simstudioai · waleedlatif1 · Aug 5, 2026 · Aug 5, 2026 · cursor · Aug 5, 2026
diff --git a/apps/sim/blocks/blocks/agent.ts b/apps/sim/blocks/blocks/agent.ts
@@ -672,6 +672,11 @@ Return ONLY the JSON array.`,
     model: { type: 'string', description: 'Model used for generation' },
     tokens: { type: 'json', description: 'Token usage statistics' },
     toolCalls: { type: 'json', description: 'Tool calls made' },
+    finishReason: {
+      type: 'string',
+      description:
+        'Why generation stopped: stop, length (truncated by the token limit), tool_calls, content_filter, error, or other',
+    },
     providerTiming: {
       type: 'json',
       description: 'Provider timing information',

diff --git a/apps/sim/executor/handlers/agent/agent-handler.ts b/apps/sim/executor/handlers/agent/agent-handler.ts
@@ -62,7 +62,9 @@ import {
   canUseProviderLargeFilePath,
   getInlineHydrationMaxBytes,
 } from '@/providers/file-attachments.server'
+import { normalizeFinishReason } from '@/providers/finish-reason'
 import { isAutoModel, SIM_AUTO_MODEL_ID } from '@/providers/models'
+import type { ProviderResponse } from '@/providers/types'
 import { getProviderFromModel, transformBlockTool } from '@/providers/utils'
 import type { SerializedBlock } from '@/serializer/types'
 import { filterSchemaForLLM, type ToolSchema } from '@/tools/params'
@@ -1487,9 +1489,32 @@ export class AgentBlockHandler implements BlockHandler {
       },
       providerTiming: result.timing,
       cost: result.cost,
+      /**
+       * Read from the last model segment rather than threaded through each provider:
+       * every family already records its raw stop reason there for the trace, so this
+       * normalizes the value the enrichment layer has already collected. A run whose
+       * provider reported nothing simply has no reason, which stays distinct from one
+       * the vocabulary could not place.
+       */
+      finishReason: normalizeFinishReason(this.lastModelSegmentFinishReasonImpl(result.timing)),
     }
   }
 
+  /**
+   * The raw stop reason from the most recent `model` segment. Later segments win
+   * because a tool loop appends one segment per turn and the final turn is the one
+   * that ended the generation.
+   */
+  private lastModelSegmentFinishReasonImpl(timing: ProviderResponse['timing']): string | undefined {
+    const segments = timing?.timeSegments
+    if (!segments) return undefined
+    for (let i = segments.length - 1; i >= 0; i--) {
+      const segment = segments[i]
+      if (segment.type === 'model' && segment.finishReason) return segment.finishReason
-      if (segment.type === 'model' && segment.finishReason) return segment.finishReason
+      if (segment.type === 'model') return segment.finishReason
-      if (segment.type === 'model' && segment.finishReason) return segment.finishReason
+      if (segment.type === 'model') return segment.finishReason
+    }
+    return undefined
+  }
+
   private formatToolCall(tc: any) {
     const toolName = stripCustomToolPrefix(tc.name)
 

diff --git a/apps/sim/providers/finish-reason.test.ts b/apps/sim/providers/finish-reason.test.ts
@@ -0,0 +1,111 @@
+/**
+ * @vitest-environment node
+ *
+ * The raw values are taken from the SDK enums this repo compiles against:
+ * `ChatCompletion.finish_reason`, Anthropic `StopReason`, Gemini `FinishReason`,
+ * and Bedrock `StopReason`. A provider adding a case must not fail a run, so an
+ * unknown value normalizes rather than throwing.
+ */
+import { describe, expect, it } from 'vitest'
+import { normalizeFinishReason } from '@/providers/finish-reason'
+
+describe('normalizeFinishReason', () => {
+  it('reports nothing when the provider reported nothing', () => {
+    expect(normalizeFinishReason(undefined)).toBeUndefined()
+    expect(normalizeFinishReason(null)).toBeUndefined()
+    expect(normalizeFinishReason('')).toBeUndefined()
+  })
+
+  /** The case this exists for: one branch catches truncation on every provider. */
+  it('maps every provider spelling of truncation to length', () => {
+    expect(normalizeFinishReason('length')).toBe('length') // OpenAI chat
+    expect(normalizeFinishReason('max_output_tokens')).toBe('length') // OpenAI Responses
+    expect(normalizeFinishReason('max_tokens')).toBe('length') // Anthropic, Bedrock
+    expect(normalizeFinishReason('MAX_TOKENS')).toBe('length') // Gemini
+    expect(normalizeFinishReason('model_context_window_exceeded')).toBe('length')
+  })
+
+  it('maps natural completion to stop', () => {
+    expect(normalizeFinishReason('stop')).toBe('stop')
+    expect(normalizeFinishReason('STOP')).toBe('stop')
+    expect(normalizeFinishReason('end_turn')).toBe('stop')
+    expect(normalizeFinishReason('stop_sequence')).toBe('stop')
+  })
+
+  it('maps tool stops to tool_calls', () => {
+    expect(normalizeFinishReason('tool_calls')).toBe('tool_calls')
+    expect(normalizeFinishReason('function_call')).toBe('tool_calls')
+    expect(normalizeFinishReason('tool_use')).toBe('tool_calls')
+  })
+
+  it('maps every safety stop to content_filter', () => {
+    for (const raw of [
+      'content_filter',
+      'content_filtered',
+      'guardrail_intervened',
+      'refusal',
+      'SAFETY',
+      'BLOCKLIST',
+      'PROHIBITED_CONTENT',
+      'SPII',
+      'RECITATION',
+      'IMAGE_SAFETY',
+    ]) {
+      expect(normalizeFinishReason(raw)).toBe('content_filter')
+    }
+  })
+
+  it('maps malformed generations to error', () => {
+    expect(normalizeFinishReason('MALFORMED_FUNCTION_CALL')).toBe('error')
+    expect(normalizeFinishReason('malformed_tool_use')).toBe('error')
+    expect(normalizeFinishReason('malformed_model_output')).toBe('error')
+  })
+
+  /** A pause is a continuation point, not an outcome the caller should branch on. */
+  it('does not treat a server-tool pause as a stop', () => {
+    expect(normalizeFinishReason('pause_turn')).toBe('other')
+  })
+
+  /**
+   * Values confirmed against each vendor's own enum by a per-provider documentation
+   * sweep. Several are the routine success path on open-weight models, so leaving
+   * them unclassified would misreport healthy runs.
