Extract agent context updates into bundled agent-context extension

AGENTS.md

@@ -177,7 +177,24 @@ def _register_builtins() -> None:
 
 Set `context_file` on the integration class. The base integration setup creates or updates the managed Spec Kit section in that file, and uninstall removes the managed section when appropriate.
 
-Only add custom setup logic when the agent needs non-standard behavior. Most integrations do not need wrapper scripts or separate context-update dispatch code.
+The managed section is owned by the bundled `agent-context` extension (`extensions/agent-context/`). All configuration flows through the extension's own config file at `.specify/extensions/agent-context/agent-context-config.yml`:
+
+```yaml
+# Path to the coding agent context file managed by this extension
+context_file: CLAUDE.md
+
+# Delimiters for the managed Spec Kit section
+context_markers:
+  start: "<!-- SPECKIT START -->"
+  end: "<!-- SPECKIT END -->"
+```
+
+- `context_file` is written automatically from the integration's class attribute when `specify init` or `specify integration use` is run.
+- `context_markers.{start,end}` defaults to `IntegrationBase.CONTEXT_MARKER_START` / `CONTEXT_MARKER_END`. Users who want custom markers edit `agent-context-config.yml` directly — both the Python layer (`upsert_context_section()` / `remove_context_section()`) and the bundled scripts (`extensions/agent-context/scripts/bash/update-agent-context.sh` and `.ps1`) read from this single source of truth.
+
+Users can opt out entirely with `specify extension disable agent-context`; while disabled, Spec Kit skips context-file creation, updates, and removal (the gates are inside `upsert_context_section()` and `remove_context_section()`).
+
+Only add custom setup logic when the agent needs non-standard behavior. Integrations no longer require per-agent thin wrapper scripts or shared context-update dispatcher scripts — the `agent-context` extension is fully generic.
 
 ### 5. Test it
 
@@ -382,7 +399,7 @@ Implementation: Extends `YamlIntegration` (parallel to `TomlIntegration`):
 ## Common Pitfalls
 
 1. **Using shorthand keys for CLI-based integrations**: For CLI-based integrations (`requires_cli: True`), the `key` must match the executable name (e.g., `"cursor-agent"` not `"cursor"`). `shutil.which(key)` is used for CLI tool checks — mismatches require special-case mappings. IDE-based integrations (`requires_cli: False`) are not subject to this constraint.
-2. **Forgetting update scripts**: Both bash and PowerShell thin wrappers and the shared context-update scripts must be updated.
+2. **Forgetting context configuration**: The bundled `agent-context` extension reads from `.specify/extensions/agent-context/agent-context-config.yml`. New integrations only need to set `context_file` on the class — markers and dispatcher scripts are managed centrally.
 3. **Incorrect `requires_cli` value**: Set to `True` only for agents that have a CLI tool; set to `False` for IDE-based agents.
 4. **Wrong argument format**: Use `$ARGUMENTS` for Markdown agents, `{{args}}` for TOML agents.
 5. **Skipping registration**: The import and `_register()` call in `_register_builtins()` must both be added.

extensions/agent-context/README.md

@@ -0,0 +1,57 @@
+# Coding Agent Context Extension
+
+This bundled extension manages the **coding agent context/instruction file** (e.g. `CLAUDE.md`, `.github/copilot-instructions.md`, `AGENTS.md`, `GEMINI.md`, …) for the active integration.
+
+It owns the lifecycle of the managed section delimited by the configurable start/end markers (defaults: `<!-- SPECKIT START -->` / `<!-- SPECKIT END -->`).
+
+## Why an extension?
+
+Not every Spec Kit user wants Spec Kit to write into the coding agent's context file. Extracting this behavior into a dedicated extension lets users:
+
+- **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.
+- **Refresh on demand** with `/speckit.agent-context.update`, or automatically through the hooks declared in `extension.yml` (`after_specify`, `after_plan`).
+
+## Commands
+
+| Command | Description |
+|---------|-------------|
+| `speckit.agent-context.update` | Refresh the managed section in the agent context file with the current plan path. |
+
+## Configuration
+
+All configuration flows through the extension's own config file at
+`.specify/extensions/agent-context/agent-context-config.yml`:
+
+```yaml
+# Path to the coding agent context file managed by this extension
+context_file: 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_markers.start` / `.end` — the delimiters around the managed section. Edit these to use custom markers.
+
+## Requirements
+
+The bundled update scripts require **Python 3** with **PyYAML** for YAML/upsert processing (PowerShell can also use `ConvertFrom-Yaml` when available).
+
+PyYAML ships with the `specify` CLI and is normally available via the same `python3` interpreter. If a hook reports *"PyYAML is required … not available in the current Python environment"*, it means the system `python3` differs from the one used to install Spec Kit. To resolve, run:
+
+```bash
+pip install pyyaml
+# or target the specific interpreter Spec Kit uses:
+/path/to/speckit-python -m pip install pyyaml
+```
+
+## Disable
+
+```bash
+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()`).

