Seedream 5.5 vs Nano Banana vs GPT Image: A Routing Guide (2026)

ByteDance’s chart prefers Seedream 5.5 to GPT Image 2.5 Sunburst and Nano Banana 2.1. Only the last two can be called.

Seedream 5.5 versus GPT Image 2.5 Sunburst versus Nano Banana 2.1 is the comparison the launch post invites, and it is the wrong comparison to ship on. Seed says 5.5 leads those two on text structure, and leads on text-to-image realism. Sunburst and Nano Banana 2.1 have SandBase cards as of 9 November 2026. Seedream 5.5 does not. A Good/Same/Bad score from the vendor’s own judges is not a model ID.

If the job is “a Seedream image today,” use Seedream 5.0 Pro. If the job is “the Sunburst or Nano Banana 2.1 named in that chart,” open those cards and test your prompts. Do not wait for a 5.5 route that has not been published, and do not treat the chart as the test.

Key takeaway

• ByteDance’s MagicArena note (9 November 2026) says Seedream 5.5 leads GPT Image 2.5 Sunburst and Nano Banana 2.1 on text structure for both text-to-image and image-to-image, with a substantial text-to-image realism advantage. That study is vendor-run.
• The same note’s only printed GSB percentage is +55.62% for image-to-image realism versus Seedream 5.0 Pro, not versus Sunburst or Nano Banana.
• Seedream 5.5 had no API ID on the Seed post, Ark’s November release table, or Ark’s price table. SandBase returned “Model Not Found.”
• Our October poster test measured Seedream 5.0 Pro, GPT Image 2.5 Flare, and Nano Banana 2. It did not measure 5.5, Sunburst, or Nano Banana 2.1.
• Callable today on SandBase: Seedream 5.0 Pro ($0.09), Seedream 5.0 Flash ($0.018), GPT Image 2.5 Sunburst, and Nano Banana 2.1.

Where Seedream is today

Seedream you can call is still the 5.0 family. The chart’s other names have their own cards. This series is linked at the end.

• Seedream 5.0 Pro introduction and Fast versus Pro: the callable Seedream tiers.
• Seedream versus Qwen Image versus Nano Banana: an earlier three-way look, not a 5.5 result.
• GPT Image 2.5 Flare vs Sunburst is a documentation comparison. Nano Banana 2.1 release status recorded an October gap that the SandBase card has since closed. GPT Image 2.6 is a later OpenAI route the chart does not name. The exact-text study is the e-commerce benchmark.
• Cards: Seedream 5.0 Flash at $0.018, Seedream 5.0 Pro Fast (HTTP 200; price not quoted here), GPT Image 2.5 Sunburst, Nano Banana 2.1. ByteDance’s catalog home is the vendor page. No 5.5 URL exists to link. Calls use the run API.

A preference score without a prompt list is a press chart. Keep it in that drawer.

Who can actually be called

Checked 9 November 2026. “Listed price” means the figure printed on the SandBase card that day, not a forecast.

Sunburst’s card publishes this list-style table. Quality down the side, resolution across. High is marked as the default.

The same page showed a 25% off badge. The structured price on the page was $0.0675, which is 25% under the high/1k cell. Read the card at order time. Do not bake either number into a year-long forecast from this sentence alone. Failed runs on the Seedream 5.0 Pro card are not charged. I am not copying that sentence onto Sunburst or Nano Banana 2.1 without their cards saying it.

SandBase GPT Image 2.5 Sunburst card on 9 Nov 2026, including the 25% off badge and a saved-example estimate of $0.0675.

Nano Banana 2.1’s card describes a fast image model with cleaner text, extreme aspect ratios, and 1K to 4K output. That sentence is SandBase catalog copy retrieved that day, not a Google specification I re-read. On 6 October our status note recorded that plausible 2.1 IDs 404’d. The card exists now. The October “not listed” line is stale. Google’s own API ID was not re-checked for this piece.

SandBase Nano Banana 2.1 card on 9 Nov 2026 (google/nano-banana-2.1).

One thousand Seedream 5.0 Pro images at the listed $0.09 is $90. One thousand Flash images at $0.018 is $18. There is no matching line for 5.5.

Vendor claims versus what we already measured

ByteDance, on MagicArena, with experienced image evaluators, six uses (e-commerce, marketing, film and television, gaming, office, fashion):

• Versus Seedream 5.0 Pro, quality scores and usability rates rose in all six. Film and office usability were more than twice the previous version. The base rates are not in the prose.
• GSB (Good / Same / Bad) versus the previous version was positive on all four cells: text structure and realism, text-to-image and image-to-image. +55.62% is image-to-image realism versus 5.0 Pro.
• Versus Sunburst and Nano Banana 2.1: lead on text structure in both task types; substantial advantage on text-to-image realism. No percentage for those matchups is printed in the prose.
• Severe text corruption 0.4%, minor 1.7%, Chinese and English, including dense small text. Other models’ rates are not printed.

What SandBase published on 3 October 2026 is a different test. Five e-commerce poster prompts, two images each, exact-string grading, square output, English prompts. The writeup records:

Seven of eleven models tied at 10/10, including Qwen Image 3 and Wan 2.7 Pro. Ten images cannot separate a 90% model from a 100% model. The study scored strings, not realism, not edit stability, not transparency. Sunburst was not in it. Nano Banana 2.1 was not in it. Seedream 5.5 did not exist in public yet. Seedream 5.0 Pro’s SandBase list price on 9 November is $0.09, not the $0.0675 billed in October. Keep the old figure as a dated bill, not as today’s rate.

I would not publish a ranking that subtracts October pass rates from November GSB points. The units do not match. The models do not match.

