fix(controller): production client_instance_id launch path and instance-aware mutation gate

Remediate review 655 blockers on PR #979 (issue #978):

B1 — Production launcher (mcp_application_launcher) mints one trusted
client_instance_id per application launch and propagates it to all five
namespace workers via GITEA_MCP_CLIENT_INSTANCE. launcher_entry and
multi_namespace_launcher_entries use that path. Workers never invent a
trusted ID; missing/malformed/user-supplied values fail closed.

B2 — _check_mcp_runtimes_diagnostics is instance-aware: two legitimate
instances sharing a profile are allowed when each has a distinct trusted
client_instance_id; duplicate workers for the same (instance, profile)
still fail closed. Worker identity/generation exported for peer scans.

Tests cover shared ID across five namespaces, distinct launches, multi-
instance same profile, same-instance duplicates, untrusted attribution,
and the production launcher path.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/instance-fleet-identity.md

@@ -49,27 +49,54 @@ model (#949 assumption) as the operating rule for multi-instance fleets.
 ## How five workers join one instance
 
 1. The host starts one application instance (for example one Codex session).
-2. The trusted launcher mints `client_instance_id` (see
-   `mcp_fleet_snapshot.generate_client_instance_id`) and injects:
+2. The **production application launcher**
+   (`mcp_application_launcher.build_application_mcp_servers` /
+   `gitea_config.multi_namespace_launcher_entries`) mints exactly one
+   `client_instance_id` via `mcp_fleet_snapshot.generate_client_instance_id`
+   and injects the same env into every namespace worker:
 
    ```text
    GITEA_MCP_CLIENT=<client_type>
    GITEA_MCP_CLIENT_INSTANCE=<client_instance_id>
+   GITEA_MCP_INSTANCE_PROVENANCE=trusted_launcher
    GITEA_MCP_CLIENT_SESSION=<session_id>          # optional but recommended
    GITEA_MCP_FLEET_RUN_ID=<enrollment id>         # when on an approved canary
+   GITEA_CLIENT_MANAGED=1
+   GITEA_MCP_PROFILE=<role-profile>
    ```
 
-3. The launcher starts the five MCP namespace processes (or attaches five
-   role profiles) with **that same environment**.
+3. The MCP client starts the five namespace processes (`gitea-author`,
+   `gitea-reviewer`, `gitea-merger`, `gitea-controller`, `gitea-reconciler`)
+   from that generated `mcpServers` map — each entry carries the **same**
+   instance ID.
 4. Each worker registers once into the worker registry with its own
    `worker_identity`, `namespace`, `generation_id`, and PID, but the shared
-   `client_instance_id`.
+   `client_instance_id`. Workers never mint a trusted instance ID themselves.
+
+Only IDs matching the launcher format `inst-<client>-<timestamp>-<digest>`
+are trusted. Missing, `legacy-pid-*` / `pid-*` placeholders, and ordinary
+user-supplied strings fail closed as untrusted and cannot authorize
+multi-instance fleet mutation safety.
 
 Worker reconnect (same process, same registration) keeps the instance ID.
 Worker restart (new process) mints a new worker identity and generation but
 must still receive the same `GITEA_MCP_CLIENT_INSTANCE` from the parent
 application if it is the same launch. Full application restart mints a new
-`client_instance_id`.
+`client_instance_id` (call the launcher without a prior ID).
+
+### Mutation gate (instance-aware)
+
+The capability / runtime diagnostic gate
+(`_check_mcp_runtimes_diagnostics`) is **instance-aware**:
+
+* Two legitimate application instances that share a profile (same
+  `GITEA_MCP_PROFILE`) are allowed when each has a distinct trusted
+  `client_instance_id`.
+* More than one live worker for the same
+  `(client_instance_id, profile/namespace)` fails closed as a duplicate
+  namespace worker.
+* Multiple processes sharing a profile **without** trusted instance
+  evidence still fail closed (indistinguishable from a duplicate).
 
 ## Approved fleet manifest
 

gitea_config.py

@@ -1206,6 +1206,12 @@ RECOGNIZED_GITEA_ENV_KEYS = frozenset({
     # #978: operator-approved fleet enrollment identity shared by one launch.
     "GITEA_MCP_FLEET_RUN_ID",
     "GITEA_MCP_PROCESS_IDENTITY",
+    # #978 B1/B2: launcher-sealed provenance + peer-visible worker identity so
+    # the instance-aware mutation gate can distinguish two legitimate
+    # application instances that share a profile from a true duplicate worker.
+    "GITEA_MCP_INSTANCE_PROVENANCE",
+    "GITEA_MCP_WORKER_IDENTITY",
+    "GITEA_MCP_GENERATION_ID",
     # #975 review 652 B1: production also consumes HEARTBEAT_INTERVAL_ENV from
     # mcp_worker_identity via gitea_mcp_server._start_worker_heartbeat. Omitting
     # it reproduced the same unsupported-env → runtime_reconnect_required
@@ -1239,24 +1245,70 @@ def get_unconsumed_gitea_env_overrides(env=None) -> dict[str, str]:
     return unconsumed
 
 
-def launcher_entry(profile_name, config_path=None):
+def launcher_entry(
+    profile_name,
+    config_path=None,
+    *,
+    client_type=None,
+    client_instance_id=None,
+    fleet_run_id=None,
+    session_id=None,
+    launch_nonce=None,
+):
     """Return a thin MCP launcher entry for *profile_name*.
 
-    Contains command/args and the GITEA_MCP_* / GITEA_CLIENT_MANAGED env vars — never a token
-    or password. Suitable for Claude / Gemini / Codex ``mcpServers`` blocks.
+    Contains command/args and the GITEA_MCP_* / GITEA_CLIENT_MANAGED env vars —
+    never a token or password. Suitable for Claude / Gemini / Codex
+    ``mcpServers`` blocks.
+
+    #978 B1: production launches mint (or reuse) a trusted
+    ``GITEA_MCP_CLIENT_INSTANCE`` so workers never fall back to the legacy
+    placeholder identity on the real serve path. Pass *client_instance_id* to
+    resume the same launch; omit it for a fresh launch (new ID).
     """
-    command, args = server_command()
-    return {
-        "gitea-tools": {
-            "command": command,
-            "args": args,
-            "env": {
-                "GITEA_MCP_CONFIG": config_path or DEFAULT_CONFIG_PATH,
-                "GITEA_MCP_PROFILE": profile_name,
-                "GITEA_CLIENT_MANAGED": "1",
-            },
-        }
-    }
+    import mcp_application_launcher as app_launcher
+
+    built = app_launcher.launcher_entry_for_profile(
+        profile_name,
+        client_type=client_type or "unknown",
+        config_path=config_path or DEFAULT_CONFIG_PATH,
+        client_instance_id=client_instance_id,
+        fleet_run_id=fleet_run_id,
+        session_id=session_id,
+        launch_nonce=launch_nonce,
+        server_key="gitea-tools",
+    )
+    # Public shape stays {server_key: {command, args, env}} for existing callers.
+    return {"gitea-tools": built["gitea-tools"]}
+
+
+def multi_namespace_launcher_entries(
+    profile_by_namespace,
+    *,
+    client_type,
+    config_path=None,
+    client_instance_id=None,
+    fleet_run_id=None,
+    session_id=None,
+    launch_nonce=None,
+):
+    """Build production mcpServers for all five namespaces of one application launch.
+
+    One shared trusted ``client_instance_id`` is minted (or reused) and
+    propagated to every namespace worker env. See
+    :func:`mcp_application_launcher.build_application_mcp_servers`.
+    """
+    import mcp_application_launcher as app_launcher
+
+    return app_launcher.build_application_mcp_servers(
+        profile_by_namespace,
+        client_type=client_type,
+        config_path=config_path or DEFAULT_CONFIG_PATH,
+        client_instance_id=client_instance_id,
+        fleet_run_id=fleet_run_id,
+        session_id=session_id,
+        launch_nonce=launch_nonce,
+    )
 
