diff --git a/packages/opencode/src/provider/models.ts b/packages/opencode/src/provider/models.ts
index 796dcb7c238..5e182a47096 100644
--- a/packages/opencode/src/provider/models.ts
+++ b/packages/opencode/src/provider/models.ts
@@ -48,6 +48,7 @@ export namespace ModelsDev {
     limit: z.object({
       context: z.number(),
       output: z.number(),
+      input: z.number().optional(),
     }),
     modalities: z
       .object({
diff --git a/packages/opencode/src/provider/provider.ts b/packages/opencode/src/provider/provider.ts
index 9967edec5dd..5c301f915a3 100644
--- a/packages/opencode/src/provider/provider.ts
+++ b/packages/opencode/src/provider/provider.ts
@@ -465,6 +465,7 @@ export namespace Provider {
       limit: z.object({
         context: z.number(),
         output: z.number(),
+        input: z.number().optional(),
       }),
       status: z.enum(["alpha", "beta", "deprecated", "active"]),
       options: z.record(z.string(), z.any()),
@@ -527,6 +528,7 @@ export namespace Provider {
       limit: {
         context: model.limit.context,
         output: model.limit.output,
+        input: model.limit.input,
       },
       capabilities: {
         temperature: model.temperature,
diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index 42bab2eb975..47bd3d1eb77 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -27,6 +27,8 @@ export namespace SessionCompaction {
     ),
   }
 
+  const NEXT_INPUT_TOKEN_MAX = 20_000
+
   export async function isOverflow(input: { tokens: MessageV2.Assistant["tokens"]; model: Provider.Model }) {
     const config = await Config.get()
     if (config.compaction?.auto === false) return false
@@ -34,7 +36,7 @@ export namespace SessionCompaction {
     if (context === 0) return false
     const count = input.tokens.input + input.tokens.cache.read + input.tokens.output
     const output = Math.min(input.model.limit.output, SessionPrompt.OUTPUT_TOKEN_MAX) || SessionPrompt.OUTPUT_TOKEN_MAX
-    const usable = context - output
+    const usable = input.model.limit.input ?  input.model.limit.input - NEXT_INPUT_TOKEN_MAX : context - output
     return count > usable
   }
 
diff --git a/packages/opencode/test/session/compaction.test.ts b/packages/opencode/test/session/compaction.test.ts
index 9070428ea54..b36134d9555 100644
--- a/packages/opencode/test/session/compaction.test.ts
+++ b/packages/opencode/test/session/compaction.test.ts
@@ -10,7 +10,7 @@ import type { Provider } from "../../src/provider/provider"
 
 Log.init({ print: false })
 
-function createModel(opts: { context: number; output: number; cost?: Provider.Model["cost"] }): Provider.Model {
+function createModel(opts: { context: number; output: number; inputLimit?: number; cost?: Provider.Model["cost"] }): Provider.Model {
   return {
     id: "test-model",
     providerID: "test",
@@ -18,6 +18,7 @@ function createModel(opts: { context: number; output: number; cost?: Provider.Mo
     limit: {
       context: opts.context,
       output: opts.output,
+      input: opts.inputLimit,
     },
     cost: opts.cost ?? { input: 0, output: 0, cache: { read: 0, write: 0 } },
     capabilities: {
@@ -102,6 +103,18 @@ describe("session.compaction.isOverflow", () => {
       },
     })
   })
+
+  test("returns true when input limit is reached", async () => {
+    await using tmp = await tmpdir()
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const model = createModel({ context: 100_000, output: 32_000, inputLimit: 50_000 })
+        const tokens = { input: 40_000, output: 5_000, reasoning: 0, cache: { read: 0, write: 0 } }
+        expect(await SessionCompaction.isOverflow({ tokens, model })).toBe(true)
+      },
+    })
+  })
 })
 
 describe("util.token.estimate", () => {