Add cross-service tracing workaround guide (WBDOCS-1249)

[dbrian57]

Summary

• Adds a new how-to guide (weave/guides/tracking/cross-service-tracing.mdx) documenting how to link Weave traces across separate processes or services into a single unified trace tree.
• Adds the new page to the "Advanced Ops" section in docs.json navigation.

Test plan

• Read the draft and verify the technical approach matches the source Loom walkthrough and example code.
• Verify the parent_call helper code is correct and the imports match the current Weave library.
• Confirm the Warning callout appropriately flags that this uses internal APIs.
• Confirm the complete example in the Accordion runs correctly against the current Weave version.
• Check that the new page renders correctly in the Mintlify local dev server (mint dev).
• Verify navigation placement in the "Advanced Ops" group is appropriate.

🤖 Generated with Claude Code

[dbrian57]

Sources and decision log

Sources

• Primary source: Loom video transcript provided in WBDOCS-1249, demonstrating the cross-service tracing approach.
• Example code: Provided directly with the ticket — the complete multiprocessing demo.
• JIRA ticket WBDOCS-1249: Summary stated "Document cross-agent tracing"; description linked to an internal Slack thread.
• Existing docs: weave/guides/tracking/tracing.mdx, weave/guides/tracking/threads.mdx, weave/guides/tracking/trace-tree.mdx — read to match style and ensure no duplication.

Key decisions

• Document type: How-to guide (task-oriented). The reader has a concrete problem — ops in separate services creating fragmented traces — and needs a step-by-step workaround.
• Internal API warning: Prominently placed at the top because weave.trace.context.call_context and weave.trace.weave_client are not public APIs. AGENTS.md says to use only public APIs in examples; this doc explicitly documents a workaround that cannot be implemented with public APIs alone. The warning makes the tradeoff clear.
• Navigation placement: "Advanced Ops" group under "Trace your application" — this is more advanced than basic tracing, and similar in audience to trace-generator-func.mdx and threads.mdx.
• Complete example in Accordion: The full multiprocessing demo is preserved but collapsed so it doesn't overwhelm readers who only need the pattern. The step-by-step section before it covers the minimal pattern.
• Removed unused imports: os and Optional/typing were in the original demo code for the DISABLE_PARENT_CALL env var feature, which was removed from the example for clarity.
• Transport mechanism: Left intentionally unspecified (HTTP, gRPC, queue) — the Loom presenter explicitly says this is up to the implementation.

Needs SME verification

• Confirm the Call constructor fields (_op_name, project_id, parent_id, inputs) are still correct for the current Weave version. The example code was provided with the ticket but was not verified against a specific Weave release.
• Confirm get_current_call() is correctly imported from weave.trace.context.call_context and set_call_stack() from the same module.
• Confirm the Call class is still importable from weave.trace.weave_client.
• Verify the title "Link traces across services" is the right framing — the ticket says "cross-agent tracing" but the Loom describes services/processes more broadly.
• Is there a target timeline for native cross-service tracing support that should be mentioned in the Warning?

Omissions

• The DISABLE_PARENT_CALL env var feature from the original demo was omitted — it was a demo convenience, not something users need in production.
• The Payload dataclass is kept in the complete example but not in the step-by-step section — it's part of the inter-process plumbing, not the tracing pattern itself.

Related

• JIRA: WBDOCS-1249

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Resume prompt

To pick up from here in a new session:

PR wandb/docs#2499 adds a how-to guide for cross-service Weave tracing at weave/guides/tracking/cross-service-tracing.mdx. The PR is open and needs SME review for technical accuracy (see "Needs SME verification" checklist in the PR comment). The key open questions are: whether the internal API import paths are correct for the current Weave version, and whether "services" is the right framing vs. "agents". JIRA ticket: WBDOCS-1249.

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docs.json

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