 
 

gitea_mcp_server.py

@@ -15734,6 +15734,9 @@ CLIENT_NAME_ENV = "GITEA_MCP_CLIENT"
 CLIENT_INSTANCE_ENV = "GITEA_MCP_CLIENT_INSTANCE"
 CLIENT_SESSION_ENV = "GITEA_MCP_CLIENT_SESSION"
 FLEET_RUN_ENV = "GITEA_MCP_FLEET_RUN_ID"
+INSTANCE_PROVENANCE_ENV = "GITEA_MCP_INSTANCE_PROVENANCE"
+WORKER_IDENTITY_ENV = "GITEA_MCP_WORKER_IDENTITY"
+GENERATION_ID_ENV = "GITEA_MCP_GENERATION_ID"
 
 
 def _worker_registry():
@@ -15760,28 +15763,51 @@ def _client_identity_hints() -> dict:
     """What the launcher told us about itself (#948 / #975 / #978).
 
     ``client_instance_id`` is established by the trusted application launcher
-    once per launch and shared by all five namespace workers. When the launcher
-    key is absent we still register under an explicit *legacy* placeholder so
-    diagnostic reads work, but the registration is marked incomplete and cannot
-    authorize multi-instance fleet mutation safety.
+    once per launch and shared by all five namespace workers. Workers inherit
+    that value from the production launcher env and never mint a trusted ID
+    themselves. When the launcher key is absent or untrusted we still register
+    under an explicit *legacy* placeholder so diagnostic reads work, but the
+    registration is marked incomplete and cannot authorize multi-instance fleet
+    mutation safety.
     """
+    import mcp_application_launcher as app_launcher
     import mcp_fleet_snapshot
 
+    inherited = app_launcher.inherit_or_refuse_client_instance(os.environ)
     client_name = (os.environ.get(CLIENT_NAME_ENV) or "").strip() or None
-    raw_instance = (os.environ.get(CLIENT_INSTANCE_ENV) or "").strip() or None
-    instance = mcp_fleet_snapshot.assess_instance_identity(raw_instance)
-    # Legacy placeholder only when the launcher omitted the key — never invent a
-    # trusted ID from PID proximity.
+    instance = {
+        "client_instance_id": inherited.get("client_instance_id"),
+        "provenance": inherited.get("provenance"),
+        "trusted": bool(inherited.get("trusted")),
+        "complete": bool(inherited.get("complete")),
+        "launcher_sealed": bool(inherited.get("launcher_sealed")),
+    }
+    # Legacy placeholder only when the launcher omitted a usable key — never
+    # invent a trusted ID from PID proximity or ordinary user env.
+    if not instance["client_instance_id"] or not instance["trusted"]:
         if not instance["client_instance_id"]:
             placeholder = f"legacy-pid-{os.getpid()}"
-        instance = mcp_fleet_snapshot.assess_instance_identity(
+            fallback = mcp_fleet_snapshot.assess_instance_identity(
                 placeholder, source="pid_fallback"
             )
+            instance = {
+                "client_instance_id": fallback["client_instance_id"],
+                "provenance": fallback["provenance"],
+                "trusted": False,
+                "complete": False,
+                "launcher_sealed": False,
+            }
+        else:
+            # Malformed / untrusted user-supplied value: keep it for diagnosis
+            # but never mark trusted.
+            instance["trusted"] = False
+            instance["launcher_sealed"] = False
     return {
         "client_name": client_name,
         "client_instance_id": instance["client_instance_id"],
         "instance_id_provenance": instance["provenance"],
         "instance_identity_trusted": instance["trusted"],
+        "instance_launcher_sealed": instance.get("launcher_sealed", False),
         "session_id": (os.environ.get(CLIENT_SESSION_ENV) or "").strip()
         or f"proc-{os.getpid()}-{_process_boot_head_sha or 'nohead'}",
         "fleet_run_id": (os.environ.get(FLEET_RUN_ENV) or "").strip() or None,
@@ -15857,6 +15883,19 @@ def _active_worker_identity() -> str | None:
             if outcome.get("registered"):
                 _WORKER_IDENTITY = identity
                 _WORKER_GENERATION = generation
+                # #978 B2: export worker/generation/instance into this process
+                # env so peer process scans (and the instance-aware mutation
+                # gate) can attribute live workers without treating shared
+                # profiles as duplicates. Never overwrite a launcher-sealed
+                # client_instance_id with a different value.
+                os.environ[WORKER_IDENTITY_ENV] = identity
+                os.environ[GENERATION_ID_ENV] = generation
+                if hints.get("client_instance_id") and not (
+                    os.environ.get(CLIENT_INSTANCE_ENV) or ""
+                ).strip():
+                    os.environ[CLIENT_INSTANCE_ENV] = str(
+                        hints["client_instance_id"]
+                    )
                 # #975: registration is the only moment identity and fencing
                 # epoch are both known, so the heartbeat supervisor is started
                 # here. Without it ``last_heartbeat_at`` never left
@@ -22375,6 +22414,20 @@ def _check_mcp_runtimes_diagnostics(task: str, matching_profiles: list[str]) ->
         )
         peer_worker_identity = peer_env.get("GITEA_MCP_WORKER_IDENTITY")
         peer_generation = peer_env.get("GITEA_MCP_GENERATION_ID")
+        # #978 B2: instance attribution for the live fleet gate. Two legitimate
+        # application instances may share a profile when each has a distinct
+        # trusted client_instance_id; only same-(instance, profile/namespace)
+        # duplicates remain blocked.
+        import mcp_fleet_snapshot as _fleet
+
+        peer_instance_raw = peer_env.get("GITEA_MCP_CLIENT_INSTANCE")
+        peer_instance_assess = _fleet.assess_instance_identity(peer_instance_raw)
+        peer_client_instance = (
+            peer_instance_assess["client_instance_id"]
+            if peer_instance_assess.get("trusted")
+            else None
+        )
+        peer_instance_trusted = bool(peer_instance_assess.get("trusted"))
 
