fix: move mission context to top of system prompt + auto-inject initial prompt

Mission context was buried at the end of a 21K char system prompt and the
agent ignored it. Two fixes:
1. Mission block now emits FIRST in build_runtime_prompt() so it's the most
   prominent instruction the agent sees
2. When an active mission exists and no user prompt is given, auto-inject
   an initial user message triggering the agent to read mission state files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bin/mosaic

@@ -138,6 +138,44 @@ build_runtime_prompt() {
     exit 1
   fi
 
+  # Inject active mission context FIRST so the agent sees it immediately
+  local mission_file=".mosaic/orchestrator/mission.json"
+  if [[ -f "$mission_file" ]] && command -v jq &>/dev/null; then
+    local m_status
+    m_status="$(jq -r '.status // "inactive"' "$mission_file" 2>/dev/null)"
+    if [[ "$m_status" == "active" || "$m_status" == "paused" ]]; then
+      local m_name m_id m_count m_completed
+      m_name="$(jq -r '.name // "unnamed"' "$mission_file")"
+      m_id="$(jq -r '.mission_id // ""' "$mission_file")"
+      m_count="$(jq '.milestones | length' "$mission_file")"
+      m_completed="$(jq '[.milestones[] | select(.status == "completed")] | length' "$mission_file")"
+
+      cat <<MISSION_EOF
+# ACTIVE MISSION — HARD GATE (Read Before Anything Else)
+
+An active orchestration mission exists in this project. This is a BLOCKING requirement.
+
+**Mission:** $m_name
+**ID:** $m_id
+**Status:** $m_status
+**Milestones:** $m_completed / $m_count completed
+
+## MANDATORY — Before ANY Response to the User
+
+You MUST complete these steps before responding to any user message, including simple greetings:
+
+1. Read \`~/.config/mosaic/guides/ORCHESTRATOR-PROTOCOL.md\` (mission lifecycle protocol)
+2. Read \`docs/MISSION-MANIFEST.md\` for full mission scope, milestones, and success criteria
+3. Read the latest scratchpad in \`docs/scratchpads/\` for session history, decisions, and corrections
+4. Read \`docs/TASKS.md\` for current task state (what is done, what is next)
+5. After reading all four, acknowledge the mission state to the user before proceeding
+
+If the user gives a task, execute it within the mission context. If no task is given, present mission status and ask how to proceed.
+
+MISSION_EOF
+    fi
+  fi
+
   cat <<'EOF'
 # Mosaic Launcher Runtime Contract (Hard Gate)
 
@@ -169,40 +207,6 @@ EOF
 
   printf '\n\n# Runtime-Specific Contract\n\n'
   cat "$runtime_file"
-
-  # Inject active mission context if present in CWD
-  local mission_file=".mosaic/orchestrator/mission.json"
-  if [[ -f "$mission_file" ]] && command -v jq &>/dev/null; then
-    local status
-    status="$(jq -r '.status // "inactive"' "$mission_file" 2>/dev/null)"
-    if [[ "$status" == "active" || "$status" == "paused" ]]; then
-      local m_name m_id m_count m_completed
-      m_name="$(jq -r '.name // "unnamed"' "$mission_file")"
-      m_id="$(jq -r '.mission_id // ""' "$mission_file")"
-      m_count="$(jq '.milestones | length' "$mission_file")"
-      m_completed="$(jq '[.milestones[] | select(.status == "completed")] | length' "$mission_file")"
-
-      printf '\n\n# Active Mission Context\n\n'
-      cat <<MISSION_EOF
-An active orchestration mission has been detected in this project.
-
-**Mission:** $m_name
-**ID:** $m_id
-**Status:** $status
-**Milestones:** $m_completed / $m_count completed
-
-## MANDATORY First Actions
-
-1. Load \`~/.config/mosaic/guides/ORCHESTRATOR-PROTOCOL.md\` (mission lifecycle protocol)
-2. Read \`docs/MISSION-MANIFEST.md\` for full mission scope, milestones, and success criteria
-3. Read \`docs/scratchpads/${m_id}.md\` for session history, decisions, and corrections
-4. Read \`docs/TASKS.md\` for current task state (what is done, what is next)
-5. Do NOT begin any coding or planning until you have read all four documents above
-
-You are resuming an existing mission. The state files are the source of truth.
-MISSION_EOF
-    fi
-  fi
 }
 
 # Ensure runtime contract is present at the runtime's native config path.
@@ -221,6 +225,22 @@ ensure_runtime_config() {
   fi
 }
 
+# Detect active mission and return an initial prompt if one exists.
+# Sets MOSAIC_MISSION_PROMPT as a side effect.
+_detect_mission_prompt() {
+  MOSAIC_MISSION_PROMPT=""
+  local mission_file=".mosaic/orchestrator/mission.json"
+  if [[ -f "$mission_file" ]] && command -v jq &>/dev/null; then
+    local m_status
+    m_status="$(jq -r '.status // "inactive"' "$mission_file" 2>/dev/null)"
+    if [[ "$m_status" == "active" || "$m_status" == "paused" ]]; then
+      local m_name
+      m_name="$(jq -r '.name // "unnamed"' "$mission_file")"
+      MOSAIC_MISSION_PROMPT="Active mission detected: ${m_name}. Read the mission state files and report status."
+    fi
+  fi
+}
+
 # Launcher functions
 launch_claude() {
   check_mosaic_home
@@ -234,8 +254,16 @@ launch_claude() {
   # Claude supports --append-system-prompt for direct injection
   local runtime_prompt
   runtime_prompt="$(build_runtime_prompt "claude")"
-  echo "[mosaic] Launching Claude Code..."
+
-  exec claude --append-system-prompt "$runtime_prompt" "$@"
+  # If active mission exists and no user prompt was given, inject initial prompt
+  _detect_mission_prompt
+  if [[ -n "$MOSAIC_MISSION_PROMPT" && $# -eq 0 ]]; then
+    echo "[mosaic] Launching Claude Code (active mission detected)..."
+    exec claude --append-system-prompt "$runtime_prompt" "$MOSAIC_MISSION_PROMPT"
+  else
+    echo "[mosaic] Launching Claude Code..."
+    exec claude --append-system-prompt "$runtime_prompt" "$@"
+  fi
 }
 
 launch_opencode() {
@@ -289,8 +317,15 @@ launch_yolo() {
       # Claude uses an explicit dangerous permissions flag.
       local runtime_prompt
       runtime_prompt="$(build_runtime_prompt "claude")"
-      echo "[mosaic] Launching Claude Code in YOLO mode (dangerous permissions enabled)..."
+
-      exec claude --dangerously-skip-permissions --append-system-prompt "$runtime_prompt" "$@"
+      _detect_mission_prompt
+      if [[ -n "$MOSAIC_MISSION_PROMPT" && $# -eq 0 ]]; then
+        echo "[mosaic] Launching Claude Code in YOLO mode (active mission detected)..."
+        exec claude --dangerously-skip-permissions --append-system-prompt "$runtime_prompt" "$MOSAIC_MISSION_PROMPT"
+      else
+        echo "[mosaic] Launching Claude Code in YOLO mode (dangerous permissions enabled)..."
+        exec claude --dangerously-skip-permissions --append-system-prompt "$runtime_prompt" "$@"
+      fi
       ;;
     codex)
       check_mosaic_home