docs: add explanation of tmux DA response filtering fix

Documents the investigation and fix for the '1;10;0c' display issue that occurred when refreshing browser sessions running tmux.
2026-01-29 20:30:38 +00:00
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+# Fix for "1;10;0c" Display Issue in tmux
+
+## Problem
+When entering or refreshing a webterm session running tmux, the text "1;10;0c" 
+appears on the screen. This is a terminal Device Attributes (DA) response that 
+should be filtered out.
+
+## Root Cause
+1. **Tmux sends a DA2 query** (`ESC[>c`) when it initializes to detect terminal capabilities
+2. The terminal responds with `ESC[>1;10;0c` (DA2 response format)
+3. The filtering code only handled DA1 responses (`ESC[?...c`) but **not DA2** (`ESC[>...c`)
+4. The unfiltered DA2 response appeared as visible text "1;10;0c" in the replay buffer
+
+## Solution
+Updated the DA response filtering patterns in three files to handle all DA variants:
+
+- **DA1** (Primary): `ESC[?...c` - already handled ✓
+- **DA2** (Secondary): `ESC[>...c` - **NOW FIXED** ✓  
+- **DA3** (Tertiary): `ESC[=...c` - added for completeness ✓
+
+### Changed Files
+1. `src/webterm/terminal_session.py`
+2. `src/webterm/docker_exec_session.py`
+3. `src/webterm/local_server.py`
+
+### Pattern Changes
+**Before:**
+```python
+DA_RESPONSE_PATTERN = re.compile(rb"\x1b\[\?[\d;]+c")
+DA_PARTIAL_PATTERN = re.compile(rb"\x1b(?:\[(?:\?[\d;]*)?)?$")
+```
+
+**After:**
+```python
+DA_RESPONSE_PATTERN = re.compile(rb"\x1b\[[?>=][\d;]*c")
+DA_PARTIAL_PATTERN = re.compile(rb"\x1b(?:\[(?:[?>=][\d;]*)?)?$")
+```
+
+## Testing
+- All 342 existing tests pass ✓
+- Verified the pattern matches DA1, DA2, and DA3 responses ✓
+- Confirmed partial buffering works for all variants ✓
+
+## Technical Details
+Device Attributes queries/responses:
+- **DA1**: `ESC[c` → `ESC[?1;10;0c` (terminal capabilities)
+- **DA2**: `ESC[>c` → `ESC[>1;10;0c` (terminal version - **sent by tmux**)
+- **DA3**: `ESC[=c` → `ESC[=1;0c` (rarely used)
+
+The fix ensures all three variants are filtered from both live output and 
+replay buffers when clients reconnect.