         for env_match in re.finditer(r'\b(GITEA_[A-Z0-9_]+)=([^\s]+)', env_out):
             k, v = env_match.group(1), env_match.group(2)
@@ -22392,6 +22445,9 @@ def _check_mcp_runtimes_diagnostics(task: str, matching_profiles: list[str]) ->
             "is_client_managed": is_client_managed,
             "worker_identity": peer_worker_identity,
             "generation_id": peer_generation,
+            "client_instance_id": peer_client_instance,
+            "instance_identity_trusted": peer_instance_trusted,
+            "raw_client_instance_id": peer_instance_raw,
         }
         if profile not in all_profile_procs:
             all_profile_procs[profile] = []
@@ -22399,44 +22455,85 @@ def _check_mcp_runtimes_diagnostics(task: str, matching_profiles: list[str]) ->
 
     running_profiles = {}
     for profile, procs in all_profile_procs.items():
-        # #948 AC40/AC43: sharing a profile is legitimate — profile is a
-        # reusable capability definition, not a worker identity. What is *not*
-        # legitimate is reusing one worker identity, or two live sessions
-        # claiming one generation. Distinctness has to be proven, though:
-        # processes carrying no identity evidence are indistinguishable, so
-        # they stay classified as duplicates and keep the #686 wall intact.
-        identified = [p for p in procs if p.get("worker_identity")]
+        # #978 B2 / #948 AC40: sharing a profile is legitimate when each live
+        # process belongs to a distinct trusted application instance. The
+        # permanent model is instance-aware — not exactly_one_per_profile.
+        # Fail closed only when:
+        #   * more than one live worker claims the same (client_instance_id,
+        #     profile/namespace), or
+        #   * worker identity / generation is reused, or
+        #   * multiple processes share a profile without trusted instance
+        #     evidence (indistinguishable → treat as duplicate).
+        # Group by trusted client_instance_id (untrusted/missing → one bucket).
+        by_instance: dict[str, list[dict]] = {}
+        for p in procs:
+            if p.get("instance_identity_trusted") and p.get("client_instance_id"):
+                key = str(p["client_instance_id"])
+            else:
+                key = "__untrusted_or_missing__"
+            by_instance.setdefault(key, []).append(p)
+
+        for instance_key, group in by_instance.items():
+            if len(group) <= 1:
+                continue
+            identified = [p for p in group if p.get("worker_identity")]
             distinct_identities = {p["worker_identity"] for p in identified}
-        all_identified = len(identified) == len(procs)
+            all_identified = len(identified) == len(group)
             duplicate_identity = len(identified) != len(distinct_identities)
             contested_generation = any(
-            len({p["worker_identity"] for p in identified if p.get("generation_id") == gen}) > 1
-            for gen in {p.get("generation_id") for p in identified if p.get("generation_id")}
+                len(
+                    {
+                        p["worker_identity"]
+                        for p in identified
+                        if p.get("generation_id") == gen
+                    }
                 )
-
-        if len(procs) > 1 and (
+                > 1
+                for gen in {
+                    p.get("generation_id")
+                    for p in identified
+                    if p.get("generation_id")
+                }
+            )
+            # Same trusted (instance, profile) with >1 live process is always a
+            # duplicate-namespace-worker, even if worker identities differ —
+            # one application launch gets exactly one worker per namespace.
+            same_trusted_instance = instance_key != "__untrusted_or_missing__"
+            if same_trusted_instance or (
                 not all_identified or duplicate_identity or contested_generation
             ):
-            pids_str = ", ".join(str(p["pid"]) for p in procs)
-            if duplicate_identity or contested_generation:
+                pids_str = ", ".join(str(p["pid"]) for p in group)
+                if same_trusted_instance:
                     detail = (
-                    "The same worker identity or generation is claimed more than once, "
-                    "so these are genuine duplicates rather than independent workers."
+                        f"More than one live worker for profile '{profile}' under "
+                        f"client_instance_id {instance_key!r} (duplicate namespace "
+                        "worker). Two legitimate application instances with "
+                        "distinct trusted client_instance_id values may share a "
+                        "profile; this collision does not."
+                    )
+                elif duplicate_identity or contested_generation:
+                    detail = (
+                        "The same worker identity or generation is claimed more "
+                        "than once, so these are genuine duplicates rather than "
+                        "independent workers."
                     )
                 else:
                     detail = (
-                    "Manual or duplicate launches defeat staleness detection and cannot "
-                    "receive client stdio."
+                        "Multiple processes share this profile without distinct "
+                        "trusted client_instance_id evidence, so they cannot be "
+                        "told apart from a duplicate MCP process. Relaunch via "
+                        "the production application launcher so each instance "
+                        "receives a trusted GITEA_MCP_CLIENT_INSTANCE."
                     )
                 reasons.append(
-                f"stale-runtime: Duplicate MCP server process(es) detected for profile '{profile}' (PIDs: {pids_str}). "
+                    f"stale-runtime: Duplicate MCP server process(es) detected "
+                    f"for profile '{profile}' (PIDs: {pids_str}). "
                     + detail
                 )
-        # Otherwise: several independently identified workers share one profile.
-        # No reason is appended, deliberately. Every reason this function
-        # returns is raised as a hard RuntimeError by its callers, so recording
-        # legitimate concurrency here as "informational" would block exactly the
-        # case #948 exists to permit.
+        # Multiple trusted instances sharing one profile intentionally produce
+        # no reason here. Callers raise every reason as a hard RuntimeError, so
+        # treating legitimate multi-instance concurrency as "informational"
+        # would re-introduce the profile-only wall #978 removes.
         client_procs = [p for p in procs if p["is_client_managed"]]
         if client_procs:
             client_procs.sort(key=lambda p: p["start_time"], reverse=True)

