---
phase: 06-structured-handoff-and-client-continuation
verified: 2026-02-23T06:00:00Z
status: passed
score: 13/13 must-haves verified
gaps: []
---

# Phase 6: Structured Handoff and Client Continuation Verification Report

**Phase Goal:** After partial execution, the prompt reply tells the LLM client exactly what was done and what to do next, and follow-up tool calls reconnect to the workflow task
**Verified:** 2026-02-23T06:00:00Z
**Status:** PASSED
**Re-verification:** No — initial verification

## Goal Achievement

### Observable Truths

| #  | Truth                                                                                                           | Status     | Evidence                                                                                      |
|----|----------------------------------------------------------------------------------------------------------------|------------|-----------------------------------------------------------------------------------------------|
| 1  | When execution pauses, the prompt reply includes a final assistant message narrating remaining steps with tool names, resolved arguments, and guidance | VERIFIED | `build_handoff_message` called at line 858-862 of `task_prompt_handler.rs` when `pause_reason.is_some()` |
| 2  | The handoff does NOT repeat completed steps                                                                     | VERIFIED   | `build_handoff_message` only iterates `StepStatus::Pending` steps (line 466-497) and retryable-failed (line 423-463) |
| 3  | Task ID appears only in `_meta`, never in the narrative text                                                   | VERIFIED   | `handoff_message_no_task_id_in_text` test passes; narrative text never constructs a task_id string |
| 4  | Arguments that cannot be resolved use placeholder syntax: `<output from step_name>`                             | VERIFIED   | `build_placeholder_args` at line 316-342; `placeholder_args_step_output` test passes          |
| 5  | Step guidance text is included when the step has a guidance field                                               | VERIFIED   | Lines 453-457 and 491-494 in `task_prompt_handler.rs`; `handoff_includes_guidance` test passes |
| 6  | The `_meta` JSON block plus the narrative assistant message together form the hybrid format                     | VERIFIED   | Handoff message pushed to `messages` vec (line 861), then `_meta` added to `GetPromptResult` (line 951) |
| 7  | A follow-up tools/call with `_task_id` in `_meta` executes the tool AND records result in workflow task variables | VERIFIED   | `ServerCore` intercept at `core.rs` line 765-800; `handle_workflow_continuation` in `router.rs` line 414 |
| 8  | When tool matches a remaining workflow step, result stored under `_workflow.result.<step_name>` and step status updated | VERIFIED   | `router.rs` lines 459-497; `handle_workflow_continuation_matches_step` test passes            |
| 9  | When tool does NOT match any workflow step, result stored under `_workflow.extra.<tool_name>`                   | VERIFIED   | `router.rs` line 469-472; `handle_workflow_continuation_unmatched_tool` test passes           |
| 10 | Continuation recording is fire-and-forget: tool result returned regardless of recording success                 | VERIFIED   | `tracing::warn!` on failure but `Self::success_response(id, ...)` always returned at line 800 |
| 11 | `tasks/cancel` with a result field completes the task (not cancels it)                                         | VERIFIED   | `handle_tasks_cancel` branches on `cancel_params.result` at line 252; `handle_tasks_cancel_with_result_completes` test passes |
| 12 | `tasks/result` returns standard task data including `_workflow.*` variables                                     | VERIFIED   | `handle_tasks_result` at `router.rs` line 190 calls `store.get_result`; returns variables     |
| 13 | Retries: last result wins — calling same step tool twice overwrites previous result                             | VERIFIED   | `handle_workflow_continuation_last_result_wins` test passes                                   |

**Score:** 13/13 truths verified

### Required Artifacts

| Artifact                                         | Expected                                                      | Status     | Details                                                              |
|--------------------------------------------------|---------------------------------------------------------------|------------|----------------------------------------------------------------------|
| `src/server/workflow/task_prompt_handler.rs`     | `build_handoff_message` method and `build_placeholder_args` helper | VERIFIED | Both methods exist and are substantive; integrated in `handle()` |
| `src/types/protocol.rs`                          | `_task_id` field on `RequestMeta`                             | VERIFIED   | Line 990-992, with `serde(rename = "_task_id")` for correct JSON    |
| `src/server/tasks.rs`                            | `handle_workflow_continuation` default no-op method on `TaskRouter` | VERIFIED | Lines 151-159, default returns `Ok(())`                        |
| `src/server/core.rs`                             | `_task_id` intercept in tool call path                        | VERIFIED   | Lines 765-800; extracts context, fires continuation, returns result  |
| `crates/pmcp-tasks/src/router.rs`                | `TaskRouterImpl` implementation of `handle_workflow_continuation` and cancel-with-result | VERIFIED | Lines 414-510 (continuation) and 248-276 (cancel) |
| `crates/pmcp-tasks/src/types/params.rs`          | Extended `TaskCancelParams` with optional `result` field      | VERIFIED   | Lines 161-174; `result: Option<serde_json::Value>` with skip_serializing_if |
| `crates/pmcp-tasks/src/types/workflow.rs`        | `WORKFLOW_EXTRA_PREFIX` constant                              | VERIFIED   | Line 74: `pub const WORKFLOW_EXTRA_PREFIX: &str = "_workflow.extra."` |

