-
Real Claude Code CLI always sends a 2-block system array: [0] {"type":"text", "text":"x-anthropic-billing-header: cc_version=X.Y.Z.{fp}; cc_entrypoint=cli; cch=00000;"} [1] {"type":"text", "text":"You are Claude Code...", "cache_control":{...}} Before this commit, sub2api's mimicry path only produced block [1]. The missing billing block is one of the primary third-party detection signals Anthropic uses for Claude-Code-scoped OAuth tokens. New file gateway_billing_block.go ports the fingerprint algorithm (byte-for-byte from Parrot cc_mimicry.py:compute_fingerprint): pick chars at positions [4,7,20] of the first user text, then `sha256(SALT + chars + cc_version)[:3]`. - claude/constants.go: CLICurrentVersion = "2.1.92" (must match UA) - gateway_billing_block.go: computeClaudeCodeFingerprint + buildBillingAttributionBlockJSON + extractFirstUserText - gateway_service.go: rewriteSystemForNonClaudeCode now emits both blocks in order; cch=00000 is filled in later by signBillingHeaderCCH in buildUpstreamRequest. Downstream compat note: syncBillingHeaderVersion's regex `cc_version=\d+\.\d+\.\d+` only matches the semver triple, leaving the `.{fp}` suffix intact when rewriting in buildUpstreamRequest.bebded28
