Fixes four production bugs hit while running DeepTutor from source (Option 2) against Claude Opus 4.8 with an Obsidian vault KB. Three are request/tool failures that break core flows; one is a Windows-only stability bug that silently swallows backend tracebacks. Each fix ships with regression tests.

[tcctvcctv]

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Summary

Fixes four production bugs hit while running DeepTutor from source (Option 2)
against Claude Opus 4.8 with an Obsidian vault KB. Three are request/tool
failures that break core flows; one is a Windows-only stability bug that
silently swallows backend tracebacks. Each fix ships with regression tests.

Bugs & Fixes

1. Anthropic: exceeds 4 cache_control breakpoints → 400 invalid_params

AnthropicProvider._apply_cache_control could emit system(1) + message(1) +
tools(N) cache_control markers. With many tools mounted (e.g. the 9 Obsidian
tools), the total exceeded Anthropic's hard limit of 4, so every request failed:

  {'error': {'code': '400', 'type': 'invalid_params',
   'message': 'A maximum of 4 blocks with cache_control may be provided. Found 5.'}}

Fix: budget the breakpoints to a max of 4 across tools + system + messages,
keeping the highest-value tool breakpoint first.
deeptutor/services/llm/provider_core/anthropic_provider.py

2. Anthropic: temperature sent to Opus 4.7+ → 400 invalid_params

temperature is deprecated on Opus 4.7 and later; sending it makes those models
reject the request. The guard only matched opus-4-7, so opus-4-8 (and 4.9/
4.10+) still broke:

  {'error': {'code': '400', 'type': 'invalid_params',
   'message': '`temperature` is deprecated for this model.'}}

Fix: omit temperature for opus-4-(7|8|9|10+) via
re.search(r"opus-4-([7-9]|\d{2,})", model_name).
deeptutor/services/llm/provider_core/anthropic_provider.py

3. obsidian_read crashes on date: frontmatter → tool failure

Obsidian notes commonly carry a date: field. yaml.safe_load parses it into a
Python datetime.date, which json.dumps cannot serialize, so any such note
failed to read:

  TypeError: Object of type date is not JSON serializable
  → "Tool obsidian_read failed"

Fix: _ok() now calls json.dumps(..., default=str) so date/datetime
values render as strings.
deeptutor/capabilities/obsidian/tools.py

4. Launcher: GBK console crash kills the output-draining thread (Windows)

_stream_output used bare print(). On a GBK/cp936 Windows console, a non-CP936
char (e.g. ✓) in a subprocess line raised UnicodeEncodeError, killing the
drain thread. That both hid backend tracebacks and could block the backend once
the pipe buffer filled (observed as a hang/freeze).

Fix: guard print() with a UnicodeEncodeError fallback that re-encodes
with errors="replace".
deeptutor/runtime/launcher.py

Tests

• tests/services/llm/test_anthropic_cache_control.py — ≤4 cache blocks across tool counts
• tests/services/llm/test_anthropic_temperature.py — temperature omitted for Opus 4.7+, sent for older models
• tests/capabilities/obsidian/test_obsidian_read_date.py — obsidian_read handles date frontmatter

All 16 tests pass. Each fix was verified two-way (revert → fails with the exact
production error; restore → passes).

Environment

Python 3.12.7 · Windows 10 · provider routed via zenmux.ai · model claude-opus-4-8.

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