feat(process-container): discover identity-less loopback proxy support

[Carlos Alexandro Becker (caarlos0)]

📖 Description

Support an identity-less loopback proxy on PSEC 1.0-only hosts and let callers discover that capability on both PSEC 1.0 and ingress-capable PSEC 1.1 hosts.

• Require explicit runtimeConfig.networkProxy, network.ingress.hostLoopback: "allow", and no processContainer.network.allowedProxyPeer. The existing Model 2 policy requirements still apply.
• Report identitylessLoopbackProxy in backend discovery and baseContainerSupportsIdentitylessLoopbackProxy in the Windows request probe, with matching Rust, Node, and .NET V1 APIs.
• Report support when normal host-loopback ingress is available, or when the host supports PSEC 1.0 but not 1.1. PSEC 1.1 or newer without the ingress flag remains unsupported; accepting a 1.0 payload does not bypass that requirement.
• Keep this separate from general ingressHostLoopbackAllow. Version-query failures omit the capability, report a false probe fact, and retain a warning.
• Require workload launch and a successful proxy fetch when the host probe advertises support. A clean rejection cannot skip those assertions. Older binaries that omit the fact retain the harness's existing fallback behavior.
• Keep detailed documentation in the ProcessContainer networking guide and correct the host requirements in docs/examples.md. SDK READMEs remain high-level. No redundant runtime compatibility warning is emitted.

import { probe } from '@microsoft/mxc-sdk/v1';

const supported =
  probe().probes.baseContainerSupportsIdentitylessLoopbackProxy;

Host	Identity-less loopback proxy
PSEC 1.0 only	Supported
PSEC 1.1 or newer, with ingress support	Supported
PSEC 1.1 or newer, without ingress support	Not supported
No BaseContainer API	Not supported

The signal reports host support, not whether a particular request will succeed or whether the proxy is reachable. Other requested features still require their own host support. The documented inbound host-to-container limitation remains; this does not establish full bidirectional host-loopback support.

The author chose to retain the request-probe output field. Commit ce9bb314 reverts the backend-discovery-only change in e6604eb2, while preserving the example correction in 5557e86b. Ordinary callers that query and read results are unaffected by the added field; callers manually constructing ProbeFacts or exhaustively destructuring it in Rust must account for it.

🔗 References

• Original runtime change: 2f7196e
• Identity-less loopback proxy discovery
• No issue linked.

🔍 Validation

Revert verification, before committing ce9bb314:

Directory	Command	Result
Repository root	git diff --cached --check	Passed.
Repository root	git diff --cached --exit-code e6604eb2^ -- . ':(exclude)docs/examples.md'	Passed: exact restoration of the tree before e6604eb2, except the retained example correction.
Repository root	git diff --cached --exit-code HEAD -- docs/examples.md	Passed: the correction in 5557e86b was untouched.
Repository root	node scripts/check-dotnet-api-parity.js	Passed.

No local build was repeated for the exact revert. Earlier local validation of the restored implementation at a0defb90:

Directory	Command	Result
src/	cargo fmt --all -- --check	Passed.
src/	CARGO_BUILD_JOBS=2 cargo test -p mxc-sdk --lib mxc_engine::probe::tests --quiet	Passed: 9 tests.
src/	CARGO_BUILD_JOBS=2 cargo test -p mxc_ffi --test ffi extern_discovery_returns_owned_json --quiet	Passed: 1 test.
src/	CARGO_BUILD_JOBS=2 cargo clippy -p mxc-sdk --lib --tests --target x86_64-pc-windows-msvc --quiet -- -D warnings	Passed, including Windows-gated test compilation.
sdk/node/	npm run build:test-unit	Passed.
sdk/node/	node --test dist-tests/tests/unit/probe.test.js dist-tests/tests/unit/platform.test.js	Passed: 96 tests; 40 platform-dependent tests skipped.

Windows runtime tests and the live Windows proxy suite were not executed on this macOS host. Cross-target compilation does not establish Windows enforcement. Local .NET tests and AOT execution were not run because dotnet is unavailable. Native/SDK coverage includes PSEC support gates, renamed probe fields, discovery, and .NET AOT serialization.

Earlier evidence, not a validation claim for the current head:

• The author reported a successful manual PSEC 1.0 test.
• All 30 reported checks passed on 0db7aec8, including the Build run. CI must validate the revert head.
• The additional validation run on 3c030b36 had failures in macOS Seatbelt and several Windows ProcessContainer T1 jobs. Their causes were not investigated in this feedback-only pass.

