diff --git a/frontend/src/components/PermissionDialog.tsx b/frontend/src/components/PermissionDialog.tsx
index 3c8afe73..cd9f4eef 100644
--- a/frontend/src/components/PermissionDialog.tsx
+++ b/frontend/src/components/PermissionDialog.tsx
@@ -135,7 +135,7 @@ export function PermissionDialog({
 							fontSize: "0.9em",
 						}}
 					>
-						Always Allow
+						Don't ask again this session
 					</button>
 				</div>
 			</div>
diff --git a/server/src/agent_mode/context.rs b/server/src/agent_mode/context.rs
index 6a8a595e..06140d9e 100644
--- a/server/src/agent_mode/context.rs
+++ b/server/src/agent_mode/context.rs
@@ -82,6 +82,7 @@ pub(super) fn build_agent_app_context(
         permission_registry,
         pending_perm_replies: crate::service::permission_router::PendingPermReplies::new(),
         permission_timeout_secs: 120,
+        remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
         status: agents.status_broadcaster(),
         chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
     });
diff --git a/server/src/chat/transport/matrix/bot/context.rs b/server/src/chat/transport/matrix/bot/context.rs
index 20c7398b..15160cc3 100644
--- a/server/src/chat/transport/matrix/bot/context.rs
+++ b/server/src/chat/transport/matrix/bot/context.rs
@@ -317,6 +317,7 @@ mod tests {
             permission_registry: ResponderRegistry::new(),
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             status: Arc::new(crate::service::status::StatusBroadcaster::new()),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         })
diff --git a/server/src/chat/transport/matrix/bot/permission_listener.rs b/server/src/chat/transport/matrix/bot/permission_listener.rs
index 5a609a76..aa06a465 100644
--- a/server/src/chat/transport/matrix/bot/permission_listener.rs
+++ b/server/src/chat/transport/matrix/bot/permission_listener.rs
@@ -173,6 +173,7 @@ mod tests {
             permission_registry: crate::service::permission_router::ResponderRegistry::new(),
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             status: Arc::new(crate::service::status::StatusBroadcaster::new()),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         })
diff --git a/server/src/chat/transport/matrix/health.rs b/server/src/chat/transport/matrix/health.rs
index 3a4a2cd9..2ccfce93 100644
--- a/server/src/chat/transport/matrix/health.rs
+++ b/server/src/chat/transport/matrix/health.rs
@@ -624,6 +624,7 @@ mod tests {
             permission_registry: registry,
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             status: Arc::new(crate::service::status::StatusBroadcaster::new()),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         });
@@ -655,6 +656,7 @@ mod tests {
             permission_registry: ResponderRegistry::new(),
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             status: Arc::new(crate::service::status::StatusBroadcaster::new()),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         });
diff --git a/server/src/chat/transport/whatsapp/commands/mod.rs b/server/src/chat/transport/whatsapp/commands/mod.rs
index 9eca793f..8df30dde 100644
--- a/server/src/chat/transport/whatsapp/commands/mod.rs
+++ b/server/src/chat/transport/whatsapp/commands/mod.rs
@@ -314,6 +314,7 @@ mod tests {
             permission_registry: crate::service::permission_router::ResponderRegistry::new(),
             pending_perm_replies: crate::service::permission_router::PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         });
         Arc::new(WhatsAppWebhookContext {
diff --git a/server/src/http/context.rs b/server/src/http/context.rs
index efad5f31..9b27748a 100644
--- a/server/src/http/context.rs
+++ b/server/src/http/context.rs
@@ -18,8 +18,12 @@ pub enum PermissionDecision {
     Deny,
     /// One-time approval.
     Approve,
-    /// Approve and persist the rule to `.claude/settings.json` so Claude Code's
-    /// built-in permission system handles future checks without prompting.
+    /// Approve, and remember `(tool, target-pattern)` for the rest of the
+    /// requesting agent's session (story 1218) — subsequent matching
+    /// requests auto-approve without forwarding to chat. Scoped in-memory to
+    /// the session that made the request (see
+    /// `service::permission_router::RememberedPermissions`); never persisted
+    /// to disk and never shared with another agent or story.
     AlwaysAllow,
 }
 
@@ -125,6 +129,7 @@ impl AppContext {
             permission_registry,
             pending_perm_replies: crate::service::permission_router::PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             status: agents.status_broadcaster(),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         });
diff --git a/server/src/http/mcp/diagnostics/permission.rs b/server/src/http/mcp/diagnostics/permission.rs
index 02aadf67..4e46d0e7 100644
--- a/server/src/http/mcp/diagnostics/permission.rs
+++ b/server/src/http/mcp/diagnostics/permission.rs
@@ -3,7 +3,8 @@
 use serde_json::{Value, json};
 
 use crate::http::context::AppContext;
-use crate::service::diagnostics::{add_permission_rule, generate_permission_rule};
+use crate::http::mcp::session;
+use crate::service::diagnostics::generate_permission_rule;
 use crate::slog;
 use crate::slog_warn;
 
