diff --git a/.gitignore b/.gitignore
index 68de41d1..88c7755a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -83,6 +83,9 @@ temp/
 *.bak
 *.backup
 
+# Observer temp files (continuous-learning-v2)
+.observer-tmp/
+
 # Rust build artifacts
 ecc2/target/
 
diff --git a/skills/continuous-learning-v2/agents/observer-loop.sh b/skills/continuous-learning-v2/agents/observer-loop.sh
index c8d02470..e4eb0972 100755
--- a/skills/continuous-learning-v2/agents/observer-loop.sh
+++ b/skills/continuous-learning-v2/agents/observer-loop.sh
@@ -62,9 +62,16 @@ analyze_observations() {
   analysis_count=$(wc -l < "$analysis_file" 2>/dev/null || echo 0)
   echo "[$(date)] Using last $analysis_count of $obs_count observations for analysis" >> "$LOG_FILE"
 
+  # Use relative path from PROJECT_DIR for cross-platform compatibility (#842).
+  # On Windows (Git Bash/MSYS2), absolute paths from mktemp may use MSYS-style
+  # prefixes (e.g. /c/Users/...) that the Claude subprocess cannot resolve.
+  analysis_relpath=".observer-tmp/$(basename "$analysis_file")"
+
   prompt_file="$(mktemp "${observer_tmp_dir}/ecc-observer-prompt.XXXXXX")"
   cat > "$prompt_file" <<PROMPT
-Read ${analysis_file} and identify patterns for the project ${PROJECT_NAME} (user corrections, error resolutions, repeated workflows, tool preferences).
+IMPORTANT: You are running in non-interactive --print mode. You MUST use the Write tool directly to create files. Do NOT ask for permission, do NOT ask for confirmation, do NOT output summaries instead of writing. Just read, analyze, and write.
+
+Read ${analysis_relpath} and identify patterns for the project ${PROJECT_NAME} (user corrections, error resolutions, repeated workflows, tool preferences).
 If you find 3+ occurrences of the same pattern, you MUST write an instinct file directly to ${INSTINCTS_DIR}/<id>.md using the Write tool.
 Do NOT ask for permission to write files, do NOT describe what you would write, and do NOT stop at analysis when a qualifying pattern exists.
 
@@ -117,10 +124,11 @@ PROMPT
     max_turns=10
   fi
 
-  # Prevent observe.sh from recording this automated Haiku session as observations
+  # Prevent observe.sh from recording this automated Haiku session as observations.
+  # Pass prompt via -p flag instead of stdin redirect for Windows compatibility (#842).
   ECC_SKIP_OBSERVE=1 ECC_HOOK_PROFILE=minimal claude --model haiku --max-turns "$max_turns" --print \
     --allowedTools "Read,Write" \
-    < "$prompt_file" >> "$LOG_FILE" 2>&1 &
+    -p "$(cat "$prompt_file")" >> "$LOG_FILE" 2>&1 &
   claude_pid=$!
 
   (