diff --git a/AGENTS.md b/AGENTS.md
index 81e1b70..c20215e 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -80,7 +80,7 @@ content.
 ### Research tag filtering
 
 - Client-side JS filtering plus pre-generated tag pages for SEO.
-- Tags must use `<div class="tags"><span>TagName</span></div>` in
+- Tags must use `<div class="tags"><button type="button">TagName</button></div>` in
   `_research/index.md`.
 
 ### Redirect pages
@@ -133,7 +133,7 @@ Add to `_research/index.md` in this exact form:
 ```markdown
 <h3 id="NUMBER">[NUMBER] Author1, A., **Author2, B.**, & Author3, C. Title. _Journal_, Volume, Pages (Year).</h3>
 
-<div class="tags"><span>Tag1</span><span>Tag2</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Tag1</button><button type="button" aria-pressed="false">Tag2</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Badge](https://img.shields.io/static/v1.svg?style=flat-square&label=LABEL&message=MESSAGE&color=COLOR)](URL)
 ```
diff --git a/README.md b/README.md
index 834f5b0..18793b6 100644
--- a/README.md
+++ b/README.md
@@ -345,7 +345,7 @@ present:
 ```markdown
 <h3 id="NUMBER">[NUMBER] Author1, A., **Author2, B.**, & Author3, C. Title. _Journal_, Volume, Pages (Year).</h3>
 
-<div class="tags"><span>Tag1</span><span>Tag2</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Tag1</button><button type="button" aria-pressed="false">Tag2</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Badge1](https://img.shields.io/static/v1.svg?style=flat-square&label=LABEL&message=MESSAGE&color=COLOR)](URL)
 [![Badge2](https://img.shields.io/static/v1.svg?style=flat-square&label=LABEL&message=MESSAGE&color=COLOR)](URL)
@@ -547,7 +547,7 @@ The search functionality includes content from our external blog at blogs.comphy
 Research papers can be tagged with multiple topics. Tags are defined in the markdown files using the following format:
 
 ```html
-<div class="tags"><span>Tag1</span><span>Tag2</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Tag1</button><button type="button" aria-pressed="false">Tag2</button></div>
 ```
 
 These tags are:
diff --git a/_layouts/research.html b/_layouts/research.html
index 6d83c4e..380b9b0 100644
--- a/_layouts/research.html
+++ b/_layouts/research.html
@@ -99,6 +99,8 @@ <h3>Contents</h3>
   /* Hidden paper (filtered out) */
   .research-content .paper-container.hidden { display: none; }
   /* Active tag (clicked) gets a teal solid treatment */
+  .research-content .tags button.active,
+  .research-content .tags button[aria-pressed="true"],
   .research-content .tags span.active,
   .r-theme__tag.active {
     background: var(--c-accent-teal);
diff --git a/_research/index.md b/_research/index.md
index 04899c4..2cd750a 100644
--- a/_research/index.md
+++ b/_research/index.md
@@ -5,29 +5,29 @@ title: Research
 
 ## Sort by topic
 
-<div class="tags"><span>Bubbles</span></div>
-<div class="tags"><span>Drops</span></div>
-<div class="tags"><span>Jets</span></div>
-<div class="tags"><span>Sheets</span></div>
-<div class="tags"><span>Non-Newtonian</span></div>
-<div class="tags"><span>Coalescence</span></div>
-<div class="tags"><span>Superamphiphobic-surfaces</span></div>
-<div class="tags"><span>Impact forces</span></div>
-<div class="tags"><span>Dissipative anomaly</span></div>
-<div class="tags"><span>Soft-matter-singularities</span></div>
-<div class="tags"><span>Elastic beads</span></div>
-<div class="tags"><span>Bouncing</span></div>
-<div class="tags"><span>Rupture</span></div>
-<div class="tags"><span>Contact line</span></div>
-<div class="tags"><span>Marangoni flows</span></div>
-<div class="tags"><span>Numerical methods</span></div>
-<div class="tags"><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Jets</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Sheets</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Non-Newtonian</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Coalescence</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Superamphiphobic-surfaces</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Impact forces</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Dissipative anomaly</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Soft-matter-singularities</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Elastic beads</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Bouncing</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Rupture</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Contact line</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Marangoni flows</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Numerical methods</button></div>
+<div class="tags"><button type="button" aria-pressed="false">Featured</button></div>
 
 ## Work in Progress
 
 ### Gordillo, J. M., Rodríguez-Rodríguez, J., & <strong>Sanjay, V.</strong> Self-similar Worthington jets. arXiv preprint arXiv:2607.08972 (2026). {#self-similar-worthington-jets}
 
-<div class="tags"><span>Bubbles</span><span>Jets</span><span>Soft-matter-singularities</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2607.08972&color=green)](https://arxiv.org/abs/2607.08972)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/comphy-lab/Bursting-Bubble)
@@ -38,13 +38,13 @@ title: Research
 
 ### Yang, Z., <strong>Sanjay, V.</strong>, Constante-Amores, C. R., & Feng, J. Confinement-Induced Suppression of Jet Drop Size by Bubble Bursting in Shallow Liquids. arXiv preprint arXiv:2606.28609 (2026).
