Kairos Plan solver

Plan solver plugin that uses Kairos, a temporal and numeric PDDL planner, as a library: no files are written and no process is started, so PlanSys2 examples plan in a few milliseconds.

• Temporal (durative actions, timed initial literals), numeric and classical domains, derived predicates, conditional effects and quantifiers.
• Anytime: the first plan comes fast, then Kairos improves it (shorter makespan) until no better plan arrives for no_improvement seconds or the time runs out.
• Every plan is validated before it is returned.
• The parsed domains are cached (by hash and text), so replanning with the same domain does not parse it again; a changed domain is parsed again.
• cancel() stops the search at once and returns the best plan found so far, if any.
• isDomainValid checks the domain without planning, and logs errors with line and column.

Usage

planner:
  ros__parameters:
    plan_solver_plugins: ["KAIROS"]
    KAIROS:
      plugin: "plansys2/KairosPlanSolver"

It can run together with other solvers (e.g. ["KAIROS", "POPF"]): the planner node returns the plans of all of them.

Parameters

All of them under the plugin name (e.g. KAIROS.anytime), read at each call:

Sequential plans (no durative actions) are returned with time = position (0, 1, 2…) and duration = 0.

Changelog for package plansys2_kairos_plan_solver

4.0.0 (2026-10-21)

• One version for Humble, Jazzy, Kilted and Lyrical (#509)
• Robust PlanSys2: one node per component, clients that wait, retry and see a lost plan (#507)
• Execute everything Kairos plans: conditional effects, durations, timed literals, object fluents, recursive derived predicates, PDDL+ and constraints (#504)
• Fixes in the executor, the build, the tests and the CI (#502)
• Kairos plan solver, and Kairos as the default planner (#465)
• New plan solver plugin that runs the Kairos planner in-process
• Contributors: Francisco Martín Rico