Resolve the command before the request is parsed

[Gudge (MGudgin)]

Resolve the command before the request is parsed

This PR changes CLI command handling so trailing commands are resolved and
inserted before request parsing, and Rust SDK requests receive their command at
construction time. It preserves behavior for valid requests and requests
without a trailing CLI command; command-preparation failures remain entry-point
errors when the command and policy are independently invalid.

Details

• Probe the request phase and reuse one duplicate-preserving raw source pass to
  select backend-specific quoting and edit process.commandLine.
• Keep typed validation authoritative for the effective document, route request
  errors through one production helper, and log replacements only after parsing
  succeeds.
• Require commands in request-builder APIs, remove post-build script mutation,
  and migrate SDK and FFI callers with direct validation coverage.
• Document native CLI syntax, state-aware exec restrictions, and the distinction
  between complete schema-valid requests and CLI templates.

Tests

• cargo fmt --all -- --check
• cargo check --workspace --all-targets
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• cargo check -p mxc_engine --tests --target x86_64-apple-darwin

Microsoft Reviewers: Open in CodeFlow

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[Copilot]

Pull request overview

Moves CLI command resolution before request parsing and makes Rust SDK requests complete at construction.

Changes:

• Adds backend/phase probing and command splicing.
• Requires commands in request-builder APIs and removes set_script.
• Updates tests, FFI callers, and documentation.

Show a summary per file

File	Description
src/ffi/mxc_ffi/src/streaming.rs	Passes commands during request construction.
src/ffi/mxc_ffi/src/lib.rs	Updates run-to-completion request creation.
src/core/wxc/src/main.rs	Integrates pre-parse CLI command resolution and tests.
src/core/wxc_common/src/state_aware_dispatch.rs	Exposes backend-prefix resolution internally.
src/core/wxc_common/src/splice.rs	Adds JSON command splicing.
src/core/wxc_common/src/probe.rs	Adds backend and phase probes.
src/core/wxc_common/src/lib.rs	Registers new internal modules.
src/core/wxc_common/src/config_parser.rs	Applies CLI commands before typed parsing.
src/core/mxc-sdk/tests/streaming.rs	Updates streaming test request construction.
src/core/mxc-sdk/tests/streaming_processcontainer.rs	Updates ProcessContainer streaming test.
src/core/mxc-sdk/tests/sdk_helpers.rs	Updates SDK helper tests.
src/core/mxc-sdk/tests/sandbox.rs	Updates sandbox tests.
src/core/mxc-sdk/src/lib.rs	Revises SDK examples.
src/core/mxc-sdk/README.md	Documents command-at-build usage.
src/core/mxc_engine/src/policy.rs	Requires commands in builder APIs.
src/core/mxc_engine/src/dispatch.rs	Updates dispatch tests.

Review details

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• Files reviewed: 16/16 changed files
• Comments generated: 3
• Review effort level: Balanced

[Darren Hoehna (dhoehna)]

Besides the comments about de-duplication the code is sound. I am concerned to see duplicate methods for one-shot and state-aware. Merging those paths is a future issue.

[Copilot]

Review details

Suppressed comments (4)

src/core/mxc-sdk/tests/streaming.rs:36

• This identifier is misspelled, so the mxc-sdk streaming integration-test target does not compile. Use the existing command parameter.

 let request = build_request(&policy, commmand, None).expect("build_request should succeed");

src/core/wxc_common/src/splice.rs:14

• Parsing into serde_json::Value before the real typed parser silently collapses duplicate object keys. With a CLI command, a request containing duplicate process, network, or other policy sections is therefore accepted using the last value instead of being rejected as a duplicate field, potentially changing the enforced policy. Preserve the original structure during splicing or explicitly reject duplicate keys before converting to Value.

 let mut doc: Value = serde_json::from_str(json).ok()?;

src/core/wxc_common/src/splice.rs:22

• Serializing the modified DOM into a compact string moves every subsequent typed parse error to line 1, contradicting parse_mxc_request_json's source-location guarantee. For example, an invalid multiline filesystem field with a CLI command no longer reports its original line/column. Splice into the original source text (or retain an offset map) rather than reserializing the whole document.

 Some(Spliced {
json: serde_json::to_string(&doc).ok()?,

src/core/wxc_common/src/config_parser.rs:254

• Command-rendering failures are always classified as Decode, even after phase identified a state-aware exec request. Previously this path emitted a state-aware stdout envelope; it now emits the pre-discrimination stderr diagnostic, contrary to ParseError's routing contract. Classify this error as StateAware when phase.is_some() (and apply the same rule to the empty-command branch below).

 let command = cmdline_from_argv_for_context(argv, context).map_err(|e| {
ParseError::Decode(WxcError::ConfigParse(format!(
"invalid CLI command override: {e}"
)))
})?;

• Files reviewed: 16/16 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

Review details

• Files reviewed: 18/18 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

Copilot review overview

Review tier: Balanced
Findings: 2 · 1

New issues introduced by this change (1)

Severity	Finding
	src/​core/​wxc_common/​src/​splice.rs — process: null now bypasses the CLI override: deserializing it as RawObject fails, so the…

Pre-existing issues (2)

Severity	Finding
	src/​core/​wxc_common/​src/​config_parser.rs — These branches now return probe/override errors before the typed parser runs, changing error… View comment
	src/​core/​mxc_engine/​src/​policy.rs — This migration replaced the test's existing Some("test-container") argument with None, leaving… View comment

Issues resolved since last review (4)

