fix: use opencode identity for zai clients. address #50663

[dlukt]

What does this PR do?

Fixes Z.ai/Zhipu peak-hour 429s by applying an OpenCode-shaped client identity only for Z.ai endpoints.

For api.z.ai and open.bigmodel.cn, including https://api.z.ai/api/coding/paas/v4 and https://open.bigmodel.cn/api/coding/paas/v4, Hermes now sends User-Agent: opencode/1.17.9 and strips SDK X-Stainless-* fingerprint headers from final outbound requests.

This is scoped to Z.ai/Zhipu hosts and covers the main OpenAI-compatible client path, auxiliary OpenAI/AsyncOpenAI clients, and Z.ai Anthropic-compatible clients. User model.default_headers still wins as the manual override. The implementation intentionally does not send Hermes session ids or parent session ids as third-party headers.

Related Issue

Fixes #50663

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Security fix
• Documentation update
• Tests (adding or improving test coverage)
• Refactor (no behavior change)
• New skill (bundled or hub)

Changes Made

• Added agent/provider_client_identity.py for Z.ai host detection, OpenCode UA defaults, case-safe header merging, and final X-Stainless-* stripping hooks.
• Updated agent/agent_init.py and run_agent.py so main OpenAI-compatible Z.ai clients receive the Z.ai identity behavior.
• Updated agent/auxiliary_client.py so auxiliary OpenAI and AsyncOpenAI clients use the same Z.ai identity behavior.
• Updated agent/anthropic_adapter.py so Z.ai Anthropic-compatible clients preserve Anthropic beta headers while stripping SDK fingerprint headers.
• Updated gateway/TUI/ACP session context setup in gateway/run.py, tui_gateway/server.py, and acp_adapter/server.py to keep local session context propagation correct.
• Added Z.ai-focused coverage in tests/agent/test_zai_opencode_identity.py.
• Added regression coverage for canonical User-Agent overrides and session context propagation.

How to Test

1. Run:
   uv run --extra dev python -m pytest -p no:enabler tests/agent/test_zai_opencode_identity.py tests/agent/test_auxiliary_client.py tests/agent/test_auxiliary_named_custom_providers.py tests/agent/test_auxiliary_user_default_headers.py tests/agent/test_anthropic_adapter.py tests/run_agent/test_provider_attribution_headers.py tests/run_agent/test_create_openai_client_proxy_env.py tests/run_agent/test_session_id_env.py tests/gateway/test_session_env.py tests/test_tui_gateway_server.py --tb=short
2. Confirm Z.ai requests get User-Agent: opencode/1.17.9 and X-Stainless-* headers are stripped.
3. Confirm non-Z.ai providers remain unchanged and user model.default_headers can override the Z.ai UA.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: Linux

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) - or N/A
• I've updated cli-config.yaml.example if I added/changed config keys - or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows - or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide - or N/A
• I've updated tool descriptions/schemas if I changed tool behavior - or N/A

Screenshots / Logs

Targeted test suite passed:

764 passed in 38.08s

Additional checks passed:

• python -m py_compile ...
• git diff --check

[dlukt]

pytest tests/ -q
ERROR: usage: pytest [options] [file_or_dir] [file_or_dir] [...]
pytest: error: unrecognized arguments: --mypy-report-style --mypy-no-status-check
  inifile: /home/darko/hermes-agent/pyproject.toml
  rootdir: /home/darko/hermes-agent

[alt-glitch]

This was generated by AI during triage.

Fix PR for #50663 (z.ai peak-hour 429s). Note the root cause is most likely upstream Z.ai throttling keyed on client signature, so this spoofs an OpenCode identity rather than fixing a Hermes-side defect. Related to #47685 (phrase-triggered 429 when the system prompt contains "Hermes Agent").

[dlukt]

The proper fix is to spoof Zcode