v1.13.10: per-tool token cost accounting (rolling 100-call view)

Surfaces per-tool prompt/completion-token rolling averages in
AgentPicker for at-a-glance agent-cost hints. Implementation is a
SQL view on top of messages_with_parts plus a read endpoint and
AgentPicker tooltip extension. No new write site; all source data
already lands via the existing tool-phase.ts:94-95 / error-handler.ts:
109-110 / sentinel-summaries.ts UPDATEs that v1.13.7's includeUsage:
true fix made non-NULL.

(1) schema.sql — new tool_cost_stats view. Window-functions over
messages_with_parts.tool_calls with LATERAL jsonb_array_elements.
Attribution: equal split — multi-tool turn divides tokens N-ways;
the 100-call rolling mean absorbs split noise. Filters: status=
'complete' + metadata.kind NOT IN ('cap_hit','doom_loop') exclude
failed turns and sentinels respectively; tool_calls IS NOT NULL is
defense-in-depth since sentinels are role='system' rows. CREATE OR
REPLACE means schema apply is idempotent.

(2) routes/tools.ts NEW + index.ts wire-in. GET /api/tools/cost_stats
returns { stats: ToolCostStat[] } with mean_prompt_tokens / mean_
completion_tokens computed at read time (sum / n_calls). Sorted by
tool_name ASC. No pagination — ≤30 tools.

(3) __tests__/tool_cost_stats.test.ts NEW — 7 integration tests
keyed off DATABASE_URL env var. Tests skip gracefully when unset
(no-DB default). beforeAll applies the schema via sql.unsafe(read
FileSync(schema.sql)) for self-contained runs. Helper insertAssistant
Turn shared across cases. Covers: empty state, single-tool attribution,
multi-tool equal split, 100-call FIFO window, NULL-tokens exclusion,
parts-authoritative read via messages_with_parts, failed/sentinel
exclusion.

(4) web/api/types.ts + client.ts — ToolCostStat interface + api.tools.
costStats() method binding.

(5) AgentPicker.tsx — fetch costStats on mount, compute per-agent
sum-of-means across whitelisted tools, render muted cost line below
description: "~5.2k prompt / 280 completion · 6/8 tools · last call
3h ago". Skips line entirely when no tool history; preserves existing
native title= for layout backward-compat. formatK/formatAgo colocated.

Tests: 202/202 pass (195 prior + 7 new view-integration). Server +
web tsc clean.

Smoke: schema applied cleanly; GET /api/tools/cost_stats returns
canonical JSON; view + endpoint agree. Single-row result expected
given the v1.13.1-A → v1.13.7 NULL latent regression window; new
traffic populates organically.

Roadmap row at boocode_roadmap.md:114 plus schema row at :474 both
match. View vs table decision documented in handoff_v1.13.10_per_
tool_cost.md (rollback-safe, microsecond-fast at BooCode scale).

~270 LoC across 8 files (5 modified + 3 new).

apps/web/src/api/client.ts

@@ -12,6 +12,7 @@ import type {
   GitMeta,
   Skill,
   AskUserAnswer,
+  ToolCostStat,
 } from './types';
 
 export class ApiError extends Error {
@@ -262,6 +263,14 @@ export const api = {
     list: () => request<{ skills: Skill[] }>('/api/skills'),
   },
 
+  // v1.13.10: per-tool cost rolling-window stats (last 100 calls per tool,
+  // equal-split attribution across multi-tool turns). Read endpoint backed by
+  // the tool_cost_stats view. AgentPicker consumes this for per-agent cost
+  // hints.
+  tools: {
+    costStats: () => request<{ stats: ToolCostStat[] }>('/api/tools/cost_stats'),
+  },
+
   settings: {
     get: () => request<Record<string, unknown>>('/api/settings'),
     patch: (body: Record<string, unknown>) =>

apps/web/src/api/types.ts

@@ -1,6 +1,18 @@
 export const PROJECT_STATUSES = ['open', 'archived'] as const;
 export type ProjectStatus = typeof PROJECT_STATUSES[number];
 
+// v1.13.10: per-tool cost rolling-window stat. Returned by
+// GET /api/tools/cost_stats — one entry per tool with mean prompt/completion
+// tokens over the last 100 invocations. AgentPicker sums across an agent's
+// whitelisted tools for per-agent cost hints.
+export interface ToolCostStat {
+  tool_name: string;
+  mean_prompt_tokens: number;
+  mean_completion_tokens: number;
+  n_calls: number;
+  updated_at: string;
+}
+
 export interface Project {
   id: string;
   name: string;