---
phase: 02-config-overlays
verified: 2026-02-09T21:05:00Z
status: passed
score: 8/8 must-haves verified
re_verification: false
---

# Phase 2: Config Overlays Verification Report

**Phase Goal:** Operator can manage dev/docker/production configs with a base file plus lightweight overlay files, selected by environment variable.
**Verified:** 2026-02-09T21:05:00Z
**Status:** passed
**Re-verification:** No — initial verification

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | Setting FLYNN_ENV=docker loads docker.yaml overlay merged on top of base config | ✓ VERIFIED | `loadConfigSafe` in shared.ts (L33-34) calls `resolveOverlayPath` then passes result to `loadConfig(path, overlayPath)`. `loadConfig` in loader.ts (L72-81) reads overlay, calls `deepMerge` before validation. Test "merges overlay on top of base config" (loader.test.ts L116-141) proves port override + base token retention. |
| 2 | Starting Flynn without FLYNN_ENV works exactly as before — zero breakage | ✓ VERIFIED | `resolveOverlayPath` returns `undefined` when FLYNN_ENV not set (shared.ts L23-24). `loadConfig` skips overlay when `overlayPath` is falsy (loader.ts L72). Test "loads base-only when no overlay provided" (loader.test.ts L143-162) proves backward compatibility. 13/13 loader tests pass. |
| 3 | Overlay values override base values at any nesting depth | ✓ VERIFIED | `deepMerge` recursively merges plain objects (loader.ts L42-61). Test "handles deeply nested objects (3+ levels)" (loader.test.ts L28-33) proves 3+ level override. |
| 4 | Overlay files do not need to repeat required base fields — merge before Zod validation | ✓ VERIFIED | Merge at loader.ts L76, then env expansion at L83, then `configSchema.parse` at L84. Overlay test uses partial YAML (only `server.port`) without telegram/models — passes validation. |
| 5 | Arrays in overlays replace base arrays (not concatenated) | ✓ VERIFIED | `deepMerge` explicitly checks `Array.isArray` and falls through to direct assignment (loader.ts L47,50,57). Test "overlay arrays replace base arrays" (loader.test.ts L13-16) proves `[1,2]` → `[3]`. |
| 6 | Running flynn doctor with FLYNN_ENV=staging (no staging.yaml) reports clear error identifying missing overlay | ✓ VERIFIED | `checkOverlayExists` in doctor.ts (L30-39) calls `resolveOverlayPath`, checks `existsSync`, returns fail with `FLYNN_ENV=${env} but ${overlayPath} not found`. Wired in `allChecks` array at position 2 (L218). |
| 7 | Running flynn doctor without FLYNN_ENV shows no overlay-related error | ✓ VERIFIED | `checkOverlayExists` returns `{ status: 'skip', label: 'Config overlay', detail: '(FLYNN_ENV not set)' }` when `resolveOverlayPath` returns undefined (doctor.ts L32-33). |
| 8 | Running flynn doctor with FLYNN_ENV=docker and docker.yaml present shows overlay check passing | ✓ VERIFIED | `checkOverlayExists` returns `{ status: 'pass', label: 'Config overlay', detail: '(${env}.yaml found)' }` when file exists (doctor.ts L36-37). |

**Score:** 8/8 truths verified

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `src/config/loader.ts` | deepMerge utility + overlay-aware loadConfig | ✓ VERIFIED | 86 lines. Exports `deepMerge` (L38) and `loadConfig` with optional `overlayPath` (L68). Merge before env expansion and Zod parse. |
| `src/config/loader.test.ts` | Tests for deep merge, overlay loading, backward compat, missing overlay | ✓ VERIFIED | 210 lines. 13 tests total: 6 deepMerge unit tests + 4 overlay integration tests + 3 original tests. All 13 pass. |
| `src/cli/shared.ts` | resolveOverlayPath + overlay-aware loadConfigSafe | ✓ VERIFIED | 81 lines. `resolveOverlayPath` (L22-27) maps FLYNN_ENV to sibling yaml. `loadConfigSafe` (L30-39) passes overlay to loadConfig. |
| `src/config/index.ts` | Re-exports deepMerge | ✓ VERIFIED | Line 1: `export { loadConfig, deepMerge } from './loader.js';` |
| `src/cli/doctor.ts` | checkOverlayExists doctor check | ✓ VERIFIED | `checkOverlayExists` (L30-39) with skip/pass/fail tristate. Positioned in `allChecks` after `checkConfigExists`, before `checkConfigParses` (L216-218). |

### Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `src/cli/shared.ts` | `src/config/loader.ts` | `loadConfigSafe` calls `loadConfig(path, overlayPath)` | ✓ WIRED | shared.ts L34: `const config = loadConfig(path, overlayPath);` |
| `src/config/loader.ts` | `src/config/loader.ts` | `loadConfig` calls `deepMerge` before `configSchema.parse` | ✓ WIRED | loader.ts L76: `rawConfig = deepMerge(...)` then L84: `configSchema.parse(expandedConfig)` |
| `src/cli/doctor.ts` | `src/cli/shared.ts` | imports `resolveOverlayPath` | ✓ WIRED | doctor.ts L3: `import { ..., resolveOverlayPath } from './shared.js';` L31: `resolveOverlayPath(ctx.configPath)` |
| `src/cli/start.ts` | `src/cli/shared.ts` | `loadConfigSafe` (overlay-aware) | ✓ WIRED | start.ts L2: `import { loadConfigSafe } from './shared.js';` L22: `loadConfigSafe(configPath)` — daemon gets merged config automatically |
| `src/config/index.ts` | `src/config/loader.ts` | Re-exports `deepMerge` | ✓ WIRED | index.ts L1: `export { loadConfig, deepMerge } from './loader.js';` |

### Requirements Coverage

| Requirement | Status | Details |
|-------------|--------|---------|
| CONF-01: User can set FLYNN_ENV to select config overlay | ✓ SATISFIED | `resolveOverlayPath` reads `process.env.FLYNN_ENV`, maps to `{configDir}/{env}.yaml`. All CLI entry points use `loadConfigSafe` which calls this. |
| CONF-02: Config loader merges env-specific overlay on top of base with deep merge | ✓ SATISFIED | `deepMerge` in loader.ts recursively merges objects. `loadConfig` applies overlay before env expansion and Zod validation. 10 tests prove behavior. |
| CONF-03: flynn doctor validates overlay file exists when FLYNN_ENV is set | ✓ SATISFIED | `checkOverlayExists` in doctor.ts checks file existence with clear error: `FLYNN_ENV=${env} but ${overlayPath} not found`. Skips when FLYNN_ENV not set. |

### Anti-Patterns Found

| File | Line | Pattern | Severity | Impact |
|------|------|---------|----------|--------|
| — | — | — | — | None found |

No TODOs, FIXMEs, placeholders, empty implementations, or console.log-only handlers found in any phase files.

### Human Verification Required

### 1. Overlay Loading End-to-End

**Test:** Create `~/.config/flynn/docker.yaml` with `server: { port: 9999 }`, run `FLYNN_ENV=docker flynn start`, verify port changes in daemon output.
**Expected:** Daemon starts on port 9999 instead of default, with all other config intact from base.
**Why human:** Requires running the actual daemon and observing startup behavior.

### 2. Doctor Missing Overlay Output

**Test:** Run `FLYNN_ENV=staging flynn doctor` without creating staging.yaml.
**Expected:** Output shows `[FAIL] Config overlay  FLYNN_ENV=staging but /path/to/staging.yaml not found`.
**Why human:** Verifying exact terminal output formatting and exit code.

### 3. Doctor No-Overlay Output

**Test:** Run `flynn doctor` without FLYNN_ENV set.
**Expected:** Output shows `[SKIP] Config overlay  (FLYNN_ENV not set)` — no errors, no noise.
**Why human:** Verifying visual output and that it doesn't confuse operators.

### Gaps Summary

No gaps found. All observable truths are verified with code evidence and passing tests. All artifacts exist, are substantive (not stubs), and are fully wired into the application. The three success criteria from the phase goal are all satisfied:

1. **FLYNN_ENV=docker loading** — `resolveOverlayPath` + `loadConfig(base, overlay)` + `deepMerge` before Zod validation. Tested.
2. **No FLYNN_ENV = same behavior** — `resolveOverlayPath` returns undefined, `loadConfig` skips overlay path. Tested.
3. **Doctor reports missing overlay** — `checkOverlayExists` with fail status and descriptive message. Wired in allChecks array.

TypeScript type checking passes clean. All 13 loader tests pass. No anti-patterns detected.

---

_Verified: 2026-02-09T21:05:00Z_
_Verifier: Claude (gsd-verifier)_
