[bug] Workflow-reference tool call times out before dispatch (referenced workflow never starts)

[mmabrouk]

Summary

Calling a workflow-reference tool (a type: reference tool that runs another workflow server-side) fails with a timeout, and traces show the referenced workflow never started. The timeout happens before dispatch, not during a slow run.

Environment

• Harness: claude (Claude Code). Runner: sidecar. Sandbox: local.
• Calling agent: Chief of Staff. Tool: a workflow-reference tool ("Product_Agent" on that agent).
• Resolved variant slug: new-agent-ms4g9hpzo7.
• 2026-07-29 ~13:30 UTC.

Observed behavior

Two calls both failed with:

tool call workflow.variant.new-agent-ms4g9hpzo7 failed: The operation was aborted due to timeout

• query_spans shows zero spans after 13:27 UTC, so the referenced workflow never ran.
• The timeout occurs before any span is created, i.e. before dispatch.
• Verified no side effect occurred (no GitHub issue was created).

Interpretation (low confidence)

The slug "new-agent-ms4g9hpzo7" is NOT stale or wrong. It is the target agent's own variant slug (confirmed when that agent later committed a revision to workflow_slug "new-agent-ms4g9hpzo7"). So the reference resolved to the correct target. The timeout is pre-dispatch (zero spans created), so the hang is in the resolve/dispatch path itself, not in variant selection and not in a slow target run.

Reproduction (proposed, needs confirmation)

1. On an agent that has a workflow-reference tool pointing at another workflow variant, invoke that tool.
2. Observe: the call aborts with "operation was aborted due to timeout"; no span is created for the referenced workflow.

Impact

Agent-to-agent handoffs via workflow-reference tools are unreliable: the call can time out before the target workflow ever starts, with no partial execution and a generic timeout message that does not indicate whether the target resolved.

Related issues (not exact duplicates)

• [feat] Reference a workflow as an agent tool (type:"reference") #4860 (closed) Reference a workflow as an agent tool (type:"reference") — the feature this occurs in.
• docs(design): plan event-driven tool relay (remove relay polling latency) #5232 (open) / feat(runner): event-driven tool relay (fs.watch + Daytona long-poll watch, polling fallback) #5243 (closed) tool-relay latency work — adjacent dispatch path.
• (feat) Warm sessions should hold client tool calls open instead of replaying the turn #5384 (open) Warm sessions should hold client tool calls open instead of replaying the turn.

Asks

• Investigate the resolve/dispatch path for reference tools for a pre-dispatch hang.
• Surface a clearer error that distinguishes "variant not resolved" from "target ran but was slow."

[linear-code]

AGE-4018