Realism

Seed’s realism claim for 5.5 is about light, materials, skin, less gloss, less overexposure. Against Sunburst and Nano Banana 2.1 they single out text-to-image realism as a substantial advantage, and they print a number only against their own 5.0 Pro (+55.62% on image-to-image realism). We have not run a realism panel on any of these November names. The October test did not score photographs for looking real. If realism is the purchase reason, the honest next step is a paired review on your products, on models that return HTTP 200. Seedream 5.5 is not one of them yet.

Text

This is the cell people will quote. Seed says 5.5 leads Sunburst and Nano Banana 2.1 on text structure, and that severe corruption is 0.4%. Our October exact-text test says Seedream 5.0 Pro, Flare, and Nano Banana 2 each put every required string on 10 posters that day, alongside four other models. Flare is not Sunburst. Nano Banana 2 is not 2.1. A 0.4% corruption rate and a 10/10 exact-string day are not the same metric. Use the October method on whichever card you can call: quote the strings, generate two, read them yourself, and send CJK to a person. The poster workflow is that checklist. Do not copy 0.4% into a Seedream 5.5 SLA, and do not copy 10/10 onto Sunburst.

Editing

Seed’s 5.5 demo holds unedited regions at what they call pixel level across 100 rounds, feeding each output back in. We have not diffed that video. Sunburst’s documented positioning, from the September Flare versus Sunburst note, is tighter control across edits. That note compared documentation, not a head-to-head generation. Nano Banana 2.1’s card does not, in the fields we read, advertise a 100-round pixel lock.

Seedream 5.0 Pro’s edit card on SandBase is a different object from the 5.5 claim. ID bytedance/seedream/5.0/pro/edit. Up to 10 reference images. $0.09 per output image plus $0.003 for each input after the first. The schema does not contain a “lock these pixels” switch. Keeping a product still is something you check with a diff, on 5.0 today and on 5.5 when an ID exists.

Transparency

Native RGBA, including partial transparency, is a 5.5 claim. It is not a field on the Seedream 5.0 Pro text-to-image card, which offers jpeg or png and does not mention an alpha switch. Sunburst’s card lists jpeg, png, and webp. I did not see an alpha parameter there either, and I will not infer one. If the deliverable is a sticker, read the workflow note and keep a cutout step until a 5.5 response actually contains an alpha channel.

Quick routing

There is a case where none of the image models is the right tool. If the only change is a price in an editable layer, change the layer. The September Sunburst note made that point about 2.5. It still applies when a newer chart shows up.

Try today on SandBase

Seedream 5.0 Pro sample on the same exact-text prompt. Not a 5.5 output.

Seedream 5.0 Flash draft of the same prompt for cost comparison. Not a 5.5 output.

API status, 9 November 2026: there is no Seedream 5.5 model string. Do not write a 5.5 client. The request below calls 5.0 Pro.

Same endpoint as the other image cards. This calls 5.0 Pro. It does not call 5.5. Swap model only to an ID in the table above. Poll GET /v1/run/{id} if status comes back pending or running, and read outputs[0].url only after completed.

curl -s https://api.sandbase.ai/v1/run \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "bytedance/seedream/5.0/pro",
    "prompt": "Square studio product photo of a matte black bottle on a light gray background. Headline exactly: \"STAY COLD 24 HOURS\". Price exactly: \"$39.99\". No other text.",
    "aspect_ratio": "1:1",
    "num_images": 1,
    "output_format": "png"
  }'

Flash is that body with bytedance/seedream/5.0/flash. Sunburst’s card uses its own fields (quality, resolution, aspect_ratio, output_format), so do not paste the Seedream body onto openai/gpt-image-2.5-sunburst and assume the defaults match. Open the card. This article did not run the curl.

FAQ

Which is better, Seedream 5.5 or GPT Image 2.5 Sunburst?

ByteDance’s evaluators preferred 5.5 on text structure and reported a substantial text-to-image realism advantage. They did not publish the prompts or the vote counts. Sunburst can be called. 5.5 cannot, as of 9 November 2026. Better for a production job means the one that answers the request.

Which is better for text, 5.5 or Nano Banana 2.1?

Seed says 5.5 leads on text structure. Our October exact-text test did not include 2.1 or 5.5. Nano Banana 2.1 is listed on SandBase now. Run your strings on that card, and on Seedream 5.0 Pro, before you believe either headline.

Is Seedream 5.5 cheaper?

No published price. Secondary reports of about 0.28 yuan are not on Ark’s price table. Seedream 5.0 Pro on SandBase is $0.09 per image. Flash is $0.018. Sunburst’s card has the quality and resolution table above, plus a 25% off badge.

Can one SandBase key call the models that exist?

Yes for the cards that return HTTP 200: Seedream 5.0 Pro, Flash, GPT Image 2.5 Sunburst, Nano Banana 2.1, and the GPT Image 2.6 routes. Seedream 5.5 is not among them.

Should I switch off 5.0 Pro because of this chart?

Not on the chart alone. Keep 5.0 Pro for Seedream work until a 5.5 ID, a price, and your own text, edit-diff, and alpha checks exist. Use Sunburst or Nano Banana 2.1 when those products are the ones you meant to buy.

Stay in the Seedream cluster: the 5.0 Pro introduction, the Fast versus Pro note, and Seedream versus Qwen Image versus Nano Banana.

Related reading

• Seedream 5.5 launch note: what was announced, and the blanks.
• E-commerce text and RGBA: posters and stickers without a 5.5 route.

The click that works today

Sign in or open the model catalog and run the prompt on Seedream 5.0 Pro. If the chart made you curious about the named rivals, run the same prompt on Sunburst and Nano Banana 2.1. Save the three files. They are a real comparison. The GSB is a published opinion about a different one.