2.0.0

Release Notes

See the migration guide
for required Rust changes, retrieval defaults, and cassette re-recording.

Breaking changes

• Rust EmbedRequest literals must include options; RerankRequest literals
  must include timeout_ms. Value and SemaError are neither Send nor
  Sync; send owned Rust data between threads.
• Synchronous evaluation from a running host callback is rejected, including
  evaluation of another interpreter on the same thread. Use async host
  functions or wait for the current call to settle before evaluating again.
• The implicit Voyage embedding model is voyage-3 (was voyage-3-lite).
  Existing indexes must keep their original model or be rebuilt. Together's
  default reranker is mixedbread-ai/mxbai-rerank-large-v2.
• Embedding cassettes use embed-v2 identities and must be re-recorded.
  Embedding inputs must be strings. Malformed options and retrieval responses
  now return errors instead of being silently coerced or partially discarded.

Added

• Public MCP embedding through sema::mcp::McpSession and McpWorker, with
  explicit presets, async host-function dispatch, typed errors, cancellation,
  bounded input/output, configurable server identity, and host callbacks.
  sema mcp --preset embedded --check lists the selected tools after loading
  their definitions. Built MCP binaries share the CLI's MCP argument parser.

• Shared embedding presets for OpenRouter, DeepInfra, Azure OpenAI, Cloudflare,
  Alibaba, and self-hosted TEI, including provider-specific option validation
  and batching. Native Ollama embeddings use /api/embed.

• Native Nomic hosted text embeddings with task selection, dimensionality,
  long-text options, endpoint overrides, and NOMIC_API_KEY detection. The
  public RerankDialect::Nomic variant remains available for existing custom
  hosts; the hosted preset supports embeddings only.

• Nomic schema-based mock tests and an opt-in live smoke test.

• Interpreter::register_async_fn: register async host functions through the
  public crate. The call runs as prepare (interpreter thread), run (Sema's
  process-wide Tokio pool) and finish (interpreter thread), suspends the calling
  Sema task while the future runs, and maps host errors, cancellation and
  worker failures to distinct, catchable errors. The stdlib async offload path
  now shares its cancel hook and assembler with the new sema_io::host_async
  module.

• Typed host functions: FromValue/IntoValue, register_fn_typed and
  register_async_fn_typed convert arguments and results, with arity and type
  errors that note the argument position.

• register_async_fn_cx: one closure with an AsyncCx that returns a value or
  cx.await_future(..), spawns tasks on Sema's pool with cx.spawn, and gets a
  CancellationToken tied to the calling task.

• ValueRef: a public, matchable view of values (ValueRef::slice(args)) with
  keyword names comparable to &str and MapRef over both map kinds.

Fixed

• Read rational components in complex literals, including 1/2+3i, 3/4i,
  and the reader's own printed arithmetic results.
• Keep embedding and reranking configuration separate from chat configuration.
  Validate complete responses and cassette replay, preserve input ordering and
  usage, and reject malformed vectors or reranking indices.
• Honor evaluation deadlines while a root is parked on an external wait.
  MCP handlers run through the cooperative runtime; output hooks are restored
  after dispatch, and later calls do not drive earlier detached tasks under
  their deadlines. Compilation borrows span tables and caches native names
  with invalidation on environment changes.
• Clear interrupted callback frames before reusing a VM, preserving captured
  values and allowing later MCP calls to run after a timeout or step limit.
• MCP file tools enforce sandbox capabilities and paths. Compile and disasm
  use session macros without retaining new compile-time bindings. Notebook
  creation preserves the host's LLM state. The CLI build hook runs in process
  and requires an unrestricted session; library adapters and built MCP
  binaries omit build unless the host installs a hook.

MCP compatibility

• Per-call timeout_ms can shorten a session limit. Zero retains the default;
  larger values are clamped. The CLI's --timeout-ms 0 disables its default.
• Hidden deftools and reserved MCP names cannot be called as user tools.
  Unknown or unavailable names in explicit tool filters are option errors.
• MCP protocol types are non-exhaustive; construct them with their methods and
  include a wildcard arm when matching ToolContent.
• MCP sessions bound input frames/source files to 16 MiB and output text to
  1 MiB by default. Collection results retain JSON text, with a depth limit of
  128. Rust hosts can configure the byte limits.

Install sema-lang 2.0.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/sema-lisp/sema/releases/download/v2.0.0/sema-lang-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/sema-lisp/sema/releases/download/v2.0.0/sema-lang-installer.ps1 | iex"

Install prebuilt binaries via Homebrew

brew install helgesverre/tap/sema-lang

Download sema-lang 2.0.0

File	Platform	Checksum
sema-lang-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
sema-lang-x86_64-apple-darwin.tar.xz	Intel macOS	checksum
sema-lang-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
sema-lang-aarch64-unknown-linux-gnu.tar.xz	ARM64 Linux	checksum
sema-lang-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

Verifying GitHub Artifact Attestations

The artifacts in this release have attestations generated with GitHub Artifact Attestations. These can be verified by using the GitHub CLI:

gh attestation verify <file-path of downloaded artifact> --repo sema-lisp/sema

You can also download the attestation from GitHub and verify against that directly:

gh attestation verify <file-path of downloaded artifact> --bundle <file-path of downloaded attestation>