mcp_application_launcher.py

@@ -0,0 +1,393 @@
+"""Production application launcher for multi-namespace MCP fleets (#978 B1).
+
+One real LLM application launch mints exactly one trusted
+``client_instance_id`` and propagates it to every Gitea MCP namespace worker
+started for that launch. Workers never invent a trusted instance identity from
+PID proximity, timestamps, or ordinary untrusted environment values.
+
+This module is the production serve-path authority for instance identity.
+Tests and fixtures may call the same functions, but production registration
+receives the identity from the env this launcher builds — not from a hand-set
+test-only helper that bypasses it.
+"""
+
+from __future__ import annotations
+
+import os
+import secrets
+from typing import Any, Mapping
+
+import mcp_fleet_snapshot as fleet
+import mcp_worker_identity as mwi
+
+#: Canonical MCP server names for the five role namespaces.
+NAMESPACE_SERVER_NAMES: tuple[str, ...] = (
+    "gitea-author",
+    "gitea-reviewer",
+    "gitea-merger",
+    "gitea-controller",
+    "gitea-reconciler",
+)
+
+#: Map MCP server name → role/namespace kind.
+SERVER_TO_NAMESPACE: dict[str, str] = {
+    "gitea-author": "author",
+    "gitea-reviewer": "reviewer",
+    "gitea-merger": "merger",
+    "gitea-controller": "controller",
+    "gitea-reconciler": "reconciler",
+}
+
+SANCTIONED_NAMESPACES: tuple[str, ...] = (
+    "author",
+    "reviewer",
+    "merger",
+    "controller",
+    "reconciler",
+)
+
+# Env the launcher may set on every worker of one application launch.
+CLIENT_NAME_ENV = "GITEA_MCP_CLIENT"
+CLIENT_INSTANCE_ENV = fleet.CLIENT_INSTANCE_ENV
+FLEET_RUN_ENV = fleet.FLEET_RUN_ENV
+CLIENT_SESSION_ENV = "GITEA_MCP_CLIENT_SESSION"
+CLIENT_MANAGED_ENV = "GITEA_CLIENT_MANAGED"
+PROFILE_ENV = "GITEA_MCP_PROFILE"
+CONFIG_ENV = "GITEA_MCP_CONFIG"
+INSTANCE_PROVENANCE_ENV = "GITEA_MCP_INSTANCE_PROVENANCE"
+WORKER_IDENTITY_ENV = "GITEA_MCP_WORKER_IDENTITY"
+GENERATION_ID_ENV = "GITEA_MCP_GENERATION_ID"
+
+# Marker the trusted launcher alone writes; ordinary user env without this
+# marker is never classified as launcher-trusted provenance.
+LAUNCHER_PROVENANCE_VALUE = fleet.INSTANCE_ID_PROVENANCE_TRUSTED
+
+
+def mint_application_launch(
+    client_type: str | None,
+    *,
+    launch_nonce: str | None = None,
+    fleet_run_id: str | None = None,
+    session_id: str | None = None,
+    now=None,
+) -> dict[str, Any]:
+    """Mint one trusted application-instance identity for a production launch.
+
+    Called exactly once per real application launch. The returned
+    ``client_instance_id`` is injected into every namespace worker environment
+    for that launch. A second call (separate launch) yields a different ID.
+    """
+    client = mwi.normalize_client_name(client_type)
+    instance_id = fleet.generate_client_instance_id(
+        client, launch_nonce=launch_nonce, now=now
+    )
+    assessment = fleet.assess_instance_identity(instance_id)
+    if not assessment["trusted"]:
+        # generate_client_instance_id always produces a trusted format; fail
+        # closed if that invariant ever breaks rather than shipping untrusted.
+        raise RuntimeError(
+            f"launcher produced untrusted client_instance_id {instance_id!r}: "
+            f"{assessment.get('reasons')}"
+        )
+    session = (session_id or "").strip() or f"launch-{secrets.token_hex(12)}"
+    return {
+        "client_type": client,
+        "client_instance_id": instance_id,
+        "instance_id_provenance": LAUNCHER_PROVENANCE_VALUE,
+        "instance_identity_trusted": True,
+        "fleet_run_id": (fleet_run_id or "").strip() or None,
+        "session_id": session,
+        "namespaces": list(SANCTIONED_NAMESPACES),
+        "namespace_server_names": list(NAMESPACE_SERVER_NAMES),
+    }
+
+
+def namespace_worker_env(
+    *,
+    profile_name: str,
+    client_type: str | None,
+    client_instance_id: str,
+    config_path: str | None = None,
+    fleet_run_id: str | None = None,
+    session_id: str | None = None,
+    extra_env: Mapping[str, str] | None = None,
+) -> dict[str, str]:
+    """Build the environment for one namespace worker of a trusted launch.
+
+    Never invents a client_instance_id. The caller must supply the launch-minted
+    identity so all five workers receive the same value.
+    """
+    assessment = fleet.assess_instance_identity(client_instance_id)
+    if not assessment["trusted"]:
+        raise ValueError(
+            "namespace_worker_env refuses untrusted client_instance_id "
+            f"{client_instance_id!r}: {assessment.get('reasons')}"
+        )
+    client = mwi.normalize_client_name(client_type)
+    env: dict[str, str] = {
+        PROFILE_ENV: str(profile_name),
+        CLIENT_MANAGED_ENV: "1",
+        "GITEA_MCP_CLIENT": client,
+        CLIENT_INSTANCE_ENV: assessment["client_instance_id"],
+        INSTANCE_PROVENANCE_ENV: LAUNCHER_PROVENANCE_VALUE,
+    }
+    if config_path:
+        env[CONFIG_ENV] = str(config_path)
+    if fleet_run_id:
+        env[FLEET_RUN_ENV] = str(fleet_run_id)
+    if session_id:
+        env[CLIENT_SESSION_ENV] = str(session_id)
+    if extra_env:
+        # Never let untrusted callers override the trusted instance keys.
+        protected = {
+            CLIENT_INSTANCE_ENV,
+            INSTANCE_PROVENANCE_ENV,
+            "GITEA_MCP_CLIENT",
+            CLIENT_MANAGED_ENV,
+        }
+        for key, value in extra_env.items():
+            if key in protected:
+                continue
+            env[str(key)] = str(value)
+    return env
+
+
+def build_application_mcp_servers(
+    profile_by_namespace: Mapping[str, str],
+    *,
+    client_type: str | None,
+    config_path: str | None = None,
+    client_instance_id: str | None = None,
+    fleet_run_id: str | None = None,
+    session_id: str | None = None,
+    launch_nonce: str | None = None,
+    command: str | None = None,
+    args: list[str] | None = None,
+    now=None,
+) -> dict[str, Any]:
+    """Build a production ``mcpServers`` map for one application launch.
+
+    Mints one ``client_instance_id`` when *client_instance_id* is omitted (fresh
+    launch). When the caller supplies a previously minted trusted ID (resume of
+    the same launch / config rewrite), that ID is reused so reconnect keeps
+    attribution. A full new application restart omits the ID and receives a
+    fresh mint.
+
+    Every namespace server entry receives the **same** instance ID. Separate
+    calls with no supplied ID receive distinct IDs.
+    """
+    missing = [
+        ns for ns in SANCTIONED_NAMESPACES if not profile_by_namespace.get(ns)
+    ]
+    if missing:
+        raise ValueError(
+            "build_application_mcp_servers requires a profile for every "
+            f"sanctioned namespace; missing: {missing}"
+        )
+
+    if client_instance_id is None:
+        launch = mint_application_launch(
+            client_type,
+            launch_nonce=launch_nonce,
+            fleet_run_id=fleet_run_id,
+            session_id=session_id,
+            now=now,
+        )
+    else:
+        assessment = fleet.assess_instance_identity(client_instance_id)
+        if not assessment["trusted"]:
+            raise ValueError(
+                "refusing to propagate untrusted client_instance_id "
+                f"{client_instance_id!r} into production launch envs: "
