feat(web): show thread API cost in composer - #9136

What Changed

The chat composer now shows the estimated API cost attributed to the current thread, with cache-write, cache-read, and fresh-token components. Attribution follows current and historical provider sessions and dedicated worktrees, and the client asks for a filtered breakdown only when the server advertises that capability.

Why

The Usage page can explain aggregate spend, but it does not answer the question while a conversation is open. This indicator makes the thread's accumulated cost available in context without fully parsing every unrelated Codex transcript: cold reads inspect bounded identity metadata and parse matching candidates, while a compatible warm summary reuses its immutable records.

Stack and Review Scope

This PR is cumulative and lands after #9019. Review the composer-cost increment; #9308 includes it.

Verification

Current candidate 089236fb8c2e6910d082bf726b3e30636925c8e0 includes upstream main 39802c06117fae0b3da43624b0d54309c5437c72. The upstream import integration preserves usage resume-cursor history and atomic imported-transcript recording, including insert-conflict options. Focused provider-directory, UsageService and composer-cost tests passed (46 tests); server package typecheck and changed-file lint passed. Two history fixtures were updated to include the required provider instance, and repository failure doubles now implement the import method.

A fresh direct claude --model claude-opus-5 --effort high --permission-mode plan --tools Read,Grep,Glob --print … review attempt exited 1 because the OAuth session expired; no Claude review occurred for this merge. Earlier evidence below retains its original revision and scope.

Candidate: 089236fb8c2e6910d082bf726b3e30636925c8e0, including upstream main 82c2b7ffb4d450572f5baf9a70693f1e25cfdfed.

• The full focused contribution check at ba873b8 passed 127 tests across 8 files, plus the affected package typechecks.
• The final 82c2b7f delta removes an unused pricing helper: 11 pricing tests, server typecheck, Knip and git diff --check passed on the pre-repair main composition. The chart/runtime contribution was unchanged by that final delta.
• The chart merge preserves upstream's live column builder and this PR's daily/hourly and range behavior. Fresh independent source review of the shared resolution found no actionable issues.

vp test run apps/server/src/provider/Layers/ProviderSessionDirectory.test.ts apps/server/src/usage/UsageService.test.ts apps/server/src/usage/usageScanCache.test.ts apps/server/src/usage/usageThreads.test.ts apps/server/src/usage/usageTranscriptReader.test.ts apps/web/src/components/chat/ThreadCostIndicator.test.tsx apps/web/src/state/threadCost.test.ts apps/web/src/components/usage/UsageProviderChart.test.ts
vp run --filter t3 typecheck
vp run --filter @t3tools/web typecheck
vp run --filter @t3tools/contracts typecheck
vp test run apps/server/src/usage/usagePricing.test.ts
vp run --filter t3 typecheck

Refresh correctness checks

The refresh repair passed the focused UsageService suite (26 tests), 3 chart-gesture regression tests, and 8 web usage-state tests. After the final thread-cache guard, 2 affected service tests were rerun and passed; the earlier full-suite count is not presented as a new full-suite run. The final targeted-refresh correction passed 4 affected tests, proving fresh selected-thread costs without parsing unrelated transcript bodies. The optional thread-refresh contract passed 2 schema tests and the contracts package typecheck. The standalone composer-cost hook passed 7 focused tests, including debounce and scope isolation. Server and web package typechecks, changed-file formatting/lint and diff checks passed. Independent source review completed; its findings were verified against the frozen source and no actionable issue remains.

These repairs cancel a chart gesture if its date window changes, let each environment progress after its own pricing request, and coalesce concurrent tokened summary scans. Thread-enabled branches await their environment summary before refreshing thread rows. The source-scan revision guard prevents older aggregation from pruning files discovered by a newer scan. Integrated web evidence and remaining client limits are described below.

Standalone composer cost refresh now sends a new optional thread-read token, so a completed turn can bypass a warm source snapshot.

UI Changes

The integrated composer shows $37.02 for checkout, matching its Usage thread row. Opening cost details shows $13.50 cache writes, $2.52 cache reads and $21.00 fresh input/output; Escape closes the details. threadCost.ts and ThreadCostIndicator.tsx are byte-identical between this PR and the integrated capture, making the UI proof directly reusable. The later server ledger differs; this PR’s own focused server tests remain listed above.

Before: main 39802c06117fae0b3da43624b0d54309c5437c72; after: cumulative #9308 7e248026469ec7be6d5c2bdaccf86f380e0c2476. Both show the same synthetic checkout conversation and viewport. The synthetic thread creation date was corrected to precede its historical transcripts before this capture; no application source changed.

Clean composer-cost recording · Annotated composer-cost recording. Idle time is trimmed from31.60s to7.30s. Packet validation passed; uploaded media were retrieved and hash-verified.

This is cumulative web integration evidence, not a separate individual-head or native-client recording. No real provider turn was launched; completed-turn refresh remains established by the focused hook/server tests, not this video. No billing or performance measurement is claimed.

Checklist

• The intended composer-cost increment is focused; its cumulative dependencies are identified above.
• I explained what changed and why.
• A current-head composer screenshot is attached; this gap is described above.
• Integrated cost-detail open/close recording is attached; actual-turn refresh remains test-backed.

Implemented and reviewed with GPT-6 and GPT-5.6 Sol in the Codex harness. A direct Claude Opus 5 high availability attempt exited 1 because OAuth had expired; no Opus review occurred.