`ecc-metrics-bridge.js#readSessionCost` summed the
`estimated_cost_usd`, `input_tokens`, and `output_tokens` of
every matching row in `~/.claude/metrics/costs.jsonl`. That breaks
the documented contract of `scripts/hooks/cost-tracker.js`, which
explicitly states (in its module docblock):
Cumulative behavior: Stop fires per assistant response, not
per session. Each row therefore represents the cumulative
session total up to that point. To get per-session cost, take
the last row per session_id.
Summing N cumulative rows over-counts by roughly (N+1)/2 ×. For a
session with 3 rows at 0.01, 0.02, 0.03 USD (true running total
0.03), the bridge today reports 0.06 USD. The over-counted value
feeds `ecc-context-monitor.js`, which then trips its
COST_NOTICE_USD / COST_WARNING_USD / COST_CRITICAL_USD thresholds
on phantom spend AND injects the inflated number as
`additionalContext` into the live model turn — so the agent
itself is told a wrong cost.
Reproduced on `main` before this commit:
$ cat > /tmp/eccc/.claude/metrics/costs.jsonl <<EOF
{"session_id":"S1","estimated_cost_usd":0.01,"input_tokens":333,"output_tokens":166}
{"session_id":"S1","estimated_cost_usd":0.02,"input_tokens":666,"output_tokens":333}
{"session_id":"S1","estimated_cost_usd":0.03,"input_tokens":1000,"output_tokens":500}
EOF
$ HOME=/tmp/eccc node -e 'const m = require("./scripts/hooks/ecc-metrics-bridge.js"); \
console.log(JSON.stringify(m.readSessionCost("S1")))'
{"totalCost":0.06,"totalIn":1999,"totalOut":999}
Expected: `{"totalCost":0.03,"totalIn":1000,"totalOut":500}` (the
last cumulative row).
Actual: 2× over-count.
Fix: replace `+=` with `=` in the matching branch so the assigned
values reflect the most recent row encountered. The iteration
order is file order, which is also event time order, so the last
assignment wins — exactly the contract cost-tracker writes
against.
After this commit the reproduction above returns
`{"totalCost":0.03,"totalIn":1000,"totalOut":500}`.
Regression test in `tests/hooks/ecc-metrics-bridge.test.js`:
`readSessionCost returns the LAST cumulative row, not the sum
(cost-tracker contract)`. The existing
`readSessionCost does not include unrelated default-session rows`
test happened to pass even with the bug because it only had one
target-session row — single-row sessions are coincidentally
correct under both formulas. The new test uses three rows so the
two formulas diverge.
A second issue in the same function — the 8 KiB tail-only read
silently drops older rows once a session's recent cumulative
totals scroll past that window — is fixed in the next commit.
Adds docs/th/README.md with a concise onboarding-style Thai
translation mirroring the docs/vi-VN format. Updates the language
switchers in the English, Simplified Chinese, Traditional Chinese,
Japanese, Korean, Portuguese (BR), Russian, Turkish, Vietnamese,
and Simplified Chinese docs READMEs to link to the new Thai page.
The English README remains the canonical source of truth; the Thai
page links back to it for full content.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>