896, @rgrinberg)
• Do not report Dune build progress when the client disables work-done progress.
  (#2082, @rgrinberg)
• Reject malformed Dune promotion commands. (#2084, @rgrinberg)
• Keep Dune promotion registrations balanced when diagnostics share a source.
  (#2089, @rgrinberg)
• Reject negative JSON-RPC Content-Length headers. (#1873, @rgrinberg)
• Report unsupported LSP request methods as unavailable instead of internal
  server errors. (#1862, @rgrinberg)
• Advertise semantic-token support only to clients that declare the capability.
  (#1851, @rgrinberg)
• Advertise semantic-token support only to clients that support the relative
  token format. (#1853, @rgrinberg)
• Advertise semantic-token support only to clients that support full-document
  requests. (#1856, @rgrinberg)
• Advertise semantic-token delta support only to clients that request it.
  (#1859, @rgrinberg)
• Advertise and encode only semantic token types supported by the client.
  (#1860, @rgrinberg)
• Advertise and encode only semantic token modifiers supported by the client.
  (#1978, @rgrinberg)
• Offer the destruct-line code action on inline match expressions with
  incomplete cases. (#1829, fixes #1595, @rgrinberg)
• Replace a lone polymorphic-variant backtick when applying completions.
  (#1823, fixes #1427, @rgrinberg)
• Report a missing project build-system executable as a diagnostic without
  discarding the opened document. (#1814, @rgrinberg)
• Advertise all code-action kinds that the server may return. (#1803, @rgrinberg)
• Respect hierarchical code-action kind filters from clients. (#1802, @rgrinberg)
• Ensure textDocument/documentSymbol returns a selectionRange contained
  within its range, so clients no longer reject the document outline.
  (#1775, fixes #1560, @Leonard013)
• Recompute Merlin diagnostics when diagnostic shortening changes. (#1804, @rgrinberg)
• Avoid eagerly computing inline code-action edits when clients support lazy
  resolution. (#1808, @rgrinberg)
• Keep URI query parameters separate from filesystem paths. (#1776, @rgrinberg)
• Preserve URI paths beginning with two slashes across serialization. (#1798, @rgrinberg)
• Preserve percent-encoded URI fragments across parsing and serialization. (#1801, @rgrinberg)
• Preserve URI paths whose first segment resembles a non-letter Windows drive. (#1800, @rgrinberg)
• Preserve unescaped Unicode in URI query components. (#1799, @rgrinberg)
• Preserve document offsets across incremental text edits. (#1777, @rgrinberg)
• Respect the client's preferred completion documentation format. (#1885, @rgrinberg)
• Parse non-ASCII completion prefixes and whitespace in CRLF input. (#1886, @rgrinberg)
• Use constructor completion kinds when clients do not support enum members. (#1887, @rgrinberg)
• Use completion deprecation tags when supported by the client. (#1903, @rgrinberg)
• Keep completion sort keys lexically ordered beyond 9,999 items. (#1883, @rgrinberg)
• Replace incorrect identifier suffixes when applying completions. (#1964, fixes #838, @rgrinberg)
• Give synthetic completion items stable ordering metadata. (#1882, @rgrinberg)
• Preserve dotted operators in completion prefixes and resolve requests. (#1890, @rgrinberg)
• Correct code-action ranges after multiline text insertions. (#1748, @rgrinberg)
• Allow clients to add their first workspace folder dynamically. (#1747, @rgrinberg)
• Unregister Dune promotion commands after their diagnostics are cleared. (#1746, @rgrinberg)
• Point workspace symbols for generated sources to their files in the build
  directory. (#1742, @tatchi)
• Stop workspace symbol searches from warning when a workspace has not been
  built yet. (#1769, @smorimoto)
• Prevent whole-document formatting requests for OCamllex, Menhir, and Cram
  files from being routed through Dune's S-expression formatter.
• Refactor ppx hover to use merlin directly (#1606, fixes #1614)

Merlin 5.9.1-505

CHANGES:

Wed Nov 04 15:27:42 CET 2026

• merlin library
  • Fix a caching issue making inconsistant units stale (#2141)
• ocaml index
  • Fix a regression due to the new "pointing indexes" mechanism (#2144)
  • Fix an issue when using absolute output paths for the indexer (#2144)

Odoc 3.2.2

CHANGES:

Added

• Support for OCaml 5.6 (@jonludlam, #1472)

Fixed

• Avoid relying on ocamllex raising Failure for an unescaped '{', which
  OCaml 5.6's ocamllex warns about (@Leonidas-from-XIV, #1494)
• Remove requirement for ppx_expect in tests (@jonludlam, #1445)

Release of OCaml 5.5.2

We have the pleasure of celebrating the anniversary of the first powered flight in Europe by announcing the release of OCaml 5.5.2.

OCaml 5.5.2 fixes various minor security issues, two rare miscompilations, a configuration issue with future versions of macOS, and one runtime events library issue.

Overall, if you were already using any versions of OCaml 5.5, we are advising you to switch to OCaml 5.5.2 .

The full list of changes can be found in the full changelog.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands:

opam update
opam switch create 5.5.2

The source code for the release is also directly available on:

• GitHub
• OCaml archives at Inria

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.5.5.2+options <option_list>

where <option_list> is a space separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 5.5.2+flambda+nffa ocaml-variants.5.5.2+options ocaml-option-flambda ocaml-option-no-flat-float-array

OCaml-LSP 1.28.0

CHANGES:

Features

• Offer parenthesized application snippets for constructors with payloads, with
  independent argument slots, while retaining name-only completions. (#2212, @rgrinberg)
• Make generated destruct branch bodies interactive for clients with snippet edit
  support. (#2204, @rgrinberg)
• Offer whole-call completions for OCaml functions with multiple labelled or
  optional arguments, with editable slots for all arguments. (#2199, @rgrinberg)
• Make generated construct completions interactive for clients with snippet support.
  (#2198, @rgrinberg)
• Support ocp-indent as an alternative for document and range formatting.
  (#2148, @rgrinberg)
• Support textDocument/onTypeFormatting through the optional, persistent
  ocp-indent-rpc helper. (#1986, @rgrinberg)
• Report Dune RPC, build progress, and Merlin configuration process activity
  through LSP trace notifications. (#1899, @rgrinberg)
• Add a code action to open the closest Dune file for the current document.
  (#1817, fixes #1491, @rgrinberg)
• Distinguish operators from functions in semantic highlighting. (#1831, @rgrinberg)
• Support textDocument/implementation for type declarations in interface files,
  including nested modules, functor results, includes, and aliases.
  (#2074, fixes #1163, @rgrinberg)
• Classify function parameters and labels in semantic highlighting.
  (#1857, @rgrinberg)
• Distinguish built-in from user-defined types in semantic highlighting.
  (#1858, fixes #1139, @rgrinberg)

