docs: ADR for stable MCP control runtime vs dev runtime

Policy: real Gitea mutations use stable control runtime only; normal sessions must not kill/restart/relaunch from worktrees or edit the stable checkout. Promotion is operator-only with proof and rollback. Refs: #615
2026-07-09 20:16:50 -04:00
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+# ADR: Stable control runtime vs dev runtime (Gitea MCP)
+
+- **Status:** Accepted (policy effective immediately for LLM sessions; tooling may lag)
+- **Date:** 2026-07-09
+- **Tracking issue:** [#615](https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools/issues/615)
+- **Related:**
+  - [#543](https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools/issues/543) / `docs/mcp-namespace-health.md` — client-namespace health
+  - `docs/mcp-namespace-eof-recovery.md` — reconnect-only EOF recovery (no PID kill)
+  - [#558](https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools/issues/558) / `docs/mcp-daemon-import-guard.md` — sanctioned daemon
+  - [#557](https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools/issues/557) / `docs/bootstrap-review-path.md` — controller bootstrap for self-hosted fixes
+  - Allocator / control-plane ADR: `docs/architecture/mcp-allocator-control-plane-observability-adr.md` (#613 / PR #614)
+
+## 1. Context
+
+The Gitea MCP server is the **control plane** for real issue/PR mutations (create, comment, lock, review, merge, etc.). When author/reviewer/merger/reconciler sessions kill or restart that process, relaunch it from a feature worktree, or edit the checkout that process loads, operators observe:
+
+- Mid-session identity/preflight resets
+- Stale-runtime vs master parity failures
+- IDE transport EOF / “tool not found” while code on disk has changed
+- Accidental production mutations from experimental code
+
+This ADR separates **stable control runtime** from **dev/test runtime** and defines promotion proof.
+
+## 2. Decision
+
+### 2.1 Stable control runtime
+
+The Gitea MCP server used for **real workflow mutations** is the **stable control runtime**.
+
+Characteristics:
+
+- Loads a known, promoted revision of Gitea-Tools (or the packaged release layout operators designate)
+- Registered in the IDE/client as the production namespaces (`gitea-tools`, `gitea-reviewer`, `gitea-merger`, `gitea-reconciler`, etc.)
+- Holds production profile credentials via sanctioned keychain/env paths only
+
+### 2.2 Dev / test runtime
+
+MCP **server code** development and testing:
+
+- Happens in isolated **`branches/`** worktrees (or other non-stable checkouts)
+- May use a **separate** dev/test MCP runtime/process when process-level testing is required
+- **Must not** be used for real Gitea mutations on production issues/PRs
+
+### 2.3 Forbidden actions (normal sessions)
+
+Normal **author, reviewer, merger, and reconciler** sessions **must not**:
+
+| Forbidden | Why |
+|-----------|-----|
+| Kill the running MCP server process | Drops all concurrent sessions; loses preflight state |
+| Restart the MCP server process | Same as kill; causes stale/identity churn mid-workflow |
+| Relaunch MCP from a development worktree | Runs unpromoted code against production mutations |
+| Edit files in the stable runtime checkout | Hot-mutates control plane under concurrent users |
+| Use experimental/dev MCP for real Gitea mutations | Bypasses promotion proof and audit expectations |
+
+EOF / transport recovery: **client reconnect only** (see `docs/mcp-namespace-eof-recovery.md`). Do not “fix” health by killing PIDs or bumping MCP config mtimes as a normal session procedure.
+
+### 2.4 Promotion (operator / release-manager only)
+
+Promotion of a new revision into the stable control runtime is an **explicit operator/release-manager action**, not an LLM self-service step.