+                f"{assessment.get('reasons')}"
+            )
+        launch = {
+            "client_type": mwi.normalize_client_name(client_type),
+            "client_instance_id": assessment["client_instance_id"],
+            "instance_id_provenance": LAUNCHER_PROVENANCE_VALUE,
+            "instance_identity_trusted": True,
+            "fleet_run_id": (fleet_run_id or "").strip() or None,
+            "session_id": (session_id or "").strip()
+            or f"launch-{secrets.token_hex(12)}",
+            "namespaces": list(SANCTIONED_NAMESPACES),
+            "namespace_server_names": list(NAMESPACE_SERVER_NAMES),
+        }
+
+    # Resolve command/args from the production server entry when not provided.
+    if command is None or args is None:
+        import gitea_config
+
+        cmd, cmd_args = gitea_config.server_command()
+        command = command or cmd
+        args = args if args is not None else list(cmd_args)
+
+    servers: dict[str, Any] = {}
+    shared_id = launch["client_instance_id"]
+    for namespace in SANCTIONED_NAMESPACES:
+        server_name = f"gitea-{namespace}"
+        profile = profile_by_namespace[namespace]
+        env = namespace_worker_env(
+            profile_name=profile,
+            client_type=launch["client_type"],
+            client_instance_id=shared_id,
+            config_path=config_path,
+            fleet_run_id=launch.get("fleet_run_id"),
+            session_id=launch.get("session_id"),
+        )
+        servers[server_name] = {
+            "command": command,
+            "args": list(args),
+            "env": env,
+        }
+
+    return {
+        "mcpServers": servers,
+        "launch": launch,
+        "client_instance_id": shared_id,
+        "client_type": launch["client_type"],
+        "namespaces": list(SANCTIONED_NAMESPACES),
+        "shared_instance_id_across_namespaces": True,
+        "namespace_count": len(SANCTIONED_NAMESPACES),
+    }
+
+
+def launcher_entry_for_profile(
+    profile_name: str,
+    *,
+    client_type: str | None = None,
+    config_path: str | None = None,
+    client_instance_id: str | None = None,
+    fleet_run_id: str | None = None,
+    session_id: str | None = None,
+    server_key: str = "gitea-tools",
+    launch_nonce: str | None = None,
+    now=None,
+) -> dict[str, Any]:
+    """Thin single-server production launcher entry with trusted instance ID.
+
+    Used when only one namespace is being configured. Still mints (or reuses)
+    a trusted ``client_instance_id`` so production never relies on the legacy
+    placeholder identity for normal launches.
+    """
+    import gitea_config
+
+    if client_instance_id is None:
+        launch = mint_application_launch(
+            client_type or "unknown",
+            launch_nonce=launch_nonce,
+            fleet_run_id=fleet_run_id,
+            session_id=session_id,
+            now=now,
+        )
+        client_instance_id = launch["client_instance_id"]
+        client = launch["client_type"]
+        fleet_run = launch.get("fleet_run_id")
+        session = launch.get("session_id")
+    else:
+        assessment = fleet.assess_instance_identity(client_instance_id)
+        if not assessment["trusted"]:
+            raise ValueError(
+                f"untrusted client_instance_id {client_instance_id!r}"
+            )
+        client = mwi.normalize_client_name(client_type)
+        fleet_run = (fleet_run_id or "").strip() or None
+        session = (session_id or "").strip() or None
+        client_instance_id = assessment["client_instance_id"]
+
+    command, args = gitea_config.server_command()
+    env = namespace_worker_env(
+        profile_name=profile_name,
+        client_type=client,
+        client_instance_id=client_instance_id,
+        config_path=config_path or gitea_config.DEFAULT_CONFIG_PATH,
+        fleet_run_id=fleet_run,
+        session_id=session,
+    )
+    return {
+        server_key: {
+            "command": command,
+            "args": args,
+            "env": env,
+        },
+        "client_instance_id": client_instance_id,
+        "client_type": client,
+    }
+
+
+def collect_instance_ids_from_mcp_servers(
+    mcp_servers: Mapping[str, Any],
+) -> dict[str, Any]:
+    """Inspect a production mcpServers map for shared instance attribution.
+
+    Returns the unique set of client_instance_id values across gitea-* servers
+    and whether all five namespaces share exactly one trusted ID.
+    """
+    ids: list[str] = []
+    by_server: dict[str, str | None] = {}
+    for name in NAMESPACE_SERVER_NAMES:
+        entry = mcp_servers.get(name) or {}
+        env = entry.get("env") or {}
+        raw = (env.get(CLIENT_INSTANCE_ENV) or "").strip() or None
+        by_server[name] = raw
+        if raw:
+            ids.append(raw)
+    unique = sorted(set(ids))
+    trusted = [
+        i
+        for i in unique
+        if fleet.assess_instance_identity(i)["trusted"]
+    ]
+    return {
+        "server_instance_ids": by_server,
+        "unique_instance_ids": unique,
+        "trusted_instance_ids": trusted,
+        "shared_single_trusted_id": (
+            len(unique) == 1
+            and len(trusted) == 1
+            and all(by_server.get(n) == unique[0] for n in NAMESPACE_SERVER_NAMES)
+        ),
+        "namespace_server_count": sum(
+            1 for n in NAMESPACE_SERVER_NAMES if n in mcp_servers
+        ),
+    }
+
+
+def inherit_or_refuse_client_instance(
+    env: Mapping[str, str] | None = None,
+) -> dict[str, Any]:
+    """Resolve instance identity for a worker process at serve time.
+
+    Production workers inherit the launcher-issued ID. They never mint a
+    trusted ID themselves. Missing / legacy / malformed values fail soft into
+    an untrusted assessment so registration can still record a diagnostic row
+    without authorizing multi-instance fleet mutation.
+    """
+    source = dict(env if env is not None else os.environ)
+    raw = (source.get(CLIENT_INSTANCE_ENV) or "").strip() or None
+    provenance_marker = (source.get(INSTANCE_PROVENANCE_ENV) or "").strip()
+    assessment = fleet.assess_instance_identity(raw)
+    # Ordinary user-supplied values without launcher provenance marker are
+    # still format-checked by assess_instance_identity. When the format is
+    # trusted but the launcher marker is absent, keep the ID but note that
+    # provenance is not launcher-sealed (operator hand-set or legacy config).
+    if assessment["trusted"] and provenance_marker != LAUNCHER_PROVENANCE_VALUE:
+        assessment = dict(assessment)
+        assessment["launcher_sealed"] = False
+        assessment["reasons"] = list(assessment.get("reasons") or []) + [
+            f"{INSTANCE_PROVENANCE_ENV} is not {LAUNCHER_PROVENANCE_VALUE!r}; "
+            "identity format is valid but not sealed by the production launcher"
+        ]
+    else:
+        assessment = dict(assessment)
+        assessment["launcher_sealed"] = bool(
+            assessment["trusted"]
+            and provenance_marker == LAUNCHER_PROVENANCE_VALUE
+        )
+    assessment["fleet_run_id"] = (source.get(FLEET_RUN_ENV) or "").strip() or None
+    assessment["session_id"] = (
+        (source.get(CLIENT_SESSION_ENV) or "").strip() or None
+    )
+    assessment["client_type"] = mwi.normalize_client_name(
+        (source.get("GITEA_MCP_CLIENT") or "").strip() or None
+    )
+    return assessment

