@BridgeAR @bengl @Qard , I am opening this as a implementation
of #63623. Test file is included. Happy to adjust the API shape
or implementation based on your feedback before CI runs.

Codecov Report

❌ Patch coverage is 98.95833% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.26%. Comparing base (3e8aa7d) to head (2fccc37).
⚠️ Report is 4 commits behind head on main.

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+ Coverage   90.25%   90.26%   +0.01%     
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  Lines      241001   241148     +147     
  Branches    45399    45445      +46     
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+ Hits       217506   217671     +165     
- Misses      15060    15062       +2     
+ Partials     8435     8415      -20     

@Qard , thanks for the detailed review. So far the checklist of what i have fixed in the latest push:

[] Removed the impossible ALS try/catch fallback
[] Removed node_errors.cc changes as you suggested
[] Replaced all IIFE wrappers with plain blocks in tests
[] Added common.mustCall() / common.mustNotCall() to all handlers
[] Ran lint and tests locally , both passing

Ready for re-review and any changes if you want, when you have time please review it.

The node_errors.cc change still seems to be present.

@DivyanshuX9 It would also be appreciated to get a proper response and assessment from you and not from AI. If I want to ask AI I have an API key for that. You own this PR, you reply.

first of all @rochdev ok i agree with you that using one ID for the subscriber reference would be just as valid for doing the check as well, but your point is still correct and should be noted.

The justification for the one ID vs. 3-line userland style is in the ability to propagate the ALS Context automatically through the Promises, setImmediate, and queueMicrotask chains in the exportTracesToBackend function Calls when doing:

bypass(kDatadog, () => exportTracesToBackend());

In this case, using jsbypass will automatically carry the context through all of the async boundaries without having to do anything extra. However, if you were to do this using the userland style, you would have to thread the ALS context through every async processing boundary, and that's where aint many vendors may do so well.

On the multiple ID's: the Set-style implemntation is already supporting this feature. Different keys for different vendors will co-exist in a manner where the two vendors will not interfere with each other, which is hard to accomplish using a single subscriber reference check.

ALso said that, I do believe your concern about the complexity to savings ratio is valid; however, at the end of the day, it will be up to @bengl and @BridgeAR if this feature fits into the core of the framework. I don't have a strong opinion one way or the other on this; I implemented what was asked in the Issue.

Also if you want you can directly go to the issue #63623 for more context regrading the issue and feature asked

@bengl both items from your review are addressed.

On the TracingChannel side, I deep-dived into this, and the per subscriber bypassId already works in TracingChannel without any additional code in traceSync, tracePromise, or traceCallback because the bypassId gets passed from TracingChannel.subscribe() down through BoundedChannel.subscribe() to its underlying Channel.subscribe() where it’s stored in _bypassSubscribers. All code paths in the 3 trace methods will hit ActiveChannel.publish() which performs the per handler bypassId check including the async continuations in tracePromise and traceCallback. Same for stores via RunStoresScope.

I also added tests 11, 12, and 13 to verify this for traceSync, tracePromise, and traceCallback, all tests 11-13 pass. Tests 12 & 13 specifically provide coverage for async boundaries to ensure bypass context is propagated correctly through the continuation window.

A note of caution: the convenience function subscribe(name, fn) does NOT support options in this PR, and bypassId would only be accessible via the instance API (ch.subscribe(fn, { bypassId })). This is done on purpose as bypass is essentially an advanced APM vendor feature and those vendors are already using the instance API pattern. If the team would like, I would be glad to add options support to the module-level helpers in a subsequent PR.

What could make sense as next steps from here:

-Docs update in doc/api/diagnostics_channel.md covering bypass() and the bypassId option with a real-world APM example.

-Mirroring this in dc-polyfill so Bun and Deno users aren't stuck waiting for runtime support.

Happy to pick up any of those or adjust anything here based on your feedback.

@bengl @BridgeAR
just following up. Latest push addressed:

• Addressed the changes what Mr BridgeAR said to do so
• Renamed suppressed/subscriberId → bypass/bypassId everywhere
• also some tracing channel tests (test 11 to 13) as per bengl stated it
• jasnell approved the implementation

Still waiting on your re-review when you have time. Let me know if there's anything specific blocking approval so I can address it.

@DivyanshuX9 Thanks for the additional details. I was trying to figure out whether bypassBy was used in the subscriber or the publisher, but I now get that it's used in neither and is just to be used anywhere in code not necessarily related to either. With that said, I think it's fine to have it built-in even if it only saves a few lines.

Additional docs are definitely needed though.

@BridgeAR @bengl @rochdev
I opened the docs PR: #64250

Covers bypass(), bypassId on subscribe/bindStore/tracingChannel,the APM recursion use case, and multi-vendor coordination.
Both MJS and CJS examples throughout.

Tell if i'm missing somethin' or I need to add anything else

@Flarna docs are in PR: #64250
since it is going to be a continuation of this PR , after all the changes and reviews i'll update them.

I think implementation + tests + docs of a new public API should come in one PR.

@Flarna Well once BridgeAR also mentioned about doc

We definitely also need documentation for the feature.

at that time was not sure how far reviews will go ,also @rochdev wanted some examples rightaway, So made a seperate PR for that to keep this one clean , yes if i get a green signal to land this one will will update and merge that pr doc in this one.

@Flarna i have moved all the docs here

@Flarna , lowkey I have addressed all feedback in latest push:

1. Added Stability: 1.1 - Active development to bypass()
2. Removed bypass example from Overview (not a typical usage pattern)
3. Rewrote key parameter description to clarify no single match required
4. Rewrote description paragraph to focus on behavior, not internals
5. Fixed channel name to http.client.request.start throughout
6. Replaced repeated subscribe/bindStore bypass examples with link to bypass() docs
7. Removed all the unrelated REPLACEME changes entry from tracingChannel.subscribe

Thank you for the thorough review.

Stability: 1.1 - Active development

also @Flarna at 251 line is this correct or should i just remove REPLACE ME with the stability:1.1 right away

No, the REPLACEME is changed by the release tooling when a release is made, see https://github.com/nodejs/node/blob/main/doc/contributing/api-documentation.md#writing-documentation

The stability index is just documentation and independent of that.