feat: make agent-context extension a full opt-in (#3097)

* docs: add Spec Kit spec for agent-context full opt-in

Use Spec Kit's own specify workflow to author the spec that makes the
agent-context extension a full opt-in, removing all agent-context
configuration/support from the Python codebase and removing the
deprecation message. Force-added despite specs/ being gitignored; the
generated artifact will be purged prior to merge.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: add Spec Kit plan artifacts for agent-context full opt-in

Phase 0/1 of the SDD plan workflow: plan.md, research.md, data-model.md,
quickstart.md, and contracts/cli-behavior.md. Constitution Check is a
documented no-op (repo has no ratified constitution). Force-added despite
specs/ being gitignored; generated artifacts will be purged prior to merge.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: correct Constitution Check against ratified v1.0.0

Earlier draft wrongly treated the gate as a no-op; the fork's main is 16
commits behind upstream/main, which carries .specify/memory/constitution.md.
Re-evaluate the feature against Principles I-V (all PASS) and note that
Principle I mandates keeping context_file as a declared class attribute,
validating the R1 metadata decision.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: refresh plan artifacts against synced upstream/main

After syncing fork main to upstream and rebasing, re-scan the current
agent-context surface. Upstream generalized the single context_file into a
plural context_files concept with new resolver helpers
(_resolve_context_files, _resolve_context_file_values,
_format_context_file_values) and upsert/remove now loop over multiple
files. Update research.md, data-model.md, contracts, quickstart grep
guards, and the plan summary to cover the expanded removal scope.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: add Spec Kit tasks for agent-context full opt-in

Phase 2 of SDD: dependency-ordered tasks.md (30 tasks) organized by the
three user stories, with mandatory test tasks (Constitution Principle II)
and a foundational phase decoupling __CONTEXT_FILE__ resolution from the
extension config. Includes the extension self-seeding task (T015) and a
static guard test (T002) enforcing zero agent-context references in the CLI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat!: remove agent-context lifecycle from the Specify CLI

Make the agent-context extension a full opt-in. The CLI no longer
installs the extension during init, writes agent-context-config.yml,
or creates/updates/removes the managed Spec Kit section in agent
context files. Context-section upsert/remove, marker resolution,
extension-enabled gating, the config helpers, and the obsolete inline
deprecation warning are all removed. Integration context_file stays as
inert metadata; __CONTEXT_FILE__ now resolves from registry metadata.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat(agent-context): self-seed context file from the active integration

When agent-context-config.yml has no context_file/context_files, the
bundled bash and PowerShell update scripts now resolve the context file
from the active integration in .specify/init-options.json via the
integration registry, so the extension no longer depends on the CLI
writing its config.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* test+docs: update suite and docs for agent-context opt-in

Update integration/extension tests to expect no agent-context install,
config, or context-section writes during init. Add a static guard test
(test_agent_context_cli_free.py) asserting the CLI source is free of
agent-context lifecycle symbols, plus backward-compatibility tests for
legacy projects. Refresh AGENTS.md, the extension README, and add a
CHANGELOG entry describing the opt-in behavior change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(agent-context): warn on self-seed failure, correct docs, speed up guard test

Address PR review feedback:
- Self-seed scripts (bash + PowerShell) now emit an actionable warning when
  an active integration is configured but specify_cli cannot be imported by
  the chosen Python (e.g. pipx installs), or when the integration declares no
  context file, instead of silently falling through to 'nothing to do'.
- Correct the extension README disable note: command rendering never reads the
  extension config; __CONTEXT_FILE__ is always substituted from integration
  metadata, so a stale context_files value cannot affect rendering.
- Cache CLI source reads in the static guard test via a module-scoped fixture
  so the directory walk happens once instead of once per forbidden symbol.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat(agent-context): ship self-owned per-agent context-file defaults

The extension now bundles agent-context-defaults.json (key→context_file
map) and self-seeds from it, dropping any dependency on the Specify CLI
registry. Both the bash and PowerShell update scripts read the bundled
JSON map keyed by the active integration from init-options.json.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* feat!: remove all agent-context state from the Specify CLI

Strip every context_file reference from the CLI: the field on all 35
integration classes, the IntegrationBase plumbing (process_template
param/step, _context_file_display, docstrings), the __CONTEXT_FILE__
resolution in agents.py, the legacy context_file/context_markers
popping in _helpers.py, and the context_file template in
integration_scaffold.py. Also drop the Agent context update step and
__CONTEXT_FILE__ placeholder from templates/commands/plan.md.

