diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index fb382530291..5095a8bb768 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -97,7 +97,8 @@ export namespace SessionCompaction {
     auto: boolean
   }) {
     const userMessage = input.messages.findLast((m) => m.info.id === input.parentID)!.info as MessageV2.User
-    const agent = await Agent.get("compaction")
+    const msgAgent = await Agent.get(userMessage.agent)
+    const agent = await Agent.get(msgAgent.options.agents?.compaction ?? "compaction")
     const model = agent.model
       ? await Provider.getModel(agent.model.providerID, agent.model.modelID)
       : await Provider.getModel(userMessage.model.providerID, userMessage.model.modelID)
diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index d651308032e..4e6b58801d8 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -67,13 +67,16 @@ export namespace LLM {
     const isCodex = provider.id === "openai" && auth?.type === "oauth"
 
     const system = []
+    const customSystem = input.agent.options.system
+      ? await SystemPrompt.environment(input.model, input.agent.options.system)
+      : input.system
     system.push(
       [
         // use agent prompt otherwise provider prompt
         // For Codex sessions, skip SystemPrompt.provider() since it's sent via options.instructions
         ...(input.agent.prompt ? [input.agent.prompt] : isCodex ? [] : SystemPrompt.provider(input.model)),
         // any custom prompt passed into this call
-        ...input.system,
+        ...customSystem,
         // any custom prompt from last user message
         ...(input.user.system ? [input.user.system] : []),
       ]
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 23ca473541c..ac610d20d64 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -1773,7 +1773,24 @@ NOTE: At any point in time through this workflow you should feel free to ask the
     const subtaskParts = firstRealUser.parts.filter((p) => p.type === "subtask") as MessageV2.SubtaskPart[]
     const hasOnlySubtaskParts = subtaskParts.length > 0 && firstRealUser.parts.every((p) => p.type === "subtask")
 
-    const agent = await Agent.get("title")
+    const msgAgent = await Agent.get(firstRealUser.info.agent)
+    const titleAgent = msgAgent.options.agents?.title ?? "title"
+    if (titleAgent === "none") {
+      const textPart = firstRealUser.parts.find((part) => part.type === "text" && !part.synthetic) as
+        | MessageV2.TextPart
+        | undefined
+      const text = textPart?.text?.trim()
+      if (!text) return
+      const title = text.length > 50 ? text.slice(0, 50) + "..." : text
+      return Session.update(
+        input.session.id,
+        (draft) => {
+          draft.title = title
+        },
+        { touch: false },
+      )
+    }
+    const agent = await Agent.get(titleAgent)
     if (!agent) return
     const model = await iife(async () => {
       if (agent.model) return await Provider.getModel(agent.model.providerID, agent.model.modelID)
diff --git a/packages/opencode/src/session/summary.ts b/packages/opencode/src/session/summary.ts
index 91a520a9bdf..2932d9154b4 100644
--- a/packages/opencode/src/session/summary.ts
+++ b/packages/opencode/src/session/summary.ts
@@ -132,8 +132,15 @@ export namespace SessionSummary {
 
     const textPart = msgWithParts.parts.find((p) => p.type === "text" && !p.synthetic) as MessageV2.TextPart
     if (textPart && !userMsg.summary?.title) {
-      const agent = await Agent.get("title")
-      if (!agent) return
+      const msgAgent = await Agent.get(userMsg.agent)
+      const titleAgent = msgAgent.options.agents?.title ?? "title"
+      if (titleAgent === "none") {
+        const title = textPart.text.length > 50 ? textPart.text.slice(0, 50) + "..." : textPart.text
+        userMsg.summary.title = title
+        await Session.updateMessage(userMsg)
+        return
+      }
+      const agent = await Agent.get(titleAgent)
       const stream = await LLM.stream({
         agent,
         user: userMsg,
diff --git a/packages/opencode/src/session/system.ts b/packages/opencode/src/session/system.ts
index d34a086fe44..d84fc590450 100644
--- a/packages/opencode/src/session/system.ts
+++ b/packages/opencode/src/session/system.ts
@@ -24,11 +24,20 @@ export namespace SystemPrompt {
     return [PROMPT_ANTHROPIC_WITHOUT_TODO]
   }
 
-  export async function environment(model: Provider.Model) {
+  export async function environment(
+    model: Provider.Model,
+    options?: { model_id?: boolean; env?: boolean; files?: boolean },
+  ) {
     const project = Instance.project
-    return [
-      [
+    const parts: string[] = []
+
+    if (options?.model_id !== false)
+      parts.push(
         `You are powered by the model named ${model.api.id}. The exact model ID is ${model.providerID}/${model.api.id}`,
+      )
+
+    if (options?.env !== false)
+      parts.push(
         `Here is some useful information about the environment you are running in:`,
         `<env>`,
         `  Working directory: ${Instance.directory}`,
@@ -36,9 +45,14 @@ export namespace SystemPrompt {
         `  Platform: ${process.platform}`,
         `  Today's date: ${new Date().toDateString()}`,
         `</env>`,
+      )
+
+    // files info was disabled during permission rework
+    if (options?.files !== false && false)
+      parts.push(
         `<files>`,
         `  ${
-          project.vcs === "git" && false
+          project.vcs === "git"
             ? await Ripgrep.tree({
                 cwd: Instance.directory,
                 limit: 200,
@@ -46,7 +60,8 @@ export namespace SystemPrompt {
             : ""
         }`,
         `</files>`,
-      ].join("\n"),
-    ]
+      )
+
+    return [parts.join("\n")]
   }
 }
diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index c87add638aa..afdbf9e2dd4 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -41,20 +41,24 @@ export const TaskTool = Tool.define("task", async (ctx) => {
     async execute(params: z.infer<typeof parameters>, ctx) {
       const config = await Config.get()
 
+      // Resolve subagent type through calling agent's mapping
+      const callingAgent = ctx.agent ? await Agent.get(ctx.agent) : undefined
+      const resolvedSubagentType = callingAgent?.options.agents?.[params.subagent_type] ?? params.subagent_type
+
       // Skip permission check when user explicitly invoked via @ or command subtask
       if (!ctx.extra?.bypassAgentCheck) {
         await ctx.ask({
           permission: "task",
-          patterns: [params.subagent_type],
+          patterns: [resolvedSubagentType],
           always: ["*"],
           metadata: {
             description: params.description,
-            subagent_type: params.subagent_type,
+            subagent_type: resolvedSubagentType,
           },
         })
       }
 
-      const agent = await Agent.get(params.subagent_type)
+      const agent = await Agent.get(resolvedSubagentType)
       if (!agent) throw new Error(`Unknown agent type: ${params.subagent_type} is not a valid agent type`)
 
       const hasTaskPermission = agent.permission.some((rule) => rule.permission === "task")