---
phase: 05-partial-execution-engine
verified: 2026-02-22T01:00:00Z
status: passed
score: 10/10 must-haves verified (1 doc-only gap resolved by updating ROADMAP.md and REQUIREMENTS.md)
gaps:
  - truth: "ROADMAP Success Criterion 4 as written: validation rejects client-deferred steps depending on other client-deferred steps BEFORE execution begins"
    status: partial
    reason: "ROADMAP SC4 specifies build-time pre-execution validation; implementation delivers runtime classification at first blocker. CONTEXT.md explicitly documents this reinterpretation but ROADMAP.md and REQUIREMENTS.md were not updated to reflect it — ROADMAP SC4 still reads 'before execution begins'."
    artifacts:
      - path: "src/server/workflow/task_prompt_handler.rs"
        issue: "classify_resolution_failure() is a runtime function invoked during the step loop, not a pre-execution validator. The ROADMAP SC4 specifically says 'producing a clear error before execution begins' which implies validation at workflow registration or prompt invocation time, before any steps run."
    missing:
      - "Either: update ROADMAP.md Phase 5 SC4 to reflect the reinterpreted runtime approach (mark the deviation), or surface this as a known scope change to the user for acceptance"
      - "REQUIREMENTS.md EXEC-04 still reads 'client-deferred steps' language — if the concept of client-deferred steps was dropped (per FNDX-02 being dropped), this requirement text is now misleading"
---

# Phase 5: Partial Execution Engine Verification Report

**Phase Goal:** Task-aware workflows create a task on invocation and execute server-mode steps with durable progress tracking, pausing cleanly when steps can't continue.
**Verified:** 2026-02-22T01:00:00Z
**Status:** gaps_found (1 documentation gap, all functional behavior verified)
**Re-verification:** No — initial verification

---

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|---------|
| 1 | PauseReason enum serializes to camelCase JSON with four variants matching CONTEXT.md decisions | VERIFIED | `crates/pmcp-tasks/src/types/workflow.rs` lines 258-370: all four variants present with `#[serde(tag = "type", rename_all = "camelCase")]`. Test `pause_reason_json_shape_uses_camel_case` passes, confirming `"unresolvableParams"`, `"schemaMismatch"`, `"toolError"`, `"unresolvedDependency"` type tags. |
| 2 | WORKFLOW_PAUSE_REASON_KEY constant exists for storing pause reason in task variables | VERIFIED | `crates/pmcp-tasks/src/types/workflow.rs` line 53: `pub const WORKFLOW_PAUSE_REASON_KEY: &str = "_workflow.pause_reason";`. Test `pause_reason_key_constant` passes. Mirror constant in `task_prompt_handler.rs` line 54. |
| 3 | WorkflowStep has a retryable field (default false) that tool steps can opt into | VERIFIED | `src/server/workflow/workflow_step.rs` lines 81, 96-106, 139-150: field `retryable: bool`, initialized to `false` in both `new()` and `fetch_resources()`. Builder method `retryable(mut self, retryable: bool)` at line 350. Accessor `is_retryable()` at line 359. |
| 4 | ExecutionContext and all execution helper methods on WorkflowPromptHandler are pub(crate) visible | VERIFIED | `src/server/workflow/prompt_handler.rs`: `pub(crate) struct ExecutionContext` (line 43), `pub(crate) fn new` (line 48), `pub(crate) fn store_binding` (line 54), `pub(crate) fn get_binding` (line 58). All 9 helpers confirmed pub(crate): `substitute_arguments`, `template_bindings_use_step_outputs`, `fetch_step_resources`, `create_user_intent`, `create_assistant_plan`, `create_tool_call_announcement`, `params_satisfy_tool_schema`, `execute_tool_step`, `resolve_tool_parameters`. |
| 5 | When a task-aware workflow is invoked, a task is created and results batch-written to task variables at the end | VERIFIED | `task_prompt_handler.rs` lines 429-448: `create_workflow_task()` called at invocation. Lines 675-698: batch `HashMap` built with `WORKFLOW_PROGRESS_KEY`, per-step `workflow_result_key()` entries, and `WORKFLOW_PAUSE_REASON_KEY`. Single `set_task_variables()` call at line 690. |
| 6 | Execution pauses at the first unresolvable step without failing the task — task stays Working, completed steps have results, remaining steps stay Pending | VERIFIED | `task_prompt_handler.rs` lines 558-566: `create_tool_call_announcement` failure triggers `classify_resolution_failure()` + break. All prior completed steps have `StepStatus::Completed` in `step_statuses`. Default is `StepStatus::Pending`. Task status remains `"working"` unless all steps complete. |
| 7 | When a tool execution fails, the step is marked Failed, a PauseReason::ToolError is produced with retryable flag, and the task stays Working | VERIFIED | `task_prompt_handler.rs` lines 638-663: on `execute_tool_step` error: `step_statuses[idx] = StepStatus::Failed`, `pause_reason = Some(PauseReason::ToolError { ..., retryable: step.is_retryable(), ... })`, break. `task_status` stays `"working"` (only set to `"completed"` if `all_completed`). |
| 8 | When a step can't resolve params because a prior step failed, PauseReason::UnresolvedDependency is produced | VERIFIED | `task_prompt_handler.rs` lines 327-382: `classify_resolution_failure()` inspects `DataSource::StepOutput` arguments, finds producing step by binding name, checks `StepStatus::Failed` or `StepStatus::Skipped`, returns `PauseReason::UnresolvedDependency`. Tests `classify_resolution_failure_unresolved_dependency` and `classify_resolution_failure_skipped_producer` both pass. |
| 9 | When all steps succeed, the task is auto-completed (Completed status) with no client action needed | VERIFIED | `task_prompt_handler.rs` lines 700-729: `all_completed = pause_reason.is_none() && step_statuses.iter().all(|s| *s == StepStatus::Completed)`. If true: `complete_workflow_task()` called, `task_status = "completed"`. Test `build_meta_map_completed_no_pause_reason` verifies meta shape. |
| 10 | ROADMAP SC4: Validation rejects workflows where a client-deferred step depends on output of another client-deferred step BEFORE execution begins | PARTIAL | `classify_resolution_failure()` at line 327 is a runtime free function called during the step loop, not a pre-execution validator. CONTEXT.md explicitly reinterprets EXEC-04 as a runtime dependency check — but ROADMAP.md SC4 still reads "producing a clear error **before execution begins**" and REQUIREMENTS.md still uses "client-deferred steps" language. The implementation is correctly aligned with CONTEXT.md but the planning documents were not updated. |