mcp_fleet_snapshot.py

@@ -88,8 +88,13 @@ INSTANCE_ID_PROVENANCE_MISSING = "missing"
 CLIENT_INSTANCE_ENV = "GITEA_MCP_CLIENT_INSTANCE"
 FLEET_RUN_ENV = "GITEA_MCP_FLEET_RUN_ID"
 PROCESS_IDENTITY_ENV = "GITEA_MCP_PROCESS_IDENTITY"
+INSTANCE_PROVENANCE_ENV = "GITEA_MCP_INSTANCE_PROVENANCE"
 
 _LEGACY_INSTANCE_PREFIXES = ("pid-", "proc-", "legacy-")
+#: Trusted launcher-issued IDs use the reserved ``inst-`` prefix
+#: (see :func:`generate_client_instance_id`). Ordinary user-supplied strings
+#: without that prefix never count as trusted attribution.
+_TRUSTED_INSTANCE_PREFIX = "inst-"
 
 
 def _utc_now() -> datetime:
@@ -131,7 +136,10 @@ def assess_instance_identity(
 ) -> dict[str, Any]:
     """Classify whether a client_instance_id is trusted enough for mutation.
 
-    Trusted instance IDs are non-empty and not the pre-#978 PID/proc fallbacks.
+    Trusted instance IDs are non-empty, match the launcher-minted ``inst-…``
+    format from :func:`generate_client_instance_id`, and are not pre-#978
+    PID/proc/legacy placeholders. Ordinary user-supplied or malformed values
+    fail closed as untrusted so they cannot spoof multi-instance attribution.
     Incomplete identities remain visible for diagnosis but cannot authorize
     unsafe mutation.
     """
@@ -159,6 +167,20 @@ def assess_instance_identity(
                 "not a trusted launcher-issued instance identity"
             ],
         }
+    if not text.startswith(_TRUSTED_INSTANCE_PREFIX) or len(text) <= len(
+        _TRUSTED_INSTANCE_PREFIX
+    ):
+        return {
+            "client_instance_id": text,
+            "complete": False,
+            "trusted": False,
+            "provenance": INSTANCE_ID_PROVENANCE_LEGACY,
+            "reasons": [
+                f"client_instance_id {text!r} is malformed or user-supplied and "
+                f"does not use the trusted launcher prefix "
+                f"{_TRUSTED_INSTANCE_PREFIX!r}; refusing trusted attribution"
+            ],
+        }
     return {
         "client_instance_id": text,
         "complete": True,

tests/test_config_menu.py

@@ -175,8 +175,21 @@ class TestLauncherSnippets(unittest.TestCase):
     def test_only_safe_keys_no_secrets(self):
         entry = gitea_config.launcher_entry("prgs", "/cfg/profiles.json")["gitea-tools"]
         self.assertEqual(set(entry), {"command", "args", "env"})
-        self.assertEqual(set(entry["env"]), {"GITEA_MCP_CONFIG", "GITEA_MCP_PROFILE", "GITEA_CLIENT_MANAGED"})
+        # #978 B1: production launcher also injects trusted client identity.
+        required = {
+            "GITEA_MCP_CONFIG",
+            "GITEA_MCP_PROFILE",
+            "GITEA_CLIENT_MANAGED",
+            "GITEA_MCP_CLIENT",
+            "GITEA_MCP_CLIENT_INSTANCE",
+            "GITEA_MCP_INSTANCE_PROVENANCE",
+        }
+        self.assertTrue(required.issubset(set(entry["env"])), entry["env"])
         self.assertEqual(entry["env"]["GITEA_MCP_PROFILE"], "prgs")
+        self.assertTrue(
+            entry["env"]["GITEA_MCP_CLIENT_INSTANCE"].startswith("inst-"),
+            entry["env"]["GITEA_MCP_CLIENT_INSTANCE"],
+        )
         blob = json.dumps(entry).lower()
         for word in ("token", "password", "secret"):
             self.assertNotIn(word, blob)

tests/test_issue_978_instance_fleet_snapshot.py

@@ -1049,6 +1049,386 @@ class ClientHintsTests(unittest.TestCase):
         self.assertEqual(hints["client_instance_id"], inst)
         self.assertEqual(hints["fleet_run_id"], "run-1")
 
