diff --git a/README.md b/README.md
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 treatments. It generally replicates the functionality developed in the MATLAB
 [open-TFUS toolbox](https://github.com/OpenwaterHealth/opw_neuromod_sw).
 
+## Supported Versions
+
+![openlifu-python maintenance by release line](docs/support-schedule.svg)
+
+Versions may fall to a lower support tier every six months or so, each time the
+downstream
+[desktop application](https://github.com/OpenwaterHealth/openlifu-desktop-application/tree/main)
+selects a newer version of openlifu. See the [support schedule](SUPPORT.md) for
+details.
+
 ## Installation
 
 ### Requirements
diff --git a/SUPPORT.md b/SUPPORT.md
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+# Support schedule
+
+This document defines the maintenance and support policy for the `openlifu`
+python package.
+
+## Release lines and patch releases
+
+A **release line** is a `MAJOR.MINOR` version series, such as `0.20`.
+Maintenance is delivered through patch releases. Only the **latest patch
+release** within a supported line is supported; earlier patches are superseded.
+
+## Maintenance tiers
+
+- **Full Maintenance:** fixes for critical and noncritical issues.
+- **Critical Maintenance:** fixes for critical issues only.
+- **Unsupported:** no maintenance releases.
+
+The
+[desktop application](https://github.com/OpenwaterHealth/openlifu-desktop-application)'s
+releases determine the support boundaries for openlifu, as described in the
+[desktop application support schedule](https://github.com/OpenwaterHealth/openlifu-desktop-application/blob/main/SUPPORT.md):
+
+- Full Maintenance runs from the latest release all the way back to the release
+  line used in the latest openlifu-desktop-application release.
+- Critical Maintenance runs back through the release line used for the previous
+  openlifu-desktop-application release.
+
+The
+[release component version table](https://github.com/OpenwaterHealth/openlifu-desktop-application/blob/main/docs/release-component-version-table.md)
+shows support status according to these rules.
+
+With roughly two desktop release lines per year, support tiers may change every
+six months or so. Support transitions follow actual releases; these durations
+are not fixed calendar deadlines.
+
+## Support at a glance
+
+![openlifu-python maintenance by release line](docs/support-schedule.svg)
+
+The graphic and table describe release lines. Always use the latest patch in a
+supported line.
+
+## What counts as critical?
+
+Critical Support applies when fixes are needed to address circumstances such as
+the following:
+
+- Impacts to essential device performance, including safety-related issues
+- Incorrectness of planning, simulation, or targeting
+- Data loss or corruption
+- Inability to perform core functionality with no reasonable workaround
+
+## Temporary Exceptions
+
+These follow the
+[desktop application's temporary exceptions](https://github.com/OpenwaterHealth/openlifu-desktop-application/blob/main/SUPPORT.md#temporary-exceptions):
+
+- The latest "legacy IO" release line is fully supported for now.
+- `v0.18` and `v0.19` are Unsupported, rather than receiving Critical Support,
+  because desktop application `v1.11` is Unsupported.
diff --git a/docs/support-schedule.svg b/docs/support-schedule.svg
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+<svg xmlns="http://www.w3.org/2000/svg" width="768" height="136" viewBox="0 0 768 136" role="img" aria-labelledby="title description">
+  <title id="title">openlifu-python: support by component and release line</title>
+  <desc id="description">Release lines for openlifu-python, grouped by maintenance status.</desc>
+  <rect x="1" y="1" width="766" height="134" rx="12" fill="#ffffff" stroke="#d0d7de"/>
+  <g font-family="Arial, Helvetica, sans-serif">
+    <g text-anchor="middle" font-size="15" font-weight="600">
+      <text x="277" y="32" fill="#424a53">Unsupported</text>
+      <text x="467" y="32" fill="#633c01">Critical Maintenance</text>
+      <text x="657" y="32" fill="#116329">Full Maintenance</text>
+    </g>
+    <g>
+      <text x="24" y="91" font-size="16" font-weight="600" fill="#24292f">openlifu-python</text>
+      <g text-anchor="middle" font-size="18" font-weight="600">
+        <rect x="190" y="52" width="174" height="64" rx="8" fill="#eaeef2" stroke="#6e7781" stroke-dasharray="5 5"/>
+        <text x="277" y="91" fill="#424a53">v0.19 and older</text>
+        <rect x="380" y="52" width="174" height="64" rx="8" fill="#fff8c5" stroke="#9a6700"/>
+        <text x="467" y="91" fill="#633c01">(none)</text>
+        <rect x="570" y="52" width="174" height="64" rx="8" fill="#dafbe1" stroke="#1a7f37"/>
+        <text x="657" y="80" fill="#116329">v0.20 - v0.21</text>
+        <text x="657" y="102" font-size="13" font-weight="400" fill="#116329">+ v0.20 legacy IO</text>
+      </g>
+    </g>
+  </g>
+</svg>