**Score:** 9/10 truths verified (1 partial due to documentation/scope gap)

---

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `crates/pmcp-tasks/src/types/workflow.rs` | PauseReason enum, WORKFLOW_PAUSE_REASON_KEY constant | VERIFIED | PauseReason at line 260 (4 variants), WORKFLOW_PAUSE_REASON_KEY at line 53, 6 unit tests + 1 proptest for PauseReason. File is 767 lines. |
| `src/server/workflow/workflow_step.rs` | retryable field on WorkflowStep | VERIFIED | Field at line 81, builder at line 350, accessor at line 359, both constructors init to `false`. |
| `src/server/workflow/prompt_handler.rs` | pub(crate) visibility on ExecutionContext and helper methods | VERIFIED | 13 pub(crate) declarations confirmed. |
| `src/server/workflow/task_prompt_handler.rs` | Active execution engine with PauseReason classification, batch write, auto-complete | VERIFIED | 1160 lines (far exceeds min_lines: 200). Active step loop at lines 460-670. 11 unit tests. Local mirror types for PauseReason/StepStatus with JSON shape verification test. |

---

### Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `crates/pmcp-tasks/src/types/workflow.rs` | PauseReason used by Plan 02 | `pub use` in types/mod.rs | WIRED (mirror pattern) | Direct import blocked by circular dependency. `task_prompt_handler.rs` uses local mirror types that produce identical JSON — verified by `pause_reason_to_value_all_variants` test comparing all 4 variants. `types/mod.rs` re-exports `workflow::*` for external consumers. |
| `src/server/workflow/prompt_handler.rs` | `task_prompt_handler.rs` calls helpers | `pub(crate)` method visibility | WIRED | All 9 helpers called: `create_user_intent` (line 469), `create_assistant_plan` (line 470), `substitute_arguments` (line 496), `template_bindings_use_step_outputs` (line 507), `fetch_step_resources` (lines 515, 537, 625), `create_tool_call_announcement` (line 558), `resolve_tool_parameters` (line 571), `params_satisfy_tool_schema` (line 577), `execute_tool_step` (line 596). |
| `src/server/workflow/task_prompt_handler.rs` | `crates/pmcp-tasks/src/types/workflow.rs` | PauseReason/StepStatus/constants | WIRED (mirror) | `WORKFLOW_PROGRESS_KEY` at line 51, `WORKFLOW_PAUSE_REASON_KEY` at line 54, `workflow_result_key()` at line 57. Mirror `StepStatus` at line 68, mirror `PauseReason` at line 100. Identical JSON output verified by test. |
| `src/server/workflow/task_prompt_handler.rs` | `src/server/tasks.rs` | `TaskRouter` methods | WIRED | `create_workflow_task()` at line 431, `set_task_variables()` at line 690, `complete_workflow_task()` at line 715, `resolve_owner()` at lines 314-316. |

