feat: add --merge flag to combine JSON exports

[pasrom]

Summary

• Adds --merge CLI flag to combine multiple JSON exports into a single heatmap
• Enables merging usage data from different machines (e.g. work laptop + home desktop)
• Handles sparse JSON exports where daily entries only contain displayValue without full token breakdowns

Usage

# Export on each machine
slopmeter --claude -f json -o machine-a.json
slopmeter --claude -f json -o machine-b.json

# Merge into one heatmap
slopmeter --merge machine-a.json --merge machine-b.json -o combined.png

# Or merge to JSON for further processing
slopmeter --merge machine-a.json --merge machine-b.json -f json -o combined.json

Test plan

• Merge two JSON exports and verify tokens are correctly summed per day
• Merge exports with different providers (e.g. claude + opencode) and verify separate heatmaps render
• Merge sparse exports (only displayValue, no token fields) without errors
• Verify --merge with --dark, --format, and --output flags

---

Summary by cubic

Adds a new --merge flag to the slopmeter CLI to combine multiple JSON exports from different machines into one output. Merges per provider into a single heatmap or a merged JSON export.

• New Features
  • --merge <files...> reads JSON exports, groups by provider, and merges daily totals across files (sparse entries supported; missing token fields default to 0).
  • Supports PNG/SVG/JSON outputs and respects --dark, -f/--format, and -o/--output.
  • Validates inputs and errors when no provider data is found.

^{Written for commit 17a996c. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/cli/src/cli.ts">

<violation number="1" location="packages/cli/src/cli.ts:311">
P1: `--merge` is documented as single-flag variadic (`<files...>`), but `parseArgs` is configured in a way that rejects the second bare filename, causing documented usage to fail at parse time.</violation>

<violation number="2" location="packages/cli/src/cli.ts:356">
P2: Single-summary providers skip merge normalization/recomputation, causing inconsistent derived values versus providers that go through `mergeUsageSummaries`.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}