Fix/sequential chain intermediate outputs

chains/sequential.go

@@ -99,17 +99,29 @@ func (c *SequentialChain) validateSeqChain() error {
 // not be called directly. Use rather the Call, Run or Predict functions that
 // handles the memory and other aspects of the chain.
 func (c *SequentialChain) Call(ctx context.Context, inputs map[string]any, options ...ChainCallOption) (map[string]any, error) { //nolint:lll
-	var outputs map[string]any
-	var err error
+	knownValues := make(map[string]any, len(inputs))
+	for k, v := range inputs {
+		knownValues[k] = v
+	}
+
 	for _, chain := range c.chains {
-		outputs, err = Call(ctx, chain, inputs, options...)
+		outputs, err := Call(ctx, chain, knownValues, options...)
 		if err != nil {
 			return nil, err
 		}
-		// Set the input for the next chain to the output of the current chain
-		inputs = outputs
+		// Merge outputs into known values so subsequent chains
+		// and the final result can access all intermediate outputs.
+		for k, v := range outputs {
+			knownValues[k] = v
+		}
+	}
+
+	// Return only the declared output keys.
+	result := make(map[string]any, len(c.outputKeys))
+	for _, key := range c.outputKeys {
+		result[key] = knownValues[key]
 	}
-	return outputs, nil
+	return result, nil
 }
 
 // GetMemory gets the memory of the chain.

chains/sequential_test.go

@@ -123,6 +123,50 @@ func TestSequentialChain(t *testing.T) {
 	assert.Equal(t, "Vey legit", res[_llmChainDefaultOutputKey])
 }
 
+func TestSequentialChainIntermediateOutputs(t *testing.T) {
+	ctx := context.Background()
+	t.Parallel()
+
+	// Reproduce issue #1095: intermediate outputs (e.g. "synopsis") should be
+	// accessible when declared in outputKeys.
+	testLLM1 := &testLanguageModel{expResult: "A gripping tale of mystery"}
+	testLLM2 := &testLanguageModel{expResult: "Five stars, must watch"}
+
+	chain1 := NewLLMChain(
+		testLLM1,
+		prompts.NewPromptTemplate("Write a synopsis for {{.title}} set in {{.era}}", []string{"title", "era"}),
+	)
+	chain1.OutputKey = "synopsis"
+
+	chain2 := NewLLMChain(
+		testLLM2,
+		prompts.NewPromptTemplate("Review this synopsis: {{.synopsis}}", []string{"synopsis"}),
+	)
+	chain2.OutputKey = "review"
+
+	// Request BOTH intermediate and final outputs.
+	seqChain, err := NewSequentialChain(
+		[]Chain{chain1, chain2},
+		[]string{"title", "era"},
+		[]string{"synopsis", "review"},
+	)
+	require.NoError(t, err)
+
+	res, err := Call(ctx, seqChain, map[string]any{
+		"title": "Mystery in the haunted mansion",
+		"era":   "1930s in Haiti",
+	})
+	require.NoError(t, err)
+
+	// Both intermediate and final outputs must be present.
+	assert.Equal(t, "A gripping tale of mystery", res["synopsis"])
+	assert.Equal(t, "Five stars, must watch", res["review"])
+
+	// chain2 must have received chain1's output as its prompt input.
+	expPrompt := "Review this synopsis: A gripping tale of mystery"
+	assert.Equal(t, expPrompt, testLLM2.recordedPrompt[0].String())
+}
+
 func TestSequentialChainErrors(t *testing.T) {
 	ctx := context.Background()
 	t.Parallel()