fix(shared): token counts never read 1000K

[ValeraZSD]

Token counts near a unit boundary rounded into the wrong suffix: 999,600 displayed as 1000K. The shared formatter now chooses a unit after displayed rounding, producing 1M, and handles the K/M/B/T boundaries consistently.

Preserves @ValeraZSD’s fix from #15599. The takeover merges main into the contributor branch to resolve its conflict, retains the small formatter algorithm after independent implementation review, and consolidates nine token test cases into three behavior tests.

Verification at 2e24daea4d against main 34c5a6d446:

• Formatter suite: 18 tests before takeover → 12 after, all passing. Using main’s production file with the takeover tests produces two failures and ten passes; restoring the fix produces 12 passes.
• Formatter and work-log presentation suites: 115 passed. Shared-package typecheck, targeted lint, formatting and git diff --check passed; no repository-wide checks.
• Two full-diff adversarial review rounds by Claude Opus 5.5 and Codex GPT-6-Sol found no remaining code blockers. After the first push, CodeRabbit identified the negative half-thousand threshold; a fresh test pass added one assertion to the existing sign test (11 passed / one failed before the fix), and a fresh implementation pass corrected the magnitude threshold. Both reviewers accepted the fix. Opus additionally passed 497 formatter/work-log tests in the second round.
• Real web Usage page in T3’s Browser panel, isolated worktree state and synthetic 999,600-token usage: main displays 1000K; head displays 1M in the total, provider, token-type and model rows. Captures use matching 1280×800 viewport, data and fixture font. No provider turn or real usage data was used. The same 1M state was rechecked after the signed-threshold follow-up.
• Shared callers include web, desktop, mobile and compaction presentation. Native macOS, Windows, Electron desktop, iOS and Android were not exercised; the compaction row was covered through its presentation suite.

Before/after verification log. Current-head CI is tracked separately; this batch will not merge.

Before (main):

After (head):

Model and harness: tests by Codex GPT-6-Astra (high), implementation by Codex GPT-6.1-Sol (high), reviews by Claude Opus 5.5 and Codex GPT-6-Sol, through T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at 209fe2b

Macroscope's review found this PR approvable — This focused bug fix changes only token-count presentation at unit boundaries and adds targeted coverage for those cases. It has no schema, default, deployment, security, or static-analysis implications.

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[coderabbitai]

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Reviewing files that changed from the base of the PR and between 886bcff and 2e24dae.

📒 Files selected for processing: 2

• packages/shared/src/usageFormat.test.ts
• packages/shared/src/usageFormat.ts

🚧 Files skipped from review as they are similar to previous changes: 2

• packages/shared/src/usageFormat.test.ts
• packages/shared/src/usageFormat.ts

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📝 Walkthrough

formatTokens updates how it selects K, M, B, and T units and formats rounded values. Tests cover rollover boundaries, values below rollover, negative values, and NaN.

Changes: Token formatting

Layer / File(s)	Summary
Format tokens and validate output packages/shared/src/usageFormat.ts, packages/shared/src/usageFormat.test.ts	formatTokens checks scaled values against 1,000 when selecting K, M, and B units, then falls back to T. It formats rounded values below 1,000 and NaN as integers. Tests cover rollover boundaries, ordinary counts, negative values, and NaN.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: t3dotgg

Merge Risk: ⚪ Minimal · up to 2e24d

The change makes token counts roll over to the next unit after rounding, so 999,600 reads 1M instead of 1000K. The change is small and covered by tests, and no merge-blocking risk is apparent.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title is concise, uses the repository's conventional format, and clearly identifies the shared token-formatting fix.
Description check		The description clearly explains the problem, implementation, scope, verification results, limitations, and model or harness details. It omits the template's section headings, but the required informa…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description clearly explains the problem, implementation, scope, verification results, limitations, and model or harness details. It omits the template's section headings, but the required information is otherwise substantially complete.

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[maria-rcks]

Note

Written by claude-opus-5-5 on behalf of Maria

Hi! We are cleaning up open PRs, and this one does not say which model or harness was used to create it. If this change is really important, we recommend rebuilding the PR with a newer model and noting the model and harness in the PR description.

[maria-rcks]

Note

Written by claude-opus-5-5 on behalf of Maria

Reopening, this was closed by mistake. Sorry for the noise!

[juliusmarminge]

Taking over this one as maintainer for batch usage-billing-01. I will preserve the token-boundary fix, merge main to resolve the conflict, and independently review the minimal tests and implementation before pushing follow-up commits. No merge is planned.

[coderabbitai]

Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @packages/shared/src/usageFormat.ts:
- Line 31: Update the integer-boundary check in formatTokens to use the rounded
magnitude of value, so negative and positive inputs roll over at the same
threshold; keep formatting the rounded signed value when it remains below that
boundary.

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Reviewing files that changed from the base of the PR and between 209fe2b and 886bcff.

📒 Files selected for processing: 2

• packages/shared/src/usageFormat.test.ts
• packages/shared/src/usageFormat.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 3 remain after this review.