---
phase: "08"
plan: "02"
subsystem: profiles
tags: [mcp-tools, profiles, resolver, merge-semantics]
dependency_graph:
  requires: ["08-01"]
  provides: ["screenshot_profile param in start_capture", "resolveScreenshotProfile function"]
  affects: ["src/server.ts", "src/profiles/profile-resolver.ts"]
tech_stack:
  added: []
  patterns: ["pure function resolver", "nullish coalescing merge", "camelCase-to-snake_case mapping"]
key_files:
  created:
    - src/profiles/profile-resolver.ts
    - src/profiles/profile-resolver.test.ts
  modified:
    - src/server.ts
decisions:
  - "Default target 'desktop' not treated as explicit override when profile is used"
  - "Profile resolver is a pure function with no I/O for testability"
metrics:
  duration: "2m 36s"
  completed: "2026-04-13T08:50:39Z"
  tasks_completed: 2
  tasks_total: 2
  test_count: 7
  test_pass: 7
---

# Phase 08 Plan 02: Profile Resolver & start_capture Integration Summary

Profile resolver wires screenshot profiles into start_capture with merge semantics -- profile provides base target config, inline params override via nullish coalescing (D-11).

## Completed Tasks

| # | Task | Commit | Key Files |
|---|------|--------|-----------|
| 1 | Profile resolver with merge semantics (TDD) | 86bae5b | src/profiles/profile-resolver.ts, src/profiles/profile-resolver.test.ts |
| 2 | Wire screenshot_profile param into start_capture | 9eff304 | src/server.ts |

## Key Implementation Details

- `resolveScreenshotProfile` is a pure function that maps camelCase profile fields (windowTitle, regionX, etc.) to snake_case start_capture params (window_title, region_x, etc.)
- Inline params override profile values via `??` (nullish coalescing) -- only undefined values fall through to profile
- When `screenshot_profile` is provided, `args.target === "desktop"` (the zod default) is treated as "not explicitly set" so the profile's target wins
- Missing profile returns structured error with `available_profiles` array listing all saved profile slugs (D-12)
- All validation and target factory logic in start_capture uses `resolvedArgs` instead of raw `args` for target-related fields
- Non-target fields (interval_ms, max_frames, jpeg_quality, etc.) continue from raw `args`

## Deviations from Plan

None -- plan executed exactly as written.

## Verification Results

1. `npx tsx --test src/profiles/profile-resolver.test.ts` -- 7/7 tests pass
2. `npx tsup src/index.ts --format esm --outDir dist --clean` -- build succeeds
3. `src/server.ts` contains `screenshot_profile` in start_capture schema
4. `src/server.ts` contains `resolvedArgs` usage pattern (38 occurrences)
5. `src/server.ts` contains `available_profiles` in error response

## Self-Check: PASSED