Ecko v2.4.0: Diff-scoped checking, session patterns, contextual hints

v2.4.0

Diff-scoped checking, session pattern detection, contextual echo hints.

New features

• Diff-scoped checking -- PostToolUse mode now only reports echoes on lines the agent actually changed. Edit tool diffs are computed from the old_string/new_string in the hook input JSON. Write tool treats all content as agent-written. Pre-existing code patterns are silently baselined. Stop mode continues full-file checks for comprehensive coverage.

• Session pattern detection -- When the same check fires on 3+ distinct files in a session, ecko emits a behavioral directive: ~~ ecko ~~ pattern: 'bare-except' flagged in 3 files this session -- use explicit exception types. Configurable via pattern_threshold (default 3, 0 to disable). Uses existing session ledger data.

• Contextual echo hints -- Echo messages now include file-type-aware suggestions. Unused imports in __init__.py get re-export hints. Test files get fixture hints. Each check has a tailored explanation. Hints appear in both compact text output (check (L1, L2) -- hint) and JSON output.

Config changes

• New field: pattern_threshold (default: 3) -- number of distinct files before session pattern directive fires. Set to 0 to disable.

Tests

• 376 Rust unit tests (~1s) + 72 validation fixtures.

Full Changelog: v2.3.0...v2.4.0