Jacquard

Jacquard is a FriendMachine research project for running, reviewing, simulating, and trusting programs written by models and reviewed by people. Start with the human-friendly introduction to Jacquard.

Concretely, it is a small programming language where every function signature lists the outside-world effects the function may perform — network, files, clock, randomness — and the runtime refuses any effect you have not granted on the command line. A reviewer reads the signature to learn what a change can touch; the checker guarantees the signature is complete. The implementation is an OCaml checker and interpreter, a compiler that accepts public .jac or lower-level .jqd files and produces standalone native binaries by emitting C, the jac command-line tool, a standard library written in Jacquard itself, and a test framework called Warp. Version 0.2 works end to end but is a research prototype, not a production language; docs/release/0.2/LIMITS.md is the honest boundary.

Install the 0.2 release without OCaml or opam:

curl -fsSL https://raw.githubusercontent.com/jbwinters/jacquard-lang/jacquard-core-0.2.0/scripts/install.sh | sh
~/.local/bin/jac run ~/.local/share/jacquard/demos/basics/m1-fact.jac

The expected output is 120. Linux x86-64, macOS Intel, and macOS Apple Silicon binaries are published; development from source is documented below.

Then run one policy under concrete and probabilistic telemetry worlds, followed by sampled and exhaustive Warp checks:

sh ~/.local/share/jacquard/demos/case-studies/release-risk/run.sh

For Humans

Most languages tell you what a program computes. Jacquard also exposes which effects it may perform, finite discrete uncertainty, and canonical program identity. Tools can inspect all three because they live in the language rather than only in comments, logs, or your memory of the codebase.

Things you can do here that most languages cannot offer:

• Read one line and see the effects a function may perform. A signature like (text) ->{net} text says the function may perform the net effect. The Jacquard runtime rejects unhandled world effects unless their authority is explicitly granted with --allow, including effects performed by dynamic code. This is language-level enforcement in a research runtime, not a substitute for an operating-system sandbox.
• Run one program against many worlds. The same code can run against the shipped deterministic network stub, a scripted response list, a recorded trace, or a probability model of how servers usually behave. A real network adapter does not ship yet; a host integration can implement the same effect boundary without changing the Jacquard program. A handler is the piece that answers a program's requests to the outside world; you swap the handler, and the code never changes. This can replace much conventional mocking at effect boundaries and makes "what would my agent do if the API went down?" an ordinary test. If this sounds like dependency injection: an injected dependency is the special case of a handler that resumes the program exactly once. A handler can also decline to resume, aborting the rest of the computation cleanly, or resume many times, forking the rest of the program to explore every outcome. That last case is what makes exhaustive testing and exact inference ordinary library code here.
• Enumerate exact probabilities for finite discrete models. A program can sample weighted choices and record evidence, and enumeration lists every reachable outcome with its exact probability. The repair demo below treats a failing test as evidence and computes which patches remain possible and how likely each is.
• Rename and reformat without changing canonical identity. Jacquard hashes canonical resolved structure rather than source bytes. Comments, formatting, provenance, and ordinary local or term renames are erased; pure tests rerun only when canonical code or dependency content changes. This is structural identity, not a proof that arbitrary programs are behaviorally equivalent.

The bet behind all of this: when most code is written by machines, the humans reviewing it need the language itself to answer "what can this touch, and how sure are we" without reading every line.

Jacquard also lets public call sites say what each argument means:

resize(image, scale: ratio) = (image, ratio)

resize(photo, scale: 2)

An unlabeled positional prefix may come first; labeled arguments may follow in any order and still run left to right as written. Labels are explicit API, not guesses from local binder names: top-level functions and effect operations declare them, while constructors reuse their declared field labels. Calls are still exact-arity and uncurried—there are no defaults, label puns, or named calls through local and higher-order values. The lower-level .jqd carrier remains positional.

The Review Case In Miniature

Suppose a model hands you this one-line change in Python:

def normalize_name(name):
    return lookup_alias(name).strip().lower()

To learn whether the change can reach the network, you read lookup_alias, then everything it calls. The answer lives in the transitive closure of the diff, and nothing checks whatever answer you settle on.

