diff --git a/packages/opencode/src/altimate/auto/routing-signals.ts b/packages/opencode/src/altimate/auto/routing-signals.ts
new file mode 100644
index 0000000000..145c691798
--- /dev/null
+++ b/packages/opencode/src/altimate/auto/routing-signals.ts
@@ -0,0 +1,109 @@
+// Auto Mode client routing signals.
+//
+// The altimate-backend gateway reads `extra_body.routing` and escalates one tier
+// on error recovery. The signals are schema-free hints derived from the message
+// history the request already carries; any datum that cannot be determined is
+// omitted so the backend falls back to its own heuristics.
+//
+// Transport: @ai-sdk/openai-compatible spreads `providerOptions[<provider name>]`
+// into the top-level POST body (minus its own typed keys), so
+// `providerOptions["altimate-backend"].extra_body = { routing }` is sent as a
+// literal top-level `extra_body` field.
+import type { ModelMessage } from "ai"
+
+export namespace RoutingSignals {
+  export const PROVIDER_ID = "altimate-backend"
+  const TIERS = ["auto", "fast", "max"] as const
+  const ROLES = ["plan", "build"] as const
+  // Only the tail of the conversation reflects the current state of the turn.
+  const RECENT_MESSAGES = 6
+  const ERROR_PATTERN = /\b(error|exception|traceback|stack trace|failed|failure|panic)\b/i
+  const CODE_FENCE = /```/
+  const CODE_TOOLS = new Set(["read", "edit", "write", "patch", "multiedit", "apply_patch"])
+
+  export type Routing = {
+    tier?: (typeof TIERS)[number]
+    last_tool_ok?: boolean
+    retry_count?: number
+    has_error_ctx?: boolean
+    has_code_ctx?: boolean
+    agent_role?: (typeof ROLES)[number]
+  }
+
+  type ToolResult = { toolName?: string; output?: { type?: string; value?: unknown } }
+
+  export type Input = {
+    providerID: string
+    modelID: string
+    agentName?: string
+    messages: ModelMessage[]
+  }
+
+  function tierOf(modelID: string): Routing["tier"] {
+    const tier = modelID.startsWith("altimate-") ? modelID.slice("altimate-".length) : undefined
+    return TIERS.find((t) => t === tier)
+  }
+
+  function toolResults(msg: ModelMessage): ToolResult[] {
+    if (msg.role !== "tool" || !Array.isArray(msg.content)) return []
+    return (msg.content as unknown as Array<{ type?: string }>).filter((p) => p?.type === "tool-result") as ToolResult[]
+  }
+
+  const failed = (r: ToolResult) => r.output?.type === "error-text" || r.output?.type === "error-json"
+
+  function textOf(msg: ModelMessage): string {
+    if (typeof msg.content === "string") return msg.content
+    if (!Array.isArray(msg.content)) return ""
+    return (msg.content as unknown as Array<Record<string, any>>)
+      .map((p) => {
+        if (typeof p?.text === "string") return p.text
+        const v = p?.output?.value
+        return typeof v === "string" ? v : ""
+      })
+      .join("\n")
+  }
+
+  export function compute(input: Input): Routing | undefined {
+    if (input.providerID !== PROVIDER_ID) return undefined
+    const routing: Routing = {}
+    const tier = tierOf(input.modelID)
+    if (tier) routing.tier = tier
+    const role = ROLES.find((r) => r === input.agentName)
+    if (role) routing.agent_role = role
+
+    const results = input.messages.flatMap(toolResults)
+    const last = results[results.length - 1]
+    if (last) {
+      routing.last_tool_ok = !failed(last)
+      let streak = 0
+      for (let i = results.length - 1; i >= 0 && failed(results[i]); i--) streak++
+      routing.retry_count = streak
+    }
+
+    const recent = input.messages.slice(-RECENT_MESSAGES)
+    if (recent.length > 0) {
+      routing.has_error_ctx = recent.some(
+        (m) => toolResults(m).some(failed) || (m.role === "tool" && ERROR_PATTERN.test(textOf(m))),
+      )
+      routing.has_code_ctx = recent.some(
+        (m) => CODE_FENCE.test(textOf(m)) || toolResults(m).some((r) => CODE_TOOLS.has(String(r.toolName))),
+      )
+    }
+    return routing
+  }
+
+  /** Merge routing signals into the provider options for altimate-backend; identity for other providers. */
+  export function attach(options: Record<string, any>, input: Input): Record<string, any> {
+    try {
+      const routing = compute(input)
+      if (!routing || Object.keys(routing).length === 0) return options