Severity	Finding
	src/​core/​wxc_common/​src/​splice.rs — A non-string process.commandLine is currently overwritten before typed deserialization, so… View resolved comment
	src/​core/​mxc_engine/​src/​policy.rs — The API change leaves tests/isolation_session.rs:109,128 calling this function with the old… View resolved comment
	src/​core/​wxc_common/​src/​config_parser.rs — Command-rendering failures are always classified as Decode, even after phase was successfully… View resolved comment
	src/​core/​wxc_common/​src/​splice.rs — Round-tripping the unvalidated policy through serde_json::Value changes the parser's validation… View resolved comment

Suppressed comments (1)

src/core/wxc_common/src/config_parser.rs:242

• The state-aware backend probe is surfaced directly, so parser-owned sandboxId failures no longer retain their existing diagnostics. For example, an exec request with "sandboxId": 42 previously went through config_deserialize and reported the sandboxId JSON path; this probe now emits plain serde text before the typed parser runs (and a missing ID also changes from phase exec requires a sandboxId to a new message). Pass through probe failures caused by malformed/missing field values so the typed parser and normal backend resolution preserve the established error text; only use the probe result when it successfully identifies a backend.

 let backend =
crate::probe::probe_state_aware_backend(json).map_err(ParseError::StateAware)?;

[Copilot]

Copilot review overview

Review tier: Balanced
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	src/​core/​wxc_common/​src/​config_parser.rs — splice_command returning None does not imply the typed parser will reject the document.…

Issues resolved since last review (2)

Severity	Finding
	docs/​state-aware-lifecycle/​mxc-state-aware-sandbox-api.md — This example propagates apply_cli_command failures immediately with ?, contradicting the… View resolved comment
	src/​core/​wxc_common/​src/​splice.rs — The override can now hide an invalid policy command. A non-empty string containing \u0000… View resolved comment

[Copilot]

Copilot review overview

Review tier: Balanced
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	src/​core/​wxc_common/​src/​config_parser.rs — This logs the override before typed parsing has succeeded. If any unrelated policy field is…

Issues resolved since last review (1)

Severity	Finding
	src/​core/​wxc_common/​src/​config_parser.rs — splice_command returning None does not imply the typed parser will reject the document.… View resolved comment

[Copilot]

Copilot review overview

🟢 Approval recommended

The API migration is complete and the new parsing behavior has comprehensive edge-case coverage.

Review tier: Balanced
Findings: None

Issues resolved since last review (1)

Severity	Finding
	src/​core/​wxc_common/​src/​config_parser.rs — This logs the override before typed parsing has succeeded. If any unrelated policy field is… View resolved comment

[Copilot]

Copilot review overview

🔵 Needs a closer look

Core parsing, command quoting, and cross-backend error routing changes warrant final human validation despite strong test coverage.

Review tier: Balanced
Findings: None

[Copilot]

Copilot review overview

🟡 Changes recommended

Two updated documents incorrectly claim command-less templates are invalid under every supported JSON schema.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review tier: Balanced
Findings: 2

New issues introduced by this change (2)

Severity	Finding
	README.md — The “not schema-valid” claim is not true for every supported schema:…
	docs/​schema.md — This conflates runtime completeness with JSON Schema validity. In particular, the immutable 0.8…

[Copilot]

Copilot review overview

🔵 Needs a closer look

The new splice path regresses trailing-command templates containing "process": null.

Review tier: Balanced
Findings: None

Issues resolved since last review (2)

Severity	Finding
	docs/​schema.md — This conflates runtime completeness with JSON Schema validity. In particular, the immutable 0.8… View resolved comment
	README.md — The “not schema-valid” claim is not true for every supported schema:… View resolved comment

Suppressed comments (1)

src/core/wxc_common/src/splice.rs:172

• A trailing command no longer completes a template with "process": null. The previous relaxed parse treated this as an absent optional process and applied the CLI command afterward; this splice instead returns None, so typed parsing now fails with “'process' section is required.” Handle JSON null like a missing process while leaving other non-object values for typed validation.

 MemberMatch::Unique(process_raw) => {
let process_source = process_raw.get();
let process: RawObject<'_> = serde_json::from_str(process_source).ok()?;

[Copilot]

Copilot review overview

🔵 Needs a closer look

Null process templates regress, and command-render failures lose rejection classification, attribution, and telemetry.

Review tier: Balanced
Findings: None

Suppressed comments (2)

src/core/wxc_common/src/splice.rs:172

• process: null is a valid “absent process” representation for the wire model (Option<Process>), and the previous allow_missing_command path accepted it when trailing CLI arguments supplied the command. Parsing null as RawObject fails here, so the source is left unchanged and the typed parser now rejects the request instead of applying the override. Treat a null process value like a missing process and replace it with an object containing commandLine; cover both one-shot and state-aware exec templates.

 MemberMatch::Unique(process_raw) => {
let process_source = process_raw.get();
let process: RawObject<'_> = serde_json::from_str(process_source).ok()?;

src/core/wxc_common/src/config_parser.rs:385

• Encoding command-render failures as generic Decode/StateAware errors loses their origin. The new main path records valid-JSON one-shot failures as malformed_json and state-aware failures as schema_violation with unknown backend/phase, then exits before telemetry initialization; the removed paths used InvalidCommandOverride, retained backend/phase attribution, and emitted early-exit telemetry. Preserve a typed command-override error with its routing/context and handle it through the dedicated rejection and telemetry paths.

 let command = cmdline_from_argv_for_context(argv, context).map_err(|e| match phase {
None => ParseError::Decode(WxcError::ConfigParse(format!(
"invalid CLI command override: {e}"
))),
Some(_) => ParseError::StateAware(MxcError::malformed_request(format!(