fix(core): resolve V2 session runner test failures after upstream sync

- gate get_tool_schema meta-tool on deferred tool presence in registry
- fix missing yield* in llm.ts publish settlement fiber
- add spawn_agent to location-layer builtin test expectations
- fix compaction select head duplication when splitPrefix is present
- adjust session-runner compaction test thresholds for L4/L5 levels
- remove leftover debug appendFileSync calls

Author: edy

packages/core/src/session/compaction.ts

@@ -180,7 +180,7 @@ const select = (
     split = index
   }
   return {
-    head: [...conversation.slice(0, split), splitPrefix].filter(Boolean).join("\n\n"),
+    head: [...conversation.slice(0, splitPrefix ? split - 1 : split), splitPrefix].filter(Boolean).join("\n\n"),
     recent: [splitSuffix, ...conversation.slice(split)].filter(Boolean).join("\n\n"),
   }
 }
@@ -281,6 +281,7 @@ export const make = (dependencies: Dependencies) => {
     const usedTokens = estimate({ system: input.request.system, messages: input.request.messages, tools: input.request.tools })
     const usageRatio = usedTokens / context
     const level = ContextLevels.computeLevel(usageRatio, config.levels)
+
     if (level <= 1) return { compacted: false, request: input.request }
     // L2 — Snip Compact: drop oldest messages (in-memory only, no durable event)
     if (level === 2) {

packages/core/src/session/runner/llm.ts

@@ -296,6 +296,7 @@ const layer = Layer.effect(
         toolChoice: isLastStep ? "none" : undefined,
         generation: maxTokensOverride === undefined ? undefined : { maxTokens: maxTokensOverride },
       })
+
       const degradation = yield* compaction.degrade({ sessionID: session.id, entries, model, request })
       const activeRequest = degradation.request
       if (degradation.compacted)
@@ -358,7 +359,7 @@ const layer = Layer.effect(
               Effect.gen(function* () {
                 const preResult = yield* hooks.runPreToolUse({ name: event.name, input: event.input })
                 if (preResult.action === "deny") {
-                  return publish(
+                  return yield* publish(
                     LLMEvent.toolResult({
                       id: event.id,
                       name: event.name,
@@ -367,7 +368,7 @@ const layer = Layer.effect(
                   )
                 }
                 if (preResult.action === "skip") {
-                  return publish(
+                  return yield* publish(
                     LLMEvent.toolResult({
                       id: event.id,
                       name: event.name,
@@ -401,7 +402,7 @@ const layer = Layer.effect(
                   postResult.action === "continue" && "additionalContext" in postResult && postResult.additionalContext
                     ? appendContextNote(settlement.result, postResult.additionalContext)
                     : settlement.result
-                return publish(
+                return yield* publish(
                   LLMEvent.toolResult({
                     id: event.id,
                     name: event.name,

packages/core/src/tool/registry.ts

@@ -170,6 +170,7 @@ const registryLayer = Layer.effect(
         const activated = yield* Ref.get(activatedToolsRef)
         const touched = yield* Ref.get(touchedPathsRef)
         const defs: Array<ToolDefinition> = []
+        let hasDeferred = false
         for (const [name, registration] of registrations) {
           const tool = registration.tool
           const deferred = isDeferred(tool)
@@ -185,6 +186,7 @@ const registryLayer = Layer.effect(
             if (!shouldActivate) continue
           }
           if (deferred && !activated.has(name)) {
+            hasDeferred = true
             const fullDef = definition(name, tool)
             defs.push(
               new ToolDefinition({
@@ -197,20 +199,22 @@ const registryLayer = Layer.effect(
           }
           defs.push(definition(name, tool))
         }
-        defs.push(
-          new ToolDefinition({
-            name: GET_TOOL_SCHEMA,
-            description:
-              'Get the full schema (including input/output parameters) for a deferred tool. Input: { "tool_name": "<name>" }',
-            inputSchema: {
-              type: "object",
-              properties: {
-                tool_name: { type: "string", description: "Name of the tool to get the full schema for" },
+        if (hasDeferred) {
+          defs.push(
+            new ToolDefinition({
+              name: GET_TOOL_SCHEMA,
+              description:
+                'Get the full schema (including input/output parameters) for a deferred tool. Input: { "tool_name": "<name>" }',
+              inputSchema: {
+                type: "object",
+                properties: {
+                  tool_name: { type: "string", description: "Name of the tool to get the full schema for" },
+                },
+                required: ["tool_name"],
               },
-              required: ["tool_name"],
-            },
-          }),
-        )
+            }),
+          )
+        }
         return {
           definitions: defs,
           settle: (input) => {

packages/core/test/location-layer.test.ts

@@ -114,6 +114,7 @@ describe("LocationServiceMap", () => {
             "question",
             "read",
             "skill",
+            "spawn_agent",
             "todowrite",
             "webfetch",
             "websearch",
@@ -132,6 +133,7 @@ describe("LocationServiceMap", () => {
             "question",
             "read",
             "skill",
+            "spawn_agent",
             "todowrite",
             "webfetch",
             "websearch",

packages/core/test/session-runner.test.ts

@@ -101,7 +101,7 @@ const replacementModel = Model.make({ id: "replacement", provider: "fake", route
 const compactModel = Model.make({
   id: "compact",
   provider: "fake",
-  route: OpenAIChat.route.with({ limits: { context: 4_000, output: 50 } }),
+  route: OpenAIChat.route.with({ limits: { context: 2_300, output: 50 } }),
 })
 const recoveryModel = Model.make({
   id: "recovery",
@@ -1090,7 +1090,7 @@ describe("SessionRunnerLLM", () => {
       response = fragmentFixture("text", "text-first", ["Earlier answer"]).completeEvents
       yield* session.prompt({
         sessionID,
-        prompt: Prompt.make({ text: "Earlier question ".repeat(180) }),
+        prompt: Prompt.make({ text: "Earlier question ".repeat(188) }),
         resume: false,
       })
       yield* session.resume(sessionID)
@@ -1103,7 +1103,7 @@ describe("SessionRunnerLLM", () => {
       ]
       yield* session.prompt({
         sessionID,
-        prompt: Prompt.make({ text: "Recent exact request ".repeat(180) }),
+        prompt: Prompt.make({ text: "Recent exact request ".repeat(188) }),
         resume: false,
       })
       yield* session.resume(sessionID)
@@ -1129,7 +1129,7 @@ describe("SessionRunnerLLM", () => {
       ]
       yield* session.prompt({
         sessionID,
-        prompt: Prompt.make({ text: "Newest exact request ".repeat(180) }),
+        prompt: Prompt.make({ text: "Newest exact request ".repeat(188) }),
         resume: false,
       })
       yield* session.resume(sessionID)