Fixes

• Avoid overlapping semantic tokens in with type constraints and destructive
  substitutions. (#2206, @rgrinberg)
• Preserve nested or-patterns when formatting destruct-line case-analysis
  replies. (#2194, @rgrinberg)
• Clear stale Dune diagnostics and promotion actions when an RPC instance exits,
  without removing a replacement instance for the same root. (#2189, @rgrinberg)
• Ensure recovered selection ranges contain the requested position. (#2170,
  @rgrinberg)
• Suppress function extraction when a constructor would move out of scope or
  resolve to a shadowing declaration. (#2169, @rgrinberg)
• Clamp recovered selection ranges to the document bounds. (#2061, @rgrinberg)
• Exclude symbol declarations from reference results when requested by the
  client. (#2164, @rgrinberg)
• Convert related locations parsed from Merlin diagnostic messages to zero-based
  LSP line numbers. (#2163, fixes #2145, @rgrinberg)
• Preserve trailing newlines when computing post-edit ranges. (#2159,
  @rgrinberg)
• Return only inlay hints within the range requested by the client. (#2155,
  @rgrinberg)
• Return document symbol kinds the client supports, falling back to
  Constructor and Class when it does not advertise the newer kinds.
  (#2122, fixes #2121, @dayangac)
• Offer the unused-code quick fixes again: they matched diagnostic messages the
  server does not emit, and marking an unused open! produced open!!.
  (#2117, fixes #2116, @dayangac)
• Offer to create a missing implementation or interface counterpart only when
  the client supports the create resource operation. (#2115, fixes #2114,
  @dayangac)
• Tag unused and deprecated values in diagnostics, so clients can grey them out
  or strike them through. (#2110, fixes #2109, @dayangac)
• Honor client support for deprecation tags in workspace-symbol results.
  (#2113, @rgrinberg)
• Respect the client's folding range capabilities: omit character positions for
  lineFoldingOnly clients, omit unsupported folding range kinds, and honor
  rangeLimit. (#2099, fixes #911, @dayangac)
• Classify module names in with constraints and in signature opens in
  semantic highlighting. (#2098, fixes #808, @dayangac)
• Report a type when hovering a variant constructor or an exception where it is
  declared. (#2102, fixes #1300, @dayangac)
• Return no location instead of failing the request when a definition,
  declaration or type definition cannot be found, so clients that request them
  eagerly no longer surface spurious errors. (#2100, fixes #1161, @dayangac)
• Prefer a same-document related location when a Dune diagnostic has an empty
  primary range, such as ml/mli mismatches. (#2093, @rgrinberg)
• Stop offering the inferred-interface code action when the interface already
  declares everything the implementation exports. (#2096, fixes #347, @dayangac)
• Unregister Dune promotion code actions when an RPC instance finishes.
  (#2076, @rgrinberg)
• Avoid unregistering promotion code actions when clearing the last promotion
  for an already open document. (#2075, @rgrinberg)
• Find destruct-line cases after module-type constraints in match scrutinees.
  (#2072, @rgrinberg)
• Keep Dune RPC registry polling responsive while connected instances are
  running. (#1919, @rgrinberg)
• Fix the build on FreeBSD, where statfs(2) is declared in <sys/mount.h>
  rather than <sys/statfs.h>. (#2070, fixes #1069, @dayangac)
• Deduplicate identical rename text edits returned by Merlin recovery.
  (#2064, @rgrinberg)
• Reject cross-line destruct recovery locations before applying line-local
  source offsets. (#2063, @rgrinberg)
• Use consistent document snapshots and versions when converting rename
  occurrences into workspace edits. (#2062, @rgrinberg)
• Reject malformed destruct-line recovery replies and find match separators
  lexically instead of treating identifier substrings as with. (#2043, @rgrinberg)
• Skip inline edit construction for bindings without applicable uses, avoiding
  stack exhaustion when printing deeply recovered expressions. (#2041, @rgrinberg)
• Keep construct-completion text edits on the request line when Merlin recovery
  returns a multiline location. (#2034, @rgrinberg)
• Advertise Dune promotion code actions using their returned quickfix kind.
  (#2055, @rgrinberg)
• Reject interface documents passed to the ocamllsp/inferIntf custom request
  with InvalidParams. (#2051, @rgrinberg)
• Report malformed type-enclosing custom-request parameters as InvalidParams
  instead of an internal error. (#2050, @rgrinberg)
• Return null from the refactor-extract custom request for empty ranges.
  (#2049, @rgrinberg)
• Return null from the destruct custom request for inapplicable ranges.
  (#2048, @rgrinberg)
• Return null from the construct custom request when the cursor is not at a
  typed hole. (#2047, @rgrinberg)
• Preserve deprecation status in workspace-symbol results. (#2044, @rgrinberg)
• Render empty odoc tables in hover documentation without raising an internal
  error. (#2038, @rgrinberg)
• Enable function parameter inlay hints when the client sends no configuration.
  (#2097, fixes #1371, @dayangac)
• Respect client support for signature-help parameter-label offsets. (#2009,
  @rgrinberg)
• Keep Merlin diagnostic ranges within document bounds. (#2008, @rgrinberg)
• Suppress triggered completion and signature help inside comments after Unicode.
  (#1994, @rgrinberg)
• Emit semantic tokens in source order so their relative positions remain valid.
  (#1992, @rgrinberg)
• Stop stale signature help at expression boundaries. (#1987, fixes #1162,
  @rgrinberg)
• Suppress signature help for completed applications. (#1982, #1162, @rgrinberg)
• Encode remove-unused code-action edits using the client's negotiated position
  encoding. (#1969, @rgrinberg)
• Exclude surrounding parentheses from infix operator rename placeholders and
  edits. (#1966, fixes #1190, @rgrinberg)
• Suppress signature help for applications after the cursor. (#1965, #1162,
  @rgrinberg)
• Use each document's current version in multi-file rename edits. (#1958, @rgrinberg)
• Handle zero-work Dune build progress updates. (#1896, @rgrinberg)
• Do not report Dune build progress when the client disables work-done progress.
  (#2082, @rgrinberg)
• Reject malformed Dune promotion commands. (#2084, @rgrinberg)
• Keep Dune promotion registrations balanced when diagnostics share a source.
  (#2089, @rgrinberg)
• Reject negative JSON-RPC Content-Length headers. (#1873, @rgrinberg)
• Report unsupported LSP request methods as unavailable instead of internal
  server errors. (#1862, @rgrinberg)
• Advertise semantic-token support only to clients that declare the capability.
  (#1851, @rgrinberg)
• Advertise semantic-token support only to clients that support the relative
  token format. (#1853, @rgrinberg)
• Advertise semantic-token support only to clients that support full-document
  requests. (#1856, @rgrinberg)
• Advertise semantic-token delta support only to clients that request it.
  (#1859, @rgrinberg)
• Advertise and encode only semantic token types supported by the client.
  (#1860, @rgrinberg)
• Advertise and encode only semantic token modifiers supported by the client.
  (#1978, @rgrinberg)
• Offer the destruct-line code action on inline match expressions with
  incomplete cases. (#1829, fixes #1595, @rgrinberg)
• Replace a lone polymorphic-variant backtick when applying completions.
  (#1823, fixes #1427, @rgrinberg)
• Report a missing project build-system executable as a diagnostic without
  discarding the opened document. (#1814, @rgrinberg)
• Advertise all code-action kinds that the server may return. (#1803, @rgrinberg)
• Respect hierarchical code-action kind filters from clients. (#1802, @rgrinberg)
• Ensure textDocument/documentSymbol returns a selectionRange contained
  within its range, so clients no longer reject the document outline.
  (#1775, fixes #1560, @Leonard013)
• Recompute Merlin diagnostics when diagnostic shortening changes. (#1804, @rgrinberg)
• Avoid eagerly computing inline code-action edits when clients support lazy
  resolution. (#1808, @rgrinberg)
• Keep URI query parameters separate from filesystem paths. (#1776, @rgrinberg)
• Preserve URI paths beginning with two slashes across serialization. (#1798, @rgrinberg)
• Preserve percent-encoded URI fragments across parsing and serialization. (#1801, @rgrinberg)
• Preserve URI paths whose first segment resembles a non-letter Windows drive. (#1800, @rgrinberg)
• Preserve unescaped Unicode in URI query components. (#1799, @rgrinberg)
• Preserve document offsets across incremental text edits. (#1777, @rgrinberg)
• Respect the client's preferred completion documentation format. (#1885, @rgrinberg)
• Parse non-ASCII completion prefixes and whitespace in CRLF input. (#1886, @rgrinberg)
• Use constructor completion kinds when clients do not support enum members. (#1887, @rgrinberg)
• Use completion deprecation tags when supported by the client. (#1903, @rgrinberg)
• Keep completion sort keys lexically ordered beyond 9,999 items. (#1883, @rgrinberg)
• Replace incorrect identifier suffixes when applying completions. (#1964, fixes #838, @rgrinberg)
• Give synthetic completion items stable ordering metadata. (#1882, @rgrinberg)
• Preserve dotted operators in completion prefixes and resolve requests. (#1890, @rgrinberg)
• Correct code-action ranges after multiline text insertions. (#1748, @rgrinberg)
• Allow clients to add their first workspace folder dynamically. (#1747, @rgrinberg)
• Unregister Dune promotion commands after their diagnostics are cleared. (#1746, @rgrinberg)
• Point workspace symbols for generated sources to their files in the build
  directory. (#1742, @tatchi)
• Stop workspace symbol searches from warning when a workspace has not been
  built yet. (#1769, @smorimoto)
• Prevent whole-document formatting requests for OCamllex, Menhir, and Cram
  files from being routed through Dune's S-expression formatter.
• Refactor ppx hover to use merlin directly (#1606, fixes #1614)

