diff --git a/.debugging b/.debugging
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+# Debugging Journal — Race Condition Hang Between opencode and omo
+
+**Date:** 2026-05-16
+**Goal:** Investigate and fix a race condition / infinite hang bug between opencode (../opencode) and omo that causes prompting to hang indefinitely.
+
+## Phase 0 — Environment Assessment
+
+- **OMO repo:** `/Users/yeongyu/local-workspaces/omo` (plugin for OpenCode)
+- **Opencode repo:** `/Users/yeongyu/local-workspaces/opencode` (OpenCode server/SDK)
+- **Worktree:** `/Users/yeongyu/local-workspaces/omo-kimi-k2.6`
+- **Runtime:** Bun (omo), Node/Bun (opencode with Effect 4.0.0-beta.65)
+
+## Phase 1 — Hypothesis Formation
+
+### Hypothesis 1: promptAsync dispatch timeout not covering hanging fetch
+- `promptAsyncAfterSessionIdle` wraps `session.promptAsync()` with `withDispatchTimeout` (default 30s)
+- But `Promise.race` doesn't cancel the underlying fetch — it just returns after timeout
+- The reservation is then held for `postDispatchHoldMs` (250ms) before expiring
+- **BUT:** If the event loop is blocked, `setTimeout` won't fire, so both promises hang
+
+### Hypothesis 2: Effect-native event system in opencode has race condition
+- Opencode commit `e11e089e4` (May 14) added Effect-native core event system
+- OMO commit `b333a5280` (May 16) added dispatch timeout to prompt-async-gate
+- The hang persists after both fixes
+- The `promptAsync` handler in opencode uses `Effect.forkIn(scope, { startImmediately: true })`
+- If `forkIn` has a bug in Effect 4.0.0-beta.65, the HTTP response might not return
+
+### Hypothesis 3: Reservation leak in prompt-async-gate
+- If `dispatchAfterSessionIdle` throws before `dispatchAttempted = true`, the finally block deletes the reservation
+- If `dispatchAttempted = true` but `postDispatchHoldMs` is very large, reservation stays until `pruneExpiredReservations` runs
+- But default is 250ms, so this should not cause "forever" hang
+
+## Phase 2 — Parallel Investigation
+
+### Key Files Read
+- `omo/src/shared/prompt-async-gate.ts` — The gate logic with timeout
+- `omo/src/shared/session-idle-settle.ts` — Simple settle logic
+- `omo/src/plugin/event.ts` — Event handler that calls `autoContinueAfterFallback`
+- `opencode/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts` — Server-side `promptAsync` handler
+- `opencode/packages/opencode/src/session/prompt.ts` — SessionPrompt service with `loop()`
+- `opencode/packages/core/src/event.ts` — Effect-native event system
+
+### Key Findings
+1. OMO `promptAsyncAfterSessionIdle` has 30s dispatch timeout (added May 16)
+2. Opencode server `promptAsync` handler forks prompt processing into a scope
+3. Opencode uses Effect 4.0.0-beta.65 — a beta version
+4. The `promptSvc.prompt()` calls `loop()` which has `while (true)`
+5. The SDK `createOpencodeClient` sets `req.timeout = false` on fetch
+
+## Next Steps
+1. Check for any OMO callers that bypass the gate (raw `session.promptAsync` calls)
+2. Check opencode logs for hanging requests
+3. Create a reproduction test
+4. Fix the root cause
diff --git a/src/hooks/shared/merge-conflict-guard.test.ts b/src/hooks/shared/merge-conflict-guard.test.ts
new file mode 100644
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+++ b/src/hooks/shared/merge-conflict-guard.test.ts
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+import { describe, expect, test } from "bun:test"
+import { readdirSync, readFileSync } from "fs"
+import { join } from "path"
+
+function* walk(dir: string): Generator<string> {
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    const path = join(dir, entry.name)
+    if (entry.isDirectory()) {
+      if (entry.name === "node_modules" || entry.name === ".git" || entry.name === "dist") {
+        continue
+      }
+      yield* walk(path)
+    } else if (entry.isFile() && (entry.name.endsWith(".ts") || entry.name.endsWith(".tsx") || entry.name.endsWith(".json"))) {
+      yield path
+    }
+  }
+}
+
+function hasConflictMarkers(content: string): boolean {
+  const lines = content.split("\n")
+  return lines.some((line) =>
+    line.startsWith("<<<<<<< ") ||
+    line === "=======" ||
+    line.startsWith(">>>>>>> ")
+  )
+}
+
+describe("#given source files in src/", () => {
+  test("#then no file contains unresolved git merge conflict markers", () => {
+    const conflicts: string[] = []
+    for (const path of walk(join(import.meta.dir, "../../../src"))) {
+      const content = readFileSync(path, "utf-8")
+      if (hasConflictMarkers(content)) {
+        conflicts.push(path)
+      }
+    }
+    expect(conflicts).toEqual([])
+  })
+})