+    def test_malformed_user_supplied_instance_not_trusted(self):
+        import gitea_mcp_server as server
+
+        with mock.patch.dict(
+            os.environ,
+            {
+                "GITEA_MCP_CLIENT": "codex",
+                "GITEA_MCP_CLIENT_INSTANCE": "user-spoofed-not-launcher",
+            },
+            clear=False,
+        ):
+            hints = server._client_identity_hints()
+        self.assertFalse(hints["instance_identity_trusted"])
+        self.assertEqual(hints["client_instance_id"], "user-spoofed-not-launcher")
+
+
+class ProductionLauncherB1Tests(unittest.TestCase):
+    """#978 review 655 B1: production launcher mints + propagates instance ID."""
+
+    def test_one_launch_shares_id_across_five_namespaces(self):
+        import mcp_application_launcher as launcher
+
+        profiles = {ns: f"prgs-{ns}" for ns in NAMESPACES}
+        built = launcher.build_application_mcp_servers(
+            profiles,
+            client_type="codex",
+            config_path="/cfg/profiles.json",
+            launch_nonce="launch-one",
+            now=NOW,
+            command="/venv/bin/python3",
+            args=["mcp_server.py"],
+        )
+        servers = built["mcpServers"]
+        self.assertEqual(len(servers), 5)
+        ids = {
+            servers[f"gitea-{ns}"]["env"]["GITEA_MCP_CLIENT_INSTANCE"]
+            for ns in NAMESPACES
+        }
+        self.assertEqual(len(ids), 1, ids)
+        shared = next(iter(ids))
+        self.assertTrue(fleet.assess_instance_identity(shared)["trusted"])
+        self.assertEqual(built["client_instance_id"], shared)
+        # No legacy placeholder on any production worker env.
+        for ns in NAMESPACES:
+            env = servers[f"gitea-{ns}"]["env"]
+            self.assertEqual(env["GITEA_MCP_CLIENT_INSTANCE"], shared)
+            self.assertEqual(
+                env["GITEA_MCP_INSTANCE_PROVENANCE"],
+                fleet.INSTANCE_ID_PROVENANCE_TRUSTED,
+            )
+            self.assertEqual(env["GITEA_MCP_CLIENT"], "codex")
+            self.assertEqual(env["GITEA_CLIENT_MANAGED"], "1")
+            self.assertFalse(env["GITEA_MCP_CLIENT_INSTANCE"].startswith("legacy-"))
+
+        proof = launcher.collect_instance_ids_from_mcp_servers(servers)
+        self.assertTrue(proof["shared_single_trusted_id"], proof)
+
+    def test_two_launches_receive_different_ids(self):
+        import mcp_application_launcher as launcher
+
+        profiles = {ns: f"prgs-{ns}" for ns in NAMESPACES}
+        a = launcher.build_application_mcp_servers(
+            profiles,
+            client_type="codex",
+            launch_nonce="L1",
+            now=NOW,
+            command="python3",
+            args=["mcp_server.py"],
+        )
+        b = launcher.build_application_mcp_servers(
+            profiles,
+            client_type="codex",
+            launch_nonce="L2",
+            now=NOW,
+            command="python3",
+            args=["mcp_server.py"],
+        )
+        self.assertNotEqual(a["client_instance_id"], b["client_instance_id"])
+
+    def test_resume_reuses_supplied_trusted_id(self):
+        import mcp_application_launcher as launcher
+
+        profiles = {ns: f"prgs-{ns}" for ns in NAMESPACES}
+        first = launcher.build_application_mcp_servers(
+            profiles,
+            client_type="claude_code",
+            launch_nonce="resume-src",
+            now=NOW,
+            command="python3",
+            args=["mcp_server.py"],
+        )
+        resumed = launcher.build_application_mcp_servers(
+            profiles,
+            client_type="claude_code",
+            client_instance_id=first["client_instance_id"],
+            command="python3",
+            args=["mcp_server.py"],
+        )
+        self.assertEqual(first["client_instance_id"], resumed["client_instance_id"])
+
+    def test_refuses_untrusted_instance_id_on_production_path(self):
+        import mcp_application_launcher as launcher
+
+        profiles = {ns: f"prgs-{ns}" for ns in NAMESPACES}
+        with self.assertRaises(ValueError):
+            launcher.build_application_mcp_servers(
+                profiles,
+                client_type="codex",
+                client_instance_id="pid-999",
+                command="python3",
+                args=["mcp_server.py"],
+            )
+        with self.assertRaises(ValueError):
+            launcher.namespace_worker_env(
+                profile_name="prgs-author",
+                client_type="codex",
+                client_instance_id="user-supplied-garbage",
+            )
+
+    def test_extra_env_cannot_override_trusted_instance_keys(self):
+        import mcp_application_launcher as launcher
+
+        trusted = fleet.generate_client_instance_id(
+            "codex", launch_nonce="seal", now=NOW
+        )
+        env = launcher.namespace_worker_env(
+            profile_name="prgs-author",
+            client_type="codex",
+            client_instance_id=trusted,
+            extra_env={
+                "GITEA_MCP_CLIENT_INSTANCE": "inst-spoofed-20260730T000000Z-deadbeefdead",
+                "GITEA_MCP_INSTANCE_PROVENANCE": "trusted_launcher",
+                "GITEA_CLIENT_MANAGED": "0",
+                "GITEA_MCP_CLIENT": "gemini",
+                "GITEA_AUTHOR_WORKTREE": "/ok/extra",
+            },
+        )
+        self.assertEqual(env["GITEA_MCP_CLIENT_INSTANCE"], trusted)
+        self.assertEqual(env["GITEA_CLIENT_MANAGED"], "1")
+        self.assertEqual(env["GITEA_MCP_CLIENT"], "codex")
+        self.assertEqual(env["GITEA_AUTHOR_WORKTREE"], "/ok/extra")
+
+    def test_gitea_config_launcher_entry_uses_production_path(self):
+        """Production launcher_entry — not a test helper — mints trusted IDs."""
+        import gitea_config
+
+        entry_a = gitea_config.launcher_entry(
+            "prgs-author",
+            "/cfg/profiles.json",
+            client_type="codex",
+            launch_nonce="cfg-a",
+        )["gitea-tools"]
+        entry_b = gitea_config.launcher_entry(
+            "prgs-author",
+            "/cfg/profiles.json",
+            client_type="codex",
+            launch_nonce="cfg-b",
+        )["gitea-tools"]
+        id_a = entry_a["env"]["GITEA_MCP_CLIENT_INSTANCE"]
+        id_b = entry_b["env"]["GITEA_MCP_CLIENT_INSTANCE"]
+        self.assertNotEqual(id_a, id_b)
+        self.assertTrue(fleet.assess_instance_identity(id_a)["trusted"])
+        self.assertTrue(fleet.assess_instance_identity(id_b)["trusted"])
+
+    def test_multi_namespace_launcher_entries_api(self):
+        import gitea_config
+
+        profiles = {ns: f"prgs-{ns}" for ns in NAMESPACES}
+        built = gitea_config.multi_namespace_launcher_entries(
+            profiles,
+            client_type="grok",
+            config_path="/cfg/profiles.json",
+            launch_nonce="multi-api",
+        )
+        self.assertTrue(built["shared_instance_id_across_namespaces"])
+        self.assertEqual(built["namespace_count"], 5)
+        proof = __import__(
+            "mcp_application_launcher", fromlist=["*"]
+        ).collect_instance_ids_from_mcp_servers(built["mcpServers"])
+        self.assertTrue(proof["shared_single_trusted_id"], proof)
+
+    def test_malformed_and_missing_fail_safely(self):
+        self.assertFalse(fleet.assess_instance_identity("")["trusted"])
+        self.assertFalse(fleet.assess_instance_identity(None)["trusted"])
+        self.assertFalse(fleet.assess_instance_identity("legacy-pid-1")["trusted"])
+        self.assertFalse(fleet.assess_instance_identity("not-an-inst-id")["trusted"])