Merlin 5.9

CHANGES:

Mon Oct 01 15:31:42 CEST 2026

• merlin library
  • destruct: allow to destruct let-bindings's patterns (#2117)
  • Fix detection of expression at cursor in case of type-constrained
    expression (#2120)
  • enclosing: drastically improve the ranges! (#2121)
  • Fix oversharing in Parsetree cache (#2131)
  • Add PPX_DEPS to advertise PPX dependencies in Merlin configuration
    (#2127)
  • Stop printing ghost bindings in outline (#2135)
• merlin binary
  • Use c library flags from ocamlc -config. Fixes Haiku build (#2124)
• test suite
  • Add a test case illustrating case-analysis command fails to load module
    in issue #1786 (#2002)
  • Add a test reproducing the locate command failure when editor position is
    in another declaration (#2033)
  • Add a test to ensure the behavior showed in issue #1980

Ppxlib 0.39.0

CHANGES:

• Fix a bug in Ast_builder.Default.pexp_apply where it would duplicate
  attributes and mess up the locations. (#643. @Skepfyr)

• Add support for OCaml 5.6 primitive aliases (#642, @NathanReb)

• Remove reduntant module type copy from migrate_504_503, preventing
  exponential blowup with many "with" constraints. (#644, @smuenzel)

• Add support for OCaml 5.6 holes (#651, @patricoferris, @NathanReb)

• Fix the 5.4/5.3 migration of attributes on package types (#650, @dra27, @patricoferris, @NathanReb)

opam 2.6.1 release

Feedback on this post is welcome on Discuss!

We are pleased to announce the release of opam 2.6.1 fixing a couple of regressions and minor annoyances.

We advise everyone to upgrade. Please read on for installation and upgrade instructions.

Regression fixes

• Fix the depexts installation on opam install --deps-only when the system packages already exist in a repository (#7153)

Improvements

• Add support for using git repositories owned by another local user (common in docker containers) (#6963)

• Since 2.6.0, to make git calls more deterministic, opam doesn't take into account the user git config. In 2.6.1, it now uses /dev/null on both Unix and Windows when setting GIT_CONFIG_* instead of NUL on Windows to work around a bug in Git-for-Windows 2.56.0.windows.1 (#7085)

Try it!

The upgrade instructions are unchanged:

1. Either from binaries: run

   For Unix systems

   bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.6.1"
   

   or from PowerShell for Windows systems

   Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) } -Version 2.6.1"
   

   or download manually from the Github "Releases" page to your PATH.

2. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Please report any issues to the bug-tracker.

Happy hacking!

Mdx 2.7.0

CHANGES:

Added

• Add mdx_skip for skipping tests (#483, @talex5).

Changed

• Paths are normalized to drop the directory prefix ("./" on macOS and Linux)
  before pretty printing them (#482, @shonfeder).

opam 2.6.0 release

Feedback on this post is welcome on Discuss!

We're happy to announce the release of opam 2.6.0 and encourage all users to upgrade. Please read on for installation and upgrade instructions.

Try it!

