Tasks: tmux-backed observable/interactive harness sessions

Phase 3 of 3, derived from the approved design.md. TDD invariant (tdd.mode: standard): each task's test goes red before the production code makes it green; transitions recorded in the execution log.

Task list

• [x] 1. Session registry carries runner metadata
  • Add runner (default "process") + tmux_target to Session; serialize as runner/tmuxTarget; from_dict defaults keep old registry files readable.
  • Depends on: none
  • Requirements: R1.3, NFR back-compat
  • Test: cli/tests/test_tmux_runner.py::TestSessionRunnerFields (red→green)
• [x] 2. interactive_argv on the harness adapters
  • Base raises UnsupportedRunnerError; claude returns ["--session-id", <id>, <prompt>] + extra_args; cursor inherits the raise.
  • Depends on: none
  • Requirements: R2.1, R2.3
  • Test: cli/tests/test_tmux_runner.py::TestInteractiveArgv (red→green)
• [x] 3. TmuxRunner (spawn / deliver / kill / has_session / target_for) + dependency check
  • New cli/the_loop/runner.py per design §1; prompt via tempfile + load-buffer; check_dependencies returns per-platform guidance lines.
  • Depends on: 2
  • Requirements: R1.1, R3.1, R6.1–R6.2, R7 (mechanics)
  • Test: cli/tests/test_tmux_runner.py::TestTmuxRunner + ::TestCheckDependencies (red→green)
• [x] 4. Routing config: runner + webTerminal
  • RoutingConfig.runner, WebTerminalConfig; schema additions in .the-loop/config.schema.json; commented keys in .the-loop/config.yaml.
  • Depends on: none
  • Requirements: R1.2, R5.1–R5.2, NFR schema
  • Test: cli/tests/test_tmux_runner.py::TestRoutingConfigRunner; make validate (red→green)
• [x] 5. Dispatcher integration: spawn/deliver/close through the tmux runner
  • _spawn_for (uuid4 + register tmux session), _dispatch_one (session's recorded runner wins), PR-close kills the tmux session; failures discard delivery ids.
  • Depends on: 1, 2, 3, 4
  • Requirements: R1.1–R1.4, R2.1–R2.2, R3.1–R3.3, R7.1
  • Test: cli/tests/test_tmux_runner_integration.py (webhook→tmux scenarios, stub tmux) (red→green)
• [x] 6. Receiver preflight + ttyd web-terminal lifecycle
  • check_dependencies on start --route; spawn/terminate ttyd child when webTerminal.enabled (tmux new-session -A -s the-loop-hub).
  • Depends on: 3, 4
  • Requirements: R5.1–R5.4, R6.1–R6.2
  • Test: cli/tests/test_tmux_runner.py::TestReceiverPreflight (red→green)
• [x] 7. Sessions CLI: list columns, attach, close kills tmux
  • Runner/Tmux columns; attach --work-item [--read-only] exec's tmux with clear errors; close best-effort kill-session.
  • Depends on: 1, 3
  • Requirements: R4.1–R4.4, R7.2–R7.3
  • Test: cli/tests/test_tmux_runner.py::TestSessionsCli (red→green)
• [x] 8. Docs fold-in: capability doc, decision record, README/config docs
  • New docs/capabilities/interactive-sessions.md + index row; history row in webhook-triggers.md; docs/decisions/decision-021.md + index; execution log.
  • Depends on: 5, 6, 7
  • Requirements: ready-to-ship gate (capability fold-in)
  • Test: make lint (markdownlint) green

Dependency graph (DAG)

graph LR
    T1[1 registry fields] --> T5[5 dispatcher]
    T2[2 interactive_argv] --> T3[3 TmuxRunner]
    T2 --> T5
    T3 --> T5
    T4[4 config] --> T5
    T3 --> T6[6 receiver+ttyd]
    T4 --> T6
    T1 --> T7[7 sessions CLI]
    T3 --> T7
    T5 --> T8[8 docs fold-in]
    T6 --> T8
    T7 --> T8

Checkpoints

After tasks 3, 5 and 7: make test; after 8: make check (lint, format-check, typecheck, validate, test — CI parity). Red→green evidence per task in execution-log.md.