Validation of the now-reverted backend-discovery-only harness and source-compatibility fixtures is not claimed as coverage of the restored request-probe path.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)
• If this PR changes Cargo.lock, the dependency-feed-check check passes (see pull request builds)

📋 Issue Type

• Bug fix
• Feature
• Task

---

GitHub Actions runs the PR validation build automatically. The ADO pipeline
(MXC-PR-Build) is the Azure version of the PR pipeline, kept in parity with the GitHub
Actions build; it runs on merge to main, and Microsoft reviewers with write access can trigger it
on a PR with /azp run. See pull request builds.

If the dependency-feed-check check fails on a new dependency, the crate must be added to
the feed before the PR can pass. See pull request builds
for the steps.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Copilot review overview

🟡 Changes recommended

The runtime regression check can skip the workaround assertion, and the Rust README link is broken.

Review effort: Balanced
Findings: 1 · 1

Open (2)

• Regression assertion is gated by the behavior it verifies · New
• Fix broken relative link to repository docs · New

What changed in this PR

Enables scoped PSEC 1.0 proxy-loopback compatibility and exposes host capability discovery across supported SDKs.

Changes:

• Adds PSEC version gating and runtime workaround behavior.
• Exposes capability and probe facts through Rust, Node, and .NET V1 APIs.
• Adds tests, AOT coverage, and documentation.

File	Description
tests/​scripts/​run_processcontainer_network_proxy_test.ps1	Adds runtime workaround assertion.
src/​mxc-sdk/​src/​core/​mxc_engine/​probe.rs	Adds backend capability discovery.
src/​mxc-sdk/​src/​backends/​process_container/​common/​probe.rs	Reports the probe fact and warnings.
src/​mxc-sdk/​src/​backends/​process_container/​common/​base_container_runner.rs	Implements the PSEC 1.0 workaround.
src/​mxc-sdk/​README.md	Documents Rust discovery APIs.
src/​ffi/​mxc_ffi/​tests/​ffi.rs	Accepts the new capability in FFI tests.
sdk/​node/​tests/​unit/​probe.test.ts	Tests Node probe parsing.
sdk/​node/​tests/​unit/​platform.test.ts	Tests Node discovery parsing.
sdk/​node/​src/​v1/​types.ts	Adds Node V1 types.
sdk/​node/​src/​v1/​probe.ts	Validates the new probe fact.
sdk/​node/​src/​v1/​platform.ts	Recognizes the discovery capability.
sdk/​node/​README.md	Documents Node discovery.
sdk/​dotnet/​README.md	Documents .NET discovery.
sdk/​dotnet/​Microsoft.Mxc.Sdk/​V1/​PlatformDiscovery.cs	Adds .NET V1 capability types.
sdk/​dotnet/​Microsoft.Mxc.Sdk/​V1/​MxcPlatform.cs	Maps the native capability.
sdk/​dotnet/​Microsoft.Mxc.Sdk/​V1/​MxcContainer.cs	Maps the probe fact.
sdk/​dotnet/​Microsoft.Mxc.Sdk/​MxcJsonSerialization.cs	Registers AOT serialization metadata.
sdk/​dotnet/​Microsoft.Mxc.Sdk.Tests/​V1/​MxcContainerTests.cs	Tests .NET parsing and enum stability.
sdk/​dotnet/​Microsoft.Mxc.Sdk.AotSmokeTest/​Program.cs	Exercises AOT serialization paths.
docs/​reference/​rust/​v1/​types.md	Updates Rust V1 reference types.
docs/​reference/​node/​v1/​types.md	Updates Node V1 reference types.
docs/​reference/​dotnet/​v1/​types.md	Updates .NET V1 reference types.
docs/​process-container/​networking.md	Documents compatibility semantics.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[Carlos Alexandro Becker (caarlos0)]

AI-assisted review of 381835f4, with independent code-review, maintainer, and anvil checks. The scoped workaround has a concrete use case; no critical production-code defect was found. The two inline findings confirm the existing automated comments after an independent source check.

No local builds or tests were run. Build success was assumed as requested; Windows runtime enforcement and .NET/AOT execution were not verified. This is a comment review because the PR belongs to the authenticated author.