The upgrade instructions are unchanged:

1. Either from binaries: run

   For Unix systems

   bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.6.0"
   

   or from PowerShell for Windows systems

   Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) } -Version 2.6.0"
   

   or download manually from the Github "Releases" page to your PATH.

2. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Note: the following section will recap the various major changes in opam 2.6.0 for anyone who haven't already read the previous pre-release announcements. For those who did, note that nothing changed between 2.6.0~rc1 and the final 2.6.0.

Major change: in-place env hook

For people using the shell hooks, this release changed the way PATH is kept up-to-date. Previously, opam took priority over any other elements of PATH by making sure to always be in front. However this causes problem for users expecting manual export PATH=some-custom-bindir:$PATH to prioritise their directory. To resolve this problem, the shell hook now instead replaces the directory managed by opam in-place, keeping the order asked by the user.

To benefit from this, make sure opam init --reinit -ni was ran once after upgrading to this version (automatically done by our install script if it detects an existing opam installation).

Thanks to @gridbugs for this contribution.

Major change: reduce the disk space usage of opam

When installing a package, opam doesn't exactly go easy on disk usage. For people with limited disk space it is a problem which can result in a "no space left on device" type error. While no-one really can get rid of this type of error completely, this release comes with some quite substential improvements to the disk space used during installs.

In particular the build directory is now deleted as soon as possible during a build instead of waiting until the end. We also used to cache both the extracted sources and the original archive of packages. However this is redundant and inefficient on some file-systems, thus opam no longer keep the extracted sources when installing the package.

While the disk usage used by opam can be reduced over time while simply reinstalling packages, you can liberate some free GB in one go using opam clean --all-switches.

Major change: performance improvements on certain file-systems (e.g. NTFS on Windows or IO constrained machines)

Some file-systems, such as NTFS on Windows famously take forever for commands such as opam update, opam init or any command upon upgrading opam. This is due to how opam stored its repositories: i.e. opam-repository is just a large number of directories and files that opam has to scan through to get the informations it needs to run. Once a repository is read once it's usually not a problem anymore as opam caches it internally, however everytime opam update is called the new repository has to be re-read, which on platforms such as Windows or a busy VPS causes long delays because the files and directories being read are not in the OS's internal cache anymore.

To remedy this while keeping the same repository format, we now leverage the existing index.tar.gz file expected to be served by HTTP opam repositories and simply don't extract it. Instead we now use the ocaml-tar library to read the file in-memory, thus only needing one read syscall (against tens of thousands previously, counting on OS-level caches to be fast).

While this only helps HTTP repositories (e.g. the default opam-repository), other types of repositories are usually either smaller (local repositories) or less impacted (VCS repositories) and overall less used than the default HTTP repository so this is less of an issue. However we will still look into it in the future. You can enable this mechanism for all non-VCS repositories by setting the environment variable OPAMREPOSITORYTARRING=1, however this is not as efficient as for HTTP, so it may or may not be worth doing depending on your file-system.

Other noteworthy changes

• Add root and rootexec sections to .install files to install files from the root prefix. Thanks to @WardBrian for this contribution.

• Reorder the list of actions by increased priority

• Improved depexts handling by caching system package availability during opam update, avoiding redundant system checks at install time

• Allow detection of installed system packages through their virtual names on ALT Linux, RHEL-based and SUSE-based distributions

• Added --ignore-available-on option to allow ignoring the available: field of certain packages. Thanks once-again to @WardBrian for this contribution.

• Fix an opam 2.5 regression where opam pin list failed abruptly when the source of the pinned package doesn't exist

• opam update now supports updating a repository that changed a file to a directory of the same name and vice versa

• Do not fail on directories named opam when scanning the packages directory of a repository during opam repo add or opam init (worked on subsequent opam update)

• Fix "undefined variable" error when a lock file filter contains an undefined variables: fail gracefully with strict mode, continue and default the variable to false otherwise

• Fix opam lock support of dependency formula that include disjunctions

• Fix package installation during opam pin add <url to archive>. Thanks to @zoggy for this contribution.

• Fix the filename check used when parsing arguments to allow / to be recognised as a directory separator on Windows

• Make git calls more deterministic regardless of the global or system config

• Read full lines when asking for user input when TERM=dumb (e.g. emacs' M-x shell). Thanks to @arvidj for this contribution.

• opam init --reinit now regenerate the list of valid switches, fix switch internal data (cache, config, packages)

• Safe mode doesn't reset debuglevel to 0 anymore. Consider updating your scripts to discard stderr or add --debug-level=0 if your script isn't resistant to output on stderr

• To avoid git underlying maintenance operation from interfering with opam (possible race condition), opam now disable git gc/maintenance on repositories it maintains

Various performance and other improvements were made and bugs were fixed. This release also includes a handful of improvement the documentation and more than two dozen improvement and extensions to our testsuite. API changes are also denoted in the release notes:

• release note for 2.6.0~alpha1
• release note for 2.6.0~beta1
• release note for 2.6.0~beta2
• release note for 2.6.0~rc1
• release note for 2.6.0

Please report any issues to the bug-tracker.

Happy hacking!

Special thanks to the Haematology department and Bone Marrow Transplant Unit of the NHS Greater Glasgow for making this release possible <3

Release of OCaml 5.5.1

We have the pleasure of celebrating the birthday of Giovanni Girolamo Saccheri by announcing the release of OCaml version 5.5.1.

This patch-level release fixes a major type system bug for module-dependent functions and also contains two security fixes for the runtime: one in the Marshal module, another inside the loading of bytecode.

At a less severe level, this release also fixes two bugs in the runtime for concurrent programs, another runtime bug for musl users; and a handful of other bugs.

The release also restores support for cloning the compiler on macOS.

Overall, we are strongly advising you to switch to OCaml 5.5.1 if you were already using OCaml 5.5.0.

