Use encoding/json instead of Go string quoting when promoting message content to cached text blocks. Add regression coverage for control characters, Unicode, literal backslashes, text preservation, and idempotence.
Implements the remaining three parity items with Parrot cc_mimicry:
D) Tool-name obfuscation
- Dynamic mapping when tools.length > 5 (matches Parrot threshold).
Fake names follow {prefix}{name[:3]}{i:02d} (e.g. 'manage_bas00').
Go port of random.Random(hash(tuple(names))) uses fnv64a seed +
math/rand; byte-exact reproduction is impossible (Python hash vs
Go hash), but the two invariants that matter are preserved:
* same input tool_names yield identical mapping (cache hit)
* prefix pool is shuffled (names look distributed)
- Static prefix map (sessions_ -> cc_sess_, session_ -> cc_ses_)
applied as fallback, matching Parrot TOOL_NAME_REWRITES verbatim.
- Server tools (web_search_20250305, computer_*, etc.) are NOT
renamed; only type=='function' and type=='custom' tools are.
- tool_choice.name is rewritten in sync (only when type=='tool').
- Response side: bytes-level replace on every SSE chunk / JSON
body at 6 injection points (standard stream/non-stream,
passthrough stream/non-stream, chat_completions stream +
non-stream, responses stream + non-stream). Reverse mapping
applied longest-fake-name-first to prevent substring conflicts
(parity with Parrot _restore_tool_names_in_chunk).
- tool_choice is no longer unconditionally deleted in
normalizeClaudeOAuthRequestBody — Parrot passes it through.
E) tools[-1] cache_control breakpoint
- Injected as {type:ephemeral, ttl:<DefaultCacheControlTTL>} when
the last tool has no cache_control. Client-provided ttl is
passed through unchanged (repo-wide policy).
F) messages cache_control strategy
- stripMessageCacheControl removes every client-provided
messages[*].content[*].cache_control (multi-turn stability).
- addMessageCacheBreakpoints then injects two stable breakpoints:
(1) last message, and (2) second-to-last user turn when
messages.length >= 4.
- Combined with the system block breakpoint and tools[-1]
breakpoint, this gives exactly the 4 breakpoints Anthropic
allows per request.
Non-trivial implementation details to be aware of when rebasing:
* Two new files, no upstream collision:
gateway_tool_rewrite.go (D + E algorithms)
gateway_messages_cache.go (F strip + breakpoints)
* Two new feature calls bolted onto the tail of
applyClaudeCodeOAuthMimicryToBody in gateway_service.go — rebase
conflicts will be ~10 lines maximum.
* Response-side injection points all wrap their existing write with
reverseToolNamesIfPresent(c, ...), preserving original behavior
when no mapping is stored (static prefix rollback still runs).
* Non-stream chat/responses switched from c.JSON to
json.Marshal + c.Data so bytes-level replace is possible.
* Retry bodies (FilterThinkingBlocksForRetry,
FilterSignatureSensitiveBlocksForRetry, RectifyThinkingBudget)
only prune blocks — they preserve the already-obfuscated tool
names, so no extra mapping re-application is needed.
Manual QA: end-to-end scenario verified with 6 tools (above threshold)
and tool_choice.type=='tool'. Obfuscation + restore roundtrip shown
in test logs; then removed the temp test file.
Tests (16 new):
- buildDynamicToolMap stability + below-threshold guard
- sanitizeToolName precedence (dynamic > static)
- restoreToolNamesInBytes longest-first + static rollback
- applyToolNameRewriteToBody skips server tools + syncs tool_choice
- applyToolsLastCacheBreakpoint defaults to 5m + passes client ttl
- stripMessageCacheControl + addMessageCacheBreakpoints in the
1/4/string-content cases + second-to-last user turn selection
- buildToolNameRewriteFromBody ReverseOrdered is desc-by-fake-length
- fake name shape follows Parrot {prefix}{head3}{i:02d}
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