 
-<div class="tags"><span>Bubbles</span><span>Jets</span><span>Drops</span><span>Soft-matter-singularities</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Soft-matter-singularities</button></div>
 
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2606.28609&color=green)](https://arxiv.org/abs/2606.28609)
 
 ### Ghaemi, A. H., Yang, Z., Huang, A., <strong>Sanjay, V.</strong>, Feng, J., & Constante-Amores, C. R. Bursting bubbles in Herschel-Bulkley fluids: dynamics and jetting transitions. arXiv preprint arXiv:2511.23345 (2025).
 
-<div class="tags"><span>Bubbles</span><span>Non-Newtonian</span><span>Jets</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Non-Newtonian</button><button type="button" aria-pressed="false">Jets</button></div>
 
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2511.23345&color=green)](https://arxiv.org/abs/2511.23345)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/comphy-lab/BurstingBubble_Herschel-Bulkley/)
@@ -54,7 +54,7 @@ title: Research
 
 <h3 id="26">[26] <strong>Sanjay, V.</strong> Singularities in Soft Matter Systems. Contemporary Physics (2026).</h3>
 
-<div class="tags"><span>Soft-matter-singularities</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Contemporary Physics](https://img.shields.io/static/v1.svg?style=flat-square&label=Contemporary%20Physics&message=DOI:%2010.1080%2F00107514.2026.2721118&color=orange)](https://doi.org/10.1080/00107514.2026.2721118)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2608.11060&color=green)](https://arxiv.org/abs/2608.11060)
@@ -63,7 +63,7 @@ title: Research
 
 <h3 id="25">[25] Verschuur, C. I., Oratis, A. T., <strong>Sanjay, V.</strong>, & Snoeijer, J. H. How elasticity affects bubble pinch-off. Phys. Rev. Fluids, 11, 073302 (2026).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Soft-matter-singularities</span><span>Elastic beads</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Elastic beads</button></div>
 
 [![PRF](https://img.shields.io/static/v1.svg?style=flat-square&label=PRF&message=DOI:%2010.1103%2F5sp3-k5l2&color=orange)](https://doi.org/10.1103/5sp3-k5l2)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2511.20075&color=green)](https://arxiv.org/abs/2511.20075)
@@ -81,7 +81,7 @@ title: Research
 
 <h3 id="24">[24] Appleford, T., <strong>Sanjay, V.</strong>, & Jalaal, M. Rheology of Two-Dimensional Dilute Emulsions. Phys. Rev. Fluids, 11, 033607 (2026).</h3>
 
-<div class="tags"><span>Emulsions</span><span>Rheology</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Emulsions</button><button type="button" aria-pressed="false">Rheology</button></div>
 
 [![PRF](https://img.shields.io/static/v1.svg?style=flat-square&label=PRF&message=DOI:%2010.1103%2F9dgt-rkp5&color=orange)](https://doi.org/10.1103/9dgt-rkp5)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2508.13022&color=green)](https://arxiv.org/abs/2508.13022)
@@ -90,7 +90,7 @@ title: Research
 
 <h3 id="23">[23] <strong>Jana, S.</strong>, Kolinski, J., Lohse, D., & <strong>Sanjay, V.</strong> Impacting spheres: from liquid drops to elastic beads. Soft Matter, 22, 2226-2236 (2026).</h3>
 
-<div class="tags"><span>Drops</span><span>Impact forces</span><span>Elastic beads</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Impact forces</button><button type="button" aria-pressed="false">Elastic beads</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Soft Matter](https://img.shields.io/static/v1.svg?style=flat-square&label=Soft%20Matter&message=DOI:%2010.1039%2FD5SM01078K&color=orange)](https://doi.org/10.1039/D5SM01078K)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2510.24855&color=green)](https://arxiv.org/abs/2510.24855)
@@ -111,7 +111,7 @@ title: Research
 
 <h3 id="22">[22] <strong>Dixit, A. K.</strong>, Zhao, C., Zaleski, S., Lohse, D., & <strong>Sanjay, V.</strong> Holes in Sheets: Double-Threshold Rupture of Draining Liquid Films. Phys. Rev. Lett., 136, 084001 (2026).</h3>
 
-<div class="tags"><span>Sheets</span><span>Rupture</span><span>Soft-matter-singularities</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Sheets</button><button type="button" aria-pressed="false">Rupture</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Phys. Rev. Lett.](https://img.shields.io/static/v1.svg?style=flat-square&label=Phys.%20Rev.%20Lett.&message=DOI:%2010.1103%2Fbdpw-7mr5&color=orange)](https://doi.org/10.1103/bdpw-7mr5)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2509.12789&color=green)](https://arxiv.org/abs/2509.12789)
@@ -122,7 +122,7 @@ title: Research
 
 <h3 id="21">[21] Díaz, D., <strong>Bhargava, A. S.</strong>, Walz, F., Sharifi, A., Summaly, S., Berger, R., Kappl, M., Butt, H.-J., Lohse, D., Willers, T., <strong>Sanjay, V.</strong>, & Vollmer, D. Stood-up Drop to Determine Receding Contact Angles. Soft Matter, 22, 657-667 (2026).</h3>
 
