fix(agent-context): support multiple context files safely

extensions/agent-context/README.md

@@ -10,6 +10,7 @@ Not every Spec Kit user wants Spec Kit to write into the coding agent's context
 
 - **Opt out** entirely with `specify extension disable agent-context` — Spec Kit will then never create or modify the agent context file.
 - **Customize the markers** by editing `.specify/extensions/agent-context/agent-context-config.yml` — both the Python layer and the bundled scripts honor the same `context_markers` value.
+- **Synchronize multiple agent anchors** by setting `context_files` when a project intentionally uses more than one coding agent context file, such as `AGENTS.md` and `CLAUDE.md`.
 - **Refresh on demand** with `/speckit.agent-context.update`, or automatically through the hooks declared in `extension.yml` (`after_specify`, `after_plan`).
 
 ## Commands
@@ -27,13 +28,20 @@ All configuration flows through the extension's own config file at
 # Path to the coding agent context file managed by this extension
 context_file: CLAUDE.md
 
+# Optional list of coding agent context files to manage together.
+# When non-empty, this takes precedence over context_file.
+context_files:
+  - AGENTS.md
+  - CLAUDE.md
+
 # Delimiters for the managed Spec Kit section
 context_markers:
   start: "<!-- SPECKIT START -->"
   end: "<!-- SPECKIT END -->"
 ```
 
 - `context_file` — the project-relative path to the coding agent context file, written by `specify init` and `specify integration install`.
+- `context_files` — optional project-relative paths to multiple coding agent context files. When non-empty, the list takes precedence over `context_file`. Absolute paths, backslash separators, and `..` path segments are rejected.
 - `context_markers.start` / `.end` — the delimiters around the managed section. Edit these to use custom markers.
 
 ## Requirements
@@ -55,3 +63,4 @@ specify extension disable agent-context
 ```
 
 When disabled, Spec Kit skips context file creation, updates, and removal (the gates are inside `upsert_context_section()` and `remove_context_section()`).
+Disabled projects also ignore stale `context_files` values during command rendering so disabling the extension remains a complete opt-out.

extensions/agent-context/agent-context-config.yml

@@ -2,12 +2,17 @@
 # These values are populated automatically by `specify init` and
 # `specify integration use` / `specify integration install`.
 
-# Path (relative to the project root) to the coding agent context file
+# Path (relative to the project root) to the default coding agent context file
 # managed by this extension (e.g. CLAUDE.md, AGENTS.md,
 # .github/copilot-instructions.md). Set automatically from the active
 # integration and regenerated during `specify init` or integration switches.
 context_file: ""
 
+# Optional list of project-relative coding agent context files managed by this
+# extension. When non-empty, this list takes precedence over `context_file`.
+# Use this for projects that intentionally keep multiple agent anchors in sync.
+context_files: []
+
 # Delimiters for the managed Spec Kit section.
 # Edit these to use custom markers.
 context_markers:

extensions/agent-context/commands/speckit.agent-context.update.md

@@ -12,11 +12,12 @@ The script reads the agent-context extension config at
 `.specify/extensions/agent-context/agent-context-config.yml` to discover:
 
 - `context_file` — the path of the coding agent context file to manage.
+- `context_files` — optional project-relative paths for multiple coding agent context files. When non-empty, the script updates each listed file and the list takes precedence over `context_file`.
 - `context_markers.start` / `.end` — the delimiters surrounding the managed section. Defaults to `<!-- SPECKIT START -->` and `<!-- SPECKIT END -->` when the field is missing.
 
 It then creates, replaces, or appends the managed block so that the section points at the most recent plan path when one can be discovered (`specs/<feature>/plan.md`).
 
-If `context_file` is empty or the file cannot be located, the command reports nothing to do and exits successfully.
+If `context_files` and `context_file` are empty, the command reports nothing to do and exits successfully. Context file paths must stay project-relative; absolute paths and `..` path segments are rejected.
 
 ## Execution
 

extensions/agent-context/scripts/bash/update-agent-context.sh

@@ -1,10 +1,10 @@
 #!/usr/bin/env bash
 # update-agent-context.sh
 #
-# Refresh the managed Spec Kit section in the coding agent's context file
+# Refresh the managed Spec Kit section in the coding agent's context file(s)
 # (e.g. CLAUDE.md, .github/copilot-instructions.md, AGENTS.md).
 #
-# Reads `context_file` and `context_markers.{start,end}` from the
+# Reads `context_files` or `context_file`, plus `context_markers.{start,end}`, from the
 # agent-context extension config:
 #   .specify/extensions/agent-context/agent-context-config.yml
 #
@@ -39,9 +39,10 @@ if [[ -z "$_python" ]]; then
   exit 0
 fi
 
-# Parse extension config once; emit three newline-separated fields:
-# context_file, context_markers.start, context_markers.end
+# Parse extension config once; emit three JSON lines:
+# context files array, context_markers.start, context_markers.end
 if ! _raw_opts="$("$_python" - "$EXT_CONFIG" <<'PY'
+import json
 import sys
 try:
     import yaml
@@ -73,7 +74,17 @@ def get_str(obj, *keys):
         else:
             return ""
     return node if isinstance(node, str) else ""
-print(get_str(data, "context_file"))
+context_files = []
+raw_files = data.get("context_files")
+if isinstance(raw_files, list):
+    for value in raw_files:
+        if isinstance(value, str) and value.strip() and value.strip() not in context_files:
+            context_files.append(value.strip())
+if not context_files:
+    raw_file = get_str(data, "context_file")
+    if raw_file:
+        context_files.append(raw_file)
+print(json.dumps(context_files))
 print(get_str(data, "context_markers", "start"))
 print(get_str(data, "context_markers", "end"))
 PY
@@ -87,31 +98,71 @@ while IFS= read -r _line || [[ -n "$_line" ]]; do
   _opts_lines+=("$_line")
 done < <(printf '%s\n' "$_raw_opts")
 if (( ${#_opts_lines[@]} < 3 )); then
-  echo "agent-context: malformed config parser output; expected 3 lines (context_file, marker_start, marker_end), got ${#_opts_lines[@]}; skipping update." >&2
+  echo "agent-context: malformed config parser output; expected 3 lines (context_files, marker_start, marker_end), got ${#_opts_lines[@]}; skipping update." >&2
   exit 0
 fi
-CONTEXT_FILE="${_opts_lines[0]}"
+CONTEXT_FILES_JSON="${_opts_lines[0]}"
 MARKER_START="${_opts_lines[1]}"
 MARKER_END="${_opts_lines[2]}"
 