The same change in Jacquard arrives with this checked signature:

normalize-name : (text) ->{net} text

Some function below lookup-alias performs a net operation, so net surfaces in the row of every caller until a handler discharges it. The checker computes the row; a signature that omits an effect is a type error. The reviewer's first question about generated code — what can this touch — is answered on the first line of the diff, before reading any body. At run time the same row is enforced: jac run refuses the program without --allow net, and that includes effects performed by dynamically loaded code.

Effect rows are also what separates this from an ordinary type system: they propagate through the call graph without hand annotation, and they are tied to runtime authority. Ordinary types describe the values a function handles; the row describes what running it may do to the world, and the runtime holds it to that.

For Agents

Read docs/SKILL.md first. It compresses the kernel, the CLI, the prelude, Warp testing, and the known gotchas into one file, and it loads as a project skill from docs/SKILL.md. The language is deliberately small enough that an agent with no Jacquard in its training data can work from that one file. Operating rules are in AGENTS.md. What will save you time:

• Behavior is pinned by evidence: cram transcripts under test/cli/, corpus goldens, demo scripts, and docs/release/0.2/CLAIMS.md. If a pin fails, treat it as information about your change, and never weaken a pin to make a diff pass.
• The kernel is 27 forms (docs/ast.md); .jac is a projection onto those forms, and bootstrap .jqd remains permanently supported. Treat the shipped surface boundary and its parked follow-ups as release evidence, not as a frozen grammar; do not add out-of-scope features (AGENTS.md lists them).
• The development gate is dune build @all && dune runtest && dune fmt followed by a clean git diff --exit-code.

Core Ingredients

For readers who speak programming languages:

• One uniform representation: every form is a (head, meta, args) triple, and the kernel grammar has 27 forms. Quoted code is ordinary data.
• Algebraic effects with deep, mode-aware handlers. A multi operation has a reusable continuation and can resume zero, one, or many times, which makes exhaustive search and exact inference ordinary library code. A once operation instead binds an affine Resume: the checker reports E0816 when one possible path consumes it twice, and the runtime retains E0906 as a repeated-resume backstop for each captured instance.
• Explicit capability grants. The runtime installs handlers for the outside world only for effects you pass with --allow; there is no ambient authority.
• Type-and-effect rows. Every arrow carries the set of effects the function may perform, so a program's inferred row is its authority manifest.
• Discrete probabilistic programming as a library: sample and observe are effect operations, and each inference algorithm is a handler.
• Content-addressed definitions. Identity is a hash of canonical resolved structure with non-identity metadata erased, so formatting, comments, and ordinary local or term renames change nothing downstream. Explicit external call labels are a separately stored, hash-bound API contract; changing those labels for the same callable identity is rejected.
• Tooling that leans on the above: formatter, structure-aware differ, Warp tests with a content-addressed cache, record/replay, and a reproducible release evidence pack.
• A native AOT path that emits C, specializes and caches units by content hash, and is differential-tested against the interpreter under clang and gcc.

Design Lineage

The design borrows deliberately from languages whose ASTs and semantics were studied during planning; docs/ast.md records each debt in detail:

• Unison: effects carried on function arrows, operations as ordinary functions, content-addressed definitions, and cycle hashing.
• Koka: effect rows, uncurried arrows, the tail-resumptive handler discipline, and a warning heeded about row-inference ergonomics.
• Racket: scope-set hygiene for quoted code.
• Haskell: strict evaluation as the verdict on laziness, and exhaustive matching as a checker obligation rather than a lint.
• OCaml: the host language, plus negative lessons on builtin structural equality and on deferring ad-hoc polymorphism.
• Roslyn (C#): full-fidelity syntax metadata so tools can round-trip source without losing comments or formatting.

