diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index d38c29765ade..07c150c79240 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -326,25 +326,7 @@ 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({
-                tool: failed.toolCall.toolName,
-                error: failed.error.message,
-              }),
-              toolName: "invalid",
-            }
+            return repairToolCall(failed, tools, l)
           },
           temperature: params.temperature,
           topP: params.topP,
@@ -431,6 +413,32 @@ export namespace LLM {
     ),
   )
 
+  /** Exported for testing. */
+  export function repairToolCall<T extends { toolName: string }>(
+    failed: { toolCall: T; error: unknown },
+    tools: Record<string, unknown>,
+    l?: { info: (msg: string, meta: Record<string, unknown>) => void },
+  ) {
+    const name = failed.toolCall.toolName
+    const lower = name.toLowerCase()
+    if (lower !== name && tools[lower]) {
+      l?.info("repairing tool call", { tool: name, repaired: lower })
+      return { ...failed.toolCall, toolName: lower }
+    }
+    // Build a clean error that never leaks internal tool names or the
+    // raw "Available tools: ..." list from the AI SDK's NoSuchToolError.
+    const isNoSuchTool =
+      typeof failed.error === "object" && failed.error !== null && "toolName" in failed.error
+    const msg = isNoSuchTool
+      ? `Tool "${name}" is not available. Please use one of the tools provided to you.`
+      : `Tool "${name}" was called with invalid arguments. Please review the tool schema and retry.`
+    return {
+      ...failed.toolCall,
+      input: JSON.stringify({ tool: name, error: msg }),
+      toolName: "invalid",
+    }
+  }
+
   function resolveTools(input: Pick<StreamInput, "tools" | "agent" | "permission" | "user">) {
     const disabled = Permission.disabled(
       Object.keys(input.tools),
diff --git a/packages/opencode/src/session/processor.ts b/packages/opencode/src/session/processor.ts
index 415639fbe56a..1d58dd87a889 100644
--- a/packages/opencode/src/session/processor.ts
+++ b/packages/opencode/src/session/processor.ts
@@ -306,16 +306,29 @@ export namespace SessionProcessor {
               const parts = MessageV2.parts(ctx.assistantMessage.id)
               const recentParts = parts.slice(-DOOM_LOOP_THRESHOLD)
 
-              if (
-                recentParts.length !== DOOM_LOOP_THRESHOLD ||
-                !recentParts.every(
+              const isExactLoop =
+                recentParts.length === DOOM_LOOP_THRESHOLD &&
+                recentParts.every(
                   (part) =>
                     part.type === "tool" &&
                     part.tool === value.toolName &&
                     part.state.status !== "pending" &&
                     JSON.stringify(part.state.input) === JSON.stringify(value.input),
                 )
-              ) {
+
+              // Circuit-break repeated invalid tool calls even when inputs vary.
+              // The "invalid" tool is an internal fallback for malformed calls;
+              // N consecutive hits signal the model is stuck regardless of the
+              // specific error each time.
+              const isInvalidLoop =
+                !isExactLoop &&
+                value.toolName === "invalid" &&
+                recentParts.length === DOOM_LOOP_THRESHOLD &&
+                recentParts.every(
+                  (part) => part.type === "tool" && part.tool === "invalid" && part.state.status !== "pending",
+                )
+
+              if (!isExactLoop && !isInvalidLoop) {
                 return
               }
 
diff --git a/packages/opencode/src/tool/invalid.ts b/packages/opencode/src/tool/invalid.ts
index aca3618b6d04..457bc85cad09 100644
--- a/packages/opencode/src/tool/invalid.ts
+++ b/packages/opencode/src/tool/invalid.ts
@@ -13,7 +13,7 @@ export const InvalidTool = Tool.define(
     execute: (params: { tool: string; error: string }) =>
       Effect.succeed({
         title: "Invalid Tool",
-        output: `The arguments provided to the tool are invalid: ${params.error}`,
+        output: `Tool "${params.tool}" was called incorrectly. ${params.error.replace(/\s*Available tools:.*$/, "")}`,
         metadata: {},
       }),
   }),
diff --git a/packages/opencode/test/session/llm.test.ts b/packages/opencode/test/session/llm.test.ts
index 4d82096f3f9a..ec7955240c44 100644
--- a/packages/opencode/test/session/llm.test.ts
+++ b/packages/opencode/test/session/llm.test.ts
@@ -119,6 +119,62 @@ describe("session.llm.hasToolCalls", () => {
   })
 })
 
+describe("session.llm.repairToolCall", () => {
+  test("case-insensitive match repairs tool name", () => {
+    const result = LLM.repairToolCall(
+      { toolCall: { toolName: "Read" }, error: { message: "...", toolName: "Read" } },
+      { read: {}, bash: {} },
+    )
+    expect(result).toMatchObject({ toolName: "read" })
+    expect((result as any).input).toBeUndefined()
+  })
+
+  test("unknown tool produces clean error without Available tools list", () => {
+    const result = LLM.repairToolCall(
+      {
+        toolCall: { toolName: "nonexistent" },
+        error: {
+          message: "Model tried to call unavailable tool 'nonexistent'. Available tools: invalid, bash, read.",
+          toolName: "nonexistent",
+        },
+      },
+      { bash: {}, read: {}, invalid: {} },
+    )
+    expect(result.toolName).toBe("invalid")
+    const input = JSON.parse((result as any).input)
+    expect(input.tool).toBe("nonexistent")
+    expect(input.error).not.toContain("Available tools")
+    expect(input.error).not.toContain("invalid")
+    expect(input.error).toContain("not available")
+  })
+
+  test("invalid arguments produces argument-specific error", () => {
+    const result = LLM.repairToolCall(
+      {
+        toolCall: { toolName: "bash" },
+        error: {
+          message: "Invalid input for tool bash: expected string got number",
+          toolInput: '{"command": 123}',
+        },
+      },
+      { bash: {}, read: {}, invalid: {} },
+    )
+    expect(result.toolName).toBe("invalid")
+    const input = JSON.parse((result as any).input)
+    expect(input.tool).toBe("bash")
+    expect(input.error).toContain("invalid arguments")
+    expect(input.error).not.toContain("Available tools")
+  })
+
+  test("exact match tool name is not repaired by case logic", () => {
+    const result = LLM.repairToolCall(
+      { toolCall: { toolName: "bash" }, error: { message: "bad args", toolInput: "{}" } },
+      { bash: {}, read: {} },
+    )
+    expect(result.toolName).toBe("invalid")
+  })
+})
+
 type Capture = {
   url: URL
   headers: Headers