Same two-script chain as `map_chain_two_script_steps_route_via_next`,
with `validate_before_run: true`, proving the validator admits the
chains the runtime executes.
A map item no longer runs a single branch node; it walks the subgraph
reachable from `branch` over `next`/`fallback` edges (branch_subgraph),
one chain per item, holding one semaphore permit for the whole chain.
Chain steps go through the shared `step()` so llm retries, fallbacks,
script `_next` and agent timeouts keep their existing semantics. A node
without `next` ends the chain (StepContext.branch_mode), a route outside
the subgraph, a fan-out, an end node or a loop past
max_loop_iterations fails the item, and every item error carries
`map node 'X': sub-branch [i] failed at node 'Y' (step n)`.
`output_key` is removed from each item's fork before the chain runs, so
the collected value must be written by the chain rather than inherited
from the parent.
Teammate identities are now per item for the whole chain: provisioned
when any flagged agent is in the subgraph, armed only before
`teammates: true` agent steps, and retired at chain exit. mark_finished
moves out of run_agent_for_graph to the two provisioning sites (frontier
task and chain exit), so timed-out and early-failing agents are also
marked finished.
`MapNode.max_concurrency` becomes `Option<ConcurrencyCap>`, where
`ConcurrencyCap` is `Fixed(usize) | Template(String)`. Integers parse
exactly as before (`4` -> `Fixed(4)`, `0` -> `Fixed(0)`, absent -> `None`);
a string parses as a template that the map executor resolves against the
parent state right before the fan-out via `StateManager::interpolate_raw`,
mirroring `over:`. A template must resolve to an integer >= 1 or a numeric
string (scripts often emit numbers as strings); anything else, including 0,
is an error naming the map node, the template, and the resolved value/type.
The fixed path keeps its `.max(1)` clamp for byte-compatibility.
`Deserialize` is hand-written so a malformed value (`-1`, `4.5`, `true`,
a list, a map) reports the offending value and the accepted forms rather
than serde's opaque untagged-enum "did not match any variant".
Validator: a string cap that contains no `{{ ... }}` pair is a load-time
error (catches `"4"` typed for `4`); a templated cap joins the map node's
read set so `validate_parallel_reads` flags a read of a sibling branch's
write. The existing `Fixed(0)` rule and every other rule keep their order.
Design: plans/map-subgraph-branches-design.md §3.5, §3.11 (C3, I3).
Agent nodes marked teammates: true whose sub-agents run concurrently (map fan-out branches or multiple flagged agent nodes in one super-step) now form a team: each member gets a pre-provisioned inbox in a messaging-only PeerRegistry before any branch starts, a teammate roster injected into its prompt, peer resolution in agent__send_message, and a peers section in agent__list_running. Registries are scoped to a single fan-out and carry no lifecycle semantics: outputs still flow exclusively through collect_into/state reducers, finished peers reject new messages, and nothing registers in a supervisor. Also hardens the agent-recursion depth guard to work without a supervisor and adds validator warnings for zero-valued orchestration limits.
Dark-Alex-17