my-pi/pi-permission-system/docs/retro/0127-extract-session-logger.md

issue, issue_title

issue	issue_title
127	refactor: extract SessionLogger interface to unify logging + notification

Retro: #127 — extract SessionLogger interface

Final Retrospective (2026-05-08T01:10:00Z)

Session summary

Extracted three separate HandlerDeps logging/notification fields (writeDebugLog, writeReviewLog, notifyWarning) into a SessionLogger interface with debug/review/warn methods. Created src/session-logger.ts with the interface and createSessionLogger() factory, updated all handler source files and 6 test makeDeps() factories. Shipped as v5.8.0 with zero behavioral change. 7 new unit tests; total suite 1252 tests across 56 files.

Observations

What went well

• Three-phase pipeline completed cleanly. Plan → TDD (4 cycles) → ship in one session with no user corrections needed.
• Plan-to-code translation was nearly 1:1. The SessionLogger interface, createSessionLogger() factory, HandlerDeps change, and handler migration all matched the plan exactly. The mechanical find-and-replace nature of the change made the TDD steps predictable.
• Test factory updates were trivially correct. Replacing 3 fields with 1 nested object (logger: { debug: vi.fn(), review: vi.fn(), warn: vi.fn() }) worked identically across all 6 files.

What caused friction (agent side)

• wrong-abstraction — Plan listed src/handlers/gates/runner.ts as needing deps.writeReviewLog → deps.logger.review changes, but runner.ts uses GateRunnerDeps (a separate interface explicitly scoped as a non-goal), not HandlerDeps. The plan confused the parameter name deps (which appears in both runGateCheck and handler functions) with the HandlerDeps type. Self-identified during step 2 by reading the import at the top of runner.ts before editing. Impact: added friction but no rework — no incorrect edit was made.

• missing-context — Multi-block edit on src/handlers/types.ts accidentally introduced a /** @deprecated Use logger.warn instead. */ comment above logResolvedConfigPaths(). The third edit block was intended to remove notifyWarning and its JSDoc, but the replacement text included a stray deprecation annotation that attached to the wrong field. Self-identified by re-reading the file immediately after the edit. Impact: one follow-up edit to remove the stray comment, ~30 seconds of rework, no incorrect commit landed.

What caused friction (user side)

• None observed.

Changes made

1. Created docs/retro/0127-extract-session-logger.md (this file).