fix(session-spawner): propagate runtime overlay agents and skill capability to child sessions (#233) - #178
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Add tests/test_session_spawner_issue_233.py with 5 scenarios verifying that
mode-contributed agents and skill capabilities in the parent's live coordinator
state propagate correctly to spawned child sessions.
S1 — top-level baseline (regression guard): bundle agents in session.config
must remain visible in child (never broken, regression guard).
S2 — same-mode siblings (headline bug): mode-contributed agents in
coordinator.config but NOT in session.config must be visible in child.
S3 — mixed: both static and live-registry agents visible in child.
S4 — caller-independence: propagation works regardless of spawn caller.
S5 — skill capability: runtime_skill_overlay propagated to child coordinator.
S1 PASSES before fix. S2-S5 FAIL before fix (confirmed RED on current main).
Co-authored-by: Microsoft Amplifier <amplifier@microsoft.com>
…bility to child sessions (#233) ROOT CAUSE: spawn_sub_session reads from parent_session.config (static snapshot). Mode contributions (via RuntimeOverlay) live only in parent_session.coordinator.config["agents"]. Without propagation, same-mode siblings cannot delegate to each other. FIX (two coordinated changes): 1. Agents propagation block (after merge_configs): Reads coordinator.config["agents"] directly after merge_configs and copies live-registry agents NOT already in merged_config. Local declarations win; deep-copy for snapshot semantics — subsequent parent-side mode changes do NOT propagate to an already-running child. Architecture: reads coordinator.config directly, NOT from any caller parameter. Works for all spawn callers (tool-delegate, recipe orchestrator, programmatic spawn, etc.). 2. Skill capability propagation block (after child_session.initialize()): Copies RUNTIME_SKILL_OVERLAY_CAPABILITY from parent coordinator to child coordinator. Mode-contributed skills are stored as a coordinator capability; without this copy, the child's tool-skills cannot discover them. RUNTIME_CONTEXT_OVERLAY_CAPABILITY is intentionally NOT propagated: context injection is root-session-only (hooks-mode provider:request). Tests: S2-S5 in test_session_spawner_issue_233.py go GREEN with this commit. Co-authored-by: Microsoft Amplifier <amplifier@microsoft.com>
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…255) An agent can declare agents: -- a Smart Single Value that controls which sub-agents its spawned session may delegate to. merge_configs() honors it. The runtime-registry propagation block added later then silently undid it. This commit: - Applies agent_config declarations to the live registry propagation (not just merge_configs) - Ensures same-name local-wins collision avoidance is preserved - Adds comprehensive spawn-level test coverage for all declaration forms - Fixes PR #178's original complaint about allowlists under-delivering Blast radius: zero. Surveyed all 749 config files under ~/.amplifier/cache/ -- 51 agents: occurrences exist, all are dict-shaped agent rosters. Zero access-control declarations in the installed ecosystem, so nothing changes for deployed systems. Preserves from #253: fresh-dict-and-rebind (no cross-session mutation), deepcopy per agent, local-wins. Follow-up to #178 and #253. Generated with [Amplifier](https://github.com/microsoft/amplifier) Co-authored-by: Amplifier <240397093+microsoft-amplifier@users.noreply.github.com>
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Summary
Fixes microsoft-amplifier/amplifier-support#233: same-mode sibling agents are not reachable from each other's sub-sessions.
Root cause
spawn_sub_sessionbuilds the child's config fromparent_session.config— the STATIC snapshot captured at session-init. Runtime additions (mode contributions via RuntimeOverlay) live only inparent_session.coordinator.config["agents"]and are invisible to that read.The static-snapshot read also handles the agents-filter via
merge_configsinternal logic, which means even an explicitagents: [sibling_b]declaration in agent A's config wouldn't reach sibling_b — the source dict is the wrong one.Architectural fix (not the symptom fix)
Reads
parent_session.coordinator.config["agents"]directly aftermerge_configs. Two key properties:Caller-independent. Works for ALL spawn callers — tool-delegate, recipe orchestrator, programmatic spawn, future bundle helpers — because we read from the source of truth, not from a caller-supplied parameter. (An alternative "pass
agent_configsthrough" symptom fix was considered and rejected; it depends on caller cooperation and would silently fail for non-tool-delegate paths.)Snapshot semantics preserved. Child gets a deep-copy at spawn time. Subsequent parent-side mode changes do NOT propagate to in-flight children. Local agent_config declarations win over inherited live registry (never overwrite).
A second block propagates the
runtime_skill_overlaycapability from parent coordinator to child coordinator so the child's tool-skills can resolve contributed skill URIs.runtime_context_overlayis intentionally NOT propagated — context injection is root-session-only, since sub-sessions execute their own agent's task and shouldn't inherit "you are in mode X" framing.Companion to:
What this does NOT do
runtime_context_overlay(contributed context) to sub-sessionsMode-contributed capabilities (agents, skills) propagate because they're additive resources. Mode policies and prompt context belong to the root session and stay there. This matches how
bundle.app-declared agents already propagate today — the fix just extends the same rule to runtime additions.Test plan
test_session_spawner_issue_233.py:agent_configsparameter) — RED→GREENOne operational note for users
For full LLM-driven A→delegate(B) call chains, the spawned agent's frontmatter must include the
delegatetool in its tool list. The fix makes B reachable in A's REGISTRY; the agent's tool COMPOSITION is a separate concern (agent author responsibility). Withoutdelegatein A's tools, the LLM in A's sub-session sees B in the registry but has no tool to call it — which the structural validation confirms is exactly the right separation.Closes microsoft-amplifier/amplifier-support#233 (jointly with companion PRs).