fix(runtime): pass the target runtime dir from install and sync too

openspec/changes/agent-claude-credentials-source-install-sync-2026-08-07-13-47/.openspec.yaml

@@ -0,0 +1,2 @@
+schema: spec-driven
+created: 2026-08-07

openspec/changes/agent-claude-credentials-source-install-sync-2026-08-07-13-47/notes.md

@@ -0,0 +1,51 @@
+# agent-claude-credentials-source-install-sync-2026-08-07-13-47 (minimal / T1)
+
+Branch: `agent/claude/credentials-source-install-sync-2026-08-07-13-47`
+
+Completes #139, whose review raised a HIGH that its own merge did not carry.
+
+## The HIGH
+
+#139 made the self-overlay guard opt-in via `options.runtimeDir`. `launch.ts`
+passes it; `cue install` and `cue sync` do not — and both rebuild runtimes
+through `prepareRuntime()`. So either command run from inside a cue session
+still took `CLAUDE_CONFIG_DIR` — its own runtime dir — as the overlay source and
+reproduced #137's self-referential symlinks. The guard was off exactly where the
+materialization happens.
+
+Both callers now pass the dir they are about to write:
+
+- `install.ts` — `runtimeDirFor(profile.name, agent)`, matching
+  `prepareRuntime`'s own `runtimeKey ?? profile.name` default.
+- `sync.ts` — `runtimeDirFor(key, agent)`; `key` is already the `runtimeKey`
+  passed to `prepareRuntime` two lines below.
+
+## Why it is a separate PR
+
+The fix was committed on #139's branch as `91c6601d` but never reached the
+remote before the PR merged — main got only the narrowing commit. Verified after
+the fact on `origin/main`: `isSelfOverlaySource` present (3 hits), `runtimeDir:`
+in install.ts / sync.ts absent (0). Cherry-picked here onto the post-#139 main.
+
+## Also carried
+
+The comment on #139's LOW finding, explaining why the wiring test asserts
+`not.toBe(target)` rather than a concrete fall-through path: `os.homedir()`
+reads the passwd entry, not `$HOME`, so a temp-HOME fixture does not pin the
+branch (measured — it still resolved the real `~/.claude`). No fall-through
+branch can return the target, so the assertion holds on any machine and stays
+mutation-proof.
+
+## Verification
+
+- `bun run typecheck` — clean.
+- `bun run lint` — warnings pre-existing; zero in the touched files.
+- `bun test src/lib/runtime-install.test.ts` — 23 pass / 0 fail.
+- `bun test` (full), branch vs base in the same worktree and shell — failing set
+  compared both directions.
+
+## Cleanup
+
+- [ ] Run: `gx branch finish --branch agent/claude/credentials-source-install-sync-2026-08-07-13-47 --base main --via-pr --gate-review --review-provider claude --wait-for-merge --cleanup`
+- [ ] Record PR URL + `MERGED` state in the completion handoff.
+- [ ] Confirm sandbox worktree is gone (`git worktree list`, `git branch -a`).

src/commands/install.ts

@@ -246,7 +246,13 @@ async function materializeProfile(profileName: string, agent: AnyAgent, force: b
       profile,
       agent,
       credentialsSource: agent === "claude-code"
-        ? await resolveClaudeCredentialsSource({ healFromRuntime: false })
+        ? await resolveClaudeCredentialsSource({
+          healFromRuntime: false,
+          // The dir prepareRuntime() is about to write — it defaults
+          // runtimeKey to profile.name. Passing it keeps a `cue install` run
+          // from inside a cue session from overlaying that runtime onto itself.
+          runtimeDir: runtimeDirFor(profile.name, agent),
+        })
         : undefined,
     });
     return { profile: profileName, agent, targetDir: result.runtimeDir, status: result.rebuilt ? "rebuilt" : "cached" };

src/commands/sync.ts

@@ -34,6 +34,7 @@ import {
   prepareRuntime,
   resolveClaudeCredentialsSource,
   runtimeAgentSubdir,
+  runtimeDirFor,
 } from "../lib/runtime-install";
 
 const RUNTIME_ROOT = join(configDir(), "runtime");
@@ -143,7 +144,13 @@ export async function run(args: string[]): Promise<number> {
           runtimeKey: key,
           credentialsSource:
             agent === "claude-code"
-              ? await resolveClaudeCredentialsSource({ healFromRuntime: false })
+              // `key` is the runtimeKey passed above, so this is exactly the
+              // dir this iteration will write — a `cue sync` run from inside a
+              // cue session must not overlay that runtime onto itself.
+              ? await resolveClaudeCredentialsSource({
+                healFromRuntime: false,
+                runtimeDir: runtimeDirFor(key, agent),
+              })
               : undefined,
         });
         rebuilt = rebuilt || out.rebuilt;

src/lib/runtime-install.test.ts

@@ -118,6 +118,11 @@ describe("pickClaudeCredentialsSource", () => {
     else process.env.CLAUDE_CONFIG_DIR = original;
   });
 
+  // Asserted as "not the target" rather than a concrete path: which fall-through
+  // branch wins (~/.claude, or an authmux profile) depends on the machine, but
+  // none of them can return `target` — only the rejected `CLAUDE_CONFIG_DIR`
+  // early-return could. `os.homedir()` reads the passwd entry, not $HOME, so
+  // there is no cheap way to pin the branch without a test-only injection point.
   test("refuses CLAUDE_CONFIG_DIR when it is the dir being rebuilt", async () => {
     process.env.CLAUDE_CONFIG_DIR = target;
     expect(await pickClaudeCredentialsSource({ runtimeDir: target })).not.toBe(target);