diff --git a/backend/src/CodeSpace.Core/Services/Workflows/Nodes/Builtin/AgentCodeNode.cs b/backend/src/CodeSpace.Core/Services/Workflows/Nodes/Builtin/AgentCodeNode.cs
index 04577032c..6a6e629e9 100644
--- a/backend/src/CodeSpace.Core/Services/Workflows/Nodes/Builtin/AgentCodeNode.cs
+++ b/backend/src/CodeSpace.Core/Services/Workflows/Nodes/Builtin/AgentCodeNode.cs
@@ -661,7 +661,7 @@ private static bool TryReadModelCredentialModelId(NodeRunContext context, out Gu
     /// <summary>Read the optional <c>baseRef</c> input — the branch/ref to clone the primary repo at (session branch continuity). Absent / blank / non-string → null (the repo default).</summary>
     private static string? ReadBaseRef(NodeRunContext context) =>
         context.Inputs.TryGetValue("baseRef", out var v) && v.ValueKind == JsonValueKind.String && !string.IsNullOrWhiteSpace(v.GetString())
-            ? v.GetString()
+            ? v.GetString()!.Trim()
             : null;
 
     /// <summary>Read the optional <c>baseRefFromSession</c> input — true ONLY when the launch projection set <c>baseRef</c> from a SESSION-inherited prior branch (a transient branch a merged PR can delete). Marks the primary ref SOFT so the clone falls back to the default branch if it was pruned. An author-pinned baseRef never carries this ⇒ stays HARD (fail loud if gone). Absent / non-true → false.</summary>
diff --git a/backend/tests/CodeSpace.UnitTests/Workflows/AgentCodeNodeTests.cs b/backend/tests/CodeSpace.UnitTests/Workflows/AgentCodeNodeTests.cs
index eeb97aba6..b0f34a4f3 100644
--- a/backend/tests/CodeSpace.UnitTests/Workflows/AgentCodeNodeTests.cs
+++ b/backend/tests/CodeSpace.UnitTests/Workflows/AgentCodeNodeTests.cs
@@ -167,6 +167,21 @@ public async Task Base_ref_input_clones_the_single_repo_at_that_ref()
         primary.RefSoftFallback.ShouldBeFalse("a baseRef with NO baseRefFromSession marker is HARD — an author-pinned ref fails loud if gone, never silently rewritten");
     }
 
