Release notes from unison

Development Build (trunk)

2026-03-06T03:34:49Z

Commits

4d64d02: Support underscore separators in numeric literals (#2228) (Taylor Fausak) #6180
85ea6e8: Reject trailing and consecutive underscores in numeric literals (Taylor Fausak) #6180
b5471b1: Add transcript test for underscore numeric literals (Taylor Fausak) #6180
86ba605: Refactor otherbase parsers and add digit_nondigit tests (Taylor Fausak) #6180
21beed9: Rename otherBase to baseWithPrefix to avoid case-only difference (Taylor Fausak) #6180
ab5c0cb: Add test that underscore after base prefix is rejected (Taylor Fausak) #6180
168ff0b: Add tests for underscores adjacent to period and exponent marker (Taylor Fausak) #6180
b6104f1: Add tests for exponent sign underscores and leading zeros (Taylor Fausak) #6180
904a2d0: Add myself to the list of contributors (Taylor Fausak) #6180
e5c5b2e: Update test proof (Taylor Fausak) #6180

release/1.1.1

2026-02-24T15:29:24Z

What's Changed

UCM improvements:

Show full type definition for new type defs in diff.update (thanks @bbarker!)
Update haskeline to support ANSI terminals
Fix prompt rendering after reverse search in Haskeline (thanks @MauScheff!)
Fix accidental swap of local<->remote in branch.diff / UCM_DIFFTOOL invocation
Use 3-way diff algorithm to render merged.u (file output when UCM_MERGETOOL is set)
Change the test command to use the sandboxed runtime instead of evalPureUnison
Make view and edit include docs automatically
Mn merge branches, classify adds/updates/deletes relative to target of merge

MCP improvements:

Add CreateBranchTool to allow AI to create branches with the MCP Server (thanks @channingwalton!)
Add UNISON_MCP_TIMEOUT environment variable for configurable tool timeouts (thanks @bbarker!)

Runtime improvements:

Add FFI support for null pointers
Add serialization/hashing for Integer / Natural

All PRs since last release

Add null pointers to new FFI API by @dolio in #6148
bump haskeline dependency to one that supports ANSI terminals by @mitchellwrosen in #6147
fix full type definition not being shown for new type defs in diff.update by @bbarker in #6101
[unison-cli] Fix prompt rendering after reverse search in Haskeline by @MauScheff in #6149
fix accidental swap of local<->remote in difftool invocation by @mitchellwrosen in #6158
Replace Nix tooling & update toolchain by @sellout in #6046
use 3-way diff algorithm to render merged.u (file output when UCM_MERGETOOL is set) by @mitchellwrosen in #6160
add unison-util-diff3 to contrib/cabal.project by @mitchellwrosen in #6164
Delete pr-description.md by @bbarker in #6168
Change the test command to use the sandboxed runtime instead of evalPureUnison by @dolio in #6169
Add serialization/hashing for integer/natural by @runarorama in #6163
Add attestation-based CI by @aryairani in #6150
consolidate checks to a single result, in the absence of mergify by @aryairani in #6171
CI required checks have to be in both groups by @aryairani in #6172
Make view and edit include docs automatically by @mitchellwrosen in #6170
On merge branches, classify adds/updates/deletes relative to target of merge by @mitchellwrosen in #6151
make checks run for contributor forks too by @aryairani in #6174
Add CreateBranchTool to allow AI to create branches with the MCP Server by @channingwalton in #6155
Add UNISON_MCP_TIMEOUT environment variable for configurable tool timeouts by @bbarker in #6167

New Contributors

@MauScheff made their first contribution in #6149
@channingwalton made their first contribution in #6155

Full Changelog: release/1.1.0...release/1.1.1

release/1.1.0

2026-01-29T00:01:15Z

What's Changed

Features:

The dependents command now work on constructors and ability requests. (#6115)
Support for "Edit Definition" and "Open on Share" in the Unison Language VS Code extension v1.5.0. (#6129, #6105)
Adds new builtins for Argon2id password hashing. (#6094, thanks @bbarker!)
Adds MCP tools for history, reflog, and share-project-info (for authenticated project lookups). (#6103, #6118, also @bbarker)
More FFI work (#6131).