### Key Link Verification

| From                                             | To                                              | Via                                                          | Status  | Details                                                                 |
|--------------------------------------------------|-------------------------------------------------|--------------------------------------------------------------|---------|-------------------------------------------------------------------------|
| `TaskWorkflowPromptHandler::handle()`            | `build_handoff_message()`                       | Called when `pause_reason.is_some()` before returning result | WIRED   | Lines 858-862 in `task_prompt_handler.rs`                               |
| `build_handoff_message()`                        | `resolve_tool_parameters()` with fallback       | Attempts resolution, falls back to `build_placeholder_args` on Err | WIRED | Lines 439-445 and 476-484                                        |
| `ServerCore::handle_request_internal` (CallTool) | `TaskRouter::handle_workflow_continuation`      | Fire-and-forget after normal tool execution when `_task_id` present | WIRED | `core.rs` lines 776-799                                          |
| `TaskRouterImpl::handle_workflow_continuation`   | `TaskStore::set_variable / get_variable`        | Loads `_workflow.progress`, matches tool, updates variables   | WIRED   | `router.rs` lines 442-508; reads `WORKFLOW_PROGRESS_KEY`, batch-writes  |
| `TaskRouterImpl::handle_tasks_cancel`            | `TaskStore::complete_with_result`               | Branches on presence of `result` field in `TaskCancelParams` | WIRED   | `router.rs` lines 252-263                                               |

### Requirements Coverage

| Requirement | Source Plan | Description                                                                              | Status    | Evidence                                                                   |
|-------------|-------------|------------------------------------------------------------------------------------------|-----------|----------------------------------------------------------------------------|
| HAND-01     | 06-01-PLAN  | Prompt reply includes structured handoff as final assistant message                      | SATISFIED | `build_handoff_message` appended to `messages` vec when `pause_reason.is_some()` |
| HAND-02     | 06-01-PLAN  | Handoff format is hybrid: JSON block for machine parsing plus natural language for LLM   | SATISFIED | `_meta` JSON block + narrative `PromptMessage` both present in `GetPromptResult` |
| HAND-03     | 06-01-PLAN  | Each remaining step includes tool name, expected arguments (resolved or placeholder), guidance text | SATISFIED | Lines 431-496 in `task_prompt_handler.rs`; 7 new tests covering all variants |
| CONT-01     | 06-02-PLAN  | Follow-up tool calls can reference workflow task via `_task_id` in request `_meta`       | SATISFIED | `RequestMeta._task_id` field; `ServerCore` intercept reads it              |
| CONT-02     | 06-02-PLAN  | Task variables updated with step results when tool calls include `_task_id` binding      | SATISFIED | `handle_workflow_continuation` writes `_workflow.result.<step>` and updates progress |
| CONT-03     | 06-02-PLAN  | Client can poll `tasks/result` to check overall workflow completion status               | SATISFIED | `handle_tasks_result` returns task data including all `_workflow.*` variables |

All 6 requirements (HAND-01, HAND-02, HAND-03, CONT-01, CONT-02, CONT-03) are satisfied. No orphaned requirements found.

### Anti-Patterns Found

None detected. All references to "placeholder" in modified files are legitimate references to the `build_placeholder_args` function and its test cases. No TODO/FIXME/HACK/unimplemented stubs in phase-modified code paths.

**Note:** A pre-existing property test failure exists in `crates/pmcp-tasks/tests/property_tests.rs` (`fresh_task_record_is_not_expired` — TTL overflow in proptest edge case). This failure predates Phase 6 (introduced in Phase 2 commit `089a6d0`) and is tracked in the regression file. It is not a regression from Phase 6 work.

### Human Verification Required

None. All behavioral invariants are verifiable programmatically through the test suite and code inspection:
- 18/18 tests pass in `workflow::task_prompt_handler`
- 33/33 router tests pass in `pmcp-tasks`
- 191/191 lib unit tests pass in `pmcp-tasks`
- 3/3 `RequestMeta._task_id` serialization tests pass
- Zero clippy warnings on both `pmcp` and `pmcp-tasks`

### Test Coverage Summary

| Test Module                                          | Tests | Result  |
|------------------------------------------------------|-------|---------|
| `pmcp::server::workflow::task_prompt_handler::tests` | 18    | All pass |
| `pmcp_tasks::router::tests` (continuation + cancel)  | 7 new | All pass |
| `pmcp_tasks::types::workflow::tests`                 | subset | All pass |
| `pmcp_tasks::types::params::tests`                   | `task_cancel_params_with_result` | Pass |
| `pmcp::types::protocol::tests` (`_task_id` serde)   | 3     | All pass |

### Gaps Summary

No gaps. All must-haves are verified at all three levels (exists, substantive, wired). The phase goal is fully achieved: when a workflow pauses, the prompt reply provides both a machine-readable `_meta` JSON block and a human-readable assistant message narrating what happened and what to do next; follow-up tool calls with `_task_id` in `_meta` reconnect to the workflow task and update step progress in a fire-and-forget pattern; `tasks/cancel` with a `result` field completes the task.

---

_Verified: 2026-02-23T06:00:00Z_
_Verifier: Claude (gsd-verifier)_