+    [Fact]
+    public async Task Base_ref_input_trims_accidental_surrounding_whitespace()
+    {
+        var inputs = new Dictionary<string, JsonElement>
+        {
+            ["repositoryId"] = Str(Guid.NewGuid().ToString()),
+            ["baseRef"] = Str("  release/2.x "),
+        };
+
+        var result = await new AgentCodeNode().RunAsync(BuildContext(RequiredConfig(), resume: null, inputs), CancellationToken.None);
+        var task = JsonSerializer.Deserialize<AgentTask>(result.SuspendUntil!.Payload, AgentJson.Options)!;
+
+        task.Workspace!.Repositories.Single().Ref.ShouldBe("release/2.x");
+    }
+
     [Fact]
     public async Task A_session_base_ref_marks_the_primary_soft_so_a_pruned_branch_falls_back()
     {
diff --git a/frontend/src/components/workflows/AgentCodeInspector.tsx b/frontend/src/components/workflows/AgentCodeInspector.tsx
index dba360d99..29541c8ad 100644
--- a/frontend/src/components/workflows/AgentCodeInspector.tsx
+++ b/frontend/src/components/workflows/AgentCodeInspector.tsx
@@ -174,6 +174,7 @@ export function AgentCodeInspector({ config, inputs, onConfigChange, onInputsCha
             repositoryId={repositoryId}
             relatedRepositories={inputs.relatedRepositories}
             drafts={inputs.workspaceRepoDrafts}
+            suggestions={suggestions}
             onChange={(next) => onInputsChange({
               ...inputs,
               repositoryId: next.repositoryId,
diff --git a/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.test.tsx b/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.test.tsx
new file mode 100644
index 000000000..36c1023f3
--- /dev/null
+++ b/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.test.tsx
@@ -0,0 +1,39 @@
+import { fireEvent, render, screen } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+
+import type { ScopeSuggestion } from "../scope-introspection";
+import { RepositoryWorkspacePicker } from "./RepositoryWorkspacePicker";
+
+vi.mock("@/hooks/use-projects", () => ({ useProjects: () => ({ data: [] }) }));
+vi.mock("@/hooks/use-repositories", () => ({ useRepositories: () => ({ data: [] }) }));
+vi.mock("../VariablePickerInput", () => ({
+  VariablePickerInput: ({ value, onChange, placeholder }: { value: string; onChange: (next: string) => void; placeholder?: string }) => (
+    <input aria-label={placeholder} value={value} onChange={(event) => onChange(event.target.value)} />
+  ),
+}));
+
+const suggestions: ScopeSuggestion[] = [{ path: "trigger.repositoryId", label: "trigger.repositoryId", category: "trigger" }];
+
+describe("RepositoryWorkspacePicker expression mode", () => {
+  it("opens in Expression mode for a repository reference and edits only the primary repository id", () => {
+    const onChange = vi.fn();
+    render(<RepositoryWorkspacePicker repositoryId="{{trigger.repositoryId}}" relatedRepositories={[{ repositoryId: "related-1" }]} drafts={undefined} suggestions={suggestions} onChange={onChange} />);
+
+    expect(screen.getByRole("button", { name: "Expression" })).toHaveAttribute("data-active", "true");
+    const expression = screen.getByRole("textbox", { name: "Type @ to reference an input or step output" });
+    fireEvent.change(expression, { target: { value: "{{trigger.otherRepositoryId}}" } });
+
+    expect(onChange).toHaveBeenCalledWith({
+      repositoryId: "{{trigger.otherRepositoryId}}",
+      relatedRepositories: [{ repositoryId: "related-1", access: "read" }],
+      workspaceRepoDrafts: undefined,
+    });
+  });
+
+  it("keeps the repository picker in Pick mode for a literal id", () => {
+    render(<RepositoryWorkspacePicker repositoryId="repo-1" relatedRepositories={undefined} drafts={undefined} suggestions={suggestions} onChange={vi.fn()} />);
+
+    expect(screen.getByRole("button", { name: "Pick" })).toHaveAttribute("data-active", "true");
+    expect(screen.getByTestId("workspace-primary-row")).toBeInTheDocument();
+  });
+});
diff --git a/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.tsx b/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.tsx
index e9b976bd6..430472987 100644
--- a/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.tsx
+++ b/frontend/src/components/workflows/selectors/RepositoryWorkspacePicker.tsx
@@ -10,6 +10,8 @@ import {
   type WorkspaceReposEmit,
 } from "@/lib/nodeRepoWorkspace";
 
+import type { ScopeSuggestion } from "../scope-introspection";
+import { VariablePickerInput } from "../VariablePickerInput";
 import { SearchSelect } from "./SearchSelect";
 
 /**
@@ -31,10 +33,11 @@ interface RepositoryWorkspacePickerProps {
   relatedRepositories: unknown;
   /** In-progress rows (blank ids) the persisted shape cannot hold — see {@link writeWorkspaceRepos}. */
   drafts: unknown;
+  suggestions?: ScopeSuggestion[];
   onChange: (next: WorkspaceReposEmit) => void;
 }
 
-export function RepositoryWorkspacePicker({ repositoryId, relatedRepositories, drafts, onChange }: RepositoryWorkspacePickerProps) {
+export function RepositoryWorkspacePicker({ repositoryId, relatedRepositories, drafts, suggestions, onChange }: RepositoryWorkspacePickerProps) {
   const rows = useMemo(
     () => readWorkspaceRepos(repositoryId, relatedRepositories, drafts),
     [repositoryId, relatedRepositories, drafts],
@@ -47,6 +50,12 @@ export function RepositoryWorkspacePicker({ repositoryId, relatedRepositories, d
 