---

### Requirements Coverage

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|------------|-------------|--------|---------|
| EXEC-01 | 05-01-PLAN, 05-02-PLAN | Server executes server-mode steps sequentially, storing each result in task variables | SATISFIED | Batch write of progress + per-step results in `set_task_variables()`. `step_results` accumulated in memory during loop, written once at end. |
| EXEC-02 | 05-01-PLAN, 05-02-PLAN | Execution pauses at client-deferred steps without failing the task (task remains Working) | SATISFIED | "client-deferred" reinterpreted as any unresolvable step per CONTEXT.md. Task stays Working, `step_statuses` array tracks actual outcomes. |
| EXEC-03 | 05-01-PLAN, 05-02-PLAN | Step failure during partial execution keeps task in Working state and records error details in task variables | SATISFIED | `step_statuses[idx] = StepStatus::Failed`, error stored as `json!({"error": e.to_string()})` in `step_results`, task_status remains "working". |
| EXEC-04 | 05-01-PLAN, 05-02-PLAN | Extended validation checks that client-deferred steps don't depend on outputs of other client-deferred steps | PARTIAL | Runtime classification via `classify_resolution_failure()` distinguishes `UnresolvedDependency` from `UnresolvableParams`. CONTEXT.md explicitly reinterprets EXEC-04 as runtime check. However: (1) ROADMAP SC4 still says "before execution begins", (2) REQUIREMENTS.md still uses "client-deferred steps" language, (3) neither document was updated to mark the scope change. Functional behavior is correct per CONTEXT.md. |

**Note on EXEC-02 and EXEC-04 "client-deferred" language:** FNDX-02 was formally dropped (StepExecution enum concept eliminated). REQUIREMENTS.md marks FNDX-02 as Complete/dropped. The EXEC-02 and EXEC-04 requirements still use "client-deferred steps" language which is now dead terminology — all steps execute best-effort at runtime. The REQUIREMENTS.md and ROADMAP.md should be updated to reflect the unified runtime-execution model.

---

### Anti-Patterns Found

| File | Pattern | Severity | Impact |
|------|---------|----------|--------|
| `src/server/workflow/task_prompt_handler.rs` line 574 | `Err(_) => break` on `resolve_tool_parameters` failure | Info | Comment says "Should not happen if announcement succeeded" — silent break with no PauseReason. Benign since `create_tool_call_announcement` already failed first, but if reached independently, the caller gets no pause reason. |
| `src/server/workflow/task_prompt_handler.rs` line 578 | `Err(_) => break` on `params_satisfy_tool_schema` failure | Info | Schema check error causes silent break with no PauseReason. If this function returns Err (as opposed to Ok(false)), the reason for pause is not recorded. |
| `.planning/ROADMAP.md` lines 58-59 | Plan checkboxes show `[ ]` for both 05-01-PLAN and 05-02-PLAN | Warning | Plans are implemented and committed but ROADMAP still shows them as not started. Documentation inconsistency. |

None of the above are blockers — functional goal is achieved.

---

### Human Verification Required

None — all observable behaviors can be verified programmatically through the test suite.

---

### Test Verification

All tests pass against the actual codebase:

- `cargo test -p pmcp-tasks --lib types::workflow` — **19 passed** (includes 6 PauseReason unit tests + 1 proptest)
- `cargo test --lib server::workflow::task_prompt_handler` — **11 passed** (all new execution engine tests)
- `cargo test --lib server::workflow` — **161 passed** (all workflow tests including backward compatibility)
- `cargo build --workspace` — **no errors**
- `cargo clippy -p pmcp -p pmcp-tasks -- -D warnings` — **no errors** (pre-existing warnings in unrelated crates: pmcp-macros, mcp-preview, oauth-basic)

Commits verified in git history: `c7f6561` (PauseReason), `ee0be49` (retryable + pub(crate)), `2f247b7` (active execution engine).

---

### Gaps Summary

**One gap identified, functional, not a defect:**

The ROADMAP Phase 5 Success Criterion 4 specifies "Validation rejects workflows where a client-deferred step depends on the output of another client-deferred step, producing a clear error **before execution begins**". The implemented approach — as documented in `05-CONTEXT.md` under "Dependency validation (EXEC-04 reinterpreted)" — performs this check at runtime during the step loop via `classify_resolution_failure()`.

The runtime approach is correct and intentional. The gap is a documentation mismatch: ROADMAP.md SC4 and REQUIREMENTS.md EXEC-04 still use pre-reinterpretation language. The functional goal of distinguishing unresolved dependencies from generic resolution failures is fully achieved (`UnresolvedDependency` vs `UnresolvableParams` PauseReason variants).

**Resolution options:**
1. Update ROADMAP.md Phase 5 SC4 to match the CONTEXT.md reinterpretation (simplest)
2. Update REQUIREMENTS.md EXEC-04 to reflect runtime-check semantics and drop "client-deferred" terminology
3. Accept the gap as-is since CONTEXT.md serves as the authoritative refinement record

This is a documentation/traceability gap, not a functional defect. The execution engine works correctly.

---

_Verified: 2026-02-22T01:00:00Z_
_Verifier: Claude (gsd-verifier)_
