fix(anthropic): use Claude Code-compatible MCP tool prefix for OAuth

[JayGwod]

Summary

• Use Claude Code-compatible mcp__ as the MCP tool-name prefix for native Anthropic OAuth requests.
• Keep stripping the MCP prefix when normalizing Anthropic tool_use responses back into Hermes tool calls.
• Cover both request serialization and response normalization with tests.

Why

Claude Code's Anthropic OAuth tool protocol uses a double-underscore MCP marker, for example:

mcp__terminal

Hermes was previously emitting a single-underscore marker on the native Anthropic OAuth path:

mcp_terminal

That can make Hermes OAuth tool requests diverge from the Claude Code-compatible shape even though the request is otherwise using Claude Code/OAuth beta headers. Using the same mcp__ marker makes the OAuth tool schema consistent with Claude Code-style MCP tool naming.

This PR is intentionally scoped only to tool-name compatibility. It does not claim to change Anthropic account/billing behavior such as extra-usage gating.

Tests

./venv/bin/python -m py_compile agent/anthropic_adapter.py agent/transports/anthropic.py
./venv/bin/python -m pytest -o 'addopts=' tests/agent/test_anthropic_adapter.py -q

Result:

140 passed

Additional sanity checks verified:

• OAuth request tool name serializes as mcp__terminal.
• Response normalization strips mcp__terminal back to Hermes tool name terminal.

[JayGwod]

Bumping — open for ~2 days.

Status on current upstream/main (f903ceece):

• Applies cleanly, no rebase needed.
• pytest tests/agent/test_anthropic_adapter.py -k "mcp or prefix" → 5 passed on a worktree at f903ceece with this commit on top.

Context: this is the prefix companion to the context-1m beta fix in #17680 → #17752. Anthropic's OAuth path expects MCP tool names to use Claude Code's double-underscore convention (mcp__server__tool). Without it, OAuth + MCP sessions get a 400 from the Anthropic API on tool registration even after the beta-header fix lands.

Happy to take feedback if you'd prefer this fold into a different code path. Thanks!

[teknium1]

Thanks for the focused compatibility fix. This is an automated hermes-sweeper review; current main now provides this behavior and a broader MCP-server-safe round trip.

• b70a4e7533dce506a41f847b3fc082d6b6fe4a9b implements mcp__ normalization for bare and MCP-server tool names on the Anthropic OAuth wire.
• agent/anthropic_adapter.py:2570-2581 preserves existing mcp__ names, promotes legacy mcp_ names, and prefixes bare tools.
• agent/transports/anthropic.py:134-153 maps the response back to the name registered by Hermes.
• tests/agent/test_anthropic_mcp_prefix_strip.py:179-255 covers the request and response invariants, including the MCP-server case described in the PR discussion.

Closing as implemented on main.