fix(headers): strategy hint covers round_robin and least_busy

README.md

@@ -190,7 +190,7 @@ All are `x-routeplane-*` and all are optional except the API key. Build them wit
 | --- | --- | --- |
 | `provider` | `x-routeplane-provider` | Provider or comma-separated fallback chain |
 | `residency` | `x-routeplane-residency` | Data-residency region (e.g. `IN`) |
-| `strategy` | `x-routeplane-strategy` | `priority` \| `weighted` \| `cost` \| `latency` |
+| `strategy` | `x-routeplane-strategy` | `priority` \| `weighted` \| `cost` \| `latency` \| `round_robin` \| `least_busy` |
 | `config` | `x-routeplane-config` | Inline routing config (JSON) |
 | `timeout_ms` | `x-routeplane-timeout-ms` | Upstream timeout, ms |
 | `use_case` | `x-routeplane-use-case` | Analytics/FinOps label |

src/routeplane/headers.py

@@ -43,7 +43,8 @@ def headers(
     *,
     provider: str | None = None,
     residency: str | None = None,
-    strategy: Literal["priority", "weighted", "cost", "latency"] | None = None,
+    strategy: Literal["priority", "weighted", "cost", "latency", "round_robin", "least_busy"]
+    | None = None,
     config: dict[str, Any] | None = None,
     timeout_ms: int | None = None,
     use_case: str | None = None,
@@ -74,7 +75,10 @@ def headers(
             request carries personal data and a residency region.
         residency: Requested data-residency region (e.g. ``"IN"``). Only enforced
             when the request also carries personal data.
-        strategy: Provider-ordering strategy.
+        strategy: Provider-ordering strategy; defaults to ``"priority"``. The
+            gateway matches case-insensitively and falls back to ``"priority"``
+            for an unknown or empty value rather than erroring, so a typo
+            silently routes by priority. Superseded by a routing config.
         config: Inline routing/policy config, JSON-serialized onto the wire.
         timeout_ms: Per-request upstream timeout in milliseconds.
         use_case: Free-form use-case label for analytics/FinOps attribution.

tests/test_headers.py

@@ -1,4 +1,5 @@
 import json
+import re
 
 from routeplane import headers
 from routeplane.headers import HEADER_NAMES
@@ -77,3 +78,26 @@ def test_literal_values_pass_through():
     assert headers(log_level="none")["x-routeplane-log-level"] == "none"
     assert headers(pii_mode="tokenize")["x-routeplane-pii-mode"] == "tokenize"
     assert headers(cache_control="no-store")["x-routeplane-cache-control"] == "no-store"
+
+
+def test_strategy_hint_covers_every_gateway_strategy():
+    # Asserted against the annotation, not a call: a Literal is not enforced at
+    # runtime, so passing "round_robin" would "work" even with the hint wrong.
+    # Type-checked callers are the ones a stale hint breaks, so pin the hint.
+    #
+    # Read as raw source (the module uses `from __future__ import annotations`)
+    # rather than via get_type_hints: resolving it would evaluate `... | None`,
+    # which is a TypeError on the 3.9 leg of the support matrix.
+    # PEP 563 stores the unparsed AST, so quoting is normalized, not verbatim
+    # source — match either style.
+    annotation = headers.__annotations__["strategy"]
+    literal = re.search(r"Literal\[(.*?)\]", annotation, re.S)
+    assert literal, f"strategy hint is no longer a Literal: {annotation}"
+    assert set(re.findall(r"['\"]([^'\"]+)['\"]", literal.group(1))) == {
+        "priority",
+        "weighted",
+        "cost",
+        "latency",
+        "round_robin",
+        "least_busy",
+    }