The REPL now wraps rustyline::Editor instead of maintaining a custom raw-mode
input stack. This preserves the existing LineEditor surface while delegating
history, completion, and interactive editing to a maintained library. The CLI
argument parser and /model command path also normalize shorthand model names to
our current canonical Anthropic identifiers.
Constraint: User requested rustyline 15 specifically for the CLI editor rewrite
Constraint: Existing LineEditor constructor and read_line API had to remain stable
Rejected: Keep extending the crossterm-based editor | custom key handling and history logic were redundant with rustyline
Rejected: Resolve aliases only for --model flags | /model would still diverge from CLI startup behavior
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep model alias normalization centralized in main.rs so CLI flag parsing and /model stay in sync
Tested: cargo check --workspace
Tested: cargo test --workspace
Tested: cargo build --workspace
Tested: cargo clippy --workspace --all-targets -- -D warnings
Not-tested: Interactive manual terminal validation of Shift+Enter behavior across terminal emulators
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