The prototype is complete against its original core plan and has since added the public surface syntax, ringed standard library, Warp properties and cache, native compilation, packaged binaries, and product-scale case studies. The RC1 semantic boundary remains historical; the current successor is pinned by 984 Alcotest/QCheck cases, 60 cram transcripts, 28 documentation examples, native sanitizer/leak/fuzz lanes, and fresh-clone evidence workflows. RC2 repaired binary-demo packaging; RC3 adds an explicit runtime/output license exception and packages the native runtime. The current successor distribution relicenses Jacquard under Apache License 2.0 and keeps that runtime/output permission as an explicit clarification. These licensing and packaging changes do not change the language semantics pinned at RC1.

What It Looks Like

Here is one handler resuming one continuation twice. The block is copied byte-for-byte to test/docs-doctest/fixtures/readme-multishot.jac and run by the documentation test lane:

multi effect Choice where {
  choose : () -> Bool
}

handle {
  match choose() {
    | True -> 1
    | False -> 2
  }
} {
  | return x -> x
  | choose() resume continue -> add(continue(True), continue(False))
}

$ jac run test/docs-doctest/fixtures/readme-multishot.jac
3

Reading it line by line: multi effect Choice declares an effect with one operation, choose, which takes nothing and answers a boolean. multi means its continuation may be resumed more than once. The handle block runs the code in the first braces. When that code calls choose(), control jumps to the matching clause below, which receives the paused rest-of-the-computation as continue. The clause calls continue twice, once per answer, so the match runs once with True (producing 1) and once with False (producing 2), and add combines the two runs into 3. The return x -> x clause says finished runs pass through unchanged.

That ability to resume more than once is why exact Bayesian inference is a library handler here rather than a runtime feature. The repair demo builds on it: mutate a buggy program's quoted AST into candidate patches, treat a failing test as an observation, and read off the updated probabilities. Running candidate code is an authority, so the pure step still runs (it counts eight candidate patches) and then the demo refuses until you grant the rest:

$ jac run demos/tooling/repair.jac
8
error[E0814]: The program requires an effect that was not granted
  Cause: This program requires eval [meta/high] — run code constructed or loaded at runtime, which is not granted (performed via `posterior-over-patches`).
  Next step: grant it with --allow eval, or handle the effect in the program
$ jac run demos/tooling/repair.jac --allow eval

Under the grant, one failing test leaves two surviving patches: the intended fix at 0.75 and a patch that games the suite at 0.25. Adding one regression test prunes the impostor, and the surviving fix prints as a one-line canonical diff: - sub + add. See sh demos/tooling/repair.sh for the full transcript.

Install A Release Binary

Most users do not need OCaml or opam. Install the reviewed 0.2 binary with:

curl -fsSL https://raw.githubusercontent.com/jbwinters/jacquard-lang/jacquard-core-0.2.0/scripts/install.sh | sh

The installer detects your OS and CPU, downloads the matching archive and SHA-256 checksum, refuses a checksum mismatch, and installs under ~/.local by default. Make sure ~/.local/bin is on PATH, then run:

jacquard --version
jac --version

jac is the short alias for jacquard. Both commands set JACQUARD_PRELUDE from the installed package, so ordinary runs do not need an environment variable:

jac run ~/.local/share/jacquard/demos/basics/m1-fact.jac

Narrative demos ship with launchers that choose the installed binary and prelude automatically. They do not require Dune:

DEMO_ROOT="$HOME/.local/share/jacquard/demos"
sh "$DEMO_ROOT/case-studies/release-risk/run.sh"
sh "$DEMO_ROOT/worlds/agent-dream.sh"
sh "$DEMO_ROOT/worlds/escrow/run.sh"

Use these launchers rather than directly running a probabilistic model or a multi-file entrypoint. The launcher selects infer where observation requires it and assembles related files in isolated scratch space.

To install under a different user-owned prefix:

curl -fsSL https://raw.githubusercontent.com/jbwinters/jacquard-lang/jacquard-core-0.2.0/scripts/install.sh \
  | JACQUARD_INSTALL_PREFIX="$HOME/.jacquard" sh

Set JACQUARD_INSTALL_VERSION to install a different release tag. Supported binary targets are linux-x86_64, macos-x86_64, and macos-arm64; other platforms currently require the development setup.

