diff --git a/rust/lithe-core/src/debug/engine.rs b/rust/lithe-core/src/debug/engine.rs
index e2ff068..c9aa4cc 100644
--- a/rust/lithe-core/src/debug/engine.rs
+++ b/rust/lithe-core/src/debug/engine.rs
@@ -1374,7 +1374,11 @@ impl DebugSession {
                 }
             }
             PendingRequest::Launch { operation_id } => {
-                self.transition(DebugSessionState::Running);
+                // Adapters may emit stopped or terminated before this acknowledgement.
+                // A late response completes the operation, but cannot resume or resurrect it.
+                if self.state == DebugSessionState::Launching {
+                    self.transition(DebugSessionState::Running);
+                }
                 self.emit(DebugEventBody::OperationCompleted {
                     operation_id,
                     result: DebugOperationResult::Acknowledged {
@@ -3161,6 +3165,62 @@ mod tests {
         serde_json::from_slice(&bytes[body_start..]).unwrap()
     }
 
+    #[test]
+    fn delayed_launch_response_preserves_a_newer_stopped_or_terminal_event() {
+        let fixture: Value = serde_json::from_str(include_str!(
+            "../../../../shared/fixtures/debug/launch-event-order.json"
+        ))
+        .unwrap();
+        for case in fixture["cases"].as_array().unwrap() {
+            let session_id = case["id"].as_str().unwrap();
+            let event = case["event"].clone();
+            let expected = case["state"].clone();
+            create_session(child_request(session_id, None)).unwrap();
+            struct Cleanup<'a>(&'a str);
+            impl Drop for Cleanup<'_> {
+                fn drop(&mut self) {
+                    // log-exempt: Expected absence if the test already disposed this process-free session.
+                    let _ = destroy_session(SessionRequest {
+                        session_id: self.0.into(),
+                    });
+                }
+            }
+            let _cleanup = Cleanup(session_id);
+            receive_messages(
+                session_id,
+                vec![response_message(1, "initialize", json!({}))],
+            );
+            let launching = launch(LaunchRequest {
+                session_id: session_id.into(),
+                operation_id: "launch".into(),
+                configuration: DebugLaunchConfiguration {
+                    name: "native target".into(),
+                    request: DebugRequestKind::Launch,
+                    arguments: Map::new(),
+                    stepping_filters: None,
+                },
+            })
+            .unwrap();
+            let frame = decode_frame(&launching.outbound_frames[0]);
+            let stopped = receive_messages(session_id, vec![event]);
+            assert_eq!(serde_json::to_value(stopped.state).unwrap(), expected);
+            // LLDB can report the first stop before acknowledging the launch request.
+            let acknowledged = receive_messages(
+                session_id,
+                vec![response_message(
+                    frame["seq"].as_i64().unwrap(),
+                    "launch",
+                    json!({}),
+                )],
+            );
+            assert_eq!(
+                serde_json::to_value(acknowledged.state).unwrap(),
+                expected,
+                "a response must not resume or resurrect the target"
+            );
+        }
+    }
+
     #[test]
     fn dap_logging_keeps_catalog_identity_and_cancellation_private() {
         let adapter = "lldb+private-adapter";
diff --git a/rust/lithe-core/src/protocol/command.rs b/rust/lithe-core/src/protocol/command.rs
index 5569461..05f45d5 100644
--- a/rust/lithe-core/src/protocol/command.rs
+++ b/rust/lithe-core/src/protocol/command.rs
@@ -182,6 +182,8 @@ pub enum CoreCommand {
     ToolchainsFailureReply,
     /// Resolves the nearest machine-local directory pin.
     ToolchainsResolvePins,
+    /// Edits a bounded batch of machine-local directory pins without native writes.
+    ToolchainsEditPins,
     /// Resolves consumer defaults while keeping workspace inheritance symbolic.
     ToolchainsResolveConsumerPreferences,
     /// Edits one machine-local consumer preference and returns its effective input.
