Phase B step 2 of the live-zone-only realignment. Replaces PR-A1's
unconditional "passthrough" stub with a real dispatcher that
inspects the Anthropic /v1/messages body, identifies the live zone
(latest user message at index >= frozen_message_count), and routes
each block to a per-type compressor. PR-B2 wires every per-type
compressor to a no-op, so the dispatcher returns
LiveZoneOutcome::NoChange on every call — bytes-in == bytes-out.
PR-B3+ replaces the no-ops with SmartCrusher, Log, Search, Diff,
and Code compressors.
Adds:
- crates/headroom-core/src/transforms/live_zone.rs — public API:
- `compress_live_zone(body, frozen_message_count, AuthMode)`
- `LiveZoneOutcome::{NoChange, Modified}`
- `CompressionManifest` with per-block outcomes (message_index,
block_index, block_type, BlockAction).
- `BlockAction::{NoOpSkeleton, Excluded { reason }}`. The
HOT_ZONE_BLOCK_TYPES list (`tool_use`, `thinking`,
`redacted_thinking`, `compaction`) excludes blocks even when
they appear in the latest user message.
- `AuthMode::{Payg, OAuth, Subscription}` — accepted but unused
in B2; PR-F2 wires the auth-mode gate.
- 12 unit tests pin: empty messages, no messages field, invalid
JSON, latest user message selection, frozen_count respect,
hot-zone block exclusion, string-shaped content, no user msg
in live zone, AuthMode no-op, NoChange contract, manifest
counters, frozen-count clamping.
- crates/headroom-proxy/src/compression/live_zone_anthropic.rs —
new entry point. `compress_anthropic_request` parses the body,
resolves frozen_count via `resolve_frozen_count` (PR-A4 helper),
dispatches via `compress_live_zone`, and returns
`Outcome::NoCompression` on PR-B2 success / `Outcome::Passthrough
{ reason: NotJson | NoMessages | ModeOff }` on body-shape /
policy issues. Six unit tests pin: mode_off short-circuit, no
messages field, invalid JSON, valid body NoCompression,
empty body, cache_control disabled.
Modifies:
- compression/mod.rs — re-exports `compress_anthropic_request` from
`live_zone_anthropic` instead of `anthropic`. The old anthropic
module is reduced to the `resolve_frozen_count` helper only
(not deleted, because its CacheControlAutoFrozen-policy gate is
reused).
- proxy.rs — passes `state.config.cache_control_auto_frozen` into
the dispatcher. Drops the obsolete "live_zone reserved for
Phase B" warning that PR-A1 emitted on every request.
- compression/anthropic.rs — pruned to the resolve_frozen_count
helper plus its tests. The PR-A1 passthrough stub
`compress_anthropic_request` is gone (live_zone_anthropic owns
the name now).
- config.rs — `compression_mode` doc updated to reflect the wired
dispatcher (no longer "reserved for Phase B").
- tests/integration_compression.rs — `compression_decision_logged`
pins the new log contract (`decision="no_change"`,
`reason="no_op_skeleton_pr_b2"`, plus manifest fields
`frozen_message_count`, `messages_total`, `live_zone_blocks`).
Asserts the obsolete Phase A warning is NOT emitted.
- proxy.rs no longer imports CompressionMode (only used inside the
retired warning).
Benchmark cleanup (B1 leftovers that surfaced now):
- benchmarks/proxy_mode_benchmark.py + claude_session_mode_benchmark.py:
drop `intelligent_context=False` arg from ProxyConfig (the field
was retired in B1; tests/test_proxy_mode_benchmark.py and
tests/test_claude_session_mode_benchmark.py imported these
factories and started failing).
- benchmarks/bench_transforms.py: delete TestRollingWindowBenchmarks
class; rewire TestTransformPipelineBenchmarks fixture without
RollingWindow.
- benchmarks/conftest.py: drop rolling_window_config fixture.
- benchmarks/run_benchmarks.py: drop the `window` suite + table
rows referencing RollingWindow.
Cache-safety invariant:
- PR-B2 dispatcher never mutates body bytes (no-op skeleton). The
proxy forwards the original buffered bytes byte-equal. Phase A's
SHA-256 fixtures pin this.
- `passthrough_mode_live_zone_currently_passthrough_byte_equal_sha256`
retitled comment to reflect the dispatcher being live but
no-op.
Acceptance:
- cargo build --workspace + clippy + fmt: green.
- cargo test --workspace --exclude headroom-py: all green
(777 + 12 new live_zone + 6 new live_zone_anthropic tests).
- pytest: 4678 passed, 240 skipped, 0 failed.
- Anthropic decision log includes manifest fields per the
observability contract documented in
REALIGNMENT/02-architecture.md.
Per-PR-B2 plan: REALIGNMENT/04-phase-B-live-zone.md.