The full list of changes can be found in the full changelog.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands:

opam update
opam switch create 5.5.1

The source code for the release is also directly available on:

• GitHub
• OCaml archives at Inria

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.5.5.1+options <option_list>

where <option_list> is a space separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 5.5.1+flambda+nffa ocaml-variants.5.5.1+options ocaml-option-flambda ocaml-option-no-flat-float-array

Ocp-indent 1.10.0

CHANGES:

• Bump OCaml lower bound to 4.11 (#343, @NathanReb)
• Add explicit support for effect syntax (#342, @NathanReb)
• Remove support for legacy camlp4 extensions that was causing misidentation of
  code using some predefined identifiers (TEST, BENCH, IFDEF)
  (#345, @NathanReb)
• Add support for starred style comments (#347, @NathanReb)
• Add explicit support for labeled tuples syntax (#349, @NathanReb)
• Fix strict_with so it applies to extensible variant types in the
  same way it applies to variant types (#350, @NathanReb)
• Fix a bug where - would be rejected as ocp-indent input argument
  instead of being interpreted as stdin (#351, @NathanReb)
• Update to cmdliner 2 and install completion scripts for common shells
  (#351, @NathanReb)
• Add explicit support for external types (#353, @NathanReb)
• Add explicit support for new 5.5 let in constructs: let type, let external, let class (#354, @NathanReb)
• Add --strict flag to make warnings fatal and parsing stricter
  (#356, @NathanReb)
• Add --check flag and corresponding check mode which does not print
  indented version but instead succeed if the input is already correctly
  indented and fails otherwise. (#357, @NathanReb)
• Add ?filename argument to Nstream functions to allow properly
  setting the filename for parsing errors. (#357, @NathanReb)

Dune 3.24.2

CHANGES:

Fixed

• Add the implicit unix dependency required by MDX 2.6 and later to
  generated MDX test executables (#15592, @avsm)

• Rescan the RPC registry when its directory mtime changes, allowing clients
  that poll before Dune registers to discover the new instance (#15634, fixes
  #15630, @rgrinberg)

OCaml introcaml0

Revisit generic printing API

Merlin 5.8.1-505

CHANGES:

Fri Jul 31 11:31:42 CEST 2026

• merlin library
  • occurrences: fix files modified since the index was built never being
    reported as out-of-sync. (#2104)
  • Fix locate and document on open paths in .mli files: resolve the
    open path in the environment before the open, so a self-shadowing
    submodule no longer hides the opened module (fixes #1748)
  • Fix occurrences staleness detection when the server is not running at the
    project's source root. (#2097)
  • Reproduce and fix a load_path staleness issue particularly visible when
    using ocaml-lsp and dune in watch mode (#2109)
  • Fix bug in document query (#2092)
• ocaml index
  • Fix staleness detection in the presence of ppxes. (#2110)

Merlin remove: Release v5.8-506~preview

CHANGES:

• merlin library
  • Experimental support for OCaml 5.6

Opam-publish 3.0.1

CHANGES:

• Stop testing OCaml < 4.11 and require OCaml >= 4.11 [#209 #210 @rjbou @kit-ty-kate]
• Add support for opam 2.6 by removing indirect calls to chdir [#204 @kit-ty-kate]
• Use the proper shell quoting mechanism instead of "OCaml quoting" when quoting filenames into the system shell [#204 @kit-ty-kate]

Mdx 2.6.0

CHANGES:

Added

• If a test takes longer than 5 seconds, display a warning with the test's location
  Also display the location on Ctrl-C (#476, @talex5 @avsm).
• Support oxcaml-5.2.0-minus39 alongside normal OCaml (#481, @avsm)

Changed

• Mark the tests as conflicting with dune 3.24.0 due to a bug in
  that release; see ocaml/dune#14724 (@avsm)

Dune 3.24.1

The Dune team is pleased to announce the release of dune 3.24.1.

This patch release includes bug fixes and a change to Melange sandboxing defaults. See the full changelog for all the changes and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

opam 2.5.2

Feedback on this post is welcomed on Discuss!

We are pleased to announce the release of opam 2.5.2 fixing a security issue (OSEC-2026-10) and other minor things.

We advise everyone to upgrade. Please read on for installation and upgrade instructions.

Security fix

• OSEC-2026-10 / CVE-2026-57825: Fix a bug that allowed a package to install files anywhere on the system using a symlink to an external directory without warning the user and asking for their permission (#7005)

Distributions maintainers that have not already done so, are invited to either upgrade their opam package to 2.5.2 or backport the fix. For any questions please send an email to the authors of this here blog post as listed above.

Other changes

• Re-allow .. in .install files, partially reverting 2.5.1's #6898 (#7009, ocaml/dune#14393)

Try it!

The upgrade instructions are unchanged:

1. Either from binaries: run

   For Unix systems

   bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.5.2"
   

   or from PowerShell for Windows systems

   Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) } -Version 2.5.2"
   

   or download manually from the Github "Releases" page to your PATH.

2. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Please report any issues to the bug-tracker.

Happy hacking!

Dune 3.24.0

The Dune team is pleased to announce the release of dune 3.24.0.

Highlights include the following

• Dune package management now uses the relocatable compiler by default, for all supported compiler versions. This brings a massive speedup to workspace setup in the many cases where built compiler versions can be reused. (ocaml/dune#14357, @Alizter)
• Directory targets are now generally available (ocaml/dune#14579), allowing tools to produce entire directory trees as targets. See the documentation on directory targets for details.
• Path handling has been refined, improving the consistency of paths across platforms (ocaml/dune#14278 and ocaml/dune#14278) and using a more consistent and disciplined location for %{bin:NAME} variable expansions (ocaml/dune#14432).
• Path-valued percent forms (%{bin:...}, %{dep:...}, %{path:...}, and friends) now expand same-directory paths with a leading ./, so that shells like bash in (bash ...) and (system ...) actions execute them directly instead of looking them up in PATH (ocaml/dune#15156). This is a breaking change for configurations that were handling paths naively, and neglected to normalize the representation before using it test fixtures or for constructing other strings.
• The deprecated lang coq has been removed, as scheduled, superseded by lang rocq. See ocaml/dune#12788 for details.

See the full changelog for all new features and fixes, and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

OCaml-LSP 1.27.0

CHANGES:

Features

• Upgrade to OCaml 5.5 (#1609)

Fixes

• Fix compatibility with upcoming Dune versions by avoiding the Stdune.Pid
  module. (#1608)

Merlin 5.8-505

CHANGES:

Tue Jun 23 12:15:42 CEST 2026

• merlin library
  • Support for OCaml 5.5 (#2077, fixes #2024)
  • Fix signature-help with type aliases (#2067, fixes #1927)
  • Fix locate on punned let bindings, to use the common identifier as the
    expression (instead of the pattern) (#2066)
• test suite
  • Remove the FIXME line for #1404 as the issue was already fixed and add two tests (#2073).

Release of OCaml 5.5.0

We have the pleasure of celebrating the birthday of Blaise Pascal by announcing the release of OCaml version 5.5.0.

Release Highlights

Some of the highlights of OCaml 5.5.0 are:

Module-dependent Functions

Modules can now be used as function arguments in a form of lightweight functors.

