Pick DeepSeek V4.1 Flash for software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0) or 1m-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak). Pick GLM 5.1 for long-horizon autonomous agentic engineering (up to 8-hour runs) or state-of-the-art open-weight coding (topped swe-bench pro at launch). On a tight budget at scale, DeepSeek V4.1 Flash is the value pick.
DeepSeek V4.1 Flash (DeepSeek) and GLM 5.1 (Z.ai) are two of the models people most often weigh against each other in 2026. DeepSeek V4.1 Flash is deepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens. GLM 5.1 is an open-weight (MIT) Chinese coding model built for long-horizon agentic engineering, topping SWE-Bench Pro at launch while running autonomously for up to 8 hours. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: DeepSeek V4.1 Flash is about 9.3× cheaper on input ($0.15/$0.6 per 1M tokens vs $1.4/$4.4 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
Context window: DeepSeek V4.1 Flash holds 5.2× more — 1.05M tokens (~1,573 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: DeepSeek V4.1 Flash is the newer model by about 5 months (released September 10, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
DeepSeek V4.1 Flash
GLM 5.1
Provider
DeepSeek (China)
Z.ai (China)
Released
September 10, 2026
April 7, 2026
Context window
1.05M tokens (~1,573 pages)
200K (~300 pages)
Price (in/out)
$0.15/$0.6 per 1M tokens
$1.4/$4.4 per 1M tokens
Open weight?
Yes — self-hostable
Yes — self-hostable
Modalities
text, image
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Software engineering (DeepSWE v1.1: 74.2, essentially level with Claude Opus 5's 74.0): DeepSeek V4.1 Flash — DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens — and it runs cheaper at $0.15/$0.6 per 1M tokens.
1M-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak): DeepSeek V4.1 Flash — Its 1.05M tokens window holds about 5.2× more than GLM 5.1's 200K in a single prompt.
Native multimodal vision, added over the text-only V4-Flash it replaces on most traffic: DeepSeek V4.1 Flash — DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens — and it carries the larger 1.05M tokens context.
Long-horizon autonomous agentic engineering (up to 8-hour runs): GLM 5.1 — GLM 5.1 lists long-horizon autonomous agentic engineering (up to 8-hour runs) among its strengths; DeepSeek V4.1 Flash does not.
State-of-the-art open-weight coding (topped SWE-Bench Pro at launch): GLM 5.1 — GLM 5.1 lists state-of-the-art open-weight coding (topped SWE-Bench Pro at launch) among its strengths; DeepSeek V4.1 Flash does not.
Sustained tool use across thousands of calls: GLM 5.1 — GLM 5.1 lists sustained tool use across thousands of calls among its strengths; DeepSeek V4.1 Flash does not.
Lowest cost at scale: DeepSeek V4.1 Flash — At $0.15/$0.6 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: DeepSeek V4.1 Flash — Its 1.05M tokens window is about 5.2× larger than GLM 5.1's 200K, fitting roughly 1,573 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: DeepSeek V4.1 Flash — At $0.15/$0.6 per 1M tokens it undercuts GLM 5.1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: DeepSeek V4.1 Flash — Larger 1.05M tokens window fits more in one prompt.
Anyone whose priority is software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0): DeepSeek V4.1 Flash — It is specifically built for that.
Anyone whose priority is long-horizon autonomous agentic engineering (up to 8-hour runs): GLM 5.1 — That is its strongest area.
DeepSeek V4.1 Flash: where it fits
DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens. Released September 10, 2026 by DeepSeek, it is built for software engineering (DeepSWE v1.1: 74.2, essentially level with Claude Opus 5's 74.0), 1M-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak), native multimodal vision, added over the text-only V4-Flash it replaces on most traffic, and mIT-licensed open weights, self-hostable.
Its trade-offs are real: the $0.15/$0.60 pricing is an off-peak rate — cost reportedly doubles during peak-demand hours, new Causal Encoder-Decoder architecture (8B active for input, 16B for output) is unproven at broader scale versus DeepSeek's mainline V4/V4-Pro line, and positioned as a cost/speed tier, not a frontier-reasoning flagship — DeepSeek kept V4-Pro running in parallel rather than replacing it outright. At $0.15 in / $0.6 out per million tokens, it sits in the budget price band.
