diff --git a/packages/app/src/project-config-import/availability.ts b/packages/app/src/project-config-import/availability.ts
index 13f59a520..858e460bb 100644
--- a/packages/app/src/project-config-import/availability.ts
+++ b/packages/app/src/project-config-import/availability.ts
@@ -12,3 +12,11 @@ export function projectConfigImportAvailabilityStatus(input: {
   }
   return input.availableCount === 1 ? "one" : "many";
 }
+
+export function projectConfigImportPreviewIsOpenable(
+  preview: { ok: true; status: string } | { ok: false; error: { code: string } } | null | undefined,
+): boolean {
+  return preview?.ok === true
+    ? preview.status === "available"
+    : preview?.error.code === "invalid_source_config";
+}
diff --git a/packages/app/src/project-config-import/project-config-import-model.test.ts b/packages/app/src/project-config-import/project-config-import-model.test.ts
index df65c91a3..327da1893 100644
--- a/packages/app/src/project-config-import/project-config-import-model.test.ts
+++ b/packages/app/src/project-config-import/project-config-import-model.test.ts
@@ -18,7 +18,10 @@ import {
   stripProjectConfigImportSearchParams,
 } from "./route";
 import { projectConfigImportApplyFailureRetryAction } from "./retry";
-import { projectConfigImportAvailabilityStatus } from "./availability";
+import {
+  projectConfigImportAvailabilityStatus,
+  projectConfigImportPreviewIsOpenable,
+} from "./availability";
 import {
   createProjectConfigImportSourceRegistry,
   type ProjectConfigImportSourceDescriptor,
@@ -301,4 +304,19 @@ describe("project config import availability", () => {
       "none",
     );
   });
+
+  it("keeps invalid advertised sources openable", () => {
+    expect(
+      projectConfigImportPreviewIsOpenable({
+        ok: false,
+        error: { code: "invalid_source_config" },
+      }),
+    ).toBe(true);
+    expect(
+      projectConfigImportPreviewIsOpenable({
+        ok: false,
+        error: { code: "source_config_not_found" },
+      }),
+    ).toBe(false);
+  });
 });
diff --git a/packages/app/src/project-config-import/use-project-config-import-model.ts b/packages/app/src/project-config-import/use-project-config-import-model.ts
index 53d718c23..b89a542b4 100644
--- a/packages/app/src/project-config-import/use-project-config-import-model.ts
+++ b/packages/app/src/project-config-import/use-project-config-import-model.ts
@@ -33,7 +33,10 @@ import {
   projectConfigImportApplyFailureRetryAction,
   type ProjectConfigImportRetryAction,
 } from "./retry";
-import { projectConfigImportAvailabilityStatus } from "./availability";
+import {
+  projectConfigImportAvailabilityStatus,
+  projectConfigImportPreviewIsOpenable,
+} from "./availability";
 
 const EMPTY_IMPORT_SOURCES: readonly ProjectConfigImportAdvertisedSource[] = [];
 type ProjectConfigImportPreviewSuccess = Extract<ProjectConfigImportPreviewResult, { ok: true }>;
@@ -302,23 +305,22 @@ export function useProjectConfigImportAvailability(input: {
     sources,
     enabled: input.enabled,
   });
-  const availableSources = sources.filter((_, index) => {
-    const data = previews[index]?.data;
-    return data?.ok === true && data.status === "available";
-  });
-  const availableKinds = new Set(availableSources.map((source) => source.kind));
+  const openableSources = sources.filter((_, index) =>
+    projectConfigImportPreviewIsOpenable(previews[index]?.data),
+  );
+  const availableKinds = new Set(openableSources.map((source) => source.kind));
   const availableSourceKeys = new Set(
-    availableSources.map((source) => stableProjectConfigImportSourceKey(source.source)),
+    openableSources.map((source) => stableProjectConfigImportSourceKey(source.source)),
   );
   const isLoading = previews.some((preview) => preview.isLoading || preview.isPending);
 
   return {
     status: projectConfigImportAvailabilityStatus({
-      availableCount: availableSources.length,
+      availableCount: openableSources.length,
       isLoading,
     }),
-    source: availableSources.length === 1 ? availableSources[0] : null,
-    sources: availableSources,
+    source: openableSources.length === 1 ? openableSources[0] : null,
+    sources: openableSources,
     availableKinds,
     availableSourceKeys,
   };
diff --git a/packages/server/src/server/session/project-config/import/sources/conductor/importer.test.ts b/packages/server/src/server/session/project-config/import/sources/conductor/importer.test.ts
index dee519394..cad949294 100644
--- a/packages/server/src/server/session/project-config/import/sources/conductor/importer.test.ts
+++ b/packages/server/src/server/session/project-config/import/sources/conductor/importer.test.ts
@@ -248,6 +248,31 @@ cwd = "apps/local-web"
     });
   });
 
+  test("merges root conductor.json before scoped JSON until TOML migration", () => {
+    const repo = makeRepo();
+    writeFileSync(
+      join(repo, "conductor.json"),
+      JSON.stringify({ scripts: { setup: "legacy setup" }, runScriptMode: "nonconcurrent" }),
+    );
+    writeSharedJson(repo, { scripts: { run: { dev: { command: "npm run dev" } } } });
+
+    const preview = inspect(repo);
+
+    expect(preview.inputs).toEqual([
+      { role: "legacy", relativePath: "conductor.json" },
+      { role: "shared", relativePath: ".conductor/settings.json" },
+    ]);
+    expect(preview.preview).toMatchObject({
+      worktree: { setup: "legacy setup" },
+      scripts: { dev: { command: "npm run dev" } },
+    });
+    expect(preview.items).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({ key: "runScriptMode", outcome: "unsupported" }),
+      ]),
+    );
+  });
+
   test("reports missing and empty repository-local Conductor configs", () => {
     const missingRepo = makeRepo();
     const emptyRepo = makeRepo();
@@ -420,6 +445,47 @@ command = "npm run dev -- --port \${CONDUCTOR_PORT:-3000}"
     });
   });
 
