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GLM-5.3-Flash

zaizai/glm-5.3-flash

How TheRouter serves this differently from the vendor

As the vendor operates it

Z.AI documents GLM-5.3-Flash under the VLM section with text parameters matching GLM-5.3 and additional image_url input support. Context is 1M tokens, reasoning is always on (effort: low/high/max). No separate Flash pricing page has been extracted.

On TheRouter

TheRouter exposes zai/glm-5.3-flash through the OpenAI Chat Completion surface with 1M context, 131,072 max completion tokens, text+image input, text output, tools, tool_choice, response_format, and reasoning_effort. Pricing is $0.162/M input and $0.54/M output.

docs.z.ai ↗

API guide

Vision + text chat

GLM-5.3-Flash accepts image_url content blocks alongside text. Pass the image as a URL or base64 data URI in the user message content array.

cURL
curl https://api.therouter.ai/v1/chat/completions \
  -H "Authorization: Bearer $THEROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "zai/glm-5.3-flash",
    "reasoning_effort": "low",
    "messages": [
      {
        "role": "user",
        "content": [
          {"type": "image_url", "image_url": {"url": "https://example.com/diagram.png"}},
          {"type": "text", "text": "Describe the architecture shown in this diagram."}
        ]
      }
    ],
    "max_tokens": 800
  }'

Text-only chat completion

For text-only tasks, GLM-5.3-Flash behaves like a cost-efficient version of GLM-5.3. Use reasoning_effort: "max" for hard tasks, "low" to reduce TTFT on quick queries.

cURL
curl https://api.therouter.ai/v1/chat/completions \
  -H "Authorization: Bearer $THEROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "zai/glm-5.3-flash",
    "reasoning_effort": "high",
    "messages": [
      {"role": "system", "content": "You are a helpful assistant."},
      {"role": "user", "content": "Summarise the key risks in this migration plan."}
    ],
    "max_tokens": 600
  }'

Tool calling

Tool calling with GLM-5.3-Flash follows the same pattern as GLM-5.3. Reasoning runs before tool selection; at low effort this is fast enough for high-frequency agentic loops while staying inside the ~9x cost saving.

cURL
curl https://api.therouter.ai/v1/chat/completions \
  -H "Authorization: Bearer $THEROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "zai/glm-5.3-flash",
    "reasoning_effort": "low",
    "messages": [{"role": "user", "content": "Get the latest CI status for the main branch."}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_ci_status",
        "description": "Fetch CI pipeline status for a git branch",
        "parameters": {
          "type": "object",
          "properties": {"branch": {"type": "string"}},
          "required": ["branch"]
        }
      }
    }],
    "tool_choice": "auto"
  }'
Fact ledger — every claim on this page traces here
sourceURLretrieved
Context windowdocs.z.ai ↗2026-09-18verified
Maximum output tokenstherouter.ai ↗2026-09-18verified
Modalitiesdocs.z.ai ↗2026-09-18verified
Image inputdocs.z.ai ↗2026-09-18verified
Reasoningdocs.z.ai ↗2026-09-18verified
TheRouter pricingtherouter.ai ↗2026-09-18verified
Cost vs GLM-5.3 flagshiptherouter.ai ↗2026-09-18verified
API capabilitiesdocs.z.ai ↗2026-09-18verified
Generation familydocs.z.ai ↗2026-09-18verified
Training data cutoff——unknown
DeepSWE v1.1 (GLM-5.3 flagship, generation reference)docs.z.ai ↗2026-09-18verified
Z.ai Code Bench Max (GLM-5.3 flagship, generation reference)docs.z.ai ↗2026-09-18verified
CyberGym vulnerability discovery (GLM-5.3 flagship, generation reference)docs.z.ai ↗2026-09-18verified
GLM-5.3: Zhipu's Open-Source Flagship with 1M Context — API Integration and Routing GuideTheRouter Blog ↗2026-09-18verified
What is different between GLM-5.3-Flash and GLM-5.3?docs.z.ai ↗2026-09-18to verify
Can I disable reasoning in GLM-5.3-Flash?docs.z.ai ↗2026-09-18to verify
Is GLM-5.3-Flash suitable for production vision pipelines?therouter.ai ↗2026-09-18to verify
How does GLM-5.3-Flash compare to Google Gemini Flash for multimodal tasks?therouter.ai ↗2026-09-18to verify
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