From cf98ca55c9efe23868953187ccd3a0ce90ba1bb5 Mon Sep 17 00:00:00 2001
From: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>
Date: Wed, 26 Aug 2026 11:21:14 -0500
Subject: [PATCH] fix(core): allow non-letter tool name prefixes (#45317)

---
 packages/core/src/tool.ts                     |  4 +-
 .../test/session-runner-tool-registry.test.ts | 67 ++++++++++++++++++-
 2 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/packages/core/src/tool.ts b/packages/core/src/tool.ts
index 13e85ee9d15..a31352d4e51 100644
--- a/packages/core/src/tool.ts
+++ b/packages/core/src/tool.ts
@@ -271,12 +271,12 @@ function schemaMakeError(error: unknown) {
 }
 
 const validateName = (name: string) =>
-  /^[A-Za-z][A-Za-z0-9_-]{0,63}$/.test(name)
+  /^[A-Za-z0-9_-]{1,64}$/.test(name)
     ? Effect.void
     : Effect.fail(new RegistrationError({ name, message: `Invalid tool name: ${name}` }))
 
 const validateNamespace = (namespace: string) =>
-  namespace.split(".").every((segment) => /^[A-Za-z][A-Za-z0-9_-]{0,63}$/.test(segment))
+  namespace.split(".").every((segment) => /^[A-Za-z0-9_-]{1,64}$/.test(segment))
     ? Effect.void
     : Effect.fail(
         new RegistrationError({
diff --git a/packages/core/test/session-runner-tool-registry.test.ts b/packages/core/test/session-runner-tool-registry.test.ts
index 7c6324345c6..69b8d936006 100644
--- a/packages/core/test/session-runner-tool-registry.test.ts
+++ b/packages/core/test/session-runner-tool-registry.test.ts
@@ -85,8 +85,10 @@ describe("Tool", () => {
   it.effect("rejects invalid and colliding normalized names", () =>
     Effect.gen(function* () {
       const service = yield* Tool.Service
-      const invalid = yield* transform(service, { "123": make() }, { codemode: false }).pipe(Effect.flip)
-      expect(invalid.message).toBe("Invalid tool name: 123")
+      for (const name of ["", "x".repeat(65)]) {
+        const invalid = yield* transform(service, { [name]: make() }, { codemode: false }).pipe(Effect.flip)
+        expect(invalid.message).toBe(`Invalid tool name: ${name}`)
+      }
 
       const collision = yield* transform(service, { "echo.tool": make(), echo_tool: make() }, { codemode: false }).pipe(
         Effect.flip,
@@ -96,6 +98,67 @@ describe("Tool", () => {
     }),
   )
 
+  it.effect("executes native tools without requiring letter-leading names or namespace segments", () =>
+    Effect.gen(function* () {
+      const service = yield* Tool.Service
+      yield* transform(
+        service,
+        { "2d_get_scene": make(), "123": make(), _lookup: make(), "-lookup": make() },
+        { codemode: false },
+      )
+      yield* transform(service, { "2d_get_scene": make() }, { namespace: "123._private.-tools", codemode: false })
+
+      const snapshot = yield* service.snapshot()
+      expect(snapshot.definitions.map((tool) => tool.name)).toEqual([
+        "-lookup",
+        "123",
+        "123__private_-tools_2d_get_scene",
+        "2d_get_scene",
+        "_lookup",
+        "execute",
+      ])
+      for (const name of ["2d_get_scene", "123", "_lookup", "-lookup", "123__private_-tools_2d_get_scene"]) {
+        expect((yield* snapshot.execute(call(name))).output).toEqual({ text: name })
+      }
+    }),
+  )
+
+  it.effect("executes Code Mode tools without requiring letter-leading names or namespace segments", () =>
+    Effect.gen(function* () {
+      const service = yield* Tool.Service
+      yield* transform(service, { "2d_get_scene": make(), "123": make(), _lookup: make(), "-lookup": make() })
+      yield* transform(service, { "2d_get_scene": make() }, { namespace: "123._private.-tools", codemode: true })
+
+      const snapshot = yield* service.snapshot()
+      expect(snapshot.definitions.map((tool) => tool.name)).toEqual(["execute"])
+      expect(snapshot.codeModeCatalog?.map((tool) => tool.path)).toEqual([
+        "-lookup",
+        "123",
+        "123._private.-tools.2d_get_scene",
+        "2d_get_scene",
+        "_lookup",
+      ])
+      const result = yield* snapshot.execute({
+        ...call("execute"),
+        call: {
+          type: "tool-call",
+          id: "call-nonletter-names",
+          name: "execute",
+          input: {
+            code: `const results = await Promise.all([
+              tools["2d_get_scene"]({ text: "digit" }),
+              tools["123"]({ text: "numeric" }),
+              tools._lookup({ text: "underscore" }),
+              tools["-lookup"]({ text: "hyphen" }),
+              tools["123"]._private["-tools"]["2d_get_scene"]({ text: "namespaced" }),
+            ]); return results.map(result => result.text).join(",");`,
+          },
+        },
+      })
+      expect(result.content).toEqual([{ type: "text", text: "digit,numeric,underscore,hyphen,namespaced" }])
+    }),
+  )
+
   it.effect("validates a registration batch before installing any tools", () =>
     Effect.gen(function* () {
       const service = yield* Tool.Service