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

@@ -0,0 +1,15 @@
+# Coding Agent Context Extension Configuration
+# 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
+# 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: ""
+
+# Delimiters for the managed Spec Kit section.
+# Edit these to use custom markers.
+context_markers:
+  start: "<!-- SPECKIT START -->"
+  end: "<!-- SPECKIT END -->"

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

@@ -0,0 +1,26 @@
+---
+description: "Refresh the managed Spec Kit section in the coding agent context file"
+---
+
+# Update Coding Agent Context
+
+Refresh the managed Spec Kit section inside the active coding agent's context/instruction file (e.g. `CLAUDE.md`, `.github/copilot-instructions.md`, `AGENTS.md`).
+
+## Behavior
+
+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_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.
+
+## Execution
+
+- **Bash**: `.specify/extensions/agent-context/scripts/bash/update-agent-context.sh [plan_path]`
+- **PowerShell**: `.specify/extensions/agent-context/scripts/powershell/update-agent-context.ps1 [plan_path]`
+
+When `plan_path` is omitted, the script auto-detects the most recently modified `specs/*/plan.md`.

extensions/agent-context/extension.yml

@@ -0,0 +1,34 @@
+schema_version: "1.0"
+
+extension:
+  id: agent-context
+  name: "Coding Agent Context"
+  version: "1.0.0"
+  description: "Manages coding agent context/instruction files (e.g., CLAUDE.md, copilot-instructions.md) with project-specific plan references and configurable markers"
+  author: spec-kit-core
+  repository: https://github.com/github/spec-kit
+  license: MIT
+
+requires:
+  speckit_version: ">=0.2.0"
+
+provides:
+  commands:
+    - name: speckit.agent-context.update
+      file: commands/speckit.agent-context.update.md
+      description: "Refresh the managed Spec Kit section in the coding agent context file"
+
+hooks:
+  after_specify:
+    command: speckit.agent-context.update
+    optional: true
+    description: "Refresh agent context after specification"
+  after_plan:
+    command: speckit.agent-context.update
+    optional: true
+    description: "Refresh agent context after planning"
+
+tags:
+  - "agent"
+  - "context"
+  - "core"