@@ -29,6 +30,23 @@ pub(crate) async fn tool_prompt_permission(
         return Ok(json!({"behavior": "allow", "updatedInput": tool_input}).to_string());
     }
 
+    let session_id = session::current();
+    let rule = generate_permission_rule(&tool_name, &tool_input);
+
+    // Auto-approve without forwarding when this exact (tool, target-pattern)
+    // was already remembered for this agent's session (story 1218). Logged
+    // here for auditability since it bypasses the chat approval dialog.
+    if ctx
+        .services
+        .remembered_permissions
+        .is_remembered(&session_id, &rule)
+    {
+        crate::slog!(
+            "[permission] Auto-approved '{tool_name}' (remembered rule '{rule}' for session '{session_id}')"
+        );
+        return Ok(json!({"behavior": "allow", "updatedInput": tool_input}).to_string());
+    }
+
     // Auto-deny immediately if no responder is currently registered to
     // receive forwarded permission requests. The Matrix bot's
     // permission_listener task, sled uplinks, and per-message chat transports
@@ -83,15 +101,14 @@ pub(crate) async fn tool_prompt_permission(
         .map_err(|_| "Permission response channel closed unexpectedly".to_string())?;
 
     if decision == PermissionDecision::AlwaysAllow {
-        // Persist the rule so Claude Code won't prompt again for this tool.
-        if let Some(root) = ctx.state.project_root.lock().unwrap().clone() {
-            let rule = generate_permission_rule(&tool_name, &tool_input);
-            if let Err(e) = add_permission_rule(&root, &rule) {
-                slog_warn!("[permission] Failed to write always-allow rule: {e}");
-            } else {
-                slog!("[permission] Added always-allow rule: {rule}");
-            }
-        }
+        // Remember for the rest of this agent's session (story 1218) — never
+        // written to disk, never visible to another session's requests.
+        ctx.services
+            .remembered_permissions
+            .remember(&session_id, &rule);
+        slog!(
+            "[permission] Remembered rule '{rule}' for session '{session_id}' — future matches auto-approve without prompting"
+        );
     }
 
     if decision == PermissionDecision::Approve || decision == PermissionDecision::AlwaysAllow {
@@ -238,91 +255,86 @@ mod tests {
         assert_eq!(rule, "mcp__huskies__create_story");
     }
 
-    // ── Settings.json writing tests ──────────────────────────────
+    // ── Remembered ("don't ask again this session") tests (story 1218) ──
 
-    #[test]
-    fn add_rule_creates_settings_file_when_missing() {
+    #[tokio::test]
+    async fn remembered_rule_auto_approves_without_forwarding() {
         let tmp = tempfile::tempdir().unwrap();
-        add_permission_rule(tmp.path(), "Edit").unwrap();
+        let ctx = test_ctx(tmp.path());
 
-        let content = fs::read_to_string(tmp.path().join(".claude/settings.json")).unwrap();
-        let settings: Value = serde_json::from_str(&content).unwrap();
-        let allow = settings["permissions"]["allow"].as_array().unwrap();
-        assert!(allow.contains(&json!("Edit")));
-    }
+        // Pre-remember the rule for the default session (no X-Huskies-Session
+        // header scope installed in this test) — no responder is registered,
+        // so if the request were forwarded it would auto-deny instead.
+        ctx.services
+            .remembered_permissions
+            .remember(&session::current(), "Bash(git *)");
 
-    #[test]
-    fn add_rule_does_not_duplicate_existing() {
-        let tmp = tempfile::tempdir().unwrap();
-        add_permission_rule(tmp.path(), "Edit").unwrap();
-        add_permission_rule(tmp.path(), "Edit").unwrap();
-
-        let content = fs::read_to_string(tmp.path().join(".claude/settings.json")).unwrap();
-        let settings: Value = serde_json::from_str(&content).unwrap();
-        let allow = settings["permissions"]["allow"].as_array().unwrap();
-        let count = allow.iter().filter(|v| v == &&json!("Edit")).count();
-        assert_eq!(count, 1);
-    }
-
-    #[test]
-    fn add_rule_skips_when_wildcard_already_covers() {
-        let tmp = tempfile::tempdir().unwrap();
-        let claude_dir = tmp.path().join(".claude");
-        fs::create_dir_all(&claude_dir).unwrap();
-        fs::write(
-            claude_dir.join("settings.json"),
-            r#"{"permissions":{"allow":["mcp__huskies__*"]}}"#,
+        let result = tool_prompt_permission(
+            &json!({"tool_name": "Bash", "input": {"command": "git status"}}),
+            &ctx,
         )
-        .unwrap();
+        .await
+        .expect("remembered rule must short-circuit before the no-responder auto-deny");
 
