diff --git a/.changeset/fix-openai-web-search-action.md b/.changeset/fix-openai-web-search-action.md
new file mode 100644
index 00000000000..ac95aedf19c
--- /dev/null
+++ b/.changeset/fix-openai-web-search-action.md
@@ -0,0 +1,5 @@
+---
+"@effect/ai-openai": patch
+---
+
+Fix OpenAI stable web search response decoding by preserving the provider action in tool call parameters.
diff --git a/packages/ai/openai/src/OpenAiLanguageModel.ts b/packages/ai/openai/src/OpenAiLanguageModel.ts
index e8559fea08e..62cc4e55cc3 100644
--- a/packages/ai/openai/src/OpenAiLanguageModel.ts
+++ b/packages/ai/openai/src/OpenAiLanguageModel.ts
@@ -1615,7 +1615,9 @@ const makeResponse = Effect.fnUntraced(
             type: "tool-call",
             id: part.id,
             name: toolName,
-            params: {},
+            params: webSearchTool?.name === "OpenAiWebSearchPreview"
+              ? {}
+              : { action: part.action },
             providerExecuted: true
           })
           parts.push({
@@ -1943,6 +1945,9 @@ const makeStreamResponse = Effect.fnUntraced(
                   id: event.item.id,
                   name: toolName
                 }
+                if (webSearchTool?.name === "OpenAiWebSearch") {
+                  break
+                }
                 parts.push({
                   type: "tool-params-start",
                   id: event.item.id,
@@ -2256,6 +2261,15 @@ const makeStreamResponse = Effect.fnUntraced(
                 const toolName = toolNameMapper.getCustomName(
                   webSearchTool?.name ?? "web_search"
                 )
+                if (webSearchTool?.name === "OpenAiWebSearch") {
+                  parts.push({
+                    type: "tool-call",
+                    id: event.item.id,
+                    name: toolName,
+                    params: { action: event.item.action },
+                    providerExecuted: true
+                  })
+                }
                 parts.push({
                   type: "tool-result",
                   id: event.item.id,
diff --git a/packages/ai/openai/test/OpenAiLanguageModel.test.ts b/packages/ai/openai/test/OpenAiLanguageModel.test.ts
index 1250b88b922..4a9ab04d607 100644
--- a/packages/ai/openai/test/OpenAiLanguageModel.test.ts
+++ b/packages/ai/openai/test/OpenAiLanguageModel.test.ts
@@ -752,6 +752,38 @@ describe("OpenAiLanguageModel", () => {
           }
         }))))
 
+      it.each(["gpt-4.1", "gpt-5.6"] as const)(
+        "maps stable web search action to tool call parameters with %s",
+        (model) =>
+          Effect.runPromise(
+            Effect.gen(function*() {
+              const toolkit = Toolkit.make(OpenAiTool.WebSearch({}))
+              const result = yield* LanguageModel.generateText({
+                prompt: "Search the web",
+                toolkit
+              }).pipe(Effect.provide(OpenAiLanguageModel.model(model)))
+
+              const toolCall = result.content.find((part) => part.type === "tool-call")
+              assert.isDefined(toolCall)
+              assert.deepStrictEqual(toolCall.params, {
+                action: { type: "search", query: "Effect TypeScript" }
+              })
+
+              const toolResult = result.content.find((part) => part.type === "tool-result")
+              assert.isDefined(toolResult)
+              assert.deepStrictEqual(toolResult.result, {
+                action: { type: "search", query: "Effect TypeScript" },
+                status: "completed"
+              })
+            }).pipe(Effect.provide(makeTestLayer({
+              body: {
+                model,
+                output: [makeWebSearchCall()]
+              }
+            })))
+          )
+      )
+
       it.effect("uses canonical OpenAiMcp name for mcp_approval_request", () =>
         Effect.gen(function*() {
           const result = yield* LanguageModel.generateText({
@@ -1099,6 +1131,59 @@ describe("OpenAiLanguageModel", () => {
         assert.isDefined(toolParamsEnd)
       }))
 
+    it.effect("waits for the stable streamed web search action before emitting the tool call", () =>
+      Effect.gen(function*() {
+        const toolkit = Toolkit.make(OpenAiTool.WebSearch({}))
+        const streamEvents = [
+          {
+            type: "response.created",
+            sequence_number: 1,
+            response: makeDefaultResponse({ status: "in_progress" })
+          },
+          {
+            type: "response.output_item.added",
+            sequence_number: 2,
+            output_index: 0,
+            item: {
+              type: "web_search_call",
+              id: "ws_123",
+              status: "in_progress"
+            }
+          },
+          {
+            type: "response.output_item.done",
+            sequence_number: 3,
+            output_index: 0,
+            item: makeWebSearchCall()
+          }
+        ] as unknown as ReadonlyArray<typeof Generated.ResponseStreamEvent.Type>
+
+        const parts = yield* LanguageModel.streamText({
+          prompt: "Search the web",
+          toolkit,
+          disableToolCallResolution: true
+        }).pipe(
+          Stream.runCollect,
+          Effect.provide(OpenAiLanguageModel.model("gpt-4o-mini")),
+          Effect.provide(makeStreamTestLayer(streamEvents))
+        )
+
+        const toolCalls = parts.filter((part) => part.type === "tool-call")
+        strictEqual(toolCalls.length, 1)
+        const toolCall = toolCalls[0]
+        assert.isDefined(toolCall)
+        assert.deepStrictEqual(toolCall.params, {
+          action: { type: "search", query: "Effect TypeScript" }
+        })
+
+        const toolResult = parts.find((part) => part.type === "tool-result")
+        assert.isDefined(toolResult)
+        assert.deepStrictEqual(toolResult.result, {
+          action: { type: "search", query: "Effect TypeScript" },
+          status: "completed"
+        })
+      }))
+
     it.effect("handles reasoning summary events when reasoning state is missing", () =>
       Effect.gen(function*() {
         const streamEvents = [
@@ -1512,6 +1597,16 @@ const makeFunctionCall = (
   ...overrides
 })
 
+const makeWebSearchCall = (
+  overrides: Partial<Generated.WebSearchToolCall> = {}
+): Generated.WebSearchToolCall => ({
+  type: "web_search_call",
+  id: "ws_123",
+  status: "completed",
+  action: { type: "search", query: "Effect TypeScript" },
+  ...overrides
+})
+
 const makeMcpCall = (
   name: string,
   args: Record<string, unknown>,