-<div class="tags"><span>Drops</span><span>Contact line</span><span>Superamphiphobic-surfaces</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Contact line</button><button type="button" aria-pressed="false">Superamphiphobic-surfaces</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![Soft Matter](https://img.shields.io/static/v1.svg?style=flat-square&label=Soft%20Matter&message=DOI:%2010.1039%2FD5SM00985E&color=orange)](https://doi.org/10.1039/D5SM00985E)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2511.20259&color=green)](https://arxiv.org/abs/2511.20259)
@@ -133,7 +133,7 @@ title: Research
 
 <h3 id="20">[20] Demirkır, Ç., Yang, R., Bashkatov, A., <strong>Sanjay, V.</strong>, Lohse, D., & Krug, D. To jump or not to jump: Adhesion and viscous dissipation dictate the detachment of coalescing wall-attached bubbles. Phys. Rev. Fluids, 10, 123602 (2025).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Coalescence</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Coalescence</button></div>
 
 [![PRF](https://img.shields.io/static/v1.svg?style=flat-square&label=PRF&message=OA&color=orange)](https://doi.org/10.1103/nq3w-57gg)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2501.05532&color=green)](https://arxiv.org/abs/2501.05532)
@@ -144,7 +144,7 @@ title: Research
 
 <h3 id="19">[19] Mclauchlan, J., Walker, J. S., <strong>Sanjay, V.</strong>, Jalaal, M., Reid, J. P., Squires, A. M., & Souslov, A. Bouncing microdroplets on hydrophobic surfaces. Proc. Natl. Acad. Sci., 122, e2507309122 (2025).</h3>
 
-<div class="tags"><span>Drops</span><span>Bouncing</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Bouncing</button></div>
 
 [![PNAS](https://img.shields.io/static/v1.svg?style=flat-square&label=PNAS&message=OA&color=orange)](https://doi.org/10.1073/pnas.2507309122)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2503.22527&color=green)](https://arxiv.org/abs/2503.22527)
@@ -152,7 +152,7 @@ title: Research
 
 <h3 id="18">[18] Saini, M., <strong>Sanjay, V.</strong>, Saade, Y., Lohse, D., & Popinet, S. Implementation of integral surface tension formulations in a volume of fluid framework and their applications to Marangoni flows. J. Comput. Phys., 542, 114348 (2025).</h3>
 
-<div class="tags"><span>Marangoni flows</span><span>Numerical methods</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Marangoni flows</button><button type="button" aria-pressed="false">Numerical methods</button></div>
 
 [![J. Comput. Phys.](https://img.shields.io/static/v1.svg?style=flat-square&label=J.%20Comput.%20Phys.&message=OA&color=orange)](https://doi.org/10.1016/j.jcp.2025.114348)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/comphy-lab/marangoniSheet)
@@ -160,7 +160,7 @@ title: Research
 
 <h3 id="17">[17] Bashkatov, A., Bürkle, F., Demirkır, Ç., Ding, W., <strong>Sanjay, V.</strong>, Babich, A., Yang, X., Mutschke, G., Czarske, J., Lohse, D., Krug, D., Lars, B., & Eckert, E. Electrolyte droplet spraying in H2 bubbles during water electrolysis under normal and microgravity conditions. Nat. Commun., 16, 4580 (2025).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Jets</span><span>Coalescence</span><span>Soft-matter-singularities</span><span>Drops</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Coalescence</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Drops</button></div>
 
 [![Nat. Commun.](https://img.shields.io/static/v1.svg?style=flat-square&label=Nat.%20Commun.&message=OA&color=orange)](https://doi.org/10.1038/s41467-025-59762-7)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2409.00515&color=green)](https://arxiv.org/abs/2409.00515)
@@ -171,7 +171,7 @@ title: Research
 
 <h3 id="16">[16] <strong>Dixit, A.</strong>, Oratis, A., Zinelis, K., Lohse, D., & <strong>Sanjay, V.</strong> Viscoelastic Worthington Jets and Droplets Produced by Bursting Bubbles. J. Fluid Mech., 1010, A2 (2025).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Non-Newtonian</span><span>Jets</span><span>Soft-matter-singularities</span><span>Drops</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Non-Newtonian</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Drops</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2025.237)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2408.05089&color=green)](https://arxiv.org/abs/2408.05089)
@@ -182,7 +182,7 @@ title: Research
 
 <h3 id="15">[15] <strong>Sanjay, V.</strong>, & Lohse, D. Unifying theory of scaling in drop impact: Forces & maximum spreading diameter. Phys. Rev. Lett., 134, 104003 (2025).</h3>
 
-<div class="tags"><span>Drops</span><span>Dissipative anomaly</span><span>Superamphiphobic-surfaces</span><span>Impact forces</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Dissipative anomaly</button><button type="button" aria-pressed="false">Superamphiphobic-surfaces</button><button type="button" aria-pressed="false">Impact forces</button></div>
 
 [![PRL](https://img.shields.io/static/v1.svg?style=flat-square&label=PRL&message=OA&color=orange)](https://doi.org/10.1103/PhysRevLett.134.104003)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2408.12714&color=green)](https://arxiv.org/abs/2408.12714)
@@ -193,7 +193,7 @@ title: Research
 