For instance, we can define a function for printing a map generated by the Map.Make functor:

let pp_map (module M: Map.S) pp_key pp_v ppf set =
  if M.is_empty set then
    Format.fprintf ppf "ø"
  else
   let pp_sep ppf () = Format.fprintf ppf ",@ " in
   let pp_binding ppf (k,v) =
     Format.fprintf ppf "@[%a@ =@ %a@]" pp_key k pp_v v
   in
   Format.fprintf ppf "@[{@ %a@ }@]"
     (Format.pp_print_seq ~pp_sep pp_binding) (M.to_seq set)

We can then apply this function on a string map

module String_map = Map.Make(String)

with

let () =
  let m = String_map.of_list ["Zero", "Zero"; "One", "Un"] in
  let pp_str = Format.pp_print_string in
  Format.printf "%a@."
  (pp_map (module String_map) pp_str pp_str) m

Compared to first-class modules, the type of the function pp_map

type 'a printer = Format.formatter -> 'a -> unit
val pp_map: (module M: Map.S) -> M.key printer -> 'a printer -> 'a M.t printer

is dependent over the value of the module S, and thus the function can only applied over a statically known module:

let f (): (module Map.S) =
  if Random.bool () then
    (module Map.Make(Int))
  else
    (module Map.Make(Float))
let fail = pp_map (f ())

Error: This expression has type
        (module M : Map.S) ->
        (Format.formatter -> M.key -> unit) ->
        (Format.formatter -> 'a -> unit) -> Format.formatter -> 'a M.t -> unit
      but an expression was expected of type (module Map.S) -> 'b
      The module M would escape its scope
This function is module-dependent. The dependency is preserved
when the function is passed a static module argument (module M : S)
or (module M). Its argument here is not static, so the type-checker
tried instead to change the function type to be non-dependent.

Relocatable Compiler

A compiler installation can now be moved or copied with no risk of hard-to-debug errors due to mixing incompatible bytecode runtime interpreters.

In practice, this means that creating a local switch when there is a global switch with the same compiler version and configuration available can be done by cloning the global switch rather than recompiling the whole compiler.

This should considerably reduce the time required to create new local opam switches out-of-the-box.

Polymorphic Functions as Function Arguments

Higher-rank polymorphic functions can now be defined directly by using an explicit type annotation in a function argument

let apply_map (map: 'a 'b. ('a -> 'b) -> 'a list -> 'b list) =
  map string_of_int [1;2;3], map List.singleton ["x"; "y"]
let _ = apply_map List.map

Previously defining such a function required going through either a record or an object with a polymorphic field or methods

type map = { map: 'a 'b. ('a -> 'b) -> 'a list -> 'b list }
let apply_map {map} =
  map string_of_int [1;2;3], map List.singleton ["x"; "y"]

Search and Replace Substring Functions

The String module has been extended with many functions for searching and replacing substrings inside a string.

let _true = String.includes ~affix:"aba" "abbaba"
let sentence = String.replace_all ~sub:"𝄽" ~by:"word" "A 𝄽 is re𝄽ed"

The substring search is using the 2-way string matching algorithm which has the advantage of requiring constant space memory overhead independently of the needle size.

Generalised Local Definitions

It is now always possible to define locally a type, a class, a module type or any kind of item that can be defined globally:

let mandelbrot n x =
  let type t = Converge | Escape of int in
  ...
  match orbit n x with
  | Converge -> 0
  | Exit_at n -> colorize n

External Types

When interfacing with foreign function libraries, it is now possible to define external type

type int_gmp = external "mpz_t"
type float_gmp = external "mpf_t"

Compared to an abstract type definition, the external type name "mpz_t" (resp. mpf_t) makes the type distinguishable from any non-abstract types or external types with a different name.

In particular, this makes FFI types better behaved when combined with Generalised Abstract Data Types (GADTs). For instance, The typechecker is able to prove that

let ok: (int_gmp,[` A] ) Type.eq -> _ = function _ -> .

is a total function because the external type int_gmp is not compatible with a polymorphic variant type.

Warning: Abstract types in the current module

The astute reader has probably noticed in the definition above that, in OCaml 5.4.0, the typechecker does accept

type int_gmp
let ok: (int_gmp, [` A] ) Type.eq -> _ = function _ -> .

as total.

Indeed until OCaml 5.5.0, abstract types defined in the current module

type a
type b

were considered as unique and provably different

let f: 'x. (a,b) Type.eq -> 'x = function _ -> .

However, this special rule for local definition of abstract types was very brittle. As soon as one moved outside of the current module, it was no longer possible to prove that the types were different.

module M = struct
  type a
  type b
end
let fail: 'x. (M.a,M.b) Type.eq -> 'x = function _ -> .

Error: This match case could not be refuted.
      Here is an example of a value that would reach it: Equal

This special typechecking rule has been removed in OCaml 5.5.0. If you were relying on it, for instance, because you used an abstract type as type-level label in a GADTs, you can change your abstract type definition to a possibly private abbreviation of a polymorphic variant

type a = private [`A]
type b = [`B]

or a (possibly private) sum type

type a = A
type b = private B

If you were using an abstract type as both a type-level label and a FFI type, you can now use an external type definition which will give you a provably distinct type even outside of the current module.

GC improvements

Some of the ongoing work to improve the pacing of the garbage collector has been integrated in OCaml 5.5.0, two of the important changes in OCaml 5.5 GC are

• the addition of a sweep-only phase at the start of major GC
• the addition of an idle phase to smooth the behaviour of the GC at the start.

Many incremental changes

• The Windows implementation is no more reliant on Winpthreads
• Around 60 new standard library functions
• Around 90 various improvements
• A dozen of documentation updates
• Around 40 bug fixes

Please report any unexpected behaviours on the OCaml issue tracker and post any questions or comments you might have on our discussion forums.

The full list of changes can be found in the full changelog.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands:

opam update
opam switch create 5.5.0

The source code for the release is also directly available on:

• GitHub
• OCaml archives at Inria

Fine-Tuned Compiler Configuration

If you want to tweak the configuration of the compiler, you can switch to the option variant with:

opam update
opam switch create <switch_name> ocaml-variants.5.5.0+options <option_list>

where <option_list> is a space separated list of ocaml-option-* packages. For instance, for a flambda and no-flat-float-array switch:

opam switch create 5.5.0+flambda+nffa ocaml-variants.5.5.0+options ocaml-option-flambda ocaml-option-no-flat-float-array

OCaml OCaml 4.14.4

• Security fix for check for size overflow in caml_ba_reshape (CVE-2026-34353, OSEC-2026-04)
• Security fix for quoting of filenames passed to Filename.quote_command on Windows
• Bug fixes for 4.14.3

See detailed list of changes.

