[codeslake]

Summary

Claude Code 2.1.280 makes claude-opus-5-5 (Claude Opus 5.5) its default Opus, and none of the model tables knew the id:

• tools/rates.json had no entry, so session-budget-breaker's exact rate lookup returned null (fails open), and tools/cost-report.mjs's lookupRates() fell through to the first key in file order that prefixes it, claude-opus-5: 25% high on input and output, 2.5x on cache reads.
• tools/update-rates.mjs had no name for it, and its multiplier check would have rejected the row anyway: Opus 5.5 prices cache reads at 0.05x input (footnoted on the pricing page), not the standard 0.1x.
• proxy/model-families.mjs had no root for claude-opus-5, claude-opus-5-5 or claude-sonnet-5, so all three read "unknown" and cache-telemetry's cross-family divergence latch could not fire for them.

Rates, from the 2.1.280 bundle's tier_4_20_cache_read_0_20 and the live pricing page, USD per MTok: input 4, output 20, 5m cache write 5, 1h cache write 8, cache read 0.2.

Claude Code 2.1.284 makes claude-sonnet-5-5 (Claude Sonnet 5.5) its default Sonnet, and the same tables lacked it: tools/rates.json had no row (the breaker's exact lookup counted no cost for it, and lookupRates() priced it through the claude-sonnet-5 prefix), and tools/update-rates.mjs had no name for it, so a refresh never wrote it. The live pricing page lists it at input 2, output 10, 5m cache write 2.5, 1h cache write 4, cache read 0.2, the same as Sonnet 5 today. proxy/model-families.mjs already classifies it as sonnet through the claude-sonnet-5 root.

Two defects surfaced while pricing Sonnet 5.5, both in code this PR already touches:

• tools/update-rates.mjs read the pricing table by position (input, 5m, 1h, hits, output). The live page now orders its columns Input, Output, 5m writes, 1h writes, Hits and refreshes under a two-row header, so a real refresh parsed 0 rates with 27 errors and failed closed. With the columns in the right order every parsed rate matches tools/rates.json.
• session-budget-breaker's onStreamEvent read the session id from ctx.headers, which the stream ctx built in proxy/stream.mjs does not carry, so no streamed turn accrued and none of its levers could fire on Claude Code traffic. The breaker's tests passed because their stream fixtures supplied headers.

Changes

• tools/rates.json: claude-opus-5-5, placed before claude-opus-5 so the prefix fallback prefers it for a dated 5.5 id; claude-sonnet-5-5, placed before claude-sonnet-5 for the same reason.
• tools/update-rates.mjs: "Claude Sonnet 5.5" in NAME_TO_WIRE and REQUIRED_WIRE_IDS.
• tools/probe-tool-addition.mjs: the default lineup probes claude-sonnet-5-5 in place of claude-sonnet-5.
• tools/update-rates.mjs: each table's column order comes from its own header row, matched by keyword; a header that does not name each price column once yields no rows, so the run still fails closed. New fixture test/fixtures/pricing-page-2026-09-28.html, the live page's model-pricing table.
• proxy/extensions/session-budget-breaker.mjs: onStreamEvent takes the session id onRequest stashed on ctx.meta, as onResponse already did. A new test drives the real streamResponse; the stream fixtures no longer supply headers, and tools/sim-session-budget-breaker.mjs builds the real ctx shape too. One CHANGELOG Fixed bullet.
• tools/update-rates.mjs: "Claude Opus 5.5" in NAME_TO_WIRE and REQUIRED_WIRE_IDS; PRICE_CELL accepts one trailing footnote marker ($0.20 / MTok 2, one space and one or two digits, so $4 / MTok2026 still fails closed); a per-model cache-read multiplier override (claude-opus-5-5: 0.05) that leaves every other row and field on the standard check.
• proxy/model-families.mjs: roots claude-opus-5 -> opus, claude-sonnet-5 -> sonnet.
• tools/cost-report.mjs: unchanged; the new exact key wins.
• Tests: test/cost-report.test.mjs (new, one case: a 1M/1M/1M-cache-read Opus 5.5 row costs 24.2, it read 30.5 before), test/tools-update-rates.test.mjs (the Opus 5.5 row parses to its own rates; the override does not loosen the guard for other models; a footnote-shaped suffix without the space fails closed; the shipped rates.json carries the id), test/model-families.test.mjs (bare Opus 5, Opus 5.5, Sonnet 5 and Sonnet 5.5 classify), test/proxy-session-budget-breaker.test.mjs (the cost lever prices claude-sonnet-5-5 instead of failing open), and in test/tools-update-rates.test.mjs the Sonnet 5.5 row parses as its own row, not as Sonnet 5's. The 2026-07-27 pricing fixture gains the Opus 5.5 and Sonnet 5.5 rows copied from the live page, noted in the test header.
• CHANGELOG.md: one Fixed bullet.

Test plan

• Each new case failed on the base (0e7aa80 for Opus 5.5, 10f2f78 for Sonnet 5.5) before its fix and passes on the head. The Sonnet 5.5 family assert is coverage and passes on both.
• The live-shaped update-rates case and the streamed-accrual breaker case each failed on the commit before their fix.
• node --test: 1957 tests, 1956 pass, 0 fail, 1 skipped.

Not changed here

• tools/cost-report.mjs --live-rates / --update-rates still use its older parser, which needs MTok</td> in every cell, so it drops the footnoted Opus 5.5 row and rewrites rates.json without it. tools/update-rates.mjs is the validated updater.
• Claude Fable 5.1 and Mythos 5.1 are on the pricing page with a 0.025x cache-read footnote and are not added.

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