 <h3 id="14">[14] <strong>Sanjay, V.</strong>, Zhang, B., Lv, C., & Lohse, D. The role of viscosity on drop impact forces on non-wetting surfaces. J. Fluid Mech., 1004, A6 (2025).</h3>
 
-<div class="tags"><span>Drops</span><span>Impact forces</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Impact forces</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2024.982)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2311.03012&color=green)](https://arxiv.org/abs/2311.03012)
@@ -214,7 +214,7 @@ title: Research
 
 <h3 id="13">[13] Kayal, L., <strong>Sanjay, V.</strong>, Yewale, N., Kumar, A., & Dasgupta, R. Focusing of concentric free-surface waves. J. Fluid Mech., 1003, A14 (2025).</h3>
 
-<div class="tags"><span>Waves</span><span>Dissipative anomaly</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Waves</button><button type="button" aria-pressed="false">Dissipative anomaly</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2024.1089)
 [![arXiv](https://img.shields.io/static/v1.svg?style=flat-square&label=arXiv&message=2406.05416&color=green)](https://arxiv.org/abs/2406.05416)
@@ -227,7 +227,7 @@ title: Research
 
 <h3 id="12">[12] Balasubramanian, A. G., <strong>Sanjay, V.</strong>, Jalaal, M., Vinuesa, R., & Tammisola, O. Bursting bubble in an elastoviscoplastic medium. J. Fluid Mech., 1001, A9 (2024).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Non-Newtonian</span><span>Jets</span><span>Soft-matter-singularities</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Non-Newtonian</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Soft-matter-singularities</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2024.1073)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/comphy-lab/2023_Bubble-bursting-in-an-elasto-viscoplastic-medium)
@@ -249,7 +249,7 @@ title: Research
 
 <h3 id="11">[11] <strong>Sanjay, V.</strong>, Chantelot, P., & Lohse, D. When does an impacting drop stop bouncing? J. Fluid Mech., 958, A26 (2023).</h3>
 
-<div class="tags"><span>Drops</span><span>Bouncing</span><span>Dissipative anomaly</span><span>Featured</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Bouncing</button><button type="button" aria-pressed="false">Dissipative anomaly</button><button type="button" aria-pressed="false">Featured</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2023.55)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/comphy-lab/Drop-Impact)
@@ -259,7 +259,7 @@ title: Research
 
 <h3 id="10">[10] <strong>Sanjay, V.</strong>, Lakshman, S., Chantelot, P., Snoeijer, J. H., & Lohse, D. Drop impact on viscous liquid films. J. Fluid Mech., 958, A25 (2023).</h3>
 
-<div class="tags"><span>Drops</span><span>Bouncing</span><span>Superhydrophobic surfaces</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Bouncing</button><button type="button" aria-pressed="false">Superhydrophobic surfaces</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2023.13)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/VatsalSy/Drop-impact-on-viscous-liquid-films)
@@ -271,7 +271,7 @@ title: Research
 
 <h3 id="thesis">➡️ <strong>Sanjay, V.</strong> Viscous free-surface flows. Ph.D. Thesis, Physics of Fluids, University of Twente (2022).</h3>
 
-<div class="tags"><span>Drops</span><span>Jets</span><span>Sheets</span><span>Bubbles</span><span>Soft-matter-singularities</span><span>Non-Newtonian</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Sheets</button><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Soft-matter-singularities</button><button type="button" aria-pressed="false">Non-Newtonian</button></div>
 
 [![PhD thesis](https://img.shields.io/static/v1.svg?logo=adobeacrobatreader&style=flat-square&label=Thesis&message=Download&color=green)](https://qrco.de/bd9SHU)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=UT&message=link&color=orange)](https://doi.org/10.3990/1.9789036554077)
@@ -281,7 +281,7 @@ title: Research
 
 <h3 id="9">[9] <strong>Sanjay, V.</strong>, Sen, U., Kant, P., and Lohse, D. Taylor–Culick retractions and the influence of the surroundings. J. Fluid Mech., 948, A14 (2022).</h3>
 
-<div class="tags"><span>Sheets</span><span>Dissipative anomaly</span><span>Retraction</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Sheets</button><button type="button" aria-pressed="false">Dissipative anomaly</button><button type="button" aria-pressed="false">Retraction</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2022.671)
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/VatsalSy/Taylor-Culick-retractions)
@@ -291,7 +291,7 @@ title: Research
 
 <h3 id="8">[8] Zhang, B., <strong>Sanjay, V.</strong>, Shi, S., and Zhao, Y., and Lv, C., and Feng, X.-Q., & Lohse, D. Impact forces of water drops falling on superhydrophobic surfaces. Phys. Rev. Lett., 129(10), 104501 (2022).</h3>
 
-<div class="tags"><span>Drops</span><span>Superhydrophobic surfaces</span><span>Impact forces</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Superhydrophobic surfaces</button><button type="button" aria-pressed="false">Impact forces</button></div>
 
