# Codec Text Boundaries Review

Date: 2026-06-10
Issue: #56
Branch: `feat/issue-56-codec-helper-boundaries`

## Scope

Define and implement the minimal binary/text helper boundary for
`bluetape-rs-codec`:

- UTF-8 text to owned bytes before binary encoders
- decoded bytes to UTF-8 text with typed non-lossy errors
- explicitly named lossy UTF-8 replacement helper
- README/Rustdoc non-goals for compression, serialization, broad text utility,
  encryption, signing, checksums, random strings, and database bind encoding

## 7-Tier Review

| Tier | Verdict | Evidence |
|---|---|---|
| 1. Public API / Contract | PASS | `encode_utf8_text`, `decode_utf8_text`, and `decode_utf8_text_lossy` expose only UTF-8 text/byte boundary behavior. Non-lossy decode returns `Result<String, TextDecodeError>`. |
| 2. Architecture / Boundary | PASS | The change stays inside `crates/codec` and README/review docs. General string utilities, normalization, compression, serialization, encryption, signing, checksums, random strings, and database bind encoding remain out of scope. |
| 3. Rust API Shape | PASS | APIs use owned `Vec<u8>` / `String` outputs, `impl AsRef` or `impl Into<Vec<u8>>` inputs, `#[must_use]` on pure conversions, and a non-exhaustive public error enum. |
| 4. Tests | PASS | Public API tests live under `crates/codec/tests/text.rs` and cover empty/non-ASCII text encoding, post-Base64 decode text conversion, invalid UTF-8 rejection, incomplete UTF-8 diagnostics, explicit lossy replacement, and error formatting. |
| 5. Static / Docs | PASS | Rustdoc examples compile. README.md, README.ko.md, and `crates/codec/README.md` document UTF-8 and lossy/non-lossy behavior. |
| 6. Release / Cargo | PASS | No Cargo metadata or dependency changes. No broad utility-bag module was introduced. |
| 7. Evidence Integrity | PASS | Codegraph review context reported low risk, 7 source/doc changed files, 0 impacted nodes, and 0 test gaps against `origin/develop`; `git diff --cached --name-only` includes the added integration test file. Local validation ran after correcting the Base64 UTF-8 example vector. |

## P0/P1 Gate

P0=0 P1=0

No P2/P3 follow-up is required for #56.

Native subagent spawn was not used in this run because the available subagent
tool is constrained to explicit user-requested delegation. The review gate was
completed locally with code-review-graph context and full workspace validation.

## Validation

- `cargo test -p bluetape-rs-codec --all-features --locked`: PASS, 41 unit tests + 6 integration tests + 18 doctests
- `git diff --check`: PASS
- `cargo fmt --all --check`: PASS
- `cargo test --workspace --all-features --locked`: PASS
- `cargo clippy --workspace --all-targets --all-features --locked -- -D warnings`: PASS
- `RUSTDOCFLAGS="-D warnings" cargo doc --workspace --all-features --no-deps --locked`: PASS