+
+A promotion **must record** (issue comment, release note, or promotion ledger):
+
+| Field | Description |
+|-------|-------------|
+| **previous runtime SHA** | Commit previously loaded by stable runtime |
+| **promoted runtime SHA** | Commit after promotion |
+| **source branch/PR** | Where the change was reviewed |
+| **restart/reload method** | How the process was cycled (e.g. supervised restart, client reload) |
+| **health check proof** | Client-namespace probe success (`gitea_whoami` / namespace health) |
+| **identity/profile proof** | Expected profile(s) and username(s) after reload |
+| **workspace/root proof** | Stable checkout path / root matches intended layout |
+| **mutation capability proof** | Required permissions for the target role present; forbidden ops still forbidden |
+| **rollback instructions** | How to restore previous SHA and re-verify health |
+
+Suggested durable marker:
+
+```text
+## MCP STABLE RUNTIME PROMOTION (#615)
+
+Status: COMPLETED | ROLLED_BACK | ABORTED
+Previous-SHA: <full sha>
+Promoted-SHA: <full sha>
+Source-PR: <number>
+Source-Branch: <name>
+Reload-Method: <text>
+Health-Proof: client_namespace whoami OK / assess_mcp_namespace_health OK
+Identity-Proof: profile=<name> user=<name>
+Workspace-Proof: root=<path>
+Mutation-Proof: allowed_ops include <…>; forbidden include <…>
+Rollback: checkout <previous sha>; reload method <…>; re-run health/identity proofs
+Operator: <username>
+Timestamp: <ISO-8601>
+```
+
+### 2.5 Unhealthy stable runtime → stop work
+
+If the stable MCP runtime is **unhealthy** (client-namespace probes fail, wrong identity, wrong root, missing mutation capability, persistent EOF after reconnect):
+
+1. **Normal PR / review / merge / issue-mutation work must stop.**
+2. Do **not** improvise by switching to a dev worktree MCP for production mutations.
+3. Resume only after:
+   - runtime is restored, **or**
+   - a **controlled** promotion/rollback completes with the promotion record above, **or**
+   - a controller invokes the narrow **bootstrap review path** (#557) when the defect is self-hosted and documented.
+
+## 3. Relationship to other controls
+
+| Doc / mechanism | Interaction |
+|-----------------|-------------|
+| Namespace health (#543) | Proves IDE client can call tools; does not authorize restart |
+| EOF recovery | Reconnect only; no process kill |
+| Daemon import guard (#558) | Mutations require sanctioned daemon; not a bare shell import |
+| Bootstrap path (#557) | Only controller-authorized exception when live runtime cannot review its own fix |
+| Allocator / control-plane ADR | Coordination DB is separate; still depends on a healthy MCP surface for Gitea writes |
+
+## 4. Consequences
+
+### Positive
+
+- Predictable control plane for concurrent LLMs
+- Clear operator-only promotion gate with rollback
+- Aligns session behavior with health/EOF docs already landed
+
+### Costs
+
+- LLM sessions must wait when runtime is sick (no DIY restart)
+- Operators must maintain promotion discipline and dual-runtime config if they use a dev MCP
+
+### Non-goals
+
+- Does not ban operator-supervised restarts during incidents
+- Does not replace CI or code review for MCP changes
+- Does not authorize editing stable checkout “because tests need a quick fix”
+
+## 5. Implementation follow-ups (optional tooling)
+
+These may land in later issues; the **policy binds sessions now**:
+
+1. Session preflight that refuses mutations if workspace root equals a `branches/` feature worktree configured as “dev only.”
+2. Explicit `runtime_kind=stable|dev` in MCP config and `gitea_whoami` profile metadata.
+3. Promotion checklist script that emits the durable promotion marker fields.
+4. Operator Guide wiki cross-link to this ADR.
+
+## 6. Acceptance for this ADR
+
+1. Document merged under `docs/architecture/`.
+2. Issue #615 references this path.
+3. LLM/operator runbooks treat kill/restart/relaunch-from-worktree as **violations**.
+4. Unhealthy runtime stops normal mutation work until restore/promotion/rollback/bootstrap.
+
+## 7. Document history
+
+| Date | Change |
+|------|--------|
+| 2026-07-09 | Initial ADR: stable vs dev runtime, forbidden session actions, promotion proof fields, stop-work rule |