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 `.specify/init-options.json`:
+
+```json
+{
+  "context_file": "CLAUDE.md",
+  "context_markers": {
+    "start": "<!-- SPECKIT START -->",
+    "end": "<!-- SPECKIT END -->"
+  }
+}
+```
+
+- `context_file` is written automatically from the integration's class attribute.
+- `context_markers.{start,end}` defaults to `IntegrationBase.CONTEXT_MARKER_START` / `CONTEXT_MARKER_END`. Users who want custom markers edit `init-options.json` 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, `setup()` and `teardown()` skip context-file creation, updates, and removal.
+
+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/init-options.json`. 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 +1,44 @@
+# 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/init-options.json` — 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 `.specify/init-options.json`:
+
+```json
+{
+  "context_file": "CLAUDE.md",
+  "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.
+
+## Disable
+
+```bash
+specify extension disable agent-context
+```
+
+When disabled, `IntegrationBase.setup()` and `IntegrationBase.teardown()` skip context file creation, updates, and removal.

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

@@ -0,0 +1,25 @@
+---
+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 project's `.specify/init-options.json` 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 +1,126 @@
+#!/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
+# `.specify/init-options.json`. Falls back to the default markers when
+# `context_markers` is absent.
+#
+# 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="$(pwd)"
+INIT_OPTIONS="$PROJECT_ROOT/.specify/init-options.json"
+DEFAULT_START="<!-- SPECKIT START -->"
+DEFAULT_END="<!-- SPECKIT END -->"
+
+if [[ ! -f "$INIT_OPTIONS" ]]; then
+  echo "agent-context: $INIT_OPTIONS not found; nothing to do." >&2
+  exit 0
+fi
+
+# Use python for JSON parsing (always available in spec-kit projects).
+read_json_field() {
+  # $1 = jq-style dotted path, e.g. "context_markers.start"
+  python3 - "$INIT_OPTIONS" "$1" <<'PY'
+import json, sys
+path = sys.argv[1]
+key = sys.argv[2]
+try:
+    with open(path, "r", encoding="utf-8") as fh:
+        data = json.load(fh)
+except Exception:
+    sys.exit(0)
+node = data
+for part in key.split("."):
+    if isinstance(node, dict) and part in node:
+        node = node[part]
+    else:
+        sys.exit(0)
+if isinstance(node, str):
+    sys.stdout.write(node)
+PY
+}
+
+CONTEXT_FILE="$(read_json_field 'context_file' || true)"
+if [[ -z "$CONTEXT_FILE" ]]; then
+  echo "agent-context: context_file not set in init-options.json; nothing to do." >&2
+  exit 0
+fi
+
+MARKER_START="$(read_json_field 'context_markers.start' || true)"
+MARKER_END="$(read_json_field 'context_markers.end' || true)"
+[[ -z "$MARKER_START" ]] && MARKER_START="$DEFAULT_START"
+[[ -z "$MARKER_END"   ]] && MARKER_END="$DEFAULT_END"
+
+PLAN_PATH="${1:-}"
+if [[ -z "$PLAN_PATH" ]]; then
+  if compgen -G "$PROJECT_ROOT/specs/*/plan.md" > /dev/null; then
+    # Pick the most recently modified plan.md
+    PLAN_PATH="$(ls -1t "$PROJECT_ROOT"/specs/*/plan.md 2>/dev/null | head -1 | sed "s|$PROJECT_ROOT/||")"
+  fi
+fi
+
+CTX_PATH="$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"
+} > "$TMP_SECTION"
+
+python3 - "$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"

