feat: Claude Code Monitor — lanes, pipelines and a merged workspace

Internal SmartGift build of a Claude Code monitoring dashboard. Lanes: a durable unit of parallel agent work, one per working directory, tracked across session restarts. Managed lanes are git worktrees the dashboard provisions and can reset or remove behind a three-check destroy guard and a counted preflight; adopted lanes are directories you already own and are never destroyable. Pipelines: a lane moves through pipeline stages. A stage the agent declares with evidence renders green; a stage inferred from the tool-event stream renders dashed amber and never counts as done. Detection is forward-only within a 30-minute window, and never writes the declared stage. Workspace: one page at /run with a lane grid, the selected lane's pipeline, and a full Claude console behind a disclosure.
2026-07-29 17:07:45 +07:00
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+---
+description: >
+  Break down Claude Code costs using the Agent Monitor pricing engine.
+  Shows per-model costs (input, output, cache_read, cache_write at $/Mtok rates),
+  per-session costs, daily trends, and compaction baseline token recovery.
+  Use when analyzing spending, comparing model costs, or planning budgets.
+---
+
+# Cost Breakdown
+
+Detailed cost analysis from the Agent Monitor's pricing engine.
+
+## Input
+
+The user provides: **$ARGUMENTS**
+
+This may be: "today", "this week", "last 30 days", a session ID, or "budget $50/week".
+
+## Data Sources
+
+| Endpoint | Returns |
+|----------|---------|
+| `GET /api/pricing` | `{ pricing: [{ model_pattern, display_name, input_per_mtok, output_per_mtok, cache_read_per_mtok, cache_write_per_mtok }] }` |
+| `GET /api/pricing/cost` | Total cost: `{ total_cost, breakdown: [{ model, input_tokens, output_tokens, cache_read_tokens, cache_write_tokens, cost, matched_rule }] }` |
+| `GET /api/pricing/cost/{sessionId}` | Per-session cost with same breakdown shape |
+| `GET /api/sessions?limit=200` | Sessions list — each includes inline `cost` field (bulk pricing) |
+| `GET /api/analytics` | Token totals (total_input, total_output, total_cache_read, total_cache_write — baselines pre-summed), daily trends |
+
+### How costs are calculated
+
+The pricing engine matches model names against `model_pattern` using SQL LIKE (e.g. `claude-sonnet-4-5%` matches `claude-sonnet-4-5-20250514`). **Longest pattern wins** for specificity. Cost per model:
+
+```
+cost = (input_tokens / 1M) × input_per_mtok
+     + (output_tokens / 1M) × output_per_mtok
+     + (cache_read_tokens / 1M) × cache_read_per_mtok
+     + (cache_write_tokens / 1M) × cache_write_per_mtok
+```
+
+Token counts are **effective totals** = `current + baseline` (baselines preserve pre-compaction tokens that would otherwise be lost when the transcript JSONL is rewritten).
+
+### Default pricing tiers (seeded on first run)
+
+| Family | Input $/Mtok | Output $/Mtok | Cache Read $/Mtok | Cache Write $/Mtok |
+|--------|-------------|--------------|-------------------|-------------------|
+| Opus 4.5/4.6 | $5 | $25 | $0.50 | $6.25 |
+| Sonnet 4/4.5/4.6 | $3 | $15 | $0.30 | $3.75 |
+| Haiku 4.5 | $1 | $5 | $0.10 | $1.25 |
+
+## Report Sections
+
+### 1. Cost by Model
+Table from `/api/pricing/cost` breakdown — each model with 4 token counts + cost. Highlight which pricing rule matched.
+
+### 2. Cost by Session (Top 10 Most Expensive)
+From sessions list with inline `cost` — sort descending. Show session name, model, duration, cost.
+
+### 3. Daily Cost Trend
+Cross-reference `daily_sessions` with per-session costs to compute daily spend. Show 7/30-day trend with direction arrows.
+
+### 4. Token Efficiency Analysis
+- **Cache hit rate**: `total_cache_read / (total_cache_read + total_input) × 100` — higher = more efficient
+- **Compaction baseline recovery**: Tokens preserved via baseline columns (tokens not lost to compaction)
+- **Output/input ratio**: Balanced ratio indicates good prompt efficiency
+
+### 5. Cost Optimization Opportunities
+- Sessions where cache_write >> cache_read (poor cache reuse)
+- Expensive models used for simple tasks (check subagent_type vs model)
+- Sessions with many compactions (context overflow = wasted tokens)
+
+## Output
+
+Structured Markdown with tables. Currency as USD to 4 decimal places. Include total and per-model subtotals.