 [![GitHub](https://img.shields.io/badge/GitHub-100000?style=flat-square&logo=github&logoColor=white)](https://github.com/VatsalSy/Impact-forces-of-water-drops-falling-on-superhydrophobic-surfaces)
 [![PDF](https://img.shields.io/static/v1.svg?logo=adobeacrobatreader&style=flat-square&label=PDF&message=Download&color=green)](https://qrco.de/bd9aV3)
@@ -311,7 +311,7 @@ title: Research
 
 <h3 id="7">[7] <strong>Sanjay, V.</strong>, Lohse, D., & Jalaal, M. Bursting bubble in a viscoplastic medium. J. Fluid Mech., 922, A2 (2021).</h3>
 
-<div class="tags"><span>Bubbles</span><span>Jets</span><span>Non-Newtonian</span><span>Soft-matter-singularities</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Bubbles</button><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Non-Newtonian</button><button type="button" aria-pressed="false">Soft-matter-singularities</button></div>
 
 [![JFM](https://img.shields.io/static/v1.svg?style=flat-square&label=JFM&message=OA&color=orange)](https://doi.org/10.1017/jfm.2021.489)
 [![arXiv](https://img.shields.io/badge/arXiv-2101.07744-green?style=flat-square)](https://arxiv.org/abs/2101.07744)
@@ -324,7 +324,7 @@ title: Research
 
 <h3 id="6">[6] Ramírez-Soto, O., <strong>Sanjay, V.</strong>, Lohse, D., Pham, J. T., & Vollmer, D. Lifting a sessile oil drop from a superamphiphobic surface with an impacting one. Sci. Adv., 6(34), eaba4330 (2020).</h3>
 
-<div class="tags"><span>Drops</span><span>Superamphiphobic-surfaces</span><span>Lifting</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Drops</button><button type="button" aria-pressed="false">Superamphiphobic-surfaces</button><button type="button" aria-pressed="false">Lifting</button></div>
 
 [![Sci. Adv.](https://img.shields.io/static/v1.svg?style=flat-square&label=Sci.%20Adv.&message=OA&color=orange)](https://doi.org/10.1126/sciadv.aba4330)
 [![arXiv](https://img.shields.io/badge/arXiv-1912.02667-green?style=flat-square)](https://arxiv.org/abs/1912.02667)
@@ -337,7 +337,7 @@ title: Research
 
 <h3 id="5">[5] Jain, A., <strong>Sanjay, V.</strong>, & Das, A. K. Consequences of inclined and dual jet impingement in stagnant liquid and stratified layers. AIChE J., 65(1), 372-384 (2019).</h3>
 
-<div class="tags"><span>Jets</span><span>Bubbles</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Bubbles</button></div>
 
 [![PDF](https://img.shields.io/static/v1.svg?style=flat-square&label=PDF&message=Available&color=green)](https://www.dropbox.com/scl/fi/ug7njhulcy9zq8lib911j/2019-Vatsal-_Consequences-of-Inclined-and-Dual-Jet-Impingement-in-Stagnant-Liquid-and-Stratified-Layers.pdf?rlkey=l00thknv7wt55sb0bcuiy8isw&dl=0)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=DOI&message=10.1002/aic.16373&color=orange)](https://doi.org/10.1002/aic.16373)
@@ -349,7 +349,7 @@ title: Research
 
 <h3 id="4">[4] Soni, A., <strong>Sanjay, V.</strong>, & Das, A. K. Formation of fluid structures due to jet-jet and jet-sheet interactions. Chem. Eng. Sci., 191, 67-77 (2018).</h3>
 
-<div class="tags"><span>Jets</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Jets</button></div>
 
 [![PDF](https://img.shields.io/static/v1.svg?style=flat-square&label=PDF&message=Available&color=green)](https://www.dropbox.com/scl/fi/zbs17s77qlu2l2i4c6sak/2018-Vatsal-preprint-_Formation-of-fluid-structures-due-to-jet-jet-and-jet-sheet-interactions.pdf?rlkey=beya847mr9hf8bbdabwyanrmf&dl=0)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=DOI&message=10.1016/j.ces.2018.06.055&color=orange)](https://doi.org/10.1016/j.ces.2018.06.055)
@@ -359,7 +359,7 @@ title: Research
 
 <h3 id="3">[3] <strong>Sanjay, V.</strong>, Das, A.K. Numerical assessment of hazard in compartmental fire having steady heat release rate from the source. Build. Simul. 11, 613–624 (2018).</h3>
 
-<div class="tags"><span>Others</span><span>Fire</span><span>Evacuation</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Others</button><button type="button" aria-pressed="false">Fire</button><button type="button" aria-pressed="false">Evacuation</button></div>
 
 [![PDF](https://img.shields.io/static/v1.svg?style=flat-square&label=PDF&message=Available&color=green)](https://www.dropbox.com/scl/fi/c9vob7a6kso4ai4mygpj2/2018-Vatsal-_Numerical-assessment-of-hazard-in-compartmental-fire-having-steady-heat-release-rate-from-the-source.pdf?rlkey=e8rjz2d3e8nt0xof863i3xb3p&dl=0)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=DOI&message=10.1007/s12273-017-0411-y&color=orange)](https://doi.org/10.1007/s12273-017-0411-y)
@@ -371,7 +371,7 @@ title: Research
 
 <h3 id="2">[2] <strong>Sanjay, V.</strong>, & Das, A. K. Formation of liquid chain by collision of two laminar jets. Phys. Fluids, 29(11), 112101 (2017).</h3>
 
-<div class="tags"><span>Jets</span><span>Sheets</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Sheets</button></div>
 
 [![PDF](https://img.shields.io/static/v1.svg?style=flat-square&label=PDF&message=Available&color=green)](https://www.dropbox.com/scl/fi/fmk08c3z9twdat138v8b3/2017-Vatsal-preprint-_Formation-of-liquid-chain-by-collision-of-two-laminar-jets.pdf?rlkey=imwh2a606aecpbvjq3ctdq168&dl=0)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=DOI&message=10.1063/1.4998288&color=orange)](https://doi.org/10.1063/1.4998288)