Fixed:

Bytes decoding and comparisons are much faster.
run now allows unquoted numbers as arguments; sorry.
branch.diff now accepts numbered args and branch hashes.
run now gives a nicer message if the program name is ambiguous.(#6111)
update no longer leaves deleted constructors in the underlying namespace of an update branch.
cases now parses correctly in Doc eval blocks.
The MCP server to avoid the use of oneOf in JSON Schema, which was defined in 2014 and will surely be supported by coding agents any moment now.
A certain kind of infinite loop no longer occurs in the runtime. (#5889)
Fixed a backwards subtyping check in pattern type checking. (thanks to @lJoublanc for reporting!)
Fixed a typo in the reflog .(showing alias.type as alias.term)
Fixed a pattern-matching bug around duplicate binding names .(thanks to @jcwilk, @etorreborre, and @gvolpe for reporting!)

ucm 1.1.0 updates the codebase version (not backwards-compatible) in order to support syncing of history comments.

All PRs Since Last Release

claude seems to not support the "oneOf" type. by @stew in #6095
Add a missing case to the lambda lifting transformation by @dolio in #6093
Fix backwards subtyping checks in pattern type checking by @dolio in #6087
delete Relative path type by @mitchellwrosen in #6097
fix reflog typo by @mitchellwrosen in #6092
bugfix: disallow duplicate binders by @mitchellwrosen in #6090
Add some better implementations for some bytes reading/decoding functions by @dolio in #6104
Open on share VS-Code plugin api endpoint by @ChrisPenner in #6105
diff.branch: include current branch in completion by @ceedubs in #6102
Rework Bytes Chunk type and tweak comparison by @dolio in #6112
improve ambiguous run error message by @mitchellwrosen in #6111
allow delete.force to delete things out of lib by @mitchellwrosen in #6088
make dependents work on constructors by @mitchellwrosen in #6115
make alias.type name the constructors as well by @mitchellwrosen in #6099
Remove unused scratch files by @ceedubs in #6114
Added message argument to history.comment by @ChrisPenner in #6123
Implements the Pull side of comment sync by @ChrisPenner in #6117
Hash history comments and sign them with the author's personal key. by @ChrisPenner in #6004
History Comment Sync API by @ChrisPenner in #6017
disallow adding or updating things in lib with update by @mitchellwrosen in #6083
Replace pseudo-extensible Foreign with a big union by @dolio in #6125
Add Argon2id password hashing builtins; switch from cryptonite to crypton by @bbarker in #6094
Fix install-hooks.bash script by @sellout in #5910
Edit Commands for VS Code plugin by @ChrisPenner in #6129
bugfix: update no longer leaves deleted constructors in underlying namespace of update branch by @mitchellwrosen in #6133
generate cabal files by @mitchellwrosen in #6132
Add additional FFI types and pointer operations by @dolio in #6131
bugfix: fix cases parsing in doc eval block by @mitchellwrosen in #6137
Don't expand numbers in non-structured arguments by @ChrisPenner in #6135
Add share project info MCP tool by @bbarker in #6118
properly handle hashes and numbered args in branch.diff arg parser by @mitchellwrosen in #6142
Add Reflog and History MCP Tools by @bbarker in #6103
update help for branch.squash by @aryairani in #6146

Full Changelog: release/1.0.2...release/1.1.0

release/1.0.2

2026-01-05T21:51:50Z

What's Changed

New diff.update command highlights changes in the scratch file. (#6080; thanks @bbarker!)
MCP improvements. (#6081, #6082; thanks @kn0ll!)
Fixed a parsing error involving multi-line match scrutinees. (#6078)
Fixed text.find which was not finding numbers that appeared in patterns. (#6073)

All PRs Since Previous Release:

Fix MCP: Successful responses contain duplicate outputs by @kn0ll in #6082
Adding MCP commands: "rename", "move", "moveTo", "delete", "delete.namespace" by @kn0ll in #6081
format trunk with ormolu 0.7.2.0 by @github-actions[bot] in #6084
fix parsing certain multiline match / indentation cases by @aryairani in #6078
let text.find detect numbers in patterns by @aryairani in #6079
update transcripts by @aryairani in #6085
[Draft] Add diff.update to show preview of changes before running update by @bbarker in #6080

New Contributors

@kn0ll made their first contribution in #6082

Full Changelog: release/1.0.1...release/1.0.2

release/1.0.1

2025-12-21T22:12:08Z

What's Changed

Faster:

big speed-up to type-checking in certain common situations. #6053 (thanks @bbarker for reporting)
faster JSON generation #6058

