Procurement Ingest

Unified email ingestion pipelines for Amazon procurement data. Two independent pipelines — purchase orders (Coupa) and work orders (APM/Hexagon EAM) — share a single repo and CDK app but deploy as separate CloudFormation stacks.

Pipelines

Purchase Orders (po-ingest stack)

Coupa PO emails are received at amazon_po@int.seahaven.com, parsed by Claude Haiku 4.5 on Amazon Bedrock, and written to the purchase-orders DynamoDB table. PO parsing is fully AI (no deterministic parser).

Flow:

1. Coupa sends a PO email (new, revision, or cancellation).
2. SES (INBOUND_MAIL rule set) drops the raw MIME into s3://po-ingest-emails-{AccountId}/inbound/.
3. S3 ObjectCreated triggers the po-email-processor Lambda.
4. Fail-closed sender authentication (INFRA-107): the SES-stamped Authentication-Results header must show dkim=pass for amazon.coupahost.com (see Sender authentication); otherwise the email is logged and dropped.
5. Claude (via Bedrock InvokeModel) extracts structured JSON (PO number, status, supplier, site code, trade classification, line items, fiscal year). Numeric amounts are decoded with parse_float=Decimal (DynamoDB rejects floats).
6. Merge write to DynamoDB:
   • new_po — merge insert. Creates the PO, or backfills data into a pre-existing Cancelled skeleton left by an out-of-order cancellation (preserving the Cancelled status). No longer silently dropped when a record already exists.
   • revision — field-level merge (update_item SETs only the fields present in the revision). A revision that omits line_items/supplier no longer deletes them. Will not un-cancel a Cancelled PO.
   • cancellation — marks the row Cancelled (creating a minimal skeleton if the cancellation arrives before the new_po).
7. DynamoDB Streams feeds downstream consumers:
   • LedgerFlow (seahaven-slack-bot/po-sync) — daily KB sync
   • Site extractor (po-ingest-site-extractor) — real-time site address extraction into verified-sites table

Lambdas (lambdas/po/):

Function	Trigger	Purpose
po-email-processor	S3 ObjectCreated	Claude extraction + DynamoDB write
po-ingest-site-extractor	DynamoDB Streams	Site code/address extraction -> verified-sites
po-web-ui	Manual invoke	HTML dashboard (public Function URL removed 2026-06-08, INFRA-74)

Tables:

• purchase-orders (PK: po_number, Streams: NEW_IMAGE) — shared with seahaven-slack-bot (read-only; see Shared Resources)
• verified-sites (PK: siteCode) — ~1,100 unique Amazon facility sites (by-state GSI removed 2026-06-03, audit M-20)
• pending-site-review (PK: po_number) — unresolvable POs for manual Payee Central verification

Work Orders (WorkorderIngestStack stack)

Amazon APM work order emails (from Hexagon EAM / HxGN SmartCloud) are received at apm@int.seahaven.com, parsed deterministic-template-first with a Claude-on-Bedrock fallback, and written to the WorkOrders DynamoDB table.

Flow:

1. Hexagon EAM sends email notifications (new assignments, comments, updates, cancellations) to amazon@seahavenind.com.
2. Gmail filter forwards APM emails to apm@int.seahaven.com (SES).
3. SES drops the raw MIME into s3://workorder-ingest-emails-{AccountId}/inbound/.
4. S3 triggers the workorder-email-processor Lambda.
5. Fail-closed sender authentication (INFRA-107): the SES-stamped Authentication-Results header must show dkim=pass for the domain that re-signs the forward (currently allowlisted as seahaven.com — see the validation caveat under Sender authentication); otherwise the email is logged and dropped.
6. Parse: a pure, offline template parser (template_parser.py) tries the two known Hexagon templates first, behind a strict fail-closed validation gate. Only on a miss/invalid result does the Lambda fall back to the Claude-on-Bedrock AI extractor. Both paths emit the identical structured-JSON contract (work order ID, site code, severity, priority, dates, assigned technician).
7. Work order upserted to WorkOrders, event/comment appended to WorkOrderComments.