+   */
+  it('classifies the non-OpenAI vocabularies of compatible vendors', () => {
+    expect(normalizeFinishReason('model_length')).toBe('length') // Mistral
+    expect(normalizeFinishReason('eos')).toBe('stop') // Together
+    expect(normalizeFinishReason('eos_token')).toBe('stop') // LiteLLM/HuggingFace
+    expect(normalizeFinishReason('error')).toBe('error') // Mistral, OpenRouter, Together
+    expect(normalizeFinishReason('insufficient_system_resource')).toBe('error') // DeepSeek
+    expect(normalizeFinishReason('network_error')).toBe('error') // Z.ai
+    expect(normalizeFinishReason('sensitive')).toBe('content_filter') // Z.ai
+  })
+
+  it('classifies the Gemini and Vertex values absent from the TS enum', () => {
+    expect(normalizeFinishReason('MODEL_ARMOR')).toBe('content_filter') // Vertex only
+    expect(normalizeFinishReason('ESCALATION')).toBe('content_filter')
+    expect(normalizeFinishReason('MALFORMED_RESPONSE')).toBe('error')
+    expect(normalizeFinishReason('MISSING_THOUGHT_SIGNATURE')).toBe('error')
+  })
+
+  /**
+   * A server-aborted tool loop is not a request to execute tools, and a repetition
+   * cutoff is a normal finish rather than a failure — both would mislead a workflow
+   * branching on the value.
+   */
+  it('does not overclaim on aborted or degenerate stops', () => {
+    expect(normalizeFinishReason('too_many_tool_calls')).toBe('other')
+    expect(normalizeFinishReason('repetition')).toBe('other')
+    expect(normalizeFinishReason('abort')).toBe('other')
+  })
+
+  it('degrades an unrecognized value to other rather than throwing', () => {
+    expect(normalizeFinishReason('some_future_reason')).toBe('other')
+    expect(normalizeFinishReason('OTHER')).toBe('other')
+    expect(normalizeFinishReason('FINISH_REASON_UNSPECIFIED')).toBe('other')
+  })
+
+  it('is insensitive to case and surrounding whitespace', () => {
+    expect(normalizeFinishReason('  Length  ')).toBe('length')
+  })
+})
diff --git a/apps/sim/providers/finish-reason.ts b/apps/sim/providers/finish-reason.ts
@@ -0,0 +1,132 @@
+/**
+ * Why a model stopped generating, normalized across providers.
+ *
+ * Providers disagree on vocabulary for the same event — a truncated generation is
+ * `length` on OpenAI, `max_tokens` on Anthropic and Bedrock, and `MAX_TOKENS` on
+ * Gemini. Traces keep each provider's raw string because it is the ground truth for
+ * debugging; this normalized value exists so a workflow can branch on the outcome
+ * without enumerating every provider's spelling.
+ */
+export type AgentFinishReason =
+  /** Generation completed naturally, or hit a caller-supplied stop sequence. */
+  | 'stop'
+  /** Truncated by a token limit — the model had more to say. */
+  | 'length'
+  /** Stopped in order to call tools. */
+  | 'tool_calls'
+  /** Blocked or refused by a safety system. */
+  | 'content_filter'
+  /** The provider reported the generation itself as failed or malformed. */
+  | 'error'
+  /** Reported, but not a case this vocabulary distinguishes. */
+  | 'other'
+
+/**
+ * Raw provider value → normalized reason, keyed on the lowercased string.
+ *
+ * A single table rather than a per-provider mapper because the vocabularies do not
+ * collide: no raw value means one thing to one provider and something else to
+ * another. Sources are the SDK types this repo compiles against —
+ * `ChatCompletion.finish_reason`, Anthropic's `StopReason`, Gemini's `FinishReason`,
+ * and Bedrock's `StopReason`.