Features:

new moveTo command collects definitions from different places into a single target namespace. #6054
new rename command lets you rename a definition with a long path without having to type the long path twice. #6054
new watch and unwatch commands let you monitor multiple locations for scratch file changes. #6063
find no longer searches transitive deps by default. #6065
support single-quotes when parsing args in ucm. #6072
more readable errors for dataBranch failures. #6068
add 16-bit and 32-bit FFI types. #6060
allow passing pinned arrays to DLL imported functions. #6067

Fewer bugs:

ucm now prints definitions within definitions in a more predictable order. #6039
show library upgrades as automatic changes (de-emphasized in diffs). #6020
correctly pretty-print "symboly" binders with surrounding parens. #6030
don't disable paged output after a file event. #6045
avoid giving an under-application error for 0 arguments. #6042

All PRs Since Last Release

fixup hpack file for unison-dynlib by @aryairani in #6019
canonicalize libnames for synhashing by @mitchellwrosen in #6020
Fail hashing if components are ambiguously ordered. by @ChrisPenner in #6007
pretty-print symboly binders with surrounding parens by @mitchellwrosen in #6030
Fix typo in init command help message by @larsw in #6022
Only check for incomplete element orderings on top-level-bindings by @ChrisPenner in #6035
Add FQN to syntax text by @ChrisPenner in #6036
Prevent hash failure errors in runtime by @ChrisPenner in #6038
Avoid giving an under-application error for 0 arguments by @dolio in #6042
Guard dll smoke tests behind cache results by @dolio in #6041
Human-centric let-rec, constructor and ability orderings by @ChrisPenner in #6039
Re-enable paged output after a file event. by @ChrisPenner in #6045
Switch to an asymptotically better typing context implementation by @dolio in #6053
implement moveTo and rename by @aryairani in #6054
Add missing fingertree dependency to parser-typechecker by @aryairani in #6056
Update runtime-tests version by @dolio in #6061
Add 16-bit and 32-bit FFI types by @dolio in #6060
test moveTo <blah> . by @aryairani in #6066
add watch / unwatch commands by @aryairani in #6063
Allow passing pinned arrays to DLL imported functions by @dolio in #6067
Support single-quotes in ucm arg parsing by @ChrisPenner in #6072
don't search transitive deps by default by @aryairani in #6065
Give more readable errors for dataBranch failures by @dolio in #6068
Speed up emitJson replacement by @dolio in #6058
block for lock during transcript.inplace by @aryairani in #6075

New Contributors

@larsw made their first contribution in #6022

Full Changelog: release/1.0.0...release/1.0.1

release/1.0.0

2025-11-25T18:38:20Z

What's Changed

README: Fix factorial example by @leetemil in #5998
don't require github templates to go through transcript runner by @aryairani in #6000
fix bug in UnisonFile.constructorsId - effects were treated as decls by @mitchellwrosen in #5999
tweak stale run output by @mitchellwrosen in #6005
make diff.branch visible and give it a help by @mitchellwrosen in #6009
make dependents look at file if nothing in codebase matches by @mitchellwrosen in #6003
Print Refs as short hashes in ambiguous hash error by @ChrisPenner in #6006
Initial implementation of actual dynamic FFI to DLLs by @dolio in #6008

New Contributors

@leetemil made their first contribution in #5998

Full Changelog: release/0.5.50...release/1.0.0

release/0.5.50

2025-11-10T21:34:41Z

What's New

ucm 0.5.50 has lots of updates and new features (and is also a 1.0 release candidate)!

workflow improvements

new branch.diff command for comparing branches, also with difftool support via UCM_DIFFTOOL variable with fallback to the UCM_MERGETOOL variable
new comment command to add comments to your branch's change history
upgrade command can now take more than one lib pair simultaneously
status line indicates 🧩 when you are piecing together an incomplete update, delete, upgrade, or merge
- in this mode, definitions removed from your scratch file will be removed from final result once you successfully update, which is different than usual, but necessary for making certain kinds of changes
- update or cancel will complete or cancel the update; the merge.commit command has gone away.
fixes to to the run command
- run will stop you from running a program in your scratch file that would result in running stale code due to needing to update first
- multi-word ucm args can be passed to run by putting them in "double quotes"
- avoid numbered args expansion with run by putting quotes around the numbers also
updated project naming rules: 1+ characters in the set {ascii letter, digit, -, _}.
add mv and rm command aliases

core language and runtime improvements

parser, type-checker, code printer, and runtime fixes
code serialization speedup
new support for zstd compression/decompression (thanks @regiskuckaertz)

editor support improvements

LSP file outline support and error highlighting improvements
vim syntax highlighting improvements (thanks @avysk)