-if [[ -z "$CONTEXT_FILE" ]]; then
-  echo "agent-context: context_file not set in extension config; nothing to do." >&2
+if ! _context_files_raw="$("$_python" - "$CONTEXT_FILES_JSON" <<'PY'
+import json
+import sys
+try:
+    data = json.loads(sys.argv[1])
+except Exception:
+    data = []
+if not isinstance(data, list):
+    data = []
+for value in data:
+    if isinstance(value, str) and value:
+        print(value)
+PY
+)"; then
+  echo "agent-context: malformed context_files parser output; skipping update." >&2
   exit 0
 fi
 
-# Reject absolute paths, backslash separators, and '..' path segments in context_file
-if [[ "$CONTEXT_FILE" == /* ]] || [[ "$CONTEXT_FILE" =~ ^[A-Za-z]: ]]; then
-  echo "agent-context: context_file must be a project-relative path; got '$CONTEXT_FILE'." >&2
-  exit 1
-fi
-if [[ "$CONTEXT_FILE" == *\\* ]]; then
-  echo "agent-context: context_file must not contain backslash separators; got '$CONTEXT_FILE'." >&2
-  exit 1
+CONTEXT_FILES=()
+while IFS= read -r _line || [[ -n "$_line" ]]; do
+  [[ -n "$_line" ]] && CONTEXT_FILES+=("$_line")
+done < <(printf '%s\n' "$_context_files_raw")
+
+if (( ${#CONTEXT_FILES[@]} == 0 )); then
+  echo "agent-context: context_files/context_file not set in extension config; nothing to do." >&2
+  exit 0
 fi
-IFS='/' read -ra _cf_parts <<< "$CONTEXT_FILE"
-for _seg in "${_cf_parts[@]}"; do
-  if [[ "$_seg" == ".." ]]; then
-    echo "agent-context: context_file must not contain '..' path segments; got '$CONTEXT_FILE'." >&2
+
+for CONTEXT_FILE in "${CONTEXT_FILES[@]}"; do
+  # Reject absolute paths, backslash separators, and '..' path segments in context files
+  if [[ "$CONTEXT_FILE" == /* ]] || [[ "$CONTEXT_FILE" =~ ^[A-Za-z]: ]]; then
+    echo "agent-context: context files must be project-relative paths; got '$CONTEXT_FILE'." >&2
+    exit 1
+  fi
+  if [[ "$CONTEXT_FILE" == *\\* ]]; then
+    echo "agent-context: context files must not contain backslash separators; got '$CONTEXT_FILE'." >&2
+    exit 1
+  fi
+  IFS='/' read -ra _cf_parts <<< "$CONTEXT_FILE"
+  for _seg in "${_cf_parts[@]}"; do
+    if [[ "$_seg" == ".." ]]; then
+      echo "agent-context: context files must not contain '..' path segments; got '$CONTEXT_FILE'." >&2
+      exit 1
+    fi
+  done
+  if ! "$_python" - "$PROJECT_ROOT" "$CONTEXT_FILE" <<'PY'
+import sys
+from pathlib import Path
+
+root = Path(sys.argv[1]).resolve()
+target = (root / sys.argv[2]).resolve(strict=False)
+try:
+    target.relative_to(root)
+except ValueError:
+    sys.exit(1)
+PY
+  then
+    echo "agent-context: context file path resolves outside the project root; got '$CONTEXT_FILE'." >&2
     exit 1
   fi
 done
@@ -142,9 +193,6 @@ PY
   fi
 fi
 
-CTX_PATH="$PROJECT_ROOT/$CONTEXT_FILE"
-mkdir -p "$(dirname "$CTX_PATH")"
-
 # Build the managed section
 TMP_SECTION="$(mktemp)"
 trap 'rm -f "$TMP_SECTION"' EXIT
@@ -158,7 +206,11 @@ trap 'rm -f "$TMP_SECTION"' EXIT
   echo "$MARKER_END"
 } > "$TMP_SECTION"
 
-"$_python" - "$CTX_PATH" "$MARKER_START" "$MARKER_END" "$TMP_SECTION" <<'PY'
+for CONTEXT_FILE in "${CONTEXT_FILES[@]}"; do
+  CTX_PATH="$PROJECT_ROOT/$CONTEXT_FILE"
+  mkdir -p "$(dirname "$CTX_PATH")"
+
+  "$_python" - "$CTX_PATH" "$MARKER_START" "$MARKER_END" "$TMP_SECTION" <<'PY'
 import sys, os
 ctx_path, start, end, section_path = sys.argv[1:5]
 with open(section_path, "r", encoding="utf-8") as fh:
@@ -197,4 +249,5 @@ with open(ctx_path, "wb") as fh:
     fh.write(new_content.encode("utf-8"))
 PY
 
-echo "agent-context: updated $CONTEXT_FILE"
+  echo "agent-context: updated $CONTEXT_FILE"
+done