Release archives are attached to jacquard-core-* GitHub releases. Each archive contains bin/jacquard, bin/jac, libexec/jacquard/jacquard, share/jacquard/prelude, share/jacquard/demos, the native C runtime, and the license, notice, exception, and trademark documents.

Development Quick Start

These commands assume a fresh clone and asdf available for installing opam. If you already have opam 2.5.x, start at the local switch step. If opam is already initialized on your machine, skip opam init.

git clone https://github.com/jbwinters/jacquard-lang.git
cd jacquard-lang

asdf plugin add opam https://github.com/asdf-community/asdf-opam.git
asdf install opam 2.5.1
asdf set opam 2.5.1
asdf reshim opam 2.5.1

opam init -y --no-setup --bare
opam switch create . ocaml-base-compiler.5.1.1 -y
eval "$(opam env)"

opam install --deps-only . --with-test --with-dev-setup --with-doc -y
opam exec -- dune build @all
opam exec -- dune runtest
opam exec -- dune fmt
git diff --exit-code

The switch step compiles OCaml 5.1.1 from source, so expect the first setup to take around ten minutes.

The final git diff --exit-code is part of the development contract: formatting must leave the worktree clean unless you intentionally commit the formatting diff.

Expected versions after setup:

• opam 2.5.1 from .tool-versions
• OCaml 5.1.1 from the repo-local _opam/ switch
• dune, ocamlformat, alcotest, qcheck, digestif, menhir, cmdliner, odoc, utop, and ocaml-lsp-server from jacquard.opam

In a new shell inside an existing checkout, run:

eval "$(opam env)"

_opam/ is intentionally ignored. It is a local build artifact, not source.

Running Jacquard

During development, use the built binary through Dune:

opam exec -- dune exec jac -- --help
opam exec -- dune exec jac -- --version

Many direct CLI commands need the prelude. From the repository root:

export JACQUARD_PRELUDE=$PWD/prelude
opam exec -- dune exec jac -- run demos/basics/m1-fact.jac

The main commands are:

jac run FILE.jac [--allow fs] [--allow net] [--dry-run]
jac relate FILE.jac --vary schedule=N --seed S [--allow EFFECT ...]
jac relate FILE.jac --vary secret=NAME --seed S [--allow EFFECT ...]
jac relate FILE.jac --vary grant=net|infer|dist --seed S
jac check FILE.jac [--print-sigs] [--manifest fs,net,console]
jac hash FILE.jac
jac fmt FILE.jac
jac diff FILE_A.jac FILE_B.jac
jac diff STORE_A STORE_B
jac infer enumerate MODEL.jac
jac infer lw MODEL.jac --seed 42 --samples 100000
jac replay TRACE.jqd PROGRAM.jqd [--fork '1=(response 500 "down")']
jac test TESTS.jac [TESTS.jqd ...] [--exhaustive] [--schedules N --seed S] [--cache-dir CACHE]
jac build FILE.jac -o PROG
jac export FILE.jac -o FILE.jqd
jac governance check FILE.jac [--output-format text|json-v1]
jac governance verify-run RUN_BUNDLE.jqd
jac governance reconcile RECONCILIATION_BUNDLE.jqd
jac governance explain PROPOSAL_ID --bundle RECONCILIATION_BUNDLE.jqd [--output-format text|json-v1]
jac why-effect EFFECT --source FILE.jac [--output-format text|json-v1]
jac host worker --store DIR

jac host worker is the opt-in serial carrier for the experimental jacquard-host-v0 protocol: a trusted host process invokes one checked stored term and answers its typed root operations over length-prefixed JSON frames on stdin/stdout (docs/host-worker-v0.md). Ordinary commands never use it.

.jac is the source format people and agents write. .jqd is the lower-level format that .jac files reduce to — a small fixed grammar of 27 forms, called the kernel — and it remains fully supported as the internal/debug syntax, quote notation, and format of record. run, check, hash, fmt, diff, infer, and test select surface syntax by extension. Native build accepts either format without writing an intermediate twin; replay programs, the prelude, and many internal fixtures continue to use .jqd.