[Carlos Alexandro Becker (caarlos0)]

AI-assisted follow-up review of 381835f4..a7b85eca: no new findings. Both prior findings are addressed. The host capability now requires workload launch and the compatibility log, and enters the proxy-fetch check even when the initial launch fails. The Rust README link resolves to the existing document and heading. The addressed threads are resolved.

This supersedes my findings in review #1406 (review); the diagram there records the old behavior at 381835f4. No local builds or Windows runtime tests were run. Source review only; build success remains assumed. GitHub does not allow approval of my own PR, so this is a comment review.

[Copilot]

Copilot review overview

🟡 Changes recommended

The PowerShell capability reader can abort under strict mode when used with an older probe binary.

Review effort: Balanced
Findings: 1

Open (1)

• Default missing compatibility hint to false under StrictMode · New

Resolved since last review (2)

• Regression assertion is gated by the behavior it verifies
• Fix broken relative link to repository docs

[Carlos Alexandro Becker (caarlos0)]

AI-assisted incremental review of a7b85eca..3c030b36: no new findings. The optional probe-field check follows the adjacent compatibility checks for older binaries and retains the required launch/log/proxy-fetch assertions when the capability is present. The other network-test changes came from the merge of main (#1401), not a new branch change. All prior threads remain resolved.

This is the current verdict, superseding review #1406 (review). No local build or Windows runtime test was run; build success was assumed as requested. Comment review only because this is the authenticated author's PR.

[Copilot]

Copilot review overview

🔵 Needs a closer look

The security-sensitive Windows networking workaround is well covered in code but lacks a live PSEC 1.0 runtime validation.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Default missing compatibility hint to false under StrictMode

[Elliot (theelliotm)]

Testing in CI: https://github.com/microsoft/mxc/actions/runs/37519009183

[Carlos Alexandro Becker (caarlos0)]

Testing in CI: https://github.com/microsoft/mxc/actions/runs/37519009183

Seems like all the images are on PSEC 1.1.

FWIW I manually tested on PSEC 1.0 and it works as expected.

[Carlos Alexandro Becker (caarlos0)]

AI-assisted incremental review of 3c030b36..f4d81337: no new findings. This removes only duplicate prose from the three SDK type references; their API declarations are unchanged. The canonical explanation and SDK README links remain. All review threads are resolved.

This supersedes my prior verdict in #1406 (review). No local build was run. Comment review only because this is the authenticated author's PR.

[Copilot]

Copilot review overview

🔵 Needs a closer look

It changes Windows security-environment enforcement, and the latest referenced validation run still contains failures requiring human review.

Review effort: Balanced
Findings: None

[Copilot]

Copilot review overview

🔵 Needs a closer look

It changes Windows PSEC policy enforcement, while live Windows validation for the latest revision and current CI remain incomplete.

Review effort: Balanced
Findings: None

[Copilot]

Copilot review overview

🟡 Changes recommended

The Rust and Node V1 type additions break published API compatibility, and an existing example retains contradictory PSEC requirements.

Review effort: Balanced
Findings: 2 · 1

Open (3)

• Required property breaks existing V1 ProbeFacts consumers · New
• Adding ProbeFacts field breaks V1 struct compatibility · New
• Update PSEC compatibility documentation example · New

[Copilot]

Copilot review overview

🟡 Changes recommended

The advertised V1 request-probe fact is absent from the native and SDK probe surfaces.

Review effort: Balanced
Findings: 1

Open (1)

• Add missing identityless loopback proxy capability to ProbeFacts · New

Resolved since last review (3)

• Adding ProbeFacts field breaks V1 struct compatibility
• Required property breaks existing V1 ProbeFacts consumers
• Update PSEC compatibility documentation example

[Copilot]

Copilot review overview

🟡 Changes recommended

The required Rust and Node V1 probe fields break published source compatibility.

Review effort: Balanced
Findings: 2

Open (2)

• Required property breaks V1 ProbeFacts object compatibility · New
• Adding field breaks V1 ProbeFacts struct compatibility · New

Resolved since last review (1)

• Add missing identityless loopback proxy capability to ProbeFacts

[Copilot]

Copilot review overview

🔵 Needs a closer look

The OS-sensitive Windows enforcement path lacks live validation on the exact head, while current CI is still running.

Review effort: Balanced
Findings: None

Resolved since last review (2)

• Adding field breaks V1 ProbeFacts struct compatibility
• Required property breaks V1 ProbeFacts object compatibility