Completes the maintainer's removal of per-call model selection from
subagent spawns (9f8aa87dbf removed it from the task tool and the
model-facing agent() docs/prompt, but the eval agent() runtime and all
four preludes still accepted and forwarded a per-call model).
Subagents now always resolve through the selected agent's frontmatter
model and settings, so an explicit model: "default" can no longer
silently route children onto the parent session model.
- agent-bridge: drops "model?" from agentArgsSchema and the request
forward; adds "+": "delete" so a legacy model argument is stripped
(same contract as the task wire schemas).
- JS/Python/Ruby/Julia preludes: remove the model parameter from
agent(); completion()'s tier selector is unchanged.
- docs (tools/eval.md, python-repl.md) updated to the removed surface.
Refs #6438
- Split the Python bridge signal: the raw abort reaches tools (so
subagents die with the turn) while a shielded signal governs how long
the host waits, so a cancel can no longer settle a cell on top of a
still-running isolation merge.
- Mirrored the contract in the JS runtime: abort in-flight tool calls
immediately, then drain any deferExternalAbort phase before killing
the worker, and refuse new bridge calls once cancelled.
- Held a finished worker result until the run's tool calls drain. A
floated agent() previously settled the cell at once, dropping the
run's abort listener and leaving the subagent running with nothing
able to cancel it.
- Added regression coverage for all three, each verified to fail
without its fix.
Slava Zavadsky