chore: drop manual CHANGELOG edits (release-please derives it from PR title)

Author: nangsontay

CHANGELOG.md

@@ -19,10 +19,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **cache/prefix-freeze:** resolve `PrefixCacheTracker`s per conversation lineage within a session id, so concurrent conversations sharing a fallback id no longer thrash one tracker's frozen-prefix state ([#2085](https://github.com/headroomlabs-ai/headroom/issues/2085)). Without an `x-headroom-session-id` header the fallback id hashes `model + system prompt` — identical across a Claude Code session and every one of its parallel subagents (and any set of sessions reusing one system prompt). On the shared tracker their interleaved histories cross-contaminate the freeze state: the forwarded prefix is byte-unstable on nearly every turn and the provider prompt cache is re-written instead of read — reported as ~4.4x cache-creation inflation and a 2.5–3x net cost increase under Claude Code. `SessionTrackerStore.resolve_tracker` now reuses the tracker whose previous request messages are a prefix of the incoming history (client histories are append-only, so a conversation's next request always extends its previous one), starts a fresh lineage when the history diverges or was rewritten (client-side compaction — that provider cache line is gone anyway), and caps lineages per session id (`PrefixFreezeConfig.max_lineages_per_session`, default 32; over-cap conversations share one overflow tracker instead of evicting established lineages, so a fan-out storm past the cap degrades only its own tail — and `0` disables lineage splitting). Matching compares the original client bytes under the same canonical cross-turn equivalence as the cache-stable delta path (`_canonicalize_for_prefix_compare`), so a moved cache breakpoint, string<->block content sugar, or per-turn transport annotations do not read as a rewrite. Separately, the fallback id now hashes only the LEADING run of `role:"system"` messages: agentic clients interleave `<system-reminder>` turns into the history as actual system-role messages (hook output, skills lists, truncation notices), and hashing those rotated the session id mid-conversation — orphaning the prefix tracker and every other session-sticky subsystem (beta headers, CCR/memory registries, the compression cache) each time a reminder landed. Both handler paths now derive the session id and the lineage from the same original client bytes, so a turn-dependent hook rewrite cannot rotate one without the other. The session id itself never changes: session-sticky state keyed on it (beta-header stickiness, CCR and memory-tool registries, the compression cache) is untouched, and a single-conversation session keeps its exact previous behavior (the first lineage lives under the bare id).
 - **proxy/bedrock:** wire `PrefixCacheTracker` updates into both Bedrock backend paths (`handle_anthropic_messages`'s non-streaming branch in `anthropic.py`, and `_stream_response_bedrock` in `streaming.py`). `update_from_response()` was previously only called from the direct-Anthropic-API branch; both Bedrock branches returned before ever reaching it, so the tracker's state stayed permanently empty for the life of a session on any `--backend bedrock` deployment: `extract_cache_stable_delta()` always saw no previous turn, and `--mode cache` fell back to full unmodified passthrough on every turn instead of freezing the already-cached prefix and compressing only the new suffix.
 - **install:** `install_supervisor`'s macOS branch did an unconditional `launchctl bootout` followed by a bare `bootstrap` with no retry, unlike `start_supervisor`, which already rides out the ~15s EIO (error 5) window launchd exhibits for several seconds after a bootout. This left `install apply`'s own reinstall path (and anything that re-applies a deployment, e.g. a future `headroom doctor --fix`) exposed to a race that previously required manual recovery (bootout + remove the plist + reapply). Extracted the retry loop already used by `start_supervisor` into a shared `_bootstrap_with_retry()` helper, now used by both call sites.
-- **proxy/anthropic:** CCR system-instruction injection (`ccr_inject_system_instructions`, default off) now appends to the top-level `body["system"]` field instead of prepending a `role:"system"` message to `messages` — the Anthropic Messages API rejects that message shape outright, so every marker-bearing turn with the flag enabled previously got a 400 from upstream. The injected text is now a static, hash-free block (`create_stable_system_instructions`) appended idempotently (existing `cache_control` breakpoints on prior system blocks are left untouched), so the system segment stays byte-identical turn over turn instead of busting the cache via the old per-turn hash list.
-- **proxy/ccr:** the messages-based system-instruction injection path (`CCRToolInjector.inject_into_system_message`, used by OpenAI-format clients when `ccr_inject_system_instructions` is enabled) now injects the same static, hash-free block via `create_stable_system_instructions` instead of `create_system_instructions`'s per-turn `Available hashes` list, so an OpenAI-format system prompt stays byte-identical turn over turn instead of busting the provider's prompt cache each time the enumerated hashes change.
-- **proxy/ccr:** CCR proactive-expansion and memory-context injection now skip appending to the live-zone tail message when that exact position was already forwarded (and byte-replayed by `overlay_cached_prefix`) last turn. Previously both injections ran unconditionally in token mode, so a same-messages re-request appended a second copy on top of the one `overlay_cached_prefix` had just replayed — busting the final segment and growing it unboundedly turn over turn. Proactive-expansion recommendations are also deduped per session (a `SessionExpansionDedupTracker`, mirroring the existing sticky-CCR-tool session store) so the same compressed-content hash is never injected twice into one conversation, and `ContextTracker.analyze_query`/`track_compression` now accept an optional `session_id` so a fresh session started after Claude Code's `/compact` no longer has pre-compact compressed content surfaced back into it ([#2186](https://github.com/headroomlabs-ai/headroom/issues/2186)).
-- **proxy/openai:** the OpenAI-format chat-completions path (`handle_openai_chat`, both the LiteLLM/any-llm backend branch and the direct-backend branch) and its streaming finalizer now pass the raw client messages as `original_messages` to `PrefixCacheTracker.update_from_response`. All three call sites previously omitted it, so the tracker fell back to recording the FORWARDED (compressed) bytes as "originals" — the next turn's append-only cache-safety check then compared raw client bytes against compressed ones, diverged immediately, and never replayed the cached prefix, silently busting the provider's prompt cache on every turn for OpenAI-format clients in token mode.
 - **proxy/savings:** `SavingsTracker.record_request()` only appended a history point when `tokens_saved > 0` (headroom's own lossy compression). In `--mode cache`, `tokens_saved` is near-always 0 by design, since the frozen prefix is byte-replayed rather than compressed to keep the provider's prompt cache warm. That silently dropped every history point on a cache-mode deployment even when `cache_read_tokens`/`cache_savings_usd` were large, making `headroom-monthly`-style tooling read as a total savings collapse. The guard now fires on `tokens_saved` OR `cache_read_tokens`, and the appended entry carries `cache_read_tokens`/`cache_savings_usd` so downstream consumers can show them; `_normalize_history_entry` defaults both fields to 0/0.0 for legacy entries that predate this change.
 - **litellm:** vendor-specific top-level fields on `/v1/chat/completions`, including vLLM's `chat_template_kwargs` for per-request Qwen3 thinking-mode toggles, now reach OpenAI-compatible backends through LiteLLM `extra_body` instead of being dropped by the standard-parameter allowlist ([#2128](https://github.com/headroomlabs-ai/headroom/issues/2128)).
 - **cache aligner:** hash the actual frozen Claude Code prefix instead of only system-message text, so `stable_prefix_hash` / `prefix_changed` now surface prompt-cache churn when a cached tool-result block changes without any system-prompt edit ([#2085](https://github.com/headroomlabs-ai/headroom/issues/2085)).