-        add_permission_rule(tmp.path(), "mcp__huskies__create_story").unwrap();
-
-        let content = fs::read_to_string(claude_dir.join("settings.json")).unwrap();
-        let settings: Value = serde_json::from_str(&content).unwrap();
-        let allow = settings["permissions"]["allow"].as_array().unwrap();
-        assert_eq!(allow.len(), 1);
-        assert_eq!(allow[0], "mcp__huskies__*");
+        let parsed: Value = serde_json::from_str(&result).unwrap();
+        assert_eq!(parsed["behavior"], "allow");
     }
 
-    #[test]
-    fn add_rule_appends_to_existing_rules() {
+    #[tokio::test]
+    async fn always_allow_decision_remembers_rule_for_session_not_disk() {
         let tmp = tempfile::tempdir().unwrap();
-        let claude_dir = tmp.path().join(".claude");
-        fs::create_dir_all(&claude_dir).unwrap();
-        fs::write(
-            claude_dir.join("settings.json"),
-            r#"{"permissions":{"allow":["Edit"]}}"#,
+        let ctx = test_ctx(tmp.path());
+
+        let (guard, mut rx) = ctx.services.permission_registry.register();
+        tokio::spawn(async move {
+            if let Some(forward) = rx.recv().await {
+                let _ = forward
+                    .response_tx
+                    .send(crate::http::context::PermissionDecision::AlwaysAllow);
+            }
+            drop(guard);
+        });
+
+        tool_prompt_permission(
+            &json!({"tool_name": "Bash", "input": {"command": "git status"}}),
+            &ctx,
         )
-        .unwrap();
+        .await
+        .expect("always-allow must succeed");
 
-        add_permission_rule(tmp.path(), "Write").unwrap();
-
-        let content = fs::read_to_string(claude_dir.join("settings.json")).unwrap();
-        let settings: Value = serde_json::from_str(&content).unwrap();
-        let allow = settings["permissions"]["allow"].as_array().unwrap();
-        assert_eq!(allow.len(), 2);
-        assert!(allow.contains(&json!("Edit")));
-        assert!(allow.contains(&json!("Write")));
+        assert!(
+            ctx.services
+                .remembered_permissions
+                .is_remembered(&session::current(), "Bash(git *)"),
+            "AlwaysAllow must remember the rule in-memory for this session"
+        );
+        assert!(
+            !tmp.path().join(".claude/settings.json").exists(),
+            "AlwaysAllow must not write to disk (story 1218: session-scoped only)"
+        );
     }
 
-    #[test]
-    fn add_rule_preserves_other_settings_fields() {
+    #[tokio::test]
+    async fn remembered_rule_does_not_cross_sessions() {
         let tmp = tempfile::tempdir().unwrap();
-        let claude_dir = tmp.path().join(".claude");
-        fs::create_dir_all(&claude_dir).unwrap();
-        fs::write(
-            claude_dir.join("settings.json"),
-            r#"{"permissions":{"allow":["Edit"]},"enabledMcpjsonServers":["huskies"]}"#,
+        let ctx = test_ctx(tmp.path());
+        ctx.services
+            .remembered_permissions
+            .remember("story-a", "Bash(git *)");
+
+        // Current (default) session never remembered this rule, and no
+        // responder is registered, so it must fall through to auto-deny.
+        let result = tool_prompt_permission(
+            &json!({"tool_name": "Bash", "input": {"command": "git status"}}),
+            &ctx,
         )
+        .await
         .unwrap();
-
-        add_permission_rule(tmp.path(), "Write").unwrap();
-
-        let content = fs::read_to_string(claude_dir.join("settings.json")).unwrap();
-        let settings: Value = serde_json::from_str(&content).unwrap();
-        let servers = settings["enabledMcpjsonServers"].as_array().unwrap();
-        assert_eq!(servers.len(), 1);
-        assert_eq!(servers[0], "huskies");
+        let parsed: Value = serde_json::from_str(&result).unwrap();
+        assert_eq!(
+            parsed["behavior"], "deny",
+            "a rule remembered for a different session must not auto-approve this one"
+        );
     }
 