MCP improvements

new MCP tools allow an agent to use the test, update, and run commands
implemented a fix for the typecheck command for agents (e.g. codex) that don't support the latest json schema version

All PRs Since Last Release

regenerate mcp.output.md by @aryairani in #5900
Prevent uName from overwriting other syntax groups by @avysk in #5901
Don’t treat docs as transcripts by @sellout in #5903
Add mv and rm command aliases by @regiskuckaertz in #5904
Handle kind-inference of unkown builtins more gracefully by @ChrisPenner in #5899
fix new project name rules by @mitchellwrosen in #5906
Prevent new dead Haskell code by @sellout in #5909
Fix use insertion when do block starts with destructuring bind by @pchiusano in #5911
Correct Semis when reordering stanzas by @sellout in #5915
Minimal nix update by @sellout in #5912
Add support for ZStandard (de)compression by @regiskuckaertz in #5907
Use Builder directly instead of Put for serialization by @dolio in #5919
add cancel command by @mitchellwrosen in #5921
remove merge.commit command by @mitchellwrosen in #5922
LSP scratch-file outline by @ChrisPenner in #5933
Speed up serialized value loading by @dolio in #5928
Fix Cabal smoke-test workflow by @sellout in #5936
feat: overhaul delete implementation by @mitchellwrosen in #5894
Implement side-by-side diffs by @ChrisPenner in #5925
Delete unison-src/transcripts/idempotent/builtins.output.md by @aryairani in #5935
Delete loop.prof.wakeup by @aryairani in #5937
put puzzle piece on prompt on update/upgrade/merge branches by @mitchellwrosen in #5938
Add (pure) tests command to MCP by @ChrisPenner in #5954
Reimplement code/value deserialization based on a custom parser by @dolio in #5943
Try to fix typecheck schema usage in Codex by @ChrisPenner in #5957
Convert a bunch of types and functions from String -> Text by @ChrisPenner in #5958
Add Run tool to MCP by @ChrisPenner in #5955
Better handle newlines in diffs by @ChrisPenner in #5959
disable nix development cache job due to failures by @aryairani in #5966
standardize wording of failed delete/update/upgrade/merge by @mitchellwrosen in #5953
Fix a runtime problem from overapplying ability requests by @dolio in #5970
Make profiler-smoketest.md delete profile files after run by @dolio in #5951
Add data type variance to type checking by @dolio in #5960
Add support for quoted UCM args. by @ChrisPenner in #5968
Parse number expansions in args by @ChrisPenner in #5973
slurp unnamed test watches properly by @mitchellwrosen in #5969
generalize upgrade to take more than one lib pair simultaneously by @mitchellwrosen in #5963
Fix completion edge-cases by @ChrisPenner in #5975
Change Comments by @ChrisPenner in #5895
Remove speech bubbles by @ChrisPenner in #5977
Make more use of inferred variances during type checking by @dolio in #5976
disallow run if an update is required by @mitchellwrosen in #5964
fix upgrade fzf behavior by @mitchellwrosen in #5981
Add branch.diff command by @mitchellwrosen in #5962
Attempt to improve function under-application and over-application errors by @ChrisPenner in #5665
Strictify LSP Vars by @ChrisPenner in #5978
Add libdeps diffs to branch.diff output by @mitchellwrosen in #5979
Try to improve information flow down through 'branching' constructs by @dolio in #5984
update macos runners due to deprecation by @aryairani in #5986
MCP Update tool by @ChrisPenner in #5952
Improve error LSP ranges on type mismatches by @ChrisPenner in #5284
Refine pull request template for clarity by @aryairani in #5994
run transcripts by @mitchellwrosen in #5996
don't launch mergetool in transcripts by @mitchellwrosen in #5995
allow diff.branch between unrelated branches by @mitchellwrosen in #5982
Create a dedicated failure type for AsyncCancelled by @ceedubs in #5991
compute fast-forward diffs much more efficiently by @mitchellwrosen in #5989

New Contributors

@avysk made their first contribution in #5901
@regiskuckaertz made their first contribution in #5904