The agent-context extension now solely owns all context-file knowledge,
including the per-agent default mapping.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* test: drop context_file coverage and guard against CLI reintroduction

Remove CONTEXT_FILE attrs and context_file assertions across the base
mixins, all 35 per-integration test files, shared integration tests, and
conftest stubs. Rewrite the base-mixin context tests to assert no managed
section is written and no __CONTEXT_FILE__ placeholder survives. Extend
the CLI-free static guard to forbid context_file, __CONTEXT_FILE__, and
_context_file_display in src/specify_cli, and have the extension tests
copy the bundled defaults JSON so self-seed runs without the CLI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: reflect full removal of agent-context state from the CLI

Update AGENTS.md (integration examples, required-fields table, context
behavior section, pitfalls), CHANGELOG, and the SDD spec artifacts
(FR-007, SC-002, data-model) to state that the CLI carries no
context_file and the extension fully owns the per-agent default mapping
via agent-context-defaults.json.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: align SDD artifacts with full context_file removal

Update research.md (R1, R2, R4, summary table), contracts/cli-behavior.md
(C3, C5), tasks.md (Phase 2, T026, notes), plan.md (Principle I, source
map), and checklists/requirements.md so the spec artifacts reflect the
implemented decision: the CLI carries no context_file attribute or
__CONTEXT_FILE__ resolution, and the per-agent defaults map lives in the
extension. Resolves PR review #4548130110.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: scrub stale context-file mentions from CLI docstrings

Update the multi_install_safe docstring (drop the removed "context file"
invariant), the RovoDev setup docstring (no longer upserts a context
section), the Copilot module docstring (drop the context-file line), and
tighten the _update_init_options_for_integration note. Pure docstring
changes — no behavioral impact. Resolves PR review #4548237085.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* test+docs: harden agent-context test helper and fix stale docs

- base.py: document multi_install_safe as an optional subclass attribute
  in the IntegrationBase docstring.
- test_cli.py: clarify the init-options assertion is guarding against
  leftover legacy agent-context keys, not relocation.
- test_extension_agent_context.py: _install_agent_context_config now
  asserts the bundled agent-context-defaults.json exists and always
  copies it, so self-seeding tests fail loudly instead of silently
  skipping when the map is missing.
- test_integration_cursor_agent.py: drop Path/IntegrationManifest imports
  left unused after removing the context-section frontmatter tests.

Resolves PR review #4548293116.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* chore: remove gitignored SDD artifacts from specs/

The specs/001-agent-context-full-optin/ artifacts were force-added for
dogfooding visibility, but specs/ is gitignored and these were always
intended to be purged before merge. Remove them so merging does not add
an intentionally-untracked directory to repo history.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* chore: keep CHANGELOG.md identical to upstream

CHANGELOG.md is auto-generated at release time, so the branch should not
carry a manual entry. Restore it to match upstream/main exactly.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: preserve Cursor .mdc frontmatter in agent-context updater scripts

The bundled agent-context updater scripts wrote the managed section as
plain text. For Cursor-style `.mdc` targets this dropped the required
`---\nalwaysApply: true\n---` frontmatter, reintroducing the rule-loading
bug originally fixed in #1699. Port the `_ensure_mdc_frontmatter` logic
into both the bash and PowerShell updaters: prepend frontmatter when
missing, repair `alwaysApply` when set to the wrong value, and leave
non-`.mdc` targets untouched. Add regression tests covering both shells.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* test: scope CLI-free guard to agent-context-specific symbols

Drop the bare "context_file" substring from FORBIDDEN_SYMBOLS so the
guard no longer fails on unrelated future CLI fields named context_file.
The list still covers agent-context-specific identifiers (__CONTEXT_FILE__,
_context_file_display, _resolve_context_files, _resolve_context_file_values).

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: harden agent-context bash self-seed against malformed init JSON

Two robustness fixes in the embedded Python self-seed logic:
- Coerce the integration value from init-options.json to a string only when
  it is actually a string; otherwise treat it as unset so a corrupted
  dict/list value degrades to the existing nothing-to-do behavior instead of
  breaking the agents-map lookup.
- Normalize agent-context-defaults.json: only use 'agents' when both the JSON
  root and the 'agents' value are dicts, so a wrong-shaped (but valid) JSON
  falls back to the warning path instead of raising on .get.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: correct PowerShell hyphenated key lookup and regex replace count

- Self-seed now reads the defaults mapping via
  $defaults.agents.PSObject.Properties[$integrationKey].Value instead of
  member access ($defaults.agents.$integrationKey), which parsed hyphenated
  keys like 'cursor-agent'/'kiro-cli' as subtraction and failed to resolve.
- Replace the static [regex]::Replace(..., 1) call, whose trailing 1 was
  interpreted as RegexOptions.IgnoreCase rather than a replacement count, with
  an instance Regex whose Replace(input, replacement, 1) limits to the first
  match as intended.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: make bash .mdc frontmatter guard case-insensitive

The bash updater only injected Cursor .mdc frontmatter when ctx_path ended
in lowercase '.mdc', so a mixed/upper-case extension (e.g. specify-rules.MDC)
was skipped and Cursor would not auto-load the rule file. Compare against the
casefolded path. The PowerShell variant already uses -match, which is
case-insensitive by default, so no change is needed there.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* docs: document separator-agnostic agent-context update invocation

