---
phase: 09-storage-abstraction-layer
verified: 2026-02-23T00:00:00Z
status: passed
score: 11/11 must-haves verified
re_verification: false
---

# Phase 9: Storage Abstraction Layer Verification Report

**Phase Goal:** Developers have a well-defined KV storage contract and a generic task store that implements all domain logic once, backend-agnostically
**Verified:** 2026-02-23
**Status:** PASSED
**Re-verification:** No — initial verification

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | StorageBackend trait defines 6 async KV methods (get, put, put_if_version, delete, list_by_prefix, cleanup_expired) | VERIFIED | `backend.rs` lines 189–261: all 6 methods present with full rustdoc |
| 2 | StorageError has domain-aware variants (NotFound, VersionConflict, CapacityExceeded, Backend with source()) | VERIFIED | `error.rs` lines 82–116; `source()` returns `Some` for Backend only, `None` for all others — confirmed by unit tests |
| 3 | VersionedRecord carries data bytes + monotonic u64 version | VERIFIED | `backend.rs` lines 50–58: `pub data: Vec<u8>` and `pub version: u64` with Debug + Clone derives |
| 4 | TaskRecord derives Serialize and Deserialize with camelCase rename | VERIFIED | `record.rs` lines 41–43: `#[derive(Debug, Clone, Serialize, Deserialize)]` + `#[serde(rename_all = "camelCase")]`; serialization_uses_camel_case test confirms ownerId/requestMethod/expiresAt fields |
| 5 | TaskError has ConcurrentModification and StorageFull variants | VERIFIED | `error.rs` lines 83–97: both variants present with expected/actual_version fields; Display and error_code tests pass |
| 6 | Variable schema validation rejects nested depth bombs and extremely long strings | VERIFIED | `record.rs` lines 232–333: `validate_variable_depth`, `validate_variable_string_lengths`, `validate_variables` all present with unit tests confirming rejection at depth 11/string 65537 |
| 7 | GenericTaskStore<B: StorageBackend> implements all domain logic (state machine, owner isolation, variable merge, TTL, size limits) | VERIFIED | `generic.rs` 1386 lines; 11 public domain methods; all state machine/owner/TTL/CAS logic confirmed in 30 unit tests |
| 8 | All mutations use put_if_version (CAS) — VersionConflict maps to TaskError::ConcurrentModification | VERIFIED | 4 calls to `put_if_version` in production code paths (update_status, set_variables, set_result, complete_with_result); `map_storage_error` maps VersionConflict to ConcurrentModification |
| 9 | Owner mismatch returns TaskError::NotFound (never reveals task exists for another owner) | VERIFIED | `generic.rs` get/update_status/set_variables/set_result/complete_with_result all return `TaskError::NotFound` on owner mismatch with tracing::warn; `owner_isolation_get_returns_not_found` test confirms |
| 10 | Canonical JSON serialization happens in GenericTaskStore, not in backends | VERIFIED | `serde_json::to_vec` and `serde_json::from_slice` appear only in `generic.rs` (serialize_record/deserialize_record helpers); backends receive/return raw bytes only |
| 11 | TaskStore trait is redesigned as a thin interface with blanket impl for GenericTaskStore | VERIFIED | `mod.rs` line 409: `impl<B: StorageBackend + 'static> TaskStore for generic::GenericTaskStore<B>`; all 11 methods delegate to GenericTaskStore; `generic_task_store_as_dyn_task_store` test confirms Arc<dyn TaskStore> works |

**Score:** 11/11 truths verified

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `crates/pmcp-tasks/src/store/backend.rs` | StorageBackend trait, StorageError enum, VersionedRecord struct, key helpers | VERIFIED | 521 lines; exports StorageBackend, StorageError, VersionedRecord, make_key, parse_key, make_prefix; 25 unit tests |
| `crates/pmcp-tasks/src/domain/record.rs` | TaskRecord with Serialize/Deserialize derives | VERIFIED | Line 41: `#[derive(Debug, Clone, Serialize, Deserialize)]` + `#[serde(rename_all = "camelCase")]`; contains version: 0 init in new() |
| `crates/pmcp-tasks/src/error.rs` | ConcurrentModification and StorageFull error variants | VERIFIED | Lines 83–97: both variants with contextual fields; Display messages match plan spec |
| `crates/pmcp-tasks/src/store/generic.rs` | GenericTaskStore<B> with all domain operations | VERIFIED | 1386 lines (well above 200 minimum); exports GenericTaskStore; 30 unit tests including TestBackend and CasConflictBackend |
| `crates/pmcp-tasks/src/store/mod.rs` | Redesigned TaskStore trait with blanket impl for GenericTaskStore | VERIFIED | Line 409: `impl<B: StorageBackend + 'static> TaskStore for generic::GenericTaskStore<B>` with all 11 delegating methods |

### Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `store/backend.rs` | `store/mod.rs` | `pub mod backend` declaration and re-export | VERIFIED | `mod.rs` lines 33, 42: `pub mod backend;` and `pub use backend::{StorageBackend, StorageError, VersionedRecord};` |
| `store/backend.rs` | StorageError | `impl std::error::Error for StorageError` with source() | VERIFIED | `backend.rs` lines 138–147: source() returns Some for Backend variant only |
| `store/generic.rs` | `store/backend.rs` | GenericTaskStore delegates all storage to B: StorageBackend | VERIFIED | 8 `.backend` calls across create/update_status/set_variables/set_result/complete_with_result/list/cleanup_expired |
| `store/generic.rs` | `domain/record.rs` | serde_json serialization/deserialization of TaskRecord | VERIFIED | `serialize_record` uses `serde_json::to_vec`, `deserialize_record` uses `serde_json::from_slice` |
| `store/mod.rs` | `store/generic.rs` | blanket TaskStore impl for GenericTaskStore | VERIFIED | Line 409: `impl<B: StorageBackend + 'static> TaskStore for generic::GenericTaskStore<B>` |
| `context.rs` | `store/mod.rs` | TaskContext uses Arc<dyn TaskStore> — still compiles | VERIFIED | `context.rs` line 95: `store: Arc<dyn TaskStore>`; full workspace compiles clean |
| `router.rs` | `store/mod.rs` | TaskRouterImpl uses Arc<dyn TaskStore> — still compiles | VERIFIED | `router.rs` lines 57, 67, 80, 90 all reference `Arc<dyn TaskStore>`; full workspace compiles clean |

### Requirements Coverage

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|------------|-------------|--------|----------|
| ABST-01 | 09-01-PLAN.md | StorageBackend trait defines KV operations (get, put, delete, list-by-prefix, cleanup-expired) | SATISFIED | `backend.rs` trait has all 6 methods including put_if_version (CAS) as first-class method |
| ABST-02 | 09-02-PLAN.md | GenericTaskStore implements all TaskStore domain logic (state machine, owner isolation, variable merge, TTL) by delegating to any StorageBackend | SATISFIED | `generic.rs`: all 11 domain operations implemented; 30 tests verify each domain concern |
| ABST-03 | 09-01-PLAN.md | Canonical serialization layer in GenericTaskStore ensures consistent JSON round-trips regardless of backend | SATISFIED | `serde_json::to_vec`/`from_slice` only in GenericTaskStore helpers; backends receive/return raw bytes; camelCase verified by test |
| ABST-04 | 09-02-PLAN.md | TaskStore trait can be simplified/redesigned to leverage the KV backend pattern | SATISFIED | TaskStore trait redesigned as type-erasure interface; blanket impl for GenericTaskStore<B: StorageBackend + 'static>; `Arc<dyn TaskStore>` confirmed working |

All 4 requirements fully satisfied. No orphaned requirements found.

### Anti-Patterns Found

None. All phase 9 files scanned for TODO, FIXME, XXX, HACK, PLACEHOLDER, unimplemented!() — all clean.

### Human Verification Required

None. All acceptance criteria are verifiable programmatically via the test suite and code inspection.

### Test Suite Summary

- Plan 01 added 46 new tests (25 backend unit tests + 21 record/error tests)
- Plan 02 added 30 new tests (29 domain logic + 1 type-erasure)
- All 536 tests pass (confirmed by cargo test run above)
- Zero clippy warnings (confirmed by `cargo clippy -p pmcp-tasks -- -D warnings`)
- Full workspace compiles clean (`cargo check` exits 0)
- All 4 commits documented in SUMMARYs verified present in git log: `9b4546e`, `35656f0`, `6b33d8d`, `0816bcf`

### Gaps Summary

No gaps. All must-haves from both plans are verified at all three levels (exists, substantive, wired).

---

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