+        self.assertFalse(fleet.assess_instance_identity("inst-")["trusted"])
+        self.assertFalse(fleet.assess_instance_identity("user-spoofed")["trusted"])
+        # Reserved inst- prefix from the launcher is trusted.
+        self.assertTrue(fleet.assess_instance_identity("inst-codex-1")["trusted"])
+
+
+class InstanceAwareMutationGateB2Tests(unittest.TestCase):
+    """#978 review 655 B2: mutation gate is instance-aware, not profile-only."""
+
+    def _ps_lines(self, rows):
+        # rows: list of (pid, lstart, command) — command ignored beyond mcp_server.py
+        header = "  PID LSTART COMMAND\n"
+        body = "".join(
+            f"{pid} {lstart} /path/to/python mcp_server.py\n"
+            for pid, lstart, _env in rows
+        )
+        return header + body
+
+    def _side_effect(self, rows, *, self_pid=1000):
+        ps_out = self._ps_lines(rows)
+        env_by_pid = {str(pid): env for pid, _ls, env in rows}
+
+        def side_effect(args, **kwargs):
+            mock_run = mock.MagicMock()
+            if args[0] == "ps" and "eww" in args:
+                mock_run.stdout = env_by_pid.get(str(args[2]), "")
+                return mock_run
+            if args[0] == "ps":
+                mock_run.stdout = ps_out
+                return mock_run
+            if args[0] == "git":
+                mock_run.stdout = "deadbeef"
+                return mock_run
+            raise ValueError(args)
+
+        return side_effect
+
+    def test_two_valid_instances_same_profile_allowed(self):
+        import gitea_mcp_server as server
+
+        inst_a = fleet.generate_client_instance_id(
+            "codex", launch_nonce="gate-a", now=NOW
+        )
+        inst_b = fleet.generate_client_instance_id(
+            "codex", launch_nonce="gate-b", now=NOW
+        )
+        lstart = "Wed Jul  8 15:00:00 2026"
+        rows = [
+            (
+                2001,
+                lstart,
+                (
+                    f"GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1 "
+                    f"GITEA_MCP_CLIENT_INSTANCE={inst_a} "
+                    f"GITEA_MCP_WORKER_IDENTITY=worker-a "
+                    f"GITEA_MCP_GENERATION_ID=gen-a"
+                ),
+            ),
+            (
+                2002,
+                lstart,
+                (
+                    f"GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1 "
+                    f"GITEA_MCP_CLIENT_INSTANCE={inst_b} "
+                    f"GITEA_MCP_WORKER_IDENTITY=worker-b "
+                    f"GITEA_MCP_GENERATION_ID=gen-b"
+                ),
+            ),
+        ]
+        with mock.patch("subprocess.run") as mock_run, mock.patch(
+            "os.path.getmtime", return_value=datetime(2026, 7, 8, 11, 0, 0).timestamp()
+        ), mock.patch("os.path.exists", return_value=True), mock.patch(
+            "os.getpid", return_value=9999
+        ):
+            mock_run.side_effect = self._side_effect(rows)
+            reasons = server._check_mcp_runtimes_diagnostics(
+                "create_issue", ["prgs-author"]
+            )
+        self.assertFalse(
+            any("Duplicate MCP server process(es) detected" in r for r in reasons),
+            reasons,
+        )
+
+    def test_duplicate_same_instance_and_namespace_blocked(self):
+        import gitea_mcp_server as server
+
+        inst = fleet.generate_client_instance_id(
+            "codex", launch_nonce="dup", now=NOW
+        )
+        lstart = "Wed Jul  8 15:00:00 2026"
+        rows = [
+            (
+                3001,
+                lstart,
+                (
+                    f"GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1 "
+                    f"GITEA_MCP_CLIENT_INSTANCE={inst} "
+                    f"GITEA_MCP_WORKER_IDENTITY=worker-1 "
+                    f"GITEA_MCP_GENERATION_ID=gen-1"
+                ),
+            ),
+            (
+                3002,
+                lstart,
+                (
+                    f"GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1 "
+                    f"GITEA_MCP_CLIENT_INSTANCE={inst} "
+                    f"GITEA_MCP_WORKER_IDENTITY=worker-2 "
+                    f"GITEA_MCP_GENERATION_ID=gen-2"
+                ),
+            ),
+        ]
+        with mock.patch("subprocess.run") as mock_run, mock.patch(
+            "os.path.getmtime", return_value=datetime(2026, 7, 8, 11, 0, 0).timestamp()
+        ), mock.patch("os.path.exists", return_value=True), mock.patch(
+            "os.getpid", return_value=9999
+        ):
+            mock_run.side_effect = self._side_effect(rows)
+            reasons = server._check_mcp_runtimes_diagnostics(
+                "create_issue", ["prgs-author"]
+            )
+        self.assertTrue(
+            any("Duplicate MCP server process(es) detected" in r for r in reasons),
+            reasons,
+        )
+        self.assertTrue(
+            any("duplicate namespace" in r.lower() or "client_instance_id" in r for r in reasons),
+            reasons,
+        )
+
+    def test_missing_instance_evidence_still_fail_closed(self):
+        """Two profile-sharing processes without trusted IDs remain blocked."""
+        import gitea_mcp_server as server
+
+        lstart = "Wed Jul  8 15:00:00 2026"
+        rows = [
+            (
+                4001,
+                lstart,
+                "GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1",
+            ),
+            (
+                4002,
+                lstart,
+                "GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1",
+            ),
+        ]
+        with mock.patch("subprocess.run") as mock_run, mock.patch(
+            "os.path.getmtime", return_value=datetime(2026, 7, 8, 11, 0, 0).timestamp()
+        ), mock.patch("os.path.exists", return_value=True), mock.patch(
+            "os.getpid", return_value=9999
+        ):
+            mock_run.side_effect = self._side_effect(rows)
+            reasons = server._check_mcp_runtimes_diagnostics(
+                "create_issue", ["prgs-author"]
+            )
+        self.assertTrue(
+            any("Duplicate MCP server process(es) detected" in r for r in reasons),
+            reasons,
+        )
+
+    def test_single_instance_still_ok(self):
+        import gitea_mcp_server as server
+
+        inst = fleet.generate_client_instance_id(
+            "codex", launch_nonce="single", now=NOW
+        )
+        lstart = "Wed Jul  8 15:00:00 2026"
+        rows = [
+            (
+                5001,
+                lstart,
+                (
+                    f"GITEA_MCP_PROFILE=prgs-author GITEA_CLIENT_MANAGED=1 "
+                    f"GITEA_MCP_CLIENT_INSTANCE={inst} "
+                    f"GITEA_MCP_WORKER_IDENTITY=worker-only "
+                    f"GITEA_MCP_GENERATION_ID=gen-only"
+                ),
+            ),
+        ]
+        with mock.patch("subprocess.run") as mock_run, mock.patch(
+            "os.path.getmtime", return_value=datetime(2026, 7, 8, 11, 0, 0).timestamp()
+        ), mock.patch("os.path.exists", return_value=True), mock.patch(
+            "os.getpid", return_value=9999
+        ):
+            mock_run.side_effect = self._side_effect(rows)
+            reasons = server._check_mcp_runtimes_diagnostics(
+                "create_issue", ["prgs-author"]
+            )
+        self.assertFalse(
+            any("Duplicate MCP server process(es) detected" in r for r in reasons),
+            reasons,
+        )
+
 
 if __name__ == "__main__":
     unittest.main()