GLM 5.1: where it fits
An open-weight (MIT) Chinese coding model built for long-horizon agentic engineering, topping SWE-Bench Pro at launch while running autonomously for up to 8 hours. Released April 7, 2026 by Z.ai, it is built for long-horizon autonomous agentic engineering (up to 8-hour runs), state-of-the-art open-weight coding (topped SWE-Bench Pro at launch), sustained tool use across thousands of calls, and self-hostable under a permissive MIT license.
Its trade-offs: text-only, with no image, audio, or video input, and 754B-parameter MoE demands heavy GPU resources to self-host. At $1.4 in / $4.4 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
DeepSeek V4.1 Flash and GLM 5.1 overlap enough that the right pick depends on your specific job. DeepSeek V4.1 Flash costs less per token; DeepSeek V4.1 Flash holds the larger context; and each leads in its own area — DeepSeek V4.1 Flash for software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0), GLM 5.1 for long-horizon autonomous agentic engineering (up to 8-hour runs). Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is DeepSeek V4.1 Flash or GLM 5.1 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, DeepSeek V4.1 Flash leans toward software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0) while GLM 5.1 leans toward long-horizon autonomous agentic engineering (up to 8-hour runs), and that positioning usually predicts which feels better on your codebase.
Which is cheaper, DeepSeek V4.1 Flash or GLM 5.1?
DeepSeek V4.1 Flash is cheaper — $0.15/$0.6 per 1M tokens vs $1.4/$4.4 per 1M tokens, roughly 9.3× apart on input.
Which has the bigger context window?
DeepSeek V4.1 Flash — 1.05M tokens vs 200K, about 5.2× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both DeepSeek V4.1 Flash and GLM 5.1 together?
Yes — a multi-model platform like LumiChats gives you DeepSeek V4.1 Flash, GLM 5.1 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, DeepSeek V4.1 Flash or GLM 5.1?
DeepSeek V4.1 Flash — released September 10, 2026, about 5 months after GLM 5.1.
DeepSeek V4.1 Flash vs GLM 5.1
DeepSeek · China | Z.ai · China · Updated June 2026
Quick verdict
Pick DeepSeek V4.1 Flash for software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0) or 1m-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak). Pick GLM 5.1 for long-horizon autonomous agentic engineering (up to 8-hour runs) or state-of-the-art open-weight coding (topped swe-bench pro at launch). On a tight budget at scale, DeepSeek V4.1 Flash is the value pick.
DeepSeek V4.1 Flash (DeepSeek) and GLM 5.1 (Z.ai) are two of the models people most often weigh against each other in 2026. DeepSeek V4.1 Flash is deepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens. GLM 5.1 is an open-weight (MIT) Chinese coding model built for long-horizon agentic engineering, topping SWE-Bench Pro at launch while running autonomously for up to 8 hours. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: DeepSeek V4.1 Flash is about 9.3× cheaper on input ($0.15/$0.6 per 1M tokens vs $1.4/$4.4 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
▸Context window: DeepSeek V4.1 Flash holds 5.2× more — 1.05M tokens (~1,573 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: DeepSeek V4.1 Flash is the newer model by about 5 months (released September 10, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
DeepSeek V4.1 Flash
GLM 5.1
Provider
DeepSeek (China)
Z.ai (China)
Released
September 10, 2026
April 7, 2026
Context window
1.05M tokens (~1,573 pages)
200K (~300 pages)
Price (in/out)
$0.15/$0.6 per 1M tokens
$1.4/$4.4 per 1M tokens
Open weight?
Yes — self-hostable
Yes — self-hostable
Modalities
text, image
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Software engineering (DeepSWE v1.1: 74.2, essentially level with Claude Opus 5's 74.0)
DeepSeek V4.1 Flash
DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens — and it runs cheaper at $0.15/$0.6 per 1M tokens.
1M-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak)
DeepSeek V4.1 Flash
Its 1.05M tokens window holds about 5.2× more than GLM 5.1's 200K in a single prompt.
Native multimodal vision, added over the text-only V4-Flash it replaces on most traffic
DeepSeek V4.1 Flash
DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens — and it carries the larger 1.05M tokens context.
Long-horizon autonomous agentic engineering (up to 8-hour runs)
GLM 5.1
GLM 5.1 lists long-horizon autonomous agentic engineering (up to 8-hour runs) among its strengths; DeepSeek V4.1 Flash does not.
