[igalshilman]

Two community fixes, cherry-picked with their authorship kept.

• Client headers (from fix(client): preserve caller headers and content type overrides #298, by @mkzung): Client copies the caller's headers before it adds a Content-Type, so one dict can be reused across handlers with different content types, and a Content-Type override is found in any letter case. Before, the first call wrote its JSON Content-Type into the caller's dict and a later call to a binary handler failed with HTTP 400.
• No MCP extra (from fix(pydantic): import restate.ext.pydantic without the pydantic-ai mcp extra #257, by @pcbeingused333; the same fix as fix(pydantic): import restate.ext.pydantic without the mcp extra #246 by @Wali05): the MCP toolset moves to _mcp_toolset.py, imported only when an MCPToolset is used, so restate.ext.pydantic imports without pydantic-ai-slim[mcp]. The test fix(pydantic): import restate.ext.pydantic without the pydantic-ai mcp extra #257 first added is left out.

Tested locally:

• Headers: one dict reused for a text and a binary handler against a real Restate server (fails with HTTP 400 on main); tests/client_headers.py passes.
• MCP: in a clean virtualenv with only the pydantic_ai extra, restate.ext.pydantic imports on this branch and fails on main; with pydantic-ai-slim[mcp] added, an MCPToolset is still wrapped as RestateMCPToolset.
• The in-process tests pass (356).

Closes #298, #257, #246.

[pullfrog]

✅ No new issues found.

Reviewed changes

I reviewed both cherry-picked fixes, and checked each one against the base locally.

• Client no longer mutates the caller's headers: do_call now copies the dict before adding Content-Type, and it finds a caller's override in any letter case. tests/client_headers.py covers no override plus three casings, checks that the caller's dict is unchanged, and passes locally (4 tests).
• restate.ext.pydantic imports without the MCP extra: RestateMCPToolset and its result types move unchanged to _mcp_toolset.py, which is imported only inside the existing try/except ImportError in set_context. In a .venv without pydantic-ai-slim[mcp], the base _toolset.py fails on its top-level pydantic_ai.mcp import, while import restate.ext.pydantic succeeds on this branch. Nothing else references the moved symbols, and ruff check and format are clean.

  ^{｜ View workflow run ｜ Using claude-opus-5-5 ｜ 𝕏}

[github-actions]

Test Results

  8 files  ±0    8 suites  ±0   3m 54s ⏱️ +9s
 71 tests ±0   71 ✅ ±0  0 💤 ±0  0 ❌ ±0 
322 runs  ±0  322 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 50cf9bf. ± Comparison against base commit 8339bbe.