Release of OCaml 4.14.4

We have the pleasure of celebrating the anniversary of the first flight of Ariane 4 by announcing the release of OCaml version 4.14.4.

This release is a collection of safe bug fixes, cherry-picked from the OCaml 5 branch. The 4.14 branch is expected to receive updates until at least the end of 2026. However, the end of its extended maintenance period is on the horizon. Consequently, please mention to us any obstacle remaining to your migration to OCaml 5.

In the meanwhile, do not hesitate to report any bugs on the OCaml issue tracker.

See the list of changes below for more details.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands:

opam update
opam switch create 4.14.4

The source code for the release candidate is also directly available on:

• GitHub
• Inria archive

OCaml lrgrep0

Bootstrap (probably not necessary)

Dune 3.23.1

The Dune team is pleased to announce the release of dune 3.23.1.

This is a patch release consisting of bug fixes. See the full changelog for all the changes and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

Odoc 3.2.1

CHANGES:

Fixed

• Fix #1426, which broke docs in packages including base in OCaml 5.5.0
  (@jonludlam, #1427)
• Fix #1429, which broke docs in packages including merlin-lib (@jonludlam,
  #1430)
• Fix #1431, a regression introduced in v3.2.0 (#1433, @jonludlam)

Dune 3.23.0

The Dune team is pleased to announce the release of dune 3.23.0.

Along with many other fixes and improvements, some highlights include:

• Add support for c_library_flags in foreign_stubs (#13484, @madroach)
• Many improvements to the promotion and diffing functionality, by @rgrinberg.
• As part of the previous, a breaking change to the promotion logic has been introduced: Dune does not automatically promote generated opam files, which must now be manually promoted with dune promote. You can trigger building .opam files with the @install, @runtest, and @opam aliases. In release mode, .opam files aren't generated at all and whatever is in the source is used (ocaml/dune#14108, @rgrinberg).
• User rules and inline test runners are now sandboxed by default (ocaml/dune#13805 and ocaml/dune#14257, @rgrinberg).
• The minimum OCaml version required to build dune is now 4.14.

See the full changelog for all new features and fixes, and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

Odoc 3.2.0

We're happy to announce the release of Odoc 3.2.0.

This release brings:

• Support for OCaml 5.5.0 (#1406).
• Support for the OxCaml compiler variant (#1399).
• Persistent LaTeX macros in the HTML/KaTeX backend (#1391), so a macro defined with \gdef in one math block can be reused in subsequent ones.
• Multiple .odocl files accepted by markdown-generate in a single invocation, removing the need for shell scripting around it (#1388).

For more details, see the full changelog below.

Merlin 5.7.1-504

We're happy to announce the release of Merlin 5.7.1-504, a patch release for the OCaml 5.4 series. This release brings:

• A fix for a typer cache invalidation bug (#2062) where Merlin would not pick up newly created .cmi files appearing in the build path, for instance when Dune built a new module.
• A change to the on-disk index format (#2051) so that merged indexes can point to existing index files, resulting in significantly smaller index files and fewer write operations.

For more details, see the full changelog below.

opam 2.5.1

Feedback on this post is welcomed on Discuss!

We are pleased to announce the release of opam 2.5.1 fixing a security issue (OSEC-2026-03) and other minor things.

We advise everyone to upgrade. Please read on for installation and upgrade instructions.

Security fix

OSEC-2026-03: Invalidate .install fields containing destination filepath trying to escape their scope. Thanks to @andrew for reporting this issue. (#6897)

Distributions maintainers that have not already done so, are invited to either upgrade their opam package to 2.5.1 or backport the fix. For any questions please send an email to the authors of this here blog post as listed above.

Other changes

• Fix a string injection from the depexts field to nix-build, when os-family=nixos. Thanks to @RyanGibb for this contribution and @andrew for the report. (#6894)

• Restore the distribution detection on Gentoo. (#6887)

• Add support for single-quoted values of the /etc/os-release file. (#6887)

• Fix rare potential GC corruptions. Thanks to @avsm for the contribution and @andrew for the report. (#6882, #6880)

Try it

The upgrade instructions are unchanged:

1. Either from binaries: run

   For Unix systems

   bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.5.1"
   

   or from PowerShell for Windows systems

   Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) } -Version 2.5.1"
   

   or download manually from the Github "Releases" page to your PATH.

2. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Please report any issues to the bug-tracker.

Happy hacking!

Dune 3.22.2

The Dune team is pleased to announce the release of dune 3.22.2.

This is a patch release consisting of bug fixes. See the full changelog for all the changes and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

OCaml-LSP 1.26.0

This new release of OCaml-LSP brings several new features and improvements, including new custom requests, support for range formatting, and enhanced hover capabilities.

See the related announcement on the Discuss forums.

Merlin 5.7.0-504

We're happy to announce the release of Merlin 5.7.0-504. This release comes with a number of bug fixes and improvements to Merlin.

For more details, we encourage you to delve into the full changelog.

See the related announcement on the Discuss forums.

Dune 3.22.1

The Dune team is pleased to announce the release of dune 3.22.1.

This is a patch release consisting of bug fixes. See the full changelog for all the changes and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

Utop 2.17.0

We're happy to announce the release of utop 2.17.0.

This release brings:

• Support for OCaml 5.5 (#510).
• Decoupling of utop.el from tuareg-mode (#511): tuareg is now loaded lazily, and other OCaml major modes for Emacs (such as neocaml) can integrate with utop via the new utop-mode-compat-alist. Existing tuareg, caml, typerex, and reason users are unaffected.

For more details, see the full changelog below.

Dune-release 2.2.1

We're happy to announce the release of Dune-release 2.2.1.

This release adds a CLI flag to mark a GitHub release as a prerelease, exposing capability that already existed in the GitHub REST API to the dune-release command line (#517).

For more details, see the full changelog below.

Mdx 2.5.2

We're happy to announce the release of MDX 2.5.2.

This is a small compatibility release that adjusts MDX's toplevel support to work with OCaml 5.5.

For more details, see the full changelog below.

Ppxlib 0.38.0

The ppxlib team is happy to announce the release of ppxlib.0.38.0.

The main features of this release are support for OCaml 5.5 and improved support of OCaml 5.4 and 5.3. It also comes with a few bug fixes and a couple new API entries, you can read the extensive release notes here.

This is our first release since we announced our new approach to supporting new compilers in this thread. All support for compilers versions >= 5.3 is implemented using this technique and new language features are encoded into the AST. We've added Ast_builder and Ast_pattern functions to allow you to manipulate some of those, such as labeled tuples or effect patterns. You can see those in our API documentation here and there. We've also illustrated how to use them in our new manual section. If you're interested in producing or consuming other new language features that cannot be represented with our current internal AST (5.2), please open an issue so we can add the relevant helpers.

