🤖 fix: git polling defers to agent commands via flock coordination

Problem: Git fetch polling would hold locks that caused agent git operations
(git add, commit, checkout, etc.) to fail with 'another git process' errors.

Solution: Use flock-based coordination between polling and agent commands:

1. Agent bash commands acquire a SHARED lock on .git/mux.lock
   - Multiple agent commands can run concurrently (shared locks compatible)
   - Lock acquired at start, released when command exits

2. Git fetch polling tries to acquire EXCLUSIVE lock (non-blocking)
   - If agents are running (shared locks held), fetch skips this cycle
   - Polling retries on next cycle (3s later with exponential backoff)

This ensures:
- Agent operations are never blocked by polling
- Multiple agent commands can run concurrently
- Polling only runs when workspace is idle

Also adds belt-and-suspenders check for git's own lock files.

_Generated with `mux`_

Author: ammar-agent

src/common/utils/git/gitStatus.ts

@@ -86,8 +86,34 @@ export function parseGitStatusScriptOutput(output: string): ParsedGitStatusOutpu
  *
  * Environment variables disable all interactive prompts (keychain, SSH, credentials).
  * Git flags optimize for speed - only fetch refs, not objects.
+ *
+ * Lock coordination: Uses flock to coordinate with agent bash commands.
+ * - Fetch acquires EXCLUSIVE lock (non-blocking) - skips if can't acquire
+ * - Agent commands acquire SHARED lock (see bash tool) - can run concurrently
+ * This ensures fetch never blocks agent operations - it just defers to next cycle.
  */
 export const GIT_FETCH_SCRIPT = `
+# Coordinate with agent commands via flock
+# Fetch uses exclusive lock (non-blocking) - skips if agents are running
+# Agent commands use shared lock - they can run concurrently with each other
+GIT_DIR=$(git rev-parse --git-dir 2>/dev/null) || exit 1
+LOCK_FILE="$GIT_DIR/mux.lock"
+
+exec 200>"$LOCK_FILE"
+if ! flock --nonblock --exclusive 200; then
+  echo "SKIP: workspace in use by agent"
+  exit 0
+fi
+
+# Also skip if git's own lock files exist (belt and suspenders)
+GIT_COMMON_DIR=$(git rev-parse --git-common-dir 2>/dev/null) || GIT_COMMON_DIR="$GIT_DIR"
+for DIR in "$GIT_DIR" "$GIT_COMMON_DIR"; do
+  if find "$DIR" -name "*.lock" -type f 2>/dev/null | grep -q .; then
+    echo "SKIP: git lock files present"
+    exit 0
+  fi
+done
+
 # Disable ALL prompts
 export GIT_TERMINAL_PROMPT=0
 export GIT_ASKPASS=echo

src/node/services/tools/bash.ts

@@ -16,6 +16,22 @@ import type { BashToolResult } from "@/common/types/tools";
 import type { ToolConfiguration, ToolFactory } from "@/common/utils/tools/tools";
 import { TOOL_DEFINITIONS } from "@/common/utils/tools/toolDefinitions";
 
+/**
+ * Bash script prefix to acquire shared lock on git workspace.
+ * Coordinates with git polling (GIT_FETCH_SCRIPT) which uses exclusive lock.
+ * - Agent commands: shared lock (can run concurrently with each other)
+ * - Git fetch polling: exclusive lock (non-blocking, skips if agents running)
+ * This ensures polling never blocks agent operations.
+ */
+const GIT_COORDINATION_LOCK_PREFIX = `
+# Acquire shared lock on git workspace to coordinate with background polling
+# This prevents git fetch from running while agent commands execute
+if GIT_DIR=$(git rev-parse --git-dir 2>/dev/null); then
+  exec 200>"$GIT_DIR/mux.lock"
+  flock --shared 200
+fi
+`;
+
 /**
  * Validates bash script input for common issues
  * Returns error result if validation fails, null if valid
@@ -242,7 +258,9 @@ export const createBashTool: ToolFactory = (config: ToolConfiguration) => {
       const truncationState = { displayTruncated: false, fileTruncated: false };
 
       // Execute using runtime interface (works for both local and SSH)
+      // Prefix with git coordination lock (shared) and stdin closure
       const scriptWithClosedStdin = `exec </dev/null
+${GIT_COORDINATION_LOCK_PREFIX}
 ${script}`;
       const execStream = await config.runtime.exec(scriptWithClosedStdin, {
         cwd: config.cwd,