A multi-file program installs its model into a store once, and separate entry points run against it; nothing is concatenated. The commands below are executable documentation: dune runtest runs them in a fresh directory against the current toolchain, with jacquard on the PATH and the repository prelude selected.

printf 'type Tier = | Bronze | Gold\nrank(t) = match t { | Bronze -> 1 | Gold -> 2 }\n' > model.jac
printf 'rank(Gold)\n' > entry.jac
printf 'add(rank(Bronze), rank(Gold))\n' > other-entry.jac
jacquard store add model-store model.jac
jacquard run entry.jac --store model-store
jacquard run other-entry.jac --store model-store

Ordinary programs and demos need only a .jac source file. Do not hand-author a .jqd twin unless a conformance test specifically needs to prove that both formats lower to the same kernel and hash. The paired files retained in the corpus and selected demos are evidence fixtures, not an authoring requirement.

Native compilation

jacquard build accepts a public .jac program directly (or a retained kernel .jqd carrier) and compiles it and its reachable declarations to a standalone binary. Within the documented native subset, its output is byte-identical to jacquard run — stdout, stderr, and exit codes, pinned by a differential harness in CI (scripts/native-diff.sh). The effect-and-handler kernel compiles, including capturing and multi-shot handlers, and code values compile since task 73 — quotes, splices, and the structural code ops. Dynamic Eval, interpreted Task scheduling, and typed Channels stay on the interpreter tier.

export JACQUARD_PRELUDE=$PWD/prelude
export JACQUARD_RUNTIME=$PWD/runtime
jac build demos/tooling/word-count.jac -o word-count
echo "some words some" | ./word-count --allow console

Build uses the same surface parse/lower/resolution pipeline as check and hash and does not create a .jqd twin. Use jac export INPUT.jac -o OUTPUT.jqd only when conformance evidence or kernel debugging needs an explicit canonical carrier. Export is deterministic and exclusive/atomic; it preserves semantic member hashes and quote namespace markers, while intentionally erasing comments, formatting, spans, documentation, and provenance metadata. Export resolves and canonicalizes input but does not typecheck it; use jac check, jac run, or jac build when typechecking is required.

Requirements and knobs:

• Release binaries discover their packaged prelude and C runtime automatically. Source checkouts may set the two variables shown above.
• A C toolchain: clang (any recent) or gcc. Tail calls are O(1) stack on every toolchain: musttail on clang and gcc 15+, a trampoline below them (the emitted C is identical either way).
• The binary parses --allow EFFECT for its implemented root grants (console, clock, fs, dist, and infer), plus --seed N for the sampling grant. It rejects unsupported grants such as net, eval, and secret, and refuses --infer-cache and --dry-run (interpreter tooling) with pointed errors.
• JACQUARD_STACK_MB sizes the program stack (default 1024): deep non-tail recursion is real C recursion in this backend.
• Compiled units cache under .jacquard-native/, keyed by content, so an unchanged program relinks without recompiling.
• Measured performance lives in docs/benchmarks.md — nine scenarios with interpreter, native (both toolchains), Python, and hand-C columns — with the claim boundaries in docs/native-compilation.md (reproduce with scripts/native-bench.sh).

Demos

Start with these from the repo root after dune build @all. The same scripts also work in an installed bundle without opam or Dune:

opam exec -- sh demos/case-studies/stormglass/run.sh
opam exec -- sh demos/case-studies/release-risk/run.sh
opam exec -- sh demos/basics/m1.sh
opam exec -- sh demos/inference/m3.sh
opam exec -- sh demos/worlds/agent-dream.sh
opam exec -- sh demos/worlds/preflight.sh
opam exec -- sh demos/tooling/repair.sh
opam exec -- sh demos/concurrency/run.sh

What they show:

