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TUI_LOCKUP_INVESTIGATION.md

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SageTUI Lockup Investigation

Symptom

The SageTUI-based TUI (default, non-legacy) locks up — no keyboard input, no rendering updates.

Changes Made (v0.6.226)

  1. Upgraded SageTUI from 0.9.3 → 0.9.4
  2. Temporarily disabled Program.withDebugger to isolate the issue

Hypotheses

H1: SSE Connection Hangs

  • The sseSub subscription calls DaemonClient.runSseListener
  • runSseListener does a blocking GetStreamAsync call
  • The /api/state endpoint in Dashboard.fs should immediately call pushJson() before subscribing to state changes (line 78 in createApiStateHandler)
  • Test: Add logging to runSseListener to see if the connection establishes and if data arrives

H2: SageTUI Render Loop Blocks

  • The App.run call from SageTUI might be blocking on something internal
  • Could be related to terminal size detection, initial render, or subscription setup
  • Test: Add logging in init, update, and view to see which one never returns

H3: Debugger Combinator Issue

  • Program.withDebugger might have introduced a deadlock or blocking behavior
  • Wraps model in DebuggerModel<Model> and messages in DebuggerMsg<Msg>
  • Status: DISABLED in v0.6.226 — if lockup persists, this hypothesis is ruled out

H4: Race Condition at Startup

  • The pre-flight connectivity check (line 763 in SageTuiClient.fs) succeeds
  • But between that check and the SSE connection, the daemon might not be fully ready
  • Test: Add a small delay or retry logic after connectivity check

Next Steps

  1. Reproduce locally: sagefs tui with a fresh daemon
  2. Add instrumentation: Log statements in sseSub, init, update, view
  3. Check SageTUI 0.9.4 CHANGELOG: Review for any breaking behavioral changes (already reviewed — only additive)
  4. Bisect: If needed, test with SageTUI 0.9.3 to confirm 0.9.4 isn't the cause
  5. Minimal repro: Create a trivial SageTUI app with SSE subscription to isolate SageFs-specific issues

Related Files

  • SageFs/SageTuiClient.fs — TUI client implementation
  • SageFs.Core/DaemonClient.fs — SSE listener (runSseListener)
  • SageFs/Dashboard.fs — /api/state endpoint (createApiStateHandler)
  • C:\Code\Repos\SageTUI\Tea.fs — CustomSub implementation

Notes

  • The legacy TUI (TuiClient.fs) is imperative and has 0% coverage — scheduled for removal in Phase A3
  • The SageTUI-based TUI (SageTuiClient.fs) is the production path — DO NOT REMOVE