diff --git a/apps/server/src/github/GitHubPrBridge.ts b/apps/server/src/github/GitHubPrBridge.ts
index 9a8f6db0e62..60fb20b82df 100644
--- a/apps/server/src/github/GitHubPrBridge.ts
+++ b/apps/server/src/github/GitHubPrBridge.ts
@@ -1218,9 +1218,9 @@ export const make = Effect.gen(function* () {
       return;
     }
 
-    // When the closed-set identity map is on, map membership is required in
-    // addition to the GitHub permission floor. Public-repo write / outside
-    // collaborators cannot drive the host unless listed.
+    // Closed-set identity map is required for agent turns (fail-closed when the
+    // map is off/empty). Public-repo write / outside collaborators cannot drive
+    // the host unless listed; permission floor alone is never enough.
     const mapEnabled = yield* identity.isMapEnabled();
     const mapPeople = yield* identity.listMapPeople();
     const trust = classifyGitHubActorTrust({
diff --git a/apps/server/src/github/githubActorTrust.test.ts b/apps/server/src/github/githubActorTrust.test.ts
index 0f6696609e1..9932ec88f92 100644
--- a/apps/server/src/github/githubActorTrust.test.ts
+++ b/apps/server/src/github/githubActorTrust.test.ts
@@ -43,7 +43,7 @@ describe("resolvePersonByGitHubActor", () => {
 });
 
 describe("classifyGitHubActorTrust", () => {
-  it("allows full access when the identity map is disabled", () => {
+  it("denies agent access when the identity map is disabled (fail-closed)", () => {
     expect(
       classifyGitHubActorTrust({
         identityMapEnabled: false,
@@ -51,7 +51,7 @@ describe("classifyGitHubActorTrust", () => {
         actorLogin: "stranger",
         people: [],
       }),
-    ).toEqual({ mode: "full", person: null, reason: "identity_map_disabled" });
+    ).toEqual({ mode: "denied", person: null, reason: "identity_map_disabled" });
   });
 
   it("trusts mapped github accounts for full agent turns", () => {
diff --git a/apps/server/src/github/githubActorTrust.ts b/apps/server/src/github/githubActorTrust.ts
index 9a2dd150ba1..fef05c57129 100644
--- a/apps/server/src/github/githubActorTrust.ts
+++ b/apps/server/src/github/githubActorTrust.ts
@@ -1,10 +1,11 @@
 /**
  * GitHub actor trust relative to the closed-set identity map.
  *
- * When the map is off, collaborator permission alone gates agent turns
- * (legacy behaviour). When the map is on, the actor must also resolve to a
+ * Fail-closed: no configured map (or empty map) is treated like an unmapped
+ * actor — no agent turns. When the map is on, the actor must resolve to a
  * mapped person (github id or login) — so public-repo write access or
- * outside collaborators cannot drive the host unless listed.
+ * outside collaborators cannot drive the host unless listed. Collaborator
+ * permission floor is still enforced separately before this gate.
  */
 import {
   findPersonByGithubId,
@@ -50,7 +51,7 @@ export function resolvePersonByGitHubActor(
 /**
  * Classify a GitHub mention actor for agent execution.
  *
- * - Map off → full (permission floor still enforced separately)
+ * - Map off / empty → denied (no agent; same as unmapped)
  * - Map on + id/login in map → full
  * - Map on + unmapped/missing → denied (no agent turn)
  */
@@ -61,7 +62,7 @@ export function classifyGitHubActorTrust(input: {
   readonly people: ReadonlyArray<IdentityMapPerson>;
 }): GitHubActorTrustDecision {
   if (!input.identityMapEnabled) {
-    return { mode: "full", person: null, reason: "identity_map_disabled" };
+    return { mode: "denied", person: null, reason: "identity_map_disabled" };
   }
   const login = input.actorLogin?.trim() ?? "";
   const hasId =
diff --git a/apps/server/src/jira/jiraActorTrust.test.ts b/apps/server/src/jira/jiraActorTrust.test.ts
index b0955aa2a13..e699ac40565 100644
--- a/apps/server/src/jira/jiraActorTrust.test.ts
+++ b/apps/server/src/jira/jiraActorTrust.test.ts
@@ -47,14 +47,14 @@ describe("resolvePersonByJiraAccountId", () => {
 });
 
 describe("classifyJiraActorTrust", () => {
-  it("allows full access when the identity map is disabled", () => {
+  it("denies agent access when the identity map is disabled (fail-closed)", () => {
     expect(
       classifyJiraActorTrust({
         identityMapEnabled: false,
         actorAccountId: "stranger",
         people: [],
       }),
-    ).toEqual({ mode: "full", person: null, reason: "identity_map_disabled" });
+    ).toEqual({ mode: "context-only", person: null, reason: "identity_map_disabled" });
   });
 
   it("trusts mapped Jira account ids for full agent turns", () => {
diff --git a/apps/server/src/jira/jiraActorTrust.ts b/apps/server/src/jira/jiraActorTrust.ts
index 454d2026386..9d7808cfe5b 100644
--- a/apps/server/src/jira/jiraActorTrust.ts
+++ b/apps/server/src/jira/jiraActorTrust.ts
@@ -1,8 +1,8 @@
 /**
  * Jira actor trust relative to the closed-set identity map.
  *
- * When the map is off, all actors keep full agent turns (legacy behaviour).
- * When the map is on, only people with a mapped Jira accountId may run the
+ * Fail-closed: no configured map (or empty map) is treated like an unmapped
+ * actor — no agent turns. Only people with a mapped Jira accountId may run the
  * agent; everyone else may only append context to an already-linked thread.
  */
 import {
@@ -15,7 +15,7 @@ export type JiraActorTrustMode = "full" | "context-only";
 
 export type JiraActorTrustDecision = {
   readonly mode: JiraActorTrustMode;
-  /** Mapped person when trusted; null when map is off or actor is unmapped. */
+  /** Mapped person when trusted; null when untrusted. */
   readonly person: IdentityMapPerson | null;
   readonly reason:
     | "identity_map_disabled"
@@ -29,7 +29,7 @@ export { normalizeJiraAccountId, resolvePersonByJiraAccountId };
 /**
  * Classify a Jira mention actor for agent execution.
  *
- * - Map off → full (backward compatible)
+ * - Map off / empty → context-only (no agent; same as unmapped)
  * - Map on + accountId in map → full
  * - Map on + missing/unmapped accountId → context-only
  */
@@ -39,7 +39,7 @@ export function classifyJiraActorTrust(input: {
   readonly people: ReadonlyArray<IdentityMapPerson>;
 }): JiraActorTrustDecision {
   if (!input.identityMapEnabled) {
-    return { mode: "full", person: null, reason: "identity_map_disabled" };
+    return { mode: "context-only", person: null, reason: "identity_map_disabled" };
   }
   const normalized = normalizeJiraAccountId(input.actorAccountId);
   if (normalized === null) {