From b4c74723d1a3072551e38d1bd3b5098e3872a51d Mon Sep 17 00:00:00 2001
From: Julius Marminge <julius0216@outlook.com>
Date: Thu, 26 Feb 2026 10:12:57 -0800
Subject: [PATCH] fix C051

---
 .plans/16c-pr89-remediation-checklist.md      |  4 +--
 .../Layers/ProviderSessionDirectory.test.ts   | 33 +++++++++++++++++++
 .../Layers/ProviderSessionDirectory.ts        |  5 ++-
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/.plans/16c-pr89-remediation-checklist.md b/.plans/16c-pr89-remediation-checklist.md
index 70203677e2ba9a45839a80490f51ca5271e8edf6..c77b59ddaab1f2e66325ebf4e7795a0981ac85f0 100644
--- a/.plans/16c-pr89-remediation-checklist.md
+++ b/.plans/16c-pr89-remediation-checklist.md
@@ -378,8 +378,8 @@ Counts: active `51` (`valid=33`, `partially-valid=18`), closed-invalid `6`
   - Threads: PRRT_kwDORLtfbc5wiLhY
   - Audit note: ProviderSessionDirectory upsert remains read-merge-write without concurrency control.
 
-- [ ] `C051` Using `??` for `providerThreadId` and `adapterKey` makes it impossible to clear these fields by passing `null`, since `null ?? existing` evaluates to `existing`. Consider using explicit `undefined` checks (like `resumeCursor` does) if clearing should be supported. <details> <summary>🚀 Reply "<strong>fix it for me</strong>" or copy this <strong>AI Prompt</strong> for your agent:</summary>
-  - Status: `TODO`
+- [x] `C051` Using `??` for `providerThreadId` and `adapterKey` makes it impossible to clear these fields by passing `null`, since `null ?? existing` evaluates to `existing`. Consider using explicit `undefined` checks (like `resumeCursor` does) if clearing should be supported. <details> <summary>🚀 Reply "<strong>fix it for me</strong>" or copy this <strong>AI Prompt</strong> for your agent:</summary>
+  - Status: `DONE`
   - Verdict: `partially-valid`
   - Severity: `Low`
   - Area: `Other`
diff --git a/apps/server/src/provider/Layers/ProviderSessionDirectory.test.ts b/apps/server/src/provider/Layers/ProviderSessionDirectory.test.ts
index 90fa94032b1fc22789fb3b3055e8c0029eb9c83e..a892c6f0fc7c82af984dbb1bb23c2187657f9c99 100644
--- a/apps/server/src/provider/Layers/ProviderSessionDirectory.test.ts
+++ b/apps/server/src/provider/Layers/ProviderSessionDirectory.test.ts
@@ -154,6 +154,39 @@ it.layer(makeDirectoryLayer(SqlitePersistenceMemory))("ProviderSessionDirectoryL
       }
     }));
 
+  it("clears providerThreadId when explicitly set to null", () =>
+    Effect.gen(function* () {
+      const directory = yield* ProviderSessionDirectory;
+      const runtimeRepository = yield* ProviderSessionRuntimeRepository;
+
+      const sessionId = ProviderSessionId.makeUnsafe("sess-clear-provider-thread-id");
+      const threadId = ThreadId.makeUnsafe("thread-clear-provider-thread-id");
+      const providerThreadId = ProviderThreadId.makeUnsafe("provider-thread-to-clear");
+
+      yield* directory.upsert({
+        sessionId,
+        provider: "codex",
+        threadId,
+        adapterKey: "custom-adapter",
+        providerThreadId,
+      });
+
+      yield* directory.upsert({
+        sessionId,
+        provider: "codex",
+        providerThreadId: null,
+      });
+
+      const runtime = yield* runtimeRepository.getBySessionId({
+        providerSessionId: sessionId,
+      });
+      assert.equal(Option.isSome(runtime), true);
+      if (Option.isSome(runtime)) {
+        assert.equal(runtime.value.providerThreadId, null);
+        assert.equal(runtime.value.adapterKey, "custom-adapter");
+      }
+    }));
+
   it("rehydrates persisted mappings across layer restart", () =>
     Effect.gen(function* () {
       const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "t3-provider-directory-"));
diff --git a/apps/server/src/provider/Layers/ProviderSessionDirectory.ts b/apps/server/src/provider/Layers/ProviderSessionDirectory.ts
index 700f8b50914af68602a6046b5e463918e1d39dc3..1b096e91e0edc686b7243d6a9cea28d7c2fbd3cf 100644
--- a/apps/server/src/provider/Layers/ProviderSessionDirectory.ts
+++ b/apps/server/src/provider/Layers/ProviderSessionDirectory.ts
@@ -108,7 +108,10 @@ const makeProviderSessionDirectory = Effect.gen(function* () {
         threadId: resolvedThreadId,
         providerName: binding.provider,
         adapterKey: binding.adapterKey ?? existingRuntime?.adapterKey ?? binding.provider,
-        providerThreadId: binding.providerThreadId ?? existingRuntime?.providerThreadId ?? null,
+        providerThreadId:
+          binding.providerThreadId !== undefined
+            ? binding.providerThreadId
+            : (existingRuntime?.providerThreadId ?? null),
         status: binding.status ?? existingRuntime?.status ?? "running",
         lastSeenAt: now,
         resumeCursor:
-- 
2.54.0