The conversation loop has forced stream=True for every turn — subagents
included — since #3120 (always-prefer-streaming for liveness health
checking). Self-hosted OpenAI-compatible backends with broken streaming
tool-call paths (e.g. vLLM --tool-call-parser qwen3_xml + reasoning
parser + MTP) can leak tool-call markup into plain text and return zero
tool_calls, so delegated tasks silently no-op instead of executing.
model.streaming was never a real config key, so users could not opt out.
Seed agent._disable_streaming from model.streaming: false at init; the
loop already routes that flag to the non-streaming path (the same path
used when a provider rejects streaming at runtime). Default stays
streaming-on, preserving #3120's behavior for everyone else. Orthogonal
to display.streaming (token rendering).
Tests: config->flag seeding (patched loader + real config.yaml E2E),
legacy string model section, multi-agent config propagation.
David Metcalfe