feat(studio): edit fleets.toml in-app — CodeMirror TOML editor (ADR #19 C) (#30)

The edit half of the config panel: the operator edits the raw fleets.toml in a
CodeMirror TOML editor and saves; the change validates, persists, and hot-reloads
without a restart. Completes declare(edit) → switch → observe → reconcile.

- studio-cp: `read_bindings_text` / `write_bindings_atomic` (temp+rename) /
  `save_bindings_text` — validate the text parses BEFORE writing (a bad edit
  never lands on disk) and store bytes verbatim, so comments/layout survive with
  no format-preserving lib. Unit tests: round-trip, reject-invalid-without-write,
  missing-file-is-empty.
- oab-mcp: `fleet_config` now also returns the raw `text`; new write tool
  `fleet_config_write { text }` validates + writes + hot-reloads (bindings moved
  behind an RwLock; the per-cluster resolved-config memo is cleared on write).
  Catalog is 10 tools.
- src-tauri: `fleet_config_write` bridge command.
- console: CodeMirror 6 TOML editor (StreamLanguage + legacy TOML mode) mounted
  imperatively in a section separate from the re-rendered panel, so switching
  fleets never wipes an open edit. "Edit config" opens it; Save calls the write
  tool and surfaces a parse error inline; Cancel discards. 1 new render test.

Slice C of the config panel, stacked on the A+B view/switch slice. Editing is
raw-text (operator chose a TOML editor over a structured form).

Co-authored-by: Orca (ecs-claude) <orca@ecs.local>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 3 people

console/index.html

@@ -19,6 +19,17 @@
     </header>
     <main class="content">
       <section id="config" class="config-wrap"></section>
+      <section id="config-editor" class="cfg-editor-wrap" hidden>
+        <div class="cfg-editor-head">
+          <span class="cfg-label">edit fleets.toml</span>
+          <span class="cfg-editor-path" id="cfg-editor-path"></span>
+          <span class="cfg-editor-spacer"></span>
+          <button class="cfg-btn" id="cfg-save" type="button">Save</button>
+          <button class="cfg-btn cfg-btn-ghost" id="cfg-cancel" type="button">Cancel</button>
+        </div>
+        <div id="cfg-editor-mount" class="cfg-editor-mount"></div>
+        <div class="cfg-editor-error" id="cfg-editor-error" hidden></div>
+      </section>
       <section id="identity" class="identity-wrap"></section>
       <section class="logs">
         <nav class="tabs" id="tabs">

console/package-lock.json

@@ -16,5 +16,12 @@
     "typescript": "^5.6.3",
     "vite": "^6.0.7",
     "vitest": "^2.1.8"
+  },
+  "dependencies": {
+    "@codemirror/language": "^6.12.4",
+    "@codemirror/legacy-modes": "^6.5.3",
+    "@codemirror/state": "^6.7.1",
+    "@codemirror/view": "^6.43.8",
+    "codemirror": "^6.0.2"
   }
 }

console/package.json

@@ -83,4 +83,19 @@ export const FIXTURE_FLEET_CONFIG: FleetConfig = {
       expected_principal: null,
     },
   ],
+  text: `# OAB Studio fleet bindings — which credential manages which fleet.
+
+[[fleet]]
+name = "prod"
+cluster = "oab"
+region = "ap-east-2"
+profile = "orca-prod"
+expected_principal = "arn:aws:iam::504190915686:role/openab-orca-task-role"
+
+[[fleet]]
+name = "staging"
+cluster = "oab-staging"
+region = "ap-southeast-1"
+profile = "orca-staging"
+`,
 };

console/src/fixtures.ts

@@ -2,6 +2,10 @@ import { defaultSource } from "./source";
 import { renderRoster, renderIdentity, renderFleetConfig } from "./render";
 import type { FleetConfig } from "./types";
 import { createPane, bindBackend, type Level } from "./log";
+import { EditorView, basicSetup } from "codemirror";
+import { EditorState } from "@codemirror/state";
+import { StreamLanguage } from "@codemirror/language";
+import { toml } from "@codemirror/legacy-modes/mode/toml";
 
 const POLL_MS = 5000;
 const DEFAULT_CLUSTER = "oab";
@@ -15,6 +19,12 @@ let fleetConfig: FleetConfig | null = null;
 const roster = document.getElementById("roster");
 const identityEl = document.getElementById("identity");
 const configEl = document.getElementById("config");
+const editorSection = document.getElementById("config-editor");
+const editorMount = document.getElementById("cfg-editor-mount");
+const editorError = document.getElementById("cfg-editor-error");
+const editorPathEl = document.getElementById("cfg-editor-path");
+const saveBtn = document.getElementById("cfg-save") as HTMLButtonElement | null;
+const cancelBtn = document.getElementById("cfg-cancel") as HTMLButtonElement | null;
 const clusterLabel = document.getElementById("cluster-label");
 const pollStatus = document.getElementById("poll-status");
 const logEl = document.getElementById("log");
@@ -138,10 +148,74 @@ function selectCluster(cluster: string): void {
   void tick();
 }
 