@@ -879,6 +881,7 @@ impl CoreCommand {
             "toolchains.decodeReply" => Some(Self::ToolchainsDecodeReply),
             "toolchains.failureReply" => Some(Self::ToolchainsFailureReply),
             "toolchains.resolvePins" => Some(Self::ToolchainsResolvePins),
+            "toolchains.editPins" => Some(Self::ToolchainsEditPins),
             "toolchains.resolveConsumerPreferences" => {
                 Some(Self::ToolchainsResolveConsumerPreferences)
             }
diff --git a/rust/lithe-core/src/runtime/dispatcher.rs b/rust/lithe-core/src/runtime/dispatcher.rs
index c35f814..33fb417 100644
--- a/rust/lithe-core/src/runtime/dispatcher.rs
+++ b/rust/lithe-core/src/runtime/dispatcher.rs
@@ -431,6 +431,9 @@ fn execute_parsed(mut parsed: CoreRequest) -> CoreResponse {
         CoreCommand::ToolchainsResolvePins => {
             plugin_response(id, parsed.payload, crate::toolchain::resolve_pins_command)
         }
+        CoreCommand::ToolchainsEditPins => {
+            plugin_response(id, parsed.payload, crate::toolchain::edit_pins_command)
+        }
         CoreCommand::ToolchainsResolveConsumerPreferences => plugin_response(
             id,
             parsed.payload,
diff --git a/rust/lithe-core/src/tests/toolchain_pins.rs b/rust/lithe-core/src/tests/toolchain_pins.rs
index bfca269..3072870 100644
--- a/rust/lithe-core/src/tests/toolchain_pins.rs
+++ b/rust/lithe-core/src/tests/toolchain_pins.rs
@@ -259,3 +259,111 @@ fn toolchain_pins_enforce_collection_and_text_limits_before_resolution() {
         "plugin.toolchain.limitExceeded"
     );
 }
+
+/// Calls the public JSON boundary so an unregistered command cannot pass.
+fn edit(payload: Value) -> Value {
+    serde_json::from_str(&crate::execute_json(
+        &json!({"id":"pin-edit","command":"toolchains.editPins","payload":payload}).to_string(),
+    ))
+    .unwrap()
+}
+
+#[test]
+fn toolchain_pin_edits_preserve_siblings_and_remove_only_the_selected_override() {
+    let document = local_pins();
+    let changed = edit(json!({"document":document,"directory":"apps/web","edits":[
+        {"tool":"java","pin":null},
+        {"tool":"node","pin":pin("/opt/lithe-fixtures/node")}
+    ]}));
+    assert_eq!(changed["ok"], true, "{changed}");
+    assert_eq!(changed["data"]["status"], "ok", "{changed}");
+    let result = &changed["data"]["edit"]["document"];
+    assert_eq!(result["toolchains"], document["toolchains"]);
+    assert_eq!(result["pins"]["."], document["pins"]["."]);
+    assert_eq!(
+        result["pins"][".config/tools"],
+        document["pins"][".config/tools"]
+    );
+    assert!(result["pins"]["apps/web"].get("java").is_none());
+    assert_eq!(
+        result["pins"]["apps/web"]["node"],
+        pin("/opt/lithe-fixtures/node")
+    );
+    assert_eq!(
+        resolve(result, "apps/web/src", "java")["sourceDirectory"],
+        "."