     // ── move_story tool tests ─────────────────────────────────────
diff --git a/server/src/http/mcp/mod.rs b/server/src/http/mcp/mod.rs
index 9f30e93e..d3babc0b 100644
--- a/server/src/http/mcp/mod.rs
+++ b/server/src/http/mcp/mod.rs
@@ -19,6 +19,10 @@ pub mod merge_tools;
 pub mod progress;
 /// MCP tools for QA request, approve, and reject workflows.
 pub mod qa_tools;
+/// Task-local session identifier for the requesting MCP client, read from
+/// the `X-Huskies-Session` header so `tool_prompt_permission` can scope
+/// remembered approvals per requesting agent.
+pub mod session;
 /// MCP tools for running shell commands and test suites.
 pub mod shell_tools;
 /// MCP tools for pipeline status, story todos, and triage dump.
@@ -71,6 +75,11 @@ pub async fn mcp_get_handler() -> Response {
 /// `tools/call`, and `notifications/*`.
 #[handler]
 pub async fn mcp_post_handler(req: &Request, body: Body, ctx: Data<&Arc<AppContext>>) -> Response {
+    let session_id = req
+        .header("x-huskies-session")
+        .unwrap_or(session::DEFAULT_SESSION)
+        .to_string();
+
     let content_type = req.header("content-type").unwrap_or("");
     if !content_type.is_empty() && !content_type.contains("application/json") {
         return json_response(JsonRpcResponse::error(
@@ -125,7 +134,7 @@ pub async fn mcp_post_handler(req: &Request, body: Body, ctx: Data<&Arc<AppConte
             .and_then(|m| m.get("progressToken"))
             .cloned();
         if let (true, Some(token)) = (accepts_sse, progress_token) {
-            return sse_tools_call(rpc.id, rpc.params, token, Arc::clone(&ctx)).await;
+            return sse_tools_call(rpc.id, rpc.params, token, Arc::clone(&ctx), session_id).await;
         }
     }
 
@@ -134,7 +143,11 @@ pub async fn mcp_post_handler(req: &Request, body: Body, ctx: Data<&Arc<AppConte
         "tools/list" => {
             JsonRpcResponse::success(rpc.id, json!({ "tools": tools_list::list_tools() }))
         }
-        "tools/call" => handle_tools_call(rpc.id, &rpc.params, &ctx).await,
+        "tools/call" => {
+            session::SESSION_ID
+                .scope(session_id, handle_tools_call(rpc.id, &rpc.params, &ctx))
+                .await
+        }
         _ => JsonRpcResponse::error(rpc.id, -32601, format!("Unknown method: {}", rpc.method)),
     };
 
@@ -152,6 +165,7 @@ async fn sse_tools_call(
     params: Value,
     progress_token: Value,
     ctx: Arc<AppContext>,
+    session_id: String,
 ) -> Response {
     use tokio::sync::mpsc::unbounded_channel;
 
