# 2026-07-31 — how the cost-accounting survey was conducted

Trail for `research/CB-RES-0002-cost-accounting.md` (CB-WP-0002 T01).
Tier L, chaos d10 = 2 (no override).

## Method

No web sources. Every candidate was exercised locally against the
CB-WP-0001 session transcript
(`~/.claude/projects/-home-worsch-clay-borg/8cbd5701-….jsonl`, 5.1 MB,
2,040 lines) and the clay-borg git history. The survey's own rule —
measured beats cited — applied to itself, which is the only reason the
errors below were found.

## What was measured, in order

1. **Transcript shape.** Counted line types and collected the union of
   `usage` keys. Found 654 usage-bearing assistant lines, and four
   distinct `message.model` values where one was assumed.
2. **`usage.iterations`.** Suspected as a double-count source. Checked
   whether iteration outputs sum to the top-level `output_tokens`: they
   match in all 654 cases, and no message had >1 iteration. Cleared.
3. **`requestId` cardinality.** 346 distinct ids across 657 lines. This
   was the finding that overturned the workplan's numbers.
4. **Dedup validation.** For all 208 multi-line groups, compared the
   serialized `usage` object across the group: 208 identical, 0
   differing, 0 mixed-model. Block-type patterns confirmed the split is
   `thinking` / `text` / `tool_use`, i.e. a transcript-writer artifact.
5. **Re-priced three ways** (per-line all-Fable, per-line per-model,
   deduped per-model) to isolate how much of the error came from each
   mistake: $289.12 / $210.05 / $93.15.
6. **Hub API.** Called `get_token_summary` on CB-WP-0001's workplan.
   401,100 tokens over 7 events for 9 tasks, all filed under Fable 5.
   Compared against the transcript to quantify the gap (~8× on output).
7. **Status bar and billing API.** Checked `~/.claude/settings.json` for
   `statusLine` (absent) and for an admin key (absent). Both eliminated
   on availability before any further evaluation.
8. **Git boundaries.** Read `git log` with ISO timestamps to confirm
   commit density and that subjects name tasks. Noted the UTC/+02:00
   mismatch against transcript timestamps.
9. **Subagent tree.** Found `<session>/subagents/` while checking whether
   `isSidechain` was ever true (it never is). Priced the one subagent
   transcript: $0.66.

## Dead ends

- **`isSidechain` as the subagent signal.** It is present on every line
  and `false` on every line in this session; it does not mark subagent
  work in the main file because subagent work is not *in* the main file.
  Looking for a flag wasted a step that a directory listing answered.
- **`tool-results/` sidecar directory** (340 KB) was inspected as a
  possible cost source. It holds raw tool outputs for replay, carries no
  usage data, and is not billed separately. Not a candidate.

## The finding worth carrying forward

The workplan that exists to make cost measurable **opened with a
mismeasured cost**, off by ~2.7×, and its two errors were of different
kinds: a format artifact (double-counted lines) and a rule that existed
but was not applied (per-model pricing, already mandated by
`specs/MetricsAndScenarios.md` §1a).

The second is the more uncomfortable one. InnerLoop v1.0's answer to bad
numbers is the positive control, and a positive control would not have
caught either of these — both sums were over real data that really
existed. What caught them was **re-deriving a number instead of quoting
it**. That belongs in the loop as its own rule, and is raised for T07:
*a number inherited from a previous pass is re-derived before it is used
as a target, or it is cited as unverified.*

Reported into CB-WP-0003 T01's rule-enforceability audit as well: this is
a fifth error instance, and it is **not** of the harness-does-nothing
class that T10 predicted. The class is "trusted arithmetic over real
data".