extensions/agent-context/scripts/powershell/update-agent-context.ps1

@@ -0,0 +1,113 @@
+#!/usr/bin/env pwsh
+# update-agent-context.ps1
+#
+# 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
+# `.specify/init-options.json`. Falls back to the default markers when
+# `context_markers` is absent.
+#
+# Usage: update-agent-context.ps1 [plan_path]
+
+[CmdletBinding()]
+param(
+    [Parameter(Position = 0)]
+    [string]$PlanPath
+)
+
+$ErrorActionPreference = 'Stop'
+$DefaultStart = '<!-- SPECKIT START -->'
+$DefaultEnd   = '<!-- SPECKIT END -->'
+$ProjectRoot  = (Get-Location).Path
+$InitOptions  = Join-Path $ProjectRoot '.specify/init-options.json'
+
+if (-not (Test-Path -LiteralPath $InitOptions)) {
+    Write-Host "agent-context: $InitOptions not found; nothing to do."
+    exit 0
+}
+
+try {
+    $Options = Get-Content -LiteralPath $InitOptions -Raw | ConvertFrom-Json
+} catch {
+    Write-Host "agent-context: failed to parse init-options.json; nothing to do."
+    exit 0
+}
+
+$ContextFile = $Options.context_file
+if (-not $ContextFile) {
+    Write-Host 'agent-context: context_file not set in init-options.json; nothing to do.'
+    exit 0
+}
+
+$MarkerStart = $DefaultStart
+$MarkerEnd   = $DefaultEnd
+if ($Options.context_markers) {
+    if ($Options.context_markers.start -is [string] -and $Options.context_markers.start) {
+        $MarkerStart = $Options.context_markers.start
+    }
+    if ($Options.context_markers.end -is [string] -and $Options.context_markers.end) {
+        $MarkerEnd = $Options.context_markers.end
+    }
+}
+
+if (-not $PlanPath) {
+    $candidate = Get-ChildItem -Path (Join-Path $ProjectRoot 'specs') -Filter 'plan.md' -Recurse -ErrorAction SilentlyContinue |
+        Sort-Object LastWriteTime -Descending |
+        Select-Object -First 1
+    if ($candidate) {
+        $PlanPath = $candidate.FullName.Substring($ProjectRoot.Length).TrimStart('/', '\').Replace('\','/')
+    }
+}
+
+$CtxPath = Join-Path $ProjectRoot $ContextFile
+$CtxDir  = Split-Path -Parent $CtxPath
+if ($CtxDir -and -not (Test-Path -LiteralPath $CtxDir)) {
+    New-Item -ItemType Directory -Path $CtxDir -Force | Out-Null
+}
+
+$lines = @($MarkerStart,
+           'For additional context about technologies to be used, project structure,',
+           'shell commands, and other important information, read the current plan')
+if ($PlanPath) {
+    $lines += "at $PlanPath"
+}
+$lines += $MarkerEnd
+$Section = ($lines -join "`n") + "`n"
+
+if (Test-Path -LiteralPath $CtxPath) {
+    $rawBytes = [System.IO.File]::ReadAllBytes($CtxPath)
+    # Strip UTF-8 BOM if present
+    if ($rawBytes.Length -ge 3 -and $rawBytes[0] -eq 0xEF -and $rawBytes[1] -eq 0xBB -and $rawBytes[2] -eq 0xBF) {
+        $content = [System.Text.Encoding]::UTF8.GetString($rawBytes, 3, $rawBytes.Length - 3)
+    } else {
+        $content = [System.Text.Encoding]::UTF8.GetString($rawBytes)
+    }
+
+    $s = $content.IndexOf($MarkerStart)
+    $e = if ($s -ge 0) { $content.IndexOf($MarkerEnd, $s) } else { $content.IndexOf($MarkerEnd) }
+
+    if ($s -ge 0 -and $e -ge 0 -and $e -gt $s) {
+        $endOfMarker = $e + $MarkerEnd.Length
+        if ($endOfMarker -lt $content.Length -and $content[$endOfMarker] -eq "`r") { $endOfMarker++ }
+        if ($endOfMarker -lt $content.Length -and $content[$endOfMarker] -eq "`n") { $endOfMarker++ }
+        $newContent = $content.Substring(0, $s) + $Section + $content.Substring($endOfMarker)
+    } elseif ($s -ge 0) {
+        $newContent = $content.Substring(0, $s) + $Section
+    } elseif ($e -ge 0) {
+        $endOfMarker = $e + $MarkerEnd.Length
+        if ($endOfMarker -lt $content.Length -and $content[$endOfMarker] -eq "`r") { $endOfMarker++ }
+        if ($endOfMarker -lt $content.Length -and $content[$endOfMarker] -eq "`n") { $endOfMarker++ }
+        $newContent = $Section + $content.Substring($endOfMarker)
+    } else {
+        if ($content -and -not $content.EndsWith("`n")) { $content += "`n" }
+        if ($content) { $newContent = $content + "`n" + $Section } else { $newContent = $Section }
+    }
+} else {
+    $newContent = $Section
+}
+
+$newContent = $newContent.Replace("`r`n", "`n").Replace("`r", "`n")
+[System.IO.File]::WriteAllText($CtxPath, $newContent, (New-Object System.Text.UTF8Encoding($false)))
+
+Write-Host "agent-context: updated $ContextFile"