@@ -174,9 +188,13 @@ async fn sse_tools_call(
     // its final state to the CRDT even on client disconnect).
     let dispatch_ctx = Arc::clone(&ctx);
     let dispatch_handle = tokio::spawn(async move {
-        progress::EMITTER
-            .scope(emitter, async move {
-                dispatch::dispatch_tool_call(&tool_name, args, &dispatch_ctx).await
+        session::SESSION_ID
+            .scope(session_id, async move {
+                progress::EMITTER
+                    .scope(emitter, async move {
+                        dispatch::dispatch_tool_call(&tool_name, args, &dispatch_ctx).await
+                    })
+                    .await
             })
             .await
     });
diff --git a/server/src/http/mcp/session.rs b/server/src/http/mcp/session.rs
new file mode 100644
index 00000000..cb183b70
--- /dev/null
+++ b/server/src/http/mcp/session.rs
@@ -0,0 +1,51 @@
+//! Task-local session identifier for the requesting MCP client.
+//!
+//! Threaded ambiently through tool dispatch (same pattern as
+//! [`super::progress::EMITTER`]) so a deeply-nested handler — currently only
+//! `tool_prompt_permission` — can scope decisions per requesting agent
+//! without adding a parameter to `dispatch_tool_call` and every one of its
+//! ~40 match arms.
+//!
+//! The HTTP MCP handler installs the scope before dispatching a `tools/call`
+//! request, populated from the `X-Huskies-Session` header that per-story
+//! worktrees embed in their `.mcp.json` (see `worktree::write_mcp_json`).
+//! Callers with no header (the main interactive chat CLI, API-based runtimes
+//! that invoke `dispatch_tool_call` directly) fall back to a fixed
+//! `"default"` key — there is only ever one such session per server process,
+//! so no cross-story leakage results from sharing that bucket.
+
+/// Session key used when no `X-Huskies-Session` header was present.
+pub const DEFAULT_SESSION: &str = "default";
+
+tokio::task_local! {
+    /// Set by the MCP HTTP handler before dispatching a `tools/call` request.
+    /// Unset in tests and in non-HTTP dispatch paths, where [`current`] falls
+    /// back to [`DEFAULT_SESSION`].
+    pub static SESSION_ID: String;
+}
+
+/// Return the current request's session id, or [`DEFAULT_SESSION`] if no
+/// scope is installed.
+pub fn current() -> String {
+    SESSION_ID
+        .try_with(Clone::clone)
+        .unwrap_or_else(|_| DEFAULT_SESSION.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn current_falls_back_to_default_without_scope() {
+        assert_eq!(current(), DEFAULT_SESSION);
+    }
+
+    #[tokio::test]
+    async fn current_reads_installed_scope() {
+        let value = SESSION_ID
+            .scope("1218".to_string(), async { current() })
+            .await;
+        assert_eq!(value, "1218");
+    }
+}
diff --git a/server/src/main.rs b/server/src/main.rs
index 88016603..ec8dee4c 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -256,6 +256,7 @@ async fn main() -> Result<(), std::io::Error> {
             .as_ref()
             .map(|c| c.permission_timeout_secs)
             .unwrap_or(120),
+        remembered_permissions: service::permission_router::RememberedPermissions::new(),
         status: agents.status_broadcaster(),
         chat_dispatcher: std::sync::Arc::new(chat::dispatcher::ChatDispatcher::new(
             bot_cfg
diff --git a/server/src/service/bot_command/io.rs b/server/src/service/bot_command/io.rs
index baa83f15..a15df154 100644
--- a/server/src/service/bot_command/io.rs
+++ b/server/src/service/bot_command/io.rs
@@ -141,6 +141,7 @@ pub(super) fn call_sync(
         permission_registry: ResponderRegistry::new(),
         pending_perm_replies: PendingPermReplies::new(),
         permission_timeout_secs: 120,
+        remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
         status: Arc::new(crate::service::status::StatusBroadcaster::new()),
         chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
     });
diff --git a/server/src/service/diagnostics/io.rs b/server/src/service/diagnostics/io.rs
deleted file mode 100644
index 6f1ed555..00000000
--- a/server/src/service/diagnostics/io.rs
+++ /dev/null
@@ -1,72 +0,0 @@
-//! Diagnostics I/O — the ONLY place in `service::diagnostics/` that may perform side effects.
-//!
-//! Side effects here include: reading and writing `.claude/settings.json` via `std::fs`.
-//! Pure permission-rule logic (pattern derivation, wildcard domination checks) lives in
-//! `permission.rs`.
-
-use serde_json::{Value, json};
-use std::fs;
-use std::path::Path;
-
-/// Add a permission rule to `.claude/settings.json` in the project root.
-///
-/// Does nothing if the rule already exists (exact match) or is already covered
-/// by a wildcard pattern in the allow list. Creates the file and any missing
-/// parent directories if they do not yet exist.
-///
-/// # Errors
-/// Returns `Err(String)` if the directory cannot be created, the file cannot be
-/// read or written, or the JSON cannot be parsed or serialised.
-pub fn add_permission_rule(project_root: &Path, rule: &str) -> Result<(), String> {
-    let claude_dir = project_root.join(".claude");
-    fs::create_dir_all(&claude_dir)
-        .map_err(|e| format!("Failed to create .claude/ directory: {e}"))?;
-
-    let settings_path = claude_dir.join("settings.json");
-    let mut settings: Value = if settings_path.exists() {
-        let content = fs::read_to_string(&settings_path)
-            .map_err(|e| format!("Failed to read settings.json: {e}"))?;
-        serde_json::from_str(&content).map_err(|e| format!("Failed to parse settings.json: {e}"))?
-    } else {
-        json!({ "permissions": { "allow": [] } })
-    };
-
-    let allow_arr = settings
-        .pointer_mut("/permissions/allow")
-        .and_then(|v| v.as_array_mut());
-
-    let allow = match allow_arr {
-        Some(arr) => arr,
-        None => {
-            settings
-                .as_object_mut()
-                .unwrap()
-                .entry("permissions")
-                .or_insert(json!({ "allow": [] }));
-            settings
-                .pointer_mut("/permissions/allow")
-                .unwrap()
-                .as_array_mut()
-                .unwrap()
-        }
-    };
-
-    let rule_value = Value::String(rule.to_string());
-
-    // Exact duplicate check.
-    if allow.contains(&rule_value) {
-        return Ok(());
-    }
-
-    // Wildcard-coverage check: if "mcp__huskies__*" exists, skip more-specific rules.
-    if super::permission::is_dominated_by_wildcard(rule, allow) {
-        return Ok(());
-    }
-
-    allow.push(rule_value);
-
-    let pretty =
-        serde_json::to_string_pretty(&settings).map_err(|e| format!("Failed to serialize: {e}"))?;
-    fs::write(&settings_path, pretty).map_err(|e| format!("Failed to write settings.json: {e}"))?;
-    Ok(())
-}
diff --git a/server/src/service/diagnostics/mod.rs b/server/src/service/diagnostics/mod.rs
index bb32919d..75261338 100644
--- a/server/src/service/diagnostics/mod.rs
+++ b/server/src/service/diagnostics/mod.rs
@@ -3,20 +3,17 @@
 //! Extracted from `http/mcp/diagnostics.rs` following the conventions in
 //! `docs/architecture/service-modules.md`:
 //! - `mod.rs` (this file) — public API, typed [`Error`], orchestration
-//! - `io.rs` — the ONLY place that performs side effects (filesystem reads/writes)
 //! - `permission.rs` — pure permission-rule generation and wildcard checks
+//!
+//! Permission rules are remembered in-memory, per requesting-agent session
+//! (`service::permission_router::RememberedPermissions`, story 1218) rather
+//! than written to disk, so there is no side-effectful I/O submodule here.
 