Deterministic template parser. ~93.6% of WO traffic is the plain-text "AMAZON UPDATE WO DETAILS <id>" comment template (T1) and ~6.4% is the HTML "AMAZON assign Work Order <id> on building <SITE>" assignment template (T2). template_parser.try_deterministic_parse() classifies by subject, extracts the contract fields, and returns a parsed result only if it passes a strict validation gate (exact contract-key set; work_order_id matches the subject and is all-digits; the T1 Work Order: <id> double-space is literally present; email_type matches the template; site_code shape; per-type required fields; and a label-bleed guard so a value that over-ran into another field fails). Anything that fails — the rare update/cancellation shapes, Hexagon template drift, or an extractor exception — falls back to the AI extractor. Data is never corrupted; only the fallback rate rises. Every record emits one CloudWatch EMF metric (see below).

Lambdas (lambdas/wo/):

Function	Trigger	Purpose
workorder-email-processor	S3 ObjectCreated	Claude extraction + DynamoDB write
workorder-web-ui	Manual invoke	HTML dashboard (public Function URL removed 2026-06-08, INFRA-74)

Tables:

• WorkOrders (PK: work_order_id) — site-code-index and status-index GSIs removed 2026-06-03 (audit M-20)
• WorkOrderComments (PK: work_order_id, SK: comment_id) — see the comment_id format note below

Architecture

IaC: AWS CDK (Python), two stacks in one app, region us-east-1.

All Lambdas: Python 3.12, ARM64, 60-day log retention.

LLM provider — Amazon Bedrock. Both email processors call Claude Haiku 4.5 through the Bedrock inference profile us.anthropic.claude-haiku-4-5-20251001-v1:0 (bedrock-runtime InvokeModel), configured via the BEDROCK_MODEL_ID env var. There is no Anthropic API key and no Secrets Manager secret any more. Each processor role is granted bedrock:InvokeModel + bedrock:InvokeModelWithResponseStream on both the inference-profile ARN and the per-region foundation-model ARNs for us-east-1 / us-east-2 / us-west-2 (empty-account foundation-model ARNs) — the us.* profile can route cross-region, so a profile-only grant would AccessDenied at runtime under load.

Retired secrets (manual cleanup outstanding): the former secrets po-ingest/anthropic-api-key and workorder-ingest/anthropic-api-key had RemovalPolicy.RETAIN, so removing them from the CDK stacks orphans them rather than deleting them. Delete both by hand post-deploy and revoke the stored keys at the provider. The processors no longer read any ANTHROPIC_API_KEY_SECRET_ARN — authentication to Bedrock is via the Lambda execution-role IAM grant, so there is no provider API key or Secrets Manager fetch on the parse path.

SES: Both stacks add rules to the shared INBOUND_MAIL receipt rule set on int.seahaven.com.

Sender authentication (INFRA-107)

The From header and any Authentication-Results header inside the raw MIME are attacker-forgeable, so neither is trusted. Instead, both email processors (lambdas/*/email_processor/ses_auth.py) authenticate the sender against the verdicts SES itself stamps at delivery time, failing closed:

1. Take only the topmost Authentication-Results header (SES prepends its trace headers; any lower copies arrived inside the message and are ignored).
2. Require its authserv-id to be amazonses.com.
3. Require a dkim=pass clause whose header.d=/header.i= domain is in the pipeline's allowlist.

The allowlist is the ALLOWED_DKIM_DOMAINS Lambda environment variable (comma-separated, set per stack in CDK — no code change needed to adjust):

Pipeline	ALLOWED_DKIM_DOMAINS	Why
Work orders	seahaven.com	APM mail reaches apm@int.seahaven.com via a forward off amazon@seahavenind.com; the allowlist trusts the domain that re-signs DKIM on that forward (the original hxgnsmartcloud.com signature does not survive it). Validated against live SES-stamped headers (2026-07-16) — real APM deliveries carry dkim=pass header.i=@seahaven.com. Note a plain Gmail auto-forward re-signs under the sending Workspace domain (seahavenind.com / a *.gappssmtp.com key), not seahaven.com; only a Google Group (or Workspace routing) with "sign as seahaven.com" produces dkim=pass header.i=@seahaven.com. If the observed re-signing domain differs, update this value (do not widen it to a shared key like *.gappssmtp.com, which any Google customer's mail would pass). The workorder-email-processor-sender-auth-rejected alarm pages if this assumption is wrong instead of silently dropping every work order.
Purchase orders	amazon.coupahost.com	Coupa signs as amazon.coupahost.com. amazonses.com also passes but is deliberately not allowlisted — every SES customer's mail passes for it

Clause-injection hardening: SES echoes attacker-controlled SMTP-session tokens (envelope-from, helo, header.from) into its own Authentication-Results value, and an RFC 5321 quoted-local-part MAIL FROM may legally contain ; and spaces. The parser therefore tokenises comment- and quoted-string-aware (RFC 8601 / RFC 5322): CFWS comments (...) are stripped and clauses are split only on semicolons outside a quoted string, so a ; inside a quoted envelope-from= value can never be torn into a forged dkim=pass clause. The DKIM signer domain is read from header.d= when present (falling back to header.i=, taking the domain after the AUID's last top-level @ so a quoted local-part cannot smuggle an allowlisted domain). Two latent comment-parsing edge cases (early comment-close, no-separator-on-strip) are tracked as hardening follow-ups — see the SES-AR-01/02 issue; neither is reachable through SES's real header encoding today.

Risk acceptance — forwarder-domain binding (INFRA-107, accepted 2026-07-16): for work orders this control authenticates the domain that re-signs the apm@ forward (seahaven.com), not the Hexagon originator (hxgnsmartcloud.com, whose signature does not survive the forward). Its strength therefore rests on the apm@ Google Group's posting policy being restricted to trusted internal senders — that restriction is the load-bearing control and is accepted as documented risk. If the apm@ group is ever opened to external posting, this finding escalates to HIGH (anyone able to post to the group could inject a forged work order) and the correct fix is to bind acceptance to the originator via DMARC alignment rather than the forwarder's re-signature. The PO pipeline is unaffected — amazon.coupahost.com is an external domain an attacker cannot get SES to sign.

On any failure (env var unset, header missing/unparseable, verdict fail, unaligned domain) the processor logs a structured sender_auth_rejected warning with the reason and S3 key, skips the email, and returns normally — rejected mail never triggers Lambda retries or DLQ messages, but the <fn>-sender-auth-rejected CloudWatch alarm (see CloudWatch alarms) pages on a rejection spike so a drift-induced outage is not silent. Unit tests live in tests/test_ses_auth.py.

Failure handling (INFRA-41): Each email-processor is async-invoked (S3 → Lambda). Both have a CDK-managed SQS dead-letter queue (dead_letter_queue=, 14-day retention, SSL-enforced) so a failed parse is captured rather than silently dropped after Lambda's retries.

CloudWatch alarms

Every alarm is ALARM-only (no OK action), sends to the shared site-alerts SNS topic (imported once per stack via Topic.from_topic_arn), and uses TreatMissingData.NOT_BREACHING.

Lambda alarms (AWS/Lambda, FunctionName dimension):

Alarm	Functions	Metric / config
<fn>-errors	po-email-processor, po-ingest-site-extractor, workorder-email-processor	Errors Sum, 5 min, > 0, eval 1
<fn>-throttles	po-email-processor, po-ingest-site-extractor, po-web-ui, workorder-email-processor	Throttles Sum, 5 min, > 0, eval 1
<fn>-duration	po-email-processor, po-ingest-site-extractor, po-web-ui (p99); workorder-email-processor (p95)	Duration percentile, 5 min, >= 45000 ms (75% of the 60s timeout), eval 3 / datapoints 2
<fn>-sender-auth-rejected	po-email-processor, workorder-email-processor	Log-metric-filter count (namespace Seahaven/ProcurementIngest, default_value=0) on sender_auth_rejected warnings, Sum 5 min, >= 1, eval 3 / datapoints 2

The <fn>-sender-auth-rejected alarm closes the silent-drop gap in INFRA-107: a rejected email returns normally (no error, no retry, no DLQ message), so without a log-metric filter a signing-domain drift or a wrong allowlist would discard 100% of legitimate mail while every other alarm stayed green. It counts sender_auth_rejected warnings per 5-minute period (default_value=0 keeps the series continuous) and pages when 2 of the last 3 periods each see at least one rejection — a lone stray spoof probe to the internal ingest address self-clears, but a sustained false-reject storm pages within ~10–15 minutes even at low mail volume; the config is easy to tune in the CDK helper. (A residual gap remains for a very sparse total-reject outage — see the SES-AR-01/02 hardening issue.)

The <fn>-duration and <fn>-throttles alarms for po-email-processor and workorder-email-processor supersede the orphaned, CLI-created Lambda-Duration-* / Lambda-Throttles-* alarms (deleted post-deploy).

DLQ alarms (AWS/SQS): po-email-processor-dlq-messages and workorder-email-processor-dlq-messages fire when any message is visible on an email-processor DLQ (ApproximateNumberOfMessagesVisible Maximum, 5 min, > 0, eval 1) — a message there means an email was dropped after Lambda exhausted its async retries.

Parse-outcome metric + fallback-rate alarm (workorder-ingest): the WO processor writes one CloudWatch EMF line per email to namespace Seahaven/WorkorderIngest, metric ParseOutcome (Unit Count, value 1), dimensioned by ParseMethod (template | ai_fallback) and TemplateId (update_plaintext | assign_html | unknown). Non-dimension EMF properties ReasonCode and work_order_id are queryable in Logs Insights but not promoted to metrics (kept low-cardinality). EMF is used instead of PutMetricData so there is no extra sync call / latency / IAM grant on the async hot path (the role already has logs:PutLogEvents). The alarm workorder-email-processor-template-fallback-rate fires when the AI-fallback share of parses exceeds 15% sustained (a MathExpression with FILL(...,0) and a ≥10-sample volume floor over 15-minute periods, eval 3 / datapoints 2) — catching Hexagon template-drift coverage collapse while the volume floor + FILL prevent low-volume false pages / INSUFFICIENT_DATA. ALARM-only SnsAction to site-alerts, no OK action, NOT_BREACHING. The 15-minute period is a deliberate deviation from the 5-minute house style to accumulate a stable denominator at the low ~760/day volume.

DynamoDB alarms (AWS/DynamoDB): each owned table gets <table>-throttles (ThrottledRequests) and <table>-system-errors (SystemErrors). These metrics emit only at the TableName + Operation dimension set, so each alarm is a Sum math expression across the operations the table uses (Get/BatchGet/Query/Scan/Put/Update/Delete/BatchWrite). Tables covered: purchase-orders, verified-sites, pending-site-review (po-ingest); WorkOrders, WorkOrderComments (workorder-ingest).

Security

Web UI auth (defense-in-depth). The po-web-ui / workorder-web-ui handlers refuse unauthenticated requests even though their public Function URLs were removed (INFRA-74). Each requires a shared secret in the X-Auth-Token header (or Authorization: Bearer <token>), compared in constant time against the configured token. The handler fails closed if the token is unset or unreadable (denies all). The token lives in the Secrets Manager secret procurement-ingest/web-ui-auth-token; only its ARN is passed to the Lambda (WEB_UI_AUTH_TOKEN_SECRET_ARN), and the value is fetched at runtime — never embedded in the CloudFormation template or Lambda env vars. The fetched value is cached in the warm container with a short TTL (5 min) so a rotated secret propagates without waiting for the execution environment to recycle. This is a defense-in-depth floor for a detached URL, not primary auth.

Output escaping. All caller-influenced values (including prompt-injectable strings Claude may return for total_amount/line-item amounts) are HTML-escaped before interpolation to prevent stored XSS.

Shared Resources

purchase-orders table (owned here)

The purchase-orders DynamoDB table is owned by this repo's po-ingest stack (defined in cdk/po_stack.py with RemovalPolicy.RETAIN, StreamViewType.NEW_IMAGE, and SSE-KMS encryption with the shared customer-managed CMK alias/seahaven-dynamodb, INFRA-95 / M-3). The po-email-processor Lambda is the authoritative writer — it performs the merge inserts, field-level revision merges, and cancellation updates described above.

Consumers (read-only):

Repo	How it reads	Purpose
seahaven-slack-bot	po-sync (DynamoDB Streams + daily scan) and wo-po-lookup	Daily KB sync + Bedrock agent PO lookups

The consumer imports the table via Table.fromTableName(...) and is granted read-only access (grantReadData); it does not own or define it.

Schema-coordination rule: Any change to the purchase-orders schema (partition key, item shape, attribute names, streams view type) must be coordinated with seahaven-slack-bot. The owner here ships the change; the consumer must be updated in lockstep so its readers do not break. Treat schema changes as a cross-repo migration, not a local edit.

Known exception (INFRA-51): amazon-po-parser currently writes directly to purchase-orders outside this stack (backfill/enrichment scripts). This second writer is being folded into the po-ingest pipeline so this stack is the sole writer; until INFRA-51 closes, coordinate any schema change with amazon-po-parser as well.

WorkOrders and WorkOrderComments tables (owned here)

Both tables are owned by this repo's WorkorderIngestStack (cdk/wo_stack.py, RemovalPolicy.RETAIN):

• WorkOrders — PK work_order_id (S).
• WorkOrderComments — PK work_order_id (S), SK comment_id (S).

comment_id format change (issue #23). The WorkOrderComments range key is now work_order_id#<comment_time|nocomment>#<sha256(s3_object_key)[:12]> (e.g. 11144580730#2026-04-27T23:51:48#a1b2c3d4e5f6, or …#nocomment#… when the source email carries no comment time). Previously it was work_order_id#<timestamp>, where two emails on the same WO with an identical/absent comment time collided and overwrote each other. The 12-hex suffix is derived from the S3 object key alone — deterministic, so a Lambda async retry of the same object produces a byte-identical key (idempotent, no duplicate row), while two distinct emails on the same WO get distinct keys. Wall-clock now() is kept out of the key. Consumers that split on # and read index [0]/[1] are unaffected; anything that treated "everything after the first #" as a bare timestamp now also captures the hash segment.

Timestamp format shift. All stored ISO timestamps (created_at, updated_at, ingested_at on WO; processed_at, cancelled_at on PO) moved from naive datetime.utcnow().isoformat() to timezone-aware datetime.now(timezone.utc).isoformat(), so they now carry a +00:00 suffix (e.g. 2026-07-15T12:00:00+00:00). Downstream parsers that assumed a naive/no-offset string must accept the offset.

Both currently use default DynamoDB encryption — they are not yet on the shared customer-managed CMK (alias/seahaven-dynamodb, INFRA-95 / M-3); that migration is tracked in INFRA-6. The workorder-email-processor role no longer holds a pre-emptive encrypt/decrypt grant on that CMK (removed in the 2026-06-17 security sweep — it was unused while the tables are unencrypted and extended the role's decrypt reach to the CMK protecting purchase-orders). Re-add the grant as part of the INFRA-6 migration, at which point grant_read_write_data on the then-encrypted tables propagates the needed key permissions automatically.

Consumer (read-only) — data contract: seahaven-slack-bot imports both tables via Table.fromTableName(...) (grantReadData) and reads them from two Lambdas: workorder-sync (daily full-table scan into the Bedrock knowledge base) and wo-po-lookup (the Bedrock agent's direct WO lookup action group). The bot depends on the PK/SK schema above and these attributes: on WorkOrders — description, wo_status, customer, site_code, building, address, severity, priority, assigned_to, date_reported, scheduled_start, due_date, updated_at; on WorkOrderComments — created_at (used to sort comments), commenter, text. Any change to table name, key schema, these attribute names, or the encryption configuration (e.g. the INFRA-6 CMK migration) must be coordinated with seahaven-slack-bot before it ships, or the Bedrock agent breaks at runtime (not at deploy — the tables are imported by name, so there is no compile-time link).

verified-sites table (owned here)

Owned by this repo's po-ingest stack (cdk/po_stack.py). PK siteCode (S); default DynamoDB encryption (NOT the shared CMK).

Consumer (read-only) — data contract: seahaven-slack-bot's wo-po-lookup Lambda imports this table via Table.fromTableName(...) for the Bedrock agent's lookup_site action. It does point lookups by siteCode and reads address, fullAddress, city, state, zip, latitude, longitude, notes. Coordinate any change to the table name, key schema, or these attribute names with seahaven-slack-bot.

GSI drift (INFRA-138): the by-state GSI was removed here on 2026-06-03 (audit M-20, "0 reads in 30d"), but seahaven-slack-bot still queries IndexName: 'by-state' for its state-listing path, so that path fails at runtime today. Restoring the GSI or removing the consumer's state path needs to be reconciled cross-repo. This is the kind of silent owner-side lifecycle change this data-contract note exists to prevent.

Documentation

The canonical map of Sea Haven's AWS infrastructure lives in Confluence. This project's po-ingest and WorkorderIngestStack stacks are represented there as Mermaid subgraphs.

• AWS Architecture Map (Confluence, IT space, page 1540098)

CI/CD

GitHub Actions with reusable workflows from Sea-Haven-Industries/.github (all pinned to a commit SHA of main):

• CI (ci.yaml, PR to main): linting + cdk synth via ci-python-sam.yaml
• CD (deploy.yaml, push to main): CDK deploy via cd-cdk.yaml (OIDC auth)
• Plus dependency review and PR labeler workflows on every PR

Branch protection on main — all changes through PR.

Setup

1. Bootstrap CDK: cdk bootstrap aws://{AccountId}/us-east-1
2. Ensure the Bedrock inference profile us.anthropic.claude-haiku-4-5-20251001-v1:0 is enabled in us-east-1 (it is; the CDK grants cover cross-region routing to us-east-2/us-west-2). No API key or secret to set — the processors authenticate to Bedrock via their IAM roles.
3. Create the web UI auth-gate shared secret. This secret is imported by name (Secret.from_secret_name_v2), not CDK-managed, so it must exist before deploy or the web-ui Lambdas fail closed:

   aws secretsmanager create-secret --name procurement-ingest/web-ui-auth-token --secret-string "$(openssl rand -hex 32)"
   

4. Deploy both stacks:

   cd cdk
   pip install -r requirements.txt
   cdk deploy --all
   

5. Post-deploy cleanup (one-time): the retired RETAIN-policy secrets po-ingest/anthropic-api-key and workorder-ingest/anthropic-api-key are orphaned by this deploy, not deleted. Remove them and revoke the keys at the provider:

   aws secretsmanager delete-secret --secret-id po-ingest/anthropic-api-key --force-delete-without-recovery
   aws secretsmanager delete-secret --secret-id workorder-ingest/anthropic-api-key --force-delete-without-recovery
   

6. Dashboards: po-web-ui and workorder-web-ui have no public endpoint (the Function URLs were removed 2026-06-08, INFRA-74). Invoke them through an authenticated path that forwards the X-Auth-Token header, e.g. aws lambda invoke --function-name po-web-ui /tmp/out.json.

Tests

Offline unit tests (no AWS, no network) run via pytest from the repo root:

pip install pytest
pytest

Coverage:

• tests/ — shared handler + cross-pipeline tests: parse_raw_email and pad_zip, the PO merge-write semantics (test_po_merge.py, #97, moto-backed), and the fail-closed sender-authentication parser (test_ses_auth.py, INFRA-107).
• lambdas/wo/email_processor/tests/ — the deterministic WO parser suite: golden-file tests over 55 real scrubbed .eml fixtures (test_parser.py), fail-closed validation-gate rules and adversarial/injection cases (test_validation_gate.py), the issue #23 comment_id idempotency invariants (test_comment_id.py), and the Bedrock-fallback dispatch/EMF-metric behavior with a mocked invoke_model (test_bedrock_fallback.py). Golden JSON lives under tests/fixtures/expected/.

Both roots are discovered by pytest.ini (testpaths).

Scripts

Reprocess PO emails (re-run parser against all emails still in S3):

python scripts/reprocess.py            # dry-run
python scripts/reprocess.py --execute  # invoke po-email-processor for each

Backfill verified sites (one-time scan of historical POs):

python scripts/backfill_sites.py

Directory Structure

cdk/
  app.py               # Two stacks: po-ingest + WorkorderIngestStack
  po_stack.py          # Purchase order pipeline resources
  wo_stack.py          # Work order pipeline resources
lambdas/
  po/                  # PO pipeline Lambdas
    email_processor/   # handler.py (Bedrock, fully AI)
    site_extractor/
    web_ui/
  wo/                  # WO pipeline Lambdas
    email_processor/
      handler.py         # template-first + Bedrock fallback, EMF metric, #23 comment_id
      template_parser.py # pure deterministic parser + fail-closed validation gate
      tests/             # golden-file + validation-gate + comment_id + fallback tests
    web_ui/
scripts/
  reprocess.py
  backfill_sites.py
test_local.py          # Parse sample emails through Bedrock locally (no AWS mutation)
tests/
  requirements.txt         # Test-only deps (moto)
  conftest.py              # AWS env stubs + per-pipeline module loader
  test_pad_zip.py          # PO zip-code padding tests
  test_parse_raw_email.py  # MIME parsing tests (PO + WO handlers)
  test_po_merge.py         # PO merge-write semantics tests (#97)
  test_ses_auth.py         # Sender-authentication parser tests (INFRA-107)