+      const existing = options[PROVIDER_ID] ?? {}
+      return {
+        ...options,
+        [PROVIDER_ID]: { ...existing, extra_body: { ...existing.extra_body, routing } },
+      }
+    } catch {
+      return options
+    }
+  }
+}
diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index 62804161a3..bca730aec3 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -24,6 +24,9 @@ import {
 // altimate_change end
 // altimate_change start — tool retrieval
 import { Retrieval } from "@/tool/retrieval"
+// altimate_change start — Auto Mode client routing signals
+import { RoutingSignals } from "@/altimate/auto/routing-signals"
+// altimate_change end
 // altimate_change end
 import { Config } from "@/config/config"
 import { Instance } from "@/project/instance"
@@ -312,7 +315,12 @@ export namespace LLM {
       topP: params.topP,
       topK: params.topK,
       // altimate_change start — use the reasoning options reconciled with the final output reservation
-      providerOptions: ProviderTransform.providerOptions(input.model, requestOptions),
+      providerOptions: RoutingSignals.attach(ProviderTransform.providerOptions(input.model, requestOptions), {
+        providerID: input.model.providerID,
+        modelID: input.model.id,
+        agentName: input.agent.name,
+        messages: input.messages,
+      }),
       // altimate_change end
       activeTools: Object.keys(tools).filter((x) => x !== "invalid"),
       tools,
diff --git a/packages/opencode/test/altimate/auto-routing-signals.test.ts b/packages/opencode/test/altimate/auto-routing-signals.test.ts
new file mode 100644
index 0000000000..9ecfa8bb74
--- /dev/null
+++ b/packages/opencode/test/altimate/auto-routing-signals.test.ts
@@ -0,0 +1,59 @@
+import { describe, expect, test } from "bun:test"
+import type { ModelMessage } from "ai"
+import { RoutingSignals } from "../../src/altimate/auto/routing-signals"
+
+const toolMsg = (toolName: string, type: string, value: string): ModelMessage =>
+  ({
+    role: "tool",
+    content: [{ type: "tool-result", toolCallId: "c", toolName, output: { type, value } }],
+  }) as unknown as ModelMessage
+
+const base = { providerID: "altimate-backend", modelID: "altimate-auto", agentName: "build" }
+
+describe("RoutingSignals", () => {
+  test("is a no-op for other providers", () => {
+    const opts = { openai: { a: 1 } }
+    expect(RoutingSignals.compute({ ...base, providerID: "openai", messages: [] })).toBeUndefined()
+    expect(RoutingSignals.attach(opts, { ...base, providerID: "openai", messages: [] })).toBe(opts)
+  })
+
+  test("omits tool signals when no tool result exists", () => {
+    const r = RoutingSignals.compute({ ...base, messages: [{ role: "user", content: "hi" }] })!
+    expect(r).toEqual({ tier: "auto", agent_role: "build", has_error_ctx: false, has_code_ctx: false })
+  })
+
+  test("counts consecutive trailing tool failures", () => {
+    const r = RoutingSignals.compute({
+      ...base,
+      messages: [toolMsg("bash", "text", "ok"), toolMsg("bash", "error-text", "boom"), toolMsg("bash", "error-text", "boom")],
+    })!
+    expect(r.last_tool_ok).toBe(false)
+    expect(r.retry_count).toBe(2)
+    expect(r.has_error_ctx).toBe(true)
+  })
+
+  test("success resets streak; code context from edit tool", () => {
+    const r = RoutingSignals.compute({
+      ...base,
+      modelID: "altimate-max",
+      agentName: "plan",
+      messages: [toolMsg("bash", "error-text", "x"), toolMsg("edit", "text", "done")],
+    })!
+    expect(r).toMatchObject({ tier: "max", agent_role: "plan", last_tool_ok: true, retry_count: 0, has_code_ctx: true })
+  })
+
+  test("ignores unknown tiers and roles", () => {
+    const r = RoutingSignals.compute({ ...base, modelID: "altimate-default", agentName: "explore", messages: [] })!
+    expect(r).toEqual({})
+  })
+
+  test("attach nests routing under extra_body and preserves existing options", () => {
+    const out = RoutingSignals.attach(
+      { "altimate-backend": { extra_body: { foo: 1 }, keep: true } },
+      { ...base, messages: [{ role: "user", content: "hi" }] },
+    )
+    expect(out["altimate-backend"].keep).toBe(true)
+    expect(out["altimate-backend"].extra_body.foo).toBe(1)
+    expect(out["altimate-backend"].extra_body.routing.tier).toBe("auto")
+  })
+})