-/// Side-effectful diagnostics I/O — log reads, CRDT dumps, filesystem writes.
-pub mod io;
 /// Pure permission-rule generation and wildcard matching.
 pub mod permission;
 
-#[allow(unused_imports)]
-pub use io::add_permission_rule;
 #[allow(unused_imports)]
 pub use permission::generate_permission_rule;
-#[allow(unused_imports)]
-pub use permission::is_dominated_by_wildcard;
 
 // ── Error type ────────────────────────────────────────────────────────────────
 
diff --git a/server/src/service/diagnostics/permission.rs b/server/src/service/diagnostics/permission.rs
index 45b3aa63..b0253324 100644
--- a/server/src/service/diagnostics/permission.rs
+++ b/server/src/service/diagnostics/permission.rs
@@ -22,21 +22,6 @@ pub fn generate_permission_rule(tool_name: &str, tool_input: &Value) -> String {
     }
 }
 
-/// Return `true` if `rule` is already covered by an existing wildcard in `allow_list`.
-///
-/// For example, if `allow_list` contains `"mcp__huskies__*"`, then the more
-/// specific rule `"mcp__huskies__create_story"` is already covered.
-pub fn is_dominated_by_wildcard(rule: &str, allow_list: &[Value]) -> bool {
-    allow_list.iter().any(|existing| {
-        if let Some(pat) = existing.as_str()
-            && let Some(prefix) = pat.strip_suffix('*')
-        {
-            return rule.starts_with(prefix);
-        }
-        false
-    })
-}
-
 // ── Tests ─────────────────────────────────────────────────────────────────────
 
 #[cfg(test)]
@@ -79,27 +64,4 @@ mod tests {
         let rule = generate_permission_rule("mcp__huskies__create_story", &json!({"name": "foo"}));
         assert_eq!(rule, "mcp__huskies__create_story");
     }
-
-    #[test]
-    fn is_dominated_by_exact_wildcard() {
-        let allow = vec![json!("mcp__huskies__*")];
-        assert!(is_dominated_by_wildcard(
-            "mcp__huskies__create_story",
-            &allow
-        ));
-    }
-
-    #[test]
-    fn is_not_dominated_by_different_prefix() {
-        let allow = vec![json!("mcp__other__*")];
-        assert!(!is_dominated_by_wildcard(
-            "mcp__huskies__create_story",
-            &allow
-        ));
-    }
-
-    #[test]
-    fn is_not_dominated_when_list_is_empty() {
-        assert!(!is_dominated_by_wildcard("Edit", &[]));
-    }
 }
diff --git a/server/src/service/gateway/io.rs b/server/src/service/gateway/io.rs
index 26e69b5c..68a93c03 100644
--- a/server/src/service/gateway/io.rs
+++ b/server/src/service/gateway/io.rs
@@ -741,6 +741,7 @@ pub fn spawn_gateway_bot(
             .as_ref()
             .map(|c| c.permission_timeout_secs)
             .unwrap_or(120),
+        remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
         chat_dispatcher: std::sync::Arc::new(crate::chat::dispatcher::ChatDispatcher::new(
             bot_cfg
                 .as_ref()
diff --git a/server/src/service/permission_router.rs b/server/src/service/permission_router.rs
index 04d4857b..6017ee77 100644
--- a/server/src/service/permission_router.rs
+++ b/server/src/service/permission_router.rs
@@ -20,7 +20,7 @@
 //! part of the server.
 
 use crate::http::context::{PermissionDecision, PermissionForward};
-use std::collections::{HashMap, VecDeque};
+use std::collections::{HashMap, HashSet, VecDeque};
 use std::sync::Arc;
 use std::sync::Mutex as StdMutex;
 use std::sync::atomic::{AtomicU64, Ordering};
@@ -241,6 +241,57 @@ impl PendingPermReplies {
     }
 }
 