   // Per-row project narrowing — UI aid only, never persisted. Keyed by row index; reset on reorder.
   const [draftProjectByIndex, setDraftProjectByIndex] = useState<Map<number, string>>(new Map());
+  const [mode, setMode] = useState<"pick" | "expr">(() => repositoryId.includes("{{") ? "expr" : "pick");
+  const [seenRepositoryId, setSeenRepositoryId] = useState(repositoryId);
+  if (repositoryId !== seenRepositoryId) {
+    setSeenRepositoryId(repositoryId);
+    setMode(repositoryId.includes("{{") ? "expr" : "pick");
+  }
 
   const projectForRow = (idx: number, row: WorkspaceRepoRow): string => {
     const draft = draftProjectByIndex.get(idx);
@@ -56,6 +65,18 @@ export function RepositoryWorkspacePicker({ repositoryId, relatedRepositories, d
   };
 
   const emit = (next: WorkspaceRepoRow[]) => onChange(writeWorkspaceRepos(next));
+  const emitRepositoryId = (next: string) => {
+    const related = rows.slice(1).map((row) => ({
+      repositoryId: row.repositoryId,
+      access: row.access,
+      ...(row.alias.trim() !== "" ? { alias: row.alias.trim() } : {}),
+    }));
+    onChange({
+      repositoryId: next || undefined,
+      relatedRepositories: related.length > 0 ? related : undefined,
+      workspaceRepoDrafts: rows.some((row) => row.repositoryId === "") ? rows : undefined,
+    });
+  };
 
   const addRow = () => emit([...rows, { repositoryId: "", alias: "", access: "read" }]);
 
@@ -94,29 +115,48 @@ export function RepositoryWorkspacePicker({ repositoryId, relatedRepositories, d
 
   return (
     <div className="wf-relrepo" data-testid="repository-workspace-picker">
-      {rows.map((row, idx) => (
-        <RepoRow
-          key={idx}
-          row={row}
-          isPrimary={idx === 0}
-          projectId={projectForRow(idx, row)}
-          projects={projectRows}
-          repositories={repoRows}
-          onPickProject={(projectId) => pickProjectForRow(idx, projectId)}
-          onPickRepo={(id) => updateRow(idx, { repositoryId: id })}
-          onChangeAlias={(alias) => updateRow(idx, { alias })}
-          onChangeAccess={(access) => updateRow(idx, { access })}
-          onMakePrimary={() => makePrimary(idx)}
-          onRemove={() => removeRow(idx)}
-        />
-      ))}
+      {suggestions && suggestions.length > 0 && (
+        <div className="wf-dualmode">
+          <div className="wf-dualmode-head" role="group" aria-label="Value mode">
+            <button type="button" className="wf-dualmode-toggle" data-active={mode === "pick"} onClick={() => setMode("pick")}>Pick</button>
+            <button type="button" className="wf-dualmode-toggle" data-active={mode === "expr"} onClick={() => setMode("expr")}>Expression</button>
+          </div>
+          {mode === "expr" && (
+            <VariablePickerInput
+              value={repositoryId}
+              onChange={emitRepositoryId}
+              suggestions={suggestions}
+              placeholder="Type @ to reference an input or step output"
+            />
+          )}
+        </div>
+      )}
+      {rows.map((row, idx) => {
+        if (idx === 0 && suggestions && suggestions.length > 0 && mode === "expr") return null;
+        return (
+          <RepoRow
+            key={idx}
+            row={row}
+            isPrimary={idx === 0}
+            projectId={projectForRow(idx, row)}
+            projects={projectRows}
+            repositories={repoRows}
+            onPickProject={(projectId) => pickProjectForRow(idx, projectId)}
+            onPickRepo={(id) => updateRow(idx, { repositoryId: id })}
+            onChangeAlias={(alias) => updateRow(idx, { alias })}
+            onChangeAccess={(access) => updateRow(idx, { access })}
+            onMakePrimary={() => makePrimary(idx)}
+            onRemove={() => removeRow(idx)}
+          />
+        );
+      })}
 
-      <button type="button" className="wf-relrepo-add" onClick={addRow}>
+      {(mode === "pick" || !suggestions || suggestions.length === 0) && <button type="button" className="wf-relrepo-add" onClick={addRow}>
         <Ic.Plus size={11} />
         <span>{rows.length === 0 ? "Add a repository" : "Add another repository"}</span>
-      </button>
+      </button>}
 
-      {rows.length === 0 && (
+      {rows.length === 0 && mode === "pick" && (
         <div className="wf-relrepo-hint">
           <span aria-hidden="true">ⓘ</span>
           <span>No repository — an analysis-only run.</span>