State-of-the-art open-weight coding (topped SWE-Bench Pro at launch)
GLM 5.1
GLM 5.1 lists state-of-the-art open-weight coding (topped SWE-Bench Pro at launch) among its strengths; DeepSeek V4.1 Flash does not.
Sustained tool use across thousands of calls
GLM 5.1
GLM 5.1 lists sustained tool use across thousands of calls among its strengths; DeepSeek V4.1 Flash does not.
Lowest cost at scale
DeepSeek V4.1 Flash
At $0.15/$0.6 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
DeepSeek V4.1 Flash
Its 1.05M tokens window is about 5.2× larger than GLM 5.1's 200K, fitting roughly 1,573 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ DeepSeek V4.1 Flash
At $0.15/$0.6 per 1M tokens it undercuts GLM 5.1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ DeepSeek V4.1 Flash
Larger 1.05M tokens window fits more in one prompt.
Anyone whose priority is software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0)
→ DeepSeek V4.1 Flash
It is specifically built for that.
Anyone whose priority is long-horizon autonomous agentic engineering (up to 8-hour runs)
→ GLM 5.1
That is its strongest area.
DeepSeek V4.1 Flash: where it fits
DeepSeek's September 2026 flash-tier update adds native vision and a 1M-token window to its cost-efficient V4 line, at $0.15/$0.60 per million tokens. Released September 10, 2026 by DeepSeek, it is built for software engineering (DeepSWE v1.1: 74.2, essentially level with Claude Opus 5's 74.0), 1M-token context window at a fraction of frontier pricing ($0.15/$0.60 per million tokens off-peak), native multimodal vision, added over the text-only V4-Flash it replaces on most traffic, and mIT-licensed open weights, self-hostable.
Its trade-offs are real: the $0.15/$0.60 pricing is an off-peak rate — cost reportedly doubles during peak-demand hours, new Causal Encoder-Decoder architecture (8B active for input, 16B for output) is unproven at broader scale versus DeepSeek's mainline V4/V4-Pro line, and positioned as a cost/speed tier, not a frontier-reasoning flagship — DeepSeek kept V4-Pro running in parallel rather than replacing it outright. At $0.15 in / $0.6 out per million tokens, it sits in the budget price band.
GLM 5.1: where it fits
An open-weight (MIT) Chinese coding model built for long-horizon agentic engineering, topping SWE-Bench Pro at launch while running autonomously for up to 8 hours. Released April 7, 2026 by Z.ai, it is built for long-horizon autonomous agentic engineering (up to 8-hour runs), state-of-the-art open-weight coding (topped SWE-Bench Pro at launch), sustained tool use across thousands of calls, and self-hostable under a permissive MIT license.
Its trade-offs: text-only, with no image, audio, or video input, and 754B-parameter MoE demands heavy GPU resources to self-host. At $1.4 in / $4.4 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
DeepSeek V4.1 Flash and GLM 5.1 overlap enough that the right pick depends on your specific job. DeepSeek V4.1 Flash costs less per token; DeepSeek V4.1 Flash holds the larger context; and each leads in its own area — DeepSeek V4.1 Flash for software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0), GLM 5.1 for long-horizon autonomous agentic engineering (up to 8-hour runs). Rather than crowning one, run the same hard task through both once and let the results decide.
Want both DeepSeek V4.1 Flash and GLM 5.1 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is DeepSeek V4.1 Flash or GLM 5.1 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, DeepSeek V4.1 Flash leans toward software engineering (deepswe v1.1: 74.2, essentially level with claude opus 5's 74.0) while GLM 5.1 leans toward long-horizon autonomous agentic engineering (up to 8-hour runs), and that positioning usually predicts which feels better on your codebase.
Which is cheaper, DeepSeek V4.1 Flash or GLM 5.1?
DeepSeek V4.1 Flash is cheaper — $0.15/$0.6 per 1M tokens vs $1.4/$4.4 per 1M tokens, roughly 9.3× apart on input.
Which has the bigger context window?
DeepSeek V4.1 Flash — 1.05M tokens vs 200K, about 5.2× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both DeepSeek V4.1 Flash and GLM 5.1 together?
Yes — a multi-model platform like LumiChats gives you DeepSeek V4.1 Flash, GLM 5.1 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, DeepSeek V4.1 Flash or GLM 5.1?
DeepSeek V4.1 Flash — released September 10, 2026, about 5 months after GLM 5.1.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.