+// ── Remembered permissions ───────────────────────────────────────────────
+
+/// In-memory "don't ask again for this tool + target-pattern" store, scoped
+/// per requesting agent session (story 1218).
+///
+/// Keyed by session id (see `http::mcp::session`) — for a per-story coding
+/// agent this is the story id, stable across a `--resume` of the same story
+/// since the worktree (and its `.mcp.json` header) doesn't change. Rules
+/// remembered here are visible only within the session that recorded them,
+/// so one agent's "don't ask again" never widens what another agent or
+/// story is auto-approved for.
+///
+/// Deliberately **not** persisted to disk: this store lives only as long as
+/// the server process does. Restarting the server clears every remembered
+/// rule (agents will be prompted again once), which is an explicit tradeoff
+/// — durability across restarts would require writing into each worktree's
+/// own `.claude/settings.json`, which adds a second persistence path for a
+/// case (server restarts mid-story) rare enough not to justify the added
+/// complexity.
+pub struct RememberedPermissions {
+    inner: StdMutex<HashMap<String, HashSet<String>>>,
+}
+
+impl RememberedPermissions {
+    /// Create an empty store.
+    pub fn new() -> Arc<Self> {
+        Arc::new(Self {
+            inner: StdMutex::new(HashMap::new()),
+        })
+    }
+
+    /// Record that `rule` is approved for `session_id` going forward.
+    pub fn remember(&self, session_id: &str, rule: &str) {
+        self.inner
+            .lock()
+            .unwrap()
+            .entry(session_id.to_string())
+            .or_default()
+            .insert(rule.to_string());
+    }
+
+    /// `true` if `rule` was previously remembered for `session_id`.
+    pub fn is_remembered(&self, session_id: &str, rule: &str) -> bool {
+        self.inner
+            .lock()
+            .unwrap()
+            .get(session_id)
+            .is_some_and(|rules| rules.contains(rule))
+    }
+}
+
 // ── Tests ─────────────────────────────────────────────────────────────────
 
 #[cfg(test)]
@@ -394,4 +445,36 @@ mod tests {
         let pending = PendingPermReplies::new();
         assert!(pending.resolve_oldest("no-such-room").await.is_none());
     }
+
+    // ── RememberedPermissions ───────────────────────────────────────
+
+    #[test]
+    fn remembered_permissions_starts_empty() {
+        let store = RememberedPermissions::new();
+        assert!(!store.is_remembered("1218", "Bash(git *)"));
+    }
+
+    #[test]
+    fn remembered_permissions_recalls_after_remember() {
+        let store = RememberedPermissions::new();
+        store.remember("1218", "Bash(git *)");
+        assert!(store.is_remembered("1218", "Bash(git *)"));
+    }
+
+    #[test]
+    fn remembered_permissions_scoped_per_session() {
+        let store = RememberedPermissions::new();
+        store.remember("1218", "Bash(git *)");
+        assert!(
+            !store.is_remembered("1216", "Bash(git *)"),
+            "a rule remembered for one story must not apply to another"
+        );
+    }
+
+    #[test]
+    fn remembered_permissions_scoped_per_rule() {
+        let store = RememberedPermissions::new();
+        store.remember("1218", "Bash(git *)");
+        assert!(!store.is_remembered("1218", "Write"));
+    }
 }
diff --git a/server/src/services.rs b/server/src/services.rs
index b2397b96..d082ae09 100644
--- a/server/src/services.rs
+++ b/server/src/services.rs
@@ -7,7 +7,9 @@
 
