Tejas Chopra 7940c05ebf feat(beacon): allowlist the routing summary key (#2818) ... One line in the receiver's allowlist. No client change; the proxy's own payload is untouched. ## Why A routing extension sees things the proxy alone cannot, and they are all measurements rather than opinions: - **Empirical `min_cacheable` per provider.** Fireworks, Together and DeepInfra publish no minimum and litellm carries no value for them, so a router has to guess. But the number is directly observable — send prefix length L, see whether the repeat reports cached tokens. Across enough installs the step function falls out. - **TTL survival.** Currently modelled as a constant. - **Conversation length distribution.** The horizon is the only free parameter in a cache-aware cost model, and it decides the answer: at a 900-token prefix, 1 remaining turn and 20 remaining turns route to different models. - **Predicted vs actual cache hits.** Every response carries `cache_read_input_tokens`. Comparing it to what was predicted is the only way to find out when the cost model is lying. ## What lands here `'routing'` added to `ALLOWED_KEYS`, and the comment above the list corrected — it claimed the set mirrors `_Session.payload()`, which is no longer the whole story now that an extension can emit its own event carrying one of these keys. The ordering constraint is the reason this is its own PR: **allowlisting is a write-side gate**, so anything sent before the key exists is dropped and unrecoverable. This has to be deployed before any client starts emitting it, not alongside. ## Shape of the block Same rule as every other key — counters and model ids, no free text: ```json "routing": { "harness": "claude-code", "decisions": 47, "would_change": 12, "enforced": 9, "holdout": 3, "at_free_boundary": 4, "cross_protocol": 0, "picked": {"claude-haiku-4-5": 12, "claude-opus-5": 35}, "requested": {"claude-opus-5": 47}, "mean_prefix_tokens": 7514, "measured_cost": 0.0236, "modelled_cost": 0.0376, "cache_read_tokens": 3200, "cache_write_tokens": 0, "predicted_hits": 4, "actual_hits": 4 } ``` `measured_cost` comes from the provider's own usage; `modelled_cost` from the router's cost function. They stay separate because the difference is the only thing that means anything. The extension's `reason` string is deliberately absent. It is code-generated, so it carries no user content, but it is unbounded — it stays out rather than being reasoned about. `holdout` is the count of turns deliberately left unrouted as a control. Without it the rest is observational: once a router is acting on every request, the corpus is entirely that router's own policy. `sample-event.json` is unchanged on purpose — it mirrors `_Session.payload()`, which does not produce this key, and adding it there would suggest the proxy emits it. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>		2026-08-05 21:05:19 -07:00
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beacon	feat(beacon): allowlist the routing summary key (#2818)	2026-08-05 21:05:19 -07:00