feat(v1.1.0): PascalCase mcp_ tools + Claude Code 2.1.112 fingerprint

Anthropic tightened OAuth validation between 2026-04-14 and 2026-04-22.
Requests are now classified as third-party and routed to extra-usage
credits (or rejected with 'Third-party apps now draw from your extra
usage, not your plan limits') unless the fingerprint matches real
Claude Code. Ports the two upstream opencode-claude-auth fixes that
address this:

- PR #191 (merged, v1.4.10): PascalCase `mcp_` tool names. Hermes
  prefixes tools with lowercase `mcp_bash`; the validator now flags
  that as non-Claude-Code. Real CC uses `mcp_Bash` / `mcp_Read` /
  `mcp_Background_output`. Adds a request-side rewrite hook plus a
  response-side unhook that lowercases the first char after hermes
  strips the prefix, so the tool dispatcher continues to receive the
  original lowercase names.

- PR #207 (open, attempted fix for Claude Code 2.1.112): updates the
  billing fingerprint. Changes the `cc_entrypoint` in the signed
  billing header from `cli` to `sdk-cli`, adds the
  `advisor-tool-2026-03-01` beta flag, injects the Stainless SDK
  headers that real CC sends (`x-stainless-*`) plus
  `anthropic-dangerous-direct-browser-access: true`, and appends
  `?beta=true` to the /v1/messages query string. All non-body signals
  ride the Anthropic Python SDK's per-request `extra_headers` and
  `extra_query` kwargs so we don't need to rewrap the HTTP client.

Other changes:
- Bump __version__ to 1.1.0 and document the rationale above in the
  module docstring.
- Extend `_EXTRA_OAUTH_BETAS` so both prompt-caching and advisor-tool
  betas are appended to hermes's `_OAUTH_ONLY_BETAS` list.
- 10 new unit tests covering PascalCase rewrite (request + response),
  sdk-cli entrypoint, Stainless headers, extra_query=beta:true, and
  preservation of pre-existing extra_headers.

Smoke-tested on Linux with hermes-agent v0.10.0 against claude-sonnet-4-6,
claude-opus-4-6, and claude-opus-4-7 \u2014 all return 200 and complete
responses with the new patch loaded. Billing-tier routing (plan vs
extra-usage) cannot be verified from the client side; this tracks the
best-known upstream bypass as of 2026-04-22 but Anthropic may tighten
validation again at any time.

Refs: #6
Upstream: https://github.com/griffinmartin/opencode-claude-auth/pull/191
Upstream: https://github.com/griffinmartin/opencode-claude-auth/pull/207

tests/test_bypass.py

@@ -1,10 +1,14 @@
 # pyright: reportPrivateUsage=false, reportUnknownParameterType=false, reportMissingParameterType=false, reportUnknownArgumentType=false, reportUnknownVariableType=false, reportUnknownMemberType=false, reportArgumentType=false
 
 import copy
+from types import SimpleNamespace
 
 from anthropic_billing_bypass import (
+    _BILLING_ENTRYPOINT,
     _SYSTEM_IDENTITY,
     _fix_temperature_for_oauth_adaptive,
+    _install_response_pascalcase_unhook,
+    _pascalcase_mcp_name,
     apply_claude_code_bypass,
 )
 
@@ -19,6 +23,14 @@ def test_apply_claude_code_bypass_injects_billing_header_and_preserves_identity(
     assert system[1]["text"] == _SYSTEM_IDENTITY
 