• case-studies/stormglass/: one checkout policy under simulated network and clock laws, exact incident forecasts, and Warp proofs over all 27 worlds.
• case-studies/release-risk/: one release policy under concrete and probabilistic telemetry, plus a Warp safety proof over all 18 worlds.
• basics/m1.sh: factorial, multi-shot choice, and gated eval.
• inference/m3.sh: one model under exact enumeration and likelihood weighting; same model hash, different inference handler.
• inference/clarifying-question.sh: an agent computes whether asking the user a question is worth the interruption (value of information).
• worlds/agent-dream.sh: one policy under scripted and probabilistic world handlers.
• worlds/preflight.sh: candidate agent plans scored under alternate worlds; the live policy still needs a Net grant after the dreams pass.
• inference/ambiguity-pipeline.sh: an extraction pipeline that keeps its uncertainty; the user's click becomes an observe.
• tooling/showcase-warp-tests.sh: Warp checks for the clarifying-question, dream-mode, and ambiguity demos.
• tooling/repair.sh: program repair as Bayesian inference; a bug report is an observation over computed single-edit patches, and the most likely patch prints as a one-line canonical-structure diff.
• concurrency/run.sh: one task program under FIFO, seeded, exhaustive, and strict replay scheduling, with exact child-authority signatures and eight replayable schedule worlds. This developer evidence demo requires a source checkout built with Dune.
• worlds/m4-hostile.sh: generated-looking code that reaches for net; signatures and manifests expose the authority.
• worlds/escrow/run.sh: product-shaped generated workflow with manifest, dry-run, Warp tests, fault exploration, replay, canonical diff, and approval by hash.

Demo paths are canonical within the categorized directories; there are no flat compatibility aliases. The full catalog is in demos/README.md.

All public demo outputs are pinned by cram tests (recorded command-line transcripts that fail on any drift), especially test/cli/demos.t, test/cli/hostile-demo.t, test/cli/escrow.t, test/cli/showcase.t, and test/cli/repair.t, test/cli/preflight.t, plus test/cli/case-studies.t for the larger applications.

Release Evidence

The current release evidence pack lives in docs/release/0.2/. Historical 0.1 evidence remains byte-preserved under docs/release/0.1/.

To reproduce the release evidence from this checkout:

JACQUARD_RELEASE_REF=HEAD JACQUARD_RELEASE_BASE=c0f570501b751865c0c0584d9b15be08b6ec1cde scripts/release/reproduce-0.2.sh

The script installs dependencies, builds, runs the full test suite, checks formatting, runs public demos, runs gauntlet tests, records jacquard --version, and writes generated evidence under .scratch/release/0.2/. It also checks the complete release-diff manifest, historical publications, parser-depth and GM.12B evidence, and native memory/differential/leak/fuzz lanes under both Clang and GCC.

Key release docs:

• docs/release/0.2/EVIDENCE.md: artifact, inventory, evidence lineage, and gate
• docs/release/0.2/CLAIMS.md: integrated claims with adjacent caveats
• docs/release/0.2/REPRO.md: fresh-clone reproduction and promotion steps
• docs/release/0.2/FREEZE.md: distribution and retained semantic identities
• docs/release/0.2/GAUNTLET.md: adversarial classes present and omitted
• docs/release/0.2/LIMITS.md: explicit non-goals and trusted boundaries
• docs/release/0.2/DECISION.md: RC1 and same-commit final decision
• docs/release/0.2/RELEASE-NOTES.md: public contents and install command
• docs/release/named-call-arguments/DECISION.md and EVIDENCE.md: post-0.2 direct named-call contract, hash-bound ABI, proving tests, and non-claims
• docs/release/structured-concurrency/EVIDENCE.md: successor C0-C2 publication claims plus the shipped interpreted C3 Channel runtime, exact counts, demo, and proving tests
• docs/release/structured-concurrency/LIMITS.md: structured-concurrency caveats and explicit C4 non-claims
• docs/release/governed-membranes/DECISION.md: bounded decision to advertise deterministic governance for the frozen typed Workspace v0 facade as an evidence-backed research reference implementation
• docs/release/governed-membranes/CLAIMS.md: D61-D73 claims mapped to exact executable evidence and adjacent negative boundaries
• docs/release/governed-membranes/LIMITS.md: trusted-host, authority, recovery, simulation, secret, Audit, and production-readiness limits

Repository Map

• .github/: CI, release evidence workflow, and PR template.
• AGENTS.md: operating notes for future coding agents.
• bin/: jacquard CLI entry point.
• corpus/: conformance corpus and golden outputs.
• demos/: runnable examples and product-shaped demos.
• docs/: design docs, tutorial, CI/CD, Warp, stdlib, errors, release evidence.
• prelude/: Jacquard standard library and effect declarations.
• scripts/release/: reproducible release evidence script.
• spec/: kernel AST, canonical serialization, and frozen host-protocol specs.
• src/: OCaml implementation.
• test/: Alcotest/QCheck suites plus cram CLI transcripts.
• jacquard.opam, dune-project: package and build metadata.

Implementation Map

• src/form.ml, src/meta.ml, src/span.ml: uniform triple and metadata.
• src/reader.ml, src/printer.ml: bootstrap .jqd notation and formatter.
• src/kernel.ml: validator and typed kernel AST.
• src/resolve.ml: names to content-addressed references.
• src/canon.ml, src/hash.ml: HASH_V0 canonical serialization and hashing.
• src/store.ml: object store and mutable name index.
• src/value.ml, src/eval.ml: CPS evaluator and mode-aware deep handlers.
• src/types.ml, src/check.ml: type/effect inference, rows, manifests, exhaustiveness.
• src/prelude.ml: prelude loader, builtin wiring, and root grants.
• src/infer_dist.ml: exact enumeration and likelihood weighting.
• src/diff.ml: canonical-structure diff over stores.
• src/warp.ml: Warp test discovery, running, cache, and properties.
• src/host_protocol_v0.ml: strict framing, JSON, limit-selection, shutdown, bounded first-order type/value codecs, invoke preflight, and serial session accounting for the experimental host protocol.
• src/host_worker.ml: the opt-in jac host worker process carrier that evaluates one preflighted invocation over stdin/stdout frames.

Documentation Map

Read these in order if you are new:

1. docs/README.md: documentation index and suggested reading paths.
2. docs/tutorial.md: runnable user-facing examples.
3. demos/README.md: demo catalog and what each demo proves.
4. docs/ci-cd.md: GitHub checks and release evidence process.
5. docs/release/0.2/EVIDENCE.md: current release evidence overview.

Deeper design references:

• docs/whitepaper.tex: historical initial design thesis, motivation, risks, and related work; its roadmap and implementation-status sections are outdated.
• docs/ast.md: implemented kernel AST contract and retained design reasoning.
• spec/jacquard-kernel-ast-m0.md: implemented kernel source-of-truth spec.
• spec/serialization.md: canonical byte format.
• docs/host-boundary.md: host/Core ownership and trust boundary.
• spec/host-protocol-v0.md: frozen experimental host envelopes, process framing, limits, failures, and conformance-vector contract. The library now validates one exact checked invocation—including its store closure, pinned interface, typed arguments, grants, and closed once-operation registry—but does not yet run it or expose a process worker.
• docs/stdlib.md: prelude and ringed standard library.
• docs/warp-testing.md: Warp testing model.
• docs/errors.md: diagnostic catalog.
• docs/development-plan.md: completed historical implementation plan.

Development Workflow

Before opening a PR:

eval "$(opam env)"
opam exec -- dune build @all
opam exec -- dune runtest
opam exec -- dune fmt
git diff --exit-code

When adding valid corpus files, regenerate golden hashes:

opam exec -- dune exec test/gen_goldens.exe

When touching release-facing demos, claims, CI, or semantics, also run:

JACQUARD_RELEASE_REF=HEAD JACQUARD_RELEASE_BASE=c0f570501b751865c0c0584d9b15be08b6ec1cde scripts/release/reproduce-0.2.sh

CI/CD

GitHub Actions separates independently retryable evidence:

