docs(bf-5k9t): verify spawn_stream_json_reader implementation

- Confirmed output_format check with matches!(output_format, crate::cli::OutputFormat::StreamJson)
- Verified spawn_stream_json_reader call with transcript_path.clone() and start_offset parameters
- Confirmed placement inside PROMPT_INJECTED detection block
- Code compiles successfully (cargo check passed)
- All acceptance criteria met

notes/bf-5k9t.md

@@ -0,0 +1,54 @@
+# Bead bf-5k9t: Verify spawn_stream_json_reader call
+
+## Task Verification
+
+Verified that the `spawn_stream_json_reader` call is properly implemented with all required components.
+
+## Location
+File: `/home/coding/claude-print/src/session.rs`
+Lines: 360-375
+
+## Implementation Details
+
+### PROMPT_INJECTED Detection Block (lines 360-375)
+```rust
+let current_phase = startup.phase();
+if last_phase != *current_phase && current_phase.is_prompt_injected() {
+    watchdog_state_clone.mark_prompt_injected();
+
+    // Spawn stream-json reader at PROMPT_INJECTED for stream-json output
+    if matches!(output_format, crate::cli::OutputFormat::StreamJson) {
+        // Calculate byte offset: current transcript file size, or 0 if not exists
+        let start_offset = std::fs::metadata(&transcript_path)
+            .map(|m| m.len())
+            .unwrap_or(0);
+
+        stream_json_handle = Some(emitter::spawn_stream_json_reader(
+            transcript_path.clone(),
+            start_offset,
+        ));
+        stream_json_spawned_clone.store(true, std::sync::atomic::Ordering::SeqCst);
+    }
+}
+```
+
+## Acceptance Criteria Status
+
+✅ **output_format check**: `matches!(output_format, crate::cli::OutputFormat::StreamJson)` (line 364)
+✅ **spawn_stream_json_reader call exists**: Lines 370-373
+✅ **Parameters passed correctly**: `transcript_path.clone()` (line 371) and `start_offset` (line 372)
+✅ **Inside PROMPT_INJECTED detection block**: Lines 360-375
+✅ **Code compiles**: Verified with `cargo check`
+
+## Notes
+
+The implementation correctly:
+1. Detects the phase transition to PromptInjected
+2. Checks if output format is StreamJson before spawning
+3. Calculates the start_offset from the current transcript file size
+4. Spawns the stream-json reader with the correct parameters
+5. Sets the stream_json_spawned flag for coordination
+
+## Conclusion
+
+All acceptance criteria met. No changes required - implementation was already correct.