ensure conversation linearity

Author: rasdani

packages/opencode/src/provider/sdk/copilot/chat/convert-to-openai-compatible-chat-messages.ts

@@ -104,6 +104,12 @@ export function convertToOpenAICompatibleChatMessages(prompt: LanguageModelV2Pro
                 type: "function",
                 function: {
                   name: part.toolName,
+                  // MITO WARNING: JSON.stringify re-serializes tool call arguments to compact JSON,
+                  // losing the model's original formatting. This breaks the MITO extension property
+                  // if the model generated non-compact JSON. The same issue exists in the npm
+                  // @ai-sdk/openai-compatible package (not our code). If MITO-DEBUG logs show
+                  // extension breaks from JSON formatting, store raw arguments via ToolStatePending.raw
+                  // and use them here instead of re-serializing.
                   arguments: JSON.stringify(part.input),
                 },
                 ...partMetadata,

packages/opencode/src/session/llm.ts

@@ -180,17 +180,6 @@ export namespace LLM {
         })
       },
       async experimental_repairToolCall(failed) {
-        const lower = failed.toolCall.toolName.toLowerCase()
-        if (lower !== failed.toolCall.toolName && tools[lower]) {
-          l.info("repairing tool call", {
-            tool: failed.toolCall.toolName,
-            repaired: lower,
-          })
-          return {
-            ...failed.toolCall,
-            toolName: lower,
-          }
-        }
         return {
           ...failed.toolCall,
           input: JSON.stringify({

packages/opencode/src/session/processor.ts

@@ -89,8 +89,6 @@ export namespace SessionProcessor {
                 case "reasoning-end":
                   if (value.id in reasoningMap) {
                     const part = reasoningMap[value.id]
-                    part.text = part.text.trimEnd()
-
                     part.time = {
                       ...part.time,
                       end: Date.now(),
@@ -305,7 +303,6 @@ export namespace SessionProcessor {
 
                 case "text-end":
                   if (currentText) {
-                    currentText.text = currentText.text.trimEnd()
                     const textOutput = await Plugin.trigger(
                       "experimental.text.complete",
                       {

packages/opencode/src/session/system.ts

@@ -36,7 +36,6 @@ export namespace SystemPrompt {
         `  Working directory: ${Instance.directory}`,
         `  Is directory a git repo: ${project.vcs === "git" ? "yes" : "no"}`,
         `  Platform: ${process.platform}`,
-        `  Today's date: ${new Date().toDateString()}`,
         `</env>`,
         `<directories>`,
         `  ${

packages/opencode/test/session/linearity.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, test } from "bun:test"
+import { SystemPrompt } from "../../src/session/system"
+
+describe("MITO linearity", () => {
+  describe("system prompt stability", () => {
+    test("environment() does not contain 'Today's date:'", async () => {
+      // SystemPrompt.environment requires Instance to be initialized, so we check
+      // the source directly — the date line was removed from system.ts
+      const source = await Bun.file(
+        new URL("../../src/session/system.ts", import.meta.url).pathname,
+      ).text()
+      expect(source).not.toContain("Today's date")
+      expect(source).not.toContain("toDateString")
+    })
+
+    test("provider() returns stable output across calls", () => {
+      const model = {
+        api: { id: "claude-sonnet-4-20250514" },
+      } as any
+      const first = SystemPrompt.provider(model)
+      const second = SystemPrompt.provider(model)
+      expect(first).toEqual(second)
+    })
+  })
+
+  describe("text content preservation", () => {
+    test("processor does not trimEnd text content", async () => {
+      const source = await Bun.file(
+        new URL("../../src/session/processor.ts", import.meta.url).pathname,
+      ).text()
+      // Neither text-end nor reasoning-end should trimEnd
+      expect(source).not.toContain("trimEnd()")
+    })
+  })
+
+  describe("tool call repair does not lowercase", () => {
+    test("experimental_repairToolCall does not lowercase tool names", async () => {
+      const source = await Bun.file(
+        new URL("../../src/session/llm.ts", import.meta.url).pathname,
+      ).text()
+      // The lowercasing branch should be removed
+      expect(source).not.toContain("toolName.toLowerCase()")
+    })
+  })
+})