feat(shell): host clipboard via OSC 52 on grain sh

[cxdy]

Summary

Grok Build (and similar TUIs) copy on highlight via OSC 52 when they are not on the local OS clipboard. That works on a laptop terminal, but grain sh only forwarded PTY bytes — terminals without native OSC 52 (e.g. Apple Terminal) never applied the sequence, and even capable terminals could miss host-side copy depending on the path.

This change intercepts OSC 52 on the host grain sh client (agent WebSocket shell, including remote GRAIN_API proxy) and writes the decoded payload to the local clipboard:

Host	Helper
macOS	pbcopy
Linux	wl-copy, else xclip, else xsel

Also handles tmux DCS-wrapped OSC 52 (ESC P tmux; …). Sequences still pass through by default so iTerm2/Ghostty/Kitty keep native handling.

Env	Effect
GRAIN_OSC52_CLIPBOARD=0	Disable intercept
GRAIN_OSC52_PASSTHROUGH=0	Swallow sequence after host copy

Test plan

• go test ./internal/osc52/
• go test ./internal/agent/
• grain sh into a sandbox, run Grok Build, highlight text → host clipboard has it
• Same over remote CLI (GRAIN_API=… grain sh)
• GRAIN_OSC52_CLIPBOARD=0 grain sh → no host copy

[github-actions]

Coverage (lines): 79% ✅ — minimum 75%

_{commit a241fe9 · 11982/15195 lines · cmd/* excluded}

Coverage report by file (79% overall — click to expand)