@@ -382,7 +382,7 @@ title: Research
 
 <h3 id="1">[1] <strong>Sanjay, V.</strong>, & Das, A. K. On air entrainment in a water pool by impingement of a jet. AIChE J., 63(11), 5169-5181 (2017).</h3>
 
-<div class="tags"><span>Jets</span><span>Bubbles</span></div>
+<div class="tags"><button type="button" aria-pressed="false">Jets</button><button type="button" aria-pressed="false">Bubbles</button></div>
 
 [![PDF](https://img.shields.io/static/v1.svg?style=flat-square&label=PDF&message=Available&color=green)](https://www.dropbox.com/scl/fi/37ek49y5ae1t1lr18q95n/2017-Vatsal-preprint-_On-Air-Entrainment-in-a-Water-pool-by-Impingement-of-a-Jet.pdf?rlkey=iqb3ejms8t990owpiuqmpy0k6&dl=0)
 [![DOI](https://img.shields.io/static/v1.svg?style=flat-square&label=DOI&message=10.1002/aic.15828&color=orange)](https://doi.org/10.1002/aic.15828)
diff --git a/assets/css/research-v2.css b/assets/css/research-v2.css
index f98d796..7954d48 100644
--- a/assets/css/research-v2.css
+++ b/assets/css/research-v2.css
@@ -509,12 +509,12 @@
    flow horizontally and wrap. The `_research/index.md` sort-by-topic
    block uses one `.tags` div per tag; inline-flex lets them queue up
    on a single line instead of stacking. Per-paper `.tags` rows still
-   look right because each contains its own spans in one div. */
+   look right because each contains its own buttons in one div. */
 .research-content .tags {
   display: inline-flex;
   flex-wrap: wrap;
-  gap: 6px;
-  margin: 0 6px 6px 0;
+  gap: var(--s-2);
+  margin: 0 var(--s-2) var(--s-2) 0;
   vertical-align: top;
 }
 
@@ -533,30 +533,48 @@
   margin: var(--s-2) 0 var(--s-3);
 }
 
+.research-content .tags button,
 .research-content .tags span {
+  appearance: none;
   display: inline-flex;
   align-items: center;
-  padding: 4px 10px;
-  background: color-mix(in srgb, var(--c-brand-purple) 10%, transparent);
-  color: var(--c-brand-purple);
-  border: 1px solid color-mix(in srgb, var(--c-brand-purple) 22%, transparent);
+  margin: 0;
+  padding: var(--s-1) var(--s-3);
+  background: color-mix(in srgb, var(--c-accent-teal) 10%, transparent);
+  color: var(--c-accent-teal);
+  border: 1px solid color-mix(in srgb, var(--c-accent-teal) 22%, transparent);
   border-radius: var(--r-pill);
   font-family: var(--t-sans);
-  font-weight: 500;
-  font-size: 12px;
-  letter-spacing: 0.02em;
+  font-weight: var(--t-weight-med);
+  font-size: var(--t-eyebrow);
+  line-height: 1.6;
+  white-space: nowrap;
   cursor: pointer;
-  transition: background var(--dur-fast) var(--ease);
+  transition:
+    background var(--dur-fast) var(--ease),
+    color var(--dur-fast) var(--ease),
+    border-color var(--dur-fast) var(--ease);
 }
 
+.research-content .tags button:hover,
 .research-content .tags span:hover {
   background: color-mix(in srgb, var(--c-accent-teal) 15%, transparent);
   color: var(--c-accent-teal);
   border-color: var(--c-accent-teal);
 }
 
-[data-theme="dark"] .research-content .tags span {
-  color: #d99adc;
+.research-content .tags button:focus-visible,
+.research-content .tags span:focus-visible {
+  outline: var(--s-1) solid var(--c-accent-teal);
+  outline-offset: var(--s-1);
+}
+
+.research-content .tags button[aria-pressed="true"],
+.research-content .tags button.active,
+.research-content .tags span.active {
+  background: var(--c-accent-teal);
+  color: var(--c-accent-teal-fg);
+  border-color: var(--c-accent-teal);
 }
 
 /* Shield badges inline. Long DOI badges are wider than a 390 px
diff --git a/assets/css/styles.css b/assets/css/styles.css
index 76b5d88..be87bb7 100644
--- a/assets/css/styles.css
+++ b/assets/css/styles.css
@@ -1938,7 +1938,9 @@ section#featured:after,
   margin: 1rem 0;
 }
 
-.featured-paper .tags span {
+.featured-paper .tags span,
+.featured-paper .tags button {
+  appearance: none;
   display: inline-block;
   padding: 0.4rem 0.8rem;
   background: var(--tag-bg);
@@ -1951,7 +1953,8 @@ section#featured:after,
   border: 1px solid var(--tag-border);
 }
 
-.featured-paper .tags span:hover {
+.featured-paper .tags span:hover,
+.featured-paper .tags button:hover {
   background: var(--tag-bg-hover);
   transform: translateY(-2px);
   border-color: var(--tag-border-hover);
diff --git a/assets/js/command-data.js b/assets/js/command-data.js
index f619013..3858a57 100644
--- a/assets/js/command-data.js
+++ b/assets/js/command-data.js
@@ -540,7 +540,9 @@
               window.matchMedia("(prefers-color-scheme: dark)").matches;
 
             // Collect all unique tags from the page
-            const tagElements = document.querySelectorAll(".tags span");
+            const tagElements = document.querySelectorAll(
+              ".tags button, .tags span"
+            );
             const tags = new Set();
             tagElements.forEach((tag) => {
               tags.add(tag.textContent);
@@ -656,7 +658,7 @@
                 // Find the actual tag in the document and simulate a click on it
