The Codec leaf-mode bypass (the architectural target the entire v0.3 contract was designed for) fires end-to-end. `[Codec][leaf]` log line confirms the gateway is a transparent ID pipe; the tokenizer sits at the leaf where it belongs.

The Codec v0.3 leaf-mode contract (the architectural target where the tool tokenizes once, the gateway forwards IDs verbatim) landed on real lab traffic for the first time today. The proof is one log line:

[INFO] [Codec][leaf] downstream tool returned pre-tokenized result

for vocab sha256:9db56ff6… gateway shim bypassed.

Two coordinated fixes shipped in v0.3.2:

1. Wire shape change. '@codecai/mcp-leaf' now annotates each text content block with a per-block '_meta['ai.codec/leaf-tokenization']' payload instead of pushing a sibling '_codec_meta' content block. The sibling form crashed the MCP SDK's validator on the server side ('-32602 Invalid tools/call result') before the result ever left the leaf process, '_codec_meta' isn't in the SDK's discriminated content-block union. The per-block '_meta' slot is a first-class MCP spec field that the SDK passes through unchanged. Bonus side-effect: the per-block representation is ~4.6× more compact than the sibling form (a 4.6 KB JSON baseline collapsed to 990 B).

2. Gateway detector. 'codec-metamcp''s 'hasExistingCodecMeta' now checks both shapes (per-block '_meta' first, legacy sibling-block as back-compat). When it finds either, the shim bypasses, the '[Codec][leaf]' log fires, and the gateway acts as a transparent ID pipe for that hop.

Bench numbers from the v0.3.2 run ('2026-05-09T12-17-48Z'):

┌─────────────────────────────────────┬─────────┬──────────────────────────────┐

│ Workload │ json │ msgpack-both+gzip+map (leaf) │

├─────────────────────────────────────┼─────────┼──────────────────────────────┤

│ 'codec-time-leaf__get_current_time' │ 990 B │ 931 B │

│ 'codec-time-leaf__convert_time' │ 1.0 KB │ 972 B │

│ 'tools/list' (40 tools) │ 21.4 KB │ 5.9 KB │

└─────────────────────────────────────┴─────────┴──────────────────────────────┘

Wire bytes between variant 4 (gzip with shim) and variant 5 (gzip with leaf-bypass) are now identical because gzip already collapses redundant content. The leaf-bypass benefit on this hop is CPU on the gateway (no tokenizer runs) and KV-cache safety (the engine receives the exact IDs the leaf produced). The '[Codec][leaf]' log is the right observability target, not a smaller number.

'tools/list' holds at 3.6× wire reduction across the 40-tool namespace.

Status of the v0.3 release: spec, polyglot clients, MCP integration, website + RSS, bench methodology, and now the leaf-mode end-to-end demo all live.