Gives AI coding agents project context: layout, build commands,
conventions (100% coverage, nightly edition 2024, clippy -D warnings),
CI pipeline, and KDL mapping rules.

Assisted-by: Claude Opus 4.6 via pi

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+# AGENTS.md
+
+## Project
+
+serde-kdl2 is a Serde integration crate for KDL v2 (KDL Document Language).
+It provides `Serialize` and `Deserialize` implementations that map Rust types
+to and from KDL documents, built on the `kdl` crate v6.5.
+
+## Repository Layout
+
+- `src/lib.rs` — public API, re-exports, module-level docs
+- `src/ser.rs` — serializer: Rust types → KdlDocument
+- `src/de.rs` — deserializer: KdlDocument → Rust types
+- `src/error.rs` — error enum with `thiserror` derives
+- `tests/integration.rs` — integration tests covering mapping rules
+- `tests/property.rs` — proptest-based property tests
+- `justfile` — task runner (`just all` runs fmt, clippy, coverage)
+
+## Build and Test
+
+Requires Rust nightly (edition 2024).
+
+```sh
+just all        # fmt + clippy + coverage (enforces 100%)
+just clippy     # clippy with -D warnings
+just coverage   # instrumented test run, grcov report, fails below 100%
+cargo test      # plain test run without coverage
+```
+
+## Conventions
+
+- Rust edition 2024 (nightly toolchain)
+- 100% line coverage required; CI fails otherwise
+- `cargo clippy -- -D warnings` must pass with no warnings
+- `cargo fmt` enforced in CI
+- Use `thiserror` for error types
+- Public items have doc comments
+- Integration tests live in `tests/`, not inline
+
+## CI
+
+GitHub Actions runs on push to main and on PRs:
+
+1. `cargo fmt --check`
+2. `just clippy coverage`
+
+Release workflow tags calver versions on successful CI runs against main.
+Crates.io publishing is configured but currently commented out.
+
+## Mapping Rules
+
+The serializer and deserializer follow these conventions for converting between
+Rust types and KDL nodes:
+
+- Struct fields become nodes; the field name is the node name, the value is the
+  first argument.
+- Nested structs use children blocks.
+- Vec of primitives becomes multiple arguments on one node.
+- Vec of structs becomes repeated nodes with the same name.
+- The `-` (dash) children convention is supported for deserialization.
+- `Option::None` omits the node; `#null` also deserializes as `None`.
+- Unit enum variants serialize as strings; newtype, tuple, and struct variants
+  use child nodes named after the variant.
+- Maps serialize identically to structs.
+
+These rules are documented in `README.md` and `src/lib.rs`. Keep all three
+locations consistent when changing mapping behavior.
+
+## Version Control
+
+Use jj (Jujutsu), not git.