Given the ecosystem hasn't yet recovered from the 5.2 AST bump and ppxlib.0.36.0, we're glad that we can add support for new compilers without introducing further breakage and keep the maintenance burden within ppxlib's bounds. We've started discussions with the compiler team to make this approach even more viable in the future on our end.

We'd like to thank @ceastlund who's our only external contributor for this release.

I'd personally like to thank @patricoferris for his help getting this out the door as well as the OCaml Software Foundation and OCamlPro for funding my work on ppxlib.

Thank you for reading and happy preprocessing!

You can comment on this announcement on the OCaml discuss forums.

Dune 3.22.0

The Dune team is pleased to announce the release of dune 3.22.0.

In addition to many fixes and small improvements, notable highlights of this release include:

• Fixes to the dune cache on Windows, thanks to @Nevor in ocaml/dune#13713.
• New tracing functionality, to inspect and diagnose the build processes thanks to @rgrinberg across many PRs. See the documentation.
• Addition of the dune-action-trace library, to instrument trace emission, thanks to @rgrinberg.
• Support for generating odoc documentation in markdown via the @doc-markdown build alias thanks to @davesnx ocaml/dune#12581.
• Full support for OxCaml's parameterised libraries, thanks to @art-w and @maiste. To learn more, see the docs.

See the full changelog for all new features and fixes, and for attribution to the contributors who made it all possible. Thank you, contributors!

If you encounter a problem with this release, please report it in our issue tracker.

You can comment on this announcement on the OCaml discuss forums.

OCamlFormat 0.29.0

We're happy to announce the release of OCamlFormat 0.29.0.

CHANGES:

Highlight

• * Support OCaml 5.5 syntax (#2772, #2774, #2775, #2777, #2780, #2781, #2782, #2783, @Julow) The update brings several tiny changes, they are listed below.

• * Update Odoc's parser to 3.0 (#2757, @Julow) The indentation of code-blocks containing OCaml code is reduced by 2 to avoid changing the generated documentation. The indentation within code-blocks is now significative in Odoc and shows up in generated documentation.

Added

• Added option letop-punning (#2746, @WardBrian) to control whether punning is used in extended binding operators. For example, the code let+ x = x in ... can be formatted as let+ x in ... when letop-punning=always. With letop-punning=never, it becomes let+ x = x in .... The default is preserve, which will only use punning when it exists in the source. This also applies to let%ext bindings (#2747, @WardBrian).

• Support the unnamed functor parameters syntax in module types (#2755, #2759, @Julow)

  module type F = ARG -> S
  

  The following lines are now formatted as they are in the source file:

  module M : (_ : S) -> (_ : S) -> S = N
  module M : S -> S -> S = N
  (* The preceding two lines are no longer turned into this: *)
  module M : (_ : S) (_ : S) -> S = N
  

Fixed

• Fix dropped comment in (function _ -> x (* cmt *)) (#2739, @Julow)

• * cases-matching-exp-indent=compact does not impact begin end nodes that don't have a match inside. (#2742, @EmileTrotignon)

  (* before *)
  begin match () with
  | () -> begin
    f x
  end
  end
  (* after *)
  begin match () with
  | () -> begin
      f x
    end
  end
  

• Ast_mapper now iterates on all locations inside of Longident.t, instead of only some. (#2737, @v-gb)

• Remove line break in M with module N = N (* cmt *) (#2779, @Julow)

Internal

• Added information on writing tests to CONTRIBUTING.md (#2838, @WardBrian)

Changed

• indentation of the end keyword in a match-case is now always at least 2. (#2742, @EmileTrotignon)

  (* before *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()
  end
  end
  (* after *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()
  
  

• * use shortcut begin end in match cases and if then else body. (#2744, @EmileTrotignon)

  (* before *)
  match () with
  | () -> begin
      match () with
      | () ->
    end
  end
  (* after *)
  match () with
  | () ->
    begin match () with
      | () ->
    end
  end
  

• * Set the ocaml-version to 5.4 by default (#2750, @EmileTrotignon) The main difference is that the effect keyword is recognized without having to add ocaml-version=5.3 to the configuration. In exchange, code that use effect as an identifier must use ocaml-version=5.2.

• The work to support OCaml 5.5 come with several improvements:

  • Improve the indentation of let structure-item with the [@ocamlformat "disable"] attribute. let structure-item means let module, let open, let include and let exception.
  • (let open M in e)[@a] is turned into let[@a] open M in e.
  • Long let open ... in no longer exceed the margin.
  • Improve indentation of let structure-item within parentheses:

    (* before *)
    (let module M = M in
    M.foo)
    (* after *)
    (let module M = M in
     M.foo)
    

Opam-publish 3.0.0

We're happy to announce the release of opam-publish 3.0.0.

This major release contains breaking changes:

• The deprecated --split option has been removed (#194).
• Following the upgrade to cmdliner 2.0, option names can no longer be abbreviated to an unambiguous prefix (for example, --dry is no longer accepted as an alias of --dry-run) (#202).
• The github-unix dependency has been dropped (#196).

For more details, see the full changelog below.

Release of OCaml 5.4.1 and 4.14.3

We have the pleasure of announcing the dual releases of OCaml 4.14.3 and OCaml 5.4.1, dedicated to the memory of Nicolaas Govert de Bruijn on the anniversary of his death.

Those releases are a collection of safe and valuable runtime bugfixes. The OCaml 5.4.1 release also contains a fix for the -pack mode for macOs and various TSAN fixes.

More importantly, those new versions harden the Marshal module against malicious inputs as described in the security announcement OSEC-2026-01.

We are encouraging you to switch to those new releases whenever possible.

Don't hesitate to report any bugs on the OCaml issue tracker and to leave comments on the discuss announcement.

See the list of changes below for more details.

Happy hacking, -- Florian Angeletti for the OCaml team.

Installation Instructions

The base compiler can be installed as an opam switch with the following commands:

opam update
opam switch create 4.14.3
opam switch create 5.4.1

The source code for the release is also directly available on:

• GitHub:

  • https://github.com/ocaml/ocaml/archive/4.14.3.tar.gz
  • https://github.com/ocaml/ocaml/archive/5.4.1.tar.gz

• Inria archive:

  • https://caml.inria.fr/pub/distrib/ocaml-4.14/ocaml-4.14.3.tar.gz
  • https://caml.inria.fr/pub/distrib/ocaml-5.4/ocaml-5.4.1.tar.gz