                 const tagText = btn.textContent;
                 const matchingTag = Array.from(
-                  document.querySelectorAll(".tags span")
+                  document.querySelectorAll(".tags button, .tags span")
                 ).find((tag) => tag.textContent === tagText);
 
                 if (matchingTag) {
diff --git a/assets/js/page-research.js b/assets/js/page-research.js
index 4ba1752..004b73b 100644
--- a/assets/js/page-research.js
+++ b/assets/js/page-research.js
@@ -76,7 +76,9 @@ document.addEventListener("DOMContentLoaded", function () {
     }
   });
 
-  var contentTags = researchContent.querySelectorAll(".tags span");
+  var contentTags = researchContent.querySelectorAll(
+    ".tags button, .tags span"
+  );
   var themeTags = document.querySelectorAll(".r-theme__tag[data-filter-tag]");
   var tagControls = Array.from(contentTags).concat(Array.from(themeTags));
   var papers = researchContent.querySelectorAll(".paper-container");
@@ -86,9 +88,16 @@ document.addEventListener("DOMContentLoaded", function () {
     return control.getAttribute("data-filter-tag") || control.textContent;
   }
 
+  function setPressed(control, pressed) {
+    control.classList.toggle("active", pressed);
+    if (control.tagName === "BUTTON") {
+      control.setAttribute("aria-pressed", pressed ? "true" : "false");
+    }
+  }
+
   function setActive(tagText) {
     tagControls.forEach(function (control) {
-      control.classList.toggle("active", getTagText(control) === tagText);
+      setPressed(control, getTagText(control) === tagText);
     });
   }
 
@@ -103,7 +112,7 @@ document.addEventListener("DOMContentLoaded", function () {
     options = options || {};
     activeTag = null;
     tagControls.forEach(function (control) {
-      control.classList.remove("active");
+      setPressed(control, false);
     });
     papers.forEach(function (paper) {
       paper.classList.remove("hidden");
@@ -119,7 +128,7 @@ document.addEventListener("DOMContentLoaded", function () {
       var tags = paper.querySelector(".tags");
       var match =
         tags &&
-        Array.from(tags.querySelectorAll("span")).some(function (tag) {
+        Array.from(tags.querySelectorAll("button, span")).some(function (tag) {
           return tag.textContent === tagText;
         });
       paper.classList.toggle("hidden", !match);
@@ -137,16 +146,20 @@ document.addEventListener("DOMContentLoaded", function () {
     control.addEventListener("click", function () {
       activateTag(control);
     });
-    if (control.tagName !== "BUTTON") {
-      control.setAttribute("role", "button");
-      control.setAttribute("tabindex", "0");
-      control.addEventListener("keydown", function (event) {
-        if (event.key === "Enter" || event.key === " ") {
-          event.preventDefault();
-          activateTag(control);
-        }
-      });
+    if (control.tagName === "BUTTON") {
+      if (!control.hasAttribute("aria-pressed")) {
+        control.setAttribute("aria-pressed", "false");
+      }
+      return;
     }
+    control.setAttribute("role", "button");
+    control.setAttribute("tabindex", "0");
+    control.addEventListener("keydown", function (event) {
+      if (event.key === "Enter" || event.key === " ") {
+        event.preventDefault();
+        activateTag(control);
+      }
+    });
   }
 
   tagControls.forEach(bindTagControl);
diff --git a/scripts/generate_filtered_research.rb b/scripts/generate_filtered_research.rb
index fa6025f..5973c3d 100755
--- a/scripts/generate_filtered_research.rb
+++ b/scripts/generate_filtered_research.rb
@@ -16,7 +16,7 @@
 
 # Find all unique tags
 all_tags = []
-doc.css('.tags span').each do |tag|
+doc.css('.tags button, .tags span').each do |tag|
   all_tags << tag.text unless all_tags.include?(tag.text)
 end
 
diff --git a/tests/command-actions-workflow.test.js b/tests/command-actions-workflow.test.js
index 4afa5c2..4fcf3cf 100644
--- a/tests/command-actions-workflow.test.js
+++ b/tests/command-actions-workflow.test.js
@@ -102,11 +102,11 @@ describe("command palette action workflows", () => {
       "beforeend",
       `
         <div class="research-content">
-          <h3 id="24">Paper A</h3><div class="tags"><span>Elastic</span></div>
-          <h3 id="23">Paper B</h3><div class="tags"><span>Newtonian</span><span>Elastic</span></div>
-          <h3 id="22">Paper C</h3><div class="tags"><span>Capillary</span></div>
-          <h3 id="21">Paper D</h3><div class="tags"><span>Inertial</span></div>
-          <h3 id="20">Paper E</h3><div class="tags"><span>Viscous</span></div>
+          <h3 id="24">Paper A</h3><div class="tags"><button type="button">Elastic</button></div>
+          <h3 id="23">Paper B</h3><div class="tags"><button type="button">Newtonian</button><button type="button">Elastic</button></div>
+          <h3 id="22">Paper C</h3><div class="tags"><button type="button">Capillary</button></div>
+          <h3 id="21">Paper D</h3><div class="tags"><button type="button">Inertial</button></div>
