fix: prevent pipeline hang when subroutine completes with empty result

[acarr]

Problem

Cyrus intermittently appears "hung" in Linear — the timer keeps running, the transcript shows work is done, but the ticket is never updated with a commit, PR, or summary. The only recourse is to manually stop the session.

Root Cause

In AgentSessionManager.completeSession(), the condition that decides whether to advance the subroutine pipeline is:

if ("result" in resultMessage && resultMessage.result) {

Some subroutines (observed on changelog-update, but could affect any) complete with subtype: "success" but no result text — result is undefined or empty string. When this happens:

1. The if above evaluates to false (result is falsy)
2. All else if branches check subtype !== "success", which is also false
3. The function silently returns — no pipeline advancement, no error, no log
4. The Linear ticket shows "still working" indefinitely

Fix

Change the primary check from requiring result text to checking the success status:

if (resultMessage.subtype === "success") {

When result text is empty, a placeholder "(completed successfully)" is synthesized so downstream code that expects a string still works.

Also fixes a secondary issue: when a user clicks "stop" in Linear but the session had already completed successfully, the pipeline was being abandoned. Now it checks whether the stop was actually effective (non-success result) vs. arrived too late (success result).

Evidence

Reproduced

• ABC-215, ABC-216: Both hung at changelog-update with diagnostic logs showing subtype=success hasResult=false followed by silence
• ABC-227, ABC-231: Hit the same hasResult=false condition, but with the fix active — logs show success with empty result — synthesizing result text and the pipeline continued to completion

Diagnostic log showing the fix in action (WAZ-227)

completeSession ENTERED ... subtype=success hasResult=true    ← normal subroutine
completeSession ENTERED ... subtype=success hasResult=true    ← normal subroutine
completeSession ENTERED ... subtype=success hasResult=false   ← BUG TRIGGERED
  success with empty result — synthesizing result text        ← FIX CAUGHT IT
  calling handleProcedureCompletion                           ← pipeline continued
completeSession ENTERED ... subtype=success hasResult=true    ← rest completed normally

Historical analysis

Analyzed 28 previous Cyrus tickets. 6 hung with the same pattern — Session completed with N messages logged by ClaudeRunner but no Subroutine completed, advancing to next from AgentSessionManager. Task type and complexity showed no correlation — both simple (Settings screen) and complex (4-package polling system) tickets hung.

Test plan

• New test: advances pipeline when success result has empty result text — the core regression test
• New test: continues pipeline when stop arrives too late — stop + success doesn't kill pipeline
• Updated test: skips pipeline when stop is effective — uses non-success subtype
• All 630 existing tests pass
• TypeScript compiles cleanly (typecheck passes in pre-commit hook)
• Verified with 16+ live Cyrus tickets across multiple batches

🤖 Generated with Claude Code

[Connoropolous]

thanks @acarr we are queueing this up for review