## Summary
First-class `Provider::OpenRouter` support joining the existing
anthropic/openai/databricks providers. Reuses the Chat Completions path
with targeted mutations for OpenRouter's routing contract.
**Core (`crates/buzz-agent`):**
- `Provider::OpenRouter` enum variant with `OPENROUTER_API_KEY`,
`BUZZ_AGENT_MODEL` → `OPENROUTER_MODEL` fallback, `OPENROUTER_BASE_URL`
env convention
- Body mutator: `reasoning: {effort}` when effort is configured, and
`max_completion_tokens` translated to OpenRouter's `max_tokens`
spelling; no `provider.require_parameters` filter (it routes only to
endpoints advertising every parameter in the body, which hard-404s a
valid model id); summaries get neither. `openai_body` is always called
with `effort=None` on the OpenRouter path — the `reasoning` object is
added by the mutator directly, so `reasoning_effort` is structurally
absent.
- Attribution headers: `HTTP-Referer: https://github.com/block/buzz`,
`X-OpenRouter-Title: Buzz`
- Error-inside-200 check in shared `parse_openai` (`finish_reason ==
"error"`)
- 401 auth handling: static API keys (`refresh_now` returns the same
token) fail terminal immediately with one wire request; PKCE/minting
sources get one retry with the fresh token.
- Status+`error_type` retry matrix (4-arm collapsed form): 429 (honor
`Retry-After`), 502 (retry), 503/`provider_overloaded` (honor
`Retry-After`), everything else including untyped 503 (bounded retries →
actionable routing message). 499 included matching shared `post()`
(#2175) for turn-timeout stall surfacing. Terminal failures wrapped in
`terminal_llm_error` for duration+attempt-count context.
- `anthropic/*` `cache_control` injection (model-gated, mixed-content
safe)
- Provider-agnostic `reasoning_details` opaque round-trip on
`HistoryItem::Assistant` for tool-call continuations — captured verbatim
in `parse_openai_with_reasoning_details`, replayed verbatim in
`openai_body`, byte-accounting charged. `provider_extra` passthrough
from `make_tool_call` composes independently.
**Desktop:**
- Readiness arms checking `OPENROUTER_API_KEY` + `OPENROUTER_MODEL`
- Model discovery via `{OPENROUTER_BASE_URL}/models` filtered on
`supported_parameters` contains `tools`
- Picker entry, credential config, effort table 3-file sync
**`desktop/src/features/agents/AGENTS.md`: no rules changed** — the
scoped rule requiring an explicit note is satisfied here.
Implements the gate-cleared plan from
`PLANS/OPENROUTER_PROVIDER_PLAN.md` (rev 3).
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Co-authored-by: npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