+    );
+}
+
+#[test]
+fn toolchain_pin_edits_reject_invalid_batches_without_a_partial_document() {
+    for edits in [
+        json!([]),
+        json!([{"tool":"java","pin":pin("relative")}]),
+        json!([{"tool":"java","pin":null},{"tool":"java","pin":null}]),
+        json!([{"tool":"java"}]),
+        json!([{"tool":"java","pin":null,"extra":true}]),
+    ] {
+        let response = edit(json!({"document":local_pins(),"directory":".","edits":edits}));
+        assert_eq!(response["data"]["status"], "rejected", "{response}");
+        assert!(response["data"].get("edit").is_none(), "{response}");
+    }
+    let response = edit(
+        json!({"document":local_pins(),"directory":"../outside","edits":[{"tool":"java","pin":null}]}),
+    );
+    assert_eq!(response["data"]["status"], "rejected", "{response}");
+}
+
+#[test]
+fn toolchain_pin_edits_prune_empty_containers_and_leave_absent_removals_inert() {
+    let document =
+        json!({"version":1,"toolchains":{},"pins":{".":{"java":pin("/opt/lithe-fixtures/java")}}});
+    let response =
+        edit(json!({"document":document,"directory":".","edits":[{"tool":"java","pin":null}]}));
+    assert_eq!(
+        response["data"]["edit"]["document"],
+        json!({"version":1,"toolchains":{}})
+    );
+    let document = json!({"version":1,"toolchains":{}});
+    let response =
+        edit(json!({"document":document,"directory":"src","edits":[{"tool":"node","pin":null}]}));
+    assert_eq!(response["data"]["edit"]["document"], document);
+}
+
+#[test]
+fn toolchain_pin_edits_match_the_shared_boundary_fixture() {
+    let fixture: Value = serde_json::from_str(include_str!(
+        "../../../../shared/fixtures/toolchain-pin-edit.json"
+    ))
+    .unwrap();
+    let response = edit(fixture["request"].clone());
+    assert_eq!(response["data"]["edit"]["document"], fixture["document"]);
+}
+
+#[test]
+fn toolchain_pin_edits_enforce_final_collection_limits_and_validate_the_source() {
+    let mut request =
+        json!({"document":local_pins(),"directory":".","edits":[{"tool":"java","pin":null}]});
+    request["document"]["unknown"] = json!(true);
+    assert_eq!(edit(request)["data"]["status"], "rejected");
+    let edits: Vec<_> = (0..65)
+        .map(|index| json!({"tool":format!("tool-{index}"),"pin":null}))
+        .collect();
+    let response = edit(json!({"document":local_pins(),"directory":".","edits":edits}));
+    assert_eq!(
+        response["data"]["error"]["code"],
+        "plugin.toolchain.limitExceeded"
+    );
+    let tools: serde_json::Map<String, Value> = (0..64)
+        .map(|index| (format!("tool-{index}"), pin("/fixture/tool")))
+        .collect();
+    let document = json!({"version":1,"toolchains":{},"pins":{".":tools}});
+    let response = edit(
+        json!({"document":document,"directory":".","edits":[{"tool":"extra","pin":pin("/fixture/extra")}]}),
+    );
+    assert_eq!(
+        response["data"]["error"]["code"],
+        "plugin.toolchain.limitExceeded"
+    );
+    assert!(response["data"].get("edit").is_none());
+}
diff --git a/rust/lithe-core/src/toolchain/mod.rs b/rust/lithe-core/src/toolchain/mod.rs
index 3a9b8ee..0e54407 100644
--- a/rust/lithe-core/src/toolchain/mod.rs
+++ b/rust/lithe-core/src/toolchain/mod.rs
@@ -54,6 +54,11 @@ pub fn resolve_pins_command(input: Value) -> Result<Value, CoreError> {
     command(input, pins::resolve, "resolution")
 }
 
+/// Applies one atomic batch of inert directory-pin edits without native writes.
+pub fn edit_pins_command(input: Value) -> Result<Value, CoreError> {
+    command(input, pins::edit, "edit")
+}
+
 /// Resolves inert consumer choices without materializing symbolic inheritance.
 pub fn resolve_consumer_preferences_command(input: Value) -> Result<Value, CoreError> {
     command(input, preferences::resolve, "preferences")
diff --git a/rust/lithe-core/src/toolchain/pins.rs b/rust/lithe-core/src/toolchain/pins.rs
index 1737798..e7c7d8b 100644
--- a/rust/lithe-core/src/toolchain/pins.rs
+++ b/rust/lithe-core/src/toolchain/pins.rs
@@ -45,6 +45,85 @@ pub(crate) fn resolve(input: &Value) -> Validation<Value> {
     }
 }
 
+/// Edits a bounded batch against one captured document without performing I/O.
+/// A null pin removes only that override; invalid batches return no document.