+ */
+const NORMALIZED_BY_RAW = new Map<string, AgentFinishReason>([
+  // OpenAI Chat Completions, and every OpenAI-compatible provider.
+  ['stop', 'stop'],
+  ['length', 'length'],
+  ['tool_calls', 'tool_calls'],
+  ['function_call', 'tool_calls'],
+  ['content_filter', 'content_filter'],
+
+  // OpenAI Responses reports truncation through `incomplete_details.reason`.
+  ['max_output_tokens', 'length'],
+
+  /** Mistral separates the model's own max length from the caller's `max_tokens`. */
+  ['model_length', 'length'],
+
+  /**
+   * Natural end-of-sequence. Together and HuggingFace-backed proxies report the
+   * model's EOS token separately from a caller-supplied stop sequence, so without
+   * these the routine success path on open-weight models is unclassified.
+   */
+  ['eos', 'stop'],
+  ['eos_token', 'stop'],
+
+  /**
+   * A generation the provider itself reported as failed. Mistral, OpenRouter,
+   * Together and Fireworks all spell this `error`; the DeepSeek and Z.ai values are
+   * the same class with a stated cause.
+   */
+  ['error', 'error'],
+  ['insufficient_system_resource', 'error'],
+  ['network_error', 'error'],
+
+  /** Z.ai (GLM) sensitive-content block. */
+  ['sensitive', 'content_filter'],
+
+  /**
+   * Cut short with no outcome to report, on vLLM and NIM-hosted models. vLLM treats
+   * a repetition cutoff as a normal finish rather than a failure, so it is not
+   * `error`.
+   */
+  ['abort', 'other'],
+  ['repetition', 'other'],
+
+  // Anthropic Messages, shared by Bedrock's Converse API.
+  ['end_turn', 'stop'],
+  ['stop_sequence', 'stop'],
+  ['max_tokens', 'length'],
+  ['model_context_window_exceeded', 'length'],
+  ['tool_use', 'tool_calls'],
+  ['refusal', 'content_filter'],
+  /** A server-tool pause is a continuation point, not an outcome. */
+  ['pause_turn', 'other'],
+
+  // Bedrock Converse additions.
+  ['content_filtered', 'content_filter'],
+  ['guardrail_intervened', 'content_filter'],
+  ['malformed_model_output', 'error'],
+  ['malformed_tool_use', 'error'],
+
+  /**
+   * Gemini. `STOP` and `MAX_TOKENS` already lowercase onto the entries above, so
+   * only the values with no counterpart elsewhere are listed here. Recitation is a
+   * content restriction, so it groups with the filters.
+   */
+  ['safety', 'content_filter'],
+  ['blocklist', 'content_filter'],
+  ['prohibited_content', 'content_filter'],
+  ['spii', 'content_filter'],
+  ['recitation', 'content_filter'],
+  ['image_safety', 'content_filter'],
+  ['image_prohibited_content', 'content_filter'],
+  ['image_recitation', 'content_filter'],
+  ['malformed_function_call', 'error'],
+  ['unexpected_tool_call', 'error'],
+  ['malformed_response', 'error'],
+  ['missing_thought_signature', 'error'],
+  ['model_armor', 'content_filter'],
+  ['escalation', 'content_filter'],
+  /** A runaway tool loop the server aborted, not a request to execute tools. */
+  ['too_many_tool_calls', 'other'],
+  ['language', 'other'],
+  ['other', 'other'],
+  ['no_image', 'other'],
+  ['image_other', 'other'],
+  ['finish_reason_unspecified', 'other'],
+])
+
+/**
+ * Normalizes a provider's raw stop reason.
+ *
+ * Returns `undefined` when the provider reported nothing, so an absent reason stays
+ * distinguishable from one the vocabulary could not place. An unrecognized value maps
+ * to `'other'` rather than throwing: a provider adding a case must not fail a run
+ * that otherwise succeeded.
+ */
+export function normalizeFinishReason(
+  raw: string | null | undefined
+): AgentFinishReason | undefined {
+  if (!raw) return undefined
+  return NORMALIZED_BY_RAW.get(raw.trim().toLowerCase()) ?? 'other'
+}
diff --git a/apps/sim/providers/types.ts b/apps/sim/providers/types.ts
@@ -1,5 +1,6 @@
 import type { BillingAttributionSnapshot } from '@/lib/billing/core/billing-attribution'
 import type { ProviderTimingSegment, StreamingExecution, UserFile } from '@/executor/types'
+import type { AgentFinishReason } from '@/providers/finish-reason'
 
 export type ProviderId =
   | 'openai'
@@ -95,6 +96,11 @@ export interface ProviderResponse {
   }
   toolCalls?: FunctionCallResponse[]
   toolResults?: Record<string, unknown>[]
+  /**
+   * Why generation stopped, normalized across providers. Absent when the provider
+   * reported nothing; see {@link AgentFinishReason}.
+   */
+  finishReason?: AgentFinishReason
   timing?: {
     startTime: string
     endTime: string