# Phase 16 Implementation Report — Secure Network Transport & Production Control-Plane Hardening

**Date:** 2026-08-18  
**Branch:** `feature/phase16`  
**Base:** Phase 15 (`86ee33aca3038222e27038ad831821ab54b31b5b`)  
**Status:** Phase 16 implementation, tracked-artifact verification, and delivery-candidate packaging complete.

## 1. Scope

Phase 16 hardens the Phase 15 authenticated worker control plane for deployment across real network boundaries. It adds TLS/mTLS, signing-key rotation, task-scoped credentials, persistent idempotency, rate limiting, artifact quotas, and a provider-neutral presigned transfer abstraction.

It does **not** move Governor, Evidence, Commit, Learning, or TCD authority onto workers or transport services.

## 2. TLS / mTLS

Added `wdc.worker_tls` with standard-library SSL contexts:

```text
build_server_ssl_context(...)
build_client_ssl_context(...)
```

The reference server supports TLS with a configurable CA and optional client-certificate requirement. The reference client supports CA validation and optional client certificate/key presentation. Tests create an ephemeral CA/server/client certificate chain and exercise real HTTPS sockets rather than only context construction.

Reference minimum TLS version: TLS 1.2.

## 3. Credential key rotation and task credentials

`wdc.worker_auth` now includes:

```text
CredentialKeyRing
CredentialKeyState.ACTIVE
CredentialKeyState.VERIFY_ONLY
CredentialKeyState.REVOKED
```

Worker-fleet credentials remain bound to:

```text
worker_id
worker_generation
scopes
issued_at
expires_at
key_id
```

Task credentials additionally bind:

```text
task_id
lease_id
attempt
fencing_token
```

Assignment issues a task credential for artifact/renew/result routes. A lease renewal now also returns a refreshed task credential; the remote client replaces both lease- and task-token caches so long-running tasks remain authorized after the original lease/token deadline while still being capped by the renewed lease.

## 4. Persistent idempotency

Added `wdc.request_guard.IdempotencyStore` backed by SQLite.

For result submission:

- same idempotency key + same canonical body returns the original successful response, even after the lease has completed;
- same key + different body returns conflict;
- authentication/task binding is verified before a cached response is replayed.

This prevents normal network retry from becoming duplicate parent ingest.

## 5. Rate limiting

Added deterministic `TokenBucketRateLimiter` with `Retry-After` support. The reference HTTP server applies limits after authentication using a worker/scope key.

This is a single-controller reference limiter, not a distributed global-rate-limit implementation.

## 6. Artifact quota

Added `wdc.artifact_quota`:

```text
max_object_bytes
max_task_bytes
max_task_objects
```

Quota is evaluated before BlobStore persistence. Re-uploading the same digest for the same task does not double-charge usage.

## 7. Artifact transfer / presigned abstraction

Added `wdc.artifact_transfer`:

```text
ArtifactTransferBackend
LocalArtifactTransferBackend
TransferGrant
PresignedTransferBroker
```

Reference grants are HMAC authenticated and bind:

```text
HTTP-style method
task_id
SHA-256 digest
issued_at
expires_at
nonce
```

The abstraction is provider-neutral. Phase 16 does not claim live S3, GCS, Azure Blob, or other object-store integration.

## 8. CLI and secure reference demo

`control credential` and `control serve` accept either a single secret file or a rotating keyring file.

`control serve` adds:

```text
--tls-cert
--tls-key
--tls-ca
--require-client-cert
--rate-capacity
--rate-refill-per-second
--max-object-bytes
--max-task-bytes
--max-task-objects
```

`remote-worker once` adds:

```text
--tls-ca
--tls-client-cert
--tls-client-key
```

New demo:

```text
wdc demo secure-network-worker
```

The demo uses a real ephemeral CA/server/client certificate chain, HTTPS + mTLS, rotating signing keys, task credentials, idempotent result replay, quota accounting, and a signed transfer grant.

## 9. Security invariants

```text
TLS != worker authorization
mTLS != lease ownership
worker-fleet credential != task credential
network retry != duplicate ingest
presigned transfer grant != evidence authority
transport hardening != epistemic promotion
```

No Phase 16 transport module directly creates EvidencePacket, CommitRecord, TCD sedimentation, Governor decisions, or learning updates.

## 10. Preliminary verification evidence

```text
full test suite: 184 passed
compileall src/wdc examples: PASS
git diff --check: PASS
lease-renew credential refresh regression: PASS
```

Additional preliminary delivery evidence:

```text
source-tree secure-network-worker demo: PASS
wheel build: PASS
clean-venv wheel install: PASS
installed `wdc control --help`: PASS
installed `wdc remote-worker --help`: PASS
installed secure-network-worker demo: PASS
```

Tracked Source ZIP and final artifact verification are recorded after the archive gate.


## 11. Tracked-artifact verification

A Source ZIP generated directly from Git-tracked HEAD was extracted into a fresh directory and independently verified:

```text
fresh Source ZIP full suite: 184 passed
fresh Source ZIP compileall: PASS
fresh Source ZIP secure-network-worker demo: PASS
fresh Source ZIP wheel build: PASS
fresh Source ZIP clean-venv install: PASS
fresh installed `wdc control --help`: PASS
fresh installed `wdc remote-worker --help`: PASS
fresh installed secure-network-worker demo: PASS
```

The final artifact SHA-256 values are kept in an external delivery manifest to avoid self-referential archive metadata.

## 12. Explicit limitations

Phase 16 is a hardened reference control plane, not a claim of public-internet production readiness. It does not provide:

- ACME or automatic public-PKI certificate lifecycle;
- production KMS/HSM/secret-manager integration;
- automatic cross-controller signing-key replication/rotation;
- distributed token-bucket state;
- HA/distributed idempotency storage;
- WAF or complete DDoS defense;
- live S3/GCS/Azure object-store adapter;
- cloud-provider presigned URL implementation;
- full production audit/SIEM pipeline.

TLS/mTLS and bearer/task credentials are complementary layers; neither changes WDC's evidence/history/authority semantics.

## External final delivery verification

Final delivery artifacts were rebuilt from the immutable final source HEAD and verified independently outside the source working tree.

```text
final source HEAD full suite: 184 passed
final source compileall: PASS
final source git diff --check: PASS
final source working tree: clean
final Source ZIP fresh extraction full suite: 184 passed
final Source ZIP secure-network-worker demo: PASS
final wheel clean-venv install: PASS
final installed `wdc --help`: PASS
final installed `wdc control --help`: PASS
final installed `wdc remote-worker --help`: PASS
final installed secure-network-worker demo: PASS
```