• CI / Development gate: build, full tests, clean formatting, version smoke, and release-doc presence on PRs, main, and release/**.
• CI / Native parity (clang|gcc): runtime memory, differential, leak, and seeded fuzz evidence for both supported C compilers.
• Governance / Governance playground: lint, types, unit/accessibility tests, production build, and browser/keyboard/offline-network checks.
• GM12B / GM12B exhaustive forwarding evidence: the scoped 50,000-case forwarding proof, with a successful no-op result outside its dependency closure.
• Release Evidence / Reproduce 0.2 evidence: release branches, jacquard-core-* tags, and manual dispatch; runs scripts/release/reproduce-0.2.sh and uploads transcripts.
• Release Binaries: jacquard-core-* tags and manual dispatch; builds Linux/macOS tarballs with jacquard, jac, the prelude, demos, and native runtime sources.

See docs/ci-cd.md for branch protection recommendations.

License

Jacquard is licensed under the Apache License, Version 2.0. See LICENSE and NOTICE.

Your programs remain yours. Jacquard claims no copyright in source merely because it is written, checked, interpreted, or compiled with Jacquard. Native executables include Jacquard runtime material, so the runtime and generated-output exception explicitly allows user programs and compiled output to use any license their authors choose, including proprietary licenses. The exception also removes Apache License notice obligations that would otherwise arise solely from embedded Runtime Material in a compiled program. This is a statement of project licensing intent, not legal advice.

The Jacquard name and project identity are governed by TRADEMARKS.md. The code license does not grant trademark rights.

Current Limits

Jacquard core is a research prototype, not a production platform. The .jac surface is implemented and supported but remains an evolving v0 projection onto the permanent 27-form kernel. Native AOT compilation and C-toolchain optimization ship. parallel.map and parallel.both remain pure, sequential optimization hints. The interpreted runtime now supports opaque scoped Tasks, cooperative cancellation, fail-fast language scopes, an OCaml-only Collect policy seam, FIFO and seeded scheduling, versioned strict replay, bounded exhaustive schedule enumeration, and scoped typed channels with rendezvous and buffered FIFO behavior, close, cancellation, and exact run/scope ownership. It does not provide native root scheduling or native Channel execution, preemptive cancellation, finalizers, shared memory, channel select or timeouts, actors/supervision, host scheduling, or real asynchronous host I/O at this evidence base. A VM/JIT, continuous distributions, gradients, typed staging, language package management, self-hosting, and formal soundness proofs also do not ship. World grants remain coarse. See docs/release/0.2/LIMITS.md for the current integrated boundary, docs/release/0.1/LIMITS.md for the historical Core 0.1 boundary, and docs/release/structured-concurrency/LIMITS.md for the successor C0-C3 boundary. docs/host-boundary.md freezes the ownership and trust model, and spec/host-protocol-v0.md freezes the experimental language-neutral envelopes, process framing, limits, and schema/state vectors. jac host worker is the experimental serial carrier for that protocol, and spec/host-protocol-v0/kit/ is the executable conformance kit external adapters pin, with its evidence and limits in docs/release/host-boundary/; no stable ABI, adapter, or HTTP server ships in this repository. The deterministic Workspace v0 governance boundary is separately advertised as an evidence-backed research reference implementation, not as a sandbox or production security system; its exact claim and trusted-host limits are in docs/release/governed-membranes/DECISION.md and docs/release/governed-membranes/LIMITS.md.

Troubleshooting

• opam: command not found: install opam with asdf using .tool-versions, or install a compatible opam manually.
• Dune cannot find packages: run eval "$(opam env)" in this shell, then reinstall deps with opam install --deps-only . --with-test --with-dev-setup --with-doc -y.
• jacquard cannot find names from the prelude: set JACQUARD_PRELUDE=$PWD/prelude or run through Dune from the repo root.
• Formatting changed files: run opam exec -- dune fmt, inspect the diff, and commit the formatting changes if they are intended.
• Release reproduction writes generated evidence under .scratch/release/0.2/ by default. Set JACQUARD_RELEASE_OUT to use another disposable output path.