NMSh Native Suggestions v2 #138

Goal

Upgrade the current history-prefix ghost text into a modern predictive engine, using ideas validated by tools such as Deja, zsh-autosuggestions and Atuin.

Target features

• Fuzzy matching (in-order subsequence with sensible spread limits)
• Frecency
• Directory / project affinity
• Previous-command sequence prediction
• Ranked alternatives
• Accept full suggestion
• Accept next word
• Optional empty-prompt prediction (setting)
• Suggestion suppression/dismissal
• Privacy / history-ignore behavior (leading space, HISTORY_IGNORE)
• Local-only storage
• Low-latency per-keystroke results

UX / product direction

• Exact scoring weights are not prescribed. Tune with benchmarks on realistic histories (for example 10k, 100k and 500k entries).
• Failed commands are de-prioritized, not hidden.

Architectural constraints

• Uses Rich history search and metadata #143 metadata (cwd, exit, session, time) when available and falls back to plain zsh history.
• Scoring must be able to move into a persistent process or cache later (for example the Live sessions: local session service owning PTY and zsh #127 service or a worker) if profiling warrants it. TypeScript first (Performance strategy: TypeScript first, native helpers only when measured #155).

Acceptance criteria

• All target features implemented behind the Suggestion providers and predictive ghost text #137 interface.
• A benchmark fixture measures query latency on large histories, and the budget is met without blocking keystrokes.
• Ranking tests cover fuzzy, frecency, directory and sequence cases.
• Ignored commands are never suggested or learned.

Dependencies / related

Part of #137. Related #75, #143, #155.

Research references

• Deja: https://github.com/Giammarco-Ferranti/deja (fuzzy, frecency with decay, directory affinity, sequence prediction)
• zsh-autosuggestions match_prev_cmd: https://github.com/zsh-users/zsh-autosuggestions
• Atuin: https://github.com/atuinsh/atuin
• McFly: https://github.com/cantino/mcfly (ranking ideas only)