The README hard-coded the dot-notation slash command
(/speckit.agent-context.update), which hyphen-separator agents like Forge and
Cline do not recognize. Document the canonical command ID plus both slash
invocations so users copy the form their agent accepts.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

AGENTS.md

@@ -75,7 +75,6 @@ class WindsurfIntegration(MarkdownIntegration):
         "args": "$ARGUMENTS",
         "extension": ".md",
     }
-    context_file = ".windsurf/rules/specify-rules.md"
 ```
 
 **TOML agent (Gemini):**
@@ -101,7 +100,6 @@ class GeminiIntegration(TomlIntegration):
         "args": "{{args}}",
         "extension": ".toml",
     }
-    context_file = "GEMINI.md"
 ```
 
 **Skills agent (Codex):**
@@ -129,7 +127,6 @@ class CodexIntegration(SkillsIntegration):
         "args": "$ARGUMENTS",
         "extension": "/SKILL.md",
     }
-    context_file = "AGENTS.md"
 
     @classmethod
     def options(cls) -> list[IntegrationOption]:
@@ -150,7 +147,6 @@ class CodexIntegration(SkillsIntegration):
 | `key` | Class attribute | Unique identifier; for CLI-based integrations (`requires_cli: True`), must match the CLI executable name |
 | `config` | Class attribute (dict) | Agent metadata: `name`, `folder`, `commands_subdir`, `install_url`, `requires_cli` |
 | `registrar_config` | Class attribute (dict) | Command output config: `dir`, `format`, `args` placeholder, file `extension` |
-| `context_file` | Class attribute (str or None) | Path to agent context/instructions file (e.g., `"CLAUDE.md"`, `".github/copilot-instructions.md"`) |
 
 **Key design rule:** For CLI-based integrations (`requires_cli: True`), `key` must be the actual executable name (e.g., `"cursor-agent"` not `"cursor"`). This ensures `shutil.which(key)` works for CLI-tool checks without special-case mappings. IDE-based integrations (`requires_cli: False`) should use their canonical identifier (e.g., `"windsurf"`, `"copilot"`).
 
@@ -175,9 +171,11 @@ def _register_builtins() -> None:
 
 ### 4. Context file behavior
 
-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.
+The Specify CLI carries **no agent-context state whatsoever**. Integration classes do **not** declare a `context_file`, and the CLI never creates, updates, removes, resolves, or migrates a context/instruction file (`CLAUDE.md`, `AGENTS.md`, `.github/copilot-instructions.md`, …). New integrations add nothing for context handling.
 
-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`:
+Managing the "Spec Kit" section in the context file is fully owned by the bundled `agent-context` extension (`extensions/agent-context/`), which is a **full opt-in**: `specify init` does not install it. A user adds/enables it through the standard extension verbs, after which the extension's own bundled scripts maintain the context section. When the extension is absent or disabled, nothing in Spec Kit touches the context file.
+
+The extension reads its own config file at `.specify/extensions/agent-context/agent-context-config.yml`:
 
 ```yaml
 # Path to the coding agent context file managed by this extension
@@ -189,10 +187,10 @@ context_markers:
   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.
+- The Specify CLI does **not** write this config. When `context_file` is empty, the extension's bundled scripts self-seed it by looking up the active integration's key in the extension's own `agent-context-defaults.json` map (`extensions/agent-context/scripts/bash/update-agent-context.sh` and `.ps1`). The CLI registry is never consulted — all agent→context-file knowledge lives inside the extension.
+- `context_markers.{start,end}` are read solely by the extension's scripts; they default to the Spec Kit markers shown above and can be customized by editing `agent-context-config.yml` directly.
 
-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()`).
+Existing projects created by older Spec Kit versions keep working: any previously written managed section or extension config is left intact and is only ever updated by the extension when run.
 
 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.
 
@@ -401,7 +399,6 @@ Implementation: Extends `YamlIntegration` (parallel to `TomlIntegration`):
 2. Extracts title and description from frontmatter
 3. Renders output as Goose recipe YAML (version, title, description, author, extensions, activities, prompt)
 4. Uses `yaml.safe_dump()` for header fields to ensure proper escaping
-5. Sets `context_file = "AGENTS.md"` so the base setup manages the Spec Kit context section there
 
 ## Branch Naming Convention
 
@@ -466,7 +463,7 @@ Disclosure is **continuous**, not a one-time event. A single AI-disclosure parag
 ## 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 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.
+2. **Reintroducing context handling into the CLI**: The opt-in `agent-context` extension owns everything about context files — including the per-agent default mapping in `agent-context-defaults.json`. Integration classes must **not** declare a `context_file`, and no CLI code should read, write, resolve, or migrate context files. All context-file logic lives in `.specify/extensions/agent-context/` and its bundled scripts.
 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.