-// One delegated listener: a click on any fleet button switches to its cluster.
+// ---- fleets.toml editor (ADR #19 slice C: the "edit" side) -------------------
+// A CodeMirror TOML editor over the raw config file. Kept imperative (CM owns
+// real DOM) and separate from the re-rendered config panel, so switching fleets
+// never wipes an open editor.
+let editorView: EditorView | null = null;
+
+function showEditorError(msg: string | null): void {
+  if (!editorError) return;
+  editorError.textContent = msg ?? "";
+  editorError.hidden = !msg;
+}
+
+function openEditor(): void {
+  if (!editorSection || !editorMount) return;
+  showEditorError(null);
+  if (editorPathEl) editorPathEl.textContent = fleetConfig?.path ?? "";
+  editorView?.destroy();
+  editorView = new EditorView({
+    parent: editorMount,
+    state: EditorState.create({
+      doc: fleetConfig?.text ?? "",
+      extensions: [basicSetup, StreamLanguage.define(toml)],
+    }),
+  });
+  editorSection.hidden = false;
+  editorView.focus();
+}
+
+function closeEditor(): void {
+  editorView?.destroy();
+  editorView = null;
+  if (editorSection) editorSection.hidden = true;
+  showEditorError(null);
+}
+
+async function saveEditor(): Promise<void> {
+  if (!editorView || !saveBtn) return;
+  const text = editorView.state.doc.toString();
+  saveBtn.disabled = true;
+  showEditorError(null);
+  try {
+    // The backend validates the TOML and rejects (without writing) on error.
+    fleetConfig = await source.writeFleetConfig(text);
+    if (configEl) renderFleetConfig(configEl, fleetConfig, activeCluster);
+    note("info", "fleet config saved");
+    closeEditor();
+    // A binding change may alter the active fleet's credential — re-observe.
+    void refreshIdentity();
+  } catch (e) {
+    showEditorError(`save failed — ${errText(e)}`);
+  } finally {
+    saveBtn.disabled = false;
+  }
+}
+
+saveBtn?.addEventListener("click", () => void saveEditor());
+cancelBtn?.addEventListener("click", () => closeEditor());
+
+// One delegated listener on the config panel: "Edit config" opens the editor;
+// a click on any fleet button switches to its cluster.
 if (configEl) {
   configEl.addEventListener("click", (ev) => {
-    const btn = (ev.target as HTMLElement).closest<HTMLElement>("[data-cluster]");
+    const target = ev.target as HTMLElement;
+    if (target.closest('[data-action="edit-config"]')) {
+      openEditor();
+      return;
+    }
+    const btn = target.closest<HTMLElement>("[data-cluster]");
     if (btn?.dataset.cluster) selectCluster(btn.dataset.cluster);
   });
 }

console/src/main.ts

@@ -154,14 +154,25 @@ describe("fleetConfigHtml", () => {
 
   it("renders an empty state with the config path when no fleets", () => {
     const html = fleetConfigHtml(
-      { path: "~/.config/oab-studio/fleets.toml", default_cluster: "oab", fleets: [] },
+      {
+        path: "~/.config/oab-studio/fleets.toml",
+        default_cluster: "oab",
+        fleets: [],
+        text: "",
+      },
       "oab",
     );
     expect(html).toContain("No fleets configured");
     expect(html).toContain("fleets.toml");
     expect(html).not.toContain("cfg-fleet");
   });
 
+  it("always offers the Edit config action (even with fleets)", () => {
+    expect(fleetConfigHtml(FIXTURE_FLEET_CONFIG, "oab")).toContain(
+      'data-action="edit-config"',
+    );
+  });
+
   it("renders an unavailable state for null", () => {
     expect(fleetConfigHtml(null, "oab")).toContain("fleet config unavailable");
   });

console/src/render.test.ts

@@ -163,6 +163,7 @@ export function fleetConfigHtml(
       <div class="cfg-head">
         <span class="cfg-label">fleets</span>
         ${path}
+        <button class="cfg-edit" type="button" data-action="edit-config">Edit config</button>
       </div>
       ${body}
     </div>`;