Summary

• Consolidates the overlapping Plan+Execute handoff fixes into one focused PR.
• Allows guidance-only executor handoffs to finish with a text-only answer while keeping the missing-action nudge for real work tasks.
• Skips the executor when the planner explicitly concludes no changes/action are needed.
• Reinforces executor handoffs so planner tool limitations or MCP-unavailable claims do not become executor facts.
• Routes PE planner gating through the same synthetic-message, low-risk-question, and optional auto-plan classifier logic used by the single-model flow.

Fixes #4867.
Fixes #4909.
Fixes #4830.
Refs #4732.

Consolidation Notes

Kept or adapted:

• fix(agent): allow guidance-only executor handoffs #4898 by @GTC2080: kept the conditional guidance-only handoff behavior rather than removing the nudge entirely.
• fix(coordinator): respect planner 'no changes needed' conclusion #4868 and part of feat: add model routing hints and ShouldDelegateTask for simple task delegation #4893 by @eghrhegpe: kept the no-op planner conclusion skip, but narrowed the phrase set to avoid treating generic positive language as no-op.
• fix(control): Goal synthetic messages should skip Planner in two-model mode #4910 and fix(planner): skip planning for synthetic goal-loop messages #4872 by @eghrhegpe: kept synthetic goal-loop messages skipping planner, including active-goal wrappers.
• fix(agent): reinforce executor tool handoff #4842 by @GTC2080: kept the executor tool-schema reminder and bounded MCP/tool context.
• fix(agent): widen planner gate and wire LLM classifier into Coordinator (#4732) #4792 by @ashishexee: kept the wider low-risk question gate and wired the optional classifier into PE routing.

Reviewed and credited as repository contributor work, but not adopted in the final code:

• fix(agent): remove executor handoff nudge for guidance-only tasks #4929 by @liaoyl830 removes the executor handoff nudge wholesale; this PR keeps the nudge for real work tasks.
• feat(coordinator): post-exec verify + /orchestrate + shouldPlan classifier + plan-exec auto-dispatch #4927 by @eghrhegpe mixes post-exec build verification, /orchestrate, and dispatch changes; those are broader than this PE bug-fix PR.
• fix(agent): reset planner session on tab switch to prevent cross-session contamination #4934 by @liaoyl830 is not included because latest main-v2 already passes planner output directly through the active Coordinator rather than a project-level handoff buffer; resetting planner state during tab activation could race with in-flight planning. test(desktop): cover PE tab handoff isolation #4930 by @GTC2080 remains a useful isolation-test direction as a separate follow-up for [Bug]: Plan-Execute dual-model: per-project handoff buffer not isolated by topicId, causes cross-session plan contamination #4926.
• Fix stale planner model startup / 修复陈旧规划模型导致启动失败 #4616 by @GTC2080 is planner_model startup/config resilience, not PE handoff or routing behavior.

Repository Contributor Credits

This integration PR intentionally credits both adopted work and reviewed alternatives. Even when a source PR was not adopted in the final code, its author still contributed to the repository by investigating the problem space, testing a possible direction, or clarifying the integration boundary.

• @GTC2080 for fix(agent): allow guidance-only executor handoffs #4898, fix(agent): reinforce executor tool handoff #4842, test(desktop): cover PE tab handoff isolation #4930, and Fix stale planner model startup / 修复陈旧规划模型导致启动失败 #4616.
• @eghrhegpe for fix(coordinator): respect planner 'no changes needed' conclusion #4868, feat: add model routing hints and ShouldDelegateTask for simple task delegation #4893, fix(control): Goal synthetic messages should skip Planner in two-model mode #4910, fix(planner): skip planning for synthetic goal-loop messages #4872, and feat(coordinator): post-exec verify + /orchestrate + shouldPlan classifier + plan-exec auto-dispatch #4927.
• @ashishexee for fix(agent): widen planner gate and wire LLM classifier into Coordinator (#4732) #4792.
• @liaoyl830 for fix(agent): remove executor handoff nudge for guidance-only tasks #4929 and fix(agent): reset planner session on tab switch to prevent cross-session contamination #4934.

Cache Impact

Cache-impact: low. This PR does not change the system prompt, memory prefix, tool schema bytes/order, provider request serialization, or compaction behavior. The handoff text is a runtime user-turn payload for PE turns only, and the tool-name summary is bounded.

Cache-guard: focused coordinator and planner-gate regressions cover the new behavior; full root and desktop Go test suites passed.
System-prompt-review: N/A.

Verification

• go test ./internal/agent ./internal/control ./internal/boot -run 'TestCoordinator|TestTaskWarrantsPlanner|TestAutoPlanScore|TestNewPlannerGate|TestBuild' -count=1
• go test ./internal/agent ./internal/control ./internal/boot -count=1
• go test ./...
• (cd desktop && go test ./...)
• go vet ./...
• (cd desktop && go vet ./...)
• git diff --check
• gofmt -l internal/agent/agent.go internal/agent/coordinator.go internal/agent/coordinator_test.go internal/boot/boot.go internal/control/auto_plan.go internal/control/auto_plan_test.go internal/control/input.go