[hijera]

Problem

pip install sgr-agent-core pulls ~75 packages transitively, though the SGR core — agent loop, schemas, config, registries, skills — uses five of them. tavily, fastmcp, fastapi/uvicorn, agent-client-protocol and langfuse are all hard requirements today, so anyone who wants "just SGR" gets the MCP stack, a web framework, an OpenTelemetry stack, cryptography, tiktoken, numpy, pywin32 and the rest.

What changed

Core install is now PyYAML, pydantic, pydantic-settings, openai, httpx[socks] — 21 packages. Everything else is an extra:

Extra	Adds	Needed for
mcp	fastmcp, jambo	MCP servers under the mcp: config key
search	tavily-python	WebSearchTool with engine: tavily, ExtractPageContentTool
server	fastapi, uvicorn	the sgr HTTP API server
acp	agent-client-protocol	the sgracp stdio server
langfuse	langfuse	langfuse.enabled: true
all	all of the above	the pre-existing install profile
examples	all + rank-bm25	what examples/ need

Missing extras surface as an actionable message, never a bare ModuleNotFoundError:

$ sgr --config-file config.yaml
The 'sgr' HTTP server requires the optional 'uvicorn' package, which is not installed.
Install it with:  pip install 'sgr-agent-core[server]'

Decoupling notes

• fastmcp was the hard part. AgentConfig.mcp was typed with fastmcp's MCPConfig, and a pydantic field type cannot be made lazy. Core now ships its own lightweight MCPConfig (sgr_agent_core/mcp_config.py) with the same shape, including the wrap-servers-at-root validator; mcp_service converts it to the fastmcp model only when servers are actually configured. agent_def.mcp had exactly one consumer, so the change is contained.
• tavily moves inside _search_tavily and _extract. The brave and perplexity engines already speak plain HTTP, so web search still works on a core-only install.
• sgr / sgracp report the missing extra and exit 1. This required acp/__init__.py to resolve its exports through PEP 562 __getattr__ — otherwise the subpackage import died before the entrypoint could say anything useful.
• langfuse was already imported lazily in agent_factory; it was simply listed as a hard dependency for no reason. Only the error text changed.
• python-dateutil is unused anywhere in the repo and is dropped. rank-bm25 is used only by examples/progressive_discovery and moves to the examples extra.

Docker / CI

• Dockerfile installs .[examples] — the image keeps its full dependency set, including rank-bm25 for the bundled examples. No capability change.
• New test-core-only CI job installs bare core and fails if an optional package is present or gets imported at module scope. Without it, one stray top-level import silently puts every heavy dependency back.

Second commit: unrelated CI breakage, fixed here to get green

test_acp_new_session_advertises_agent_and_model_options was already failing on main before this PR (verified by running it against the previous commit). agent-client-protocol 0.12 narrowed SessionConfigOptionSelect.category to "mode" | "model" | "model_config" | "thought_level" | dict, and its schema salvages invalid values to None rather than raising — so the bridge's category="_agent" was being silently dropped.

"_agent" was never a standard value, so clients already treated the option as uncategorised. The fix removes it and asserts None, matching what clients actually see. The model selector keeps category="model", which is still valid. Happy to split this out if you'd rather land it separately.

Verification

Clean venv, pip install .:

• 21 dependencies (was ~75); no fastmcp / tavily / fastapi / uvicorn / acp / langfuse / rank-bm25 / dateutil installed or imported
• AgentFactory.create builds a working SGRToolCallingAgent; all 13 tools register
• sgrsh --help works; sgr and sgracp name their extra and exit 1
• pip install ".[mcp,search]" restores the fastmcp client and Tavily; server/acp/langfuse stay absent
• self-referential extras (all, examples, tests, dev) resolve correctly (needs pip ≥ 21.2)

New tests/test_optional_deps.py — 26 tests covering install hints, the core MCPConfig, both tavily call sites, MCP with fastmcp blocked, and both entrypoints. CI is green: 614 passed, and the suite now also runs clean on Windows (it did not before this branch).

Reviewer notes

• This is a breaking change. Upgrading without extras loses the sgr server and MCP. Worth a minor version bump and a release note pointing at pip install "sgr-agent-core[all]".
• openai deliberately stays in core. Its types (ChatCompletionMessageParam, ChatCompletionChunk, AsyncOpenAI) run through base_agent, stream, models, prompt_loader and the public API; removing it means rewriting the core typing, not adding a lazy import.
• One test was genuinely broken by this change and is fixed: test_extract_calls_tavily_api patched the now-absent module attribute AsyncTavilyClient; it patches tavily.AsyncTavilyClient at the source instead.
• The third commit fixes a separate pre-existing problem: GlobalConfig caches its instance on the class, and TestLangfuseConfiguration cleared that cache before building a config with langfuse.enabled=True but never after, so every later test inherited it. On a machine without the optional langfuse package that surfaced as 23 failures in test_agent_factory.py; on CI, where langfuse is installed, the pollution was silent — later tests ran with tracing enabled and passed for the wrong reason. An autouse fixture in conftest.py now resets the singleton around every test, making the suite order-independent. Happy to split this out too.

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