File	Coverage		Missing
All files	79%	✅
internal/osc52/writer.go	56%	❌	55-57 62-66 78-82 84-86 93-95 107-111 119-121 139-147 152-159 168-170 183-185 191-193 2…
internal/sshkey/sshkey.go	68%	❌	33-35 38-41 46-48 50-52
internal/mcp/tools.go	69%	❌	389-391 393-395 401-406 427-429 463-468 471-476 481-484 514-516 524-526 531-533 538 544…
internal/cli/cp.go	70%	❌	80-82 88 136-139 141-143 145 169-171 179-181 188-190 200-202 205-207 209-211 240-242 25…
internal/cli/root.go	70%	❌	96-98 100-102 179-181 188-193 204-206 211-213 217-219 227-232 235-240 247-254 256 258-2…
internal/update/update.go	71%	❌	85-87 89-91 93-98 112-114 135-137 169-171 195 220-222 224-226 228-230 240-245 247-249 2…
internal/mcp/connect.go	71%	❌	56-58 68-72 79-81 83-85
internal/recipe/recipe.go	71%	❌	151-153 155-157 159-161 170-172 181-183 192-194 201-203 214 226-228 231-233 235-238 249…
internal/daemon/daemon.go	73%	❌	29-31 59-62 90-92 100-102 107-109 118-130
internal/cli/stats.go	73%	❌	23-25 27-29 40-42
internal/proxy/store.go	73%	❌	34-36 61 64-66 73-75 77-79 88-90 110-112 121-123 165 168-171 177-179 181-183 192-194 19…
internal/store/store.go	73%	❌	21-23 39-41 43-45 47-49 61 74-78 107-109
internal/image/catalog.go	74%	❌	69-79 119-132
internal/agent/server.go	75%	✅	92-94 96-98 104 216-218 305-311 344-346 350-353 355-358 400-409 421-433 483-486 488-491…
internal/cli/image_doctor.go	75%	✅	34-38 53-58 62-71 74-76 102-104 150-152 157 161-163 174-176 181-187 190-192 203-206 209…
internal/manager/manager.go	75%	✅	88-90 185-187 203-207 209-211 217-219 240-242 254-260 265-270 358-362 389-391 439-441 4…
internal/cli/progress.go	75%	✅	43-49 51-54 63-65 103-111 113-116 131-133 169-174 201-203
internal/mcp/http.go	75%	✅	33-35 40-42 72-74 84-88
internal/cli/fwd.go	76%	✅	46-48 127-129 131-133 136-138 143-145 149-151 189-192 207-209 211-213 221-226 233-235 2…
internal/cli/uninstall.go	76%	✅	33-36 63-70 72-74 79-81 88-90 110-112 116-117 140-142
internal/presets/presets.go	76%	✅	31-33 40-42 45-46 49-50 62-64
internal/secrets/store.go	76%	✅	58-60 84-88 101 119-121 148-150 153-159 171-173 197-203 217-219 235 247-249 259 273-275…
internal/cli/proxy.go	76%	✅	43-45 80-82 91-93 96-99 104-105 116 129-131 133-135 141-143 155-159 164 174-176 183-185…
internal/cli/logs.go	77%	✅	37-39 44-46 52 55-59 84-86 104-109 113 123 127-128 141-143 158-160 182 209-211 219-221
internal/agent/client.go	77%	✅	56-58 79-81 83-85 87-90 92-94 101-103 126-128 147-149 156-158 179-181 200-202 245-247 2…
internal/cli/mcp.go	78%	✅	38-40 50-52 56-58 69-71 81
internal/hypervisor/qemu.go	78%	✅	33-35 50-52 66-68 72-74 79-81 88-90 95-97 155-162 168-170 174-184 186-189 196-198 202-2…
internal/cli/recipe.go	78%	✅	37-39 62-64 66-68 86-88 90-92 97-102
internal/image/pull.go	78%	✅	106-108 136 157-159 170-172 175-177 188-190 201-205 214-218 220-223 237-239 262-264 267…
internal/api/api.go	78%	✅	112-115 215-219 228-251 273-275 398-401 412-415 427-429 437-439 500-503 512-514 519-522…
scripts/mcp-handshake.go	78%	✅	16-20 42-44 60-62
internal/hypervisor/disk_local.go	79%	✅	38-40 45-47 73-76 78-80 112-114 123
internal/mcp/host.go	79%	✅	68-72 79-81 87-92 115
internal/proxy/server.go	79%	✅	65-67 114-118 124-127 168-170 173-175 178-181 191-194 198-202 205-208 222-224 227-233 2…
internal/hypervisor/virtiofs.go	80%	✅	28-30 32-34 64-66 104-106 111-114 119-121 126-129 170-172 190-192 199-201
internal/cli/fs.go	80%	✅	60-62 87-89 91-93 127-129 131-133 146-148 150-152 179-181 183-185 192-194 214-216 218-2…
internal/cli/volume.go	82%	✅	24-29
internal/guest/sshwait.go	83%	✅	32-34 39-41 58
internal/hypervisor/fsdev.go	83%	✅	34-40
internal/agent/stats.go	83%	✅	62-64 71-73 80-82 116-118 125-127
internal/hypervisor/qmp.go	84%	✅	50-52 62-69 93-95 97-99
internal/api/client.go	85%	✅	66-68 74-76 97-99 105-107 154-156 169-171 190-192 211-213 228-230 245-247 262-264 279-2…
internal/hypervisor/firecracker.go	86%	✅	142-144 164-166 171-173 208-213 229-231 238-239 242-246 249-250 253-254 257-259 268-277…
internal/agent/readiness.go	87%	✅	27-29 33 57-59
internal/cli/act.go	87%	✅	97-99 101-103 112-116 119-121 143-145 150-152 166-168 209-211 218-220 254-256 337-339
internal/guest/agentdeploy.go	87%	✅	59-61 65-67 75-77
internal/cloudinit/seed.go	90%	✅	64-69 93
internal/cli/update.go	91%	✅	42-44 131-135 140-142 177-178
internal/config/config.go	91%	✅	325-327 345-347 363-365 409 420-422 450-452 459-461 471-473
internal/hypervisor/transport.go	91%	✅	69-71
internal/agent/binary.go	91%	✅	58-59 65-66
internal/hostbin/hostbin.go	91%	✅	28-30
internal/cli/preset.go	92%	✅	36-38
client/client.go	93%	✅	96-98 186-188 194-196 218-220 226-228 274-276 448-450 508-510 517-519 567-569 610-612 6…
internal/hypervisor/netdev.go	93%	✅	43-45
scripts/handshake_lib.go	93%	✅	54-56
internal/cli/agent_dial.go	95%	✅	44-48 150 159
internal/cloudinit/merge.go	96%	✅	124-126 180-182 238-240
internal/agent/dial.go	97%	✅	82-83
internal/cli/secret.go	97%	✅	56-58 225-227
internal/cli/profile.go	97%	✅	28-30
internal/hypervisor/mock.go	97%	✅	161-163