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

@@ -0,0 +1,182 @@
+#!/usr/bin/env bash
+# update-agent-context.sh
+#
+# Refresh the managed Spec Kit section in the coding agent's context file
+# (e.g. CLAUDE.md, .github/copilot-instructions.md, AGENTS.md).
+#
+# Reads `context_file` and `context_markers.{start,end}` from the
+# agent-context extension config:
+#   .specify/extensions/agent-context/agent-context-config.yml
+#
+# Usage: update-agent-context.sh [plan_path]
+#
+# When `plan_path` is omitted, the script picks the most recently modified
+# `specs/*/plan.md` if any exist, otherwise emits the section without a
+# concrete plan path.
+
+set -euo pipefail
+
+PROJECT_ROOT="$(pwd)"
+EXT_CONFIG="$PROJECT_ROOT/.specify/extensions/agent-context/agent-context-config.yml"
+DEFAULT_START="<!-- SPECKIT START -->"
+DEFAULT_END="<!-- SPECKIT END -->"
+
+if [[ ! -f "$EXT_CONFIG" ]]; then
+  echo "agent-context: $EXT_CONFIG not found; nothing to do." >&2
+  exit 0
+fi
+
+# Locate a suitable Python interpreter (python3, then python).
+_python=""
+if command -v python3 >/dev/null 2>&1; then
+  _python="python3"
+elif command -v python >/dev/null 2>&1 && python --version 2>&1 | grep -q "^Python 3"; then
+  _python="python"
+fi
+
+if [[ -z "$_python" ]]; then
+  echo "agent-context: Python 3 not found on PATH; skipping update." >&2
+  exit 0
+fi
+
+# Parse extension config once; emit three newline-separated fields:
+# context_file, context_markers.start, context_markers.end
+if ! _raw_opts="$("$_python" - "$EXT_CONFIG" <<'PY'
+import sys
+try:
+    import yaml
+except ImportError:
+    print(
+        "agent-context: PyYAML is required to parse extension config but is not available "
+        "in the current Python environment.\n"
+        "  To resolve: pip install pyyaml (or install it into the environment used by python3).\n"
+        "  Context file will not be updated until PyYAML is importable.",
+        file=sys.stderr,
+    )
+    sys.exit(2)
+try:
+    with open(sys.argv[1], "r", encoding="utf-8") as fh:
+        data = yaml.safe_load(fh)
+except Exception as exc:
+    print(
+        f"agent-context: unable to parse {sys.argv[1]} ({exc}); cannot update context.",
+        file=sys.stderr,
+    )
+    sys.exit(2)
+if not isinstance(data, dict):
+    data = {}
+def get_str(obj, *keys):
+    node = obj
+    for k in keys:
+        if isinstance(node, dict) and k in node:
+            node = node[k]
+        else:
+            return ""
+    return node if isinstance(node, str) else ""
+print(get_str(data, "context_file"))
+print(get_str(data, "context_markers", "start"))
+print(get_str(data, "context_markers", "end"))
+PY
+)"; then
+  echo "agent-context: skipping update (see above for details)." >&2
+  exit 0
+fi
+
+_opts_lines=()
+while IFS= read -r _line || [[ -n "$_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 ${#_opts_lines[@]}; skipping update." >&2
+  exit 0
+fi
+CONTEXT_FILE="${_opts_lines[0]}"
+MARKER_START="${_opts_lines[1]}"
+MARKER_END="${_opts_lines[2]}"
+
+if [[ -z "$CONTEXT_FILE" ]]; then
+  echo "agent-context: context_file not set in extension config; nothing to do." >&2
+  exit 0
+fi
+
+[[ -z "$MARKER_START" ]] && MARKER_START="$DEFAULT_START"
+[[ -z "$MARKER_END"   ]] && MARKER_END="$DEFAULT_END"
+
+PLAN_PATH="${1:-}"
+if [[ -z "$PLAN_PATH" ]]; then
+  # Pick the most recently modified plan.md one level deep (specs/<feature>/plan.md).
+  # Use find + sort by modification time to avoid ls/head fragility with
+  # spaces in paths or SIGPIPE from pipefail.
+  _plan_abs="$("$_python" - "$PROJECT_ROOT" <<'PY'
+import sys, os
+from pathlib import Path
+specs = Path(sys.argv[1]) / "specs"
+plans = sorted(
+    specs.glob("*/plan.md"),
+    key=lambda p: p.stat().st_mtime,
+    reverse=True,
+)
+print(plans[0] if plans else "")
+PY
+)"
+  if [[ -n "$_plan_abs" ]]; then
+    PLAN_PATH="${_plan_abs#"$PROJECT_ROOT/"}"
+  fi
+fi
+
+CTX_PATH="$PROJECT_ROOT/$CONTEXT_FILE"
+mkdir -p "$(dirname "$CTX_PATH")"
+
+# Build the managed section
+TMP_SECTION="$(mktemp)"
+trap 'rm -f "$TMP_SECTION"' EXIT
+{
+  echo "$MARKER_START"
+  echo "For additional context about technologies to be used, project structure,"
+  echo "shell commands, and other important information, read the current plan"
+  if [[ -n "$PLAN_PATH" ]]; then
+    echo "at $PLAN_PATH"
+  fi
+  echo "$MARKER_END"
+} > "$TMP_SECTION"
+
+"$_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:
+    section = fh.read().rstrip("\n") + "\n"
+
+if os.path.exists(ctx_path):
+    with open(ctx_path, "r", encoding="utf-8-sig") as fh:
+        content = fh.read()
+    s = content.find(start)
+    e = content.find(end, s if s != -1 else 0)
+    if s != -1 and e != -1 and e > s:
+        end_of_marker = e + len(end)
+        if end_of_marker < len(content) and content[end_of_marker] == "\r":
+            end_of_marker += 1
+        if end_of_marker < len(content) and content[end_of_marker] == "\n":
+            end_of_marker += 1
+        new_content = content[:s] + section + content[end_of_marker:]
+    elif s != -1:
+        new_content = content[:s] + section
+    elif e != -1:
+        end_of_marker = e + len(end)
+        if end_of_marker < len(content) and content[end_of_marker] == "\r":
+            end_of_marker += 1
+        if end_of_marker < len(content) and content[end_of_marker] == "\n":
+            end_of_marker += 1
+        new_content = section + content[end_of_marker:]
+    else:
+        if content and not content.endswith("\n"):
+            content += "\n"
+        new_content = (content + "\n" + section) if content else section
+else:
+    new_content = section
+
+new_content = new_content.replace("\r\n", "\n").replace("\r", "\n")
+with open(ctx_path, "wb") as fh:
+    fh.write(new_content.encode("utf-8"))
+PY
+
+echo "agent-context: updated $CONTEXT_FILE"