Adapt the story suite to the merged 2026 client surface

Rebased onto main: mode='auto' is now the Client default, so the harness drops the workaround prose; the mrtr/subscriptions stubs note their lowlevel surface is in this base.

Author: maxisbey

examples/stories/_harness.py

@@ -92,12 +92,13 @@ def run_client(main: Callable[..., Awaitable[None]]) -> None:
     targets = target_from_args(file)
     build_auth: AuthBuilder | None = globals_.get("build_auth")
     transport = "http" if "--http" in sys.argv else "stdio"
-    # Never rely on the SDK's mode= default — be explicit. stdio is legacy-only until
-    # the SDK's stdio entry can negotiate the era, so only --http gets a modern arm.
+    # The era is an axis of the story matrix, so ``mode=`` is always passed explicitly
+    # even though it often matches the ``Client`` default of "auto". stdio is legacy-only
+    # until the SDK's stdio entry can negotiate the era, so only --http gets a modern arm.
     era = "modern" if transport == "http" and "--legacy" not in sys.argv else "legacy"
     if cfg["era"] == "dual-in-body":
-        # The story pins its connection modes inside ``main`` itself, so hand it the
-        # real-user "auto" default and let those in-body pins decide. A hard version pin
+        # The story pins its connection modes inside ``main`` itself, so hand it "auto"
+        # (the ``Client`` default) and let those in-body pins decide. A hard version pin
         # here would skip the discover probe and leave ``server_info`` blank.
         era = "in-body"
     mode = {"modern": LATEST_MODERN_VERSION, "legacy": "legacy", "in-body": "auto"}[era]

examples/stories/mrtr/README.md

@@ -7,11 +7,11 @@ the server resumes from the carried state. The story will show both the
 auto-fulfil helper and a manual resubmit loop.
 
 **Status: not yet implemented** ([#2898](https://github.com/modelcontextprotocol/python-sdk/issues/2898)).
-The lowlevel registration surface exists on `main` as of
+The lowlevel registration surface is in this base —
 [#2967](https://github.com/modelcontextprotocol/python-sdk/pull/2967)
-(`ae13ede`), which widened the tool/prompt/resource handler return types to
-include `InputRequiredResult`. This story graduates from a README stub to a
-runnable example once this branch's base includes that commit.
+(`ae13ede`) widened the tool/prompt/resource handler return types to include
+`InputRequiredResult`. The runnable story is deliberately a follow-up PR to
+keep this one reviewable.
 
 ## Spec
 

examples/stories/subscriptions/README.md

@@ -6,12 +6,11 @@ them. Replaces the handshake-era `resources/subscribe` + standalone-GET
 notification path.
 
 **Status: not yet implemented** ([#2901](https://github.com/modelcontextprotocol/python-sdk/issues/2901)).
-The lowlevel registration surface exists on `main` as of
+The lowlevel registration surface is in this base —
 [#2967](https://github.com/modelcontextprotocol/python-sdk/pull/2967)
-(`ae13ede`), which added the lowlevel `on_subscriptions_listen` handler slot.
-There is no `Client.listen()` or `ServerEventBus` yet; this story graduates
-from a README stub to a runnable example once this branch's base includes that
-commit.
+(`ae13ede`) added the lowlevel `on_subscriptions_listen` handler slot — but
+there is no `Client.listen()` or `ServerEventBus` yet. The runnable story is
+deliberately a follow-up PR to keep this one reviewable.
 
 ## Spec
 

tests/examples/conftest.py

@@ -45,7 +45,8 @@
 _ERA_TO_MODE = {"modern": LATEST_MODERN_VERSION, "legacy": "legacy", "in-body": "auto"}
 """``Client`` rejects handshake-era version strings, so ``legacy`` resolves to
 ``mode='legacy'`` rather than ``LATEST_HANDSHAKE_VERSION``. ``in-body`` legs pin
-their connection modes inside ``main`` themselves, so they get the real-user default."""
+their connection modes inside ``main`` themselves, so they get ``"auto"`` — the
+``Client`` default; the era axis still passes every ``mode=`` explicitly."""
 
 
 def story_cfg(name: str) -> dict[str, Any]: