feat(mcp): add hosted httpSMS server

[AchoArnold]

Summary

• add a hosted, stateless MCP server using the official Go SDK with 2026-07-28 and 2025-11-25 compatibility
• add Firebase-backed OAuth 2.1, scoped audience-bound JWT delegation, Redis state/rate limits, and seven httpSMS tools
• add the authenticated incoming-message API, Cloud Run deployment assets, CI gates, and full-stack integration coverage

Tools

• list_phones
• send_sms
• list_message_threads
• list_thread_messages
• list_incoming_messages
• create_phone_api_key
• rotate_user_api_key

Validation

• API unit and full suites
• MCP unit suite and server build
• full Docker integration stack: 44 tests before merging main, 53 tests after merging main's adapter-emulator changes
• final targeted auth/cache review and validation

[gitguardian]

⚠️ GitGuardian has uncovered 2 secrets following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secrets in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
36901872	Triggered	RSA Private Key	bf06243	mcp/internal/config/config_test.go	View secret
36901871	Triggered	Generic High Entropy Secret	a13bc7d	mcp/internal/tools/api_keys_test.go	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secrets safely. Learn here the best practices.
3. Revoke and rotate these secrets.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

---

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[codacy-production]

Not up to standards ⛔

🔴 Issues 13 critical · 23 high · 22 medium · 42 minor

Alerts:
⚠ 100 issues (≤ 0 issues of at least minor severity)

Results:
100 new issues

Category	Results
Security	2 minor 23 high 13 critical 22 medium
CodeStyle	40 minor

View in Codacy

🟢 Metrics 1762 complexity · 768 duplication

Metric	Results
Complexity	1762
Duplication	768

View in Codacy

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TIP This summary will be updated as you push new changes.}

[greptile-apps]

Greptile Summary

The PR adds a standalone, stateless MCP service with Firebase-backed OAuth, scoped delegated JWT authentication, Redis state and rate limits, seven httpSMS tools, and a dedicated incoming-message API.

• Adds OAuth metadata, authorization-code and refresh-token grants, client registration, signing keys, and JWKS publication.
• Adds API-side verification for audience-, scope-, method-, and path-bound MCP delegation tokens.
• Adds MCP tool handlers and a typed httpSMS API client for phones, messages, threads, and API-key operations.
• Adds Cloud Run assets and expanded unit and full-stack integration coverage.

Confidence Score: 4/5

The PR is not ready to merge because the checked-in production deployment leaves API-side MCP delegation disabled, causing all hosted MCP tool calls to fail authorization.

The MCP service correctly mints delegated API tokens, but the production API deployment supplies none of the trust settings required to install their verifier, so those tokens cannot authenticate against api.httpsms.com.

Files Needing Attention: api/pkg/di/config.go, api/pkg/di/container.go, api/cloudbuild.yaml

Important Files Changed

Filename	Overview
api/pkg/di/config.go	Introduces optional MCP verifier configuration whose disabled-by-default behavior leaves production delegation inactive without coordinated deployment settings.
api/pkg/di/container.go	Installs delegated authentication before Firebase bearer authentication, but only when the missing production trust configuration enables it.
api/pkg/auth/mcp_token_verifier.go	Adds bounded RS256 verification with issuer, audience, scope, method, and exact request-path enforcement.
api/pkg/handlers/message_handler.go	Adds the authenticated incoming-message endpoint and forces searches to mobile-originated messages.
mcp/internal/oauth/token.go	Implements PKCE-bound authorization-code exchange and scope-narrowing refresh-token rotation with atomic Redis state transitions.
mcp/internal/oauth/clients.go	Implements bounded client metadata retrieval with public-address validation, DNS pinning, redirect rejection, and exact client-ID binding.
mcp/internal/tools/api_keys.go	Adds scoped API-key tools with one-time, user/client/operation-bound confirmation before primary-key rotation.
mcp/internal/tools/messages.go	Adds scoped message and thread tools with bounded schemas and direct mapping to operation-bound API calls.
mcp/cloudbuild.yaml	Deploys the hosted MCP service and its secrets, but cannot by itself establish the required trust configuration on the API service.
api/cloudbuild.yaml	Continues deploying the API without the MCP issuer, audience, or JWKS variables required for the newly added delegated authentication path.

Sequence Diagram

sequenceDiagram
  participant Client as MCP Client
  participant MCP as Hosted MCP Server
  participant Firebase as Firebase
  participant Redis as Redis
  participant API as httpSMS API
  Client->>MCP: OAuth authorization + PKCE
  MCP->>Firebase: Verify identity token
  MCP->>Redis: Store/consume grant state
  MCP-->>Client: MCP access + refresh tokens
  Client->>MCP: Authenticated tool call
  MCP->>MCP: Check scope and mint operation-bound JWT
  MCP->>API: HTTP request with delegated JWT
  API->>MCP: User-scoped result
  MCP-->>Client: Structured tool result

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_{Reviews (1): Last reviewed commit: "fix(auth): bound token metadata caches" | Re-trigger Greptile}

[greptile-apps]

Production delegation stays disabled

The production API deployment supplies none of MCP_AUTH_ISSUER, MCP_AUTH_AUDIENCE, or MCP_AUTH_JWKS_URL, so this branch disables MCPDelegationAuth while the hosted service sends delegated bearer tokens, causing all seven MCP tools to fail API authorization.