fix(#2702): workstream config-get inherits absent keys from root config (#2833)

* test(#2702): failing-first regression for workstream config-get root inheritance

* fix(#2702): workstream config-get inherits absent keys from root config

* fix(#2702): root inheritance wins over --default; gate on GSD_WORKSTREAM not path (review)

* test(#2702): make GSD_PROJECT test exit-safe (--default sentinel, no error path)

* docs(changeset): #2702 workstream config-get root inheritance

* docs(changeset): backfill #2702 PR number to 2833

src/config.cts

@@ -18,7 +18,7 @@ const { CONFIG_DEFAULTS } = configLoader;
 import { platformWriteSync, platformEnsureDir } from './shell-command-projection.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import planningWorkspace = require('./planning-workspace.cjs');
-const { planningDir, withPlanningLock } = planningWorkspace;
+const { planningDir, planningRoot, withPlanningLock } = planningWorkspace;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import modelProfiles = require('./model-profiles.cjs');
 const { VALID_PROFILES, getAgentToModelMapForProfile, formatAgentToModelMapAsTable } = modelProfiles;
@@ -965,10 +965,15 @@ function cmdConfigGet(cwd: string, keyPath: string | undefined, raw: boolean, de
   try {
     if (fs.existsSync(configPath)) {
       config = JSON.parse(fs.readFileSync(configPath, 'utf-8')) as Record<string, unknown>;
-    } else if (hasDefault) {
-      emitResolvedDefault(kp, defaultValue, raw);
-      return;
     } else {
+      // #2702: when a workstream is active and has no config.json of its own, fall
+      // back to the project ROOT config first — a key the user configured at root is
+      // a real, present value and must inherit (per #1893: a present key wins over
+      // --default). Only when root also misses do --default / schema default apply.
+      // (When no workstream is active, resolveFromRootConfig is a no-op: same file.)
+      const rootVal = resolveFromRootConfig(cwd, kp);
+      if (rootVal.found) { emitResolvedDefault(kp, rootVal.value, raw); return; }
+      if (hasDefault) { emitResolvedDefault(kp, defaultValue, raw); return; }
       const sd = resolveSchemaDefault(cwd, kp);
       if (sd.found) { emitResolvedDefault(kp, sd.value, raw); return; }
       error('No config.json found at ' + configPath, ERROR_REASON.CONFIG_NO_FILE);
@@ -983,6 +988,9 @@ function cmdConfigGet(cwd: string, keyPath: string | undefined, raw: boolean, de
   let current: unknown = config;
   for (const key of keys) {
     if (current === undefined || current === null || typeof current !== 'object') {
+      // #2702: root-config inheritance before --default / schema default (see above).
+      const rootVal = resolveFromRootConfig(cwd, kp);
+      if (rootVal.found) { emitResolvedDefault(kp, rootVal.value, raw); return; }
       if (hasDefault) { emitResolvedDefault(kp, defaultValue, raw); return; }
       const sd = resolveSchemaDefault(cwd, kp);
       if (sd.found) { emitResolvedDefault(kp, sd.value, raw); return; }
@@ -1003,6 +1011,9 @@ function cmdConfigGet(cwd: string, keyPath: string | undefined, raw: boolean, de
   }
 
   if (current === undefined) {
+    // #2702: root-config inheritance before --default / schema default (see above).
+    const rootVal = resolveFromRootConfig(cwd, kp);
+    if (rootVal.found) { emitResolvedDefault(kp, rootVal.value, raw); return; }
     if (hasDefault) { emitResolvedDefault(kp, defaultValue, raw); return; }
     const sd = resolveSchemaDefault(cwd, kp);
     if (sd.found) { emitResolvedDefault(kp, sd.value, raw); return; }
@@ -1020,6 +1031,51 @@ function cmdConfigGet(cwd: string, keyPath: string | undefined, raw: boolean, de
   output(current, raw, String(current));
 }
 
+/**
+ * #2702: resolve a dot-notation key against the project ROOT config
+ * (`.planning/config.json`), ignoring any active workstream scope. Returns
+ * `{found:false}` when the root config is absent, unparseable, or does not
+ * contain the key. This is the inheritance rung `cmdConfigGet` was missing —
+ * when a workstream's own config doesn't set a key, the project root value
+ * must show through (workstream overrides root; it never fully replaces it),
+ * exactly as `loadConfigResolved`'s root+workstream merge already does for
+ * every other config consumer. No-op (found:false) when no workstream is
+ * active, because `planningDir === planningRoot` and the caller already read
+ * that file directly.
+ */
+function resolveFromRootConfig(cwd: string, kp: string): { found: boolean; value: unknown } {
+  // Only meaningful when a workstream is active (GSD_WORKSTREAM set) — that is what
+  // redirects planningDir away from root AND what loadConfigResolved gates root-reading
+  // on. Gating on `process.env.GSD_WORKSTREAM` (not on a planningDir !== planningRoot
+  // path inequality) avoids a false trigger under GSD_PROJECT alone, where planningDir
+  // diverges from planningRoot without a workstream and loadConfigResolved does NOT
+  // inherit root — matching the runtime's own `if (ws)` gate keeps the two surfaces
+  // from diverging on the project-scoped (non-workstream) case.
+  if (!process.env['GSD_WORKSTREAM']) return { found: false, value: undefined };
+  const root = planningRoot(cwd);
+  const rootConfigPath = path.join(root, 'config.json');
+  let rootConfig: Record<string, unknown>;
+  try {
+    if (!fs.existsSync(rootConfigPath)) return { found: false, value: undefined };
+    rootConfig = JSON.parse(fs.readFileSync(rootConfigPath, 'utf-8')) as Record<string, unknown>;
+  } catch {
+    // Unparseable root config → don't inherit (do not let a corrupt root file
+    // change config-get's verdict). Fall through to schema default / error.
+    return { found: false, value: undefined };
+  }
+  let current: unknown = rootConfig;
+  for (const key of kp.split('.')) {
+    if (current === undefined || current === null || typeof current !== 'object') {
+      return { found: false, value: undefined };
+    }
+    current = Object.prototype.hasOwnProperty.call(current, key)
+      ? (current as Record<string, unknown>)[key]
+      : undefined;
+  }
+  if (current === undefined) return { found: false, value: undefined };
+  return { found: true, value: current };
+}
+
 /**
  * Command to set the model profile in the config file.
  *