 use crate::agents::AgentPool;
 use crate::chat::dispatcher::ChatDispatcher;
-use crate::service::permission_router::{PendingPermReplies, ResponderRegistry};
+use crate::service::permission_router::{
+    PendingPermReplies, RememberedPermissions, ResponderRegistry,
+};
 use crate::service::status::StatusBroadcaster;
 use std::collections::HashSet;
 use std::path::PathBuf;
@@ -41,6 +43,11 @@ pub struct Services {
     /// Seconds to wait for a user to respond to a permission prompt before
     /// auto-denying (fail-closed).
     pub permission_timeout_secs: u64,
+    /// In-memory, per-session "don't ask again" permission rules (story
+    /// 1218). Checked by `tool_prompt_permission` before forwarding a
+    /// request to chat; never persisted to disk and never affects a
+    /// different session's agent.
+    pub remembered_permissions: Arc<RememberedPermissions>,
     /// Project-scoped status broadcaster.
     ///
     /// Consumers (chat transports, Web UI, agent context) call
@@ -73,6 +80,7 @@ impl Services {
             permission_registry: ResponderRegistry::new(),
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: RememberedPermissions::new(),
             chat_dispatcher: std::sync::Arc::new(ChatDispatcher::new(1_500)),
         })
     }
diff --git a/server/src/sled_uplink.rs b/server/src/sled_uplink.rs
index 8f732a25..8746a392 100644
--- a/server/src/sled_uplink.rs
+++ b/server/src/sled_uplink.rs
@@ -483,6 +483,7 @@ mod tests {
             permission_registry: ResponderRegistry::new(),
             pending_perm_replies: PendingPermReplies::new(),
             permission_timeout_secs: 120,
+            remembered_permissions: crate::service::permission_router::RememberedPermissions::new(),
             chat_dispatcher: Arc::new(crate::chat::dispatcher::ChatDispatcher::new(1_500)),
         })
     }
diff --git a/server/src/worktree/create.rs b/server/src/worktree/create.rs
index 2bab753b..ae2d1ecd 100644
--- a/server/src/worktree/create.rs
+++ b/server/src/worktree/create.rs
@@ -53,7 +53,7 @@ pub async fn create_worktree(
         tokio::task::spawn_blocking(move || configure_sparse_checkout(&wt_clone))
             .await
             .map_err(|e| format!("spawn_blocking: {e}"))??;
-        write_mcp_json(&wt_path, port)?;
+        write_mcp_json(&wt_path, port, story_id)?;
         return Ok(WorktreeInfo {
             path: wt_path,
             branch,
@@ -68,7 +68,7 @@ pub async fn create_worktree(
         .await
         .map_err(|e| format!("spawn_blocking: {e}"))??;
 
-    write_mcp_json(&wt_path, port)?;
+    write_mcp_json(&wt_path, port, story_id)?;
     run_setup_commands(&wt_path, config).await;
 
     Ok(WorktreeInfo {
diff --git a/server/src/worktree/mod.rs b/server/src/worktree/mod.rs
index 611d05d5..d5a5bc12 100644
--- a/server/src/worktree/mod.rs
+++ b/server/src/worktree/mod.rs
@@ -40,10 +40,23 @@ pub fn worktree_path(project_root: &Path, story_id: &str) -> PathBuf {
 
 /// Write a `.mcp.json` file in the given directory pointing to the huskies
 /// HTTP MCP endpoint at the given port.
-pub fn write_mcp_json(dir: &Path, port: u16) -> Result<(), String> {
-    let content = format!(
-        "{{\n  \"mcpServers\": {{\n    \"huskies\": {{\n      \"type\": \"http\",\n      \"url\": \"http://localhost:{port}/mcp\"\n    }}\n  }}\n}}\n"
-    );
+///
+/// Embeds an `X-Huskies-Session` header set to `story_id` so the server can
+/// scope remembered permission approvals to this worktree's agent session
+/// (see `http::mcp::session`) without affecting other stories' agents.
+pub fn write_mcp_json(dir: &Path, port: u16, story_id: &str) -> Result<(), String> {
+    let value = serde_json::json!({
+        "mcpServers": {
+            "huskies": {
+                "type": "http",
+                "url": format!("http://localhost:{port}/mcp"),
+                "headers": { "X-Huskies-Session": story_id }
+            }
+        }
+    });
+    let content = serde_json::to_string_pretty(&value)
+        .map_err(|e| format!("Serialize .mcp.json: {e}"))?
+        + "\n";
     std::fs::write(dir.join(".mcp.json"), content).map_err(|e| format!("Write .mcp.json: {e}"))
 }
 
@@ -91,7 +104,7 @@ mod tests {
     #[test]
     fn write_mcp_json_uses_given_port() {
         let tmp = TempDir::new().unwrap();
-        write_mcp_json(tmp.path(), 4242).unwrap();
+        write_mcp_json(tmp.path(), 4242, "1218").unwrap();
         let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
         assert!(content.contains("http://localhost:4242/mcp"));
     }
@@ -99,11 +112,23 @@ mod tests {
     #[test]
     fn write_mcp_json_default_port() {
         let tmp = TempDir::new().unwrap();
-        write_mcp_json(tmp.path(), 3001).unwrap();
+        write_mcp_json(tmp.path(), 3001, "1218").unwrap();
         let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
         assert!(content.contains("http://localhost:3001/mcp"));
     }
 
+    #[test]
+    fn write_mcp_json_embeds_session_header_with_story_id() {
+        let tmp = TempDir::new().unwrap();
+        write_mcp_json(tmp.path(), 3001, "42_story_test").unwrap();
+        let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
+        let parsed: serde_json::Value = serde_json::from_str(&content).unwrap();
+        assert_eq!(
+            parsed["mcpServers"]["huskies"]["headers"]["X-Huskies-Session"],
+            "42_story_test"
+        );
+    }
+
     #[test]
     fn worktree_path_is_inside_project() {
         let project_root = Path::new("/home/user/my-project");