+pub(crate) fn edit(input: &Value) -> Validation<Value> {
+    let request = object(input, "input", &["document", "directory", "edits"])?;
+    let document = required(request, "document", "input")?;
+    validate(document)?;
+    let directory = text(
+        required(request, "directory", "input")?,
+        "directory",
+        MAX_DIRECTORY_BYTES,
+    )?;
+    if !valid_directory(directory) {
+        return Err(invalid(
+            "directory",
+            "Expected a normalized workspace-relative directory.",
+        ));
+    }
+    let edits = required(request, "edits", "input")?
+        .as_array()
+        .ok_or_else(|| invalid("edits", "Expected an array."))?;
+    count(edits.len(), MAX_TOOLS_PER_DIRECTORY, "edits")?;
+    if edits.is_empty() {
+        return Err(invalid("edits", "Expected at least one edit."));
+    }
+    let mut seen = std::collections::BTreeSet::new();
+    let mut updated = document.clone();
+    for (index, edit) in edits.iter().enumerate() {
+        let field = format!("edits.{index}");
+        let edit = object(edit, &field, &["tool", "pin"])?;
+        let tool = text(
+            required(edit, "tool", &field)?,
+            &format!("{field}.tool"),
+            192,
+        )?;
+        if !valid_tool_id(tool) || !seen.insert(tool) {
+            return Err(invalid(
+                format!("{field}.tool"),
+                "Expected a unique valid tool identifier.",
+            ));
+        }
+        let pin = required(edit, "pin", &field)?;
+        if pin.is_null() {
+            if let Some(pins) = updated.get_mut("pins").and_then(Value::as_object_mut) {
+                if let Some(tools) = pins.get_mut(directory).and_then(Value::as_object_mut) {
+                    tools.remove(tool);
+                    if tools.is_empty() {
+                        pins.remove(directory);
+                    }
+                }
+                if pins.is_empty() {
+                    updated
+                        .as_object_mut()
+                        .expect("validated document")
+                        .remove("pins");
+                }
+            }
+        } else {
+            validate_pin(pin, &format!("{field}.pin"))?;
+            let pins = updated
+                .as_object_mut()
+                .expect("validated document")
+                .entry("pins")
+                .or_insert_with(|| json!({}));
+            let tools = pins
+                .as_object_mut()
+                .expect("validated pins")
+                .entry(directory.to_string())
+                .or_insert_with(|| json!({}));
+            tools
+                .as_object_mut()
+                .expect("validated tools")
+                .insert(tool.to_string(), pin.clone());
+        }
+    }
+    // Enforce document budgets after the entire batch, allowing replacement at capacity.
+    validate(&updated)?;
+    Ok(json!({"document":updated}))
+}
+
 /// Checks the complete local document, retaining legacy entries and dormant tool IDs.
 /// This validation is lexical only; paths are never probed, canonicalized, or launched.
 pub(crate) fn validate(document: &Value) -> Validation<()> {
diff --git a/shared/contracts/rust-core-api.md b/shared/contracts/rust-core-api.md
index 463b5e1..2fc45a1 100644
--- a/shared/contracts/rust-core-api.md
+++ b/shared/contracts/rust-core-api.md
@@ -1585,6 +1585,7 @@ package manager owns the download and Lithe does not infer bytes from logs.
 | `toolchains.decodeReply` | Validate an inert toolchain query/reply pair against bound provider identity, generation, declared tools and host-native filesystem evidence; no transport or native I/O |
 | `toolchains.failureReply` | Build the JSON-RPC error reply for a query that missed its deadline or found no backend, so the host passes it to `toolchains.decodeReply` like a provider's own error; cancellation has none |
 | `toolchains.resolvePins` | Validate a captured local document and find the nearest ancestor directory pin, retaining dormant and legacy entries without probing or writing |
+| `toolchains.editPins` | Apply one bounded batch of directory pin edits to a captured local document without writing native files |
 | `toolchains.resolveConsumerPreferences` | Validate an inert consumer preference document and resolve one tool's explicit Run, consumer, directory or workspace choice while keeping workspace/consumer inheritance symbolic; no native files or launch authority |
 | `toolchains.editConsumerPreferences` | Edit or reset one exact consumer/directory tool preference; return the document and effective input without native writes |
 | `toolchains.resolve` | Resolve the fixed/project/global/automatic layers from one generation-bound snapshot, retaining unmet requirements, unavailable providers with their cause, conflicts and terminal fixed-value failures |
@@ -7015,3 +7016,30 @@ rename) before deleting anything. The result is `{delete, keep, seed}`, the firs
 seven days old or of unknown age), `abandoned` and `expired` (deleted). The cache and the
 ledger live in the platform cache directory, never in the app bundle or install directory.