 
+def test_apply_claude_code_bypass_uses_sdk_cli_entrypoint(basic_api_kwargs):
+    apply_claude_code_bypass(basic_api_kwargs, "2.1.112")
+
+    billing_text = basic_api_kwargs["system"][0]["text"]
+    assert "cc_entrypoint=sdk-cli;" in billing_text
+    assert _BILLING_ENTRYPOINT == "sdk-cli"
+
+
 def test_apply_claude_code_bypass_relocates_non_identity_system_text_to_first_user_message(
     basic_api_kwargs,
 ):
@@ -93,3 +105,135 @@ def test_fix_temperature_for_oauth_adaptive_without_temperature_is_noop():
     api_kwargs = {"model": "claude-opus-4-6-20260101"}
     _fix_temperature_for_oauth_adaptive(api_kwargs, site="test")
     assert api_kwargs == {"model": "claude-opus-4-6-20260101"}
+
+
+def test_pascalcase_mcp_name_uppercases_first_char_after_prefix():
+    assert _pascalcase_mcp_name("mcp_bash") == "mcp_Bash"
+    assert _pascalcase_mcp_name("mcp_read") == "mcp_Read"
+    assert _pascalcase_mcp_name("mcp_background_output") == "mcp_Background_output"
+
+
+def test_pascalcase_mcp_name_leaves_already_pascalcase_unchanged():
+    assert _pascalcase_mcp_name("mcp_Bash") == "mcp_Bash"
+    assert _pascalcase_mcp_name("mcp_Background_output") == "mcp_Background_output"
+
+
+def test_pascalcase_mcp_name_ignores_unprefixed_names():
+    assert _pascalcase_mcp_name("bash") == "bash"
+    assert _pascalcase_mcp_name("not_mcp_bash") == "not_mcp_bash"
+    assert _pascalcase_mcp_name("") == ""
+
+
+def test_apply_claude_code_bypass_rewrites_tool_names_to_pascalcase(basic_api_kwargs):
+    basic_api_kwargs["tools"] = [
+        {"name": "mcp_bash"},
+        {"name": "mcp_background_output"},
+        {"name": "mcp_Already_pascal"},
+    ]
+    basic_api_kwargs["messages"] = [
+        {
+            "role": "user",
+            "content": [
+                {"type": "text", "text": "hello world"},
+                {"type": "tool_use", "name": "mcp_bash", "id": "tool_1", "input": {}},
+            ],
+        }
+    ]
+
+    apply_claude_code_bypass(basic_api_kwargs, "2.1.112")
+
+    tool_names = [tool["name"] for tool in basic_api_kwargs["tools"]]
+    assert tool_names == ["mcp_Bash", "mcp_Background_output", "mcp_Already_pascal"]
+
+    tool_use_block = basic_api_kwargs["messages"][0]["content"][-1]
+    assert tool_use_block["name"] == "mcp_Bash"
+
+
+def test_apply_claude_code_bypass_injects_stainless_and_direct_browser_headers(
+    basic_api_kwargs,
+):
+    apply_claude_code_bypass(basic_api_kwargs, "2.1.112")
+
+    extra_headers = basic_api_kwargs["extra_headers"]
+    assert extra_headers["anthropic-dangerous-direct-browser-access"] == "true"
+    assert extra_headers["x-stainless-lang"] == "js"
+    assert extra_headers["x-stainless-runtime"] == "node"
+    assert extra_headers["x-stainless-package-version"] == "0.81.0"
+    assert extra_headers["x-stainless-retry-count"] == "0"
+    assert extra_headers["x-stainless-timeout"] == "600"
+    assert extra_headers["x-stainless-os"] in ("MacOS", "Linux", "Windows")
+    assert extra_headers["x-stainless-arch"] in ("x64", "arm64", "ia32", "unknown")
+
+
+def test_apply_claude_code_bypass_sets_beta_true_query_param(basic_api_kwargs):
+    apply_claude_code_bypass(basic_api_kwargs, "2.1.112")
+
+    assert basic_api_kwargs["extra_query"] == {"beta": "true"}
+
+
+def test_apply_claude_code_bypass_preserves_existing_extra_headers(basic_api_kwargs):
+    basic_api_kwargs["extra_headers"] = {"anthropic-beta": "fast-mode-2026-02-01"}
+
+    apply_claude_code_bypass(basic_api_kwargs, "2.1.112")
+
+    assert basic_api_kwargs["extra_headers"]["anthropic-beta"] == "fast-mode-2026-02-01"
+    assert (
+        basic_api_kwargs["extra_headers"]["anthropic-dangerous-direct-browser-access"]
+        == "true"
+    )
+
+
+def _make_fake_adapter_module(tool_names):
+    def original_normalize(response, strip_tool_prefix=False):
+        tool_calls = []
+        for name in tool_names:
+            stripped = name[len("mcp_"):] if strip_tool_prefix and name.startswith("mcp_") else name
+            tool_calls.append(
+                SimpleNamespace(
+                    id="tool_1",
+                    type="function",
+                    function=SimpleNamespace(name=stripped, arguments="{}"),
+                )
+            )
+        msg = SimpleNamespace(content=None, tool_calls=tool_calls or None, reasoning=None)
+        return msg, "tool_calls"
+
+    module = SimpleNamespace(normalize_anthropic_response=original_normalize)
+    return module
+
+
+def test_response_unhook_lowercases_first_char_of_tool_names_after_strip():
+    adapter = _make_fake_adapter_module(["mcp_Bash", "mcp_Background_output"])
+
+    assert _install_response_pascalcase_unhook(adapter) is True
+
+    msg, _reason = adapter.normalize_anthropic_response(
+        response=object(), strip_tool_prefix=True
+    )
+
+    names = [tc.function.name for tc in msg.tool_calls]
+    assert names == ["bash", "background_output"]
+
+
+def test_response_unhook_is_noop_when_strip_tool_prefix_false():
+    adapter = _make_fake_adapter_module(["mcp_Bash"])
+
+    _install_response_pascalcase_unhook(adapter)
+
+    msg, _reason = adapter.normalize_anthropic_response(
+        response=object(), strip_tool_prefix=False
+    )
+
+    assert msg.tool_calls[0].function.name == "mcp_Bash"
+
+
+def test_response_unhook_is_idempotent():
+    adapter = _make_fake_adapter_module(["mcp_Bash"])
+
+    assert _install_response_pascalcase_unhook(adapter) is True
+    assert _install_response_pascalcase_unhook(adapter) is True
+
+    msg, _reason = adapter.normalize_anthropic_response(
+        response=object(), strip_tool_prefix=True
+    )
+    assert msg.tool_calls[0].function.name == "bash"