v0.3.0 — two providers, two migrations documented

v0.3.0 — 2026-09-02

• Second provider: Anthropic Messages API (--provider anthropic, endpoint messages),
  same statistics and repair loop, no provider forks in the core. Prompt caching on the
  cached prefix; cache-write pricing; identity-linked keys via ANTHROPIC_WORKSPACE_ID.
• Anthropic's documented Fable 5 → 5.1 changes as detectors and repairs: forced
  tool_choice 400 (remove + instruction), thinking-block invalidation (detect, refuse
  with the documented pointer), serialized tool calls (turns_at_most + the documented
  batching sentence), reduced retrieval at low effort (effort ladder + documented nudge),
  unsupported sampling params (drop). Effort calibration is a first-class repair.
• sim-fable-5 / sim-fable-5-1 for keyless rehearsal; upshift adapt reads Anthropic
  call sites and Jupyter notebooks.
• Release-day report on four open-source Claude agents (reports/fable-5-1-upgrade.md).
• Runner aborts on billing/quota errors instead of recording junk reps.

Full evidence: reports/fable-5-1-upgrade.md · reports/shellgpt-upgrade.md