 The fixture is `shared/fixtures/agent/attachment-retention-v1.json`.
+
+### Atomic local toolchain pin editing
+
+`toolchains.editPins` accepts `{document,directory,edits:[{tool,pin}]}` and returns
+`{status:"ok",edit:{document}}`. It uses the v1 local toolchain document and the
+same normalized directory, tool ID, pin and size limits as `resolvePins`.
+A batch contains 1–64 unique tool IDs. `pin:null` removes that directory's explicit
+override (ancestor inheritance remains effective); a pin object replaces it.
+Only emptied containers on the edited path are pruned. Legacy `toolchains`,
+dormant pins and unrelated directories remain intact. Unknown fields, duplicate
+IDs, malformed pins and over-budget documents reject the whole batch with no
+partial document. Rejections use the existing `plugin.toolchain.invalidParams`
+and `plugin.toolchain.limitExceeded` structured error envelope.
+
+The command performs no I/O and grants no execution authority. The host owns
+explicit Save confirmation, byte-baseline conflict detection, cancellation,
+ignore-file preparation, atomic native replacement, and re-reading the source.
+See `shared/fixtures/toolchain-pin-edit.json` for the cross-client vector.
+
+### Debug launch response ordering
+
+A debug adapter may emit `stopped` or `terminated` before replying to `launch`
+or `attach`. The acknowledgement completes that operation; it changes state to
+`running` only if the session is still `launching`. It never resumes a paused
+target or resurrects a terminated one. See
+`shared/fixtures/debug/launch-event-order.json`. Hosts serialize each Core update,
+its outbound frames and its UI publication in the order returned by the engine.
diff --git a/shared/fixtures/debug/launch-event-order.json b/shared/fixtures/debug/launch-event-order.json
new file mode 100644
index 0000000..52200d2
--- /dev/null
+++ b/shared/fixtures/debug/launch-event-order.json
@@ -0,0 +1,25 @@
+{
+  "cases": [
+    {
+      "id": "late-launch-paused",
+      "event": {
+        "type": "event",
+        "event": "stopped",
+        "body": {
+          "reason": "breakpoint",
+          "threadId": 1
+        }
+      },
+      "state": "paused"
+    },
+    {
+      "id": "late-launch-ended",
+      "event": {
+        "type": "event",
+        "event": "terminated",
+        "body": {}
+      },
+      "state": "terminated"
+    }
+  ]
+}
diff --git a/shared/fixtures/toolchain-pin-edit.json b/shared/fixtures/toolchain-pin-edit.json
new file mode 100644
index 0000000..598e42e
--- /dev/null
+++ b/shared/fixtures/toolchain-pin-edit.json
@@ -0,0 +1,56 @@
+{
+  "request": {
+    "document": {
+      "version": 1,
+      "toolchains": {
+        "legacy": {
+          "home": "legacy home"
+        }
+      },
+      "pins": {
+        ".": {
+          "java": {
+            "home": "/fixture/java",
+            "version": "21",
+            "provider": "host:manual"
+          }
+        }
+      }
+    },
+    "directory": "apps/web",
+    "edits": [
+      {
+        "tool": "node",
+        "pin": {
+          "home": "/fixture/node",
+          "version": "22",
+          "provider": "host:manual"
+        }
+      }
+    ]
+  },
+  "document": {
+    "version": 1,
+    "toolchains": {
+      "legacy": {
+        "home": "legacy home"
+      }
+    },
+    "pins": {
+      ".": {
+        "java": {
+          "home": "/fixture/java",
+          "version": "21",
+          "provider": "host:manual"
+        }
+      },
+      "apps/web": {
+        "node": {
+          "home": "/fixture/node",
+          "version": "22",
+          "provider": "host:manual"
+        }
+      }
+    }
+  }
+}