fix: pass a real ScopeHandle to Node withScope callbacks

[zhongxuanwang-nv]

Overview

withScope in the Node.js binding handed its callback a plain JSON object ({ uuid, name, scopeType, ... }) instead of a real ScopeHandle. Passing that object back into event, toolCallExecute, or llmCallExecute (which accept null or a ScopeHandle) threw internal error: Failed to recover ScopeHandle type from napi value on the first call, and because the rejection skipped deregisterSubscriber, the process hung. This fixes the binding so the callback receives a real, reusable ScopeHandle, matching the Rust, Python, and WebAssembly bindings where the scope helper hands back a usable handle. The existing Node quick start and nemo-relay-node README examples already pass the handle, so they now run as written with no doc changes.

• I confirm this contribution is my own work, or I have the right to submit it under this project's license.
• I searched existing issues and open pull requests, and this does not duplicate existing work.

Details

Root cause: Node's with_scope invokes the callback across a ThreadsafeFunction boundary, and a napi_wrap'd ScopeHandle cannot cross that boundary, so the previous code serialized the handle to a plain JSON object. That object carries no wrapped native handle, so napi_unwrap fails when it is later passed to an API typed Option<&ScopeHandle>.

Changes:

• crates/node/src/promise_call.rs: add an Arg0Builder (Box<dyn FnOnce(&Env) -> napi::Result<JsUnknown> + Send>) and a call_with_arg0 method so the first callback argument can be materialized on the JS thread inside the threadsafe call. The existing call / call_with_json_next / call_with_stream_next JSON paths are unchanged.
• crates/node/src/api/mod.rs: with_scope now builds a real ScopeHandle instance through that builder (ToNapiValue::to_napi_value) instead of serde_json::json!({...}), so the callback receives a handle it can pass straight into event, toolCallExecute, and llmCallExecute. The auto-pop and error paths are unchanged.
• crates/node/tests/scope_tests.mjs: add callback receives a reusable ScopeHandle, which passes the callback handle into event, pushScope (as an explicit parent), toolCallExecute, and llmCallExecute and asserts the results.

This aligns Node with the existing cross-binding behavior and does not change the shared runtime contract or the other bindings. No documentation changes are required: the quick start and README already pass the handle, and LlmRequest is delivered to llmCallExecute correctly, so those examples run unchanged once the binding is fixed.

Validation:

• just build-node and just test-node: 226/226 pass, including the new test.
• Ran the existing Node quick start end to end against the fixed build: it prints the scope/mark/tool/LLM event lines, { echo: 'hello' }, and the LLM result, then exits 0 with no hang (previously it threw on the first event(...) call and hung).
• cargo fmt --all, cargo clippy -p nemo-relay-node --all-targets -- -D warnings, and uv run pre-commit pass.

Where should the reviewer start?

Start with with_scope in crates/node/src/api/mod.rs: the callback argument is now a real ScopeHandle built on the JS thread through the new Arg0Builder path in crates/node/src/promise_call.rs. Cross-check crates/node/tests/scope_tests.mjs (callback receives a reusable ScopeHandle), which reuses the handle across event, pushScope, toolCallExecute, and llmCallExecute — the calls that previously threw.

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• Relates to: none

[coderabbitai]

Walkthrough

This PR refactors promise-aware callback invocation to support non-JSON argument builders, enabling with_scope to pass real ScopeHandle instances instead of JSON snapshots to JavaScript callbacks. The infrastructure change is tested with scope reusability verification and documentation is simplified to use plain request objects.

Changes

ScopeHandle Callback Materialization

Layer / File(s)	Summary
Promise call Arg0Builder infrastructure crates/node/src/promise_call.rs	PromiseAwareFn introduces Arg0Builder type and call_with_arg0 method; threadsafe-function payload refactored from plain Json to PrimaryArg enum supporting builder-based materialization on the JS thread; existing call, call_with_json_next, call_with_stream_next route through new PrimaryArg-aware infrastructure.
with_scope callback receives ScopeHandle crates/node/src/api/mod.rs	with_scope clones the ScopeHandle and creates an Arg0Builder closure that materializes it to an N-API value on the JS thread; promise-aware call updated to use call_with_arg0 instead of passing JSON metadata snapshot.
Test coverage for ScopeHandle reusability crates/node/tests/scope_tests.mjs	New withScope test verifies the callback receives a reusable ScopeHandle that can emit events, serve as parent for child scopes, and act as execution target for tool and LLM calls; asserts child scope's parentUuid matches the handle.
Documentation update to plain request objects docs/getting-started/quick-start/nodejs.mdx	Quick-start example removes unused LlmRequest import and updates llmCallExecute to pass a plain request object { headers: {}, content: { messages: [...] } } instead of new LlmRequest(...).

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Title follows Conventional Commits format with 'fix' type, clear scope '(Node withScope callbacks)', and concise imperative summary under 72 characters.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	PR description is comprehensive and well-structured with all required template sections completed: Overview with confirmations, Details explaining root cause and changes, Where to start guidance, and Related Issues.

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@crates/node/README.md`:
- Line 80: Update the explanatory comment that mentions handle to wrap the
literal null in inline code formatting; specifically change the comment "//
`handle` describes the active scope; pass null to target the current scope." so
that the word null is surrounded by backticks (i.e., `null`) to match
documentation formatting and coding guidelines for code elements.

In `@docs/getting-started/quick-start/nodejs.mdx`:
- Line 60: The sentence "For lifecycle calls inside the scope, pass null to
target the current scope." should format the literal null as inline code; update
the docs text in docs/getting-started/quick-start/nodejs.mdx so that `null` is
wrapped in backticks (i.e., change the plain word null to a monospace code
element) to follow the project's docs formatting guidelines for code elements.

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[github-actions]

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[willkill07]

Manually specifying a handle should work though. What was the raised panic?

[zhongxuanwang-nv]

Manually specifying a handle should work though. What was the raised panic?

@willkill07 Hey Will, yes I think manually specifying a handle does work; here it's mainly a rejected Promise / thrown napi error; I should've included the error output:

(nemo-relay) daniewang@DKF2M99Y76 1 % node 1.js
event=scope name=demo-agent
event=scope name=demo-agent
[Error: internal error: Failed to recover `ScopeHandle` type from napi value] {
  code: 'GenericFailure'
}

And then it's stuck there forever.

It's because withScope gives its callback a plain JSON object ({ uuid, name, scopeType, ... }) across the ThreadsafeFunction thread boundary, not a napi_wrap's ScopeHandle. So when that object hits event/toolCallExecute/llmCallExecute (Option<&ScopeHandle>), napi_unwrap returns invalid_arg → the error above. It throws on the first such call (event("initialized", handle, ...)), which skips the following deregisterSubscriber and leaves the subscriber hang.

Therefore, I made withScope pass a real ScopeHandle. I'm wondering what do you think?

[willkill07]

@zhongxuanwang-nv i think this PR should also fix that bug -- in other languages, we do get a scope handle back.

[zhongxuanwang-nv]

@zhongxuanwang-nv i think this PR should also fix that bug -- in other languages, we do get a scope handle back.

Thanks Will! I think the new proposed changes fixed that to make it consistent with other languages :)

[willkill07]

Approving with one open question

[zhongxuanwang-nv]

/merge