Known limitations — v0.5.0-beta.1

This list describes the Java stage-0 implementation, not every feature proposed by the historical design kit in docs/history/design-kit/.

• The compiler is written in Java and emits Java source before invoking javac. It does not compile itself and is not self-hosted.
• conform C to J is v1-scoped: Java interfaces only, a non-generic source class and target interface, no overloaded abstract methods and no method renaming or adapters. It declares a foreign JVM contract; it does not add inheritance or interfaces to the language. Generic methods witness by erasure; boxed Short/Byte/Character parameters are not expressible because of the existing interop adapters.
• Generics accept one or more parameters (generic K, V:) but are fully explicit: no inference, no variance, and partial type arguments are never guessed. A type parameter T has no operators, ordering or methods, and equality only under requires T: Equatable; Comparable and user-defined capabilities are not implemented (SPR-GENERIC-CONSTRAINT).
• Generic code is erased and boxed in generated Java (type parameters become Object). Boxing/unboxing is compiler-controlled, but generic values carry no JVM-level type information at runtime.
• Local/Git Sprig and Maven JVM dependencies are resolved by sprig resolve, sprig add and sprig remove. Schema-4 locks verify graph identity, manifests, owner-relative locators and JAR/POM SHA-256. Shared project classpaths work for check/build/run/api/doctor; only explicit dependency-resolution commands use Maven networking. Apache Resolver handles effective POMs and mediation. Missing/invalid POMs fail. Publishing/registry, authentication, Maven plugins and non-JAR runtime artifacts remain unsupported. See DEPENDENCIES.md.
• The small std/ slice covers UTF-8 filesystem/path, arguments/environment, text/time and a typed JSON model. The first-party sprig-http library adds a small synchronous JDK HTTP client; it does not provide an HTTP server, streaming, async requests or a stable package registry. The ecosystem remains intentionally small and experimental. LSP, debugger integration and incremental compilation are absent. The local VS Code preview offers lexical highlighting, CLI checks/run and Java viewing; see editors/vscode/README.md.
• JVM interop covers common imported classes, constructors, fields, method calls, overloads, and checked exceptions. Java arrays cross the boundary as opaque values (no source array syntax; varargs remain unsupported). Concrete generic arguments are preserved for explicit Type[Arg] application on imported classes and methods; wildcards, inference, recursive and intersection bounds, generic arrays and Short/Byte/Character generic arguments are rejected with structured reasons, class bounds are validated, raw evidence never promotes to concrete arguments, and raw boundaries stay erased. Collection conversion is explicit through @std/jvm.spr; there is no implicit Java/Sprig collection conversion. Type-use nullability annotations are not interpreted. Java reference results are conservatively nullable; Java reference parameters are conservatively non-null.
• Sprig throws and catch are implemented, but their relationship to Java exception classes and top-level execution remains provisional.
• Lambdas have single-expression bodies, support arities zero through three, and cannot declare a throws type. A lambda that calls a checked-throwing operation must handle that effect inside the lambda.
• Runtime numeric failures report SPR-RUNTIME-EXCEPTION with the nearest statement range for local and imported Int/Int32 checked arithmetic, plus data.origin="checked-arithmetic"; the span is the statement, not a sub-expression. JVM library operations do not inherit Sprig's checked integer arithmetic rules.
• Floating-point operations follow Java float/double behavior. The compiler does not promise cross-JVM bitwise identity for transcendental functions, numerical stability, physical units, or mathematically correct algorithms.
• Compiler classes use javac --release 17. Supported release platforms are Linux/macOS with JDK 17 and 26; Windows is an experimental, non-blocking preview; definitions are not execution evidence. The current release validation report records which exact source/archive gates ran. No production or architecture-wide portability guarantee is made.
• Portable local locks carry owner-relative locators and survive relocation of the whole workspace; absolute-path declarations are not portable and need resolve after the target moves. The lock does not attest source bytes or symlink targets. It also does not pin bundled @std bytes: @std comes from the installed SDK, whose published archive is checked separately through release checksums and extracted-archive smoke tests. Manifest semantic errors can point to line 1. Cache tree verification adds IO; OS locks have no timeout. Git submodules are unsupported. Offline Git builds require Git and a complete verified cache. Concurrent hostile mutation after validation is outside the cooperative cache model.
• sprig fmt is canonical and comment-preserving, without configuration or aggressive wrapping. See formatter for file safety and comment indentation policy. LSP integration remains future work.
• sprig test is a sequential project runner for ordinary .spr programs. It has a fixed 30-second runtime timeout and no parallel execution, watch mode, coverage, snapshots or test-function discovery. It requires a current lockfile and checks negative fixtures by diagnostic code, not message. See testing for its JSON and temporary directory contracts.
• tests/agent_eval provides deterministic fixtures and scoring only. No LLM run has been performed, and no model performance is claimed.
• The managed SDK installer/upgrader is supported only on Linux/macOS and targets public GitHub releases. Published SHA-256 assets detect archive mismatch but do not provide signed provenance. Older SDKs are retained. SQLite migrations record filenames without content digests; changing an applied migration is unsupported by convention, not automatically detected. Migration SQL is trusted project code.
• The stage-1 frontend is a subset probe, not a self-hosted compiler.
• Sprig targets v0.5.0-beta.1, an experimental Beta under Apache-2.0 (LICENSE, NOTICE), not a production stability or numerical correctness guarantee.

Callable boundary

Source function types now use fn(A) -> R, arities 0–3. Parameters and results are invariant. Callable types carry no recoverable throws effects: handle those inside named wrappers before placing them in a lambda. Arbitrary Java SAM interfaces are not converted. Only concrete Fn0..Fn3 generic signatures preserve callable types; raw, wildcard or unresolved type variables are rejected. Character/Short/Byte callable slots and arbitrary parameterized Java slots are unsupported because they would require additional erased-value adapters. Nullable callable values use (fn(A) -> R)?; fn(A) -> R? means nullable result.

Project discovery currently compares normalized source-root prefixes rather than canonicalizing alternate symlink spellings. On macOS an explicit absolute /var source while cwd discovers /private/var can be treated as standalone and lose package aliases. Use project-relative source paths from the project directory; this existing path-alias behavior was reproduced during the SDK web experiment.