+          <h3 id="20">Paper E</h3><div class="tags"><button type="button">Viscous</button></div>
         </div>`
     );
     require("../assets/js/page-research.js");
@@ -137,7 +137,7 @@ describe("command palette action workflows", () => {
       "beforeend",
       `
       <div class="tags">${["A", "B", "C", "D", "E"]
-        .map((tag) => `<span>${tag}</span>`)
+        .map((tag) => `<button type="button">${tag}</button>`)
         .join("")}</div>`
     );
     initPage("/research/");
diff --git a/tests/command-data-actual.test.js b/tests/command-data-actual.test.js
index 2214829..1a1ab41 100644
--- a/tests/command-data-actual.test.js
+++ b/tests/command-data-actual.test.js
@@ -4,7 +4,7 @@
 
 // Mock dependencies
 global.Fuse = jest.fn().mockImplementation(() => ({
-  search: jest.fn().mockReturnValue([])
+  search: jest.fn().mockReturnValue([]),
 }));
 global.sortCoursesByDate = jest.fn();
 
@@ -124,10 +124,10 @@ describe("command-data.js actual implementation", () => {
     window.history.replaceState({}, "", "/research");
     document.body.innerHTML = `
       <div class="tags">
-        <span></span>
+        <button type="button"></button>
       </div>
     `;
-    document.querySelector(".tags span").textContent = "<img src=x>";
+    document.querySelector(".tags button").textContent = "<img src=x>";
 
     require("../assets/js/command-data.js");
 
diff --git a/tests/research-filter.test.js b/tests/research-filter.test.js
index 32019f6..d565058 100644
--- a/tests/research-filter.test.js
+++ b/tests/research-filter.test.js
@@ -11,9 +11,9 @@ describe("research tag filtering user paths", () => {
       <button class="r-theme__tag" data-filter-tag="Viscoelastic">Elasticity</button>
       <div class="research-content">
         <h2>Published work</h2>
-        <h3 id="24">Paper A</h3><div class="tags"><span>Viscoelastic</span></div>
+        <h3 id="24">Paper A</h3><div class="tags"><button type="button" aria-pressed="false">Viscoelastic</button></div>
         <p>Elastic material</p>
-        <h3 id="23">Paper B</h3><div class="tags"><span>Newtonian</span></div>
+        <h3 id="23">Paper B</h3><div class="tags"><button type="button" aria-pressed="false">Newtonian</button></div>
         <h2 id="methods">Methods</h2><p>Methods text</p>
       </div>`;
     require("../assets/js/page-research.js");
@@ -64,15 +64,21 @@ describe("research tag filtering user paths", () => {
 
   test("published paper tags filter and a second activation clears", () => {
     load();
-    const tag = document.querySelector(".tags span");
+    const tag = document.querySelector(".tags button");
+    expect(tag.tagName).toBe("BUTTON");
     expect(visiblePapers()).toEqual(["24", "23"]);
     tag.click();
     expect(visiblePapers()).toEqual(["24"]);
     expect(window.location.search).toBe("?tag=Viscoelastic");
+    expect(tag.getAttribute("aria-pressed")).toBe("true");
+    expect(
+      document.querySelector(".r-theme__tag").getAttribute("aria-pressed")
+    ).toBe("true");
     expect(document.querySelector(".r-theme__tag").classList).toContain(
       "active"
     );
     tag.click();
+    expect(tag.getAttribute("aria-pressed")).toBe("false");
     expect(visiblePapers()).toEqual(["24", "23"]);
     expect(window.location.search).toBe("");
   });
@@ -80,6 +86,27 @@ describe("research tag filtering user paths", () => {
   test("keyboard Enter and Space operate tags with stable deep links", () => {
     load("?tag=Newtonian");
     expect(visiblePapers()).toEqual(["23"]);
+    const tag = document.querySelector(".tags button");
+    expect(tag.getAttribute("type")).toBe("button");
+    expect(tag.tabIndex).toBe(0);
+    // Enter and Space activate a real button through click.
+    tag.click();
+    expect(tag.getAttribute("aria-pressed")).toBe("true");
+    expect(visiblePapers()).toEqual(["24"]);
+    tag.click();
+    expect(tag.getAttribute("aria-pressed")).toBe("false");
+    expect(visiblePapers()).toEqual(["24", "23"]);
+  });
+
+  test("legacy span chips still filter from Enter and Space", () => {
+    window.history.replaceState({}, "", "/research/");
+    document.body.innerHTML = `
+      <div class="research-content">
+        <h3 id="24">Paper A</h3><div class="tags"><span>Viscoelastic</span></div>
+        <h3 id="23">Paper B</h3><div class="tags"><span>Newtonian</span></div>
+      </div>`;
+    require("../assets/js/page-research.js");
+    ready();
     const tag = document.querySelector(".tags span");
     expect(tag.getAttribute("role")).toBe("button");
     expect(tag.tabIndex).toBe(0);
@@ -91,7 +118,13 @@ describe("research tag filtering user paths", () => {
     tag.dispatchEvent(enter);
     expect(enter.defaultPrevented).toBe(true);
     expect(visiblePapers()).toEqual(["24"]);
-    tag.dispatchEvent(new KeyboardEvent("keydown", { key: " " }));
+    tag.dispatchEvent(
+      new KeyboardEvent("keydown", {
+        key: " ",
+        bubbles: true,
+        cancelable: true,
+      })
+    );
     expect(visiblePapers()).toEqual(["24", "23"]);
   });