Full Changelog: release/0.5.49...release/0.5.50

release/0.5.49

2025-09-25T00:17:02Z

What's Changed

Setting the UNISON_DEBUG variable with TIMING now displays runtimes for individual tests when using test.
Setting the UNISON_DEBUG variable with TESTS now displays names for individual tests when using test.
A new murmur hash primitive which doesn't tumble in type info. It's much faster than the existing one, but good chance of collisions when you're mixing hashes from values of different types, so choose appropriately.
Everything from the stealth release of 0.5.48:

New Features ✨ 🦄 🌈 ⭐
- Profiling!
- Arbitary precision integer arithmetic!
- git-style mergetool support!
- Like when resolving an incomplete update, resolving an incomplete upgrade supports deletions. That's a little different from before, so be careful while you get used to it! undo is your friend.
Fixes
- We updated project naming rules to match Unison Share; sorry not sorry!
  Project names may now consist of ASCII letters, digits, and hyphens; between 2–40 characters.
Fiddling
- Namespaces in ls output now end in . instead of /
- There are a few new command aliases:
  - lib.install can be run as install.lib or just install
  - lib.upgrade can be run as upgrade.lib or just upgrade
- namespace.dependencies command has been removed in favor of todo.

All PRs Since Last Release

Delete old Name Lookup methods in UCM by @ChrisPenner in #5875
Add Dependents/Dependencies API for UCM Desktop by @ChrisPenner in #5876
Add debug info for tests by @runarorama in #5890
Implement a direct murmur hash on values that omits type references by @dolio in #5884
Fix the return type of Integer.signum by @runarorama in #5892

Full Changelog: release/0.5.48...release/0.5.49

release/0.5.48

2025-09-24T23:47:28Z

What's Changed

New Features ✨ 🦄 🌈 ⭐

Profiling!
Arbitary precision integer arithmetic!
git-style mergetool support!
Like when resolving an incomplete update, resolving an incomplete upgrade supports deletions.
That's a little different from before, so be careful while you get used to it! undo is your friend.

Fixes

We updated project naming rules to match Unison Share; sorry not sorry!
Project names may now consist of ASCII letters, digits, and hyphens; between 2–40 characters.

Fiddling

Namespaces in ls output now end in . instead of /
There are a few new command aliases:
- lib.install can be run as install.lib or just install
- lib.upgrade can be run as upgrade.lib or just upgrade
namespace.dependencies command has been removed in favor of todo.

All PRs Since Last Release

Add profiling support to UCM by @dolio in #5856
Transcript change: help from new profiling commands by @dolio in #5857
Fix interpreter tests by @sellout in #5853
swap trailing slash for trailing dot in ls output by @mitchellwrosen in #5860
Builtins for arbitrary precision integer arithmetic by @runarorama in #5852
Report internal errors more clearly by @sellout in #5661
Improve displayed names in profiles by @dolio in #5861
Better name out-of-scope error message by @mitchellwrosen in #5863
Avoid redundant re-hashing when squashing an already squashed branch by @ChrisPenner in #5867
Don’t prettify exceptions written to the stack by @sellout in #5868
Defer error serialization by @sellout in #5869
Add message when pulling to indicate from and to causal hashes. by @ChrisPenner in #5870
Rename BigInt and BigNat to Integer and Natural by @runarorama in #5871
allow deleting while resolving an upgrade failure by @mitchellwrosen in #5872
Add Codex notes for mcp.md by @bbarker in #5873
add more restrictive project name check by @mitchellwrosen in #5862
fix bad transcript caching and syntax error in mcp.md by @aryairani in #5879
silence typechecking output after merge failure by @mitchellwrosen in #5874
make $MERGED absolute by @mitchellwrosen in #5882
Add a few new aliases by @ChrisPenner in #5881
delete namespace.dependencies by @mitchellwrosen in #5865
Add a second type of profile that samples after wakeup by @dolio in #5883

Full Changelog: release/0.5.47...release/0.5.48

release/0.5.47

2025-08-30T14:11:04Z

What's Changed

Faster update, diff, and merge.
Support a few more TLS operations.

All PRs Since Last Update

consolidate timing helpers by @mitchellwrosen in #5847
Sanity check Cabal build by @sellout in #5827
Fix CI download-artifact “unknown input” warning by @sellout in #5851
improve update performance by @mitchellwrosen in #5849
Don’t override hashtables version in stack.yaml by @sellout in #5855
add some new builtins for TLS by @stew in #5854
tweak: don't bother synhashing when synhashes would be the same by @mitchellwrosen in #5718

Full Changelog: release/0.5.46...release/0.5.47