+  test("rewrites bare Conductor ports inside shell arithmetic", () => {
+    const repo = makeRepo();
+    writeSharedToml(
+      repo,
+      `
+[scripts.run.dev]
+command = "npm run dev -- --hmr-port $((CONDUCTOR_PORT + 1))"
+`,
+    );
+
+    expect(inspect(repo).preview).toMatchObject({
+      scripts: {
+        dev: {
+          type: "service",
+          command: "npm run dev -- --hmr-port $((PASEO_PORT + 1))",
+        },
+      },
+    });
+  });
+
+  test("preserves shell arithmetic expansion in script arguments", () => {
+    const repo = makeRepo();
+    writeSharedToml(
+      repo,
+      `
+[scripts.run.dev]
+command = "npm run dev"
+args = ["--hmr-port=$((CONDUCTOR_PORT + 1))"]
+`,
+    );
+
+    expect(inspect(repo).preview).toMatchObject({
+      scripts: {
+        dev: {
+          type: "service",
+          command: `npm run dev '--hmr-port='"$((PASEO_PORT + 1))"`,
+        },
+      },
+    });
+  });
+
   test("does not import scripts available only in Conductor cloud", () => {
     const repo = makeRepo();
     writeSharedToml(
diff --git a/packages/server/src/server/session/project-config/import/sources/conductor/importer.ts b/packages/server/src/server/session/project-config/import/sources/conductor/importer.ts
index 635dee100..dbb7193e5 100644
--- a/packages/server/src/server/session/project-config/import/sources/conductor/importer.ts
+++ b/packages/server/src/server/session/project-config/import/sources/conductor/importer.ts
@@ -113,15 +113,15 @@ function discoverConductorSources(
   const worktreeIncludePath = join(repoRoot, ".worktreeinclude");
   const files: SourceFile[] = [];
 
+  if (!existsSync(sharedTomlPath) && existsSync(rootLegacyPath)) {
+    files.push(readSourceFile(repoRoot, rootLegacyPath, "legacy", true, source));
+  }
   if (existsSync(sharedJsonPath)) {
     files.push(readSourceFile(repoRoot, sharedJsonPath, "shared", true, source));
   }
   if (existsSync(sharedTomlPath)) {
     files.push(readSourceFile(repoRoot, sharedTomlPath, "shared", true, source));
   }
-  if (!existsSync(sharedJsonPath) && !existsSync(sharedTomlPath) && existsSync(rootLegacyPath)) {
-    files.push(readSourceFile(repoRoot, rootLegacyPath, "legacy", true, source));
-  }
   if (existsSync(localJsonPath)) {
     files.push(readSourceFile(repoRoot, localJsonPath, "local", true, source));
   }
@@ -516,12 +516,34 @@ function rewriteVariables(
 
 function replaceShellVariable(command: string, from: string, to: string): string {
   const pattern = new RegExp(`\\$\\{${from}(?=[}:#%+\\-=?])|\\$${from}(?![A-Za-z0-9_])`, "g");
-  return command.replace(pattern, (match) => (match.startsWith("${") ? `\${${to}` : `$${to}`));
+  return replaceArithmeticVariable(
+    command.replace(pattern, (match) => (match.startsWith("${") ? `\${${to}` : `$${to}`)),
+    from,
+    to,
+  );
 }
 
 function containsShellVariable(command: string, name: string): boolean {
   const pattern = new RegExp(`\\$\\{${name}(?=[}:#%+\\-=?])|\\$${name}(?![A-Za-z0-9_])`);
-  return pattern.test(command);
+  return pattern.test(command) || containsArithmeticVariable(command, name);
+}
+
+function replaceArithmeticVariable(command: string, from: string, to: string): string {
+  return command.replace(/\$\(\(([\s\S]*?)\)\)/g, (expression, body: string) => {
+    const identifier = new RegExp(`(^|[^A-Za-z0-9_])${from}(?![A-Za-z0-9_])`, "g");
+    const rewrittenBody = body.replace(identifier, (_match, prefix: string) => `${prefix}${to}`);
+    return rewrittenBody === body ? expression : `$((` + rewrittenBody + `))`;
+  });
+}
+
+function containsArithmeticVariable(command: string, name: string): boolean {
+  const identifier = new RegExp(`(^|[^A-Za-z0-9_])${name}(?![A-Za-z0-9_])`);
+  for (const match of command.matchAll(/\$\(\(([\s\S]*?)\)\)/g)) {
+    if (identifier.test(match[1])) {
+      return true;
+    }
+  }
+  return false;
 }
 
 function appendArgs(command: string, args: string[]): string {
@@ -565,7 +587,7 @@ function normalizeAvailableIn(value: unknown): string | string[] | undefined {
 
 function shellQuoteArgument(value: string): string {
   const variablePattern =
-    /\$(?:\{[A-Za-z_][A-Za-z0-9_]*(?:(?:[^{}])|\{[^{}]*\})*\}|[A-Za-z_][A-Za-z0-9_]*)/g;
+    /\$\(\([\s\S]*?\)\)|\$(?:\{[A-Za-z_][A-Za-z0-9_]*(?:(?:[^{}])|\{[^{}]*\})*\}|[A-Za-z_][A-Za-z0-9_]*)/g;
   const parts: string[] = [];
   let offset = 0;
   for (const match of value.matchAll(variablePattern)) {